ORCID Profile
0000-0002-8271-3041
Current Organisation
University of South Australia
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Publisher: Elsevier BV
Date: 03-2006
Publisher: American Chemical Society (ACS)
Date: 18-01-2012
DOI: 10.1021/JP211378S
Publisher: Elsevier BV
Date: 02-2010
Publisher: American Chemical Society (ACS)
Date: 09-02-2002
DOI: 10.1021/LA011379L
Publisher: Elsevier BV
Date: 07-1981
Publisher: AIP Publishing
Date: 24-06-2008
DOI: 10.1063/1.2931574
Abstract: We present a high energy x-ray reflectivity study of the density profiles of water and ice at hydrophobic and hydrophilic substrates. At the hydrophobic water/octadecyl-trichlorosilane (water-OTS) interface, we find clear evidence for a thin density depletion layer with an integrated density deficit corresponding to approximately 40% of a monolayer of water molecules. We discuss the experimental results in terms of a simple model of hydrophobic/hydrophilic solid-liquid interfaces. Our results also exclude the presence of nanobubbles. A detailed study of possible radiation damage induced by the intense x-ray beam at the dry OTS surface and at the ice-OTS, as well as at water-OTS interfaces, discloses that noticeable damage is only induced at the water-OTS interface, and thus points to the dominant role of highly mobile radicals formed in bulk water close to the interface.
Publisher: American Chemical Society (ACS)
Date: 07-09-2011
DOI: 10.1021/JP2065826
Publisher: Deakin University
Date: 13-04-2023
DOI: 10.21153/JTLGE2023VOL14NO1ART1654
Abstract: Most students acknowledge shared responsibility, with the university, for their employability development. Many academics use assessments as the main driver for motivating students to learn. At the intersection between employability, assessment and learning, the emergent research question is - what are the mechanisms by which course-based employability is fostered? Prior research reveals that although academics identified course-based assessment as the key employability mechanism, neither students nor employers registered this conceptualisation, and thus purpose of assessment. The aim of this research was to stimulate and communicate the direct connection between assessment and employability to students and interpret their response. Over 100 first-year students, across a metropolitan and regional Australian university, participated. Students were directed to use a simple reflective tool, dubbed iASK by the researchers, that probed employability elements of identity, Attributes, Skills, and Knowledge. The research revealed the resulting student view that regular course-based assessment can develop their employability skills in communication and independence, but not in critical thinking and global citizenship.
Publisher: American Chemical Society (ACS)
Date: 04-1999
DOI: 10.1021/LA971012+
Publisher: Royal Society of Chemistry (RSC)
Date: 2000
DOI: 10.1039/B001213K
Publisher: Elsevier BV
Date: 04-1999
Publisher: American Chemical Society (ACS)
Date: 31-10-2013
DOI: 10.1021/JP4062863
Publisher: American Geophysical Union (AGU)
Date: 07-2009
DOI: 10.1029/2008JB005928
Publisher: Elsevier BV
Date: 06-2005
DOI: 10.1016/J.JCIS.2005.01.028
Abstract: The foam behavior of three polypropylene glycols covering the molecular weight range between 192 and 725 g/mol has been examined. Static and dynamic surface tension data, as well as bubble size distribution and retention time in the foam, were incorporated into a simple model of foam stability. The latter clearly indicates that surface tension differences between the plateau border and lamellar region adjacent to the bubble surface are the dominant factor in controlling foamability, causing liquid flow in the direction opposite to liquid drainage, a process termed the Marangoni effect.
Publisher: Elsevier BV
Date: 07-2013
DOI: 10.1016/J.JCIS.2013.03.058
Abstract: Glass capillaries are prepared with well-defined regions of tuneable wettability on the interior walls using an inexpensive and simple approach. A homogeneous layer of hydrophilic TiO2 nanoparticles is adsorbed on the capillary wall and chemically hydrophobized using octadecyltrihydrosilane (OTHS). The hydrophobic OTHS monolayer is then patterned by spatially-selective removal of the OTHS via TiO2-catalysed decomposition by ultraviolet irradiation. By patterning the capillaries with hydrophilic-hydrophobic rings, modulated penetration of a liquid (glycerol, in this study) can be achieved. For given wettability contrast, the penetration dynamics and equilibrium rise heights are very sensitive to the characteristic length-scale of the pattern, and may offer greater, time-dependent s ling control in fluidic devices.
Publisher: Elsevier BV
Date: 2007
Publisher: Elsevier BV
Date: 09-1999
Publisher: Royal Society of Chemistry (RSC)
Date: 1999
DOI: 10.1039/A900974D
Publisher: Royal Society of Chemistry (RSC)
Date: 2010
DOI: 10.1039/C0CP01367F
Abstract: The contact between fine hydrophilic α-Al(2)O(3) particles and nitrogen bubbles was studied as a function of solution composition in single bubble capture experiments, where the bubble collection efficiency was measured. The surface charges of both bubble and particle were controlled by varying the electrolyte concentration and pH of the solution. In all experiments the bubbles were negatively charged while the α-Al(2)O(3) particles were either negatively (above pH of the isoelectric point, pH(IEP)) or positively (below pH(IEP)) charged. The collection efficiency was found to be strongly influenced by the surface charge of the particles. The maximum collection efficiency occurred when the bubble and particle were oppositely charged (at low pH values) and at low salt concentration, i.e. when a long range attractive electrostatic interaction is present. In the case where both bubble and particle were of the same charge, the collection efficiency was near to zero within experimental error and was not influenced by either salt concentration or pH. This is the first experimental proof of the concept of 'contactless flotation', first proposed by Derjaguin and Dukhin in 1960, with far reaching implications from minerals processing to biology.
Publisher: IEEE
Date: 2005
Publisher: Elsevier BV
Date: 02-2005
Publisher: Elsevier BV
Date: 02-2010
DOI: 10.1016/J.JCIS.2009.10.068
Abstract: We have studied the stability and structure of emulsions formed in the presence of colloidal mixtures of partially hydrophobic titania particles and hydrophilic silica particles. On their own, the titania particles attached strongly to the oil-water interface and stabilised emulsions, while the silica particles did not attach to the interface. Adding silica particles to the titania dispersions enhanced coalescence processes during emulsion formation, except under mixing conditions that favoured particle heteroaggregation. The destabilisation of the emulsions was linked to the presence of silica particles in the particle layers at the interface.
Publisher: Elsevier BV
Date: 07-2000
Publisher: American Chemical Society (ACS)
Date: 14-10-2010
DOI: 10.1021/LA103351T
Abstract: The wettability of a titania surface, partially covered with octadecyltrihydrosilane, has been investigated as a function of solution pH. The results show that surface charge affects both static wettability and wetting kinetics. The static contact angle decreases above and below the point of zero charge of the titania surface in a Lippman-like manner as the pH is altered. The dependence of dynamic contact angle on velocity is also affected by pH. The molecular-kinetic theory (MKT) is used to interpret the dynamic contact angle data. The frequency of molecular displacement κ(0) strongly varies with surface charge, whereas the mean molecular displacement length λ is essentially unaffected. There is an exponential dependence of contact-line friction upon work of adhesion, which is varied simply by altering the pH.
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C3SM27772K
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C7CP06404G
Abstract: Experimental data and theoretical fitting for ionic liquid wetting on application-relevant substrates.
Publisher: Royal Society of Chemistry (RSC)
Date: 2000
DOI: 10.1039/B001672L
Publisher: Elsevier BV
Date: 02-2001
Publisher: American Chemical Society (ACS)
Date: 21-10-1999
DOI: 10.1021/LA990558O
Publisher: IOP Publishing
Date: 11-12-2012
Publisher: Elsevier BV
Date: 12-2005
Publisher: Elsevier BV
Date: 06-2001
Publisher: Elsevier BV
Date: 04-1985
Publisher: Elsevier BV
Date: 03-1999
Publisher: Elsevier BV
Date: 09-2010
DOI: 10.1016/J.JCIS.2010.05.089
Abstract: The remarkable stability of nanoparticles attached to oil-water interfaces in macroemulsions hinders controlled detachment of these particles from emulsions. In this work it is shown that adding surfactant molecules which preferentially adsorb at the oil-water interface displaces nanoparticles from the interface. Surfactant adsorption at the oil-water interface is energetically favoured and readily occurs on mixing nanoparticle-stabilised oil-in-water emulsions with surfactant solutions. Depending on the surfactant concentration, there is a significant reduction in the interfacial tension. Hence there is substantial fragmentation of the oil droplets and foaming of the emulsion during mixing. Surfactant concentrations above the critical micelle concentration are required to achieve complete interfacial displacement and hence recovery of the nanoparticles from the emulsions. The effects of surfactant addition have important implications for tailoring the interfacial composition of emulsions.
Publisher: Elsevier BV
Date: 11-2005
Publisher: Elsevier BV
Date: 03-2004
DOI: 10.1016/J.JCIS.2003.09.042
Abstract: Nonionic polyethylene oxide (PEO) and anionic polyacrylamide (PAM) flocculation of kaolinite dispersions has been investigated at pH 7.5 in the temperature range 20-60 degrees C. The surface chemistry (zeta potential), particle interactions (shear yield stress), and dewatering behavior were also examined. An increase in the magnitude of zeta potential of kaolinite particles, in the absence of flocculant and at a fixed PEO and PAM concentration, with increasing temperature was observed. The zeta potential behavior of the flocculated particles indicated a decrease in the adsorbed polymer layer thickness, while at the same time, however, the adsorbed polymer density showed a significant increase with increasing temperature. These results suggest that polymer adsorption was accompanied by temperature-influenced conformation changes. The hydrodynamic diameter and supernatant solution viscosity of both polymers decreased with increasing temperature, consistent with a change in polymer-solvent interactions and conformation, prior to adsorption. The analysis of the free energy (DeltaG(ads)) of adsorption showed a strong temperature dependence and the adsorption process to be more entropically than enthalpically driven. The polymer conformation change and increased negative charge at the kaolinite particle surface with increasing temperature resulted in decreased polymer bridging and flocculation performance. Consequently, the shear yield stress and the rate and the extent of dewatering (consolidation) of the pulp decreased significantly at higher temperatures (>40 degrees C). The temperature effect was more pronounced in the presence of PEO than PAM, with 40 and 20 degrees C indicated as the optima for enhanced performance of the latter and former flocculants, respectively. The results demonstrate that a temperature-induced conformation change, together with polymer structure type, plays an important role in flocculation and dewatering behavior of kaolinite dispersions.
Publisher: American Chemical Society (ACS)
Date: 15-04-2010
DOI: 10.1021/JP912115N
Publisher: Springer Science and Business Media LLC
Date: 03-08-2000
Publisher: American Chemical Society (ACS)
Date: 20-03-2003
DOI: 10.1021/LA020660C
Publisher: Elsevier BV
Date: 06-1997
Publisher: American Chemical Society (ACS)
Date: 02-11-2005
DOI: 10.1021/LA051457V
Abstract: We show that the DNA base thymine and other uracil derivatives, when alkylated with a hydrocarbon chain and assembled at a gold interface, dimerize when subjected to UV irradiation. The process is robust and reversible and is accompanied by a substantial decrease in wettability as well as a marked decrease in acidity constant when the dimer is formed. There is a concerted molecular reorientation that accompanies photodimerization, with the dimer displaying a marked affinity for the gold surface. The spatial requirements for this reorganization are satisfied during dimerization by the reduction in intermolecular distance that occurs when the cyclobutane ring is formed between adjacent bases. The structural changes observed here for a tethered DNA base provide a direct route for exploring reactions, in two dimensions, that are of central interest in biology.
Publisher: American Physical Society (APS)
Date: 13-07-2007
Publisher: Royal Society of Chemistry (RSC)
Date: 2008
DOI: 10.1039/B713584J
Abstract: The surfaces of three imidazolium based ionic liquids with a common anion were studied with angle-resolved X-ray photoelectron spectroscopy (XPS). The room temperature ionic liquids (RTILs): 1-butyl-3-methylimidazolium (bmim), 1-hexyl-3-methylimidazolium (hmim), and 1-octyl-3-methylimidazolium (omim) tetrafluoroborates, were meticulously purified and dried under vacuum. Survey and high-resolution spectra were obtained at different take-off angles (0-84 degrees ), thus increasing the surface sensitivity of the measurement. No impurities were detected and the survey spectra at normal emission (0 degrees ) confirmed the stoichiometric composition of the liquids. However, the spectra at take-off angles of 60, 70, 80 and 84 degrees indicated a higher amount of carbon. High resolution spectra of C1s, at these angles, showed an increased amount of aliphatic carbon when compared to the spectra at normal emission. The longer the side chain (R) of the imidazolium cation (Rmim), the larger was the amount of aliphatic carbon detected. Previous studies with other surface sensitive techniques have yielded contradictory conclusions about the surface orientation of the Rmim. We conclude unequivocally that the alkyl chain of the imidazolium ring of the investigated RTILs is oriented away from the liquid. Our study demonstrates the ability of XPS to probe the structure, along with the composition, of the free liquid surface by comparing signals from different penetration depths.
Publisher: Royal Society of Chemistry (RSC)
Date: 2014
DOI: 10.1039/C4CP03910F
Abstract: For capillary-driven liquid–liquid displacement in rectangular open microchannels, the square of the position of the liquid–liquid front increases linearly with time, whereas the flow velocity decreases with increasing channel width.
Publisher: Informa UK Limited
Date: 02-01-2014
Publisher: Elsevier BV
Date: 09-2000
Publisher: Elsevier BV
Date: 06-1994
Publisher: American Chemical Society (ACS)
Date: 12-02-2003
DOI: 10.1021/LA026692H
Publisher: Elsevier BV
Date: 03-2000
DOI: 10.1016/S0001-8686(99)00030-5
Abstract: A critical review of the various models existing in the literature for the calculation of the collision efficiency between particles and single, rising gas bubbles is presented. Although all of these collision models predict that the collision efficiency increases with particle size, their dependence on the latter is different because of the various assumptions and hydrodynamic conditions used in each model. Collision efficiencies of quartz particles with single bubbles have been obtained from experimental flotation experiments under conditions where the attachment and stability efficiencies were at, or near, unity. These collision efficiencies were then used to test various collision models. Good agreement between the experimental and calculated collision efficiencies was only obtained with the Generalised Sutherland Equation. The differences in collision efficiencies obtained between the various models were mainly explained in terms of, firstly, the degree of mobility of the bubble surface and, secondly, a consideration of the inertial forces acting on the particles.
Publisher: Elsevier BV
Date: 03-1999
Publisher: Elsevier BV
Date: 02-2002
DOI: 10.1016/S0001-8686(01)00084-7
Abstract: Electrokinetic (zeta)-potentials of methylated (trimethylchlorosilane) quartz capillaries (5-6 microm in radius) were determined in 10(-4) M KCl solution. Over the course of time, the absolute values of the zeta-potential decrease, as a result of the formation of small bubbles on the rough methylated surface, generated from the flowing, nitrogen gas-saturated solution. This decrease is attributed to screening of a part of the solid surface. After the passage of time, a sharp increase in the zeta-potentials was observed, as the pressure was increased and the initial potential values were recovered. Sometimes, oscillations in the zeta-potentials were observed. This behaviour was explained by detachment of bubbles from the methylated surfaces by the flowing solution. Addition of non-ionic surfactant, which made the methylated surface hydrophilic, decreased the measured zeta-potentials. This was attributed to suppression of water slippage, an effect known to occur for hydrophobic solid surfaces. A mixed mechanism of charge formation is characteristic for these methylated quartz surfaces and is connected with presence of hydrophobic and hydrophilic areas. The ratio between these areas controls both the formation of surface charge as well as the contact angles.
Publisher: American Chemical Society (ACS)
Date: 16-02-2000
DOI: 10.1021/LA990524G
Publisher: Elsevier BV
Date: 07-1994
Publisher: Elsevier BV
Date: 10-1998
Publisher: Elsevier BV
Date: 06-2005
DOI: 10.1016/J.JCIS.2005.01.056
Abstract: The colloid stability of synthetic titania particles was studied as a function of KCl concentration at pH values of 6.3, 6.7, and 8.4, using static light scattering to obtain stability ratios. Standard DLVO theory was then used to calculate the stability ratios as a function of salt concentration. Reasonable agreement between theory and experiment could only be obtained if an effective interaction radius, corresponding to surface asperities on the titania particles, was used in the calculation. High-resolution TEM images suggest that the effective interaction radius corresponds to the size of surface crystallites formed during synthesis.
Publisher: Elsevier BV
Date: 04-2005
Publisher: Emerald
Date: 05-10-2015
DOI: 10.1108/IJHMA-07-2015-0031
Abstract: – This paper aims to advance best practice by gaining insights into key multi-owned property (MOP) issues challenging policymakers and communities. Ontario (Canada) and Victoria (Australia) are internationally recognised for best practice in MOP living and law. Yet, both jurisdictions struggle with the emerging urbanism related to condominium MOP. – Different ways of recognising community in MOP urbanism will be examined against public policy and political theory perspectives promoting social sustainability. A rich mixed-data and content analysis method is relied upon which synthesises three pillars of MOP community governance: harmonious high-rise living residential-neighbourhood interface and metropolitan community engagement. The article cross-examines Canadian policy and law reform documents and Australian dispute case law from the state of Victoria to explore and showcase critical MOP management, residential and policy issues. – A theory-building typology formally recognises “community” as an affective performance across MOP governance contexts: cosmopolitan, civic-citizen and neighbourly. These ideal types differentiate community affects in and beyond (case) law and land-use planning: from determining alternative dispute resolution remedies addressing neighbourhood and metropolitan NIMBY-ism in urban consolidation to bridging the critical policy and civic gap between the limits and aims of socially sustainable MOP vertical-tenured community affects. – Strong cross-jurisdictional MOP community lessons exist, as other cities follow best practice in legal and governance structures to effect change at the frontiers of twenty-first century urbanism. – Past studies emphasise classifying dispute issues, single-issue concerns or historical and life cycle evaluations. This theory-building article advances why and how community must be better understood holistically across community contexts to inform cutting-edge governance practices.
Publisher: Elsevier BV
Date: 08-2009
Publisher: Elsevier BV
Date: 11-2008
Publisher: American Chemical Society (ACS)
Date: 03-2006
DOI: 10.1021/LA052303I
Abstract: Advancing water contact angles were measured on freshly cleaved talc faces as well as on talc particles. The intrinsic hydrophobicity of talc was shown to be due to the dominance of the apolar components of the work of adhesion. Polyacrylamides and polysaccharides adsorb onto the surface of talc, displaying strikingly different morphologies. Adsorbed amount, apparent layer thickness, and polymer structure control talc wettability.
Publisher: Royal Society of Chemistry (RSC)
Date: 1981
DOI: 10.1039/F19817702585
Publisher: American Chemical Society (ACS)
Date: 28-12-2002
DOI: 10.1021/JP0118221
Publisher: American Chemical Society (ACS)
Date: 22-01-2003
DOI: 10.1021/JP026723H
Publisher: Elsevier BV
Date: 1990
Publisher: CSIRO Publishing
Date: 2005
DOI: 10.1071/CH05140
Abstract: The interaction between a liquid and a solid surface is the key to understanding wetting phenomena. A very large number of natural and industrial processes rely on the delicate manipulation of this interaction. Controlled wetting is of central importance in microfluidics, mineral flotation, high speed coating, electronic display technologies, oil recovery, lubrication, and plant protection. At the molecular level, one can alter the distribution and charge of surface groups on functional surfaces, vary the number of hydrogen bonds, change molecular configuration, perform chemical grafts, and so forth. External stimuli such as light, electric potential, and heat can lead to subtle control of wettability, which is based strictly on thermodynamics.
Publisher: Elsevier BV
Date: 12-1998
Abstract: The adsorption of a series of monoalkyl phosphates (MAP) of varying alkyl chain lengths (Cn) on a pure natural s le of zircon (ZrSiO4) at 25 degreesC has been studied as a function of concentration and pH. Electrokinetic (zeta-potential) studies showed a significant shift of the isoelectric point of zircon (pH approximately 5.7) to lower pH values, indicating specific interactions between zircon and MAP. Diffuse reflectance infrared Fourier transform spectroscopy and pH increment studies suggested that adsorption of MAP onto zircon proceeded via chelate formation. Adsorption was aided by an attractive lateral alkyl chain interaction energy (phi) of approximately -0.85kT per CH2 group, which suggested that surface aggregates form on the zircon surface. Adsorption isotherms were best described by a Langmuir model, indicating that attractive lateral alkyl chain interactions were compensated by repulsive headgroup interactions, resulting in a pseudo-ideal system. Copyright 1998 Academic Press.
Publisher: Elsevier BV
Date: 1990
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2007
Publisher: Elsevier BV
Date: 10-1987
Publisher: American Chemical Society (ACS)
Date: 19-04-2008
DOI: 10.1021/JP7100732
Publisher: Elsevier BV
Date: 02-2002
DOI: 10.1016/S0001-8686(00)00083-X
Abstract: Single bubble experiments performed with different size fractions of quartz particles and different, but known, contact angles revealed two modes of flotation dynamics in superclean water. (1.) A monotonic increase of collection efficiency Ecoll with increasing particle size was observed at high particle hydrophobicity and, correspondingly, a low wetting film stability (WFS). (2.) At low particle hydrophobicity and, correspondingly, high WFS, an extreme dependence of Ecoll on particle size was observed. The use of superclean water in our experiments prevented the retardation of bubble surface movement caused by surfactants or other impurities that is usual for other investigations and where particle-bubble inertial hydrodynamic interactions are suppressed. In the present study the free movement of the bubble surface enhances particle-bubble inertial interaction, creating conditions for different flotation modes, dependent on WFS. At the instant of inertial impact, a particle deforms the bubble surface, which may cause its rebound. Where the stability of the thin water film, formed between opposing surfaces of a bubble and a particle, is low, its rupture is accompanied with three phase contact line extension and contact angle formation before rebound. This prevents rebound, i.e. the first collision is accompanied by attachment. A high WFS prevents rupture during an impact. As a result, a contact angle does not arise and rebound is not prevented. However, rebound is accompanied by a second collision, the kinetic energy of which is smaller and can cause attachment at repetitive collision. These qualitative considerations are confirmed by the model quantification and comparison with measured Ecoll. For the first time the Sutherland equation (SE) for Ecoll is confirmed by experiment for smaller particle sizes and, correspondingly, very small Stokes numbers. The larger the particle size, the larger is the measured deviation from the SE. The SE is generalized, accounting for the centrifugal force, pressing hydrodynamic force and drainage in the low WFS case and, correspondingly, attachment occurs at first collision or during sliding. The derived generalized Sutherland equation (GSE) describes experimental data at low WFS. However, its application without account for possible rebound does not explain the measured extreme dependence in the case of high WFS. The theory for drainage during particle impact and the beginning of rebound enables conditions for either attachment or rebound in terms of the normal component of the impact velocity and the critical film thickness to be derived. Combining this condition with the GSE allowed the equation for Ecoll to be derived, accounting for attachment area shrinkage and attachment during a repetitive collision. This equation predicts the extreme dependence. Thus the WFS determines the modes of flotation dynamics and, in turn, probably affects the mechanisms, which control the flotation domain. At low WFS its upper boundary is controlled by the stability of the particle-bubble aggregate. At high WFS the upper boundary can be controlled by rebound because the latter reduces the attachment efficiency by a factor of 30 or more even with repetitive collision.
Publisher: Informa UK Limited
Date: 03-07-2017
Publisher: Elsevier BV
Date: 2006
Publisher: Elsevier BV
Date: 04-1995
Publisher: Elsevier BV
Date: 03-2006
Publisher: Elsevier BV
Date: 07-1999
Publisher: American Chemical Society (ACS)
Date: 25-01-2012
DOI: 10.1021/JP210870V
Publisher: American Chemical Society (ACS)
Date: 21-05-2009
DOI: 10.1021/JP901719D
Publisher: Elsevier BV
Date: 12-2019
DOI: 10.1016/J.JCIS.2019.08.110
Abstract: One of the major challenges in applying CO The tunability of switching pH for this group of surfactants was demonstrated by in situ probing of the CO The switching pH of the CO
Publisher: American Chemical Society (ACS)
Date: 08-01-2003
DOI: 10.1021/JP0216326
Publisher: Elsevier BV
Date: 05-2009
Publisher: SAGE Publications
Date: 17-06-2021
Abstract: The conditions for studentification are changing with increasing numbers of students living in high-rise – and high-quality – micro-apartment-style accommodation provided through purpose-built student accommodation (PBSA) blocks. This ‘verticalisation’ of studentification is a global phenomenon, with Australia representing a frontier with distinctive geographies that result from its rapid ascension to the second-ranked global destination for international students. Yet, despite rising student numbers being recognised as positively impacting national and state economies, little is understood of how student accommodation development fits within the broader scheme of Australian urban revitalisation. To address this, we combine concepts relating to condo-ism and condo-isation to offer an original analytical framework that examines how PBSA has created new conditions through which vertical studentification can be produced in and of cities. We therefore ask how vertical studentification relates to wider Australian housing and urban development trends in ways that differentiate PBSA development and trajectories from other forms of accommodation. We also question how vertical studentification relates to the realities and regulation expressed as intra-urban geographies of Australian university cities and their resident-host communities. We argue that deliberately recognising and dovetailing several self-reinforcing and contradicting urban development dimensions invites a foundation for further interrogating vertical studentification in existing and emerging sites in Australia and beyond.
Publisher: American Chemical Society (ACS)
Date: 03-03-2009
DOI: 10.1021/LA803838K
Abstract: The adsorption of a modified polyacrylamide on gold surfaces coated with varying proportions of -CH3- and -OH-terminated alkanethiols (producing substrates of varying hydrophobicity: thetac=75, 98, and 119 degrees), was investigated using quartz crystal microbalance with dissipation (QCM-D), tapping-mode atomic force microscopy (TM-AFM), and captive bubble contact angle measurements. The QCM-D data for the polymer adsorbing on the different substrates indicates that the polymer adsorbs faster and to a greater extent on surfaces with higher hydrophobicity. Dissipation data from the QCM-D suggests that the adsorbed polymer undergoes a conformational change when adsorbing onto the substrates of higher hydrophobicity, forming a less rigid extended layer as the adsorption progresses toward the maximum adsorbed amount. AFM imaging of the adsorbed layer illustrates that the polymer layer is incomplete on all three substrates, and that the underlying substrate hydrophobicity has a role in determining the morphology (distribution, coverage, and thickness) of the adsorbed layer. Contact angle measurements of the polymer-coated substrates show variation in the ability of the polymer to reduce the hydrophobicity of the substrates. The role of coverage and distribution of adsorbed polymer on the surface hydrophobicity reduction is discussed.
Publisher: American Chemical Society (ACS)
Date: 29-11-2011
DOI: 10.1021/JP209140A
Publisher: American Chemical Society (ACS)
Date: 20-09-2010
DOI: 10.1021/LA101695W
Abstract: The adsorption of carboxymethyl cellulose (CMC) onto a hydrophobic self-assembled monolayer has been characterized using the quartz crystal microbalance (with dissipation monitoring, QCM-D). Adsorption was studied as a function of initial solution conditions. CMC adsorbs to a greater extent at high ionic strength (10(-1) M KCl as opposed to 10(-2) M KCl) or low pH (3 as opposed to 9). The solution conditions that yielded the lowest initial adsorbed amount (10(-2) M KCl, pH 9) were used as a reference to investigate the response of the adsorbed layer to a switch in solution conditions after adsorption (i.e., to higher ionic strength (10(-1) M KCl) or lower pH (pH 3)). The adsorbed layer released significant amounts of hydration water after each solution switch, as determined by the QCM-D measurements. This expulsion of hydration water was fully reversible. For the two solution switches, reducing the solution pH resulted in a more pronounced change in the amount of hydration water within the adsorbed CMC, accompanied by a distinct conformational change, as determined from a QCM D-f plot. In addition to studying adsorption using QCM-D, the effect of adsorbed CMC on surface hydrophobicity has been investigated using captive bubble contact angle measurements. The effect of the polymer on the contact angle of the surface was seen to be greatest when adsorbed at low pH or at higher ionic strength. CMC was also seen to have a significantly enhanced ability to reduce the surface hydrophobicity after both the ionic strength and pH switches, lowering the advancing water contact angle by 6 and 23° and the receding water contact angle by 10 and 40° for the ionic strength and pH switches, respectively. As with the change in hydration water content, the change in the contact angle of the polymer-coated surface following the solution switches was reversible.
Publisher: American Chemical Society (ACS)
Date: 12-07-2011
DOI: 10.1021/JP203714A
Publisher: Elsevier BV
Date: 10-1985
Publisher: Elsevier BV
Date: 05-1996
Publisher: Elsevier BV
Date: 07-2008
DOI: 10.1016/J.JCIS.2008.04.038
Abstract: Although surfactants and particles are often mixed together in emulsions, the contribution of each species to the stabilisation of the oil-water interface is poorly understood. We report the results of investigations into the formation of emulsions from solutions of surfactant in oil and aqueous suspensions of laponite. Depending on the salt concentration in the aqueous suspensions, the laponite dispersed as in idual disc-shaped particles, 30 nm in diameter, or flocculated into aggregates tens of micrometres in diameter. At the concentrations studied, the flocculated particles alone stabilized oil-in-water emulsions. Synergistic interactions between the particles and octadecylamine at the oil-water interface reduced the average emulsion drop size, while antagonistic interactions with octadecanoic acid enhanced coalescence processes in the emulsions. The state of particle dispersion had dramatic effects on the emulsions formed. Measurements of the oil-water interfacial tension revealed the origins of the interactions between the surfactants and particles.
Publisher: Elsevier BV
Date: 11-1994
Publisher: Elsevier BV
Date: 07-1997
Publisher: Wiley
Date: 25-07-2023
Abstract: Representations of love appear across many disciplines and discursive fields that are and should be in conversation with geography. It is imperative that geographers engage in formidable but worthy tasks to distil erse renderings of love into the regenerative interventions we urgently need. Those interventions require geographically minded interpretations of love to drive radical research, pedagogies, policies, and practices in ways that have direct and indirect effects across the life course and life worlds. Such labours are mediated by state and law, by intersectional relations, or by neuroscience, and involve asking how love underwrites critical infrastructures—of place (making), care and entanglements, colonialism, and human‐nature relations in the Anthropocene and posthuman—that lead to the flourishing futures we seek. Rich geographical studies oriented to those tasks still face charges of flattening difference. This commentary picks up one aspect of this agenda: a blind spot in geographical research relating to the ethical imperative to love based on benevolence. Instead, I ch ion the revolutionary possibilities for geography to inform policies, pedagogies, and practices by using a love based on alterity aligned with social weight, reasserting accessible science as an effective driver of social and system transformative changes. Specifically, I argue for a regenerative socio‐political analytic of love in a time of disaster, decolonisation, and diffraction.
Publisher: Elsevier BV
Date: 06-1993
Publisher: American Chemical Society (ACS)
Date: 11-03-2003
DOI: 10.1021/JP021751L
Publisher: Elsevier BV
Date: 1996
Publisher: American Chemical Society (ACS)
Date: 09-02-2006
DOI: 10.1021/JA057606D
Abstract: We have successfully demonstrated that imidazolium- and pyrrolidinium-based commercial room-temperature ionic liquids can electrowet (with a dc voltage) a smooth fluoropolymer (Teflon AF1600) surface. Qualitatively, the process is analogous to the electrowetting of aqueous electrolyte solutions: the contact angle versus voltage curve has a parabolic shape which saturates at larger voltages (positive or negative). On the other hand we observed several peculiarities: (i) the efficiency is significantly lower (by about an order of magnitude) (ii) the influence of the bulky cation is larger and the importance of the smaller anion is lesser, especially with respect to electrowetting saturation (iii) there is an asymmetry in the saturation contact angles found for positive and negative voltages. The asymmetry may be correlated with the cation-anion asymmetry of the ionic liquids. The low efficiency may be caused by the presence of water and other impurities in these commercial materials.
Publisher: Wiley
Date: 23-07-2023
DOI: 10.1111/JEP.13901
Publisher: Elsevier BV
Date: 1993
Publisher: Elsevier BV
Date: 2003
Publisher: Proceedings of the National Academy of Sciences
Date: 05-12-2006
Abstract: The knowledge of the microscopic structure of water at interfaces is essential for the understanding of interfacial phenomena in numerous natural and technological environments. To study deeply buried liquid water–solid interfaces, high-energy x-ray reflectivity measurements have been performed. Silicon wafers, functionalized by a self-assembled monolayer of octadecyl-trichlorosilane, provide strongly hydrophobic substrates. We show interfacial density profiles with angstrom resolution near the solid–liquid interface of water in contact with an octadecyl-trichlorosilane layer. The experimental data provide clear evidence for the existence of a hydrophobic gap on the molecular scale with an integrated density deficit ρ d = 1.1 Å g cm −3 at the solid–water interface. In addition, measurements on the influence of gases (Ar, Xe, Kr, N 2 , O 2 , CO, and CO 2 ) and HCl, dissolved in the water, have been performed. No effect on the hydrophobic water gap was found.
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C2SC21321D
Publisher: Elsevier BV
Date: 11-2006
DOI: 10.1016/J.JCIS.2006.07.078
Abstract: Patterned self-assembled monolayers of functionalised alkane thiols were prepared on gold substrates, using UV-photolithography. Two alkane thiols, 11-mercaptoundecanoic acid (MUA) and a fluorinated decane thiol (FDT, CF3(CF2)7CH2CH2SH) were used to fabricate chemically structured surfaces which served as templates for zinc oxide (ZnO) crystallisation. When these patterns, containing high (MUA) and low (FDT) surface energy regions were exposed to a 10 mM zinc nitrate crystallising solution, nucleation occurred selectively on the low energy regions. After 90 min, hexagonal prisms had grown upright on these areas. The crystal growth is uniform with a crystal length of about 1 mum and a diameter between 50 and 100 nm. We attribute the selective growth to a combination of crystallographic frustration of the zinc ions on the high energy regions and an accumulation of hydroxide ions on the low energy regions.
Publisher: Elsevier BV
Date: 09-2011
DOI: 10.1016/J.JCIS.2011.05.046
Abstract: This work reports on coalescence in oil-in-water Pickering emulsions subjected to simple shear flow. The emulsions were stabilized by silanized fumed silica particles forming layers a few hundred nanometers thick around drops that are tens of micrometers in size. The drop size and particle concentration in the emulsions were fixed, while the salt concentration was varied to adjust the colloidal interactions between the drops and particles. At rest the oil drops do not coalesce. The susceptibility of the drops to orthokinetic coalescence was found to depend on the extent of particle flocculation in the attached particle layer. The evolution of the drop size with time and shear rate was consistent with phenomenological models used to describe the behavior of emulsions under shear.
Publisher: Elsevier BV
Date: 11-1999
Publisher: Elsevier BV
Date: 05-1988
Publisher: American Chemical Society (ACS)
Date: 26-06-2008
DOI: 10.1021/LA800490T
Abstract: Carboxymethyl cellulose (CMC), in solution and adsorbed on the surface of talc, has been studied with ATR FTIR spectroscopy as a function of the solution pH. The solution spectra enable the calculation of the extent of ionization of the polymer (due to protonation and deprotonation of the carboxyl group) at various pH values, yielding a value of 3.50 for the pK(app)(1/2) (pH at which half of all carboxyl groups are ionized) in a simple electrolyte solution and a value of 3.37 for the pK(app)(1/2) in solutions containing magnesium ions (3.33 x 10(-4) M). The spectra of the adsorbed layer reveal that CMC interacts with the talc surface through a chemical complexation mechanism, via the carboxyl groups substituted on the polymer backbone. The binding mechanism is active at all pH values down to pH 2 and up to pH 11. The adsorbed layer spectra reveal that protonation and deprotonation of the polymer are affected by adsorption, with an increase in the pK(app)(1/2) to a value of 4.80. Spectra of the adsorbed polymer were also acquired as a function of the adsorption time. Adsorption kinetic data reveal that the polymer most likely has two different interactions with the talc surface, with a stronger interaction with the talc edge through chemical complexation and a weaker interaction with the talc basal plane presumably through the hydrophobic interaction.
Publisher: Elsevier BV
Date: 10-1984
Publisher: Elsevier BV
Date: 06-2003
Publisher: Elsevier BV
Date: 06-1999
Publisher: Elsevier BV
Date: 06-1994
Publisher: Royal Society of Chemistry (RSC)
Date: 2000
DOI: 10.1039/B005505K
Publisher: American Chemical Society (ACS)
Date: 04-10-2008
DOI: 10.1021/LA801753T
Abstract: The classic description of the rate of capillary rise given by the Washburn equation, which assumes that the contact angle preserves the equilibrium value at all times, has been recently questioned in the light of the known experimental dependence of the dynamic contact angle on the velocity of the contact line. For a number of such proposed functions of velocity for the dynamic contact angle, we analyze the resulting dependences of the contact angle and of the time of rise, respectively, on the height of the capillary rise. By applying our results to the particular cases of a high-viscosity silicone oil and water, respectively, in a glass capillary, we show that, in general, strong similarities arise between the various approaches and the classic theory in what concerns the time dependence of the capillary rise, which explains the lack of consistent experimental evidence for deviations in the rate of capillary rise from the Washburn equation. However, for a strong dependency of the contact angle on the velocity in the range of small velocities, as in the case of water on glass, one of the models predicts significant deviations even for the time dependence of the capillary rise. Moreover, our results show that the time or height dependence of the contact angle during the capillary rise can clearly discriminate between the various models.
Publisher: Elsevier BV
Date: 08-2010
DOI: 10.1016/J.JCIS.2010.04.073
Abstract: The foamability of a triblock copolymer solution was strongly influenced by the presence of particles. The stability of the foam was evaluated by measuring the foam volume, the drainage of water and particles, and the bubble size as a function of time. The higher stability of foams produced with hydrophilic quartz particles, compared with hydrophobic graphite particles, was related to the presence of quartz aggregates in the lamellae and Plateau borders reducing water drainage, and therefore thin film rupture and bubble coalescence. The copolymer adsorbed slightly more on the hydrophobic graphite, causing the particles to disperse and drain, with the water out of the foam, whereas the hydrophilic quartz aggregated and remain in the lamellar and Plateau borders of the foam.
Publisher: SAGE Publications
Date: 07-2002
DOI: 10.1177/147309520200100203
Abstract: This article conceptualizes two interrelated constellations of effects produced by practices of power in New Zealand planning. These are symbolic violence and institutional victimization. This article contends that acts of submission and obedience become symbols of violence when the state’s planning regimes allow no elements of choice, or freedom to resist, for those acted upon. This is compounded further into institutional victimization when the oppressors are also the final practicable, or actual, arbiters of appeal. We provide evidence that suggests this is a regular occurrence in New Zealand and, further, is indicative of a wider ranging consequence of modern governance that Foucault called governmentality. In New Zealand, the provision of a theoretically consultative statutory planning process obscures the actual rationality of exclusion underlining many of its planning practices.
Publisher: Elsevier BV
Date: 05-1998
Publisher: Elsevier BV
Date: 05-1994
Publisher: Elsevier BV
Date: 08-2000
Publisher: Elsevier BV
Date: 09-2003
Publisher: Elsevier BV
Date: 04-1992
Publisher: Springer Science and Business Media LLC
Date: 1994
Publisher: American Chemical Society (ACS)
Date: 09-10-2019
Publisher: Elsevier BV
Date: 1991
Publisher: American Chemical Society (ACS)
Date: 30-12-2009
DOI: 10.1021/JP911104B
Publisher: Elsevier BV
Date: 11-2001
Publisher: Elsevier BV
Date: 06-1999
Publisher: Elsevier BV
Date: 12-1988
Publisher: Elsevier BV
Date: 05-2002
Publisher: Elsevier BV
Date: 06-2003
Publisher: American Chemical Society (ACS)
Date: 11-03-2005
DOI: 10.1021/JP040478F
Abstract: Electrowetting is the phenomenon of contact angle decrease under the influence of an external voltage applied across the solid/liquid interface. Electrowetting offers an interesting possibility to enhance the wettability of hydrophobic materials without altering the chemical composition of the system and thus could be incorporated in various microfluidic devices. Electrowetting is fundamentally an electrocapillary effect occurring on an insulated solid electrode (hence the change of the solid/liquid interfacial tension with voltage follows Lippmann's equation). A limiting contact angle value larger than zero is achieved even at very large external voltages. Saturation precludes full wetting of the substrate and restricts the magnitude of the capillary force variation. Contact angle saturation has been given various interpretations (e.g., charge trapping, air ionization) but appears to reflect a natural thermodynamic limit rather than being simply a defective property. The limiting value of the contact angle is given by the Young equation when the value of the solid/liquid interfacial tension reaches zero. The model is in excellent agreement with our own results and often gives an adequate description of published data. It also suggests that the saturation limit is determined by the material properties of the system and electrowetting at voltages exceeding this threshold is essentially a nonequilibrium process.
Publisher: Elsevier BV
Date: 1999
Publisher: IOP Publishing
Date: 04-1991
Publisher: Elsevier BV
Date: 05-2006
DOI: 10.1016/J.JCIS.2005.10.037
Abstract: The adsorption of a low molecular weight unmodified polyacrylamide (Polymer-N) and a hydroxyl-substituted polyacrylamide (Polymer-H) onto talc was studied using in situ particle film ATR-FTIR spectroscopy in the multiple internal reflection mode. Spectra of the adsorbed polymer were collected as a function of increasing concentration and as a function of time. Measurement of the peak intensities of the adsorbed polymer allowed adsorption isotherms and adsorption kinetics to be determined for both polymers. Langmuir adsorption isotherm analysis of in situ data yielded Gibbs free energies of adsorption (deltaG0(ads)) for Polymer-N and Polymer-H of -44.5 and -45.7 kJ/mol, respectively, which correlate well with similar values determined from ex situ adsorption isotherms. Kinetic analysis indicated that the adsorption of both polymers was a pseudo-first-order process. The apparent rate constants for Polymer-N and Polymer-H were 0.10 and 0.15 min(-1), respectively. Absence of spectral shifts in the spectra of adsorbed polymer is indicative of a hydrophobic interaction between the polyacrylamides and the talc surface.
Publisher: American Chemical Society (ACS)
Date: 10-05-2012
DOI: 10.1021/JP2120274
Publisher: Elsevier BV
Date: 09-2009
DOI: 10.1016/J.JCIS.2009.04.086
Abstract: The distribution and movement of fluids in porous media are important in a variety of situations arising naturally and industrially (e.g., water migration in soils, oil recovery, chromatography, filtration and separation processes). Our specific interest is in deriving advancing and receding contact angles from capillary pressure measurements in packed beds of particles partially saturated with liquids. The simplest model of a porous medium treats the porous body as an equivalent uniform capillary giving rise to the same capillary pressure. Pressure measurements were performed successfully with advancing as well as receding liquids. For an advancing liquid front a measurement with a second liquid is needed to calibrate the equivalent capillary radius and obtain the advancing contact angle. For a receding liquid front--an additional determination of the amount of liquid trapped behind in smaller pores is required. The equivalent capillary radius is mainly determined by the porosity of the packed bed and is easily corrected to account for capillary retention. Only then can the receding contact angle be obtained reliably. This new methodology for contact angle measurement was validated with model systems and applied successfully to various real particulate systems.
Publisher: Springer Science and Business Media LLC
Date: 04-2005
Publisher: SPIE
Date: 21-12-2011
DOI: 10.1117/12.903293
Publisher: Elsevier BV
Date: 12-2004
Publisher: Elsevier BV
Date: 12-1993
Publisher: Elsevier BV
Date: 09-2002
Publisher: Elsevier BV
Date: 02-2005
Publisher: Elsevier BV
Date: 08-2014
Publisher: Elsevier BV
Date: 1998
Abstract: The collection efficiency of single bubbles rising through a very dilute pulp of hydrophobized quartz particles has been determined. Measurements have been performed under conditions in which the bubble surface is mobile, as a function of electrolyte concentration, particle diameter (7 to 70 &mgr m), bubble diameter (0.77 x 10(-3) to 1.52 x 10(-3) m), and particle advancing water contact angle. Situations in which the product of attachment and stability efficiency is at its maximum value have been identified, permitting a stringent, critical test of collision theory to be performed. A collision theory has been developed which accounts for the influence of positive and negative inertial forces in the case of bubbles with mobile surfaces. The approach considers only long-range hydrodynamic interactions under conditions where short-range interactions are strongly suppressed (i.e., high particle contact angle and high electrolyte concentrations) and attachment occurs at first collision. In this instance, good agreement between theory and experiment is achieved for particle diameters between 7 and 60 &mgr m and Stokes numbers up to 0.27. The analytical equation developed is termed the generalized Sutherland equation (GSE). Copyright 1998 Academic Press. Copyright 1998Academic Press
Publisher: Elsevier BV
Date: 11-2012
DOI: 10.1016/J.CIS.2012.06.008
Abstract: A model of collision and collection of Brownian submicron particles based on the creation of a convective-diffusion layer near a bubble surface and overcoming the energy barrier created by particle/bubble interaction is developed. Simple analytical expressions describing the rate of collision and collection efficiency are obtained. The collision and collection minimums and the limits of theory applicability are analysed.
Publisher: Elsevier BV
Date: 06-1996
Publisher: American Chemical Society (ACS)
Date: 09-09-2008
DOI: 10.1021/JP8067969
Publisher: Elsevier BV
Date: 09-1993
Publisher: Elsevier BV
Date: 09-2003
DOI: 10.1016/S0021-9797(03)00345-X
Abstract: An analytical model that enables the calculation of the flotation rate constant of particles as a function of particle size with, as input parameters, measurable particle, bubble, and hydrodynamic quantities has been derived. This model includes the frequency of collisions between particles and bubbles as well as their efficiencies of collision, attachment, and stability. The generalized Sutherland equation collision model and the modified Dobby-Finch attachment model developed previously for potential flow conditions were used to calculate the efficiencies of particle-bubble collision and attachment, respectively. The bubble-particle stability efficiency model includes the various forces acting between the bubble and the attached particle, and we demonstrate that it depends mainly on the relative magnitude of particle contact angle and turbulent dissipation energy. The flotation rate constants calculated with these models produced the characteristic shape of the flotation rate constant versus particle size curve, with a maximum appearing at intermediate particle size. The low flotation rate constants of fine and coarse particles result from their low efficiency of collision and low efficiencies of attachment and stability with gas bubbles, respectively. The flotation rate constants calculated with these models were compared with the experimental flotation rate constants of methylated quartz particles with diameters between 8 and 80 micro m interacting with gas bubbles under turbulent conditions in a Rushton flotation cell. Agreement between theory and experiment is satisfactory.
Publisher: Elsevier BV
Date: 12-1995
Publisher: Elsevier BV
Date: 05-1994
Publisher: Elsevier BV
Date: 05-1994
Publisher: Elsevier BV
Date: 1992
Publisher: Elsevier BV
Date: 12-2023
Publisher: American Chemical Society (ACS)
Date: 13-05-1999
DOI: 10.1021/LA981525W
Publisher: American Chemical Society (ACS)
Date: 09-04-2005
DOI: 10.1021/LA047352U
Abstract: The adsorption of a polyacrylamide (MW 14600) and two polysaccharides (MW 9260 and 706 x 10(3)) onto model silica surfaces of different hydrophobicities was investigated. In all cases, adsorption adhered to the Freundlich isotherm, reflecting the heterogeneous character of the solid substrates. The latter strongly influenced the character of the adsorbed polymer, with morphologies from chainlike structures to thin films and patches being observed. Surface roughness, polymer type, and molecular weight also play roles in controlling adsorbed polymer morphology. Surface wettability is strongly influenced by the thickness of the adsorbed layer.
Publisher: Elsevier BV
Date: 12-2013
DOI: 10.1016/J.JCIS.2013.05.077
Abstract: The classic description of capillary rise given by the Washburn equation was recently questioned in the light of experimental evidence for a velocity dependent dynamic contact angle at a moving contact line. We present a systematic investigation of the capillary rise dynamics of glycerol and aqueous glycerol solutions in vertical glass capillaries of various radii. For pure glycerol, the results of our experiments are in almost perfect agreement with the predictions of the Washburn equation using independently measured values for the liquid and capillary parameters. For aqueous glycerol solutions we observe discrepancies between the theoretical expectations and the experimental results, which are increasing with the water content of the solution. A thorough analysis, combined with scaling arguments, allows us to conclude that dynamic contact angle effects alone cannot provide a consistent explanation for these discrepancies. Rather, they can be perfectly accounted for if the mixture flowing in the capillary would have an effective, increased viscosity (in respect to the nominal value). We suggest and briefly discuss various mechanisms that could contribute to this observed behavior.
Publisher: Elsevier BV
Date: 12-2022
Publisher: Walter de Gruyter GmbH
Date: 2005
Abstract: The atomic force microscope (AFM) is designed to provide high-resolution (in the ideal case, atomic) topographical analysis, applicable to both conducting and nonconducting surfaces. The basic imaging principle is very simple: a s le attached to a piezoelectric positioner is rastered beneath a sharp tip attached to a sensitive cantilever spring. Undulations in the surface lead to deflection of the spring, which is monitored optically. Usually, a feedback loop is employed, which holds the spring deflection constant, and the corresponding movement of the piezoelectric positioner thus generates the image. From this it can be seen that the scanning AFM has all the attributes necessary for the determination of surface and adhesion forces a sensitive spring to determine the force , a piezoelectric crystal to alter the separation of the tip and surface, which if sufficiently well-calibrated also allows the relative separation of the tip and surface to be calculated. One can routinely quantify both the net surface force (and its separation dependence) as the probe approaches the s le, and any adhesion (pull-off) force on retraction . Interactions in relevant or practical systems may be studied, and, in such cases, a distinct advantage of the AFM technique is that a particle of interest can be attached to the end of the cantilever and the interaction with a s le of choice can be studied, a method often referred to as colloid probe microscopy. The AFM, or, more correctly, the scanning probe microscope, can thus be used to measure surface and frictional forces, the two foci of this article. There have been a wealth of force and friction measurements performed between an AFM tip and a surface, and many of the calibration and analysis issues are identical to those necessary for colloid probe work. We emphasize that this article confines itself primarily to elements of colloid probe measurement using the AFM.
Publisher: Elsevier BV
Date: 2009
DOI: 10.1016/J.JCIS.2008.09.056
Abstract: We investigated the structure and stability of dodecane-in-water emulsions stabilised by partially hydrophobised silica particles after dilution of the emulsions in solutions of sodium dodecyl sulfate and sodium chloride. The emulsions were stable to coalescence on dilution in salt solutions, but did cream over time. The rate and extent of creaming gradually decreased as the salt concentration in the diluted emulsion increased. Dilution in low concentrations of the anionic surfactant did not affect the emulsion stability to coalescence or alter the creaming behaviour of the emulsion. At surfactant concentrations above the critical micelle concentration, however, the rate and extent of creaming and flocculation of the drops were enhanced.
Publisher: Springer Science and Business Media LLC
Date: 17-08-2011
Publisher: Elsevier BV
Date: 2012
Publisher: Elsevier BV
Date: 09-2003
Publisher: Elsevier BV
Date: 1991
Publisher: American Chemical Society (ACS)
Date: 17-05-2008
DOI: 10.1021/LA8003382
Abstract: The adsorption of three modified dextrins on the basal plane of talc has been studied using in situ tapping mode atomic force microscopy (TMAFM). The images have been used to determine the layer thickness and coverage of the adsorbed polymers. Adsorption isotherms of the polymers on talc particles were also determined using the depletion technique. Values of the adsorbed amount at equilibrium were compared with the volume of adsorbed material as determined using in situ TMAFM, revealing the presence of significant amounts of hydration water in the adsorbed layer structure. This deduction was confirmed by comparing in and ex situ TMAFM images of the adsorbed dextrins. The effect of layer thickness, coverage, and hydration water content on the contact angle of talc particles treated with polymer was investigated using the Washburn method and the equilibrium capillary pressure (ECP) method. Distinct correlations were observed between adsorbed layer properties and the measured contact angles, with the ECP measurements especially highlighting the effect of the adsorbed polymer layer hydration water. The implications for the performance of the modified dextrins in flotation are discussed.
Publisher: Elsevier BV
Date: 1988
Publisher: American Chemical Society (ACS)
Date: 15-02-2005
DOI: 10.1021/LA047721M
Abstract: The surface properties of silica and titania are mainly determined by the presence, density, and type of terminal hydroxyl groups (Si-OH "silanol" and Ti-OH "titanol"). Thermal treatment at elevated temperatures causes dehydroxylation on both surfaces, confirmed by streaming potential and ToF-SIMS measurements. The magnitude of the zeta potential markedly decreases after heat treatment, but the IEP is not affected. The intensity ratio MOH(+)/M(+) (M = Si or Ti), which reflects the surface density of OH groups, also decreases noticeably after high-temperature treatment. The mechanism is condensation of adjacent silanol/titanol groups into siloxane/titanoxane bonds. Ultraviolet light (lambda = 254 nm) has little effect on silica but rapidly induces hydrophilicity on titania surfaces. There is a strong correlation between the amount of hydrocarbons adsorbed on the surface and the density of titanol groups (thence the water contact angle). The effect of UV radiation can be entirely attributed to photolytic decomposition of organic contaminants. Dehydroxylated titania and silica (at 1050 degrees C) show very different wetting behavior: silica is moderately hydrophobic (water contact angle of about 40 degrees), while titania is hydrophilic (0 degrees). This dissimilarity can be explained with a simple model estimating the van der Waals and acid-base interfacial interactions.
Publisher: Elsevier BV
Date: 1986
Publisher: Elsevier BV
Date: 05-1991
Publisher: Elsevier BV
Date: 10-2011
DOI: 10.1016/J.CIS.2011.08.002
Abstract: The capture of solid particles suspended in aqueous solution by rising gas bubbles involves hydrodynamic and physicochemical processes that are central to colloid science. Of the collision, attachment and aggregate stability aspects to the bubble-particle interaction, the crucial attachment process is least understood. This is especially true of hydrophilic solids. We review the current literature regarding each component of the bubble-particle attachment process, from the free-rise of a small, clean single bubble, to the collision, film drainage and interactions which dominate the attachment rate. There is a particular focus on recent studies which employ single, very small bubbles as analysis probes, enabling the dynamic bubble-hydrophilic particle interaction to be investigated, avoiding complications which arise from fluid inertia, deformation of the liquid-vapour interface and the possibility of surfactant contamination.
Publisher: Royal Society of Chemistry (RSC)
Date: 1993
DOI: 10.1039/FT9938900817
Publisher: Elsevier
Date: 1995
Publisher: Elsevier BV
Date: 07-1996
Publisher: Elsevier BV
Date: 12-1996
Abstract: The wettability of ethyl xanthate coated galena particles has been determined from measurements of the equilibrium capillary pressure across a packed bed. Both the advancing liquid powder contact angle, thetap, and the specific wettable surface area, Awet, of galena particles have been obtained. The influence of particle size and ethyl xanthate surface coverage on the powder contact angle have been investigated and compared with floatability. Ethyl xanthate at a surface coverage of less than ten percent of an equivalent monolayer significantly increases both thetap and particle floatability.
Publisher: American Chemical Society (ACS)
Date: 17-05-2011
DOI: 10.1021/JP200387W
Publisher: Elsevier BV
Date: 1995
Publisher: Elsevier BV
Date: 06-1995
Publisher: Royal Society of Chemistry (RSC)
Date: 2011
DOI: 10.1039/C0CP02035D
Abstract: The spontaneous spreading of ionic liquids on a fluoropolymer surface (Teflon AF1600) in air is investigated by high-speed video microscopy. Six ionic liquids (EMIM BF(4), BMIM BF(4), OMIM BF(4), EMIM NTf(2), BMIM NTf(2) and HMIM NTf(2)) are used as probe liquids. The dependence of the dynamic contact angle on contact line velocity is interpreted with a hydrodynamic model and a molecular-kinetic model. The usefulness of the hydrodynamic model is rather limited. There is a good correspondence between the molecular dimensions of the liquids and the physical parameters of the molecular-kinetic model. The viscous and molecular-kinetic contributions to energy dissipation are calculated, revealing that energy is dissipated in the bulk as well as at the contact line during dynamic wetting. There are wide ramifications of these results in areas ranging from lubrication and biology to minerals processing and petroleum recovery.
Publisher: Elsevier BV
Date: 04-1999
Publisher: Elsevier BV
Date: 2019
Publisher: Elsevier BV
Date: 08-1994
Publisher: Elsevier BV
Date: 12-1993
Publisher: Elsevier BV
Date: 07-2002
Publisher: Elsevier BV
Date: 11-1995
Publisher: American Chemical Society (ACS)
Date: 15-01-2010
DOI: 10.1021/JP9099754
Publisher: Wiley
Date: 11-12-2020
DOI: 10.1111/INFA.12360
Publisher: Emerald
Date: 03-08-2021
DOI: 10.1108/JPPEL-02-2021-0015
Abstract: Humanity has a weakness in how we approach the “challenge” of using outer space. This paper aims to show how the global and national frameworks that address our planetary activities and crises are inadequate for the opportunities and challenges of life in outer space. The authors draw on multidisciplinary perspectives to refine an organising governance framework that better showcases the challenges and pathways needed for living and thriving in space-age. The authors prioritise two key pillars and overview the practical and social implications that space-age humanity must address. Social sciences and humanities are vital to problematising post-war colonial legacies of governance by distinguishing the unique and overlooked challenges for thriving and working offworld and identifying progressive research agendas. The highlighted agenda has implications for collaborative research institutes and project design. As the vital basis for continuous learning, university-based research institutes span bodies of knowledge, experience, convention and imagination that can support vibrant and overdue debate on good governance that is out of this world. This expansive approach has practical implications for the decision-making processes and subjects of spacescape, from reconciling the space commons with prospecting and human occupation to potential governance regimes that capitalise on the zeal for moving beyond merely “existing” off-world. Examining the governance deficit as we pursue developing spacescape frontiers is an enriching (not reductionist) agenda that deliberately troubles the existing and emerging regime for governing our scientific and imagined off-world society. This framework appeals to humanity’s highest evolution in co-producing a fair and flourishing off-world governance framework (beyond replicating planetary regimes).
Publisher: Royal Society of Chemistry (RSC)
Date: 1995
DOI: 10.1039/FT9959101997
Publisher: Elsevier BV
Date: 04-2008
DOI: 10.1016/J.JCIS.2008.01.042
Abstract: Time-of-flight secondary ion mass spectrometry (ToF-SIMS) has been examined as a possible predictive tool for surface wettability. Heterogeneous surfaces were prepared with hydrophilic and hydrophobic regions of known surface coverage using self-assembled monolayers. The surface coverage of each component was then correlated with ToF-SIMS fragmentation of the hydrophobic and hydrophilic surface groups and static contact angle measurements. From these measurements, a clear relationship between the surface wettability and relative intensity of characteristic secondary ions was identified. Moreover, our results for planar surfaces can be extrapolated to predict the wettability of particulate s les for which direct contact angle measurements are not straightforward. The ability to infer particle wettability by ToF-SIMS is well suited to mineral characterization and in particular, the prediction of mineral flotation efficiencies.
Publisher: Elsevier BV
Date: 2005
Publisher: Informa UK Limited
Date: 03-1987
Publisher: Elsevier BV
Date: 08-1999
Publisher: Informa UK Limited
Date: 11-06-2021
Publisher: American Chemical Society (ACS)
Date: 11-05-2011
DOI: 10.1021/NL200801N
Abstract: Biocompatibility is of paramount importance for drug delivery, tumor labeling, and in vivo application of nanoscale bioprobes. Until now, biocompatible surface processing has typically relied on PEGylation and other surface coatings, which, however, cannot minimize clearance by macrophages or the renal system but may also increase the risk of chemical side effects. Cell membranes provide a generic and far more natural approach to the challenges of encapsulation and delivery in vivo. Here we harness for the first time living cells as "factories" to manufacture cell membrane capsules for encapsulation and delivery of drugs, nanoparticles, and other biolabels. Furthermore, we demonstrate that the built-in protein channels of the new capsules can be utilized for controlled release of encapsulated reagents.
Publisher: Informa UK Limited
Date: 06-2004
Publisher: Elsevier BV
Date: 08-2005
Publisher: Elsevier BV
Date: 06-2008
DOI: 10.1016/J.JCIS.2008.02.072
Abstract: Single bubbles of very pure N2, He, air and CO2 were formed in a quiescent environment in ultra-clean water, with diameters ranging from 10 to 100 mum. Their terminal rise velocities were measured by high-speed video microscopy. For N2, He and air, excellent agreement with the Hadamard-Rybczynski (H-R) equation was observed, indicating that slip was occurring at the liquid-vapor interface. For CO2 bubbles with diameters less than 60 microm, the terminal rise velocities exceeded those predicted by the H-R equation. This effect was ascribed to the enhanced solubility of CO2 compared with the other gases examined. The presence of a diffusion boundary layer may be responsible for the increased terminal velocity of very small CO2 bubbles.
Publisher: Annual Reviews
Date: 08-2008
DOI: 10.1146/ANNUREV.MATSCI.38.060407.130231
Abstract: This review critically examines the experimental aspects of dynamic wetting, considering extant data for different geometries. Both partial wetting and complete wetting are considered for cases that include droplets, fibers, tubes, and plates. The wetting of porous materials is also considered, along with the new field of micro- and nanofluidics.
Publisher: Informa UK Limited
Date: 17-05-2012
Publisher: Elsevier BV
Date: 04-2020
Publisher: Elsevier BV
Date: 2001
Publisher: Elsevier BV
Date: 05-2006
Publisher: Elsevier BV
Date: 05-1988
Publisher: Springer Berlin Heidelberg
Date: 2006
DOI: 10.1007/10991459_45
Publisher: Springer Berlin Heidelberg
Date: 2006
DOI: 10.1007/10991459_46
Publisher: Elsevier BV
Date: 10-1999
Publisher: Elsevier BV
Date: 09-2001
Publisher: Elsevier BV
Date: 12-1994
Publisher: Elsevier BV
Date: 06-1995
Publisher: Elsevier BV
Date: 05-2006
Publisher: American Chemical Society (ACS)
Date: 03-05-2013
DOI: 10.1021/JA3104846
Abstract: The motion of a solid-liquid-liquid contact line over nanorough surfaces is investigated. The surface nanodefects are varied in size, density, and shape. The dynamics of the three-phase contact line on all nanorough substrates studied is thermally activated. However, unlike the motion of a liquid-vapor interface over smooth surfaces, this thermally activated process is not adequately described by the molecular kinetic theory. The molecular parameters extracted from the experiments suggest that on the nanorough surfaces, the motion of the contact line is unlikely to simply consist of molecular adsorption-desorption steps. Thermally activated pinning-depinning events on the surface nanodefects are also important. We investigate the effect of surface nanotopography on the relative importance of these two mechanisms in governing contact line motion. Using a derivation for the hysteresis energy based on Joanny and de Gennes's model, we evaluate the effect of nanotopographical features on the wetting activation free energy and contact line friction. Our results suggest that both solid-liquid interactions and surface pinning strength contribute to the energy barriers hindering the three-phase contact line motion. For relatively low nanodefect densities, the activation free energy of wetting can be expressed as a sum of surface wettability and surface topography contributions, thus providing a direct link between contact line dynamics and roughness parameters.
Publisher: Faculty of Geoengineering, Mining and Geology, Wrocław University of Technology, Wrocław
Date: 2018
DOI: 10.5277/PPMP1838
Publisher: Elsevier BV
Date: 10-2004
Publisher: American Chemical Society (ACS)
Date: 03-2007
DOI: 10.1021/LA062920M
Abstract: Large-scale molecular dynamics simulations are used to model the dewetting of solid surfaces by partially wetting thin liquid films. Two levels of solid-liquid interaction are considered that give rise to large equilibrium contact angles. The initial length and thickness of the films are varied over a wide range at the nanoscale. Spontaneous dewetting is initiated by removing a band of molecules either from each end of the film or from its center. As observed experimentally and in previous simulations, the films recede at an initially constant speed, creating a growing rim of liquid with a constant receding dynamic contact angle. Consistent with the current understanding of wetting dynamics, film recession is faster on the more poorly wetted surface to an extent that cannot be explained solely by the increase in the surface tension driving force. In addition, the rates of recession of the thinnest films are found to increase with decreasing film thickness. These new results imply not only that the mobility of the liquid molecules adjacent to the solid increases with decreasing solid-liquid interactions, but also that the mobility adjacent to the free surface of the film is higher than in the bulk, so that the effective viscosity of the film decreases with thickness.
Publisher: American Chemical Society (ACS)
Date: 27-10-2009
DOI: 10.1021/LA903145H
Abstract: The influence of adsorbed dextrin-based polymers on the attachment of a rising air bubble to a talc surface has been investigated. Liquid film rupture and dynamic contact angle studies have highlighted the major role that adsorbed polymers can play in bubble-particle attachment. No direct link was established between the equilibrium contact angle of polymer-treated talc surfaces and talc flotation recovery. However, clear correlations were observed between the flotation recovery of polymer-treated talc and the measured wetting film rupture time and rate of dewetting for a bubble attaching to a talc basal plane surface treated with the polymers. The retardation of the three-phase contact line expansion caused by the adsorbed polymers was found to have the largest influence on the bubble-particle attachment. The effect of the morphology (coverage, distribution, and shape) of the adsorbed layer on the wetting film rupture and the motion of the receding water front is discussed.
Publisher: American Chemical Society (ACS)
Date: 25-10-2008
DOI: 10.1021/LA802264D
Abstract: The velocity dependence of the dynamic contact angle for a glycerol-water mixture wetting two different chemically heterogeneous surfaces (mixed thiols on gold and partially methylated titania, 16 s les in all) was studied. The molecular kinetic theory (MKT) of wetting was used to interpret the dynamic contact angle data. The equilibrium displacement frequency ( K 0) was predominantly determined by the viscous contribution from the bulk liquid, with a minor contribution from the surface. The mean distance between surface sites (lambda) decreased with increasing work of adhesion. The contact line friction coefficient zeta 0 was found to vary exponentially with the work of adhesion, enabling the unit flow volume of the liquid to be obtained.
Publisher: Elsevier BV
Date: 10-2007
Publisher: Elsevier BV
Date: 12-1990
Publisher: Elsevier BV
Date: 12-2006
Publisher: Royal Society of Chemistry (RSC)
Date: 2010
DOI: 10.1039/C0CP00683A
Abstract: The structure of the liquid-vacuum interface in room temperature ionic liquids (ILs) is investigated using angle-resolved X-ray photoelectron spectroscopy (ARXPS) and synchrotron X-ray photoelectron spectroscopy (SXPS). By varying the polar angle and comparing the results for the chosen ionic liquids, we identify the presence of a surface layer that is chemically different to the bulk. In particular, this layer: (i) is enriched by aliphatic carbon atoms from the saturated carbon chains of the anions and cations, and (ii) contains an unequal distribution of cations and anions in a direction normal to the surface. This unequal distribution creates a potential gradient which extends from the surface into the liquid. We show unequivocally that this layer is not due to the presence of impurities.
Publisher: Royal Society of Chemistry (RSC)
Date: 2010
DOI: 10.1039/C001222J
Abstract: We report on the influence of heat treatment on the surface chemistry of an α-alumina crystal. We compare its electrical double layer behaviour with that of 150 nm diameter α-Al(2)O(3) particles. Surface spectroscopy and zeta potential studies are used to understand the changes in surface chemistry. The pH(pzc) of an α-Al(2)O(3) (0001) single crystal (∼4) is more acidic than that of α-Al(2)O(3) particles (8.5), a difference explained by the dominance of [triple bond, length as m-dash]Al(2)OH surface groups on the single crystals and their charging behaviour. Heat treatment of the alumina surface causes a substantial decrease in the number of surface OH groups. Heating at 500 °C decreases the surface density of hydroxyl groups. Heating at 1050 °C also affects surface morphology and surface chemistry. The increased magnitude of the zeta potential and the pH(pzc) shift to lower pH suggest a surface reconstruction and the appearance of more acidic aluminium sites.
Publisher: Elsevier BV
Date: 09-2005
Publisher: Elsevier BV
Date: 09-1999
Publisher: Elsevier BV
Date: 05-1994
Publisher: Springer Science and Business Media LLC
Date: 03-10-2012
Publisher: Elsevier BV
Date: 05-2010
DOI: 10.1016/J.JCIS.2010.01.075
Abstract: The adsorption of three dextrin-based polymers, regular wheat dextrin (Dextrin TY), phenyl succinate dextrin (PS Dextrin), and styrene oxide dextrin (SO Dextrin) on a model hydrophobic surface, consisting of a mixed alkanethiol layer on gold, has been characterized using the quartz crystal microbalance with dissipation monitoring (QCM-D). The three polymers exhibited varying affinities and capacity for adsorption on the hydrophobic substrate. Atomic force microscope (AFM) imaging of the polymer layers indicates that all three polymers fully cover the surface. The effect of the three polymers on the static contact angle of the surface was studied using captive bubble contact angle measurements. The three polymers were seen to reduce the receding contact angle by similar amounts (approximately 14°) in spite of having varying adsorbed amounts and differences in adsorbed layer water content. Although no differences were observed in the ability of the polymers to reduce the static contact angle, measurements of the dynamic contact angle between a rising air bubble and the polymer covered substrate yielded stark differences between the polymers, with one polymer (SO Dextrin) slowing the dewetting by an order of magnitude more than the other two polymers. The differences in dewetting behavior correlate with the adsorbed layer characteristics determined by QCM-D and AFM. The role of the dynamic and static contact angle in the performance of a polymer as depressant is discussed.
Publisher: Elsevier BV
Date: 05-2003
Publisher: Royal Society of Chemistry (RSC)
Date: 2010
DOI: 10.1039/C0CP00170H
Abstract: The differential capacitance of the electrical double layer at glassy carbon, platinum and gold electrodes immersed in various ionic liquids was measured using impedance spectroscopy. We discuss the influence of temperature, the composition of the ionic liquids and the electrode material on the differential capacitance otential curves. For different systems these curves have various overall shapes, but all include several extremes and a common minimum near the open circuit potential. We attribute this minimum to the potential of zero charge (PZC). Significantly, the differential capacitance generally decreases if the applied potential is large and moving away from the PZC. This is attributed to lattice saturation [A. A. Kornyshev, J. Phys. Chem. B, 2007, 111, 5545] effects which result in a thicker double layer. The differential capacitance of the double layer grows and specific adsorption diminishes with increasing temperature. Specific adsorption of both cations and anions influences the shapes of curves close to the PZC. The general shape of differential capacitance otential does not depend strongly on the identity of the electrode material.
Publisher: Royal Society of Chemistry (RSC)
Date: 2007
DOI: 10.1039/B709624K
Abstract: The kinetics of adsorption of CO(2) molecules dissolved in aqueous solution onto a hydrophobised silica surface were investigated using a quartz crystal microbalance (QCM). The results of this investigation were compared with those obtained earlier from tapping mode atomic force microscopy (TMAFM) under the same experimental conditions (J. Yang, J. Duan, D. Fornasiero, J. Ralston, J. Phys. Chem. B., 2003, 107(25), 6139-6147 ref. 1). The QCM results represent the early stage of CO(2) gas adsorption (<20 min), before CO(2) gas bubbles adsorbed on the surface can be directly observed by TMAFM. The QCM results confirmed our observation from TMAFM imaging: that CO(2) gas molecules present in solution only adsorb on silica when its surface is hydrophobic. More importantly, the results showed that gas adsorption/bubble growth undergoes two consecutive kinetic processes: a slow and a fast adsorption process.
Publisher: Elsevier BV
Date: 05-1992
Publisher: Elsevier BV
Date: 11-2002
Publisher: Informa UK Limited
Date: 30-10-2023
Publisher: Informa UK Limited
Date: 1993
Publisher: Elsevier BV
Date: 08-1986
Publisher: Informa UK Limited
Date: 2004
Publisher: American Chemical Society (ACS)
Date: 10-03-2009
DOI: 10.1021/LA804246A
Abstract: The wetting behavior of hydrophobic, microstructured surfaces containing arrays of pillars or holes has been investigated. The size of the surface features was fixed (20 microm), while their separation was varied to adjust the area fraction (0-80%). The wettability of structured surfaces for liquids resting in the Cassie state is strongly dependent on the continuity of the solid component. Microstructured square pillars and holes showed distinct, asymmetric wetting hysteresis, consistent with our previous observations on flat, chemically heterogeneous surfaces. Furthermore, clear trends for the magnitude of contact angle hysteresis versus area fraction for the two types of microstructured surfaces are evident. The pinning energy associated with these surface features is estimated.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 17-10-2008
Abstract: Room-temperature ionic liquids (RTILs) are promising candidates for a broad range of “green” applications, for which their interaction with solid surfaces plays a crucial role. In this high-energy x-ray reflectivity study, the temperature-dependent structures of three ionic liquids with the tris(pentafluoroethyl)trifluorophosphate anion in contact with a charged sapphire substrate were investigated with submolecular resolution. All three RTILs show strong interfacial layering, starting with a cation layer at the substrate and decaying exponentially into the bulk liquid. The observed decay length and layering period point to an interfacial ordering mechanism, akin to the charge inversion effect, which is suggested to originate from strong correlations between the unscreened ions. The observed layering is expected to be a generic feature of RTILs at charged interfaces.
Publisher: Royal Society of Chemistry (RSC)
Date: 2011
DOI: 10.1039/C0LC00339E
Abstract: A rapid, high-precision method for localised plasma-treatment of bonded PDMS microchannels is demonstrated. Patterned electrodes were prepared by injection of molten gallium into preformed microchannel guides. The electrode guides were prepared without any additional fabrication steps compared to conventional microchannel fabrication. Alignment of the "injected" electrodes is precisely controlled by the photomask design, rather than positioning accuracy of alignment tools. Surface modification is detected using a fluorescent dye (Rhodamine B), revealing a well-defined micropattern with regions less than 100 µm along the length of the microchannel.
Publisher: Elsevier BV
Date: 09-2001
Publisher: American Chemical Society (ACS)
Date: 27-05-2010
DOI: 10.1021/JA9106397
Abstract: A droplet of an ionic liquid (1-butyl-3-methylimidazolium tetrafluoroborate, bmim.BF(4)) is immersed in an immiscible liquid (n-hexadecane) and electrowetted on a flat Teflon AF1600-coated ITO electrode. The static contact angle decreases significantly when voltage is applied between the droplet and the electrode: from 145 degrees down to 50 degrees (with DC voltage) and 15 degrees (with AC voltage). The electrowetting curves (contact angle versus voltage) are similar to the ones obtained in other solid/liquid/vapor and solid/liquid/liquid systems: symmetric with respect to zero voltage and correctly described by Young-Lippmann equation below saturation. The reversibility is excellent and contact angle hysteresis is minimal (approximately 2 degrees). The step size used in applying the DC voltage and the polarity of the voltage are unimportant. The saturation contact angle cannot be predicted with the simple zero-interfacial tension theory. Spreading (after applying a DC voltage) and retraction (after switching off the voltage) of the droplet is monitored. The base area of the droplet varies exponentially during wetting (exponential saturation) and dewetting (exponential decay). The characteristic time is 20 ms for spreading and 35 ms for retraction (such asymmetry is not observed with water-glycerol mixtures of a similar viscosity). The spreading kinetics (dynamic contact angle versus contact line speed) can be described by the hydrodynamic model (Voinov's equation) for small contact angles and by the molecular-kinetic model (Blake's equation) for large contact angles. The role of viscous and molecular dissipation follows the scheme outlined by Brochard-Wyart and de Gennes.
Publisher: Royal Society of Chemistry (RSC)
Date: 2008
DOI: 10.1039/B808826H
Abstract: Exploiting microfluidic principles, the potential for chip-based multilayer assembly for the synthesis of polymer microcapsules was investigated. We demonstrate that continuous flow microfluidic multilayer synthesis is a fast, efficient, automated alternative to conventional batch synthesis. In this work, we dispersed liquid crystal (LC) molecules (organic phase) as monodisperse droplets in an aqueous continuous phase containing the primary polymer and a suitable surfactant. The primary polymer was coadsorbed with the surfactant at the organic/aqueous interface, stabilizing the LC droplets against coalescence and providing a template for subsequent polymer adsorption. As the droplet templates are transported through the microfluidic channel, the polymer-containing aqueous continuous phase is selectively withdrawn and replaced with rinse solution, and then with an alternative polymer solution. This selective withdrawal and infusion cycle was repeated to assemble polymer multilayers onto the emulsion droplets. The process was followed using fluorescence microscopy of the fluorescently-labelled polymers at the LC interface and of the flowing polymer solutions during the sequential rinse stages. Cross-linking of the multilayers and removal of the dispersed LC phase resulted in polymer capsules retaining the high monodispersity of the droplet templates. This microfluidic approach significantly reduces the multilayer formation time (to <2 min for 3-layer capsules) of well-defined capsules that are envisaged to have benefits in biomedical applications, including drug delivery and encapsulated biochemical reactions.
Publisher: American Chemical Society (ACS)
Date: 04-06-2009
DOI: 10.1021/LA900584S
Abstract: Capillary driven liquid-liquid displacement in a system with two immiscible liquids of comparable viscosity was investigated by means of optical high speed video microscopy. For the first time, the impact of substrate wettability on contact line dynamics in liquid-liquid systems was studied. On all substrates, qualitatively different dynamics, in two distinct velocity regimes, were found. Hydrodynamic models apply to the fast stage of initial spreading, while nonhydrodynamic dissipation dominates contact line motion in a final stage at low speed, where the molecular kinetic theory (MKT) successfully captured the dynamics. The MKT model parameter values showed no systematic dependence on substrate wettability. This unexpected result is interpreted in terms of local contact line pinning.
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C4CP05558F
Abstract: HMIM NTf 2 adsorbs on gold from ethanol to form a patchy bilayer. ‘Bound’ anion (filled anion) and ‘bound’ cation (filled blue) sit underneath a layer of cation (empty blue) and anion (empty orange). The IL regions are separated by oxidised gold (darker colour).
Publisher: American Chemical Society (ACS)
Date: 13-05-1999
DOI: 10.1021/LA981526O
Publisher: Elsevier BV
Date: 05-2001
Publisher: Elsevier BV
Date: 2022
Publisher: Elsevier BV
Date: 11-2008
DOI: 10.1016/J.COLSURFB.2008.08.002
Abstract: A combination of complementary analytical techniques has provided valuable information on the physicochemical properties of lipid-DNA complexes such as their size, shape, structure and surface charge. The experimental conditions for producing small and stable lipid-DNA complexes were determined. These complexes consist of spherical primary particles of approximately 60 nm in diameter connected to each other by DNA strands to form small clusters of approximately 70-200 nm in diameter. At high salt concentrations these complexes were not stable and aggregated. Several methods were used to stabilise the lipid-DNA complexes at physiological salt concentrations.
Publisher: MDPI AG
Date: 06-07-2023
DOI: 10.3390/FERMENTATION9070635
Abstract: A rapidly growing population, resource scarcity, and the future sustainability of our food supply are among the major concerns of today’s food industry. The importance of resilient food crops that will sustain in the future is imperative, and legumes are ideal future food crops owing to their rich nutrient profile, cost-effective production and resource usage efficiency. Furthermore, they have the potential to meet the protein needs of the future. There are however several limitations associated with legumes in terms of their sensory, nutritional, and functional properties, which make them challenging for the food industry to use. In this review, these challenges are discussed in detail with particular reference to fermentation as a strategy for overcoming them. A major focus is on examining the potential application of fermentation for modifying techno-functional properties, such as foaming and emulsifying properties, solubility, and water and oil binding capacities of legume substrates. In many studies, fermentation has been demonstrated to enhance the techno-functional, sensory and nutritional attributes of various legume substrates. Future studies must focus on developing scalable fermentation processes to utilize the technology for improving the techno-functional and sensory properties of legume-based ingredients at industrial scale.
Publisher: Informa UK Limited
Date: 06-2013
Publisher: Elsevier BV
Date: 07-1983
Publisher: Elsevier BV
Date: 10-1996
Publisher: Elsevier BV
Date: 07-1998
Publisher: Elsevier BV
Date: 09-2006
DOI: 10.1016/J.JCIS.2006.04.071
Abstract: Very small bubbles which partially coat the surface of particles influence whether or not heterocoagulation between a particle and a bubble occurs. The electrostatic and van der Waals forces of interaction between particles and bubbles were calculated as a function of electrolyte concentration, particle size, and the size and distributions of these very small bubbles present on the particle surface. The height of the surface force barrier was compared with the hydrodynamic pressing force under conditions of flotation. The presence of these very small bubbles has a profound effect on the interaction between particles and bubbles and, in particular, strongly decreases the critical particle radius for heterocoagulation.
Publisher: American Chemical Society (ACS)
Date: 07-12-2012
DOI: 10.1021/AC3028905
Abstract: Analytical technologies of ultrasmall volume liquid, in particular femtoliter to attoliter liquid, is essential for single-cell and single-molecule analysis, which is becoming highly important in biology and medical diagnosis. Nanofluidic chips will be a powerful tool to realize chemical processes for such a small volume s le. However, a technical challenge exists in fluidic control, which is femtoliter to attoliter liquid generation in air and handling for further chemical analysis. Integrating mechanical valves fabricated by MEMS (microelectric mechanical systems) technology into nanofluidic channels is difficult. Here, we propose a nonmechanical valve, which is a Laplace nanovalve. For this purpose, a nanopillar array was embedded in a nanochannel using a two-step electron beam lithography and dry-etching process. The nanostructure allowed precise wettability patterning with a resolution below 100 nm, which was difficult by photochemical wettability patterning due to the optical diffraction. The basic principle of the Laplace nanovalve was verified, and a 1.7 fL droplet (water in air) was successfully generated and handled for the first time.
Publisher: American Chemical Society (ACS)
Date: 07-2010
DOI: 10.1021/JP103279U
Publisher: Informa UK Limited
Date: 02-01-2015
Publisher: Springer Science and Business Media LLC
Date: 04-2010
DOI: 10.1140/EPJE/I2010-10593-3
Abstract: We study theoretically the phoretic motion of a spheroidal particle, which generates solute gradients in the surrounding unbounded solvent via chemical reactions active on its surface in a cap-like region centered at one of the poles of the particle. We derive, within the constraints of the mapping to classical diffusio-phoresis, an analytical expression for the phoretic velocity of such an object. This allows us to analyze in detail the dependence of the velocity on the aspect ratio of the polar and the equatorial diameters of the particle and on the fraction of the particle surface contributing to the chemical reaction. The particular cases of a sphere and of an approximation for a needle-like particle, which are the most common shapes employed in experimental realizations of such self-propelled objects, are obtained from the general solution in the limits that the aspect ratio approaches one or becomes very large, respectively.
Publisher: Elsevier BV
Date: 1996
Publisher: Elsevier BV
Date: 09-1995
Publisher: Elsevier BV
Date: 04-2014
DOI: 10.1016/J.CIS.2013.04.005
Abstract: The paramount importance of wetting applications and the significant economic value of controlling wetting-based industrial processes has stimulated a deep interest in wetting science. In many industrial applications the motion of a complex liquid front over nano-textured surfaces controls the fate of the processes. However our knowledge of the impact of nano-heterogeneities on static and dynamic wetting is very limited. In this article, the fundamentals of wetting are briefly reviewed, with a particular focus on hysteresis and roughness issues. Present knowledge and models of dynamic wetting on smooth and rough surfaces are then examined, with particular attention devoted to the case of nano-topographical heterogeneities and solid-fluid-fluid systems.
Publisher: Elsevier BV
Date: 12-1995
Publisher: Elsevier BV
Date: 03-2004
Publisher: American Chemical Society (ACS)
Date: 07-07-2011
DOI: 10.1021/JP203581J
Publisher: Elsevier
Date: 2000
Publisher: Elsevier BV
Date: 06-1992
Publisher: Royal Society of Chemistry (RSC)
Date: 1999
DOI: 10.1039/A900977I
Publisher: American Chemical Society (ACS)
Date: 24-08-2009
DOI: 10.1021/LA902296D
Abstract: The wettability of surfaces microstructured with square pillars was studied, where the static advancing contact angle on the planar surface was 72 degrees. We observed elevated advancing angles (up to 140 degrees) on these structures for droplets in the Wenzel state. No air was trapped in the structured surfaces beneath the liquid, ruling out the well-known Lotus leaf effect. Instead, we show that the apparent hydrophobicity is related to contact line pinning at the pillar edges, giving a strong dependence of wetting hysteresis on the fraction of the contact line pinned on pillars. Simulating the contact line pinning on these surfaces showed similar behavior to our measurements, revealing both strong pinning at the edges of the pillars as well as mechanistic details.
Publisher: Elsevier BV
Date: 03-2003
Publisher: American Chemical Society (ACS)
Date: 14-02-2013
DOI: 10.1021/LA304088T
Abstract: The dynamic electrowetting and dewetting of ionic liquids are investigated with high-speed video microscopy. Five imidazolium-based ionic liquids ([BMIM]BF(4), [BMIM]PF(6), [BMIM]NTf(2), [HMIM]NTf(2), and [OMIM]BF(4)) are used as probe liquids. Droplets of ionic liquids are first spread on an insulated electrode by applying an external voltage (electrowetting) and then allowed to retract (dewetting) when the voltage is switched off. The base area of the droplet varies exponentially during both the electrowetting and retraction processes. The characteristic time increases with the viscosity of the ionic liquid. The electrowetting and retraction kinetics (dynamic contact angle vs contact line speed) can be described by the hydrodynamic or the molecular-kinetic model. Energy dissipation occurs by viscous and molecular routes with a larger proportion of energy dissipated at the three-phase contact line when the liquid meniscus retracts from the solid surface. The outcomes from this research have implications for the design and control of electro-optical imaging systems, microfluidics, and fuel cells.
Publisher: Elsevier BV
Date: 05-1992
Publisher: American Chemical Society (ACS)
Date: 18-05-2005
DOI: 10.1021/LA046837F
Abstract: The preparation of patterned inorganic surfaces consisting of silica (SiO2) and titania (TiO2) is described. The approach is based on a combination of standard photolithography and plasma-enhanced chemical vapor deposition. Silicon wafers coated with a titania layer (40 nm) were patterned by use of a positive photoresist and then a thin silica layer (10-40 nm) was plasma-deposited. The photoresist was removed by decomposition at 800 degrees C. The inorganic patterned surfaces possessed excellent high-temperature resistance. Since the silica patches were effectively dehydroxylated during the thermal treatment, the patterns consisted of moderately hydrophobic (silica) and hydrophilic (titania) domains with a significant wettability contrast (40 degrees for water). The surface was further hydrophobized with a self-assembled monolayer of fluoroalkylsilane (FAS) and exposed to UV light. The FAS layer was locally oxidized on the TiO2 patches and the wettability contrast was maximized to 120 degrees (the highest possible value on smooth surfaces).
Publisher: Elsevier BV
Date: 04-2010
No related grants have been discovered for John Ralston.