ORCID Profile
0000-0003-2048-4500
Current Organisation
University of Adelaide
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Macromolecular and Materials Chemistry | Physical Chemistry of Materials | Transition Metal Chemistry | Nanochemistry and Supramolecular Chemistry | Theoretical and Computational Chemistry | Organic Semiconductors | Statistical Mechanics in Chemistry | Theory and Design of Materials | Transport Properties and Non-Equilibrium Processes | Structural Chemistry and Spectroscopy
ANZSRC Socio-Economic Objective (SEO)
Expanding Knowledge in the Chemical Sciences | Expanding Knowledge in the Physical Sciences | Renewable Energy not elsewhere classified | Consumer Electronic Equipment (excl. Communication Equipment) |
Related Links
Publications
Carbohydrates@MOFs
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C8MH01611A
Abstract: MOFs have demonstrated outstanding properties for the protection and controlled release of different bio-entities, from proteins to living cells.
Comment on “Magnetic Field Effects on Singlet Fission and Fluorescence Decay Dynamics in Amorphous Rubrene”
Publisher: American Chemical Society (ACS)
Date: 14-10-2016
Solution-Processed Dendrimer-Based TADF Materials for Deep-Red OLEDs
Publisher: American Chemical Society (ACS)
Date: 30-11-2020
A simple predictor of interface orientation of fluids of disk-like anisotropic particles and its implications for organic semiconductors
Publisher: American Chemical Society (ACS)
Date: 02-2022
DOI: 10.26434/CHEMRXIV-2022-235CJ-V2
Abstract: From classical molecular dynamics simulations, we identify a simple and general predictor of molecular orientation at solid and vapour interfaces of isotropic fluids of disk-like anisotropic particles based on their shape and interaction anisotropy. For a wide variety of inter-particle interactions, temperatures, and substrate types within the range of typical organic semiconductors and their processing conditions, we find remarkable universal scaling of the orientation at the interface with the free energy calculated from pair interactions between close-packed nearest neighbours and an empirically derived universal relationship between the entropy and the shape anisotropy and bulk volume fraction of the fluid particles. The face-on orientation of fluid particles at the solid interface is generally predicted to be the equilibrium structure, although the alignment can be controlled by tuning the particle shape and substrate type, while changing the strength of fluid--fluid interactions is likely to play a less effective role. At the vapour interface, only the side-on structure is predicted, and conditions for which the face-on structure may be preferred, such as low temperature, low interaction anisotropy, or low shape anisotropy, are likely to result in little orientation preference (due to the low anisotropy) or be associated with a phase transition to an anisotropic bulk phase for systems with interactions in the range of typical organic semiconductors. Based on these results, we propose a set of guidelines for the rational design and processing of organic semiconductors to achieve a target orientation at a solid or vapour interface.
Power Dependence of the Magnetic Field Effect on Triplet Fusion: A Quantitative Model
Publisher: American Chemical Society (ACS)
Date: 15-05-2023
Self‐Assembly of Selective Interfaces in Organic Photovoltaics
Publisher: Wiley
Date: 22-11-2012
Ion-Specific Anomalous Electrokinetic Effects in Hydrophobic Nanochannels
Publisher: American Physical Society (APS)
Date: 26-04-2007
Molecular dynamics simulations of classical sound absorption in a monatomic gas
Publisher: Elsevier BV
Date: 05-2018
Organizing Crystalline Functionalized Pentacene Using Periodicity of Poly(Vinyl Alcohol)
Publisher: American Chemical Society (ACS)
Date: 28-12-2020
DOI: 10.1021/ACS.JPCLETT.9B03373
Abstract: Nanoparticles of acenes exhibit highly efficient intermolecular singlet fission (SF). Recent reports indicate that altering the morphology of 6,13-bis-(triisopropylsilylethynyl)pentacene (TIPS-Pn) nanoparticles has a profound influence on their SF dynamics. Here, we show that poly(vinyl alcohol) (PVA) induces a phase transition in preformed TIPS-Pn nanoparticles. These nanoparticles are amorphous when initially formed but crystalline after addition of PVA. Surface characterization indicates that a diffuse PVA layer surrounds the nanoparticles. We propose that a periodic interaction between the hydroxyl groups of PVA and TIPS groups of TIPS-Pn on the nanoparticle surface induces a large-scale structural rearrangement to yield crystalline TIPS-Pn. Such reorganization in preformed organic nanoparticles is unprecedented, and we believe that this is the first report of such an effect induced by polymer adsorption. Transient absorption spectroscopic results reveal that SF within these nanoparticles is accelerated by an order of magnitude upon structural rearrangement.
Controlling the Efficiency of Singlet Fission in TIPS-Pentacene/Polymer Composite Nanoparticles
Publisher: American Chemical Society (ACS)
Date: 19-02-2019
A bioinspired, one-step total synthesis of peshawaraquinone
Publisher: Royal Society of Chemistry (RSC)
Date: 2023
DOI: 10.1039/D2SC05377B
Abstract: A new proposal for the biosynthesis of peshawaraquinone via the unsymmetrical dimerization of dehydro-α-lapachone led to its total synthesis in one step from inexpensive starting materials.
Red-Light-Mediated Photocatalytic Hydrogen Evolution by Hole Transfer from Non-Fullerene Acceptor Y6
Publisher: American Chemical Society (ACS)
Date: 23-08-2022
Total Synthesis of Atrachinenins A and B
Publisher: American Chemical Society (ACS)
Date: 12-12-2022
DOI: 10.1021/JACS.2C09978
Enhanced Activity of Enzymes Encapsulated in Hydrophilic Metal-Organic Frameworks
Publisher: American Chemical Society (ACS)
Date: 12-01-2019
DOI: 10.1021/JACS.8B10302
Abstract: Encapsulation of biomacromolecules in metal-organic frameworks (MOFs) can preserve biological functionality in harsh environments. Despite the success of this approach, termed biomimietic mineralization, limited consideration has been given to the chemistry of the MOF coating. Here, we show that enzymes encapsulated within hydrophilic MAF-7 or ZIF-90 retain enzymatic activity upon encapsulation and when exposed to high temperatures, denaturing or proteolytic agents, and organic solvents, whereas hydrophobic ZIF-8 affords inactive catalase and negligible protection to urease.
Molecular design of amorphous porous organic cages for enhanced gas storage
Publisher: American Chemical Society (ACS)
Date: 04-2015
DOI: 10.1021/JP512944R
The Effect of Hydrodynamic Slip on Membrane-Based Salinity-Gradient-Driven Energy Harvesting
Publisher: American Chemical Society (ACS)
Date: 30-03-2016
DOI: 10.1021/ACS.LANGMUIR.6B00433
Abstract: The effect of hydrodynamic slip on salinity-gradient-driven power conversion by the process of reverse electrodialysis, in which the free energy of mixing of salt and fresh water across a nanoporous membrane is harnessed to drive an electric current in an external circuit, is investigated theoretically using a continuum fluid dynamics model. A general one-dimensional model is derived that decouples transport inside the membrane pores from the effects of electrical resistance at the pore ends, from which an analytical expression for the power conversion rate is obtained for a perfectly ion-selective membrane as a function of the slip length, surface charge density, membrane thickness, pore radius, and other membrane and electrolyte properties. The theoretical model agrees quantitatively with finite-element numerical calculations and predicts significant enhancements--up to several times--of salinity-gradient power conversion due to hydrodynamic slip for realistic systems.
Water Slippage versus Contact Angle: A Quasiuniversal Relationship
Publisher: American Physical Society (APS)
Date: 25-11-2008
Anisotropic molecular coarse-graining by force and torque matching with neural networks
Publisher: AIP Publishing
Date: 10-07-2023
DOI: 10.1063/5.0143724
Abstract: We develop a machine-learning method for coarse-graining condensed-phase molecular systems using anisotropic particles. The method extends currently available high-dimensional neural network potentials by addressing molecular anisotropy. We demonstrate the flexibility of the method by parametrizing single-site coarse-grained models of a rigid small molecule (benzene) and a semi-flexible organic semiconductor (sexithiophene), attaining structural accuracy close to the all-atom models for both molecules at a considerably lower computational expense. The machine-learning method of constructing the coarse-grained potential is shown to be straightforward and sufficiently robust to capture anisotropic interactions and many-body effects. The method is validated through its ability to reproduce the structural properties of the small molecule’s liquid phase and the phase transitions of the semi-flexible molecule over a wide temperature range.
Singlet fission preserves polarisation correlation of excitons
Publisher: Royal Society of Chemistry (RSC)
Date: 2023
DOI: 10.1039/D2CP01943D
Abstract: Time-resolved polarisation anisotropy and Monte Carlo simulations show that singlet fission preserves polarisation correlation between photons absorbed and emitted by a material through removing excitons decorrelated by migration.
Speedup techniques for molecular dynamics simulations of the interaction of acoustic waves and nanomaterials
Publisher: Modelling and Simulation Society of Australia and New Zealand
Date: 29-11-2015
Waveshape distortion of high frequency acoustic waves in gas media
Publisher: Elsevier BV
Date: 07-2019
DOI: 10.1016/J.ULTRAS.2019.02.001
Abstract: In molecular dynamics simulations of an acoustic domain excited by a sinusoidally oscillating plane acoustic source in the frequency range of hundreds of megahertz, the density and velocity perturbations adjacent to the source are observed to be non-sinusoidal in shape. This distortion in the shape of the waves is investigated using a number of simulations of frequencies in the hundred of megahertz range and velocities up to 0.50 Å s. The relative distortion of the wave shape is characterised by a developed nested trigonometric function. The distortion is shown to be a function of the Mach number of the acoustic source rather than the source velocity litude. Trends in the distortion with source litude and frequency indicate that distortion of the velocity and density are independent of frequency. It is shown that the density and velocity perturbation can be approximated for any sound source Mach number within the range examined using the parametrised developed equation. The developed approximation could be used to accurately simulate the influence of an oscillating plane using a stationary analytical source. This could be used to develop a hybrid molecular/continuum model that will allow lower frequency simulations. The improved understanding of the causes of the distorted high frequency waveshape could also improve the fidelity of parametric arrays.
Optical Dedoping Mechanism for P3HT:F4TCNQ Mixtures
Publisher: American Chemical Society (ACS)
Date: 17-10-2016
DOI: 10.1021/ACS.JPCLETT.6B02048
Abstract: Doping-induced solubility control (DISC) is a recently introduced photolithographic technique for semiconducting polymers, which utilizes reversible changes in polymer solubility upon doping to allow the polymer to function as its own photoresist. Central to this process is a wavelength sensitive optical dedoping reaction, which is poorly understood but generates subdiffraction-limited topographic features and provides optical control of the polymer doping level. Here, we examine the mechanism of optical dedoping in the semiconducting polymer poly-3-hexylthiophene (P3HT) doped by 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ), via a combination of ultrafast and steady-state spectroscopy, ab initio calculations, and multidimensional NMR. A simple photoinduced back electron transfer mechanism from reduced F4TCNQ to oxidized P3HT does not explain the observed photophysics. Instead, photoexcited F4TCNQ* reacts with THF solvent molecules to form a neutral, nondoping, and highly soluble F4TCNQ-THF complex. Hence, ionized F4TCNQ is removed from the P3HT indirectly by depletion of the neutral F4TCNQ. Because the reaction involves only the dopant and similar photoreactivity would expected for most other dopant molecules, we expect optical DISC patterning should be generalizable to a wide range of polymer:dopant systems.
DNA triplex structure, thermodynamics, and destabilisation: insight from molecular simulations
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C8CP02385A
Abstract: Molecular dynamics simulations are used to elucidate the structure and thermodynamics of DNA triplexes associated with the neurodegenerative disease Friedreich's ataxia (FRDA), as well as complexes of these triplexes with the small molecule netropsin, which is known to destabilise triplexes.
A random walk through the dynamics of homogeneous vapor-liquid nucleation
Publisher: AIP Publishing
Date: 29-04-2005
DOI: 10.1063/1.1884086
Abstract: A method of calculating rates of homogeneous vapor-liquid nucleation based on Langevin dynamics of a few relevant degrees of freedom on a free-energy surface is proposed. The surface is obtained here from simulation and from a semi empirical expression. The mass and friction coefficients are derived from atomistic umbrella-s ling molecular-dynamics simulations. The calculated nucleation rate agrees with atomistic simulations for one particular state point of the Lennard-Jones fluid. The present method is about four orders of magnitude more computationally efficient than the direct atomistic simulation of the transmission coefficient.
Light-Driven Transformation Processes of Anisotropic Silver Nanoparticles
Publisher: American Chemical Society (ACS)
Date: 17-06-2013
DOI: 10.1021/NN4013059
Abstract: The photoinduced formation of silver nanoprisms from smaller silver seed particles in the presence of citrate anions is a classic ex le of a photomorphic reaction. In this case, light is used as a convenient tool to dynamically manipulate the shape of metal nanoparticles. To date, very little is known about the prevailing reaction mechanism of this type of photoreaction. Here we provide a detailed study of the shape transformation dynamics as a function of a range of different process parameters, such as photon energy and photon flux. For the first time, we provide direct evidence that the photochemical synthesis of silver nanoprisms from spherical seed nanoparticles proceeds via a light-activated two-dimensional coalescence mechanism. On the other hand, we could show that Ostwald ripening becomes the dominant reaction mechanism when larger silver nanoprisms are grown from photochemically synthesized smaller nanoprisms. This two-step reaction proceeds significantly faster and yields more uniform, sharper nanoprisms than the classical one-step photodevelopment process from seeds. The ability to dynamically control nanoparticle shapes and properties with light opens up novel synthesis avenues but also, more importantly, allows one to conceive new applications that exploit the nonstatic character of these nanoparticles and the ability to control and adjust their properties at will in a highly dynamic fashion.
Erratum: “Entrance effects in concentration-gradient-driven flow through an ultrathin porous membrane” [J. Chem. Phys. 151, 044705 (2019)]
Publisher: AIP Publishing
Date: 08-2023
DOI: 10.1063/5.0167179
A simple predictor of interface orientation of mesogenic fluids and its implications for organic semiconductors
Publisher: American Chemical Society (ACS)
Date: 10-01-2022
DOI: 10.26434/CHEMRXIV-2022-235CJ
Abstract: From classical molecular dynamics simulations, we identify a simple and general predictor of molecular orientation at solid and vapour interfaces of isotropic fluids of anisotropic particles based on their shape and interaction anisotropy. For a wide variety of inter-particle interactions, temperatures, and substrate types within the range of typical organic semiconductors and their processing conditions, we find remarkable universal scaling of the orientation at the interface with the free energy calculated from pair interactions between close-packed nearest neighbours and an empirically derived universal relationship between the entropy and the shape anisotropy and bulk volume fraction of the fluid particles. The face-on orientation of fluid particles at the solid interface is generally predicted to be the equilibrium structure, although the alignment can be controlled by tuning the particle shape and substrate type, while changing the strength of fluid--fluid interactions is likely to play a less effective role. At the vapour interface, only the side-on structure is predicted, and conditions for which the face-on structure may be preferred, such as low temperature, low interaction anisotropy, or low shape anisotropy, are likely to result in little orientation preference (due to the low anisotropy) or be associated with a phase transition to an anisotropic bulk phase for systems with interactions in the range of typical organic semiconductors. Based on these results, we propose a set of guidelines for the rational design and processing of organic semiconductors to achieve a target orientation at a solid or vapour interface.
Protected DNA strand displacement for enhanced single nucleotide discrimination in double-stranded DNA
Publisher: Springer Science and Business Media LLC
Date: 04-03-2015
DOI: 10.1038/SREP08721
The impact of film deposition and annealing on the nanostructure and dielectric constant of organic semiconductor thin films
Publisher: Royal Society of Chemistry (RSC)
Date: 2023
DOI: 10.1039/D3CP03038E
Abstract: Different processing conditions lead to a range of molecular packing motifs for films of a novel organic semiconductor, which enables tuning of the optical frequency dielectric constant.
Temperature and length scale dependence of hydrophobic effects and their possible implications for protein folding
Publisher: Proceedings of the National Academy of Sciences
Date: 11-07-2000
Abstract: The Lum–Chandler–Weeks theory of hydrophobicity [Lum, K., Chandler, D. & Weeks, J. D. (1999) J. Phys. Chem. 103, 4570–4577] is applied to treat the temperature dependence of hydrophobic solvation in water. The application illustrates how the temperature dependence for hydrophobic surfaces extending less than 1 nm differs significantly from that for surfaces extending more than 1 nm. The latter is the result of water depletion, a collective effect, that appears at length scales of 1 nm and larger. Because of the contrasting behaviors at small and large length scales, hydrophobicity by itself can explain the variable behavior of entropies of protein folding.
Intramolecular Tricarbonyl‐Ene Reactions and α‐Hydroxy‐β‐Diketone Rearrangements Inspired by the Biosynthesis of Polycyclic Polyprenylated Acylphloroglucinols
Publisher: Wiley
Date: 14-07-2022
Abstract: Structurally unique natural products pose biosynthetic puzzles whose solution can inspire new chemical reactions. Herein, we propose a unified biosynthetic pathway towards some complex meroterpenoids—the hyperireflexolides, biyoulactones, hybeanones and hypermonones. This hypothesis led to the discovery of uncatalyzed, intramolecular carbonyl‐ene reactions that are spontaneous at room temperature. We also developed an anionic cascade reaction featuring an α‐hydroxy‐β‐diketone rearrangement and an intramolecular aldol reaction to access four distinct natural product scaffolds from a common intermediate.
Competing single-chain folding and multi-chain aggregation pathways control solution-phase aggregate morphology of organic semiconducting polymers
Publisher: Royal Society of Chemistry (RSC)
Date: 2022
DOI: 10.1039/D2NR04750K
Abstract: Using computer simulations and theory, we explain the unexpected formation in poor solvents of extended rod-like semiconducting-polymer aggregates, which are correlated with enhanced electron mobility but are not predicted by existing theories.
Coarse-grained simulations of the effects of chain length, solvent quality, and chemical defects on the solution-phase morphology of MEH-PPV conjugated polymers
Publisher: CSIRO Publishing
Date: 2012
DOI: 10.1071/CH12029
Abstract: A mesoscale coarse-grained model of the conjugated polymer poly(2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV) in implicit solvent is developed. The model is parametrized to reproduce the local structure and dynamics of an atomistic simulation model and accounts for the effects of solvent quality and saturation chemical defects on the polymer structure. Polymers with defect concentrations of 0 to 10 % are simulated using Langevin dynamics in tetrahydrofuran (THF) and in a model poor solvent for chain lengths and solution concentrations used experimentally. The polymer chains are extended in THF and collapse into compact structures in the poor solvent. The radius of gyration decreases with defect content in THF and agrees quantitatively with experiment. The structures formed in poor solvent by chains with 300 monomer units change from toroidal to cylindrical with increasing defect content, while chains containing 1000 monomers form cylinders regardless of defect content. These results have implications for energy transfer in MEH-PPV.
Nanoparticle Size-Dependent Singlet Fission and Exciton Dynamics in Amorphous TIPS-Pentacene
Publisher: American Chemical Society (ACS)
Date: 28-09-2021
A simple predictor of interface orientation of fluids of disk-like anisotropic particles and its implications for organic semiconductors.
Publisher: Royal Society of Chemistry (RSC)
Date: 2022
DOI: 10.1039/D2SM00026A
Abstract: From classical molecular dynamics simulations, we identify a simple and general predictor of molecular orientation at solid and vapour interfaces of isotropic fluids of disk-like anisotropic particles based on their shape and interaction anisotropy. For a wide variety of inter-particle interactions, temperatures, and substrate types within the range of typical organic semiconductors and their processing conditions, we find remarkable universal scaling of the orientation at the interface with the free energy calculated from pair interactions between close-packed nearest neighbours and an empirically derived universal relationship between the entropy and the shape anisotropy and bulk volume fraction of the fluid particles. The face-on orientation of fluid particles at the solid interface is generally predicted to be the equilibrium structure, although the alignment can be controlled by tuning the particle shape and substrate type, while changing the strength of fluid-fluid interactions is likely to play a less effective role. At the vapour interface, only the side-on structure is predicted, and conditions for which the face-on structure may be preferred, such as low temperature, low interaction anisotropy, or low shape anisotropy, are likely to result in little orientation preference (due to the low anisotropy) or be associated with a phase transition to an anisotropic bulk phase for systems with interactions in the range of typical organic semiconductors. Based on these results, we propose a set of guidelines for the rational design and processing of organic semiconductors to achieve a target orientation at a solid or vapour interface.
Structural modulation of the photophysical and electronic properties of pyrene-based 3D metal–organic frameworks derived from s-block metals
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D0CE01505A
Abstract: Materials in which charge delocalization and migration can be tuned are critical for electronic applications.
Computational Study of P3HT/C60-Fullerene Miscibility
Publisher: CSIRO Publishing
Date: 2014
DOI: 10.1071/CH13518
Abstract: Classical molecular dynamics simulations and statistical thermodynamics are used to investigate the miscibility of blends of the conjugated polymer poly(3-hexylthiophene) (P3HT) and fullerene C60 for blend ratios typically used in organic photovoltaic devices over a range of temperatures. Depending on which of two slightly different simulation force fields is used, the calculations suggest that amorphous P3HT/fullerene blends are either miscible or immisicble under typical processing conditions. The former result is consistent with recent experiments and suggests that experimentally observed nano-scale phase separation is driven by polymer or fullerene crystallisation. But the inconsistency between the different force fields indicates that these blends are close to phase coexistence between the separated and homogeneously mixed phases and suggests that care must be taken in interpreting simulation data on P3HT/fullerene blends. These findings have implications for organic photovoltaics, in which the microstructure of conjugated-polymer/fullerene blends plays a crucial role in device performance.
Electron transfer through α-peptides attached to vertically aligned carbon nanotube arrays: a mechanistic transition
Publisher: Royal Society of Chemistry (RSC)
Date: 2012
DOI: 10.1039/C2CC16665H
Abstract: The mechanism of electron transfer in α-aminoisobutyric (Aib) homoligomers is defined by the extent of secondary structure, rather than just chain length. Helical structures (Aib units ≥3) undergo an electron hopping mechanism, while shorter disordered sequences (Aib units <3) undergo an electron superexchange mechanism.
Normal incidence acoustic absorption characteristics of a carbon nanotube forest
Publisher: Elsevier BV
Date: 12-2017
Molecular dynamics simulations of acoustic absorption by a carbon nanotube
Publisher: AIP Publishing
Date: 06-2018
DOI: 10.1063/1.5026528
Abstract: Acoustic absorption by a carbon nanotube (CNT) was studied using molecular dynamics (MD) simulations in a molecular domain containing a monatomic gas driven by a time-varying periodic force to simulate acoustic wave propagation. Attenuation of the sound wave and the characteristics of the sound field due to interactions with the CNT were studied by evaluating the behavior of various acoustic parameters and comparing the behavior with that of the domain without the CNT present. A standing wave model was developed for the CNT-containing system to predict sound attenuation by the CNT and the results were verified against estimates of attenuation using the thermodynamic concept of exergy. This study demonstrates acoustic absorption effects of a CNT in a thermostatted MD simulation, quantifies the acoustic losses induced by the CNT, and illustrates their effects on the CNT. Overall, a platform was developed for MD simulations that can model acoustic d ing induced by nanostructured materials such as CNTs, which can be used for further understanding of nanoscale acoustic loss mechanisms associated with molecular interactions between acoustic waves and nanomaterials.
Endohedrally functionalised porous organic cages
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C6CC04423A
Abstract: The synthesis and characterisation of two novel, endohedrally functionalised porous organic cages are presented.
Relating Molecular Morphology to Charge Mobility in Semicrystalline Conjugated Polymers
Publisher: American Chemical Society (ACS)
Date: 22-02-2016
Pitfalls of quantifying intersystem crossing rates in singlet-fission chromophore solutions
Publisher: AIP Publishing
Date: 26-08-2022
DOI: 10.1063/5.0100619
Abstract: Singlet fission (SF), a process that produces two triplet excitons from one singlet exciton, has attracted recent interest for its potential to circumvent the detailed-balance efficiency limit of single-junction solar cells. For the potential of SF to be fully realized, accurate assignment and quantification of SF is necessary. Intersystem crossing (ISC) is another process of singlet to triplet conversion that is important to distinguish from SF to avoid either over- or under-estimation of SF triplet production. Here, we quantify an upper bound on the rate of ISC in two commonly studied SF chromophores, TIPS–pentacene and TIPS–tetracene, by using transient absorption spectroscopy of solutions of varying concentrations in toluene. We show that SF in solutions of these acenes has previously been misidentified as ISC, and vice versa. By determining a bimolecular SF rate constant in concentrated solutions in which SF dominates over ISC, we distinguish triplet formation due to SF from triplet formation due to ISC and show that the characteristic time scale of ISC must be longer than 325 ns in TIPS–pentacene, while it must be longer than 118 ns in TIPS–tetracene. We additionally note that no excimer formation is observed in the relatively dilute (up to 8 mM) solutions studied here, indicating that previous excimer formation observed at much higher concentrations may be partially due to aggregate formation. This work highlights that an accurate quantification of ISC is crucial as it leads to accurate determination of SF rate constants and yields.
Coarse-grained simulations of the solution-phase self-assembly of poly(3-hexylthiophene) nanostructures
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C3NR33324H
Abstract: Under certain conditions the conjugated polymer poly(3-hexylthiophene) (P3HT) self-assembles into high-aspect-ratio nanostructures (known as nanofibres, nanowires, or nanoribbons) when cooled below its solubility limit in a marginal solvent such as anisole. Such nanostructures are potentially beneficial for organic photovoltaic device performance. In this work, Langevin dynamics simulations of a coarse-grained model of P3HT in implicit anisole solvent are used to study the self-assembly of P3HT nanostructures for polymer chain lengths and concentrations used experimentally to prepare P3HT nanofibres. The coarse-grained model is parametrised to match the local structure and dynamics of an atomistic model with explicit solvent. Nanofibres are also prepared experimentally and characterised by atomic force microscopy and UV-vis spectroscopy. The simulations match the experimental phase behaviour of P3HT in anisole, showing aggregation of P3HT at 293 and 308 K but not at 323 or 353 K. Single-chain simulations at 293 K reveal two distinct nano-scale aggregate morphologies: hairpins and helices. Hairpin aggregates, which are the precursors of nanofibres, are slightly favoured energetically at 293 K for nuclei of the critical size of ≈80 monomers for aggregation. Consequently, chains in multi-chain aggregates adopt the hairpin morphology exclusively in simulations at experimental concentrations at 293 K. The simulated aggregate sizes match experimentally measured nanofibre widths. An estimate of the shift in UV-vis absorption of P3HT due to the change in conjugation length with aggregation in the simulations agrees reasonably well with experiment and shows that most of the spectral red shift that occurs with nanofibre formation is due to increased planarisation of the P3HT chains. In addition to providing insight into the mechanisms of nanofibre formation, the simulations resolve details of the molecular-level organisation of chains in P3HT nanofibres hitherto inaccessible by experiment.
Molecular-Level Details of Morphology-Dependent Exciton Migration in Poly(3-hexylthiophene) Nanostructures
Publisher: American Chemical Society (ACS)
Date: 19-03-2015
Corrigendum to: Coarse-Grained Simulations of the Effects of Chain Length, Solvent Quality, and Chemical Defects on the Solution-Phase Morphology of MEH-PPV Conjugated Polymers
Publisher: CSIRO Publishing
Date: 2013
DOI: 10.1071/CH12029_CO
Abstract: A mesoscale coarse-grained model of the conjugated polymer poly(2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV) in implicit solvent is developed. The model is parametrized to reproduce the local structure and dynamics of an atomistic simulation model and accounts for the effects of solvent quality and saturation chemical defects on the polymer structure. Polymers with defect concentrations of 0 to 10 % are simulated using Langevin dynamics in tetrahydrofuran (THF) and in a model poor solvent for chain lengths and solution concentrations used experimentally. The polymer chains are extended in THF and collapse into compact structures in the poor solvent. The radius of gyration decreases with defect content in THF and agrees quantitatively with experiment. The structures formed in poor solvent by chains with 300 monomer units change from toroidal to cylindrical with increasing defect content, while chains containing 1000 monomers form cylinders regardless of defect content. These results have implications for energy transfer in MEH-PPV.
A Theoretical Study of Propagation Rate Coefficients for Methacrylonitrile and Acrylonitrile
Publisher: American Chemical Society (ACS)
Date: 22-07-1998
DOI: 10.1021/MA980229N
The Consequences of Interface Mixing on Organic Photovoltaic Device Characteristics
Publisher: Wiley
Date: 25-03-2011
Massive Amplification of Surface-Induced Transport at Superhydrophobic Surfaces
Publisher: American Physical Society (APS)
Date: 08-08-2008
High-Throughput Screening of Metal–organic Frameworks for Macroscale Heteroepitaxial Alignment
Publisher: American Chemical Society (ACS)
Date: 27-08-2018
DOI: 10.26434/CHEMRXIV.7012007.V1
Abstract: The ability to align porous metal–organic frameworks (MOFs) on substrate surfaces on a macroscopic scale is a vital step towards integrating MOFs into functional devices. But macroscale surface alignment of MOF crystals has only been demonstrated in a few cases. To accelerate the materials discovery process, we have developed a high-throughput computational screening algorithm to identify MOFs that are likely to undergo macroscale aligned heterepitaxial growth on a substrate. Screening of thousands of MOF structures by this process can be achieved in a few days on a desktop workstation. The algorithm filters MOFs based on surface chemical compatibility, lattice matching with the substrate, and interfacial bonding. Our method uses a simple new computationally efficient measure of the interfacial energy that considers both bond and defect formation at the interface. Furthermore, we show that this novel descriptor is a better predictor of aligned heteroepitaxial growth than other established interface descriptors, by testing our screening algorithm on a s le set of copper MOFs that have been grown heteroepitaxially on a copper hydroxide surface. Application of the screening process to several MOF databases reveals that the top candidates for aligned growth on copper hydroxide comprise mostly MOFs with rectangular lattice symmetry in the plane of the substrate. This result indicates a substrate-directing effect that could be exploited in targeted synthetic strategies. We also identify that MOFs likely to form aligned heterostructures have broad distributions of in-plane pore sizes and anisotropies. Accordingly, this suggests that aligned MOF thin films with a wide range of properties may be experimentally accessible.
Pressure-Induced Enlargement and Ionic Current Rectification in Symmetric Nanopores
Publisher: American Chemical Society (ACS)
Date: 13-10-2020
A solution-processed bis-tridentate iridium(iii ) complex-cored dendrimer for green OLEDs
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D1TC01816G
Abstract: We report a solution-processable dendronised bis-tridentate iridium( iii ) complex composed of a bis(imidazolyl)phenyl ligand with a first-generation biphenyl dendron containing t -butyl surface groups and a 2-pyrazolyl-6-phenylpyridine co-ligand.
Femtosecond dynamics of excitons and hole-polarons in composite P3HT/PCBM nanoparticles
Publisher: American Chemical Society (ACS)
Date: 19-02-2013
DOI: 10.1021/JP308876Z
Abstract: The dynamics of charge separation in aqueous suspensions of regioregular P3HT nanoparticles containing PCBM were investigated for the first time using femtosecond transient absorption spectroscopy. This investigation is supported by the recently reported use of regioregular P3HT/PCBM nanoparticles as charge trapping and storage devices. In this study, the presence of excited-state and charge-separated species, including singlet excitons, polymer polarons and free charges, generated in rr-P3HT/PCBM nanoparticles was identified through visible pump and visible/near-infrared probe femtosecond transient absorption spectroscopy at a range of electron acceptor concentrations. The decrease of the singlet exciton lifetime by charge transfer to PCBM is well described by a one-dimensional diffusion model with a P3HT domain size of approximately 5 nm for 5-50 wt % PCBM. This model also indicates that bimolecular recombination is the dominant charge recombination mechanism at 20 wt % PCBM and above.
The interplay of interfaces, supramolecular assembly, and electronics in organic semiconductors
Publisher: IOP Publishing
Date: 23-07-2019
What Next for Singlet Fission in Photovoltaics? The Fate of Triplet and Triplet-Pair Excitons
Publisher: American Chemical Society (ACS)
Date: 22-03-2022
Visible‐Light Photoredox Catalysis Enables the Biomimetic Synthesis of Nyingchinoids A, B, and D, and Rasumatranin D
Publisher: Wiley
Date: 04-02-2019
Abstract: The total synthesis of nyingchinoids A and B has been achieved through successive rearrangements of a 1,2-dioxane intermediate that was assembled using a visible-light photoredox-catalysed aerobic [2+2+2] cycloaddition. Nyingchinoid D was synthesised with a competing [2+2] cycloaddition. Based on NMR data and biosynthetic speculation, we proposed a structure revision of the related natural product rasumatranin D, which was confirmed through total synthesis. Under photoredox conditions, we observed the conversion of a cyclobutane into a 1,2-dioxane through retro-[2+2] cycloaddition followed by aerobic [2+2+2] cycloaddition.
A comparative MD study of the local structure of polymer semiconductors P3HT and PBTTT
Publisher: Royal Society of Chemistry (RSC)
Date: 2010
DOI: 10.1039/C0CP00785D
Abstract: Atomistic molecular dynamics simulations of P3HT and PBTTT-C12 at finite temperatures are carried out to investigate the nanoscale structural properties that lead to higher measured hole mobility in PBTTT versus P3HT field-effect transistors. Simulations of the polymer melts show that the structural properties in PBTTT facilitate both intra- and inter-chain charge transport compared with P3HT due to a greater degree of planarity, closer and more parallel stacking of the thiophene and thienothiophene rings, and possible interdigitation of the dodecyl side chains. The crucial role played by the bulky dodecyl side chain and thienothiophene ring, respectively, in determining intra-chain and inter-chain structural order is clarified.
Synthesis of Triple‐Stranded Diruthenium(II) Compounds
Publisher: Wiley
Date: 14-06-2022
Abstract: A series of ligands containing a 1,4‐disubstituted 1,2,3‐triazole unit have been used for the formation of triple‐stranded dinuclear Ru(II) complexes. In contrast to the previously reported complexes of labile metals, the use of inert Ru(II) enabled stereoisomeric mixtures of triple‐stranded diruthenium(II) complexes to be accessed. The chromatographic resolution of the enantiomers of a reported helicate containing a more rigid 1,4‐xylyl spacer was carried out on cellulose. The ligand spacer was modified and as the flexibility increased the production of isomeric mixtures was detected the mesocate and helicate forms were separated when an n ‐propyl spacer was used. This pair of diastereomers was found to exhibit photoconversion, a unique observation for Ru(II) compounds of this type. Partial separation via chromatographic resolution was achieved for compounds containing an n ‐butyl spacer, and the presence of a mesocate/helicate pair confirmed.
Anisotropic Triplet Exciton Diffusion in Crystalline Functionalized Pentacene
Publisher: American Chemical Society (ACS)
Date: 14-10-2020
Calculating transition dipole moments of phosphorescent emitters for efficient organic light-emitting diodes
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C9CP01045A
Abstract: Quantum-chemical calculations show that the direction of the transition dipole moment of organometallic phosphorescent emitters is sensitive to molecular geometry.
Ab initio calculation of the rate coefficient for short-chain branching in free-radical polymerizations
Publisher: Elsevier BV
Date: 03-2001
Twisted Carbazole Dendrons for Solution-Processable Green Emissive Phosphorescent Dendrimers
Publisher: American Chemical Society (ACS)
Date: 03-2023
Systematic bottom-up molecular coarse-graining via force and torque matching using anisotropic particles
Publisher: American Chemical Society (ACS)
Date: 05-04-2022
DOI: 10.26434/CHEMRXIV-2022-G44DJ-V2
Abstract: We derive a systematic and general method for parametrizing coarse-grained molecular models consisting of anisotropic particles from fine-grained (e.g. all-atom) models for condensed-phase molecular dynamics simulations. The method, which we call anisotropic force-matching coarse-graining (AFM-CG), is based on rigorous statistical mechanical principles, enforcing consistency between the coarse-grained and fine-grained phase-space distributions to derive equations for the coarse-grained forces, torques, masses, and moments of inertia in terms of properties of a condensed-phase fine-grained system. We verify the accuracy and efficiency of the method by coarse-graining liquid-state systems of two different anisotropic organic molecules, benzene and perylene, and show that the parametrized coarse-grained models more accurately describe properties of these systems than previous anisotropic coarse-grained models parametrized using other methods that do not account for finite-temperature and many-body effects on the condensed-phase coarse-grained interactions. The AFM-CG method will be useful for developing accurate and efficient dynamical simulation models of condensed-phase systems of molecules consisting of large, rigid, anisotropic fragments, such as liquid crystals, organic semiconductors, and nucleic acids.
The Hydrophobic Effect and the Influence of Solute−Solvent Attractions
Publisher: American Chemical Society (ACS)
Date: 02-2002
DOI: 10.1021/JP013289V
Dielectric Constant Engineering of Organic Semiconductors: Effect of Planarity and Conjugation Length
Publisher: Wiley
Date: 11-08-2022
Abstract: Bulk heterojunction organic solar cells continue to show steady photoconversion efficiency improvements. However, single component organic solar cells are a particularly attractive alternative due to the relative simplicity of device manufacture. It has been proposed that organic semiconductors with a high dielectric constant (≈10) could give rise to spontaneous free charge carrier generation upon photoexcitation. In this manuscript, factors are explored that affect the dielectric constant of organic semiconductors, particularly the optical‐frequency dielectric constant. The properties of monomers, dimers and trimers of two isoelectronic families of materials that have acceptor units composed of one or two dicyanovinylbenzothiadiazole moieties and one to three donor units are compared. The donor components are composed of either fluorenyl or cyclopentadithiophene moieties with the same glycol‐based solubilizing groups. It is found that chromophore planarity and orientation with respect to the substrate, and film density affect the optical and electronic properties of the materials, especially the high‐frequency dielectric constant. The results also indicate that delocalization of the highest occupied and lowest unoccupied molecular orbitals is a critical factor. The dimer with two dicyanovinylbenzothiadiazole moieties and two dithienocyclopentadiene units is found to have the highest optical frequency dielectric constant and overall performance.
Quantitative Measurements of the Temperature-Dependent Microscopic and Macroscopic Dynamics of a Molecular Dopant in a Conjugated Polymer
Publisher: American Chemical Society (ACS)
Date: 14-07-2017
Protein surface functionalisation as a general strategy for facilitating biomimetic mineralisation of ZIF-8
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C8SC00825F
Abstract: The surface charge and chemistry of a protein determines its ability to facilitate biomimetic mineralisation.
Pitfalls of quantifying intersystem crossing rates in singlet-fission chromophore solutions
Publisher: American Chemical Society (ACS)
Date: 27-05-2022
DOI: 10.26434/CHEMRXIV-2022-7JZV6
Abstract: Singlet fission (SF), a process that produces two triplet excitons from one singlet exciton, has attracted recent interest for its potential to circumvent the detailed-balance efficiency limit of single-junction solar cells. For the potential of SF to be fully realized, accurate assignment and quantification of SF is necessary. Intersystem crossing (ISC) is another process of singlet to triplet conversion that is important to distinguish from SF to avoid either over- or under-estimation of SF triplet production. Here, we quantify an upper bound on the rate of ISC in two commonly studied SF chromophores, TIPS-pentacene and TIPS-tetracene, by using transient absorption spectroscopy of solutions of varying concentrations in toluene. We show that SF in solutions of these acenes has previously been misidentified as ISC, and vice versa. By determining a bimolecular SF rate constant in concentrated solutions in which SF dominates over ISC, we distinguish triplet formation due to SF from triplet formation due to ISC, and show that the characteristic time scale of ISC must be longer than 325 ns in TIPS-pentacene, while it must be longer than 118 ns in TIPS- tetracene. We additionally note that no excimer formation is observed in the relatively dilute (up to 8 mM) solutions studied here, indicating that previous excimer formation observed at much higher concentrations may be partially due to aggregate formation. This work highlights that an accurate quantification of ISC is crucial as it leads to accurate determination of SF rate constants and yields.
Protecting-Group-Free Site-Selective Reactions in a Metal–Organic Framework Reaction Vessel
Publisher: American Chemical Society (ACS)
Date: 26-04-2018
DOI: 10.1021/JACS.8B02896
Abstract: Site-selective organic transformations are commonly required in the synthesis of complex molecules. By employing a bespoke metal-organic framework (MOF, 1·[Mn(CO)
Optical description of solid-state dye-sensitized solar cells. I. Measurement of layer optical properties
Publisher: AIP Publishing
Date: 10-2009
DOI: 10.1063/1.3204982
Abstract: The efficiency of a photovoltaic device is limited by the portion of solar energy that can be captured. We discuss how to measure the optical properties of the various layers in solid-state dye-sensitized solar cells (SDSC). We use spectroscopic ellipsometry to determine the complex refractive index of each of the various layers in a SDSC. Each of the ellipsometry fits is used to calculate a transmission spectrum that is compared to a measured transmission spectrum. The complexities of pore filling on the fitting of the ellipsometric data are discussed. Scanning electron microscopy and energy dispersive x-ray spectroscopy is shown to be an effective method for determining pore filling in SDSC layers. Accurate effective medium optical constants for each layer are presented and the material limits under which these optical constants can be used are discussed.
Front Cover: Synthesis of Triple‐Stranded Diruthenium(II) Compounds (Eur. J. Inorg. Chem. 25/2022)
Publisher: Wiley
Date: 27-07-2022
Ion Mobility-Mass Spectrometry Reveals Details of Formation and Structure for GAA·TCC DNA and RNA Triplexes
Publisher: American Chemical Society (ACS)
Date: 19-10-2018
DOI: 10.1007/S13361-018-2077-9
Abstract: DNA and RNA triplexes are thought to play key roles in a range of cellular processes such as gene regulation and epigenetic remodeling and have been implicated in human disease such as Friedreich's ataxia. In this work, ion mobility-mass spectrometry (IM-MS) is used with supporting UV-visible spectroscopy to investigate DNA triplex assembly, considering stability and specificity, for GAA·TTC oligonucleotide sequences of relevance to Friedreich's ataxia. We demonstrate that, contrary to other ex les, parallel triplex structures are favored for these sequences and that stability is enhanced by increasing oligonucleotide length and decreasing pH. We also provide evidence for the self-association of these triplexes, consistent with a proposed model of higher order DNA structures formed in Friedreich's ataxia. By comparing triplex assembly using DNA- and RNA-based triplex-forming oligonucleotides, we demonstrate more favorable formation of RNA triplexes, suggesting a role for their formation in vivo. Finally, we interrogate the binding properties of netropsin, a known polyamide triplex destabilizer, with RNA-DNA hybrid triplexes, where preference for duplex binding is evident. We show that IM-MS is able to report on relevant solution-phase populations of triplex DNA structures, thereby further highlighting the utility of this technology in structural biology. Our data therefore provides new insights into the possible DNA and RNA assemblies that may form as a result of GAA triplet repeats. Graphical Abstract ᅟ.
Scaling of Hydrophobic Solvation Free Energies
Publisher: American Chemical Society (ACS)
Date: 10-05-2001
DOI: 10.1021/JP0104029
Systematic Bottom-Up Molecular Coarse-Graining via Force Matching using Anisotropic Particles
Publisher: American Chemical Society (ACS)
Date: 04-01-2022
DOI: 10.26434/CHEMRXIV-2022-G44DJ
Abstract: We derive a systematic and general method for parametrizing coarse-grained molecular models consisting of anisotropic particles from fine-grained (e.g. all-atom) models for condensed-phase molecular dynamics simulations. The method, which we call anisotropic force-matching coarse-graining (AFM-CG), is based on rigorous statistical mechanical principles, enforcing consistency between the coarse-grained and fine-grained phase-space distributions to derive equations for the coarse-grained forces, masses, and moments of inertia in terms of properties of a condensed-phase fine-grained system. We verify the accuracy and efficiency of the method by coarse-graining liquid-state systems of two different anisotropic organic molecules, benzene and perylene, and show that the parametrized coarse-grained models more accurately describe properties of these systems than previous anisotropic coarse-grained models parametrized using other methods that do not account for finite-temperature and many-body effects on the condensed-phase coarse-grained interactions. The AFM-CG method will be useful for developing accurate and efficient dynamical simulation models of condensed-phase systems of molecules consisting of large, rigid, anisotropic fragments, such as nucleic acids, liquid crystals, and organic semiconductors.
Molecular shape and the energetics of chemisorption: From simple to complex energy landscapes
Publisher: American Physical Society (APS)
Date: 27-07-2012
The Molecular Origin of Anisotropic Emission in an Organic Light-Emitting Diode
Publisher: American Chemical Society (ACS)
Date: 18-09-2017
DOI: 10.1021/ACS.NANOLETT.7B03528
Abstract: Atomistic nonequilibrium molecular dynamics simulations have been used to model the induction of molecular orientation anisotropy within the emission layer of an organic light-emitting diode (OLED) formed by vapor deposition. Two emitter species were compared: racemic fac-tris(2-phenylpyridine)iridium(III) (Ir(ppy)
A unifying paradigm for naphthoquinone-based meroterpenoid (bio)synthesis
Publisher: Springer Science and Business Media LLC
Date: 31-07-2017
DOI: 10.1038/NCHEM.2829
Systematic bottom-up molecular coarse-graining via force and torque matching using anisotropic particles
Publisher: AIP Publishing
Date: 13-05-2022
DOI: 10.1063/5.0085006
Abstract: We derive a systematic and general method for parameterizing coarse-grained molecular models consisting of anisotropic particles from fine-grained (e.g., all-atom) models for condensed-phase molecular dynamics simulations. The method, which we call anisotropic force-matching coarse-graining (AFM-CG), is based on rigorous statistical mechanical principles, enforcing consistency between the coarse-grained and fine-grained phase-space distributions to derive equations for the coarse-grained forces, torques, masses, and moments of inertia in terms of properties of a condensed-phase fine-grained system. We verify the accuracy and efficiency of the method by coarse-graining liquid-state systems of two different anisotropic organic molecules, benzene and perylene, and show that the parameterized coarse-grained models more accurately describe properties of these systems than previous anisotropic coarse-grained models parameterized using other methods that do not account for finite-temperature and many-body effects on the condensed-phase coarse-grained interactions. The AFM-CG method will be useful for developing accurate and efficient dynamical simulation models of condensed-phase systems of molecules consisting of large, rigid, anisotropic fragments, such as liquid crystals, organic semiconductors, and nucleic acids.
Mapping‐Out Catalytic Processes in a Metal–Organic Framework with Single‐Crystal X‐ray Crystallography
Publisher: Wiley
Date: 03-02-2017
Abstract: Single-crystal X-ray crystallography is employed to characterize the reaction species of a full catalytic carbonylation cycle within a Mn
Thermally activated delayed fluorescence poly(dendrimer)s – detrapping excitons for reverse intersystem crossing
Publisher: Royal Society of Chemistry (RSC)
Date: 2022
DOI: 10.1039/D1TC05151B
Abstract: We compare the effect of donor strength on the optoelectronic properties of thermally activated delayed fluorescence poly(dendrimer)s and their dendrimer analogues.
Electrochemical and Computational Studies on Intramolecular Dissociative Electron Transfer in β-Peptides
Publisher: American Chemical Society (ACS)
Date: 06-12-2012
DOI: 10.1021/JP3082563
Molecular basis of binding and stability of curcumin in diamide-linked γ-cyclodextrin dimers
Publisher: American Chemical Society (ACS)
Date: 04-10-2013
DOI: 10.1021/JP406125X
Abstract: Curcumin is a naturally occurring molecule with medicinal properties that is unstable in water, whose efficacy as a drug can potentially be enhanced by encapsulation inside a host molecule. In this work, the thermodynamics and mechanism of binding of curcumin to succinamide- and urea-linked γ-cyclodextrin (γ-CD) dimers in water are investigated by molecular dynamics simulations. The simulated binding constants of curcumin to succinamide- and urea-linked γ-CD dimers at 310 K are 11.3 × 10(6) M(-1) and 1.6 × 10(6) M(-1), respectively, matching well with previous experimental results of 8.7 × 10(6) M(-1) and 2.0 × 10(6) M(-1). The simulations reveal structural information about the encapsulation of curcumin inside the diamide-linked γ-CD dimers, with distinct qualitative differences observed for the two dimers. In particular, (1) the predominant orientation of curcumin inside the urea-linked γ-CD dimer is perpendicular to that in the succinamide-linked γ-CD dimer (2) the magnitude of the angle between the planes of the cyclodextrins is larger for the succinamide-linked γ-CD dimer and (3) curcumin exhibits greater configurational freedom inside the urea-linked γ-CD dimer. A consequence of some of these structural differences is that the dimer interior is more accessible to water in the succinamide-linked γ-CD dimer. These observations explain the higher stability and lower binding constant observed experimentally for curcumin in the urea-linked cyclodextrin γ-CD dimer compared with the succinamide-linked γ-CD dimer. More generally, the results demonstrate how stability and binding strength can be decoupled and thus separately optimized in host-guest systems used for drug delivery.
Aqueous Electrolytes near Hydrophobic Surfaces: Dynamic Effects of Ion Specificity and Hydrodynamic Slip
Publisher: American Chemical Society (ACS)
Date: 06-12-2007
DOI: 10.1021/LA7021787
Abstract: We demonstrate, using molecular-dynamics computer simulations, the strong influence of surface wettability on the equilibrium structure of the electrical double layer at solid interfaces and on electrokinetic transport in aqueous electrolytes due to the effects of interfacial ion specificity and hydrodynamic slip. In particular, we show that anomalous electrokinetic effects such as nonzero zeta potentials for uncharged surfaces are general features of electro-osmotic flow in hydrophobic channels for electrolytes with substantial cation/anion size asymmetry, as a result of the stronger attraction of the larger ion to the "vapor-liquid-like" interface induced by a hydrophobic surface. We establish that the simulated velocity profiles obey continuum hydrodynamics on the nanoscopic length scales studied and show that the anomalous flow profiles can be accurately predicted by using a modified Poisson-Boltzmann description for the ion density distributions that incorporates an ion-size-dependent hydrophobic solvation energy as a crucial component. We also demonstrate that, counterintuitively, the flow for a charge-neutral fluid is independent of the solid-fluid friction coefficient.
Feasibility of mixed matrix membrane gas separations employing porous organic cages
Publisher: American Chemical Society (ACS)
Date: 09-01-2014
DOI: 10.1021/JP4079184
Competing single-chain folding and multi-chain aggregation pathways control solution-phase aggregate morphology of organic semiconducting polymers
Publisher: American Chemical Society (ACS)
Date: 09-2022
DOI: 10.26434/CHEMRXIV-2022-J0P8N
Abstract: Understanding the solution-phase behaviour of organic semiconducting polymers is important for systematically improving the performance of devices based on solution-processed thin films of these molecules. Conventional polymer theory predicts that polymer conformations become more compact as solvent quality decreases, but recent experiments have shown the high-performance organic-semiconducting polymer P(NDI2OD-T2) to form extended rod-like aggregates much larger than a single chain in poor solvents, with the formation of these extended aggregates correlated with enhanced electron mobility in films deposited from these solutions. We explain the unexpected formation of extended aggregates using a novel coarse-grained simulation model of P(NDI2OD-T2) that we have developed to study the effect of solvent quality on its solution-phase behaviour. In poor solvents, we find that aggregation through only a few monomers gives effectively inseparable chains, leading to the formation of extended structures of partially overlapping chains via non-equilibrium assembly. This behaviour requires that multi-chain aggregation occurs faster than chain folding, which we show is the case for the chain lengths and concentrations shown experimentally to form rod-like aggregates. This kinetically controlled process introduces a dependence of aggregate structure on concentration, chain length, and chain flexibility, which we show is able to reconcile experimental findings and is generalisable to the solution-phase assembly of other semiflexible polymers.
Surfactant Effects on Hydrogen Evolution by Small-Molecule Nonfullerene Acceptor Nanoparticles
Publisher: American Chemical Society (ACS)
Date: 23-08-2022
Molecular Insight into Assembly Mechanisms of Porous Aromatic Frameworks
Publisher: American Chemical Society (ACS)
Date: 25-07-2017
An optical spacer is no panacea for light collection in organic solar cells
Publisher: AIP Publishing
Date: 26-01-2009
DOI: 10.1063/1.3073710
Abstract: The role of an optical spacer layer has been examined by optical simulations of organic solar cells with various bandgaps. The simulations have been performed with the transfer matrix method and the finite element method. The results show that no beneficial effect can be expected by adding an optical spacer to a solar cell with an already optimized active layer thickness.
Characterization of polymer–fullerene mixtures for organic photovoltaics by systematically coarse-grained molecular simulations
Publisher: Elsevier BV
Date: 03-2011
Controlling Adsorbate Diffusion on a High-Symmetry Surface through Molecular Shape Selection
Publisher: American Chemical Society (ACS)
Date: 21-04-2011
DOI: 10.1021/JP1108619
Cavity formation and the drying transition in the Lennard-Jones fluid
Publisher: American Physical Society (APS)
Date: 02-2000
Abstract: By simulation and theory, we study the probability of observing N molecular centers within molecular sized volumes for a Lennard-Jones fluid near liquid-vapor coexistence. For large volumes and small N, the probability distribution differs markedly from Gaussian. The free energy per unit surface area to form empty volumes (i.e., cavities) is a rapidly varying function of the radius for small cavities. It becomes constant for large volumes. The source of these behaviors is the occurrence of drying (i.e., solvent depletion) at the cavity surface. The crossover to drying occurs on microscopic length scales, with significant density depletion found for cavities with radii of the order of two or more Lennard-Jones diameters. Reasonable agreement is found between the simulation results and the theory developed by Lum, Chandler, and Weeks [J. Phys. Chem. B 103, 4570 (1999)].
High-Throughput Screening of Metal-Organic Frameworks for Macroscale Heteroepitaxial Alignment
Publisher: American Chemical Society (ACS)
Date: 29-10-2018
Abstract: The ability to align porous metal-organic frameworks (MOFs) on substrate surfaces on a macroscopic scale is a vital step toward integrating MOFs into functional devices. But macroscale surface alignment of MOF crystals has only been demonstrated in a few cases. To accelerate the materials discovery process, we have developed a high-throughput computational screening algorithm to identify MOFs that are likely to undergo macroscale aligned heterepitaxial growth on a substrate. Screening of thousands of MOF structures by this process can be achieved in a few days on a desktop workstation. The algorithm filters MOFs based on surface chemical compatibility, lattice matching with the substrate, and interfacial bonding. Our method uses a simple new computationally efficient measure of the interfacial energy that considers both bond and defect formation at the interface. Furthermore, we show that this novel descriptor is a better predictor of aligned heteroepitaxial growth than other established interface descriptors, by testing our screening algorithm on a s le set of copper MOFs that have been grown heteroepitaxially on a copper hydroxide surface. Application of the screening process to several MOF databases reveals that the top candidates for aligned growth on copper hydroxide comprise mostly MOFs with rectangular lattice symmetry in the plane of the substrate. This result indicates a substrate-directing effect that could be exploited in targeted synthetic strategies. We also identify that MOFs likely to form aligned heterostructures have broad distributions of in-plane pore sizes and anisotropies. Accordingly, this suggests that aligned MOF thin films with a wide range of properties may be experimentally accessible.
Entrance effects in concentration-gradient-driven flow through an ultrathin porous membrane
Publisher: AIP Publishing
Date: 28-07-2019
DOI: 10.1063/1.5108700
Abstract: Transport of liquid mixtures through porous membranes is central to processes such as desalination, chemical separations, and energy harvesting, with ultrathin membranes made from novel 2D nanomaterials showing exceptional promise. Here, we derive, for the first time, general equations for the solution and solute fluxes through a circular pore in an ultrathin planar membrane induced by a solute concentration gradient. We show that the equations accurately capture the fluid fluxes measured in finite-element numerical simulations for weak solute–membrane interactions. We also derive scaling laws for these fluxes as a function of the pore size and the strength and range of solute–membrane interactions. These scaling relationships differ markedly from those for concentration-gradient-driven flow through a long cylindrical pore or for flow induced by a pressure gradient or an electric field through a pore in an ultrathin membrane. These results have broad implications for transport of liquid mixtures through membranes with thickness on the order of the characteristic pore size.
Optical description of solid-state dye-sensitized solar cells. II. Device optical modeling with implications for improving efficiency
Publisher: AIP Publishing
Date: 10-2009
DOI: 10.1063/1.3204985
Abstract: We use the optical transfer-matrix method to quantify the spatial distribution of light in solid-state dye-sensitized solar cells (DSCs), employing material optical properties measured experimentally in the accompanying article (Part I) as input into the optical model. By comparing the optical modeling results with experimental photovoltaic action spectra for solid-state DSCs containing either a ruthenium-based dye or an organic indoline-based dye, we show that the internal quantum efficiency (IQE) of the devices for both dyes is around 60% for almost all wavelengths, substantially lower than the almost 100% IQE measured for liquid DSCs, indicating substantial electrical losses in solid-state DSCs that can account for much of the current factor-of-two difference between the efficiencies of liquid and solid-state DSCs. The model calculations also demonstrate significant optical losses due to absorption by 2,2′,7,7′-tetrakis-(N,N-di-p-methoxyphenyl-amine)-9,9′-spirobifluorene (spiro-OMeTAD) and TiO2 in the blue and to a lesser extent throughout the visible. As a consequence, the more absorptive organic dye, D149, should outperform the standard ruthenium complex sensitizer, Z907, for all device thicknesses, underlining the potential benefits of high extinction coefficient dyes optimized for solid-state DSC operation.
Computational identification of organic porous molecular crystals
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C6CE00064A
Coarse-Grained Computer Simulations of Polymer/Fullerene Bulk Heterojunctions for Organic Photovoltaic Applications
Publisher: American Chemical Society (ACS)
Date: 30-12-2009
DOI: 10.1021/CT900496T
Abstract: We develop coarse-grained (CG) computer simulation models of poly(3-hexylthiophene) (P3HT) and P3HT/fullerene-C60 mixtures, in which collections of atoms from a physically accurate atomistic model are mapped onto a smaller number of "superatoms". These CG models allow much larger systems to be simulated for longer durations than is achievable atomistically, making it possible to study in molecular detail the morphology of polymer/fullerene bulk heterojunctions at length and time scales relevant to organic photovoltaic devices. We demonstrate that our CG models, parametrized at two state points, accurately capture the structure of atomistic systems at other points in the mixture phase diagram. Finally, we use our CG models to study the dynamic evolution of the microstructure of a P3HT/C60 bulk heterojunction in a system approaching the device scale.
Related Organisations
University Of California, Berkeley
Location: United States of America
Related Funding Activities
Discovery Projects - Grant ID: DP190102100
Start Date: 07-2019
End Date: 12-2022
Amount: $370,000.00
Funder: Australian Research Council
View Funded ActivityDiscovery Projects - Grant ID: DP160103234
Start Date: 2016
End Date: 12-2018
Amount: $314,900.00
Funder: Australian Research Council
View Funded ActivityDiscovery Projects - Grant ID: DP210102155
Start Date: 2021
End Date: 12-2023
Amount: $330,000.00
Funder: Australian Research Council
View Funded Activity