ORCID Profile
0000-0003-0823-4111
Current Organisation
Nanyang Technological University
Does something not look right? The information on this page has been harvested from data sources that may not be up to date. We continue to work with information providers to improve coverage and quality. To report an issue, use the Feedback Form.
Publisher: Wiley
Date: 22-01-2021
Publisher: Royal Society of Chemistry (RSC)
Date: 2014
DOI: 10.1039/C4CC01949K
Abstract: Ag nanowire-based catalytic liquid marbles are fabricated as miniature reactors, which demonstrate highly efficient, support-free and rate-controllable heterogeneous degradation of methylene blue, with catalytic efficiency close to 100%.
Publisher: American Chemical Society (ACS)
Date: 08-04-2016
DOI: 10.1021/ACS.JPCLETT.6B00501
Abstract: Current microscale tracking of chemical kinetics is limited to destructive ex situ methods. Here we utilize Ag nanocube-based plasmonic liquid marble (PLM) microreactor for in situ molecular-level identification of reaction dynamics. We exploit the ultrasensitive surface-enhanced Raman scattering (SERS) capability imparted by the plasmonic shell to unravel the mechanism and kinetics of aryl-diazonium surface grafting reaction in situ, using just a 2-μL reaction droplet. This reaction is a robust approach to generate covalently functionalized metallic surfaces, yet its kinetics remain unknown to date. Experiments and simulations jointly uncover a two-step sequential grafting process. An initial Langmuir chemisorption of sulfonicbenzene diazonium (dSB) salt onto Ag surfaces forms an intermediate sulfonicbenzene monolayer (Ag-SB), followed by subsequent autocatalytic multilayer growth of Ag-SB3. Kinetic rate constants reveal 19-fold faster chemisorption than multilayer growth. Our ability to precisely decipher molecular-level reaction dynamics creates opportunities to develop more efficient processes in synthetic chemistry and nanotechnology.
Publisher: Wiley
Date: 27-11-2018
Abstract: Gas–liquid reactions form the basis of our everyday lives, yet they still suffer poor reaction efficiency and are difficult to monitor in situ, especially at ambient conditions. Now, an inert gas–liquid reaction between aniline and CO 2 is driven at 1 atm and 298 K by selectively concentrating these immiscible reactants at the interface between metal–organic framework and solid nanoparticles (solid@MOF). Real‐time reaction SERS monitoring and simulations affirm the formation of phenylcarbamic acid, which was previously undetectable because they are unstable for post‐reaction treatments. The solid@MOF ensemble gives rise to a more than 28‐fold improvement to reaction efficiency as compared to ZIF‐only and solid‐only platforms, emphasizing that the interfacial nanocavities in solid@MOF are the key to enhance the gas–liquid reaction. Our strategy can be integrated with other functional materials, thus opening up new opportunities for ambient‐operated gas–liquid applications.
Publisher: American Chemical Society (ACS)
Date: 20-12-2017
DOI: 10.1021/ACS.JPCLETT.6B02743
Abstract: The ability of an artificial microdroplet to mimic the rotational behaviors of living systems is crucial for dynamic mass transportation but remains challenging to date. Herein, we report dynamic microdroplet rotation using a liquid marble (RLM) and achieve precise control over mass transportation and distribution in a three-dimensional (3D) microdroplet. RLM rotates synchronously with an external magnetic field, creating circular hydrodynamic flow and an outward centrifugal force. Such spin-induced phenomena direct a spiral movement of entrapped molecules and accelerate their diffusion and homogenization in the entire liquid. Moreover, we demonstrate the rotation rate-controlled (between 0 and 1300 rpm) modulation of shell-catalyzed reaction kinetics from 0.13 to 0.62 min
Publisher: Wiley
Date: 04-2014
Abstract: Inspired by aphids, liquid marbles have been studied extensively and have found application as isolated microreactors, as micropumps, and in sensing. However, current liquid‐marble‐based sensing methodologies are limited to qualitative colorimetry‐based detection. Herein we describe the fabrication of a plasmonic liquid marble as a substrate‐less analytical platform which, when coupled with ultrasensitive SERS, enables simultaneous multiplex quantification and the identification of ultratrace analytes across separate phases. Our plasmonic liquid marble demonstrates excellent mechanical stability and is suitable for the quantitative examination of ultratrace analytes, with detection limits as low as 0.3 fmol, which corresponds to an analytical enhancement factor of 5×10 8 . The results of our simultaneous detection scheme based on plasmonic liquid marbles and an aqueous–solid–organic interface quantitatively tally with those found for the in idual detection of methylene blue and coumarin.
Publisher: Wiley
Date: 26-06-2015
Abstract: Colloidosomes are robust microcapsules attractive for molecular sensing because of their characteristic micron size, large specific surface area, and dual-phase stability. However, current colloidosome sensors are limited to qualitative fluorogenic receptor-based detection, which restrict their applicability to a narrow range of molecules. Here, we introduce plasmonic colloidosome constructed from Ag nanocubes as an emulsion-based 3D SERS platform. The colloidosomes exhibit excellent mechanical robustness, flexible size tunability, versatility to merge, and ultrasensitivity in SERS quantitation of food/industrial toxins down to sub-femtomole levels. Using just 0.5 μL of s le volumes, our plasmonic colloidosomes exhibit >3000-fold higher SERS sensitivity over conventional suspension platform. Notably, we demonstrate the first high-throughput multiplex molecular sensing across multiple liquid phases.
Publisher: American Chemical Society (ACS)
Date: 11-2013
DOI: 10.1021/AM403655G
Abstract: An analytical platform suitable for trace detection using a small volume of analyte is pertinent to the field of toxin detection and criminology. Plasmonic nanostructures provide surface-enhanced Raman scattering (SERS) that can potentially achieve trace toxins and/or molecules detection. However, the detection of highly diluted, small volume s les remains a challenge. Here, we fabricate a superhydrophobic SERS platform by assembling Ag nanocubes that support strong surface plasmon and chemical functionalization for trace detection with s le volume of just 1 μL. Our strategy integrates the intense electromagnetic field confinement generated by Ag nanocubes with a superhydrophobic surface capable of analyte concentration to lower the molecular detection limit. Single crystalline Ag nanocubes are assembled using the Langmuir-Blodgett technique to create surface roughness. To create a stable superhydrophobic SERS platform, an additional 25 nm Ag coating is evaporated over the Ag nanocubes to "weld" the Ag nanocubes onto the substrate followed by chemical functionalization with perfluorodecanethiol. The resulting substrate has an advancing contact angle of 169° ± 5°. Our superhydrophobic platform confines analyte molecules within a small area and prevents the random spreading of molecules. An analyte concentrating factor of 14-fold is attained, as compared to a hydrophilic surface. Consequently, the detection limit of our superhydrophobic SERS substrate reaches 10(-16) M (100 aM) for rhodamine 6G using 1 μL analyte solutions. An analytical SERS enhancement factor of 10(11) is achieved. Our protocol is a general method that provides a simple, cost-effective approach to develop a stable and uniform superhydrophobic SERS platform for trace molecular sensing.
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C6AN01239F
Abstract: Designing substrate-less plasmonic metacrystals for the multiplex ultratrace detection of analytes from both organic and aqueous phases.
Publisher: Wiley
Date: 14-06-2017
Abstract: Liquid marbles are emergent microreactors owing to their isolated environment and the flexibility of materials used. Plasmonic liquid marbles (PLMs) are demonstrated as the smallest spectroelectrochemical microliter-scale reactor for concurrent spectro- and electrochemical analyses. The three-dimensional Ag shell of PLMs are exploited as a bifunctional surface-enhanced Raman scattering (SERS) platform and working electrode for redox process modulation. The combination of SERS and electrochemistry (EC) capabilities enables in situ molecular read-out of transient electrochemical species, and elucidate the potential-dependent and multi-step reaction dynamics. The 3D configuration of our PLM-based EC-SERS system exhibits 2-fold and 10-fold superior electrochemical and SERS performance than conventional 2D platforms. The rich molecular-level electrochemical insights and excellent EC-SERS capabilities offered by our 3D spectroelectrochemical system are pertinent in charge transfer processes.
Publisher: Wiley
Date: 11-04-2017
Abstract: 3D plasmonic colloidosomes are superior SERS sensors owing to their high sensitivity and excellent tolerance to laser misalignment. Herein, we incorporate plasmonic colloidosomes in a microfluidic channel for online SERS detection. Our method resolves the poor signal reproducibility and inter-s le contamination in the existing online SERS platforms. Our flow system offers rapid and continuous online detection of 20 s les in less than 5 min with excellent signal reproducibility. The isolated colloidosomes prevent cross-s le and channel contamination, allowing accurate quantification of s les over a concentration range of five orders of magnitude. Our system demonstrates high-resolution multiplex detection with fully preserved signal and Raman features of in idual analytes in a mixture. High-throughput multi-assay analysis is performed, which highlights that our system is capable of rapid identification and quantification of a sequence of s les containing various analytes and concentrations.
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C8NR04053B
Abstract: Nanoscale shaping of NPG's thermo-plasmonic effect is investigated to optimize localized light-to-heat conversion and its application in ultrasensitive heat-mediated actuation.
Publisher: American Chemical Society (ACS)
Date: 07-07-2016
Publisher: American Chemical Society (ACS)
Date: 29-08-2016
Abstract: Liquid marble offers an attractive droplet manipulation approach by isolating microdroplet in a nonstick encapsulating shell formed via the spontaneous coating of hydrophobic particles onto the liquid surface. While liquid marble prepared using magnetic nanoparticles enables precise spatiotemporal actuation of microdroplets, these manipulations are generally limited to simple and linear spatial maneuver of microdroplets. Herein, we demonstrate the unique and three-dimensional spinning of microliter-sized liquid marble (LM) and its subsequent dual applications as (1) the world's smallest centrifuge and (2) a miniature and localized viscometer. Our LM is responsive to an applied rotating magnetic field, with its spinning speed programmable between 0 and 1300 rpm. This spinning generates an unprecedented centrifugal force of >2g in a LM of ∼1 mm radius. Such centrifugal force facilitates an outward and radial hydrodynamic flow in the enclosed microdroplet, enabling LM to serve as a microcentrifuge for the sedimentation of nanoparticles with >85% separation efficiency. Furthermore, we apply spinning LM as an ultrasensitive spin-to-viscosity transducer to quantify the viscosity of the external suspended liquid in the relative viscosity (η/ηwater) range of 1-70 using ≤1 mL liquid s le. Collectively, the ensemble of benefits offered by spinning LM creates enormous opportunities in the development of multifunctional micromagneto-mechanical devices as promising surface-sensitive microsensor, miniature centrifugal pump, and even microreactor with directed heat and mass transfer mechanism.
Publisher: Wiley
Date: 07-07-2016
Abstract: Controlling sub-10 nm ligament sizes and open-shell structure in nanoporous gold (NPG) to achieve strained lattice is critical in enhancing catalytic activity, but it remains a challenge due to poor control of reaction kinetics in conventional dealloying approach. Herein, a ligament size-controlled synthesis of open-shell NPG bowls (NPGB) through hetero-epitaxial growth of NPGB on AgCl is reported. The ligament size in NPGB is controlled from 6 to 46 nm by varying the hydroquinone to HAuCl4 ratio. The Williamson-Hall analysis demonstrates a higher lattice strain in smaller ligament size. In particular, NPGB with 6 nm (NPGB 6) ligament size possess the highest strain of 15.4 × 10(-3) , which is nearly twice of conventional 2D NPG sheets (≈8.8 × 10(-3) ). The presence of high surface energy facets in NPGBs is also envisaged. The best electrocatalytic activity toward methanol oxidation is observed in NPGB 6 (27.8 μA μg(-1) ), which is ≈9-fold and 3-fold higher than 8 nm solid Au nanoparticles, and conventional NPG sheets. The excellent catalytic activity in NPGB 6 is attributed to the open-shell structure, lattice strain, and higher electro-active surface area, allowing efficient exposure of catalytic active sites to facilitate the methanol oxidation. The results offer a potential strategy for designing next generation electrocatalysts.
Publisher: Springer Science and Business Media LLC
Date: 29-04-2015
DOI: 10.1038/NCOMMS7990
Abstract: A major challenge in nanoparticle self-assembly is programming the large-area organization of a single type of anisotropic nanoparticle into distinct superlattices with tunable packing efficiencies. Here we utilize nanoscale surface chemistry to direct the self-assembly of silver octahedra into three distinct two-dimensional plasmonic superlattices at a liquid/liquid interface. Systematically tuning the surface wettability of silver octahedra leads to a continuous superlattice structural evolution, from close-packed to progressively open structures. Notably, silver octahedra standing on vertices arranged in a square lattice is observed using hydrophobic particles. Simulations reveal that this structural evolution arises from competing interfacial forces between the particles and both liquid phases. Structure-to-function characterizations reveal that the standing octahedra array generates plasmonic ‘hotstrips’, leading to nearly 10-fold more efficient surface-enhanced Raman scattering compared with the other more densely packed configurations. The ability to assemble these superlattices on the wafer scale over various platforms further widens their potential applications.
Publisher: American Chemical Society (ACS)
Date: 07-06-2020
DOI: 10.1021/JACS.0C04144
Publisher: Wiley
Date: 19-04-2018
Abstract: Molecular-level airborne sensing is critical for early prevention of disasters, diseases, and terrorism. Currently, most 2D surface-enhanced Raman spectroscopy (SERS) substrates used for air sensing have only one functional surface and exhibit poor SERS-active depth. "Aerosolized plasmonic colloidosomes" (APCs) are introduced as airborne plasmonic hotspots for direct in-air SERS measurements. APCs function as a macroscale 3D and omnidirectional plasmonic cloud that receives laser irradiation and emits signals in all directions. Importantly, it brings about an effective plasmonic hotspot in a length scale of approximately 2.3 cm, which affords 100-fold higher tolerance to laser misalignment along the z-axis compared with 2D SERS substrates. APCs exhibit an extraordinary omnidirectional property and demonstrate consistent SERS performance that is independent of the laser and analyte introductory pathway. Furthermore, the first in-air SERS detection is demonstrated in stand-off conditions at a distance of 200 cm, highlighting the applicability of 3D omnidirectional plasmonic clouds for remote airborne sensing in threatening or inaccessible areas.
Publisher: American Chemical Society (ACS)
Date: 11-2017
Abstract: We demonstrate a one-step precise direct metal writing of well-defined and densely packed gold nanoparticle (AuNP) patterns with tunable physical and optical properties. We achieve this by using two-photon lithography on a Au precursor comprising poly(vinylpyrrolidone) (PVP) and ethylene glycol (EG), where EG promotes higher reduction rates of Au(III) salt via polyol reduction. Hence, clusters of monodisperse AuNP are generated along raster scanning of the laser, forming high-particle-density, well-defined structures. By varying the PVP concentration, we tune the AuNP size from 27.3 to 65.0 nm and the density from 172 to 965 particles/μm
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C8CC00564H
Abstract: A plasmonic nose is designed using a ZIF-encapsulated Ag nanocube array to concentrate molecules and electromagnetic field at the 3D nanometer scale.
Publisher: American Chemical Society (ACS)
Date: 03-09-2019
Publisher: Wiley
Date: 30-05-2016
Abstract: Miniaturized liquid-liquid interfacial reactors offer enhanced surface area and rapid confinement of compounds of opposite solubility, yet they are unable to provide in situ reaction monitoring at a molecular level at the interface. A picoreactor operative at the liquid-liquid interface is described, comprising plasmonic colloidosomes containing Ag octahedra strategically assembled at the water-in-decane emulsion interface. The plasmonic colloidosomes isolate ultrasmall amounts of solutions (<200 pL), allowing parallel monitoring of multiple reactions simultaneously. Using the surface-enhanced Raman spectroscopy (SERS) technique, in situ monitoring of the interfacial protonation of dimethyl yellow (p-dimethylaminoazobenzene (DY)) is performed, revealing an apparent rate constant of 0.09 min(-1) for the first-order reaction. The presence of isomeric products with similar physical properties is resolved, which would otherwise be indiscernible by other analytical methods.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 02-03-2018
Abstract: Originally unfavored nitrogen-to-ammonia electroconversion is now preferred over competing reaction using reticular chemistry.
Publisher: American Chemical Society (ACS)
Date: 28-01-2020
Publisher: American Chemical Society (ACS)
Date: 13-09-2019
Abstract: Stand-off Raman spectroscopy combines the advantages of both Raman spectroscopy and remote detection to retrieve molecular vibrational fingerprints of chemicals at inaccessible sites. However, it is currently restricted to the detection of pure solids and liquids and not widely applicable for dispersed molecules in air. Herein, we realize real-time stand-off SERS spectroscopy for remote and multiplex detection of atmospheric airborne species by integrating a long-range optic system with a 3D analyte-sorbing metal-organic framework (MOF)-integrated SERS platform. Formed via the self-assembly of Ag@MOF core-shell nanoparticles, our 3D plasmonic architecture exhibits micrometer thick SERS hotspot to allow active sorption and rapid detection of aerosols, gas, and volatile organic compounds down to parts-per-billion levels, notably at a distance up to 10 m apart. The platform is highly sensitive to changes in atmospheric content, as demonstrated in the temporal monitoring of gaseous CO
Publisher: Wiley
Date: 27-07-2020
Abstract: The electrochemical nitrogen reduction reaction (NRR) offers a sustainable solution towards ammonia production but suffers poor reaction performance owing to preferential catalyst–H formation and the consequential hydrogen evolution reaction (HER). Now, the Pt/Au electrocatalyst d‐band structure is electronically modified using zeolitic imidazole framework (ZIF) to achieve a Faradaic efficiency (FE) of % with high ammonia yield rate of μg mg cat −1 h −1 under ambient conditions. The strategy lowers electrocatalyst d‐band position to weaken H adsorption and concurrently creates electron‐deficient sites to kinetically drive NRR by promoting catalyst–N 2 interaction. The ZIF coating on the electrocatalyst doubles as a hydrophobic layer to suppress HER, further improving FE by ‐fold compared to without ZIF (ca. 1 %). The Pt/Au‐N ZIF interaction is key to enable strong N 2 adsorption over H atom.
Publisher: Springer Science and Business Media LLC
Date: 17-09-2014
DOI: 10.1038/NCOMMS5947
Abstract: Nanoporous gold with networks of interconnected ligaments and highly porous structure holds stimulating technological implications in fuel cell catalysis. Current syntheses of nanoporous gold mainly revolve around de-alloying approaches that are generally limited by stringent and harsh multistep protocols. Here we develop a one-step solution phase synthesis of zero-dimensional hollow nanoporous gold nanoparticles with tunable particle size (150-1,000 nm) and ligament thickness (21-54 nm). With faster mass diffusivity, excellent specific electroactive surface area and large density of highly active surface sites, our zero-dimensional nanoporous gold nanoparticles exhibit ~1.4 times enhanced catalytic activity and improved tolerance towards carbonaceous species, demonstrating their superiority over conventional nanoporous gold sheets. Detailed mechanistic study also reveals the crucial heteroepitaxial growth of gold on the surface of silver chloride templates, implying that our synthetic protocol is generic and may be extended to the synthesis of other nanoporous metals via different templates.
Publisher: Wiley
Date: 16-09-2020
Publisher: Springer Science and Business Media LLC
Date: 17-07-2018
DOI: 10.1038/S41467-018-05102-X
Abstract: Organizing nanoparticles into supercrystals comprising multiple structures remains challenging. Here, we achieve one assembly with dual structures for Ag polyhedral building blocks, comprising truncated cubes, cuboctahedra, truncated octahedra, and octahedra. We create two micro-environments in a solvent evaporation-driven assembly system: one at the drying front and one at the air/water interface. Dynamic solvent flow concentrates the polyhedra at the drying front, generating hard particle behaviors and leading to morphology-dependent densest-packed bulk supercrystals. In addition, monolayers of nanoparticles adsorb at the air/liquid interface to minimize the air/liquid interfacial energy. Subsequent solvent evaporation gives rise to various structurally erse dual-structure supercrystals. The topmost monolayers feature distinct open crystal structures with significantly lower packing densities than their densest-packed supercrystals. We further highlight a 3.3-fold synergistic enhancement of surface-enhanced Raman scattering efficiency arising from these dual-structure supercrystals as compared to a uniform one.
Publisher: Wiley
Date: 30-09-2019
Abstract: Full genome sequencing of organisms with large and complex genomes is intractable and cost ineffective under most research budgets. Cycads (Cycadales) represent one of the oldest lineages of the extant seed plants and, partly due to their age, have incredibly large genomes up to ~60 Gbp. Restriction site-associated DNA sequencing (RADseq) offers an approach to find genome-wide informative markers and has proven to be effective with both model and nonmodel organisms. We tested the application of RADseq using ezRAD across all 10 genera of the Cycadales including an ex le data set of Cycas calcicola representing 72 s les from natural populations. Using previously available plastid and mitochondrial genomes as references, reads were mapped recovering plastid and mitochondrial genome regions and nuclear markers for all of the genera. De novo assembly generated up to 138,407 high-depth clusters and up to 1,705 phylogenetically informative loci for the genera, and 4,421 loci for the ex le assembly of C. calcicola. The number of loci recovered by de novo assembly was lower than previous RADseq studies, yet still sufficient for downstream analysis. However, the number of markers could be increased by relaxing our assembly parameters, especially for the C. calcicola data set. Our results demonstrate the successful application of RADseq across the Cycadales to generate a large number of markers for all genomic compartments, despite the large number of plastids present in a typical plant cell. Our modified protocol was adapted to be applied to cycads and other organisms with large genomes to yield many informative genome-wide markers.
Publisher: American Chemical Society (ACS)
Date: 24-07-2017
Publisher: American Chemical Society (ACS)
Date: 18-01-2022
Publisher: Royal Society of Chemistry (RSC)
Date: 2014
DOI: 10.1039/C4CP03679D
Abstract: A high-throughput fabrication of a stable and uniform superhydrophobic SERS platform is demonstrated. It is able to detect trace molecules at ultra-low detection limit of 10 −17 M (10 aM) using just 4 μL of analyte solutions.
Publisher: Royal Society of Chemistry (RSC)
Date: 2014
DOI: 10.1039/C3NR04375D
Abstract: We present the next generation covert plasmonic security labels based on Ag nanowire structures and their polarization dependent surface-enhanced Raman scattering (SERS) imaging. The security labels consist of Ag nanowires fabricated by two-photon lithography and thermal evaporation, where molecular probes of choice are deposited. Simulation and experimental results show that the SERS signals from the embedded molecules depend significantly on the polarization of the incident field. The covert molecular information cannot be revealed directly from the physical features, but can only be read-out selectively by polarization-dependent SERS imaging. Our plasmonic security labels exhibit very narrow spectral fingerprint vibration, which is more specific than broadband colorimetry-based systems. The polarization-dependent SERS intensity, molecular fingerprint of SERS spectra, and versatile geometrical design by two-photon lithography have made our plasmonic Ag nanowire structures an ideal candidate as advanced security solutions for anti-counterfeiting application.
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C7CS00786H
Abstract: This review summarizes recent SERS developments, focusing on analyte manipulation strategies and hybrid SERS platforms that venture beyond hotspot engineering.
Publisher: American Chemical Society (ACS)
Date: 10-2014
DOI: 10.1021/AC502955W
Abstract: The ultratrace detection and quantification of toxins in both water and organic liquids remains a challenge due to the random spreading and dilution of liquids on substrate-based sensors, especially for organic liquids with low surface tension. Herein, we fabricate a superhydrophobic-oleophobic (SHP-OP) 3D Ag nanowire mesh-like surface-enhanced Raman scattering (SERS) platform to overcome the random spreading issue, demonstrating ultratrace toxin sensing in both water and organic liquid. Our SHP-OP SERS platform is able to concentrate analyte solutions in water and toluene to 100-fold and 8-fold smaller areas, respectively, as compared to its omniphilic counterparts. The synergy of analyte-concentrating ability and intense SERS-enhancing properties on our SHP-OP SERS platform enables quantitative and ultratrace detection of melamine and Sudan I down to 0.1 fmol in water and toluene, respectively, using just 1 μL of analyte solution. These detection limits are 10(3)-fold lower than the regulatory limits, clearly indicating our SHP-OP SERS platform as an appealing universal ultratrace toxin sensor. The ultratrace detection of spiked melamine in liquid milk down to 100 fmol also highlights the suitability of our SHP-OP SERS platform for the sensing of food toxins in real s les.
Publisher: American Chemical Society (ACS)
Date: 14-08-2017
DOI: 10.1021/JACS.7B04936
Abstract: We demonstrate a molecular-level observation of driving CO
Publisher: American Chemical Society (ACS)
Date: 24-06-2020
Publisher: Elsevier BV
Date: 06-2016
Publisher: Wiley
Date: 04-02-2015
Abstract: We demonstrate the fabrication of graphene liquid marbles as photothermal miniature reactors with precise temperature control for reaction kinetics modulation. Graphene liquid marbles show rapid and highly reproducible photothermal behavior while maintaining their excellent mechanical robustness. By tuning the applied laser power, swift regulation of graphene liquid marble's surface temperature between 21-135 °C and its encapsulated water temperature between 21-74 °C are demonstrated. The temperature regulation modulates the reaction kinetics in our graphene liquid marble, achieving a 12-fold superior reaction rate constant for methylene blue degradation than at room temperature.
Publisher: Wiley
Date: 19-04-2018
Publisher: American Chemical Society (ACS)
Date: 31-10-2017
Abstract: Miniaturizing the continuous multistep operations of a factory into a microchemical plant offers a safe and cost-effective approach to promote high-throughput screening in drug development and enforcement of industrial/environmental safety. While particle-assembled microdroplets in the form of liquid marble are ideal as microchemical plant, these platforms are mainly restricted to single-step reactions and limited to ex situ reaction monitoring. Herein, we utilize plasmonic liquid marble (PLM), formed by encapsulating liquid droplet with Ag nanocubes, to address these issues and demonstrate it as an ideal microchemical plant to conduct reaction-and-detection sequences on-demand in a nondisruptive manner. Utilizing a two-step azo-dye formation as our model reaction, our microchemical plant allows rapid and efficient diazotization of nitroaniline to form diazonium nitrobenzene, followed by the azo coupling of this intermediate with target aromatic compound to yield azo-dye. These molecular events are tracked in situ via SERS measurement through the plasmonic shell and further verified with in silico investigation. Furthermore, we apply our microchemical plant for ultrasensitive SERS detection and quantification of bisphenol A (BPA) with detection limit down to 10 amol, which is 50 000-fold lower than the BPA safety limit. Together with the protections offered by plasmonic shell against external environments, these collective advantages empower PLM as a multifunctional microchemical plant to facilitate small-volume testing and optimization of processes relevant in industrial and research contexts.
Publisher: Wiley
Date: 27-07-2020
Publisher: American Chemical Society (ACS)
Date: 22-09-2015
Abstract: Two-dimensional (2D) geometrical shape-shifting is prevalent in nature, but remains challenging in man-made "smart" materials, which are typically limited to single-direction responses. Here, we fabricate geometrical shape-shifting bovine serum albumin (BSA) microstructures to achieve circle-to-polygon and polygon-to-circle geometrical transformations. In addition, transformative two-dimensional microstructure arrays are demonstrated by the ensemble of these responsive microstructures to confer structure-to-function properties. The design strategy of our geometrical shape-shifting microstructures focuses on embedding precisely positioned rigid skeletal frames within responsive BSA matrices to direct their anisotropic swelling under pH stimulus. This is achieved using layer-by-layer two photon lithography, which is a direct laser writing technique capable of rendering spatial resolution in the sub-micrometer length scale. By controlling the shape, orientation and number of the embedded skeletal frames, we have demonstrated well-defined arc-to-corner and corner-to-arc transformations, which are essential for dynamic circle-to-polygon and polygon-to-circle shape-shifting, respectively. We further fabricate our shape-shifting microstructures in periodic arrays to experimentally demonstrate the first transformative 2D patterned arrays. Such versatile array configuration transformations give rise to structure-to-physical properties, including array porosity and pore shape, which are crucial for the development of on-demand multifunctional "smart" materials, especially in the field of photonics and microfluidics.
No related grants have been discovered for Hiang Kwee Lee.