GOVPH

Sex: Female
Education:

• Doctor of Philosophy in Physical Chemistry, University of California, Los Angeles
• Postdoctoral Fellow, Physical Chemistry, University of California, Berkeley
• Postdoctoral Fellow, Physical Chemistry, Columbia University in the City of New York

Field of Specialization:
Biomaterials
Nanotechnology
Physical Chemistry

Researches:

Article title: Hierarchical AgAu alloy nanostructures for highly efficient electrocatalytic ethanol oxidation
Authors: CaiqinWang, Danil Bukhvalov, M. Cynthia Goh, Yukou Du, Xiaofei Yang
Publication title: Chinese Journal of Catalysis, 43(3): 851-861, March 2022

Abstract:
The ethanol oxidation reaction is a significant anodic reaction for direct alcohol fuel cells. The most commonly used catalysts for this reaction are Pt-based materials; however, Pt-based electrocatalysts cause carbon monoxide poisoning with intermediates before the complete transformation of alcohol to CO2. Herein, we present hierarchical AgAu bimetallic nanoarchitectures for ethanol electrooxidation, which were fabricated via a partial galvanic reduction reaction between Ag and HAuCl4. The ethanol electrooxidation performance of the optimal AgAu nanohybrid was increased to 1834 mA mg−1, which is almost 10 times higher than that of the pristine Au catalyst (190 mA mg−1) in alkaline solutions. This was achieved by introducing Ag into the Au catalyst and controlling the time of the replacement reaction. The heterostructure also presents a higher current density than that of commercial Pt/C (1574 mA mg−1). Density functional theory calculations revealed that the enhanced activity and stability may stem from unavoidable defects on the surface of the integrated AgAu nanoarchitectures. Ethanol oxidation reactions over these defects are more energetically favorable, which facilitates the oxidative removal of carbonaceous poison and boosts the combination with radicals on adjacent Au active sites.
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Article title: Facile oxidation reaction to produce monolayered highly crystalline nitrogen-doped graphene quantum dots
Authors: Reece T. Lawrence, Cheng Lu, Mark P. Croxall, Kevin Yu, M.Cynthia Goh
Publication title: Applied Surface Science 578(2):151919, November 2021

Abstract:
Nitrogen-doped graphene quantum dots (NGQDs) made by standard hydrothermal synthesis route were found to produce non-uniform nanostructures that exhibit poor crystallinity and unstable optical properties. In this study, a simple post synthesis oxidation step was shown to significantly improve the overall crystallinity and stability of the nanostructures via removal of reaction by-products and oxidation of reactive functional groups, generating oxidized nitrogen-doped graphene quantum dots (Ox-NGQDs). Through transmission electron microscopy (TEM) and atomic force microscopy (AFM) the Ox-NGQDs were found to be uniform monolayered nanostructures with lateral size of 20-25nm. The appearance of G and D bands in the Raman spectrum of the Ox-NGQDs sample confirmed that the reaction by-products had been removed, and indicated that the Ox-NGQDs were composed of a highly ordered graphitic structure. X-ray photoelectron spectroscopy (XPS) indicated that oxidation of the surface functional groups took place. The Ox-NGQDs produced in this work gained a significant increase in visible absorbance, which is important in a wide range of potential light harvesting applications and uses.
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Article title: Ultra-stable Electrochemical Sensor for Detection of Caffeic Acid Based on Platinum and Nickel Jagged-Like Nanowires
Authors: Jin Wang, Beibei Yang, Fei Gao, Pingping Song, Lei Li, Yangping Zhang, Cheng Lu, M. Cynthia Goh & Yukou Du
Publication title: Nanoscale Research Letters 14(1), December 2019

Abstract:
Electrochemical sensors have the high sensitivity, fast response, and simple operation for applications in biological, medical, and chemical detection, but limited by the poor stability and high cost of the electrode materials. In this work, we used PtNi lagged-like nanowire for caffeic acid (CA) electrochemical detection. The removal of outer layer Ni during reaction process contributed to the rehabilitation of active Pt sites at the surface, leading to the excellent electrocatalytic behavior of CA sensing. Carbon-supported PtNi-modified glassy carbon electrode (PtNi/C electrode) showed a broad CA detecting range (from 0.75 to 591.783 μM), a low detection limit (0.5 μM), and excellent stability. The electrode preserved high electrocatalytic performance with 86.98% of the initial oxidation peak current retained after 4000 potential cycles in 0.5 mM caffeic acid solution. It also demonstrates excellent anti-interference capability and is ready for use in the real sample analysis. Electronic supplementary material The online version of this article (10.1186/s11671-018-2839-0) contains supplementary material, which is available to authorized users.
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Article title: Simply synthesized nitrogen-doped graphene quantum dot (NGQD)-modified electrode for the ultrasensitive photoelectrochemical detection of dopamine
Authors: Jin Wang, Cheng Lu, Tingting Chen, Lanping Hu, Yukou Du, Yong Yao and M. Cynthia Goh
Publication title: Nanophotonics 9(12), November 2019

Abstract:
Recently, nitrogen-doped graphene quantum dots (NGQDs), as a new type of quantum semiconductor and photoelectrochemical material, are promising candidates in photoelectric sensing, water splitting, and biological imaging and have various potential application prospects. In this work, NGQDs were prepared by a simple calcination method, and then a photoelectrochemical sensing platform based on the NGQDs electrode with superior photoelectrochemical activity was designed and fabricated for the detection of dopamine (DA). Benefitting from the quantum effect and size effect, NGQDs displayed an enhanced photocurrent effective within ultra-low detection limit (0.03 μm), wide detection range (0.03–450 and 450–9680 μm), and high sensitivity in detecting DA with the assistance of ultraviolet light irradiation. The NGQDs electrode also showed continuous and stable photocurrent densities after long-term experiment, indicating the excellent durability of NGQDs for DA detection.
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Article title: 1H NMR as a Quick Screen for Photocatalytic Reaction Efficiency
Authors: Mark P. Croxalla, Reece T. Lawrence, M. Cynthia Goh
Publication title: Journal of Photochemistry and Photobiology A: Chemistry 382:111965, July 2019

Abstract:
1H NMR is a common technique for tracking chemical reactions; here it is demonstrated that it can be used effectively to evaluate efficiency of photocatalysts. The photocatalytic degradation of acetylsalicylic acid (Aspirin) by P25 TiO2 and its photolytic degradation by UV light were examined; and they were found to be comparable, suggesting that this breakdown reaction does not benefit greatly from the catalyst’s presence. Due to its chemical specificity, 1H NMR enables identification of breakdown products, which is a useful consideration in wastewater treatment and mechanistic studies.
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Article title: Anchoring Gold Nanoparticles on Poly(3,4-ethylenedioxythiophene) (PEDOT) Nanonet as Three-dimensional Electrocatalysts toward Ethanol and 2-propanol Oxidation
Authors: Caiqin Wang, Ke Zhang, Hui Xu, Yukou Du, M. Cynthia Goh
Publication title: Journal of Colloid and Interface Science 541, April 2019

Abstract:
Renewable alcohol oxidation is of vital significance for clean energy conversion and storage. Here, we fabricated a three-dimensional (3D) nanonet-like hybrid catalyst combining Au nanoparticles and poly(3,4-ethylenedioxythiophene) (PEDOT) together, in which PEDOT nanonets act as the framework of the 3D catalyst and the support for the dispersion of Au nanoparticles. The catalyst was designated as Au-PEDOT. By using conductive carbon cloth (CC) as electrode substrates, the as-fabricated Au-PEDOT/CC electrodes were applied to evaluate the electrocatalytic activity towards ethanol and 2-propanol in the alkaline media, respectively. The catalytic activity on Au-PEDOT/CC in terms of the peak current and/or peak current density towards ethanol and 2-propanol oxidation is five times higher than that on comparative Au/CC catalysts, respectively, which is also higher than that on some similar materials reported in the literature. In addition, the Au-PEDOT/CC electrode also possessed great durability and reproducibility. This enhancement in electrocatalytic activity can be attributed to a number of factors: the nano-scale of the Au catalysts, the 3D nanostructure of the catalysts, the conductivity of PEDOT, as well as the effect of alkaline media. These results indicate the as-synthesized Au-PEDOT is a promising electrocatalyst for liquid fuel oxidation.
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Article title: Chemical Interaction in Nitrogen-Doped Graphene Quantum Dots/Graphitic Carbon Nitride Heterostructures with Enhanced Photocatalytic H 2 Evolution
Authors: Zhigang Mou,Cheng Lu,Kevin Yu,Hao Wu,Hui Zhang,Jianhua Sun,Mingshan Zhu,M. Cynthia Goh
Publication title: Energy Technology 7(3), March 2019

Abstract:
Strong electronic coupling between graphene quantum dots (GQDs) and graphitic carbon nitride (g‐C3N4) enables the multiple charge transfer pathways, offers a new approach for light harvesting and opens novel thrilling applications for carbon based materials. Herein, we designed a new nitrogen doped graphene quantum dots (NGQDs)/g‐C3N4 composite by stitching NGQDs with g‐C3N4 through thermal condensation approach, which conjugated via NGQDs‐lone pair electrons in ternary N ‐g‐C3N4 nanosheet (π‐p‐π) network. It's found that the H2 evolution rate under visible light (λ≥420 nm) irradiation with NGQDs/g‐C3N4 was nearly 7.7, 7.2, and 2.5 times than that of pristine g‐C3N4, the mxiture of NGQD and g‐C3N4, and non‐nitrogen doped GQDs/g‐C3N4 composite, respectively. Owing to better light harvesting in the NGQDs/g‐C3N4 composite, higher photocatalytic activities also were observed compared to others when they were illuminated by 520 and 550 nm light, respectively. It's demonstrated that the electronic coupling between NGQDs and g‐C3N4 generates new bands driving the charge transfer along the π‐p‐π network and extending the visible light response range.
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Article title: Whole-field macro- and micro-deformation characteristic of unbound water-loss in dentin hard tissue
Authors: Zhenning Chen,Bobby Nadeau,Kevin Yu,Xinxing Shao,Xiaoyuan He,M. Cynthia Goh,Anil Kishen
Publication title: Journal of Biophotonics 11(9):e201700368, April 2018

Abstract:
High-resolution deformation measurements in a functionally graded hard tissue such as human dentin are essential to understand the unbound water-loss mediated changes and their role in its mechanical integrity. Yet a whole-field, 3-dimensional (3D) measurement and characterization of fully hydrated dentin in both macro- and micro-scales remain to be a challenge. This study was conducted in 2 stages. In stage-1, a stereo-digital image correlation approach was utilized to determine the water-loss and load-induced 3D deformations of teeth in a sagittal section over consecutively acquired frames, from a fully hydrated state to nonhydrated conditions for a period up to 2 hours. The macroscale analysis revealed concentrated residual deformations at the dentin-enamel-junction and the apical regions of root in the direction perpendicular to the dentinal tubules. Significant difference in the localized deformation characteristics was observed between the inner and outer aspects of the root dentin. During quasi-static loadings, further increase in the residual deformation was observed in the dentin. In stage-2, dentin microstructural variations induced by dynamic water-loss were assessed with environmental scanning electron microscopy and atomic force microscopy (AFM), showing that the dynamic water-loss induced distention of dentinal tubules with concave tubular edges, and concurrent contraction of intertubular dentin with convex profile. The findings from the current macro- and micro-scale analysis provided insight on the free-water-loss induced regional deformations and ultrastructural changes in human dentin.
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Article title: Universal Aqueous Synthesis of Ultra-small Polymer-templated Nanoparticles: Synthesis Optimization Methodology for Counterion-collapsed Poly(acrylic acid)
Authors: Nari Kim, Calvin C.H. Cheng, and M. Cynthia Goh
Publication title: Canadian Journal of Chemistry 96(2), November 2017

Abstract:
A long polyelectrolyte chain collapses into a nano-sized particle upon the addition of counterions under appropriate solution conditions. This phenomenon forms the basis for a simple universal method for aqueous synthesis of ultra-small (<10 nm) metal, metal oxide, and other types of nanoparticles in the following manner: the counterion-collapsed polyelectrolyte chains are made stable by crosslinking, effectively trapping the counterions, which are subsequently chemically modified, to form metal nanoparticles via reduction or metal oxides nanoparticles via oxidation, within the collapsed polymer nanoparticle. This highly versatile platform methodology can be applied to almost any polyelectrolyte-counterion pair, making possible the rapid development of syntheses of different nanoparticles within the same chemical environment. Using poly(acrylic acid) as a model system, a methodology for the optimization of conditions for the polyelectrolyte collapse by various mono-and multi-valent metal cations is developed. The optimal counterion concentration did not correlate with ionic strength and metal ion valency and was highly variable from system to system. By monitoring the polyelectrolyte conformation using viscosity and turbidity measurements, the appropriate metal ion concentration for each nanoparticle system was determined.
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Article title: High Efficiency Photoelectrocatalytic Methanol Oxidation on CdS Quantum Dots Sensitized Pt Electrode
Authors: Chunyang Zhai, Mingshan Zhu, Fenzhi Pang, Duan Bin, Cheng Lu, M. Cynthia Goh, Ping Yang, and Yukou Du
Publication title: ACS Applied Materials & Interfaces 8(9), February 2016

Abstract:
A cadmium sulfide quantum dots sensitized Pt (Pt-CdS) composite was synthesized using a solvothermal method and characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV-vis diffuse reflectance spectroscopy. The catalytic properties of the as-prepared electrode for methanol oxidation were evaluated by cyclic voltammetry (CV), chronoamperometry, electrochemical impedance spectrum (EIS) and photocurrent responses. The as-prepared Pt-CdS electrode displayed a significant enhancement in the electrocatalytic activity and stability for methanol oxidation in the presence of visible light irradiation. The synergistic effect of both the electro- and photo- catalytic reaction contributes to this enhanced catalytic performance. Our result suggests a new paradigm to construct photoelectrocatalysts with high performance and good stability for direct methanol fuel cells with the assistance of visible-light illumination.
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Article title: A New Method to Synthesize S-Doped TiO2 with Highly Efficient and Stable Indoor Sunlight Photocatalytic Performance
Authors: Mingshan Zhu, Chunyang Zhai, Liqun Qiu, Cheng Lu, Andrew S. Paton, Yukou Du, and M. Cynthia Goh
Publication title: ACS Sustainable Chemistry & Engineering 3(12), November 2015

Abstract:
In this paper, we report a new, low-cost, and facile solvothermal approach to synthesize visible-light-active S-doped TiO2 (S-TiO2) by using dimethyl sulfoxide (DMSO) as both the S source and the solvent. Energy-dispersive X-ray (EDX) and X-ray photoelectron spectroscopy (XPS) solidly confirmed the presence of S element in the final product. The as-prepared S-TiO2 nanoparticles exhibited excellent and long-term stable photocatalytic performance for the degradation of organic pollutants under visible and indoor sunlight illumination. The catalyst still maintained high photoactivity even after several months of exposure to the indoor sunlight irradiation. This result suggests a new approach to achieve stable and highly efficient solar light driven photocatalysts for water purification.
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Article title: White/blue-emitting, water-dispersible CdSe quantum dots prepared by counter ion-induced polymer collapse
Authors: Jing Wang, Jane Betty Goh, M. Cynthia Goh, Neeraj Kumar Giri, Matthew F. Paige
Publication title: Optical Materials 47:420-427, September 2015

Abstract:
The synthesis and characterization of water-dispersible, luminescent CdSe/ZnS semiconductor quantum dots that exhibit nominal “white” fluorescence emission and have potential applications in solid-state lighting is described. The nanomaterials, prepared through counter ion-induced collapse and UV cross-linking of high-molecular weight polyacrylic acid in the presence of appropriate aqueous inorganic ions, were of ∼2–3 nm diameter and could be prepared in gram quantities. The quantum dots exhibited strong luminescence emission in two bands, the first in the blue-region (band edge) of the optical spectrum and the second, a broad emission in the red-region (attributed to deep trap states) of the optical spectrum. Because of the relative strength of emission of the band edge and deep trap state luminescence, it was possible to achieve visible white luminescence from the quantum dots in aqueous solution and in dried, solid films. The optical spectroscopic properties of the nanomaterials, including ensemble and single-molecule spectroscopy, was performed, with results compared to other white-emitting quantum dot systems described previously in the literature.
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Article title: Angiopoietin-1 peptide QHREDGS promotes osteoblast differentiation, bone matrix deposition and mineralization on biomedical materials
Authors: Nicole T. Feric, Calvin C. H. Cheng, M. Cynthia Goh, Vyacheslav Dudnyk, Val Di Tizio and Milica Radisic
Publication title: Biomaterials Science 2(10), June 2014

Abstract:
Bone loss occurs as a consequence of a variety of diseases as well as from traumatic injuries, and often requires therapeutic intervention. Strategies for repairing and replacing damaged and/or lost bone tissue include the use of biomaterials and medical implant devices with and without osteoinductive coatings. The soluble growth factor angiopoietin-1 (Ang-1) has been found to promote cell adhesion and survival in a range of cell types including cardiac myocytes, endothelial cells and fibroblasts through an integrin-dependent mechanism. Furthermore, the short sequence QHREDGS has been identified as the integrin-binding sequence of Ang-1, and as a synthetic peptide it has been found to show similar integrin-dependent effects as Ang-1 in the aforementioned cell types. Integrins have been implicated in osteoblast differentiation and bone mineralization, processes critical to bone regeneration. By binding integrins on the osteoblast surface, QHREDGS could promote cell survival and adhesion, as well as conceivably osteoblast differentiation and bone mineralization. Here we immobilized QHREDGS onto polyacrylate (PA)-coated titanium (Ti) plates and polyethylene glycol (PEG) hydrogels. The osteoblast differentiation marker, alkaline phosphatase, peaked in activity 4–12 days earlier on the QHREDGS-immobilized PA-coated Ti plates than on the unimmobilized, DGQESHR (scrambled)- and RGDS-immobilized surfaces. Significantly more bone matrix was deposited on the QHREDGS-immobilized Ti surface than on the other surfaces as determined by atomic force microscopy. The QHREDGS-immobilized hydrogels also had a significantly higher mineral-to-matrix (M/M) ratio determined by Fourier transform infrared spectroscopy. Alizarin Red S and von Kossa staining and quantification, and environmental scanning electron microscopy showed that while both the QHREDGS- and RGDS-immobilized surfaces had extensive mineralization relative to the unimmobilized and DGQESHR-immobilized surfaces, the mineralization was more considerable on the QHREDGS-immobilized surface, both with and without the induction of osteoblast differentiation. Finally, treatment of cell monolayers with soluble QHREDGS was demonstrated to upregulate osteogenic gene expression. Taken together, these results demonstrate that the QHREDGS peptide is osteoinductive, inducing osteoblast differentiation, bone matrix deposition and mineralization.
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Article title: Synthesis of water-soluble luminescent poly(acrylic acid)-encapsulated CdTe/CdS nanoparticles
Authors: Jane Betty Goh, Richard W. Loo, and M. Cynthia Goh
Publication title: Canadian Journal of Chemistry 92(1), January 2014

Abstract:
Described is the synthesis in water under ambient conditions of water-soluble, luminescent poly(acrylic acid)-encapsulated CdTe/CdS nanoparticles. Counterion-collapsed poly(acrylic acid) is used as a nanotemplate for the formation of the quantum dot core. Gram quantities of nanoparticles are easily obtained. Simply varying the amount of thioacetamide used in the synthesis can shift the emission wavelengths of the resulting nanoparticles from green to yellow to red.
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Article title: In vitro Synthesis of Native, Fibrous Long Spacing and Segmental Long Spacing Collagen
Authors: Richard W. Loo, Jane Betty Goh, Calvin C.H. Cheng, Ning Su, M. Cynthia Goh
Publication title: Journal of Visualized Experiments, September 2012

Abstract:
Collagen fibrils are present in the extracellular matrix of animal tissue to provide structural scaffolding and mechanical strength. These native collagen fibrils have a characteristic banding periodicity of ~67 nm and are formed in vivo through the hierarchical assembly of Type I collagen monomers, which are 300 nm in length and 1.4 nm in diameter. In vitro, by varying the conditions to which the monomer building blocks are exposed, unique structures ranging in length scales up to 50 microns can be constructed, including not only native type fibrils, but also fibrous long spacing and segmental long spacing collagen. Herein, we present procedures for forming the three different collagen structures from a common commercially available collagen monomer. Using the protocols that we and others have published in the past to make these three types typically lead to mixtures of structures. In particular, unbanded fibrils were commonly found when making native collagen, and native fibrils were often present when making fibrous long spacing collagen. These new procedures have the advantage of producing the desired collagen fibril type almost exclusively. The formation of the desired structures is verified by imaging using an atomic force microscope.
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Article title: Direct visualization of the formation of RecA/dsDNA complexes at the single-molecule level
Authors: Bing Shi Li, Bo Wei, M. Cynthia Goh
Publication title: Micron 43(10):1073-5, May 2012

Abstract:
The assembly of RecA on linear dsDNA with ATPγS in the reaction was elucidated using atomic force microscopy (AFM) on a single-molecule level. It was found that assembly generally (∼95%) proceeded from a single nucleation site that started from one end of the DNA strand. About 5% of the complexes were formed starting either from both ends or from the middle of dsDNA strand. In all these cases, the RecA coating was contiguous for each region suggesting the binding of RecA to DNA is cooperative. The AFM observation provides direct experimental evidence to show how RecA binds to linear dsDNA in the presence of ATPγS.
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Article title: Note: A scanning electron microscope sample holder for bidirectional characterization of atomic force microscope probe tips
Authors: Alon Eisenstein and M. Cynthia Goh
Publication title: The Review of scientific instruments 83(3):036108, March 2012

Abstract:
A novel sample holder that enables atomic force microscopy (AFM) tips to be mounted inside a scanning electron microscopy (SEM) for the purpose of characterizing the AFM tips is described. The holder provides quick and easy handling of tips by using a spring clip to hold them in place. The holder can accommodate two tips simultaneously in two perpendicular orientations, allowing both top and side view imaging of the tips by the SEM. (C) 2012 American Institute of Physics.
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