30 results on '"Wing-Cheung Law"'
Search Results
2. Corrigendum to 'Bismuth-doped gadolinium oxide films for UV-Vis multicolor conversion: Combined XPS, DFT and photoluminescence study' [J. Alloys Compd. 949, (2023), 169815]
- Author
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Anatoly F. Zatsepin, Yulia A. Kuznetsova, Dmitry A. Zatsepin, Chi-Ho Wong, Wing-Cheung Law, Chak-Yin Tang, Nikolay V. Gavrilov, and Danil W. Boukhvalov
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Mechanics of Materials ,Mechanical Engineering ,Materials Chemistry ,Metals and Alloys - Published
- 2023
3. Development of poly(vinyl alcohol)/starch/ethyl lauroyl arginate blend films with enhanced antimicrobial and physical properties for active packaging
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Zeguang Zhou, Yang Chen, Nannan Li, Fuqi Wu, Chak Yin Tang, Wing Cheung Law, and Lei Zhong
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chemistry.chemical_classification ,Vinyl alcohol ,Chemical Phenomena ,Starch ,Food Packaging ,Active packaging ,Biocompatible Materials ,Membranes, Artificial ,General Medicine ,Polymer ,Arginine ,Biochemistry ,Acetic acid ,chemistry.chemical_compound ,Anti-Infective Agents ,chemistry ,Structural Biology ,Polyvinyl Alcohol ,Fourier transform infrared spectroscopy ,Antibacterial activity ,Molecular Biology ,Mechanical Phenomena ,Antibacterial agent ,Nuclear chemistry - Abstract
Active packaging films have emerged as alternatives to replace petroleum-based packaging materials. In this work, poly(vinyl alcohol) (PVA)/starch/ethyl lauroyl arginate (LAE) films possessing enhanced properties were prepared. Scanning electron microscopy (SEM) showed that PVA and starch were compatible, the concentrations of LAE greatly affected the structural integrity. Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction showed that the inclusion of LAE did not significantly affect the intermolecular interactions and crystal structures of the polymer matrix. With an increase of the LAE content, the tensile strength (TS) was slightly decreased due to the altered microstructures, the elongation at break (EB) significantly increased ascribed to the synergistic effect of acetic acid, glycerol and LAE. The values of TS and EB were 17.25 MPa and 586.08%, respectively when LAE was 10%. Active films showed good barrier properties from UV while retaining the transmittance in the visible light region. The films containing 1% of LAE exhibited antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), the inhibition zone of bacterial growth gradually expanded with increasing LAE content. This study demonstrates the potential of using LAE as the antibacterial agent for synthesizing natural-based polymeric films for active packaging applications.
- Published
- 2021
4. Bismuth-doped gadolinium oxide films for UV-Vis multicolor conversion: Combined XPS, DFT and photoluminescence study
- Author
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Anatoly A. Zatsepin, Yulia A. Kuznetsova, Dmitry A. Zatsepin, Chi Ho Wong, Wing-Cheung Law, Chak-Yin Tang, Nikolay V. Gavrilov, and D. W. Boukhvalov
- Subjects
History ,Polymers and Plastics ,Mechanics of Materials ,Mechanical Engineering ,Materials Chemistry ,Metals and Alloys ,Business and International Management ,Industrial and Manufacturing Engineering - Published
- 2023
5. Photodegradable and pH responsive nanocapsules encapsulated with upconversion nanoparticles for diagnosis and treatment
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Xiaotao Wang, Wei Hu, Yebin Yang, Yonggui Liao, Wing-Cheung Law, and Chak-Yin Tang
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Polymers and Plastics ,Organic Chemistry ,Materials Chemistry ,General Physics and Astronomy - Published
- 2023
6. A mitochondrion-targeting two-photon photosensitizer with aggregation-induced emission characteristics for hypoxia-tolerant photodynamic therapy
- Author
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Yihang Jiang, Wei Zhu, Zhourui Xu, Zhijun Zhang, Shuo Tang, Miaozhuang Fan, Zhengzheng Li, Jianyu Zhang, Chengbin Yang, Wing-Cheung Law, Ken-Tye Yong, Dong Wang, Gaixia Xu, and Ben Zhong Tang
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General Chemical Engineering ,Environmental Chemistry ,General Chemistry ,Industrial and Manufacturing Engineering - Published
- 2022
7. Near-infrared and pH responsive molecular machine for controlled encapsulation and release of drugs
- Author
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Xiaotao Wang, Zhuofan Chen, Yebin Yang, Huiling Guo, Yingkui Yang, Chak-Yin Tang, Xuefeng Li, and Wing-Cheung Law
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Polymers and Plastics ,Organic Chemistry - Published
- 2022
8. Towards a consistent methodology for testing the electromechanical performance of strip polymer composite actuators
- Author
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Yuqing Dong, Ka-Wai Yeung, Wing-Cheung Law, Gary Chi-Pong Tsui, Xiaolin Xie, and Chak-Yin Tang
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Computer Science::Robotics ,Bending evaluation ,TP1080-1185 ,Polymers and Plastics ,Computer Science::Systems and Control ,Actuator ,Organic Chemistry ,Polymers and polymer manufacture ,Least-square method ,Computer Science::Other ,Interpolation - Abstract
Strip actuators have attracted tremendous attention in bionics due to the controllable deformation under various stimuli. However, it is currently hard to compare their performance owing to the different approaches for evaluating their actuation. Most of the studies determine the maximum or average value of the bending angle or strain, the deformation profile of the entire actuator strip was not quantified. In this study, a versatile method was proposed to evaluate the bending profile of typical strip actuators with bending deformation, thus analyzing the actuation performance. This method has been verified by synthetic curves, and less than 2% of global error was found. We have also demonstrated the implementation of this method for examining the actuation of typical strip actuators and showed that it can also be used for comparing the performance of different actuators prepared from other studies.
- Published
- 2022
9. Processing and characterisation of carbon nanotube-reinforced magnesium alloy composite foams by rapid microwave sintering
- Author
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Gary Chi-Pong Tsui, Wing Cheung Law, Man-Tik Choy, Ling Chen, Akeem Damilola Akinwekomi, Xusheng Yang, and Chak Yin Tang
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Materials science ,Mechanical Engineering ,Alloy ,Composite number ,Sintering ,02 engineering and technology ,Carbon nanotube ,engineering.material ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,0104 chemical sciences ,law.invention ,Mechanics of Materials ,law ,Powder metallurgy ,engineering ,General Materials Science ,Magnesium alloy ,Composite material ,0210 nano-technology ,Porosity ,Susceptor - Abstract
The present study proposes an efficient processing scheme for fabricating carbon nanotubes (CNTs)-reinforced magnesium (Mg) alloy AZ61 composite foams with enhanced compressive and energy absorption properties. The scheme combines powder metallurgy, rapid microwave (MW) sintering, and pore wall reinforcement to overcome the low strength, non-uniform pore structure, prolonged sintering process, and high production cost associated with conventional unreinforced Mg-based foams. In the proposed scheme, a dual-stage mixing method is used to homogeneously disperse and incorporate CNTs into the matrix for strength enhancement, and susceptor role, and carbamide granules are used to control the pore size and porosity fractions. In addition, MW sintering is used to rapidly consolidate the samples in 20 min through the synergy between an external and an internal susceptor (i.e. CNTs), which facilitates uniform and volumetric heating of the entire samples. Thus, sample oxidation and the formation of deleterious secondary phases are minimised, while up to 69% energy is saved. Experimental results show that the dispersion and incorporation of CNTs into the matrix, via the present processing scheme, clearly enhance the compressive and energy absorption properties of the composite foams, as compared with the unreinforced foams. The proposed processing scheme is a rapid and energy-saving efficient technique, which can be used to fabricate high quality Mg alloy composite foams with improved compression and energy absorption properties.
- Published
- 2018
10. In situ synthesis of osteoconductive biphasic ceramic coatings on Ti6Al4V substrate by laser-microwave hybridization
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Man-Tik Choy, Ling Chen, Wing Cheung Law, Gary Chi-Pong Tsui, Ka-Wai Yeung, and Chak Yin Tang
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Laser ablation ,Materials science ,Simulated body fluid ,Titanium alloy ,030206 dentistry ,02 engineering and technology ,Surfaces and Interfaces ,General Chemistry ,engineering.material ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Apatite ,Surfaces, Coatings and Films ,03 medical and health sciences ,0302 clinical medicine ,Coating ,visual_art ,Materials Chemistry ,visual_art.visual_art_medium ,engineering ,Surface modification ,Ceramic ,Composite material ,0210 nano-technology ,Micropatterning - Abstract
Microwave heating is an efficient alternative approach for synthetic chemistry with many distinctive advantages of high heating rate, selective and homogeneous heating. In this study, a new laser-microwave hybridization method, which comprises laser micropatterning, microwave heating and in situ synthesis has been developed to produce titania/hydroxyapatite/tricalcium phosphate (TiO 2 /HA/TCP) composite coating on titanium alloy (Ti6Al4V) substrate. The composite coating with a fine porous network microarchitecture was selectively produced on the Ti6Al4V surface by laser ablation and alkaline treatment. Using TiO 2 sol-gel and mixed powders of calcium carbonate (CaCO 3 ) and dicalcium phosphate dihydrate (CaHPO 4 ·2H 2 O), the composite coating synthesized at a temperature of 800 °C in a short time of 20 min exhibited homogeneous microstructure, strong hydrophilicity and good adhesion strength of 34 MPa. The in vitro apatite-forming capability of the coating was examined by immersing the coated Ti6Al4V specimen into a simulated body fluid (SBF) for up to 7 days. Biodissolution was observed in the early stage of incubation, followed by apatite precipitation. The quantity and size of the apatite globules increased over time. After 7 days of immersion, the coating surface was nearly covered by a layer of bone-like apatite, showing a significant improvement of its osteoconductive property over the uncoated sample. The laser-microwave hybridization provides an efficient route to synthesize HA/TCP based coatings for bioactivity enhancement, and serves as an effective sterilization tool for implant materials.
- Published
- 2017
11. Photo- and pH-responsive drug delivery nanocomposite based on o-nitrobenzyl functionalized upconversion nanoparticles
- Author
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Wing Cheung Law, Chuang Liu, Chak Yin Tang, Yebin Yang, Yonggui Liao, Junyong Xia, Xiaotao Wang, Zhuofan Chen, and Huiling Guo
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Nanocomposite ,Polymers and Plastics ,Chemistry ,Organic Chemistry ,technology, industry, and agriculture ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Controlled release ,Nanocapsules ,0104 chemical sciences ,Drug delivery ,Materials Chemistry ,Precipitation polymerization ,Irradiation ,0210 nano-technology ,Visible spectrum ,Template method pattern ,Nuclear chemistry - Abstract
A near infrared (NIR) and pH dual-responsive nanocomposite, composed of a lanthanide-doped upconversion nanoparticle (UCNP) core and a transformable poly-o-nitrobenzyl shell, was prepared by the distillation precipitation polymerization and template method. The poly-o-nitrobenzyl shell can undergo hydrophobic-hydrophilic transformation upon an irradiation of 980 nm, rendering the capability of NIR-activated drug release. The anticancer drug, doxorubicin (DOX), can be loaded into these nanocomposites with a loading efficiency of 7.23 wt%. Furthermore, pH responsiveness caused by the hydrogen bond and charge interactions between DOX and nanocapsules can trigger the release of drugs at low pH. Under visible light irradiation and neutral (pH 7.4) conditions, the cumulative release of DOX was only 8.35% after 300 min, while it reached 59.5% under the synergistic effect of NIR irradiation and acidic conditions. The Baker-Lonsdale model was used to describe the drug release kinetics of this system, and the diffusion coefficient (3DCs/r02C0) and R2 under different conditions were determined to be 4.15 × 10−6 and 0.98 (pH 7.4 and visible light), 2.64 × 10−5 and 0.99 (NIR light), 3.26 × 10−5 and 0.97 (pH 4.5 and visible light), 2.59 × 10−4 and 0.99 (pH 4.5 and NIR light), respectively. This controlled release feature makes the nanocomposite a promising therapeutic agent for treating diseases.
- Published
- 2021
12. Fabrication of monodisperse drug-loaded poly(lactic-co-glycolic acid)–chitosan core-shell nanocomposites via pickering emulsion
- Author
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Chak Yin Tang, Dazhu Chen, Jiaxin Wang, Wing Cheung Law, and Ling Chen
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Materials science ,Mechanical Engineering ,Dispersity ,technology, industry, and agriculture ,macromolecular substances ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Industrial and Manufacturing Engineering ,Pickering emulsion ,0104 chemical sciences ,Chitosan ,chemistry.chemical_compound ,PLGA ,chemistry ,Mechanics of Materials ,Drug delivery ,Emulsion ,Ceramics and Composites ,Composite material ,0210 nano-technology ,Drug carrier ,Dispersion (chemistry) - Abstract
Pickering emulsion, in which the oil–water emulsion interface is stabilised by colloids, has emerged as a promising approach for the preparation of drug delivery systems in the biomedical field. In this study, Pickering emulsion and solvent evaporation were incorporated with high-intensity ultrasonication to successfully fabricate biodegradable poly(lactic-co-glycolic acid) (PLGA)–chitosan core-shell nanocomposites (PLGA-CS) with a narrow size distribution. Our strategy was based on using aqueous-phase chitosan colloids to stabilise the hydrophobic PLGA core without the addition of molecular surfactants or chemical cross-linkers. The use of high-intensity ultrasonication was found to facilitate the efficient dispersion of emulsion droplets so that the particle size of PLGA-CS (255.1–824.8 nm) could be controlled with the application of different amplitudes. A low amplitude (20% of total power) enables the formation of drug-loaded PLGA-CS with a small diameter (255.1 nm) and a high level of monodispersity (polydispersity index, 0.078). The PLGA core allows hydrophobic drugs to be loaded and is encapsulated in a chitosan shell that offers two functions: (i) dispersion of PLGA in an aqueous solution and (ii) modulation of in vitro drug release. Our results reveal that the modified strategy shows promise for the design and preparation of monodisperse polymer-based drug carriers.
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- 2017
13. Enhancing the cell proliferation performance of NiTi substrate by laser diffusion nitriding
- Author
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Nanxi Rao, Wing Cheung Law, Xiaomei Wang, Hau Chung Man, Chi Ho Ng, Tai Lok Cheung, Gaixia Xu, and Fai Tsun Cheng
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Materials science ,Biocompatibility ,02 engineering and technology ,engineering.material ,010402 general chemistry ,01 natural sciences ,law.invention ,Contact angle ,Coating ,law ,Materials Chemistry ,Composite material ,Metallurgy ,Surfaces and Interfaces ,General Chemistry ,Shape-memory alloy ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Laser ,0104 chemical sciences ,Surfaces, Coatings and Films ,Nickel titanium ,engineering ,Wetting ,0210 nano-technology ,Nitriding - Abstract
Nickel-titanium (NiTi) shape memory alloy is one of the popular implant materials in orthopaedic applications due to its special mechanical properties. However, the presence of Ni has raised safety concerns and hence limited its applications. In the present study, this issue was addressed through laser diffusion nitriding on NiTi to form TiN coating on the surface. Optimum laser parameters to produce desirable surface without changing the surface topography of NiTi substrate were determined. This paper detailed the nitriding of NiTi by fiber laser for enhancing the hydrophilicity and biological performance. The laser treated surfaces were characterized by scanning-electron microscopy (SEM) and X-ray diffraction (XRD). The wettability and cell viability performance were studied using contact angle measurement and MTT assay. The results demonstrated that an optimized laser treated surface could lead to improvements in biocompatibility of NiTi.
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- 2017
14. Shape memory effect of thermal-responsive nano-hydroxyapatite reinforced poly-d-l-lactide composites with porous structure
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Chak Yin Tang, Ling Chen, Da Zhu Chen, Jia Xin Wang, and Wing Cheung Law
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chemistry.chemical_classification ,Nanocomposite ,Materials science ,Mechanical Engineering ,Composite number ,02 engineering and technology ,Dynamic mechanical analysis ,Polymer ,Shape-memory alloy ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Industrial and Manufacturing Engineering ,0104 chemical sciences ,Shape-memory polymer ,Differential scanning calorimetry ,chemistry ,Mechanics of Materials ,Ceramics and Composites ,Composite material ,0210 nano-technology ,Thermal analysis - Abstract
In this study, the effect of the inclusion of nano-hydroxyapatite (nano-HAp) and the porous structure on the shape memory behavior of poly- d - l -lactide (PDLLA) composites was investigated. Porous, thermal-responsive shape memory composites, PDLLA/nano-HAp, were prepared by a newly developed polymer coagulation, particulate leaching, and cold compression moulding technique. The inclusion of nano-HAp to PDLLA led to a higher shape memory transition temperature, improved mechanical strength and larger recovery force as compared with the neat PDLLA. The nanocomposite with 10 wt% of nano-HAp exhibited the best shape fixity and recoverability with the shortest recovery time. Further increase in the filler content of nano-HAp would reduce the recovery force and prolong the recovery time due to restriction in the movement of the amorphous PDLLA chain segments. The morphologies, thermal properties and shape memory behavior were measured by scanning electron microscopy, thermal gravimetric analyzer, differential scanning calorimeter, dynamic mechanical analysis, physical bending test and cyclic thermo-mechanical test. These results provide important information for designing biomedical devices using this novel type of bioabsorbable shape memory polymer composite.
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- 2016
15. Microstructure and compressive properties of silicon carbide reinforced geopolymer
- Author
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Chi Pong Tsui, Sui Sui Xie, Chak Yin Tang, Zhang Fang, Ling Chen, Fei Peng Du, and Wing Cheung Law
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Materials science ,Mechanical Engineering ,Whiskers ,Composite number ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Microstructure ,01 natural sciences ,Industrial and Manufacturing Engineering ,0104 chemical sciences ,Geopolymer ,chemistry.chemical_compound ,Compressive strength ,chemistry ,Mechanics of Materials ,Whisker ,Ceramics and Composites ,Silicon carbide ,Composite material ,0210 nano-technology ,Metakaolin - Abstract
Geopolymers have emerged as a promising alternative to ordinary cement due to their attractive physical and thermal properties. The typical compressive strength of geopolymers and their composites is usually limited to around 80 MPa, therefore they should be further strengthened for wider applications, such as ultrahigh strength concrete and bone replacement. This paper presents a facile method for enhancing the compressive strength by incorporating silicon carbide particles (SiCp) and silicon carbide whiskers (SiCw) into a geopolymer matrix via the geopolymerization of metakaolin (MK). The effects of the reinforcement of SiCp and SiCw on the microstructure, thermal properties and compressive properties of the composites were investigated. The SEM images showed that both SiCp and SiCw were well dispersed in the geopolymer matrix. Due to the bridging effect among the SiCw particles, the silicon carbide whisker/geopolymer (SiCw/GP) composites possessed higher porosity and lower density, and thus lower thermal stability and thermal conductivity as compared with the silicon carbide particle/geopolymer (SiCp/GP). The mechanical tests showed that the compressive strength of SiCp/GP composites increased with the increase of SiCp concentration. With an optimum concentration of 10 wt % of SiCp, the compressive strength of the composite was enhanced to 155 MPa, corresponding to a 100% increase as compared with the unfilled geopolymer.
- Published
- 2016
16. A new strategy for designing high-performance sulfonated poly(ether ether ketone) polymer electrolyte membranes using inorganic proton conductor-functionalized carbon nanotubes
- Author
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Guangjin Wang, Chak Yin Tang, Zheng Xuan, Zheng Genwen, Chi Pong Tsui, Wing Cheung Law, Hai Liu, Gong Chunli, Cheng Fan, and Sheng Wen
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Materials science ,Renewable Energy, Sustainability and the Environment ,Energy Engineering and Power Technology ,Proton exchange membrane fuel cell ,Nanoparticle ,02 engineering and technology ,Carbon nanotube ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Nanomaterials ,law.invention ,chemistry.chemical_compound ,Membrane ,Chemical engineering ,Boron phosphate ,chemistry ,law ,Polymer chemistry ,Thermal stability ,Electrical and Electronic Engineering ,Physical and Theoretical Chemistry ,0210 nano-technology ,Proton conductor - Abstract
Remarkable progress has been made on the use of polymer electrolyte membranes (PEMs) for renewable-energy-related research. In particular, carbon nanotubes (CNTs) have emerged as versatile nanomaterials to modify PEMs. However, the inert ionic conduction ability and possible short-circuiting risk are the two major obstacles to their further development. In this work, CNTs are firstly functionalized with an inorganic proton conductor, boron phosphate (BPO 4 ), using a facile polydopamine-assisted sol-gel method to yield BPO 4 @CNTs. This new additive is then used to modify sulfonated poly(ether ether ketone) (SPEEK). Polydopamine coating layer can act as an extraordinary glue to homogeneously adhere BPO 4 nanoparticles on CNTs, thereby not only reducing the risk of short-circuiting, but also fabricating new proton-conducting pathways in the composite membranes. A comprehensive characterization reveals that the thermal stability, tensile properties, and dimensional stability of PEMs are significantly improved. Compared with pure SPEEK, the proton conductivity of SPEEK/BPO 4 @CNTs-2 is improved by 45% and 150% at 20 °C and at 80 °C, respectively. Furthermore, the H 2 /O 2 cell performance of SPEEK/BPO 4 @CNTs-2 membrane exhibits a peak power density of 340.7 mW cm −2 at 70 °C, which is significantly better than that of pure SPEEK (254.2 mW cm −2 ), demonstrating the great potential of proton conductors-functionalized CNTs in PEMs.
- Published
- 2016
17. Rapid microwave sintering of carbon nanotube-filled AZ61 magnesium alloy composites
- Author
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Wing Cheung Law, Ling Chen, Chak Yin Tang, Chi-Pong Tsui, and Akeem Damilola Akinwekomi
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010302 applied physics ,Materials science ,Mechanical Engineering ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Indentation hardness ,Industrial and Manufacturing Engineering ,law.invention ,Compressive strength ,Mechanics of Materials ,law ,Powder metallurgy ,0103 physical sciences ,Volume fraction ,Ceramics and Composites ,Magnesium alloy ,Composite material ,0210 nano-technology ,Porosity ,Powder mixture ,Susceptor - Abstract
In this study, a powder metallurgy processing technique combined with rapid microwave sintering was used to synthesise carbon nanotubes (CNTs) filled AZ61 magnesium alloy composites under ambient conditions, without recourse to any secondary process. In order to determine the appropriate amount of CNTs for taking full advantage of the AZ61/CNTs composite, a powder mixture of the CNTs, in varying volume fractions of 1–3%, and the AZ61 alloy was prepared through a mechanical milling process. The optimized milling intensity allowed for reducing the powder size for effective microwave absorption, and thus improved the dispersion of the CNTs in the Mg alloy matrix without reducing the structural integrity of CNTs. In addition to the incorporation of the CNTs with the dual role of mechanical reinforcement and microwave susceptor, microwave sintering was achieved in only 8 min by using a synergetic combination of graphite and silicon carbide as microwave susceptors in a microwave furnace. The sintered samples, whose porosity ranged between 4 and 6%, were characterised for microstructural, hardness, compressive and fracture properties. The results of hardness and compression tests indicated that these properties of all the composites were significantly improved compared to the monolithic samples. The highest microhardness value (∼105% increment) was recorded for the composite with 3.0% volume fraction of CNTs, while the composite sample with 1.0% volume fraction of CNTs had the highest ultimate compressive yield strength and 0.2% offset yield strength with approximate increments of 59% and 127%, respectively. The failure mechanisms of the composites as compared with the monolithic samples were discussed.
- Published
- 2016
18. Investigating the crystallization behavior of poly(lactic acid) using CdSe/ZnS quantum dots as heterogeneous nucleating agents
- Author
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Xiaotao Wang, Xinghou Gong, Chunqing Li, Ling Chen, Ling Pan, Chonggang Wu, Chak Yin Tang, Xiaolin Xie, Chi Pong Tsui, and Wing Cheung Law
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chemistry.chemical_classification ,Materials science ,Nanocomposite ,Mechanical Engineering ,Nucleation ,Nanoparticle ,02 engineering and technology ,Polymer ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Industrial and Manufacturing Engineering ,0104 chemical sciences ,law.invention ,Crystallinity ,Differential scanning calorimetry ,chemistry ,Mechanics of Materials ,law ,Ceramics and Composites ,Crystallization ,Composite material ,0210 nano-technology ,Glass transition - Abstract
Heterogeneous nucleation is a frequently encountered phenomenon in the crystallization of inorganic nanoparticle/polymer systems, and has a great influence on the morphology and properties (such as optical, mechanical and degradable properties) of the nanocomposites. In this study, a solution casting method was adopted to fabricate CdSe–ZnS quantum dots (QDs)/poly(lactic acid) (PLA) nanocomposites films of various QDs concentrations by using chloroform as the solvent. Fourier transform infrared (FT-IR) spectroscopy, polarized optical microscopy (POM), differential scanning calorimetry (DSC), and X-ray diffractometry (XRD) were used to characterize the crystallization behavior of the nanocomposites films that had been thermally treated differently from the as-cast state. The FT-IR and POM results showed that the nucleation density and the crystallization ability of PLA are greatly enhanced with addition of the QDs in the processes of isothermal crystallization at 403 K. The results of DSC revealed that the glass transition temperature of PLA has no obvious change with the addition of QDs. For the QDs/PLA samples which were isothermally annealed at 403 K for 30 min, the degree of (melt) crystallinity increased with increase of QD concentrations in the PLA matrix. All the results obtained from FT-IR spectroscopy, POM, DSC, and XRD were consistent, suggesting that the CdSe–ZnS QDs can serve as an efficient heterogeneous nucleating agent for the acceleration and enhancement of the melt crystallization of PLA at the optimized condition.
- Published
- 2016
19. Microwave assisted-in situ synthesis of porous titanium/calcium phosphate composites and their in vitro apatite-forming capability
- Author
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Man Tik Choy, Chak Yin Tang, William W. Lu, Wing Cheung Law, Chi Pong Tsui, and Ling Chen
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Materials science ,Precipitation (chemistry) ,Mechanical Engineering ,Simulated body fluid ,Composite number ,Industrial and Manufacturing Engineering ,Apatite ,Calcium titanate ,chemistry.chemical_compound ,Compressive strength ,chemistry ,Mechanics of Materials ,visual_art ,Powder metallurgy ,Ceramics and Composites ,visual_art.visual_art_medium ,Atomic ratio ,Composite material - Abstract
Microwave irradiation has been proven to be an effective heating source in synthetic chemistry, and can accelerate the reaction rate, provide more uniform heating and help in developing better synthetic routes for the fabrication of bone-grafting implant materials. In this study, a new technique, which comprises microwave heating and powder metallurgy for in situ synthesis of Ti/CaP composites by using Ti powders, calcium carbonate (CaCO 3 ) powders and dicalcium phosphate dihydrate (CaHPO 4 ·2H 2 O) powders, has been developed. Three different compositions of Ti:CaCO 3 :CaHPO 4 ·2H 2 O powdered mixture were employed to investigate the effect of the starting atomic ratio of the CaCO 3 to CaHPO 4 ·2H 2 O on the phase, microstructural formation and compressive properties of the microwave synthesized composites. When the starting atomic ratio reaches 1.67, composites containing mainly alpha-titanium ( α -Ti), hydroxyapatite (HA), beta-tricalcium phosphate ( β -TCP) and calcium titanate (CaTiO 3 ) with porosity of 26%, pore size up to 152 μm, compressive strength of 212 MPa and compressive modulus of 12 GPa were formed. The in vitro apatite-forming capability of the composite was evaluated by immersing the composite into a simulated body fluid (SBF) for up to 14 days. The results showed that biodissolution occurred, followed by apatite precipitation after immersion in the SBF, suggesting that the composites are suitable for bone implant applications as apatite is an essential intermediate layer for bone cells attachment. The quantity and size of the apatite globules increased over the immersion time. After 14 days of immersion, the composite surface was fully covered by an apatite layer with a Ca/P atomic ratio approximately of 1.68, which is similar to the bone-like apatite appearing in human hard tissue. The results suggested that the microwave assisted- in situ synthesis technique can be used as an alternative to traditional powder metallurgy for the fabrication of Ti/CaP biocomposites.
- Published
- 2015
20. Flexible, stretchable and conductive PVA/PEDOT:PSS composite hydrogels prepared by SIPN strategy
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Ya Zhang, Yuqing Dong, Can Jiang, Chak Yin Tang, Ming Ming Guo, Fei Peng Du, Yun Fei Zhang, and Wing Cheung Law
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Materials science ,Polymers and Plastics ,Organic Chemistry ,Composite number ,Electronic skin ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Polyvinyl alcohol ,0104 chemical sciences ,chemistry.chemical_compound ,PEDOT:PSS ,chemistry ,Gauge factor ,Self-healing hydrogels ,Ultimate tensile strength ,Glutaraldehyde ,Composite material ,0210 nano-technology - Abstract
Stretchable conductive hydrogels have received significant attention due to their possibility of being utilized in wearable electronics and healthcare devices. In this work, a semi-interpenetrating polymer network (SIPN) strategy was employed to fabricate a set of flexible, stretchable and conductive composite hydrogels composed of polyvinyl alcohol (PVA) in the presence of glutaraldehyde as the crosslinker, HCl as the catalyst and poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) as the conductive medium. The results from FTIR, Raman, SEM and TGA indicate that a chemical crosslinking network and interactions of PVA and PEDOT:PSS exist in the SIPN hydrogels. The swelling ratio of hydrogels decreased with increasing content of PEDOT:PSS. Due to the chemical crosslinking network and interactions of PVA and PEDOT:PSS, PVA networks semi-interpenetrated with PEDOT:PSS exhibited excellent tensile and compression properties. The tensile strength and elongation at breakage of the composite hydrogels with 0.14 wt% PEDOT:PSS were 70 KPa and 239%, respectively. The compression stress of the composite hydrogels with 0.14 wt% PEDOT:PSS at a strain of 50% was about 216 KPa. The electrical conductivity of the hydrogels increased with increasing PEDOT:PSS content. The flexible, stretchable and conductive properties endow the composite hydrogel sensor with a superior gauge factor of up to 4.4 (strain: 100%). Coupling the strain sensing capability to the flexibility, good mechanical properties and high electrical conductivity, we consider that the designed PVA/PEDOT:PSS composite hydrogels have promising applications in wearable devices, such as flexible electronic skin and sensitive strain sensors.
- Published
- 2020
21. Melt extrudate swell behavior of graphene nano-platelets filled-polypropylene composites
- Author
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Shu-Xin Zhang, Q. Du, Chi Pong Tsui, J. Z. Liang, Wing Cheung Law, L. Y. Wei, and Chak Yin Tang
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Polypropylene ,Materials science ,Polymers and Plastics ,Organic Chemistry ,Composite number ,Die swell ,Atmospheric temperature range ,Shear rate ,chemistry.chemical_compound ,chemistry ,Shear stress ,Extrusion ,Composite material ,Mass fraction - Abstract
The extrudate swell ratios of polypropylene (PP) composite melts filled with graphene nano-platelets (GNPs) were measured using a capillary rheometer within a temperature range of 180–230 °C and apparent shear rate varying from 100 to 4000 s−1 in order to identify the effects of the filler content and test conditions on the melt die-swell behavior. It was found that the values of the extrudate swell ratio of the composites increased with increasing apparent shear rate, with the correlation between them obeying a power law relationship, while the values of the extrudate swell ratio decreased almost linearly with rise in temperature. The values of the melt extrudate swell ratio increased approximately linearly with increasing shear stress, and decreased roughly linearly with an increase of the GNP weight fraction. In addition, the extrudate swell mechanisms are discussed from the observation of the fracture surface of the extrudate using scanning electronic microscopy. This study provides a basis for further development of graphene reinforced polymer composites with desirable mechanical performance and good damage resistance.
- Published
- 2015
22. Electroactive shape memory polymer based on optimized multi-walled carbon nanotubes/polyvinyl alcohol nanocomposites
- Author
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Tian Han Shen, Fei Peng Du, Chak Yin Tang, En Zhou Ye, Wing Cheung Law, Wen Yang, Xingping Zhou, and Xiaolin Xie
- Subjects
chemistry.chemical_classification ,Materials science ,Nanocomposite ,Mechanical Engineering ,Shape-memory alloy ,Polymer ,Carbon nanotube ,Microstructure ,Casting ,Polyvinyl alcohol ,Industrial and Manufacturing Engineering ,law.invention ,Shape-memory polymer ,chemistry.chemical_compound ,chemistry ,Mechanics of Materials ,law ,Ceramics and Composites ,Composite material - Abstract
The development of shape memory polymers (SMPs) has gained remarkable attention due to their wide range of applications, from biomedical to electromechanical. In this work, we have developed and optimized an electroactive SMP based on polyvinyl alcohol/multi-walled carbon nanotubes (PVA/MWNTs) composites. When a constant voltage of 60 V was applied to the optimized sample, the polymer shape could be recovered to the original form within 35 s. Different weight fractions of MWNT/PVA composites were prepared by using a simple solution blending and transitional solution casting method, and their microstructures, electrical conductivities, thermal conductivities, and electroactive shape memory properties were investigated. According to our systematic analysis, the enhanced performance can be attributed to the reinforcement of MWNTs that led to the improved electrical and thermal conductivities of the PVA matrix.
- Published
- 2015
23. Preparation, optical and thermal properties of CdSe–ZnS/poly(lactic acid) (PLA) nanocomposites
- Author
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Zhonghua Hao, Wing Cheung Law, Ling Pan, Chi Pong Tsui, Xiaotao Wang, Chonggang Wu, Chak Yin Tang, Xinghou Gong, and Ling Chen
- Subjects
Thermogravimetric analysis ,Photoluminescence ,Nanocomposite ,Materials science ,Mechanical Engineering ,Nucleation ,Industrial and Manufacturing Engineering ,law.invention ,Differential scanning calorimetry ,Mechanics of Materials ,Quantum dot ,law ,Transmission electron microscopy ,Ceramics and Composites ,Composite material ,Crystallization - Abstract
In this study, CdSe–ZnS/poly(lactic acid) (PLA) nanocomposite films, containing different concentrations of surface-modified CdSe–ZnS quantum dots (QDs), were prepared via a solution casting method. The optical microstructural and thermal properties of the as-prepared QDs/PLA films were investigated. The QDs/PLA films exhibited strong and stable photoluminescence (PL) intensity with concentration dependent amplitudes. The transmission electron microscopy (TEM) pictures revealed that QDs of ∼5 nm diameter were uniformly dispersed in the PLA matrix. According to the results of thermogravimetric analysis, the weight-loss onset temperature of PLA clearly decreased with the QD content. A combination of Fourier transform infrared (FT-IR) spectroscopy, X-ray diffractometry (XRD) and differential scanning calorimetry (DSC) results suggested that the QDs exhibit obvious nucleation activity on the crystallization behavior of the PLA matrix. This research provides useful information to the foundations of practical applications of QDs/PLA nanocomposites as fluorescent and biodegradable functionalized materials.
- Published
- 2014
24. Multimodal nanoparticles that provide immunomodulation and intracellular drug delivery for infectious diseases
- Author
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Gene D. Morse, Paras N. Prasad, Jessica L. Reynolds, Admire Dube, Charles C. Maponga, and Wing Cheung Law
- Subjects
Male ,Drug ,media_common.quotation_subject ,Biomedical Engineering ,Pharmaceutical Science ,Medicine (miscellaneous) ,Bioengineering ,Biology ,Monocytes ,Microbiology ,Mycobacterium tuberculosis ,chemistry.chemical_compound ,Drug Delivery Systems ,Immune system ,Polylactic Acid-Polyglycolic Acid Copolymer ,Humans ,Immunologic Factors ,Tuberculosis ,General Materials Science ,Secretion ,Lactic Acid ,media_common ,Chitosan ,biology.organism_classification ,PLGA ,chemistry ,Cytokines ,Nanoparticles ,Molecular Medicine ,Female ,Cytokine secretion ,Tumor necrosis factor alpha ,Polyglycolic Acid ,Intracellular - Abstract
Infectious diseases are a worldwide health concern. For some infections, a common feature is the intracellular residence of the pathogen and evasion of the host immune response. In the case of tuberculosis (TB), Mycobacterium tuberculosis evades clearance within macrophages through suppression of intracellular reactive oxygen and nitrogen species (ROS/RNS) and pro-inflammatory cytokines. We propose new nanoparticle designs for infectious diseases, functionalized with ligands able to modulate the cellular immune response and concurrently deliver drug. We have designed 1,3-β-glucan functionalized chitosan shell, poly(lactide)co-glycolide core nanoparticles to stimulate ROS/RNS, pro-inflammatory cytokine secretion, and delivery of rifampicin inside human alveolar like macrophages (ALM). Nanoparticles significantly enhanced ALM secretion of IL-12p70 (2.9-fold), TNF-α (16-fold) and INF-γ (23-fold) compared to controls over 24h, and doubled ROS/RNS generation over 6h. Nanoparticles could deliver 4-fold greater rifampicin into ALM compared to rifampicin solution. These results provide proof-of-concept of multimodal nanoparticles and support their further development. From the Clinical Editor In this paper, a new nanoparticle design is proposed to address hard to treat infectious diseases such as TB, through the use of nanoparticles functionalized with ligands that are able to concurrently modulate the cellular immune response and deliver a drug. The authors have designed 1,3-β-glucan functionalized chitosan shell - poly(lactide)co-glycolide core nanoparticles to stimulate reactive oxygen and nitrogen species production, pro-inflammatory cytokine secretion, and delivery of rifampicin inside human alveolar-like macrophages.
- Published
- 2014
25. Phospholipid micelle-based magneto-plasmonic nanoformulation for magnetic field-directed, imaging-guided photo-induced cancer therapy
- Author
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Moran Guo, Tymish Y. Ohulchanskyy, Mansik Jeon, Edward P. Furlani, Wing Cheung Law, Paras N. Prasad, Chulhong Kim, and Atcha Kopwitthaya
- Subjects
Materials science ,Biomedical Engineering ,Pharmaceutical Science ,Medicine (miscellaneous) ,Nanoparticle ,Bioengineering ,Nanotechnology ,Micelle ,law.invention ,Photoacoustic Techniques ,chemistry.chemical_compound ,Drug Delivery Systems ,Confocal microscopy ,law ,Neoplasms ,Humans ,General Materials Science ,Surface plasmon resonance ,Magnetite Nanoparticles ,Micelles ,Phospholipids ,Plasmon ,Nanotubes ,Hyperthermia, Induced ,Phototherapy ,Photothermal therapy ,Magnetic Fields ,chemistry ,Molecular Medicine ,Nanorod ,Gold ,Iron oxide nanoparticles ,HeLa Cells - Abstract
We present a magnetoplasmonic nanoplatform combining gold nanorods (GNR) and iron-oxide nanoparticles within phospholipid-based polymeric nanomicelles (PGRFe). The gold nanorods exhibit plasmon resonance absorbance at near infrared wavelengths to enable photoacoustic imaging and photothermal therapy, while the Fe 3 O 4 nanoparticles enable magnetophoretic control of the nanoformulation. The fabricated nanoformulation can be directed and concentrated by an external magnetic field, which provides enhancement of a photoacoustic signal. Application of an external field also leads to enhanced uptake of the magnetoplasmonic formulation by cancer cells in vitro. Under laser irradiation at the wavelength of the GNR absorption peak, the PGRFe formulation efficiently generates plasmonic nanobubbles within cancer cells, as visualized by confocal microscopy, causing cell destruction. The combined magnetic and plasmonic functionalities of the nanoplatform enable magnetic field-directed, imaging-guided, enhanced photo-induced cancer therapy. From the Clinical Editor In this study, a nano-formulation of gold nanorods and iron oxide nanoparticles is presented using a phospholipid micelle-based delivery system for magnetic field-directed and imaging-guided photo-induced cancer therapy. The gold nanorods enable photoacoustic imaging and photothermal therapy, while the Fe 3 O 4 nanoparticles enable magnetophoretic control of the formulation. This and similar systems could enable more precise and efficient cancer therapy, hopefully in the near future, after additional testing.
- Published
- 2013
26. Synthesis of near-infrared silver-indium-sulfide (AgInS2) quantum dots as heavy-metal free photosensitizer for solar cell applications
- Author
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Wing Cheung Law, Paras N. Prasad, Kai Chun Cheng, Jeremy S. Nevins, Ho-Pui Ho, David F. Watson, and Ken-Tye Yong
- Subjects
Materials science ,business.industry ,Band gap ,General Physics and Astronomy ,chemistry.chemical_element ,law.invention ,chemistry.chemical_compound ,chemistry ,Quantum dot ,law ,Electrode ,Solar cell ,Optoelectronics ,Photosensitizer ,Physical and Theoretical Chemistry ,business ,Bifunctional ,Mesoporous material ,Indium - Abstract
We report the use of silver-indium-sulfide (AgInS 2 ) quantum dots (QDs) as heavy metal-free photosensitizer for QDs-sensitized solar cell. For fabricating the TiO 2 /AgInS 2 electrode, the QDs were attached to a mesoporous TiO 2 surface by using bifunctional linker molecules. The fabricated TiO 2 /AgInS 2 electrode exhibits light absorption in the visible region and serves as the photoanode. Upon bandgap excitation, injection of photoexcited electrons from AgInS 2 QDs into the TiO 2 matrix produces photocurrents accordingly. The proof-of-concept AgInS 2 QDs-sensitized solar cell exhibits a short-circuit current of 0.49 mA/cm2 and open-circuit voltage of 0.24 V, under one sun illumination.
- Published
- 2011
27. Phase-sensitive surface plasmon resonance biosensor using the photoelastic modulation technique
- Author
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Chinlon Lin, S.P. Wong, X.H. Liu, Wing Cheung Law, Ho-Pui Ho, Siu Kai Kong, and Shu-Yuen Wu
- Subjects
Physics::Biological Physics ,Analyte ,Chemistry ,Physics::Medical Physics ,Metals and Alloys ,Analytical chemistry ,Phase (waves) ,Physics::Optics ,Condensed Matter Physics ,Signal ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Modulation ,Materials Chemistry ,Electrical and Electronic Engineering ,Surface plasmon resonance ,Instrumentation ,Biosensor ,Phase modulation ,Refractive index - Abstract
In this paper, a novel biosensing technique based on detecting the phase difference between p- and s-polarization associated with the surface plasmon resonance (SPR) effect is presented. This is a single beam system in which a photoelastic phase modulator produces a carrier frequency so that the phase quantity can be extracted by measuring the relative amplitude of the first harmonic signal. From the phase quantity, we can directly calculate the shift of refractive index in the analyte. The presence of SPR not only enhances the phase change but also confines the volume of interrogation very close (approximately 200 nm) to the sensing surface. Such properties are important to affinity biosensors. We have used the setup to perform measurement on refractive index changes associated with varying the concentration of glycerin/water mixtures. In addition, real-time monitoring of binding reaction between bovine serum albumin (BSA) and BSA antibodies is also demonstrated.
- Published
- 2006
28. Real-time optical biosensor based on differential phase measurement of surface plasmon resonance
- Author
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Wing Cheung Law, Shu-Yuen Wu, Ho-Pui Ho, Siu Kai Kong, and Chinlon Lin
- Subjects
Optics and Photonics ,Biomedical Engineering ,Biophysics ,Phase (waves) ,Biosensing Techniques ,Optics ,Computer Systems ,Electrochemistry ,Sensitivity (control systems) ,Surface plasmon resonance ,Bovine serum albumin ,Immunoassay ,biology ,business.industry ,Chemistry ,Microchemistry ,Surface plasmon ,technology, industry, and agriculture ,Resonance ,Serum Albumin, Bovine ,Equipment Design ,General Medicine ,Surface Plasmon Resonance ,Differential phase ,Equipment Failure Analysis ,biology.protein ,business ,Biosensor ,Biotechnology - Abstract
We report a real-time differential phase measurement technique which can be implemented in optical surface plasmon resonance biosensors. The important feature of our design is that sensitivity has been greatly improved by measuring the differential phase change between the s and p-polarizations. Real-time measurement capability is achieved by using a phase extracting routine which continuously monitors the waveforms captured by two photo-detectors. Measurement capability of our setup is demonstrated through real-time monitoring of bovine serum albumin (BSA)/anti-BSA binding reaction. The estimated sensitivity of our current setup is 7.4 ng/ml.
- Published
- 2005
29. An unusual cause of status epilepticus in end stage kidney disease: Star fruit intoxication
- Author
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W.M. Zaw, C.H.H. Tan, K.F. Chew, J.S. Wong, D. Dix, N. Ahmad, and Wing Cheung Law
- Subjects
Pediatrics ,medicine.medical_specialty ,business.industry ,030231 tropical medicine ,Status epilepticus ,03 medical and health sciences ,0302 clinical medicine ,Neurology ,medicine ,030212 general & internal medicine ,Neurology (clinical) ,medicine.symptom ,End-stage kidney disease ,business - Published
- 2017
30. WITHDRAWN: Synthesis and Characterization of Anticancer Drug and Antibody conjugated Quantum Dots as A Novel Theranostic Probe for Pancreatic Cancer Detection and Therapy
- Author
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Earl J. Bergey, Fang Wu, Hong Ding, Indrajit Roy, Wing Cheung Law, Ken-Tye Yong, Gaixia Xu, and Paras N. Prasad
- Subjects
biology ,business.industry ,Quantum dot ,Pancreatic cancer ,biology.protein ,Pharmaceutical Science ,Medicine ,Pharmacology ,Conjugated system ,Antibody ,business ,medicine.disease ,Anticancer drug - Abstract
This article has been withdrawn at the request of the author(s) and/or editor. The Publisher apologizes for any inconvenience this may cause. The full Elsevier Policy on Article Withdrawal can be found at http://www.elsevier.com/locate/withdrawalpolicy.
- Published
- 2011
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