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428 results on '"Yeung, King Lun"'

113. Preparation and antibacterial behaviour of nanostructured Ag@SiO2–penicillin with silver nanoplates.

Author

Malekzadeh, Mahdieh, Yeung, King Lun, Halali, Mohammad, and Chang, Qing

Subjects
*ANTIBACTERIAL agents, *SILVER, *CELL lines, *BEHAVIOR, *PENICILLIN, *SILVER sulfide
Abstract

In this study, we investigated the antibacterial properties of nanostructured Ag@SiO2–penicillin synthesized from triangular silver nanoplates (Ag NPs) against methicillin-susceptible S. aureus (MSSA) and methicillin-resistant S. aureus (MRSA) bacteria. The Ag@SiO2–penicillin nanoparticles contained approximately 33.2 wt% Ag as determined by ICP-OES. Grafting of about 2.8 wt% penicillin on Ag@SiO2 remarkably enhanced the bactericidal properties against MSSA and MRSA bacteria and showed no cell-death inducing effects towards the A431 cell line. [ABSTRACT FROM AUTHOR]

Published
2019
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117. OperandoInvestigation of Toluene Oxidation over 1D Pt@CeO2Derived from Pt Cluster-Containing MOF

Author

Wang, Qingyue, Li, Yuxin, Serrano-Lotina, Ana, Han, Wei, Portela, Raquel, Wang, Ruixuan, Bañares, Miguel A., and Yeung, King Lun

Abstract

A unique 1D nanostructure of Pt@CeO2–BDC was prepared from Pt@CeBDC MOF. The Pt@CeO2–BDC was rich in oxygen vacancies (i.e., XPS Oβ/(Oα+ Oβ) = 39.4%), and on the catalyst, the 2 nm Pt clusters were uniformly deposited on the 1D mesoporous polycrystalline CeO2. Toluene oxidation was conducted in a spectroscopic operandoRaman–online FTIR reactor to elucidate the reaction mechanism and establish the structure–activity relationship. The reaction proceeds as follows: (I) adsorption of toluene as benzoate intermediates on Pt@CeO2–BDC at low temperature by reaction with surface peroxide species; (II) reaction activation and ring-opening involving lattice oxygen with a concomitant change in defect densities indicative of surface rearrangement; (III) complete oxidation to CO2and H2O by lattice oxygen and reoxidation of the reduced ceria with consumption of adsorbed oxygen species. The Pt clusters, which mainly exist as Pt2+with minor amounts of Pt0and Pt4+on the surface, facilitated the adsorption and reaction activation. The Pt-CeO2interface generates reduced ceria sites forming nearby adsorbed peroxide at low temperature that oxidize toluene into benzoate species by a Langmuir–Hinshelwood mechanism. As the reaction temperature increases, the role of lattice oxygen becomes important, producing CO2and H2O mainly by the Mars-van Krevelen mechanism.

Published
2021
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118. Chemical Engineering Process Miniaturisation for Chemical Production and Material Manufacture

Author

Yeung King Lun and Chen Xinqing

Subjects
Materials science, General Engineering, Mesoporous silica, equipment and supplies, Catalysis, Benzaldehyde, chemistry.chemical_compound, chemistry, Chemical engineering, Yield (chemistry), Knoevenagel condensation, Microreactor, Mesoporous material, human activities, Iron oxide nanoparticles
Abstract

Chemical process miniaturisation was used to develop new microreactor systems for the synthesis and preparation of catalysts and for the production of fine chemicals. Mesoporous silica MCM-41 was successfully prepared by flow synthesis in a microreactor at shorter reaction times (ie minutes versus day) at high yield (ie 98 %) to give particles of more uniform size and shape compared to samples prepared by conventional batch synthesis. Magnetic iron oxide nanoparticles were incorporated and aminopropyls were grafted on MCM-41 to obtain a magnetic mesoporous catalyst for the Knoevenagel condensation reaction of benzaldehyde and ethyl cyanoacetate. Iron oxide nanoparticles in NH2-magMCM-41 have promotion effect on the aminopropyls catalytic sites resulting in a twofold increase in the catalytic activity of the magnetic mesoporous catalyst compared to NH2-MCM-41. The magnetic catalyst was used in a new magnetized capillary microreactor. The catalysts were captured and held in place by the magnets, and used to...

Published
2012

123. Selective ammonia oxidation on vanadia-titania catalysts

Author

Chen, Hao, Portela, Raquel, Li, Yan, Han, Wei, Ávila García, Pedro, Bañares, Miguel A., and Yeung, King Lun

Abstract

Trabajo presentado en la 248th American Chemical Society National Meeting & Exposition (Chemistry & Global Stewardship), celebrada en San Francisco del 10 al 14 de agosto de 2014.

Published
2014

124. Vanadia-titania based catalysts for ammonia removal

Author

Chen, Hao, Portela, Raquel, Bañares, Miguel A., and Yeung, King Lun

Abstract

Trabajo presentado en el 8th Symposium on Group Five Compounds, celebrado en Málaga del 24 al 27 de junio de 2014.

Published
2014

128. Zeolite membrane microreactor for carbonylation of glycerol with urea

Author

Kwan, S. M., Yeung, King Lun, Calvino Casilda, Vanesa, Rubio Marcos, Fernando, Fernández Lozano, José Francisco, and Bañares, Miguel A.

Abstract

Trabajo presentado en UBIOCHEM IV: 4th International Workshop of COST Action CM0903, celebrado en Valencia (España) del 14 al 16 de octubre de 2013.

Published
2013

129. Fabrication of zeolite membrane microreactor for carbonylation of glycerol with urea

Author

Kwan, S. M., Yeung, King Lun, Calvino Casilda, Vanesa, Rubio Marcos, Fernando, Fernández Lozano, José Francisco, Bañares, Miguel A., Research Grants Council (Hong Kong), and Ministerio de Ciencia e Innovación (España)

Subjects
Microreactor, Urea, ZSM-5 membrane, Template-free synthesis, Glycerol Carbonate
Abstract

Trabajo presentado en la 11th International Conference on Catalysis in membrane Reactors, celebrada en Oporto (Portugal) del 7 al 11 de julio de 2013., The authors gratefully acknowledge finnancial supports from the Hong Kong Research Grant Council, RGC-CSIC 2010HK0004 and Spanish CTQ2011-13343-E

Published
2013

130. Repair of defects created by Ar+ sputtering on graphite surface by annealing as confirmed using ToF‐SIMS and XPS.

Author

Xie, Wenjing, Weng, Lu‐Tao, Yeung, King Lun, and Chan, Chi‐Ming

Subjects
GRAPHITE, ARGON, SPUTTERING (Physics), PYROLYSIS, ANNEALING of crystals, SECONDARY ion mass spectrometry
Abstract

Defects were created on the surface of highly oriented pyrolytic graphite (HOPG) by sputtering with an Ar+ ion beam, then characterized using X‐ray photoelectron spectroscopy (XPS) and time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) at 500°C. In the XPS C1s spectrum of the sputtered HOPG, a sp3 carbon peak appeared at 285.3 eV, representing surface defects. In addition, 2 sets of peaks, the Cx− and CxH− ion series (where x = 1, 2, 3...), were identified in the ToF‐SIMS negative ion spectrum. In the positive ion spectrum, a series of CxH2+• ions indicating defects was observed. Annealing of the sputtered samples under Ar was conducted at different temperatures. The XPS and ToF‐SIMS spectra of the sputtered HOPG after 800°C annealing were observed to be similar to the spectra of the fresh HOPG. The sp3 carbon peak had disappeared from the C1s spectrum, and the normalized intensities of the CxH− and CxH2+• ions had decreased. These results indicate that defects created by sputtering on the surface of HOPG can be repaired by high‐temperature annealing. [ABSTRACT FROM AUTHOR]

Published
2018
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131. Reactions of SO2 and NH3 with epoxy groups on the surface of graphite oxide powder.

Author

Xie, Wenjing, Weng, Lu-Tao, Chan, Chak-Keung, Yeung, King Lun, and Chan, Chi-Ming

Abstract

Graphite oxide powder was obtained using the modified Hummers’ method and characterized using X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The XPS results indicated that the epoxy groups were the main functional groups on the graphite oxide powder surface. The graphite oxide powder was then reacted with SO2 and NH3 gases, respectively, at 25 °C. The XPS and ToF-SIMS analyses of the surface of the reacted graphite oxide powder showed that the reactions mainly occurred in the epoxy groups. Bisulfate and amine groups were formed on the surface of the graphite oxide powder after the reactions between the graphite oxide powder and SO2 and NH3 gases. This work demonstrates a new method of removing SO2 and NH3 gases using graphite oxide powder. [ABSTRACT FROM AUTHOR]

Published
2018
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132. ToF‐SIMS and computation analysis: Fragmentation mechanisms of polystyrene, polystyrene‐d5, and polypentafluorostyrene.

Author

Ng, Kai‐Mo, Lau, Yiu‐Ting R., Weng, Lu‐Tao, Yeung, King‐Lun, and Chan, Chi‐Ming

Subjects
FRAGMENTATION reactions, POLYSTYRENE, REACTION mechanisms (Chemistry), CYCLOPENTANE, IONS, BENZOCYCLOBUTENE
Abstract

We studied the time‐of‐flight secondary ion mass spectrometry fragmentation mechanisms of polystyrenes—phenyl‐fluorinated polystyrene (5FPS), phenyl‐deuterated polystyrene (5DPS), and hydrogenated polystyrene (PS). From the positive ion spectra of 5FPS, we identified some characteristic molecular ion structures with isomeric geometries such as benzylic, benzocyclobutene, benzocyclopentene, cyclopentane, and tropylium systems. These structures were evaluated by the B3LYP‐D/jun‐cc‐pVDZ computation method. The intensities of the C7H2F5+ (m/z = 181), CyPent‐C9H3F4+ (m/z = 187), CyPent‐C9H4F5+ (m/z = 207), and CyPent‐C9H2F5+ (m/z = 205) ions were enhanced by resonance stabilization. The positive fluorinated ions from 5FPS tended to rearrange and produce fewer fluorine‐containing molecular ions through the loss of F (m/z = 19), CF (m/z = 31), and CF2 (m/z = 50) ion fragments. Consequently, the fluorine‐containing polycyclic aromatic ions had much lower intensities than their hydrocarbon counterparts. We propose the fragmentation mechanisms for the formation of C5H5+, C6H5+, and C7H7+ ion fragments, substantiated with detailed analyses of the negative ion spectra. These ions were created through elimination of a pentafluoro‐phenyl anion (C6F5−) and H+, followed by a 1‐electron‐transfer process and then cyclization of the newly generated polyene with carbon‐carbon bond formation. The pendant groups with elements of different electronegativities exerted strong influences on the intensities and fragmentation processes of their corresponding ions. [ABSTRACT FROM AUTHOR]

Published
2018
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