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148 results on '"Leung, Chi-Fai"'

3. Analysis of STEM Activities in Primary Students' Science Projects in an Informal Learning Environment

Author

So, Winnie Wing Mui, Zhan, Ying, Chow, Stephen Cheuk Fai, and Leung, Chi Fai

Abstract

This study adopted a researcher-generated framework to analyze STEM activities demonstrated in primary students' science projects in an annual extracurricular event held in Hong Kong. Ten students' project reports were randomly selected from each of the three groups of 24 outstanding, 45 merit, and 68 consolation awarded projects. Content analysis was conducted to code the activities in each project. The coded information was then changed into numerical data for quantitative analysis. The results showed that, in general, more engineering and science activities than technology and mathematics activities were adopted by the primary students in their projects. More projects with the Outstanding Award conducted STEM activities than those projects with Merit and Consolation Awards, and significant group differences existed in the science and mathematics activities. Besides, science activities significantly positively related to engineering and mathematics activities. Furthermore, STEM-related content knowledge of discipline core ideas and crosscutting concepts were reported. This study sheds light on the pattern of STEM activities in students' science projects, and has implications for promoting STEM integration in primary education.

Published
2018
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4. A study of the relationship between creativity and fieldwork performance of social work students

Author

Leung, Chi Fai Simon and Cooper, P.

Subjects
378
Abstract

This study investigates the relationship between social work students’ creativity and their fieldwork performance. Systems theory provides a theoretical framework to explain the ambiguity, indeterminacy and uncertainty in social work practice, and account for the need for creativity during the helping process in fieldwork training. In this study, creativity was defined as the ability in divergent thinking with five dimensions, which are fluency, originality, elaboration, abstractness of titles and resistance to premature closure. The existing literature suggests that social work students’ creativity may have impact on their fieldwork performance in three areas, namely problem solving, application of theories and empathy. 52 social work students from a university in Hong Kong participated in this study and data regarding their creativity and fieldwork performance were collected. Multiple regression analyses were conducted to investigate relationships between participants’ competences in different dimensions of creativity and their fieldwork performance in each of the three fieldwork performance areas. Significant relationships were found between competences in two dimensions of creativity and fieldwork performance in those three areas. Both quadratic and linear significant relationships were found, and in some of them, the competences in some dimensions of creativity were found interacting with each other, and affecting each other’s relationship with fieldwork performance. The findings of this study provided detailed information about the possible relationships between social work students’ competences in different dimensions of creativity and their fieldwork performance in the three selected areas, and some tentative suggestions regarding potential use of the findings of this study for further development of social work curriculum were discussed. Further studies to confirm the findings of this study and to further investigate the possibility of enhancing social works students’ fieldwork performance through improving their competences in certain dimensions of creativity were recommended.

Published
2009

7. Synthesis, structure and photoluminescence of Cu(I) complexes containing new functionalized 1,2,3-triazole ligands.

Author

Wang, Li-Xin, Cheng, Shun-Cheung, Liu, Yingying, Leung, Chi-Fai, Liu, Ji-Yan, Ko, Chi-Chiu, Lau, Tai-Chu, and Xiang, Jing

Subjects
COPPER, CHARGE transfer, LIGANDS (Chemistry), PHOTOLUMINESCENCE, X-ray crystallography, DENSITY functional theory, COPPER compounds
Abstract

The reaction of a triazole ligand, 2-(1H-1,2,3-triazol-4-yl)pyridine (L1), with 2-bromopyridine afforded three new ligands, 2,2′-(1H-1,2,3-triazole-1,4-diyl)dipyridine (L2), 2,2′-(2H-1,2,3-triazole-2,4-diyl)dipyridine (L3) and 2,2′-(1H-1,2,3-triazole-1,5-diyl)dipyridine (L4). A series of luminescent mononuclear copper(I) complexes of these ligands [Cu(Ln)(P^P)](ClO4) [n = 1, P^P = (PPh3)2 (1); n = 1, P^P = POP (2); n = 2, P^P = (PPh3)2 (3); n = 2, P^P = POP (4); n = 3, P^P = (PPh3)2 (5); n = 3, P^P = POP (6); n = 4, P^P = (PPh3)2 (9); n = 4, P^P = POP (10)] have been obtained from the reaction of Ln with [Cu(MeCN)4]ClO4 in the presence of PPh3 and POP. L3 was also found to form dinuclear compounds [Cu2(L3)(PPh3)4](ClO4)2 (7) and [Cu2(L3)(POP)2](ClO4)2 (8). All of the Cu(I) compounds have been characterized by IR, UV/vis, CV, 1H NMR, and 31P{1H} NMR. The molecular structures of 1–3, 5, and 7 have been further determined by X-ray crystallography. In CH2Cl2 solutions, these Cu(I) complexes exhibit tunable green to orange emissions (563–621 nm) upon excitation at λex = 380 nm. In the solid state, these complexes show intense emissions and it is interesting to note that 1 and 3 are blue-light emitters. Density functional theory (DFT) calculations revealed that the lowest energy electronic transition associated with these complexes predominantly originates from metal-to-ligand charge transfer transitions (MLCT). [ABSTRACT FROM AUTHOR]

Published
2023
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9. Visible Light-Induced Oxidation of Alcohols by a Luminescent Osmium(VI) Nitrido Complex: Evidence for the Generation of PhIO+ as a Highly Active Oxidant in the Presence of PhIO

Author

Xiang, Jing, primary, Pan, Yi, additional, Liu, Lu-Lu, additional, Wang, Li-Xin, additional, Yang, Huan, additional, Cheng, Shun-Cheung, additional, Yiu, Shek-Man, additional, Leung, Chi-Fai, additional, Ko, Chi-Chiu, additional, Lau, Kai-Chung, additional, and Lau, Tai-Chu, additional

Published
2023
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12. Cover Feature: Ligand Substituent Effects on Light‐Driven Hydrogen Evolution by Cobalt(II) Tripodal Iminopyridine Catalysts under Precious‐Metal‐Free Conditions (Eur. J. Inorg. Chem. 31/2022)

Author

Kwok, Chun‐Leung, primary, Cheng, Shun‐Cheung, additional, Ho, Pui‐Yu, additional, Yiu, Shek‐Man, additional, Au, Vonika Ka‐Man, additional, Ho, Wing‐Kei, additional, Tsang, Po‐Keung, additional, Xiang, Jing, additional, Leung, Chi‐Fai, additional, and Ko, Chi‐Chiu, additional

Published
2022
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13. Ligand Substituent Effects on Light‐Driven Hydrogen Evolution by Cobalt(II) Tripodal Iminopyridine Catalysts under Precious‐Metal‐Free Conditions

Author

Kwok, Chun‐Leung, primary, Cheng, Shun‐Cheung, additional, Ho, Pui‐Yu, additional, Yiu, Shek‐Man, additional, Au, Vonika Ka‐Man, additional, Ho, Wing‐Kei, additional, Tsang, Po‐Keung, additional, Xiang, Jing, additional, Leung, Chi‐Fai, additional, and Ko, Chi‐Chiu, additional

Published
2022
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22. Visible Light-Induced Oxidation of Alcohols by a Luminescent Osmium(VI) Nitrido Complex: Evidence for the Generation of PhIO+as a Highly Active Oxidant in the Presence of PhIO

Author

Xiang, Jing, Pan, Yi, Liu, Lu-Lu, Wang, Li-Xin, Yang, Huan, Cheng, Shun-Cheung, Yiu, Shek-Man, Leung, Chi-Fai, Ko, Chi-Chiu, Lau, Kai-Chung, and Lau, Tai-Chu

Abstract

Although alcohols are readily oxidized by a variety of oxidants, their oxidation by metal nitrido complexes is yet to be studied. We report herein visible-light-induced oxidation of primary and secondary alcohols to carbonyl compounds by a strongly luminescent osmium(VI) nitrido complex (OsN). The proposed mechanism involves initial rate-limiting hydrogen-atom transfer (HAT) from the α-carbon of the alcohol to OsN*. Attempts to develop catalytic oxidation of alcohols by OsN*using PhIO as the terminal oxidant resulted in the formation of novel osmium(IV) iminato complexes in which the nitrido ligand is bonded to a δ-carbon of the alcohol. Experimental and theoretical studies suggest that OsN*is reductively quenched by PhIO to generate PhIO+, which is a highly active oxidant that readily undergoes α- and δ-C–H activation of alcohols.

Published
2023
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28. Multifunctional Luminescent Sensor Based on the Pb2+Complex Containing a Tetrazolato Ligand

Author

Wang, Li-Xin, Xiang, Jing, Xiang, Dong, Cheng, Shun-Cheung, Leung, Chi-Fai, Ko, Chi-Chiu, and Xiang, Jing

Abstract

A series of luminescent Pb2+complexes, [Pb(L1)2]n(1), [Pb(L2)2]n(2), [Pb(L3)(NO3)(H2O)2]n(3), [Pb(L3)(Br)(H2O)]n(4), [Pb(L3)(Cl)(H2O)]n(5), and [Pb(L4)(H2O)2] (6) have been synthesized by treatment of polydentate tetrazolato ligands with various hydrated Pb2+salts (HL1= 2-(1H-tetrazol-5-yl)pyridine, HL2= 3-(1H-tetrazol-5-yl)isoquinoline, HL3= 6-(1H-tetrazol-5-yl)-2,2′-bipyridine, and H2L4= 6,6′-bis(1H-tetrazol-5-yl)-2,2′-bipyridine). These complexes have been characterized by IR, TGA, and elemental analysis. Their crystal structures have been determined by X-ray crystallography, and the phase purity of bulk samples were further confirmed by PXRD. Their luminescence properties have been investigated in detail, and their emission origin may involve ligand-centered π–π* transition, metal-centered s-p transition and charge-transfer character. It is interesting to note that 5exhibits obviously enhanced red-shifted emission, whose photoluminescence quantum yield (PLQY = 16.5%) is much higher than the other compounds (≤2%). Most importantly, the emission property of 5was strongly affected by temperature. When the temperature rises from 295 to 493 K, the emission maximum gradually shifts to high energy due to the loss of the aqua ligand. In contrast, when the temperature is lowered from 295 to 13 K, two emission bands were observed. The low-energy emission band exhibits a slight blue shift, while a new high-energy emission band appears at around 520 nm, which is assigned to ligand-centered phosphorescence. After removal of the coordinated aqua ligand, the emission of 5–H2Ois very sensitive to the vapors of volatile primary amines and acids, although they have different response mechanisms. This result indicates that 5–H2Omay be a potential multifunctional sensor for temperature, volatile amines, and acids. To decipher the emission origin, DFT calculations have also been carried out based on the structure units of these compounds.

Published
2022
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38. Molecular quaterpyridine-based metal complexes for small molecule activation: water splitting and CO2 reduction.

Author

Chen, Lingjing, Chen, Gui, Leung, Chi-Fai, Cometto, Claudio, Robert, Marc, and Lau, Tai-Chu

Subjects
ORGANIC conductors, METAL complexes, ARTIFICIAL photosynthesis, SMALL molecules, PHOTOCATALYSTS
Abstract

Artificial photosynthesis is considered as one of the most promising strategies for solar-to-fuel conversion through sunlight-driven water splitting and CO2 reduction. This tutorial describes recent developments in the use of metal quaterpyridine complexes as electrocatalyts and photocatalysts for artificial photosynthesis. [ABSTRACT FROM AUTHOR]

Published
2020
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49. Photocatalytic Conversion of CO2 to CO by a Copper(II) Quaterpyridine Complex.

Author

Guo, ZhENguo, Yu, Fei, Yang, Ying, Leung, Chi ‐ Fai, Ng, Siu ‐ Mui, Ko, Chi ‐ Chiu, Cometto, Claudio, Lau, Tai ‐ Chu, and Robert, Marc

Subjects
PHOTOCATALYSIS, COPPER, METAL catalysts, PHOTOREDUCTION, LIGHT scattering
Abstract

The invention of efficient systems for the photocatalytic reduction of CO2 comprising earth-abundant metal catalysts is a promising approach for the production of solar fuels. One bottleneck is to design highly selective and robust molecular complexes that are able to transform the CO2 gas. The CuII quaterpyridine complex [Cu(qpy)]2+ ( 1) is found to be a highly efficient and selective catalyst for visible-light driven CO2 reduction in CH3CN using [Ru(bpy)3]2+ (bpy: bipyridine) as photosensitizer and BIH/TEOA (1,3-dimethyl-2-phenyl-2,3-dihydro-1 H-benzo[ d]imidazole/triethanolamine) as sacrificial reductant. The photocatalytic reaction is greatly enhanced by the presence of H2O (1-4 % v/v), and a turnover number of >12 400 for CO production can be achieved with 97 % selectivity, which is among the highest of molecular 3d CO2 reduction catalysts. Results from Hg poisoning and dynamic light scattering experiments suggest that this photocatalyst is homogenous. To the best of our knowledge, 1 is the first example of molecular Cu-based catalyst for the photoreduction of CO2. [ABSTRACT FROM AUTHOR]

Published
2017
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50. Synthesis and crystal structure of a 3-D Ag+ coordination polymer with white-light emission.

Author

Hu, Lin‐Li, Shen, Chang, Xiang, Jing, and Leung, Chi‐Fai

Abstract

Treatment of AgNO3 with a tetrazolyl ligand H2L1 afforded a 3-D coordination polymer [Ag2( L1)]n ( 1). The crystal structure was determined by X-ray crystallography and it shows that both Ag1 and Ag2 atoms in the asymmetric unit exhibit distorted tetrahedron geometries, which are modified by Ag⋯Ag interactions. The flexible methylene -CH2- linkage between tetrazolate and phenyl ring effectively reduces the steric strain in the resultant 3D-framework. L1 exhibits an unsual coordination mode in which all nitrogen atoms in the two tetrazolato units are coordinated to the AgI centers. The luminescent property of 1 was also investigated. It exhibits multiple emission bands; the high energy emission band is assigned to the ligand-centered π⋯π transition, while the low energy emission bands are tentatively assigned to ligand-to-metal charge transfer (LMCT) that are modified by Ag⋯Ag interaction. The independence of the chromaticity coordinates of 1 on the excitation wavelength also suggests that it is a potentially useful single-component white-light-emitting material. [ABSTRACT FROM AUTHOR]

Published
2017
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