Commonwealth Fellowship, Univ. of Bristol, 1994; Ph.D., National Univ. of Singapore, 1993; B.Sc.(Hons), National Univ. of Singapore, 1987.
Contact Information:
Office: S8-02-05B
Tel: (65)-6516-8031
Fax: (65)-6779-1691
Email: chmcws@nus.edu.sg
Our research focuses on the fabrication and applications of nanostructures and their hybrids. We explore methodologies to synthesize size-, morphology- and phase-controllable nanomaterials, and to fabricate them into heterostructured or hybrid materials for specific applications. Current projects include synthesis of doped and layered oxide/hydroxide nanocomposites for energy, sensor and photocatalytic applications.
Ref. Tan, X. Y.; Ungur, L.; Chin, W. S., Carbonate-free CoAl layered double hydroxides supercapacitors: Controlled precipitation via acid mediated decomplexation. Appl. Clay Sci. 2022, 224, 106519.
Layered double hydroxides (LDH) belong to a class of highly versatile compounds used in a myriad of applications such as energy storage, catalysis, heavy metal adsorption, etc. One of the inherent problems of LDH lies in the presence of CO32- anions in the intercalation, which greatly affects the versatility and tunability of LDH. In this work, we address the problem with the use of ethylenediamine (EDA) complexation followed by controlled decomplexation to prepare CoAl LDH (LDH-EDA). It is shown that the obtained LDH-EDA is carbonate-free and outperforms the CoAl LDH obtained using conventional urea method (LDH-Urea) in terms of crystallinity, surface area and pseudocapacitive properties. Through a detailed experimental and computational study of the preparation mechanism, we propose that ammonium nitrate acts as an acid that mediates the decomplexation of the cobalt (II) trisethylenediamine complex, freeing Co2+ ion in a control manner for the second precipitation process. The multistep process has allowed a controlled rate of formation of LDH, resulting in the highly crystalline LDH-EDA microstructures with pure nitrate intercalation and a flower-like morphology.
Ref. Li, L.; Chin, W.S., Rapid Fabrication of a Flexible and Transparent Ag Nanocubes@PDMS Film as a SERS Substrate with High Performance. ACS Appl. Mater. Interfaces 2020, 12, 37538-37548.
We demonstrate the fabrication of high performance SERS substrate consisting of plasmonic Ag nanocubes (Ag NCs) arrays anchored onto flexible transparent polydimethylsiloxane (PDMS) membrane. Through simple organic/water interfacial self-assembly method, arrays of pre-synthesized Ag NCs are obtained and directly retrieved onto PDMS membrane without the aid of rigid substrates (e.g. Si wafer or glass slide). The plasmonic Ag NCs arrays can produce strong electromagnetic enhancement, achieving high SERS enhancement factor (~ 3.43×106) and ideal detection capability for methylene blue and Rhodamine 6G at respective trace amount of 10-10 M and 10-9 M.
