Publications

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Chang, CS, Chattopadhyay S, Chen* LC, Chen KH, Chen CW, Chen YF, Collazo R, Sitar Z.  2003.  Band gap dependence of field emission from one dimensional nanostructures grown on n-type and p-type silicon substrates. Phys. Rev.. B68:125322-(1-5).
Chang, CK, Kataria S, Kuo CC, Ganguli A, Wang BY, Hwang JY, Huang KJ, Yang WH, Wang SB, Chuang CH, Chen M, Huang CI, Pong WF, Song KJ, Chang SJ, Guo J, Tai Y, Tsujimoto M, Isoda S, Chen CW, Chen LC, Chen KH.  2013.  Band gap engineering of chemical vapor deposited graphene by in-situ BN doping. ACS Nano. 7:1333-1341.
Shelke, AR, Wang H-T, Chiou J-W, Shown I, Sabbah A, Chen K-H, Teng S-A, Lin I-A, Lee C-C, Hsueh H-C, Liang Y-H, Du C-H, Yadav PL, Ray SC, Hsieh S-H, Pao C-W, Tsai H-M, Chen C-H, Chen K-H, Chen L-C, Pong W-F.  2022.  Bandgap Shrinkage and Charge Transfer in 2D Layered SnS2 Doped with V for Photocatalytic Efficiency Improvement. Small. n/a:2105076., Number n/a AbstractWebsite

Abstract Effects of electronic and atomic structures of V-doped 2D layered SnS2 are studied using X-ray spectroscopy for the development of photocatalytic/photovoltaic applications. Extended X-ray absorption fine structure measurements at V K-edge reveal the presence of VO and VS bonds which form the intercalation of tetrahedral OVS sites in the van der Waals (vdW) gap of SnS2 layers. X-ray absorption near-edge structure (XANES) reveals not only valence state of V dopant in SnS2 is ≈4+ but also the charge transfer (CT) from V to ligands, supported by V Lα,β resonant inelastic X-ray scattering. These results suggest V doping produces extra interlayer covalent interactions and additional conducting channels, which increase the electronic conductivity and CT. This gives rapid transport of photo-excited electrons and effective carrier separation in layered SnS2. Additionally, valence-band photoemission spectra and S K-edge XANES indicate that the density of states near/at valence-band maximum is shifted to lower binding energy in V-doped SnS2 compare to pristine SnS2 and exhibits band gap shrinkage. These findings support first-principles density functional theory calculations of the interstitially tetrahedral OVS site intercalated in the vdW gap, highlighting the CT from V to ligands in V-doped SnS2.

Lee, C-P, Chen W-F, Billo T, Lin Y-G, Fu F-Y, Samireddi S, Lee C-H, Hwang J-S, Chen K-H, Chen L-C.  2016.  Beaded stream-like CoSe2 nanoneedle array for efficient hydrogen evolution electrocatalysis, 2016. Journal of Materials Chemistry A. 4(12):4553-4561.: The Royal Society of Chemistry AbstractWebsite

The development of earth-abundant and efficient electrocatalysts for the hydrogen evolution reaction (HER) is one of the keys to success for future green energy systems using hydrogen fuel. Nanostructuring of electrocatalysts is a promising way to enhance their electrocatalytic performance in the HER. In this study, pure pyrite-type beaded stream-like cobalt diselenide (CoSe2) nanoneedles are directly formed on flexible titanium foils through treating a cobalt oxide (Co3O4) nanoneedle array template with selenium vapor. The beaded stream-like CoSe2 nanoneedle electrode can drive the HER at a current density of 20 mA cm−2 with a small overpotential of 125 mV. Moreover, the beaded stream-like CoSe2 nanoneedle electrode remains stable in an acidic electrolyte for 3000 cycles and continuously splits water over a period of 18 hours. The enhanced electrochemical activity is facilitated by the unique three-dimensional hierarchical structure, the highly accessible surface active sites, the improved charge transfer kinetics and the highly attractive force between water and the surface of the nanoneedles that exceeds the surface tension of water.

Lee, CP, Chen* WF, Billo T, Lin YG, Fu FY, Samireddi S, Lee CH, Hwang JS, Chen* LC, Chen* KH.  2016.  Beaded-stream-like CoSe2 nanoneedles array for efficient hydrogen evolution electrocatalysis. J. Mater. Chem. A . 4 :4553-4561.
Lin, YR, Tunuguntla V, Wei SY, Chen WC, Wong D, Lai CH, Liu LK, Chen LC, Chen KH.  2015.  Bifacial sodium-incorporated treatments: tailoring deep traps and enhancing carrier transport properties in Cu2ZnSnS4 solar cells. Nano Energy . 16:438.
Wong, DP, Suriyaprabha R, Yuvakumar R, Rajendran V, Chen YT, Hwang BJ, Chen LC, Chen KH.  2014.  Binder-free rice husk-based silicon-graphene composite as energy efficient Li-ion battery anodes. J. Mater. Chem. A. 2:13437-13441.
Dhara*, S, Chandra S, Magudapathy P, Kalavathi S, Panigrahi BK, Nair KGM, Sastry VS, Hsu CW, Wu CT, Chen KH, Chen LC.  2004.  Blue luminescence of Au nanoclusters embedded in silica matrix. J. Chem. Phys.. 121:12595-12599.
Dhara, SK, Datta A, Lan ZH, Chen* KH, Wang YL, Shen CS, Chen LC, Hsu CW, Lin HM, Chen CC.  2004.  Blue shift of yellow band in self-ion beam irradiated GaN nanowires. Appl. Phys. Lett.. 84:3486-3488.
Lo, HC, Wu JJ, Wen CY, Wong TS, Lin ST, Chen* KH, Chen LC.  2001.  Bonding characterization and nano-indentation study of the amorphous SiCxNy films with and without hydrogen incorporation. Diamond Relat. Mater.. 10:1916-1920.
Sabbah, A, Shown I, Qorbani M, Fu F-Y, Lin T-Y, Wu H-L, Chung P-W, Wu C-I, Santiago SRM, Shen J-L, Chen K-H, Chen L-C.  2022.  Boosting photocatalytic CO2 reduction in a ZnS/ZnIn2S4 heterostructure through strain-induced direct Z-scheme and a mechanistic study of molecular CO2 interaction thereon, 2022. Nano Energy. 93:106809. AbstractWebsite

Employing direct Z-scheme semiconductor heterostructures in photocatalysis offers efficient charge carrier separation and isolation of both redox reactions, thus beneficial to reduce CO2 into solar fuels. Here, a ZnS/ZnIn2S4 heterostructure, comprising cubic ZnS nanocrystals on hexagonal ZnIn2S4 (ZIS) nanosheets, is successfully fabricated in a single-pot hydrothermal approach. The composite ZnS/ZnIn2S4 exhibits microstrain at its interface with an electric field favorable for Z-scheme. At an optimum ratio of Zn:In (~ 1:0.5), an excellent photochemical quantum efficiency of around 0.8% is reached, nearly 200-fold boost compared with pristine ZnS. Electronic levels and band alignments are deduced from ultraviolet photoemission spectroscopy and UV-Vis. Evidence of the direct Z-scheme and carrier dynamics is verified by photo-reduction experiment, along with photoluminescence (PL) and time-resolved PL. Finally, diffuse-reflectance infrared Fourier transformed spectroscopy explores the CO2 and related intermediate species adsorbed on the catalyst during the photocatalytic reaction. This microstrain-induced direct Z-scheme approach opens a new pathway for developing next-generation photocatalysts for CO2 reduction.