ORCID Profile
0000-0003-4049-2719
Current Organisation
Nanyang Technological University
Does something not look right? The information on this page has been harvested from data sources that may not be up to date. We continue to work with information providers to improve coverage and quality. To report an issue, use the Feedback Form.
Publisher: AIP Publishing
Date: 15-03-2010
DOI: 10.1063/1.3340930
Abstract: We report the correlated d0 ferromagnetism and photoluminescence in undoped single-crystalline ZnO nanowires synthesized by using a vapor transport method. We systematically tune the oxygen deficiency in the ZnO nanowires from 4% to 20% by adjusting the growth conditions, i.e., selecting different catalyst (Au or Ag) and varying the growth temperature. Our study suggests that oxygen vacancies induce characteristic photoluminescence and significantly boost the room-temperature ferromagnetism. Such undoped ZnO nanowires with tunable magnetic and optical properties are promising to find applications in multifunctional spintronic and photonic nanodevices.
Publisher: American Chemical Society (ACS)
Date: 07-06-2008
DOI: 10.1021/JP710837H
Publisher: Inderscience Publishers
Date: 2004
Publisher: American Chemical Society (ACS)
Date: 04-07-2018
Publisher: AIP Publishing
Date: 15-12-2008
DOI: 10.1063/1.3046673
Abstract: We present the results of a systematic investigation of crystal structure, dc magnetization, ac susceptibility, resistivity, and magnetoresistance (MR) of Nd0.75Sr1.25Co1−xMnxO4 (0≤x≤0.3) polycrystals. All synthesized specimens are indexed in the same tetragonal space group I4/mmm with random occupation of Co and Mn ions at the identical site. The refinement result confirms the tetragonal distortion of the CoO6 octahedron with elongation along the c axis. The substitution of the Mn ions at Co site brings about the suppression of ferromagnetism as well as the enhancement of antiferromagnetism. The coexistence of ferromagnetic double exchange interactions and antiferromagnetic superexchange interactions and the suppression of ferromagnetism with increasing Mn doping are substantiated by the isothermal magnetization hysteresis loops. The result suggests that the substitution creates more antiferromagnetic bonds with superexchange interactions at the expense of the existing Co–O–Co bonds with ferromagnetic double exchange interactions. At low temperature, a crossover from ferromagnetic cluster-glass phase to spin-glass phase is shown in the dc and ac magnetic measurements. For all the specimens, the resistivity ρ(T) follows semiconducting behavior (dρ/dT& ) in the whole measured temperature region. The substitution induces an obvious increase in resistivity, which originates from the diminishing of ferromagnetic double exchange interactions and the localization of charge carriers caused by the disorder for the substitution. The system presents negative MR due to tunneling effect at low temperatures and positive MR at high-temperature range.
Publisher: Wiley
Date: 03-01-2013
Abstract: A hetero-nanostructured photoanode with enhanced near-infrared light harvesting is developed for photo-electrochemical cells. By spatially coating upconversion nanoparticles and quantum dot photosensitizers onto TiO2 inverse opal, this architecture allows direct irradiation of upconversion nanoparticles to emit visible light that excites quantum dots for charge separation. Electrons are injected into TiO2 with minimal carrier losses due to continuous electron conducting interface.
Publisher: Royal Society of Chemistry (RSC)
Date: 2014
DOI: 10.1039/C3RA47377E
Abstract: Novel 2-D supramolecular networks were made by metal-ion coordination, and their properties compared with similar 3-D networks.
Publisher: Royal Society of Chemistry (RSC)
Date: 2011
DOI: 10.1039/C1CE05357D
Publisher: AIP Publishing
Date: 17-08-2004
DOI: 10.1063/1.1784035
Abstract: Proton-beam writing (PBW) is a direct-write micromachining technique capable of fabricating low-loss single-mode polymer waveguides with straight and smooth sidewalls. Recently, the sidewall morphologies of such proton beam written polymer waveguide structures were directly measured using an atomic force microscope (AFM). Statistical information such as the rms roughness and the correlation length of the sidewall profile obtained from the AFM scans allows us to quantify the quality of the sidewalls and optimize the fabrication parameters using PBW. For structures fabricated using a stage scanning speed of ∼10μm∕s, a rms roughness of 3.8±0.3nm with a correlation length of 46±6nm was measured.
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C6NR02430K
Abstract: Highly photoactive and durable photoanode materials are the key to photoelectrochemical water splitting. In this paper, hierarchically branched Fe2O3@TiO2 nanorod arrays (denoted as Fe2O3@TiO2 BNRs) composed of a long Fe2O3 trunk and numerous short TiO2 nanorod branches were fabricated and used as photoanodes for water splitting. Significant improvement of photoelectrochemical water splitting performance was observed based on Fe2O3@TiO2 BNRs. The photocurrent density of Fe2O3@TiO2 BNRs reaches up to 1.3 mA cm(-2) at 1.23 V versus RHE, which is 10 times higher than that of pristine Fe2O3 nanorod arrays under the same conditions. Furthermore, an obvious cathodic shift in the onset potential of photocurrent was observed in the Fe2O3@TiO2 BNRs. More significantly, the Fe2O3@TiO2 BNRs are quite stable even after 3600 s continuous illumination, and the photocurrent density shows almost no decay. Finally, a tentative mechanism was proposed to explain the superior performance of Fe2O3@TiO2 BNRs for PEC water splitting and discussed in detail on the basis of our experimental results.
Publisher: American Chemical Society (ACS)
Date: 29-03-2021
Publisher: Springer Science and Business Media LLC
Date: 30-06-2022
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D0NR08093D
Abstract: Demonstration of Rb 2 CuX 3 (X = Br, Cl) colloidal nanocrystals under UV light with a representation of one-dimensional Rb 2 CuBr 3 crystal structure.
Publisher: American Chemical Society (ACS)
Date: 18-09-2015
Abstract: Both solution-processed polymers and small molecule based solar cells have achieved PCEs over 9% with the conventional device structure. However, for the practical applications of photovoltaic technology, further enhancement of both device performance and stability are urgently required, particularly for the inverted structure devices, since this architecture will probably be most promising for the possible coming commercialization. In this work, we have fabricated both conventional and inverted structure devices using the same small molecular donor/acceptor materials and compared the performance of both device structures, and found that the inverted structure based device gave significantly improved performance, the highest PCE so far for inverted structure based device using small molecules as the donor. Furthermore, the inverted device shows a remarkable stability with almost no obvious degradation after three months. Systematic device physics and charge generation dynamics studies, including optical simulation, light-intensity-dependent current-voltage experiments, photocurrent density-effective voltage analyses, transient absorption measurements, and electrical simulations, indicate that the significantly enhanced performance using inverted device is ascribed to the increasing of Jsc compared to the conventional device, which in turn is mainly attributed to the increased absorption of photons in the active layers, rather than the reduced nongeminate recombination.
Publisher: American Chemical Society (ACS)
Date: 14-10-2019
Publisher: OSA
Date: 2013
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D1RA03965B
Abstract: Structural and optical properties of MA x Cs 1−x PbBr 3 mixed cation colloidal nanoparticles with 13 mol% Cs composition exhibiting the longest charge carrier lifetime and enhancement in radiative pathways.
Publisher: American Chemical Society (ACS)
Date: 28-09-2021
Publisher: Elsevier BV
Date: 07-2001
Publisher: Elsevier BV
Date: 08-2001
Publisher: Springer Science and Business Media LLC
Date: 29-01-2019
DOI: 10.1038/S41467-019-08326-7
Abstract: Halide perovskites possess enormous potential for various optoelectronic applications. Presently, a clear understanding of the interplay between the lattice and electronic effects is still elusive. Specifically, the weakly absorbing tail states and dual emission from perovskites are not satisfactorily described by existing theories based on the Urbach tail and reabsorption effect. Herein, through temperature-dependent and time-resolved spectroscopy on metal halide perovskite single crystals with organic or inorganic A-site cations, we confirm the existence of indirect tail states below the direct transition edge to arise from a dynamical Rashba splitting effect, caused by the PbBr 6 octahedral thermal polar distortions at elevated temperatures. This dynamic effect is distinct from the static Rashba splitting effect, caused by non-spherical A-site cations or surface induced lattice distortions. Our findings shed fresh perspectives on the electronic-lattice relations paramount for the design and optimization of emergent perovskites, revealing broad implications for light harvesting hoto-detection and light emission/lasing applications.
Publisher: The Optical Society
Date: 05-01-2018
DOI: 10.1364/OE.26.00A153
Publisher: Wiley
Date: 02-06-2015
Abstract: A simple and portable colorimetric assay for creatinine detection is fabricated based on the synergistic coordination of creatinine and uric acid with Hg(2+) on the surface of gold nanoparticles, which exhibits good selectivity and sensitivity. Point-of-care clinical creatinine monitoring can be supported for monitoring renal function and diagnosing corresponding renal diseases at home.
Publisher: American Chemical Society (ACS)
Date: 19-08-2019
Publisher: The Optical Society
Date: 05-01-2018
DOI: 10.1364/OME.8.000231
Publisher: Elsevier BV
Date: 04-2005
Publisher: American Chemical Society (ACS)
Date: 18-07-2023
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 10-2006
Publisher: American Physical Society (APS)
Date: 18-03-2013
Publisher: Wiley
Date: 27-11-2017
Abstract: High pressure (HP) can drive the direct sintering of nanoparticle assemblies for Ag/Au, CdSe/PbS nanocrystals (NCs). Instead of direct sintering for the conventional nanocrystals, this study experimentally observes for the first time high-pressure-induced comminution and recrystallization of organic-inorganic hybrid perovskite nanocrystals into highly luminescent nanoplates with a shorter carrier lifetime. Such novel pressure response is attributed to the unique structural nature of hybrid perovskites under high pressure: during the drastic cubic-orthorhombic structural transformation at ≈2 GPa, (301) the crystal plane fully occupied by organic molecules possesses a higher surface energy, triggering the comminution of nanocrystals into nanoslices along such crystal plane. Beyond bulk perovskites, in which pressure-induced modifications on crystal structures and functional properties will disappear after pressure release, the pressure-formed variants, i.e., large (≈100 nm) and thin (<10 nm) perovskite nanoplates, are retained and these exhibit simultaneous photoluminescence emission enhancing (a 15-fold enhancement in the photoluminescence) and carrier lifetime shortening (from ≈18.3 ± 0.8 to ≈7.6 ± 0.5 ns) after releasing of pressure from 11 GPa. This pressure-induced comminution of hybrid perovskite NCs and a subsequent amorphization-recrystallization treatment offer the possibilities of engineering the advanced hybrid perovskites with specific properties.
Publisher: Royal Society of Chemistry (RSC)
Date: 2014
DOI: 10.1039/C4RA01049C
Abstract: Four polyaromatic compounds with 11- or 13-fused rings have been synthesized and their physical properties have been studied.
Publisher: Springer Science and Business Media LLC
Date: 17-05-1970
DOI: 10.1038/SREP25771
Abstract: Although being considered as one of the most promising cathode materials for Lithium-ion batteries (LIBs), LiNi 1/3 Co 1/3 Mn 1/3 O 2 (NCM) is currently limited by its poor rate performance and cycle stability resulting from the thermodynamically favorable Li + /Ni 2+ cation mixing which depresses the Li + mobility. In this study, we developed a two-step method using fluffy MnO 2 as template to prepare hierarchical porous nano-/microsphere NCM (PNM-NCM). Specifically, PNM-NCM microspheres achieves a high reversible specific capacity of 207.7 mAh g −1 at 0.1 C with excellent rate capability (163.6 and 148.9 mAh g −1 at 1 C and 2 C), and the reversible capacity retention can be well-maintained as high as 90.3% after 50 cycles. This excellent electrochemical performance is attributed to unique hierarchical porous nano-/microsphere structure which can increase the contact area with electrolyte, shorten Li + diffusion path and thus improve the Li + mobility. Moreover, as revealed by XRD Rietveld refinement analysis, a negligible cation mixing (1.9%) and high crystallinity with a well-formed layered structure also contribute to the enhanced C-rates performance and cycle stability. On the basis of our study, an effective strategy can be established to reveal the fundamental relationship between the structure/chemistry of these materials and their properties.
Publisher: Elsevier BV
Date: 02-2006
Publisher: Wiley
Date: 10-12-2015
Abstract: In this work, a facile aqueous synthesis method is optimized to produce Mn:ZnSe/ZnS/ZnMnS sandwiched quantum dots (SQDs). In this core-shell co-doped system, paramagnetic Mn(2+) ions are introduced as core and shell dopants to generate Mn phosphorescence and enhance the magnetic resonance imaging signal, respectively. T1 relaxivity of the nanoparticles can be improved and manipulated by raising the shell doping level. Steady state and time-resolved optical measurements suggest that, after high level shell doping, Mn phosphorescence of the core can be sustained by the sandwiched ZnS shell. Because the SQDs are free of toxic heavy metal compositions, excellent biocompatibility of the prepared nanocrystals is verified by in vitro MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. To explore the theranostic applications of SQDs, liposome-SQD assemblies are prepared and used for ex vivo optical and magnetic resonance imaging. In addition, these engineered SQDs as nanocarrier for gene delivery in therapy of Panc-1 cancer cells are employed. The therapeutic effects of the nanocrystals formulation are confirmed by gene expression analysis and cell viability assay.
No related grants have been discovered for Tze Chien Sum.