Dunman High School

Singapore, Singapore

Dunman High School

Singapore, Singapore
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Lim X.,National University of Singapore | Xu H.,National University of Singapore | Nicole Chew Y.H.,Dunman High School | Phua Y.H.,Dunman High School | And 5 more authors.
Nanotechnology | Year: 2010

A technique utilizing the capillary assisted sieving capability of carbon nanotubes (CNTs) to achieve fractionation of nanoparticles of small size distribution is presented. By dipping aligned CNT arrays into a solution comprising different sized quantum dots (QDs), size-selective gradient decoration of QDs onto CNTsis achieved. The fractionating capability of CNTs is alsodemonstrated for poly-dispersed manganese doped zinc sulfide nanoparticles and QDs of varying sizes and chemical compositions, which we attribute to the size-selective sieving effect of CNTs. By controlling the terminating point for the flow of QDs across the CNT array, a QD size specific CNT/QD hybrid structure is achieved. © 2010 IOP Publishing Ltd.

Lim X.,National University of Singapore | Gary Foo H.W.,Dunman High School | Chia G.H.,Dunman High School | Sow C.-H.,National University of Singapore
ACS Nano | Year: 2010

In this work, detailed studies of three different capillary-assisted techniques for the formations of large-scale multiwalled carbon-nanotube (MWNT)-based microstructures were presented. Using laser induced artificial vacancies, new insights into the effect of laser power, densities of MWNTs, and oxidation process dependencies for the creations of MWNT polygons were presented. With organized initiations, MWNT pillars were crafted out of MWNT arrays and 0.21 pL of water was found to produce sufficient force to bring about 14.7 μm deflections of a 9.19×9.19×24.1 μm3 pillar, thereby allowing well-controlled formations of threedimensional top-gathering MWNTs. Lastly, by twisting densified MWNT microbelts, 14 times improvements in resistivity as compared to undensified MWNT microwalls were achieved. Through prepatterning, the amount of twisting effect could be controlled, and this in turn allowed control of the resistance of the densified MWNT microwalls. These new insights and techniques presented could further encourage the use of self-organized MWNT structures with initiation as a flexible and viable route for the implementations of carbon-nanotube-based electronic devices. © 2010 American Chemical Society.

Lim S.X.,National University of Singapore | Woo K.W.,Dunman High School | Ng J.,Dunman High School | Lu J.,National University of Singapore | And 4 more authors.
Nanoscale | Year: 2015

Few-layer MoS2 film has been successfully assembled over an array of CNTs. Using different focused laser beams with different wavelengths, site selective patterning of either the MoS2 film or the supporting CNT array is achieved. This paves the way for applications and investigations into the fundamental properties of the hybrid MoS2/CNT material with a controlled architecture. Through Raman mapping, straining and electron doping of the MoS2 film as a result of interaction with the supporting CNT array are detected. The role of the MoS2 film was further emphasized with a lower work function being detected from Ultra-violet Photoelectron Spectrsocopy (UPS) measurements of the hybrid material, compared to the CNT array. The effect of the changes in the work function was illustrated through the optoelectronic behavior of the hybrid material. At 0 V, 3.49 nA of current is measured upon illuminating the sample with a broad laser beam emitting laser light with a wavelength of 532 nm. With a strong response to external irradiation of different wavelengths, and changes to the power of the excitation source, the hybrid material has shown potential for applications in optoelectronic devices. © The Royal Society of Chemistry 2015.

Lim S.X.,National University of Singapore | Lim Y.H.,Dunman High School | Loh C.L.C.,Dunman High School | Yap Y.Y.W.,Dunman High School | And 2 more authors.
Journal of Physical Chemistry C | Year: 2011

An assembly technique based on crystallization of thin CuSO 4·5H2O microcrystals from salt solution onto patterned three-dimensional (3D) multiwalled carbon nanotube (MWNT) platform was developed. The vertically aligned MWNT arrays served as nucleation sites for the formation of microstructured CuSO4·5H2O crystals. In the presence of MWNTs, the CuSO4·5H2O crystal exhibited preferential crystallization in the (2̄22) orientation. Sculpting the MWNT platforms using a focused laser beam, as well as utilizing capillary forces that occurred during the drying process of the salt solution, a variety of 3D MWNT-microcrystal hybrid systems were created. In addition to the 3D MWNT platform created by focused laser beam pruning, we have also achieved assembly of the microcrystals onto MWNT array with patterned hydrophilic and hydrophobic regions. Such chemical modifications of the MWNT surface were achieved without introducing any physical destruction to the MWNT arrays. As such, two-dimensional template-directed assembly of crystals onto the hydrophilic regions on the MWNT surface was realized. © 2011 American Chemical Society.

Chan P.Y.,Institute for Infocomm Research | Chan P.Y.,Nanyang Technological University | Dong M.,Institute for Infocomm Research | Lim Y.Q.,Hwa Chong Institution | And 5 more authors.
International Conference on Digital Signal Processing, DSP | Year: 2015

This paper presents our work in formant excursion in the human singing voice. In singing voice synthesis, numerous methods have been proposed to modify pitch and energy over time in order to achieve better expressiveness and naturalness [1]-[3]. Methods to modify the spectral envelop, however, remain conservative [4], [5]. An expressive singer, nevertheless, employs different techniques to modify his vocal spectra extensively throughout a song [6]. This motivates our study on formant excursion. We hypothesize that the level of semantic reliance on vowels limits the range of formant excursion and develop a method to find Ξ, a measure of isolated spectral distortion attributed to singing expressiveness, independent of the spectral differences inherent between speech and singing. With this, we are able to better parameterize spectral modifications in the singing voice towards a dynamic spectral model for singing synthesis. © 2015 IEEE.

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