CONTROLLED FABRICATIONS OF 3D CARBON NANOTUBES ARCHITECTURES WITH IMPROVED FUNCTIONALITIES

Master'sMASTER OF SCIENC

A Focused Laser Beam: A Useful and Versatile Tool for 1D Nanomaterials Research: A Review

10.1016/j.jmst.2014.12.006Journal of Materials Science and Technology316616-62

Upcycling fish scales through heating for steganography and Rhodamine B adsorption application

Abstract With increasing population and limited resources, a potential route for improving sustainability is increased reuse of waste materials. By re-looking at wastes, interesting properties and multifunctionalities can be discovered in materials previously explored. Despite years of research on bio-compatible fish scales, there is limited study on the fluorescence property of this abundant waste material. Controlled denaturation of collagen and introduction of defects can serve as a means to transform the fluorescence property of these fish scale wastes while providing more adsorption sites for pollutant removal, turning multifunctional fish scales into a natural steganographic material for transmitting text and images at both the macroscopic and microscopic levels and effectively removing Rhodamine B pollutants (91 % removal) within a short contact time (10 minutes). Our work offers a glimpse into the realm of engineering defects-induced fluorescence in natural material with potential as bio-compatible fluorescence probes while encouraging multidimensional applicability to be established in otherwise overlooked waste resources

Metal-insulator transition switching in VOx-VSe2 heterojunctions

First-order metal-insulator transition (MIT) observed in strongly correlated systems such as vanadium dioxide (VO2) holds potential in electronics, energy, to optical applications. Starting from a vanadium diselenide (VSe2) bulk crystal, we demonstrated a direct surface conversion from VSe2 to VO2 via laser exposure in ambient condition. The process generates defects, and the heat from the laser promotes oxidation forming VOx. Raman spectra at room temperature suggest the resulting oxide formed is monoclinic (M1) VO2. Above the transition temperature (TC), all the phonon modes are damped indicating formation of the rutile phase (metallic). Photoluminescence (PL) intensity enhancement and peak shifts observed at TC suggest correlation to the band structure transformation. In addition, we observed electrically induced MIT in our lateral VSe2-VOx heterojunction device.Ministry of Education (MOE)National Research Foundation (NRF)Published versionThis work was financially supported by MOE2017-T2-2- 139, MOE2018-T2-1-088 (Ministry of Education, Singapore), and NRF-NSFC R-144-000-405-281 (National Research Foundation Singapore as a department within the Prime Minister’s Office) grants

Field Emission from Decorated Carbon Nanotube–QDs Microstructures with a View to the Dominant Electron Paths

We present a study on the field emission properties of a hybrid system comprised of carbon nanotube (CNT) micropillars decorated with quantum dots (QDs). With controlled decoration of QDs on the CNT micropillars through a simple assisted self-assembly process, further enhancement in the field emitting property of the hybrid microstructures was detected. Upon irradiation of the hybrid structure with a broad visible-light laser beam, additional enhanced field emission was observed. Analyses using fluorescence and confocal microscopy, as well as ultraviolet photoelectron spectroscopy, suggested that electron transfer from QDs to the CNT strands and the reduced work function of the hybrid system as the contributing factors behind the enhanced field emissions. In addition, we discovered that the field emission process gave rise to lost of the QDs’ fluorescence luminosity on the microstructures in specific patterns attributable to transfers of charge carrier from QDs to the CNTs. This observation provided a new means to understand and to determine the predominant 3D path of the emission of electrons from the sample down to a micrometer scale level

Dynamic Tuning of Moiré Superlattice Morphology by Laser Modification

© In artificial van der Waals (vdW) layered devices, twisting the stacking angle has emerged as an effective strategy to regulate the electronic phases and optical properties of these systems. Along with the twist registry, the lattice reconstruction arising from vdW interlayer interaction has also inspired significant research interests. The control of twist angles is significantly important because the moiré periodicity determines the electron propagation length on the lattice and the interlayer electron-electron interactions. However, the moiré periodicity is hard to be modified after the device has been fabricated. In this work, we have demonstrated that the moiré periodicity can be precisely modulated with a localized laser annealing technique. This is achieved with regulating the interlayer lattice mismatch by the mismatched lattice constant, which originates from the variable density of sulfur vacancy generated during laser modification. The existence of sulfur vacancy is further verified by excitonic emission energy and lifetime in photoluminescence measurements. Furthermore, we also discover that the mismatched lattice constant has the equivalent contribution as the twist angle for determining the lattice mismatch. Theoretical modeling elaborates the moiré-wavelength-dependent energy variations at the interface and mimics the evolution of moiré morphology.11Nsciescopu

Directed crystallization of CuSO4·5H2O onto carbon nanotube microarchitectures

10.1021/jp2062805Journal of Physical Chemistry C1154320964-2096