Search

ZnO quantum dots of average size 10 nm are embedded in a matrix (polyvinyl alcohol (PVA)) following chemical route. They are irradiated by 100 MeV Ni7+ ion beam with fluences 1 × 1011, 3 × 1011, 1 × 1012 and 3 × 1012 ions/cm2. The optical absorption edge of irradiated quantum dots reveal negligible red shift with an increase in fluences with respect to that of unirradiated (virgin) ones. This fact clearly indicates no significant change in particle diameter under ion irradiation and is confirmed by high resolution transmission electron microscopy (TEM). AFM study also reveals the r.m.s surface roughness of the particles. It has also been observed that irradiated quantum dots produce similar type of photo luminescence and electroluminescence like virgin samples but the emission intensity increases remarkably after irradiation due to creation of large numbers oxygen vacancies by the ion beam.

This article reports the synthesis of ZnS quantum dots (QDs) embedded in polyvinylpyrrolidone matrix via a simple chemical technique and its novel application as a nano-light-emitting device. The synthesized specimen has been characterized by using UVVis spectroscopy, X-ray diffraction study, atomic force microscopy, and high-resolution transmission electron microscopy. These studies indicate the sizes of QDs to be within 8nm. The prepared QD samples have been examined in a fabricated ZnOQD-based nano-light-emitting device by exploring the variation of electroluminescence (EL) (light emission phenomenon) with supply voltage at room temperature. The almost linear variation of EL intensity with voltage is obtained for a specific range of voltage, which makes ZnS nanoparticles suitable for light-emitting devices.

The properties of materials drastically change when matter performs a transition from bulk to nano size. The quantum dots (QDs) of lead sulphide (PbS) embedded into Polyvinyl alcohol (PVA) are synthesized via one pot synthesis chemical method. The specimen has been analyzed by UV/VIS absorption spectroscopy, High resolution transmission electron microscopy (HRTEM) and fluorescence spectroscopy. Quantum Dot size is calculated from the absorption spectra using hyperbolic band model and sizes of the dots are found to be around 6nm and the calculated value is in agreement with the size as determined by HRTEM. The photoluminescence spectra was also obtained for the samples.

Silver nanoparticles have been synthesised by chemical reduction of silver nitrate solution by ethanol. The samples have been characterised by X-ray diffraction study. Transmission electron microscopy reveals the nanostructure of the particles produced. This study infers that the particles are mostly spherical in shape and the sizes are within 18 nm. The surface plasmon resonance peak in the UV-Vis absorption spectra shows maximum absorption at 422 nm. Fluorescence spectra of silver nanoparticles, which show an emission peak at 470 nm have also been studied.

We report synthesis of ZnO quantum dot embedded in polyvinylpyrrolidone (PVP) matrix and its functioning as acetone sensor. The specimen is prepared via quenching technique where bulk ZnO powder is calcined at very high temperature of 1200 °C and then quenched into ice cold polyvinylpyrrolidone solution. The samples have been characterized by using UV/vis spectroscopy, X-ray diffraction study, high resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM). These studies infer the sizes of quantum dots to be within 10 nm. The prepared quantum dot samples have been tested for sensing acetone vapour by exploring the variation of their resistance with time at different operating temperatures. It has been revealed that ZnO quantum dots can sense acetone at low operating (230 °C) temperature with less response time.

We report synthesis, optical absorption and luminescence spectroscopy of Ni +7 ion irradiated ZnS semiconductor quantum dots over coated with Silica (SiO 2 ) embedded in PVA matrix. Quantum dot samples are prepared via Chemical route. 100 MeV Nickel ion is selected for the irradiation experiment with different doses of 1 x 1011, 3 x10 11 , 3 x10 12 and 10 13 ions/cm 2 . With an increase in doses, the optical absorption edge of irradiated quantum dots reveal negligible shift with respect to that of unirradiated (virgin) quantum dots. This phenomenon clearly indicates no appraisable change in particle size under ion irradiation which is confirmed from high resolution transmission electron microscope images. It has been observed that like virgin samples, irradiated quantum dots produce similar kind of green luminescence but the emission intensity increases significantly after irradiation due to creation of Zn vacancies by ion irradiation.

Quantum dot sensitised solar cells (QDSSC) is generally fabricated using transparent conducting (TCO) glass plates and platinum or gold as electrodes. The article reports a modified back side illuminated QDSSC structure utilising aluminium foil as electrodes. PbS quantum dots have been synthesised using simple chemical method and are utilised as sensitisers in a ZnO-based solar cell structure. Two types of QDSSCs are fabricated using the same quantum dots, i.e., one using ITO glass plate and the other using aluminium. The solar cell parameters are obtained for both the structures and their comparative analysis is reported in the paper.

We report synthesis of ZnS quantum dots by chemical method at room temperature. In this technique, ZnS quantum dots are produced by simple chemical reactions where zeolite, acts as matrix, plays the key role in controlling particle growth during synthesis. Quantum dots exhibit luminescence properties such as Zn2+ related emission, efficient low voltage electroluminescence, and super linear voltage-brightness EL characteristics. This study demonstrates the technological importance of semiconductor nanosystems prepared by low cost chemical route.

We report the synthesis of ZnS and ZnS:Cu (copper doped ZnS) quantum dots by chemical method at room temperature. In this technique ZnS and ZnS:Cu quantum dots are produced by simple chemical reactions where zeolite acts as matrix and plays the key role in controlling particle growth during synthesis. ZnS exhibits luminescence properties such as Zn2+ related emission. ZnS:Cu possesses Cu related emission, efficient low voltage electroluminescence, and super linear voltage-brightness electroluminescence characteristics. This study demonstrates the technological importance of semiconductor quantum dots prepared by low cost chemical route.