Volume 2 Issue 1
Authors: Rajeswari Yogamalar N; Arumugam Chandra Bose
Abstract: The advantageous crystal structure properties along with the ease growth of one-dimensional (1-D) zinc oxide (ZnO) nanostructures define the material to possess wide technological applications. The ultimate goal of this review article is to provide an overview of research activities prevailing on ZnO nanostructures from the basic synthesis technique to world-wide scientific and industrial applications. The article covers the recent progress, growth of ZnO nanostructures with unique and dimensionality confined morphology through surfactant-assisted simple chemical precipitation methods and through newly emerging self assembly techniques. Much emphasis is showered on the growth of nanostructures with controlled size and shape, synthesized by means of precipitation of a solid phase from solution. It also highlights the superior physio-chemical properties including structural, optical, electrical, and magnetic properties with the addition and substitution of dopant atoms. The optical properties including UV absorption and luminescence studies are rigorously probed for samples in the form of nanostructures and thin film prepared by various methods and doped with different impurities. The review further outlines the implementation of material properties in opto-electronic device applications and their commercial availability. This article extensively explores the achievements, research prospects, limitations and updates upcoming in n-type and p-type ZnO nanostructures. Additionally, we devote our attention to the study of native defects, origin of surface defects, defect emissions and their role in producing unintentional n-type ZnO. Finally, the review concludes with the homo- and hetero-type junction formation, device characterization and the open challenges to stabilize the device construction. This article also includes the research work carried out in our nanomaterials laboratory on ZnO preparation (both powder and thin film) and their characterizations and property studies will be presented briefly. We trust this review will be beneficial to expand the practical applications and offer some inspirations to the researchers in the fields of engineering, biomedicine, and materials science.
Keywords: One-dimensional; Solid Phase; Dopant Atoms; Native Defects; Physio-Chemical Properties
Authors: N. Rajmuhon Singh; Reena Okram
Abstract: Highly luminescent Tb3+ doped CePO4 nanoparticles (NPs) co-doped with some metal ions (Li+, Ba2+, Bi3+) are prepared using different solvents. The prepared samples show changes in phase and luminescent properties with the solvent used. Samples prepared in EG shows maximum luminescence intensity compared to other solvents. Highly green luminescence properties of the prepared NPs are due to the emission peak at 544 nm corresponding to 5D4→7F5 transition of Tb3+. The hexagonal phase of the samples prepared in water and water mixed solvent transformed to monoclinic phase after heating at 900oC. The luminescence intensity further enhanced with co-doping of Li+ ions while co-doping of Ba2+ and Bi3+ ions reduces the intensity. These NPs can be incorporated in polymer films such as polyvinyl alcohol (PVA). Thus the prepared phosphors can be used as green emitting material in the field of illuminations and display devices.
Keywords: Rare Earth; Enhanced Luminescence; Phase Change; Nanoparticles; Re-dispersible
Authors: Edwin Paul; Rajeswari Arunachalam; Sujatha Dhanasingh; Uthirappan Mani; Ponnusamy Shanmugam; Chellan Rose; Asit Baran Mandal
Abstract: A simple and green approach for the synthesis of nanocrystals of silver (Ag) using Ricinus communis leaf extract at room temperature is described. Treatment of aqueous silver ions with aqueous leaf extract got Ag+ ions reduced and resulted in the formation of silver nanoparticles (NPs). The silver NPs were characterized by UV-Vis spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), thermo gravimetric analysis (TGA), differential scanning calorimetry (DSC), Fourier-transform infra red spectroscopy (FTIR) and high-resolution transmission electron microscopy (HRTEM). The nanoparticles obtained are in the size range of 20-30 nm and crystallized in the form of face centered cubic (fcc) symmetry. This green chemical method has several advantages such as cost-effectiveness, compatibility for biomedical and pharmaceutical applications as well as for large scale commercial production.
Keywords: Metals; Electron Microscopy; X-Ray Diffraction; Optical Properties
Authors: Bengkang Tay; Xincai Wang; Hangtong Teo; Chongwei Tan; Siuhon Tsang; Naiyu Xu
Abstract: Previous work has shown that the bonding structure and phase of amorphous carbon (a-C) can be modified by laser annealing. In this work, the effect of surface modification by metal coating on a-C during laser annealing was studied. A-C film was deposited by the filtered cathodic vacuum arc (FCVA) technique onto n-type (100) silicon substrate at room temperature. Nickel (Ni) was deposited on the surface of a-C films by electron beam (e-beam) evaporation method, and laser annealing with different laser energy density was performed on the a-C films with and without Ni coating. Visible Raman spectroscopy was used to examine the bonding structure evolution upon laser annealing and the effect on the bonding structure of a-C by introducing Ni onto the DLC film surface. The Raman spectra shows more pronounced change for a-C films with Ni coating than those without Ni coating upon laser annealing, and the Raman features also suggest that the Ni surface coating can enhance formation of the six-ring graphitic-like sp2 ordering. Electrical measurement shows a low resistive characteristic for both set of films due to laser induced conducting sp2 clusters formation.
Keywords: Amorphous Carbon;Graphitization; Laser Annealing; Visible Raman Spectroscopy