Spectral information from minerals relevant for luminescence dating

Development of ion-implanted optical waveguides in optical materials: A review

Along with the development of industry and the improvement of people’s living standards, peoples’ demand on resources has greatly increased, causing energy crises and environmental pollution. In recent years, photocatalytic technology has shown great potential as a low-cost, environmentally-friendly, and sustainable technology, and it has become a hot research topic. However, current photocatalytic technology cannot meet industrial requirements. The biggest challenge in the industrialization of photocatalyst technology is the development of an ideal photocatalyst, which should possess four features, including a high photocatalytic efficiency, a large specific surface area, a full utilization of sunlight, and recyclability. In this review, starting from the photocatalytic reaction mechanism and the preparation of the photocatalyst, we review the classification of current photocatalysts and the methods for improving photocatalytic performance; we also further discuss the potential industrial usage of photocatalytic technology. This review also aims to provide basic and comprehensive information on the industrialization of photocatalysis technology.

https://www.mdpi.com/2076-3417/9/12/2489/pdf

Recent Advances and Applications of Semiconductor Photocatalytic Technology

Functionalization of Single Walled Carbon Nanotubes B y Lei Zhang Single walled carbon nanotubes (SWNTs) exhibit unique mechanical and physical properties and immediately after their discovery they were regarded as novel materials for future technologies. SWNTs are widely thought o f as one o f the basic building blocks to nanotechnology. However, they are very hard to disperse and dissolve in either water or organic solvent. The insolubility o f nanotubes makes it very difficult to make composites o f nanotubes with other materials. This limits nanotubes from the application for future technology. A feasible functionalization o f nanotubes, i.e., the attachment o f “chemical functional groups” provides a strategy for overcoming these barriers and has thus attracted synthetic chemists and materials scientists to contribute their efforts to making breakthrough. Functionalization can improve solubility and processibility, and will be able to link the unique properties o f nanotubes to those o f other types o f materials. Through the chemical functional groups, nanotube may show improved solubility and compatibility with solvents, polymers, nanoparticles and other nanotubes. A functionalized SWNT may have mechanical or electrical properties that are different from those o f the pristine SWNT, and thus may be used for fine-tuning the chemistry and physical properties o f SWNTs. Fluorination o f side walls o f the SWNTs has been performed by using the technology developed for the fluorination o f graphite, and then subsequent nucleophilic substitutions have been explored. It has been ascertained that in fluorination at the optimal temperature, C:F ratios o f up to 2:1 can be achieved without disruption o f the tubular structure. The fluorinated SWNTs proved to be much more soluble than pristine SWNTs in alcohols, N,N-dimethylformamide and some other selected organic solvents. This improved solubility and the high fluorine addition allow much more efficient solution-phase chemistry on the fluorinated SWNTs. R e p ro d u c e d with p erm iss ion of th e copyright ow ner. F u r the r reproduction prohibited without perm iss ion . The goals o f this work were to examine novel type o f reactions that one can do with fluorinated SWNTs and study the basic aspects o f functionalization o f SWNTs, i.e. the mechanism o f functionalization, the structure o f fluorinated SWNTs, and the distribution o f functional groups in the functionalized SWNTs. In this thesis, an extensive NMR study o f fluorinated SWNTs has been explored (Chapter 1) and this study gives us a deeper insight to the structure o f fluorinated SWNTs and the mechanism o f fluorination. A series o f “hydroxyl nanotube” have been simply prepared by two types o f one-step methods (Chapter 2). Amino-acid functionalized nanotubes with high water solubility and sensitive pH value dependence have been achieved, and the influence o f different chain length o f amino acid on the water solubility was detailed (Chapter 3). The nanotube-nanoparticle heterostructures have been prepared and used to investigate the distribution o f functional groups along the axis o f nanotubes (Chapter 4). Finally, a novel type o f reaction, Diels-Alder cycloaddition to fluorinated nanotubes was successfully performed under a mild reaction conditions (Chapter 5). R e p ro d u c e d with p erm iss ion of th e copyright ow ner. F u r the r reproduction prohibited without perm iss ion .

Functionalization of single walled carbon nanotubes

Carbon nanotube–metal oxide nanocomposites: Fabrication, properties and applications

In this research high-quality zinc oxide (ZnO) nanowires have been synthesized by thermal oxidation of metallic Zn thin films. Metallic Zn films with thicknesses of 250 nm have been deposited on a glass substrate by the PVD technique. The deposited zinc thin films were oxidized in air at various temperatures ranging between 450 °C to 650 °C. Surface morphology, structural and optical properties of the ZnO nanowires were examined by scanning electron microscope (SEM), X-ray diffraction (XRD), energy dispersive X-ray (EDX) and photoluminescence (PL) measurements. XRD analysis demonstrated that the ZnO nanowires has a wurtzite structure with orientation of (002), and the nanowires prepared at 600 °C has a better crystalline quality than samples prepared at other temperatures. SEM results indicate that by increasing the oxidation temperature, the dimensions of the ZnO nanowires increase. The optimum temperature for synthesizing high density, ZnO nanowires was determined to be 600 °C. EDX results revealed that only Zn and O are present in the samples, indicating a pure ZnO composition. The PL spectra of as-synthesized nanowires exhibited a strong UV emission and a relatively weak green emission.

https://www.mdpi.com/1420-3049/17/5/5021/pdf

Synthesis and Characterization of ZnO Nanowires by Thermal Oxidation of Zn Thin Films at Various Temperatures

During ion beam implantation there is associated luminescence from insulators which contains information on the crystallinity of the host lattice, the structural perfection of the surface region, impurity content, intrinsic defects and variations in phase, nanoparticle inclusions and lattice stability. Hence, ion beam luminescence can provide both an immediate diagnostic probe of the changes which occur during implantation and an independent means of analysing defects in the near surface region. The technique is similar to cathodoluminescence but has advantages that it probes a greater depth of material with a more controllable rate of energy deposition in the layer. By the use of different ions and molecular beams one can explore dose rate dependence effects and distinguish between alternative defect models. In the diagnostic role there are further benefits from varying the target temperature and from using beam modulation to probe differences in lifetime of the excited luminescence sites. Ion beam signals are less sensitive to surface contaminants than cathodoluminescence and by changing the ion beam energy one may progressively interrogate the surface structure over depths of tens of microns. Examples from each of the various situations will be presented and these will underline the fact that the technique is extremely powerful. Since it is under exploited suggestions for new experiments are considered.

M. R. Khanlary

Papers

Synthesis and Characterization of ZnO Nanowires by Thermal Oxidation of Zn Thin Films at Various Temperatures

Information obtainable from ion beam luminescence

TL spectra of single crystal and crushed calcite

Effect of gamma radiation on the optical and structural properties of ZnO nanowires with various diameters

Red-orange photoluminescence emission of sol-gel dip-coated prepared ZnO and ZnO:Al nano-crystalline films