Synthesis and Luminescent Properties of Carbon Nanodots Dispersed in Nanostructured Silicas

Luminescent carbon nanoparticles are a relatively new class of luminescent materials that have attracted the increasing interest of chemists, physicists, biologists and engineers. The present review has a particular focus on the synthesis and luminescent properties of carbon nanoparticles dispersed inside nanostructured silica of different natures: oxidized porous silicon, amorphous thin films, nanopowders, and nanoporous sol–gel-derived ceramics. The correlations of processing conditions with emission/excitation spectral properties, relaxation kinetics, and photoluminescence photodegradation behaviors are analyzed. Following the evolution of the photoluminescence (PL) through the “from-bottom-to-up” synthesis procedure, the transformation of molecular-like ultraviolet emission of organic precursor into visible emission of carbon nanoparticles is demonstrated. At the end of the review, a novel method for the synthesis of luminescent and transparent composites, in form of nanoporous silica filled with luminescent carbon nanodots, is presented. A prototype of white light emitting devices, constructed on the basis of such luminophores and violet light emitting diodes, is demonstrated.

Dye Sensitization for Ultraviolet Upconversion Enhancement

Upconversion nanocrystals that converted near-infrared radiation into emission in the ultraviolet spectral region offer many exciting opportunities for drug release, photocatalysis, photodynamic therapy, and solid-state lasing. However, a key challenge is the development of lanthanide-doped nanocrystals with efficient ultraviolet emission, due to low conversion efficiency. Here, we develop a dye-sensitized, heterogeneous core–multishelled lanthanide nanoparticle for ultraviolet upconversion enhancement. We systematically study the main influencing factors on ultraviolet upconversion emission, including dye concentration, excitation wavelength, and dye-sensitizer distance. Interestingly, our experimental results demonstrate a largely promoted multiphoton upconversion. The underlying mechanism and detailed energy transfer pathway are illustrated. These findings offer insights into future developments of highly ultraviolet-emissive nanohybrids and provide more opportunities for applications in photo-catalysis, biomedicine, and environmental science.

Room-temperature printing of 2D GaN semiconductor via liquid metal gallium surface confined nitridation reaction

Outstanding wide-bandgap semiconductor materials like gallium nitride (GaN) have been extensively utilized in power electronics, radiofrequency power amplifiers, and harsh environment adaptability. Due to its quantum confinement impact in enabling desired deep-ultraviolet emission, excitonic impact, and electronic transport features, two-dimensional (2D) GaN has been one of the most remarkable areas for the future growth of microelectronic devices. Here, for the first time, we report a large area, wide bandgap, and room-temperature 2D GaN synthesis and printing strategy via liquid metal gallium surface-confined nitridation reaction. The developed low-temperature synthesis and printing process is consistent with various electronic device manufacturing methods and thus opens a way for the cost-effective growth of the third-generation semiconductor. In particular, the fully printed field-effect transistors relying on the GaN show p-type switching with an on/off ratio greater than 105, maximum field-effect hole mobility of 53 cm2 V−1 s−1, and a small sub-threshold swing at room temperature. The current study establishes a room temperature way to produce the GaN, which can be further verified, generalized, and realized for various upcoming electronic and photoelectronic applications.

Preparation and Characterizations of NiS/ZnS Bilayer Thinfilm by Chemical Bath Deposition Method

NiS/ZnS thin films were grown by Chemical Bath Deposition (CBD) technique using eqimolar aqueous solutions of zinc chloride, nickel chloride and thiourea as precursor. Silicon glass substrates were placed in glass bottles with polypropylene autoclave screw caps containing the precursors described above, and the bath temperature is maintained at 95°C. X-ray diffraction 28/8 scans showed that the only crystallographic phase present was the hexagonal wurtzite structure. Scanning electron microscopy showed the formation of nanostructures, consisting of hexagonal structures of a few hundred nanometers. The photoluminescence spectra of NiS/ZnS bilayer were recorded at 18-295 K using a cw He-Cd laser (325 nm) and pulsed laser (266 nm). The NiS/ZnS nanostructure exhibit an ultraviolet emission band centered at ;:::; 3.87eV in the vicinity of the band edge, which is attributed to the well-known excitonic transition in ZnS. The optical properties such as refractive index, electrical and optical conductivities were determined by using UV- VIS absorption spectrometry. The band gap energy was determined as 1.45 eV.