UV-curable polyurethane acrylate–Ag/TiO2 nanocomposites with superior UV light antibacterial activity

Polyurethane acrylate (PUA)–Ag/TiO₂ nanocomposites were synthesized through in situ polymerization. The well-dispersed Ag/TiO₂ nanorods serve as photoinitiator. Meanwhile, the PUA–Ag/TiO₂ nanocomposite films exhibit superior activity toward the photocatalytic degradation of Escherichia coli under UV light. The excellent UV curing and antibacterial activities can be ascribed to the synergistic effect of Ag and TiO₂, which promotes the effective electron/hole separation and thus generates various reactive species. Thin films with these nanoparticles are more hydrophilic after UV illumination. And the antibacterial mechanism of the UV-curable PUA–Ag/TiO₂ nanocomposites was proposed.     

Enhanced ethanol sensing and mechanism of Cr-doped ZnO nanorods: Experimental and computational study

The pristine and Cr-doped ZnO nanorods were successfully synthesized via a facile hydrothermal route. We found that the ethanol gas response of ZnO was improved significantly by Cr doping. In particular, the enhanced gas-sensing mechanism was investigated by first-principles calculations upon proposed surface adsorption models. The calculated results revealed that the Cr-doped ZnO (0 0 0 1) surface enabled transfer larger electrons and adsorb more oxygen molecules than that of undoped one, thus holding the potential for further enhancement in gas response of ZnO-based sensors.     

Fabrication of urchin-like ZnO-MXene nanocomposites for high-performance electromagnetic absorption

The recently developed two-dimensional transition metal carbides (such as MXene) have shown amazing electrical properties. MXene and derivative two dimensional (2D) materials are widely used in electron devices, and have large potential application in electromagnetic (EM) absorber. Herein we describe a mild method to prepare an urchin-like ZnO-MXene Ti₃C₂T_x nanocomposite through a coprecipitation process. The nanocomposite delivers a substantially enhanced EM absorbing performance with an optimum reflection loss of −26.30 dB, which is significantly better than that of primitive Ti₃C₂T_x (−6.70 dB), owing to the construction of unique semiconductive networks and larger interfaces. The EM absorption performance can be effectively controlled in the range of 14.0–18.0 bands by changing the growth time of ZnO. Considering the large amount of members in MXene, this study demonstrates a new strategy applicable in maximizing their applications in EM absorbing materials.     

Plasmonic Dual‐Enhancement and Precise Color Tuning of Gold Nanorod@SiO2 Coupled Core–Shell–Shell Upconversion Nanocrystals

The last decade has witnessed the remarkable research progress of lanthanide‐doped upconversion nanocrystals (UCNCs) at the forefront of promising applications. However, the future development and application of UCNCs are constrained greatly by their underlying shortcomings such as significant nonradiative processes, low quantum efficiency, and single emission colors. Here a hybrid plasmonic upconversion nanostructure consisting of a GNR@SiO₂ coupled with NaGdF₄:Yb³⁺,Nd³⁺@NaGdF₄:Yb³⁺,Er³⁺@NaGdF₄ core–shell–shell UCNCs is rationally designed and fabricated, which exhibits strongly enhanced UC fluorescence (up to 20 folds) and flexibly tunable UC colors. The experimental findings show that controlling the SiO₂ spacer thickness enables readily manipulating the intensity ratio of the Er³⁺ red, green, and blue emissions, thereby allowing us to achieve the emission color tuning from pale yellow to green upon excitation at 808 nm. Electrodynamic simulations reveal that the tunable UC colors are due to the interplay of plasmon‐mediated simultaneous excitation and emission enhancements in the Er³⁺ green emission yet only excitation enhancement in the blue and red emissions. The results not only provide an upfront experimental design for constructing hybrid plasmonic UC nanostructures with high efficiency and color tunability, but also deepen the understanding of the interaction mechanism between the Er³⁺ emissions and plasmon resonances in such complex hybrid nanostructure.     

Manipulable and Hybridized,Ultralow‐Threshold Lasing in a Plasmonic Laser Using Elliptical InGaN/GaN Nanorods

Manipulating stimulated‐emission light in nanophotonic devices on scales smaller than their emission wavelengths to meet the requirements for optoelectronic integrations is a challenging but important step. Surface plasmon polaritons (SPPs) are one of the most promising candidates for sub‐wavelength optical confinement. In this study, based on the principle of surface plasmon amplification by the stimulated emission of radiation (SPASER), III‐Nitride‐based plasmonic nanolaser with hybrid metal–oxide–semiconductor (MOS) structures is designed. Using geometrically elliptical nanostructures fabricated by nanoimprint lithography, elliptical nanolasers able to demonstrate single‐mode and multimode lasing with an optical pumping power density as low as 0.3 kW cm^?2 at room temperature and a quality Q factor of up to 123 at a wavelength of ≈490 nm are achieved. The ultralow lasing threshold is attributed to the SPP‐coupling‐induced strong electric‐field‐confinement in the elliptical MOS structures. In accordance with the theoretical and experimental results, the size and shape of the nanorod are the keys for manipulating hybridization of the plasmonic and photonic lasing modes in the SPASER. This finding provides innovative insight that will contribute to realizing a new generation of optoelectronic and information devices.     

Synthesis of nanocrystalline materials through reverse micelles: A versatile methodology for synthesis of complex metal oxides

We have been successful in obtaining monophasic nanosized oxides with varying chemical compositions using the reverse micellar method. Here we describe our methodology to obtain important metal oxides like ceria, zirconia and zinc oxide. The oxalate of cerium, zirconium and zinc were synthesized using the reverse micellar route. While nanorods of zinc oxalate with dimension, 120 nm in diameter and 600 nm in length, could be obtained, whereas spherical particles of size, 4–6 nm, were obtained for cerium oxalate. These precursors were heated to form their respective oxides. Mixture of nanorods and nanoparticles of cerium oxide was obtained. ZrO₂ nanoparticles of 3–4 nm size were obtained by the thermal decomposition of zirconium oxalate precursor. ZnO nanoparticles (55 nm) were obtained by the decomposition of zinc oxalate nanorods. Photoluminescence (PL) studies at 20 K shows the presence of three peaks corresponding to free excitonic emission, free to bound and donor-acceptor transitions. We also synthesized nanoparticles corresponding to Ba_1−x Pb _x ZrO₃ using the reverse micellar route. The dielectric constant and loss were stable with frequency and temperature for the solid solution.     

Growth of compact arrays of optical quality single crystalline ZnO nanorods by low temperature method

We report the synthesis and optical properties of compact and aligned ZnO nanorod arrays (dia, ∼ 50–200 nm) grown on a glass substrate with varying seed particle density. The suspension of ZnO nanoparticles (size, ∼ 15 nm) of various concentrations are used as seed layer for the growth of nanorod arrays via selfassembly of ZnO from solution. We studied the effect of various growth parameters (such as seeding density, microstructure of the seed layer) as well as the growth time on the growth and alignment of the nanorods. We find that the growth, areal density and alignment of the nanorods depend on the density of seed particles which can be controlled. It is observed that there is a critical density of the seed particles at which nanorod arrays show maximum preferred orientation along [002] direction. The minimum and maximum radius of the aligned nanorods synthesized by this method lie in the range 50–220 nm which depend on the seeding density and time of growth. These nanorods have a bandgap of 3.3 eV as in the case of bulk crystals and show emission in the UV region of the spectrum (∼ 400 nm) due to excitonic recombination and defect related emission in the visible region.