Insights into non-noble metal based nanophotonics: exploration of Cr-coated ZnO nanorods for optoelectronic applications

Nanomaterial-enabled photothermal-based solar water disinfection processes: Fundamentals, recent advances, and mechanisms

The pathogenic microorganisms in water pose a great threat to human health. Photothermal and photothermocatalytic disinfection using nanomaterials (NPs) has offered a promising and effective strategy to address the challenges in solar water disinfection (SODIS), especially in the point-of-use operations. This review aims at providing comprehensive and state-of-the-art knowledge of photothermal-based disinfection by NPs. The fundamentals and principles of photothermal-based disinfection were first introduced. Then, recent advances in developing photothermal/photothermocatalytic catalysts were systematically summarized. The light-to-heat conversion and disinfection performance of a large variety of photothermal materials were presented. Given the complicated mechanisms of photothermal-based disinfection, the attacks from reactive oxygen species and heat, the destruction of bacterial cells, and the antibacterial effects of released metal ions were highlighted. Finally, future challenges and opportunities associated with the development of cost-effective photothermal/photothermocatalytic disinfection systems were outlined. This review will provide guidance in designing future NPs and inspire more research efforts from environmental nano-communities to move towards practical water disinfection operations.

Excitonic properties of layer-by-layer CVD grown ZnO hexagonal microdisks

We have investigated the excitonic properties of highly crystalline ZnO hexagonal microdisks grown by the chemical vapour deposition technique. It was observed that a suitable negative catalyst like chlorine suppresses the crystal growth along the (0001) direction. We propose a qualitative model for the experimentally observed layer-by-layer growth mechanism of the microdisks. Room temperature photoluminescence of the microdisks manifests a very high near-band-edge (NBE) emission peak in the UV region and a minor defect peak in the visible region. The excitonic emission of the microdisks was studied using the low-temperature photoluminescence down to 83 K, which reveals a surface exciton peak in the NBE region and well fitted higher-order phonon replicas.

Refractory materials and plasmonics based perfect absorbers

In the past decades, metamaterial light absorbers have attracted tremendous attention due to their impressive absorption efficiency and significant potential for multiple kinds of applications. However, the conventional noble metals based metamaterial and nanomaterial absorbers always suffer from the structural damage by the local high temperature resulting from the strong plasmonic photo-thermal effects. To address this challenge, intensive research has been conducted to develop the absorbers which can realize efficient light absorption and simultaneously keep the structural stability under high temperatures. In this review, we present detail discussion on the refractory materials which can provide robust thermal stability and high performance for light absorption. Moreover, promising theoretical designs and experimental demonstrations that possess excellent features are also reviewed, including broadband strong light absorption, high temperature durability, and even the easy-to-fabricate configuration. Some applications challenges and prospects of refractory materials based plasmonic perfect absorbers are also introduced and discussed.

Review on the Properties of Boron-Doped Diamond and One-Dimensional-Metal-Oxide Based P-N Heterojunction Optoelectronic

This review is mainly focused on the optoelectronic properties of diamond-based one-dimensional-metal-oxide heterojunction. First, we briefly introduce the research progress on one-dimensional (1D)-metal-oxide heterojunctions and the features of the p-type boron-doped diamond (BDD) film; then, we discuss the use of three oxide types (ZnO, TiO2 and WO3) in diamond-based-1D-metal-oxide heterojunctions, including fabrication, epitaxial growth, photocatalytic properties, electrical transport behavior and negative differential resistance behavior, especially at higher temperatures. Finally, we discuss the challenges and future trends in this research area. The discussed results of about 10 years' research on high-performance diamond-based heterojunctions will contribute to the further development of photoelectric nano-devices for high-temperature and high-power applications.

Au nanoparticle-decorated ZnO nanorods as fluorescent non-enzymatic glucose probe

ZnO nanorods (NRs) synthesized by a hydrothermal method and decorated with Au nanoparticles (NPs) were used for fluorescent non-enzymatic glucose detection. The detection is based on the photoluminescence (PL) quenching of ZnO NRs/Au NPs (at 382 nm under 325 nm excitation) exposed to glucose. The sensor exhibits a high sensitivity of (22 ± 2) % mM^-1 (defined as percentage change of the PL peak intensity per mM) and a limit of detection (LOD) as low as 0.01 mM, along with an excellent selectivity and a short response time (less than 5 s). In comparison with a fluorescent non-enzymatic ZnO nanostructure-based glucose sensor, the addition of Au NPs significantly enhances the sensitivity. This is attributed to the surface plasmon resonance, which increases not only the photoluminescence intensity but also the photo-oxidation property of the ZnO NRs. Thus, ZnO NRs/Au NPs can act as an efficient photocatalyst for glucose detection. Most importantly, the probe is applicable to glucose detection in human blood serum. The outstanding performance of the material and its cost-effectiveness allow for potential application in single-use, noninvasive glucose devices.Graphical abstract A sensitive non-enzymatic fluorescent glucose probe-based ZnO nanorod decorated with Au nanoparticles.

Alloy, Janus and core-shell nanoparticles: numerical modeling of their nucleation and growth in physical synthesis

While alloy, core-shell and Janus binary nanoclusters are found in more and more technological applications, their formation mechanisms are still poorly understood, especially during synthesis methods involving physical approaches. In this work, we employ a very simple model of such complex systems using Lennard-Jones interactions and inert gas quenching. After demonstrating the ability of the model to well reproduce the formation of alloy, core-shell or Janus nanoparticles, we studied their temporal evolution from the gas via droplets to nanocrystalline particles. In particular, we showed that the growth mechanisms exhibit qualitative differences between these three chemical orderings. Then, we determined how the quenching rate can be used to finely tune structural characteristics of the final nanoparticles, including size, shape and crystallinity.

Near Infrared Random Lasing in Multilayer MoS2

We demonstrated room temperature near infrared (NIR) region random lasing (RL) (800-950 nm), with a threshold of nearly 500 μW, in ∼200 nm thick MoS2/Au nanoparticles (NPs)/ZnO heterostructures using photoluminescence spectroscopy. The RL in the above system arises mainly due to the following three reasons: (1) enhanced multiple scattering because of Au/ZnO disordered structure, (2) exciton-plasmon coupling because of Au NPs, and (3) enhanced charge transfer from ZnO to thick MoS2 flakes. RL has recently attracted tremendous interest because of its wide applications in the field of telecommunication, spectroscopy, and specifically in biomedical tissue imaging. This work provides new dimensions toward realization of low power on-chip NIR random lasers made up of biocompatible materials.

Improved electrical transport properties of an n-ZnO nanowire/p-diamond heterojunction

A heterojunction of n-ZnO nanowire (NW)/p-B-doped diamond (BDD) was fabricated. The rectifying behavior was observed with the turn on voltage of a low value (0.8 V). The forward current at 5 V is 12 times higher than that of a larger diameter n-ZnO nanorod (NR)/p-BDD heterojunction. The electrical transport behaviors for the comparison of n-ZnO NWs/p-BDD and n-ZnO NRs/p-BDD heterojunctions are investigated over various bias voltages. The carrier injection process mechanism for ZnO NWs/BDD is analyzed on the basis of the proposed equilibrium energy band diagrams. The ZnO NWs/BDD heterojunction displays improved I–V characteristics and relatively high performance for the electrical transport properties.

A heterojunction of n-ZnO nanowire/p-diamond was fabricated and exhibits improved electrical transport properties, which offer a promising design for developing optoelectronic nanodevices working at the nano-scale and with severe environments.