Hybrid Anodic and Metal-Assisted Chemical Etching Method Enabling Fabrication of Silicon Carbide Nanowires.

Silicon carbide (SiC) is one of the most important third-generation semiconductor materials. However, the chemical robustness of SiC makes it very difficult to process, and only very limited methods are available to fabricate nanostructures on SiC. In this work, a hybrid anodic and metal-assisted chemical etching (MACE) method is proposed to fabricate SiC nanowires based on wet etching approaches at room temperature and under atmospheric pressure. Through investigations of the etching mechanism and optimal etching conditions, it is found that the metal component plays at least two key roles in the process, i.e., acting as a catalyst to produce hole carriers and introducing band bending in SiC to accumulate sufficient holes for etching. Through the combined anodic and MACE process the required electrical bias is greatly lowered (3.5 V for etching SiC and 7.5 V for creating SiC nanowires) while enhancing the etching efficiency. Furthermore, it is demonstrated that by tuning the etching electrical bias and time, various nanostructures can be obtained and the diameters of the obtained pores and nanowires can range from tens to hundreds of nanometers. This facile method may provide a feasible and economical way to fabricate SiC nanowires and nanostructures for broad applications.

Silver nanoclusters functionalized with Ce(III) ions are a viable "turn-on-off" fluorescent probe for sulfide.

The authors show that silver nanoclusters functionalized with Ce(III) ions are a viable fluorescent probe for selective and sensitive detection of sulfide at pH 7.0. The blue fluorescence of silver nanoclusters (with excitation/emission peaks at 358/426 nm) is enhanced on the addition of Ce(III) ions but is quenched in the presence of a trace concentrations of sulfide. A fluorometric assay was worked out using the Ce(III)/AgNCs as the probe. Sulfide can be detected in concentrations up to 2.0 µM, and the detection limit is 15 nM. The method was successfully applied to the determination of sulfide in spiked real samples. Graphical abstract Silver nanoclusters functionalized with Ce(III) ions are a viable "turn-on-off" fluorescent probe for selective and sensitive detection of sulfide at pH 7.0.

Biomimetic superhydrophobic metal/nonmetal surface manufactured by etching methods: A mini review.

As an emerging fringe science, bionics integrates the understanding of nature, imitation of nature, and surpassing nature in one aspect, and it organically combines the synergistic complementarity of function and structure-function integrated materials which is of great scientific interest. By imitating the microstructure of a natural biological surface, the bionic superhydrophobic surface prepared by human beings has the properties of self-cleaning, anti-icing, water collection, anti-corrosion and oil-water separation, and the preparation research methods are increasing. The preparation methods of superhydrophobic surface include vapor deposition, etching modification, sol-gel, template, electrostatic spinning, and electrostatic spraying, which can be applied to fields such as medical care, military industry, ship industry, and textile. The etching modification method can directly modify the substrate, so there is no need to worry about the adhesion between the coating and the substrate. The most obvious advantage of this method is that the obtained superhydrophobic surface is integrated with the substrate and has good stability and corrosion resistance. In this article, the different preparation methods of bionic superhydrophobic materials were summarized, especially the etching modification methods, we discussed the detailed classification, advantages, and disadvantages of these methods, and the future development direction of the field was prospected.

Boosted CO2 photoreduction performance on Ru-Ti3CN MXene-TiO2 photocatalyst synthesized by non-HF Lewis acidic etching method.

Photocatalytic CO2 reduction to produce value-added products is considered a promising solution to solve the global energy crisis and the greenhouse effect. In this study, Ti3CN MXene was synthesized using a Lewis acidic etching method without the usage of toxic hydrofluoric acid (HF). Ti3CN MXene was then used as a support for the in situ hydrothermal growth of TiO2 and Ru nanoparticles. In the presence of 0.5 wt% Ru, Ru-Ti3CN-TiO2 shows CO and CH4 production rates of 99.58 and 8.97 µmol/g, respectively, in 5 h under Xenon lamp irradiation, more than 20.5 and 9.3 times that of commercial P25. The enhancement in photocatalytic activity was attributed to the synergy between the in-situ growth of TiO2 on Ti3CN MXene and Ru nanoparticles. It was proven experimentally that Ti3CN MXene can provide abundant pathways for electron transfer. The separation and transfer of the photo-induced charge were further increased with the help of Ru and Ti3CN MXene, leaving more electrons to participate in the subsequent CO2 reduction reaction. We believe that this work will encourage more attention to designing environment-friendly MXene-based photocatalysts for CO2 photoreduction using the non-HF method.

γ-Fe2O3 nanoparticles stabilized by holey reduced graphene oxide as a composite anode for lithium-ion batteries.

Integrating nanoscale active materials on conductive holey reduced graphene oxide (RGO) framework is an effective strategy to synthesize composite electrode materials for advanced lithium-ion batteries. Herein, a composite of γ-Fe2O3 nanoparticles stabilized by the engineered holes on RGO was successfully synthesized by using a facile in-situ etching route, which exhibited high lithium storage performance. The fundamental insight of its enhancement mechanism was discussed. This work offers a newly route to synthesize the composite of holey RGO confined metal oxide nanoparticles for the applications in lithium ion batteries and beyond.

Etched p-Type Si Nanowires for Efficient Ozone Decomposition.

High concentration ozone can damage greatly to the respiratory, cardiovascular systems, and fertility of people, and catalytic decomposition is an important strategy to reduce its harm. However, it remains a challenge to develop efficient ozone decomposition catalysts with high efficiency. In this study, p- and n-type silicon nanowires (Si NWs) are fabricated by wet chemical etching method and are firstly applied to catalytic decompose ozone at room temperature. The p-type Si NWs exhibit 90% ozone (20 ppm O3/air) decomposition efficiency with great stability, which is much better than that of n-type Si NWs (50%) with same crystal orientation, similar diameter and specific surface area. The catalytic property difference is mainly attributed to the more delocalization holes in the p-type Si NWs, which can accelerate the desorption of ozone decomposition intermediates (i.e., adsorbed oxygen species).

FIB Secondary Etching Method for Fabrication of Fine CNT Forest Metamaterials.

Anisotropic materials, like carbon nanotubes (CNTs), are the perfect substitutes to overcome the limitations of conventional metamaterials; however, the successful fabrication of CNT forest metamaterial structures is still very challenging. In this study, a new method utilizing a focused ion beam (FIB) with additional secondary etching is presented, which can obtain uniform and fine patterning of CNT forest nanostructures for metamaterials and ranging in sizes from hundreds of nanometers to several micrometers. The influence of the FIB processing parameters on the morphology of the catalyst surface and the growth of the CNT forest was investigated, including the removal of redeposited material, decreasing the average surface roughness (from 0.45 to 0.15 nm), and a decrease in the thickness of the Fe catalyst. The results showed that the combination of FIB patterning and secondary etching enabled the growth of highly aligned, high-density CNT forest metamaterials. The improvement in the quality of single-walled CNTs (SWNTs), defined by the very high G/D peak ratio intensity of 10.47, demonstrated successful fine patterning of CNT forest for the first time. With a FIB patterning depth of 10 nm and a secondary etching of 0.5 nm, a minimum size of 150 nm of CNT forest metamaterials was achieved. The development of the FIB secondary etching method enabled for the first time, the fabrication of SWNT forest metamaterials for the optical and infrared regime, for future applications, e.g., in superlenses, antennas, or thermal metamaterials.

Soft-Etching Copper and Silver Electrodes for Significant Device Performance Improvement toward Facile, Cost-Effective, Bottom-Contacted, Organic Field-Effect Transistors.

Poor charge injection and transport at the electrode/semiconductor contacts has been so far a severe performance hurdle for bottom-contact bottom-gate (BCBG) organic field-effect transistors (OFETs). Here, we have developed a simple, economic, and effective method to improve the carrier injection efficiency and obtained high-performance devices with low cost and widely used source/drain (S/D) electrodes (Ag/Cu). Through the simple electrode etching process, the work function of the electrodes is more aligned with the semiconductors, which reduces the energy barrier and facilitates the charge injection. Besides, the formation of the thinned electrode edge with desirable micro/nanostructures not only leads to the enlarged contact side area beneficial for the carrier injection but also is in favor of the molecular self-organization for continuous crystal growth at the contact/active channel interface, which is better for the charge injection and transport. These effects give rise to the great reduction of contact resistance and the amazing improvement of the low-cost bottom-contact configuration OFETs performance.