Oxygen-Terminated Polycrystalline Boron-Doped Diamond Superhydrophobic Surface with Excellent Mechanical and Thermal Stabilities.

Superhydrophobic surfaces are of great interest because of their remarkable properties. Due to its maximal hardness and chemical inertness, diamond film has great potential in fabricating robust superhydrophobic surfaces. In the present study, an oxygen-terminated polycrystalline boron-doped diamond (O-PBDD) superhydrophobic surface with micro/nano-hierarchical porous structures is developed. The preparation method is very simple, requiring only sputtering and dewetting procedures. The former involves sputtering gold and copper particles onto the hydrogen-terminated polycrystalline boron-doped diamond (H-PBDD) to form gold/copper films, whereas the latter involves placing the samples in an atmospheric tube furnace to form hierarchical pores. By controlling the etching parameters, the wettability of the O-PBDD surface can be adjusted from hydrophilic to superhydrophobic, which is significantly different to the normal hydrophilicity feature of O-termination diamonds. The water contact angle of the obtained O-PBDD surface can reach 165 ± 5°, which is higher than the superhydrophobic diamond surfaces that are reported in the literature. In addition, the O-PBDD surface exhibits excellent durability; it can maintain satisfactory superhydrophobicity even after high-pressure, high-temperature, and sandpaper friction tests. This work provides a new research direction for fabricating robust superhydrophobic materials with diamond film.

Recent progress in TiO2-biochar-based photocatalysts for water contaminants treatment: strategies to improve photocatalytic performance.

Toxic organic pollutants in wastewater have seriously damaged human health and ecosystems. Photocatalytic degradation is a potential and efficient tactic for wastewater treatment. Among the entire carbon family, biochar has been developed for the adsorption of pollutants due to its large specific surface area, porous skeleton structure, and abundant surface functional groups. Hence, combining adsorption and photocatalytic decomposition, TiO2-biochar photocatalysts have received considerable attention and have been extensively studied. Owing to biochar's adsorption, more active sites and strong interactions between contaminants and photocatalysts can be achieved. The synergistic effect of biochar and TiO2 nanomaterials substantially improves the photocatalytic capacity for pollutant degradation. TiO2-biochar composites have numerous attractive properties and advantages, culminating in infinite applications. This review discusses the characteristics and preparation techniques of biochar, presents in situ and ex situ synthesis approaches of TiO2-biochar nanocomposites, explains the benefits of TiO2-biochar-based compounds for photocatalytic degradation, and emphasizes the strategies for enhancing the photocatalytic efficiency of TiO2-biochar-based photocatalysts. Finally, the main difficulties and future advancements of TiO2-biochar-based photocatalysis are highlighted. The review gives an exhaustive overview of recent progress in TiO2-biochar-based photocatalysts for organic contaminants removal and is expected to encourage the development of robust TiO2-biochar-based photocatalysts for sewage remediation and other environmentally friendly uses.

A Nanograss Boron and Nitrogen Co-Doped Diamond Sensor Produced via High-Temperature Annealing for the Detection of Cadmium Ions.

The high-performance determination of heavy metal ions (Cd2+) in water sources is significant for the protection of public health and safety. We have developed a novel sensor of nanograss boron and nitrogen co-doped diamond (NGBND) to detect Cd2+ using a simple method without any masks or reactive ion etching. The NGBND electrode is constructed based on the co-doped diamond growth mode and the removal of the non-diamond carbon (NDC) from the NGBND/NDC composite. Both the enlarged surface area and enhanced electrochemical performance of the NGBND film are achievable. Scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, cyclic voltammetry, electrochemical impedance spectroscopy, and differential pulse anodic stripping voltammetry (DPASV) were used to characterize the NGBND electrodes. Furthermore, we used a finite element numerical method to research the current density near the tip of NGBND. The NGBND sensor exhibits significant advantages for detecting trace Cd2+ via DPASV. A broad linear range of 1 to 100 µg L-1 with a low detection limit of 0.28 µg L-1 was achieved. The successful application of this Cd2+ sensor indicates considerable promise for the sensitive detection of heavy metal ions.

Vertical Diamond p-n Junction Diode with Step Edge Termination Structure Designed by Simulation.

In this paper, diamond-based vertical p-n junction diodes with step edge termination are investigated using a Silvaco simulation (Version 5.0.10.R). Compared with the conventional p-n junction diode without termination, the step edge termination shows weak influences on the forward characteristics and helps to suppress the electric field crowding. However, the breakdown voltage of the diode with simple step edge termination is still lower than that of the ideal parallel-plane one. To further enhance the breakdown voltage, we combine a p-n junction-based junction termination extension on the step edge termination. After optimizing the structure parameters of the device, the depletion regions formed by the junction termination extension overlap with that of the p-n junction on the top mesa, resulting in a more uniform electric field distribution and higher device performance.

Semiconductor SERS of diamond.

In this work, we report a favorable diamond substrate to realize semiconductor surface-enhanced Raman spectroscopy (SERS) for trace molecular probes with high sensitivity, stability, reproducibility, recyclability and universality. The boron-doped diamond (BDD) with surface hydrogenation or oxygenation has matched energy levels corresponding to the target molecules and plays a critical role in achieving SERS. The enhancement factor based on BDD substrates can reach 104-105, which approaches those obtained with most nanostructured compound semiconductors and is nearly 3-4 orders of magnitude higher than those of state-of-the-art single-element semiconductors (silicon, germanium, and graphene). The mechanism of SERS is determined to be charge transfer with vibronic coupling, which could enhance the molecular polarizability tensor. Because of its unique properties such as chemical inertness, wide bandgap, modulated doping, surface functionalization, biocompatibility, and high thermal conductivity, the single-element semiconductor diamond can serve a high-performance semiconductor SERS platform with applications in broad fields.

Two dimensional monolayer rhombic silicene on the diamond (111) surface.

Two-dimensional rhombic silicene (named r-silicene) bonded on the diamond (111) surface with a (1 × 1) configuration is predicted by density functional theory. The planar structure of r-silicene has P6/mmm symmetry, and it is dynamically and thermodynamically stable on the diamond surface. r-Silicene has a metallic character, which is different to both bulk cubic Si and hexagonal silicene. The hybrid structure of r-silicene/diamond consists of a metallic surface and a wide band gap semiconductor diamond substrate, providing a novel low-dimensional composite based on silicon-diamond to realize high performance nanodevices. Moreover, a similar rhombic configuration of monolayer germanene has been theoretically constructed on the diamond (111) substrate.

Robust diamond meshes with unique wettability properties.

Robust diamond meshes with excellent superhydrophobic and superoleophilic properties have been fabricated. Superhydrophobicity is observed for water with varying pH from 1 to 14 with good recyclability. Reversible superhydrophobicity and hydrophilicity can be easily controlled. The diamond meshes show highly efficient water-oil separation and water pH droplet transference.