Single-step grown boron doped nanocrystalline diamond-carbon nanograss hybrid as an efficient supercapacitor electrode

CoNiO2/Co3O4 Nanosheets on Boron Doped Diamond for Supercapacitor Electrodes

Developing novel supercapacitor electrodes with high energy density and good cycle stability has aroused great interest. Herein, the vertically aligned CoNiO2/Co3O4 nanosheet arrays anchored on boron doped diamond (BDD) films are designed and fabricated by a simple one-step electrodeposition method. The CoNiO2/Co3O4/BDD electrode possesses a large specific capacitance (214 mF cm-2) and a long-term capacitance retention (85.9% after 10,000 cycles), which is attributed to the unique two-dimensional nanosheet architecture, high conductivity of CoNiO2/Co3O4 and the wide potential window of diamond. Nanosheet materials with an ultrathin thickness can decrease the diffusion length of ions, increase the contact area with electrolyte, as well as improve active material utilization, which leads to an enhanced electrochemical performance. Additionally, CoNiO2/Co3O4/BDD is fabricated as the positive electrode with activated carbon as the negative electrode, this assembled asymmetric supercapacitor exhibits an energy density of 7.5 W h kg-1 at a power density of 330.5 W kg-1 and capacity retention rate of 97.4% after 10,000 cycles in 6 M KOH. This work would provide insights into the design of advanced electrode materials for high-performance supercapacitors.

Early stages of polycrystalline diamond deposition: laser reflectance at substrates with growing nanodiamonds

The chemical vapor deposition of polycrystalline diamond (PCD) films is typically done on substrates seeded with diamond nanoparticles. Specular laser reflectance has been used in tandem with a continuous film model to monitor the thickness of these films during their deposition. However, approaches to gain information on properties that strongly affect film morphology, such as the areal density of seeds, remain largely unexplored. This work outlines a strategy for using laser reflectance measurements to refine the monitoring of film thickness during deposition, estimate the mean equivalent radii and the areal density of seeds, and estimate growth incubation periods. We present a general model based on the Rayleigh theory of scattering for laser reflectance at substrates with growing nanoparticles that captures the early stages of PCD deposition. We test our model experimentally by depositing diamond under identical conditions on silicon substrates with various seed densities and by comparing seed densities obtained by scanning electron microscopy to those determined by our strategy. We also explore the different deposition stages for which our model and a continuous film model can be used safely. In addition to providing guidelines for characterizing PCD deposition, this work may also advance the general understanding of nanoparticle growth and formation.

Influence of B/N co-doping on electrical and photoluminescence properties of CVD grown homoepitaxial diamond films

Boron doped diamond (BDD) has great potential in electrical, and electrochemical sensing applications. The growth parameters, substrates, and synthesis method play a vital role in the preparation of semiconducting BDD to metallic BDD. Doping of other elements along with boron (B) into diamond demonstrated improved efficacy of B doping and exceptional properties. In the present study, B and nitrogen (N) co-doped diamond has been synthesized on single crystalline diamond (SCD) IIa and SCD Ib substrates in a microwave plasma-assisted chemical vapor deposition process. The B/N co-doping into CVD diamond has been conducted at constant N flow of N/C ∼ 0.02 with three different B/C doping concentrations of B/C ∼ 2500 ppm, 5000 ppm, 7500 ppm. Atomic force microscopy topography depicted the flat and smooth surface with low surface roughness for low B doping, whereas surface features like hillock structures and un-epitaxial diamond crystals with high surface roughness were observed for high B doping concentrations. KPFM measurements revealed that the work function (4.74-4.94 eV) has not varied significantly for CVD diamond synthesized with different B/C concentrations. Raman spectroscopy measurements described the growth of high-quality diamond and photoluminescence studies revealed the formation of high-density nitrogen-vacancy centers in CVD diamond layers. X-ray photoelectron spectroscopy results confirmed the successful B doping and the increase in N doping with B doping concentration. The room temperature electrical resistance measurements of CVD diamond layers (B/C ∼ 7500 ppm) have shown the low resistance value ∼9.29 Ω for CVD diamond/SCD IIa, and the resistance value ∼16.55 Ω for CVD diamond/SCD Ib samples.

3D nitrogen-doped graphene created by the secondary intercalation of ethanol with enhanced specific capacity

Here, we report an improved synthesis strategy for 3D nitrogen-doped graphene to increase the specific capacity of supercapacitors. Ethanol replaces the strong oxidant hydrogen peroxide in the improved Hummers method, and the loose porous structure is conducive to charge transfer. N-doped porous 3D graphene was synthesized from RGO-C prepared by ethanol secondary intercalation modification of functional groups. Ammonia was selected as the dopant; the microstructure and electrochemical performance of samples synthesized at different temperatures were examined. The results demonstrate that the 3D nitrogen-doped graphene (N-RGO-5) had a layered tuple shape with a sheet thickness of 0.612 nm.The specific surface area of the 3D N-RGO-5, which was prepared at 190°C, was 258.371 m²g^-1, which was higher than that (5.877 m²g^-1) of the original graphite. The 3D N-RGO-5 exhibited a specific capacitance of 236 F g^-1and an energy density of 32.78 Wh kg^-1at a current density of 1 A g^-1, which is 27% higher than the specific capacitance of RGO. The 3D N-RGO-5 demonstrated an excellent capacity retention rate of 93.6% after 5000 cycles at a current density of 1 A g^-1. This study demonstrates that the unique 3D structure and N-doping of N-RGO considerably improved the overall energy storage performance of graphene-based nanomaterials.

Ultrathin Diamond Nanofilms-Development, Challenges, and Applications

Diamond is a highly attractive material for ample applications in material science, engineering, chemistry, and biology because of its favorable properties. The advent of conductive diamond coatings and the steady demand for miniaturization in a plethora of economic and scientific fields resulted in the impetus for interdisciplinary research to develop intricate deposition techniques for thin (≤1000 nm) and ultra-thin (≤100 nm) diamond films on non-diamond substrates. By virtue of the lowered thickness, diamond coatings feature high optical transparency in UV-IR range. Combined with their semi-conductivity and mechanical robustness, they are promising candidates for solar cells, optical devices, transparent electrodes, and photochemical applications. In this review, the difficulty of (ultra-thin) diamond film development and production, introduction of important stepping stones for thin diamond synthesis, and summarization of the main nucleation procedures for diamond film synthesis are elucidated. Thereafter, applications of thin diamond coatings are highlighted with a focus on applications relying on ultrathin diamond coatings, and the excellent properties of the diamond exploited in said applications are discussed, thus guiding the reader and enabling the reader to quickly get acquainted with the research field of ultrathin diamond coatings.

Classification of submandibular salivary stones based on ultrastructural studies

INTRODUCTION

Sialolithiasis remains a clinical problem with unclear etiopathogenesis, lack of prevention methods, and only surgical treatment.

MATERIALS AND METHODS

An ultrastructure examination of submandibular sialoliths obtained from patients with chronic sialolithiasis was conducted using a scanning electron microscope and X-ray photoelectron spectroscopy.

RESULTS

Based on the results, we divided sialoliths into three types: calcified (CAL), organic/lipid (LIP), and mixed (MIX). The core structure of the CAL and MIX is very similar. The core of the LIP has a prevalence of organic components. The intermediate layers' structure of the CAL is different from LIP and MIX. In LIP and MIX, the organic component begins to increase in intermediate layers rapidly. The structure of the superficial layers for all types of sialoliths is similar.

CONCLUSIONS

We introduced a new classification of the submandibular salivary gland stones. Based on the results, it can be said that sialoliths type CAL and LIP have their separate path of origin and development, while MIX is formed as CAL stone, and the further pathway of their growth passes as LIP stones. Organic components were much more than inorganic in all layers of salivary gland stones, which highly prevents their dissolution in the patient's salivary gland duct.