Highly Occupied Surface States at Deuterium-Grown Boron-Doped Diamond Interfaces for Efficient Photoelectrochemistry

Polycrystalline boron-doped diamond is a promising material for high-power aqueous electrochemical applications in bioanalytics, catalysis, and energy storage. The chemical vapor deposition (CVD) process of diamond formation and doping is totally diversified by using high kinetic energies of deuterium substituting habitually applied hydrogen. The high concentration of deuterium in plasma induces atomic arrangements and steric hindrance during synthesis reactions, which in consequence leads to a preferential (111) texture and more effective boron incorporation into the lattice, reaching a one order of magnitude higher density of charge carriers. This provides the surface reconstruction impacting surficial populations of C C dimers, C H, CO groups, and  COOH termination along with enhanced kinetics of their abstraction, as revealed by high-resolution core-level spectroscopies. A series of local densities of states were computed, showing a rich set of highly occupied and localized surface states for samples deposited in deuterium, negating the connotations of band bending. The introduction of enhanced incorporation of boron into (111) facet of diamond leads to the manifestation of surface electronic states below the Fermi level and above the bulk valence band edge. This unique electronic band structure affects the charge transfer kinetics, electron affinity, and diffusion field geometry critical for efficient electrolysis, electrocatalysis, and photoelectrochemistry.     

fabrication of diamond membranes for MEMS using reactive ion etching of silicon

Polycrystalline diamond thin film has been grown on a silicon substrate using high pressure microwave plasma-assisted chemical vapor deposition from a gas mixture of methane and hydrogen at a substrate temperature of 950°C. A simple process flow has been developed to fabricate optically transparent polycrystalline synthetic diamond membranes/windows employing reactive ion etching (RIE) of a single crystal silicon substrate using an electron beam evaporated aluminum thin film mask pattern formed by photolithography. Scanning electron microscopy has been used to study the morphology of as-grown diamond thin films.     

Flexible and Biocompatible Physical Unclonable Function Anti-Counterfeiting Label

Optical physical unclonable functions (PUFs) have been proven to be one of the most effective anti-counterfeiting strategies. However, optical PUFs endowed with flexibility and biocompatibility have not been developed, limiting their application scenarios. Herein, biocompatible and flexible optical PUF labels are developed by randomly embedding microdiamonds in silk fibroin films. The PUF labels can be conformally attached onto the surface of complex shaped objects, providing the desired protection against fake and interior products. In this system, silk fibroin films serve as a flexible and biocompatible substrate, while the Raman signal of the microdiamonds serves as response of the excitation. The extremely high stability and random distribution of the microdiamonds ensure the performance of PUFs, and the maximum encoding capability of 2¹⁰⁰⁰⁰ is finally realized. The cytotoxicity analysis results also verify the biosafety of the PUF system. In addition, the as-prepared PUF labels are attached onto the surface of polyethylene material, and human skin, and even have been implanted under chicken skin tissue, promising their practical applications.     

Fracture and Stiffness Characteristics of Particulate Composites of Diamond in Zinc Sulfide

Diamond particles have been embedded in hot-pressed zinc sulfide (ZnS) ceramic to improve various mechanical properties while preserving special optical properties. Roomtemperature mechanical tests on small specimens have shown that adding 10 wt% diamond to ZnS has no effect on the yield stress, but increases the tensile strength and the elastic moduli ∼20%, and increases the fracture toughness ∼100%. The doubling in fracture toughness can be explained by elastic interaction of the diamond particles with the crack-tip stress field. The results and the interpretation presented here are believed to represent a class of composite materials where both constituents are brittle but the dispersed phase has a much higher elastic modulus than the matrix.     

微型光纤光谱仪在钻石检测中的运用

现代技术对钻石业的影响在不断的扩大,通过改善钻石的颜色并由此提高其价格的方法变得尤为先进,如何有效的区分天然与优化处理的钻石一直是宝石学的研究热点,对鉴别彩色钻石而言其任务更加艰巨。笔者运用美国海洋光学公司生产的微型光纤光谱仪（USB4000）,对来自中国、俄罗斯、韩国等地的17颗钻石样品进行了谱学分析,结果表明该测试方法能高效、快速、低成本地区分天然、高温高压处理、辐照处理的钻石,且同种类型不同颜色的钻石样品之间又存在着较明显的差异。因此,该方法为钻石的检测提供了可行性依据,具有非常广阔的应有前景。     

Microstructure of a Shock-Consolidated Diamond Compact Consisting of Fine Particles

Transmission electron microscopy clearly demonstrates two types of grain boundaries in a shock-consolidated diamond compact consisting of fine particles: one is thick (40 nm) and irregular, whereas the other is thin (less than a few nanometers) and straight. The former is formed during the first compression (21 GPa) while the latter is formed after passage of the first shock-wave front. Numerical calculations describing thermal diffusion support the proposed mechanism under a multiple-compression process.     

Recent advances and applications of high resolution electron microscopy

This review covers several broad areas: firstly, recent developments in HREM instrumentation, and then novel techniques for imaging are discussed, including some of the problems of image interpretation. Applications of HREM techniques to a wide range of materials problems are described and include solid state chemistry, ceramics, semiconductors, metals and natural diamonds. The next generation of high resolution microscopes will operate in the 300–400 kV range, have low C_s objective lenses, and have sufficiently good vacuum to allow the combined use of CBED and EELS facilities with imaging in the sub-2 Å range. Microprocessor control of instrumental parameters such as astigmatism, alignment and defocus are seen as an important way forward in achieving the optimum performance of these instruments.     

Nanodiamond as a vector for siRNA delivery to Ewing sarcoma cells

The ability of diamond nanoparticles (nanodiamonds, NDs) to deliver small interfering RNA (siRNA) into Ewing sarcoma cells is investigated with a view to the possibility of in-vivo anticancer nucleic-acid drug delivery. siRNA is adsorbed onto NDs that are coated with cationic polymer. Cell uptake of NDs is demonstrated by taking advantage of the NDs' intrinsic fluorescence from embedded color-center defects. Cell toxicity of these coated NDs is shown to be low. Consistent with the internalization efficacy, a specific inhibition of EWS/Fli-1 gene expression is shown at the mRNA and protein level by the ND-vectorized siRNA in a serum-containing medium.     

Paramagnetic defects and exchange coupled spins in pristine ultrananocrystalline diamonds

Electron paramagnetic resonance (EPR) and magnetic susceptibility measurements were done on nanodiamond samples fabricated by the detonation method and purified by acids. Comprehensive acid treatment leads to the reduction of EPR signals of magnetic impurities and revealing two weak and narrow EPR lines with g₁ = 4.26, H_pp = 2.9 mT and g₂ = 4.00, H_pp = 1.4 mT at T = 4 K, separated by the distance of 10.4 mT. The origin of this new doublet EPR signal observed in the well purified sample is discussed. The magnetic susceptibility behavior and doublet EPR signal (g  4) suggest the weak antiferromagnetically exchange coupling of S = 1/2 paramagnetic defects as well as the presence of isolated dimers with S = 1.