Generation of Tin-Vacancy Centers in Diamond via Shallow Ion Implantation and Subsequent Diamond Overgrowth.

Group IV color centers in diamond have garnered great interest for their potential as optically active solid-state spin qubits. The future utilization of such emitters requires the development of precise site-controlled emitter generation techniques that are compatible with high-quality nanophotonic devices. This task is more challenging for color centers with large group IV impurity atoms, which are otherwise promising because of their predicted long spin coherence times without a dilution refrigerator. For example, when applied to the negatively charged tin-vacancy (SnV-) center, conventional site-controlled color center generation methods either damage the diamond surface or yield bulk spectra with unexplained features. Here we demonstrate a novel method to generate site-controlled SnV- centers with clean bulk spectra. We shallowly implant Sn ions through a thin implantation mask and subsequently grow a layer of diamond via chemical vapor deposition. This method can be extended to other color centers and integrated with quantum nanophotonic device fabrication.

Synergistic enhancement of electrocatalytic CO2 reduction to C2 oxygenates at nitrogen-doped nanodiamonds/Cu interface.

To date, effective control over the electrochemical reduction of CO2 to multicarbon products (C ≥ 2) has been very challenging. Here, we report a design principle for the creation of a selective yet robust catalytic interface for heterogeneous electrocatalysts in the reduction of CO2 to C2 oxygenates, demonstrated by rational tuning of an assembly of nitrogen-doped nanodiamonds and copper nanoparticles. The catalyst exhibits a Faradaic efficiency of ~63% towards C2 oxygenates at applied potentials of only -0.5 V versus reversible hydrogen electrode. Moreover, this catalyst shows an unprecedented persistent catalytic performance up to 120 h, with steady current and only 19% activity decay. Density functional theory calculations show that CO binding is strengthened at the copper/nanodiamond interface, suppressing CO desorption and promoting C2 production by lowering the apparent barrier for CO dimerization. The inherent compositional and electronic tunability of the catalyst assembly offers an unrivalled degree of control over the catalytic interface, and thereby the reaction energetics and kinetics.

Vertical-Substrate MPCVD Epitaxial Nanodiamond Growth.

Color center-containing nanodiamonds have many applications in quantum technologies and biology. Diamondoids, molecular-sized diamonds have been used as seeds in chemical vapor deposition (CVD) growth. However, optimizing growth conditions to produce high crystal quality nanodiamonds with color centers requires varying growth conditions that often leads to ad-hoc and time-consuming, one-at-a-time testing of reaction conditions. In order to rapidly explore parameter space, we developed a microwave plasma CVD technique using a vertical, rather than horizontally oriented stage-substrate geometry. With this configuration, temperature, plasma density, and atomic hydrogen density vary continuously along the vertical axis of the substrate. This variation allowed rapid identification of growth parameters that yield single crystal diamonds down to 10 nm in size and 75 nm diameter optically active center silicon-vacancy (Si-V) nanoparticles. Furthermore, this method may provide a means of incorporating a wide variety of dopants in nanodiamonds without ion irradiation damage.

Analysis of genetic diversity in cytoplasmic male sterility, and association of mitochondrial genes with petaloid-type cytoplasmic male sterility in tuber mustard (Brassica juncea var. tumida Tsen et Lee).

In our previous study, we bred a stable cytoplasmic male sterility (CMS) line of tuber mustard by using distant hybridization and subsequent backcrosses. In this CMS plants, all floral organs are normal except the anthers, which are transformed into petals or tubular structures. Recently, 2 mitochondrial genes-atpA and orf220-that are distinctively present in the CMS line of tuber mustard were cloned and partially characterized. In our study of genetic diversity analysis of CMS, 7 species of Brassica and Raphanus crops, which included 5 CMS lines and their respective maintainer lines, were used to compare the constitution of protein-coding genes in the mitochondrial genomes. In 4 of the 43 mitochondrial genes, namely, atpA, orf220, orf256, and orf305/orf324, polymorphisms were detected among the tuber mustard CMS line and its maintainer line. The results of a cluster analysis indicate that petaloid CMS phenotype of tuber mustard is a novel CMS type and is nearer to the nap CMS in Brassica napus at the phylogenetic level. The results of individual amplifications of these genes indicate the presence of 4 sequence-characterized amplified region (SCAR) markers, which enable rapid and reliable identification of this CMS. Expressions of the orf220 and orf256 genes were detected only in the CMS line, while expression of the orf305 gene was detected in the maintainer line. The different expression patterns of different mitochondrial-specific marker genes indicate that the quantity of mitochondrial proteins is differentially regulated during organ/tissue development in tuber mustard. The results of this study suggest that the above mentioned 4 mitochondrial genes are associated with the petaloid CMS phenotype in tuber mustard.