Nitrogen doping of 4H-SiC during vapor phase epitaxy is still lacking of a general model explaining the apparently contradictory trends obtained by different teams. In this paper, the evolutions of nitrogen incorporation (on both polar Si and C faces) as a function of the main growth parameters (C/Si ratio, temperature, pressure and growth rate) are reviewed and explained using a model based on surface exchanges between the gas phase and the uppermost 4H-SiC atomic layers. In this model, N incorporation is driven mainly by the transient formation of C vacancies, due to H etching, at the surface or near the surface. It is shown that all the growth parameters are influencing the probability of C vacancies formation in a similar manner as they do for N incorporation. The surface exchange model proposes a new framework for explaining the experimental results even beyond the commonly accepted reactor type dependency.
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http://dx.doi.org/10.1038/srep43069 | DOI Listing |
Angew Chem Int Ed Engl
January 2025
Hunan University, Chemistry and Chemical Engineering, Lushan South Road, Yuelu District, 410082, Changsha, CHINA.
Site density and turnover frequency are the two fundamental kinetic descriptors that determine the oxygen reduction activity of iron-nitrogen-carbon (Fe-N-C) catalysts. However, it remains a grand challenge to simultaneously optimize these two parameters in a single Fe-N-C catalyst. Here we show that treating a typical Fe-N-C catalyst with ammonium iodine (NH4I) vapor via a one-step chemical vapor deposition process not only increases the surface area and porosity of the catalyst (and thus enhanced exposure of active sites) via the etching effect of the in-situ released NH3, but also regulates the electronic structure of the Fe-N4 moieties by the iodine dopants incorporated into the carbon matrix.
View Article and Find Full Text PDFAnal Chem
January 2025
Institute of Molecular Metrology, College of Chemistry and Chemical Engineering, Qingdao University, Qingdao 266071, P. R. China.
The elementary mechanism and site studies of nanozyme-based inhibition reactions are ambiguous and urgently require advanced nanozymes as mediators to elucidate the inhibition effect. To this end, we develop a class of nanozymes featuring single Cu-N catalytic configurations and B-O sites as binding configurations on a porous nitrogen-doped carbon substrate (B/Cu) for inducing modulable inhibition transfer at the atomic level. The full redistribution of electrons across the Cu-N sites, induced by B-O sites incorporation, yields B/Cu with enhanced peroxidase-like activity versus Cu.
View Article and Find Full Text PDFInt J Biol Macromol
January 2025
Science and Technology Center for Sustainability (CCTS), Federal University of São Carlos (UFSCar), João Leme dos Santos, km 110, 18052-780 Sorocaba, SP, Brazil. Electronic address:
The growing demand for sustainable solutions in agriculture, driven by global population growth and increasing soil degradation, has intensified the search for sustainable soil conditioners. This study investigated the impact of adding nanoclay (NC) and nano lignin (NL) to thermoplastic starch (TPS) on its physical, chemical, and thermal properties, its effectiveness as a soil conditioner, and its resistance to UV-C degradation. TPS nanocomposites were prepared with varying NC (3 %, 5 %, 7 %) and NL (0.
View Article and Find Full Text PDFJ Colloid Interface Sci
January 2025
Key Laboratory for Water Quality and Conservation of the Pearl River Delta, Ministry of Education, School of Environmental Science and Engineering, Guangzhou University, Guangzhou 510006, China. Electronic address:
Emerging single-atom materials and metal sulfides hold significant promise as alternatives to precious metal catalysts for nitroaromatics conversion; however, their intrinsic activity and durability remain insufficiently understood. Herein, sulfur and nitrogen co-doped carbon matrices incorporating CoS nanoparticles and single-atom Co with Co-N-S coordination were constructed through a facile pyrolysis approach. Advanced characterization techniques, such as X-ray absorption fine structure (XAFS) and aberration-corrected electron microscopy, unveiled unique structural features underpinning exceptional catalytic efficiency and recyclability.
View Article and Find Full Text PDFBio Protoc
January 2025
Department of Biochemistry, Microbiology and Biotechnology, Kenyatta University, Nairobi, Kenya.
Agrobacterium-mediated gene transformation method is a vital molecular biology technique employed to develop transgenic plants. Plants are genetically engineered to develop disease-free varieties, knock out unsettling traits for crop improvement, or incorporate an antigenic protein to make the plant a green factory for edible vaccines. The method's robustness was validated through successful transformations, demonstrating its effectiveness as a standard approach for researchers working in plant biotechnology.
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