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Honeycomb Carbon: A Review of Graphene

Electrolytes and interphases in Li-ion batteries and beyond.

To realize graphene-based electronics, various types of graphene are required; thus, modulation of its electrical properties is of great importance. Theoretic studies show that intentional doping is a promising route for this goal, and the doped graphene might promise fascinating properties and widespread applications. However, there is no experimental example and electrical testing of the substitutionally doped graphene up to date. Here, we synthesize the N-doped graphene by a chemical vapor deposition (CVD) method. We find that most of them are few-layer graphene, although single-layer graphene can be occasionally detected. As doping accompanies with the recombination of carbon atoms into graphene in the CVD process, N atoms can be substitutionally doped into the graphene lattice, which is hard to realize by other synthetic methods. Electrical measurements show that the N-doped graphene exhibits an n-type behavior, indicating substitutional doping can effectively modulate the electrical properties of graphene. Our finding provides a new experimental instance of graphene and would promote the research and applications of graphene.

Synthesis of N-Doped Graphene by Chemical Vapor Deposition and Its Electrical Properties

Graphitic carbon nitride, g-C3N4, can be made by polymerization of cyanamide, dicyandiamide or melamine. Depending on reaction conditions, different materials with different degrees of condensation, properties and reactivities are obtained. The firstly formed polymeric C3N4 structure, melon, with pendant amino groups, is a highly ordered polymer. Further reaction leads to more condensed and less defective C3N4 species, based on tri-s-triazine (C6N7) units as elementary building blocks. High resolution transmission electron microscopy proves the extended two-dimensional character of the condensation motif. Due to the polymerization-type synthesis from a liquid precursor, a variety of material nanostructures such as nanoparticles or mesoporous powders can be accessed. Those nanostructures also allow fine tuning of properties, the ability for intercalation, as well as the possibility to give surface-rich materials for heterogeneous reactions. Due to the special semiconductor properties of carbon nitrides, they show unexpected catalytic activity for a variety of reactions, such as for the activation of benzene, trimerization reactions, and also the activation of carbon dioxide. Model calculations are presented to explain this unusual case of heterogeneous, metal-free catalysis. Carbon nitride can also act as a heterogeneous reactant, and a new family of metal nitride nanostructures can be accessed from the corresponding oxides.

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Graphitic carbon nitride materials: variation of structure and morphology and their use as metal-free catalysts

Polymeric graphitic carbon nitride materials (for simplicity: g-C(3)N(4)) have attracted much attention in recent years because of their similarity to graphene. They are composed of C, N, and some minor H content only. In contrast to graphenes, g-C(3)N(4) is a medium-bandgap semiconductor and in that role an effective photocatalyst and chemical catalyst for a broad variety of reactions. In this Review, we describe the "polymer chemistry" of this structure, how band positions and bandgap can be varied by doping and copolymerization, and how the organic solid can be textured to make it an effective heterogenous catalyst. g-C(3)N(4) and its modifications have a high thermal and chemical stability and can catalyze a number of "dream reactions", such as photochemical splitting of water, mild and selective oxidation reactions, and--as a coactive catalytic support--superactive hydrogenation reactions. As carbon nitride is metal-free as such, it also tolerates functional groups and is therefore suited for multipurpose applications in biomass conversion and sustainable chemistry.

Polymeric Graphitic Carbon Nitride as a Heterogeneous Organocatalyst: From Photochemistry to Multipurpose Catalysis to Sustainable Chemistry

Arizona State University (ASU) is one the largest universities in the United States, with more than 79,000 students attending in-person classes. We conducted a seroprevalence study from September 13-17, 2021 to estimate the number of people in our community with SARS-CoV-2-specific antibodies due to previous exposure to SARS-CoV-2 and/or vaccination. Participants provided their age, gender, race, status (student or employee), and general COVID-19 health-related information like previous exposure and vaccination status. The seroprevalence of the anti-receptor binding domain (RBD) antibody was 90% by a lateral flow assay and 88% by a semi-quantitative chemiluminescent immunoassay. The seroprevalence for anti-nucleocapsid (NC) was 20%. In addition, individuals with previous natural COVID infection plus vaccination had higher anti-RBD antibody levels compared to those who had vaccination only or infection only. Individuals who had a breakthrough infection had the highest anti-RBD antibody levels. Accurate estimates of the cumulative incidence of SARS-CoV-2 infection can inform the development of university risk mitigation protocols such as encouraging booster shots, extending mask mandates, or reverting to online classes. It could help us to have clear guidance to take action at the first sign of the next surge as well, especially since there is a surge of COVID subvariant infections.

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Serosurvey of SARS-COV-2 at a large public university

The synthesis of the entire silyl−germyl sequence of molecules (H3Ge)xSiH4-x (x = 1−4) has been demonstrated. These include the previously unknown (H3Ge)2SiH2, (H3Ge)3SiH, and (H3Ge)4Si species as well as the H3GeSiH3 analogue which is obtained in practical high-purity yields as a viable alternative to disilane and digermane for semiconductor applications. The molecules are characterized by FTIR, multinuclear NMR, mass spectrometry, and Rutherford backscattering. The structural, thermochemical, and vibrational properties are studied using density functional theory. A detailed comparison of the experimental and theoretical data is used to corroborate the synthesis of specific molecular structures. The (H3Ge)xSiH4-x family of compounds described here is not only of intrinsic molecular interest but also provides a unique route to a new class of Si-based semiconductors including epitaxial layers and coherent islands (quantum dots), with Ge-rich stoichiometries SiGe, SiGe2, SiGe3, and SiGe4 reflecting the Si/G...

Synthesis and Fundamental Studies of (H3Ge)xSiH4-x Molecules: Precursors to Semiconductor Hetero- and Nanostructures on Si.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S143192760000917X

Characterization of Sil-ycy Alloy Layers Incorporating Si4c Building Blocks

Anhydrous In(CN)3 and In1-xGax(CN)3 phases with empty Prussian-blue-type structures have been prepared via low-temperature solution methods utilizing molecular templating agents. Quantitative X-ray powder diffraction was used to refine the In(CN)3 cubic structure in which In is octahedrally surrounded by an average of three C and three N atoms. The symmetry is Pm3m, a = 5.627(1) A, and the In−(C,N) and C−N bond lengths are 2.251(1) and 1.125(1) A, respectively. The compound reversibly incorporates krypton atoms into the empty cavities to form In(CN)3·Kr, which is readily identified by powder diffraction. Similar inclusion systems with n-hexane in the porous framework are also synthesized. In1-xGax(CN)3 solid solutions are formed by suitable combinations of the binary systems and have lattice constants adjustable between 5.293 A for Ga(CN)3 and 5.627(1) A for In(CN)3. The variation of the lattice parameters with composition obeys Vegard's Law.

Synthesis of Nanoporous Cubic In(CN)3 and In1‐xGax(CN)3 and Corresponding Inclusion Compounds.

We fabricate a GeSn photonic crystal laser. The simulation shows a high Q-factor and wide spectral tunability. An improved net gain and lowered power consumption are expected via strain-relaxation and reducing active mode volume, respectively.

John Kouvetakis

Papers

Serosurvey of SARS-COV-2 at a large public university

Synthesis and Fundamental Studies of (H3Ge)xSiH4-x Molecules: Precursors to Semiconductor Hetero- and Nanostructures on Si.

Characterization of Sil-ycy Alloy Layers Incorporating Si4c Building Blocks

Synthesis of Nanoporous Cubic In(CN)3 and In1‐xGax(CN)3 and Corresponding Inclusion Compounds.

Single-defect hexapole mode GeSn photonic crystal laser: Fabrication and simulation