Electrophysical Properties and Structure of Natural Disordered sp2 Carbon.

The progress in the practical use of glassy carbon materials has led to a considerable interest in understanding the nature of their physical properties. The electrophysical properties are among the most demanded properties. However, obtaining such materials is associated with expensive and dirty processes. In nature, in the course of geological processes, disordered sp2 carbon substances were formed, the structure of which is in many respects similar to the structure of glassy carbon and black carbon, and the electrical properties are distinguished by a high-energy storage potential and a high efficiency of shielding electromagnetic radiation. Given the huge natural reserves of such carbon (for example, in the shungite rocks of Karelia) and the relative cheapness and ease of producing materials from it, the study of potential technological applications and the disclosure of some unique electrophysical properties are of considerable interest. In this paper, we present an overview of recent studies on the structure, electrophysical properties, and technological applications of natural disordered sp2 carbon with the addition of novel authors' results.

Bifunctional nanozyme of copper organophyllosilicate for the ultrasensitive detection of hydroquinone.

The rapid development of nanozymes for ultrasensitive detection of contaminate has resulted in considerable attention. Herein, a carboxyl- and aminopropyl-functionalized copper organophyllosilicate (Cu-CAP) was synthesized by a facile, one-pot sol-gel method. The bifunctional groups endow it with superior catalytic activity than that of natural enzyme. Besides, it possesses outstanding catalytic stability under harsh conditions such as high temperature, extremely high or low pH, and high salinity. Apart from laccase-mimetic activity, Cu-CAP also shows oxidation of the peroxidase substrate 3,3',5,5'-tetramethylbenzidine (TMB) to the blue-colored TMBox in the presence of H2O2, which is similar to natural horseradish peroxidase (HRP). Interestingly, this colorimetric system was suppressed by hydroquinone (HQ) specifically. Inspired by this, Cu-CAP was used to develop a highly sensitive and selective colorimetric method for the determination of HQ. This assay displayed an extremely low detection limit of 23 nM and was applied for the detection of HQ in environmental water with high accuracy. This approach offers a new route for the rational design of high performance nanozymes for environmental and biosensing applications.

Graphene Domain Signature of Raman Spectra of sp2 Amorphous Carbons.

The standard D-G-2D pattern of Raman spectra of sp2 amorphous carbons is considered from the viewpoint of graphene domains presenting their basic structure units (BSUs) in terms of molecular spectroscopy. The molecular approximation allows connecting the characteristic D-G doublet spectra image of one-phonon spectra with a considerable dispersion of the C=C bond lengths within graphene domains, governed by size, heteroatom necklace of BSUs as well as BSUs packing. The interpretation of 2D two-phonon spectra reveals a particular role of electrical anharmonicity in the spectra formation and attributes this effect to a high degree of the electron density delocalization in graphene domains. A size-stimulated transition from molecular to quasi-particle phonon consideration of Raman spectra was experimentally traced, which allowed evaluation of a free path of optical phonons in graphene crystal.