Digital Twins Solve the Mystery of Raman Spectra of Parental and Reduced Graphene Oxides

Effect of photoconversion conditions on the spectral and cytotoxic properties of photoconvertible fluorescent polymer markers

Fluorescence labeling of cells is a versatile tool used to study cell behavior, which is of significant importance in biomedical sciences. Fluorescent photoconvertible markers based on polymer microcapsules have been recently considered as efficient and perspective ones for long-term tracking of individual cells. However, the dependence of photoconversion conditions on the polymeric capsule structure is still not sufficiently clear. Here, we have studied the structural and spectral properties of fluorescent photoconvertible polymeric microcapsules doped with Rhodamine B and irradiated using a pulsed laser in various regimes, and shown the dependence between the photoconversion degree and laser irradiation intensity. The effect of microcapsule composition on the photoconversion process was studied by monitoring structural changes in the initial and photoconverted microcapsules using X-ray diffraction analysis with synchrotron radiation source, and Fourier transform infrared, Raman and fluorescence spectroscopy. We demonstrated good biocompatibility of free-administered initial and photoconverted microcapsules through long-term monitoring of the RAW 264.7 monocyte/macrophage cells with unchanged viability. These data open new perspectives for using the developed markers as safe and precise cell labels with switchable fluorescent properties.

Virtual Free-Radical Polymerization of Vinyl Monomers in View of Digital Twins

The first case of virtual polymerization based on the concept of digital twins (DTs) is presented. The free-radical polymerization of vinyl monomers is considered to be a chain reaction consisting of a set of elementary ones. Those three types, related to the polymerization initiation and propagation as well as to the termination of polymer chain growth, are discussed. Special sets of DTs, whose total number approaches 60, distinguish each reaction type. The calculations are carried out using a semi-empirical version of the unrestricted Hartree-Fock approximation. The main energy and spin-density parameters of the ground state of the DTs are determined. The barrier profiles of two pairs of DTs are calculated, based on which two Evans-Polanyi-Semenov relations, attributed to elementary reactions of type (1) and (2), are constructed. These provide a quite reliable evaluation of the activation energy for the initiation and propagation of the free-radical polymerization of vinyl monomers in all the cases. The decisive role of spins in the formation of the elementary reaction transition states is established.

A Neoteric View of sp2 Amorphous Carbon

Presented is a concentrated synopsis of facilities of empirical and virtual analytics that, once applied, have provided a fully new vision of sp² amorphous carbons. This study proved that the solids are multilevel structures, started with the first-level basic structural units (BSUs) and accomplished as macroscopic agglomerates of globular structures, consisting, in its turn, of stacked BSUs. BSUs present necklaced graphene molecules, size, and shape of which are governed by the relevant graphene domains while chemical composition in addition to basic carbon is controlled with heteroatoms of the necklaces. This study shows that BSUs and stacks of BSUs determine the short-range order of the solids and are the main subject of the applied analytics. The synopsis consists of two parts related to empirical and virtual analytics. The former is composed of sections related to structural determination, total and atomic chemical content evaluation and elicitation of the covalent bond composition. The second presents new analytic approaches based on the Digital Twins concept and virtual vibrational spectrometry. The synopsis is configured as an atlas composed of generalized pictures accompanied with necessary explanations to be discussed in detail in the extended references.

Humidity Effect on Low-Temperature NH3 Sensing Behavior of In2O3/rGO Composites under UV Activation

The nature of the constituent components of composite materials can significantly affect the character of their interaction with the gas phase. In this work, nanocrystalline In₂O₃ was synthesized by the chemical precipitation method and was modified using reduced graphene oxide (rGO). The obtained composites were characterized by several analysis techniques-XRD, TEM, SEM, FTIR and Raman spectroscopy, XPS, TGA, and DRIFTS. The XPS and FTIR and Raman spectroscopy results suggested the formation of interfacial contact between In₂O₃ and rGO. The results of the gas sensor's properties showed that additional UV illumination led to a decrease in resistance and an increase in sensor response at room temperature. However, the presence of humidity at room temperature led to the disappearance of the response for pure In₂O₃, while for the composites, an inversion of the sensor response toward ammonia was observed. The main reason may have been the formation of NH₄NO₃ intermediates with further hydrolysis and decomposition under light illumination with the formation of nitrite and nitrate species. The presence of these species was verified by in situ DRIFT spectroscopy. Their strong electron-accepting properties lead to an increase in resistance, which possibly affected the sensor signal's inversion.