Exceptional electrostatic phenomenon in ultrathin nanorods: the terminal σ‑hole

An in-depth understanding of the physicochemical properties of nanorods during the initial growth process has a profound impact on the rational design of high-performance nanorods catalysts. Herein, we conducted a systematic DFT study on the transition metal Co, Ni and alloyed nanoclusters/rods systems to simulate an atomic process from the initial nanoclusters growth to nanorods/wires. We found that the highly active sites of nanorods depend on an interesting electrostatic phenomenon. The surface electrostatic potential analysis shows that all nanoclusters and nanorods structures have formed σ-hole. Unlike nanoclusters, the σ-hole only appears at terminal sites in nanorods, called terminal σ-hole. The elemental composition in nanorods has a certain influence on the maximal surface electrostatic potential (VS,max) i.e., terminal σ-hole. Interestingly, we found that the terminal σ-hole formed in nanorods is generally higher in magnitude than smaller nanoclusters. First-principle calculations show that terminal σ-hole is closely related to the physicochemical activities of nanorods. For example, the work function of the directions forming terminal σ-hole is smaller than other directions. More interestingly, we found that in almost all nanorods, compared with other atoms, the d-orbital of the atoms forming terminal σ‑hole shifts close to the Fermi level and exhibits a shallower d-band center, showing higher chemical activity. In short, it is the first time that we discovered terminal σ-hole in nanorods, explained the theoretical basis of terminal σ-hole in nanorod systems, and provided theoretical guidance for the rational design of high-performance nanorods catalysts.

Acidic and Electrosurface Properties of Binary TiO2–SiO2 Xerogels Using EPR of pH-Sensitive Nitroxides

The binary xerogels TiO2–SiO2 are widely used as catalysts and their carriers in organic synthesis. Characterization and adjustment of the electrostatic properties of the surface and the local acidity inside the pores, are necessary for the further development of TiO2–SiO2 xerogels applications. This research investigates acid–base equilibria in the pores, and the surface electrostatic potential (SEP) of binary TiO2–SiO2 xerogels, by the EPR of stable pH-sensitive nitroxide radicals. These radicals are small enough to penetrate directly into the pores, and to be adsorbed onto the surface of the material under study. This makes it possible to obtain valuable information on the acidic and electrosurface properties of the studied system. The highest negative surface electrical charge associated with surface electrical potential (SEP) was equal to –196 ± 6 mV. It was induced by the surface of the sample with a 7% TiO2 content. Тhe local acidity inside the pores of this sample was found to be higher, by approximately 1.49 pH units, as compared to that in the external bulk solution.

SARS-CoV-2 B.1.617 Indian variants: are electrostatic potential changes responsible for a higher transmission rate?

Lineage B.1.617+, also known as G/452R.V3, is a recently described SARS-CoV-2 variant under investigation (VUI) firstly identified in October 2020 in India. As of May 2021, three sublineages labelled as B.1.617.1, B.1.617.2 and B.1.617.3 have been already identified, and their potential impact on the current pandemic is being studied. This variant has 13 amino acid changes, three in its spike protein, which are currently of particular concern: E484Q, L452R and P681R. Here we report a major effect of the mutations characterizing this lineage, represented by a marked alteration of the surface electrostatic potential (EP) of the Receptor Binding Domain (RBD) of the spike protein. Enhanced RBD-EP is particularly noticeable in the B.1.617.2 sublineage, which shows multiple replacements of neutral or negatively-charged amino acids with positively-charged amino acids. We here hypothesize that this EP change can favor the interaction between the B.1.617+ RBD and the negatively-charged ACE2 thus conferring a potential increase in the virus transmission.

Atomic Charges, Surface Electrostatic Potential Analysis, and Bond Order Analysis on Nitriles and Isocyanides

Isocyanide-nitrile rearrangement has long been a continuing and interesting topic. A series of nitriles and isocyanides with the substituents of R=-AlH2, -BeH, -BH2, -C ≡ CH, -CF3, -CH3, -Cl, -C ≡ N, -COOH, -F, -H, Li, -MgH, -Na, -NH2, -NO2, -OH, -PH2, -SH, -SiH3, -CH = CH2 were investigated systematically based on full optimization at B3LYP-D3(BJ)/def2-QZVP level, and the isomerization energies from R-C ≡ N to :C = N-R were estimated. The substituent effect and bonding characters were analyzed by surface ESP colored van der Waals surfaces in conjunction with the global and local electrostatic extrema, the population analyses in terms of Hirshfeld and ADCH atomic charges, and bond order analyses via Laplacian and fuzzy bond orders.

Two models to estimate the density of organic cocrystals

Taking the organic cocrystals as the datasets, an artificial neural network was built based on six input parameters (Ms, RTm, E1u), and a model was also built based on the surface electrostatic potential correction method.