Theoretical Spectroscopic Study of Normal Raman and Charge Transfer Surface-Enhanced Raman Scattering (SERS) Spectra of the Adsorbed l- and d-Cysteine on the Chiral Au34 and Ag4@Au30 Nanoclusters: Chirality Discrimination.

In this work, the discrimination of the enantiomers of cysteine (l- and d-CYS) using the chiral Au34 and Ag4@Au30 clusters was theoretically investigated in the gas phase and water. Two modes were considered for the interaction of each enantiomer with the clusters (via only its S atom or its S atom and NH2 group, simultaneously). The interaction energy (Eint) and adsorption energy (Ead) for the complexation of each enantiomer with the clusters for each interaction mode were calculated. Considering the calculated interaction energies, the interaction of d-CYS with Au34 is stronger than that of l-CYS with the same cluster. Also, it was observed that the substitution of the Au4 core of the Au34 cluster with the Ag4 cluster caused the increase of the interaction energy of l-CYS with the Ag4@Au30 cluster compared to the Au34 cluster, while the reverse trend was observed for d-CYS. Quantum theory of atoms in molecules (QTAIM) analysis was employed to calculate the interaction paths and their related bond critical points (BCPs) between the CYS enantiomers and the clusters to explain the difference between the interaction energy of the enantiomers with the clusters. The IR, normal Raman (NR), and surface-enhanced Raman scattering (SERS) spectra of the enantiomers interacting with the Au34 and Ag4@Au30 clusters were calculated, and the discrimination between l-CYS and d-CYS using the calculated spectra was explained. It was found that the discrimination of the enantiomers based on their interaction with the clusters is controlled by the charge transfer between the enantiomers and the clusters.

Starch valorization: Direct conversion of starch to hexyl levulinate over SO4/ZrO2-KIT5 composite.

Valorization of biomass for the synthesis of valuable chemicals is a promising toolbox for replacing fossil fuel consumption. Long-chain hexyl levulinate (HL) is one of the attractive high-value chemicals obtained from biomass valorization. The current paper investigates the synthesis of KIT5-supported SO4/ZrO2 and its application in the successive hydrolysis and dehydration of starch to HL. The acidity of the prepared catalyst was modified, and its effect on the conversion of starch and HL yield was thoroughly studied. The parameters effective on the reaction yield and selectivity were optimized, and the possibility of 5-((hexyloxy)methyl) furan-2-carbaldehyde formation was explored. The prepared SO4/ZrO2-KIT5 can be used at least in four successive runs with a slight decrease in its reactivity. The HL yield was increased to a maximum of 28 %, while the starch conversion increased to a maximum of 100 % by conducting the reactions at 220 °C for 10 h. The accessibility and low cost of the starting materials as well as the method's simplicity, can give a practical outlook of its possible industrial application.

DFT Study on Corrosion Inhibition by Tetrazole Derivatives: Investigation of the Substitution Effect.

Corrosion is one of the problems that most industries face. Our aim in the current study is to perform density functional theory calculations and Monte Carlo simulation to theoretically investigate the corrosion inhibition of the copper (1 1 1) surface by tetrazole molecules and a group of their derivatives. These compounds have electron-donating groups (CH3, CH3O, and OH) and electron-withdrawing groups (F, CN, and NO2). Two different isomeric forms of tetrazole molecules and their derivatives, including 1H and 2H tautomers, were studied in two configurations, parallel and perpendicular to the Cu (1 1 1) surface. With the help of DMol3 calculations, the most important parameters related to the molecular ability of tetrazole derivatives as corrosion inhibitors include the adsorption energy (ΔE), E HOMO, E LUMO, E gap, and issues related to chemical reactions, including total hardness (η), electronegativity (χ), and electron fraction transitions from the anti-corrosion molecule to the copper atom (ΔN), were calculated and compared in the tetrazole molecules and their derivatives. Also, with the help of adsorption locator calculations, the inhibitory effects of these compounds were theoretically investigated in an acidic environment. Through these calculations, it was determined that tetrazole molecules with electron-donating groups adsorbed perpendicularly to the copper (1 1 1) surface, by forming a stronger bond, are considered suitable corrosion inhibitors. Also, among the examined molecules, the 2H-tetrazole isomer form plays a more influential role than the 1H-tetrazole form.

Boron nitride nanosheets supported highly homogeneous bimetallic AuPd alloy nanoparticles catalyst for hydrogen production from formic acid.

Formic acid (FA) has been recently regarded as a safe and stable source of hydrogen (H2). Selective and efficient dehydrogenation of FA by an effective catalyst under mild conditions is still a challenge. So, different molar ratios of bimetallic Pd-Au alloy nanoparticles were effectively stabilized and uniformly distributed on boron nitride nanosheets (BNSSs) surface via the precipitation process. Obtained catalysts were employed in FA decomposition for H2production. Pd-Au@BNNS containing 3% Au and 5% Pd (Au.03Pd.05@BNNS) exhibited high activity and 100% H2selectivity for H2production from FA at 50 °C. In order to optimize the reaction conditions, various factors including, time, temperature, solvent, base type, and amount of catalyst, were examined.

Glycerol adsorption and mechanism of dehydration to acrolein over TiO2 surface: A density functional theory study.

Glycerol as major by-product of biodiesel production cab be converted to high-value added materials such as acrolein. The details of this transformation mechanism is obscure using metal oxide catalysts. In this study, DFT calculations using the generalized gradient approximation with periodic boundary conditions was used to study the mechanism of dehydration of glycerol to acrolein on the (1 0 0) surface of anatase TiO2. For this purpose, the (1 0 0) TiO2 crystal face was built with a slab of Ti24O48. The various interaction of glycerol with the surface was surveyed, and energy barriers and reaction energies were employed to analyze the possible dehydration mechanisms. Three paths were proposed for dehydration of glycerol to acrolein that starts with adsorption through central hydroxyl group. According to the third path, TiO2 surface shows the most activity in proton transfer reaction with 89.1 kcal/mol activation energy in comparison with path 1 and 2 is the appropriate path for the formation of acrolein. The rate-limiting step of this pathway is the adsorption of H2' and Oγ on the surface and simultaneous creation of a double bond between Cα and Cß (G1h â†’ G1o).

The effect of the diameter of cyclic peptide nanotube on its chirality discrimination.

In this work, the transport behaviors of the enantiomers of lactic acid (LA) in two cyclic peptide nanotubes (CPNTs) with different diameters were studied using steered molecular dynamic (SMD) simulation to investigate the effect of the diameter of CPNT on the discrimination of the enantiomers of LA. For this purpose, two cyclic peptides with two different sizes ([Ala-D-Ala-L]5 and [Ala-D-Ala-L]4) were used for constructing two CPNTs so that each CPNT was composed of eight cyclic peptide units. The docking calculations were performed to obtain the appropriate position of each enantiomer at the lumen of each CPNT. The variation of the pulling force versus time, exerted on the enantiomers moving in the CPNTs was calculated using the SMD simulations with two different strategies (positional and directional).The obtained results showed that the diameter of CPNT has considerable effect on the discrimination of the LA enantiomers so that the increase of the diameter of CPNT, increased the velocity difference between two enantiomers and improved the performance of CPNT for the chirality discrimination. The SMD simulations indicated that the velocity of S-enantiomer became more than R-enantiomer and its motion became more comfortable than R-enantiomer when the diameter of CNPT increased. The RDFs of the H and O atoms of the LA enantiomers relative to the O atoms of CPNT were calculated and it was found that the increase of the diameter of CPNT creates the significant changes in the RDFs of H1, H2 and H3 atoms of the enantiomers.

The effects of second electron acceptor group on the performance of tetrazole-based nanocrystalline TiO2 sensitizers in DSSCs.

Three new organic sensitizers with two electron acceptor groups were synthesized and applied to nanocrystalline TiO2 solar cells. The ethyl 2-(1H-tetrazol-5-yl) acetate, (2H-tetrazol-5-yl) acrylonitrile and 1H-tetrazole-5-acetic acid moieties were introduced to the triphenylamine as electron acceptor groups. The photophysical, electrochemical and photovoltaic properties of the solar cells based on the synthesized sensitizers were studied and compared with their counterparts of single electron acceptor type. Quantum chemical calculations were also carried out to consideration of the electronic and optical properties of these dyes. The dye with the (2H-tetrazol-5-yl) acrylonitrile electron acceptors showed the absorption maxima in the longer wavelength, compared to the dyes with ethyl 2-(1H-tetrazol-5-yl) acetate and 1H-tetrazole-5-acetic acid. The solar cell based on the dye with 1H-tetrazole-5-acetic acid showed the highest conversion efficiency of 3.53% (open circuit voltage=569mV, short circuit photocurrent density=11.50mAcm-2, and fill factor of 54% under AM 1.5G conditions). The results also showed that the dyes with two electron acceptor groups gave the higher performance than the dyes with single electron acceptor.