Journal of Chemical Sciences最新文献

The ever-increasing global energy demand has necessitated alternate sources of energy. Photoelectrochemical water splitting proved to be a viable method of green hydrogen production. In the present study, four different one-dimensional titanium dioxide nanotube arrays (TNAs) were fabricated by varying the time duration of the second anodization. The highly ordered TNAs proved to be potential photoanodes for photoelectrochemical water splitting, for production of hydrogen. The fabricated TNAs were confirmed as stable anatase crystal structures using X-ray diffraction and Raman spectroscopy analysis. The TNAs showed an increase in length with an increase in anodization time. The morphological studies revealed the formation of the one-dimensional tube-like morphology of TNAs with lengths varying from 1.41 μm to 6.35 μm. The increased length and one-dimensional nanotube formation implied an increased number of active sites and an increased surface-to-volume ratio. The observed increase in photocurrent may be attributed to increased electrode–electrolyte interfacial area, where charge and mass transport occured. The band-gap of the TNAs showed a minimal progressive decrease with an increase in anodization time. The oxidation states of the constituent elements were confirmed using X-ray photoelectron spectroscopy. Contact angle measurement indicated a transition from slight hydrophobicity to slight hydrophilicity with an increase in the anodization time of the TNAs. Electrochemical studies of TNAs exhibited increased photo-response with an increase in anodization time. The influence of anodization time on the characteristics of TNAs is explored in this study.

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TiO₂ Nanotube Arrays (TNAs) were synthesized by two – step anodization method, by varying second anodization time. The TNAs were tested for their efficacy as photo-anode, following exhaustive characterization techniques. The activity of the potential photoanodes for PEC water splitting was analyzed using LSV, CA, EIS and Tafel plots

Microhydration of neutral and anionic nitromethane molecules was investigated up to (n =10) water molecules using dispersion-corrected density functional B2PLYPD with aug-cc-pVDZ basis sets. The calculated interaction energies of both anion and neutral nitromethane–water clusters were extrapolated to the complete basis set (CBS) limit. It was observed that the water molecules interact with the methyl group of the nitromethane in the case of a neutral molecule, whereas in anionic nitromethane hydration, water molecules build a hydrogen bond network strongly around the nitro group of the nitromethane. The SAPT analysis and MED critical point calculations have revealed that the anionic nitromethane–water cluster is more stable as compared to the neutral one. Further, the SAPT analysis showed that an increase in stability in case of the interaction in an anionic nitromethane–water complex is because of a higher attractive contribution from the electrostatic and dispersion components. The vertical detachment energy (VDE) and electron affinity (EA) values of nitromethane were also calculated, and the VDE values were found to be in good agreement with the experimental values.

Graphical abstract

Anionic Nitromethane-(H₂O)_n clusters investigated using Dispersion Corrected Density Functional Theory and compared with neutral counterparts. The calculated VDE values show good agreement with Experimental values.

The proposed research aims to investigate the structure and lowest excitation properties of GG-CC and GC-CG (G, guanine; C, cytosine) peptide nucleic acid (PNA) dimers, incorporating different amino acids such as serine, aspartic acid, and histidine using the density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods. The structures under consideration have been optimized at the Becke’s three-parameter hybrid density functional (B3) with correlation function of Lee, Yang and Parr (LYP)/6-31G* level of theory. The study involves calculating the backbone torsions and backbone-base linker torsions, correlating them with experimental data. The computed excitation energy for the GG-CC PNA system is compared with the natural GG-CC DNA system. The lowest excitation properties, such as excitation energy, wavelength, and oscillator strength, reveal their dependency on both the stacking arrangement and the molecular environment, irrespective of whether the PNA is modified or unmodified. Additionally, a highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) analyses were conducted. This study is intended to serve as a foundational tool for understanding the molecular behaviour of PNAs under light absorption, potentially leading to further exploitation in photo-related applications.

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This article explores the application of conceptual density functional theory (CDFT) and information-theoretic approach (ITA) to various chemical phenomena, demonstrating their predictive power in diverse molecular systems. IT descriptors have been employed to investigate conformational stability, molecular acidity, aromaticity, and electrophilicity/nucleophilicity, revealing strong correlations between information-theoretic measures and experimental observations. Moreover, CDFT-based QSAR and QSPR models have shown significant predictive capabilities in pharmacological toxicity and physicochemical properties, such as partition coefficient and enthalpy of vaporization. The integration of CDFT and IT descriptors has provided deeper insights into reactivity trends in pericyclic reactions, allowing for the classification of mechanisms based on electrophilicity indices. Additionally, periodic trends in CDFT and IT descriptors have been examined, reaffirming the fundamental chemical principles. The review article underscores the robustness of IT and CDFT methodologies in capturing electronic structure variations and predicting the chemical behavior of molecules. The integration of these descriptors offers a comprehensive approach to understanding chemical reactivity, stability, and molecular interactions, paving the way for future advancements in theoretical and computational chemistry.

Graphical abstract

The applications of Conceptual Density Functional Theory (CDFT) and the Information-Theoretic Approach (ITA) have been widely used in predicting the toxicity, activity, and reactivity of chemical systems. Moreover, Quantitative Structure–Activity Relationship (QSAR) studies are conducted using CDFT and ITA descriptors through regression equations.

A recent study by Liam Longo and co-workers at the Earth-Life Science Institute, published in Angewandte Chemie, reports the discovery of an ancient helix-hairpin-helix protein motif capable of functioning in both left- and right-handed forms, thus challenging the concept that biomolecular interactions are strictly dependent on homochirality. This rather rare “ambidextrous” property suggests that such motifs may be molecular relics from a pre-LUCA era when mirror-image life forms coexisted, and offers new insights into the origins and evolution of molecular asymmetry seen in living matter.

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The ‘helix-hairpin-helix’ motif allows the binding of a simple peptide to both DNA and its mirror image. Credit: Liam M S Longo.

Linoleic acid modified through autoxidation, hydroxylation, and bromination was utilized for the first time in controlled/living radical polymerization methods such as atom transfer radical polymerization (ATRP). A brominated polymeric linoleic acid macromonomer initiator (ATRP–MIM) was synthesized as a macromolecular initiator (MIM) based on polymeric linoleic acid for use in ATRP. Using this ATRP–MIM and styrene monomer, novel graft copolymers were successfully synthesized via ATRP. The effects of various reaction parameters, including monomer concentration, initiator concentration, and polymerization kinetics, were systematically investigated. Additionally, the impact of reaction conditions on molecular weight and polydispersity was studied. The percentage compositions of the structural contents of graft copolymers were determined using ¹H NMR. Detailed characterization, including structural analysis, thermal properties, and molecular weight determination, was performed using techniques such as Fourier-transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The obtained graft copolymers exhibited enhanced thermal stability and well-defined molecular structures, contributing to the development of bio-based polymeric materials with specialized properties for applications in coatings, biocompatible systems, and advanced functional materials.

Graphical abstract

This study introduces the use of modified linoleic acid, altered through autoxidation, hydroxylation, and bromination, in controlled radical polymerization methods such as atom transfer radical polymerization (ATRP) for the first time. The research focuses on the synthesis of graft copolymers by using a brominated polymeric linoleic acid initiator (ATRP-MIM) in copolymerization with styrene.

In a previous communication (Comp. Theor. Chem. 1091 (2016) 150), concerted isomerization reactions of 15 C₇H₇⁺ cations in the gas phase had been studied. The present study deals with the kinetics of these concerted isomerization reactions using the M06-2X functional. From the potential energy profiles of these reactions, the rate coefficients are estimated by using transition state theory along with the estimation of Wigner’s empirical transmission coefficient for quantum tunnelling. The rate coefficient values are calculated over a temperature range of 200–500 K, where the Arrhenius activation energies, along with the pre-exponential factors, are determined for each of these reactions.

Graphical abstract

The graphical abstract highlight the two representative isomerisation reactions of bicyclo[3.2.0]heptadienyl cation 4 to tropyl cation 1 (global minimum) by C-C σ-bond collapse to π-bond via transition state TS1 and o-tolyl cation 5 to benzyl cation 2 by 1,3-hydride shift via TS4.