Indium-doped ZnOas efficient photosensitive material for sunlight driven hydrogen generation and DSSC applications: integrated experimental and computational approach

Electricity generation using simple and cheap dye-sensitized solar cells and photocatalytic water splitting to produce future fuel, hydrogen, directly under natural sunlight fascinated the researchers worldwide. Herein, synthesis of indium-doped wurtzite ZnO nanostructures with varying molar percentage of indium from 0.25 to 3.0% with concomitant characterization indicating wurtzite structure is reported. The shift of (002) reflection plane to higher 2θ degree with increase in indium-doping thus is a clear evidence of doping of indium in zinc oxide nanoparticles. Surface morphological as well as microstructural studies of In@ZnO exhibited generation of ZnO nanoparticles and nanoplates of diameter 10–30 nm. The structures have been correlated well using computational density functional (DFT) studies. Diffuse reflectance spectroscopy depicted the extended absorbance of these materials in the visible region. Hence, the photocatalytic activity towards hydrogen generation from water under natural sunlight as well as efficient DSSC fabrication of these newly synthesized materials has been demonstrated. In-doped ZnO exhibited enhanced photocatalytic activity towards hydrogen evolution (2465 μmol/h/g) via water splitting under natural sunlight. DSSC fabricated using 2% In-doped ZnO exhibited an efficiency of 3.46% which is higher than other reported In-doped ZnO based DSSCs.

     

Kinetic Behavior of Quaternary Ammonium Hydroxides in Mixed Methane and Carbon Dioxide Hydrates

This study evaluates the kinetic hydrate inhibition (KHI) performance of four quaternary ammonium hydroxides (QAH) on mixed CH₄ + CO₂ hydrate systems. The studied QAHs are; tetraethylammonium hydroxide (TEAOH), tetrabutylammonium hydroxide (TBAOH), tetramethylammonium hydroxide (TMAOH), and tetrapropylammonium hydroxide (TPrAOH). The test was performed in a high-pressure hydrate reactor at temperatures of 274.0 K and 277.0 K, and a concentration of 1 wt.% using the isochoric cooling method. The kinetics results suggest that all the QAHs potentially delayed mixed CH₄ + CO₂ hydrates formation due to their steric hindrance abilities. The presence of QAHs reduced hydrate formation risk than the conventional hydrate inhibitor, PVP, at higher subcooling conditions. The findings indicate that increasing QAHs alkyl chain lengths increase their kinetic hydrate inhibition efficacies due to better surface adsorption abilities. QAHs with longer chain lengths have lesser amounts of solute particles to prevent hydrate formation. The outcomes of this study contribute significantly to current efforts to control gas hydrate formation in offshore petroleum pipelines.     

Heterocyclic Substitutions Greatly Improve Affinity and Stability of Folic Acid towards FRα. an In Silico Insight

Folate receptor alpha (FRα) is known as a biological marker for many cancers due to its overexpression in cancerous epithelial tissue. The folic acid (FA) binding affinity to the FRα active site provides a basis for designing more specific targets for FRα. Heterocyclic rings have been shown to interact with many receptors and are important to the metabolism and biological processes within the body. Nineteen FA analogs with substitution with various heterocyclic rings were designed to have higher affinity toward FRα. Molecular docking was used to study the binding affinity of designed analogs compared to FA, methotrexate (MTX), and pemetrexed (PTX). Out of 19 FA analogs, analogs with a tetrazole ring (FOL03) and benzothiophene ring (FOL08) showed the most negative binding energy and were able to interact with ASP81 and SER174 through hydrogen bonds and hydrophobic interactions with amino acids of the active site. Hence, 100 ns molecular dynamics (MD) simulations were carried out for FOL03, FOL08 compared to FA, MTX, and PTX. The root mean square deviation (RMSD) and root mean square fluctuation (RMSF) of FOL03 and FOL08 showed an apparent convergence similar to that of FA, and both of them entered the binding pocket (active site) from the pteridine part, while the glutamic part was stuck at the FRα pocket entrance during the MD simulations. Molecular mechanics Poisson-Boltzmann surface accessible (MM-PBSA) and H-bond analysis revealed that FOL03 and FOL08 created more negative free binding and electrostatic energy compared to FA and PTX, and both formed stronger H-bond interactions with ASP81 than FA with excellent H-bond profiles that led them to become bound tightly in the pocket. In addition, pocket volume calculations showed that the volumes of active site for FOL03 and FOL08 inside the FRα pocket were smaller than the FA–FRα system, indicating strong interactions between the protein active site residues with these new FA analogs compared to FA during the MD simulations.     

Amperometric determination of nanomolar mercury(II) by layered double nanocomposite of zinc/aluminium hydroxide-3(4-methoxyphenyl)propionate modified single-walled carbon nanotube paste electrode

Ionics - A mercury(II) sensor was developed by using single-walled carbon nanotube (SWCNT) paste electrode modified with layered double Zn/Al hydroxide-3(4-methoxyphenyl)propionate nanocomposite...     

Synthesis,Characterization and Properties of Single-Walled Carbon Nanohorns

Single-walled nanohorns (SWNHs) have been prepared by sub-merged arc discharge of graphite electrodes in liquid nitrogen. The samples were examined by scanning electron microscopy, transmission electron microscopy and Raman spectroscopy. Nitrogen and boron doped SWNHs have been prepared by the sub-merged arc discharge method using melamine and elemental boron as precursors. Intensification of Raman D-band and stiffening of G-band has been observed in the doped samples. The electrical resistance of the SWNHs varies in opposite directions with nitrogen and boron doping. Functionalization of SWNHs through amidation has been carried out for solubilizing them in non-polar solvents. Water-soluble SWNHs have been produced by acid treatment and non-covalent functionalization with a coronene salt. SWNHs have been decorated with nanoparticles of Au, Ag and Pt. Interaction of electron donor (tetrathiafulvalene, TTF) and acceptor molecules (tetracyanoethylene, TCNE) with SWNHs has been investigated by Raman spectroscopy. Progressive softening and stiffening of Raman G-band has been observed respectively with increase in the concentration of TTF and TCNE.     

Polysaccharide‐Based Oleogels Prepared with an Emulsion‐Templated Approach

The preparation and characterization of oleogels structured by using a combination of a surface‐active and a non‐surface‐active polysaccharide through an emulsion‐templated approach is reported. Specifically, the oleogels were prepared by first formulating a concentrated oil‐in‐water emulsion, stabilized with a combination of cellulose derivatives and xanthan gum, followed by the selective evaporation of the continuous water phase to drive the network formation, resulting in an oleogel with a unique microstructure and interesting rheological properties, including a high gel strength, G′>4000 Pa, shear sensitivity, good thixotropic recovery, and good thermostability.     

Mononuclear High-spin Octahedral Cobalt(II) Complex with Positive Axial Magnetic Anisotropy: Synthesis,Crystal Structure,and DFT Studies

This article outlines the magnetic features of a new six–coordinate high-spin cobalt(II) complex cis-[Co^II(tmphen)₂(NCS)₂] ( 1 ) achieved via the reactions of cobalt(II) thiocyanate with 3,4,7,8-tetramethyl-1,10-phenanthroline. The complex 1 was thoroughly characterized by different analytical and spectroscopic techniques and further confirmed by single X-ray crystal diffraction pattern. Complex 1 is a neutral molecule and adopt highly distorted six-coordinate CoN₆ octahedral coordination sphere surrounded by two thiocyanate N atoms in cis locations and the equatorial plane is occupied by two imine N atoms from the two tmphen ligand while the remaining two imine N atoms reside in the axial positions. Magnetic susceptibility data of complex 1 revealed that the χ_ΜT values decrease significantly to a value of 1.49 cm³ · K · mol^–1 at 2.0 K on decreasing temperatures below 100 K, mainly ascribed to the significant spin–orbit coupling (SOC) of six-coordinate Co^II ions. Furthermore, a field-dependence measurement was performed at 2 K, which shows a positive curvature up to 27 kOe, while it becomes linear up to 2.01 Nμ_B, which authenticated the fact that only the lowest Kramers doublet of ground state is appreciably populated.     

Catalytic activity of Mn(III) and Co(III) complexes: evaluation of catechol oxidase enzymatic and photodegradation properties

We have synthesized two mononuclear complexes, Mn-hq and Co-hq, to serve as sustainable catalysts (for degrading dyes from organic pollutant) and as biocatalysts (for promoting oxidation of catechol to quinone). The two complexes have been characterized by various spectroscopic tools, and with the assistance of single-crystal X-ray diffraction data, their molecular structures were established. The present complexes were exploited for the catalytic activity, i.e., enzymatic activity and photocatalytic property. In methanolic solution, Mn-hq and Co-hq were examined for catecholase-like activity and Mn-hq particularly catalyzes the oxidation of 3,5-di-tert-butyl catechol to analogous quinone with a K_cat value of 835.2 h^?1. Additionally, Mn-hq and Co-hq demonstrated remarkable photocatalytic activity for the degradation of methylene blue (MB) in the aqueous medium beneath visible light. Co-hq shows excellent stability and recyclability toward MB. Further, trapping experiment along with degradation pathways is also explored. Thus, the present research throws light on the excellent catalytic properties of simply designed complexes and this activity can be tuned for desired efficiencies in future prospects.

     

Effect of Bulky Functional Groups on Donor and Acceptor Interactions and their Photoluminescence Properties

Material designs that use donor and acceptor units are often found in organic optoelectronic devices. Molecular level insight into the interactions between donors and acceptors are crucial for understanding how such interactions can modify the optical properties of the organic optoelectronic materials. In this paper, tris(4-(tert-butyl)phenyl)amine (pTPA) was synthesized as a donor in order to compare with unmodified triphenylamine (TPA) in a donor–acceptor system by having 2,4,6-triphenyl-1,3,5-triazine (TRZ) as an acceptor. Dimerization of donors and acceptors occurred in solvent when the concentration of solute is high. At 0 K, using a polarizable continuum model, the nitrogen atom of TPA is found to stack on top of the center of triazine of TRZ, whereas such alignment is offset in pTPA and TRZ. We attributed such alignment in TPA-TRZ as the result of attractive interactions between partial localization of 2p_z electrons at the nitrogen atom of TPA and the π deficiency of triazine in TPA-TRZ. By taking into account random motions of the solvent effect at 300 K in quantum molecular dynamics and classical molecular dynamics simulations to interpret the marked difference in emission spectra between TPA-TRZ and pTPA-TRZ, it was revealed that the attractive interaction between pTPA and TRZ in toluene is weaker than TPA and TRZ. Because of the weaker attractive interaction between pTPA and TRZ in toluene, the dimers adopted numerous ground state conformations resulting in broad emission bands superimposed with multiple small Gaussian peaks. This is in contrast to TPA-TRZ which has only one dominant dimer conformation. This study demonstrates that the strength of intermolecular interactions between donors and acceptors should be taken into consideration in designing supramolecular structures.