Band 93, Heft 5

Metal nanocrystals (NCs), particularly for plasmonic metal NCs with specific morphology and size, can strongly interact with ultraviolet-visible or even near-infrared photons to generate energetic charge carriers, localized heating, and electric field enhancement. These unique properties offer a promising opportunity for maneuvering solar-to-chemical energy conversion through different mechanisms. As distinct from previous works, in this review, recent advances of various characterization techniques in probing and monitoring the photophysical/photochemical processes, as well as the reaction mechanisms of plasmon-mediated photoredox catalysis are thoroughly summarized. Understanding how to distinguish and track these reaction mechanisms would furnish basic guidelines to design next-generation photocatalysts for plasmon-enhanced catalysis.

This article describes the journey of a young girl born to poor cotton farmers in the early 40s who grew up to become a chemist and then became the President of the World’s Largest Scientific Society, the American Chemical Society. It describes the obstacles she had to overcome as a woman as she earned a Ph.D. in Chemistry and the successes she celebrated along the way. It also features undergraduate research success stories and how these have contributed to her success. Hopefully it will inspire women to follow her footprints in a journey that reached many corners of the world.

The design of new chemical reactions that are convenient, sustainable, and innovative is a preeminent concern for modern synthetic chemistry. While the use of earth abundant element catalysts remains underdeveloped by chemists, nature has developed a cornucopia of powerful transformation using only base metals, demonstrating their viability for sustainable method development. Here we show how study of nature’s approach to disparate chemical problems, from alkene desaturation to photodetection in bacteria, can inspire and enable new approaches to difficult synthetic chemistry problems past, present, and future.

Biorefinery is defined as a sustainable process where biomass is converted in a spectrum of marketable products and fuels. In this view, C6 furan-based compounds, usually referred as furanics, have been extensively investigated as aromatic promising building blocks from renewables. 5-Hydroxymethylfurfural (HMF) and 2,5-furan dicarboxylic acid (FDCA) are well known examples of furanics whose syntheses and applications have been extensively reviewed in the literature. Herein for the first time it is reported a comprehensive overview on the synthetic procedures to another bio-derived furan compounds, i.e. 2,5-bis(hydroxymethyl)furan (BHMF), a stable bio-based diol with numerous applications as monomer for bio-materials and fuels. Advantages and limitations of the different synthetic approaches are addressed, as well as possible future developments to render this compound part of the biorefinery market.

The first comparative DFT (B3LYP/6-31G*) study of the Zn-porphyrin and its two derivatives, ZnP(P) 4 and ZnP(As) 4 , is reported. For all three species studied, ZnP, ZnP(P) 4 and ZnP(As) 4 , the singlet was calculated to be the lowest-energy structure and singlet-triplet gap was found to decrease from ca. 41—42 kcal/mol for N to ca. 17—18 kcal/mol for P and to ca. 10 kcal/mol for As. Both ZnP(P) 4 and ZnP(As) 4 were calculated to attain very pronounced bowl-like shapes. The frontier molecular orbitals (MOs) of the core-modified porphyrins are quite similar to the ZnP frontier MOs. For the HOMO-2 of the core-modified porphyrins due to the ZnP(P) 4 /ZnP(As) 4 bowl-like shapes we might suppose the existence of “internal” electron delocalization inside the ZnP(P) 4 /ZnP(As) 4 “bowls”. Noticeable reduction of the HOMO/LUMO gaps was calculated for ZnP(P) 4 and ZnP(As) 4 , by ca. 1.10 and 1.47 eV, respectively, compared to ZnP. The core-modification of porphyrins by P and especially by As was found to result in significant decrease of the charge on Zn-centers, by ca. 0.61—0.67e for P and by ca. 0.69—0.76e for As. Charges on P- and As-centers were computed to have large positive values, ca. 0.41—0.45e and ca. 0.43—0.47e, for P and As, respectively, compared to significant negative values, ca. −0.65 to −0.66e for N. The porphyrin core-modification by heavier N congeners, P and As, can noticeably modify the structures, electronic, and optical properties of porphyrins, thus affecting their reactivity and potential applications.

B-cell epitope will be recognized and attached to the surface of receptors in B-lymphocytes to trigger immune response, thus are the vital elements in the field of epitope-based vaccine design, antibody production and therapeutic development. However, the experimental approaches in mapping epitopes are time consuming and costly. Computational prediction could offer an unbiased preliminary selection to reduce the number of epitopes for experimental validation. The deposited B-cell epitopes in the databases are those with experimentally determined positive/negative peptides and some are ambiguous resulted from different experimental methods. Prior to the development of B-cell epitope prediction module, the available dataset need to be handled with care. In this work, we first pre-processed the B-cell epitope dataset prior to B-cell epitopes prediction based on pattern recognition using support vector machine (SVM). By using only the absolute epitopes and non-epitopes, the datasets were classified into five categories of pathogen and worked on the 6-mers peptide sequences. The pre-processing of the datasets have improved the B-cell epitope prediction performance up to 99.1 % accuracy and showed significant improvement in cross validation results. It could be useful when incorporated with physicochemical propensity ranking in the future for the development of B-cell epitope prediction module.

Computational methods were used to analyse the interactions around the metal centres in three transition metal (TM) complexes for which the X-ray data are available. We were particularly interested in understanding the metal–metal interactions. We used concepts of bond order, natural population, quantum theory of atom in molecules, electron localisation functions (ELFs) and non-covalent interactions (NCIs). Our results indicate that these tools can be used effectively to help in having insights into the bonding of TM complexes.

Iron-based chalcopyrite materials have diverse applications in solar cells, spintronic, thermoelectric devices, LEDs and medical sciences. In this report we have studied structure, electronic and optical properties of chalcopyrite-type nano-cluster XFeY 2 (X=Cu, Ag, Au; Y=S, Se, Te) systematically by using Density Functional Theory (DFT). Our computed HOMO-LUMO energy gap of XFeY 2 is in the range of 1.568–3.982 eV, which endorses its potential application in optoelectronic devices and solar cells. The result shows that chalcopyrite-type material AuFeS 2 having a star-type structure with point group C 2v and sextet spin multiplicity, is the most stable cluster with HOMO-LUMO energy gap of 3.982 eV. The optical properties viz. optical electronegativity, refractive index, dielectric constant, IR and Raman activity of these nano-clusters are also investigated. The result exhibits that HOMO-LUMO energy gap of XFeY 2 along with optical electronegativity and vibrational frequency decreases from S to Se to Te, whereas refractive index and dielectric constant increases in the reverse order.

Fe/CeO 2 –SiO 2 nanocomposite was synthesized by using zwitterionic surfactant 3-( N , N -dimethyloctadecylammonio) propane sulfonate (SB3-18) by sol–gel and hydrothermal methods. The nanocomposite was well characterized before its use. X-ray diffraction (XRD) results confirmed the synthesis of the Fe/CeO 2 –SiO 2 nanocomposite. Crystallite size calculated by using Scherrer equation was 5.33 nm while it was found 5.26 nm by Williamson–Hall equation. Bandgap of Fe/CeO 2 –SiO 2 nanocomposite shows redshift after the doping of Fe. Degradation studies of methylene blue (MB) and chlorpyrifos (CP) were investigated by nanofiltration (NF) column under visible light irradiation. Degradation and adsorption of MB was investigated by three different types of columns under visible light irradiation. It was observed to achieve 100 % removal of MB and 91 % of CP through column in which rice husk ash (RHA) slurry was mixed with the nanocomposite.

The synthesis and comparative study on the antibacterial activity of three organotin(IV) compounds, namely dibutyltin(IV) bis-(3-hydroxybenzoate), [Bu 2 Sn(3-HBz) 2 ] ( 7 ), diphenyltin(IV) bis-(3-hydroxybenzoate), [Ph 2 Sn(3-HBz) 2 ] ( 8 ), and triphenyltin(IV) 3-hydroxybenzoate, [Ph 3 Sn(3-HBz)] ( 9 ) which were prepared by the reaction of dibutyltin(IV) oxide, [Bu 2 SnO] ( 4 ), diphenyltin(IV) dihydroxide, [Ph 2 Sn(OH) 2 ] ( 5 ), and triphenyltin(IV) hydroxide, [Ph 3 SnOH] ( 6) with 3-hydroxybenzoic acid (3-HBz) has successfully been performed. The characterization of these compounds were done using 1 H and 13 C NMR, IR, UV spectroscopies and their compositions were determined based on microanalytical data. Antibacterial activity of these compounds was demonstrated at concentrations of 1.89 × 10 −4 , 1.81 × 10 −4 , and 1.72 × 10 −4  M, respectively by dilution method against Pseudomonas aeruginosa . Similarly, the compounds were active at concentration of 1.87 × 10 −4 , 1.79 × 10 −4 , and 1.71 × 10 −4  M, respectively, against Bacillus subtilis. These activities are comparable to that of streptomycin at a concentration of 1.70 × 10 −4  M as a positive control, but the halozone of compounds 7 , 8 , and 9 were slightly lower than that of streptomycin’s halozone. The results obtained suggest that the compounds synthesized have potential as antibacterial agents.

Many calculations for science or trade require the evaluation and propagation of measurement uncertainty. Although relative atomic masses (standard atomic weights) of elements in normal terrestrial materials and chemicals are widely used in science, the uncertainties associated with these values are not well understood. In this technical report, guidelines for the use of standard atomic weights are given. This use involves the derivation of a value and a standard uncertainty from a standard atomic weight, which is explained in accordance with the requirements of the Guide to the Expression of Uncertainty in Measurement. Both the use of standard atomic weights with the law of propagation of uncertainty and the Monte Carlo method are described. Furthermore, methods are provided for calculating uncertainties of relative molecular masses of substances and their mixtures. Methods are also outlined to compute material-specific atomic weights whose associated uncertainty may be smaller than the uncertainty associated with the standard atomic weights.