Incorporations of gold,silver and carbon nanomaterials to kombucha-derived bacterial cellulose: Development of antibacterial leather-like materials

Bacterial cellulose (BC), derived from kombucha scoby have extraordinary organoleptic properties suitable for development of leather-like materials. An improvement in physical and mechanical property is desirable for the practical applications. This work deals with the treatment of BC by incorporations of three different nanomaterials such as gold nanoparticles (AuNP), silver nanoparticles (AgNP) and graphene oxide (GO). Achieving combined benefits via synergic interactions of different nanomaterials is the major objective herein. While graphene oxide can influence some of the parameters related to mechanical properties, silver nanomaterials can offer antibacterial characteristics. Gold nano materials can bridge the BC/silver/graphene oxide as well as provide the desirable aesthetic colour. Different physical chemical and mechanical characteristics were studied in detail. For example, changes in morphology by imaging fiber network were studied using scanning electron microscopy. Fibre properties were studied by Small Angle X-Ray Scattering (SAXS) and X-Ray Diffraction (XRD). Elemental composition was studied by X-ray photoelectron spectroscopy (XPS) analysis and Raman analysis. The improvement of hydrophobicity was studied by Contact angle meter. Thermal analysis was performed using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). A Picture was provided in ESI to show the modified material's leather-like appearances.     

Barbier allylation-Prins reaction of PEG-bound aldehydes—soluble polymer-supported synthesis of 2,4,6-trisubstituted tetrahydropyrans

PEG-bound aldehydes undergo zinc-mediated Barbier allylation to form homoallylic alcohols, which on further reaction with various aldehydes in the presence of BF₃·Et₂O through a Prins cyclization afford 4-hydroxytetrahydropyrans and 4-fluorotetrahydropyrans.     

A Novel ‘Domino‐Click Approach’ to Unsymmetrical Bis‐1H‐1,2,3‐triazoles

Aryl azides 1 were treated with allenylmagnesium bromide ( 2 ) to generate 1,5‐disubstituted butynyl‐1H‐1,2,3‐triazoles 3 in a domino fashion, which upon Cu^I‐catalyzed 1,3‐dipolar cycloaddition with aryl azides 4 afforded novel bis‐1H‐1,2,3‐triazoles 5 in quantitative yields (Scheme 1 and Table).     

An efficient synthesis,spectral characterization,antimicrobial, and antioxidant activities of novel α-hydroxyphosphonates and α-hydroxyphosphinates

A simple, novel, and an efficient synthesis of α-hydroxy phosphonates (3a–d) and phosphinates (5a–f) has been accomplished from febuxostat aldehyde (1) with various dialkylphosphites (2) and dialkylphosphinates (4) in the presence of 1, 4-dimethylpiperazine as a strong base with good to excellent yields (78%–95%) is reported. The structures of the title compounds were established by elemental analysis and spectral data (IR, ¹H, ¹³C and ³¹P NMR, and LC-MS). All the title compounds (3a–d) and (5a–f) were tested for their antimicrobial and antioxidant activities. Bioassay results reveal that a few of the title compounds exhibited promising antimicrobial and antioxidant activities.     

Catalytic asymmetric dihydroxylation of substituted trans-stilbene derivatives: implications of the variation of enantioselectivities on the mechanism of OsO4 addition to olefins

The OsO₄ catalyzed asymmetric dihydroxylation of substituted trans-stilbene derivatives using 9-O-acetyldihydrocinchonidine as chiral ligand gives the corresponding diols with lower enantioselectivity in the case of substrates containing electron-donating and electron-withdrawing substituents. The Hammett correlations of the enantiomeric ratios exhibit non-linear plots, in accordance with the conclusion that the reaction involves a 1,3-dipolar type [3+2] cycloaddition transition state.     

Thermal analysis of nanofluid flow containing gyrotactic microorganisms in bioconvection and second-order slip with convective condition

Journal of Thermal Analysis and Calorimetry - Bioconvection in magneto-nanoliquid embedded with gyrotactic microorganisms across an elongated sheet with velocity slip of second order is addressed....     

Multilayer assemblies of polyelectrolyte-gold nanoparticles for the electrocatalytic oxidation and detection of arsenic(III)

Multilayers of poly(diallyldimethylammonium chloride) (PDDA) and citrate capped Au nanoparticles (AuNPs) anchored on sodium 3-mercapto-1-propanesulfonate modified gold electrode by electrostatic layer-by-layer assembly (LbL) technique are shown to be an excellent architecture for the direct electrochemical oxidation of As(III) species. The growth of successive layers in the proposed LbL architecture is followed by atomic force microscopy, UV-vis spectroscopy, quartz crystal microbalance with energy dissipation, and electrochemistry. The first bilayer is found to show rather different physico-chemical characteristics as compared to the subsequent bilayers, and this is attributed to the difference in the adsorption environments. The analytical utility of the architecture with five bilayers is exploited for arsenic sensing via the direct electrocatalytic oxidation of As(III), and the detection limit is found to be well below the WHO guidelines of 10ppb. When the non-redox active PDDA is replaced by the redox-active Os(2,2'-bipyridine)(2)Cl-poly(4-vinylpyridine) polyelectrolyte (PVPOs) in the LbL assembly, the performance is found to be inferior, demonstrating that the redox activity of the polyelectrolyte is futile as far as the direct electro-oxidation of As(III) is concerned.     

New data on decomposition of nitric solutions of acetohydroxamic acid

Acetohydroxamic acid (AHA) is an important complexant/reductant for Pu(IV) in the UREX process. It decomposes in the presence of nitric acid. In literature, its decomposition kinetics in nitric acid is traditionally reported as pseudo-first order reaction. In this study, new experimental data were reported for kinetics experiments under wide consecration conditions. It was found that the decomposition reaction was first order with respect to both the components hence overall second order.     

Flow injection on-line solid phase extractive preconcentration of palladium(II) in dust and rock samples using exfoliated graphite packed microcolumns and determination by flame atomic absorption spectrometry

A sensitive and efficient flow injection preconcentration and matrix-separation technique using exfoliated graphite (EG) as column material was developed prior to flame atomic absorption spectrometry (FAAS) determination of palladium(II) in street/fan blade dust and rock samples. The method is based on the sorption of palladium(II)—diethylammonium dithiocarbamate chelate (which was found to be better among various thioligands) complex on to EG material and its subsequent elution with acidified methanol (0.01 M HCl in methanol). Using 8 ml of the sample, the detection limit achieved was 1.0 μg l⁻¹. The accuracy of the method developed was checked by analysing certified reference material SARM-7. The precision obtained for five successive determination of 100 μg l⁻¹ of palladium(II) was 2.4%. The performance of EG material was compared with allotropes of carbon in terms of pH, chelate concentration, weight of column material, sensitivity enhancement (w.r.t. conventional FAAS), detection limit, calibration range, selectivity and precision. Furthermore, performance of the EG material packed column was compared with commercially available C₁₈ bonded silica gel/alumina columns for on-line FIA-FAAS determination of palladium(II).