Microwave assisted polymer stabilized synthesis of silver nanoparticles and its application in the degradation of environmental pollutants

Graft copolymers of polyacrylamide (PAM) and dextran (Dx) are synthesized by grafting PAM chains onto a Dx backbone (Dx-g-PAM) with ceric ion induced solution polymerization technique. Partial hydrolysis of Dx-g-PAM is carried out with sodium hydroxide solution to obtain HDx-g-PAM. To synthesize silver nanoparticles dispersed copolymer nano-composite (Ag-HDx-g-PAM), reduction of silver ions with HDx-g-PAM is carried out using microwave heating. The environmentally benign and biodegradable copolymer, HDx-g-PAM acts as both stabilizer and reducing agent. The copolymer nano-composite, Ag-HDx-g-PAM is characterized by FT-IR, transmission electron microscopy, scanning electron microscopy and optical spectroscopy. Further, the catalytic activity of Ag-HDx-g-PAM nano-composite towards the reduction of environmental pollutants like phenosafranine dye and aromatic nitro compounds are studied.     

Facile synthesis of BSCF perovskite oxide as an efficient bifunctional oxygen electrocatalyst

We present a facile way to synthesize BSCF by using glycine-nitrate auto-combustion followed by annealing at different conditions, which work as high-performance bifunctional electrocatalyst for oxygen evolution (OER) as well as oxygen reduction (ORR) reactions in alkaline solution with comparatively better efficiency for OER. Annealing condition plays an important role towards catalytic performance due to morphological control and surface composition. Although, there is no significant change in onset potentials but these catalysts afford a current density >10 mA cm^?2 at the potential of 1.65 V for oxygen evolution reaction and a current density >2.5 mA cm^?2 at the potential of 0.009 V for oxygen reduction reaction with respect to RHE in 0.1 M KOH. The underlying mechanism for ORR and OER as well as catalytic activity differences were understood with the help of different analytical characterization techniques.     

Structural,Mechanical and Biological Insights on Reduced Graphene Nanosheets Reinforced Sonochemically Processed Nano‐Hydroxyapatite Ceramics

In this study, we have attempted to prepare reduced graphene nanosheets (RGNS) reinforced nano-hydroxyapatite (nHAp) nanocomposites via different sonochemical treatments of nHAp. Structural properties of RGNS-nHAp nanocomposites were investigated by XRD and Raman analysis. In vitro bioactivity of RGNS-nHAp nanocomposites were examined by immersing them in hank's balanced salt solution and further in vitro apatite layer formation was confirmed by systematic investigations using FESEM and ICP-OES analyses. Interactions of RGNS, pure nHAp and their nanocomposites with human erythrocytes were explored. Hemocompatibility of BGO-nHAp nanocomposites were found to be superior to pristine RGNS. The nanocomposites were mechanically improved when compared to nHAp through effective load transfer onto their 2D lattice of RGNS. However, 20PGO-nHAp nanocomposites were mechanically weaker than 20BGO-nHAp due to the formation of β-TCP as an additional phase, thus decreases its mechanical strength.     

Determination of hydrazine by polyNi(II) complex modified electrodes with a wide linear calibration range

Polymeric [Ni^II(teta)]²⁺ (poly(Ni); teta = C-meso-(5,5,7,12,12,14-hexamethyl-1,4,8,11-tetra-azacyclotetradecane)) modified glassy carbon and Nafion (Nf)-coated glassy carbon electrodes (GC/poly(Ni) and GC/Nf/poly(Ni), respectively) were used for the efficient electrocatalytic oxidation of hydrazine (HZ) in 0.1 M NaOH. The catalytic currents were proportional to the concentration of HZ with a wide linear calibration range (LCR). GC/poly(Ni) had a LCR from 1.0 μM to 10.0 mM, whereas that of GC/Nf/poly(Ni) ranged from 1.0 μM to 100.0 mM. The latter is the widest LCR reported to date. The presence of the Nf film (i.e., in GC/Nf/poly(Ni)) not only increased the stability of the poly(Ni) film but also widened the LCR. The electrocatalytic oxidation of HZ obeyed first-order kinetics with respect to HZ concentration. The kinetic parameters were investigated by cyclic voltammetry and chronoamperometry.     

Divergent Synthesis and Evaluation of the in vitro Cytotoxicity Profiles of 3,4-Ethylenedioxythiophenyl-2-propen-1-one Analogues

A new series of 3,4-ethylenedioxythiophene (EDOT)-appended propenones were prepared by condensation reaction and their in vitro cytotoxicity effects were evaluated against five human cancer cell lines. Preliminary structure–activity relationships of EDOT-incorporated 2-propenone derivatives were also established. The EDOT-appended enones demonstrated significant cytotoxicity against human cancer cell lines. The most active analogue, (E)-3-(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-1-(3,4,5-trimethoxyphenyl)prop-2-en-1-one ( 3 p , GI₅₀=110 nm ), severely inhibited the clonogenic potential of cancer cells, and induced cell-cycle arrest in the G2/M phase and caused an accumulation of HCT116 colon cancer cells with >4 N DNA content. Also, 3 p exhibited weak inhibition of the enzymatic activity of human topoisomerase I. Molecular docking studies indicated preferential binding of the compounds to the ATP-binding pocket of the human checkpoint 2 kinase (Chk2) catalytic domain, thus, identifying a novel diaryl 2-propenone chemotype for the development of potent inhibitors of Chk2.     

AgNP/crystalline PANI/EBP-composite-based supercapacitor electrode with internal chemical interactions

In this article, polyaniline (PANI) was conformally coated on epoxide-functionalized buckypaper (EBP). Because of the presence of epoxide functional groups, chemical interactions occurred between oxygen in the epoxide groups and NH in the PANI. These chemical interactions were identified by peak shifts and intensity changes in Raman spectra. Additionally, crystalline peaks were clearly observed through X-ray diffraction. However, Raman peak changes or crystalline peaks were not observed in nonfunctionalized buckypaper (purified pristine buckypaper [PPBP])-based composites. Both hydrogen bonding and crystalline nature of EBP-PANI enhanced its electrical conductivity, producing a specific capacitance better than that of PPBP-PANI. Finally, Ag nanoparticles (AgNPs) were applied to EBP-PANI to further enhance its electrical conductivity. Owing to the presence of AgNPs and their interactions with the N in PANI, the specific capacitance of EBP-PANI-AgNP reached 915.62 F/g. These results emphasize the positive effect of chemical interactions and crystalline nature of EBP-based composites on their electrochemical performance. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48164.     

Evaluation of kinetic parameters for the crystallization and degradation process of synthesized strontium mercaptosuccinate functionalized poly(ε-caprolactone) by non-isothermal approach

Strontium (Sr) mercaptosuccinate (MS) functionalized poly(ε-caprolactone) (PCL) was prepared by ring opening polymerization technique in the presence of Sr-MS nanohybrid initiator and stannous octoate (SO) catalyst for 2 h at 160 °C under nitrogen atmosphere. FTIR, NMR, DSC, TGA, GPC, POM, TEM and AFM techniques were employed to characterize the Sr-MS functionalized polymer. The FTIR spectrum showed a small peak at 526 cm⁻¹ due to the Sr–O stretching. The particle size of the Sr-MS nanohybrid functionalized PCL matrix was determined as less than 30 nm. The crystallization rate and crystallinity percentage were estimated from the non-isothermal exothermic curves. The crystallization temperature (T_c) was found to be decreased with increasing the cooling rate whereas the degradation temperature (T_d) was increased with increasing the heating rate. Various kinetic models were applied to comprehend the degradation behaviour of Sr-MS functionalized PCL as well as its related kinetic parameters under non-isothermal condition. The activation energy (E_a) was calculated for both crystallization (138.5 kJ/mol) and degradation (187 kJ/mol) behaviours of Sr-MS functionalized PCL under non-isothermal condition.