Application of synthesized copper nanoparticles using aqueous extract ofZiziphus mauritiana L. leaves as a colorimetric sensor for the detection of Ag.

The presented work demonstrates the preparation of copper nanoparticles (CuNPs) via aqueous leaves extract of Ziziphus mauritiana L. ( Zm ) using hydrazine as a reducing agent. Various parameters such as volume of extract, concentration of hydrazine hydrate, concentration of copper chloride, and pH of the solution were optimized to obtain Ziziphus mauritiana L. leaves extract derived copper nanoparticles ( Zm -CuNPs). Brownish red color was initial indication of the formation of Zm -CuNPs while it was confirmed by surface plasmon resonance (SPR) band at wavelength of 584 nm using ultraviolet-visible (UV-vis) spectroscopy. Synthesized Zm -CuNPs were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray diffractometry (XRD). AFM images showed that the particle size of Zm -CuNPs was from 7 to 17 nm with an average size of 11.3 nm. Fabricated sensor ( Zm -CuNPs) were used as a colorimetric sensor for the detection of Ag + at a linear range between 0.67 × 10 -6 - 9.3 × 10 -6 with R 2 value of 0.992. For real water samples, limit of quantification (LOQ) and limit of detection (LOD) for Ag + was found to be 330 × 10 -9 and 100 × 10 -9 , respectively.

Effects of gel morphology on the lysozyme adsorption and desorption kinetics of temperature sensitive magnetic gel composites.

Tuning the adsorption and desorption rate constant of proteins is a hot topic for broad range of applications in biotechnology and medical science; especially controlled drug delivery and protein separation are the prominent examples in this field. In this study, Gel-MNPs (Poly(N-isopropylacrylamid) PNIPA-Magnetic Nano Particles) composites were synthesized by using different concentrations of monomer and cross-linker to observe the effect of gel morphology on the adsorption and desorption rate constant and kinetics of lysozyme protein. The synthesized composites were characterized by XRD, VSM, SEM and FTIR techniques. The characterization results showed that superparamagnetic Fe3O4 nanoparticles were synthesized inside the temperature sensitive PNIPA hydrogels. Fluorescence measurements were performed for monitoring the adsorption and desorption of lysozyme through Gel-MNPs composites. The adsorption process obeyed pseudo first and second order kinetic models at above and below the lower critical solution temperature (LCST) of PNIPA gels. Pseudo first order kinetic indicates physisorption, between the lysozyme and composite material for both adsorption and desorption. The adsorption was effective below LCST, but it was not effective at a temperatures higher than LCST; the adsorption rate constant was found between 0.59 and 0.082 s-1 at 22 °C. On the other side, samples show well desorption ability at the temperature above than LCST; the desorption rate constant was found between 0.080 and 0.092 s-1 at 45 °C. Moreover, the effects of monomer and cross-linker concentration on the adsorption and desorption kinetics are determined and discussed at the end of the manuscript.

One pot synthesis and characterization of Fe3O4 Nanorod-PNIPA Nanogel Composite for protein adsorption.

In this study, Fe3O4 Nanorod-PNIPA Nanogel Composite nanomaterial is synthesized, characterized and used for lysozyme adsorption. XRD, ATR-FTIR, AFM and SEM measurements reveal that nanorods-nanogels composite was prepared successfully. The diameter of nanorods and the average particle size of nanogels are found around 150nm and 300nm, respectively. VSM measurement shows that the Fe3O4 particles are in rod shape and has superparamagnetic behavior, no hysteresis and remnant is detected. The adsorption kinetic of lysozyme on composite material is studied via fluorescence method, and the adsorption reaction rate constant is calculated as 0.904s(-1) by using Langmuir-Hinshelwood pseudo second order model. Fe3O4 Nanorod-PNIPA Nanogel Composite is appeared as a fast catalyst for lysozyme like protein immobilization.

Selective heterogeneous catalytic hydrogenation of ketone (C═O) to alcohol (OH) by magnetite nanoparticles following Langmuir-Hinshelwood kinetic approach.

Magnetite nanoparticles were successfully synthesized and effectively employed as heterogeneous catalyst for hydrogenation of ketone moiety to alcohol moiety by NaBH4 under the microwave radiation process. The improvement was achieved in percent recovery of isopropyl alcohol by varying and optimizing reaction time, power of microwave radiations and amount of catalyst. The catalytic study revealed that acetone would be converted into isopropyl alcohol (IPA) with 99.5% yield in short period of reaction time, using 10 µg of magnetite NPs (Fe3O4). It was observed that the catalytic hydrogenation reaction, followed second-order of reaction and the Langmuir-Hinshelwood kinetic mechanism, which elucidated that both reactants get adsorb onto the surface of silica coated magnetite nanocatalyst to react. Consequently, the rate-determining step was the surface reaction of acetone and sodium borohydride. The current study revealed an environment friendly conversion of acetone to IPA on the basis of its fast, efficient, and highly economical method of utilization of microwave irradiation process and easy catalyst recovery.