Shanza Rauf Khan

Synthesis, Characterization, and Silver Nanoparticles Fabrication in N-isopropylacrylamide-Based Polymer Microgels for Rapid Degradation of p-Nitrophenol

Multiresponsive poly(N-isopropylacrylamide-co-methacrylic acid) microgels were synthesized by precipitation polymerization in aqueous medium. Then silver-poly(N-isopropylacrylamide-co-methacrylic acid) hybrid microgels were prepared by in-situ reduction of silver ions. Formation of microgels was confirmed by Fourier transform infrared spectroscopic analysis. pH and temperature sensitivity of microgel was studied by dynamic light scattering. Hydrodynamic radius of microgels decreases with increase in temperature at pH 8.20 and show volume phase transition temperature around 45°C. At pH 2.65, hydrodynamic radius decreases with increase in temperatures upto 35°C but further increase in temperature causes aggregation and microgel becomes unstable due to increase of hydrophobicity. With increase in pH of medium, the hydrodynamic radius of microgels increases sigmoidally. Formation of silver nanoparticles inside microgel and pH dependence of surface plasmon resonance wavelength of the hybrid microgels were investigated by ultraviolet-visible spectroscopy. The value of surface plasmon resonance band and absorbance associated with surface plasmon resonance band increases with increases in pH of the medium. The apparent rate constant of reduction of p-nitrophenol was found to be linearly dependent on volume of hybrid microgels used as catalyst. The system has a potential to be used as effective catalyst for rapid degradation of industrial pollutant.

Effect of crosslinker feed content on catalaytic activity of silver nanoparticles fabricated in multiresponsive microgels

We investigated the effect of crosslinking density of poly(N-isopropyl acrylamide-co-acrylic acid) microgels on catalytic activity of silver nanoparticles fabricated hybrid microgels. Multiresponsive poly(N-isopropyl acrylamide-co-acrylic acid) microgels with 2, 4, 6 and 8 mole percentage of N,N-methylene-bis-acrylamide were synthesized by emulsion polymerization. These microgels were characterized by dynamic light scattering and were used as microreactors to synthesize silver nanoparticles. Hybrid system was characterized by ultraviolet-visible spectroscopy. The catalytic activity of hybrid microgels with different crosslinker content was compared by studying the reduction of pnitrophenol as a model reaction. Kinetics of reaction was monitored by spectrophotometry. The value of the apparent rate constant decreases from 0.568 to 0.313min−1, when content of crosslinker are increased from 2 to 8 mole percentage respectively. This decreases in value of apparent rate constant is due to increase in diffusional barrier offered by high crosslinking of polymer network at high mole percentages of N,N-methylene-bis-acrylamide.

Synthesis, characterization and fabrication of copper nanoparticles in N-isopropylacrylamide based co-polymer microgels for degradation of p-nitrophenol

Abstract Poly(N-isopropylacrylamide-co-acrylic acid) [P(NIPAM-co-AAc)] microgels were synthesized by precipitation polymerization. Copper nanoparticles were successfully fabricated inside the microgels by in-situ reduction of copper ions in an aqueous medium. The microgels were characterized by Fourier Transform Infrared Spectroscopy (FT-IR) and Dynamic Light Scattering (DLS). Hydrodynamic radius of P(NIPAM-co-AAc) microgel particles increased with an increase in pH in aqueous medium at 25 °C. Copper-poly(N-isopropylacrylamide-co-acrylic acid) [Cu-P(NIPAM-co-AAc)] hybrid microgels were used as a catalyst for the reduction of 4-nitrophenol (4-NP). Effect of temperature, concentration of sodium borohydride (NaBH4) and catalyst dosage on the value of apparent rate constant (kapp) for catalytic reduction of 4-NP in the presence of Cu-P(NIPAM-co-AAc) hybrid microgels were investigated by UV-Vis spectrophotometry. It was found that the value of kapp for catalytic reduction of 4-NP in the presence of Cu-P(NIPAM-co-AAc) hybrid microgel catalyst increased with an increase in catalyst dosage, temperature and concentration of NaBH4 in aqueous medium. The results were discussed in terms of diffusion of reactants towards catalyst surface and swelling-deswelling of hybrid microgels.

Cobalt and nickel nanoparticles fabricated p(NIPAM-co-MAA) microgels for catalytic applications

Abstract In this research work, multi-responsive poly(N-isopropylacrylamide-co-methacrylic acid) copolymer microgels were synthesized via emulsion polymerization in aqueous medium. Then, nickel and cobalt nanoparticles were fabricated within these microgels by in situ reduction of metal ions using sodium borohydride (NaBH4) as a reducing agent. Fourier transform infrared spectroscopy was used to characterize these microgels. The pH sensitivity of these copolymer microgels was studied using dynamic light scattering technique (DLS). DLS studies revealed that the hydrodynamic radius of these microgels increased with the increase in pH of the medium at 25°C. The catalytic activity of hybrid microgels for the reduction of p-nitrophenol (4-NP) to p-aminophenol (4-AP) was investigated by UV-visible spectrophotometery. The value of apparent rate constant of reaction was found to change linearly with catalyst dosage. The nickel-based hybrid system was found to be five times more efficient as a catalyst compared to the cobalt-based hybrid system for the reduction of 4-NP to 4-AP in aqueous medium.

Temperature-responsive hybrid microgels for catalytic applications: a review

Temperature-responsive hybrid microgels have been extensively used as catalyst for degradation of toxic chemicals in the last 10 years. Various architectures of such kind of hybrid microgels with tunable catalytic activity have been reported in literature. Recent research progress in synthesis, characterisation and catalytic applications of various hybrid microgels based on N-isopropylacrylamide has been described critically in this article. Mechanism of catalysis and factors affecting the rate of catalysis by hybrid microgels have been discussed in the light of research done in this area. Possible future studies for further development in this area have been also predicted in this article.

Review on synthesis, properties, characterization, and applications of responsive microgels fabricated with gold nanostructures

Abstract In this article, the classification, synthesis, properties, and applications of responsive microgels fabricated with gold (Au) nanostructures have been systematically reviewed. Microspheres, core-shell, core-shell-shell, hollow rings, and yolk-shell are different types of hybrid microgels containing Au nanostructures that have been reported in the literature. Hybrid microgels have tunable properties of both Au nanomaterial and smart polymeric material. Due to this unique combination, hybrid microgels containing Au nanomaterial are potential candidates for applications in drug delivery, photothermal therapy, glucose sensing, insulin delivery, catalysis, photonics, and ultrasensitive analyte analysis. Recent research progress in the design, characterization, and applications of Au nanomaterial containing smart polymer microgels has been described here. Many gaps in the literature and future perspectives of Au nanomaterial-based hybrid microgels have been highlighted in this review, which will be helpful for the people working in this area to plan their future work.

Poly(N-isopropylacrylamide-acrylic acid) copolymer microgels for various applications: A review

ABSTRACT Smart polymer microgels have been attracting a lot of attention due to their quick response to variation in environmental stimuli like temperature, pH, ionic strength, and presence of some biological molecules. Poly(N-isopropylacrylamide) and its copolymer microgels have been synthesized and characterized for various applications in last 10 years. Synthesis, properties, and applications of poly(N-isopropylacryamide-co-acrylic acid) [P(NIPAM-AA)] copolymer microgels have been extensively reported in literature. This article describes synthesis, fundamental properties, and applications of P(NIPAM-AA) microgels in the field of medical science, environment, nanotechnology, catalysis, and photonics. GRAPHICAL ABSTRACT

Synthesis of Self-Assembled Co3O4 Nanoparticles with Porous Sea Urchin-Like Morphology and their Catalytic and Electrochemical Applications

Novel self-assembled cobalt oxide nanoparticles with sea urchin-like morphology were synthesized using a solvothermal method. It was observed that the product consists of a tube-like arrangement of nanoparticles arising from a base. The base is formed by the arrangement of nanoparticles in the form of dense aggregates. A series of comparative experiments were performed over different time intervals to investigate the mechanism of formation of this morphology. The electrochemical performance of an electrode prepared based on this product was analysed by cyclic voltammetry, chronopotentiometry, and alternating current impedance. The electrochemical study shows that the prepared electrode possesses high capacitance and offers very low resistance against the flow of electrons. The product was used as a catalyst for the reduction of nitrobenzene in aqueous medium. The value of the apparent rate constant of catalysis was found to be as high as previously reported values.

First Synthetic Study of Cube-Like Cobalt Hydroxystannate Nanoparticles as Photocatalyst for Drimarene Red K-4BL Degradation and Fuel Additive

This research article describes the development of a simple and sensitive approach with less runtime for the estimation of photo degradation of an anthraquinone dye drimarene red K-4BL in the presence of newly synthesized nano catalyst. Hydrothermal approach is used to synthesize cobalt hydroxystannate by using precursor salts of chloride i.e. stannic chloride, cobalt chloride and sodium hydroxide is used as a precipitating agent. Various techniques were used to analyze the product. Two major applications of synthesized nanocubes are investigating the efficiency of modified fuel and as a photocatalyst for dye degradation. Anthraquinone dye (drimarene red K-4BL) is degraded by the newly synthesized nanoparticles which is used as a catalyst in aqueous medium. In the presence of sun irradiation at different concentrations of hydrogen peroxide and catalyst, kinetics of photo catalytic degradation of dye is monitored on ultra violet visible spectrophotometer. Efficiency of modified fuel is analyzed by studying the various parameters such as flash point, fire point, pour point and cloud point, etc. at different dosage of Cobalt hydroxystannate. By changing the dosage of the catalyst, values of these parameters changed significantly.Graphical Abstract

Photocatalytic degradation of reactive black 5 on the surface of tin oxide microrods

A simple co-precipitation technique is proposed for synthesis of tin oxide (SnO2) microrods. Stannous chloride and urea were used during synthesis. X-ray powder diffraction (XRD) analysis revealed that the annealed product consists of SnO2 microrods having tetragonal unit cells, while scanning electron microscopy (SEM) analysis revealed the rod-like morphology of a synthesized product. These synthesized microrods are used as photocatalyst for the degradation of reactive black 5 (RB5). Degradation kinetics of RB5 are monitored under daylight in different concentrations of hydrogen peroxide (H2O2) and catalyst. The percentage of RB5 conversion is also calculated at various concentrations of hydrogen peroxide and catalyst which demonstrate that RB5 shows high catalytic degradation at high concentrations of hydrogen peroxide and catalyst.