Systematic study of catalytic degradation of nitrobenzene derivatives using core@shell composite micro particles as catalyst

Catalytic reduction of nitroarenes by palladium nanoparticles decorated silica@poly(chitosan-N-isopropylacrylamide-methacrylic acid) hybrid microgels

Conversion of toxic nitroarenes into less toxic aryl amines, which are the most suitable precursors for different types of compounds, is done with various materials which are costly or take more time for this conversion. In this regards, a silica@poly(chitosan-N-isopropylacrylamide-methacrylic acid) Si@P(CS-NIPAM-MAA) Si@P(CNM) core-shell microgel system was synthesized through free radical precipitation polymerization (FRPP) and then fabricated with palladium nanoparticles (Pd NPs) by in situ-reduction method to form Si@Pd-P(CNM) and characterized with XRD, TEM, FTIR, SEM, and EDX. The catalytic efficiency of Si@Pd-P(CNM) hybrid microgels was studied for reduction of 4-nitroaniline (4NiA) under diverse conditions. Different nitroarenes were successfully transformed into their corresponding aryl amines with high yields using the Si@Pd-P(CNM) system as catalyst and NaBH4 as reductant. The Si@Pd-P(CNM) catalyst exhibited remarkable catalytic efficiency and recyclability as well as maintaining its catalytic effectiveness over multiple cycles.

Polymer hydrogels for stabilization of inorganic nanoparticles and their application in catalysis for degradation of toxic chemicals

Poly(styrene-N-isopropylmethacrylamide-methacrylic acid) core-shell [P(SNM)CS] microgel particles were synthesised by seed-mediated emulsion polymerisation method. Silver nanoparticles were loaded into shell of P(SNM)CS microgels by in situ reduction of Ag⁺ ions. Synthesised core-shell microgels and hybrid core-shell microgels were characterised by using Fourier transformed infrared spectroscopy (FTIR), Transmission electron microscopy (TEM), UV-Visible spectroscopy and Dynamic light scattering (DLS). Stability of Ag nanoparticles within P(SNM)CS system was also investigated over the time using UV-Visible spectroscopy. Catalytic properties of silver nanoparticles loaded microgel system [Ag-P(SNM)CS] were studied by reducing Eosin-Y and Methylene blue with NaBH₄ in water. The values of observed rate constant (k_obs) were determined under different reaction conditions. The hybrid system was capable to degrade both dyes and may be used for degradation of several other toxic chemicals efficiently.

Herbal molecule-mediated dual network hydrogels with adhesive and antibacterial properties for strain and pressure sensing

Multifunctional integration is the focus of hydrogel-based flexible sensors, and formation of a dual network (DN) could shed light on the fabrication of hydrogels with multifunctionality and enhanced properties. In this study, a DN hydrogel was fabricated by the self-assembly of herbal molecule glycyrrhizic acid (GA) as the first hydrogel network and subsequent photocrosslinking of methacrylated sodium alginate (SA-MA) to form the second network. Profiting from the good compatibility between the two hydrogel networks, the obtained DN hydrogels with a homogeneous porous microstructure were endowed with remarkably enlarged stretching (114.5%) and compression (74.4%) strains. In addition, they were demonstrated to display excellent bacteriostatic activity (>99.9%) against Escherichia coli and Staphylococcus aureus owing to the synergetic antibacterial effect of GA and SA-MA. The DN hydrogels as strain sensors possessed high sensitivity (GF = 1.39), linear sensing (R 2 > 0.99), rapid response (180 ms), and good stability (1300 times) for human motion detection. Besides, the DN hydrogels could also be used to conduct pressure sensing such as application of heavy weights and even human pulses. All results suggest that the developed DN hydrogels have great potential in serving as epidermal and implantable flexible sensors for human health monitoring.

Extraction of copper ions from aqueous medium by microgel particles for in-situ fabrication of copper nanoparticles to degrade toxic dyes

Most of the transition metal ions are toxic and their removal from water is important. For this purpose, nearly monodisperse spherical core shell microgel particles with diameter of 88 ± 3 nm have been synthesized by free radical precipitation polymerization method and characterized by fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), dynamic light scattering (DLS), and transmission electron microscopy (TEM). Extraction of copper ions from water under several conditions of pH, copper ions content and core shell microgel concentrations was undertaken. Several adsorption isotherms were tested to explore the process of adsorption of copper ions on the microgel particles. Kinetics of adsorption process was examined by pseudo first order, pseudo second order, intra-particle diffusion and Elovich models. Copper ions adsorbed in shell region of core shell microgel were reduced to copper nanoparticles. The hybrid microgel was used to reduce organic pollutants such as 4-nitrophenol (4NP), methylene blue (MB), and methyl orange (MO) in aqueous medium. The value of pseudo first order rate constant for catalytic reduction of 4NP, MB, and MO was found 0.602, 0.831, and 0.874 min−1 respectively. The resultant core shell hybrid microgel system can serve as efficient catalyst for numerous other organic transformations.

Magnetic nanoparticles (Fe3O4 NPs) fabricated composite microgels and their applications in different fields

This article encircles the research progress of Fe3O4 NPs loaded composite microgel particles. Preparation methodologies, properties and applications of Fe3O4 NPs loaded composite microgel particles are elaborated here. The effect of different factors on the stability and tunable properties of Fe3O4 NPs loaded composite microgel particles was also investigated in detail. These composite particles have exceptional magnetic properties that make them demanding composite nano-formulation in different fields. Applications of these composite microgel particles in different fields as micro-reactor, drug delivery vehicles, and in adsorption and catalysis have also been elaborated in detail. These composite microgel particles can easily be recovered from the reaction mixture by applying an external magnet due to the presence of fabricated Fe3O4 NPs.

Environmental occurrence, toxicity concerns, and remediation of recalcitrant nitroaromatic compounds

Nitroaromatic compounds (NACs) are considered important groups of chemicals mainly produced by human and industrial activities. The large-scale application of these xenobiotics creates contamination of the water and soil environment. Despite applicability, NACs have been caused severe hazardous side effects in animals and human systems like different cancers, anemia, skin irritation, liver damage and mutagenic effects. The effective remediation of the NACs from the environment is a significant concern. Researchers have implemented physicochemical and biological methods for the remediation of NACs from the environment. Most of the applied methods are based on adsorption and degradation approaches. Among these methods, degradation is considered a versatile method for the subsequent removal of NACs due to its exceptional properties like simplicity, easy operation, cost-effectiveness, and availability. Most importantly, the degradation process does not generate hazardous side products and wastes compared to other methods. Hence, the importance of NACs, their remediation, and supreme attributes of the degradation method have encouraged us to review the recent progress and development for the removal of these perilous materials using degradation as a versatile method. Therefore, in this review, (i) NACs, physicochemical properties, and their hazardous side effects on humans and animals are discussed; (ii) Physicochemical methods, microbial, anaerobic bioremediation, mycoremediation, and aerobic degradation approaches for the degradation of NACs were thoroughly vetted; (iii) The possible mechanisms for degradation of NACs were investigated and discussed. (iv) The applied kinetic models for evaluation of the rate of degradation were also assessed and discussed. Finally, (vi) current challenges and future prospects of proposed methods for degradation and removal of NACs were also directed.

Plant Extract Induced Biogenic Preparation of Silver Nanoparticles and Their Potential as Catalyst for Degradation of Toxic Dyes

This study focusses on the synthesis of silver nanoparticles (Ag-nPs) by citrus fruit (Citrus paradisi) peel extract as reductant while using AgNO3 salt as source of silver ions. Successful preparation of biogenic CAg-nPs catalyst was confirmed by turning the colorless reaction mixture to light brown. The appearance of surface Plasmon resonance (SPR) band in UV-Vis spectra further assured the successful fabrication of nPs. Different techniques such as FTIR, TGA and DLS were adopted to characterize the CAg-nPs. CAg-nPs particles were found to excellent catalysts for reduction of Congo red (CR), methylene blue (MB), malachite green (MG), Rhodamine B (RhB) and 4-nitrophenol (4-NP). Reduction of CR was also performed by varying the contents of NaBH4, CR and catalyst to optimize the catalyst activity. The pseudo first order kinetic model was used to explore the value of rate constants for reduction reactions. Results also interpret that the catalytic reduction of dyes followed the Langmuir–Hinshelwood (LH) mechanism. According to the LH mechanism, the CAg-nPs role in catalysis was explained by way of electrons transfer from donor (NaBH4) to acceptor (dyes). Due to reusability and green synthesis of the CAg-nPs catalyst, it can be a promising candidate for the treatment of water sources contaminated with toxic dyes.

Synthesis of Core-Shell Micro/Nanoparticles and Their Tribological Application: A Review

Owing to the diverse composition, adjustable performance, and synergistic effect among components, core–shell micro/nanoparticles have been widely applied in the field of tribology in recent years. The strong combination with the matrix and the good dispersion of reinforcing fillers in the composites could be achieved through the design of core–shell structural particles based on the reinforcing fillers. In addition, the performance of chemical mechanical polishing could be improved by optimizing the shell material coated on the abrasive surface. The physical and chemical state of the core–shell micro/nanoparticles played important effects on the friction and wear properties of materials. In this paper, the synthesis methods, the tribological applications (acted as solid/liquid lubricant additive, chemical mechanical polishing abrasives and basic units of lubricant matrix), and the functionary mechanisms of core–shell micro/nanoparticles were systematically reviewed, and the future development of core–shell micro/nanoparticles in tribology was also prospected.

Ultra-small iridium nanoparticles as active catalysts for the selective and efficient reduction of nitroarenes

The ultra-small noble metal iridium nanoparticles (IrNPs) possessing super catalytic activity can be applied in the efficient and selective catalytic reduction of nitroarenes under mild reaction conditions for the first time.