Facile synthesis of silver nanoparticles in a crosslinked polymeric system by in situ reduction method for catalytic reduction of 4-nitroaniline

Spectroscopic monitoring of polyurethane-based nanocomposite as a potential catalyst for the reduction of dyes

In this study, AgNPs-loaded polyurethane-sodium alginate (PU-S/Alg) composite polymers were prepared by precipitation polymerization and in-situ reduction method. Their catalytic potential was evaluated for the reduction of methyl orange (MO), brilliant blue (BB), Rhodamine B (RhB), 4-nitroaniline (4-NA), and 4-nitrophenol (4-NP). Successful preparation of samples was confirmed by UV-Visible spectrophotometry (UV-Visible), Fourier transform infrared (FTIR), and Scanning electron microscopy (SEM) analysis. During the catalytic study, the value of kapp for the reduction of MO in the presence of NaBH4 and catalyst was found 0.488 min-1 while, in the presence of NaBH4 and catalyst alone, were found as 0.9 × 10-4 and 0.8 × 10-5 min-1, respectively which indicates the role of catalyst in making the reaction speedy. The value of kapp for the reduction of BB, RhB, 4-NA, and 4-NP was found as 0.764, 0.475, 0.212 and 0.757 min-1, respectively. Simultaneous reduction of dyes induced a decreased reaction completion time under the same reaction conditions. A slight increase in the value of kapp for the catalytic reduction of MO was also observed when reactions were performed in the presence of ionic media of different salts such as NaCl, KCl, CaCl2, and MnCl2. The rate of reduction of MO was increased with the increase in ionic strength of the medium. However, the presence of SDS (surfactant) in the reaction mixture induced the decreased activity of the catalyst and increased reaction completion time. The same value of kapp for the reduction of MO was observed in the case of freshly prepared and several days old nanocomposite catalyst. These results illustrate the stability and maintained catalytic potential of metal NPs for a prolonged time. Our reported catalyst also showed good potential for the treatment of dyes-polluted textile industry wastewater.

Deciphering the catalytic activity of nickel anchored on Fe3O4@SiO2@3-CPMS@L as a magnetically recoverable nanocatalyst for the efficacious reduction of 4-nitrophenol, nitrobenzene, and methyl orange

In this paper, a versatile heterogeneous nanocatalyst was fabricated employing a self-assembly technique. To commence, Fe3O4 MNPs were coated with a thin layer of SiO2 using the stobbers method. Subsequently, the surface was further functionalized with 3-CPMS, followed by a reaction with a Schiff base. Finally, nickel NPs were deposited on the surface through in situ deposition, forming the Fe3O4@SiO2@3-CPMS@L-Ni magnetic nanocatalyst. The architecture of this magnetic nanocatalyst was meticulously characterized through an array of sophisticated techniques: XRD, FT-IR, SEM, TEM, BET and VSM. The XRD diffraction pattern confirmed the presence of Fe3O4 MNPs, SiO2, and Ni peaks, providing evidence for successful synthesis. Moreover, the successful functionalization with a Schiff base was demonstrated by the presence of an azomethane peak in the FTIR spectra of the synthesized nanocatalyst. The fabricated nanocatalyst was adeptly utilized for the reduction of 4-NP, NB, and MO demonstrating a remarkably elevated rate of catalytic efficacy. Moreover, this catalyst was effortlessly retrievable through the application of an external magnet, and it maintained its catalytic prowess across at least six consecutive cycles. The utilization of water as an environmentally friendly solvent, coupled with the utilization of abundant and cost-effective nickel catalyst instead of the costly Pd or Pt catalysts, along with the successful recovery and scalability of the catalyst, render this method highly advantageous from both environmental and economic perspectives for the reduction of 4-NP, NB, and MO.

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.

Synergistic effect of silver NPs immobilized on Fe3O4@L-proline magnetic nanocomposite toward the photocatalytic degradation of Victoria blue and reduction of organic pollutants

The surface of magnetite (Fe₃O₄) nanoparticles was subject to modification through the incorporation of L-proline (LP) by simple co-precipitation method in which silver nanoparticles were deposited by in situ method, thereby yielding the Fe₃O₄@LP-Ag nanocatalyst. The fabricated nanocatalyst was characterized using an array of techniques including Fourier-transform infrared (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometry (VSM), Brunauer-Emmett-Teller (BET), and UV-Vis spectroscopy. The results evince that the immobilization of LP on the Fe₃O₄ magnetic support facilitated the dispersion and stabilization of Ag NPs. The SPION@LP-Ag nanophotocatalyst exhibited exceptional catalytic efficiency facilitating the reduction of MO, MB, p-NP, p-NA, NB, and CR in the presence of NaBH₄. The rate constants obtained from the pseudo-first-order equation were 0.78, 0.41, 0.34, 0.27, 0.45, 0.44, and 0.34 min^-1 for CR, p-NP, NB, MB, MO, and p-NA, respectively. Additionally, the Langmuir-Hinshelwood model was deemed the most probable mechanism for catalytic reduction. The novelty of this study lies in the use of L-proline immobilized on Fe₃O₄ MNPs as a stabilizing agent for the in-situ deposition of silver nanoparticles, resulting in the synthesis of Fe₃O₄@LP-Ag nanocatalyst. This nanocatalyst exhibits high catalytic efficacy for the reduction of multiple organic pollutants and azo dyes, which can be attributed to the synergistic effects between the magnetic support and the catalytic activity of the silver nanoparticles. The easy recyclability and low cost of the Fe₃O₄@LP-Ag nanocatalyst further enhance its potential application in environmental remediation.

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.

π-Electron-Extended Triazine-Based Covalent Organic Framework as Photocatalyst for Organic Pollution Degradation and H2 Production from Water

Herein, we report the efficient preparation of π-electron-extended triazine-based covalent organic framework (TFP-TPTPh COF) for photocatalysis and adsorption of the rhodamine B (RhB) dye molecule, as well as for photocatalytic hydrogen generation from water. The resultant TFP-TPTPh COF exhibited remarkable porosity, excellent crystallinity, high surface area of 724 m2 g−1, and massive thermal stability with a char yield of 63.41%. The TFP-TPTPh COF demonstrated an excellent removal efficiency of RhB from water in 60 min when used as an adsorbent, and its maximum adsorption capacity (Qm) of 480 mg g−1 is among the highest Qm values for porous polymers ever to be recorded. In addition, the TFP-TPTPh COF showed a remarkable photocatalytic degradation of RhB dye molecules with a reaction rate constant of 4.1 × 10−2 min−1 and an efficiency of 97.02% under ultraviolet–visible light irradiation. Furthermore, without additional co-catalysts, the TFP-TPTPh COF displayed an excellent photocatalytic capacity for reducing water to generate H2 with a hydrogen evolution rate (HER) of 2712 μmol g−1 h−1. This highly active COF-based photocatalyst appears to be a useful material for dye removal from water, as well as solar energy processing and conversion.

The catalytic performance of CuFe2O4@CQD nanocomposite as a high-perform heterogeneous nanocatalyst in nitroaniline group reduction

In this study, we fabricated an economical, non-toxic, and convenient magnetic nanocomposite of CuFe₂O₄ nanoparticles (NPs)/carbon quantum dots (CQDs) of citric acid via the co-precipitation method. Afterward, obtained magnetic nanocomposite was used as a nanocatalyst to reduce the ortho-nitroaniline (o-NA) and para-nitroaniline (p-NA) using a reducer agent of sodium borohydride (NaBH₄). To investigate the functional groups, crystallite, structure, morphology, and nanoparticle size of the prepared nanocomposite, FT-IR, XRD, TEM, BET, and SEM were employed. The catalytic performance of the nanocatalyst was experimentally evaluated based on the ultraviolet-visible absorbance to assess the reduction of o-NA and p-NA. The acquired outcomes illustrated that the prepared heterogeneous catalyst significantly enhanced the reduction of o-NA and p-NA substrates. The analysis of the absorption showed a remarkable decrease for ortho-NA and para-NA at λ_max = 415 nm in 27 s and λ_max = 380 nm in 8 s, respectively. The constant rate (k_app) of ortho-NA and para-NA at the stated λ_max was 8.39 × 10^-2 s^-1 and 5.48 × 10^-1 s^-1. The most highlighted result of this work was that the CuFe₂O₄@CQD nanocomposite fabricated from citric acid performed better than absolute CuFe₂O₄ NPs, since nanocomposite containing CQDs had a more significant impact than copper ferrite NPs.

The Catalytic Reduction of Nitroanilines Using Synthesized CuFe2 O4 Nanoparticles in an Aqueous Medium

The primary objective of this research is to investigate the reduction of 4-nitroaniline (4-NA) and 2-nitroaniline (2-NA) using synthesized copper ferrite nanoparticles (NPs) via facile one-step hydrothermal method as a heterogeneous nano-catalyst. Nitroanilines were reduced in the presence and without the catalyst with a constant amount (100 mg) of reducing agent of sodium borohydride (NaBH4 ) at room temperature in water to amino compounds. To characterize the functional groups, size, structure, and morphology of as-prepared magnetic NPs, FTIR, XRD, SEM, and TEM were employed. The UV-Vis spectrum was utilized to explore the catalytic effect of CuFe2 O4 . The outcomes revealed that the synthesized CuFe2 O4 as a heterogeneous magnetic nano-catalyst catalyzed the reduction of 4-NA and 2-NA significantly faster than other candidate catalysts. The outcomes demonstrated that the catalyst catalyzed 4-nitroaniline to para-phenylenediamine (p-PDA) and 2-nitroaniline to ortho-phenylenediamine (o-PDA) with a constant rate of 7.49×10-2  s-1 and 3.19×10-2  s-1 , and conversion percentage of 96.5 and 95.6, in 40 s and 90 s, sequentially. Furthermore, the nanoparticles could be recovered by a magnetic separation method and reused for six consecutive cycles without remarkable loss of catalytic ability.

Green synthesis of silver nanoparticles from plant latex and their antibacterial and photocatalytic studies

The present work describes a facile synthesis of silver nanoparticles from calotropis procera (CP-AgNPs). The CP-AgNPs were well characterized by many methods. The synthesized CP-AgNPs are stable for more than 5 months. Then we have used CP-AgNPs as photo catalysts for the degradation of methyl orange (MO) dye. The photocatalytic degradation efficiency was 0.0076. Moreover, we also have studied the antibacterial activity against pseudomonas aeruginosa (PA), klebsiella pneumonia (KP), staphylococcus aureus (SA) and bacillus subtilis (BS) bacteria. Interestingly, all four different bacteria causing biofilm were inhibited by CP-AgNPs by 80%. To the best of our knowledge, this is the first report for the synthesis of silver nanoparticles from calotropis procera plant latex. Furthermore, CP-AgNPs effectively were applied as photo catalysts for the degradation of MO dye and also as anti-biofilm agents.

Methacrylic acid based microgels and hybrid microgels

Methacrylic acid based microgels have got much consideration in the last two decades because of their potential uses in different fields owing to their responsive behaviour towards external stimuli. Synthesis, properties and uses of methacrylic acid based microgels and their hybrids have been critically reviewed in this article. With minute change in external stimuli such as pH and ionic strength of medium, these microgels show quick swelling/deswelling reversibly. The methacrylic acid based microgels have been widely reported for applications in the area of nanotechnology, drug delivery, sensing and catalysis due to their responsive behaviour. A critical review of current research development in this field along with upcoming perception is presented here. This discussion is concluded with proposed probable future studies for additional growth in this field of research.

Effects of transglutaminase cross-linking process on printability of gelatin microgel-gelatin solution composite bioink

Three-dimensional (3D) bioprinting has emerged as a powerful engineering approach for various tissue engineering applications, particularly for the development of 3D cellular structures with unique mechanical and/or biological properties. For the jammed gelatin microgel-gelatin solution composite bioink, comprising a discrete phase of microgels (enzymatically gelled gelatin microgels) and a cross-linkable continuous gelatin precursor solution-based phase containing transglutaminase (TG), its rheological properties and printability change gradually due to the TG enzyme-induced cross-linking process. The objective of this study is to establish a direct mapping between the printability of the gelatin microgel-gelatin solution based cross-linkable composite bioink and the TG concentration and cross-linking time, respectively. Due to the inclusion of TG in the composite bioink, the bioink starts cross-linking once prepared and is usually prepared right before a printing process. Herein, the bioink printability is evaluated based on the three metrics: injectability, feature formability, and process-induced cell injury. In this study, the rheological properties such as the storage modulus and viscosity have been first systematically investigated and predicted at different TG concentrations and times during the cross-linking process using the first-order cross-linking kinetics model. The storage modulus and viscosity have been satisfactorily modeled as exponential functions of the TG concentration and time with an experimentally calibrated cross-linking kinetic rate constant. Furthermore, the injectability, feature formability, and process-induced cell injury have been successfully correlated to the TG concentration and cross-linking time via the storage modulus, viscosity, and/or process-induced shear stress. By combing the good injectability, good feature formability, and satisfactory cell viability zones, a good printability zone (1.65, 0.61, and 0.31 h for the composite bioinks with 1.00, 2.00, and 4.00% w/v TG, respectively) has been established during the printing of mouse fibroblast-based 2% gelatin B microgel-3% gelatin B solution composite bioink. This printability zone approach can be extended to the use of other cross-linkable bioinks for bioprinting applications.

Rhenium Nanostructures Loaded into Amino-Functionalized Resin as a Nanocomposite Catalyst for Hydrogenation of 4-Nitrophenol and 4-Nitroaniline

The present work presents a new nanocomposite catalyst with rhenium nanostructures (ReNSs) for the catalytic hydrogenation of 4-nitrophenol and 4-nitroaniline. The catalyst, based on an anion exchange resin with functionality derived from 1,1'-carboimidazole, was obtained in the process involving anion exchange of ReO4- ions followed by their reduction with NaBH4. The amino functionality present in the resin played a primary role in the stabilization of the resultant ReNSs, consisting of ≈1% (w/w) Re in the polymer mass. The synthesized and capped ReNSs were amorphous and had the average size of 3.45 ± 1.85 nm. Then, the obtained catalyst was used in a catalytic reduction of 4-nitrophenol (4-NP) and 4-nitroaniline (4-NA). Following the pseudo-first-order kinetics, 5 mg of the catalyst led to a 90% conversion of 4-NP with the mass-normalized rate constant (km1) of 6.94 × 10-3 min-1 mg-1, while the corresponding value acquired for 4-NA was 7.2 × 10-3 min-1 mg-1, despite the trace amount of Re in the heterogenous catalyst. The obtained material was also conveniently reused.

Green synthesis of gold nanoparticles for immune response regulation: Mechanisms, applications, and perspectives

Immune responses are involved in the pathogenesis of many diseases, including cancer, autoimmune diseases, and chronic inflammation. These responses are attributed to immune cells that produce cytokines, mediate cytotoxicity, and synthesize antibodies. Gold nanoparticles (GNPs) are novel agents that intervene with immune responses because of their unique physical-chemical properties. In particular, GNPs enhance anti-tumour activity during immunotherapy and eliminate excessive inflammation in autoimmune diseases. However, GNPs synthesized by conventional methods are toxic to living organisms. Green biosynthesis provides a safe and eco-friendly method to obtain GNPs from microbes or plant extracts. In this review, we describe several patterns for green GNP biosynthesis. The applications of GNPs to target immune cells and modulate the immune response are summarized. In particular, we elaborate on how GNPs regulate innate immunity and adaptive immunity, including inflammatory signaling and immune cell differentiation. Finally, perspectives and challenges in utilizing green biosynthesized GNPs for novel therapeutic approaches are discussed.

Multi-functional organic–inorganic hydrogel microspheres as efficient catalytic system for reduction of toxic dyes in aqueous medium

Poly(N-isopropylacrylamide-acrylamide-methacrylic acid) [p(NAM)] colloidal particles were synthesized and stabilized in aqueous medium. Ag nanoparticles were fabricated inside the p(NAM) system by in-situ reduction of Ag+ ions with NaBH4 to obtain Ag-p(NAM) organic–inorganic hybrid with fascinating catalytic properties. Various characterization techniques including XRD, FTIR, DLS, TEM and UV–visible spectroscopy were used to confirm the fabrication of p(NAM) and Ag-p(NAM) in aqueous medium. Loading of silver nanoparticles into the p(NAM) does not affect responsive properties of the colloidal system. Ag-p(NAM) system was used as catalyst for reduction of toxic dyes including methyl orange (MO) and Congo red (CR) from aqueous medium. Ag-p(NAM) catalyzed reduction of dyes was carried out under different reaction conditions to explore the catalytic process of degradation. The Ag-p(NAM) catalytic system is recyclable and reusable with almost same catalytic activity up to four cycles.

Direct Z-scheme α-MnO2@MnIn2S4 hierarchical photocatalysts with atomically defined junctions for improved photocatalytic activities

The use of semiconductor photocatalysts to generate electrons with efficient reducing capability for organic photoreduction synthesis and the removal of harmful substances has become a hotspot in the field of green chemistry research. In this work, α-MnO₂ nanocubes and α-MnO₂@MnIn₂S₄ hybrid photocatalysts with a core-shell structure were synthesized successively by a two-step method. XRD and XPS verified the coexistence of the two substances (α-MnO₂ and MnIn₂S₄) in hybrid systems. According to the SEM and TEM characterization, it is clearly seen that MnIn₂S₄ nanosheets grow on α-MnO₂ nanocubes to form a hierarchical structure. Furthermore, HRTEM showed that the interface contact between α-MnO₂ and MnIn₂S₄ resulted in an atomically defined junction. The photocatalytic performance of the composite catalyst was evaluated by reducing 4-nitroaniline to 4-phenylenediamine and Cr(vi) to Cr(iii), respectively. The results show that the catalytic activity of the composite material is effectively improved compared to that of the single components. The Z-scheme electron transport mechanism was proved by ultraviolet-visible diffuse reflectance spectroscopy, valence band XPS, energy band structure calculation and active species detection experiments. The constructed Z-scheme hierarchical α-MnO₂@MnIn₂S₄ system with an atomically defined junction can improve the redox performance of semiconductors for organic synthesis and environmental remediation.

Uniformly distributed ruthenium nanocrystals as highly efficient peroxidase for hydrogen peroxide colorimetric detection and nitroreductase for 4-nitroaniline reduction

Here, we report highly dispersed small ruthenium nanoparticles (NPs) anchored onto a porous carbon (Ru/PC) with a clean catalytic surface and explore their excellent peroxidase-like activity for 3,3',5,5'-tetramethylbenzidine oxidation mediated by H₂O₂, which allows sensitive colorimetric detection of H₂O₂ with a low detection limit of 3.8 μM. Moreover, it is also found that the Ru/PC has a high nitroreductase-like activity for 4-nitroaniline reduction triggered by NaBH₄.

Synthesis and characterization of poly(N-isopropylmethacrylamide-acrylic acid) smart polymer microgels for adsorptive extraction of copper(II) and cobalt(II) from aqueous medium: kinetic and thermodynamic aspects

Extraction of toxic heavy metal ions from aqueous medium using poly(N-isopropylmethacrylamide-acrylic acid) (P(NiPmA-Ac)) microgels as adsorbent has been investigated in present study. P(NiPmA-Ac) microgel particles were prepared by free radical precipitation polymerization in aqueous medium. Morphology and size of the prepared microgel particles was investigated by transmission electron microscopy (TEM). The Fourier transform infrared (FT-IR) analysis of pure and metal ion-loaded microgel particles was performed to confirm the presence of various functionalities of microgel particles and their interaction with metal ions extracted from aqueous medium. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used to investigate the thermal stability and thermal behavior of pure and metal ion-loaded microgel particles. Contents of metal ions loaded into microgel particles were determined by TGA analysis. It was observed that P(NiPmA-Ac) particles have a potential to extract Cu²⁺ and Co²⁺ ions from aqueous medium. The Freundlich adsorption isotherm model best interprets the adsorption process as compared with the Langmuir model. Value of R² according to the Freundlich adsorption isotherm was found to be 0.994 and 0.993 for Cu²⁺ and Co²⁺ ions, respectively. Adsorption process was followed by pseudo second order kinetics for Cu²⁺ and Co²⁺ ions with R² values of 0.999 for both metal ions. Thermodynamic study showed that adsorption process was spontaneous, feasible, and endothermic in nature. Entropy was decreased at adsorbate-adsorbent interface during adsorption process. Adsorbent was recycled and reused for removal of Cu²⁺ ions, and adsorption efficiency was found to be maintained up to three cycles. Microgel particles also have ability to extract Cu²⁺ ions efficiently from electroplating wastewater. Graphical abstract.

Silver Nanoparticles for Water Pollution Monitoring and Treatments: Ecosafety Challenge and Cellulose-Based Hybrids Solution

Silver nanoparticles (AgNPs) are widely used as engineered nanomaterials (ENMs) in many advanced nanotechnologies, due to their versatile, easy and cheap preparations combined with peculiar chemical-physical properties. Their increased production and integration in environmental applications including water treatment raise concerns for their impact on humans and the environment. An eco-design strategy that makes it possible to combine the best material performances with no risk for the natural ecosystems and living beings has been recently proposed. This review envisages potential hybrid solutions of AgNPs for water pollution monitoring and remediation to satisfy their successful, environmentally safe (ecosafe) application. Being extremely efficient in pollutants sensing and degradation, their ecosafe application can be achieved in combination with polymeric-based materials, especially with cellulose, by following an eco-design approach. In fact, (AgNPs)-cellulose hybrids have the double advantage of being easily produced using recycled material, with low costs and possible reuse, and of being ecosafe, if properly designed. An updated view of the use and prospects of these advanced hybrids AgNP-based materials is provided, which will surely speed their environmental application with consequent significant economic and environmental impact.

Green Plasmonic Nanoparticles and Bio-Inspired Stimuli-Responsive Vesicles in Cancer Therapy Application

: In the past years, there is a growing interest in the application of nanoscaled materials in cancer therapy because of their unique physico-chemical properties. However, the dark side of their usability is limited by their possible toxic behaviour and accumulation in living organisms. Starting from this assumption, the search for a green alternative to produce nanoparticles (NPs) or the discovery of green molecules, is a challenge in order to obtain safe materials. In particular, gold (Au NPs) and silver (Ag NPs) NPs are particularly suitable because of their unique physico-chemical properties, in particular plasmonic behaviour that makes them useful as active anticancer agents. These NPs can be obtained by green approaches, alternative to conventional chemical methods, owing to the use of phytochemicals, carbohydrates, and other biomolecules present in plants, fungi, and bacteria, reducing toxic effects. In addition, we analysed the use of green and stimuli-responsive polymeric bio-inspired nanovesicles, mainly used in drug delivery applications that have revolutionised the way of drugs supply. Finally, we reported the last examples on the use of metallic and Au NPs as self-propelling systems as new concept of nanorobot, which is able to respond and move towards specific physical or chemical stimuli in biological entities.

Critical review on the chemical reduction of nitroaniline

Conversion of nitroaniline (NA), a highly toxic pollutant that has been released into aquatic systems due to unmanaged industrial development in recent years, into the less harmful or a useful counterpart is the need of the hour. Various methods for its conversion and removal have been explored. Owing to its nominal features of advanced effectiveness, the chemical reduction of 4-NA using various different nanocatalytic systems is one such approach that has attracted tremendous interest over the past few years. The academic literature has been confined to case studies involving silver (Ag) and gold (Au) nanoparticles, as these are the two most widely used materials for the synthesis of nanocatalytic assemblies. Focus has also been given to sodium borohydride (NaBH₄), which is used as a reductant during the chemical reduction of NA. This systematic review summarizes the fundamentals associated with the catalytic degradation of 4-NA, and presents a comprehensive and critical study of the latest modifications used in the synthesis of these catalytic systems. In addition, the kinetics, mechanisms, thermodynamics, as well as the future directions required for understanding this model reaction, have been provided in this particular study.

Schematic illustration of catalytic reduction of 4-NA in the presence of nanocatalysts and a reducing agent.

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.

Cultivar-Dependent Anticancer and Antibacterial Properties of Silver Nanoparticles Synthesized Using Leaves of Different Olea Europaea Trees

The green synthesis of nanoparticles (NPs) is currently under worldwide investigation as an eco-friendly alternative to traditional routes (NPs): the absence of toxic solvents and catalysts make it suitable in the design of promising nanomaterials for nanomedicine applications. In this work, we used the extracts collected from leaves of two cultivars (Leccino and Carolea) belonging to the species Olea Europaea, to synthesize silver NPs (AgNPs) in different pH conditions and low temperature. NPs underwent full morphological characterization with the aim to define a suitable protocol to obtain a monodispersed population of AgNPs. Afterwards, to validate the reproducibility of the mentioned synthetic procedure, we moved on to another Mediterranean plant, the Laurus Nobilis. Interestingly, the NPs obtained using the two olive cultivars produced NPs with different shape and size, strictly depending on the cultivar selected and pH. Furthermore, the potential ability to inhibit the growth of two woman cancer cells (breast adenocarcinoma cells, MCF-7 and human cervical epithelioid carcinoma, HeLa) were assessed for these AgNPs, as well as their capability to mitigate the bacteria concentration in samples of contaminated well water. Our results showed that toxicity was stronger when MCF-7 and Hela cells were exposed to AgNPs derived from Carolea obtained at pH 7 presenting irregular shape; on the other hand, greater antibacterial effect was revealed using AgNPs obtained at pH 8 (smaller and monodispersed) on well water, enriched with bacteria and coliforms.

Hybrid Microgels for Catalytic and Photocatalytic Removal of Nitroarenes and Organic Dyes From Aqueous Medium: A Review

Polymer microgels loaded with inorganic nanoparticles have gained much attention as catalytic systems for reduction of toxic chemicals. Enhanced catalytic properties of hybrid microgels are related to the stimuli responsive nature of microgels and extraordinary stability of nanoparticles within network of polymer microgels. Catalytic properties of hybrid microgels can be tuned very easily by slight variation in environmental conditions. Herein we have reviewed catalytic reduction of toxic chemicals such as nitroarenes and organic dyes in the presence of appropriate hybrid microgel catalytic systems under different operating conditions of reaction. Recent advancements in catalytic behavior of hybrid microgels with special emphasis on their ability to catalytically degrade various toxic chemicals has been presented in this review.

Single-Step Preparation of Silver-Doped Magnetic Hybrid Nanoparticles for the Catalytic Reduction of Nitroarenes

This study adopts a simple but facile process for preparing silver-doped magnetic nanoparticles by the spontaneous oxidation-reduction/coprecipitation method. The preparation can be achieved in one pot with a single step, and the prepared silver-doped magnetic nanoparticles were utilized as nanocatalysts for the reduction of o-nitroaniline. Utilizing the magnetic characteristics of the prepared nanoparticles, the catalytic reactions can be carried out under quasi-homogeneous condition and the nanocatalysts can be easily collected after the conversion is achieved. It can be revealed from the results that the morphologies and the composition of the prepared silver-doped magnetic nanoparticles can be adjusted by changing the conditions during the production, which affects the efficacy of the catalysis. In addition, the catalysis efficiency is also controlled by the pH, temperature, and the amounts of nanocatalysts used during the catalytic reaction. Finally, the silver-doped magnetic nanocatalysts prepared in this study own the advantages of easy preparation, room-temperature catalysis, high conversion ability, and recyclability, which make them more applicable in real utilities.

Silver nanoparticle-loaded microgel-based etalons for H2O2sensing

Silver nanoparticles (AgNPs) were generated inside the network structure of poly(N-isopropylacrylamide)-co-acrylic acid (pNIPAm-co-AAc) microgels that were sandwiched between two thin Au layers (15 nm) of an etalon. This was done by introducing Ag⁺ to the etalons composed of deprotonated microgels, followed by its subsequent reduction with NaBH₄. The resultant microgels were collected and then characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS), verifying the loading of AgNPs with relatively uniform diameter (5–7 nm) within the microgels. Furthermore, the optical properties of the resultant etalons and their response to H₂O₂ were evaluated by reflectance spectroscopy. Specifically, upon the addition of H₂O₂, the AgNP-loaded etalons exhibited both a red shift in the position of the reflectance peaks and an increase in reflected wavelength intensity. We hypothesize that the dual signal response of the devices was a result of oxidative decomposition of the AgNPs, enabling the microgels to swell and for more light to be reflected (due to the loss of the light absorbing AgNPs). Finally, we showed that the AgNPs could be regenerated in the used etalons multiple times without a loss in performance. This work provides a cost-effective means to detect H₂O₂, which could be modified to sense a variety of other species of physiological and environmental importance through rationally loading other functional nanomaterials.

Silver nanoparticle (AgNP)-loaded poly(N-isopropylacrylamide)-co-acrylic acid (pNIPAm-co-AAc)-based microgels were generated and used to make etalons. The etalons were shown to exhibit optical properties that depended on the concentration of H₂O₂ in solution.