Green Synthesized Silver Nanoparticles: A Potential Antibacterial Agent, Antioxidant, and Colorimetric Nanoprobe for the Detection of Hg2+ Ions

Silver nanoparticles (AgNPs) prepared by green synthesis have a lot of potentials in various fields. Among them, as an antioxidant, antibacterial agent, and nanoprobe for the colorimetric detection of mercury (Hg2+) ions is thought to be the most important. The antibacterial, antioxidant, and colorimetric sensing potential of the greenly produced AgNPs utilizing Piper chaba stem extract are all predicted in this investigation. By using the disc diffusion method, the antibacterial activity of greenly produced AgNPs are assessed, and the findings are measured from the zone of inhibition (ZOI). It is revealed that the Staphylococcus aureus, Micrococcus spp., Escherichia coli, and Pseudomonas aeruginosa bacterial strains are significantly resisted by the greenly produced AgNPs. The antioxidant activity test of AgNPs reveals a considerable impact on free radical scavenging having the inhibitory concentration (IC 50) is 1.13 mL (equivalent to 0.45 mg mL-1). Also, with a low limit of detection of 28 ppm, the resulting AgNPs are used as highly selective and economical colorimetric sensors for Hg2+ detection. The study's findings support the hypothesis that Piper chaba stems can serve as a source for the production of AgNPs with high antibacterial and antioxidant activity and usefulness for simple colorimetric readings of Hg2+.

Progress and opportunities for metal-organic framework composites in electrochemical sensors

Metal-organic framework composites have the advantages of large surface area, high porosity, strong catalytic efficiency and good stability, which provide a great possibility of finding excellent electrode materials for electrochemical sensors. However, MOF composites still face various challenges and difficulties, which limit their development and application. This paper reviews the application of MOF composites in electrochemical sensors, including MOF/carbon composites, MOF/metal nanoparticle composites, MOF/metal oxide composites and MOF/enzyme composites. In addition, the application challenges of MOF composites in electrochemical sensors are summarized. Finally, the application prospect for MOF composites is considered to promote the synthesis of more MOF composites with excellent properties.

Biogenic Synthesis and Catalytic Efficacy of Silver Nanoparticles Based on Peel Extracts of Citrus macroptera Fruit

Biogenically synthesized silver nanoparticles (AgNP) increase the fascination over chemical ones due to their facile and green synthetic process. This study reports the development of an eco-friendly and cost-effective synthesis of AgNPs using an aqueous extract of Citrus macroptera fruit peel, an agricultural waste, as a sole agent with both reducing and capping abilities. The formation of AgNPs was verified by the surface plasmon resonance peak at 426 nm in the UV-vis spectrum, X-ray diffraction pattern, and transmission electron micrography images. The AgNPs obtained under the optimized conditions consist of face-centered cubic crystals and spherical morphology with an average size of 11 nm. The AgNPs are coated with phytochemicals in the C. macroptera fruit peel extract and are stably dispersible due to their negatively charged nature. The AgNPs effectively catalyzed the reduction of 4-nitrophenol to 4-aminophenol and the degradation of methyl orange and methylene blue in the presence of sodium borohydride. This method employing a fruit peel extract is facile, efficient, eco-friendly, and cost-effective and has potential for industrial green fabrication of AgNPs.

Chitosan as capping agent in a robust one-pot procedure for a magnetic catalyst synthesis

Here, we report a one-pot solvothermal method for the development of magnetically recoverable catalysts with Ru or Ag nanoparticles (NPs) capped by chitosan (CS), a derivative of natural chitin. The formation of iron oxide NPs was carried out in situ in the presence of CS and iron acetylacetonate in boiling triethyleneglycol (TEG) due to CS solubilization in warm TEG. Coordination with Ru or Ag species and the NP formation take place in the same reaction solution, eliminating intermediate steps. In optimal conditions the method developed allows stabilization of 2.2 nm monodisperse Ru NPs (containing both Ru⁰ and Ru⁴⁺ species) that are evenly distributed through the catalyst, while for Ag NPs, this stabilizing medium is inferior, leading to exceptionally large Ag nanocrystals. Catalytic testing of CS-Ru magnetically recoverable catalysts in the reduction of 4-nitrophenol to 4-aminophenol with excess NaBH₄ revealed that the catalyst with 2.2 nm Ru NPs exhibits the highest catalytic activity compared to samples with larger Ru NPs (2.9-3.2 nm). Moreover, this catalyst displayed extraordinary shelf-life in the aqueous solution (up to ten months) and excellent reusability in ten consecutive reactions with easy magnetic separation at each step which were assigned to its conformational rigidity at a constant pH. These characteristics as well as favorable environmental factors of the catalyst fabrication, make it promising for nitroarene reduction.

Stable Coloured Micrometric Films from Highly Concentrated Nano-Silver Sols: The Role of the Stabilizing Agents

The synthesis of highly concentrated aqueous silver nanoparticles (NPs), exploiting different types of polymeric stabilizing agents, has been extensively investigated, especially for the stabilization of spherical yellow nanoparticles. In this context, here, a successful and easy wet chemical method was adopted to synthesize concentrated primary colored (yellow, red, blue and green) sols. The influence of polyvinylpyrrolidone (PVP) and polyvinyl alcohol (PVA) in affecting the final stability was finely investigating via UV/Vis spectroscopy, dynamic light scattering, TEM and colorimetric analysis. The next step consisted on the deposition of obtained sols onto a crown-treated polyethylene terephthalate (PET) support to obtain transparent colored micrometric homogeneous films. The fabricated PVP-based Ag films were revealed to be outstandingly UV-stable, contrarily to PVA-based films, probably due to the degradation of the polymer itself. Indeed, after UV aging tests, the PVA macromolecules could be broken and chemically modified (demonstrated by FT-IR analyses). This resulted in there being insufficient macromolecules to efficiently cover the surface of the nanoparticles, meaning that the nanoparticles tended to aggregate with each other, destabilizing the system itself. Hence, the obtained colored films described herein could represent a promising tool for different applications, from color shifting to optoelectronic devices.

Green Synthesis and Catalytic Activity of Silver Nanoparticles Based on Piper chaba Stem Extracts

A green synthesis of silver nanoparticles (AgNPs) was conducted using the stem extract of Piper chaba, which is a plant abundantly growing in South and Southeast Asia. The synthesis was carried out at different reaction conditions, i.e., reaction temperature, concentrations of the extract and silver nitrate, reaction time, and pH. The synthesized AgNPs were characterized by visual observation, ultraviolet-visible (UV-vis) spectroscopy, dynamic light scattering (DLS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), x-ray diffraction (XRD), energy dispersive x-ray (EDX), and Fourier transform infrared (FTIR) spectroscopy. The characterization results revealed that AgNPs were uniformly dispersed and exhibited a moderate size distribution. They were mostly spherical crystals with face-centered cubic structures and an average size of 19 nm. The FTIR spectroscopy and DLS analysis indicated that the phytochemicals capping the surface of AgNPs stabilize the dispersion through anionic repulsion. The synthesized AgNPs effectively catalyzed the reduction of 4-nitrophenol (4-NP) and degradation of methylene blue (MB) in the presence of sodium borohydride.

Synthesis of Sub 3 nm-Sized Uniform Magnetite Nanoparticles Using Reverse Micelle Method for Biomedical Application

We report a synthetic method for small and uniform Fe3O4 (magnetite) nanoparticles under mild conditions. Spherical sub-3 nm-sized magnetite nanoparticles were prepared via reverse micelles composed of oleylamine, F127, xylene, and water for the reaction of iron(III) stearate with hydrazine at a reaction temperature of 90 °C in air atmosphere. These synthesized magnetite nanoparticles exhibited good size uniformity. By controlling experimental conditions, we could easily control both size and size uniformity of these magnetite nanoparticles. We further investigated whether Fe3O4 could be used in biomedical applications. Cytotoxicity of Fe3O4 was evaluated with human adipose-derived stem cells (hADSCs). Our results showed that the number of hADSCs did not significantly decrease when these cells were treated with Fe3O4 nanoparticles at a concentration of up to 9 μg/mL. Apoptotic activity and cell proliferation of hADSCs treated with Fe3O4 nanoparticles were similar to those of hADSCs without any treatment. This novel method could be used for synthesizing uniform and biocompatible Fe3O4 nanoparticles with further biomedical applications.

Facile Synthesis of Magnetically Recoverable Pd and Ru Catalysts for 4-Nitrophenol Reduction: Identifying Key Factors

This paper reports the development of robust Pd- and Ru-containing magnetically recoverable catalysts in a one-pot procedure using commercially available, branched polyethyleneimine (PEI) as capping and reducing agent. For both catalytic metals, ∼3 nm nanoparticles (NPs) are stabilized in the PEI shell of magnetite NPs, whose aggregation allows for prompt magnetic separation. The catalyst properties were studied in a model reaction of 4-nitrophenol hydrogenation to 4-aminophenol with NaBH4. A similar catalytic NP size allowed us to decouple the NP size impact on the catalytic performance from other parameters and to follow the influence of the catalytic metal type and amount as well as the PEI amount on the catalytic activity. The best catalytic performances, the 1.2 min-1 rate constant and the 433.2 min-1 turnover frequency, are obtained for the Ru-containing catalyst. This is discussed in terms of stability of Ru hydride facilitating the surface-hydrogen transfer and the presence of Ru4+ species on the Ru NP surface facilitating the nitro group adsorption, both leading to an increased catalyst efficiency. High catalytic activity as well as the high stability of the catalyst performance in five consecutive catalytic cycles after magnetic separation makes this catalyst promising for nitroarene hydrogenation reactions.

Bioinspired interconnected hydrogel capsules for enhanced catalysis

Polysaccharide-based hydrogel capsules with cristae-like internal membranes loaded with Ag nanoparticles exhibited effective catalytic activity as micro-reaction systems.

One pot synthesis of amine-functionalized and angular-shaped superparamagnetic iron oxide nanoparticles for MR/fluorescence bimodal imaging application

Herein, we report the simple preparation of water dispersible angular-shaped amine-functionalized super-paramagnetic iron oxide nanoparticles (A-SPIONs).

CO2-switchable polymer-hybrid silver nanoparticles and their gas-tunable catalytic activity

A new type CO₂-switchable AgNPs hybrids show switchable and monotonous tunable catalytic activity for the reduction of 4-nitrophenol by varying the flow rate of CO₂purged into the reaction system.

One-step synthesis and applications of highly concentrated silver nanoparticles with an ultra-thin silica shell

One-step synthesis resulting in highly concentrated silver nanoparticles with ultra-thin silica shell that were used for SERS & chemiresistor applications.

Size dependence of silver nanoparticles in carboxylic acid functionalized mesoporous silica SBA-15 for catalytic reduction of 4-nitrophenol

Silver nanoparticles with a size around 3 nm are formed within the mesopores of –COOH functionalized mesoporous silica SBA-15, and they are highly active in the catalytic reduction of 4-nitrophenol.

pH dependent size control, formation mechanism and antimicrobial functionality of bio-inspired AgNPs

Sechium edule is rich in ascorbic acid which was extracted from aqueous media for the synthesis of AgNPs.

Controlling the morphology and composition of Ag/AgBr hybrid nanostructures and enhancing their visible light induced photocatalytic properties

Ag/AgBr hybrid nanostructures were prepared by reducing AgBr nanoparticles synthesized by reaction of Ag⁺ with Br⁻. The Ag/AgBr hybrid nanostructures exhibited enhanced photocatalytic activity and recyclability for decomposing methylene blue (MB).

A facile synthesis of Ag/AgCl hybrid nanostructures with tunable morphologies and compositions as advanced visible light plasmonic photocatalysts

Ag/AgCl plasmonic photocatalysts are synthesized by a simple and rapid method in an aqueous-phase. The Ag/AgCl hybrid nanostructures exhibited enhanced photocatalytic activity and stability toward the degradation of methyl orange under visible light irradiation because of their strong surface plasmon resonance (SPR) effect.

Cost-effective aqueous-phase synthesis of long copper nanowires

This work describes a simple and cost-effective aqueous-phase synthesis of Cu nanowires with long-term stability. Chloride ions and branched polyethyleneimine (BPEI) were found to be of great importance to the formation and stabilization of Cu nanowires.