Palladium nanostructures: Solvent-less, one-pot mechano-chemical synthesis using poly(vinylpyrolidone) and catalytic activity

Mechanochemical hydroquinone regeneration promotes gold salt reduction in sub-stoichiometric conditions of the reducing agent

Bottom-up mechanochemical synthesis (BUMS) has been demonstrated to be an efficient approach for the preparation of metal nanoparticles (NPs), protected by surface agents or anchored on solid supports. However, there are limitations, such as precise size and morphological control, due to a lack of knowledge about the mechanically induced processes of NP formation under milling. In this article, we further investigate the BUMS of AuNPs. Using SiO2 as a solid support, we studied the effect of typical reducing agents, namely NaBH4, L-ascorbic acid, and hydroquinone (HQ), on the conversion of a AuIII source. XANES showed that HQ is the strongest reducing agent under our experimental conditions, leading to the quantitative conversion of gold salt in a few minutes. Interestingly, even when HQ was used in sub-stoichiometric amounts, AuIII could be reduced to ratios higher than 85% after two minutes of milling. Investigations into the byproducts by 1H NMR and GC-FID/MS enabled the identification HQ regeneration and the formation of its derivatives. We mainly focused on benzoquinone (BQ), which is the product of the oxidation of HQ as it reduces the gold salt. We could demonstrate that HQ is regenerated from BQ exclusively under milling and acidic conditions. The regenerated HQ and other HQ-chlorinated molecules could then reduce gold-oxidized species, leading to higher conversions and economy of reactants. Our study highlights the intriguing and complex mechanisms of mechanochemical systems, in addition to fostering the atom and energy economy side of mechanochemical means to produce metal nanoparticles.

A general one-pot, solvent-free solid-state synthesis of biocompatible metal nanoparticles using dextran as a tool: Evaluation of their catalytic and anti-cancer activities

We propose a general green method coupled with a solid-state vibration ball milling strategy for the synthesis of various metal nanoparticles (MNPs), employing a polymeric carbohydrate dextran (Dx) as a reducing and stabilizing molecule. The synthesis of size-controlled Dx-based MNPs (Dx@MNPs), featuring comparatively narrow size distributions, was achieved by controlling the mass ratio of the reactants, reaction time, frequency of the vibration ball mill, and molecular weight of Dx. Notably, this process was conducted at ambient temperatures, without the aid of solvents and accelerating agents, such as NaOH, and conventional reductants as well as stabilizers. Thermal properties of the resulting Dx@MNPs nanocomposites were extensively investigated, highlighting the influence of metal precursors and reaction conditions. Furthermore, the catalytic activity of synthesized nanocomposites was evaluated through the reduction reaction of 4-nitrophenol, exhibiting great catalytic performance. In addition, we demonstrated the excellent biocompatibility of the as-prepared Dx@MNPs toward human embryonic kidney (HEK-293) cells, revealing their potential for anticancer activities. This novel green method for synthesizing biocompatible MNPs with Dx expands the horizons of carbohydrate-based materials as well as MNP nanocomposites for large-scale synthesis and controlled size distribution for various industrial and biomedical applications.

Investigating the role of reducing agents on mechanosynthesis of Au nanoparticles

The influence of reducing agents on the mechanochemical synthesis of Au nanoparticles differ significantly from analogous solution syntheses. Environmentally benign mechanochemical syntheses of metal nanoparticles therefore require dedicated studies.

Tandem X-ray absorption spectroscopy and scattering for in situ time-resolved monitoring of gold nanoparticle mechanosynthesis

A new tandem approach combines XRD and XANES for time-resolved in situ monitoring of the mechanochemical synthesis of gold nanoparticles.

A mechano-colloidal approach for the controlled synthesis of metal nanoparticles

We propose a mechano-colloidal approach marrying the attractive features of both mechanochemical and colloidal syntheses to produce well-defined Au nanoparticles.

Solvent-free and one-pot synthesis of silver and zinc oxide nanoparticles: Activity toward cell membrane component and insulin signaling pathway in experimental diabetes

OBJECTIVE

To investigate and compare between the effect of both silver nanoparticles (AgNPs) and zinc oxide nanoparticles (ZnONPs) on insulin signaling pathway and insulin sensitivity in experimental diabetes. Preparation of AgNPs and ZnONPs in their solid state were carried out using pullulan (Natural polymer) as both reducing and stabilizing agent. The synthesis of these nanoparticles in a large scale were carried out without using any solvents. The experimental male albino rats received diluted solutions of AgNPs and ZNONPs. After the experimental period, blood was withdrawn; erythrocyte membrane lipids were extracted and fatty acids were determined by HPLC. Oxidant, antioxidant profile and phosphatidylinositol 3-kinase (PI₃K) were estimated.

RESULTS

It was observed that the as synthesized AgNPs and ZnONPs have nearly spherical shape with small size due to the stabilization effect of pullulan as proved by UV-vis spectroscopy (UV-vis), Transmission electron microscy (TEM) and Field emission scanning electron microscopy (FESEM), Zeta potential, Dynamic light scattering (DLS) and X-ray diffraction (XRD) techniques. The average hydrodynamic size of the formed AgNPs was 15 nm which is considered as very small size when compared with that of ZnONPs (above 50 nm). Fasting blood sugar was significantly increased in diabetic group along with elevation of MDA and DNA damage indicating the oxidative properties of streptozotocin. Whereas, the treatment with nanoparticles significantly attenuated these elevations.

CONCLUSION

AgNPs and ZnONPs represent promising materials in attenuating diabetic complications and insulin resistance in experimental diabetes; no Impressive differences were observed between the effect of ZnONPs and AgNPs in this current research.

Impact of Covalent Functionalization on the Aqueous Processability, Catalytic Activity, and Biocompatibility of Chemically Exfoliated MoS2 Nanosheets

Chemically exfoliated MoS₂ (ce-MoS₂) has emerged in recent years as an attractive two-dimensional material for use in relevant technological applications, but fully exploiting its potential and versatility will most probably require the deployment of appropriate chemical modification strategies. Here, we demonstrate that extensive covalent functionalization of ce-MoS₂ nanosheets with acetic acid groups (∼0.4 groups grafted per MoS₂ unit) based on the organoiodide chemistry brings a number of benefits in terms of their processability and functionality. Specifically, the acetic acid-functionalized nanosheets were furnished with long-term (>6 months) colloidal stability in aqueous medium at relatively high concentrations, exhibited a markedly improved temporal retention of catalytic activity toward the reduction of nitroarenes, and could be more effectively coupled with silver nanoparticles to form hybrid nanostructures. Furthermore, in vitro cell proliferation tests carried out with murine fibroblasts suggested that the chemical derivatization had a positive effect on the biocompatibility of ce-MoS₂. A hydrothermal annealing procedure was also implemented to promote the structural conversion of the functionalized nanosheets from the 1T phase that was induced during the chemical exfoliation step to the original 2H phase of the starting bulk material, while retaining at the same time the aqueous colloidal stability afforded by the presence of the acetic acid groups. Overall, by highlighting the benefits of this type of chemical derivatization, the present work should contribute to strengthen the position of ce-MoS₂ as a two-dimensional material of significant practical utility.

Silver nanoparticle-embedded RGO-nanosponge for superior catalytic activity towards 4-nitrophenol reduction

The present work highlights a bio-inspired synthesis of uniform 2 nm sized plasmonic silver nanospheres (Ag-NSs) embedded in reduced graphene oxide nanosponge (RGONS) using Tabebuia berteroi leaf extract.

Controllable synthesis of Ni/SiO2 hollow spheres and their excellent catalytic performance in 4-nitrophenol reduction

Hierarchical Ni nanoparticle supported silica hollow microspheres were synthesized by a unique and simple two-step method. Excellent catalytic activity in the reduction of 4-nitrophenol can be achieved on the catalysts.