The Effect of Poly(vinylpyrrolidone) (PVP) on the Au Catalyzed Reduction of p–nitrophenol: The Fundamental Role of NaBH₄.

Abstract

The effect of polymeric ligands, like poly(vinylpyrrolidone) (PVP), on the reduction of p‐nitrophenol by NaBH4 in presence of gold nanoparticles (NPs) is systematically investigated. Distinctive trends could be identified depending on the extent of the NaBH4 excess. At rather low NaBH4 concentration excess, PVP had a deleterious effect, probably due to the steric hindrance of the PVP layer on the gold surface that acted partially blocking gold active sites. However, under a large excess of NaBH4, an enhanced catalytic performance was observed, what was attributed to the exchange of the polymer by hydride anions and other ions formed during hydrolysis of NaBH4. This exchange occurred without aggregation of NPs and without compromising recycling capability. Based on these results, the design of new routes for the synthesis of supported catalysts based on PVP stabilized metal colloids can be envisaged, as no additional steps would be necessary for removing the stabilizer prior to use.

Synthesis, characterization and kinetic study of silver and gold nanoparticles produced by the archaeon Haloferax volcanii

“…The sequence of reagents addition, the operating conditions as well as the nature of the capping ligands have shown to strongly affect both the induction period and p‐NP reduction rate (ÁlvarezCerimedo et al . 2019). Haloferax volcanii Ag and Au NPs were able to catalyse p‐NP reduction in presence of 100 mmol l −1 NaBH 4 (Fig.…”

“…2013; Ansar and Kitchens 2016; ÁlvarezCerimedo et al . 2019), enhancing accessibility of the reactants to the NPs surface. In this case, partial replacement of proteins by these anions may explain the observed catalytic improvement.…”

“…The experimental procedure and the starting operating conditions were initially set from conclusions arisen from a previous study in which the catalytic activity of Au NPs coated and uncoated with poly‐vinylpyrrolidone (PVP) was compared (ÁlvarezCerimedo et al . 2019). Hence, for catalytic testing, 1·3 mg of Ag NPs or Au NPs were dispersed in 1 ml of MilliQ (MQ) water and sonicated 1 h at 40°C to improve homogenization.…”

Mussel-inspired Ag/poly(norepinephrine)/MnO2 heterogeneous nanocatalyst for efficient reduction of 4-nitrophenol and 4-nitroaniline: an alternative approach

“…To find the catalytic efficiency of fabricated heterogeneous MNP-Ag nanocomposite, catalytic reduction of 4-NP was already renowned as one of the suitable model reactions. On the other hand, removal of anthropogenic water soluble 4-NP pollutant from waste industrial effluent has earned significant attention to the researcher [53,54]. The major advantage of selecting reduction of 4-NP as model reaction is that the single product, 4-aminophenol (4-AP), is obtained and the kinetic of the reaction can be easily monitored with high precision by characteristic absorption peaks at 300 nm and 400 nm of UV-visible absorption spectra [55].…”

Revealing the Active Site of Gold Nanoparticles for the Peroxidase-Like Activity: The Determination of Surface Accessibility

“…Typically, unmodified AuNPs without additional surface modifiers could retain the highest number of active sites on the surface, resulting in the best catalytic performance. Since PVP and GA are typically used to protect colloidal AuNPs without any chemical bonding in-between, the surface accessibility of PVP-AuNPs and GA-AuNPs might be confined by the steric hindrance of such macromolecules (i.e., PVP and GA) around the surface of AuNPs [28]. As for Cit-AuNPs, the possible explanation was that a fraction of the surface gold atoms was oxidized to the Au(I) state either by binding with citrate COO − or by balancing the adsorption stability of negatively-charged citrate [20]; thereby, the accessible Au(I) on the surface of Cit-AuNPs might also be restricted.…”