N,N-Dimethylformamide-stabilized gold nanoclusters as a catalyst for the reduction of 4-nitrophenol

Abstract

In this study, we investigated the catalytic properties of N,N-dimethylformamide (DMF)-stabilized gold nanoclusters (AuNCs) in the reduction of 4-nitrophenol (PNP) to 4-aminophenol by NaBH(4), a well known model reaction to be catalyzed by metal surfaces. The DMF-stabilized AuNCs were prepared in DMF by a surfactant-free method. The DMF-stabilized AuNCs showed high catalytic activity even when used in small quantities (∼10(-7) g). The pseudo-first-order rate constant (k(app)) and activation energy were estimated to be 3 × 10(-3) s(-1) and 31 kJ mol(-1), respectively, with 1.0 μM of the gold catalyst at 298 K. The catalytic activity of the DMF-stabilized AuNCs was strongly influenced by the layer of adsorbed DMF on the Au NCs. This layer of adsorbed DMF prohibited the reactants from penetrating to the surface of the AuNCs via the diffusion at the beginning of the reaction, resulting in an induction time (t(0)) before PNP reduction began. Restructuring of the DMF layer (essentially a form of activation) was the key to achieving high catalytic activity. In addition, atomically monodisperse Au(25)(SG)(18)NCs (SG: glutathione) showed higher catalytic activity in the PNP reduction (k(app) = 8 × 10(-3) s(-1)) even with a low catalyst concentration (1.0 μM), and there was no induction time (t(0)) in spite of the strongly binding ligand glutathione. This suggested that the catalytically active surface sites of the Au(25)(SG)(18)NCs were not sterically hindered, possibly because of the unique core-shell-like structure of the NCs. Retaining these open sites on AuNCs may be the key to making the NCs effective catalysts.

A Comparison Reduction of 4-Nitrophenol by Gold Nanospheres and Gold Nanostars

“…The effect of the second metal in the catalysis will be extensively explored in our on-going project. Compared with some previously reported anisotropic gold nanoparticles [2,[37][38][39][40][41][42], the present gold nanostars (with kapp = 4.36 min −1 ) presented better catalytic activity than that of gold nanocages (with kapp = 2.83 min −1 ) [33] and gold nanoantennas (with kapp = 1.61 min −1 ) [13] for the reduction of 4-NP at room temperature. Moreover, compared with some previously reported gold nanoparticles capped with macrocycles (e.g., cyclodextrin, calixarene, and cucurbiturils) [32,43,44], cucurbituril- The k app values were then correlated to the inverse temperature, and we calculated the apparent activation energies (E a ) based on the Arrhenius equation ( Figure S4 and Table 1) [13,33].…”

Fabrication of composite thin films with microstructures of honeycomb, foam, and nanosphere arrays through adsorption and self-assembly of block copolymers at the liquid/liquid interface

“…The linear fit indicates that relation of lnk to 1/T follows Arrhenius equation. The active energy (E a ) was derived to be 27.3 kJ mol À1 based on the slop of the linear fitting line, which is lower than [46,[51][52][53][54] or close to [55,56] the E a values reported in the literatures when gold metal nanoparticles were used as catalysts for reduction of 4-NP. It has been demonstrated that the lower the activation energy is, the higher the catalytic activity is [52].…”

Preparation of Monodispersed Copper Nanoparticles by an Environmentally Friendly Chemical Reduction

“…In recent decades, metal nanomaterials have attracted much attention because of their extensive applications in catalysis, [1][2][3] electrooptical devices, [4,5] electronic devices [6,7] and biological sensors. [8] Among various metal particles, copper nanoparticles have been extensively investigated for their promising applications in different fields, such as catalysts, [9][10][11] optical devices, [12][13][14] magnetic devices, [15] antibacterial agents [16,17] and thermal conducting materials.…”