Formation of self-inhibiting copper(ii) nanoparticles in an autocatalytic Fenton-like reaction

Abstract

Cu(II)-catalysed decomposition of hydrogen peroxide at alkaline pH in the presence of etidronic acid (HEDP) showed a sigmoid kinetic profile typical of autocatalytic reactions. However, the reaction abruptly stopped well before all hydrogen peroxide had decomposed, and further addition of Cu(II) and HEDP did not restart the reaction. Results of a mechanistic study suggest that the reaction involves the formation of an active catalyst which decomposes hydrogen peroxide and oxidizes HEDP. Once all HEDP has been consumed, the active complex triggers Cu(II) aggregation to form remarkably stable but catalytically inactive nanoparticles. The nanoparticles were found to be basic Cu(II) phosphate/carbonate. They exhibit self-poisoning behaviour in the hydrogen peroxide decomposition and undergo seed-mediated growth upon addition of further Cu(II).

Peptizing Mechanism at the Molecular Level of Laponite Nanoclay Gels

“…The UV–vis spectra of the freshly prepared dispersions are shown in Figure S5 (Supporting Information), where the upper trace and lower trace correspond to the samples prepared at 20 and 60 °C, respectively. The UV–vis spectra revealed a broad featureless spectra that is typical of inorganic nanoparticles with no aggregation or flocculation during the measurement time. − Moreover, many organic molecules upon adsorption on the clay particles show sufficient changes in their UV–vis spectra to enable the differentiation between absorbed and unabsorbed species. , This is not the case for HEPD molecules used as additive for Laponite RD dispersions. The UV–vis spectra shown in Figure S5 (Supporting Information) reveal that the Rayleigh light scattering intensity is dominated for the sample prepared at 60 °C by a big number of platelets due to accelerated exfoliation.…”

Elucidating Self-Assembly Mechanisms of Uranyl–Peroxide Capsules from Monomers

“…At such high alkaline condition, most likely copper produces copper hydroxide precipitates 33 or associates and precipitates with highly negatively charged ions such as [(UO 2 )(O 2 )] 4− or U 24 in solution or even plausibly form nanoparticles. 34 During the reaction we noticed a shift in the uranyl-bound peroxide peak. Initially, the peroxide peak shifts slightly to higher wave numbers as it starts to diminish over time, which is not observed for nonreactive samples, indicating formation of intermediate species (Figure 4b).…”

Synthesis of AgWCNx Nanocomposites for the One‐Step Conversion of Cyclohexene to Adipic Acid and Its Mechanistic Studies

“…It was observed the yield of adipic acid yield gradually increases with an increase of the added amount of H 2 O 2 . The use of an excess of the oxidant does not cause complete oxidation, which may be due to a saturation on the catalyst surface with H 2 O 2 , which decomposes spontaneously . It has been experienced that 4.5 mL of H 2 O 2 are sufficient for reaching an optimum yield of adipic acid (Figure c).…”

“…It was observed the yield of adipic acid yield gradually increases with an increaseofthea dded amount of H 2 O 2 .The use of an excess of the oxidantd oes not cause complete oxidation, which may be due to as aturation on the catalyst surface with H 2 O 2 ,w hich decomposes spontaneously. [29] It has been experienced that 4.5 mL of H 2 O 2 are sufficient for reaching an optimum yield of adipic acid( Figure6c). Increasing the amount of H 2 O 2 (e.g.,t o 5mL) does not affect the yield of adipic acid, whichm ight be due to the release of excessH 2 O, which will suppress the adsorptiono ft he substrate on the catalytic surface.…”