PVP stabilized Pt nano particles catalyzed de-oxygenation of phenoxazine group by hydrazine in physiological buffer media: surfactant competes with reactants for the same surface sites

Abstract

PVP capped platinum nano particles (PNP) of 5 nm diameter were prepared and characterized as homogeneous and of spherical nature. At physiological pH range (6.0-8.0), these PNP catalyze the deoxygenation of phenoxazine group containing resazurin (1) by hydrazine. The observed rate constants (k(o)), increase linearly with [PNP] at constant [1] and [Hydrazine]; but first increase and then after reaching a maximum it decrease with increase in [1] as well as in [Hydrazine]. The k(o) values increase linearly with 1/[H(+)] indicating N(2)H(4) as the reducing species that generates from the PNP assisted deprotonation of N(2)H(5)(+). The kinetic observations suggest Langmuir-Hinshelwood type surface reaction mechanism where both 1 and hydrazine are adsorbed on nano particles surface and compete for the same sites. Interestingly, the surfactant molecules, polyvinylpyrrolidone (PVP), though do not take part into reduction reaction but having same type of functional groups as reactants, competes with them for the same surface sites. Adsorption on PNP with same type of functional group is further supported by the FTIR spectra of Pt-PVP and Pt-1. Thus on increasing [PVP], k(o) decreases linearly and only when [PVP] is held constant, the plot of k(o) vs. [PNP] passes through the origin indicating the insignificance of uncatalyzed reaction. The plot of ln k(o) vs. [1] or [Hydrazine] shows two different linear zones with different exponent values with respect to [1] and [Hydrazine]. This indicates that along with the complex heterogeneous surface adsorption processes, the mutual interactions between the reactants are also changing with the relative concentrations of reactants or, in general, with the molar ratio ([Hydrazine]/[1]).

Homogeneous Palladium Nanoparticles Surface Hosts Catalyzed Reduction of the Chromophoric Azo (-N=N-) Group of Dye, Acid Orange 7 by Borohydride in Alkaline Media

“…If the interaction had been heterogeneous, there would have been break in plots [53]. The observed continuous nature is further supported by the near constancy of the exponent values over the total reactant concentrations or in general at different molar ratios of [NaBH 4 ]/[AO7].…”

“…The plot passes through the origin, which signifies that the reduction reaction between AO7 and borohydride happens only in the presence of the catalyst, and the contribution of the uncatalyzed reaction is negligible. Moreover, the plot ensures that the increasing gelatin concentration (0.0015-0.0075%) along with increasing [GPd] does not interfere with the reaction or passivate the catalyst in any way [53]. that both the reactants AO7 and borohydride are adsorbed on the GPd surface and both the reactants compete with the same reaction sites [63][64][65][66][67] Figure 9 FTIR spectrum of pure AO7.…”

Development of l-lactate dehydrogenase biosensor based on porous silicon resonant microcavities as fluorescence enhancers

“…Further reaction with thionyl chloride and resazurin ( Fig. 1(a) -Spectrum 3) shows a distinctive band at 1354 cm À 1 which was assigned to the νN-O bond of the dye (Das et al, 2013), while bands at 1457 and 1538-1592 cm À 1 were attributed to the νC-C stretching of the aromatics. The carbonyl peak at 1714 cm À 1 shifted to 1704 cm À 1 consistent with ester formation.…”

“…The compound consists of a phenoxazine group which contains a heterocylic N-oxide group that loses its oxygen upon reduction and forms the strongly fluorescent product, resorufin (ex/em 545 nm/583 nm). The reduction of the dye into resorufin procedes by accepting electrons from NADH and NADPH (Das et al, 2013;O'Brien et al, 2000;Candeias et al, 1998). This indirect detection is advantageous as the excitation and maximum emission wavelengths of resorufin are higher than that of NADH, thus avoiding damaging of cells and background autofluorescence.…”

Kinetics of palladium nano-particles catalyzed reduction of Methylene Green by hydrazine: Role of induction period in determining mechanistic pathway

“…Palladium nano-particles (Pdn) were prepared following a simple procedure [35]: an aqueous solution of PdCl 2 (50 mL, 2.5 Â 10 À4 M) was heated to boiling with vigorous stirring. Then 2 ml of aqueous tri sodium citrate solution (1% w/v) was added to this solution and the solution mixture was allowed to boil for one hour with vigorous stirring.…”