Understanding the induction time associated with the photoredution of resazurin by hydroxylamine in the presence of gold
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Understanding the induction time associated with the photoredution of resazurin by hydroxylamine in the presence of gold nanoparticles as a photocatalyst Keeniya‑Gamalage‑Gehan Chaturanga De Silva1 · Mahinda I. Ranasinghe1 · Sanchari Chowdhury2 Received: 20 July 2020 / Accepted: 20 September 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract Recently, there has been an increasing interest in using the photoreduction of resazurin by aliphatic amines such as hydroxylamine as a model reaction to assess the efficiency of metal nanoparticles as photocatalysts. However, some features of this reaction are still not understood well. In particular, one of the most important still misconstrued feature of resazurin photoreduction reaction is the lag time in the beginning of the reaction, when no turnover of resazurin is observed. This lag time is often known as the induction time. In order to understand the origin of the induction time, we investigate the factors governing the induction time associated with the reaction. We found that the concentrations of the hydroxylamine and the dissolved oxygen are most important factors influencing the induction time. In the ambient condition, the induction time for resazurin reduction reaction can be as long as 30 min in the absence of any catalyst. Decreasing the dissolved oxygen concentration or increasing the hydroxylamine concentration can significantly reduce the induction time. We attributed the induction time to a side reaction, autoxidation of hydroxylamine by dissolved oxygen. Interestingly, we found that the presence of metal nanocatalyst such as gold can also reduce the induction time. We concluded that in addition to catalyzing the photoreduction of resazurin, gold nanocatalyst can also accelerate the autoxidation reaction of hydroxylamine. Keywords Resazurin · Photoreduction · Induction time · Hydroxylamine · Photocatalyst
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s1114 4-020-01875-9) contains supplementary material, which is available to authorized users. * Sanchari Chowdhury [email protected] 1
Department of Chemistry, New Mexico Tech, Socorro, NM 87801, USA
2
Department of Chemical Engineering, New Mexico Tech, Socorro, NM 87801, USA
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Reaction Kinetics, Mechanisms and Catalysis
Introduction Resazurin, commonly known as Alamar blue is an important redox indicator. The reduction of resazurin (blue) to resorufin (pink) can be easily monitored by the colorimetric method or with spectroscopic techniques such as UV–Vis and fluorescence spectroscopy. This reduction reaction can also be performed by photochemical and electrochemical methods where aliphatic amines are used as the reducing agents [1–3]. There has been an increasing interest in applying the photoreduction reaction of resazurin as a model reaction to assess the efficiency of a catalyst [1, 4–11]. Also it has been commonly used to evaluate cell viability and cytotoxicity in many different biological and environm
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