Accelerated Leaching of Unmodified Gold Nanoparticles for Environmental and Biological Monitoring of Nitrite and Nitrate

Abstract

Accurate, simple, and economical control of nitrite and nitrate concentrations is of great importance because of the adverse environmental effects and threats to the food chain of living organisms. Due to the high potential of plasmonic nanoparticles (NPs) especially gold NPs (AuNPs) in sensor design, in this study, we have presented a method for nitrite and nitrate measurement based on leaching of spherical AuNPs. We have utilized a non‐toxic thiol‐containing compound that forms cationic complexes with gold ions and consequently speeds up the leaching process. Therefore, it is possible to measure nitrite ions at room temperature by changing the size of plasmonic NPs and subsequently producing measurable signals, including spectral and color changes. Due to the easy synthesis of spherical NPs, which are the most thermodynamically and kinetically favorable morphology, this probe is simple and cost‐effective with no need for well‐trained personnel. Under optimal conditions, a linear range was obtained from 10.0 to 80.0 μmol L−1 with a limit of detection as low as 0.13 μmol L−1. Nitrate was measured indirectly and after reduction to nitrite by zinc powder. The linear range obtained for nitrate was 1.2 to 3.5 mmol L−1 and the detection limit was as low as 96.2 μmol L−1. Furthermore, the designed probe could determine nitrite and nitrate in environmental, food, and biological samples with high quantitative accuracy. Due to its simplicity and high accuracy, this method can reliably smooth the problems caused by other laboratory methods in measuring nitrite and nitrate.

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