Electrochemical Sensor for the Detection of Nitrite Based on PEDOT and Hollow Gold - Palladium Nanoparticles

Abstract

Nitrites are chemical compounds commonly used as additives in food industry, especially to improve organoleptic properties of meat and prevent its degradation. According to the World Health Organization, nitrite concentrations exceeding 3 mg/L in drinking water and wastewater are hazardous for the environment and human health [1]. Nitrites can react with hemoglobin and form methemoglobin which blocks oxygen transport and generates cyanosis in infants. Also, N–nitroso compounds, potentially carcinogenic products, can be formed by the reaction of nitrites with amines [1]. For those reasons, monitoring the level of nitrite in water is extremely important.Nitrite ions are traditionally detected and quantified by colorimetry, chemiluminescence and chromatographic and spectrophotometric techniques. However, these techniques are time consuming, require complex devices or the pretreatment of the samples to prevent interferences and moreover, imply the use or the production of some toxic reagents. Electrochemical sensors based on nanomaterials like graphene, metal nanoparticles and conducting polymers have also been used for the detection of nitrite [2,3]; however, to the authors´ best knowledge, sensors based on PEDOT and hollow bimetallic nanoparticles have not been tested as potential material for this purpose.In this work, hollow AuPd nanoparticles were produced by galvanic replacement from cobalt cores. The nanoparticles were analyzed by SEM, EDX and TEM/STEM. Results revealed the hollow structure of the nanoparticles (size 30-45 nm, Fig. 1). It was confirmed that they contain Au and Pd. EDX was performed to evaluate the elemental profile through the nanoparticle. Hollow AuPd nanoparticles, previously centrifuged and resuspended in water, were co-deposited from a solution of the monomer EDOT, the surfactant SDS, LiClO4 at potentiostatic conditions. The analytical performance of the composite material for the detection of nitrite was evaluated by differential pulse voltammetry (Fig. 2) in the range of 50 to 250 µM. The sensitivity of the sensor was 0.04 +/-0.01 µA µM-1.[1] World Health Organization, Guidelines for Drinking – water Quality. (2017) 398pp. Available from: https://www.ncbi.nlm.nih.gov/books/NBK442376/[2] Fu L., Yu S., Thompson L. And Yu A. RSC Adv. 5 (2015) 40111.[3] Li G., Xia Y. Tian Y., Wu Y., Liu J., He Q. and Chen D. J. Electrochem. Soc. 166(12) (2019) B881. Figure 1