Gold Nanoparticle-Modified Tungsten Oxide Flakes as Nitric Oxide Sensor Electrodes for Fruit Quality Monitoring

Development of low-cost, handheld nitric oxide (NO) sensors is very much important due to its major role in environmental pollution, biomedical research, and food safety applications. In this study, an electrochemical NO sensor has been fabricated using gold nanoparticle (Au NP)-modified tungsten oxide (WO 3 ) nanoflakes. WO 3 nanoflakes were grown hydrothermally on fluorine doped tin oxide (FTO) substrates, and Au NPs were attached by a photoreduction method. The sensing characteristics of pristine WO 3 and Au NP-coated WO 3 electrodes have been studied by amperometric techniques. The sensor performance has been optimized at various Au NP loadings. The optimized sensor demonstrated a high sensitivity (∼39.37 μA cm –2 mM –1 ) over a wide linear range (∼10 μM to 5.78 mM) with a low detection limit (∼0.12 μM). The Au NP-coated WO 3 sensing electrode demonstrated high stability. The sensor current only decreases 7.54% after 31 days of continuous measurements. The sensor also showed fast response (1.7 s) and high selectivity toward NO detection. NO detection in fruit samples (apple and orange) has been studied with the Au NP-modified WO 3 electrode for fruit quality monitoring application.