Gold nanorods assisted silver mirror reaction for consecutive color change based on-site visual semi-quantification of indoor formaldehyde

Abstract

In the present study, a multicolor conversion strategy based on gold nanorods (AuNRs) assisted silver mirror reaction is developed for visual quantification of formaldehyde (HCHO). The method involves the silver deposition on the surface of AuNRs via the reduction reaction of Tollens' reagent in the presence of HCHO. The peak shifts of the longitudinal localized surface plasmon resonance (LSPR) and color variations of AuNRs solution are sensitive to the thickness of silver layer deposited on the surface of AuNRs. Under the optimized conditions, there is a good linear relationship between the peak shift and the concentration of HCHO (for both liquid sample and gas sample) in a wide range of concentration, thus an AuNRs based colorimetric assay for quantitative analysis of HCHO is established. Moreover, a series of consecutive color changes (from mauve to dusty blue, nattier blue, blue, mazarine blue, dark green, clay bank and finally orange red) responding to the presence and amount of HCHO enables visual semi-quantitative determination of HCHO within 15 min, and the clearly discernible dosage scale is as low as 0.10 μM. This assay exhibits desirable selectivity for HCHO over several common interfering organic molecular species and potential gas interferents, which has been successfully applied to measure the concentration of HCHO indoor.