Colorimetric determination of Formaldehyde based on localized surface plasmon resonance of gold nanoparticles

The development of sensitive colorimetric sensors has become widely popular, due in part to their simplicity, rapidity; precision and common availability of the basic equipment in laboratory and field uses [1]. In this area, noble metal nanoparticles (NPs) have fascinated scientists because of their physico-chemical properties and potential applications in different areas such as catalysis, electronics, plasmonics, biotechnology, and so on. Among these nanoparticles, gold and silver nanoparticles have drawn much research attention because of their various promising properties [2]. These properties of nano particles, which give rise to localized surface plasmon resonance (LSPR) absorption and scattering, can be used in the development of analytical methods such as optical sensing and detection [1-3].Formaldehyde (CH2O) is the most common aldehyde in the environment and its application covers a wide range. Formaldehyde (FRD) is considered one of the most significant industrial hazards and air pollutants. So, determination of FRD is very important [4].In this work a new simple and sensitive method for the determination of FRD is proposed. The method is based on the reaction of FRD with an oxidizing agent (gold ion) and preparation of gold nanoparticles (Au NPs). The intensity of LSPR of Au NPs was monitored spectro photometrically at the maximum wavelength of 530 nm vs. time. With the increase of FRD concentration, the LSPR spectrum intensity of formed Au NPs was increased, and the enhanced intensity of LSPR was linearly proportional to the FRD concentration. There is a linear relationship between absorbance intensity of AuNPs and the concentration of FRD over the range of 0.01-0.40 μg mL-1(n=16) at 530 nm. The detection limit was 0.003 μg mL-1. Finally, the proposed method has been successfully applied for the determination of FRD in different water samples.