Detection of Formaldehyde by Surface-Enhanced Raman Spectroscopy Based on PbBiO2Br/Au4Ag4 Nanospheres.

In this work, a portable surface-enhanced Raman spectroscopy (SERS) substrate based on perovskite-like PbBiO₂Br/AuAg hybrid nanoalloys (PbBiO₂Br/Au₄Ag₄ nanospheres) was fabricated for the rapid, sensitive, and selective detection of formaldehyde. PbBiO₂Br nanospheres with thin nanosheets on the surface of the microsphere structure were synthesized via the hydrothermal method. The formation of nanospheres was controlled by an ionic liquid ([C₁₆mim]⁺). [C₁₆mim]⁺ can be simultaneously used as a solvent, reactant, and template for fabricating a porous microstructure of PbBiO₂Br nanospheres. AuAg nanoalloys were grown on PbBiO₂Br nanospheres in situ in the presence of Au³⁺ and Ag⁺. SERS performance was further optimized by adjusting the ratio of Au/Ag. PbBiO₂Br/Au₄Ag₄ membranes as the SERS substrate were further obtained via simple filtration of the PbBiO₂Br/Au₄Ag₄ nanospheres on filter paper. The PbBiO₂Br/Au₄Ag₄ membranes displayed better SERS activity for molecules with an −SH group than for molecules with nonsulfhydryl targets owing to the high affinity between AuAg nanoalloys and −SH. Under optimum conditions, the method developed herein determined that the analytical enhancement factor of 4-mercaptobenzoic acid and 4-nitrothiophenol could reach 4.5 × 10⁸ and 3.2 × 10⁷, respectively. The proposed strategy showed a wide linear range (20.0–500.0 μg L^–1) and a low limit of detection (2.6 μg L^–1) for formaldehyde determination. The membrane-based substrate developed in this study offers a novel strategy for fabricating portable and reliable SERS substrates and provides a valid SERS method for rapid on-site monitoring of formaldehyde. [ABSTRACT FROM AUTHOR]