Ratiometric response to formaldehyde by 3D silver SERS substrate with polyoxometalate as internal label
Jie Wang, Wen-Jing Zhu, Jiayuan Zhang, Bin Qi, Junpeng Wang, Guang‐Gang Gao, Linlin Fan, Hong Liu
Abstract
For surface-enhanced Raman scattering (SERS) analytical technology, the rational design of efficient substrate and effective internal standard is the key issue to implement the reliable detection. In this paper, a novel three-dimensional (3D) silver(I)-polyoxometalate complex of Ag 2 [Ag(trz) 2 ][H 6 CrMo 6 O 24 ]·2H 2 O ( Ag 3 CrMo 6 , trz = 1, 2, 4-triazole) has been designed and synthesized, which can be used for the quantitative detection of formaldehyde (FA). Structural analysis reveals that the [H 6 CrMo 6 O 24 ] 3- polyoxoanions link Ag + by diverse Ag−O (Mo−O) bonds to form a stable 3D framework. When Ag 3 CrMo 6 is exposed to FA, the Ag + can be partially reduced to Ag 0 species to become the label-free SERS active substrate and and present the enhanced signals ascribed to the Mo−O vibrations. Due to that the reduced Ag 0 species is only close to Mo−O groups, the Raman signals for Cr−O bonds are almost constant and can be used as internal standards. Therefore, the I Mo−O /I Cr−O values can be used as ratiometric SERS signals to fulfill the elusive SERS quantitative analysis for FA with the detection limit of 0.05 ng/L. This work opens up an innovative way to the rational design of label-free SERS substrate based on polyoxoanions and silver ions , by which the quantitative detection can be realized via the ratiometric Raman signals.