Phenylboronic acid modification-based novel dumbbell-shaped Au-Ag nanorod SERS substrates for ultrasensitive detection of SO 4 2 .

Based on the coordination principle of Lewis acids, a 4-mercaptophenylboronic acid (4-MPBA)-modified novel dumbbell-shaped Au-Ag nanorod (4-MPBA@DS Au-AgNR) substrate was developed, which could be combined with the surface-enhanced Raman scattering (SERS) technique to detect SO4 2- with high sensitivity and specificity. DS Au-AgNRs synthesized in this study with a dumbbell-shaped structure were verified by finite-difference time domain (FDTD) simulation to be capable of stimulating strong localized electromagnetic enhancement (EM) at nano-edge and gap, generating a large number of "hot spots" exhibiting excellent SERS performance. The 4-MPBA modified on its surface could specifically recognize SO4 2- , producing a change in the spectral peak at 1382 cm-1 , thus realizing highly sensitive and specific sensing of SO4 2- . Under optimized conditions, this SERS sensor responded rapidly to SO4 2- within 2 minutes and demonstrated outstanding specificity. Calculation of the ratio of the characteristic peaks at 1382 and 1070 cm-1 ( I 1382 / I 1070 ) enabled the quantitative detection of SO4 2- in the range of 1 × 10-8 -1 × 10-3 M, and the detection threshold was as low as 1 nM, which was superior to those of similar detection methods. Importantly, the utility and reliability of this SERS substrate for the determination of SO4 2- in actual samples were evaluated using ion chromatography as the gold standard, and there was no significant difference between the two protocols ( P > 0.05), and the RSD was less than 6% with a satisfactory recovery rate (97.6-102.3%). Therefore, the present protocol has the advantages of simplicity and rapidity, high sensitivity, specificity, stability, and practicability in the determination of SO4 2- in aqueous solution, providing a reliable solution for tracing SO4 2- in the fields of food safety and environmental testing.