Highly sensitive and reproducible SERS sensor for biological pH detection based on uniform gold nanorod array platform.

Conventional research on surface-enhanced Raman scattering (SERS)-based pH sensor often depends on nanoparticle aggregation, whereas the variability in nanoparticle aggregation gives rise to poor repeatability in SERS signal. Herein, we fabricated gold nanorod array platform via an efficient evaporative self-assembly method. The platform exhibits great SERS sensitivity with enhancement factor (EF) of 5.6 × 107 and maintains excellent recyclability and reproducibility with relative standard deviation (RSD) values of less than 8%. Based on the platform, we developed a highly sensitive bovine serum albumin (BSA)-coated 4-mercaptopyridine (4-MPy)-linked (BMP) SERS-based pH sensor to report pH ranging from pH 3.0 to pH 8.0. The intensity ratio variation of 1004 cm-1 and 1096 cm-1 in 4-MPy showed excellent pH sensitivity, which decreased as the surrounding pH increased. Furthermore, this BMP SERS-based pH sensor was employed to measure the pH value in C57BL/6 mouse blood. We have demonstrated the pH sensor has great advantages for good stability, reliability and accuracy, which could be extended for the design of point-of-care devices.