Green Synthesis of Three-Dimensional Au Nanorods@TiO2 Nanocomposites as Self-Cleaning SERS Substrate for Sensitive, Recyclable, and In Situ Sensing Environmental Pollutants

In this work, a simple, low-cost, green, and mild method for the preparation of three-dimensional nanocomposite materials of gold nanorods (Au NRs)@TiO2 is reported. The surface of Au NRs was coated with TiO2 in situ reduction at room temperature without a complicated operation. The synthetic Au NRs@TiO2 nanocomposites were used as surface-enhanced Raman spectroscopy (SERS) active substrates for the reusable and sensitive detection of environmental pollutants. The results showed that the pollutants on Au NRs@TiO2 nanocomposites have higher SERS activity and reproducibility than those on the Au NR substrate without the presence of TiO2. Moreover, the SERS substrate can be readily recycled by UV-assisted self-cleaning to remove residual analyte molecules. Malachite green (MG) and crystal violet (CV) were used as examples to demonstrate the feasibility of the proposed sensor for the sensitive detection of environmental pollutants. The results showed that the limit of detections (LODs) were 0.75 mu g/L and 0.50 mu g/L for MG and CV, respectively, with the recoveries ranging from 86.67% to 91.20% and 83.70% to 89.00%. Meanwhile, the SERS substrate can be easily regenerated by UV light irradiation. Our investigation revealed that within three cycles, the Au NRs@TiO2 substrates still maintained the high SERS enhancement effect that they showed when first used for SERS detection. These results indicated that the method can be used to detect MG and CV in really complex samples. Due to the high sensitivity, reusability, and portability and the rapid detection property of the proposed sensor, it can have potential applications in the on-site detection of environmental pollutants in a complex sample matrix.

Automated summary

This study reports a simple, low-cost, green, and mild method for preparing three-dimensional nanocomposite materials of gold nanorods (Au NRs)@TiO2. The Au NRs were coated with TiO2 through in situ reduction at room temperature without complicated operations. The synthesized Au NRs@TiO2 nanocomposites were used as surface-enhanced Raman spectroscopy (SERS) active substrates for sensitive and reusable detection of environmental pollutants. The results showed that the pollutants on Au NRs@TiO2 nanocomposites exhibited higher SERS activity and reproducibility compared to those on Au NR substrates without TiO2. In addition, the SERS substrate could be easily recycled by UV-assisted self-cleaning to remove residual analyte molecules. Malachite green (MG) and crystal violet (CV) were used as examples to demonstrate the feasibility of the proposed sensor for sensitive detection of environmental pollutants. The results showed that the limit of detections (LODs) for MG and CV were 0.75 μg/L and 0.50 μg/L, respectively, with recoveries ranging from 86.67% to 91.20% and 83.70% to 89.00%. Furthermore, the SERS substrate maintained its high SERS enhancement effect even after three cycles of use, indicating the potential of the method for detecting MG and CV in complex samples. The proposed sensor, with its high sensitivity, reusability, portability, and rapid detection capability, could have potential applications in on-site detection of environmental pollutants in complex sample matrices.