Controlled depositing of silver nanoparticles on flexible film and its application in ultrasensitive detection

Surface-enhanced Raman scattering (SERS) has been proven to be a powerful analytical tool for the detection of trace molecules because of its integration of high sensitivity, unique spectroscopic fingerprint, and non-destructive data acquisition. However, the lack of reliable, stable, well-defined, and uniform SERS substrates impedes their further practical applications. Herein, we have developed a SERS-active substrate based on a flexible and stable polymer (PDMS) film loaded with nanoparticles for ultrasensitive Raman signal readout and trace detection of pesticide residues in agricultural products and environments. By controlling the deposition of Ag nanoparticles, tremendous Raman enhancement can be achieved due to numerous hot spots generated among the Ag nanoparticles on the PDMS composite film. The flexible SERS film can be employed to detect rhodamine 6G (R6G) with an enhancement factor (EF) of 3.37 x 10(11) and the pesticide thiram in commercial grape juice with a detection limit of as low as 0.1 mu m (0.03 ppm), which is considerably lower than the maximum residue limit (MRL) of 7 ppm in fruit prescribed by the U. S. Environmental Protection Agency (EPA). Furthermore, spiked detection indicated that the AgNP-PDMS flexible film can be used to monitor thiram in commercial grape juice and natural lake water without further treatment. Therefore, the AgNP-PDMS flexible film enhanced Raman spectroscopic technique offers great potential for practical applications in the on-site monitoring and assessment of pesticide residues in agricultural products and environments.