Tunable porous silver nanostructures for efficient surface-enhanced Raman scattering detection of trace pesticide residues

Analytical methods based on surface-enhanced Raman scattering (SERS) suffer from a lack of reproducibility and reliability, thus limiting their practical applications. Herein, we explore a simple and rational strategy that allows the controllable design and synthesis of uniform porous nanostructures with adjustable porosity without a hard template. By varying the synthetic parameters, silver porous nanostructures were formed with tunable porosity ranging from 20 nm to 400 nm. The as-synthesized silver porous nanostructures could serve as an excellent enhancing substrate for SERS sensing, and the SERS intensities were dependent on the pore size of the Ag samples. The Ag porous nanostructures can be employed to detect rhodamine 6G with an enhancement factor of about 1014 and the pesticide thiram in commercial orange juice with a detection limit of as low as 0.1 μm (0.03 ppm), much lower than the maximum residue limit (MRL) of 7 ppm in fruit prescribed by the U.S. Environmental Protection Agency. Furthermore, spiked analysis indicated that the Ag porous nanostructures can be used to monitor thiram in commercial orange juice and natural lake water without further treatment. Therefore, the Ag porous nanostructure enhanced Raman spectroscopic technique offers wider practical applications for the on-site monitoring and assessment of pesticide residues in agricultural products and environments.