SERS-active vertically aligned silver/tungsten oxide nanoflakes for ultrasensitive and reliable detection of thiram

As an emerging technique for rapid detection, Surface-enhanced Raman scattering (SERS) has received much practical attention. Here, we report a uniformly distributed silver nanoparticles on well-defined tungsten oxide nanoflakes hierarchical nanostructures (Ag/WO 3-x ) as flexible solid SERS substrate. The vertically aligned Ag/WO 3-x nanoflakes were prepared by in situ redox reaction without reductant additives, ensuring the clean surface and free of extra interferences with good signal-to-noise ratio. Using rhodamine 6G (R6G) as probe molecule, the enhancement factor of developed Ag/WO 3-x nanoflakes SERS substrate was found to be high as 2.41 × 10 7 with an ultrasensitive detection concentration of 10 -12 M. Additionally, Ag/WO 3-x nanoflakes SERS substrate exhibited good reproducibility and long-time stability. Meanwhile, the pesticide thiram with a 1.3 pM limit of detection (LOD) can be readily determined via developed SERS substrate. To illustrate the potential practical value of the prepared substrates, 2.4 ppb spiked thiram on apple peel surface were both successfully detected. Notably, the developed SERS substrates could be cut into small pieces for detecting trace chemical or biological molecules and the flexible utilization of substrates would be improved dramatically. As a result, vertically aligned Ag/WO 3-x nanoflakes with well-defined shape and hierarchical structure have great potential as solid SERS substrate in the field of fast detection and trace analysis.