Surface-enhanced Raman spectroscopy (SERS) is a useful analytical technique for detecting extremely small amounts of molecules. Herein, we designed a paper-based quasi-three-dimensional SERS substrate (P-SERS) that can provide potential to improve Raman analyses for food safety, pesticide poisoning, precision medicine, drug abuse and DNA/RNA testing. The sensitive, low-cost, flexible and disposable SERS substrate could be easily fabricated by physical deposition of gold nanoparticles array onto a filter paper. In this case, we are able to create non-continuous Au islands on the fiber surfaces, where the gaps between AuNPs can dramatically generate the high electric field to enhance Raman signal of target molecules.

In recent years, some studies demonstrate that three-dimensional substrates perform better than two-dimensional planer substrates. Three-dimensional substrates break the two-dimensional limitation and extend the hotspots into the third dimension along the z-axis. For example, papers intrinsically exhibit a quasi-three-dimensional morphology consisting of cellulose nanofibers and microfiber matrices. which significantly enhance the Raman signals of target molecules within the depth of focus of the Raman optical system. Thus, thanks to the enriched hot-spots and target molecules attributed to the increased Z-direction and concentrating effect, our P-SERS could perform a SERS enhancement factor up to 1010 and the detection limit of methylene blue is 1 pM. 

SERS is a useful analytical technique for detecting extremely small amounts of molecules. Over the past few years, SERS has been believed as a molecular fingerprint technique and widely applied in health and environment monitoring. 
Our sensitive (~pM), low-cost (~300 NTD), stable (> 6 months) flexible and disposable P-SERS could significantly improve the detection techniques for food safety (Rhodamine B, Allura red, New Coccine, etc.), pesticide poisoning (Chlorpyrifos, Paraquat, Thiram, etc.), precision medicine (Vancomycin, Cefazolin, Levetiracetam, etc.), drug abuse (Methamphetamine, Mephedrone, MDPV) and DNA/RNA testing. For example, the level of Paraquat (> 1 ppm) in the serum from poisoning patients could be rapidly determined in 1 hour, with our P-SERS platform.

Cooperation project and technology transfer are welcomed.