Planar transition metal oxides SERS chips: a general strategy

Noble metal surface-enhanced Raman scattering (SERS) chips based on plasmonic nanostructures have been commercialized. However, replacing the complex and high-cost preparation method remains a challenge. In this case, the expansion of noble metal-comparable SERS materials for commercial chip applications is a fundamental issue. Non-metals fabricated using the chemical method have achieved SERS activity comparable to that of noble metals, but it is hard to obtain planar materials using this technique and therefore non-metal chips have not yet been developed. Herein, we systematically studied the possibility that transition metal oxides (TMOs) could rival noble metals for SERS activity. Nonstoichiometric group-IVB, VB and VIB TMOs materials were fabricated using a general strategy based on magnetron sputtering with a H-2 annealing treatment. The limit of detection was below 10(-9) M owing to the process of photoinduced charge transfer (PICT). For the first time, we obtained commercially viable non-metal SERS chips using a convenient and cheap physical method. A theoretical explanation of PICT proves that this technique can be used to achieve more SERS chips.