Low temperature synthesis and SERS application of silver molybdenum oxides

Abstract

Ag_xMo_yO_z (Ag/α-MoO₃, Ag/h-MoO₃, Ag/β-MoO₃, Ag₂Mo₂O₇, and Ag₂MoO₄) nanomaterials are synthesized at relatively low temperature (80 °C) and with a short hydrothermal treatment time (3 h) using glucose (Glc) as a catalyst. Contrary to previous studies, it is possible to synthesize one of the Ag_xMo_yO_z binaries at 80 °C by altering the pH of the reaction media in the presence of glucose. In addition, further experiments indicate that Ag/h-MoO₃, Ag₂Mo₂O₇ and Ag/β-MoO₃ can be converted to Ag/α-MoO₃ which can also be synthesized from a reaction involving ammonium heptamolybdate tetrahydrate and AgNO₃ at room temperature using cysteamine in both methods. Characterization with UV-Vis, XRD and Raman spectroscopy reveals high purity of as-synthesized product. These synthesized products are finally used to fabricate SERS substrates by coating a silicon wafer with a mixture of silver nanoparticles (Ag NPs) and Ag_xMo_yO_z (Si@Ag/Ag_xMo_yO_z). The results show a good sensitivity and stability. In addition, it is also found that the SERS activity of Si@Ag/Ag_xMo_yO_z is higher than that of Si@Ag.