Ideal SERS substrates and rapid sampling are crucial for on-site detection of pesticide residues. In this work, silver nanoparticles and graphene oxide were successfully prepared on cellulose paper (Ag NPs/GO paper) using a screen printing technique. The screen printing ink containing graphene oxide and silver nanoparticles was orderly printed onto cellulose paper substrates by controlling the printing cycles to fabricate controllable SERS substrates in large batches for the detection of pesticide residues. It was found that for up to four cycles, the SERS effect increased with the number of Ag NP printing cycles and no obvious change was observed. The prepared Ag NPs/GO paper may exhibit a high enrichment ability due to the π–π stacking and electrostatic interactions of GO toward pesticide molecules. The results suggest that the high density of Ag NPs/GO on the prepared paper is enough for ultrasensitive SERS detection of thiram, thiabendazole and methyl parathion in complex surfaces with a low limit of detection of 0.26 ng cm⁻², 28 ng cm⁻², and 7.4 ng cm⁻², which are much lower than the maximal residue limits in fruit prescribed by the U.S. Environmental Protection Agency. Thus, the sensitive SERS detection of pesticide residues based on Ag NPs/GO paper offers great potential for its practical application in environmental analysis and food safety.

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.