Pham et al. fabricate silver/gold alloy nanoparticles with controlled Ag:Au molar ratios by co-reduction of AgNO3 and HAuCl4 with trisodium citrate. Ag3Au alloy nanoparticles (three parts silver, one part gold) achieved the highest SERS activity with a LOD of 10^-11 M rhodamine B, an enhancement factor exceeding 10^10, and stable performance after one year of storage.
Key numbers
- LOD for rhodamine B by SERS: 10^-11 M using Ag3Au alloy nanoparticles (abstract).
- Enhancement factor: greater than 10^10 for the Ag3Au composition (abstract).
- Nanoparticle diameter: 40 to 60 nm for all alloy compositions (abstract).
- Optimal composition: Ag3Au (highest Ag content tested with stable alloy formation).
Methods (brief)
Ag/Au alloy NPs were synthesized by simultaneous reduction of metal salts with trisodium citrate at varying Ag+/Au3+ molar ratios, producing AgNPs, AuNPs, Ag3Au, AgAu, and AgAu3 compositions. SERS substrates were characterized by TEM, UV-Vis, and Raman spectroscopy. Rhodamine B at concentrations from 10^-11 to 10^-5 M was used as the model analyte.
Evidence fitness
Supports documentation of silver-gold alloy nanoparticles as SERS substrates with application to food dye detection. Rhodamine B is a banned synthetic dye sometimes used as a food adulterant; the analytical relevance to food safety is in dye detection, not silver analysis. No silver was measured in food.
Limitations
No food matrix validation; rhodamine B concentrations tested are well below food adulteration levels (the analyte is typically found at mg/kg levels when used as a food adulterant, not fM levels). Practical food sample application would require extraction and concentration steps.
Related evidence
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