Electrodeposited Ag, Au, and AuAg nanoparticles on graphene oxide-modified screen-printed carbon electrodes for the voltammetric determination of free sulfide in alkaline solutions

• S2− was determined using voltammetry and nanoparticle (NP)-modified electrodes.
• Au, Ag, and AuAgNPs were formed via electrodeposition on the electrodes.
• Graphene oxide (GO) enhanced the NPs activity on S2− detection.
• The electrode performance is determined by the types of NP deposited on GO.

Free sulfide anion (S2−) in alkaline media was determined using cathodic stripping voltammetry (CSV) and a graphene oxide-modified screen-printed carbon electrode (SPCE/GO) electrodeposited with Ag, Au, or AuAg nanoparticles (NPs). Electrodeposition was achieved using cyclic voltammetry in dilute sulfuric acid containing AgNO3 and/or HAuCl4·4H2O in which thiourea was essential for stabilizing Ag+. The existence of GO resulted in higher density and more uniform distribution of NPs, compared with those electrodeposited on bare SPCE. The composite electrode SPCE/GO/AgNPs showed the greatest sensitivity but poorest reproducibility. The SPCE/GO/AuNPs, in contrast, showed the best reproducibility with a linear dynamic range of S2− from 6.25 to 400 μM and no significant interference from various inorganic anions and cations. EDTA, however, was essential to eliminate the interfering effects from metal cations. By co-depositing Au and Ag to form SPCE/GO/AuAgNPs, the sensitivity was significantly improved in contrast to SPCE/GO/AuNPs, and the reproducibility was approximately reserved. By using differential-pulse CSV (DPCSV), a linear dynamic range of 0.05∼1.5 μM was observed. A wider but two-segmented dynamic range, 0.5∼12.5 and 12.5∼312.5 μM, was obtained by using liner-scan CSV (LSCSV). SPCE/GO/AuAgNPs, however, showed a poorer resistance against metal cationic interferents, compared with SPCE/GO/AuNPs, although EDTA was used. This study reveals a facile approach of preparing sensitive modified electrodes for the determination of S2− in alkaline aqueous media.

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