Surface ligand modified silver nanoparticles-based SERS sensing platform for ultrasensitive detection of the pesticide thiram in green tea leaves: roles of coating agents in sensing performance†
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Dao Thi
Nguyet Nga,
a
Nguyen Tuan
Anh,
a
Hoang
Van Tuan,
a
Ha Anh
Nguyen,
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Anh-Tuan
Le
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Abstract
Silver nanoparticles (AgNPs) have been regarded as a highly promising substrate for surface-enhanced Raman scattering (SERS) sensors. In this study, we focused on the electrochemical synthesis method by developing three kinds of AgNPs using three different electrolytes: citrate (e-Ag-C), oleic acid (e-Ag-O) and fish mint (Houttuynia cordata Thunb.) extract (e-Ag-bio). The as-prepared AgNPs were characterized and then employed as SERS substrates to detect the pesticide thiram. The obtained results show that e-Ag-O exhibits the best SERS performance. The effect of the coating agent was explained by chemical and electromagnetic enhancements (CM and EM). Although thiram could absorb onto e-Ag-C at the highest level, allowing its Raman signal to be best enhanced via the CM, the smallest interparticle distance of e-Ag-O could have resulted in the largest improvement in the EM. Using e-Ag-O to develop SERS-based sensors for thiram, we obtain the impressive detection limit of 1.04 × 10−10 M in standard samples and 10−9 M in tea leaves. The linear ranges are from 10−4 M to 10−7 M and from 10−7 M to 10−9 M, covering the maximum residue levels for plant commodities established by the United States Environment Protection Agency and European Food Safety Authority (2–13 ppm ∼7.7 × 10−6 M to 5 × 10−5 M).
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