Mercaptothiadiazole capped gold nanoparticles as fluorophore for the determination of nanomolar mercury(II) in aqueous solution in the presence of 50,000-fold major interferents.
The present work describes the determination of picogram Hg(II) using 2,5-dimercapto-1,3,4-thiadiazole stabilized gold nanoparticles (DMT-AuNPs) by a spectrofluorimetry method. DMT-AuNPs show emission maximum at 773 nm with excitation at 514 nm. They show a large stock shift (259 nm), narrow emission profile and good photostability. While adding 10 μM Hg(II) the red color solution of DMT-AuNPs changes to purple and the UV-visible spectrum of DMT-AuNPs band at 514 nm was decreased. This is due to aggregation of DMT-AuNPs and it was confirmed by high resolution transmission electron microscopy (HR-TEM). UV-visible spectra of DMT-AuNPs in the presence of nanomolar concentrations of Hg(II) do not show any significant changes at 514 nm. However, the emission intensity of DMT-AuNPs was enhanced during adding even at picomolar concentration of Hg(II) due to photoinduced electron transfer and metal binding-induced conformational restriction upon complexation. Based on the enhancement of emission intensity the concentration of Hg(II) was determined. The binding constant (K(A) = 2.6514 × 10(4) mol(-1) L) value suggested that there is a strong binding force between Hg(II) and DMT-AuNPs. The present fluorophore showed an extreme selectivity towards Hg(II). The emission intensity was increased linearly against a wide range of Hg(II) concentration from 1 × 10(-12) to 1 × 10(-7) M and a detection limit of 0.64 pg L(-1) Hg(II) (S/N = 3) was achieved for the first time using DMT-AuNPs by spectrofluorimetry method. The proposed method was successfully applied for the determination of Hg(II) in environmental samples. The obtained results were validated by ICP-AES.
Department of Chemistry, Gandhigram Rural Institute, Gandhigram-624 302, Dindigul, Tamilnadu, India.
N
N
Vasimalai
S Abraham
SA
John
D004785:Environmental Pollutants / Q000032:analysis* / Q000737:chemistry; D005456:Fluorescent Dyes / Q000737:chemistry*; D006046:Gold / Q000737:chemistry*; D008628:Mercury / Q000032:analysis* / Q000737:chemistry; D053768:Metal Nanoparticles / Q000737:chemistry*; D012996:Solutions; D013053:Spectrophotometry; D013830:Thiadiazoles / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
D004785:Environmental Pollutants; D005456:Fluorescent Dyes; D012996:Solutions; D013830:Thiadiazoles; D014867:Water; C012291:2,5-dimercapto-1,3,4-thiadiazole; D006046:Gold; D008628:Mercury