A sensitive colorimetric nanoprobe based on gold nanoparticles functionalized with thiram fungicide for determination of TNT and tetryl

Water and soil pollution (especially by explosive residues) is a global environmental problem, and tackling with this problem involves the selective and sensitive development of analytical techniques for trace explosives detection. In this regard, a gold nanoparticles (AuNPs)-based colorimetric probe was developed for the determination of TNT and tetryl as nitro-explosives. Au-nanoparticles were synthesized and their surface was modified with a fungicide, tetramethylthiuram disulfide (thiram), having both Au-anchoring S-atoms and TNT/tetryl ligating tert-amine groups as charge donors. The prepared probe (AuNPs@Thr) rapidly aggregated as a result of donor-acceptor (D-A) interaction between the amine group of thiram and the nitro-groups of explosives (TNT and tetryl), resulting in a bathochromic shift in the characteristic surface plasmon resonance band of AuNPs@Thr. Detection and quantification limits (LOD and LOQ) for TNT and tetryl were found as 5 and 15 ppb (mu g L-1), respectively. Common soil ions (Cd2+, Fe2+, Fe2+, Mn2+, Zn2+, Mg2+, Cu2+, Al3+, Co3+, Ca2+, K+, Na+, Cl-, NO3-, SO42-, NO2-, and CO32-) did not interfere, and the explosive mixtures (comp B, synthetic comp B, and tetrytol) having TNT and tetryl constituents could be effectively analyzed with the proposed method. The method was validated against the reference LC-MS/MS method, applied to sandy soil samples contaminated with TNT and tetryl. Thiram as AuNPs -modifier was much cheaper than other aminothiols for probe manufacture, but could compete with them with respect to selectivity and sensitivity of nitro-explosives assay.