Surface selective binding of 2,5-dimercapto-1,3,4-thiadiazole (DMTD) on silver and gold nanoparticles: a Raman and DFT study

Abstract

The optimized structures of all possible Ag and Au complexes of DMTD and the Raman spectra of solid DMTD and its solution at pH 1.5 from 2000-3800 cm -1 region are included in the Supporting Information. SeeThe binding affinity of 2,5-Dimercapto-1,3,4-thiadiazole (DMTD) on noble metal silver (Ag) and gold (Au) nanoparticles (NPs) was investigated using the surface-enhanced Raman scattering (SERS) technique in combination with density functional theoretical (DFT) calculations. DMTD contains different anchoring groups; firstly the thiadiazole ring nitrogen atoms, secondly the ring sulphur atom, thirdly the thiocarbonyl sulfur atoms and fourthly the ring п electrons. SERS combined with DFT calculations provided useful insight into the interaction between the molecule and metal, thus, illustrating the active sites of DMTD and the metal substrates being directly involved in binding. Raman, SERS and DFT studies were further exploited to study the tautomeric conformations of DMTD present in solid, aqueous solution and on the Ag and Au NP surfaces. The Raman spectrum indicated the existence of mainly the dithiol tautomer in the solid state with little contribution from the dithione and the thione-thiol forms. The pH-dependent Raman study of DMTD in aqueous solution clearly demonstrated the existence of different tautomers of DMTD with the changes in acidity or basicity. The SERS study of DMTD on the Ag NP surface with support from DFT calculations clearly suggested the abundance of mainly the thiol-thiolate tautomer at neutral pH while the dithiol form was predominant at acidic pH. The concentrationdependent SERS study on the Ag NP surface at acidic pH, indicated the preferential existence of the dithione form at low concentrations while the dithiol form is predominant at higher concentrations. On the Au NP surface at acidic pH, the abundance of the dithiol tautomer with slight contributions from the thione-thiol and the dithione forms are indicated. The binding is mainly through the thiadiazole ring N atom in case of Ag NPs whereas it is from the thiocarbonyl or the thiadiazole ring S atom in case of Au NPs. This selective binding observed in case of DMTD may be further extended in designing novel plasmonic nanostructures.

Surface‐enhanced Raman scattering based sensing of trans‐urocanic acid, an epidermal photoreceptor using silver nanoparticles aided by density functional theoretical calculations

“…SERS has been proved to be a proficient method in the detection of trace amounts of molecules down to single molecule level, to study the metal–adsorbate interaction and elucidate the orientation of the adsorbate on the metal surface with the help of “surface selection rules.” Over the years, SERS technique has been used to detect various types of biomolecules such as amino acids, folic acid, glucose, and nucleic acids for the medical and diagnostic application and also used to generate the fingerprint spectra for the identification of various types of molecules present in aqueous environment at trace level concentration . Various SERS studies were carried to probe the molecule–surface interaction and to understand the orientation of molecules, the type of conformers adsorbed on the metal surface . SERS technique has also been exploited to study surface‐induced catalytic reactions and to probe the effect of silver nanoparticles (Ag NPs) on the sorption behavior of boroaluminosilicate glass …”

Corrosion protection of bronze using 2,5-dimercapto-1,3,4-thiadiazole as organic inhibitor: spectroscopic and electrochemical investigations

“…Literature survey on DMDT adsorption on Ag [27,29], Au [29,31] and Cu [31][32][33] From this study the following conclusions can be drawn:…”

“…In order to shed more light on these results, Raman bands are reported in table 3 with A and B species presenting the more intense bands at 1 mM and at 10 mM DMTD respectively, together with DMDT molecule ones and from literature those corresponding to monoanion (monothiolate form: DMTD -) [28], dianion (dithiolate form: DMTD 2-) [27,28] and Raman bands assignments [27][28][29][30].…”

Conformational Selectivity of Merocyanine on Nanostructured Silver Films: Surface Enhanced Resonance Raman Scattering (SERRS) and Density Functional Theoretical (DFT) Study

“…Traces of drugs ( Edwin et al, 2017 ; Kumar et al, 2019b ), toxic heavy metal ions ( Wang et al, 2016 ; Guselnikova et al, 2017 ; Chadha et al, 2021a ), insecticides ( Dissanayake et al, 2019 ; Mane et al, 2020 ; Chadha et al, 2022 ), etc. can be detected using SERS, which also provides valuable structural and vibrational information pertaining to the metal-analyte interaction ( Thomas et al, 2013 ; SenGupta et al, 2014 ; Maiti et al, 2015 , Maiti et al, 2016 ; Das et al, 2019 ; Mirajkar et al, 2020 ). The advantages of RRS and SERS can be combined in surface-enhanced resonance Raman scattering (SERRS) ( Biswas et al, 2006 ; Biswas et al, 2008 ; Kitahama and Ozaki, 2016 ; Nicolson et al, 2018 ; Litti et al, 2020 ) technique that displays very high sensitivity and selectivity.…”