Synthesis of mercaptothiadiazole-functionalized gold nanoparticles and their self-assembly on Au substrates

Abstract

Gold nanoparticles (AuNPs) stabilized with mercaptothiadiazole ligands, 2,5-dimercapto-1,3,4-thiadiazole (DMT), 5-amino-2-mercapto-1,3,4-thiadiazole (AMT) and 5-methyl-2-mercapto-1,3,4-thiadiazole (MMT), were prepared by the reaction of the respective ligands with HAuCl(4) and NaBH(4) in an aqueous medium. TEM images show that the average size of AuNPs was 6.5 ± 0.5 nm, irrespective of the capping ligands. The colloidal solution of both DMT-capped AuNPs (DMT-AuNPs) and AMT-capped AuNPs (AMT-AuNPs) were highly stable for several months. However, several changes were noticed for MMT-capped AuNPs (MMT-AuNPs) after 2 h from its formation. The SPR band intensity at 518 nm decreases and the narrow SPR absorption band slowly changes into a flat absorption pattern with a broad peak from 518 to 1000 nm which was accompanied by a colour change of the solution from red to purple and then blue and thereafter unchanged. The TEM image of MMT-AuNPs after 96 h shows that most of the spherical shape of the AuNPs assembled to form a nanowire-like structure. The observed changes may be due to the absence of a strong stabilizing force on the surface of the MMT-AuNPs. The amino and thiolate groups on the surface of the AMT-AuNPs and DMT-AuNPs, respectively, were directly self-assembled on Au electrodes. They exhibit excellent electrocatalytic activity towards the oxidation of AA by enhancing its oxidation current twice in addition to more than 200 mV negative shift in the oxidation potential in contrast to bare Au electrode.

Biosynthesis of gold nanoparticles using chloroplasts

“…These observations suggested that the (111) plane was the predominant orientation of as-prepared GNPs. 30 The selected areas electron diffraction patterns of the GNPs (Figure 2B), corresponding to the face-centered cubic crystalline structure, further corroborated the results of XRD measurement.…”

Hydrothermal assisted biosynthesis of silver nanoparticles from Streptomyces sp. GUT 21 (KU500633) and its therapeutic antimicrobial activity

“…A single peak observed at 1600.43 cm -1 corresponds to amide linkage and bending vibration of N-H groups of proteins, respectively where as in case of AgNPs spectra, the peaks observed at 1750, and 1631 cm -1 , represents the C=O stretch, -C=C stretch of esters and amide group respectively, which corresponds to heterocyclic compounds like proteins. This serves as support for proteins present in the supernatant extract as capping agents for the biosynthesized AgNPs [12,13]. It has been reported that proteins may bind to the nanoparticles either with the free amine groups or cysteine residues and cap the nanoparticles [8].…”

Biogenic synthesis and spectroscopic characterization of silver nanoparticles using leaf extract of Indoneesiella echioides: in vitro assessment on antioxidant, antimicrobial and cytotoxicity potential

“…The IR bands at *1709.83 and 1369 cm -1 are characteristic of C-O and C-O stretching modes, respectively, of the carboxylic group (Kathiraven et al 2015). The strong band at *1037 cm -1 arises from C-O-C and C-OH vibrations (Solomun et al 2004;Ankamwar et al 2005;Huang et al 2007;Kannan and Abraham John 2008). Earlier studies revealed that the absorbance bands at *1109 and 1726 cm -1 in curve were associated with the stretch vibration of -C-O and -C=C respectively (Zhu 2000).…”