Thioglycolic Acid FTIR Spectra on Ag2S Quantum Dots Interfaces

Abstract

The mechanism features of colloidal quantum dots (QDs) passivation with thioglycolic acid molecules (TGA) for cases of different luminescent properties is considered using FTIR. This problem is considered based on FTIR spectra analysis for various ionic forms of TGA. Experimental TGA molecules FTIR spectra is interpreted, basing on the data on modeling of TGA vibrational modes, realized in the framework of density functional method (DFT /B3LYP/6-31+G(d)) taking into account the vibrations anharmonicity of every functional group. This approach provides a significant improvement in the agreement between the experimental and calculated data. FTIR spectra of Ag 2 S/TGA QDs with exciton and recombination luminescence are differ from each other and B “freeB” TGA molecules. The ν ( S − H ) TGA peak (2559 cm − 1 ) disappears in FTIR spectra of Ag 2 S/TGA QD samples. This fact indicates the interactions between TGA thiol group and dangling bonds of Ag 2 S nanocrystals. Ag 2 S QDs passivation with TGA molecules leads to emergence ν a s (COO − ) (1584 cm − 1 ) and ν s (COO − ) (1387 cm − 1 ) peaks. It indicates TGA adsorption in ionic form. For Ag 2 S/TGA QDs with exciton luminescence we observed (a) significant low-frequency shift of ν s (COO − ) peak from 1388 cm − 1 to 1359 cm − 1 and high-frequency shift of ν a s (COO − ) peak from 1567 cm − 1 to 1581 cm − 1 ; (b) change in the ratio of intensities of ν a s (COO − ) and ν s (COO − ) vibrations. This feature is caused by the change in the symmetry of TGA molecules due to passivation of Ag 2 S quantum dots.For Ag 2 S/TGA QDs with recombination luminescence, the insignificant high-frequency shift of 7–10 cm − 1 for ν a s (COO − ) at 1567 cm − 1 and low-frequency shift of 3–5 cm − 1 for ν s (COO − ) at 1388 cm − 1 , probably caused by the interaction of thiol with Ag 2 S surface is observed. Using FTIR spectra, it was found that IR luminescence photodegradation is also accompanied by changes in the thioglycolic acid molecules, which capped Ag 2 S QDs. In the case of Ag 2 S QDs with exciton luminescence, the degradation process is non-reversible. It is accompanied by TGA photodegradation with the formation of α -thiol-substituted acyl radical (S-CH 2 -CO • ) TGA.

Charge Transfer Dynamics of Two-Dimensional Ruddlesden Popper Perovskite in the Presence of Short-Chain Aromatic Thiol Ligands

“…In the case of pure thiols, an S–H stretching peak is observed in the range 2550–2600 cm –1 , which noticeably diminishes upon coupling with RPP. This indicates deprotonation of the −SH group in the presence of the 2D perovskite nanoplatelets . The subsequent appearance of another peak at around 780 cm –1 can be ascribed to the Pb–S stretching vibration.…”

“…This indicates deprotonation of the −SH group in the presence of the 2D perovskite nanoplatelets. 51 The subsequent appearance of another peak at around 780 cm −1 can be ascribed to the Pb−S stretching vibration. This confirms the binding of the deprotonated thiols with the lead atom of PbBr 6 4− octahedra of 2D RPP in the three RPP-thiol samples.…”

Programmed self-assembly of enzyme activity-inhibited nanomedicine for augmenting chemodynamic tumor nanotherapy

“…2e). The weak absorption peaks at 2568 and 2684 cm −1 present in the TGA spectrum belong to the -SH group, 43 which disappear in the TGA–Cu NPs spectrum. This result reveals that the TGA–Cu NPs have been constructed by the coordination of a deprotonated -SH group with Cu ions, 44 in agreement with the appearance of the 1154 cm −1 peak, 45 which was accomplished at the first stage and served as the primary building block for micelle formation in the second stage.…”

One-pot fabrication of Ag @Ag2O core–shell nanostructures for biosafe antimicrobial and antibiofilm applications

“…The peaks at 2357 cm −1 and 1655 cm −1 prove the existence of O–H carboxylic acids 23 and OH bending, respectively 24 . The band at 1387 cm −1 assigned to O–H bend of carboxylate 25 . The absorption band on 675 cm −1 is due to Ag–O stretching mode, which corresponds to Ag–O vibration in Ag 2 O.Furthermore, the appearance of follower peak at 868.68 cm −1 corresponds to the metal–oxygen vibrations for the formation of (Ag@Ag 2 O) NCs 15 ; thus, synchronizing with the aforementioned XRD results; confirming the formation of (Ag@Ag 2 O) NCs.…”