Peroxidase Mimic Activity of Au–Ag/l-Cys-rGO Nanozyme toward Detection of Cr(VI) Ion in Water: Role of 3,3′,5,5′-Tetramethylbenzidine Adsorption

Abstract

This study demonstrated the adsorption behavior of 3,3′,5,5′-tetramethylbenzidine (TMB) on graphene oxide (GO) and L-cysteine functionalized reduced graphene oxide (L-Cys-rGO) sheets for the first time. To investigate the adsorption phenomenon of TMB on GO and L-Cys-rGO sheets, the effect of different pH values, adsorbent concentrations, and adsorption times were explored. The abundant hydroxyl groups contained on the GO surface has played an eminent role in TMB adsorption. The presence of the −SH functional group in the L-Cys molecule facilitates the π−π* and hydrogen bonding interaction between the L-Cys-rGO surface and TMB which results in efficient adsorption. On the basis of this finding, L-Cys-rGO decorated with bimetallic Au−Ag nanoparticles (Au−Ag/L-Cys-rGO) is utilized as peroxidase mimic activity for the TMB oxidation in the presence of H 2 O 2 . The adsorption of TMB on the catalytic surface is essential for the formation of blue color oxidized product (oxTMB); moreover, in the presence of Cr(VI) ion, it promotes the decomposition of H 2 O 2 to •OH radicals which enhances the TMB oxidation rate. On the basis of this mechanism, the proposed colorimetric probe has been utilized for selective and sensitive detection of Cr(VI) ions in aqueous medium up to the lower concentration of 26.39 μM. This work establishes the presence of L-Cys on a graphene oxide surface (L-Cys-rGO) which controls the growth of bimetallic Au−Ag nanoparticles and also helps in the adsorption of TMB on the catalytic surface. Thus, bimetallic Au−Ag nanoparticles-decorated on L-Cys functionalized GO opens a new path for easy naked eye colorimetric detection of environmentally toxic metal ions in an aqueous medium providing bright prospects in environmental monitoring.

Self-Catalyzed Surface Reaction-Induced Fluorescence Resonance Energy Transfer on Cysteine-Stabilized MnO2 Quantum Dots for Selective Detection of Dopamine

“…34 While 2900 and 1390 cm −1 may be assigned to the stretching vibration and deformation vibration peaks of C−H, 3400 cm −1 is the stretching vibration peak of O−H, 1044 cm −1 is the stretching vibration peak of C−S, and the peak at 1600 cm −1 is the deformation vibration peak of N−H. These functional groups come from cysteine, 35,36 and the facts demonstrated that cysteine may act as a capping agent to stabilize the MnO 2 QDs. These results suggested that the Cys-MnO 2 QDs have been successfully synthesized by the simple one-step ultrasonic method.…”

Colorimetric assay based on NiCo2S4@N,S-rGO nanozyme for sensitive detection of H2O2 and glucose in serum and urine samples

“…The co-doping of N and S on rGO nanosheets provides abundant functional groups to facilitate the interactions with TMB, thereby improving the catalytic efficiency. 46 Meanwhile, the large SSA of NiCo 2 S 4 @N,S-rGO increased the active sites of its precursor NiCo 2 S 4 . (2) Under irradiation of visible light, the electrons of NiCo 2 S 4 are excited at the conduction band (CB), holes are generated at the valence band (VB), and the transfer from CB to VB is promoted by N and S-doped rGO.…”

CuS and NiS Nanoparticle-Decorated Porous-Reduced Graphene Oxide Sheets as Efficient Peroxidase Nanozymes for Easy Colorimetric Detection of Hg(II) Ions in a Water Medium and Using a Paper Strip

“…After each catalytic cycle, oxTMB and Hg­(II) ions may present on the nanocomposite surface, and thus, the active sites of the nanocomposites are blocked. TMB molecules adsorb on the graphene-based nanocomposites through covalent interactions , and Hg­(II) ions can bind easily with the S-containing sites of TMS/p-rGO-based nanocomposites . Moreover, successive uses and washing of the nanocomposites cause agglomeration of nanoparticles due to the weakening of the van der Waals interactions between the counterparts and thus the catalytic active sites of the nanocomposites become fatigued, which leads to the decrease of catalytic proficiency of the reported nanozyme after each repeated cycle .…”