Hexavalent Chromium as a Smart Switch for Peroxidase-like Activity Regulation via the Surface Electronic Redistribution of Silver Nanoparticles Anchored on Carbon Spheres

Abstract

Although some ions, due to their unique chemical properties, can regulate the enzyme-like activity of nanomaterials, it is still a huge challenge to explore the mechanism of regulation. Herein, we found that Cr 6+ (CrO 4 2− ) as a smart switch can significantly increase the peroxidase-like (POD-like) activity of silver nanoparticles (Ag NPs), which were anchored efficiently on carbon spheres (Cal-CS/PEG/Ag) using amino-modified poly(ethylene glycol) (PEG) as a bridge. Density functional theory (DFT) calculations demonstrated that the addition of Cr 6+ can not only adjust the surface electronic redistribution of Ag atoms but also improve the geometric structure of the adsorbed intermediate, which resulted in the optimization of free energy and change of bond lengths in the catalytic reaction process, increasing the POD-like activity of Cal-CS/PEG/Ag. Based on the Cr 6+ -increased POD-like activity of Cal-CS/PEG/Ag, we successfully constructed a visual sensor of Cr 6+ along with quantitative analysis by the UV spectrum. The sensor has good selectivity for other 29 interfering ions and molecules with a detection limit of 79 nM. In this work, the detailed mechanism of the Cr 6+ -increased POD-like activity of Ag NPs was studied and a new possibility for the rational design of ion visual sensors using nanomaterials was proposed.

Few-Shot Learning-Based, Long-Term Stable, Sensitive Chemosensor for On-Site Colorimetric Detection of Cr(VI)

“…In addition, the anti-interference ability of DPC/PAN/SG for selective determination of Cr­(VI) is excellent, under the optimum reaction conditions. The influence of coexisting ions (29 kinds − ) on the color and gray value change (Δ G ) on DPC/PAN/SG after the reaction with Cr­(VI) (10 mg/L), i.e., colorimetric determination, is not obvious (shown in Figure ).…”

Stabilized and Controlled Release of Radicals within Copper Formate-Based Nanozymes for Biosensing

“…These merits enable their diverse applications, ranging from biological analysis to disease diagnosis and the development of biomedicine. − Typical nanozymes capable of imitating the catalytic activity of peroxidase (POD) have been discovered since Yan’s group unexpectedly showed the intrinsic POD-like activity of magnetic Fe 3 O 4 nanoparticles . To date, POD nanozymes can be categorized into metal-based nanozymes (Pd, Au, Ag, etc. ), metal-oxide or sulfide-based nanozymes (Fe 3 O 4 , CeO 2 , MoS 2 , etc.…”

Synergistic Effect Improves the Response of Active Sites to Target Variations for Picomolar Detection of Silver Ions

“…30−34 23 In our previous work, Cr 6+ was used to regulate the electronic structure of polyethylene glycol (PEG) connected Ag, and the regulation of Cal-Cs/PEG/Ag enzymatic activity was realized to specifically detect Cr 6+ . 35 Although some exciting advances have been achieved by regulating active sites for chromogenic reactions, the performances of such colorimetric detections that are based on the regulation of nanozyme activity still have a lot of room to improve, because the response sensitivities between the analytes and the active sites of the nanozyme are always depressed. 35 The common characteristic of these existing nanozymes is that they generally very weakly interact with metal ions, due to nanozymes usually containing surface ligands and the low absorptivity of metal ions on solid substrates.…”

“…Actually, accommodating the active sites of the nanozyme to pander to the target ions, multiple ions, including Cr 3+ , Pb 2+ , Hg 2+ , Ce 3+ , and Cd 2+ , etc., have been achieved in colorimetric measurement. − Gao et al used a poly­(vinylpyrrolidone) (PVP)-capped Pt cube (PVP-Pt cube) as an artificial peroxidase to absorb Ag + on the surface, which inhibited the contact between the catalytic site and TMB/H 2 O 2 , achieving sensitive detection of Ag + . In our previous work, Cr 6+ was used to regulate the electronic structure of polyethylene glycol (PEG) connected Ag, and the regulation of Cal-Cs/PEG/Ag enzymatic activity was realized to specifically detect Cr 6+ . Although some exciting advances have been achieved by regulating active sites for chromogenic reactions, the performances of such colorimetric detections that are based on the regulation of nanozyme activity still have a lot of room to improve, because the response sensitivities between the analytes and the active sites of the nanozyme are always depressed .…”