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

Abstract

Heavy metal ions seriously threaten human health; even a trace of them can damage the renal, nervous, and immune systems irreversibly. Although established nanozyme-based colorimetric assays have been designed for the rapid detection of heavy metal ions, the general contained surface organic ligands of nanocatalysts and low absorptivity of metal ions on solid substrates might result in a weak effect on active sites and prevent the realization of their full detection potential. Here, we developed a nanozyme-based colorimetric sensor (CPM-Pt) made by pyrolysis of peat moss with preabsorbed traces of Pt ions to ultrasensitively detect Ag+. The calcination removes organic components and produces bare nanozymes that expose rich active sites. The strong protective effect from the porous carbon support enables the embedded Pt nanoparticles (Pt NPs) with a partially stable positive charge after pyrolysis (∼28% Pt2+ species). By the d 8–d 10 metal–metal interactions between Pt2+ (4f 145d 8) and Ag+ (4d 10), the high proportion of Pt2+ species on the surface of Pt NPs can readily capture/absorb Ag+. Subsequently, Ag+ accepts electrons from the support to form Ag atoms, which rapidly cover the peroxidase-like active sites of bare Pt NPs, weakening the activation of H2O2 to realize the response of Ag+. The colorimetric detection limit of Ag+ reached an unprecedented 1.1 pM, and the corresponding naked-eye color recognition is ultrasensitive to extremely low levels (100 pM).

Nanozymes: powerful catalytic materials for environmental pollutant detection and degradation

“…Introduction of Ag + can affect the intrinsic activity of these noble metal nanozymes, which has been utilized to detect Ag + with catalytic signal amplification. [87][88][89] As a typical example, Dai and co-workers developed a nanozyme (CPM-Pt) made by the calcination of peat moss with a pre-absorbed Pt precursor for the sensitive determination of Ag + . 89 The calcination procedure removed organic components and generated a bare nanozyme with abundant surfaces and sites.…”

Recent progress in nanozyme-based sensors for ion detection: strategies, trends, and challenges

“…For example, Dai et al achieved ultrasensitive colorimetric detection of Ag + by synergistic interaction between different components as well as active site modulation (Figure 6A). 62 In this work, natural peat moss (PM) leaves were selected as a carbon source, enabling the in-situ reduction and stabilization of Pt NPs on the formed support (carbonized peat moss, CPM). The porous structure and large surface area of CPM allowed more Pt NPs to be uniformly loaded, and the abundant active sites give the material good peroxidase activity and boost the detection performance.…”

Amino-Functionalized Hierarchical Porous Carbon Derived from Zeolitic Imidazolate Frameworks for Ultrasensitive Electrochemical Sensing of Heavy Metals in Water

“…Spectroscopic techniques, such as atomic absorption spectroscopy (AAS) and inductively coupled plasma–mass spectrometry (ICP–MS), have very high sensitivity and accuracy in metal analysis. − However, for the detection of metal ions, these methods have to be coupled with separation procedures. , Moreover, the spectroscopic methods often need professional operation and advanced equipment, impeding their wide applications, particularly in rapid, in situ , and real-time HMI detection. Alternatively, electrochemical sensors have attracted increasing attention due to their unique merits of rapid response, cost-effectiveness, good portability, and simple operation. − As the core module of the electrochemical sensor, electrode materials determine the electrochemical performances of the sensors. − For HMI detection by differential pulse stripping voltammetry (DPSV), the sensitivity of the electrochemical sensor is closely correlated to the deposition of adsorbed HMIs on the electrode surface.…”