Van-Tuan Hoang

Mn substitution in ZnCo ₂ O ₄ tuned redox properties and enhanced oxidase-like activity. Mn–O–Co centers promoted O ₂ activation and electron transfer. A colorimetric platform reliably detected ascorbic acid in juice, proving cation tuning for nanozymes.

Co-MnO₂ nanoparticles with oxygen vacancies and Mn/Co redox couples exhibit enhanced oxidase-mimicking activity. This highlights Co ion-doping as an effective strategy for performance improvement in nanozymes for colorimetric assays.

This study presents a visible light-enhanced electrochemical sensor for detecting furazolidone (FZD), a widely used antibiotic, using a magnetoplasmonic Ag@Fe₃O₄ nanoparticle (MagPlas NPs)-modified screen-printed electrode (SPE). Under visible light irradiation, the MagPlas-based electrochemical sensor demonstrates significantly enhanced sensitivity compared to its performance in the absence of light. This enhancement is attributed to multiple synergistic mechanisms, including photosensitization of MagPlas NPs, improved electron transfer kinetics, and increased adsorption capacity. The sensor exhibits a linear response to FZD concentrations over a wide range, achieving a low limit of detection (LOD) of 0.477 μM with visible light irradiation, demonstrating the sensor's high sensitivity. It also demonstrates good repeatability and anti-interference ability, and can be successfully applied for the determination of FZD in real milk samples. This electrochemical sensor offers a promising approach for rapid, sensitive, and reliable detection of FZD in various applications.

Nanozymes based on manganese oxide (MnO₂) are demonstrated to be promising probes in colorimetric sensing applications. In this study, the r-MnO₂/β-MnO₂ heterophase nanostructure was simply prepared by a calcination process with controllable temperature. The characterization of the nanostructured material was confirmed by SEM, UV–vis spectroscopy, Raman, TGA–DSC, and XRD analysis. The r-MnO₂/β-MnO₂ exhibits a remarkably good catalytic activity in the oxidation process of 3,3′,5,5′-tetramethylbenzidine (TMB) compared with the r-MnO₂ or Mn₂O₃ nanostructure owing to its heterophase junctions. The enhanced performance of the colorimetric sensor for ascorbic acid (AA) detection was investigated using the r-MnO₂/β-MnO₂ heterophase nanostructure as probe. The r-MnO₂/β-MnO₂ material enhanced the monitoring of AA in the wide linear range from 1 µM to 50 μM with a limit of detection of 0.84 µM. This work presents a promising and straightforward approach for the construction of MnO₂-based colorimetric sensor and their practical application in plant growth monitoring. Graphical Abstract

Silver nanoparticles (AgNPs) have been regarded as a highly promising substrate for surface-enhanced Raman scattering (SERS) sensors. In this study, we focused on the electrochemical synthesis method by developing three kinds of AgNPs using three different electrolytes: citrate (e-Ag-C), oleic acid (e-Ag-O) and fish mint (Houttuynia cordata Thunb.) extract (e-Ag-bio). The as-prepared AgNPs were characterized and then employed as SERS substrates to detect the pesticide thiram. The obtained results show that e-Ag-O exhibits the best SERS performance. The effect of the coating agent was explained by chemical and electromagnetic enhancements (CM and EM). Although thiram could absorb onto e-Ag-C at the highest level, allowing its Raman signal to be best enhanced via the CM, the smallest interparticle distance of e-Ag-O could have resulted in the largest improvement in the EM. Using e-Ag-O to develop SERS-based sensors for thiram, we obtain the impressive detection limit of 1.04 × 10⁻¹⁰ M in standard samples and 10⁻⁹ M in tea leaves. The linear ranges are from 10⁻⁴ M to 10⁻⁷ M and from 10⁻⁷ M to 10⁻⁹ M, covering the maximum residue levels for plant commodities established by the United States Environment Protection Agency and European Food Safety Authority (2–13 ppm ∼7.7 × 10⁻⁶ M to 5 × 10⁻⁵ M).

Introducing a rapid, color-changing assay for Cl⁻ detection in water, this study showcases high sensitivity, selectivity, and stability, suitable for both environmental and biomedical applications, and offers versatility in detecting various anions for on-site screening.

In this study, we investigate the role of graphene oxide (GO) on the analytical performance of MnO ₂ /GO/e-Ag nanocomposite-based SERS sensors for the detection of carbaryl pesticide.

The role of MnO ₂ in SERS enhancement of tricyclazole on MnO ₂ /e-Ag was described in terms of charge transfer. The relationship between the morphology of MnO ₂ nanostructures and the SERS sensing performance of nanocomposites was clarified.