Kinetic-photometric monitoring of the formation of MnO2 nanoparticles and their application to the determination of iodide

Selenium Hydride-Induced Oxidase-like Activity Inhibition of Amorphous/Crystalline Manganese Dioxide: Colorimetric Assay for Selenium Detection

Hydride generation-based optical sensors have achieved on-site visual selenium (Se) determination with high anti-interference capability, yet they rely on the change of single-color intensity with a narrow linear dynamic range. Herein, we combined selenium hydride (H2Se)-induced activity inhibition of a manganese dioxide (MnO2) nanozyme with different degrees of 3,3',5,5'-tetramethylbenzidine (TMB) oxidation to realize sensitive multicolor visual detection of Se(IV). Due to its high oxidase-like (OXD-like) activity and sensitive response to H2Se, amorphous/crystalline manganese dioxide (ac-MnO2) was selected to form the headspace single droplet for microextraction and recognition. Via headspace redox reaction with H2Se, ac-MnO2 was reduced into low valence accompanied by in situ generation of Se nanoparticles, leading to the formation of a Se-MnOx aggregate. The experimental results and theoretical calculation indicated that, compared with MnO2, Se-MnOx had decreased active sites for adsorbing O2 to generate •O2-, resulting in the nanozyme activity inhibition that was totally dependent on Se(IV) concentration. The implementation of this strategy enabled accurate Se(IV) detection with a linear range from 10 to 600 μg L-1 and a limit of detection of 1.8 μg L-1. The portable smartphone-based detection for real sample analysis further demonstrated that this assay can be an easy, convenient, and intelligent tool for on-site selenium determination.

Two donor–acceptor (D–A) type Zn(ii) complexes as fluorescent probes for highly selective detection of iodide

Two noval donor-acceptor (D–A) type Zn(ii) complexes ([Zn₂(L¹)₂(MeCN)(MeOH)]·(MeCN) (1) and [ZnL²(H₂O)] (2)) were obtained and selectively detected iodide as fluorescent probes.

Facile method for iodide ion detection via the fluorescence decrease of dihydrolipoic acid/beta-cyclodextrin protected Ag nanoclusters

In this work, novel photoluminescent Ag nanoclusters (Ag NCs) with red emission are synthesized and successfully used for detecting iodide ion (I^-). The dihydrolipoic acid (DHLA) is used as the stabilizing agent and beta-cyclodextrin (β-CD) is used as the auxiliary stabilizing agent. DHLA and β-CD are combined with Ag atoms by the formation of AgS bonds and hydrophobic interaction, respectively. Functionalization of β-CD endows good photoluminescent properties and solubility in water to the Ag NCs. The obtained DHLA and β-CD-protected Ag NCs (DHLA/β-CD-Ag NCs) are spherical and display a dispersed state. However, the DHLA/β-CD-Ag NCs are aggregated in the presence of I^-, accompanied by the decrease in their fluorescence intensity. Because the integrity of β-CD cavities is retained on the surface of DHLA/β-CD-Ag NCs, which preserves their capability for I^- host-guest recognition, the DHLA/β-CD-Ag NCs combine with I^- through the formation of inclusion complexes. Based on this phenomenon, the prepared DHLA/β-CD-Ag NCs can be designed as a novel fluorescent probe for I^- detection. The limit of detection (LOD) is calculated as 0.06 μM, indicating that it is an ideal probe for I^- detection in practical applications.