Selective and sensitive cation exchange reactions in the aqueous starch capped ZnS nanoparticles with tunable composition, band gap and color for the detection and estimation of Pb2+, Cu2+ and Hg2+

β-Cyclodextrin capped ZnS nanoparticles for CER-assisted colorimetric and spectrophotometric detection of Pb2⁺, Cu2⁺, and Hg2⁺ in an aqueous solution

Herein, simple, low-cost, and room-temperature synthesis of beta-cyclodextrin (β-CD) stabilized zinc sulfide nanoparticle (ZnS NP) through the chemical precipitation method has been reported for cation exchange reaction (CER) based colorimetric sensing of Pb2+, Cu2+, and Hg2+. Formation of β-CD stabilized ZnS NPs (ZnS@β-CD) was verified by physicochemical characterization techniques such as XRD, XPS, FE-SEM, and TEM. ZnS@β-CD NPs showed color change selectively for the metal ions Pb2⁺, Cu2⁺, and Hg2⁺ among the various metal ions including Sn2⁺, Cr³⁺, Mn2⁺, Fe³⁺, Co2⁺, Ni2⁺, and Cd2⁺. The solubility product of reactants and the transformed products are the reason for selective CER of ZnS@β-CD NPs towards Pb2⁺, Cu2⁺, and Hg2⁺ ions. ZnS@β-CD NPs dispersion revealed rapid color change from white to orange, black, and bright yellow on the addition of higher concentrations of Pb2⁺, Cu2⁺, and Hg2⁺ respectively. This color change is due to the formation of complete CER-transformed nanostructures such as PbS, CuS, and HgS in higher concentrations (10⁻1- 10⁻³ M) of corresponding metal ions. The partial CER altered products Zn1-x,PbxS, Zn1-xCuxS and Zn1-xHgxS were detected due to the appearance of pale color in the lower metal ions concentrations of 10⁻⁴ - 10⁻⁶ M. This CER assisted transformation was also monitored through spectrophotometric methods. Moreover, infrared spectroscopic analysis was used to testify the structure of CER transformed product. The synthesized ZnS@β-CD NPs act as an efficient CER-based sensor for distinguishing and determining Pb2⁺, Cu2⁺, and Hg2⁺ at different level concentrations in the aqueous solution.

A new benzothiazole azo dye colorimetric chemosensor for detecting Pb2+ ion

In this work, a new benzothiazole azo dye sensor (BTS) was synthesized, and its cation binding affinity was studied using the colorimetric method, UV-vis, and ¹H NMR spectral data. The results revealed that the sensor BTS exhibits a remarkable tendency for Pb²⁺ ion to perform spontaneous visual color change from blue (BTS) to pink (BTS + Pb²⁺), without any color change in the aqueous solutions of other cations such as Hg²⁺, Cu²⁺, Al³⁺, Ni²⁺, Cd²⁺, Ag⁺_, Ba²⁺, K⁺, Co²⁺, Mg²⁺, Na⁺, Ca²⁺, Fe²⁺, and Fe³⁺ ions. The observed selectivity could be due to the formation of the complex (BTS + Pb²⁺⁾, which led to a blue shift from 586 nm (BTS) to 514 nm (BTS + Pb²⁺) in the UV spectrum. The job's plot provided the stoichiometry ratio of the complex (BTS + Pb²⁺) to be 1:1. The limit of detection (LOD) of BTS for Pb²⁺ ion sensing was obtained at 0.67 µM. Additionally, the binding constant for BTS toward Pb ²⁺ ion was studied using the Benesi-Hildebrand equation. As a result of the BTS test paper strips investigations, it was found that the synthesized sensor BTS could be used as a rapid colorimetric chemosensor for the detection of the Pb²⁺ ions in the distilled, tap, and sea waters.

An ultrasensitive electrochemical sensor based on antimonene simultaneously detect multiple heavy metal ions in food samples

Here, we constructed a novel ultra-sensitive electrochemical sensor based on ZIF-67@antimonene (AMNFs) nanocomposites which are based on the first-principles density functional theory the adsorption properties of antimonene on heavy metal ions were studied for simultaneous determination of Cu²⁺, Pb²⁺ and Hg²⁺. The ZIF-67@AMNFs was prepared by using ZIF-67 MOF surface loaded with a large amount of antimonene sheet. Its morphology and crystal structure were characterized by Transmission electron microscope (TEM), Energy Dispersive Spectroscopy (EDS), X-ray diffractometry (XRD) and X-ray photoelectron spectroscopy (XPS). Functional ZIF-67@AMNFs due to its unique layered structure, large active surface area, strong adsorption capacity and good electrical conductivity. In addition, the adsorption capacity of the sensor electrode for Cu²⁺, Pb²⁺ and Hg²⁺ was effectively enhanced. The detection limits of Cu²⁺, Pb²⁺ and Hg²⁺ were 0.01 pM, 0.042 pM and 0.031 pM, respectively. The determination mechanism of Cu²⁺, Pb²⁺ and Hg²⁺ was further clarified based on the adsorption properties and electrochemical accumulation of antimonene on metal atoms. It has been successfully applied to the simultaneous determination of Cu²⁺, Pb²⁺ and Hg²⁺ in rice, sorghum, corn, milk, honey and tea samples, and has good practicability.

Starch-Assisted Synthesis of Bi2S3 Nanoparticles for Enhanced Dielectric and Antibacterial Applications

Starch [(C₆H₁₀O₅) _n ]-stabilized bismuth sulfide (Bi₂S₃) nanoparticles (NPs) were synthesized in a single-pot reaction using bismuth nitrate pentahydrate (Bi(NO₃)₃·5H₂O) and sodium sulfide (Na₂S) as precursors. Bi₂S₃ NPs were stable over time and a wide band gap of 2.86 eV was observed. The capping of starch on the Bi₂S₃ NPs prevents them from agglomeration and provides regular uniform shapes. The synthesized Bi₂S₃ NPs were quasispherical, and the measured average particle size was ∼11 nm. The NPs are crystalline with an orthorhombic structure as determined by powder X-ray diffraction and transmission electron microscopy. The existence and interaction of starch on the NP's surface were analyzed using circular dichroism. Impedance spectroscopy was used to measure the electronic behavior of Bi₂S₃ NPs at various temperatures and frequencies. The dielectric measurements on the NPs show high dielectric polarizations. Furthermore, it was observed that the synthesized Bi₂S₃ NPs inhibited bacterial strains (Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus) and demonstrated substantial antibacterial activity.

Remarkable Difference in Pre-Cation Exchange Reactions of Inorganic Nanoparticles in Cases with Eventual Complete Exchange

Postsynthetic modification of inorganic nanoparticles (NPs) involving appropriate cation pairs at or near ambient conditions can exchange their spatial positions. The characterization of final products from these reactions although attracted...

Optimal control of the compositions, interfaces, and defects of hollow sulfide for electromagnetic wave absorption

The aimlessness in the selection of dielectric absorbing materials and the regulation of complex permittivity consumes time and resources. It is an effective way to construct electromagnetic wave (EMW)-absorbing materials dominated by dielectric loss to select materials and adjust complex permittivity based on theory. With sulfide as an example, a hollow ZnO/ZnS composite was constructed using ZnO as a hard template. Subsequently, based on the diverse binding ability of Cu and Zn ions to S ions, the compositions, interfaces, and defects of the sample were simultaneously regulated. There was competition and synergy between the relaxation process caused by the defects and interfaces and the conductivity loss, resulting in the regulation of complex permittivity. Furthermore, the hollow structure effectively reduced the density of the material and improved the impedance matching ability of the sample. As a result, the effective absorption bandwidth (EAB) of the hollow nanoflower ZnO/ZnS/CuS composite reached 5.2 GHz (from 12.8 to 18 GHz) with a matching thickness of 1.59 mm. This method provides a direction for ameliorating the complex permittivity of EMW-absorbing materials dominated by dielectric loss to realize broadband absorption.