Highly Sensitive Electrochemiluminescence Detection of Mercury(II) Ions Based on DNA-Linked Luminol-Au NPs Superstructure

Advances in electrochemiluminescence luminophores based on small organic molecules for biosensing

Electrochemiluminescence (ECL) has several advantages, such as a near-zero background signal, high sensitivity, wide dynamic range, simplicity, and is widely used for sensing, imaging, and single cell analysis. ECL luminophores are the key factors in the performance of various applications. Among various luminophores, small organic luminophores exhibit many intriguing features including good biocompatibility, facile modification, well-defined molecular structure, and sustainable raw materials, making small organic luminophores attractive for the use in the ECL field. Although many great achievements have been made in the synthesis of new small organic luminophores, solving various challenges, and expanding new applications, there are almost no comprehensive reviews on small organic ECL luminophores. In this review, we briefly introduce the advantages and emission mechanisms of small organic ECL luminophores, summarize the main types, molecular characteristics, and ECL properties of most existing small organic ECL luminophores, and present the important applications and design principles in sensors, imaging, single cell analysis, sterilization, and other fields. Finally, the challenges and outlook of organic ECL luminophores to be popularized in biosensing applications are also discussed.

Functionalized layered double hydroxide with nitrogen and sulfur co-decorated carbondots for highly selective and efficient removal of soft Hg2+ and Ag+ ions

A facile composite was fabricated via direct assembly of nitrogen and sulfur co-decorated carbon dots with abundant oxygen-containing functional groups on the surface of the positively charged layered double hydroxide (N,S-CDs-LDH). The novel N,S-CDs-LDH demonstrates highly selective bindings (M-S) and an extremely efficient removal capacity for soft metal ions such as Ag⁺ and Hg²⁺ ions. N,S-CDs-LDH displayed a selectivity order of Ag⁺> Hg²⁺ >> Cu²⁺ >>> Pb²⁺ > Zn²⁺ > Cd²⁺ for their adsorption. The enormous capacities for Hg²⁺ (625.0 mg g^-1) and Ag⁺ (714.3 mg g^-1) and very high distribution coefficients (K_d) of 9.9 × 10⁶ mL g^-1 (C₀ = 20 mg L^-1) and 2.0 × 10⁷ mL g^-1 (C₀ = 20 mg L^-1) for Hg²⁺ and Ag⁺, respectively, place the N,S-CDs-LDH at the top of LDH based materials known for such removal. The adsorption kinetic curves for Hg²⁺ and Ag⁺ fitted well with the pseudo-second order model. For Hg²⁺ and Ag⁺, an exceptionally rapid capture with removal ∼100% within 80 min was observed (C_ions = 30 mg L^-1 and V/m ratio of 1000). The adsorption isotherms were well described using Langmuir isotherm. The N,S-CDs-LDH was successfully applied to highly efficient removal of Hg²⁺ and Ag⁺ from aqueous solutions.

A label-free electrochemical sensor for detection of mercury(II) ions based on the direct growth of guanine nanowire

A simple, sensitive and label-free electrochemical sensor is developed for detection of Hg(2+) based on the strong and stable T-Hg(2+)-T mismatches. In the presence of Mg(2+), the parallel G-quadruplex structures could be specifically recognized and precipitated in parallel conformation. Therefore, the guanine nanowire was generated on the electrode surface, triggering the electrochemical H2O2-mediated oxidation of 3,3',5,5'-tetramethylbenzidine (TMB). In this research, a new method of signal amplification for the quantitative detection of Hg(2+) was described based on the direct growth of guanine nanowire via guanine nanowire. Under optimum conditions, Hg(2+) was detected in the range of 100 pM-100 nM, and the detection limit is 33 pM. Compared to the traditional single G-quadruplex label unit, this electrochemical sensor showed high sensitivity and selectivity for detecting Hg(2+).

Multiple signal amplified electrochemiluminescent immunoassay for Hg2+ using graphene-coupled quantum dots and gold nanoparticles-labeled horseradish peroxidase

A multiple signal amplification strategy was designed for an ultrasensitive competitive immunoassay for Hg(2+). This strategy was achieved using graphene conjugated with a large number of CdSe quantum dots to enhance the basal signal and enormous horseradish peroxidase (HRP) labeled with gold nanoparticles (AuNPs) to consume the coreactant H2O2 generated in situ. The immunosensor was constructed by immobilization of coating antigen on poly(diallyldimethylammonium chloride)-graphene-CdSe composites (PDDA-GN-CdSe), and a strong electrochemiluminescence (ECL) signal was obtained. When the immunosensor was immersed in antibody-AuNPs-HRP composites, the ECL signal greatly decreased, which was ascribed to the bound enzyme on the electrode surface. The self-produced coreactant H2O2 was consumed by o-phenylenediamine in the presence of enzyme, effectively decreasing the ECL intensity from the quantum dots. The Hg(2+) in solution and the corresponding coating antigen competed for the limited antibody, and thus, the ECL intensity was linearly dependent on the logarithm of the mercury(II) concentration from 0.2 to 1000 ng mL(-1) with a detection limit of 0.06 ng mL(-1). The immunoassay exhibited good stability and accuracy and acceptable reproducibility, indicating that it provides a promising approach for the detection of trace mercury and other small molecular compounds in environmental samples.

Flow injection chemiluminescence immunoassay based on resin beads, enzymatic amplification and a novel monoclonal antibody for determination of Hg2+

A convenient competitive immunoassay of Hg²⁺ using carboxylic resin beads, specific monoclonal antibody and enzymatic amplification is proposed with flow injection chemiluminescence detection.