In this work, we developed a highly sensitive and reproducible electrochemiluminescent sensor based on a heterostructure of cadmium selenide quantum dots capped with 3-mercaptopropionic acid (MPA) + 3-morpholinoethanesulfonic acid (MES) (QDs CdSe) and carbon nitride nanosheets (g-C₃N₄) for the detection of H₂O₂ in lyophilized serum samples. To enhance the sensor sensitivity, g-C₃N₄ nanosheets were utilized as a platform to immobilize the QDs CdSe. An exhaustive characterization of the heterostructure was conducted, elucidating the interaction mechanism between QDs CdSe and g-C₃N₄. It was revealed that g-C₃N₄ acts as a hole (h⁺) donor, while QDs CdSe act as energy acceptors in a resonance energy transfer process, with the electrochemiluminescence emission originating from the QDs CdSe. The electrochemiluminescence intensity decreases in the presence of H₂O₂ due to the deactivation of the excited states of the QDs CdSe. This electrochemiluminescent sensor demonstrates exceptional performance for detecting H₂O₂ in aqueous systems, achieving a remarkably low limit of detection (LOD) of 1.81 nM, which is more sensitive than most reported sensors to detect H₂O₂. The applicability of the sensor was successfully tested where sub-µM levels of H₂O₂ were accurately quantified. These results highlight the potential of this electrochemiluminescent sensor as a reliable and pre-treatment-free tool for H₂O₂ detection in biochemical studies and human health applications.

This work investigates the photo-Fenton degradation of azo dyes in an aqueous medium rich in sodium dodecyl sulfate (SDS), using methyl orange (MO) as a model contaminant. Chemometric modeling was integrated with mechanistic analysis to elucidate the role of the micellar pseudophase in radical distribution, dye partitioning, and overall reaction efficiency. A sequential experimental design strategy was applied, combining fractional factorial design and response surface methodology (RSM) to evaluate the individual and interactive effects of key operational variables and determine the optimal operating conditions for maximum degradation efficiency. Under optimized conditions (pH 2.85, [H₂O₂] = 100 mM, [Fe²⁺] = 0.5 mM, [SDS] = 13 mM, [MO] = 0.01 mM), MO degradation reached 98.4% in 5 minutes. Spectroscopic and partitioning studies revealed a strong affinity of MO for the micellar interface, indicating preferential localization in a microheterogeneous environment. Radical scavenging experiments confirmed that hydroxyl radicals are the dominant oxidizing species in water, while the reduction observed in the presence of SDS suggested secondary radical pathways derived from the surfactant under micellar conditions. Kinetic analyses highlighted the role of intermolecular interactions and micellar compartmentalization in radical generation. The optimized system was successfully extended to other azo dyes, underscoring the potential of surfactant-rich organized media to enhance photo-Fenton reactions in complex aqueous environments.

Sterigmatocystin (STE) is a precursor of aflatoxin B1, the most potent carcinogenic mycotoxin. STE frequently found in grains, cereals, and their manufactured products. Its toxicological relevance and the absence of global regulatory limits highlight the need for analytical tools capable of detecting STE at ultratrace levels in complex food matrices. In this work, a highly sensitive electrochemiluminescent immunosensor was developed for the detection of STE in corn grain samples. The immunosensor platform was constructed by immobilizing a monoclonal anti STE antibody onto a graphitic carbon nitride (g-C3N4) film deposited on an indium tin oxide electrode. This operates under a competitive immunoassay format using a CdSe quantum dot–STE bioconjugate (CdSe@STE) as tracer. An electrochemiluminescence (ECL) enhancement effect based on ECL resonance energy transfer (ECL-RET) between g-C3N4 and cadmium selenide quantum dots (CdSe QDs) was observed and used to create an ultrasensitive immunoassay. Under optimized conditions, the immunosensor exhibited excellent analytical performance, with limits of detection and quantification of 9.77x10-7 and 2.96x10-6 ng mL-1 (sub fg mL-1), respectively, with a linear range of three magnitude order. The electrochemiluminescent immunosensor was successfully applied to the analysis of corn samples contaminated with STE, providing satisfactory recoveries and reproducibility values. Comparison with HPLC/UV–Vis analysis demonstrated an excellent correlation between both methods. These results position the developed ECL immunosensor as a powerful and practical alternative for the ultrasensitive determination of STE in corn samples.

This work investigates the photo-Fenton degradation of azo dyes in an aqueous medium rich in sodium dodecyl sulfate (SDS), using methyl orange (MO) as a model contaminant. Chemometric modeling was integrated with mechanistic analysis to elucidate the role of the micellar pseudophase in radical distribution, dye partitioning, and overall reaction efficiency. A sequential experimental design strategy was applied, combining fractional factorial design and response surface methodology (RSM) to evaluate the individual and interactive effects of key operational variables and determine the optimal operating conditions for maximum degradation efficiency. Under optimized conditions (pH 2.85, [H₂O₂] = 100 mM, [Fe²⁺] = 0.5 mM, [SDS] = 13 mM, [MO] = 0.01 mM), MO degradation reached 98.4% in 5 min. Spectroscopic and partitioning studies revealed a strong affinity of MO for the micellar interface, indicating preferential localization in a microheterogeneous environment. Radical scavenging experiments confirmed that hydroxyl radicals are the dominant oxidizing species in water, while the reduction observed in the presence of SDS suggested secondary radical pathways derived from the surfactant under micellar conditions. Kinetic analyses highlighted the role of intermolecular interactions and micellar compartmentalization in radical generation. The optimized system was successfully extended to other azo dyes, underscoring the potential of surfactant-rich organized media to enhance photo-Fenton reactions in complex aqueous environments.