Herein, new carbon dots doped with nitrogen (N.C-dots) were fabricated from chicken feet bio-waste via facile pyrolysis method. It was utilized to determine diosmin (DIS) fluorometrically and electrochemically (dual-mode). Its fluorescence emission was decreased after DIS addition as a result of inner-filtration effect (IFE). In addition, DIS exhibited a redox activity on the carbon paste electrode (CPE) decorated with N.C-dots (N.C-dots/CPE), enabling its detection via electrochemical method. Different techniques were used to characterize the sensing interfaces. There was a linear decrease in the fluorescence emission of N.C-dots at λ_em. = 430 nm with increasing the amount of DIS over the range of 0.01–0.6 µg mL⁻¹, while there was a linear increase in the oxidation current (Ipa) of DIS with increasing its amount over the range of 0.1–12 µg mL⁻¹. The detection limits (LODs) were calculated to be 3.12 ng mL⁻¹, and 32.91 ng mL⁻¹ for the fluorometric and electrochemical methods, respectively. The as-synthesized sensor possesses many advantages including simplicity, cost-effectiveness, long-term stability, excellent sensitivity, and good selectivity. These advantages enabled the sensor(s) to be applied successfully for the dual-mode detection of DIS in human plasma samples with acceptable results.

This work presents a novel approach for the accurate determination of naringin (NAR) in grapefruit juice. In the proposed method, N-doped carbon dots were employed, which were synthesized via hydrothermal synthesis using eggplant peel food waste as a green precursor. Detection of NAR relied on measuring the probe's emission response, which exhibited a decrease at 430 nm in the presence of NAR. The bitterness caused by NAR in grapefruit juice significantly impacts customer acceptability and can lead to economic losses if its levels exceed a certain threshold. It was found that the fluorescence quenching method showed excellent linearity in the concentration range of 0.0–2500.0 ng mL⁻¹ (R² = 0.9990), with a remarkable limit of detection(S/N = 3) of 16.37 ng mL⁻¹. Furthermore, selective extraction of NAR from grapefruit juice samples was achieved using Amberlite IRA-400 ion exchange resin. The adsorption parameters were carefully selected, and adsorption isotherm models were evaluated to determine the adsorption mechanism. The efficacy of the developed method was demonstrated by its successful application in determining NAR levels in grapefruit juice at various stages of maturity. This study demonstrates the potential of the proposed method as a reliable and efficient tool for accurately determining NAR in grapefruit juice.

A novel and simple hybrid sensor was constructed for the electrochemical sensing of ciprofloxacin (CPX) and metanil yellow (MEY). The sensor consists of fired brick microparticles (FB) modified with a thin film of poly(pyrrole) (PPy), which were used as a modifier for carbon paste electrode (CPE). Adding HCl to FB (which is predominantly made of Fe₂O₃) resulted in the release of Fe³⁺ ions, which aided in the oxidative polymerization of pyrrole monomer. The polar groups and aromatic rings found in the composition of PPy@FB provide more anchoring sites for adsorption of CPX and MEY, facilitating their electro-chemical oxidation. Under optimum conditions, the anodic peak currents (Ipa) showed a linear increase with increasing the concentration of CPX over the concentration range of 0.011–16.0 µmol/L and MEY in the range of 0.012–16.0 µmol/L. Limit of detections (LODs, S/N = 3) were calculated as 0.0035 µmol/L and 0.0042 µmol/L for CPX in milk and water samples, respectively. LOD for MEY in turmeric and water samples were 0.0032 µmol/L and 0.0036 µmol/L, respectively. The advantages of the as-fabricated sensor compromise greenness, simplicity, low-cost, reproducibility, sensitivity, selectivity, and adequate stability. The fabricated sensor was efficiently applied to detect CPX and MEY in different matrices including industrial water, milk, and turmeric samples with satisfactory recoveries % and low RSDs values.