Carlos M. Pereira

Abstract The presence of emerging organic contaminants in water and effluents, including antibiotics, poses significant environmental and health risks. Moreover, while photocatalysis is a promising approach for their removal, the inefficient utilization of natural sunlight by common photocatalysts limits its large-scale use. This work demonstrates the enhanced sunlight-driven photodegradation of the antibiotic Ciprofloxacin (CIP) using a nanocomposite composed of carbon dots (CDs) and TiO2 (NC50:50). The CDs were obtained from corn stover, a major agricultural waste product. Initial testing was performed under artificial solar radiation: CIP was virtually fully degraded within 20 min, with a rate constant of 0.2372 min(-1) and a 217% enhancement of catalytic activity over commercial TiO2. Validation under real-world irradiation conditions was subsequently made by performing photocatalytic assays under natural sunlight on different days under diverse meteorological conditions. The performance of NC50:50 was retained, degrading CIP within 30 min under natural conditions. Notably, while degradation by-products were identified under both artificial and natural sunlight, they were subsequently photodegraded by the nanocomposite under these conditions. This enhanced performance was attributed to a combination of effects resulting from CDs' incorporation, namely, improved absorption of visible light, enhanced charge separation, and increased specific surface area. Furthermore, the addition of CDs resulted in changes in the reactive species generation profile, which can alter the available degradation pathways. Thus, this study provides insight that can be useful for strategies aimed at the rational design of sunlight-active TiO2-based photocatalysts with tunable surface reactivity.

Abstract Over the past few decades, ionic liquids (ILs) have gained attention as electrolytes, although concerns about their environmental persistence and toxicity challenge their status as green solvents. In this framework, choline chloride (ChCl) offers a more sustainable alternative due to its low toxicity, biodegradability, and cost-effectiveness. Although ChCl has a high melting point, its combination with hydrogen bond donor compounds (HBDs) can result in liquid mixtures at much lower temperatures, known as deep eutectic solvents (DESs). This study presents a comparative evaluation of three ChCl-based DESs, glyceline, ethaline, and reline (obtained from mixtures of ChCl and glycerol, ethylene glycol, and urea), with a focus specifically on their potential as electrolyte candidates for supercapacitors. Using differential scanning calorimetry (DSC), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and nuclear magnetic resonance (NMR), we assess their thermal, electrochemical, and structural properties. All DESs displayed amorphous behavior and a strong tendency to remain liquid even at very low temperatures. Among them, ethaline showed the most promising electrochemical performance, exhibiting the lowest resistivity and the highest capacity.

Abstract This work aimed to develop a new indirect ELISA for detecting the soybean allergen Gly m TI in processed and complex food matrices and to investigate the influence of antibody batch variability on immunoassay performance. During method development, inconsistencies in Gly m TI detection prompted a comparative evaluation of several batches of anti-Gly m TI IgG using both the newly developed ELISA and an electrochemical immunosensor. The ELISA was optimised in terms of protein extraction, antibody concentration, and linear dynamic range, and successfully applied to model foods simulating biscuits, sausages, and cooked hams, achieving a limit of detection (LOD) of 1,000 mg/kg irrespective of matrix or processing. Given this limited sensitivity, antibody batch variability was further assessed across both ELISA and immunosensor. Antibodies obtained approximately at the same time showed comparable performance, whereas those acquired five years earlier differed substantially. In particular, antibodies of older batches (Ab1/Ab3) outperformed the most recent ones (Ab2/Ab4), exhibiting wider dynamic ranges, lower LOD (0.1 mg/kg), and requiring lower antibody concentrations. These results highlight the significant variability of commercial antibodies and its critical impact on immunoassay sensitivity and reproducibility in food allergen detection.

Abstract While heteroatom doping is widely used to enhance the fluorescence of carbon dots, the actual mechanism underlying this claimed enhancement remains unclear. Herein, we report a systematic comparison between nitrogen-doped carbon dots (N-CDs) and nitrogen/sulfur co-doped carbon dots (N,S-CDs) synthesized hydrothermally, with ethylenediamine and sodium thiosulfate as the N- and S-dopants, respectively. Contrary to expectations, the inclusion of the S-precursor significantly reduced the quantum yield by 63%, from 35.9% to 13.2%, while leaving the emission profile and response largely unchanged. Characterization assays revealed that S-doping in N,S-CDs was residual, whereas the surface oxygen content increased markedly, indicating surface oxidation. The data suggest that sodium thiosulfate acted not as a dopant but overall as an oxidant, generating oxygen-based surface defects that introduced nonradiative recombination pathways. Thus, our findings show that co-doping with this S-precursor can decrease the quantum yield by promoting surface oxidation and the effective formation of more oxidized N-CDs, rather than heteroatom incorporation and production of co-doped CDs. This decreasing effect on the quantum yield was also observed when using thiourea as the S-precursor. Future work should include the study of other common S-precursors. In conclusion, our research shows that specific heteroatom-based precursors can alter the optical characteristics of CDs through redox/surface-modification effects instead of actual compositional doping, and thus, claims based on heteroatom doping may need closer examination.

Abstract Food allergies are a growing global health concern, demanding reliable tools for allergen detection to ensure consumers' safety. This work proposes the development of sustainable carbon dots (CDs) as immunosensor bioreceptors for the sensitive quantification of soybean trypsin inhibitor (Gly m TI) in foods. CDs were synthesised via a green hydrothermal method using eucalyptus leaves as a precursor and integrated onto a gold electrode as a platform to enhance electron transfer, surface functionality, and antibody immobilisation. The resulting immunosensor, constructed with CDs-PAMAM-anti-Gly m TI IgG, exhibited good analytical performance, including a wide dynamic range (1 fg mL(-1) to 0.1 ng mL(-1)), a limit of detection (LOD) of 1 ag mL(-1) in buffer, and high specificity, as confirmed by adsorption isotherm modelling. Its applicability was further validated in complex non-/processed food matrices (dough/biscuits, and raw ham/cooked ham), where it maintained a robust performance (LOD <0.1 mg kg(-1)) regardless of matrix interferences and/or thermal processing effects. At this sensitivity level, the platform meets international food safety requirements, protecting more than 95% of soybean-allergic consumers worldwide. These findings demonstrate the potential of sustainable CDs-based nanointerfaces as eco-friendly, high-performance platforms for food allergen monitoring and future point-of-care diagnostics.