Luís Pinto da Silva

Abstract [No abstract available]

Abstract Wastewater-based epidemiology (WBE) has emerged as a powerful approach for population-level monitoring of chemical exposure, health status, and disease transmission by analysing wastewater. Although chromatographic and molecular techniques remain the gold standard in WBE, their high cost, infrastructural demands, and limited suitability for decentralized and real-time monitoring motivate the development of complementary sensing technologies. In this context, optical (bio)sensors, particularly fluorescence-based platforms, have attracted increasing attention due to their high sensitivity, rapid response, and potential for on-site monitoring. This review discusses recent advances in fluorescent optical (bio)sensors for WBE, with a particular focus on carbon dots (CDs), including waste- and biomass-derived CDs produced via green synthesis as well as CDs obtained from commercial chemicals. The applicability of CD-based sensors to wastewater-relevant analytes is evaluated, highlighting current achievements, as well as existing limitations and challenges related to real-sample validation and the translation of these platforms into robust, field-deployable systems for their implementation in sustainable wastewater monitoring and public health surveillance.

Abstract Urban parks are essential to sustainable cities, providing climate regulation, supporting biodiversity, and offering vital spaces for recreation and overall well-being. At the same time, their soils can act as long-term reservoirs for persistent organic pollutants (POPs), reflecting decades of atmospheric deposition, diffuse urban emissions, and historical land-use practices. This review synthesises current knowledge on the occurrence, sources, and environmental behaviour of priority POPs, including OCPs, PCBs, PCDD/Fs, PBDEs, PFAS, and PAHs, in the soils of urban parks and gardens worldwide. Evidence from multiple regions reveals consistent patterns: urban parks accumulate complex mixtures of legacy and emerging contaminants, reflecting both historical inputs and ongoing urban activities. These contaminants primarily contribute to scenarios of chronic, low-level exposure through the ingestion of soil and dust, inhalation of resuspended particles, dermal contact, and, in some cases, dietary intake when food is cultivated in contaminated park soils. While such exposure pathways have been associated with a range of adverse health outcomes in toxicological and epidemiological studies, the presence of POPs in park soils does not imply that urban parks represent hazardous environments. Instead, it emphasises the importance of proportionate, evidence-based assessments within spaces that yield substantial net benefits to public health. Despite growing research interest, significant gaps remain, including limited understanding of mixture toxicity, insufficient data on temporal trends, a lack of harmonised monitoring strategies, and the absence of exposure scenarios specifically tailored to recreational soils. This review also examines major international and European regulatory frameworks and soil-quality guideline approaches relevant to urban and recreational soils, identifying mismatches between scientific evidence and regulatory practice. By integrating perspectives from environmental chemistry, toxicology, urban ecology, and policy, this review highlights the importance of targeted monitoring and context-specific management strategies to ensure that urban parks remain safe, healthy, and equitable components of increasingly complex urban landscapes.

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 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.