Carlos M. Pereira

Abstract Herein we report a visible-light-active photocatalytic nanocomposite (NC50:50) prepared from carbon dots (CDs) and TiO2 nanoparticles, which was applied to the photodegradation of organic dyes in water. The CDs incorporated corn stover, a major agricultural waste, and were prepared via hydrothermal treatment. Using a visible- light irradiation source and the dye methylene blue as a representative of the organic dyes class, we observed that a 374 % enhancement of the catalytic performance was achieved by adding CDs relative to bare TiO2. This was possible due to increased visible-light absorption and better photonic efficiency. Tests using reactive species scavengers indicated that three active species (superoxide anion, hydroxyl radicals, and electrons) were responsible for the photodegradation process, differing from bare TiO2 in which only the hydroxyl radical has a relevant role. Photocatalytic degradation was also observed toward Rhodamine B, Orange II and Methyl Orange. Finally, we performed a life cycle assessment (LCA) study to assess and analyse the associated environmental impacts of NC50:50 compared with other alternatives, which revealed that NC50:50 is the alternative resulting in the least environmental impacts. In summary, NC50:50 could, under visible-light irradiation, efficiently remove different organic dyes while incorporating organic waste materials and reducing the impacts associated with their use. We expect that this study provides a base for a more environmentally sustainable design of visible- light-active photocatalysts via waste upcycling.

Abstract Efficient and rapid detection of bacterial pathogens is crucial for food safety and effective disease control. While conventional methods such as PCR and ELISA are accurate, they are time-consuming, costly, and often require specialized infrastructure. Recently, electrochemical biosensors integrating graphene nanomaterials with bacteriophages-termed graphages-have emerged as promising platforms for pathogen detection, offering fast, specific, and highly responsive detection. This review critically examines all electrochemical biosensors reported to date that utilize graphene-phage hybrids. Key aspects addressed include the types of graphene nanomaterials and bacteriophages used, immobilization strategies, electrochemical transduction mechanisms, and sensor metrics-such as detection limits, linear ranges, and ability to perform in real matrices. Particular attention is given to the role of phage orientation, surface functionalization, and the use of receptor binding proteins. Finally, current limitations and opportunities for future research are outlined, including prospects for genetic engineering and sensor miniaturization. This review serves as a comprehensive reference for researchers developing phage-based biosensors, especially those interested in integrating carbon nanomaterials for improved electroanalytical performance.

Abstract The incorporation of lambda-cyhalothrin (LC) in lipid nanoparticles (LN) could be a sustainable strategy to increase its efficacy and decrease its hazard to the environment. The purpose of the present work was to perform the interaction between LC and LN after nanoencapsulation and to evaluate their effect on species from different aquatic trophic levels such as Aliivibrio fischeri, Raphidocelis subcapitata, Lemna minor, and Daphnia magna. LN loaded with LC (LN-LC) were produced by green and simple methodology without organic solvents using Precirol ATO5 (R) and Capryol 90 (R) as solid and liquid lipids, respectively, and soy lecithin and TEGO (R) Care as emulsifiers. The physicochemical interaction between LC and LN was assessed by differential scanning calorimetry (DSC), Fourier-transform infrared (FTIR), and X-ray, confirming that LC is associated with the lipid lattice of nano- particles, characterized by an amorphous matrix. The data from biological tests showed no or low toxicity of LNLC on the selected aquatic organisms. Thus, encapsulation in lipid-based nanoparticles may be a promising and sustainable choice for using this insecticide in agricultural practices, reducing its environmental risk.

Abstract This study presents an environmentally friendly approach for synthesis Ag-TiO2 composite using pulsed reverse current (PRC) electrodeposition from green electrolytes, specifically deep eutectic solvents (DESs). The combination of PRC and DESs offers better control over nanoparticle synthesis while eliminating the need for toxic or expensive precursors, representing a significant advancement in sustainable nanomaterial synthesis. Different electrochemical parameters were adjusted, and their influence on the structure and morphology of the composite was investigated using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). TEM analysis revealed that silver nanoparticles (Ag NPs) are attached to TiO2 nanopowder, with the coexistence of TiO2 and Ag further confirmed by XRD and XPS. The recorded UV-Vis diffuse reflectance spectra (DRS) displayed a broad peak in the range of 400 - 650 nm, associated with the localized surface plasmon resonance (LSPR) of Ag NPs on the semiconductor's surface. The photocatalytic activity of TiO2 nanopowder and Ag-TiO2 composite was evaluated based on the degradation of methyl orange (MO) dye under UV and visible light illumination. Our findings clearly demonstrated that the incorporation of Ag improved the photocatalytic efficiency. The mechanism of MO dye degradation was explored by using various scavengers, revealing that superoxide radicals (center dot O-2(-)) play a dominant role. Furthermore, the incorporation of Ag NPs significantly enhanced the antimicrobial activity of the oxide against both Gram-positive (B. subtilis) and Gram-negative (E.coli) strains.

Abstract Biomass-derived carbon dots (CDs) are gaining much interest in recent times, as they provide a sustainable option with abundant availability, a low cost and tunable luminescence. Herein, we report a simple green synthesis method to produce highly fluorescent CDs from Eucalyptus globulus leaves using the one-pot hydrothermal approach. The fabricated CDs exhibit strong blue fluorescence with an excitation and emission maxima of 320 nm and 445 nm, respectively. The highest quantum yield (QY) obtained was 60.7%. With the reported optical properties and biocompatibility, CDs can be looked at as a promising candidate for potential biosensing applications. Moreover, we employed a life cycle assessment (LCA) cradle-to-gate approach to study the environmental impacts of the synthesis strategy used for the fabrication of CDs. The results point out that citric acid is the main hotspot in CD synthesis, regarding environmental impacts in most categories. This justifies the introduction of biomass, which reduces the amount of citric acid, thus leading to a more sustainable synthesis strategy for fabricating CDs.