Carbon dots (CDs) emerged as a new class of carbon nanomaterials recognized for their exceptional water solubility, (photo)chemical stability, biocompatibility, and low toxicity. The versatility of fluorescent carbon-based nanomaterials underpins their deployment in light-emitting devices, photocatalysis, bioimaging, and sensing. In these applications, a high fluorescence quantum yield (QY_FL) is critical for achieving optimal performance. Notably, CDs can be produced from a wide variety of carbon sources, where converting organic waste into CDs offers a true circular-economy route. However, waste-based CDs typically exhibit QY_FL values below 20%, which severely limits their practical utility. Thus, a robust and reproducible synthesis procedure is required to deliver consistently high QY_FL, regardless of the waste precursor.

This study aimed to establish a simple upcycling strategy for transforming diverse organic waste into brightly fluorescent CDs via hydrothermal treatment. This procedure considers waste materials and citric acid as carbon precursors and ethylenediamine (EDA) as a nitrogen dopant. Optimization at 200 °C for 8 h using corn stover (CS-CDs_8h) set the core parameters. We then validated the procedure on spent coffee grounds, cork powder, and sawdust, which showed CDs with appreciable QY_FL, reaching up to ~40%. CDs were thoroughly characterized by AFM, XPS, FTIR, XRD, fluorescence, and UV–Vis spectroscopy. It is worth mentioning that these CDs displayed compatibility with human cell lines. Finally, a Life Cycle Assessment (LCA) demonstrated that these waste-based CDs are associated with lower environmental impacts when compared with CDs from commercial reagents. Thus, this study provides an efficient, environmentally responsible framework for upcycling a wide range of organic wastes into high-performance carbon dots without sacrificing fluorescence efficiency.

Acknowledgments

We thank the “Fundação para a Ciência e Tecnologia” (FCT, Portugal) for the following funding: UIDB/00081/2020 (CIQUP), LA/P/0056/2020 (IMS), project 2023.13127.PEX, and 2021.05479.BD (Sónia Fernandes PhD grant).

The arsenic contamination of surface and groundwater represents a worldwide environmental issue, mainly caused by arsenic mobilization from soils due to anthropogenic activities. Among various technologies, adsorption is a promising method for the removal of As(III)/As(V) due to its low cost, high efficiency, simplicity, and the possibility of regeneration.
Iron oxyhydroxide nanopowders exhibit remarkable adsorption capabilities due to their high surface area, abundant hydroxyl groups, strong arsenic affinity, low toxicity, and facile green synthesis.
In this study, three iron oxyhydroxides—akaganeite, ferrihydrite, and feroxyhyte— were synthesized via eco-friendly precipitation and characterized using XRD, TGA, N₂ physisorption, ELS, TEM, FTIR, Mössbauer spectroscopy, and DC magnetometry. Adsorption tests evaluated As(III) and As(V) removal under identical conditions, varying pH (2–8), arsenic concentration (10–500 mg/L), contact time (10–960 min), and competing ions. Total arsenic concentrations before and after adsorption were determined by ICP-OES.
Akaganeite removed nearly 100% of As(V) (C₀ = 100 mg/L) across all pH levels. Ferrihydrite showed high As(V) removal at pH 2 and 3 (100% and 94%), but performance dropped to 23% at pH 8. Feroxyhyte performed well at pH 2 (99%) and maintained 77–80% efficiency up to pH 6, then decreased sharply to 50% at pH 7 and 38% at pH 8. For As(III), akaganeite showed limited removal at pH 2 (64%) but improved (~80%) from pH 3 to 8. Ferrihydrite and feroxyhyte both maintained high As(III) removal (~90–96%). Per unit surface area, feroxyhyte had the highest As(III) uptake, followed by ferrihydrite and akaganeite; for As(V), akaganeite was most active, followed by feroxyhyte and ferrihydrite.
Due to the higher toxicity and mobility of As(III), its oxidation to As(V) combined with adsorption is a promising approach. Manganese-doped iron oxyhydroxides were synthesized to provide both oxidation and adsorption capabilities, and preliminary tests are ongoing.
These findings support the further development of Fe-oxyhydroxide and Mn-doped Fe-oxyhydroxide hybrid materials for practical application in real-world scenarios.

The modification of nanofiltration membranes plays a significant role in the performance of membranes for synthetic and environmental water samples. Specifically, varying the addition of monomers during the interfacial polymerization process enhances the permselectivity of heavy metal removal from water samples. Lead is one of the naturally occurring heavy metals utilized by many industries; however, its presence in water has harmful effects for the environment and human health. Therefore, the removal of Pb(II) from water is a critical societal concern. In this study, the addition of trimesoyl chloride (TMC) with different concentration loadings (0.1, 0.2, and 0.3 w/v%) was varied to enhance the morphological architecture, surface roughness, hydrophilicity, and permselectivity of the membranes. The enhanced morphological structure illustrated from the Scanning Electron Microscopy images elucidates the role of TMC addition. The Fourier Transform Infrared spectra confirmed the successful formation of nanofiltration membranes through the presence of amine and acyl chloride groups. Performance studies illustrated that NF3 (0.1 w/v% of TMC) achieved an optimal removal of salt rejections, with a removal efficiency of 50.91% for Na₂SO₄ and 12.67 % for MgCl₂ attributed to charge density and pore structure. Furthermore, NF3 showed the enhanced adsorption rate of Pb(II) removal attributed to the synergistic Donna exclusion effect and tailored surface chemistry. The maximum Langmuir adsorption capacity of NF3 was 8.8573 mg/L. Therefore, the tailored adsorptive PES/core–shell-Fe₃O₄/ZnO nanofiltration membranes showed an 87.09% Pb(II) removal efficiency, showing significant potential for removing other competing ions from environmental wastewater.

Micro- and nanoplastic pollution has emerged as a critical environmental issue over the past decades, with pervasive contamination detected in aquatic systems, soils, wildlife, and even human tissues. Despite growing concerns, research efforts have largely focused on model systems or localized studies, often yielding highly variable results due to seasonal fluctuations, differing sampling methodologies, and site-specific conditions. This variability complicates the assessment of contamination levels and hinders the development of effective mitigation strategies.

Our study provides a comprehensive evaluation of micro- and nanoplastic pollution in the freshwater systems of the Carpathian Basin, a region of significant ecological and economic importance in Central Europe. By analyzing water samples from multiple rivers across different seasons, we aim to establish a clearer understanding of contamination ranges, identify key sources, and assess spatial and temporal trends. Additionally, we evaluate the potential ecological and human health risks associated with plastic pollution in these waters.

Beyond environmental monitoring, this study also reviews policy and management solutions that could mitigate plastic pollution in the region. We discuss the effectiveness of existing regulatory frameworks, explore innovative waste management strategies, and highlight the need for regional cooperation to address transboundary contamination. By integrating scientific data with policy analysis, this work seeks to contribute to more informed decision-making and sustainable water resource management in the Carpathian Basin and beyond.

Nanotechnology is emerging as a transformative force in sustainable construction, advanced material development, and environmental health by enabling nanoscale modifications in building systems. Engineered nanomaterials significantly enhance mechanical performance, thermal insulation, and energy efficiency, contributing to reduced carbon emissions, optimized material utilization, and improved indoor environmental quality. In the post-pandemic context, nanotechnology has further demonstrated its relevance through antimicrobial coatings, photocatalytic surfaces, and nanoparticle-based air filtration technologies aimed at mitigating pathogenic transmission in built environments. However, the production and deployment of nanomaterials present considerable challenges, including high energy consumption, substantial manufacturing costs, and unresolved toxicological and ecotoxicological risks. Documented concerns include inhalation-related respiratory dysfunction, cardiovascular effects, and potential neurotoxicity, necessitating stringent exposure assessments and standardized regulatory oversight. Advances in green synthesis methods and continuous-flow microreactor technologies offer promising alternatives for scalable and environmentally sustainable production. A comprehensive life-cycle assessment is essential to evaluate long-term performance, occupational exposure, and end-of-life scenarios. Interdisciplinary collaboration between materials scientists, toxicologists, and urban health researchers is required to guide the safe integration of nanotechnologies. Embedding circular economy strategies, prioritizing low-impact manufacturing, and establishing harmonized international safety standards will facilitate the responsible application of nanotechnology in the transition toward energy-efficient, health-supportive, and ecologically sustainable urban systems.

Multilayer graphene oxide (mGO) was synthesized from the oxidation of graphite using a modified Hummers' method. Subsequently, mGO was functionalized with dimethyl sulfoxide (DMSO) and potassium thiocyanate to obtain the new thiol-functionalized multilayer graphene oxide (mGO-SH). Characterization analyses using Infrared Spectroscopy (FTIR), Raman Spectroscopy, X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Dynamic Light Scattering (DLS), and Thermogravimetric Analysis (TGA) were performed to unravell the properties of mGO and mGO-SH. Both materials were then evaluated as adsorbents for the organic contaminant furfural through a comparative approach. Batch studies on kinetics, equilibrium, thermodynamics, and adsorbent regeneration were conducted to investigate the affinity of mGO and mGO-SH for furfural. Initial adsorption assessment showed that graphene oxide was unable to adsorb furfural. After functionalizing mGO, it was found that the contaminant was adsorbed, and kinetic studies indicated that the system reached equilibrium after 5 minutes. The equilibrium adsorption capacity (q_e) was 636.93 mg.g⁻¹, and the kinetic constant k₂ was 0.01575 g.mg⁻¹.min⁻¹ for furfural. Moreover, the pseudo-second-order model best fit the experimental data. Equilibrium studies showed a maximum monolayer adsorption capacity of 722.12 mg.g⁻¹ for furfural, and the Langmuir–Freundlich isotherm provided the best fit for the adsorption in the evaluated systems. Thermodynamic experiments revealed that all systems were spontaneous [ΔGº < 0] and evidenced the physical nature of furfural adsorption by mGO-SH [ΔGº = -11.74 kJ.mol⁻¹]. Adsorbent recycling experiments showed that thiol-functionalized graphene oxide had a removal rate of over 40% after five cycles.

Due to their small size and high reactivity, ZnO nanoparticles (NPs) can increase yarrow yields and control worms, enhance the activity of mustard cells and improve their antioxidant capacity, and promote plant growth. Meanwhile, there are data showing that ZnO NPs may inhibit the root formation of plants toxic to wheat. Due to the wide variety of research methods, conditions, NPs synthesis and properties, it is impossible to fully analyze and predict the effects of NPs concentrations on plants.

This study explored the treatment of wheat seeds with different concentrations of engineered ZnO NPs with average particle sizes of 40 and 300 nm. After the treatment, we measured the germination energy and root/shoots length of young wheat seedlings.

The results showed that 40 nm ZnO NPs had a promoting effect on wheat seeds when the concentration of NPs was 1-100 mg per liter. At higher concentrations (100-1000 mg per liter), the inhibitory effect on wheat roots continued to increase. For 300 nm of ZnO, the promoting effect was smaller compared to that of 40 nm ZnO NPs. In contrast, the larger 300 nm ZnO NPs induced a consistently smaller promoting effect across the tested concentrations compared to the 40 nm particles, indicating that nanoparticle size played a critical role in determining biological activity and phytotoxicity thresholds. These findings underscore the necessity of precise size and concentration control in agricultural nanoparticle applications.

Nanotechnology offers promising solutions for the control of waterborne pathogens by enhancing disinfection treatments using specialized nanomaterials. This study explores whether coffee waste-based nanostructures (CNs) enhance water solar disinfection (SODIS) against Cryptosporidium parvum, a waterborne protozoan parasite that resists conventional treatments and is classified by the WHO as a reference pathogen. Coffee waste was carbonized at 600 °C for an hour, and CNs were obtained via pyrolysis and hydrogen peroxide treatment, followed by dialysis membrane removal. CNs were characterized by particle size and zeta potential. Quartz tubes containing several CNs concentrations (0.1, 0.4, 0.9, and 1.4 mg/mL) in distilled water were spiked with 2×10⁶ oocysts/mL of C. parvum and exposed to simulated solar radiation (40 W/m², 290–400 nm) at 40 °C under polyethylene terephthalate cover. Oocyst viability was assessed at 2, 4, and 6 hours through hsp70 mRNA quantification using reverse transcription qPCR with previous induction at 42 °C. After 6 hours, oocyst inactivation rates were 0.87±0.01, 1.71±0.06, 2.55±0.08, and 1.96±0.02 log reductions (LR) at CNs concentrations of 0.1, 0.4, 0.9, and 1.4 mg/mL, respectively, significantly higher than those observed in distilled water without CNs (0.60±0.09 LR). These findings highlight the improvement of the C. parvum inactivation by SODIS by using CNs, achieving ≥2 LR at a concentration of 0.9 mg/mL. The optimization of water treatment technologies could provide sustainable alternatives to conventional methods, addressing the challenges posed by resilient protozoan pathogens and contributing to better public health. At the same time, reusing coffee waste in a circular economy reduces environmental impact while promoting innovation.

Acknowledgments. This project was funded by the Autonomous Government of Galicia (grant ED431C 2021/26) and the European Union's Horizon 2020 research and innovation programme (grant 820718). S.D. was granted by a Doctoral Fellowship of the National Operational Programme Research and Innovation 2014-2020 (grant CCI2014IT16M2OP005).

The paper examines chitosan aspartate shell nanoparticles formed in situ in the process of counterion condensation using novel bioactive sol–gel precursors: silicon methyltriglycerolate (MeSi(OGly)₃), silicon dimethyldiglycerolate (Me₂Si(OGly)₂), silicon tetraglycerolate (Si(OGly)₄), and silicon tetrapolyethylene glycolate (Si[O(C₂H₄O)₉H]), as well as titanium tetrapolyethylene glycolate (Ti[O(C₂H₄O)₉H]). The diameter of nanoparticles in the freshly prepared dispersion increases in the series of sol–gel precursors Me₂Si(OGly)₂→Si[O(C₂H₄O)₉H]→MeSi(OGly)₃→Si(OGly)₄→Ti[O(C₂H₄O)₉H], with the lowest polydispersity for Si(OGly)₄ and the highest for Ti[O(C₂H₄O)₉H]. Si- or Ti- coated nanoparticles (excluding Me₂Si(OGly)₂) correspond to kinetically stable nanodispersions: the electrokinetic potential was within 35‒40 mV and the conductivity was 0.58‒0.73 mS/cm. Modification with Me₂Si(OGly)₂ led to abnormally high values of the ζ-potential of the nanoparticles and the conductivity of the system. It was found that dispersions of chitosan aspartate nanoparticles with a sol–gel shell exhibited surface activity. During two-year storage, Si(OGly)₄ -stabilized dispersions maintained stable size and stable electrochemical and surface properties. A slight decrease in particle size and an increase in polydispersity were observed during storage of the samples functionalized with the sol–gel precursor Si[O(C₂H₄O)₉H]; a significant decrease in the size and ζ-potential of particles were observed for Ti[O(C₂H₄O)₉H], while a significant increase in size, polydispersity, and surface tension were noted for MeSi(OGly)₃ and Me₂Si(OGly)₂. Silicon tetraglycerolate was identified as the optimal modifier for stable chitosan aspartate nanoparticles, with the resulting polysiloxane-stabilized particles exhibiting dual bioactivity: plant growth stimulation across taxa and antifungal action against soil pathogens.

Acknowledgment

This research was funded by a grant from the Russian Science Foundation No. 24-16-00172, https://rscf.ru/project/24-16-00172/.

Abstract:

Introduction:
Environmental pollution, especially of water resources with heavy metal ions, is of great concern. The removal of heavy metal ions from wastewater remains a challenge for scientific research. Polymer-based microsphere adsorbents are promising due to their design flexibility and chemical tunability, but classical synthesis methods often lack control over the morphology, porosity and wettability. In the current work, we introduce a new method for facile synthesis of polymer microspheres, namely Pickering emulsion polymerization technology (PemPTech) and utilize them as adsorbents for Cu(II) ion extraction and recovery from water.

Methods:
Polymer microspheres were synthesized by polymerization of w/o Pickering emulsions stabilized by surface functionalized silica nanoparticles with thiol groups. The water phase comprised of water and water soluble monomers, such as vinyl imidazole and methacrylic acid with varying amounts of ligands, crosslinkers or porogens. A homologous series of microspheres were prepared by systematically varying these components. Structural and morphological characterization was performed using FTIR and SEM, and the adsorption and desorption capacities of Cu(II) were evaluated via UV–vis spectrophotometry.

Results:
In this work, we highlight the versatility of the PemPTech. For example, by adjusting the chemical composition in terms of the relative ratio of the ligands, vinyl imidazole to methacrylic acid, we were able to fine tune the adsorption capacity of the adsorbent. The adsorbtion capacities were comparable or exceeding those of similar adsorbents obtained via alternative methods. Kinetic adsorbtion studies were performed, and isotherm profile were established for each adsorbent, indicating a good performance. The adsorbents were also tested for other divalent heavy metal ions.

Conclusions:
PEmPTech enables precise compositional and morphological tuning of polymer microspheres, offering a green and scalable route to high-performance adsorbents. This study provides critical insight into the design parameters governing metal ion uptake, laying the groundwork for applications in water purification and environmental remediation.