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Particle size affects the toxicity and environmental fate of engineered nanoparticles (NPs). Although size effects have been widely studied in the experimental NP fate and toxicity literature, no numerical models published to date have attempted to identify and compare state-of-the-art particle modeling methods commonly applied in closely related fields. We compare four numerical frameworks for modeling changes in the size distribution of a NP suspension undergoing dissolution and aggregation: the Sectional Method (SM), Direct Simulation Monte Carlo (DSMC), the Direct Quadrature Method of Moments (DQMOM), and the Extended Quadrature Method of Moments (EQMOM). The SM and the DQMOM were faster or more accurate than the EQMOM and DSMC in nearly every trial. For cases simulating aggregation, the DQMOM took seconds to achieve solutions with ≤2% error, while the SM (a rigorous implementation of the most popular population balance method to date for NPs) took up to 1.5 hours. The SM was far more accurate than the DQMOM for dissolution test cases; however, up to 50 size bins were required to achieve ≤10% error. This raises questions about the validity of the current practice of using five or fewer bins in models of NP fate in rivers. Because runtimes become prohibitive as environmental complexity and particle properties are added, the DQMOM is promising for field-scale models and models that describe NPs with complex morphologies or compositions, such as non-spherical NPs, coated NPs, and nanohybrids. MATLAB code for all models is provided in the ESI.

We have demonstrated the use of the inner lumen of halloysite nanotubes as a nanoconfined reactor for the synthesis of nanoscale inorganic materials. Selective modification of the lumen has been carried out using a chelating ligand like ethylenediaminetetraacetic acid (EDTA) which selectively binds only to the alumina surfaces of the tubes and thus facilitates the adsorption of iron and subsequently the formation of nanoscale iron oxide within the lumen of the clay nanotubes. Lumen modification followed by the formation of iron oxide in the clay nanotubes has been evidenced by several physical methods, authenticating the successful incorporation of EDTA as well as formation of α-Fe 2 O 3 nanorods inside the lumen and finally producing α-Fe 2 O 3 /HNTs nanocomposites that exhibit solar light-induced enhanced photocatalytic activity. This study represents the first demonstration of the selective modification of the halloysite lumen using a chelating ligand to direct the in situ synthesis of iron oxide nanorods. Thus, the selective lumen modification under mild conditions to produce novel inorganic–organic hybrid nanocomposites may open up a new direction in the frontier area of nanoconfined reactions and hence may impart a broader impact in the field of catalysis, environmental remediation and even in drug delivery.

To understand the dependence of activation processes of sludge carbons on CO 2 adsorption, five sludge carbons (SC 1 –SC 5 ) were prepared by direct pyrolysis, pyrolysis–citric acid (CA) activation, pyrolysis–(CA + ZnCl 2 ) activation, pyrolysis–(CA + ZnCl 2 + KOH) activation and pyrolysis–(CA + ZnCl 2 + KOH)–HF activation, respectively. It was unexpectedly found that the features of SC 5 were very different from the others. Its specific surface area reached as high as 2654 mg g ?1 , being 4.2, 12.0, 71.5 and 88.4 fold that of SC 4 , SC 3 , SC 2 and SC 1 , correspondingly. Moreover, many ultramicropores and C–F groups were formed, in addition to the intended desilication. These microstructural changes lead to a great adsorption capacity of 215.2 mg g ?1 for CO 2 , which was 2.5, 8.9, 26.9 and 40.6 fold that of SC 4 , SC 3 , SC 2 and SC 1 , respectively. The significant increase of the surface area was attributed to the combined activation effect of HF chemical etching on SC and the expansion of d 002 interlayers of SC due to the physical action of SiF 4 gas in HF activation. And, the enhancement of CO 2 adsorption was demonstrated to be due to the formation of extensive CO 2 -philic expanded interlayer space-type micropores and C–F functional groups in SC 5 activated by HF.

Cu-containing nanopesticides are increasingly being used as fungicides in modern agriculture . However, their fate, transport and toxicity in crop plants have been less studied. Here, we exposed 3 week-old cucumber plants cultivated in artificial media to different concentrations of a Cu(OH) 2 nanopesticide (0, 2.5 and 25 mg) for 7 d. The physiological and molecular responses were investigated. In order to elucidate the contribution of copper ions to the response, we also exposed the plants to CuSO 4 . Results showed that the Cu(OH) 2 nanopesticide did not reduce the photosynthetic pigment production. In contrast, 10 mg Cu ions induced a significant decrease in photosynthetic pigment levels (around 25%) and leaf chlorosis symptoms. Foliar exposure to 25 mg Cu(OH) 2 nanopesticide induced significant changes in mRNA levels of antioxidant and detoxification-related genes; 6 genes ( SOD , GPX4 , GPX , MDAR , POD , WRKY6 ) were up-regulated up to 9-fold, and one ( cAPX ) was down-regulated by 32%. The Cu(OH) 2 nanopesticide at both dose levels (2.5 and 25 mg per plant) decreased the transcript production of a stress-related gene ( DNAJ) by 40% and 80%, respectively. The up-regulation of the transcript levels of SOD, GPX4 , GPX , MDAR , POD , and WRKY6 and down-regulation of DNAJ was also observed in CuSO 4 treated plants (with increases of up to 7-fold), indicating that most of the responses are due to released copper ions. We postulate that the increased mRNA levels of antioxidants and detoxification enzymes reflect plant adaptation to over-generated reactive oxygen species (ROS) triggered by copper ions. The activated genes could serve as potential biomarkers of nanopesticide exposure and may be applicable to other plant/Cu nanopesticide interactions.

Graphene quantum dots (GQDs) are 0D materials belonging to the carbon-based family that present some interesting characteristics of graphene combined with a tunable bandgap emerging from their reduced size, which gives them final outstanding physical–chemical properties. Furthermore, GQDs can be combined with other materials to produce nanocomposites with remarkable properties and superior performance. In this review, we present a timely survey on how the structural characteristics and physical–chemical properties of GQDs enable their use in advanced composite materials for agricultural and environmental applications. Specifically, emphasis is given to GQD-based composites in the form of films, nanofibers, aerogels, and molecularly imprinted polymers. The unique properties of GQD nanocomposites are suitable for designing devices employed in: i) filtration membranes and adsorbent materials for contaminant removal; ii) optical devices and (bio)sensors with different transduction modes for detecting hazardous analytes including pesticides, heavy metals, antibiotics, and food contaminants; iii) and novel catalyst systems for degrading pollutants. Finally, current challenges and future prospects on industrial applications of GQD-based composites are also discussed.

This study explored the potential of ceria nanoparticles (CeO 2 NPs) to alleviate stress in hydroponic rice caused by low N (LN) and high N (HN) stresses. The N content in plants was measured after 3 weeks of treatment with CeO 2 NPs. The impact of CeO 2 NPs on plants under medium N (MN, a normal condition) was studied as a comparison. LN resulted in N deficiency while HN led to N excess in plants while impairing plant growth. CeO 2 NPs (100 and 500 mg L ?1 ) increased the N levels in roots and shoots under LN by 6–12% and 22–30%, respectively. However, under HN stress, 500 mg L ?1 CeO 2 NPs reduced the N levels in roots and shoots by 9% and 6%, respectively. CeO 2 NP treatment enhanced the activities of key enzymes involved in N assimilation, glutamine synthetase (GS), glutamine oxoglutarate aminotransferase (GOGAT) and glutamate dehydrogenase (GDH), accounting for the increased N content in plants under LN. Under HN, 500 mg L ?1 CeO 2 NPs downregulated the GS and GDH activity by 42% and 36%, respectively. CeO 2 NPs reduced oxidative membrane and DNA damage and enhanced plant tolerance to N-stress by regulating the antioxidant enzyme system and the levels of proline and phytohormones including gibberellin 3, abscisic acid, zeatin riboside and indole-3-acetic acid. However, when N is supplied normally, CeO 2 NPs caused oxidative stress in plants thereby impairing plant growth. A change of N conditions altered the root exudate composition and led to different extents of transformation of CeO 2 NPs at the root interface and different Ce uptake and translocation in plants. This study for the first time reported that CeO 2 NPs could act as an alleviator of N stress in rice, while it might be a risk when the N supply is normal.

Iron-based nanoparticles form the basis for a host of sustainable alternative technologies based on this earth-abundant, low-toxicity element that can adopt a variety of oxidation states, crystal phases, and functions. Control of size, shape, and phase stability is a challenge for many nano-iron-based technologies, especially those involving Fe 0 that is susceptible to oxidation under ambient conditions. This article presents a continuous method for hybridizing Fe-based nanoparticles with carbon in the form of graphene-encapsulated Fe-based particles with core–shell symmetry that allows flexible control of iron particle size, shape, and phase stability. The method uses FeOOH nanorods and graphene oxide as precursors, and subjects them to an aerosol-phase microdroplet drying and annealing process to yield a range of Fe/C nanohybrids whose structure can be controlled through adjustment of aerosol process temperature and post-synthesis thermal treatment conditions. We demonstrate that FeOOH nanorods can be successfully encapsulated in graphene, and transform during annealing into encapsulated Fe 3 O 4 or Fe 0 nanoparticles by reductive fragmentation, where the graphene nanosack acts as a carbothermic reductant. The hybrids are characterized by vibrating sample magnetometry and Cr( VI ) removal rates in aqueous media. The Fe 0 –graphene hybrids show high activity, good stability, and good recyclability in aqueous Cr( VI ) removal due to the effect of graphene encapsulation. The present work suggests this rapid and continuous synthesis method can produce stable Fe-based materials, and can be extended to other metal systems, where graphene encapsulation can induce in situ reduction of metal oxide precursors into zero-valent metal–graphene hybrids.

The analysis of the protein corona on (reduced) graphene oxides demonstrated that these nanomaterials preferentially adsorbed high-molecular-weight proteins through hydrophobic interaction. The counterintuitive observation that more reduced, and thus more hydrophobic, graphene oxides had lower adsorption capacities was attributable to the surface-functionality-determined, more significant aggregation of the reduced materials.

The widespread presence of fluorinated nuclear effluent (F-) in the nuclear fuel cycle encourages the efficient extraction of hexavalent uranium (U(VI)) under the interference of F-. Nano zero-valent iron (n-ZVI) is a promising material for U(VI) extraction but suffered from labor-intensive production and storage procedures. Herein, we reported on the in-situ ultrasonic texturization of commercial Fe powder for U(VI) extraction in F--containing wastewater to replace the n-ZVI. At various molar ratios of F-/U(VI), the uranium extraction efficiency of the commercial Fe powder under ultrasonic conditions sustained a high value of > 90% within 120 min. Moreover, the ultrasonic texturization of commercial Fe possessed a wide pH adaption from 2 to 9, which remarkably outperformed the reported n-ZVI at pH<4. The mechanistic study revealed that the Kirkendall effect of the reduction reaction and mechanical disturbance of the ultrasonication induced the surface texturization of the commercial Fe powder, leading to the in-situ construction of n-ZVI and thus continually provided reduction sites for U(VI).

The growing applications of carbon nanomaterials (CNMs) are speculated to exert potential risks to aquatic ecosystems. However, little is known about the response of aquatic microalgae to surface modified nanodiamonds (NDs), which could limit the safer design and scientific assessment for further application. Here, we comprehensively integrated phenotypic and transcriptional analyses to investigate the response of Chlorella pyrenoidosa to both graphitized nanodiamonds (GNDs) and oxidized nanodiamonds (ONDs). Results indicated that 50 mg L ?1 GNDs could induce higher growth inhibition with severe organelle damage and oxidative stress than the OND treatment. Intriguingly, extracellular polymeric substances (EPSs) stimulated by OND exposure alleviated the adverse effects. Meanwhile, the conventional global molecular response to surface modified NDs was meticulously disclosed to fill in the knowledge gap. Additionally, the photosynthetic mechanism, amino acid synthesis, protein synthesis and protein export were further investigated under OND treatment, confirming a positive correlation for the crucial strategy to mitigate the negative effect. The underlying mechanism response to GNDs/ONDs has been thoroughly and completely revealed, providing a novel insight for the estimation of ND surface modification and the apperception of aquatic environmental risk.