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The transport of nanoplastics (NPs) in porous media has received a lot of attention, but the studies on the long-term release of NPs retained in porous media and the particle fracture during this process are seriously lacking. For filling this deficiency, we examined the individual or synergistic effects of surfactants, natural organic matters (NOMs), antibiotics, and bacteria on the desorption, long-term release, and particle fracture behaviors of polystyrene NPs (PS-NPs) retained in porous media. It was found that the change in hydrophilicity of PS-NPs dominated the long-term release of PS-NPs retained in porous media when surfactants were present. In the single system of surfactants and the dual system of surfactants and NOMs, the release of PS-NPs were improved owing to the increasing hydrophilicity of PS-NPs, although cationic surfactants also reduced the electrostatic repulsion between PS-NPs and porous media. Increasing antibiotic concentration reduced the electrostatic repulsion between PS-NPs and porous media to inhibit the release of PS-NPs. When bacteria were present whether containing antibiotics or not, the effects on roughness of PS-NPs dominated the release of PS-NPs. The effects of surfactants and NOMs on the PS-NP desorption were similar with the long-term release, with changes in hydrophilicity dominating the process. Whereas the effects of antibiotics and bacteria on the PS-NP desorption were different with the long-term release. Surfactants and NOMs in the presence of surfactants inhibited the fracture of PS-NPs by increasing the hydrophilicity of PS-NPs brought about the coating of water molecules on PS-NPs for protection. Antibiotics had no significant effects on the fracture of PS-NPs due to unaltered vertical forces on PS-NPs and no protective effect. Bacteria in the presence or absence of antibiotics inhibited the fracture of PS-NPs by coating PS-NPs retained in porous media to protect PS-NPs from fracture., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

Hyaluronic acid (HA) is a naturally polysaccharide that has been used for drug delivery, but is limited by low drug loading capacity and drug leakage in circulation. To improve drug delivery efficient, HA modified porous silica (pSiO 2 ) nanocarriers were successfully prepared for drug delivery and combining therapy. pSiO 2 nanocarriers have stable porous structure and high loading capacity, and pSiO 2 /HA nanocarriers would possess advantages of HA-based carriers and pSiO 2 nanoparticles. Herein, pSiO 2 nanocarriers were prepared by two-phase process, followed by embedding Ag 2 S QDs in the pore walls of pSiO 2 carriers, which render the carriers photothermal effect. pSiO 2 nanocarriers have size of 30 nm, large channels, and high loading capacity (29.3 %). To graft HA, a sensitive linker with alkyl amine and disulfide bond was conjugated on the surface of Ag 2 S/pSiO 2 nanocarriers by three-step reaction. After loading doxorubicin (DOX), HA was grafted via sensitive linker onto the surface of Ag 2 S/pSiO 2 carriers via the formation of amide bonds to seal the loaded drugs. The interaction between HA and CD44 confers the carrier targeting ability to cancer cells. HA coating can be degraded by hyaluronidase resulting in the release of internal cargo. The Ag 2 S/pSiO 2 /HA nanocarriers performs responsive drug release and combining photothermal chemotherapy., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Immunotherapy has achieved remarkable research outcomes and shows the potential to cure cancer. However, its therapeutic response is limited in terms of the immunosuppressive tumor microenvironment induced by hypoxia, in which the adenosinergic A2A receptor (A2AR) pathway is mainly participated. Here, we developed a novel core/shell structured nanoplatform composed of macrophage membrane-coated mesoporous silica nanoparticles which loaded catalase, doxorubicin (Dox), and resiquimod (R848), to promote the efficacy of immunotherapy. The nanoplatform is able to actively target the tumor site via ligand binding, and the A2AR of T regulatory (Treg) cells can further be blocked due to in situ oxygen production by hydrogen peroxide catalysis. Meanwhile, Dox and R848 released from the nanoplatform can induce immunogenic cell death and enhance the activation of dendritic cells (DCs), respectively. Thus, the improved microenvironment by A2AR blockade and the stimulation of the DCs to enhance the CD8 + T cells mediated immune response were achieved. Consequently, the expression of Treg cells decreased to 9.79% in tumor tissue and the inhibition rate of tumor growth reached 73.58%. Therefore, this nanoplatform provides a potential strategy for clinical application in cancer immunotherapy., Competing Interests: Declaration of Competing Interest The authors declare no competing financial interest., (Copyright © 2022. Published by Elsevier B.V.)

Recently, there is an increasing concern regarding the toxicity of nanoplastics (NPs) on freshwater organisms. However, knowledge about the potential impacts of NPs with different surface modification on freshwater biofilms is still very limited. In this research, biofilms were cultured in lab and exposed to nano polystyrene (PS) beads: non-functionalized PS NPs, PS-COOH NPs, and the carbon source utilization of biofilms were measured by BIOLOG ECO microplates. The results showed that both two types of PS NPs significantly reduced the total carbon metabolic activity of biofilms, compared with the controls, whereas the carbon metabolic rate increased notably, especially for the PS-COOH NPs treatments at day 14. Moreover, results from six categories of carbon sources analysis suggested that PS NPs with different surface chemical properties exhibit distinct effects on the carbon utilization of biofilms, and the divergent changes of the specific carbon source category were observed at day 21 from the two PS NPs treatments. In addition, the metabolic functional diversity of biofilms were not altered by the PS NPs treatments. These findings highlighted that chemical properties of NPs play an important role in the toxic effects on the carbon metabolism activities of the biofilms. This study offers new insights that nanoplastics of different chemical characteristics have the ability to affect the microbial-mediated carbon cycling process in aquatic ecosystems.

Aggregation behaviors of bare, and sodium polyacrylate (PAA) and starch modified zero-valent-iron nanoparticles (nZVI), as well as their effects on the Cr (VI) removal were investigated by simulating the groundwater. Results showed that increased concentration of PAA (1-6 wt%) and starch (0.1-0.6 wt%) alleviated the aggregation of modified nZVI (abbreviated as P-nZVI and S-nZVI), while there was an optimum dosage of 4 wt% PAA and 0.3 wt% starch for the Cr (VI) removal, respectively. Moreover, as one of the fundamental water chemistry parameters, Ca 2+ (0, 5, and 10 mg L -1 ) greatly promoted the aggregation of modified nZVI, and decreased the Cr (VI) removal efficiency by them via forming bidentate bridging structure (between Ca 2+ and PAA) or complexes (between Ca 2+ and starch). Additionally, fulvic acid (FA) (0, 2, 5, and 10 mg L -1 ) decreased the Cr (VI) removal by P-nZVI because of the significantly improved electronic repulsion. However, FA enhanced the aggregation of S-nZVI, but diminished its performance on Cr (VI) removal due to the bridging effect between FA and starch. The present study was of great importance in predicting the migration of nZVI and contaminants removal under complex geological conditions in groundwater., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

There is an increasing concern regarding the potential effects of nanoplastics (NPs) on freshwater ecosystems. Considering the functional values of biofilms in freshwater, knowledge on whether and to what extent NPs can influence the ecosystem processes of biofilms were still limited. Herein, the freshwater biofilms cultured in lab were exposed to 100 nm polystyrene NPs (PS-NPs) of different dosages (1 and 10 mg/L) for 14 days. Confocal laser scanning microscope observation indicated that biofilms were dominated by filamentous, and spiral algae species and the intensity of extracellular polymeric substances increased under PS-NPs exposure. GeoChip 5.0 analysis revealed that PS-NPs exposure triggered a significant increase in functional genes α diversity (p < 0.05) and altered biofilms' functional structure. Furthermore, the abundance of genes involved in the total carbon and nitrogen cycling were increased under PS-NPs exposure. The abundance of nitrogen fixation genes experienced the most pronounced increase (24.4%) under 1 mg/L PS-NPs treatment, consistent with the increase of ammonium in overlying water. Whereas antibiotic resistance genes and those related to photosynthetic pigments production were suppressed. These results provided direct evidence for PS-NPs' effects on the biofilm functions in terms of biogeochemical cycling, improving our understanding of the potentials of NPs on freshwater ecosystems., (Copyright © 2021 Elsevier B.V. All rights reserved.)

The physicochemical transformations as well as the redox reaction-induced toxicity changes of ceria nanoparticles (CeO 2 NPs) in reducing conditions is extremely lacking. Herein, the behaviors, chemical modifications and toxicity of CeO 2 NPs in the presence of reduction-active ions (namely Fe 2+ and S 2- ) were investigated, with a particular emphasis on the cytotoxicity mechanism associated with their physicochemical transformations. The presence of Fe 2+ and S 2- differently altered the surface properties and toxicity of CeO 2 NPs. Redox reactions with Fe 2+ led to form small aggregates, boosted the reduction of Ce IV O 2 and enhanced dissolved Ce 3+ concentration. Moreover, CeO 2 NPs possessed a high affinity for Escherichia coli (E. coli) and induced the generation of •OH abiotically after reaction with Fe 2+ , provoking serious disruption of cell membranes and causing high toxicity to E. coli. In contrast, the amending of S 2- protected E. coli from direct contact with CeO 2 NPs by creating new Ce 2 S 3 precipitated on the surface, accelerating the aggregation of NPs and reducing the concentration of dissolved Ce 3+ . This study suggested that the chemical interactions between the reactive surfaces of CeO 2 and reduction-active ions highly determined the stability and cytotoxicity of CeO 2 NPs, which provides fundamental insights into the environmental risks of CeO 2 NPs., (Copyright © 2021 Elsevier B.V. All rights reserved.)

The development of multidrug resistance (MDR) is a commonly observed phenomenon in many cancer types. It contributed significantly to the poor outcome of many currently available chemotherapies. Considering autophagy as one of the most important physiological process in cancer progression, we thereby proposed an anti-autophagy siRNA and doxorubicin (Dox) co-delivery system (MC/D-siR) to combat MDR breast cancer using sequential construction. Our results demonstrated the potential of MC/D-siR to effectively transfect the loaded siRNA to result in significant downregulation of intracellular autophagy level in MCF-7/Adr (Dox resistance MCF-7 cell line) cells, which in turn cut off the ATP supply and to reverse the MDR and potentiated accumulated drug retention in cells. As a result, MC/D-siR showed much elevated anticancer benefits than single loaded platforms (MC/Dox or MC/siRNA), indicating the ability for effective MDR cancer treatment through the combination of autophagy regulation and chemotherapy.

Increasing production and utilization of cerium oxide nanoparticles (CNPs) in recent years have raised wide concerns about their toxicity. Numerous studies have been conducted to reveal the toxicity of CNPs, but the results are sometimes contradictory. In this review, the most important factors in mediating CNPs toxicity are discussed, including (1) the roles of physicochemical properties (size, morphology, agglomeration condition, surface charge, coating and surface valence state) on CNPs toxicity; (2) the phase transfer and transformation process of CNPs in various aqueous, terrestrial, and airborne environments; and (3) reductive dissolution of CNPs core and their chemical reactions with phosphate, sulfate/S 2- , and ferrous ions. The physicochemical properties play key roles in the interactions of CNPs with organisms and consequently their environmental transformations, reactivity and toxicity assessment. Also, the speciation transformations of CNPs caused by reactions with (in)organic ligands in both environmental and biological systems would further alter their fate, transport, and toxicity potential. Thus, the toxicity mechanisms are proposed based on the physical damage of direct adsorption of CNPs onto the cell membrane and chemical inhibition (including oxidative stress and interaction of CNPs with biomacromolecules). Finally, the current knowledge gaps and further research needs in identifying the toxicological risk factors of CNPs under realistic environmental conditions are highlighted, which might improve predictions about their potential environmental influences. This review aims to provide new insights into cost-effectiveness of control options and management practices to prevent environmental risks from CNPs exposure.

Growing international exploitation of ceria nanoparticles (CeO 2 NPs) for varied applications has increased their release into wastewater treatment plants. Mass transfer of oxygen (MTO) in wastewater biofilm is of considerable importance to influence the activity and purification ability of biofilm. Herein, we investigated the spatial distribution of oxygen in gas-liquid-biofilm phases, the microstructure of interfaces and the in-situ microbial activity to reveal the impacts of CeO 2 NPs on MTO in wastewater biofilm and the related mechanisms. After exposure to 1 and 10 mg/L CeO 2 NPs, the oxygen transfer coefficient (K La ) from gas to wastewater increased by 28.1% and 75.3% with a reduction of thickness in gas-liquid boundary layer, indicating the enhanced MTO in gas-liquid interface. In contrast, the MTO in liquid-biofilm interface was negatively affected and the thickness of liquid-biofilms boundary layer significantly increased, which was mainly attributed to the smoother surface and the decreased surface area difference of biofilm. Within biofilm, the microbial activity was inhibited by 10 mg/L CeO 2 NPs, whereas the production of extracellular polymeric substance (EPS) was significantly improved, leading to a decline of 35.0% in the internal effective diffusivity (D B ) and a 300-μm reduction of oxygen penetration depth. Moreover, the relative activities of key enzymes involved in glycometabolism indicated the transition of Embden-Meyerhof pathway to pentose phosphate pathway, which probably contributed to the enhanced EPS production and consequently increased mass transfer resistance in liquid-biofilm interface and inner biofilm. These results could potentially expand the knowledge on mass transfer of nutrients or pollutants in wastewater biofilm in response to NPs exposure., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020. Published by Elsevier Ltd.)

Parameters such as the settling rate, aggregation rate, and collision frequency in predictive models used to describe the fate of nanoparticles (NPs) are very important for the risk assessment of NPs in the environment. In this study, CeO 2 NPs were chosen as the model particles to investigate such parameters through aggregation-settling experiments under environmentally relevant conditions. The results indicate that natural colloids (Ncs) have no effect on the settling of NPs in seawaters, whereas they stabilize the NPs at a low initial particle concentration and promote the heteroaggregation of NPs at a high initial particle concentration in lake waters. In all cases, a suspended sediment absorbs the NPs and Ncs as mixed aggregates, resulting in a rapid settling. Furthermore, the calculation results of the model indicate that the shear force increases the collision frequency of the NPs by 4-5 orders of magnitude higher than that in quiescent waters. However, the break-up effect by the shear force is more obvious, namely, the shear force hinders the aggregation of NPs in natural waters, instead of promoting aggregation. Remarkably, a negative value of the dis-heteroaggregation rate based on the combined von Smoluchowski-Stokes equation can reflect the hindering effect on the aggregation process. The results of this study will provide scientific and accurate guidance for the parameter selection in the existing prediction model and contribute to a prediction of the fate and transport of NPs in the environment., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Microplastics (MPs) can disintegrate into smaller sized microplastics and even nanoplastics (NPs). The toxicity of nanoplastics and microplastics on freshwater organisms have been well explored recently, however, very little is known about the potential impacts of NPs on freshwater biofilms, which are essential for primary production and nutrient cycling in aquatic ecosystems. In this study, we studied the acute effects (3 h of exposure) of polystyrene beads (PS, with diameter range from 100 nm to 9 μm) on five biological endpoints targeting community and ecosystem-level processes in biofilms: chlorophyll a, photosynthetic yield, and three extracellular enzyme activities. The results showed that the large size PS beads (500 nm, 1 μm, and 9 μm) exhibited negligible effects on the determined biological endpoints in biofilms within the range of concentrations (5-100 mg/L) in this study. However, high concentration of PS beads (100 nm, 100 mg/L) significantly decreased the content of chlorophyll a, and the functional enzyme activities of β-glucosidase and leucine aminopeptidase, suggesting negative effects on the carbon and nitrogen cycling of freshwater biofilms. Moreover, the influences of PS NPs (100 nm) on biofilms strongly depended on the surface modification of PS particles, with the positively charged PS NPs (amide-modified) exhibiting the highest toxicity to biofilms. The excess generation of reactive oxygen species (ROS) in this study indicated oxidative stress induced by PS NPs, which might lead to the observed nano-toxic effects on biofilms. In response, the antioxidant activity of biofilm was enhanced as indicated by the increased total antioxidant capacity (T-AOC). Overall, our findings highlight nanoplastics have potential to disrupt the basic ecological functions of biofilms in aquatic environments., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

In this paper, the effects of cerium oxide nanoparticles (CeO 2 NPs) on the group bacterial behaviors were elaborated. After 36-h cultivation, the biofilm biomass was enhanced by the sub-lethal concentrations of 0.5 and 2 mg/L CeO 2 NP exposure. Meanwhile, the promoted production of total amino acids in microbes further resulted in the increased surface hydrophobicity and percentage aggregation. To resist the CeO 2 NPs stress, the biofilm exhibited a double-layer microstructure, with the protein (PRO) and living cells occupying the bottom, the polysaccharide (PS), and dead cells dominating the top. The bacterial diversity was highly suppressed and Citrobacter and Pseudomonas from the phylum of γ-Proteobacteria strongly dominated the biofilm, indicating the selective and enriched effects of CeO 2 NPs on resistant bacteria. The stimulated inherent resistance of biofilm was reflected by the reduced adenosine triphosphate (ATP) content after 4 h exposure. The increased levels of reactive oxygen species (ROS) in the treatments of 8 h CeO 2 NP exposure led to the upregulated quorum sensing signals of acylated homoserine lactone (AHL) and autoinducer 2 (AI-2), beneficial to mitigating the environmental disturbance of CeO 2 NPs. These results provide evidences for the accelerating effects of CeO 2 NPs on biofilm formation through oxidative stress, which expand the understanding of the ecological effects of CeO 2 NPs.

In this study, we investigated the effects of copper oxide (CuO) NPs on freshwater sediment biofilms in terms of the functional properties and microbial community structure. Biofilms were incubated in microcosms and CuO NPs (1 mg/L uncoated and humic-acid-coated) were exposed with Cu 2+ (Cu(NO 3 ) 2 ) as the positive control. As determined from DO (dissolved oxygen) microelectrodes measurements, a high-DO region emerged inside the biofilms after 5-day exposure to CuO NPs compared with those before NP additions, which suggested CuO NPs inhibit the oxygen respiration activity. These results were consistent with the decreased heterotrophic respiration. CuO NPs significantly altered the bacterial community composition and decreased the abundances of Anaerolineaceae, Acidobacteria, Aminicenantes, and Anaerolinea. Functional analysis from PICRUSt (Phylogenetic Investigation of Communities by Reconstruction of Unobserved States)-predicted metagenomes indicated that bacterial genera depleted by CuO NP treatments were related to carbohydrate and glycan biosynthesis and metabolism, and biosynthesis of other secondary metabolites. These functional profiles combined with the decreased activities of extracellular enzymes, β-glucosidase (GLU) and l-leucine aminopeptidase (LAP), suggested that the introduction of CuO NPs exhibit negative effects on the biogeochemical processes and the cycling of carbon and nitrogen in biofilm systems. Whereas these toxic effects of CuO NPs could be mitigated when the aquatic environment is enriched with natural organic matters such as humic acid., (Copyright © 2018 Elsevier B.V. All rights reserved.)

In this study, the biofilm formation of Pseudomonas aeruginosa in the presence of cerium oxide nanoparticles (CeO 2 NPs) was investigated. With the addition of 0.1 mg/L and 1 mg/L CeO 2 NPs, the biofilm development was substantially enhanced. During the attachment process, the enhanced surface hydrophobicity and excess production of mannosan and rhamnolipids in CeO 2 NP treatments were detected, which were conductive to the colonization of bacterial cells. During the maturation period, the biofilm biomass was accelerated by the improved aggregation percentage as well as the secretion of extracellular DNA and pyocyanin. The reactive oxygen species (ROS) generated by CeO 2 NPs were found to activate the N-butyryl homoserine lactone (C 4 -HSL) and quinolone signals secreted by Pseudomonas aeruginosa. Moreover, the quorum sensing (QS) systems of rhl and pqs were initiated, reflected by the stimulated expression levels of biofilm formation-related genes rhlI-rhlR, rhlAB, and pqsR-pqsA. The addition of a quorum quencher, furanone C-30, significantly declined the activities of QS-controlled catalase and superoxide dismutase. A dose of antioxidant, ascorbic acid, effectively relieved the accelerating effects of NPs on biofilm formation. These results indicated that CeO 2 NPs could accelerate biofilm formation through the interference of QS system by generating ROS, which provides possible targets for controlling biofilm growth in the NP exposure environments.

The presence of abundant extracellular polymeric substances (EPS) play a vital role in affecting heteroaggregation process and toxicity of nanoparticles (NPs) to Microcystis aeruginosa. Interactions between n-CeO 2 and cyanobacteria with/without EPS and the toxicity of n-CeO 2 to M. aeruginosa were investigated in this study. Aggregation kinetics of n-CeO 2 under both soluble EPS (SEPS) and bound EPS (BEPS) indicated the presence of EPS could induced the formation of EPS-NPs aggregates. Heteroaggregation between cells and n-CeO 2 was confirmed through co-settling experiment and SEM-EDS observation. SEPS contributed to the observable heteroaggregation using spectral measurement. Heteroaggregation between cells and n-CeO2 under no BEPS was hardly obtained through spectral measurement, but SEM-EDS observation convinced this process. And the DLVO theory explained this heteroaggregation process under various EPS conditions, where the energy barrier decreased with gradual EPS extraction. In addition, the order for 96 h half growth inhibition concentration (IC 50 ) was Raw M9 > M9-SEPS > M9+BEPS > M9-BEPS. These results revealed that not all heteroaggregation between cell-NPs can lead to the NPs toxicity to cells. BEPS act more important role in buffering against the toxicity of NPs from ambient adverse factors, but SEPS increase the stability of NPs which could aggravate the adverse effects of NPs in the environment., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

With the accelerated application of copper oxide (CuO) and zinc oxide (ZnO) nanoparticles (NPs) in commercial products, concerns about the potential impacts on the environment have been growing. Environmental behaviors of NPs are expected to significantly influence their fate and ecological risk in the aquatic environment. In this study, the environmental behaviors of two metallic NPs (CuO and ZnO NPs), including aggregation, sedimentation, and dissolution, were systematically evaluated in five representative waters (pool water, lake water, rainwater, tap water, and wastewater) with varying properties. Remarkable aggregation, sedimentation, and dissolution were observed for both metallic NPs, among which ZnO NPs exhibited greater influence. CuO (ZnO) NPs aggregated to 400 (500) nm, 500 (900) nm, and 800 (1500) nm in lake water, wastewater, and tap water, respectively. The sedimentation rates of CuO and ZnO NPs in the five waters were ranked as tap water > wastewater > lake water > pool water > rainwater. The dissolution of CuO and ZnO NPs in waters follows a first-order reaction rate model and is affected by ionic type, ionic strength (IS), and NOM (natural organic matter) concentrations. Redundancy analysis (RDA) indicated that the aggregation and sedimentation of NPs have a strong correlation, insofar as the sedimentation rates increase with increasing aggregation rates. The aggregation and dissolution of NPs have a negative correlation, insofar as the dissolution rates reduce with increasing aggregation rates. The aggregation, sedimentation, and dissolution of NPs can be influenced by ionic types, IS, and TOC in waters, among which, TOC may the dominant factor.

Cerium oxide nanoparticles (CeO 2 NPs) affected the production of extracellular polymeric substances (EPSs), and thus might bring challenges for sludge pumping and mixing. In the present study, we investigated the rheological behavior of sludge before and after extraction of different EPSs fractions under various CeO 2 NPs concentrations. It was found that the removal of loosely bound EPSs (LB-EPSs) could affect the shear stress (τ) and apparent viscosity (η), and the changes were dependent on CeO 2 NPs concentrations. The removal of tightly bound EPSs (TB-EPSs) either with or without the addition of CeO 2 NPs significantly decreased the yield stress (τ y ) and the limiting viscosity (η ∞ ). Furthermore, the dynamic (strain, frequency and time) sweep measurements proved that the storage modulus (G') decreased after the extraction of TB-EPSs, indicating the weakened elastic and solid-like properties. The fluctuated content of polysaccharide in LB-EPSs and the increased amount of protein in TB-EPSs were likely to contribute to the variation of viscoelastic behaviors after the removal of LB-EPSs and TB-EPSs, respectively. In addition, the decreased rheological properties of sludge was also related to the increased zeta potential, decreased particle size and the removal of key organic matters of (10 4 -10 6 Da) with the extraction of stratified EPSs. These results were significant to take advantages of the rheological properties for sludge treatment in the presence of NPs., (Copyright © 2018 Elsevier Inc. All rights reserved.)

With the rapid development of CeO 2 nanoparticles (NPs), the released CeO 2 NPs entering into wastewater treatment plants might bring the challenges for sludge pumping and mixing. In this study, we firstly elucidated the rheological behavior of 4.0 wt% sludge at various concentrations of CeO 2 NPs. With the increase of CeO 2 NPs to 5 mg/L, the shear stress at any given shear rate was reduced and the limiting viscosity was also decreased, indicating the sludge became more flowability. The dynamic sweep tests further demonstrated the decreased elastic behavior and weakened internal structure in response to low concentrations of CeO 2 NPs (≤ 5 mg/L). However, 20 mg/L CeO 2 NPs had negative effects on the rheological evolution of sludge, namely, better solid-like property and higher elastic structure. These results were mainly attributed to the combination of the decreased β-D-glucopyranose polysaccharides which support the rigid structure of sludge and the dramatically increased protein content (especially in 20 mg/L CeO 2 NPs). These results can potentially provide novel information for the efficient design of sludge treatment when coped with CeO 2 NPs. Graphical abstract ᅟ.

The influences of cerium dioxide nanoparticles (CeO 2 NPs) on nitrogen removal in biofilm were investigated. Prolonged exposure (75d) to 0.1mg/L CeO 2 NPs caused no inhibitory effects on nitrogen removal, while continuous addition of 10mg/L CeO 2 NPs decreased the treatment efficiency to 53%. With the progressive concentration of CeO 2 NPs addition, the removal efficiency could nearly stabilize at 67% even with the continues spike of 10mg/L. The micro-profiles of dissolved oxygen, pH, and oxidation reduction potential suggested the developed protection mechanisms of microbes to progressive CeO 2 NPs exposure led to the less influence of microenvironment, denitrification bacteria and enzyme activity than those with continuous ones. Furthermore, high throughput sequencing illustrated the drastic shifted communities with gradual CeO 2 NPs spiking was responsible for the adaption and protective mechanisms. The present study demonstrated the acclimated microbial community was able to survive CeO 2 NPs addition more readily than those non-acclimated., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Widely used titanium dioxide (TiO 2 ) nanoparticles are likely to accumulate ultimately in sediments and potentially pose a risk to water ecosystems. This study evaluated the effect of TiO 2 nanoparticles on the photodissolution of particulate organic matter (POM) through fluorescence spectroscopy. Excitation-emission matrices and parallel factor analyses revealed that the fluorescent characteristics of produced dissolved organic matter (DOM) during photodissolution of suspended sediment and synthetic particulate organic matter (SPOM) were primarily humic-like. SPOM particles appeared to simulate well the photodissolution of suspended sediment. Quasi-complete increases in fluorescence intensity and chromophoric DOM (CDOM) abundance were reached after 90, 60, and 50 min irradiation for TiO 2 concentrations of 0, 2, and 5 mg L -1 , respectively. The faster increment of fluorescence intensity and CDOM abundance indicated the photocatalytic dissolution of SPOM, as opposite charges between TiO 2 and SPOM at pH = 4 favored the adsorption of TiO 2 onto SPOM. For sediments, the CDOM abundance and fluorescence intensity decreased with increasing TiO 2 concentration, resulting from the photocatalytic degradation of photoproduced DOM from sediments. These results demonstrated that pH plays an important role in the photocatalytic dissolution of POM by TiO 2 . Therefore, appropriate pH controls should be implemented when TiO 2 are used to treat sediments contaminated with organic pollutants. Finally, with increasing use of TiO 2 , its accumulation in sediments may affect the fate of carbon, nutrients, and heavy metals in shallow-water ecosystems., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

As CeO 2 nanoparticles (NPs) are used in many applications, the released particles eventually enter wastewater treatment plants, influencing sludge dewatering and increasing the disposal costs. We conducted tests to gain insight into the sludge dewatering performance and the potential mechanism related to the distribution and production of extracellular polymeric substances (EPS). In addition, we conducted single-factor tests with six concentrations of CeO 2 NPs in sequencing batch reactors containing matured activated sludge. Overall, the specific resistance to filtration (SRF) improved with an increase in the CeO 2 NPs dosage. The SRF significantly increased from 1.460 × 10 12 to 1.632 × 10 12  m/kg after the addition of 5 mg/L CeO 2 NPs (p < 0.05). The bound water content was enhanced from 2.43 to 2.75 kg/kg dry solid, indicating a deteriorated dewaterability. We found that the increased EPS production, especially the dominant protein (r = 0.987, p < 0.01), was correlated significantly with the SRF. This is ascribed to the inhibited activity of leucyl aminopeptidase and the reduced adenosine 5'-triphosphate concentrations after exposure to CeO 2 NPs. The fluorescence region integration technique and protein secondary structures revealed the reasons for the poor dewatering performance in the presence of CeO 2 NPs. These are the enhanced amount of soluble microbial by-product-like material and the low value of the α-helix/(β-sheet + random coil). These results could potentially expand the knowledge on sludge dewatering in the presence of NPs., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

The growing production and application of CuO nanoparticles increase the chance that these particles will be released into wastewater treatment plants (WWTPs) and interact with microorganisms. However, the toxicity response mechanism of biofilm to NP exposure may be different from that of activated sludge due to the denser and stronger microbial aggregate structure of biofilm. Thus, in this study, the response to CuO NPs of wastewater biofilm collected from a rotating biological contactor was investigated. Short-term exposure (24h) to CuO NPs led to a great loss in cell viability, and SEM-EDS images revealed that the nano-CuO aggregates were not transformed to Cu-S species in the biofilm samples. In response, more extracellular polymeric substance (EPS) (especially loosely bound-EPS) was produced in wastewater biofilm exposed to CuO NPs, with a higher content of protein compared to polysaccharides. The shifts of fluorescence intensity and peak locations in 3D-EEM fluorescence spectra indicated chemical changes of the EPS components. FT-IR analysis revealed that exposure to nano-CuO had more distinct effects on the functional groups of proteins and polysaccharides in LB-EPS. Illumina sequencing of 16S rRNA gene amplicons revealed that CuO NPs enhanced bacterial diversity. The bacterial community structure significantly shifted, with a significantly increased abundance of Comamonas, a slight increase in Zoogloea, and a notable decrease in Flavobacterium. The shifts of these dominant genera may be associated with altered EPS production, which might result in microbial community function fluctuations. In conclusion, exposure to high concentrations of CuO NPs has the potential to shape wastewater biofilm bacterial community structure., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Extracellular polymeric substances (EPS) are key components of the cyanobacterium Microcystis aeruginosa and play an important role in cyanobacteria blooms formation. Here, we analyzed the effects of 48-h exposure to nanosized CeO 2 (n-CeO 2 ), CuO (n-CuO), and ZnO (n-ZnO) on the production and composition of EPS of M. aeruginosa. Toxicity experiments revealed that soluble nanoparticles (NPs) (n-ZnO, n-CuO) demonstrated higher toxicity to cells and caused membrane damage. The production of LB-EPS increased by 34.48, 20.09, and 46.33 %, and TB-EPS increased by -5.78, 22.3, and -2.67 % in the presence of n-CeO 2 , n-CuO, and n-ZnO NPs, respectively, and polysaccharides are the main incremental portion compared with protein and humic acids. Three-dimensional excitation-emission fluorescence spectra revealed the enhancement of fulvic-humic-like and disappearance of tyrosine aromatic substances in TB-EPS compared with the slight changes observed in LB-EPS. Fourier-transform infrared spectroscopy illustrated the susceptibility of -NH 2 and double-bonded carbon and oxygen in amides to three types of NPs. These results improve our understanding of the potential influence of NPs on the aggregation behaviors of cyanobacteria and formation process of cyanobacteria blooms. Graphical abstract ᅟ.

In this study, we examined the long-term effects of copper oxide nanoparticles (CuO NPs) on the production and properties of EPS and the resulting variations in surface physicochemical characteristics of biofilms in a sequencing batch biofilm reactor. After exposure to 50 mg/L CuO NPs for 45 days, the protein (PRO) and polysaccharide (PS) contents in loosely bound EPS (LB-EPS) decreased as the production of LB-EPS decreased from 34.4 to 30 mg TOC/g EPS. However, the production of tightly bound EPS (TB-EPS) increased by 16.47 % as the PRO and PS contents increased. The content of humic-like substances (HS) increased significantly, becoming the predominant constituent in EPS with the presence of 50 mg/L CuO NPs. Furthermore, the results of three-dimensional excitation-emission fluorescence spectra confirmed the various changes in terms of the LB-EPS and TB-EPS contents after exposure to CuO NPs. Fourier transform infrared spectroscopy showed that the -OH and -NH 2 groups of proteins in EPS were involved in the reaction with CuO NPs. Moreover, the chronic exposure to CuO NPs induced a negative impact on the flocculating efficiency of EPS and on the hydrophobicity and aggregation ability of microbial cells. The PRO/PS ratios of different EPS fractions were consistent with their hydrophobicities (R 2 >0.98) and bioflocculating efficiencies (R 2 >0.95); however, there was no correlation with aggregation ability. Additionally, the presence of bovine serum albumin (BSA) prevented the physical contact between CuO NPs and EPS as a result of NP aggregation and electrostatic repulsion.

The extended DLVO (XDLVO) theory was applied to elucidate the potential effects of CeO 2 nanoparticles (CeO 2 NPs) on sludge aggregation and the role of extracellular polymeric substances (EPS). In this study, seven different concentrations of CeO 2 NPs were added to activated sludge cultured in sequencing batch reactors (SBRs) and compared with a control test that received no CeO 2 NPs. After exposure to 50mg/L CeO 2 NPs, a negligible change (p>0.1) occurred in the sludge volume index (SVI), whereas the flocculability and aggregation of the sludge decreased by 18.8% and 11.2%, respectively, resulting in a high effluent turbidity. The XDLVO theory demonstrated that the adverse effects of the CeO 2 NPs on sludge aggregation were due to an enhanced barrier energy. Compared to the van der Waals energies (W A ) and the electric double layer (W R ), the acid-base interaction (W AB ) markedly changed for the various concentrations of CeO 2 NPs. The EPS played a decisive role in the sludge surface characteristics, as the removal of EPS equals to the negative effects induced by 5-10mg/L CeO 2 NPs on the sludge flocculability and aggregation. The presence of CeO 2 NPs induced negative contributions to the tight boundary EPS (TB-EPS) and core bacteria while positive contributions to the total interaction energy of the loose boundary EPS (LB-EPS)., (Copyright © 2016 Elsevier Inc. All rights reserved.)

The transport behaviors of copper oxide (CuO) NPs in wastewater matrix and their possible impacts on microbial activities of stable wastewater biofilms cultivated in a lab scale rotating biological contactor (RBC) were investigated. Significant aggregation of CuO NPs was observed in the wastewater samples, depending on their mass concentrations. Extracellular polymeric substance (EPS)-adsorbed copper accounted for a large proportion of the total copper accumulated in biofilms. The microelectrode profiles showed that a single pulse exposure to 50mg/L CuO resulted in a deeper penetration depth of oxygen in biofilms compared to the CuO NP free biofilms. The maximum oxygen consumption rate shifted to the deeper parts of biofilms, indicating that the respiration activities of bacteria in the top region of the biofilms was significantly inhibited by CuO NPs. Biofilms secreted more EPS in response to the nano-CuO stress, with higher production of proteins compared to polysaccharides., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Extracellular polymeric substances (EPS) are a major component of biofilms that act as a gel-like matrix, binding the cells together to form their three-dimensional structure. The effects of ceria nanoparticles (CeO2 NPs) on the production and physicochemical characteristics of EPS in biofilms in a sequencing batch biofilm reactor were investigated. Total EPS production, including loosely bound EPS (LB-EPS) and tightly bound EPS (TB-EPS), increased by 35.41% compared to in control tests without CeO2 NPs. Protein production increased by 47.02% (LB-EPS) and 58.83% (TB-EPS) after 50 mg/L CeO2 NP exposure. Three-dimensional excitation-emission fluorescence spectra revealed that tyrosine (LB-EPS) and aromatic (TB-EPS) protein-like substances formed after CeO2 NP exposure. Fourier transform infrared spectroscopy results indicated the susceptibility of -OH and -NH2 in EPS hydroxyl and amine groups to CeO2 NPs. Exposure to 50 mg/L CeO2 NPs reduced the flocculating capacity of LB-EPS (51.78%) and TB-EPS (17.14%), consistent with the decreased zeta potential., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

The effects of CeO2 nanoparticles (CeO2 NPs) exposure on biological nitrogen removal in a sequencing batch biofilm reactor (SBBR) were investigated. At low concentration (1 mg/L), no significant effect was observed on total nitrogen (TN) removal. However, at high concentrations (10 and 50 mg/L), the TN removal efficiency reduced from 74.09% to 64.26% and 55.17%, respectively. Scanning electron microscope imaging showed large amounts of CeO2 NPs adsorbed on the biofilm, which increased the production of reactive oxygen species. The exposure at only 50 mg/L CeO2 NPs measurably affected the lactate dehydrogenase release. Confocal laser scanning microscopy showed that high concentrations of CeO2 NPs reduced bacterial viability. Moreover, after a short-term exposure, extracellular polymeric substances (EPS) were observed to increase, forming a compact matrix to protect the bacteria. The activities of nitrate reductase and ammonia monooxygenase were inhibited, but there was no significant impact on the activity of nitrite oxidoreductase., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

The presence of nanoparticles (NPs) in natural aquatic environment is a potential risk to aquatic and human life. Periphyton, ubiquitous in aquatic environment, has been used to remove pollutants from aquatic systems. Understanding the interaction between NPs and periphyton will help to better predict the behavior and fate of NPs in aquatic media. This study was aimed to investigate the CuO NP biosorption mechanism by periphyton at acidic, neutral, and alkaline pH and with varying natural organic matter (NOM) concentrations. The rate of adsorption and removal of CuO NPs was decreased with increase in initial pH and NOM concentration. The zeta potential study suggests that the biosorption of CuO NPs by periphyton was related to electrostatic force of attraction. The particle size distribution of CuO NPs in solution with different NOM concentrations played an important role in CuO NP removal. The well fit between pseudo-first-order kinetics and adsorption process indicated that physical sorption appears to be the dominating process. These results show that periphyton can be employed for an environmentally benign and effective solution for NP removal.

Highlights • Effect of Ca2+ and alginate on stability of CeO 2 NPs studied. • Dynamic light scattering (DLS) and nanoparticle tracking analysis (NTA) employed. • Aggregation of CeO 2 NPs with alginate exhibited a heteroaggregation mechanism. • DLS and NTA provided insight into aggregation mechanisms. • DLS and NTA are complementary techniques to study nanoparticles in water. Abstract The effect of Ca2+ and alginate on the stability of CeO 2 nanoparticles (NPs) was investigated using dynamic light scattering (DLS) and nanoparticle tracking analysis (NTA); the two methods were then compared. DLS showed rapid aggregation of CeO 2 NPs in 8 mM Ca2+ solution; however, NTA showed that some primary aggregates (200–400 nm) still remained—a result that was obscured in DLS measurements. Aggregation of alginate molecules was also studied using DLS and NTA, where NTA particle concentration and video provided additional information on the alginate aggregation progress. Finally, DLS showed that in the presence of alginate, the aggregation rate and size of CeO 2 NPs increased. NTA intensity measurements provided insight into a heteroaggregation and bridging mechanism. NTA particle concentration and video also showed CeO 2 NPs were linked by alginate gel in high Ca2+ concentration (>4 mM). the DLS and NTA had different advantages in measuring particle size. DLS could better study the initial aggregation stage and large aggregates, while NTA could better detect small aggregates. NTA also measured particle number concentration, individual intensity, and particle motion video, which provided additional insight. Combining these two methods could help us to better understand the behavior and fate of NPs in water. [ABSTRACT FROM AUTHOR]

With the rapid development of CeO2 nanoparticles (NPs), the released CeO2 NPs entering into wastewater treatment plants might bring the challenges for sludge pumping and mixing. In this study, we firstly elucidated the rheological behavior of 4.0 wt% sludge at various concentrations of CeO2 NPs. With the increase of CeO2 NPs to 5 mg/L, the shear stress at any given shear rate was reduced and the limiting viscosity was also decreased, indicating the sludge became more flowability. The dynamic sweep tests further demonstrated the decreased elastic behavior and weakened internal structure in response to low concentrations of CeO2 NPs (≤ 5 mg/L). However, 20 mg/L CeO2 NPs had negative effects on the rheological evolution of sludge, namely, better solid-like property and higher elastic structure. These results were mainly attributed to the combination of the decreased β-D-glucopyranose polysaccharides which support the rigid structure of sludge and the dramatically increased protein content (especially in 20 mg/L CeO2 NPs). These results can potentially provide novel information for the efficient design of sludge treatment when coped with CeO2 NPs.ᅟ [ABSTRACT FROM AUTHOR]

Extracellular polymeric substances (EPS) are key components of the cyanobacterium Microcystis aeruginosa and play an important role in cyanobacteria blooms formation. Here, we analyzed the effects of 48-h exposure to nanosized CeO (n-CeO), CuO (n-CuO), and ZnO (n-ZnO) on the production and composition of EPS of M. aeruginosa. Toxicity experiments revealed that soluble nanoparticles (NPs) (n-ZnO, n-CuO) demonstrated higher toxicity to cells and caused membrane damage. The production of LB-EPS increased by 34.48, 20.09, and 46.33 %, and TB-EPS increased by −5.78, 22.3, and −2.67 % in the presence of n-CeO, n-CuO, and n-ZnO NPs, respectively, and polysaccharides are the main incremental portion compared with protein and humic acids. Three-dimensional excitation-emission fluorescence spectra revealed the enhancement of fulvic-humic-like and disappearance of tyrosine aromatic substances in TB-EPS compared with the slight changes observed in LB-EPS. Fourier-transform infrared spectroscopy illustrated the susceptibility of −NH and double-bonded carbon and oxygen in amides to three types of NPs. These results improve our understanding of the potential influence of NPs on the aggregation behaviors of cyanobacteria and formation process of cyanobacteria blooms. [ABSTRACT FROM AUTHOR]

The presence of ZnO nanoparticles (ZnO NPs) in natural waters has raised concerns about their environmental impacts, but the potential influences of ZnO NPs on fluvial biofilm have not been reported. In this study, the utility of antioxidant enzyme activities (AEA) as biomarkers of fluvial biofilm to ZnO NPs toxicity and a method that combines AEA into an index of “Integrated Biomarker Responses (IBR)” were studied. Compared with the absence of ZnO NPs, scanning electron microscopy (SEM) images revealed that a large amount of ZnO NPs were adsorbed onto biofilm and these NPs exerted adverse effects on the viability of bacteria in biofilm. The production of reactive oxygen species (ROS) with high concentrations (30 and 100 mg/L) of ZnO NPs exposure reached to 184% and 244% of the control, while no cell leakage and membrane damage were observed. After exposure to ZnO NPs for 0.25 and 3 days, the activities of catalase (CAT), superoxide dismutase (SOD) and glutathione reductase (GR), glutathione peroxidase (GSH-Px) were significantly increased, respectively. At the end of exposure period (21 days), the AEA with the presence of 1 mg/L ZnO NPs exposure were comparable to the control, while most of those in high concentrations of ZnO NPs were decreased. The results of IBR showed that the biofilm can adapt to 1 mg/L ZnO NPs exposure, while be seriously damaged by 30 and 100 mg/L ZnO NPs after 3 and 0.25 days. IBR can be used as an appropriate evaluation system of the toxicity effects of ZnO NPs on fluvial biofim. [ABSTRACT FROM AUTHOR]

The stability of CuO nanoparticles (NPs) is expected to play a key role in the environmental risk assessment of nanotoxicity in aquatic systems. In this study, the effect of alginate (model polysaccharides) on the stability of CuO NPs in various environmentally relevant ionic strength conditions was investigated by using time-resolved dynamic light scattering. Significant aggregation of CuO NPs was observed in the presence of both monovalent and divalent cations. The critical coagulation concentrations (CCC) were 54.5 and 2.9 mM for NaNO and Ca(NO), respectively. The presence of alginate slowed nano-CuO aggregation rates over the entire NaNO concentration range due to the combined electrostatic and steric effect. High concentrations of Ca (>6 mM) resulted in stronger adsorption of alginate onto CuO NPs; however, enhanced aggregation of CuO NPs occurred simultaneously under the same conditions. Spectroscopic analysis revealed that the bridging interaction of alginate with Ca might be an important mechanism for the enhanced aggregation. Furthermore, significant coagulation of the alginate molecules was observed in solutions of high Ca concentrations, indicating a hetero-aggregation mechanism between the alginate-covered CuO NPs and the unabsorbed alginate. These results suggested a different aggregation mechanism of NPs might co-exist in aqueous systems enriched with natural organic matter, which should be taken into consideration in future studies. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The effects of the volume ratios of micro and nano-SiC particles (SiCp) on the grain refinement, distribution of SiCp particle, and tensile properties of the as-cast AZ31B (Mg-3Al-1Zn-0.3Mn) magnesium-based metal matrix composites have been investigated. As the volume fraction of micron SiCp decreases to 9 vol.% and the nano-SiCp increases to 1 vol.%, excellent grain refinement effect is achieved. This is due to both the uniform distribution and refining effects of micro- and nano-SiCp. Moreover, the micron SiCp distribute along the grain boundaries, while nano-SiCp is mainly distributed around the micron SiCp. The room-temperature tensile results show that the optimal room-temperature yield and tensile strengths are achieved with a 9/1 ratio of micro to nano-SiCp, while the 9.5/0.5 ratio yielded the highest elongation. [ABSTRACT FROM AUTHOR]

In this work, a series of novel flower-like Bi2O2CO3/CdS heterojunctions were prepared by a simple and feasible two-step process. The phase structures of as-prepared samples were examined by X-ray diffraction (XRD). Scanning electron microscopy (SEM), Transmission Electron Microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) were used to confirm the flower-like heterostructures of the Bi2O2CO3/CdS composites. The Brunauer–Emmett–Teller (BET) specific surface area (SBET) of samples were analyzed by N2 adsorption–desorption isotherms. UV-vis diffuse reflectance spectrometry (DRS) revealed that Bi2O2CO3/CdS heterojunctions exhibited better light absorptive properties than pure Bi2O2CO3. The photocatalytic activity was investigated by the degradation of MB under visible light irradiation. The results showed that the as-prepared Bi2O2CO3/CdS heterojunctions exhibited much higher activity than pure Bi2O2CO3. The photoluminescence (PL) spectra and photocurrent studies indicated that the recombination of photogenerated electron–hole pairs was decreased effectively due to the formation of heterojunctions between flower-like Bi2O2CO3 and CdS nanoparticles. Trapping experiments indicated that ṖO2− radicals were the main reactive species for MB degradation in the present photocatalytic system. Furthermore, the cycling experiments revealed the good stability of Bi2O2CO3–CdS composites. [ABSTRACT FROM AUTHOR]

The effects of CuO nanoparticles (NPs) on the production and composition of extracellular polymeric substances (EPS) and the physicochemical stability of activated sludge were investigated. The results showed enhanced production of loosely bound extracellular polymeric substances (LB-EPS), protecting against nanotoxicity. Specifically, polysaccharide production increased by 89.7% compared to control upon exposure to CuO NPs (50 mg/L). Fourier transform-infrared spectroscopy analysis revealed changes in the polysaccharide C O C group and the carboxyl group of proteins in the EPS in the presence of CuO NPs. The sludge flocs were unstable after exposure to CuO NPs (50 mg/L) because of excess LB-EPS. This also corresponded with decreased cell viability of the sludge flocs, as determined by the production of reactive oxygen species and the release of lactate dehydrogenase. These results are key to assessing the adverse effects of the CuO NPs on activated sludge in wastewater treatment plants. [ABSTRACT FROM AUTHOR]

Abstract: A rigid conjugated pyridinylthiazole derivative (1) and two bithiazole derivatives with similar structures (2, 3) were synthesized and characterized. Their optical properties were investigated through spectral analysis. By applying the three compounds to Cu2+ ions detection, it was shown that compound 1 could be employed as a selective and sensitive Cu2+ ions fluorescent chemosensor. For aqueous assay, the nanoparticles of compound 1 were prepared in aqueous media. Compared to the monomer, 1 nanoparticles were more fluorescence sensitive to Cu2+ ions. Its binding mode with Cu2+ ions was correlated well with Langmuir equation. Compound 1 nanoparticles exhibit a dynamic working range for Cu2+ ions from 0.02 to 0.50μM with a detection limit of 10nM. The proposed chemosensor has been used for the direct measurement of Cu2+ content in drinking water samples with satisfying results. [Copyright &y& Elsevier]

Parameters such as the settling rate, aggregation rate, and collision frequency in predictive models used to describe the fate of nanoparticles (NPs) are very important for the risk assessment of NPs in the environment. In this study, CeO 2 NPs were chosen as the model particles to investigate such parameters through aggregation-settling experiments under environmentally relevant conditions. The results indicate that natural colloids (Ncs) have no effect on the settling of NPs in seawaters, whereas they stabilize the NPs at a low initial particle concentration and promote the heteroaggregation of NPs at a high initial particle concentration in lake waters. In all cases, a suspended sediment absorbs the NPs and Ncs as mixed aggregates, resulting in a rapid settling. Furthermore, the calculation results of the model indicate that the shear force increases the collision frequency of the NPs by 4–5 orders of magnitude higher than that in quiescent waters. However, the break-up effect by the shear force is more obvious, namely, the shear force hinders the aggregation of NPs in natural waters, instead of promoting aggregation. Remarkably, a negative value of the dis-heteroaggregation rate based on the combined von Smoluchowski–Stokes equation can reflect the hindering effect on the aggregation process. The results of this study will provide scientific and accurate guidance for the parameter selection in the existing prediction model and contribute to a prediction of the fate and transport of NPs in the environment. Image 1 • The input parameters in the NP exposure model were investigated. • The different aggregation mechanisms were predominant in different natural waters. • Turbulence can break up the aggregates and transport them to a greater distance. • Collision frequency of CeO 2 NPs in turbulent waters was experimentally calculated. • The co-sedimentation of NPs with SS in the exposure modeling should be redefined. The hydrodynamic effect on the environmental behavior of NPs was investigated to ensure the accuracy of the parameter selection of the prediction model. [ABSTRACT FROM AUTHOR]

Inhibitory effects of ceria nanoparticles (CeO 2 NPs) on biofilm were investigated individually and in combination with phosphate (P), ethylene diamine tetraacetic acid (EDTA), humic acid (HA) and citrate (CA) to further explore the toxicity alleviating solutions. Exposure to 20 mg/L CeO 2 NPs significantly decreased the performance of biofilm in nutrients removal. Distribution experiments suggested >98% of the CeO 2 NPs retained in microbial aggregates, leading to 51.26 μg/L Ce ions dissolution. The dissolved Ce IV and its further being reduced to Ce III stimulated the formation of O 2 − and OH, which increased lipid peroxidation level to 130.93% in biofilms. However, P/EDTA/CA captured or precipitated Ce ions, whereas EDTA/HA/CA shielded NPs-bacteria direct contacts, both disturbing the NPs adsorption, intercepting the redox transition between Ce IV and Ce III , reducing the generation of O 2 − and OH, thus mitigating the toxicity of CeO 2 NPs. These results illustrate the main drivers of CeO 2 NPs biotoxicity and provide safer-by-design strategies. [ABSTRACT FROM AUTHOR]

The widespread use of commercial silver nanoparticles (Ag NPs) inevitably results in their increased release into natural waters and subsequent deposition in sediments, requiring the environmental impact of such deposition to be closely investigated. Hence, the effects of Ag NPs, polyvinylpyrrolidone (PVP)-Ag NPs, and sliver sulfide nanoparticles (Ag 2 S NPs) on denitrification-induced gas production (N 2 O and 15 N-N 2 ), and denitrifying microbes in freshwater sediments were investigated. Slurry experiments (8 h) combined with a 15 NO 3 − addition technique were performed to determine the gaseous production. The abundance of relative functional genes ( nirK , nirS and nosZ ) and the composition of functional community were determined through RT-PCR and high-throughput sequencing, respectively. The obtained results showed that the toxicity of NPs on denitrification depended on their type (Ag +  > Ag NPs > PVP-Ag NPs > Ag 2 S NPs) and concentration, e.g., all 1 mg/L NPs exhibited no effects on denitrification, whereas evident hormesis effect–induced acceleration was observed in the case of Ag + . Conversely, 10 mg/L Ag + and Ag NPs significantly inhibited the release rates of N 2 O and N 2 by decreasing the abundance of functional genes ( nirK and/or nirS ) and the predominant bacteria Paracoccus . PVP-Ag and Ag 2 S NPs had no effects on N 2 release rates and the composition of denitrifiers, however, inhibited the emission of N 2 O (by reducing the abundance of nirK ), suggesting that normal denitrification-induced N 2 formation in sediments could still be sustained when the N 2 O production decrease lied within a certain range. Further, the inhibiting ability of Ag-containing NPs was caused by their intrinsic nanotoxicity to functional microbes rather than by the general toxicity of Ag + . Besides, Ag 2 S NPs (as a main detoxification form of AgNPs) were revealed to be intrinsically nanotoxic to denitrifiers, albeit showing the lowest inhibitory effect among the three tested NPs. Thus, this study demonstrated that the inhibitory effect of Ag-containing NPs on denitrification in sediments depends on their morphology and type, implying that the stability and toxicity of Ag-containing NPs should be considered with caution. [ABSTRACT FROM AUTHOR]

The fate of nanoparticles in natural waters is affected by the combination of various factors, especially the flow disturbance which plays a decisive role in the transport of nanoparticles. This study investigated the aggregation behavior of CeO 2 nanoparticles (NPs) in natural waters by using a unique instrument to simulate flow disturbance. The results indicated that, in the absence of a shear force, the CeO 2 NPs formed linear, chain-like aggregates in seawater, owing to the high IS, which compressed the electrical double layer of particles. On the other hand, the NPs formed more compact aggregates in lake water, owing to an ion bridge effect between the NPs and the dissolved organic matter (DOM). It was also found that shear forces affected the aggregation behavior of the NPs. A low shear force promoted the aggregation of the NPs by increasing the collision efficiency while the aggregates were broken by a high shear force. Remarkably, the NPs maintained their potential for continuous aggregation when the slow stirring was reintroduced, suggesting that the aggregates began to grow again under renewed stirring. The results of this study could help in predicting the fate and transport behavior of CeO 2 NPs in actual aquatic environments. [ABSTRACT FROM AUTHOR]

The short term (8 h) influences of cerium oxide nanoparticles (CeO 2 NPs) on the process of phosphorus removal in biofilm were investigated. At concentration of 0.1 mg/L, CeO 2 NPs posed no impacts on total phosphorus (TP) removal. While at 20 mg/L, TP removal efficiency reduced from 85.16% to 59.62%. Results of P distribution analysis and 31 P nuclear magnetic resonance spectroscopy implied that the anaerobic degradation of polyphosphate (polyP) and the release of orthophosphate in extracellular polymeric substances (EPS) were inhibited. After aerobic exposure, the average chain length of polyP in microbial cells and EPS was shorter than control, and monoester and diester phosphates in cells were observed to release into EPS. Moreover, the EPS production and its contribution to P removal increased, while the capacity of EPS in P storage declined. X-ray diffraction analysis and saturation index calculation revealed that the formation of inorganic P precipitation in biofilm was inhibited. [ABSTRACT FROM AUTHOR]

Zinc oxide nanoparticles (ZnO NPs) used in consumer products are largely released into the environment through the wastewater stream. The health hazard of ZnO NPs and the contribution of dissolved Zn 2 + in toxicity of ZnO NPs has attracted extensive worldwide attention. In this study, the toxic effects of ZnO nanoparticles (ZnO NPs) and the effects of dissolved Zn 2 + on fluvial biofilms were investigated. At the end of the exposure time (21 days), scanning electron microscopy (SEM) images and bioaccumulation experiments revealed that large quantities of ZnO NPs were adsorbed on the biofilm. The algal biomasses were significantly decreased by six- and eleven-fold compared with the control (1.43 μg/L) by exposure to concentrations of 100 mg/L ZnO NPs and 7.85 mg/L Zn 2 + , respectively. Moreover, under the same exposure conditions, the quantum yields presented contents of 53.33 and 33.33% relative to the control, and a shift in the community composition that manifested as a strong reduction in diatoms was observed from 7 days and reached 15.63 and 6.25% of the control after 21 days of exposure, respectively. The reductions in bacteria viability and reactive oxygen species (ROS) production were noticeably enhanced following exposure to 100 mg/L ZnO NPs and 7.85 mg/L Zn 2 + , respectively. Additionally, the acute and rapid toxicity of Zn 2 + and the increasing toxicity of the ZnO NPs with increased bioaccumulation were noted in the exposure experiment. [ABSTRACT FROM AUTHOR]

Magnetic solid-phase extraction is an effective and useful technique to preconcentrate trace analytes from food samples. In this study, a magnetic trimeric chromium octahedral metal-organic framework (Fe 3 O 4 -NH 2 @MIL-101) was fabricated and characterized. Fe 3 O 4 -NH 2 @MIL-101 was applied as an adsorbent of magnetic solid-phase extraction combined with high performance liquid chromatography to effectively isolate and simultaneously determine six Sudan dyes (Para Red, Sudan I–IV, and Sudan Red 7B) from tomato sauce. Potential factors affecting the MSPE were investigated in detail, and adsorption efficiency of Fe 3 O 4 -NH 2 @MIL-101 was compared with those of conventional adsorbents, such as neutral alumina, HLB, and C 18 . The developed method facilitated the extraction with using only 3 mg of adsorbent in 2 min. In addition, enhancement factors of 50, linear range of 0.01–25 μg/mL, and detection limit (S/N = 3) of 0.5–2.5 μg/kg were obtained. The intra-day and inter-day recoveries for spiked Sudan dyes were in the range of 72.6%–92.9% and 69.6%–91.6%, respectively, with relative standard deviations of ≤9.2%. [ABSTRACT FROM AUTHOR]

Environmental concerns regarding the potential ecological risks of metallic oxide nanoparticles (MNPs) in aquatic ecosystems are increasing; sediment is considered a sink for these MNPs. Although several studies have studied the potential impact of MNPs on microbial communities in freshwater and estuarine sediments, limited information is available regarding the influence of MNPs on the metabolic activity of surficial sediment microbial communities and related biogeochemical conditions. To address these issues, a microcosm approach was established to study the metabolic response of surficial sediment microbial communities to a single addition of TiO 2 or CeO 2 NPs (5 mg/L) using oxygen microelectrodes, enzyme activity measurements, and high-throughput sequencing. Rapid sedimentation of MNPs (regardless of NP type) was observed in freshwater samples, and most (up to 85%) accumulated in surface sediments (<5 mm). Microelectrode profile measurements in pre-incubated sediments treated with MNPs showed that the oxygen concentration decreased at a slower rate with increasing sediment depth compared to that in untreated controls. Biological oxygen consumption in the uppermost sediment layer (0–1500 μm) was significantly inhibited by MNPs, as calculated from steady-state microprofiles, with CeO 2 NPs resulting in enhanced acute toxicity than TiO 2 NPs. High-throughput sequencing showed that MNP exposure increased the bacterial diversity and altered the bacterial community structure, regardless of NP type. The abundance of three dominant bacterial genera, Methylotenera , Cytophagceae_uncultured (classified as an aerobic bacterium), and Cyanobacteria_norank (a facultative bacterium), was markedly reduced by MNPs, which was primarily responsible for inhibiting microbial-mediated oxygen consumption in surficial sediments. In summary, short-term exposure to MNPs negatively affected the metabolic activity of benthic microbial communities, which could influence the biogeochemical functions along the sediment-water interface. [ABSTRACT FROM AUTHOR]

In this work, BiOCl modified titanium phosphate nanoplates (BiOCl/TP) composite photocatalysts with p-n heterojunctions were prepared by a in-situ growth method. The morphology, crystal structure and optical properties of the prepared samples were characterized by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-ray diffraction (XRD), UV–vis diffuse reflectance spectrometry (DRS). Rhodamine B (RhB), reactive brilliant Red X-3B (X-3B), methylene blue (MB), ciprofloxacin (CIP) and phenol were used to investigate the photocatalytic performance of the prepared samples under ultraviolet light irradiation. Results showed that the BiOCl/TP exhibited much higher activity for the degradation of all these model organic pollutants than pure TP. The mechanism for the enhancement of the photocatalytic performance was established with the help of the results of photocurrent measurements and Photoluminescence spectra. The results illustrated that the enhanced activity could be attributed to the formation of p-n heterojunctions between p-type BiOCl and n-type titanium phosphate, which effectively suppressed the recombination of photo-induced electron-hole pairs. Furthermore, the possible photocatalytic mechanisms on the degradation of the organic pollutants were also proposed. [ABSTRACT FROM AUTHOR]

A facile anion-exchange precipitation method was employed to synthesize 3D flower-like Ag 2 CO 3 /Mg-Al layered double hydroxide composite photocatalyst. Results showed that Ag 2 CO 3 nanoparticles dispersed uniformly on the petals of the flower-like Mg-Al LDH. The obtained nanocomposites exhibited high photocatalytic activities on different organic pollutants (cationic and anionic dyes, phenol) under visible light illumination. The high photocatalytic activity can be ascribed to the special structure which accomplishes the wide-distribution of Ag 2 CO 3 nanoparticles on the surfaces of the 3D flower-like nanocomposites. Therefore, it can provide much more active sites for the degradation of organic pollutant. Then the photocatalytic mechanism was also verified by reactive species trapping experiments in detail. The work would pave a facile way to prepare LDHs based hierarchical photocatalysts with high activity for the degradation of wide range organic pollutants under visible light irradiation. [ABSTRACT FROM AUTHOR]