A low red/far-red ratio restricts nitrogen assimilation by inhibiting nitrate reductase associated with downregulated TaNR1.2 and upregulated TaPIL5 in wheat (Triticum aestivum L.).

Understanding the physiological mechanism underlying nitrogen levels response to a low red/far-red ratio (R/FR) can provide new insights for optimizing wheat yield potential but has been not well documented. This study focused on the changes in nitrogen levels, nitrogen assimilation and nitrate uptake in wheat plants grown with and without additional far-red light. A low R/FR reduced wheat nitrogen accumulation and grain yield compared with the control. The levels of total nitrogen, free amino acid and ammonium were decreased in leaves but nitrate content was temporarily increased under a low R/FR. The nitrate reductase (NR) activity in leaves was more sensitive to a low R/FR than glutamine synthetase, glutamate synthase, glutamic oxalacetic transaminase and glutamic-pyruvic transaminase. Further analysis showed that a low R/FR had little effect on the NR activation state but reduced the level of NR protein and the expression of encoding gene TaNR1.2. Interestingly, a low R/FR rapidly induced TaPIL5 expression rather than TaHY5 and other members of TaPILs in wheat, suggesting that TaPIL5 was the key transcription factor response to a low R/FR in wheat and might be involved in the downregulation of TaNR1.2 expression. Besides, a low R/FR downregulated the expression of TaNR1.2 in leaves earlier than that of TaNRT1.1/1.2/1.5/1.8 in roots, which highlights the importance of NR and nitrogen assimilation in response to a low R/FR. Our results provide revelatory evidence that restricted nitrate reductase associated with downregulated TaNR1.2 and upregulated TaPIL5 mediate the suppression of nitrogen assimilation under a low R/FR in wheat.

Significantly enhanced the light absorption and charge separation of Bi0.5Na0.5TiO3 by coupling with CdS for high-performance piezo-photocatalysis.

Sodium bismuth titanate (Bi0.5Na0.5TiO3, BNT) is a typical lead-free piezoelectric material with perovskite structure, which exhibits great potential as piezo-photocatalyst but limited by the little response on visible light and insufficient carriers for efficient catalytic reactions. Herein, a novel BNT/CdS heterojunction was facilely synthesized by the two-step hydrothermal process for significantly enhanced piezo-photocatalytic degradation of organic dyes. The CdS nanoparticles with 35 nm in diameter are uniformly decorated on the highly crystallized BNT spheres. The obtained BNT/CdS heterojunction displays strong absorption of visible light because of the narrow band gap of CdS. Due to the strong built-in electric field under ultrasonic and efficient excitation by visible light, the photogenerated carriers can be efficiently separated at the BNT/CdS interface and migrate to the surface for catalytic reactions. As a result, the BNT/CdS shows much higher piezo-photocatalytic activity than that of BNT and can degrade 99% RhB within 60 min. Meanwhile, the piezo-photocatalytic performance of BNT/CdS is far better than that of individual photocatalysis or piezocatalysis. Moreover, the catalytic experiments in the presence of different scavengers indicate that ·O2- is the predominant active specie. The synthetic process is simple, low-cost, and controllable to produce high-performance BNT/CdS and is believed to show promising application prospect.

Ozone mechanism, kinetics, and toxicity studies of halophenols: Theoretical calculation combined with toxicity experiment.

Aromatic disinfection by-products (DBPs), which are generally more toxic than aliphatic DBPs, have attracted increasing attention. The toxicity of 13 typical halophenols on Scenedesmus obliquus was experimentally investigated, and the ozonation mechanism and kinetics of representative halophenols were further studied by quantum chemical calculations. The results showed that the EC50 values of halophenols ranged from 2.74 to 60.23 mg/L, and their toxicity ranked as follows: di-halogenated phenols > mono-halogenated phenols, mixed halogen-substituted phenols > single halogen-substituted phenols, and iodophenols > bromophenols > chlorophenols. The toxicity of halophenols was well described by the electronegativity index (ω) as lg(EC50)-1 = 6.228ω - 3.869, indicating halophenols capturing electrons as their potential toxicity mechanism. The reactions of O3 with halophenolate anions were dominated by three mechanisms: 1,3-dipolar cycloaddition, oxygen addition, and single electron transfer. The kinetic calculation indicated that O3 oxidized aqueous halophenols by reacting with halophenolate anions with the reaction rate constants as high as (0.91-3.47) × 1010 M-1 s-1. The number of halogen substituents affected the kO3, cal values of halophenolate anions, which are in the order of 2,4-dihalophenolate anions >4-halophenolate anions > 2,4,6-trihalophenolate anions. During the ozonation of 2,4,6-tribromophenol (246TBP), the toxic products (dimers and brominated benzoquinones) could be synergistically degraded by O3 and HO•. Thus, ozonation is feasible as a strategy to degrade aromatic DBPs.

Microplastics increases the heat tolerance of Daphnia magna under global warming via hormetic effects.

The ecological risk assessment of microplastics under global warming receives increasing attention. Yet, such studies mostly focused on increased mean temperatures (MT), ignoring another key component of global warming, namely daily temperature fluctuations (DTF). Moreover, we know next to nothing about the combined effects of multigenerational exposure to microplastics and warming. In this study, Daphnia magna was exposed to an environmentally relevant concentration of polystyrene microplastics (5 µg L-1) under six thermal conditions (MT: 20 â„ƒ, 24 â„ƒ; DTF: 0 â„ƒ, 5 â„ƒ, 10 â„ƒ) over two generations to investigate the interactive effects of microplastics and global warming. Results showed that microplastics had no effects on Daphnia at standard thermal conditions (constant 20 °C). Yet, microplastics increased the fecundity, heat tolerance, amount of energy storage, net energy budget and cytochrome P450 activity, and decreased the energy consumption when tested under an increased MT or DTF, indicating a hormesis effect induced by microplastics under warming. The unexpected increase in heat tolerance upon exposure to microplastics could be partly explained by the reduced energy consumption and/or increased energy availability. Overall, the present study highlighted the importance of including DTF and multigenerational exposure to improve the ecological risk assessment of microplastics under global warming.

Warming, temperature fluctuations and thermal evolution change the effects of microplastics at an environmentally relevant concentration.

Microplastics are sometimes considered not harmful at environmentally relevant concentrations. Yet, such studies were conducted under standard thermal conditions and thereby ignored the impacts of higher mean temperatures (MT), and especially daily temperature fluctuations (DTF) under global warming. Moreover, an evolutionary perspective may further benefit the future risk assessment of microplastics under global warming. Here, we investigated the effects of two generations of exposure to an environmentally relevant concentration of polystyrene microplastics (5 µg L-1) under six thermal conditions (2 MT × 3 DTF) on the life history, physiology, and behaviour of Daphnia magna. To assess the impact of thermal evolution we thereby compared Daphnia populations from high and low latitudes. At the standard ecotoxic thermal conditions (constant 20 °C) microplastics almost had no effect except for a slight reduction of the heartbeat rate. Yet, at the challenging thermal conditions (higher MT and/or DTF), microplastics affected each tested variable and caused an earlier maturation, a higher fecundity and intrinsic growth rate, a decreased heartbeat rate, and an increased swimming speed. These effects may be partly explained by hormesis and/or an adaptive response to stress in Daphnia. Moreover, exposure to microplastics at the higher mean temperature increased the fecundity and intrinsic growth rate of cold-adapted high-latitude Daphnia, but not of the warm-adapted low-latitude Daphnia, suggesting that thermal evolution in high-latitude Daphnia may buffer the effects of microplastics under future warming. Our results highlight the critical importance of DTF and thermal evolution for a more realistic risk assessment of microplastics under global warming.

Foliar dust as a reliable environmental monitor of heavy metal pollution in comparison to plant leaves and soil in urban areas.

Pollution of atmospheric particulate matter carrying heavy metals has posed a great threat to various ecosystem compartments. Here, a total of 540 samples from four ecosystem compartments (plant leaves, foliar dust, surface soil, and subsoil) were collected in urban soil-plant systems to characterize the heavy metal concentration and composition of foliar dust, to verify the suitability of foliar dust as an environmental monitor, and to explore the importance of foliar dust in shaping the heavy metal composition in plant leaves. We found that the concentrations of all detected elements (lead, zinc, copper, chromium, nickel, and manganese) in foliar dust were the highest among the four ecosystem compartments. The mass of element per unit leaf area, considering both the dust retention amount and the heavy metal concentration of foliar dust, had significant positive correlations with the degree of heavy metal pollution in soil. Foliar dust could reflect ambient elemental composition most reliably among the four ecosystem compartments. The above findings show that foliar dust is more suitable for environmental monitoring than soil and plant materials in urban areas. In addition, the elemental composition of plant leaves differed significantly with different soil-plant systems although species identity dominated the leaf elemental composition. The variation partitioning model and the partial correlation analysis confirm that foliar dust plays a more important role in shaping the elemental composition of plant leaves than soil. This study provides a new way for environmental pollution monitoring and contributes to a comprehensive understanding of atmospheric particulate matter.

Suppression of Sunscreen Leakage in Water by Amyloid-like Protein Aggregates.

A sunscreen offers indispensable skin protection against UV damage and related skin diseases. However, due to the poor interfacial stability of sunscreen coatings on the skin, the synthetic ingredients in sunscreen creams easily fall off and enter aquatic environments, causing large ecological hazards and skin protection failure. Herein, we tackle this issue by introducing amyloid-like protein aggregates into a sunscreen to noticeably enhance the interfacial robustness of sunscreen coatings on the skin. The synthesis of such an agent to suppress sunscreen leakage can be achieved by manipulating the phase transition of bovine serum albumin (BSA) in a mild aqueous solution at room temperature. The resulting phase-transitioned BSA (PTB) aggregates effectively entrap the sunscreen ingredients to generate a uniform cream coating on the skin with robust amyloid-mediated interfacial adhesion stability. With continuous flushing in aquatic environments, such as salt water and seawater, this PTB-modified sunscreen (PTB sunscreen) coated on the skin maintains a retention ratio as high as >92%, which is 2-10 times higher than those of commercially available sunscreen products. The high retention ratio of the PTB sunscreen in aquatic environments demonstrates the great potential of amyloid-like protein aggregates in the development of leakage-free sunscreens with low ecosystem hazards and long-lasting UV protection in aquatic environments.

The ecology of the plastisphere: Microbial composition, function, assembly, and network in the freshwater and seawater ecosystems.

Microplastics provide a unique habitat for microorganisms, forming the plastisphere. Yet the ecology of the plastisphere, including the microbial composition, functions, assembly processes, and interaction networks, needs to be understood. Here, we collected microplastics and their surrounding water samples in freshwater and seawater ecosystems. The bacterial and fungal communities of the plastisphere and the aquatic environment were studied based on 16S and internal transcribed spacer (ITS) high-throughput sequencing. We found that the plastisphere had a distinct microbial community and recruited a noteworthy proportion of unique species compared to the aquatic environment community, potentially altering ecosystem microbial community and causing microbial invasion. Using a random-forest machine-learning model, we identified a group of biomarkers that could best distinguish the plastisphere from the aquatic environment. Significant differences exist in microbial functions between the plastisphere and the aquatic environment, including functions of pathogenicity, compound degradation, as well as functions related to the cycling of carbon, nitrogen, and sulfur. And these functional differences were expressed differently in freshwater and seawater ecosystems. The oxidation-reduction potential, salinity, the concentrations of nitrogen-related ions (NO3-, NO2-, and NH4+), and the concentration of dissolved organic carbon in the surrounding environment drive the variation of the plastisphere. But environmental physicochemical properties explain less of the microbial community variation in the plastisphere than that in the aquatic environment. Niche-based processes govern the assembly of the plastisphere community, while neutral-based processes dominate the community assembly of the aquatic environment. Furthermore, compared to the aquatic environment, the plastisphere has a network of less complexity, more modules, higher modularity, and more competitive links in freshwater ecosystems, but the pattern is reversed in seawater ecosystems. Altogether, the microbial ecology of the new anthropogenic ecosystem-plastisphere-is unique and exerts different effects in freshwater and seawater ecosystems.

Unexpected optical limiting properties from MoS2 nanosheets modified by a semiconductive polymer.

Direct solvent exfoliation of bulk MoS2 with the assistance of poly(3-hexylthiophene) (P3HT) produces a novel two-dimensional organic/inorganic semiconductor hetero-junction. The obtained P3HT-MoS2 nanohybrid exhibits unexpected optical limiting properties in contrast to the saturated absorption behavior of both P3HT and MoS2, showing potential in future photoelectric applications.

Broadband optical limiting response of a graphene-PbS nanohybrid.

Graphene-based materials have shown promising nonlinear optical properties in the visible range. To extend their nonlinear optical response to the near infrared (NIR) region, we prepared a new nanohybrid consisting of uniform PbS quantum dots (QDs) attached on the reduced graphene oxide, named rGO-PbS, via a facile, low-cost, and phosphine-free method. The rGO-PbS nanohybrid exhibited superior optical limiting properties to either graphene oxide or PbS QDs upon both 532 nm and 1064 nm excitation in the nanosecond laser pulse regime, which is attributed to the synergetic effects stemming from charge transfer between the two components. Meanwhile, the thin films containing the rGO-PbS nanohybrid dispersed in polymethylmethacrylate (PMMA) also showed excellent optical limiting properties with high transparency, implying the potential applications of this hybrid material in broadband nonlinear optical devices.

Size-dependent nonlinear optical properties of atomically thin transition metal dichalcogenide nanosheets.

Size-dependent nonlinear optical properties of modification-free transition metal dichalcogenide (TMD) nanosheets are reported, including MoS2 , WS2 , and NbSe2 . Firstly, a gradient centrifugation method is demonstrated to separate the TMD nanosheets into different sizes. The successful size separation allows the study of size-dependent nonlinear optical properties of nanoscale TMD materials for the first time. Z-scan measurements indicate that the dispersion of MoS2 and WS2 nanosheets that are 50-60 nm thick leads to reverse saturable absorption (RSA), which is in contrast to the saturable absorption (SA) seen in the thicker samples. Moreover, the NbSe2 nanosheets show no size-dependent effects because of their metallic nature. The mechanism behind the size-dependent nonlinear optical properties of the semiconductive TMD nanosheets is revealed by transient transmission spectra measurements.

Fabrication of microlens arrays by localized hydrolysis in water droplet microreactors.

We report a facile self-assembly strategy for fabricating TiO2 microlens arrays by localized hydrolysis of TiCl4 precursor in water droplets. Microcontact printing was used to define hydrophilic areas on a substrate for space resolved hydrolytic reaction. The water droplets served as the templates, reactant, and microreactors. Highly ordered TiO2 microlens arrays could be produced, which exhibit excellent ability to focus light. Because both size and shape of the final TiO2 microlens can be controlled by the printed chemical pattern and the precursor concentration, it is possible to define TiO2 microlens arrays with different imaging properties. This new method shows attractive features of simplicity, low cost, and requires no heating process, hence is suitable for a range of applications.

Monitoring the layer-by-layer self-assembly of graphene and graphene oxide by spectroscopic ellipsometry.

Thin films of graphene oxide, graphene and copper (II) phthalocyanine dye have been successfully fabricated by electrostatic layer-by-layer (LbL) assembly approach. We present the first variable angle spectroscopic ellipsometry (VASE) investigation on these graphene-dye hybrid thin films. The thickness evaluation suggested that our LbL assembly process produces highly uniform and reproducible thin films. We demonstrate that the refractive indices of the graphene-dye thin films undergo dramatic variation in the range close to the absorption of the dyes. This investigation provides new insight to the optical properties of graphene containing thin films and shall help to establish an appropriate optical model for graphene-based hybrid materials.

High spatial resolution label-free detection of antigen-antibody binding on patterned surface by imaging ellipsometry.

High spatial resolution and large area thickness mapping of label-free protein microarray has been achieved using imaging ellipsometry (IE) under optimized conditions. The protein patterns with feature size down to 8×8 µm(2) was readily imaged, and the binding between the surface immobilized antigen and the antibody was monitored. Quantitative thickness analysis of antibody-antigen binding on the 32×32 µm(2) micron spots was successfully performed, and we have obtained a limit of detection as low as 1.2 pg/spot. This work demonstrates that appropriately optimized IE could be used as a highly sensitive and high through-put label-free technique for studying surface antigen-antibody recognition in sub-40 µm scale.