Selenium (Se) biofortification in rice addresses dietary Se deficiencies. While Se fertilization is key, the efficiency and molecular mechanisms differ among Se forms (selenate, nano-Se (SeNPs)) and application methods (soil vs. foliar). This study aimed to compare the effects of selenate and biosynthesized SeNPs, applied via soil and foliar methods, on rice growth, Se accumulation, speciation, and the associated transcriptional responses. Rice plants were treated with selenate or biosynthesized SeNPs via soil application or foliar spraying. Biomass, yield, grain Se concentration and speciation were analyzed. Transcriptomic profiling of roots (soil-applied Se) and leaves (foliar-applied Se) was performed, with validation by qPCR and WGCNA. Both application methods enhanced biomass and yield. Foliar spraying was more efficient for grain Se enrichment, increasing Se concentration by 28.13-fold (selenate) and 89.87-fold (SeNPs), versus 7.83–9.87-fold for soil application. Selenomethionine was the predominant Se species in grains. Transcriptomics revealed selenate upregulated sulfate transporter and xylem-related genes in roots, whereas SeNPs enhanced aquaporin and sulfur assimilation gene expression. Foliar SeNPs triggered stomatal and aquaporin-related gene expression. Both forms influenced sulfur/nitrogen metabolism, with SeNPs additionally modulating organic acid and amino acid pathways. WGCNA identified co-expression modules correlated with grain Se content and selenomethionine proportion, enriched in transcription factors (MYB, WRKY, bHLH) and ABC transporters. Foliar application, particularly of SeNPs, is highly effective for Se biofortification in rice, associated with distinct molecular uptake and assimilation pathways. These findings provide insights for optimizing Se fertilization strategies to enhance dietary Se supply.

Soil cadmium (Cd) pollution poses severe threats to food security and human health. Previous studies have reported that both nanoparticles (NPs) and biochar have potential for soil Cd remediation. In this study, a composite material (BN) was synthesized using low-dose TiO2 NPs and silkworm excrement-based biochar, and the mechanism of its effect on the Cd-contaminated soil-pak choi system was investigated. The application of 0.5 % BN to the soil effectively reduced 24.8 % of diethylenetriaminepentaacetic acid (DTPA) Cd in the soil and promoted the conversion of Cd from leaching and HOAc-extractive to reducible forms. BN could improve the adsorption capacity of soil for Cd by promoting the formation of humic acid (HA) and increasing the cation exchange capacity (CEC), as well as activating the oxygen-containing functional groups such as CO and CO. BN also increased soil urease and catalase activities and improved the synergistic network among soil bacterial communities to promote soil microbial carbon (C) and nitrogen (N) cycling, thus enhancing Cd passivation. Moreover, BN increased soil biological activity-associated metabolites like T-2 Triol and altered lipid metabolism-related fatty acids, especially hexadecanoic acid and dodecanoic acid, crucial for bacterial Cd tolerance. In addition, BN inhibited Cd uptake and root-to-shoot translocation in pak choi, which ultimately decreased Cd accumulation in shoots by 51.0 %. BN significantly increased the phosphorus (P) uptake in shoots by 59.4 % by improving the soil microbial P cycling. This may serve as a beneficial strategy for pak choi to counteract Cd toxicity. These findings provide new insights into nanomaterial-doped biochar for remediation of heavy metal contamination in soil-plant systems.

MXenes is a new two-dimensional material with good electrical conductivity and high theoretical pseudocapacitance, which is widely used in various energy storage devices. Heterogeneous atom doping is one of the effective strategies to adjust the properties of MXenes and improve its electrochemical performance. In this work, a facile and cost-effective KTPP (potassium tripolyphosphate, phosphorus source) assistance strategy is demonstrated to dope Ti3C2Tx MXene with phosphorus atoms by heat treatment. The results show that the phosphorus doping level reached 1.25 at.%. As expected, the specific capacitance of the phosphate-doped Ti3C2Tx electrode is 365.1 F g- 1 at the scanning rate of 10 mV s- 1, which is twice that of the pristine Ti3C2Tx (183.1 F g- 1). Besides, the flexible supercapacitor device assembled with Ti3C2Tx-P-300 degrees C-3h sample has a high energy density of 10.76 Wh kg- 1 at 483.03 W kg- 1 power density and the capacitance retention rate is 84.51 % after 5000 cycles at the current density of 1 A g- 1. With bent at different angles (0 degrees, 60 degrees, 90 degrees, 120 degrees), the specific capacitance values of flexible supercapacitor devices have not changed significantly, and the capacitance retention rate reached 90.09 %. The reason for the enhanced electrochemical performance is that the phosphorus doping can increase the active sites of Ti3C2Tx, bring P-O bonds that enhance activity, optimize the redox reaction process, and accelerate the ion transport rate. Therefore, a simple and effective method to improve the electrochemical performance of Ti3C2Tx MXene is proposed in this work.

Deficiencies of selenium (Se), a necessary microelement for humans, can be remedied by appropriately supplying Se-enriched rice. However, overconsumption of Se-enriched rice poses a potential risk. To accurately assess Se human health risks associated with Se-enriched rice consumption, we developed a rat in vivo model to systematically explore the relative bioavailability of Se (Se-RBA) from Se-enriched rice from a wide geographic range. Se concentrations were in the range of 0.06 +/- 0.05 to 0.15 +/- 0.15 mg kg(-1), averaging 0.12 +/- 0.11 mg kg(-1), in 196 rice samples from 21 Chinese provinces, and selenomethionine (SeMet) was the dominant Se fraction (58.0-96.5%). The Se-RBA of Se-enriched rice calculated from urine ranged from 34.86% to 102.29%, averaging 62.27% (n = 12), and was positively correlated with the proportion of SeMet in rice (p < 0.05, R-2 = 0.51). Furthermore, the Se intake calculated based on the Se-RBA indicated that the Se intake of consumers of Se-enriched rice was far less than the tolerable upper intake level. Thus, the limits established by law assume overestimates of the actual nutritional value of the Se content in Se-enriched rice, and it is important to consider Se bioavailability. The current study offers suggestions for future research and provides methods to reduce the uncertainty in estimating the health risks associated with Se intake from rice.

Although selenium (Se) is an essential trace element in humans, the intake of Se from food is still generally inadequate throughout the world. Inoculation with arbuscular mycorrhizal fungi (AMF) improves the uptake of Se in rice (Oryza sativa L.). However, the mechanism by which AMF improves the uptake of Se in rice at the transcriptome level is unknown. Only a few studies have evaluated the effects of uptake of other elements in rice under the combined effects of Se and AMF. In this study, Se combined with the AMF Funneliformis mosseae (Fm) increased the biomass and Se concentration of rice plants, altered the pattern of ionomics of the rice roots and shoots, and reduced the antagonistic uptake of Se with nickel, molybdenum, phosphorus, and copper compared with the treatment of Se alone, indicating that Fm can enhance the effect of fertilizers rich in Se. Furthermore, a weighted gene co-expression network analysis (WGCNA) showed that the hub genes in modules significantly associated with the genes that contained Se and were related to protein phosphorylation, protein serine/threonine kinase activity, membrane translocation, and metal ion binding, suggesting that the uptake of Se by the rice roots may be associated with these genes when Fm and Se act in concert. This study provides a reference for the further exploration of genes related to Se uptake in rice under Fm treatment.

In this work, nitrogen-doped graphene is achieved in a short time at low temperature by UV light radiation which induces thermal decomposition of ammonium bicarbonate (NH4HCO3) to release NH3 as nitrogen source. XRD and XPS results confirm that the most of oxygen-containing functional groups are removed from graphene oxide after photoreduction and nitrogen doping, and thus graphene oxide was reduced to form N-doped graphene. The N content of the obtained graphene is 2.91 at.%. The SEM images show that the graphene film on Ni foam is composed of spherical graphene nanoparticles, making it easy to adsorb more ions to form electric double-layer capacitance effect and increase the specific capacitance. As expected, the specific capacitance of UV assisted N -doped graphene is as high as 328.85 F g-1 at 0.5 A g-1, which is larger than that of graphene without nitrogen doping (261.13 F g-1 at 0.5 A g-1). Meanwhile, N-doped graphene shows good rate performance and cycle stability (capacitance retention rate: 96.1 % after 10, 000 cycles). This work shows the excellent supercapacitive performance of N-doped graphene, and also provides a simple and environmentally friendly method for rapid reduction and nitrogen doping of graphene oxide to prepare high-performance graphene.

The surface modification of MXene by heterogeneous atoms shows great potential in improving the charge storage capacity of MXene. Herein, a strategy of rapid in-situ phosphorus doping at low temperature is demonstrated for preparing functionalized Ti3C2Tx MXene (Ti3C2Tx-P) using sodium hypophosphate as phosphorus source. The phosphorus doping can increase the layer spacing of Ti3C2Tx and yield P-O and P-C bonds in Ti3C2Tx, resulting in more rapid paths for the migration of electrolyte ions into electrode and more active sites for pseudocapacitance effects. As flexible electrode of supercapacitor, the specific capacitance of Ti3C2Tx-P reaches as high as 476.9F g(-1) (745.4F cm(-3)), which is far larger than that of the raw Ti3C2Tx (344.4F g(-)1, 438.5F cm(-3)). In addition, a flexible quasi-solid supercapacitor device assembled by Ti3C2Tx-P film shows high specific capacitance of 103F g(-1) at 5 mV s(-1). When the power density is 250 W kg(-1) and 10000 W kg (-1), the corresponding energy density reaches 15.8 Wh kg(-1 )and 6.1 Wh kg (-1), respectively. Therefore, our work not only reveals the role of P atom doping in improving the structure, composition and electrochemical performance of Ti3C2Tx, but provides a method for surface modification and functionalization of MXene materials.