Heterogeneous bimetallic selenides encapsulated within graphene aerogel as advanced anodes for sodium ion batteries.

Metal selenides are promising anode candidates for sodium ion batteries (SIBs) because of their high theoretical capacity, low cost, and environmental friendship. However, the low rate capability at high current density due to its inherent low electrical conductivity and poor cycle stability caused by inevitable volume variations during cycling frustrate its practical applications. Herein, we have developed a simple metallic-organic frameworks (MOFs)-derived selenide strategy to synthesize a series of heterogeneous bimetallic selenides encapsulated within graphene aerogels (GA) as anodes for SIBs. The bimetallic selenides/GA composites have unique structural characteristics that can shorten the migration path for Na+/electrons and accommodate the volume variations via additional void space during cycling. The built-in electric fields induced at the heterointerfaces can greatly reduce the activation energy for rapid charge transfer kinetics and promote the diffusion of Na+/electrons. GA is also beneficial for accommodating the volume variations during cycling and improving conductivity. As an advanced anode for SIBs, the MoSe2-Cu1.82Se@GA with a special porous octahedron can deliver the highest capacity of 444.8 mAh/g at a high rate of 1 A/g even after 1000 cycles among the bimetallic selenides/GA composites.

Population identification and genetic diversity analysis of Fritillaria ussuriensis (Fritillaria) based on chloroplast genes atpF and petB.

The chloroplast genomes of five Fritillaria ussuriensis materials from different production areas were comparatively analyzed, atpF and petB were screened as specific DNA barcodes, and the population identification and genetic diversity of F. ussuriensis were analyzed based on them. The F. ussuriensis chloroplast genome showed a total length of 151 515-151 548 bp with a typical tetrad structure and encoded 130 genes. atpF and petB were used to amplify 183 samples from 13 populations, and they could identify 6 and 9 haplotypes, respectively. Joint analysis of the two sequences revealed 18 haplotypes, named H1-H18, with the most widely distributed and most abundant being H4. Ten haplotypes were unique for 7 populations that they could be used to distinguish from others. Haplotype diversity and nucleotide diversity were 0.99 and 2.09 × 10-3, respectively, indicating the genetic diversity was relatively rich. The results of the intermediary adjacency network showed that H5 was the oldest haplotype, and stellate radiation was centered around it, indicating that population expansion occurred in genuine production areas. This study lays a theoretical foundation for the population identification, genetic evolution, and breed selection of F. ussuriensis.

PnNAC2 promotes the biosynthesis of Panax notoginseng saponins and induces early flowering.

KEY MESSAGE: PnNAC2 positively regulates saponin biosynthesis by binding the promoters of key biosynthetic genes, including PnSS, PnSE, and PnDS. PnNAC2 accelerates flowering through directly associating with the promoters of FT genes. NAC transcription factors play an important regulatory role in both terpenoid biosynthesis and flowering. Saponins with multiple pharmacological activities are recognized as the major active components of Panax notoginseng. The P. notoginseng flower is crucial for growth and used for medicinal and food purposes. However, the precise function of the P. notoginseng NAC transcription factor in the regulation of saponin biosynthesis and flowering remains largely unknown. Here, we conducted a comprehensive characterization of a specific NAC transcription factor, designated as PnNAC2, from P. notoginseng. PnNAC2 was identified as a nuclear-localized protein with transcription activator activity. The expression profile of PnNAC2 across various tissues mirrored the accumulation pattern of total saponins. Knockdown experiments of PnNAC2 in P. notoginseng calli revealed a significant reduction in saponin content and the expression level of pivotal saponin biosynthetic genes, including PnSS, PnSE, and PnDS. Subsequently, Y1H assays, dual-LUC assays, and electrophoretic mobility shift assays (EMSAs) demonstrated that PnNAC2 exhibits binding affinity to the promoters of PnSS, PnSE and PnDS, thereby activating their transcription. Additionally, an overexpression assay of PnNAC2 in Arabidopsis thaliana witnessed the acceleration of flowering and the induction of the FLOWERING LOCUS T (FT) gene expression. Furthermore, PnNAC2 demonstrated the ability to bind to the promoters of AtFT and PnFT genes, further activating their transcription. In summary, these results revealed that PnNAC2 acts as a multifunctional regulator, intricately involved in the modulation of triterpenoid saponin biosynthesis and flowering processes.

[DNA barcode screening, identification of germplasm resources, and analysis of genetic diversity of Anemarrhena asphodeloides].

Anemarrhena asphodeloides is a common medicinal material used in clinical prescriptions and Chinese patent medicine. In this study, the Illumina platform was used to obtain the chloroplast genome sequences of seven kinds of A. asphodeloides from different areas. The specific DNA barcodes were screened by comparative genomics analysis, and the DNA barcodes were used to identify the germplasm resources and analyze the genetic diversity of A. asphodeloides samples from different areas in China. All the seven chloroplast genomes had a ring structure. The total length was 156 801-156 930 bp, and 113 genes were annotated, including 79 protein-coding genes, 30 tRNA genes, and four rRNA genes. The comparative genomics analysis showed that rps16, trnG-GCC, atpF, rpoB, ycf3, rpl16, ndhF, trnS-GCU＿trnG-GCC, petN-psbM, and ndhF-rpl32 were potential candidates for specific DNA barcodes of A. asphodeloides. In this study, the second intron of ycf3 and atpF intron sequences with a sequence length of 700-800 bp and easy amplification were selected for polymerase chain reaction(PCR) amplification and sequencing of 594 samples from 26 areas. The sequence analysis showed that six and eight haplotypes of ycf3 and atpF sequences could be identified, respectively, and 17 haplotypes could be identified by combined analysis of the two sequences, which were named Hap1-Hap17. The haplotype diversity(H_d), nucleotide diversity(P_i), and genetic distance of A. asphodeloides in 26 populations were 0.68, 0.93×10~(-3), and 0-0.003 1, respectively, indicating that the genetic diversity within the species of A. asphodeloides is rich. The intermediary adjacent network analysis showed that Hap5 was the oldest haplotype, which was mainly distributed in Yixian county of Baoding, Hebei province, Hequ county of Xinzhou, Shanxi province, and Xiangfen county of Linfen, Shanxi province. This study has important guiding significance for the identification of A. asphodeloides species, the protection and development of germplasm resources, and the identification of production areas, and it provides a research basis for further revealing the genetic evolution law of A. asphodeloides.

A facile approach for oil-water separation using superhydrophobic polystyrene-silica coated stainless steel mesh bucket.

Inspired by traditional shaduf technology in the irrigation field, we fabricated a superhydrophobic stainless steel mesh bucket by layering polystyrene and SiO2 nanoparticles through a facile dip coating technique for effective oil-water separation. The superhydrophobic steel mesh bucket could effectively lift oil as well as microplastic pollutants from the water surface. The water contact angle of a two-layered polystyrene-silica coating was 158.5° ± 2°, while the oil contact angle was nearly 0°. The oil-water separation performance of superhydrophobic mesh was tested using several kinds of oil. The separation efficiency achieved for low viscous oil was 99.33 %, while 86.66 % efficiency was recorded for high viscous oil. The superhydrophobic mesh showed high durability against mechanical tests including bending, folding, twisting, adhesive tape tearing (25 cycles), and sandpaper abrasion (20 cycles). The mesh presented admirable thermal and chemical durability. The present superhydrophobic steel mesh bucket is a suitable candidate for large-scale application.

PnMYB4 negatively modulates saponin biosynthesis in Panax notoginseng through interplay with PnMYB1.

Saponins are the main triterpenoid ingredients from Panax notoginseng, a well-known Chinese medicine, and are important sources for producing drugs to prevent and treat cerebrovascular and cardiovascular diseases. However, the transcriptional regulatory network of saponin biosynthesis in P. notoginseng is largely unknown. In the present study we demonstrated that one R2R3-MYB transcription factor, designated PnMYB4, acts as a repressor of saponin accumulation. Suppression of PnMYB4 in P. notoginseng calli significantly increased the saponin content and the expression level of saponin biosynthetic genes. PnMYB4 directly bound to the promoters of key saponin biosynthetic genes, including PnSS, PnSE, and PnDS, to repress saponin accumulation. PnMYB4 and the activator PnMYB1 could interacted with PnbHLH, which is a positive regulator of saponin biosynthesis, to modulate the biosynthesis of saponin. PnMYB4 competed with PnMYB1 for binding to PnbHLH, repressing activation of the promoters of saponin structural genes induced by the PnMYB1-PnbHLH complex. Our study reveals that a complex regulatory module of saponin biosynthesis is associated with positive and negative MYB transcriptional regulators and provides a theoretical basis for improving the content of saponins and efficacy of P. notoginseng.

[Specific DNA barcodes, germplasm resources, and genetic diversity of Eleutherococcus senticosus].

Eleutherococcus senticosus is one of the Dao-di herbs in northeast China. In this study, the chloroplast genomes of three E. senticosus samples from different genuine producing areas were sequenced and then used for the screening of specific DNA barcodes. The germplasm resources and genetic diversity of E. senticosus were analyzed basing on the specific DNA barcodes. The chloroplast genomes of E. senticosus from different genuine producing areas showed the total length of 156 779-156 781 bp and a typical tetrad structure. Each of the chloroplast genomes carried 132 genes, including 87 protein-coding genes, 37 tRNAs, and 8 rRNAs. The chloroplast genomes were relatively conserved. Sequence analysis of the three chloroplast genomes indicated that atpI, ndhA, ycf1, atpB-rbcL, ndhF-rpl32, petA-psbJ, psbM-psbD, and rps16-psbK can be used as specific DNA barcodes of E. senticosus. In this study, we selected atpI and atpB-rbcL which were 700-800 bp and easy to be amplified for the identification of 184 E. senticosus samples from 13 genuine producing areas. The results demonstrated that 9 and 10 genotypes were identified based on atpI and atpB-rbcL sequences, respectively. Furthermore, the two barcodes identified 23 genotypes which were named H1-H23. The haplotype with the highest proportion and widest distribution was H10, followed by H2. The haplotype diversity and nucleotide diversity were 0.94 and 1.82×10~(-3), respectively, suggesting the high genetic diversity of E. senticosus. The results of the median-joining network analysis showed that the 23 genotypes could be classified into 4 categories. H2 was the oldest haplotype, and it served as the center of the network characterized by starlike radiation, which suggested that population expansion of E. senticosus occurred in the genuine producing areas. This study lays a foundation for the research on the genetic quality and chloroplast genetic engineering of E. senticosus and further research on the genetic mechanism of its population, providing new ideas for studying the genetic evolution of E. senticosus.

[Identification and quality evaluation of germplasm resources of commercial Scutellaria baicalensis based on DNA barcode and HPLC].

Scutellaria baicalensis is a commonly used Chinese medicinal herb. In this study, we identified the germplasm resources of commercial S. baicalensis samples based on trnH-psbA, petA-psbJ, and ycf4-cemA sequences according to the available chloroplast genome sequencing results, and measured the content of baicalin by HPLC. Through the above means we determined the best DNA barcode that can be used to detect the germplasm resources and evaluate the quality of commercial S. baicalensis samples. A total of 104 samples were collected from 24 provinces, from which DNA was extracted for PCR amplification. The amplification efficiencies of trnH-psbA, petA-psbJ, and ycf4-cemA sequences were 100%, 59.62%, and 25.96%, respectively. The results of sequence analysis showed that 5, 4, and 2 haplotypes were identified based on trnH-psbA, petA-psbJ, and ycf4-cemA sequences, respectively. However, the sequences of haplotypes in commercial samples were different from that of the wild type, and the joint analysis of three fragments of S. baicalensis only identified 6 haplotypes. Furthermore, the phylogenetic analysis and genetic distance analysis indicated that trnH-psbA could be used to identify S. baicalensis from adulterants. The above analysis showed that trnH-psbA was the best fragment for identifying the germplasm resources of commercial S. baicalensis samples. We then analyzed the haplotypes(THap1-THap5) of commercial S. baicalensis samples based on trnH-psbA and found that THap2 was the main circulating haplotype of the commercial samples, accounting for 86.55% of the total samples, which indicated the scarce germplasm resources of commercial S. baicalensis samples. The content of baicalin in all the collected commercial S. baicalensis samples exceeded the standard in Chinese Pharmacopoeia and had significant differences(maximum of 12.21%) among samples, suggesting that the quality of commercial S. baicalensis samples varied considerably. However, there was no significant difference in baicalin content between different provinces or between different haplotypes. This study facilitates the establishment of the standard identification system for S. baicalensis, and can guide the commercial circulation and reasonable medication of S. baicalensis.

Overexpression of PnMYB2 from Panax notoginseng induces cellulose and lignin biosynthesis during cell wall formation.

MAIN CONCLUSION: Panax notoginseng PnMYB2 is a transcriptional activator of primary and secondary cell wall formation by promoting the PCW-specific gene CesA3 and key lignin biosynthetic gene CCoAOMT1, respectively. R2R3-MYB transcription factors play important roles in regulation secondary cell wall (SCW) formation. However, there are few reports on the functions of MYB transcription factors which involved in both primary cell wall (PCW) and SCW formation. Here, we isolated an R2R3-MYB transcription factor, PnMYB2, from Panax notoginseng roots which are widely used in Chinese traditional medicines and contain abundant cellulose and lignin. The expression pattern of PnMYB2 was similar to the accumulation pattern of cellulose and lignin contents in different organs. PnMYB2 localized in the nucleus and may function as a transcriptional activator. Overexpression of PnMYB2 in Arabidopsis thaliana enhanced cellulose and lignin biosynthesis, and remarkably increased thickness of PCW and SCW in the stem of transgenic plants compared with wild-type plants. The expression levels of genes associated with PCW-specific cellulose synthase (CesA) genes and key SCW-specific lignin biosynthetic genes were significantly increased in PnMYB2-overexpressing plants compared to the wild type plants. Furthermore, yeast one-hybrid, dual-luciferase reporter assays and electrophoretic mobility shift assays (EMSA) results verified that PnMYB2 could bind and activate the promoters of AtCesA3 and PnCesA3, which are the PCW-specific cellulose biosynthetic genes, and AtCCoAOMT1 and PnCCoAOMT1, which are the key lignin biosynthetic genes. These results demonstrated the central role of PnMYB2 in PCW-specific cellulose formation and SCW-specific lignin biosynthesis.

Electrochemical nitrogen reduction: recent progress and prospects.

Ammonia is one of the most useful chemicals for the fertilizer industry and is also promising as an important energy carrier for fuel cell application, and is currently mostly produced by the traditional Haber-Bosch process under high temperature and pressure conditions. This energy-intensive process is detrimental to the environment due to the dependence on fossil fuels and the emission of significant greenhouse gases (such as CO2). Ammonia production via the electrochemical nitrogen reduction reaction (ENRR) has been recognized as a green sustainable alternative to the Haber-Bosch process in recent years. Current ENRR research mainly focuses on the catalyst for ammonia selective production and the enhancement of faradaic efficiency at high current density; however, these have not been explored well due to the unavailability of highly efficient and cheap catalysts. Herein, this review provides information on the ENRR process along with (i) theoretical background, (ii) experimental methodology of the electrocatalytic process and (iii) computational screening of promising catalysts. The impact of active sites and defects on the activity, selectivity, and stability of the catalysts is deeply understood. Furthermore, we demonstrate the mechanistic understanding of the ENRR process on the surface of catalysts, with the aim of boosting the improvement of the ENRR activities. The ammonia detection methods are also summarized along with thorough discussion of control experiments. Finally, this review highlights prevailing problems in existing ENRR methods of ammonia production along with technical advancements proposed to address these issues and concludes with comments on opportunities and future directions of the ENRR process.

Insight into the inhibitory mechanism of soluble ionic liquids on the transport of TiO2 nanoparticles in saturated porous media: Roles of alkyl chain lengths and counteranion types.

Column experiments were carried out to investigate the transport of TiO2 nanoparticles (nTiO2) in water-saturated porous media in the presence of various imidazolium-based ionic liquids (ILs) with different alkyl chain lengths and counteranions. The results indicated that the effects of ILs on nTiO2 transport were considerably dependent upon IL species. In general, the transport-inhibition effects increased with the increasing length of branched alkyl chain on the ILs (i.e., [C6mim]Cl > [C4mim]Cl > [C2mim]Cl). The trend was dominated by the hydrophobicity effects of ILs. Meanwhile, the inhibitory effects of ILs were strongly related to the counteranions and followed the order of [C4mim]Cl > [C4mim][TOS] > [C4mim][PF6], mainly due to different electrostatic repulsion force between nanoparticles and porous media in the presence of various ILs. Furthermore, the inhibitory role of [C4mim][TOS] in nTiO2 transport under acidic conditions (i.e., pH 6.5) was greater than that under alkaline conditions (i.e., pH 8.0). The dominant mechanism was that the differences in the extent of electrostatic repulsion between sand grains and nTiO2 with or without ILs at pH 6.5 were larger than that at pH 8.0. Moreover, two-site kinetic retention model and DLVO theory provided good descriptions for the transport behaviors of nTiO2 with different ILs.

From mouse to mouse-ear cress: Nanomaterials as vehicles in plant biotechnology.

Biological applications of nanomaterials as delivery carriers have been embedded in traditional biomedical research for decades. Despite lagging behind, recent significant breakthroughs in the use of nanocarriers as tools for plant biotechnology have created great interest. In this Perspective, we review the outstanding recent works in nanocarrier-mediated plant transformation and its agricultural applications. We analyze the chemical and physical properties of nanocarriers determining their uptake efficiency and transport throughout the plant body.

Dual labeled mesoporous silica nanospheres based electrochemical immunosensor for ultrasensitive detection of carcinoembryonic antigen.

Carcinoembryonic antigen (CEA) is a well-known cancer biomarker for the detection of several malignancies. The development of ultrasensitive CEA diagnostic tools is crucial for early detection and progression observation of tumors. Herein, a dual signal amplified sandwich-type electrochemical immunoassay was developed based on dual-labeled mesoporous silica nanospheres as a signal amplifier, combined with NiO@Au decorated graphene as a conductive layer for ultrasensitive and rapid determination of CEA. The dual-labeled mesoporous silica (DLMS) nanosphere, which was synthesized by entrapping Au nanorod (Au NR) and horseradish peroxidase (HRP) in the channels of amine-functionalized SBA-15 followed by subordinate antibody (Ab2) conjugation which was denoted as Au NR@SBA-15/Ab2-HRP. The dual signal amplification from Au NR@SBA-15 and HRP enhanced the sensitivity of the proposed immunoassay. Consequently, the developed DLMS based immunosensor displayed ultra-low limits of detection of 5.25 fg/mL and a wide range of linearity (0.1-5 pg/mL), which was extended for CEA determination in real-time samples with improved recoveries of >98%. Therefore, this dual amplification prototype would cater to the clinical requirements for the ultrasensitive detection of CEA biomarkers.

[Phytochemical and pharmacological progress on genus Syringa].

The genus Syringa, belonging to the family Oleaceae, are distributed naturally in the European and Asian regions.This genus is composed of more than 20 species worldwide, among which about 16 species including 10 endemic ones are discovered in China.The Syringa sp.are extensively used as herbal medicine and ornamental aspects, such as the roots and stems of S. pinnatifolia, which is one of the typical Mongolian folk medicines in China for the treatment of cardiovascular and pulmonary symptoms. As a continuous research following the previous summary in 2015, the present reriew describes the phytochemical and pharmacological progress of the genus, which hopes to provide a valuable reference to its research, development and clinic application.

Effects of clay colloids on ciprofloxacin transport in saturated quartz sand porous media under different solution chemistry conditions.

Antibiotics, a highly prevalent class of environmental organic pollutants, are becoming a matter of global concern. Clay minerals that are ubiquitous in subsurface environments may play an important role in the fate and transport of antibiotics. Taking ciprofloxacin (CIP) as a model antibiotic, this work explored the role of clay colloids (kaolinite and montmorillonite) on the adsorption and transport of CIP under different chemical solution conditions. The adsorption isotherms showed that montmorillonite colloids had a larger CIP sorption capacity than kaolinite colloids. The results of transport experiments indicated that montmorillonite colloids could promote CIP transport in saturated sand columns, but the addition of kaolinite colloids affected CIP mobility to a much smaller extent. The much stronger transport-enhancement effect of montmorillonite colloids was due to CIP adsorbed strongly to the colloids and desorption hysteresis of colloid-adsorbed CIP, likely stemming from the intercalation of this antibiotic in the interlayer of montmorillonite. Interestingly, transport of clay colloids increased with the increasing pH from 5.0 to 9.0; however, CIP transport decreased with the increasing pH in the presence of clay colloids. The observations were likely attributable to pH-dependent ciprofloxacin adsorption/desorption to clay minerals. Increasing the concentrations of NaCl and CaCl2 generally decreased the contaminant-mobilizing ability of montmorillonite colloids, mainly by increasing the aggregation of colloids and thus, decreasing the transport of colloid-adsorbed CIP. Moreover, under the test conditions (1 mM NaCl and pH 7.0), the presence of CIP inhibited the transport of clay colloids due to the increase in aggregate size of clay colloids with the addition of CIP. Overall, these findings suggest that clay colloids with high adsorption abilities for antibiotics in the subsurface environment may act as a carrier for certain antibiotic compounds.

Spatial Compartmentalization of Cobalt Phosphide in P-Doped Dual Carbon Shells for Efficient Alkaline Overall Water Splitting.

Highly durable and earth-abundant bifunctional catalysts with low cell voltage are desirable for alkaline overall water splitting in the industrial fields. Herein, a novel carbon-based CoP hybrid with spatial compartmentalization of CoP nanoparticles (NPs) in P-doped dual carbon shells is achieved via a cheap Co-glycerate-template strategy. Benefitted from the uniform atomic blending of Co2+ ions in the Co-glycerate precursors, CoP NPs in situ formed in the confined space with NaH2PO2 as phosphorus source during the annealing process; meanwhile, glycerate suffered carbonization and transformed into P-doped dual carbon shells during the annealing process, including interior thin carbon coating, closely encircled CoP NP, and peripheral hollow carbon sphere loading a lot of CoP NPs. Not only does spatial compartmentalization of CoP NPs avoid the aggregation and expose more active sites but also P-doped dual carbon shells improve the conductivity and durability of the catalyst. As expected, the optimized hybrid exhibits outstanding electrocatalytic activities in alkaline media, such as hydrogen evolution reaction (HER) overpotential of 101 mV, oxygen evolution reaction (OER) overpotential of 280 mV, and a low cell voltage of 1.66 V to deliver a current density of 10 mA cm-2. Moreover, durability and stability are greatly improved under harsh electrochemical conditions. The current strategy shades new insight into the development of carbon-based transition metal phosphides (TMP) catalysts for electrocatalysis applications.

A mesoporous silver-doped TiO2-SnO2 nanocomposite on g-C3N4 nanosheets and decorated with a hierarchical core-shell metal-organic framework for simultaneous voltammetric determination of ascorbic acid, dopamine and uric acid.

An electrochemical sensor is described for the simultaneous voltammetric determination of ascorbic acid (AA), dopamine (DA), and uric acid (UA). An indium-tin oxide (ITO) electrode was modified with a hierarchical core-shell metal-organic framework and Ag-doped mesoporous metal-oxide based hybrid nanocomposites on g-C3N4 nanosheets. The morphology, structural and chemical composition of the hybrid nanocomposite was characterized using different analytical methods. The modified ITO showed superior electrocatalytic performance towards the oxidation of AA, DA and UA due to the enhanced surface area, synergistic effects and well-organized porous assembly. Figures of merit, include (a) linear responses from 0.1 to 200 µM, 2.5 to 100 µM and 2.5 to 625 µM; (b) detection limits (at S/N = 3) of 0.02, 0.01 and 0.06 µM, and (c) well separated oxidation peaks near -50, 186 and 390 mV (vs. Ag/AgCl) for simultaneous sensing AA, DA and UA, respectively. The sensor was evaluated by analysing spiked serum samples and gave data with precision, with recoveries of >98%. Graphical abstractSchematic Representation of a Mesoporous Silver-doped TiO2-SnO2 Nanocomposite (h-ATS) on g-C3N4 Nanosheets and Decorated with a Hierarchical Core-Shell Metal-Organic Framework (NC@GC) Based Electrochemical Sensor for Simultaneous Voltammetric Detection of Ascorbic acid, Dopamine and Uric acid.

Transport of Cd2+ through saturated porous media: Insight into the effects of low-molecular-weight organic acids.

Low-molecular-weight organic acids (LMWOAs) are ubiquitous in the aquatic environment and consequently may affect the heavy metal transport in aquifer systems. In this study, the influences of LMWOAs on the transport of Cd2+ under different pH conditions in saturated porous media were evaluated. For this, three LMWOAs such as acetic acid, tartaric acid, and citric acid were employed. A two-site nonequilibrium transport model was applied to simulate the transport data. Under acidic conditions (pH 5.0), the results indicated that LMWOAs inhibited the transport of Cd2+ even at the low concentrations of organic acids (i.e., 0.05 and 0.1 mM). The inhibition effects might be attributed to the complexation role of the sand surface-bound organic acids and also electrostatic interaction. Meanwhile, the inhibition effects of LMWOAs on Cd2+ transport in the following order of citric acid > tartaric acid > acetic acid, which was also in agreement with the decreasing complex stability constants between Cd2+ and LMWOAs. This order may be dependent on their molecular structures (i.e., amount and type of functional groups) and complexing strength. Interestingly, when the LMWOA concentrations 0.5 mM, tartaric acid and citric acid still inhibited Cd2+ transport, while acetic acid slightly enhanced the Cd2+ mobility due to its weaker complexing strength. However, under neutral conditions (pH 7.0), LMWOAs generally enhanced the transport of Cd2+. The transport-enhancement of LMWOAs was ascribed to the formation of stable aqueous non-adsorbing Cd-organic acid complexes. In addition, citric acid could obviously inhibit the transport of Cd2+ under competitive transport conditions (i.e., with competing cations), which is mainly due to different complex affinities of citric acid to Pb2+ and Cd2+. These findings demonstrate that LMWOAs may inhibit or facilitate Cd2+ transport under different environmental conditions. Thus, environmental assessment concerning the transport of heavy metals should consider the roles of organic acids.

Ti3+ self-doped TiO2-x nanowires for efficient electrocatalytic N2 reduction to NH3.

Electrochemical N2 reduction is an environmentally friendly and sustainable approach for NH3 synthesis under mild conditions, while an efficient electrocatalyst is crucial for the N2 reduction reaction (NRR). Herein, we report Ti3+ self-doped TiO2-x nanowires on Ti mesh (Ti3+-TiO2-x/TM) as an efficient non-noble-metal NRR electrocatalyst with excellent selectivity. In 0.1 M Na2SO4, the Ti3+-TiO2-x/TM achieves a high faradaic efficiency of 14.62% with a NH3 yield of 3.51 × 10-11 mol s-1 cm-2 at -0.55 V vs. the reversible hydrogen electrode. Density functional theory calculations further reveal that introducing Ti3+ decreases the reaction energy barrier and increases the number of active sites on the TiO2 surface for the NRR.