Tuning Hole Transport Properties and Perovskite Crystallization via Pyridine-Based Molecules for Quasi-2D Perovskite Solar Cells.

Quasi-2D perovskites show great potential as photovoltaic devices with superior stability, but the power conversion efficiency (PCE) is limited by poor carrier transport. Here, it is simultaneously affected the hole transport layer (HTL) and the perovskite layer by incorporating pyridine-based materials into poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT:PSS) to address the key problem above in 2D perovskites. With this approach, the enhanced optoelectronic performance of the novel PEDOT:PSS is due to electron transfer between the additives and PEDOT or PSS, as well as a dissociation between PEDOT and PSS based on experimental and theoretical studies, which facilitates the charge extraction and transfer. Concurrently, in-situ X-ray scattering studies reveal that the introduction of pyridine-based molecules alters the transformation process of the perovskite intermediate phase, which leads to a preferred orientation and ordered distribution caused by the Pb─N chemical bridge, achieving efficient charge transport. As a result, the pyridine-treated devices achieve an increased short-circuit current density (Jsc ) and PCE of over 17%.

Recognizing Functional Groups of MES/APG Mixed Surfactants for Enhanced Solubilization toward Benzo[a]pyrene.

Benzo[a]pyrene is difficult to remove from soil due to its high octanol/water partition coefficient. The use of mixed surfactants can increase solubility but with the risk of secondary soil contamination, and the compounding mechanism is still unclear. This study introduced a new approach using environmentally friendly fatty acid methyl ester sulfonate (MES) and alkyl polyglucoside (APG) to solubilize benzo[a]pyrene. The best result was obtained when the ratio of MES/APG was 7:1 under 6 g/L total concentration, with an apparent solubility (Sw) of 8.58 mg/L and a molar solubilization ratio (MSR) of 1.31 for benzo[a]pyrene, which is comparable to that of Tween 80 (MSR, 0.95). The mechanism indicates that the hydroxyl groups (-OH) in APG form "O-H···OSO2-" hydrogen bonding with the sulfonic acid group (-SO3-) of MES, which reduces the electrostatic repulsion between MES molecules, thus facilitating the formation of large and stable micelles. Moreover, the strong solubilizing effect on benzo[a]pyrene should be ascribed to the low polarity of ester groups (-COOCH3) in MES. Functional groups capable of forming hydrogen bonds and having low polarity are responsible for the enhanced solubilization of benzo[a]pyrene. This understanding helps choose suitable surfactants for the remediation of PAH-contaminated soils.

Directed Electron Delivery from a Pb-Free Halide Perovskite to a Co(II) Molecular Catalyst Boosts CO2 Photoreduction Coupled with Water Oxidation.

The development of high-performance photocatalytic systems for CO2 reduction is appealing to address energy and environmental issues, while it is challenging to avoid using toxic metals and organic sacrificial reagents. We here immobilize a family of cobalt phthalocyanine catalysts on Pb-free halide perovskite Cs2AgBiBr6 nanosheets with delicate control on the anchors of the cobalt catalysts. Among them, the molecular hybrid photocatalyst assembled by carboxyl anchors achieves the optimal performance with an electron consumption rate of 300±13 µmol g-1 h-1 for visible-light-driven CO2-to-CO conversion coupled with water oxidation to O2, over 8 times of the unmodified Cs2AgBiBr6 (36±8 µmol g-1 h-1), also far surpassing the documented systems (<150 µmol g-1 h-1). Besides the improved intrinsic activity, electrochemical, computational, ex-/in situ X-ray photoelectron and X-ray absorption spectroscopic results indicate that the electrons photogenerated at the Bi atoms of Cs2AgBiBr6 can be directionally transferred to the cobalt catalyst via the carboxyl anchors which strongly bind to the Bi atoms, substantially facilitating the interfacial electron transfer kinetics and thereby the photocatalysis.

Nanoscale Janus Z-Scheme Heterojunction for Boosting Artificial Photosynthesis.

Artificial photosynthesis for CO2 reduction coupled with water oxidation currently suffers from low efficiency due to inadequate interfacial charge separation of conventional Z-scheme heterojunctions. Herein, an unprecedented nanoscale Janus Z-scheme heterojunction of CsPbBr3 /TiOx is constructed for photocatalytic CO2 reduction. Benefitting from the short carrier transport distance and direct contact interface, CsPbBr3 /TiOx exhibits significantly accelerated interfacial charge transfer between CsPbBr3 and TiOx (8.90 × 108 s-1 ) compared with CsPbBr3 :TiOx counterpart (4.87 × 107 s-1 ) prepared by traditional electrostatic self-assembling. The electron consumption rate of cobalt doped CsPbBr3 /TiOx can reach as high as 405.2 ± 5.6 µmol g-1 h-1 for photocatalytic CO2 reduction to CO coupled with H2 O oxidation to O2 under AM1.5 sunlight (100 mW cm-2 ), over 11-fold higher than that of CsPbBr3 :TiOx , and surpassing the reported halide-perovskite-based photocatalysts under similar conditions. This work provides a novel strategy to boost charge transfer of photocatalysts for enhancing the performance of artificial photosynthesis.

Catalase-Like Nanozymes: Classification, Catalytic Mechanisms, and Their Applications.

The field of nanozymes has developed rapidly over the past decade. Among various oxidoreductases mimics, catalase (CAT)-like nanozyme, acting as an essential part of the regulation of reactive oxygen species (ROS), has attracted extensive research interest in recent years. However, CAT-like nanozymes are not as well discussed as other nanozymes such as peroxidase (POD)-like nanozymes, etc. Compared with natural catalase or artificial CAT enzymes, CAT-like nanozymes have unique properties of low cost, size-dependent properties, high catalytic activity and stability, and easy surface modification, etc., which make them widely used in various fields, especially in tumor therapy and disease treatment. Consequently, there is a great requirement to make a systematic discussion on CAT-like nanozymes. In this review, some key aspects of CAT-like nanozymes are deeply summarized as: 1) Typical CAT-like nanozymes classified by different nanomaterials; 2) The catalytic mechanisms proposed by experimental and theoretical studies; 3) Extensive applications in regard to tumor therapy, cytoprotection and sensing. Therefore, it is prospected that this review will contribute to the further design of CAT-like nanozymes and optimize their applications with much higher efficiency than before.

A two-dimensional metallic SnB monolayer as an anode material for non-lithium-ion batteries.

Na-, K- and Mg-ion batteries (NIBs, KIBs and MIBs) have drawn considerable interest due to their high abundance and excellent safety. However, the lack of high-performance anode materials is a major obstacle to its development. A metallic SnB planar monolayer is predicted by using the two-dimensional global minimum structure search method of swarm intelligence. Based on first-principles calculations, we proved that the metal SnB monolayer has high binding energy and excellent dynamical, thermal and mechanical stability. It is worth noting that the SnB monolayer has several stable adsorption sites for Na-, K- and Mg-ions, so it has a high theoretical capacity of 620.93, 517.44 and 620.93 mA h g-1, respectively. For Na-, K- and Mg-ion batteries, the low diffusion barriers of the SnB monolayer are 0.22, 0.07 and 0.68 eV, and the low average open circuit voltages are 0.42, 0.49 and 0.23 V, which ensure long service life and fast charging in practical applications. In addition, it is proved that the SnB monolayer maintains excellent conductivity and stability during the charge-discharge process. The results show that the SnB monolayer offers innovative advantages for the development of new two-dimensional planar structures that further advance the development of anode materials for metal ion batteries.

DA-6 improves sunflower seed vigor under Al3+ stress by regulating Al3+ balance and ethylene metabolic.

Aluminum (Al3+) stress restricts plant seed germination and seedling growth seriously. Here, the sunflower "S175″ variety was used to explore the technique of improving seed vigor under Al3+ stress and investigate the effect of diethyl aminoethyl hexanoate (DA-6) on physiological characteristics in sunflower seeds during germination under Al3+ stress. The results showed that 3.0 mmol·L-1 Al3+ treatment significantly suppressed the sunflower seed germination and seedling growth. Al3+ stress significantly increased Al3+ content and secretion rates of citric and malic acids in sunflower seeds during germination. Besides, endogenous ethylene content was increased in Al3+-treated seeds. DA-6 serves as a positive signal to regulate the sunflower seed germination under Al3+ stress. Moreover, DA-6 enhanced the activities of malic dehydrogenase, citrate synthase, and isocitrate dehydrogenase, up-regulated the expressions of organic acid transport-related genes (ALMT and MATE), resulting in reduced accumulation of Al3+. Furthermore, exogenous DA-6 mitigated excessive accumulation of ethylene by decreasing the 1-aminocyclopropane-1-dihydrodipicolinate synthase activity and related-gene expression. However, DA-6 treatment had no effect on abscisic acid or gibberellin metabolism in sunflower seeds under Al3+ stress. These results confirmed that DA-6 application enhanced the germination capacity through induction of the synthesis and transport of malic and citric acids, and suppression of the excessive accumulation of endogenous ethylene, thus contributing to alleviate Al3+ toxicity in sunflower seeds.

The HKT Transporter HvHKT1;5 Negatively Regulates Salt Tolerance.

Maintaining low intracellular Na+ concentrations is an essential physiological strategy in salt stress tolerance in most cereal crops. Here, we characterized a member of the high-affinity K+ transporter (HKT) family in barley (Hordeum vulgare), HvHKT1;5, which negatively regulates salt tolerance and has different functions from its homology in other cereal crops. HvHKT1;5 encodes a plasma membrane protein localized to root stele cells, particularly in xylem parenchyma cells adjacent to the xylem vessels. Its expression was highly induced by salt stress. Heterogenous expression of HvHKT1;5 in Xenopus laevis oocytes showed that HvHKT1;5 was permeable to Na+, but not to K+, although its Na+ transport activity was inhibited by external K+ HvHKT1;5 knockdown barley lines showed improved salt tolerance, a dramatic decrease in Na+ translocation from roots to shoots, and increases in K+/Na+ when compared with wild-type plants under salt stress. The negative regulation of HvHKT1;5 in salt tolerance distinguishes it from other HKT1;5 members, indicating that barley has a distinct Na+ transport system. These findings provide a deeper understanding of the functions of HKT family members and the regulation of HvHKT1;5 in improving salt tolerance of barley.

Calmodulin HvCaM1 Negatively Regulates Salt Tolerance via Modulation of HvHKT1s and HvCAMTA4.

Calcium (Ca2+) signaling modulates sodium (Na+) transport in plants; however, the role of the Ca2+ sensor calmodulin (CaM) in salt tolerance is elusive. We previously identified a salt-responsive calmodulin (HvCaM1) in a proteome study of barley (Hordeum vulgare) roots. Here, we employed bioinformatic, physiological, molecular, and biochemical approaches to determine the role of HvCaM1 in barley salt tolerance. CaM1s are highly conserved in green plants and probably originated from ancestors of green algae of the Chlamydomonadales order. HvCaM1 was mainly expressed in roots and was significantly up-regulated in response to long-term salt stress. Localization analyses revealed that HvCaM1 is an intracellular signaling protein that localizes to the root stele and vascular systems of barley. After treatment with 200 mm NaCl for 4 weeks, HvCaM1 knockdown (RNA interference) lines showed significantly larger biomass but lower Na+ concentration, xylem Na+ loading, and Na+ transportation rates in shoots compared with overexpression lines and wild-type plants. Thus, we propose that HvCaM1 is involved in regulating Na+ transport, probably via certain class I high-affinity potassium transporter (HvHKT1;5 and HvHKT1;1)-mediated Na+ translocation in roots. Moreover, we demonstrated that HvCaM1 interacted with a CaM-binding transcription activator (HvCAMTA4), which may be a critical factor in the regulation of HKT1s in barley. We conclude that HvCaM1 negatively regulates salt tolerance, probably via interaction with HvCAMTA4 to modulate the down-regulation of HvHKT1;5 and/or the up-regulation of HvHKT1;1 to reduce shoot Na+ accumulation under salt stress in barley.

A new and practical surgical technique of transvaginal natural orifice specimen extraction surgery (NOSES) in laparoscopic nephroureterectomy-an initial clinical experience.

OBJECTIVE: To explore the safety, feasibility and clinical effect of transvaginal natural orifice specimen extraction surgery (NOSES) in 3D laparoscopic nephroureterectomy (LNU) for upper tract urothelial carcinoma (UTUC). METHODS: A retrospective analysis was made of 16 female patients who underwent 3D LNU and NOSES in the Department of Urology, Cancer Hospital, Chinese Academy of Medical Sciences from June 2019 to December 2020. The basic clinical data, perioperative related data, perioperative complications, visual analogue pain score (VAS), postoperative scar assessment questionnaire (PSAQ) at 3 months, female pelvic floor dysfunction questionnaire (PFDI-20) and female sexual function index questionnaire (FSFI) at preoperative and postoperative 3 months were analyzed and evaluated. RESULTS: The surgery was successfully completed in all 16 patients, and none of them was converted to open surgery. No postoperative complications, such as abdominal incision-related infection. No cases of local recurrence and distant metastasis were observed during follow-up of 3 to 21 months. The VAS scores at 24 h and 48 h after operation were 2.9 ± 0.7, 1.3 ± 0.6, respectively. PSAQ scores at 3 months after operation were 34.3 ± 3.3. PFDI-20 scores of women preoperative and postoperative 3 months were 6.25 ± 1.75, 6.3 ± 1.8, respectively, and the difference was not statistically significant (p = 0.924). There was no significant difference in FSFI scores between preoperative and postoperative 3 months (p = 0.892). CONCLUSION: Transvaginal NOSES in 3D LNU for UTUC is safe, feasible and practical. The successful development of this technique has laid a solid foundation for further clinical application and promotion.

Quasiparticle energies and significant exciton effects of monolayered blue arsenic phosphorus conformers.

Low-dimensional systems have strong multi-body interactions and fewer geometric constraints due to the screening effect of the Coulomb interaction. We use the single-shot GW-Bethe Salpeter equation (G0W0-BSE) to calculate the electronic and optical properties of six-blue arsenic phosphorus (ß-AsP) conformers. The results show significant anisotropic exciton effects of covering visible regions, which apparently changed the light absorption. The maximum exciton binding energy is up to 0.99 eV, which is more extensive than the black phosphorus monolayer (0.9 eV). We predict that the different orbital contributions to valence bands may cause the anisotropic exciton effect difference. Our results indicate that ß-AsP monolayers with the large binding energies of exciton hold a great promise for applications in optoelectronic devices.

Novel high-performance anodic materials for lithium ion batteries: two-dimensional Sn-X (X = C, Si, and Ge) alloy monolayers.

Lithium-ion batteries (LIBs) have always been the focus of researchers for energy storage applications. Here, the first-principles density functional theory method was used to explore the possibility of using stanene derived structures as LIB anodes. And such two-dimensional structures are similar to graphene or stanene, but half of the Sn atoms are replaced by group-IV atoms to form new structures, which are called Sn-X (X = C, Si, and Ge). Our calculation results showed that the optimized structure, lattice constant and other parameters are consistent with those reported in previous studies. Meanwhile, we found out that the semiconductor properties of pristine Sn-X transform into metal properties after the adsorption of Li. Then, by calculating the adsorption concentration of Li ions on the Sn-X monolayers, we found that these kinds of materials can meet the requirements of battery anodes very well, not only in terms of their open-circuit voltage, but also storage capacity. For Sn-Si and Sn-Ge, their theoretical capacities can be as high as 1095.78 mA h g-1 (Li6Sn-Si) and 840.88 mA h g-1 (Li6Sn-Ge). At last, based on the investigation of their diffusion path, Sn-X has been found to have high charge and discharge rates because of its low barrier. By reason of the foregoing, 2D Sn-X monolayers will be excellent battery anodes.

Application of Electrocardiogram Localization during Peripherally Inserted Central Catheter Line Insertion into the Persistent Left Superior Vena Cava of Neonates.

BACKGROUND: Most neonates with persistent left superior vena cava (PLSVC) have no clinical symptoms or hemodynamic changes, and this anomaly is only found during cardiac catheterization, pacemaker implantation, or central venous catheterization. Electrocardiogram (ECG) localization is helpful for the application of the peripherally inserted central catheter (PICC) technique in neonates with PLSVC. OBJECTIVE: To explore the characteristic waveforms of the P wave when a PICC under ECG localization is applied in neonates with PLSVC. STUDY DESIGN: The observation and management strategies for the P wave changes during catheter insertion (CI) of two neonates with PLSVC admitted to our institution between January and July 2020, who underwent PICC line insertion, were summarized. RESULTS: The characteristic P wave changes in two children with a PICC line inserted via the PLSVC were observed. When a wide inverted P wave appeared on ECG, the catheter was immediately withdrawn by 0.5 cm, a bidirectional P wave gradually appeared and then disappeared. After that, the catheter was further withdrawn by 0.5 cm. After catheterization, the optimal position of the PICC was confirmed by X-ray photography and bedside B-ultrasound. The PICC line was removed as scheduled after indwelling for 18 and 29 days, respectively, in the two cases, and no PICC-related complications occurred during indwelling. CONCLUSION: The characteristic P wave changes on ECG during CI provide important clinical reference values for the application of the PICC technique under ECG localization in neonates with PLSVC. KEY POINTS: · Electrocardiogram localization.. · Peripherally inserted central catheter.. · Persistent left superior vena cava..

1D/2D Heterostructures as Ultrathin Catalysts for Hydrogen Evolution Reaction.

2D MoS2 has emerged as a promising alternative to Pt-based catalysts for hydrogen evolution reaction (HER) due to its low cost and earth abundance. However, insufficient active sites of basal plane and poor conductivity become the foremost factors restricting the catalytic performance of MoS2 . Here, a facile strategy is presented to enhance the HER performance of MoS2 by converting its 2D structure into 1D/2D heterostructures of Mo6 Te6 /MoS2(1- x ) Te2 x by the in situ tellurization. As-prepared 1D/2D heterostructures exhibit excellent HER performance with the Tafel slope of ≈56 mV dec-1 (only one-third of that for pristine MoS2 ). The enhanced HER catalytic activity is attributed to more Te/S vacancies introduced by tellurization, which serve as the active sites as suggested by theoretical calculations. Besides, the formation of highly conductive well-aligned quasi-1D Mo6 Te6 nanobelts facilitate charge transport in HER. Previous work provides a facile approach to construct mixed dimensional materials, and opens up a new avenue to the properties modulation of 2D transition metal chalcogenides.

The zinc finger transcription factor ATF1 regulates aluminum tolerance in barley.

Aluminum (Al) toxicity is a major abiotic stress that restricts crop production in acid soils. Plants have evolved internal and external mechanisms of tolerance, and among them it is well known that AtSTOP1 and OsART1 are key transcription factors involved in tolerance through regulation of multiple downstream genes. Here, we identified the closest homolog of these two proteins in barley, namely HvATF1, Al-tolerance Transcription Factor 1, and determined its potential function in Al stress. HvATF1 is expressed in the nucleus, and functions in transcriptional activation. The transcription of HvATF1 was found to be constitutive in different tissues, and was little affected by Al stress. Knockdown of HvATF1 by RNAi resulted in increased Al sensitivity. Transcriptomics analysis identified 64 differently expressed genes in the RNAi lines compared to the wild-type, and these were considered as candidate downstream genes regulated by HvATF1. This study provides insights into the different molecular mechanisms of Al tolerance in barley and other plants.

Application of a modified electrocardiogram-guided technique for umbilical venous catheterisation in neonates: A retrospective trial.

AIM: To investigate the effectiveness and safety of modified electrocardiogram (ECG)-guided technique in umbilical venous catheterisation in neonates. METHODS: Sixty-six critically ill neonates underwent umbilical venous catheterisation with (ECG group) or without (control group) ECG guidance from January 2017 to March 2019. We retrospectively analysed and compared the rate of correct tip placement on first try, unplanned extubation rate and incidence of catheter-related complications between the two groups. RESULTS: There were 33 patients in each group. The ECG group showed significantly higher rate of correct tip placement on first try (P < 0.001), lower unplanned extubation rate (P < 0.001), but identical incidence of catheter-related complications (P = 0.492) comparing with the control group. CONCLUSION: The ECG-guided technique is an effective and safe method for umbilical venous catheterisation. The connecting method we modified made this technique more practical and can be promoted to areas without access to specific ECG adaptors.

Phase-selective synthesis of 1T' MoS2 monolayers and heterophase bilayers.

Two-dimensional (2D) MoS2, which has great potential for optoelectronic and other applications, is thermodynamically stable and hence easily synthesized in its semiconducting 2H phase. In contrast, growth of its metastable 1T and 1T' phases is hampered by their higher formation energy. Here we use theoretical calculations to design a potassium (K)-assisted chemical vapour deposition method for the phase-selective growth of 1T' MoS2 monolayers and 1T'/2H heterophase bilayers. This is realized by tuning the concentration of K in the growth products to invert the stability of the 1T' and 2H phases. The synthesis of 1T' MoS2 monolayers with high phase purity allows us to characterize their intrinsic optical and electrical properties, revealing a characteristic in-plane anisotropy. This phase-controlled bottom-up synthesis offers a simple and efficient way of manipulating the relevant device structures, and provides a general approach for producing other metastable-phase 2D materials with unique properties.

Comparison of intracorporeal and extracorporeal urinary diversions after laparoscopic radical cystectomy in females with bladder cancer.

PURPOSE: To compare the peri-operative outcomes of females undergoing laparoscopic intracorporeal urinary diversions (ICUD) and extracorporeal urinary diversions (ECUD) after laparoscopic radical cystectomies (LRC). PATIENTS AND METHODS: Thirty-eight females who underwent LRCs and urinary diversions from February 2008 to October 2018 were divided into two groups: the ECUD group (19 patients) and the ICUD group (19 patients). We retrospectively analysed the patients in terms of patients' demographics, peri-operative outcomes, and oncological follow-ups. RESULTS: There were significant differences in the mean operative times between ECUDs and ICUDs (364.6 vs. 297.1 min, p = 0.007), transfusion rates (37% vs. 5%, p = 0.042), time to flatus (5 vs. 3 days, p = 0.020), time to ambulation (2 vs. 1 days, p = 0.022), and duration of postoperative hospital stays (22 vs. 13 days, p = 0.002). The mean lymph node yield was 12.9 in the ECUD group and 18.6 in the ICUD group (p = 0.140). Seven out of 19 patients (37%) in the ECUD group and 6 out of 19 patients (32%) in the ICUD group had positive lymph nodes (p > 0.9). Two out of 19 ECUD patients (11%) and 4 of 19 ICUD patients (21%) had positive surgical margins (p = 0.660). Although there were no differences in major complications at 30 days and in all complications at 90 days, the Clavien grade II complications were significantly different at 30 days (ECUD 8, ICUD 2; p = 0.026). The mean follow-up times were 48.7 months (ECUD group) and 26.4 months (ICUD group). There were no statistically significant differences in estimated glomerular filtration rates postoperatively (p = 0.516). Seven patients had disease metastases (ECUD 2 out of 19, ICUD 5 out of 19; p = 0.405) and 5 died (ECUD 3 out of 19, ICUD 2 out of 19; p > 0.9). CONCLUSIONS: ICUDs benefit females by having smaller incisions, faster recoveries, and decreased complication rates.

Encapsulating Perovskite Quantum Dots in Iron-Based Metal-Organic Frameworks (MOFs) for Efficient Photocatalytic CO2 Reduction.

Improving the stability of lead halide perovskite quantum dots (QDs) in a system containing water is the key for their practical application in artificial photosynthesis. Herein, we encapsulate low-cost CH3 NH3 PbI3 (MAPbI3 ) perovskite QDs in the pores of earth-abundant Fe-porphyrin based metal organic framework (MOF) PCN-221(Fex ) by a sequential deposition route, to construct a series of composite photocatalysts of MAPbI3 @PCN-221(Fex ) (x=0-1). Protected by the MOF the composite photocatalysts exhibit much improved stability in reaction systems containing water. The close contact of QDs to the Fe catalytic site in the MOF, allows the photogenerated electrons in the QDs to transfer rapidly the Fe catalytic sites to enhance the photocatalytic activity for CO2 reduction. Using water as an electron source, MAPbI3 @PCN-221(Fe0.2 ) exhibits a record-high total yield of 1559 µmol g-1 for photocatalytic CO2 reduction to CO (34 %) and CH4 (66 %), 38 times higher than that of PCN-221(Fe0.2 ) in the absence of perovskite QDs.

Identification of microRNAs in response to aluminum stress in the roots of Tibetan wild barley and cultivated barley.

BACKGROUND: Barley is relatively sensitive to Aluminum (Al) toxicity among cereal crops, but shows a wide genotypic difference in Al tolerance. The well-known Al-tolerant mechanism in barley is related to Al exclusion mediated by a citrate transporter HvAACT1 (Al-activated citrate transporter 1). A 1-kb insertion in the promoter region of HvAACT1 gene results in a dramatic increase of its expression level, which only occurs in some Al-tolerant cultivars. However, Al-tolerant Tibetan wild barley accession XZ29 did not have the 1-kb insertion. RESULTS: We confirmed that the expression of HvAACT1 and secretion of citrate and other organic acids did not explain the difference in Al-tolerant wild barley XZ29 and Al-sensitive cultivated barley Golden Promise. To identify microRNAs (miRNAs) and their target genes responsive to Al stress in barley roots, eight small RNA libraries with two biological replicates from these two genotypes exposed to control and Al-treated conditions were constructed and submitted to deep sequencing. A total of 342 miRNAs were identified in Golden Promise and XZ29, with 296 miRNAs being commonly shared in the two genotypes. Target genes of these miRNAs were obtained through bioinformatics prediction or degradome identification. Comparative analysis detected 50 miRNAs responsive to Al stress, and some of them were found to be exclusively expressed in XZ29 and associated with Al tolerance. CONCLUSIONS: miRNAs exclusively expressing in the wild barley were identified and found to be associated with Al stress tolerance. The current results provide a model of describing the roles of some special miRNAs associated with Al tolerance in the Tibetan wild barley.