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1.
Cell Mol Biol Lett ; 29(1): 72, 2024 May 14.
Artigo em Inglês | MEDLINE | ID: mdl-38745296

RESUMO

BACKGROUND: Aberrant mitochondrial fission, a critical pathological event underlying myocardial ischemia/reperfusion (MI/R) injury, has emerged as a potential therapeutic target. The long non-coding RNA (lncRNA) Oip5-as1 is increasingly recognized for its regulatory roles, particularly in MI/R injury. However, its precise mechanistic role in modulating mitochondrial dynamics remains elusive. This study aims to elucidate the mechanistic role of Oip5-as1 in regulating mitochondrial fission and evaluate its therapeutic potential against MI/R injury. METHODS: To simulate in vitro MI/R injury, HL-1 cardiomyocytes were subjected to hypoxia/reoxygenation (H/R). Lentiviral vectors were employed to achieve overexpression or knockdown of Oip5-as1 in HL-1 cells by expressing Oip5-as1 or shRNA targeting Oip5-as1, respectively. The impact of Oip5-as1 on mitochondrial dynamics in HL-1 cells was assessed using CCK-8 assay, flow cytometry, immunofluorescence staining, and biochemical assays. MI/R injury was induced in mice by ligating the left anterior descending coronary artery. Conditional knockout mice for Oip5-as1 were generated using the CRISPR/Cas9 genome editing technology, while overexpression of Oip5-as1 in mice was achieved via intramyocardial administration of AAV9 vectors. In mice, the role of Oip5-as1 was evaluated through echocardiographic assessment, histopathological staining, and transmission electron microscopy. Furthermore, Western blotting, RNA pull-down, RNA immunoprecipitation, and co-immunoprecipitation assays were conducted to investigate Oip5-as1's underlying mechanisms. RESULTS: The expression levels of Oip5-as1 are significantly decreased in MI/R-injured HL-1 cells and myocardium. In HL-1 cells undergoing H/R injury, overexpression of Oip5-as1 attenuated excessive mitochondrial fission, preserved mitochondrial functionality, and reduced cellular apoptosis, while knockdown of Oip5-as1 exhibited the opposite effects. Furthermore, in a mouse model of MI/R injury, overexpression of Oip5-as1 diminished mitochondrial fission, myocardial infarct size and improved cardiac function. However, knockout of Oip5-as1 exacerbated myocardial injury and cardiac dysfunction, which were significantly reversed by treatment with a mitochondrial division inhibitor-1 (Mdivi-1). Mechanistically, Oip5-as1 selectively interacts with AKAP1 and CaN proteins, inhibiting CaN activation and subsequent DRP1 dephosphorylation at Ser637, thereby constraining DRP1's translocation to the mitochondria and its involvement in mitochondrial fission. CONCLUSIONS: Our study underscores the pivotal role of Oip5-as1 in mitigating excessive mitochondrial fission during MI/R injury. The findings not only enhance our comprehension of the molecular mechanisms underlying MI/R injury but also identify Oip5-as1 as a potential therapeutic target for ameliorating MI/R injury.


Assuntos
Dinaminas , Dinâmica Mitocondrial , Traumatismo por Reperfusão Miocárdica , Miócitos Cardíacos , RNA Longo não Codificante , RNA Longo não Codificante/genética , RNA Longo não Codificante/metabolismo , Animais , Dinâmica Mitocondrial/genética , Traumatismo por Reperfusão Miocárdica/metabolismo , Traumatismo por Reperfusão Miocárdica/genética , Traumatismo por Reperfusão Miocárdica/patologia , Dinaminas/metabolismo , Dinaminas/genética , Camundongos , Fosforilação , Miócitos Cardíacos/metabolismo , Miócitos Cardíacos/patologia , Linhagem Celular , Camundongos Knockout , Masculino , Camundongos Endogâmicos C57BL
2.
Carcinogenesis ; 44(5): 426-435, 2023 08 10.
Artigo em Inglês | MEDLINE | ID: mdl-37105709

RESUMO

Due to the characteristics of high recurrence and metastasis, it is still difficult to cure lung cancer. Cancer stem cells (CSCs) are a group of tumor cells with self-renewal ability and differentiation potential, which are responsible for lung cancer recurrence. Therefore, targeting CSCs may provide a new strategy for lung cancer treatment. Thymoquinone (TQ), the main active ingredient isolated from black seed oil, has shown significant anti-cancer effects in various cancers. However, the effect of TQ on lung cancer stem cells (LCSCs) has never been clarified. In the present study, we successfully separated and enriched lung cancer tumorsphere cells. Our data showed that TQ significantly inhibited the stem-like properties of LCSCs. In addition, we found TQ promoted Yes-associated protein (YAP) phosphorylation and ubiquitination, and the inhibitory effects of TQ on LCSCs could be enhanced by silencing YAP. Taken together, these results suggest that TQ, functions by targeting YAP, may be a potential therapeutic agent against lung cancer.


Assuntos
Neoplasias Pulmonares , Recidiva Local de Neoplasia , Humanos , Linhagem Celular Tumoral , Recidiva Local de Neoplasia/patologia , Neoplasias Pulmonares/patologia , Pulmão/patologia , Células-Tronco Neoplásicas/patologia
3.
Int J Gen Med ; 15: 7523-7534, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36196373

RESUMO

Purpose: Chronic obstructive pulmonary disease (COPD) is one of the main risk factors for lung carcinomas. This study aimed to analyze and construct a model to assess scientific publications on the relationship between COPD and lung carcinomas. Patients and Methods: A literature search of the Web of Science database was performed for publications until November 2, 2021. Microsoft Excel and CiteSpace software were used to perform bibliometric and visual analysis of source journals, countries/regions, institutions, authors, research areas, and hot topics of selected publications. Results: A total of 2175 publications on the relationship between COPD and lung carcinomas were identified. The annual number of papers published and the total annual citation frequency in the field of COPD and lung carcinoma show an upward trend, and the current research hot topics are health, disease risk factors, disease burden, prevention and serious complications. The top three countries/regions with the number of published articles are the United States, China, and the United Kingdom. The author with the most signatures was Castaldi PJ of USA, followed by Xian JF of China. The lack of multinational/regional multi-center research illustrated that the distribution of research forces is unbalanced. Conclusion: According to this study, researchers can identify hot topics and explore new research directions in research of the relationship between COPD and lung carcinomas.

4.
Front Cardiovasc Med ; 9: 788958, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35387434

RESUMO

Background: Cardiac calcification is a type of ectopic pathologic calcification of unknown etiology and mechanisms. Once diagnosed, the location, extent and morphology of the calcified lesions, as well as their functional significance in the heart, are usually the focus of case reports. Calcification is mostly distributed in myocardium, but rarely reported in atrium. In addition, because of limited sampling and complex pathological mechanisms, the etiology underlying the formation of these calcified lesions also remains unclear. Methods: Two cardiac calcifications were found in a patient, died of trauma-induced subarachnoid hemorrhage after slightly drinking, during a standard autopsy. The location and morphological characteristics of the calcified lesions were determined by computed tomography (CT) and CT-based 3D reconstruction. The specific histopathological characteristics of the lesions were determined by multi-staining. The concentration of free calcium and inorganic pyrophosphate (PPi) in plasma reflected the change of calcium metabolism. The expression and membranal localization of the ATP Binding Cassette Subfamily C Member 6 (ABCC6) in hepatocytes were detected by immunofluorescence. The variants of the ABCC6 were detected by Sanger sequencing and potential pathogenic variants were further identified by in silico analysis. Results: The present study describes a patient with idiopathic calcification with two pear-shaped and irregularly hollow lesions symmetrically distributed in the patient's atrium. Massive accumulation of calcium salts was identified by multi-staining. For this patient, the plasma concentration of free calcium was higher than the control, indicating that calcium metabolism was disturbed. Furthermore, the plasma PPi of the patient was lower than the normal. By using immunofluorescence, the expression and membranal localization of ABCC6 was decreased and impaired in hepatocytes, respectively. Combined with Sanger sequencing and in silico analysis, 7 variants were identified. Conclusions: This study described a novel patient with symmetrically distributed idiopathic atrial calcifications. Furthermore, all the results indicated that these pathologic calcifications may be secondary to reduced plasma PPi content due to ABCC6 dysfunction in hepatocytes. Moreover, these findings provided novel clues to the pathogenesis, clinical diagnosis and treatment of idiopathic atrial calcification in future.

5.
Int J Chron Obstruct Pulmon Dis ; 15: 3025-3037, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33244228

RESUMO

Purpose: To evaluate the accuracy of inflammatory biomarkers in differentiating patients with asthma-COPD overlap (ACO) from those with COPD alone. Methods: Clinical data of 134 patients with COPD and 48 patients with ACO admitted to the First Affiliated Hospital of Xi'an Jiaotong University from January 2016 to June 2019 were retrospectively analyzed. Receiver operating characteristic (ROC) curve analysis was performed to determine the best cut-off values of fractional exhaled nitric oxide (FeNO), blood eosinophil counts (EOS), and neutrophil to lymphocyte ratio (NLR) for differentiating between ACO and COPD alone. Spearman correlation analysis was conducted to evaluate the relationships between these inflammatory biomarkers and the forced expiratory volume in one second/prediction (FEV1%pred). Results: FeNO and EOS in the ACO patients were significantly higher than those in the COPD patients (FeNO: median 37.50 vs 24.50 ppb, P < 0.001; EOS: median 0.20 vs 0.10 ×109/L, P = 0.004). FeNO was positively correlated with FEV1%pred (r = 0.314, P = 0.030), while NLR was negatively correlated with FEV1%pred (r = -0.372, P = 0.009) in patients with ACO. In addition, a positive correlation between FeNO and EOS was also found in ACO, especially in patients without history of inhaled corticosteroids (ICS) use (r = 0.682, P < 0.001). The optimal cut-off value of FeNO was 31.5 ppb (AUC = 0.758, 95% CI = 0.631-0.886) in patients with smoking history, with 70.0% sensitivity and 89.9% specificity for differentiating ACO from COPD. In patients without history of ICS use, the best cut-off value of FeNO was 39.5 ppb (AUC = 0.740, 95% CI = 0.610-0.870), with 58.3% sensitivity and 84.9% specificity. Among patients without history of ICS use and smoking, 27.5 ppb was optimal cut-off level for FeNO (AUC = 0.744, 95% CI = 0.579-0.908) to diagnose ACO, with 81.8% sensitivity and 60.7% specificity, and the sensitivity was improved to 91.7% when FeNO was combined with EOS. Conclusion: The inflammatory biomarkers FeNO and EOS can be used as indicators for differentiating between ACO and COPD alone.


Assuntos
Asma , Doença Pulmonar Obstrutiva Crônica , Asma/diagnóstico , Asma/tratamento farmacológico , Biomarcadores , Testes Respiratórios , Expiração , Volume Expiratório Forçado , Humanos , Óxido Nítrico , Doença Pulmonar Obstrutiva Crônica/diagnóstico , Estudos Retrospectivos
6.
Clin Exp Med ; 20(3): 461-468, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32350633

RESUMO

This study aimed to explore whether the polymorphisms of CYP4F2 and CYP3A5 are correlated with the risk of lung cancer development. A case-control study was conducted among 510 patients with pathologically confirmed lung cancer as the case group and 504 healthy individuals as the control group. Four single-nucleotide polymorphisms of the CYP4F2 and CYP3A5 genes were genotyped, and their correlations with the risk of lung cancer were examined using Chi-square test and logistic regression analysis. Stratified analysis found that the rs3093105 and rs3093106 loci of CYP4F2 gene were significantly associated with lower risk of lung cancer (P = 0.012, OR 0.64, 95% CI 0.45-0.91). The correlation was related to patients' age and sex and pathological type of lung cancer. Similarly, the rs10242455 loci of CYP3A5 gene showed a statistical significance between the case group and the control group (P = 0.018, OR 0.71, 95% CI 0.53-0.94), which also was associated with reduced risk of squamous cell lung cancer in the dominant and additive models (dominant: OR 0.66, 95% CI 0.46-0.94, P = 0.021; additive: OR 0.71, 95% CI 0.53-0.95, P = 0.023). CYP4F2 and CYP3A5 gene polymorphisms are associated with the reduced risk of non-small cell lung cancer, and its correlation is related to patients' age and sex and pathological type of lung cancer.


Assuntos
Carcinoma de Células Escamosas/genética , Citocromo P-450 CYP3A/genética , Família 4 do Citocromo P450/genética , Neoplasias Pulmonares/genética , Polimorfismo de Nucleotídeo Único , Idoso , Carcinoma de Células Escamosas/etnologia , Carcinoma de Células Escamosas/patologia , Estudos de Casos e Controles , China/etnologia , Feminino , Estudos de Associação Genética , Predisposição Genética para Doença , Técnicas de Genotipagem , Humanos , Modelos Logísticos , Neoplasias Pulmonares/etnologia , Masculino , Pessoa de Meia-Idade
7.
Nat Commun ; 11(1): 541, 2020 Jan 28.
Artigo em Inglês | MEDLINE | ID: mdl-31992713

RESUMO

The fast development of high-resolution electron microscopy (EM) demands a background-noise-free substrate to support the specimens, where atomically thin graphene membranes can serve as an ideal candidate. Yet the preparation of robust and ultraclean graphene EM grids remains challenging. Here we present a polymer- and transfer-free direct-etching method for batch fabrication of robust ultraclean graphene grids through membrane tension modulation. Loading samples on such graphene grids enables the detection of single metal atoms and atomic-resolution imaging of the iron core of ferritin molecules at both room- and cryo-temperature. The same kind of hydrophilic graphene grid allows the formation of ultrathin vitrified ice layer embedded most protein particles at the graphene-water interface, which facilitates cryo-EM 3D reconstruction of archaea 20S proteasomes at a record high resolution of ~2.36 Å. Our results demonstrate the significant improvements in image quality using the graphene grids and expand the scope of EM imaging.


Assuntos
Grafite/química , Microscopia Eletrônica/instrumentação , Microscopia Eletrônica/métodos , Fenômenos Químicos , Microscopia Crioeletrônica/métodos , Elétrons , Desenho de Equipamento , Processamento de Imagem Assistida por Computador , Membranas , Polímeros , Proteínas
8.
Cancer Med ; 8(10): 4892-4905, 2019 08.
Artigo em Inglês | MEDLINE | ID: mdl-31264381

RESUMO

BACKGROUND: Cytochrome P450 (CYPs) are heme proteins involved in the metabolism of a variety of endogenous and exogenous substances and play an important role in the carcinogenesis mechanisms of environmental and hereditary factors. The objective of this study was to investigate how polymorphisms of CYPs correlate with lung cancer (LC) susceptibility. METHODS: Six single nucleotide polymorphisms (SNPs) were genotyped in this study. The chi-square test and unconditional logistic regression model were used to evaluate the correlation between SNPs and LC susceptibility. The expressions and survival data of genes in patients with LC were mined using Oncomine and Kaplan-Meier Plotter database. RESULTS: Four SNPs were found to be significantly associated with the risk of LC development (P < 0.05). The most significant correlation was that the A allele and AA genotype of CYP2D6 rs1065852 were associated with increased risk of LC development (adjusted odds ratio [OR] = 1.35, 95% confidence interval [95%CI] = 1.13-1.60, P = 9.04e-4; OR = 1.83, 95%CI = 1.29-2.59, P = 0.001 respectively). Similar association of this variant was also found in the subgroups of male patients, cases in III-IV stages, positive lymph node, squamous cell carcinomas and adenocarcinomas. Whereas rs1065852 was considered as protective factor in females (adjusted OR = 0.33, 95% CI = 0.16-0.70, P = 0.004). In stratified analyses, the association of CYP24A1 rs2762934, CYP24A1 rs6068816, CYP20A1 rs2043449 polymorphism with LC risk appeared stronger in some subgroups. CYP2D6, CYP24A1 and CYP20A1 are overexpressed in some pathological types of LC (P < 0.05), and high levels of CYP2D6 and CYP20A1 indicate poor and good prognosis of LC, respectively. CONCLUSION: This study revealed that rs1065852, rs2043449, rs2762s934, and rs6068816 of CYPs were associated with LC susceptibility in the Northwestern Chinese Han population; CYP2D6 and CYP20A1 were overexpressed and correlated with prognosis of LC.


Assuntos
Sistema Enzimático do Citocromo P-450/genética , Estudos de Associação Genética/métodos , Neoplasias Pulmonares/patologia , Polimorfismo de Nucleotídeo Único , Idoso , Estudos de Casos e Controles , China/etnologia , Feminino , Predisposição Genética para Doença , Humanos , Estimativa de Kaplan-Meier , Neoplasias Pulmonares/etnologia , Neoplasias Pulmonares/genética , Masculino , Pessoa de Meia-Idade , Estadiamento de Neoplasias , Prognóstico , Fatores Sexuais , Análise de Sobrevida
9.
ACS Nano ; 11(12): 12337-12345, 2017 12 26.
Artigo em Inglês | MEDLINE | ID: mdl-29191004

RESUMO

Wrinkles are ubiquitous for graphene films grown on various substrates by chemical vapor deposition at high temperature due to the strain induced by thermal mismatch between the graphene and substrates, which greatly degrades the extraordinary properties of graphene. Here we show that the wrinkle formation of graphene grown on Cu substrates is strongly dependent on the crystallographic orientations. Wrinkle-free single-crystal graphene was grown on a wafer-scale twin-boundary-free single-crystal Cu(111) thin film fabricated on sapphire substrate through strain engineering. The wrinkle-free feature of graphene originated from the relatively small thermal expansion of the Cu(111) thin film substrate and the relatively strong interfacial coupling between Cu(111) and graphene, based on the strain analyses as well as molecular dynamics simulations. Moreover, we demonstrated the transfer of an ultraflat graphene film onto target substrates from the reusable single-crystal Cu(111)/sapphire growth substrate. The wrinkle-free graphene shows enhanced electrical mobility compared to graphene with wrinkles.

10.
Adv Mater ; 29(26)2017 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-28464279

RESUMO

The atomically thin 2D nature of suspended graphene membranes holds promising in numerous technological applications. In particular, the outstanding transparency to electron beam endows graphene membranes great potential as a candidate for specimen support of transmission electron microscopy (TEM). However, major hurdles remain to be addressed to acquire an ultraclean, high-intactness, and defect-free suspended graphene membrane. Here, a polymer-free clean transfer of sub-centimeter-sized graphene single crystals onto TEM grids to fabricate large-area and high-quality suspended graphene membranes has been achieved. Through the control of interfacial force during the transfer, the intactness of large-area graphene membranes can be as high as 95%, prominently larger than reported values in previous works. Graphene liquid cells are readily prepared by π-π stacking two clean single-crystal graphene TEM grids, in which atomic-scale resolution imaging and temporal evolution of colloid Au nanoparticles are recorded. This facile and scalable production of clean and high-quality suspended graphene membrane is promising toward their wide applications for electron and optical microscopy.

11.
Nano Lett ; 17(5): 3021-3026, 2017 05 10.
Artigo em Inglês | MEDLINE | ID: mdl-28398056

RESUMO

Non-neutral layered crystals, another group of two-dimensional (2D) materials that lack a well-defined van der Waals (vdWs) gap, are those that form strong chemical bonds in-plane but display weak out-of-plane electrostatic interactions, exhibiting intriguing properties for the bulk counterpart. However, investigation of the properties of their atomically thin counterpart are very rare presumably due to the absence of efficient ways to achieve large-area high-quality 2D crystals. Here, high-mobility atomically thin Bi2O2Se, a typical non-neutral layered crystal without a standard vdWs gap, was synthesized via a facial chemical vapor deposition (CVD) method, showing excellent controllability for thickness, domain size, nucleation site, and crystal-phase evolution. Atomically thin, large single crystals of Bi2O2Se with lateral size up to ∼200 µm and thickness down to a bilayer were obtained. Moreover, optical and electrical properties of the CVD-grown 2D Bi2O2Se crystals were investigated, displaying a size-tunable band gap upon thinning and an ultrahigh Hall mobility of >20000 cm2 V-1 s-1 at 2 K. Our results on the high-mobility 2D Bi2O2Se semiconductor may activate the synthesis and related fundamental research of other non-neutral 2D materials.

12.
Nat Nanotechnol ; 12(6): 530-534, 2017 07.
Artigo em Inglês | MEDLINE | ID: mdl-28369044

RESUMO

High-mobility semiconducting ultrathin films form the basis of modern electronics, and may lead to the scalable fabrication of highly performing devices. Because the ultrathin limit cannot be reached for traditional semiconductors, identifying new two-dimensional materials with both high carrier mobility and a large electronic bandgap is a pivotal goal of fundamental research. However, air-stable ultrathin semiconducting materials with superior performances remain elusive at present. Here, we report ultrathin films of non-encapsulated layered Bi2O2Se, grown by chemical vapour deposition, which demonstrate excellent air stability and high-mobility semiconducting behaviour. We observe bandgap values of ∼0.8 eV, which are strongly dependent on the film thickness due to quantum-confinement effects. An ultrahigh Hall mobility value of >20,000 cm2 V-1 s-1 is measured in as-grown Bi2O2Se nanoflakes at low temperatures. This value is comparable to what is observed in graphene grown by chemical vapour deposition and at the LaAlO3-SrTiO3 interface, making the detection of Shubnikov-de Haas quantum oscillations possible. Top-gated field-effect transistors based on Bi2O2Se crystals down to the bilayer limit exhibit high Hall mobility values (up to 450 cm2 V-1 s-1), large current on/off ratios (>106) and near-ideal subthreshold swing values (∼65 mV dec-1) at room temperature. Our results make Bi2O2Se a promising candidate for future high-speed and low-power electronic applications.

13.
Small ; 13(18)2017 05.
Artigo em Inglês | MEDLINE | ID: mdl-28263026

RESUMO

Nanostructures of ternary topological insulator (TI) Bi2 Te2 Se are, in principle, advantageous to the manifestation of topologically nontrivial surface states, due to significantly enhanced surface-to-volume ratio compared with its bulk crystals counterparts. Herein, the synthesis of 2D Bi2 Te2 Se crystals on mica via the van der Waals epitaxy method is explored and systematically the growth behaviors during the synthesis process are investigated. Accordingly, 2D Bi2 Te2 Se crystals with domain size up to 50 µm large and thickness down to 2 nm are obtained. A pronounced weak antilocalization effect is clearly observed in the 2D Bi2 Te2 Se crystals at 2 K. The method for epitaxial growth of 2D ternary Bi2 Te2 Se crystals may inspire materials engineering toward enhanced manifestation of the subtle surface states of TIs and thereby facilitate their potential applications in next-generation spintronics.

14.
ACS Nano ; 10(11): 10317-10323, 2016 11 22.
Artigo em Inglês | MEDLINE | ID: mdl-27749039

RESUMO

The key challenge of direct integration of two-dimensional (2D) chalcogenide crystals into functional modules is precise control of the nucleation sites of the building blocks. Herein, we exploit the chemical activities and surface engineering of the substrates to manipulate the nucleation energy barrier of 2D crystals and thereby realize the patternable growth of 2D crystals. The selective-region chemical modifications of the substrates are achieved via microcontact printing combined with the elegant self-assembly of octadecyltrichlorosilane molecules on the substrates. The patternable growth method is versatile and can be used as a general strategy for growing a broad class of high-quality 2D chalcogenide crystals with tailorable configurations on a variety of chemically engineered substrates. Moreover, we demonstrate flexible transparent electrodes based on large-scale patterned nanogrids of topological insulator Bi2Se3, which possess tailored trade-off between electric conductivity and optical transmittance across the visible to near-infrared regime. We hope this method may open an avenue to the efficient integration and batch production of 2D chalcogenide crystals and could inspire ongoing efforts of the fabrication of van der Waals heterostructures.

15.
Adv Mater ; 28(40): 8968-8974, 2016 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-27562642

RESUMO

Wafer-sized single-crystalline Cu (100) surface can be readily achieved on stacked polycrystalline Cu foils via simple oxygen chemisorption-induced reconstruction, enabling fast growth of large-scale millimeter-sized single-crystalline graphene arrays under molecular flow. The maximum growth rate can reach 300 µm min-1 , several orders of magnitude higher than previously reported values for millimeter-sized single-crystalline graphene growth on Cu foils.

16.
Nat Chem ; 4(4): 281-6, 2012 Feb 26.
Artigo em Inglês | MEDLINE | ID: mdl-22437712

RESUMO

Topological insulators are an intriguing class of materials with an insulating bulk state and gapless Dirac-type edge/surface states. Recent theoretical work predicts that few-layer topological insulators are promising candidates for broadband and high-performance optoelectronic devices due to their spin-momentum-locked massless Dirac edge/surface states, which are topologically protected against all time-reversal-invariant perturbations. Here, we present the first experimental demonstration of near-infrared transparent flexible electrodes based on few-layer topological-insulator Bi(2)Se(3) nanostructures epitaxially grown on mica substrates by means of van der Waals epitaxy. The large, continuous, Bi(2)Se(3)-nanosheet transparent electrodes have single Dirac cone surface states, and exhibit sheet resistances as low as ~330 Ω per square, with a transparency of more than 70% over a wide range of wavelengths. Furthermore, Bi(2)Se(3)-nanosheet transparent electrodes show high chemical and thermal stabilities as well as excellent mechanical durability, which may lead to novel optoelectronic devices with unique properties.


Assuntos
Bismuto/química , Nanoestruturas/química , Compostos de Selênio/química , Silicatos de Alumínio/química , Eletrodos , Raios Infravermelhos
17.
J Am Chem Soc ; 134(14): 6132-5, 2012 Apr 11.
Artigo em Inglês | MEDLINE | ID: mdl-22455625

RESUMO

The orientation- and position-controlled synthesis of single-crystal topological insulator (Bi(2)Se(3) and Bi(2)Te(3)) nanoplate arrays on mica substrates was achieved using van der Waals epitaxy. Individual ultrathin nanoplates with the lateral dimension up to ~0.1 mm or uniform thickness down to 1-2 nm were produced. Single-Dirac-cone surface states of nanoplate aggregates were confirmed by angle-resolved photoemission spectroscopy measurements. The large-grain-size, single-crystal nanoplate arrays grown on mica can act as facile platforms for a combination of spectroscopy and in situ transport measurements, which may open up new avenues for studying exotic physical phenomena, surface chemical reactions, and modification in topological insulators.

18.
Nano Lett ; 10(8): 2870-6, 2010 Aug 11.
Artigo em Inglês | MEDLINE | ID: mdl-20698599

RESUMO

The authors present a van der Waals epitaxy of high-quality ultrathin nanoplates of topological insulator Bi(2)Se(3) on a pristine graphene substrate using a simple vapor-phase deposition method. Sub-10-nm-thick nanoplates of layered Bi(2)Se(3) with defined orientations can be epitaxially grown on a few-layer pristine graphene substrate. We show the evolution of Raman spectra with the number of Bi(2)Se(3) layers on few-layer graphene. Bi(2)Se(3) nanoplates with a thickness of three quintuple-layers (3-QL) exhibit the strongest Raman intensity. Strain effects in the Bi(2)Se(3)/graphene nanoplate heterostructures is also studied by Raman spectroscopy. 1-QL and 2-QL Bi(2)Se(3) nanoplates experience tensile stress, consistent with compressive stress in single-layer and bilayer graphene substrates. Our results suggest an approach for the synthesis of epitaxial heterostructures that consist of an ultrathin topological insulator and graphene, which may be a new direction for electronic and spintronic applications.

19.
Nano Lett ; 10(6): 2245-50, 2010 Jun 09.
Artigo em Inglês | MEDLINE | ID: mdl-20486680

RESUMO

A topological insulator (TI) represents an unconventional quantum phase of matter with insulating bulk band gap and metallic surface states. Recent theoretical calculations and photoemission spectroscopy measurements show that group V-VI materials Bi(2)Se(3), Bi(2)Te(3), and Sb(2)Te(3) are TIs with a single Dirac cone on the surface. These materials have anisotropic, layered structures, in which five atomic layers are covalently bonded to form a quintuple layer, and quintuple layers interact weakly through van der Waals interaction to form the crystal. A few quintuple layers of these materials are predicted to exhibit interesting surface properties. Different from our previous nanoribbon study, here we report the synthesis and characterizations of ultrathin Bi(2)Te(3) and Bi(2)Se(3) nanoplates with thickness down to 3 nm (3 quintuple layers), via catalyst-free vapor-solid (VS) growth mechanism. Optical images reveal thickness-dependent color and contrast for nanoplates grown on oxidized silicon (300 nm SiO(2)/Si). As a new member of TI nanomaterials, ultrathin TI nanoplates have an extremely large surface-to-volume ratio and can be electrically gated more effectively than the bulk form, potentially enhancing surface state effects in transport measurements. Low-temperature transport measurements of a single nanoplate device, with a high-k dielectric top gate, show decrease in carrier concentration by several times and large tuning of chemical potential.

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