Selective synthesis of Bi2Se3 nanostructures by solvothermal reaction

Bi₂Se₃ nanobelts, nanoflakes and sheets embedded nanotubes were prepared via solvothermal process with different solvents. The reaction conditions influencing the synthesis of Bi₂Se₃ nanostructures such as solvents, and reaction temperatures were studied and optimized. Results indicated that the mixed solvent composed of triethanolamine and ethanol (TEA-EtOH) or triethanolamine and distilled water (TEA-H₂O) can decrease the threshold temperature (TT) of Bi₂Se₃. With the solvents TEA-EtOH and TEA-H₂O, we originally accomplished the shape-controlled synthesis of Bi₂Se₃ nanocrystals by controlling reaction temperature. Based on the viewpoint of crystallography about Bi₂Se₃, the possible growth mechanisms of Bi₂Se₃ nanostructures were discussed.     

Interface-hydrothermal synthesis of Sn3S4/graphene sheet composites and their application in electrochemical capacitors

An efficient interface-hydrothermal approach is developed to synthesize Sn₃S₄/graphene sheet composites (SSGSCs), where the graphene sheets (GSs) are separated by fine Sn₃S₄ nanoparticles (NPs) well-dispersed onto their surfaces. The SSGSCs are investigated as electroactive materials for electrochemical capacitors (ECs) application. Due to the positive synergistic effect of GSs and Sn₃S₄ NPs, the unique SSGSCs electrode owns the ability to deliver large specific capacitance and good electrochemical stability at high rates. Moreover, the method we proposed here provides a universal and simple approach to synthesize other metal sulfides/GSs composites for ECs and even for Li-ion battery applications.     

Efficient Bi → Nd energy transfer in Gd2O3:Bi,Nd

Bi³⁺,Nd³⁺ co-doped Gd₂O₃ were prepared by solid state reaction and the optical properties were investigated. The results show that the near-infrared emission of Nd³⁺ ions is significantly enhanced by the introducing of Bi³⁺ in co-doped samples. An efficient energy transfer from Bi³⁺ to Nd³⁺ corresponds to the near-infrared emission enhancement. The energy transfer efficiency reaches 64.1% for the sample with the strongest near-infrared emission, which has the optimized doping concentrations of 0.5% for Bi³⁺ and 2% for Nd³⁺. The interesting optical properties make Bi³⁺,Nd³⁺ co-doped Gd₂O₃ promising as the luminescent down-conversion layers in front of c-Si solar cells to enhance the performance of the solar cells.     

In situ fabrication of Bi2S3 nanocrystal film for photovoltaic devices

A facile wet-chemical method to prepare Bi₂S₃ thin films with flake nanostructures directly on ITO glass substrate is presented in this paper for the first time. The product was characterized by X-ray powder diffractometer (XRD), Raman spectrometer, scanning electron microscope (SEM), and atomic force microscope (AFM). The one-step solvothermal elements treatment on the ITO substrate spare time to form film by spin-coating process and the film could be tightly attached to the ITO electrode. A conjugated polymer, poly 3-hexylthiophene (P3HT), was then spin-coated on the as-prepared Bi₂S₃ film to form an inorganic-organic hybrid thin film. The photovoltaic performance of the resulting solar cell device was also investigated.     

CTAB assisted immobilization of RuO2 nanoparticles on graphene oxide for electrochemical sensing of hydrazine

A novel method has been presented to modify glassy carbon electrode (GCE) with graphene oxide (GO) nanocomposite without introducing any electrode binder such as chitosan and Nafion. First, modify GCE with RuO₂ nanoparticles which have been dispersed in cetyltrimethyl ammonium bromide (CTAB) aqueous solution. Then, highly adhesive RuO₂/CTAB/GO nanocomposite membrane formed on GCE by immersing RuO₂/CTAB modified GCE in GO suspension. CTAB plays significant roles not only in the preparation of the nanocomposite but also in the immobilization of nanocomposite on GCE surface. First, CTAB was used as the dispersant of RuO₂ nanoparticles. Second, CTAB acted as the molecular linker to bind RuO₂ nanoparticles on graphene sheets. Third, CTAB formed CTAB/GO nanocomposite which is highly adhesive on the surface of electrodes such as GCE and ITO (indium tin oxide). The obtained RuO₂/CTAB/GO/GCE shows excellent electrocatalytic ability towards the oxidation of hydrazine. The oxidation of hydrazine on RuO₂/CTAB/GO/GCE is an adsorption-controlled process and the oxidation current is linear with the concentration of hydrazine in the range of 1 × 10^?5～1 × 10^?3 M with a detection limit of 2.3 × 10^?6 M. The application of this sensor in the sensing of hydrazine in real water samples confirmed its reliability and accuracy.     

Chemical Intercalation of Topological Insulator Grid Nanostructures for High‐Performance Transparent Electrodes

2D layered nanomaterials with strong covalent bonding within layers and weak van der Waals' interactions between layers have attracted tremendous interest in recent years. Layered Bi₂Se₃ is a representative topological insulator material in this family, which holds promise for exploration of the fundamental physics and practical applications such as transparent electrode. Here, a simultaneous enhancement of optical transmittancy and electrical conductivity in Bi₂Se₃ grid electrodes by copper‐atom intercalation is presented. These Cu‐intercalated 2D Bi₂Se₃ electrodes exhibit high uniformity over large area and excellent stabilities to environmental perturbations, such as UV light, thermal fluctuation, and mechanical distortion. Remarkably, by intercalating a high density of copper atoms, the electrical and optical performance of Bi₂Se₃ grid electrodes is greatly improved from 900 Ω sq^?1, 68% to 300 Ω sq^?1, 82% in the visible range; with better performance of 300 Ω sq^?1, 91% achieved in the near‐infrared region. These unique properties of Cu‐intercalated topological insulator grid nanostructures may boost their potential applications in high‐performance optoelectronics, especially for infrared optoelectronic devices.     

All-chemically deposited Bi2S3/PbS solar cells

We report on solar cells with a cross-sectional layout: TCO/window/Bi₂S₃/PbS, in which a commercial SnO₂ transparent conductive oxide (TCO-PPG Sungate 500); chemically deposited window layers of CdS, ZnS or their oxides; n-type Bi₂S₃ (100 nm) and p-type PbS (360-550 nm) absorber films constitute the cell structures. The crystalline structure, optical, and electrical properties of the constituent films are presented. The open circuit voltage (V_oc) and short-circuit current density (J_sc), for 1000 W/m² solar radiation, of these solar cells depend on the window layers, and vary in the range, 130-310 mV and 0.5-5 mA/cm², respectively. The typical fill factors (FF) of these cells are 0.25-0.42, and conversion efficiency, 0.1-0.4%.     

Preparation and photoelectrochemical performance of TiO2/HS-CH2-COOH/Cu3Se2 composite film

In this paper, the TiO₂/HS-CH₂-COOH/Cu₃Se₂ composite film photoanodes were fabricated on conducting glass plates. Cu₃Se₂ nanoparticles were used as the sensitizer and the bi-functional modifier HS-CH₂-COOH was used at the interface between Cu₃Se₂ and TiO₂ films to improve the properties of the film photoanode. The characterization results show that the sol-gel prepared anatase TiO₂ film has a compact and uniform surface, while the tetragonal Cu₃Se₂ film has a coarse surface which is made up of uniform elongated particles. The photoelectrochemical experimental results indicate that the TiO₂/HS-CH₂-COOH/Cu₃Se₂ composite film photoanodes have a good photovoltaic property.     

Cu2ZnSnS4 solar cell prepared entirely by non-vacuum processes

Cu₂ZnSnS₄ (CZTS) solar cell with superstrate structure of fluorine-doped tin oxide glass/TiO₂/In₂S₃/CZTS/Carbon was prepared entirely by non-vacuum processes. The compact TiO₂ window and In₂S₃ buffer layers, CZTS absorber layer and Carbon electrode layer were prepared by spray pyrolysis method, ball milling and screen printing combination processes and screen printing process, respectively. The short-circuit current density, open-circuit voltage, fill factor and conversion efficiency of the best fabricated solar cell are 8.76 mA/cm², 250 mV, 0.27 and 0.6%, respectively. The fabrication process for the CZTS solar cell did not employ any vacuum conditions or high-toxic materials (such as CdS, H₂Se, H₂S or Se).     

Improvement of photon collection in Cu(In,Ga)Se2 solar cells and modules by fluorescent frequency conversion

Fluorescent photon down conversion for the improvement of the blue response of ZnO/CdS/Cu(In,Ga)Se₂ heterojunction solar cells and modules is investigated. Fluorescent dyes of the series Lumogen® F are analyzed by optical transmission and reflection as well as by photoluminescence measurements. A spectral transfer matrix formalism is introduced that allows to predict the suitability of a luminescent dye as a down-converter for a given solar cell from its absorption/emission properties. We find that Lumogen® F Violet 570 and Lumogen® F Yellow 083 as well as a combination of both yields improvements for Cu(In,Ga)Se₂ solar modules. Particularly, we find that the short circuit current density of a Cu(In,Ga)Se₂ mini-module is improved by 1.5 mA cm^− 2 when applying a varnish with a combination of Lumogen® F Violet and Yellow. About 0.5 mA cm^− 2 of this improvement is due to a reduced overall reflectance and an improvement of 1 mA cm^− 2 results from the frequency conversion by the dyes.     

纳米二氧化锡/三维大孔石墨烯复合电极的制备及其储锂性能的研究

以维生素C(VC)为还原剂,通过溶剂热还原法制备了纳米二氧化锡/三维大孔石墨烯复合负极材料(SnO_2/3DGr)。SEM和TEM测试表明,SnO_2/3DGr具有均匀分布的微米级孔隙,其中SnO_2晶粒尺寸为6~8nm,且均匀分布在石墨烯片层表面。电化学测试表明所制备的SnO_2/3DGr复合电极材料具有优异的电化学性能,该材料在电流密度为100mA/g时,循环100周之后仍然具有1678mAh/g的可逆比容量,在极高电流密度5A/g下,仍然保持405mAh/g的可逆比容量,表现出非常优异的循环稳定性和倍率性能。该材料独特的三维大孔结构以及SnO_2与石墨烯的协同作用,很好地抑制了SnO_2在循环过程中的体积效应,大大改善了SnO_2负极材料的电化学性能。     

Three-dimensional heterostructured MnO2/graphene/carbon nanotube composite on Ni foam for binder-free supercapacitor electrode

In this article, three-dimensional (3D) heterostructured of MnO₂/graphene/carbon nanotube (CNT) composites were synthesized by electrochemical deposition (ELD)-electrophoretic deposition (EPD) and subsequently chemical vapour deposition (CVD) methods. MnO₂/graphene/CNT composites were directly used as binder-free electrodes to investigate the electrochemical performance. To design a novel electrode material with high specific area and excellent electrochemical property, the Ni foam was chosen as the substrate, which could provide a 3D skeleton extremely enhancing the specific surface area and limiting the huge volume change of the active materials. The experimental results indicated that the specific capacitance of MnO₂/graphene/CNT composite was up to 377.1 F g^?1 at the scan speed of 200 mV s^?1 with a measured energy density of 75.4 Wh kg^?1. The 3D hybrid structures also exhibited superior long cycling life with close to 90% specific capacitance retained after 500 cycles.     

Photoluminescence and Raman study of Cu2ZnSn(SexS1 − x)4 monograins for photovoltaic applications

The quaternary semiconductors Cu₂ZnSnSe₄ and Cu₂ZnSnS₄ have attracted a lot of attention as possible absorber materials for solar cells due to their direct bandgap and high absorption coefficient (> 10⁴ cm⁻¹). In this study we investigate the optical properties of Cu₂ZnSn(Se_xS_1 − x)₄ monograin powders that were synthesized from binary compounds in the liquid phase of potassium iodide (KI) flux materials in evacuated quartz ampoules. Radiative recombination processes in Cu₂ZnSn(Se_xS_1 − x)₄ monograins were studied by using low-temperature photoluminescence (PL) spectroscopy. A continuous shift from 1.3 eV to 0.95 eV of the PL emission peak position with increasing Se concentration was observed indicating the narrowing of the bandgap of the solid solutions. Recombination mechanisms responsible for the PL emission are discussed. Vibrational properties of Cu₂ZnSn(Se_xS_1 − x)₄ monograins were studied by using micro-Raman spectroscopy. The frequencies of the optical modes in the given materials were detected and the bimodal behaviour of the A₁ Raman modes of Cu₂ZnSnSe₄ and Cu₂ZnSnS₄ is established.     

Effect of the thickness of Bi2Se3 sheets on the morphologies of Bi2Se3–ZnS nanocomposites and improved photoresponsive characteristic

Bi₂Se₃–ZnS nanocomposites were synthesized with different morphologies and their photoluminescence were investigated. The compounds formed hexagonal rods as the thickness of Bi₂Se₃ sheets stayed about a few nanometers; while the Bi₂Se₃ sheets’ thickness increased to tens of nanometers, the compounds formed novel morphologies of Bi₂Se₃–ZnS nanocomposites with small ZnS nanoparticles randomly decorated onto Bi₂Se₃ sheets. The formation mechanism was proposed based on the different thickness of Bi₂Se₃ sheets used in experimental processes. In addition, the significant fluorescence quench and obvious improvement in photoresponsive characteristic were shown after the integration of ZnS with Bi₂Se₃ sheets, which showed potential application in optoelectronic devices.     

The effect of substitution of Bi2O3 for alkali oxides on thermal properties, structure and wetting behavior of the borosilicate glass

The effect of substitution of Bi₂O₃ for alkali oxides in the borosilicate sealing glass on thermal properties, structure and wetting behavior of the borosilicate glass was studied. The thermal expansion coefficient (TEC) decreased with the substitution, however, the TEC varied little while the alkali oxides were completely consumed. The variation in glass transition temperature (T_g) and the FTIR results of the glasses indicated significant effect of Bi₂O₃ substitution on the glass structure, which caused a progressive conversion of BO₃ to BO₄ unit in the glass. The appropriate amount of Bi₂O₃ obviously improved the wetting performance of the borosilicate glass on Al₂O₃ substrate due to the high polarizability of Bi³⁺ ion.     

Bifunctional Au@Bi2Se3 Core–Shell Nanoparticle for Synergetic Therapy by SERS‐Traceable AntagomiR Delivery and Photothermal Treatment

For the first time, topological insulator bismuth selenide nanoparticles (Bi₂Se₃ NP) are core–shelled with gold (Au@Bi₂Se₃) i) to represent considerably small‐sized (11 nm) plasmonic nanoparticles, enabling accurate bioimaging in the near‐infrared region; ii) to substantially improve Bi₂Se₃ biocompatibility, iii) water dispersibility, and iv) surface functionalization capability through straightforward gold–thiol interaction. The Au@Bi₂Se₃ is subsequently functionalized for v) effective targeting of SH‐SY5Y cancer cells, vi) disrupting the endosome/lysosome membrane, vii) traceable delivery of antagomiR‐152 and further synergetic oncomiR knockdown and photothermal therapy (PTT). Unprecedentedly, it is observed that the Au shell thickness has a significant impact on evoking the exotic plasmonic features of Bi₂Se₃. The Au@Bi₂Se₃ possesses a high photothermal conversion efficiency (35.5%) and a remarkable surface plasmonic effect (both properties are approximately twofold higher than those of 50 nm Au nanoparticles). In contrast to the siRNA/miRNA delivery methods, the antagomiR delivery is based on strand displacement, in which the antagomiR‐152 is displaced by oncomiR‐152 followed by a surface‐enhanced Raman spectroscopy signal drop. This enables both cancer cell diagnosis and in vitro real‐time monitoring of the antagomiR release. This selective PTT nanoparticle can also efficiently target solid tumors and undergo in vivo PTT, indicating its potential clinical applications.     

Electrochemical Biosensor Composed of Silver Ion‐Mediated dsDNA on Au‐Encapsulated Bi2Se3 Nanoparticles for the Detection of H2O2 Released from Breast Cancer Cells

A newly developed electrochemical biosensor composed of a topological insulator (TI) and metallic DNA (mDNA) is fabricated. The bismuth selenide nanoparticle (Bi₂Se₃ NP) is synthesized and sandwiched between the gold electrode and another Au‐deposited thin layer (Bi₂Se₃@Au). Then, eight‐silver‐ion mediated double‐stranded DNA (mDNA) is immobilized onto the substrate (Bi₂Se₃@Au‐mDNA) for the further detection of hydrogen peroxide. The Bi₂Se₃ NP acts as the electrochemical‐signal booster, while unprecedentedly its encapsulation by the Au thin layer keeps the TI surface states protected, improves its electrochemical‐signal stability and provides an excellent platform for the subsequent covalent immobilization of the mDNA through Au–thiol interaction. Electrochemical results show that the fabricated biosensor represents much higher Ag⁺ redox current (≈10 times) than those electrodes prepared without Bi₂Se₃@Au. The characterization of the Bi₂Se₃@Au‐mDNA film is confirmed by atomic force microscopy, scanning tunneling microscopy, and cyclic voltammetry. The proposed biosensor shows a dynamic range of 00.10 × 10^?6m to 27.30 × 10^?6m , very low detection limit (10 × 10^?9m ), unique current response (1.6 s), sound H₂O₂ recovery in serum, and substantial capability to classify two breast cancer subtypes (MCF‐7 and MDA‐MB‐231) based on their difference in the H₂O₂ generation, offering potential applications in the biomedicine and pharmacology fields.     

Metabolizable Ultrathin Bi2Se3 Nanosheets in Imaging‐Guided Photothermal Therapy

Poly(vinylpyrrolidone)‐encapsulated Bi₂Se₃ nanosheets with a thickness of 1.7 nm and diameter of 31.4 nm are prepared by a solution method. Possessing an extinction coefficient of 11.5 L g^?1 cm^?1 at 808 nm, the ultrathin Bi₂Se₃ nanosheets boast a high photothermal conversion efficiency of 34.6% and excellent photoacoustic performance. After systemic administration, the Bi₂Se₃ nanosheets with the proper size and surface properties accumulate passively in tumors enabling efficient photoacoustic imaging of the entire tumors to facilitate photothermal cancer therapy. In vivo biodistribution studies reveal that they are expelled from the body efficiently after 30 d. The ultrathin Bi₂Se₃ nanosheets have large clinical potential as metabolizable near‐infrared‐triggered theranostic agents.     

Poly(Vinylpyrollidone)‐ and Selenocysteine‐Modified Bi2Se3 Nanoparticles Enhance Radiotherapy Efficacy in Tumors and Promote Radioprotection in Normal Tissues

The development of a new generation of nanoscaled radiosensitizers that can not only enhance radiosensitization of tumor tissues, but also increase radioresistance of healthy tissue is highly desirable, but remains a great challenge. Here, this paper reports a new versatile theranostics based on poly(vinylpyrollidone)‐ and selenocysteine‐modified Bi₂Se₃ nanoparicles (PVP‐Bi₂Se₃@Sec NPs) for simultaneously enhancing radiotherapeutic effects and reducing the side‐effects of radiation. The as‐prepared nanoparticles exhibit significantly enhanced free‐radical generation upon X‐ray radiation, and remarkable photothermal effects under 808 nm NIR laser irradiation because of their strong X‐ray attenuation ability and high NIR absorption capability. Moreover, these PVP‐Bi₂Se₃@Sec NPs are biodegradable. In vivo, part of selenium can be released from NPs and enter the blood circulation system, which can enhance the immune function and reduce the side‐effects of radiation in the whole body. As a consequence, improved superoxide dismutase and glutathione peroxidase activities, promoted secretion of cytokines, increased number of white blood cell, and reduced marrow DNA suppression are found after radiation treatment in vivo. Moreover, there is no significant in vitro and in vivo toxicity of PVP‐Bi₂Se₃@Sec NPs during the treatment, which demonstrates that PVP‐Bi₂Se₃@Sec NPs have good biocompatibility.     

Adsorption of formaldehyde molecule on the intrinsic and Al-doped graphene: A first principle study

To search for a high sensitivity sensor for formaldehyde (H₂CO), we investigated the adsorption of H₂CO on the intrinsic and Al-doped graphene sheets using density functional theory (DFT) calculations. Compared with the intrinsic graphene, the Al-doped graphene system has high binding energy value and short connecting distance, which are caused by the chemisorption of H₂CO molecule. Furthermore, the density of states (DOS) results show that orbital hybridization could be seen between H₂CO and Al-doped graphene sheet, while there is no evidence for hybridization between the H₂CO molecule and the intrinsic graphene sheet. Therefore, Al-doped graphene is expected to be a novel chemical sensor for H₂CO gas. We hope our calculations are useful for the application of graphene in chemical sensor.