Preparation of cauliflower-like bismuth sulfide and its application in electrochemical sensor

A solvothermal process was developed for the preparation of cauliflower-like Bi2S3 from N,N-dimethylformamide （DMF） solution of bismuth nitrate [Bi（NO3）3.5H2O] and thioacetamide （TAA） with 2-undecyl-1-dithioureido-ethyl-imidazoline （SUDEI） as the morphology-controlling agent. The obtained Bi2S3 products were characterized by transmission electron microscopy （TEM）, scanning electron microscopy （SEM）, and X-ray diffraction （XRD）, etc. The sensing properties of Bi2S3 with different morphologies were evaluated by the electrochemical analysis of dopamine （DA） and ascorbic acid （AA） coexisting solution. The results showed that cauliflower-like Bi2S3 showed a better resolving ability than rod-like Bi2S3 for the simultaneous determination of DA and AA,     

Bi2S3 nanomaterials: morphology manipulation and related properties

The Bi(2)S(3) nanomaterials with various morphologies such as nanorods, nanowires, nanowire bundles, urchin-like microspheres and urchin-like microspheres with cavities have been successfully synthesized through a simple hydrothermal method. Experimental results indicate that sulfur sources play crucial roles in determining the morphologies of Bi(2)S(3) products. Moreover, formation mechanisms of different Bi(2)S(3) nanostructures are discussed based on understanding of the growth habit of Bi(2)S(3) crystal. Finally, we also studied the morphologies-dependent electrochemical and optical properties of the as-synthesized Bi(2)S(3) nanomaterials.     

High-quality ultralong Sb2Se3 and Sb2S3 nanoribbons on a large scale via a simple chemical route

Large-scale ultralong single-crystalline Sb2Se3 and Sb2S3 nanoribbons were prepared respectively by reacting SbCl3 with selenium and sulfur powders in glycol solution. Both Sb2Se3 and Sb2S3 nanoribbons are usually hundreds of microns in length, and the structures of the nanoribbons are determined to be of the orthorhombic phases. The Sb2Se3 nanoribbons are typically 100-300 nm in width and 20-60 nm in thickness and grow along the [12] direction. Sb2S3 nanoribbons are wider than Sb2Se3 nanoribbons; Sb2S3 nanoribbons are about 200-500 nm in width and grow along the [001] direction. The growth mechanism of the nanoribbons is investigated based on high-resolution transmission electron microscopy (HRTEM) observations. Optical absorption experiment reveals that Sb2Se3 and Sb2S3 nanoribbons are two semiconductors with bandwidth Eg approximately 1.15 eV and Eg approximately 1.56 eV, respectively.     

Controlled synthesis of CuO nanostructures by a simple solution route

A simple solution route has been developed to prepare nanostructured CuO with Cu(NO₃)₂·3H₂O and NaOH as starting materials. CuO nanoribbons or nanorods and their assemblies into hierarchical structures have been synthesized, respectively, by controlling the molar ratio of NaOH to Cu(NO₃)₂, reaction temperature and the concentration of the starting NaOH solution. Experiments demonstrate that the molar ratio of NaOH to Cu(NO₃)₂ is an important parameter which may decide whether CuO exists in nanoribbons (nanorods) or assemblies into hierarchical structures. Whether Cu(NO₃)₂ is dissolved in ethanol or water also influences the formation of monodispersed CuO nanoribbons (nanorods). The growth mechanism of these nanostructures is discussed. The products were characterized by X-ray diffraction, field-emission scanning electron microscopy and transmission electron microscopy (HRTEM) and their optical absorption spectra were also studied.     

Porous peanut-like Bi2O3-BiVO4 composites with heterojunctions: one-step synthesis and their photocatalytic properties

For the first time, porous peanut-like Bi(2)O(3)-BiVO(4) composites with heterojunctions have been synthesized by a one-step mixed solvothermal method with the assistance of a l-lysine template. A mixture of ethylene glycol (EG) and H(2)O (volume ratio of EG-H(2)O = 3:1) is used as the solvent. Unlike the traditional methods, no concentrated HNO(3) and/or NaOH are involved in diluting Bi and V sources in the adopted approach. The as-synthesized peanut-like samples are rough and porous on the surface and to some extent are interior-hollow. The degradation of methylene blue (MB) is employed to evaluate the photocatalytic activity of the Bi(2)O(3)-BiVO(4) composite. It is observed that the composite performs much better than Bi(2)O(3) and BiVO(4), plausibly due to heterojunctions formed between Bi(2)O(3) and BiVO(4). To investigate the relationship between structure and performance, the as-synthesized samples are characterized by XRD, XPS, SEM, TEM (HRTEM), UV-vis DRS, PL and nitrogen adsorption-desorption methods. Additionally, a possible growth mechanism of this hollow peanut-like structure and the separation process of photogenerated electron-hole pairs on the heterojunctions have been discussed.     

Synthesis of Bi-doped TiO2 Nanotubes and Enhanced Photocatalytic Activity for Hydrogen Evolution from Glycerol Solution

Bi‐doped TiO₂ nanotubes with variable Bi/Ti ratios were synthesized by hydrothermal treatment in 10 mol·L^?1 NaOH (aq.) through using Bi‐doped TiO₂ particles derived from conventional sol‐gel method as starting materials. The effects of Bi content on the morphology, textural properties, photo absorption and photocatalytic activity of TiO₂ nanotubes were investigated. The scanning electron microscopy (SEM), transmission electron microscopy (TEM), X‐ray diffraction (XRD) and X‐ray photoelectron spectroscopy (XPS) observations of the obtained samples revealed the formation of titanate nanotube structure doped with Bi, which exists as a higher oxidation state than Bi³⁺. Bi‐doping TiO₂ nanotubes exhibited an extension of light absorption into the visible region and improved photocatalytic activities for hydrogen production from a glycerol/water mixed solution as compared with pure TiO₂ nanotubes. There was an optimal Bi‐doped content for the photocatalytic hydrogen production, and high content of Bi would retard the phase transition of titanate to anatase and result in morphology change from nanotube to nanobelt, which in turn decreases the photocatlytic activity for hydrogen evolution.     

Bismuth sulfide thin films with low resistivity on self-assembled monolayers

Using self-assembled monolayers (SAMs), highly crystalline bismuth sulfide thin films with low electrical resistivity have been prepared from aqueous solution at low temperature (40-70 degrees C). The nucleation and growth process of Bi2S3 thin films was investigated in detail by XPS, AES, SEM, XRD, SAED, and HRTEM. Solution conditions have marked effects on the microstructure, growth rate, and mechanism of Bi2S3 films. Increased solution temperature resulted in a higher growth rate and a shorter induction time due to a higher supersaturation degree. In the solution of pH 1.12, homogeneous nucleation and the attachment process dominated the formation of Bi2S3 films. In contrast, at pH 0.47 Bi2S3 thin films were formed via heterogeneous nucleation and growth. The c-axial orientation of bismuthinite films was enhanced with the increase of reaction time. By controlling the solution supersaturation and reaction duration, highly crystalline Bi2S3 films composed of closely packed and coalescent crystallites could be realized, whose dark electrical resistivity could reach as low as 0.014 Omega cm without any post-treatment.     

Controlled synthesis, growth mechanism, and properties of monodisperse CdS colloidal spheres

Highly monodisperse submicrometer CdS colloidal spheres (CSCS) with a controllable and tunable size (between 80 and 500 nm) have been synthesized through a facile solvothermal technique. Owing to the controllability of the reaction process, the growth mechanism of the colloidal spheres has been elucidated in detail. The whole growth process can be summarized as homogenous and slow nucleation of nanocrystals, formation of "cores" through 3D-oriented attachment of nanocrystals, and further surface-induced growth to monodisperse colloidal spheres through in situ formation and random attachment of additional nanocrystals. It has been demonstrated that the obtained CSCS colloidal particles are able to be assembled into films which show characteristic stop band gaps of photonic crystals. By using the CSCS as a template, Ag2S, Bi2S3, Cu2S, HgS, and Sb2S3 colloidal spheres, which are difficult to obtain directly, have also been prepared successfully through ion exchange.     

Solution-phase template approach for the synthesis of Cu(2)S nanoribbons

In this paper, we have developed a solution-phase template approach to synthesize Cu(2)S nanoribbons for the first time. Bi(2)S(3) nanoribbons act as both template and reactant when treated with small CuCl particles, generating Cu(2)S nanoribbons with the assistance of the solvent ethanol. Nanoribbons with different compositions of Bi(2)S(3) and Cu(2)S also could be obtained through controlling the reaction time. This kind of template method is expected to be a general template approach due to its slow reaction rate and simplicity.     

离子交换法制备高光催化活性Bi2WO6@Bi2S3异质结纳米片

社会经济快速发展的同时, 也带来了日益严峻的环境污染问题. 半导体光催化氧化技术因节能环保而在环境领域有广阔的应用前景. 作为最具有代表性的半导体光催化材料, TiO2因为其禁带宽度(3.2 eV)比较大, 只能被紫外光激发, 因而对太阳能的利用率较低. 作为一种最简单的含铋层状氧化物, Bi2WO6的禁带宽度(2.7 eV)相对较小, 可以部分利用太阳光中的可见光, 因而受到广大研究者的青睐. 但是, Bi2WO6光催化材料的可见光响应范围较窄, 仅能被波长小于450 nm的光激发, 且激发后的光生载流子容易复合, 导致光催化效率不高. 因此, 迫切需要对Bi2WO6光催化材料进行结构修饰与改性,采用拓展其光响应范围和抑制载流子复合, 来提高其光催化活性.本文采用离子交换法原位合成了具有核-壳结构的Bi2S3@Bi2WO6纳米片, 充分利用Bi2S3优良的可见光响应性能和半导体异质结光催化剂的构建, 来提高Bi2WO6的光催化活性. 结果表明, 随着Na2S·9H2O用量从0增加到1.5 g, 所得催化剂的光活性不断提高, X3B的降解速率常数由0.40×10-3min-1增加到6.6×10-3min-1, 催化剂活性提高了16.5倍. 当进一步增加Na2S·9H2O的用量时(1.5-3.0 g), 复合催化剂的光活性下降. 这是由于过多Na2S·9H2O的引入导致在催化剂表面生成了没有光活性的NaBiS2层(Bi2S3+ Na2S = 2NaBiS2), 占据了催化剂的活性位点, 阻碍了染料分子与催化剂的直接接触. Bi2WO6@Bi2S3异质结纳米片光活性的提高, 可归因于Bi2S3的敏化作用极大拓展了复合催化剂的光响应范围; 另一方面, Bi2WO6和Bi2S3两者之间的半导体异质结效应有效促进了光生载流子在空间的有效分离, 抑制了光生电子-空穴的复合, 从而提高了复合催化剂的催化效率. 本研究为其他半导体复合材料的原位生长制备提供了新的思路.     

Bi2O2Se纳米带的气-液-固生长与高性能晶体管的构筑

Nanostructured bismuth oxyselenide (Bi₂O₂Se) semiconductor, a two-dimensional (2D) materials with high-mobility, air-stability, and tunable bandgap, has recently emerged as a candidate of channel material for future digital (electronic and optoelectronic) applications. In terms of material morphology, some basic issues will be addressed when a two-dimensional layered crystal is shaped into a one-dimensional (1D) geometry due to size effect; these include the space-confined transport in a plane, which leads to dramatic changes in electronic, optical, and thermal properties. These novel 1D nanostructures with unique properties are an optimal choice for fabricating next-generation integrated circuits and functional devices within the nanometer scale such as gate-all-around field-effect transistors, single-electron transistors, chemical sensors, and THz detectors. As one of the high-mobility 2D semiconductor, 1D high-quality Bi₂O₂Se nanoribbons could be promising for applications in high-performance transistors; however, their synthesis has not been completely developed yet. In our study, we report on the facile growth of Bi₂O₂Se nanoribbons on mica substrates via a bismuth-catalyzed vapor-liquid-solid (VLS) mechanism. The preparation of Bi₂O₂Se nanoribbons is based on a previous work that emphasized on the oxidation of Bi₂Se₃ in a chemical vapor deposition (CVD) system and the use of bismuth (Bi) particles as the precursor of Bi catalysis. The morphology, composition, and structure of the as-grown Bi₂O₂Se nanoribbons were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), Raman spectroscopy, transmission electron microscopy (TEM), as well as other methods. For a Bi mediated VLS growth process, the growth of Bi₂O₂Se nanoribbons can be self-assembled; further, in this process, as-grown epitaxial Bi₂O₂Se nanoribbons are free-standing with out-of-plane morphology on the mica substrate. Additionally, combining the spherical aberration corrected transmission electron microscope (ACTEM) and selected electron diffraction (SAED) methods, we discovered that the as-synthesized Bi₂O₂Se nanoribbons were single crystalline with high quality. We further investigated the controllable growth for domain size by optimizing the growth temperature of the Bi₂O₂Se nanoribbons. As-synthesized single-crystal Bi₂O₂Se nanoribbons have widths in the range of 100 nm to 20 μm and lengths in the sub-millimeter range. By employing a polymer poly(methyl methacrylate) (PMMA) assisted clean transfer method with the assistance of deionized water, the Bi₂O₂Se nanoribbons can be easily transferred onto a SiO₂/Si substrate. Fabricated into the top-gated field-effect device, the Bi₂O₂Se nanoribbon sample (transferred to the SiO₂/Si substrate) exhibited high electronic performances; these included a high electron mobility of ∼220 cm²∙V⁻¹∙s⁻¹ at room temperature, good switching behavior with on/off ratio of > 10⁶, and high on current density of ∼42 μA∙μm⁻¹ at a channel length of 10 μm. Therefore, Bi₂O₂Se nanoribbons are expected to be a promising materials for building high-performance transistors in the future.     

Development of one-dimensional nanostructures through the crystallization of amorphous colloids

In this paper we have demonstrated that the crystallization method of amorphous colloids is convenient and feasible in the large-scale production of one-dimensional (1D) nanostructures. For the crystals with highly anisotropic structures, such as orthorhombic, trigonal, and hexagonal crystals, the crystallization generally tends to occur along the (001) axis. The preparation of orthorhombic bismuth sulfide (Bi2S3) nanorods and trigonal selenium ( t-Se) nanowires by the crystallization route was used as typical examples to illustrate the process and mechanism of crystallization. The as-prepared products were characterized with transmission electron microscopy, field-emission scanning electron microscopy, X-ray diffraction, and selected area electron diffraction. Additionally, the detailed crystal growth processes involved in the crystallization of amorphous Bi2S3 colloid were investigated by studying the morphology and structure of intermediates. It demonstrates that the growth of the nanorods is through two key steps: (1) the formation of multiple activated sites on the surface of spherical Bi2S3 colloid and (2) the subsequent preferential growth along these sites.     

A Mixed Solvothermal Route to Synthesis of Dice‐Like PbS

The authors developed a simple solvothermal route to synthesis of PbS nanocrystals in the mild binary mixed solvent made of diethylenetriamine (DETA) and water. Two kinds of PbS nanostructures (dice‐like and cubic) have been successfully synthesized in the binary mixed solvothermal system at 150 °C by changing the sulfur source. The products were characterized by X‐ray diffraction (XRD), field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM). The results show that the as‐prepared dice‐like PbS crystals have a hole on each of their faces. To elucidate the relationship between reaction systems and the morphologies of the final products, the authors also investigated the crystal growth by using different sulfur source. Based on the experimental results, the possible growth mechanism of the dice‐like PbS crystals was proposed.     

Controlled synthesis of olive-shaped Bi2S3/BiVO4 microspheres through a limited chemical conversion route and enhanced visible-light-responding photocatalytic activity

Well-defined olive-shaped Bi(2)S(3)/BiVO(4) microspheres were synthesized through a limited chemical conversion route (LCCR), where olive-shaped BiVO(4) microspheres and thioacetamide (TAA) were used as precursors and sulfur source, respectively. The as-synthesized products were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), high-resolution transmission microscope (HRTEM), X-ray photoelectron spectra (XPS), UV-visible diffuse-reflectance spectroscopy (UV-vis DRS), and photoluminescence (PL) spectra in detail. Compared with pure BiVO(4) microspheres and Bi(2)S(3) nanorods, the Bi(2)S(3)/BiVO(4) products showed obviously enhanced photocatalytic activity for the degradation of rhodamine B (Rh B) in aqueous solution under visible-light irradiation (λ > 400 nm). In addition, the Bi(2)S(3)/BiVO(4) composite microspheres showed good visible-light-driven photocatalytic activity for the degradation of refractory oxytetracycline (OTC) as well. On the basis of UV-vis DRS, the calculated energy band positions, and PL spectra, the mechanism of enhanced photocatalytic activity of Bi(2)S(3)/BiVO(4) was proposed. The present study provides a new strategy to design composite materials with enhanced photocatalytic performance.     

BiOCl纳米片微球的制备及其形成机理

以乙二醇为溶剂,采用溶剂热法制备了BiOCl纳米片微球.BiOCl纳米片交织在一起,形成开放的微孔结构.不同条件下合成的BiOCl形貌分析表明,纳米片微球的形成是乙二醇辅助生长的过程:乙二醇的2个氧原子与1个或2个铋离子配位生成含铋多聚络合物.在溶剂热过程中,Bi3+离子催化乙二醇聚合脱水,生成的水分子反过来原位促进金...     

Single-crystal Bi2S3 nanosheets growing via attachment-recrystallization of nanorods

High-quality Bi(2)S(3) discrete single-crystal nanosheets with orthorhombic structure have been synthesized through the thermal decomposition of a single-source precursor, Bi(S(2)CNEt(2))(3), in amine media. The morphology evolution reveals that the Bi(2)S(3) nanosheets are developed through the assembly of nanorods, and an attachment-recrystallization growth mechanism is proposed for the formation of nanosheets with the use of nanorods as building blocks. High-resolution transmission electron microscopy studies reveal that the nanosheets have the largest exposed surface of (100) facets. The effects of experimental variables, such as the reaction temperature, time, precursor concentration, and media, on the morphology of the obtained nanocrystals have been systematically investigated in which the amine has served as the solvent, surfactant, and electron donor.     

Pr掺杂Bi_2MoO_6/TiO_2复合纳米纤维的制备及可见光催化性能

以电纺TiO_2纳米纤维为基质,采用溶剂热法制备了稀土Pr掺杂Bi_2MoO_6/TiO_2复合纳米纤维,利用X射线衍射仪、扫描电子显微镜、透射电子显微镜、紫外-可见-近红外分光光度计和荧光光谱仪等对不同样品的物相、形貌和光学性能等进行表征,以甲基橙为模拟有机污染物,考察了样品的光催化性能.结果表明,在复合样品中,Pr~(3+)进入Bi_2MoO_6晶格,部分取代Bi~(3+)形成施主能级,导致能级带隙变窄,不仅有利于提高样品的可见光催化活性,抑制光生电子-空穴对复合,而且还提高了Bi_2MoO_6/TiO_2的光催化活性和稳定性.当Pr的掺杂量为3%(摩尔分数)时,光催化降解甲基橙的效果最佳,可见光照射180 min时降解率达到93.8%,比纯Bi_2MoO_6/TiO_2的降解率有明显提高.     

From hollow olive-shaped BiVO4 to n-p core-shell BiVO4@Bi2O3 microspheres: controlled synthesis and enhanced visible-light-responsive photocatalytic properties

In this study, hollow olive-shaped BiVO(4) and n-p core-shell BiVO(4)@Bi(2)O(3) microspheres were synthesized by a novel sodium bis(2-ethylhexyl)sulfosuccinate (AOT)-assisted mixed solvothermal route and a thermal solution of NaOH etching process under hydrothermal conditions for the first time, respectively. The as-obtained products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy, Brunauer-Emmett-Teller surface area, and UV-vis diffuse-reflectance spectroscopy in detail. The influence of AOT and solvent ratios on the final products was studied. On the basis of SEM observations and XRD analyses of the samples synthesized at different reaction stages, the formation mechanism of hollow olive-shaped BiVO(4) microspheres was proposed. The photocatalytic activities of hollow olive-shaped BiVO(4) and core-shell BiVO(4)@Bi(2)O(3) microspheres were evaluated on the degradation of rhodamine B under visible-light irradiation (λ > 400 nm). The results indicated that core-shell BiVO(4)@Bi(2)O(3) exhibited much higher photocatalytic activities than pure olive-shaped BiVO(4). The mechanism of enhanced photocatalytic activity of core-shell BiVO(4)@Bi(2)O(3) microspheres was discussed on the basis of the calculated energy band positions as well. The present study provides a new strategy to enhancing the photocatalytic activity of visible-light-responsive Bi-based photocatalysts by p-n heterojunction.     

A Facile Controllable Synthesis, Growth Mechanism, and Photocatalytic Properties of Nanoscale BiOCl

Nanoscale tetragonal BiOCl samples have been synthesized using Bi[SC12H25]3 and CHCl3 as bismuth and chlorine sources by solvothermal reactions. The structure, morphology, and formation process have been investigated by SEM, TEM, HRTEM, XRD, and EDX analyses. The layered crystal structure feature of BiOCl may induce the growth of nano plates, which can subsequently aggregate into 3D spherical or flower-like microstructures under the presence of ethanol. The reaction temperature and the identity of secondary solvent influence the morphology. The yield of BiOCl depends on the completeness of the reaction and the degree of a competition reduction of BiOCl to Bi by ethanol. The as-synthesized 3D quasi-spherical BiOCl sample has an optical band gap of 3.15 eV, and shows much better photocatalytic performance on the degradation of methyl orange than that of commercial P25.     

A small biomolecule-assisted synthesis of iron sulfide nanostructures and magnetic properties

In this article, a facile l-cysteine-assisted solvothermal method is described, which is about the large-scale synthesis of Fe_0.985S novel nanostructures in a mixed solution composed of ethylenediamine (EN) and distilled water. By varying process parameters, such as the molar ratio of Fe³⁺-to-l-cysteine (reactants), the volume ratio of water to ethylenediamine, and the reaction temperature, different kinds of architectural structures can be controllably synthesized in large quantities. At the same time, a reasonable mechanism for the growth of iron sulfide structures has been proposed. The as-prepared iron sulfide products were characterized using diverse techniques including X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution TEM, superconducting quantum interface device (SQUID) magnetometer (Quantum Design MPMS XL).