Enhancement of photosensitivity by annealing in Bi2S3 thin films grown using SILAR method

Bi₂S₃ thin films were grown by successive ionic layer adsorption and reaction method (SILAR) onto the glass substrates at room temperature. The as prepared thin film were annealed at 250 °C in air for 30 min. These films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and electrical measurement systems. The X-ray diffraction patterns reveal that Bi₂S₃ thin film have orthorhombic crystal structure. SEM images showed uniform deposition of the material over the entire glass substrate. The optical energy band gap observed to be decreased from 1.69 to 1.62 eV for as deposited and annealed films respectively. The I–V measurement under dark and illumination condition (100 W) show annealed Bi₂S₃ thin film gives good photoresponse as compared to as deposited thin film and Bi₂S₃ thin film exhibits photoconductivity phenomena suggesting its useful in sensors device. The thermo-emf measurements of Bi₂S₃ thin films revealed n-type electrical conductivity.     

D-penicillamine assisted hydrothermal synthesis of Bi2S3 nanoflowers and their electrochemical application

Single crystalline flower-like Bi₂S₃ nanostructures were successfully synthesized via a simple, facile and green hydrothermal method, with the assistance of D-penicillamine. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), and found their morphologies mainly depend on the ratios of Bi^3 + to D-penicillamine, as well as the reaction temperature and time. And the possible growth mechanism has been discussed in some detail. In addition, the as-prepared Bi₂S₃ nanoflowers show good hydrogen storage ability. This strategy can be potentially expanded to prepare other metal chalcogenides materials.     

Preparation of Bi2S3 nanorods via a hydrothermal approach

Large-scale bismuth sulfide (Bi₂S₃) nanorods with uniform size have been prepared by hydrothermal method using bismuth chloride (BiCl₃) and sodium sulfide (Na₂S·9H₂O) as raw materials at 180 °C and pH = 1-2 for 12 h. The powder X-ray diffraction (XRD) pattern shows the Bi₂S₃ crystal belongs to the orthorhombic phase with calculated lattice constants a = 1.1187 nm, b = 1.1075 nm and c = 0.3976 nm. Furthermore, the quantification of X-ray photoelectron spectra (XPS) analysis peaks gives an atomic ratio of 1.9:3.0 for Bi:S. Field emission scanning electron microscopy (FE-SEM) and transmission electron microscopic (TEM) studies reveal that the appearance of the as-prepared Bi₂S₃ is rod-like with typical lengths in the range of 2-5 μm and diameters in the range of 10-30 nm. Finally the influences of the reaction conditions are discussed and a possible mechanism for the formation of Bi₂S₃ nanorods is proposed.     

Fabrication of three-dimensional snowflake-like bismuth sulfide nanostructures by simple refluxing

Three-dimensional snowflake-like bismuth sulfide nanostructures were successfully synthesized by simple refluxing at 160 °C in ethylene glycol, using bismuth citrate and thiourea as reactants. The crystal structures and morphologies of the products were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and energy dispersive X-ray spectroscopy (EDX). The Bi₂S₃ nanostructure was built up by highly ordered one-dimensional Bi₂S₃ nanorods, which was aligned in an orderly fashion. Ethylene glycol plays a critical role in the creation of bismuth sulfide three-dimensional nanostructures, which serves as an excellent solvent and structure director. Bismuth citrate, a linear polymer, also makes for the formation of the three-dimensional nanostructures.     

Effect of mixed solvent on the morphologies of nanostructured Bi2S3 prepared by solvothermal synthesis

Different morphologies of nanostructured bismuth sulfide (Bi₂S₃) including nanotubes and nanorods have been prepared by solvothermal synthesis at a low temperature of 120 °C for 12 h using various mixed solvents as the reaction medium and urea as the mineralizer. X-ray diffraction analysis showed that all the as-prepared Bi₂S₃ samples are orthorhombic phase. Transmission electron microscopy analysis showed that the morphologies of the nanostructures are mainly related to the viscosity and surface tension of the mixed solvent used in the solvothermal synthesis.     

Uniform Bi2S3 nanowires: Structure, growth, and field-effect transistors

Large-scale single-crystalline Bi₂S₃ nanowires were prepared by a simple one-step hydrothermal reaction between Bi(NO₃)₃ and Na₂S₂O₃, without using any organics in the experiment. These Bi₂S₃ nanowires have uniform size diameters which are about 60 nm. The structure of the nanowires is determined to be of the orthorhombic phase, and the growth direction is along the [001] direction. The growth mechanism of the nanowires was investigated based on high-resolution transmission electron microscopy observations. The field-effect transistors (FETs) have been fabricated using a single Bi₂S₃ nanowire, n-type semiconductor behavior has been observed, and high on/off ratio of about 3 orders of magnitude has been achieved.     

Preparation and characterization of CdS–Bi2S3 nanocomposite thin film by successive ionic layer adsorption and reaction (SILAR) method

CdS, Bi₂S₃ and CdS–Bi₂S₃ nanocomposite thin films were grown by successive ionic layer adsorption and reaction method (SILAR) onto the glass substrates at room temperature. These films were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and electrical measurement systems. A comparative study was made between CdS, Bi₂S₃ and CdS–Bi₂S₃ nanocomposite thin films. The XRD patterns reveal that CdS, Bi₂S₃ and CdS–Bi₂S₃ nanocomposite thin film have hexagonal, orthorhombic and mixed phase of hexagonal CdS and orthorhombic Bi₂S₃ crystal structure, respectively. SEM images showed uniform deposition of the material over the entire glass substrate. The energy band gap for CdS, Bi₂S₃ and CdS–Bi₂S₃ thin films were revealed from the optical studies and were found to be 2.4, 1.6 and 1.69 eV, respectively. The thermoemf measurements of CdS–Bi₂S₃ nanocomposite thin film revealed n-type electrical conductivity, while the I–V measurement of CdS, Bi₂S₃ and CdS–Bi₂S₃ nanocomposite thin film under dark and illumination condition (100 mW/cm²) exhibited photoconductivity phenomena suggesting its applicability in photosensors devices.     

Rapid synthesis of Bi2S3 nanocrystals with different morphologies by microwave heating

Single-crystalline Bi₂S₃ nanocrystals with urchinlike and rod-like morphologies have been successfully synthesized using Bi₂O₃, HCl, Na₂S₂O₃ and ethylene glycol (EG) by a simple and fast microwave heating method. Both urchinlike and rod-like Bi₂S₃ nanostructures could be formed under microwave heating at 190 °C for 30 s. Urchin-like Bi₂S₃ nanostructures were prepared using sodium dodecyl sulfate (SDS) or in the absence of any surfactant. However, Bi₂S₃ nanorods were obtained in the presence of cetyltrimethylammonium bromide (CTAB). The products were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), electron diffraction (ED) and ultraviolet-visible (UV-Vis) absorption spectra.     

Preparation and photoluminescence of Bi-doped strontium choloapatite nanorods

The photoluminescence properties of Bi³⁺-doped Sr₅(PO₄)₃Cl nanocrystals with rod-like structures prepared by a simple precipitation method were investigated. The obtained nanorods had diameters of 10-20 nm and lengths of 50-200 nm observed by transmission electron micrograph (TEM). The photoluminescence spectra revealed that a strong blue emission band centered at 416 nm excited by 385 nm was ascribed to ³P₁-¹S₀ transition in Bi³⁺ ions. The optimum dopant concentration for Bi³⁺ ions was 1.5 mol%, which could be attributed to energy migration to quenching centers.     

Influence of sintering temperature on thermoelectric properties of Bi<Subscript>2</Subscript>Te<Subscript>3</Subscript>/Polythiophene composite materials

Bi₂Te₃/Polythiophene (PTH) thermoelectric bulk composite materials were prepared by a two-step method. Firstly, Bi₂Te₃ and PTH nanopowders were prepared by hydrothermal synthesis and chemical oxidative polymerization, respectively. Secondly, the mixture of the Bi₂Te₃ and PTH nanopowders (50:50 wt) was pressed under vacuum at 80 MPa and 298, 473, or 623 K. For comparison, Bi₂Te₃ powders were hot pressed at 623 K. The bulk materials were analyzed by conventional methods, such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy, thermogravimetric analysis (TGA) and field emission scanning electron microscopy equipped with electron dispersive X-ray spectroscopy. The XRD and TGA results showed that the PTH decomposed when the hot pressing temperature exceeded 473 K, and Bi₂Te₂S phase was formed. The thermoelectric properties of the bulk composite materials were investigated. The composite pressed at 623 K showed a higher power factor, ~2.54 μ Wm⁻¹ K⁻² at 473 K, which is as ~20 times as that of the composite pressed at 473 K, although, it is still much lower than that of the pressed Bi₂Te₃ material (~1,266 μ Wm⁻¹ K⁻² at 348 K).     

l-Cystine-assisted growth of Sb2S3 nanoribbons via solvothermal route

l-Cystine was successfully used as a novel kind of sulfur source to grow Sb₂S₃ nanoribbons at 180 °C for 24 h in a mixed solution made of ethylene glycol and distilled water. The nanoribbons were usually tens of micronmeters in length, typically 100–300 nm in width. The structure of the nanoribbons was determined to be of the orthorhombic phase. A reasonable possible mechanism for the growth of Sb₂S₃ nanoribbon structures has been proposed. The as-obtained Sb₂S₃ products were examined using diverse techniques including X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), selected-area electron diffraction, and high-resolution TEM.     

Influence of gamma irradiation on structural,optical, and electrical characterization of Bi2S3 thin films

The induced effects of the gamma rays on properties of bismuth sulfide (Bi₂S₃) thin films synthesized using successive ionic layer adsorption and reaction (SILAR) have been investigated in details in this work. The Bi₂S₃ thin films are prepared on glass substrate and then exposed with low gamma radiation dose in the range of 0–1000 Gy. X-ray diffraction (XRD) confirmed the orthorhombic structural phase. Also, it was noticed in the XRD result that the crystallite size decreased from 115.29 to 73.63 nm with increasing gamma rays doses. For surface properties as well as stoichiometry of the prepared and irradiated thin film have been studied by field emission scanning electron microscope (FESEM). The optical transmission of irradiated samples increased and the energy band gap (E) decreased from 2.78 to 2.52 eV with gamma dose. Photoluminescence (PL) spectra revealed the improvement in the emission characteristics of Bi₂S₃ thin films with irradiation in the range of 250–1000 Gy. Impedance spectroscopy investigation exhibited that the resistance due to grain boundaries meaningfully contributed to the electrical characteristics of the Bi₂S₃ thin films. The achieved results suggested that Bi₂S₃ thin films are a good tool for further study of dosimetry and radiation sensing application.

     

Bi2S3-modified TiO2 nanotube arrays: easy fabrication of heterostructure and effective enhancement of photoelectrochemical property

A novel heterostructure of Bi₂S₃ nanoparticles (NPs) and TiO₂ nanotube arrays (NAs) was fabricated by a conventional hydrothermal method. The morphological features and the X-ray diffractogram of the obtained Bi₂S₃/TiO₂ NAs were characterized by field-emission scanning electron microscopy, transmission electron microscopy, and powder X-ray diffraction. The photoelectrochemical property of Bi₂S₃/TiO₂ NAs was also evaluated. The results demonstrated that photoelectrochemical solar cells based on Bi₂S₃/TiO₂ NAs had a short-circuit current of 4.54 mA/cm² and photoelectric conversion efficiency of 1.86 %. Surface photovoltage spectroscopy and field-induced surface photovoltage spectroscopy data indicated the existence of a strong interfacial electronic field between the two components Bi₂S₃ NPs and TiO₂ NAs, which can enhance the separation of photogenerated charge carriers.     

Synthesis of Sb2S3 peanut-shaped superstructures

Peanut-shaped Sb₂S₃ superstructures have been synthesized via a hydrothermal process at 120 °C for 8 h using hydrochloric acid and antimony O-benzyl dithiocarbonate (benzylxanthate, Sb(S₂COC₇H₇)₃) as starting materials. The powder X-ray diffraction (XRD) pattern shows the product corresponds to the pure orthorhombic phase of Sb₂S₃, the purity and composition of which are further confirmed by X-ray photoelectron spectroscopy (XPS). Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) studies reveal that the peanut-shaped Sb₂S₃ superstructures are aggregated by nanorods. The possible mechanistic pathways in the formation of the structures are discussed.     

Synthesis and characterization of bismuth sulfide nanowires through microwave solvothermal technique

One-dimensional (1D) bismuth sulfide (Bi₂S₃) semiconducting nanowires have been successfully synthesized through mircrowave assisted solvothermal technique. The obtained product was characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and UV-vis spectrophotometry. The result shows that the Bi₂S₃ nanowires are single crystals grown along the [001] (c-axis) direction. The growth of Bi₂S₃ nanofibers with a preferential direction of c-axis can be ascribed to its particular structure. The optical measurement shows a blue shift relative to the bulk orthorhombic Bi₂S₃, which might be ascribed to the high aspect ratio of the nanowires.     

Characterization of Bi2S3 nanorods and nano-structured flowers prepared by a hydrothermal method

Bismuth sulfide nanorods and nano-structured flowers were synthesized by hydrothermal reaction of bismuth nitrate pentahydrate and thiourea solutions, containing 1 and 2 ml of 65% HNO₃, respectively. By using X-ray diffraction (XRD), selected area electron diffraction (SAED), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and high resolution TEM (HRTEM), the products were specified as orthorhombic Bi₂S₃ in the shapes of nanorods and flower-like clusters of nanorods, with the growth of nanorods in the [001] direction. A diffraction pattern was also simulated, and was in good accordance with the SAED pattern obtained from the experiment.     

Phosphorus-doped bismuth telluride films by electrodeposition

Phosphorus-doped Bi₂Te₃ films were synthesized on a stainless-steel electrode by electrochemical deposition. X-ray diffraction, scanning electron microscopy and transmission electron microscopy confirmed that the films are single-phased Bi₂Te₃ solid solutions with a rhombohedral structure. The as-prepared films exhibit n-type characteristics with the Hall coefficient −1.76E−2 m³ C⁻¹ and the electrical conductivity 280 S cm⁻¹. The thermal conductivity is 0.47 W m⁻¹ K⁻¹, which is as low as one-third of the value observed in the bulk material. The doped P atoms occupy the interstitial positions between the two adjacent Te(1) layers connected by Van der Waals interaction in Bi₂Te₃.     

Characterization of Bi2S3 with different morphologies synthesized using microwave radiation

Bi₂S₃ with different morphologies (nanoparticles, nanorods and nanotubes) was synthesized using bismuth nitrate pentahydrate (Bi(NO₃)₃·5H₂O) and two kinds of sulfur sources (CH₃CSNH₂ and NH₂CSNH₂) in different solvents (water, ethylene glycol and propylene glycol) via a microwave radiation method at 180 W for 20 min. X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) indicated that all of the products are orthorhombic Bi₂S₃ phase of nanoparticles, nanorods and nanotubes, influenced by the sulfur sources and solvents. Formation mechanisms of the products with different morphologies are also proposed.     

Effects of cation doping on thermoelectric properties of Bi2S3 materials

Bi₂S₃ polycrystals doped with Al, Mn, Ag, and In were fabricated by vacuum melting and plasma activated sintering process, and the phase, microstructure, electrical, and thermal properties were investigated. The electrical conductivity is enhanced via Al and Ag doping. Compared with the Ag dopant, a higher electrical conductivity is achieved in the Al-doped sample, resulting in a peak power factor value of 1.96 μW/cmK² at 423 K. Meanwhile, the thermal conductivity of Bi_1.99Al_0.01S₃ sample is very low in the Bi₂S₃ system due to the high-density defects, and is only 0.39 Wm^?1 K^?1 at 740 K. By combining a power factor and a low thermal conductivity, a peak ZT value of 0.29 at 740 K is achieved in the Bi_1.99Al_0.01S₃ sample, being about two times larger than that of pristine Bi₂S₃.

     

Preparation,characterization and photocatalytic properties of nanoplate Bi<Subscript>2</Subscript>MoO<Subscript>6</Subscript> catalysts

Bismuth molybdate (Bi₂MoO₆) nanoplates have been successfully synthesized by a simple hydrothermal process. The nanoplates were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, and IR spectroscopy. The effects of hydrothermal temperature and reaction time on the structures and morphologies of the nanoplates were investigated. On the basis of TEM observation of time series samples, a possible formation mechanism of the nanoplates was proposed. Optical absorption experiments revealed that Bi₂MoO₆ nanoplates had absorption in visible-light region, but a blue shift appeared compared with the corresponding bulk materials. Photocatalytic experiments showed that the nanoplates exhibited good photocatalytic activities for degradation of N,N,N′,N′-tetraethylated rhodamine (RhB) under visible-light irradiation (λ > 420 nm).