Thermoelectric properties of antimony selenide hexagonal nanotubes

Antimony selenide (Sb₂Se₃) is a material widely used in photodetectors and relatively new as a possible material for thermoelectric applications. Taking advantage of the new properties after nanoscale fabrication, this material shows great potential for the development of efficient low temperature thermoelectric devices. Here we study the synthesis, the crystal properties and the thermal and thermoelectric transport response of Sb₂Se₃ hexagonal nanotubes (HNT) in the temperature range between 120 and 370 K. HNT have a moderate electrical conductivity ∼10² S m^-1 while maintaining a reasonable Seebeck coefficient ∼430 μV K^-1 at 370 K. The electrical conductivity in Sb₂Se₃ HNT is about 5 orders of magnitude larger and its thermal conductivity one half of what is found in bulk. Moreover, the calculated figure of merit (ZT) at room temperature is the largest value reported in antimony selenide 1D structures.

The High Anisotropy of the Epitaxial Growth of the Well-Aligned Sb2Se3 Nanoribbons on Mica

One-dimensional semiconductor nanostructures, which are different from those of bulk materials, have attracted considerable interest in either scientific research or practical application. Herein, the Sb₂Se₃ nanoribbons have been successfully synthesized by the epitaxial growth process on mica using the rapid physical vapor deposition method. The density of the Sb₂Se₃ nanoribbons increased quickly when the temperature decreased, and finally, the nanoribbons connected to each other and formed a network structure even in film. These nanoribbons were all well aligned along the preferred direction that either is parallel to each other or forms 60° angles. Further structural investigation demonstrated that the Sb₂Se₃ nanoribbons grew along the [001] directions, which are aligned along the directions [11̅0] and [100] or [100] and [110] on the mica surface. Then, an asymmetric lattice mismatch growth mechanism causing incommensurate heteroepitaxial lattice match between the Sb₂Se₃ and mica crystal structure was suggested. Furthermore, a polarized photodetector based on the film with the well-aligned Sb₂Se₃ nanoribbons was constructed, which illustrated strong photosensitivity and high anisotropic in-plane transport either in the dark or under light. The incommensurate heteroepitaxial growth method shown here may provide access to realize well-ordered nanostructures of other inorganic materials and promote the anisotropic photodetector industrialization.

PVP-coated Sb2Se3 nanorods as nanotheranostic agents for photoacoustic imaging and photothermal therapy in NIR-I bio-windows

Antimony selenide (Sb₂Se₃) as a simple, low toxicity, low-cost p-type semiconductor material with broad absorbance ranging from the UV to the NIR region has many potential applications in photovoltaic, thermoelectric, and phase-change memory devices. Owing to these excellent properties, Sb₂Se₃ nanorods were firstly synthesized with triphenylantimony and dibenzyldiselenide under solvothermal conditions. In order to enhance the biocompatibility of the Sb₂Se₃ nanorods, polyvinylpyrrolidone (PVP) was coated onto the surface of the Sb₂Se₃ nanorods to form PVP-coated Sb₂Se₃ nanorods. The cell viability of PVP-coated Sb₂Se₃ nanorods toward Hep-2 cells was assessed for 24 h using a Cell Counting Kit-8 (CCK-8) assay. The results showed that Hep-2 cells treated with PVP-coated Sb₂Se₃ nanorods were alive at a concentration as high as 100 μg mL⁻¹ in the absence of NIR irradiation. In vivo assessment confirmed that PVP-coated Sb₂Se₃ nanorods exhibited excellent photoacoustic imaging and PTT performance, which yielded complete ablation of tumors after laser irradiation (808 nm or 980 nm) in the NIR-I bio-window.

Herein we reported a biocompatible PVP-coated Sb₂Se₃ nanorods as PTT nanotheranostic agent, which is responsive to the light (808 and 980 nm) in NIR-I bio-windows and effective for photoacoustic imaging and photothermal destruction of cancer cell.

Solution-synthesis of Sb2Se3 nanorods using KSeCN as a molecular selenium source

Potassium selenocyanate (KSeCN) is used as a molecular selenium source to prepare Sb₂Se₃ nanorods, in which selenocyanate (SeCN⁻) anions are thermally decomposed to elemental Se(0) and then reduced to Se²⁻ anions in the organic amine medium.

Real-Time TEM Study of Nanopore Evolution in Battery Materials and Their Suppression for Enhanced Cycling Performance

Battery materials, which store energy by combining mechanisms of intercalation, conversion, and alloying, provide promisingly high energy density but usually suffer from fast capacity decay due to the drastic volume change upon cycling. Particularly, the significant volume shrinkage upon mass (Li⁺, Na⁺, etc.) extraction inevitably leads to the formation of pores in materials and their final pulverization after cycling. It is necessary to explore the failure mechanism of such battery materials from the microscopic level in order to understand the evolution of porous structures. Here, prototyped Sb₂Se₃ nanowires are targeted to understand the structural failures during repetitive (de)sodiation, which exhibits mainly alloying and conversion mechanisms. The fast growing nanosized pores embedded in the nanowire during desodiation are identified to be the key factor that weakens the mechanical strength of the material and thus cause a rapid capacity decrease. To suppress the pore development, we further limit the cutoff charge voltage in a half-cell against Na below a critical value where the conversion reaction of such a material system is yet happening, the result of which demonstrates significantly improved battery performance with well-maintained structural integrity. These findings may shed some light on electrode failure investigation and rational design of advanced electrode materials with long cycling life.

Beyond methylammonium lead iodide: prospects for the emergent field of ns2 containing solar absorbers

The field of photovoltaics is undergoing a surge of interest following the recent discovery of the lead hybrid perovskites as a remarkably efficient class of solar absorber. Of these, methylammonium lead iodide (MAPI) has garnered significant attention due to its record breaking efficiencies, however, there are growing concerns surrounding its long-term stability. Many of the excellent properties seen in hybrid perovskites are thought to derive from the 6s² electronic configuration of lead, a configuration seen in a range of post-transition metal compounds. In this review we look beyond MAPI to other ns² solar absorbers, with the aim of identifying those materials likely to achieve high efficiencies. The ideal properties essential to produce highly efficient solar cells are discussed and used as a framework to assess the broad range of compounds this field encompasses. Bringing together the lessons learned from this wide-ranging collection of materials will be essential as attention turns toward producing the next generation of solar absorbers.

Colloidal synthesis and characterization of single-crystalline Sb2Se3 nanowires

Single-crystalline Sb₂Se₃ nanowires have been synthesized by a hot-injection phosphine-free colloidal method and show excellent photoelectrochemical properties.

Thermal and Thermoelectric Transport in Highly Resistive Single Sb2Se3 Nanowires and Nanowire Bundles

In this study, we measured the thermal conductivity and Seebeck coefficient of single Sb₂Se₃ nanowires and nanowire bundles with a high resistivity (σ ~ 4.37 × 10⁻⁴ S/m). Microdevices consisting of two adjacent suspended silicon nitride membranes were fabricated to measure the thermal transport properties of the nanowires in vacuum. Single Sb₂Se₃ nanowires with different diameters and nanowire bundles were carefully placed on the device to bridge the two membranes. The relationship of temperature difference on each heating/sensing suspension membranes with joule heating was accurately determined. A single Sb₂Se₃ nanowire with a diameter of ~ 680 nm was found to have a thermal conductivity (k_NW) of 0.037 ± 0.002 W/m·K. The thermal conductivity of the nanowires is more than an order of magnitude lower than that of bulk materials (k ~ 0.36–1.9 W/m·K) and highly conductive (σ ~ 3 × 10⁴ S/m) Sb₂Se₃ single nanowires (k ~ 1 W/m·K). The measured Seebeck coefficient with a positive value of ~ 661 μV/K is comparable to that of highly conductive Sb₂Se₃ single nanowires (~ 750 μV/K). The thermal transport between wires with different diameters and nanowire bundles was compared and discussed.

Organometallically Anisotropic Growth of Ultralong Sb2Se3 Nanowires with Highly Enhanced Photothermal Response

Ultralong orthorhombic Sb2Se3 nanowires have been successfully fabricated via an alternative facile organometallic synthetic route from the reaction of triphenylantimony(III) with dibenzyldiselenide in oleylamine at 180-240 °C without any other additives. The formation and growth mechanism of the Sb2Se3 nanowires is intensively investigated, and it is found that the anisotropic growth of the nanowires with almost constant diameters is resulted from the synergistic effects of the intrinsic property of the orthorhombic crystal structure and the weak binding assistance of oleylamine, and the length of the nanowires can be elongated easily by increasing reaction time in the synthetic route. Moreover, the photothermal response of the Sb2Se3 nanowires is first evaluated under illumination of UV light (320-390 nm), and it is especially noted that the Sb2Se3 nanowires exhibit highly enhanced photothermal responses (more than two times the intensity) as compared to the bulk Sb2Se3. In addition, the Sb2Se3 nanowires show excellent light-to-heat performance, which is superior to that of the nanostructured titanium dioxide and silicon powder under the same conditions.

Facile synthesis of hybrid nanorods with the Sb2Se3/AgSbSe2 heterojunction structure for high performance photodetectors

An effective colloidal process involving the hot-injection method is developed to synthesize uniform single-crystalline Sb2Se3 nanorods in high yields. The photoconductive characteristics of the as-synthesized Sb2Se3 nanorods are investigated by developing a film-based photodetector and this device displays a remarkable response to visible light with an "ON/OFF" ratio as high as 50 (with an incident light density of 12.05 mW cm(-2)), short response/recovery times and long-term durability. To overcome the challenge of the intrinsic low electrical conductivity of Sb2Se3, hybrid nanorods with the Sb2Se3/AgSbSe2 heterojunction structure having a type-II band alignment are firstly prepared. The electric current of the photodetector based on the Sb2Se3/AgSbSe2 hybrid nanorod film has been significantly increased both in the dark and under light illumination. The responsivity of the photodetector based on the Sb2Se3/AgSbSe2 hybrid nanorod film is about 4.2 times as much as that of the photodetector based on the Sb2Se3 nanorod film. This improvement can be considered as an important step to promote Sb2Se3 based semiconductors for applications in high performance photodetectors.

Solvothermal synthesis and electrochemical properties of S-doped Bi2Se3 hierarchical microstructure assembled by stacked nanosheets

Hierarchical S-doped Bi₂Se₃ microspheres assembled by stacked nanosheets were successfully synthesized as the anode of a lithium ion battery, which shows an initial discharge capacity of 771.3 mA h g⁻¹ with great potential in energy storage.

High-performance flexible photodetectors based on single-crystalline Sb2Se3 nanowires

Flexible visible-light photodetectors were fabricated by dispersing a large number of Sb₂Se₃ nanowires onto the Au interdigitated electrodes on PET substrates, which showed fast response speed and excellent flexibility.

Controlled Synthesis of Ultrathin Sb2Se3 Nanowires and Application for Flexible Photodetectors

A new solvothermal approach is introduced to synthesize ultrathin Sb₂Se₃ nanowires with diameters ranging from 10 to 20 nm and with length up to 30 μm. The Sb₂Se₃ nanowire-based photodetectors are firstly fabricated on polyethylene terephthalate and printing paper substrates, which exhibit excellent response to visible light with fast response time (0.18 and 0.22 s), high flexibility, and durability.

Liquid-solid spinodal decomposition mediated synthesis of Sb₂Se₃ nanowires and their photoelectric behavior

The convenient synthesis of one-dimensional nanostructures of chalcogenide compounds with a visible band-gap is an essential research topic in developing next-generation photoelectronic devices. In particular, the design of a theoretically predictable synthesis process provides great flexibility and has a considerable ripple effect in nanotechnology. In this study, a novel rational growth approach is designed using the spinodal decomposition phenomenon for the synthesis of the Sb2Se3 nanowires, which is based on the thermodynamic phase diagram. Using a stacked elemental layer (Sb/Sb-Se/Se) and heat treatment at 623 K for 30 min under an N2 atmosphere, the vertically inclined one-dimensional nanostructures are experimentally demonstrated. An additional annealing process at 523 K in a vacuum effectively removed excess Se elements due to their high vapor pressure, resulting in highly dense single crystal Sb2Se3 nanowire arrays. Adaption of our synthesis approach enables significantly improved photocurrent generation in the vertically stacked structure (glass/ITO/Sb2Se3 nanowires/ITO/PEN) from 6.4 (dark) to under 690 μA (at 3 V under AM 1.5G). In addition, a photoelectrochemical test demonstrated their p-type conductivity and robust photocorrosion performance in 0.5 M H2SO4.

Electrospun In@C nanofibers as a superior Li-ion battery anode

In this communication, we have successfully obtained electrospun indium@carbon nanofibers. When applied as the Li-ion battery anode, the indium@carbon nanofibers could exhibit a high discharge capacity of 500 mA h g⁻¹ after 200 cycles at 100 mA g⁻¹.

Diameter-controlled and surface-modified Sb₂Se₃ nanowires and their photodetector performance

Due to its direct and narrow band gap, high chemical stability, and high Seebeck coefficient (1800 μVK⁻¹), antimony selenide (Sb₂Se₃) has many potential applications, such as in photovoltaic devices, thermoelectric devices, and solar cells. However, research on the Sb₂Se₃ materials has been limited by its low electrical conductivity in bulk state. To overcome this challenge, we suggest two kinds of nano-structured materials, namely, the diameter-controlled Sb₂Se₃ nanowires and Ag₂Se-decorated Sb₂Se₃ nanowires. The photocurrent response of diameter-controlled Sb₂Se₃, which depends on electrical conductivity of the material, increases non-linearly with the diameter of the nanowire. The photosensitivity factor (K = I_light/I_dark) of the intrinsic Sb₂Se₃ nanowire with diameter of 80–100 nm is highly improved (K = 75). Additionally, the measurement was conducted using a single nanowire under low source-drain voltage. The dark- and photocurrent of the Ag₂Se-decorated Sb₂Se₃ nanowire further increased, as compared to that of the intrinsic Sb₂Se₃ nanowire, to approximately 50 and 7 times, respectively.

Gas sensing of SnO2 nanocrystals revisited: developing ultra-sensitive sensors for detecting the H2S leakage of biogas

As a typical mode of energy from waste, biogas technology is of great interest to researchers. To detect the trace H2S released from biogas, we herein demonstrate a high-performance sensor based on highly H2S-sensitive SnO2 nanocrystals, which have been selectively prepared by solvothermal methods using benzimidazole as a mineralization agent. The sensitivity of as-obtained SnO2 sensor towards 5 ppm H2S can reach up to 357. Such a technique based on SnO2 nanocrystals opens up a promising avenue for future practical applications in real-time monitoring a trace of H2S from the leakage of biogas.

Thermal evaporation and characterization of Sb2Se3 thin film for substrate Sb2Se3/CdS solar cells

Sb2Se3 is a promising absorber material for photovoltaic cells because of its optimum band gap, strong optical absorption, simple phase and composition, and earth-abundant and nontoxic constituents. However, this material is rarely explored for photovoltaic application. Here we report Sb2Se3 solar cells fabricated from thermal evaporation. The rationale to choose thermal evaporation for Sb2Se3 film deposition was first discussed, followed by detailed characterization of Sb2Se3 film deposited onto FTO with different substrate temperatures. We then studied the optical absorption, photosensitivity, and band position of Sb2Se3 film, and finally a prototype photovoltaic device FTO/Sb2Se3/CdS/ZnO/ZnO:Al/Au was constructed, achieving an encouraging 2.1% solar conversion efficiency.

In2O3 cubes: synthesis, characterization and photocatalytic properties

Two-step prepare of In₂O₃ cubes, which have excellent photocatalytic performance for degeneration of organic dyes.

Gram-scale synthesis of ultrasmall SnO2 nanocrystals with an excellent electrochemical performance

The gram-scale synthesis of ultrasmall SnO2 nanocrystals has been successfully realized via a solvothermal process, during which the solvent used plays an important role in inhibiting the growth and aggregation of the nanocrystals. When investigating their electrochemical behaviour, the nanocrystal electrode shows an excellent performance in capacity retention and a better rate capacity.

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.