Bi2Se3 Nanostructures Research Articles

Bi2Se3@SWCNT heterostructures with beyond theoretical capacity as perspective binder-free anodes for lithium-ion batteries

Bi2Se3 has shown potential for implementation as an anode material for lithium-ion batteries (LIBs), however, the significant volume expansion and dissolution of selenium pose major challenges. In this work, Bi2Se3 nanostructures are synthesized by physical vapor deposition directly on top of a single-wall carbon nanotube (SWCNT) network to fabricate a binder-free Bi2Se3@SWCNT anode materials with different Bi2Se3/SWCNT ratios. Nanostructuring the Bi2Se3 directly on the top of the SWCNT network provides a large accessible contact area and improves mechanical and electrical contact. The heterostructures exhibit capacity, that is beyond the theoretical of pristine Bi2Se3, which can be attributed to the binding of the Se to C, resulting in the resilience against the dissolution of Se, while providing additional electron transport pathways and increased capacitive contribution. A Bi2Se3@SWCNT anode with a mass ratio of (1:1) has the highest capacity in a half-cell after 100 cycles (523 mAh g−1 at 0.1 A g−1) and shows excellent capacity retention after 500 cycles at large current densities (2 A g−1 and 5 A g−1): 1080 mAh g−1 and 809 mAh g−1 respectively. In addition, in a full-cell system Bi2Se3@SWCNT (1:1) delivers high reversible capacity after 150 cycles (484 mAh g−1) at 0.4 A g−1.

The Impact of Topological States on the Thermoelectric Performance of p- and n-Type Sb2Te3/Bi2Se3-Multiwalled Carbon Nanotubes Heterostructured Networks

The resistance and magnetoresistance of flexible thermoelectric p-type Sb2Te3-MWCNT, p-type Bi2Se3-MWCNT, and n-type Bi2Se3-MWCNT heterostructures were studied in the temperature range from 2 K to 300 K to reveal the conductance mechanisms governing the thermoelectric properties of these heterostructured networks. It was found that the conductance in heterostructured networks at different temperatures is governed by different processes and components of the networks. This effect was found to be related to the growth mechanisms of the Sb2Te3 and Bi2Se3 nanostructures on the MWCNT networks. At near-room temperatures, the Sb2Te3 and Bi2Se3 nanostructures were found to have the dominant contribution to the total conductance of the p-type Sb2Te3-MWCNT and n-type Bi2Se3-MWCNT networks. In turn, the conduction of p-type Bi2Se3-MWCNT heterostructured networks in a full temperature range and p-type Sb2Te3-MWCNT and n-type Bi2Se3-MWCNT heterostructured networks at temperatures below 30 K was governed by the MWCNTs; however, with the contribution from 2D topological states of Sb2Te3 and Bi2Se3 nanostructures, these were manifested by the weak antilocalization effect (WAL) cusps observed at temperatures below 5–10 K for all heterostructured networks considered in this work.

Electrochemical properties of bismuth chalcogenide/MXene/CNT heterostructures for application in Na-ion batteries

The development of high-performance anodes for sodium-ion batteries (SIBs) has recently attracted great attention. Most of the proposed anode materials for SIB systems suffer from insufficient electrical and mechanical contact of the active material with the current collector causing low reversible capacity and short lifespan. To solve this issue, an innovative approach could be the direct synthesis of the active material around and on the top of an electrically conductive network. The nanostructuring with SWCNTs and MXenes increases the active surface area, improves expansion/contraction properties, and establishes a direct mechanical and electrical contact. In this work the performance of binder-free Bi2Se3/SWCNT and Bi2Se3/MXene/SWCNT anode materials, which were synthesized by the direct physical vapor deposition of Bi2Se3 nanostructures on SWCNT and MXene/SWCNT network systems, was investigated. The results showed that the Bi2Se3/SWCNT electrode with the mass ratio of (1:1) exhibits excellent rate performance and high discharge capacity in the short-term (0.1 A g−1) and long-term (5.0 A g−1) cycling by delivering 247 and 120 mAh g−1 respectively demonstrating its perspectives for the application as an anode in SIBs.

EIS characterization of aging and humidity-related behavior of Bi2Se3 films of different morphologies

Bi2Se3 thin films are widely studied as topological insulators and as prospective materials for thermoelectric and sensor applications. Storage of films under ambient conditions, especially at different humidities, may influence the physical properties of thin films.In the present work, electrochemical impedance spectroscopy is used to investigate the dependence of properties of continuous planar and partly disordered Bi2Se3 thin films, as well as nanoplate networks, deposited on mica, quartz and glass substrates by physical vapor deposition on the humidity in oxygen and nitrogen atmospheres. It has been shown that electrochemical impedance spectroscopy (EIS) can be used as an effective tool for the determination of the oxidation level of Bi2Se3 surfaces, the quality of the surface covering and for characterization of the type and parameters of the nanopores in Bi2Se3 thin films. Equivalent circuit models developed in this work characterize the interaction of gaseous water with non-oxidized and oxidized surfaces of Bi2Se3 nanostructures, as well as and with the substrate areas located between the Bi2Se3 nanoplates in the Bi2Se3 networks and open to the surrounding environment, in oxygen and nitrogen atmospheres.

Screen-printed film deposited using quasi 2-dimensional Bi2Se3 nanostructures for desalination membrane filler application

Chalcogenides and 2D graphene are the emerging materials being investigated rigorously as efficient membrane filler materials for recovering minerals from seawater and for desalination through recrystallization. In this work quasi-2-dimensional bismuth selenide (Bi2Se3) nanostructure synthesized by microwave-assisted solvothermal method - mixed in ethylene glycol is used as the ink for depositing screen-printed film (SPF). A laboratory-scale experiment univocally demonstrates the possibility of application of SPF as an efficient membrane filler material for desalination processes such as in direct contact membrane distillation (DCMD). Morphology and topography studies confirm the growth of homogeneous hexagonal micro structures with an edge-to-edge length of 20–40 µm with a thickness of ~ 2–3 µm respectively and elemental mapping studies confirm the growth of sodium chloride (NaCl) crystals over the Bi2Se3 SPF. Growth of different morphology of NaCl (20–40 µm) including the metastable (111) oriented NaCl depicts that Bi2Se3 film assists the efficient crystallization process and helps in retaining the morphology of NaCl crystals with an enhanced crystal growth rate of the order of 10−8–10−9 m/s. Interestingly, thermoelectric power measurement in these Bi2Se3 nanostructures with n-type carriers and with Seebeck coefficient value of − 98 μV/K around the room temperature open up a new possibility for a combined desalination membrane filler application along with thermoelectric (TEP) application where the waste heat used for desalination/membrane crystallization can also be harvested in the form of useful electrical energy.

Synergistic effect of grain boundaries and phonon engineering in Sb substituted Bi2Se3 nanostructures for thermoelectric applications

Phonon scattering by intrinsic defects and nanostructures has been the primary strategy for minimizing the thermal conductivity in thermoelectric materials. In this work, we present the effect of Isovalent substitution as a method to decouple the Seebeck coefficient and the thermal conductivity of antimony (Sb) substituted bismuth selenide (Bi2Se3). Transmission electron microscopy studies present the nanostructured Bi2-xSbxSe3 thermoelectric system represents the coexistence of hierarchical defect structure and dislocations. The observed giant reduction in thermal conductivity is due to the multi-scale phonon scattering caused by a combination of stacking faults, lattice dislocations and grain boundary scattering. This study reveals that a large number of dislocations about ∼1.09 × 1016 m−2 are particularly effective at lowering thermal conductivity. We achieved one of the ultra-low thermal conductivity values (∼0.26 W/m K) for the maximized dislocation concentration. Moreover, Isovalent substitution provides a new avenue for the reduction in thermal conductivity and significant enhancement in the Seebeck coefficient of thermoelectric materials.

Highly stable nanostructured Bi2Se3 anode material for all solid-state lithium-ion batteries

Abstract The electrochemical reaction mechanism of lithium (Li)-ion with Bi2Se3 anode material in all solid-state lithium-ion batteries (LIBs) has been successfully established in this work. Firstly, commercial bulk Bi2Se3 was directly used as anode in LIB and then hydrothermally synthesized Bi2Se3 nanostructures were used as anode material in order to improve the electrochemical performance of the battery. The structure of obtained nanostructures was characterized using powder x-ray diffraction, which verified the formation of Bi2Se3 phase. Scanning electron microscopy and transmission electron microscopy studies confirmed the existence of mixed morphology, i.e., nanoparticles and nanosheets, with the diameter of nanoparticles in the range of 20–150 nm and the thickness of nanosheets, about 5–30 nm. Furthermore, electrochemical measurements indicated the initial discharge and charge capacity of bulk Bi2Se3 as 621 mAhg−1 and 499 mAhg−1 respectively, which was slightly higher than the Bi2Se3 nanostructures (discharge and charge capacities: 594 mAhg−1 and 468 mAhg−1). However, the nanostructures showed better cycling stability up to 50 cycles as compared to the bulk, which shed light on a new way to improve the lithium storage properties of the Bi2Se3.

Microwave-assisted synthesis of localized surface plasmon resonance enhanced bismuth selenide (Bi2Se3) layers for non-enzymatic glucose sensing

Three-dimensional (3D) bismuth selenide (Bi2Se3) nanostructures were synthesized by microwave synthesis using water as a solvent and hydrazine hydrate as a reducing agent and exfoliated into few layers of Bi2Se3. Bi2Se3- Few Layers (Bi2Se3- FL) exhibited localized surface plasmon resonance and enhanced electrocatalytic behavior. The scanning electron microscope (SEM) and transmission electron microscopy (TEM) characterization indicated the layered structure of Bi2Se3. The electrocatalytic properties of the Bi2Se3-FLmodified GC electrode towards non-enzymatic glucose oxidation were evaluated by cyclic voltammetry (CV) and chronoamperometry. The designed non-enzymatic glucose sensor showed a low detection limit of 6.1 ​μM, a linear range from 10 ​μM to 100 ​μM of glucose concentration and a current sensitivity of 0.112 ​μAμM−1.The electrochemical sensor constructed using Bi2Se3-FL attained steady-state level within 3 ​s upon adding glucose and remained stable even after 19 days with only 17% loss in current signal. The obtained electrodes can be applied for determining glucose in urine samples. The results obtained here are of great significance to use nanostructured Bi2Se3-FL electrode as a potential candidate for non-enzymatic glucose detection.

Oxygen Nanoshuttles for Tumor Oxygenation and Enhanced Cancer Treatment

Oxygen Nanoshuttles for Tumor Oxygenation and Enhanced Cancer Treatment

Optical and transport properties of few quintuple-layers of Bi2-xSbxSe3 nanoflakes synthesized by hydrothermal method

Hydrothermal synthesis as a commonly bottom-up growth method has considerable advantages for manufacturing thermoelectric nanomaterials with advanced thermoelectric properties. However, the hydrothermally synthesized thermoelectric nanostructures often show a low thermoelectric performance due to their low power factor. In this work, we report on using a hydrothermal method for the growth of n-type Bi2-xSbxSe3 nanoflakes with a fixed thickness of ∼16 quintuple-layers. The controlling of the stoichiometric composition, phase purity and crystallinity of the Bi2-xSbxSe3 nanoflakes are demonstrated by the X-ray diffraction, Raman spectroscopy, and high resolution transmission electron microscopy. We further prove that adding of antimony into Bi2Se3 compound mostly influences the in-plane vibration mode. The optical energy gap is sharply increased as the Sb content increases. The effect of the antimony incorporation on the electrical conductivity, Seebeck coefficient and power factor of Bi2-xSbxSe3 nanoflakes is systematically investigated. The Bi1.92Sb0.08Se3 sample is found to have the highest power factor ∼13.17 μW/cm.K2 at 470 K which is much higher than those published for other various nanostructured or bulk Bi2Se3 compounds. The results propose a great prospect for further enhancing the thermoelectric power factor of the Bi2Se3 nanostructures synthesized by this hydrothermal method. Taking into consideration the progress in Bi–Se compounds, the results of this work advocate the promise of Bi–Se nanostructures towards producing high performance thermoelectric devices.

Scalable polyol synthesis for few quintuple layer thin and ultra high aspect ratio Bi2Se3 structures

The production of topological insulator and thermoelectric nanostructures is mostly done with physical vapor deposition techniques. Because Bi2Se3 nanostructures are used in a variety of different disciplines in science, such as medicine, material science or condensed matter research, a simple synthesis with the possibility of a scale up is required. Here we report on a simple and cheap, chemical synthesis of 2D Bi2Se3 nanostructures with an ultra high aspect ratio of 103 and correspondingly high surface area to volume ratio of 0.4 nm−1. The size and stoichiometry of these nanostructures are adjustable. With one temperature, one precursor per element and a surfactant, we synthesize the nanostructures with an open or closed synthesis and analyze them with size histograms, TEM, EDX, SEM, Raman spectroscopy, and AFM. For the closed synthesis, our results show all four Raman peaks, the correct stoichiometry, and single crystallinity. The synthesis can be extended to make markers for cancer treatment, samples for the condensed matter research on the transport behavior of protected surface states or for thermoelectric applications.

Materials analysis and focused ion beam nanofabrication of topological insulator Bi2Se3

Focused ion beam milling allows manipulation of the shape and size of nanostructures to create geometries potentially useful for opto-electronics, thermoelectrics, and quantum computing. We focus on using the ion beam to control the thickness of Bi2Se3 and to create nanowires from larger structures. Changes in the material structure of Bi2Se3 nanomaterials that have been milled using a focused ion beam are presented. In order to characterize the effects of ion beam processing on the samples, we use a variety of techniques including analytical transmission electron microscopy and atomic force microscopy. The results show that while part of the material remains intact after shaping, amorphous regions form where the beam has been used to thin the sample. For wires created by thinning the material down to the substrate, the sidewalls of the wires appear intact based on diffraction images from samples cut at an angle, but thin crystalline regions remain at the wire edges. Even with the resulting defects and limitations when thinning, focused ion beam milling can be used to fabricate custom geometries of Bi2Se3 nanostructures.

Structure-Dependent Optical Properties of Self-Organized Bi2Se3 Nanostructures: From Nanocrystals to Nanoflakes.

Bismuth selenide (Bi2Se3), with a wide bulk band gap and single massless Dirac cone at the surface, is a promising three-dimensional topological insulator. Bi2Se3 possesses gapless surface states and an insulator-like bulk band gap as a new type of quantum matter. Different Bi2Se3 nanostructures were prepared using electron beam evaporation with high production efficiency. Structural investigations by energy-dispersive X-ray analysis, scanning electron microscopy, and X-ray diffraction revealed the sample stoichiometries and the structural transition mechanism from nanocrystals to nanoflakes. The optical properties systematically probed and analyzed by spectroscopic ellipsometry showed strong dependence on the nanostructures and were also predicted to have structure-modifiable technological prospects. The optical parameters, plasma frequencies, scattering rates of the free electrons, and optical band gaps were related to the topological properties of the Bi2Se3 nanostructures via light-matter interactions, offering new opportunities and approaches for studies on topological insulators and spintronics. The high-quality Bi2Se3 nanostructures provide advantages in exploring novel physics and exploiting prospective applications.

Patterning Superconductivity in a Topological Insulator.

Topologically protected states in combination with superconductivity hold great promise for quantum computing applications, but the progress on electrical transport measurements in such systems has been impeded by the difficulty of fabricating devices with reliable electrical contacts. We find that superconductivity can be patterned directly into Bi2Se3 nanostructures by local doping with palladium. Superconducting regions are defined by depositing palladium on top of the nanostructures using electron beam lithography followed by in situ annealing. Electrical transport measurements at low temperatures show either partial or full superconducting transition, depending on the doping conditions. Structural characterization techniques indicate that palladium remains localized in the targeted areas, making it possible to pattern superconducting circuits of arbitrary shapes in this topological material.

The high-yield growth of Bi2Se3 nanostructures via facile physical vapor deposition

The growth of Bi2Se3 nanostructures by physical vapor deposition in presence or absence of Au catalysts on Si and mica substrates is investigated. In the presence of Au nanodroplets on substrate surfaces, the growth of Bi2Se3 nanostructures in diverse crystallographic orientations is initiated via a catalyst-assisted process at low source flux condition. At elevated flux supply, nearly free-standing vapor-solid growth dominates and an array consisting of dense inclined standing nanoribbons are achieved. The morphologies of the obtained Bi2Se3 nanoribbons can be easily manipulated by changing growth temperature.

Ethylenediaminetetraacetic acid-assisted synthesis of Bi2Se3 nanostructures with unique edge sites

Nanomaterials with unique edge sites have received increasing attention due to their superior performance in various applications. Herein, we employed an effective ethylenediaminetetraacetic acid (EDTA)-assisted method to synthesize a series of exotic Bi2Se3 nanostructures with distinct edge sites. It was found that the products changed from smooth nanoplates to half-plate-containing and crown-like nanoplates upon increasing the molar ratio of EDTA to Bi3+. Mechanistic studies indicated that, when a dislocation source and relatively high supersaturation exist, the step edges in the initially formed seeds can serve as supporting sites for the growth of epilayers, leading to the formation of half-plate-containing nanoplates. In contrast, when the dislocation source and a suitably low supersaturation are simultaneously present in the system, the dislocation-driven growth mode dominates the process, in which the step edges form at the later stage of the growth responsible for the formation of crown-like nanoplates.

Single-crystalline Bi2Se3 nanowires grown by catalyst-free ambient pressure chemical vapor deposition

Bi2Se3 nanostructures are very promising in the thermoelectrics, optics and electronics. In the letter, Bi2Se3 single-crystal nanowires (NWs) were successfully synthesized via catalyst-free ambient pressure chemical vapor deposition (CVD) using high purity Bi2Se3 powder as the source material. The morphology, microstructure and chemical compositions of the prepared Bi2Se3 NWs were characterized in details. The results reveal that the NWs have well-crystallized rhombohedral structure with smooth surface and their length can be up to 50µm. The growth direction of the NWs is along [110] direction and the growth mechanism is discussed. The high-quality Bi2Se3 NWs have potential applications in thermoelectric, optical and electronic devices. The present method could be extended to synthesize NWs of other layer-structured materials.

Band Bending Inversion in Bi2Se3 Nanostructures.

Shubnikov-de Haas oscillations were studied under high magnetic field in Bi2Se3 nanostructures grown by chemical vapor transport, for different bulk carrier densities ranging from 3 × 10(19) cm(-3) to 6 × 10(17) cm(-3). The contribution of topological surface states to electrical transport can be identified and separated from bulk carriers and massive two-dimensional electron gas. Band bending is investigated, and a crossover from upward to downward band bending is found at low bulk density as a result of a competition between bulk and interface doping. These results highlight the need to control electrical doping both in the bulk and at interfaces in order to study only topological surface states.

One-pot synthesis of Bi2Se3 nanostructures with rationally tunable morphologies

Shape control has proven to be a powerful and versatile means of tailoring the properties of Bi2Se3 nanostructures for a wide variety of applications. Here, three different Bi2Se3 nanostructures, i.e., spiral-type nanoplates, smooth nanoplates, and dendritic nanostructures, were prepared by manipulating the supersaturation level in the synthetic system. This mechanism study indicated that, at low supersaturation, defects in the crystal growth could cause a step edge upon which Bi2Se3 particles were added continuously, leading to the formation of spiral-type nanoplates. At intermediate supersaturation, the aggregation of amorphous Bi2Se3 particles and subsequent recrystallization resulted in the formation of smooth nanoplates. Furthermore, at high supersaturation, polycrystalline Bi2Se3 cores formed initially, on which anisotropic growth of Bi2Se3 occurred. This work not only advances our understanding of the growth mechanism but also offers a new approach to control the morphology of Bi2Se3 nanostructures.

Catalyst-free Growth of Single Crystalline Bi2Se3 Nanostructures for Quantum Transport Studies

In this work we report on the growth of single crystalline Bi2Se3 nanostructures (nanoribbons, nanoflakes, and nanowires) by catalyst-free decomposition sublimation in sealed silica ampules. The nanostructures directly grow on Si/SiO2 substrates by a vapor–solid growth mechanism and show high degree of crystallinity with dimensions of >10 μm in length and simultaneously <10 nm in height (nanoribbons). In order to optimize the growth process in a reproducible way, thermodynamic calculations were realized. The high quality of as-grown nanostructures was confirmed by transmission electron microscopy including selected area electron diffraction as well as electrical transport measurements. Our electrical transport data are evidence, on the one hand, of the high crystal quality and efficiency of the synthesis by decomposition sublimation. On the other hand, the catalyst-free approach offers the chance to investigate crystals with high purity and to measure surface state properties.