Bismuth Selenide Research Articles

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 (Bi2 Se3 NP) is synthesized and sandwiched between the gold electrode and another Au-deposited thin layer (Bi2 Se3 @Au). Then, eight-silver-ion mediated double-stranded DNA (mDNA) is immobilized onto the substrate (Bi2 Se3 @Au-mDNA) for the further detection of hydrogen peroxide. The Bi2 Se3 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 Bi2 Se3 @Au. The characterization of the Bi2 Se3 @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 × 10-6 m to 27.30 × 10-6 m, very low detection limit (10 × 10-9 m), unique current response (1.6 s), sound H2 O2 recovery in serum, and substantial capability to classify two breast cancer subtypes (MCF-7 and MDA-MB-231) based on their difference in the H2 O2 generation, offering potential applications in the biomedicine and pharmacology fields.

Bacteria-Mediated Ultrathin Bi2Se3 Nanosheets Fabrication and Their Application in Photothermal Cancer Therapy

Bismuth selenide (Bi2Se3) attracts a lot of attention nowadays due to its unique electronic and thermoelectric properties. In this study, fabrication of Bi2Se3 nanosheets by selenite-reducing bacterium (SeRB) was first reported. Morphology, size, and location of the biogenic Bi2Se3 are bacteria-dependent. It is difficult to separate Bi2Se3 generated by Bacillus cereus CC-1 (Bi2Se3-C) from the biomass because of strong interaction with the cell membrane. However, Bi2Se3 produced by Lysinibacillus sp. ZYM-1 (Bi2Se3-Z), is highly dispersed in extracellular space with high stability. Further characterization by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM) on Bi2Se3-Z indicates that the product is a rhombohedral-phase, ultrathin nanosheet-like structure with an average size of ∼100 nm. Subsequently, the photothermal performance of Bi2Se3-Z with the irradiation of 808 nm near-infrared (NIR) laser was determined. When the B...

Layer structured bismuth selenides Bi2Se3 and Bi3Se4 for high energy and flexible all-solid-state micro-supercapacitors

In this work, bismuth selenides (Bi2Se3 and Bi3Se4), both of which have a layered rhombohedral crystal structure, have been found to be useful as electrode materials for supercapacitor applications. In a liquid electrolyte system (6M KOH), Bi2Se3 nanoplates exhibit much better performance as an electrode material than Bi3Se4 nanoparticles do, delivering a higher specific capacitance (272.9 F g−1) than that of Bi3Se4 (193.6 F g−1) at 5 mV s−1. This result may be attributed to the fact that Bi2Se3 nanoplates possess more active electrochemical surfaces for the reversible surface redox reactions owing to their planar quintuple stacked layers (septuple layers for Bi3Se4). To meet the demands of electronic skin, we used a novel flexible annular interdigital structure electrode to support the all-solid-state micro-supercapacitors (AMSCs). The Bi2Se3 AMSC device delivers a much better supercapacitor performance, exhibits a large stack capacitance of 89.5 F cm−3 at 20 mV s−1 (Bi3Se4: 79.1 F cm−3), a high energy density of 17.9 mWh cm−3 and a high power density of 18.9 W cm−3. The bismuth selenides also exhibit good cycle stability, with 95.5% retention after 1000 c for Bi2Se3 (Bi3Se4:90.3%). Clearly, Bi2Se3 nanoplates can be promising electrode materials for flexible annular interdigital AMSCs.

Evidence of β-antimonene at the Sb/Bi2Se3 interface

We report a study of the interface between antimony and the prototypical topological insulator Bi2Se3. Scanning tunnelling microscopy measurements show the presence of ordered domains displaying a perfect lattice match with bismuth selenide. Density functional theory calculations of the most stable atomic configurations demonstrate that the ordered domains can be attributed to stacks of β-antimonene.

Possible structural origin of superconductivity in Sr-doped Bi2Se3

Doping bismuth selenide (Bi2Se3) with elements such as copper and strontium (Sr) can induce superconductivity, making the doped materials interesting candidates to explore potential topological superconducting behaviors. It was thought that the superconductivity of doped Bi2Se3 was induced by dopant atoms intercalated in van der Waals gaps. However, several experiments have shown that the intercalation of dopant atoms may not necessarily make doped Bi2Se3 superconducting. Thus, the structural origin of superconductivity in doped Bi2Se3 remains an open question. Herein, we combined material synthesis and characterization, high-resolution transmission electron microscopy, and first-principles calculations to study the doping structure of Sr-doped Bi2Se3. We found that the emergence of superconductivity is strongly related with n-type dopant atoms. Atomic-level energy-dispersive X-ray mapping revealed various n-type Sr dopants that occupy intercalated and interstitial positions. First-principles calculations showed that the formation energy of a specific interstitial Sr doping position depends strongly on Sr doping level. This site changes from a metastable position at low Sr doping level to a stable position at high Sr doping level. The calculation results explain why quenching is necessary to obtain superconducting samples when the Sr doping level is low and also why slow furnace cooling can yield superconducting samples when the Sr doping level is high. Our findings suggest that Sr atoms doped at interstitial locations, instead of those intercalated in van der Waals gaps, are most likely to be responsible for the emergence of superconductivity in Sr-doped Bi2Se3.

Enhancement of field electron emission in topological insulator Bi2Se3 by Ni doping.

Nanostructures of bismuth selenide (Bi2Se3), a 3D topological insulator material, and nickel (Ni) doped Bi2Se3 samples were prepared by a hydrothermal method to explore the field emission properties. An enrichment in the field electron emission (FE) properties in terms of the threshold and turn-on field values of Bi2Se3 and Ni doped Bi2Se3 nanostructures was measured at a base pressure of ∼1 × 10-8 mbar. Using the background of the Fowler-Nordheim (FN) theory a field enhancement factor (β) of 5.7 × 103 and a threshold field value of 2.5 V μm-1 for 7.5% Ni doped Bi2Se3 were determined by investigating the J-E plot of the FE data. The value of β is three times higher than that of pure Bi2Se3 confirming the superior FE properties. The emission current was found to be very stable with the property of long standing durability as a negligible amount of variation was observed when measured at a constant value of 5 mA for 3 hours. The experimental results signify many opportunities for potential applications of Ni doped Bi2Se3 as a source of electrons in scanning as well as transmission electron microscopy, flat panel displays and as an X-ray generator, etc.

Near infrared light activatable PEI-wrapped bismuth selenide nanocomposites for photothermal/photodynamic therapy induced bacterial inactivation and dye degradation.

The inactivation of bacteria and the degradation of organic pollutants by engineered nanomaterials (NMs) are very effective approaches for producing safe and clean drinking water. The development of new NMs which can act as NIR light mediated antimicrobial agents as well as photocatalytic agents is highly desired. In this study, a novel Bi2Se3 nanoplates (NPs) NM was prepared by a high-temperature reaction (colloidal synthesis) followed by wrapping of the surface with polyethyleneimine (PEI) through electrostatic interactions. The developed Bi2Se3 NPs/PEI exhibited excellent NIR light activated antimicrobial properties for bacterial eradication and efficient photocatalytic properties for organic dye degradation. The results showed that upon 808 nm laser irradiation the engineered Bi2Se3 NPs/PEI eradicated ∼99% of S. aureus and ∼97% of E. coli bacteria within 10 minutes of irradiation through combined dual-modal photothermal therapy (PTT) and photodynamic therapy (PDT) via the generation of heat and reactive oxygen species, respectively. The contributions of PTT and PDT were found to be in a ratio of nearly 4 : 1 in the killing of both species of bacteria. In addition, Bi2Se3 NPs/PEI also acted as an excellent photocatalyst under illumination by a halogen lamp equipped with a 700–1100 nm band pass filter to achieve degradation efficiencies of ∼95% for methylene blue and ∼93% for Rhodamine B within 3 and 4 h, respectively. To the best of our knowledge, this is the first demonstration of these NIR light activated antimicrobial properties, photodynamic properties and photocatalytic properties mediated by Bi2Se3 NPs.

2D Material-Based Nanofibrous Membrane for Photothermal Cancer Therapy.

One of the clinical challenges facing photothermal cancer therapy is health risks imposed by the photothermal nanoagents in vivo. Herein, a photothermal therapy (PTT) platform composed of a 2D material-based nanofibrous membrane as the agent to deliver thermal energy to tumors under near-infrared (NIR) light irradiation is described. The photothermal membrane, which is fabricated by an electrospinning poly(l-lactic acid) (PLLA) nanofibrous membrane loaded with bismuth selenide (Bi2Se3) nanoplates, exhibits very high photothermal conversion efficiency and long-term stability. Cell experiments and hematological analyses demonstrate that the Bi2Se3/PLLA membranes have excellent biocompatibility and low toxicity. PTT experiments performed in vivo with the Bi2Se3/PLLA membrane covering the tumor and NIR irradiation produce local hyperthermia to ablate the tumor with high efficiency. Different from the traditional systematical and local injection techniques, this membrane-based PTT platform is promising in photothermal cancer therapy, especially suitable for the treatment of multiple solid tumors or skin cancers, and long-term prevention of cancer recurrence after surgery or PTT, while eliminating the health hazards of nanoagents.

Surfactant mediated synthesis of bismuth selenide thin films for photoelectrochemical solar cell applications

In the present report, nanostructured bismuth selenide (Bi2Se3) thin films have been successfully deposited by using arrested precipitation technique (APT) at room temperature. The effect of three different surfactants on the optostructural, morphological, compositional and photoelectrochemical properties of Bi2Se3 thin films were investigated. Optical absorption data indicates direct and allowed transition with a band gap energy varied from 1.4 eV to 1.8 eV. The X-ray diffraction pattern (XRD) revealed that Bi2Se3 thin films are crystalline in nature and confirmed rhombohedral crystal structure. SEM micrographs shows morphological transition from interconnected mesh to nanospheres like and finally granular morphology. Surface topography of Bi2Se3 thin films was determined by AFM. Compositional analysis of all samples was carried out by energy dispersive X-ray spectroscopy (EDS). Finally, all Bi2Se3 thin films shows good PEC performance with highest photoconversion efficiency 1.47%. In order to study the stability of Bi2Se3 thin films four cycles are repeated after gap of one week each. Further PEC performance of all Bi2Se3 thin films are also supported by electrochemical impedance (EIS) measurement study.

Two-band induced superconductivity in single-layer graphene and topological insulator bismuth selenide

Proximity-induced superconductivity in single-layer graphene (SLG) and in topological insulators represent almost ideal examples of superconductivity in two dimensions. Fundamental mechanisms governing superconductivity in the 2D limit are of central interest for modern condensed-matter physics. To deduce fundamental parameters of superconductor/graphene/superconductor and superconductor/bismuth selenide/superconductor junctions we investigate the self-field critical currents in these devices using the formalism of the Ambegaokar–Baratoff model. Our central finding is that the induced superconducting state in SLG and bismuth selenide each exhibits gapping on two superconducting bands. Based on recent results obtained on ultra-thin films of natural superconductors, including single-atomic layer of iron selenide, double and triple atomic layers of gallium, and several atomic layer tantalum disulphide, we conclude that a two-band induced superconducting state in SLG and bismuth selenide is part of a wider, more general multiple-band phenomenology of currently unknown origin.

Core–Shell Bi2Se3@mSiO2‐PEG as a Multifunctional Drug‐Delivery Nanoplatform for Synergistic Thermo‐Chemotherapy with Infrared Thermal Imaging of Cancer Cells

AbstractThermo‐chemotherapy combining photothermal therapy (PTT) with chemotherapy has become a potent approach for antitumor treatment. In this study, a multifunctional drug‐delivery nanoplatform based on polyethylene glycol (PEG)‐modified mesoporous silica‐coated bismuth selenide nanoparticles (referred to as Bi2Se3@mSiO2‐PEG NPs) is developed for synergistic PTT and chemotherapy with infrared thermal (IRT) imaging of cancer cells. The product shows no/low cytotoxicity, strong near‐infrared (NIR) optical absorption, high photothermal conversion capacity, and stability. Utilizing the prominent photothermal effect, high‐contrast IRT imaging and efficient photothermal killing effect on cancer cells are achieved upon NIR laser irradiation. Moreover, the successful mesoporous silica coating of the Bi2Se3@mSiO2‐PEG NPs cannot only largely improve the stability but also endow the NPs high drug loading capacity. As a proof‐of‐concept model, doxorubicin (DOX) is successfully loaded into the NPs with rather high loading capacity (≈50.0%) via the nanoprecipitation method. It is found that the DOX‐loaded NPs exhibit a bimodal on‐demand pH‐ and NIR‐responsive drug release property, and can realize effective intracellular drug delivery for chemotherapy. The synergistic thermo‐chemotherapy results in a significantly higher antitumor efficacy than either PTT or chemotherapy alone. The work reveals the great potential of such core–shell NPs as a multifunctional drug‐delivery nanosystem for thermo‐chemotherapy.

Transport properties of Cu-doped bismuth selenide single crystals at high magnetic fields up to 60 Tesla: Shubnikov–de Haas oscillations and [formula omitted]-Berry phase

We report Shubnikov-de Haas (SdH) and Hall oscillations in Cu-doped high quality bismuth selenide single crystals. To increase the accuracy of Berry phase determination by means of the of the SdH oscillations phase analysis we present a study of n-type samples with bulk carrier density n∼1019−1020cm−3 at high magnetic field up to 60Tesla. In particular, Landau level fan diagram starting from the value of the Landau index N=4 was plotted. Thus, from our data we found π-Berry phase that directly indicates the Dirac nature of the carriers in three-dimensional topological insulator (3D TI) based on Cu-doped bismuth selenide. We argued that in our samples the magnetotransport is determined by a general group of carriers that exhibit quasi-two-dimensional (2D) behaviour and are characterized by topological π-Berry phase. Along with the main contribution to the conductivity the presence of a small group of bulk carriers was registered. For 3D-pocket Berry phase was identified as zero, which is a characteristic of trivial metallic states.

Probing the Topological Surface State in Bi2Se3Thin Films Using Temperature-Dependent Terahertz Spectroscopy

Strong spin–momentum coupling in topological insulators gives rise to topological surface states, protected against disorder scattering by time reversal symmetry. The study of these exotic quantum states not only provides an opportunity to explore fundamental phenomenon in condensed matter physics, such as the spin Hall effect, but also lays the foundation for applications in quantum computing to spintronics. Conventional electrical measurements suffer from substantial bulk interference, making it difficult to clearly identify topological surface state from the bulk. We use terahertz time-domain spectroscopy to study the temperature-dependent optical behavior of a 23-quintuple-thick film of bismuth selenide (Bi2Se3), allowing the deconvolution of the surface state response from the bulk. The signatures of the topological surface state at low temperatures (<30 K) with the optical conductance of Bi2Se3 exhibiting a metallic behavior are observed. Measurement of carrier dynamics results in an optical mobilit...

Decorated ultrathin bismuth selenide nanosheets as targeted theranostic agents for in vivo imaging guided cancer radiation therapy

An efficient radiotherapeutic agent is synthesized using ultrathin two-dimensional 30-nm-wide and 2-nm-thick Bi2Se3 nanosheets (NSs) as a radiosensitizer. Chitosan (CS) and RGD peptide are employed to enhance the radiotherapy efficiency and biocompatibility. The Bi2Se3-CS-RGD NSs exhibit excellent targeting ability to αvβ3 integrin-overexpressing cancer cells and potent radiosensitization efficiency with high stability. Detailed in vitro experiments show that the Bi2Se3-CS-RGD NSs enhance the sensitivity of HeLa cells to X-ray-induced cell death by inhibiting TrxR activities and activating downstream reactive oxygen species-mediated signaling pathways. In vivo experiments using intravenous or intratumor injection demonstrate that the Bi2Se3-CS-RGD NSs are more efficient tumor growth inhibitors compared to bare Bi2Se3 NSs. The multifunctionality of the NSs enables the use of photoacoustic imaging and magnetic resonance imaging to examine their targeting ability and therapeutic effects, respectively. In addition, the RGD-decorated Bi2Se3 NSs show much better in vivo biocompatibility and can be efficiently expelled from the body after 48 h post injection. This study reveals an effective and safe theranostic agent for next-generation cancer radiotherapy.

Enhanced thermoelectric performance of n-type bismuth selenide doped with nickel

Bismuth selenide (Bi2Se3) and transition metal (nickel) doped (5 and 7.5 mol %) Bi2Se3 have been prepared by solvothermal approach for investigation of thermoelectric properties of the materials. The morphological characterization reveals plate and flake like structures for undoped and doped samples respectively. There is a decrease in lattice constant, computed from Rietveld refinement data and crystallite size, found using Debye-Scherrer equation for doped samples. Doping by nickel increases the electrical conductivity and reduces both thermo power and thermal conductivity of the materials than pure Bi2Se3. Reduction in thermal conductivity of the doped samples by 42%, results in an increase in figure of merit (ZT) of nickel doped (5%) materials by one order of magnitude (0.02–0.22) compared to pure Bi2Se3.

Tuning Electrodeposition Conditions Towards the Formation of Smooth Bi2Se3 Thin Films

Bismuth selenide (Bi2Se3) is a semiconductor presenting two distinct crystalline phases, one with rhombohedral structure (R-3M), and another, metastable, with orthorhombic phase (Pnma). Each phase has distinct band gap and interesting optical, thermoelectric and topological electronic properties. Thin films of thicknesses up to 1.5 μm were grown by electrodeposition under constant potential onto silicon (100) substrate. It is shown that under an optimum set of deposition parameters, simultaneous heating and electrolyte stirring, very smooth and thick films can be obtained. Morphological characterization evidences the formation of compact, uniform and smooth layers, attributed to the growth of very small grains of ~50 nm. Structural characterization of the samples indicates a majority of a metastable orthorhombic phase with traces of a rhombohedral phase. The films grow initially with a rhombohedral crystalline structure, which progressively changes to orthorhombic, likely due to the accumulation of internal stresses and successive stress relaxation. In addition, a full recrystallization to the rhombohedral structure can be achieved by using short time and low temperature thermal treatments. These results show the possibility to grow smooth samples and also to control the crystalline structure of Bi2Se3. This is of interest since both phases present different but complementary properties, and each one or the combination of the two may be successfully exploited to the construction of low cost, efficient novel devices based on thermoelectric, optical or topological insulator technologies.

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.

Photochemical Water Splitting by Bismuth Chalcogenide Topological Insulators.

As one of the major areas of interest in catalysis revolves around 2D materials based on molybdenum sulfide, we have examined the catalytic properties of bismuth selenides and tellurides, which are among the first chalcogenides to be proven as topological insulators (TIs). We find significant photochemical H2 evolution activity with these TIs as catalysts. H2 evolution increases drastically in nanosheets of Bi2 Te3 compared to single crystals. First-principles calculations show that due to the topology, surface states participate and promote the hydrogen evolution.

Fabrication of multi-layer Bi2Se3 devices and observation of anomalous electrical transport behaviors

In this paper, we report on the fabrication of multi-layer bismuth selenide (Bi2Se3) devices by lithography process and their electrical transport characteristics studied at room temperature. The observation of a non-linear current-voltage characteristic is analyzed with various current transport mechanisms such as Schottky barrier, space-charge limited conduction (SCLC), Fowler-Nordheim (F-N) tunneling and Poole-Frenkel (P-F) conduction. The F-N tunneling via field emission current induced in high-voltage was found to be the dominant conduction mechanism which could responsible for the nonlinear behavior as compared to SCLC and P-F conduction phenomena. The charge traps present in the Bi2Se3 bulk causes SCLC and P-F conduction. A carrier mobility in Bi2Se3 is extracted as ~ 1220cm2V−1s−1. Our study further advances the understanding of the fundamental charge transport mechanisms appeared in Bi2Se3 which will be an essential parameter in the development of various electronic applications such as resistive memory switching and sensing devices.

Structure determination of the high-pressure phases of topological insulator Bi2Se3 using experiments and calculations

The pressure-induced phase transition of bismuth selenide (Bi2Se3) was investigated by combining theoretical calculations with synchrotron powder X-ray diffraction measurements up to 57.4 GPa. We demonstrated that the ambient-pressure rhombohedral Bi2Se3 crystallized into a monoclinic structure with the space group C2/m at 9.1 GPa, and eventually to a body-centered tetragonal structure with the space group I4/mmm at about 27.2 GPa. This behavior was different from the transformation sequences of Bi2Te3 and Sb2Te3. The stabilities of five structures of Bi2Se3 were studied by density functional theory calculations. Furthermore, an unusual irreversible relaxation process was observed. We attempted to make clear the unusual structural behavior of Bi2Se3 occurring in the compression process and the relaxation process.