Te NWs Research Articles

Synthesis of Ultralong, Monodispersed, and Surfactant-Free Gold Nanowire Catalysts: Growth Mechanism and Electrocatalytic Properties for Methanol Oxidation Reaction

The understanding of factors influencing the growth of nanowires is critical for the precise control of the nanowire morphologies and the design of active nanowire catalysts for fuel cell reactions. While the formation of gold nanoparticles followed by self-assembly into short strings of nanowires is known, little is understood in terms of the control of the morphologies and surface properties toward enhanced electrocatalytic properties. This report describes novel findings of an investigation of the growth mechanism of ultralong, highly monodispersed, and surface surfactant-free gold nanowires (Au NWs) synthesized by a galvanic replacement reaction of Te NWs as an initial template. By manipulating reaction time and Au precursor concentration, an aggregative growth mechanism in terms of 1D and 3D growth pathways for the NW length and diameter, respectively, is revealed to be operative in the template-directed Au NW formation process, shinning some fresh insight into the controllability of the nanowire mor...

Synthesis and thermoelectric characterization of high density Ag2Te nanowire/PMMA nanocomposites

N-type thermoelectric nanocomposites based on monoclinic silver telluride nanowires (Ag2Te NWs) and poly(methyl methacrylate) beads were prepared by means of a simple hot compaction technique. Control of Ag2Te NW composition and crystal structure was achieved by tuning the AgNO3 content in the electrolyte while maintaining a fixed reaction time of the topotactic reaction with Te NWs. The curved shapes and high aspect ratios of the Ag2Te NWs were important in fabricating composites of high density in our system and resulted in reduced contact resistance between the nanowires, which was critical in enhancing the composites' electrical and thermoelectric properties. The thermal conductivity of the composites increased somewhat with nanowire content, but all composites had thermal conductivity nearly the same as that of polymeric material. Consequently, figure of merit (ZT) of 0.005 was achieved in a nanocomposite containing 50 wt% Ag2Te NWs at room-temperature.

Improved Thermoelectric Performance in Flexible Tellurium Nanowires/Reduced Graphene Oxide Sandwich Structure Hybrid Films

With a high flexibility and an adjustable electronic structure, reduced graphene oxide (RGO) is a potential candidate for flexible thermoelectric materials. Here, we report that flexible RGO/tellurium nanowires (Te NWs)/RGO sandwich structure hybrid films are prepared on glass fabrics through the drop-cast method. The addition of 20 wt.% Te NWs into a RGO matrix remarkably improves the Seebeck coefficient from 15.2 μV/K to 89.7 μV/K while maintaining relatively high electrical conductivity, thus resulting in a one order of magnitude higher power factor value compared with the Te NWs. According to the values of carrier mobility and concentration of hybrid films, the improved thermoelectric properties are presented because of the energy filtering effect on the interfaces in hybrid films. This article suggests that RGO/Te NWs/RGO hybrid films would be promising for fabricating flexible energy sources.

Fabrication of Te and Te-Au Nanowires-Based Carbon Fiber Fabrics for Antibacterial Applications.

Pathogenic bacteria that give rise to diseases every year remain a major health concern. In recent years, tellurium-based nanomaterials have been approved as new and efficient antibacterial agents. In this paper, we developed the approach to directly grow tellurium nanowires (Te NWs) onto commercial carbon fiber fabrics and demonstrated their antibacterial activity. Those Te NWs can serve as templates and reducing agents for gold nanoparticles (Au NPs) to deposit. Three different Te-Au NWs with varied concentration of Au NPs were synthesized and showed superior antibacterial activity and biocompability. These results indicate that the as-prepared carbon fiber fabrics with Te and Te-Au NWs can become antimicrobial clothing products in the near future.

PtCu bimetallic alloy nanotubes with porous surface for oxygen reduction reaction

PtCu bimetallic alloy nanotubes with porous surface were synthesized in aqueous solution using Te NWs as templates. The nanotubes with optimized composition present enhanced electrocatalytic performance for oxygen reduction reaction.

Anisotropic Molecular Ionization at 1 V from Tellurium Nanowires (Te NWs).

Ionization of molecular species from one-dimensional (1D) tellurium nanowires (Te NWs) has been achieved at 1 V. Molecules with a range of chemical functional groups gave quality mass spectra with high signal/noise ratios and no fragment ions. Experiments suggest the possibility of emission of microdroplets of solution due to the intense fields at the ends or interfaces of nanostructures. It appears that electrolytic conduction of the solution wetting of the nanostructures and not the electronic conduction of the nanostructures themselves is involved in the ionization event. Anisotropy was seen when two-dimensionally aligned Te NWs were used for ionization. The orientation effect of aligned Te NWs on molecular ion intensity is demonstrated for many analytes including organic molecules and amino acids with experiments done using a silicon substrate having aligned Te NWs. These measurements suggest the possibility of creating a MS source that extends the applicability of mass spectrometry. Analysis of a variety of analytes, including amino acids, pesticides, and drugs, in pure form and in complex mixtures, is reported. These experiments suggest that 1D nanostructures in general could be excellent ionization sources.

Nanowires as Building Blocks to Fabricate Flexible Thermoelectric Fabric: The Case of Copper Telluride Nanowires.

A general approach to fabricate nanowires based inorganic/organic composite flexible thermoelectric fabric using a simple and efficacious five-step vacuum filtration process is proposed. As an excellent example, the performance of freestanding flexible thermoelectric thin film using copper telluride nanowires/polyvinylidene fluoride (Cu1.75Te NWs/PVDF = 2:1) as building block is demonstrated. By burying the Cu1.75Te NWs into the PVDF polymer agent, the flexible fabric exhibits room-temperature Seebeck coefficient and electric conductivity of 9.6 μV/K and 2490 S/cm, respectively, resulting in a power factor of 23 μW/(mK(2)) that is comparable to the bulk counterpart. Furthermore, this NW-based flexible fabric can endure hundreds of cycles of bending tests without significant performance degradation.

Electrochemical synthesis of ultrafast and gram-scale surfactant-free tellurium nanowires by gas-solid transformation and their applications as supercapacitor electrodes for p-doping of graphene transistors.

We herein report a gas-solid transformation mechanism for the surfactant-free synthesis of Te NWs at room temperature by electrolysis of bulk Bi2Te3 using H2Te gas. Te NWs, with an average diameter below 20 nm, grow along the [001] direction due to the unique spiral chains in the crystal structure and show an enhanced Raman scattering effect, a broad absorption band over the range of 350-750 nm and an emission band over the range of 400-700 nm in the photoluminescence spectrum. In terms of device applications, we demonstrate how Te NWs can be directly applied as a p-type dopant source in order to shift the Dirac point in ambipolar field effect graphene transistors. Finally, the favorable capacitive properties of Te NWs are established as supercapacitor electrodes with negligible internal resistance and excellent electrochemical reversibility and a specific capacitance of 24 F g(-1).

Synthesis of enzyme mimics of iron telluride nanorods for the detection of glucose

Iron telluride nanorods (FeTe NRs, length 45 ± 11 nm) prepared from tellurium nanowires (Te NWs, length 785 ± 170) have been used to detect H(2)O(2) and glucose with a limit of detection (LOD) of 55 nM (linear range = 0.1-5 μM) and 0.38 μM (linear range = 1-100 μM) respectively.

Heterojunction double dumb-bell Ag2Te–Te–Ag2Te nanowires

Growth of isolated axial heterojunction nanowires by a solution phase growth process is reported. The dumb-bell shaped nanowires contain two silver telluride sections at the extremes joined by a tellurium section. Reaction of silver nitrate with tellurium NWs in aqueous solution at a molar ratio of 1 : 1 leads to the formation of amorphous partially silver reacted Te NWs. Low temperature (75 °C) solution phase annealing of these silver deficient NWs results in phase segregation producing crystalline Ag(2)Te and Te phases with clear phase boundaries along the wire axis. Structural characterization of these dumb-bell shaped NWs was performed with different microscopic and spectroscopic tools. Solution phase silver concentration over the course of annealing indicated leaching of silver into the solution during the formation of biphasic NWs. Similar Ag : Te ratios were observed in both partially silver reacted Te NWs and phase segregated Ag(2)Te-Te-Ag(2)Te NWs and this was attributed to redeposition of leached silver on the amorphous NW tips which eventually resulted in complete phase segregation. Successful integration of different chemical components in single NWs is expected to open up new application possibilities as physical and chemical properties of the heterostructure can be exploited.

Selective Tellurium Nanowire‐based Sensors for Mercury(II) in Aqueous Solution

AbstractWe have developed a simple, colorimetric, and label‐free tellurium nanowire (Te NW)‐based probe for the detection of mercury ions (Hg(II)) in aqueous solution, operating on the principle of strong hybridization and galvanic replacement reaction of Te–Hg. The Te NWs (length: 920 nm; diameter: 20 nm) reacted with Hg(II) to induce dissolution and aggregation of the Te NWs. As a result, the absorption band of the Te NWs in a solution undergoes a decrease in the presence of Hg(II). Energy‐dispersive X‐ray spectroscopy and surface‐assisted laser desorption/ionization measurements demonstrated the presence of Hg on the Te NWs. The Te NW probe specifically and sensitively detected Hg(II) ions under optimal concentrations of pH, temperature, and sodium dodecyl sulfate (SDS) concentration. When using a mixture of Te NWs (3.0 nM) and SDS (5 μM) in 5 mM sodium phosphate (pH 4) at 50 °C, this sensor provides a limit of detection of 0.5 nM for Hg(II) (signal‐to‐noise ratio of 3) with high selectivity (at least 100 fold over other metal ions). Our approach abrogates the need for complicated chemosensors or sophisticated equipment. This cost‐effective sensing system allows the rapid and simple determination of the concentrations of Hg(II) ions in real samples (in this case, river, lake, and tap water samples).

Tubular Nanostructures of Cr2Te4O11and Mn2TeO6through Room-Temperature Chemical Transformations of Tellurium Nanowires

Tubular ternary nanostructures of tellurium were made through chemical transformations of tellurium nanowires (Te NWs). These transformations occur through reactions with CrO3 and KMnO4, two of the strongest oxidizing agents. In the case of CrO3, the 1D structure of the NWs remained intact and the morphology changed to hollow wires of Cr2Te4O11, but reaction with KMnO4 resulted in the loss of 1D structure, forming a carbon onion-like object composed of Mn2TeO6. As the reaction proceeded, the crystallinity of the NWs decreased, and the final products were amorphous. The reaction products were characterized using different spectroscopic and microscopic techniques. Time-dependent transmission electron microscopic (TEM) analysis of both of the reaction products showed that first a shell is formed around the NWs. Further reaction results in the formation of hollow structures. During the reaction with CrO3, TEM in the intermediate stages showed that the periphery of the material was amorphous, whereas the insid...

Using Rhodamine 6G-Modified Gold Nanoparticles To Detect Organic Mercury Species in Highly Saline Solutions

We developed a gold nanoparticle (Au NP)-based fluorescence sensor for the detection of mercury ions in aqueous solutions. After introducing bovine serum albumin (BSA) to a solution of rhodamine 6G (R6G) and 3-mercaptopropionic acid (MPA)-modified Au NPs, the as-prepared BSA@R6G/MPA-Au NP probe could sense mercury ions under high salt conditions. This probe operated through a mechanism involving mercury species depositing onto the surfaces of the Au NPs and releasing R6G molecules into the solution, causing the fluorescence intensity of the BSA@R6G/MPA-AuNP solution to increase. We improved the selectivity of the nanosensor by adding masking agents (ethylenediamine tetraacetic acid (EDTA) and Na2S) or tellurium nanowires (Te NWs) to the sample solutions. In the presence of 1.0 mM EDTA and 10 μM Na2S, the selectivities of this system toward phenylmercury (PhHg(I)) over other metal ions and mercury species were greater than 200- and 10-fold, respectively. The limit of detection (LOD), at a signal-to-noise ratio of 3, for PhHg(I) was 20 nM. Selective detection of the total organic mercury (methylmercury (MeHg(I)), ethylmercury (EtHg(I)), and PhHg(I)) was possible when using the BSA@R6G/MPA-Au NPs in conjunction with Te NWs (3.0 nM). The selectivity of this nanosensor system for the total organic mercury over Hg(II) was remarkably high (100-fold) with an LOD for organic mercury of 10 nM. We also demonstrated the feasibility of using the developed nanosensor for rapid determination of mercury species in river, sea, and tap water as well as in fish samples.

Pt3Te4Nanoparticles from Tellurium Nanowires

We report the synthesis of platinum telluride nanoparticles (Pt(3)Te(4) NPs) in the solution phase at room temperature using a template-assisted method. The dendrimeric aggregates formed are composed of several small units of Pt(3)Te(4) NPs of ∼4 nm diameter. Tellurium nanowires (Te NWs) are used as the template and the reducing agent in the growth of NPs which occurs due to the galvanic replacement reaction between Te NWs and PtCl(6)(2-). Surface-enhanced Raman scattering (SERS) of the dispersed Pt(3)Te(4) NPs was studied using crystal violet (CV) as the analyte. SERS sensitivity up to 10(-8) M of CV was observed. The Raman enhancement factor (EF) of adsorbed CV on NP aggregates was calculated to be 1.74 × 10(5). The catalytic ability of the as-synthesized Pt(3)Te(4) NPs for the reduction of 4-nitrophenol (4-NP) was studied.

Lanthanum Telluride Nanowires: Formation, Doping, and Raman Studies

A new approach for the synthesis of freely dispersible one-dimensional (1D) lanthanum telluride nanowires (La2Te3 NWs) in the solution phase is reported. The process involves a reaction between tellurium nanowires (Te NWs) and lanthanum nitrate (La(NO3)3) at room-temperature. Te NWs act as templates for the formation of La2Te3 NWs. The aspect ratio of the as prepared La2Te3 NWs is the same as the parent Te NWs. Various microscopic and spectroscopic tools such as HRTEM, SEM, EDAX, XRD, XPS, Raman, UV−visible, and fluorescence were used for the characterization of the NWs. A new surface enhanced Raman active substrate was synthesized by doping silver in La2Te3 NWs. Surface enhanced Raman spectra were studied using crystal violet (CV) as the analyte. Raman features have been observed up to a concentration of 10−8 M of CV. Different concentrations of Ag in Ag-doped La2Te3 NWs were investigated. The monodispersity, homogeneity, and Raman enhancement properties of the NWs, synthesized through a simple solution ...

Bending and Shell Formation of Tellurium Nanowires Induced by Thiols

The reactivity of tellurium nanowires (Te NWs) with thiol-containing molecules was probed. Depending upon the presence or absence of the stabilizing surfactant in the solution, the product differs drastically. When excess surfactant was present, the reaction resulted in a core-shell-like structure. Through various spectroscopic and microscopic techniques, it was understood that there is a redox reaction between TeO2, present on the NW surface, and thiols added into the solution that resulted in the reduction of TeO2 to Te(0) with simultaneous oxidation of thiols to disulfides. Energy-dispersive analysis of X-rays (EDAX) confirmed that the shell has large sulfur and oxygen content. Raman spectra as well as the spectral image showed that the shell contains sulfur in the form of disulfides. Time-dependent Raman measurements established the redox nature of the conversion. The redox reaction was confirmed by X-ray photoelectron spectroscopy (XPS) also. When the excess surfactant was removed by repeated centrif...

Room-Temperature Chemical Synthesis of Silver Telluride Nanowires

We have developed a room-temperature solution-phase route for the preparation of one-dimensional silver telluride nanowires (Ag2Te NWs). The Ag2Te NWs of 600 nm length and 20 nm diameter were synthesized by the reaction of tellurium nanowires (Te NWs) with silver nitrate (AgNO3) in water. We propose that Te NWs act as the template and the reducing agent simultaneously, enabling the formation of polycrystalline Ag2Te NWs. Various microscopic and spectroscopic tools, such as HRTEM, SEM, EDAX, XRD, DSC, XPS, and Raman, were used for the characterization of Ag2Te NWs. The phase transition corresponding to the structural transition from the low-temperature monoclinic phase to the high-temperature face-centered cubic phase occurs at 417.7 K. We studied the electrical resistance and investigated the influence of temperature on the thermal emf. The Seebeck coefficient showed a maximum of ∼142 μV K−1, a value much higher than that of the bulk material and thin films (65−130 μV K−1). A surface-enhanced Raman scattering investigation of dispersed Ag2Te NWs showed them to be sensitive up to 10−7 M crystal violet. The monodispersity and the homogeneity of the NWs through a simple solution-phase protocol would pave the way for further studies and applications.

Tellurium Nanowire-Induced Room Temperature Conversion of Graphite Oxide to Leaf-like Graphenic Structures

A simple nanomaterial-based reduction strategy that can form leaf-like graphenic structures from graphite oxide (GO) at room temperature is described. Mixing of Te nanowires (Te NWs) with GO at roo...