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 roomerature. Te NWs act as templates for the formation of La2Te 3 NWs. The aspect ratio of the as prepared La2Te 3 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 La 2Te3 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 phase protocol, are expected to motivate further studies on this material. © 2010 American Chemical Society.

Pradeep Thalappil

Department Of Chemistry

Analytes

Concentration of

Crystal violet

LANTHANUM NITRATES

Monodispersity

New approaches

RAMAN ENHANCEMENT

RAMAN FEATURE

Raman studies

Solution phase

SPECTROSCOPIC TOOL

SURFACE ENHANCED RAMAN

SURFACE-ENHANCED RAMAN SPECTRUM

TELLURIUM NANOWIRES

Aspect ratio

Doping (additives)

Lanthanum alloys

Nanowires

Raman spectroscopy

Silver

Synthesis (chemical)

Tellurium

Tellurium compounds

X ray diffraction

Lanthanum

Fulltext

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Journal of Physical Chemistry C

Reactivity of two different nanosystems of silver, namely nanoparticles and atomically precise clusters, toward 1D tellurium nanowires (NWs) was probed and compared with the reaction of silver ions. While the reaction of nanoparticles and ions led to silver telluride nanowires, a different reactivity was exhibited by clusters which resulted in silver islands at different positions on the Te NWs. These hybrid Ag nodule-decorated Te NWs are sensitive to temperature, and they transform to dumbbell-shaped silver-tipped Te NWs upon solution phase annealing. Differences in chemical reactivity of nanoparticles of two different size regimes with nanowires are demonstrated. Synthetic methods of this kind will be useful in creating complex nanostructures which are difficult to be made in the solution phase. © 2014 American Chemical Society.

Chemistry of Materials

Manifestation of the difference in reactivity of silver clusters in contrast to its ions and nanoparticles: The growth of metal tipped Te 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 Ag2Te 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 Ag2Te-Te-Ag 2Te 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. © 2012 The Royal Society of Chemistry.

Nanoscale

Heterojunction double dumb-bell Ag2Te-Te-Ag2Te nanowires

Herein, we report the emergence of multicolor photoluminescence in a mixed-valence manganite nanoparticle La0.67Sr0.33MnO 3 (LSMO NP) achieved through electronic structural modification of the nanoparticles upon functionalization with a biocompatible organic ligand, sodium tartrate. From UV-vis absorption, X-ray photoelectron spectroscopy (XPS), time-resolved photoluminescence study, and Raman spectroscopic measurements, it is revealed that ligand-to-metal charge transfer transitions from highest occupied molecular orbital (HOMO, centered in tartrate ligand) to lowest unoccupied molecular orbital (LUMO, centered in Mn3+/4+ of the NPs), and d-d transitions involving Jahn-Teller sensitive Mn3+ ions in the NPs plays the central role behind the origin of multiple photoluminescence from the ligand functionalized LSMO NPs. © 2012 American Chemical Society.

Emergence of multicolor photoluminescence in La0.67Sr 0.33MnO3 nanoparticles

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 Cr 2Te4O11, 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 inside, where unreacted parts of Te NWs remained, was crystalline with a clear lattice structure. X-ray photoelectron spectroscopy (XPS) as well as Raman spectroscopy showed a redox reaction in both cases. Studies suggest that both redox reactions and nanoscale Kirkendall effect might be involved in the formation mechanism. © 2011 American Chemical Society.

Tubular nanostructures of Cr2Te4O11 and Mn2TeO6 through room-temperature chemical transformations of tellurium nanowires

Hybrid A-B-A type nanowires (NWs) with Ag 5Te 3-HgTe- Ag 5Te 3 composition have been created by the reaction of Hg 2+ with Ag 2Te NWs. The NW morphology of Ag 2Te is preserved upon reaction with minor changes and the two separate phases formed are spatially separated within the same NW. The reaction of Hg 2+ with Ag 2Te NWs was monitored at different concentrations and the reactivity was attributed to cationic exchange depending on solubility products. Hybrid NWs were formed by partial cation exchange only at low concentrations (below 50 ppm) resulting in Ag 5Te 3 and HgTe within the same NW. However, at high concentrations (above 100 ppm), the HgTe phase alone was formed. These studies have been extended to other metal ions such as Pb 2+, Cd 2+, and Zn 2+ whose reactivity towards Ag 2Te NWs is different from that of Hg 2+. These ions form a passivating Te oxide layer upon reaction with other metal ions. The mechanism of reactivity of Hg 2+ is explained on the basis of free energy of formation of the ionic solid. Phase transition of Hg 2+-reacted NWs occurs at a lower temperature than the parent (Ag 2Te NWs) and other metal ions-reacted Ag 2Te NWs. Details of the process were elucidated using microscopic and spectroscopic investigations. The physical and chemical properties of the individual components within a NW are expected to provide a novel functionality to the metal chalcogenide systems. © 2011 The Royal Society of Chemistry.

Hybrid A-B-A type nanowires through cation exchange

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 Ag 2Te 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. © 2009 American Chemical Society.

Room-temperature chemical synthesis of silver telluride nanowires

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 room temperature was found to reduce GO while Te NWs are oxidized to TeO32-. The reaction was followed time-dependently with use of UV/vis spectroscopy, fluorescence spectroscopy, and transmission electron microscopy (TEM). Raman spectroscopy was used to characterize the graphenic material. The G band, which was blue-shifted (with respect to graphite) in the case of GO, came back to the original position confirming the reduction. From IR spectroscopy, it was confirmed that the carboxylic acid groups in the GO are not getting reduced and the product gets stabilized electrostatically because of the repulsion between the negatively charged carboxylic acid groups. Reduction was confirmed by X-ray photoelectron spectroscopy (XPS) also. The reaction showed strong pH dependence and was found to be happening only in basic pH. In acidic medium, GO aggregates, making reduction difficult, while at higher temperature, the reaction was faster and at lower temperature it was retarded considerably.© 2009 American Chemical Society.

Tellurium nanowire-Induced room temperature conversion of graphite oxide to Leaf-like graphenic structures

Solid State Sciences

Characterization of spray deposited CdTe films grown under different ambient conditions

Journal of Crystal Growth

From Te nanotubes to CoTe2 nanotubes: A general strategy for the formation of 1D metal telluride nanostructures

Inorganic Chemistry

An Efficient Templating Approach for Synthesis of Highly Uniform CdTe and PbTe Nanowires

Lanthanum telluride nanowires: Formation, doping, and Raman studies

Journal	Journal of Physical Chemistry C
ISSN	19327447
Open Access	No