Controlled synthesis of crystalline tellurium nanorods, nanowires, nanobelts and related structures by a self-seeding solution process

Single crystalline nanorods and nanowires of t-Te have been prepared by a simple solution route. The procedure involves the disproportionation of NaHTe, prepared by the reduction of Te with NaBH4. By carefully controlling the reaction conditions, the diameter of the nanorods could be varied in the 20-300 nm range. Nanowires of 10 nm diameter were obtained in the presence of sodium dodecylbenzenesulfonate. Te nanobelts and nano junctions were obtained by employing hydrothermal and solvothermal conditions. The nanorods have been characterized by a variety of microscopic and spectroscopic techniques. UV-Visible spectra reveal two absorption bands, one around 300 nm which is size-sensitive and the other at 600 nm insensitive to size

Soft chemical routes to semiconductor nanostructures

Soft chemistry has emerged as an important means of generating nanocrystals, nanowires and other nanostructures of semiconducting materials. We describe the synthesis of CdS and other metal chalcogenide nanocrystals by a solvothermal route. We also describe the synthesis of nanocrystals of AlN, GaN and InN by the reaction of hexamethyldisilazane with the corresponding metal chloride or metal cupferronate under solvothermal conditions. Nanowires of Se and Te have been obtained by a self-seeding solution-based method. A single source precursor based on urea complexes of metal chlorides gives rise to metal nitride nanocrystals, nanowires and nanotubes. The liquidliquid interface provides an excellent medium for preparing single-crystalline films of metal chalcogenides

Unravelling Charge-transfer in Pd to pyrrolic-N bond for superior electrocatalytic performance

Fuel cells require large quantities of Pt for oxygen reduction reaction (ORR) to subvert the activity-loss during prolonged use. Pd can complement Pt in the near future by exhibiting a similar activity and stability in alkaline fuel cells. Herein we show that by depositing Pd atom-by-atom on an N-doped reduced graphene oxide (NRGO), it is possible to create a strong bond between Pd and pyrrolic-fraction of the N-moieties. This bond further strengthens in the presence of an by a from the Pd 3d-orbitals to the 2p-orbitals of C, N and O, thereby lowering the Pd- 3d binding-energy and the resulting Pd/NRGO exhibits a very high ORR activity (E1/2 = 0.93 V vs. RHE) and stability (∆E1/2 = 0.013 V after 15000. Usually pyridinic-N is considered for imparting high-performance while N-doping creates nearly as many pyrrolic-N in graphene-substrates, the role of which is evidenced in this study

Nanocrystals of metals, semiconductors and oxides: novel synthesis and applications

Films of nanocrystals such as Au, Ag and Pd, semiconducting sulphides such as CdS, ZnS and CoS, and oxides such as Fe2O3 and CuO have been prepared by employing reactions at liquid-liquid (organic-aqueous) interfaces. In this method, a suitable organic derivative of the metal taken in the organic layer reacts at the interface with the appropriate reagent present in the organic layer. Two typical applications of nanocrystals pertaining to magnetic devices and dip-pen lithography are briefly presented

Controlled synthesis of crystalline tellurium nanorods, nanowires, nanobelts and related structures by a self-seeding solution process

Single crystalline nanorods and nanowires of t-Te have been prepared by a simple solution route. The procedure involves the disproportionation of NaHTe, prepared by the reduction of Te with $NaBH_4$. By carefully controlling the reaction conditions, the diameter of the nanorods could be varied in the 20–300 nm range. Nanowires of 10 nm diameter were obtained in the presence of sodium dodecylbenzenesulfonate. Te nanobelts and nano junctions were obtained by employing hydrothermal and solvothermal conditions. The nanorods have been characterized by a variety of microscopic and spectroscopic techniques. UV-Visible spectra reveal two absorption bands, one around 300 nm which is size-sensitive and the other at 600 nm insensitive to size

Scanning tunneling microscopy and spectroscopy of Se and Te nanorods

Se and Te nanorods obtained by a self-seeding solution growth process have been examined by scanning tunneling microscopy and spectroscopy(STM/STS). The diameters of the rods, as revealed by STM images were in the range of 1060 nm, with aspect ratios of 10-20. The I-V data of the Se and Te nanorods exhibit band gaps of similar to 1.3 and similar to 0.4 eV, respectively, nearly independent of the diameter, and these values are close to the bulk values of Se and Te. In both the cases,the nanorods possess a small but finite conductance even in the bandgap regions, the conductance value increasing with the diameter of the rod. A tunneling mechanism involving the surface states is proposed to explain this phenomenon

Preparation of PbS and PbSe nanocrystals by a new solvothermal route

A new solvothermal route for the preparation of nanocrystals of PbS and PbSe, involving the reaction of lead stearate with sulfur or selenium and tetralin (tetrahydronaphthalene) in toluene solvent is described. Tetralin in the presence of S/Se gives $H_2S/H_2Se$ and gets aromatized to naphthalene. The nanocrystals have been characterized by powder X-ray diffraction and electron microscopy. Use of surfactant Triton X-100 (polyoxyethylene(10)isooctylphenyl ether) resulted in both nanorods and nanoparticles of PbSe. Capping by citric acid and malonic acid reduce the particle sizes to less than 10 nm

Scanning tunneling microscopy and spectroscopy of Se and Te nanorods

Se and Te nanorods obtained by a self-seeding solution growth process have been examined by scanning tunneling microscopy and spectroscopy (STM/STS). The diameters of the rods, as revealed by STM images were in the range of 10–60 nm, with aspect ratios of 10–20. The I–V data of the Se and Te nanorods exhibit band gaps of ∼1.3 and ∼0.4 eV, respectively, nearly independent of the diameter, and these values are close to the bulk values of Se and Te. In both the cases, the nanorods possess a small but finite conductance even in the band gap regions, the conductance value increasing with the diameter of the rod. A tunneling mechanism involving the surface states is proposed to explain this phenomenon

New strategies for the synthesis of t-selenium nanorods and nanowires

Two different strategies for the synthesis of t-selenium nanorods and nanowires are described, wherein the solution based method involves a reaction of selenium powder with $NaBH_4$ while the other employs the thermal decomposition of $[(CH_3)_4N]_4Ge_4Se_{10}$