Diameter-controlled Growth of Single-crystalline In2O3 Nanowires and Their Electronic Properties

TOPICAL REVIEW: Nanoparticle catalysts

Porous anodic alumina formed by anodization of aluminum alloy (AA1050) and high purity aluminum

We use density functional theory to resolve the role of polyvinylpyrrolidone (PVP) in the shape-selective synthesis of Ag nanostructures. At the segment level, PVP binds more strongly to Ag(100) than Ag(111) because of a surface-sensitive balance between direct binding and van der Waals attraction. At the chain level, correlated segment binding leads to a strong preference for PVP bind to Ag(100). Our study underscores differences between small-molecule and polymeric structure-directing agents.

Adsorption of Polyvinylpyrrolidone on Ag Surfaces: Insight into a Structure-Directing Agent

Tin(II) selenide is an important binary IV–VI semiconductor compound with a wide range of potential applications (e.g. memory switching devices, infrared optoelectronic devices, and anode materials for rechargeable lithium batteries). Bulk SnSe has both an indirect band gap at 0.90 eV and a direct band gap at 1.30 eV. Owing to the quantum confinement effect, tunable band gaps of SnSe nanostructured materials (e.g. thin films and nanocrystals) 3] have been demonstrated, which makes them capable of absorbing a major portion of solar energy. As an earth-abundant, environmentally benign, and chemically stable material, SnSe is placed among the most promising candidates for solar cells. Most recently, the interest in the controllable synthesis of colloidal tin chalcogenide (SnX; X = S, Se, Te) nanoparticles (NPs) has grown. However, nanowires (NWs) are expected to have properties superior to those of nanoparticles owing to their anisotropic geometry and the exciton confinement in two dimensions. It has been demonstrated that, for photovoltaic applications, high-aspect-ratio nanowires have the potential for enhancement of electron transport owing to their direct electron pathway that does not rely on electron hopping, in contrast to nanoparticles. Furthermore, as remarkably powerful building blocks in nanoscale electronic and optoelectronic devices, the synthesis of versatile semiconductor nanowires with superior controllability in structure and dimension is pivotal for exploiting their device applications. In 2003, Qian and co-workers reported the tentative synthesis of SnSe nanowires with a relatively large mean diameter of 50 nm, but the yield was low and the morphology (including irregular crystals) and purity (including tin oxides) were hard to control. In 2006, Zhao et al. developed a template route to synthesize SnSe nanowires, but only polycrystalline products were obtained after a long reaction time (e.g. 36 h), and a tedious process was required to remove the hard template. To date, high-yield synthesis of monocrystalline SnSe nanowires with relatively small diameters, decent aspect ratios, and good quality has remained a challenge; optical and electrical properties and optoelectronic applications of monocrystalline SnSe nanowires have not been described. We present herein a facile, solution-phase synthetic approach to colloidal SnSe nanowires, which have a mean diameter of approximately 20.8 nm, lengths tunable from hundreds of nanometers to tens of micrometers, and more importantly, a monocrystalline structure. Their optical and electric properties are examined by UV/Vis/NIR spectroscopy, cyclic voltammetry (CV), and transient photocurrent measurements, and a quantum confinement effect is clearly revealed. Furthermore, the fabrication of hybrid solar cells based on a blend of SnSe nanowires and poly(3hexylthiophene) (P3HT) is demonstrated. Colloidal SnSe nanowires were prepared from commercially available Sn[N(SiMe3)2]2, and trioctylphosphine selenide (TOP-Se) in oleylamine (OLA) or OLA/TOPO (trioctylphosphine oxide) solvent mixture by using monodisperse bismuth nanoparticles to catalyze the nanowire growth through the solution-liquid-solid (SLS) mechanism. In a typical synthesis, an injection solution consisting of Sn[N(SiMe3)2]2 (0.2 mmol) and Bi-nanoparticle catalysts (2.4 mmol) in octadecene (ODE, 600 mL) was introduced into a three-neck flask that contained a solution of TOP-Se (0.2 mmol) in OLA (4 g) or TOPO/OLA mixture (3.5 g/2.5 g) at 290 8C. The resulting reaction solution was kept at this temperature for 1–2 min before being cooled to room temperature. The product was cleaned and precipitated using hexane and isopropyl alcohol as the solvent and antisolvent, respectively. Finally the purified nanowires were dispersed in common organic solvents such as toluene. The scanning electron microscopy (SEM) image in Figure 1a shows the ensemble of randomly aligned SnSe nanowires with lengths exceeding 10 mm. The TEM image in Figure 1b displays smooth nanowires with mean diameters of (20.8 2.2) nm ( 10.6%), which correlates to the size of monodisperse Bi-nanoparticle catalysts (Figure S1 in the Supporting Information). The frozen Bi-nanoparticle seeds were usually observed at the nanowire tips (see arrows in the [*] Dr. S. Liu, Prof. W.-H. Zhang, Prof. C. Li State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences Dalian 116023 (China) and Dalian National Laboratory for Clean Energy Dalian 116023 (China) E-mail: whzhang@dicp.ac.cn canli@dicp.ac.cn

Solution‐Phase Synthesis and Characterization of Single‐Crystalline SnSe Nanowires

This review presents the advancement in synthesis and characterisation techniques of one-dimensional nanostructures (ODNS) as well as their potential for novel applications. In the first section of the review, the authors describe the synthesis techniques of one-dimensional nanostructures, i.e. template based synthesis, vapour phase growth, solution based growth and other innovative techniques. Various characterisation techniques such as scanning electron microscopy (SEM) and transmission electron microscopy (TEM) are described in detail, followed by a comprehensive review of the unique material properties of one-dimensional nanostructures. The final section of this paper presents current state of the art chemical and biological sensing applications as well as other potential technologies which may emerge due to the advantage nanomaterials have over their bulk counterparts.

Souhail Zekri

Papers

One-dimensional nanostructures : fabrication, characterisation and applications