Formation Of Long Nanowires Research Articles

Limited volume heating method: a simple low cost approach to synthesize additive free long nanowires

A new type of limited volume heating system (LVH) is designed for the enhancement of the efficiency of conventional hydrothermal method to obtain additive free long nanowires (NWs). In LVH system, the period of chemical reaction is enhanced due to the supply of fresh chemicals by the convection of precursors between different temperature zones. In this work, the performance of the LVH system is investigated by synthesizing an array of long zinc oxide (ZnO) NWs as a case study. Morphological characterizations revealed the formation of long NWs of different dimension with growth temperatures, precursor concentrations and growth durations. The length of the NWs is greatly influenced by the variation in growth time and temperature, whereas their diameter was controlled by changing precursor concentration. The growth of NWs is along (002) direction as revealed by X-ray diffraction and transmission electron microscopy studies. In this technique, the length of the NWs is increased upto five times in comparison to those grown by conventional global heating (CGH) method and thereby proving an enhanced performance of LVH system without any additives. Further, photoresponse behavior of the LVH grown long ZnO NWs is evaluated for ultraviolet detection, where photoresponse of 1.7 s and recovery time of 0.8 s is observed.

Organic‐Stabilizer‐Free Polyol Synthesis of Silver Nanowires for Electrode Applications

AbstractThe polyol reduction of a Ag precursor in the presence of an organic stabilizer, such as poly(vinylpyrrolidone), is a widely used method for the production of Ag nanowires (NWs). However, organic capping molecules introduce insulating layers around each NW. Herein we demonstrate that Ag NWs can be produced in high yield without any organic stabilizers simply by introducing trace amounts of NaCl and Fe(NO3)3 during low‐temperature polyol synthesis. The heterogeneous nucleation and growth of Ag NWs on initially formed AgCl particles, combined with oxidative etching of unwanted Ag nanoparticles, resulted in the selective formation of long NWs with an average length of about 40 μm in the absence of a capping or stabilizing effect provided by surface‐adsorbing molecules. These organic‐stabilizer‐free Ag NWs were directly used for the fabrication of high‐performance transparent or stretchable electrodes without a complicated process for the removal of capping molecules from the NW surface.

Organic-Stabilizer-Free Polyol Synthesis of Silver Nanowires for Electrode Applications.

The polyol reduction of a Ag precursor in the presence of an organic stabilizer, such as poly(vinylpyrrolidone), is a widely used method for the production of Ag nanowires (NWs). However, organic capping molecules introduce insulating layers around each NW. Herein we demonstrate that Ag NWs can be produced in high yield without any organic stabilizers simply by introducing trace amounts of NaCl and Fe(NO3 )3 during low-temperature polyol synthesis. The heterogeneous nucleation and growth of Ag NWs on initially formed AgCl particles, combined with oxidative etching of unwanted Ag nanoparticles, resulted in the selective formation of long NWs with an average length of about 40 μm in the absence of a capping or stabilizing effect provided by surface-adsorbing molecules. These organic-stabilizer-free Ag NWs were directly used for the fabrication of high-performance transparent or stretchable electrodes without a complicated process for the removal of capping molecules from the NW surface.

Effect of seeding modification of substrate on the growth and UV detection properties of ZnO nanowires

Effect of seeding modification of a glass substrate on the growth of ZnO nanowires and their UV detection properties have been investigated. Seeding functionalization was carried out by two methods including several times dip-coating inside a zinc acetate solution and coating of ZnO on the substrate by sputtering. The functionalized substrates then were used for growth of ZnO nanowires by chemical bath deposition. Various characterizations of the nanowires indicate that the seeding of both methods leads to formation of long nanowires with hexagonal cross section. The photocurrent measurement under UV illumination indicates the superiority of the sputtering pre-seeding due to its better crystalline nanowires and higher quantum efficiency for UV detection.

Rapid formation of single crystalline Ge nanowires by anodic metal assisted etching

Germanium nanowires are produced by a novel approach, combining two well known electrochemical and metal assisted chemical etching. The metal assisted etching procedure is enhanced by incorporation of HF in the catalytic solution and application of a constant bias to the substrate. Fast etching, caused by metal nanoparticles, facilitate pore nucleation for further pore growth. The improved current transport developed in the vicinity of the metal nanoparticles maintains a concentrated current density at the pore tip which results in an elongation of the pores in one direction and formation of long nanowires. With this new approach it is possible to fabricate nanowires with diameter below 100 nm and tens of micrometers long.

Oriented attachment growth of ultra-long Ag2Se crystalline nanowires via water evaporation-induced self-assembly

Ultra-long Ag2Se crystalline nanowires with lengths up to several hundred micrometers and diameters of 100–300 nm have been successfully fabricated by water evaporation-induced growth method at 120 °C for 6 h. Experiments have revealed that the growth of Ag2Se crystalline nanowires is dominated by oriented attachment mechanism. The continuous water evaporation plays an important role for the formation of long nanowires, since it can cause high overall supersaturation and crystallite–solution interfacial supersaturation in the system, which can induce secondary nucleation, and thus promote the oriented attachment growth of long crystalline nanowires. Therefore, it is promising that the water evaporation-induced growth method could be developed for the synthesis of other 1D inorganic nanomaterials.

Growth dynamics of low-dimensional CoSi2 nanostructures revisited: Influence of interface structure and growth temperature

The growth of cobalt silicide nanostructures on clean Si(001) was studied using scanning tunnelling microscopy and transmission electron microscopy. Two types of CoSi2 nanostructures, flat and ridge-type islands, were formed when 0.1ML Co was deposited onto clean Si(001) between 500°C and 800°C. These islands form elongated islands along [110] directions and grow into the Si-substrate within the temperature range. The formation of the two types of islands arises primarily due to the type of CoSi2{111}–Si{111} interface formed between the island and the substrate. Flat islands are bound by CoSi2{111}–Si{111} Type-A interfaces such that CoSi2(001)//Si(001) and CoSi2[001]//Si[001]. Ridge islands, on the other hand, are bound by a “twinned” CoSi2{111}–Si{111} Type-B interface such that CoSi2(221)//Si(001) and CoSi2[11¯0] //Si[11¯0]. This leads to the formation of three less energetically-favourable interfaces: CoSi2(1¯1¯1¯)–Si(115¯), CoSi2(1¯1¯2¯)–Si(112¯), and CoSi2(1¯1¯5¯)–Si(111¯). Analysis of the interfacial energies through dangling bond counting per interfacial area for each interface shows that the formation of the Type-B interface is energetically more favourable compared to the rest of the interfaces. As a result, the island elongates preferentially along the Type B interface leading to the formation of long nanowires with large length–width aspect ratio of 20:1. However, this formation is only achieved at high growth temperatures due to the presence of corner-barriers constraining the growth at low temperatures. Conversely, flat islands are slightly elongated at low growth temperatures with aspect ratio reaching 7:1 at 650°C. As temperature increases towards 760°C, they are brought closer to equilibrium and hence become less elongated with aspect ratio reduced to 1.6:1.

Self-Assembling Branched and Hyperbranched Nanostructures of Poly(3-hexylthiophene) by a Solution Process

As a typical linear conjugated polymer, poly(3-hexylthiophene) (P3HT) has been successfully used in organic electronic and optoelectronic devices. Strong anisotropic π−π interactions between planar molecular backbones and weak van der Waals interactions between their alkyl side groups make P3HT favorable for the formation of long nanowires. Herein, we propose a facile solution strategy to prepare branched and hyperbranched P3HT nanostructures. A P3HT nanowire was first generated as the trunk, and then branches formed by a heterogeneous nucleation process. The process was realized by a slow evaporation of P3HT in a blend solvent, in which 1,2-dichlorobenzene acted as a good solvent and trimethanolamine acted as a poor solvent. Interestingly, the hyperbranched P3HT nanostructures can be produced using the same principle by changing the evaporation conditions. The molecular direction of P3HT in the trunks and branches was determined clearly by selected area electron diffraction. Due to its good crystallinity and unique morphology, branched and hyperbranched nanostructures might have potential opportunities for organic electronic and optoelectronic devices.

Synthesis and characterization of silver phthalocyanine nanowires and nanobelts

Thermal evaporation technique has been employed to grow silver phthalocyanine nanostruc- tures on glass substrates kept at different substrate temperature in vacuum of 10 �5 Torr. These samples have been studied for their structural and optical properties. TEM investigations show the formation of long nanowires in AgPc thin films prepared at substrate temperature of 298 and 303 K, whereas films prepared at 308 K show the formation of nanobelts. XRD observations reveal that silver phthalocyanine nanowires are crystalline in nature. The significant blue shift in the UV-VIS absorption spectra of the silver phthalocyanine nanowires in comparison to bulk sample, indicate of effect of quantum confinement. PACS. 71.20.Rv Polymers and organic compounds - 68.55.-a Thin film structure and morphology - 78.66.-w Optical properties of specific thin films