ZnO Nanorod Template Research Articles

Annealing induced solid-state structure dependent performance of ultraviolet photodetectors made from binary oxide-based nanocomposites

In this study, one-dimensional core–shell nanorods of ZnO–TiO2 (ZnO–TiO2 nanorods) were successfully prepared through the atomic layer deposition of amorphous TiO2 ultra-thin films onto ZnO nanorod templates. The subsequent postannealing procedures at 400–800 °C induced core–shell nanorods to transform into high quality crystalline wurtzite ZnO-anatase TiO2 and wurtzite ZnO-cubic Zn2TiO4 (ZnO–ZTO) nanorods. Structural analyses revealed that the surfaces of the ZnO–ZTO nanorods are more irregular and rougher than those of ZnO–TiO2 nanorods. Moreover, ZnO–ZTO nanorods have a higher oxygen vacancy size near the nanostructure surfaces because of a relatively high-temperature solid-state reaction. The surface electron depletion size is associated with the degree of nanorod crystal-imperfection defects, and this might affect the oxide nanorod ultraviolet photoresponse efficiency.

Photo-induced electron transfer at nanostructured semiconductor–zinc porphyrin interface

Electron transfer at metal oxide–organic dye interface on ZnO nanorod (ZnOr) templates was studied by femtosecond absorption spectroscopy method. Further confirmation of the electron transfer was obtained from photoelectrical studies. The fastest electron transfer from zinc porphyrin (ZnP) to semiconductor was observed for ZnOr modified by a 5nm layer of TiO2 (<0.2ps). The charge recombination processes were not affected by the TiO2 being faster than at the interface of TiO2 nanoparticle and ZnP. This indicates that the charge recombination depends mainly on semiconductor bulk properties whereas the charge separation is determined by the organic-semiconductor interface.

Fabrication of periodically aligned vertical single-crystalline anatase TiO2 nanotubes with perfect hexagonal open-ends using chemical capping materials

A vertically aligned anatase TiO2 (A-TiO2) nanotube array has been fabricated by coating a ZnO nanorod (NR) template with a TiO2 precursor solution. After coating, the ZnO NR cores were selectively etched in an acidic environment to form TiO2 nanotubes (NTs). More specifically, after growing the ZnO NRs via a hydrothermal method, one drop of the TiO2 precursor solution was cast to coat the ZnO NRs, the tops of which were previously covered with chemical capping materials by electrostatic interaction, and then the sample was sintered. Finally, the sample was immersed in an acidic solution resulting in selective etching of the ZnO NR cores. Thus, only TiO2 NTs remained on the substrate. The capping material is effectively used to create a perfect, hexagonal open-ended TiO2 NT array, which interestingly extends onset absorption towards the visible region.

Visible light-driven CdSe nanotube array photocatalyst

Large-scale CdSe nanotube arrays on indium tin oxide (ITO) glass have been synthesized using ZnO nanorod template. The strong visible light absorption in CdSe, its excellent photoresponse, and the large surface area associated with the tubular morphology lead to good visible light-driven photocatalytic capability of these nanotube arrays. Compared to freestanding nanoparticles, such one-piece nanotube arrays on ITO make it very convenient for catalyst recycling after their usage

Inverted Organic Photovoltaic Cells Using Three-Dimensionally Interconnected TiO&lt;SUB&gt;2&lt;/SUB&gt; Nanotube Arrays

Here we describe a simple sol-gel method to fabricate inverted organic photovoltaics (OPV) using interconnected TiO2 nanotubes (inter-TiO2 NT) as an efficient electron transport layer. Three-dimensionally inter-TiO2 NT arrays were prepared by spin-coating a TiO2 precursor solution on the ZnO nanorod (NR) template grown via the liquid phase deposition method. Upon etching of ZnO NRs, inter-TiO2 NT arrays were generated, as confirmed by X-ray diffraction (XRD), energy-filtering transmission electron microscopy (EF-TEM) and field-emission scanning electron microscopy (FE-SEM). A blend of poly(3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM) deeply infiltrated into the pores of inter-TiO2 NT, as revealed by FE-SEM and atomic force microscopy (AFM) images. The power conversion efficiency (PCE) of inter-TiO2 NT-based inverted OPV reached 3.0% at an air mass of 1.5 (100 mW/cm2), which is a 25% performance improvement compared to flat TiO2 films derived from the sol-gel process or commercial paste. The efficiency improvement arises from facilitated charge separation and collection due to the increased TiO2 interface arera and efficient transport pathway.

Self-Assembly of NiO-Coated ZnO Nanorod Electrodes with Core–Shell Nanostructures as Anode Materials for Rechargeable Lithium-Ion Batteries

A porous nickel hydroxide shell was self-assembled by hydrolysis of aqueous nickel chloride in the presence of hexagonal ZnO nanorod template at room temperature. The nickel hydroxide shell converted to cubic NiO after heat treatment at 500 °C. Galvanostatic charge and discharge results indicated that the NiO-coated ZnO nanorod electrode is capable of delivering a higher capacity than the bare ZnO nanorod and carbon-coated ZnO nanorod electrodes especially in high-rate charge and discharge processes. The presence of porous NiO shell might prevent the disintegration of ZnO nanorods because of the large volume change during charge and discharge. In addition, the porous NiO shell ensured good electrical contact of ZnO with the current collector and facilitated the charge transfer and transport of lithium ions. The amount of NiO coated on ZnO nanorods significantly affected the electrochemical performance of ZnO electrode toward lithium. Insufficient NiO shell would not provide enough electrical conductivity and protection against disintegration. When the NiO content was higher than 32.6 wt %, the electrode performance could be significantly improved.

Tailoring CoO–ZnO nanorod and nanotube arrays for Li-ion battery anode materials

Hydrothermal treatment of cobalt nitrate in the presence of ZnO nanorod templates results in the generation of free-standing CoO–ZnO composite arrays on a copper substrate. The result shows that tuning the molar concentration of cobalt nitrate can controllably prepare CoO–ZnO nanotube and ZnCo2O4 hierarchical nanorod structures. The electrochemical properties of the resultant nanorod and nanotube arrays are investigated. Due to the short insertion and extraction length for lithium ions, the free space between the adjacent tubes or rods, and the high contact area, the as-prepared one-dimensional CoO–ZnO composites exhibit excellent cycling performance and high capacities as anode materials for Li-ion batteries.

Template-guided growth of well-aligned ZnO nanocone arrays on FTO substrate

Well-aligned ZnO nanocone arrays (NCAs) were prepared on fluorine doped tin oxide (FTO) substrates using highly ordered ZnO nanorod arrays (NRAs) as templates to guide the growth via a hydrothermal method. In contrast, only disordered ZnO nanocones on FTO were obtained in the absence of the highly ordered ZnO nanorod templates. The well-aligned ZnO nanocone arrays were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), UV–visible absorption, and photoluminescence (PL) spectroscopies. It was found that the highly ordered ZnO NRAs pre-formed on FTO played a critical role in dictating the further growth of the well-aligned ZnO NCAs from them. Significantly, strong light-trapping effect was revealed for the well-aligned ZnO NCAs, which may find important applications in, e.g., photovoltaics.

Coaxial multi-shelled TiO2 nanotube arrays for dye sensitized solar cells

The performance of one-dimensional (1D) TiO2 nanotube based dye-sensitized solar cells (DSCs) was limited by the insufficient surface area of TiO2 nanotubes. To solve this issue, coaxial multiple-shelled TiO2 nanotube arrays were successfully synthesized on the transparent conductive oxide (TCO) substrates by using improved ZnO nanorod template assisted layer by layer absorption and reaction (LbL-AR) technique. To fabricate tube-in-tube nanostructures, LbL-AR TiO2 coatings were successively deposited on the exterior walls of the ZnO nanowires and the sacrificial sol–gel ZnO spacers, which were removed together by selective etching to form the hollow tubal structures. The performance of dye-sensitized solar cells (DSCs) increases with increasing the shell number of multi-shelled TiO2 nanotube photoanodes, attributed to the increase of the surface area, which was confirmed by N2 adsorption-desorption isotherms and the dye-loading capacities. A maximum efficiency of 6.2% was achieved for a quintuple shelled TiO2 nanotube photoanode with a short-circuit current density (Jsc) = 15 mA cm2, open-circuit voltage (Voc) = 0.73 V and fill factor (FF) = 0.57.

Fabrication of 3D interconnected porousTiO2 nanotubes templatedby poly(vinyl chloride-g-4-vinyl pyridine) for dye-sensitized solar cells

Porous TiO2 nanotube arrays with three-dimensional (3D) interconnectivity wereprepared using a sol–gel process assisted by poly(vinyl chloride-graft-4-vinylpyridine), PVC-g-P4VP graft copolymer and a ZnO nanorod template. A7 µm long ZnO nanorod array was grown from the fluorine-doped tinoxide (FTO) glass via a liquid phase deposition method. TheTiO2 sol–gel solutiontemplated by the PVC-g-P4VP graft copolymer produced a random 3D interconnection betweenthe adjacent ZnO nanorods during spin coating. Upon etching of ZnO,TiO2 nanotubes consisting of 10–15 nm nanoparticles were generated, as confirmed by wide-anglex-ray scattering (WAXS), energy-filtering transmission electron microscopy (EF-TEM) andfield-emission scanning electron microscopy (FE-SEM). The ordered and interconnectednanotube architecture showed an enhanced light scattering effect and increased penetrationof polymer electrolytes in dye-sensitized solar cells (DSSC). The energy conversionefficiency reached 1.82% for liquid electrolyte, and 1.46% for low molecular weight(Mw) and 0.74%for high Mw polymer electrolytes.

Hiearchical ZnO rod-in-tube nano-architecture arrays produced via a two-step hydrothermal and ultrasonication process

Vertically aligned hierarchical ZnO rod-in-tube nano-architecture arrays are produced via a two-step process including an initial hydrothermal reaction followed by ultrasonication growth. The ZnO nanorod arrays grow firstly on FTO glass through a hydrothermal process and then act as templates for the fabrication of rod-in-tube nano-architectures during ultrasonication. The as-prepared ZnO rod-in-tube nano-architectures are assembled by the self-stacking of hexagonal nanorings along with orientation of ZnO nanorod templates. Both hexamethylenetetramine and sodium citrate are found to play key roles in the formation of the novel ZnO rod-in-tube nano-architectures. The power conversion efficiency of dye-sensitized solar cell based on hierarchical ZnO rod-in-tube nano-architectures photoelectrode (0.91%) exhibits a significant improvement (75%) compared to that of ZnO nanorods (0.52%).

ランダム成長ZnOナノロッドによるプラズモン増強ラマン散乱

ランダム成長ZnOナノロッドによるプラズモン増強ラマン散乱

Enhanced Photovoltaic Performance of Nanostructured Hybrid Solar Cell Using Highly Oriented TiO2 Nanotubes

Highly oriented TiO2 nanotubes have been fabricated using ZnO nanorod template through liquid reactive deposition on the ITO substrates. The diameter and length of TiO2 nanotubes can be effectively controlled for the suitable use for a hybrid solar cell by varying the diameter and length of the ZnO nanorod template. A mixture of P3HT/PCBM was infiltrated into the gaps between TiO2 nanotubes to form hybrid solar cells. The open circuit voltage, short circuit current density, fill factor, and power conversion efficiency of the hybrid solar cell using highly oriented TiO2 nanotubes were 646 mV, 9.95 mA cm−2, 51.6%, and 3.32%, respectively, much higher than 1.2% of hybrid solar cell based on ZnO nanorods tested under otherwise identical conditions and significantly higher than 0.7% of the same type hybrid solar cells reported in literature. The enhancement of the power conversion efficiency could be resulted from the highly oriented TiO2 nanotubes with smaller diameter and large specific surface area for the ...

Functionalization of ZnO nanorods with γ-Fe 2O 3 nanoparticles: Layer-by-layer synthesis, optical and magnetic properties

Bifunctional magnetic–optical ZnO-γ-Fe 2O 3 hybrid nanomaterials have been synthesized via a layer-by-layer assembly technique on ZnO nanorod templates. X-ray diffraction, transmission electron microscope, field emission scanning electron microscope, high-resolution transmission electron microscope and X-ray photoelectron spectroscopy have been used to characterize the as-synthesized products. The photoluminescence spectra indicate that ZnO-γ-Fe 2O 3 hybrid nanomaterials exhibit enhanced UV emission and passivated defect emission. The magnetic property investigation reveals that ZnO-γ-Fe 2O 3 hybrid nanomaterials exhibit a superparamagnetic behavior.

A facile route to n-type TiO2-nanotube/p-type boron-doped-diamond heterojunction for highly efficient photocatalysts

Anatase TiO(2) nanotube (TiNT) arrays have been fabricated on a p-type boron-doped diamond substrate by a liquid phase deposition method using a ZnO nanorod template. The n-type TiNT/p-type diamond heterojunction structures which are realized show significantly enhanced photocatalytic activities with good recyclable behavior, with respect to the cases of sole TiNTs.

A Versatile Approach for the Synthesis of ZnO Nanorod-Based Hybrid Nanomaterials via Layer-by-Layer Assembly

A layer-by-layer (LBL) assembly approach has been developed to synthesize ZnO nanorod-based hybrid nanomaterials such as ZnO/CeO2, ZnO/CdS, and ZnO/Ag on ZnO nanorod templates at room temperature. The morphology, structure, and composition of the ZnO nanorod-based hybrid nanomaterials have been characterized by transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray powder diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analysis. It is indicated that a uniform coating layer consisting of homogeneous nanoparticles is deposited on the surface of ZnO nanorods due to the strong electrostatic attraction between metal ions and polyelectrolyte modified ZnO nanorods. The general approach presented here can be extended to the synthesize other one-dimensional (1D) nanostructure-based hybrid nanomaterials.

Controlled growth of ZnO nanorod templates and TiO2 nanotube arrays by using porous TiO2 film as mask

Porous TiO2 thin films obtained from sol–gel self-organize approach were firstly used as masks to control the growth of ZnO nanorod arrays by aqueous solution method. The effect of TiO2 pore size on the density of ZnO nanorod arrays was investigated by atomic force microscopy and field emission scanning electron microscope. The results show that the density of ZnO nanorod arrays obviously decreases after using porous TiO2 masks, and increases with increasing the TiO2 pore size. Additionally, the existence of TiO2 mask can also effectively prolong the wet-chemical etching time of TiO2 nanotube arrays manufactured from ZnO nanorod templates assisted sol–gel method, to completely remove the ZnO nanorod templates and to avoid collapsing of TiO2 nanotube arrays from the substrates.

TiO2 Nanotube Arrays by using ZnO Nanorod Template through Liquid Phase Deposition for Organic- Inorganic Hybrid Photovoltaic Cells

ABSTRACTTiO2 nanotube arrays had been selected as electron transport material incorporate with P3HT:PCBM blended polymer to fabricate the hybrid organic-inorganic solar cells. Well aligned TiO2 nanotube arrays has been synthesized though the liquid phase deposition by using ZnO nanorod arrays as templates. Three types of dyes (viz. NKX-2677, D149, N719) were adsorbed onto the surface of TiO2 nanotube arrays to increase the interfacial contacts between the organic polymer and inorganic metal oxide. Surface modification with NKX-2677 exhibited remarkable improvement of the cell efficiencies in terms of current density, open circuit voltage, and fill factor as compared with those of other dyes.

Fabrication of TiO 2 nanotubes by using electrodeposited ZnO nanorod template and their application to hybrid solar cells

Vertically aligned TiO 2 nanotubes have been fabricated on the indium-doped tin oxide (ITO) by a simple and versatile technique using the electrochemically deposited ZnO nanorods, oriented along the c-axis, as a template in the spin-on based sol–gel reaction of a Ti precursor. The diameter, length, and shape of TiO 2 nanotubes were controlled by changing the initial ZnO nanorod template and the spin conditions during sol–gel process of a Ti precursor. Scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) analysis, and X-ray diffraction (XRD) were used to confirm the successful formation of TiO 2 nanotubes and characterize their structure and morphology. Furthermore, as an application of the TiO 2 nanotubes, hybrid solar cells based on TiO 2 and poly[2-methoxy,5-(2′-ethyl-hexyloxy)1,4-phenylenevinylene] (MEH-PPV) were successfully fabricated.

The evolution of morphology of ordered porous TiO2 films fabricated from sol-gel method assisted ZnO nanorod template

Ordered porous TiO2 films, including TiO2 nanotube arrays, are fabricated by a sol-gel dip-coating approach via ZnO nanorod templates obtained from aqueous solution approach. The results indicate that the morphologies of ordered porous TiO2 films have been great affected by the sol-gel dip-coating cycle number. Open-ended TiO2 nanotube arrays can be obtained in optimum dip-coating cycle numbers. The TiO2 nanotubes with the inner diameter matching well with the diameters of ZnO nanorods, are well assembled and separate each other. When the cycle number is less than this optimum value, no intact porous TiO2 film can be obtained. As the cycle number is larger than this optimum value, an ordered porous TiO2 film with many throughout holes is formed. The evolutive mechanism of ordered porous TiO2 films is proposed.