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For any future cost-effective applications of inorganic nanostructures, in particular, hybrid photovoltaic cells, it is essential that these inorganic nanomaterials be solution processable and selectively printable. This letter reports the selective growth of single-crystal ZnO nanostructures based on the microcontact printing of an inorganic nanocrystal seeding film. The pattern-transfer quality is dependent on the concentration of the inking solution. Variable yet controllable anisotropic growth of ZnO nanowires has been demonstrated on the transferred patterns of ZnO nanocrystal films. The patterning and growth of these highly ordered arrays of ZnO nanostructures employ a simple soft lithography technique and mild reaction conditions at low temperature and in the absence of harmful organic additives.

Hierarchical heterostructures of beta-iron oxyhydroxide (β-FeOOH) nanostructures on electrospun TiO2 nanofibers were synthesized by a facile hydrothermal method. This synthesis method proves to be versatile to tailoring of β-FeOOH structural design that cuts across zero-dimensional particles (TF-P), one-dimensional needles (TF-N) to two-dimensional flakes (TF-F). In addition, synthesizing such oxyhyroxide nanostructures presents the advantage of exhibiting similar functional performances to its oxides counterpart however, without the need to undergo any annealing step which leads to undesirable structural collapse or sintering. The as-prepared hierarchical heterostructures possess high surface area for dye adsorptivity, efficient charge separation and visible photocatalytic activity. Also, for the first time, hydrogen gas sensing has been demonstrated on β-FeOOH nanostructures at room temperature. The reported hierarchical heterostructures of β-FeOOH on TiO2 nanofibers afford multiple functions of photocatalysis and sensing which are highly promising for environment monitoring and clean up applications.

SnO2/ZnO hierarchical heterostructures have been successfully synthesized by combining electrospinning technique and hydrothermal method. Various morphologies of the secondary ZnO nanostructures including nanorods (NRs) and nanosheets (NSs) can be tailored by adding surfactants. Photocatalytic performance of the heterostructures was investigated and obvious enhancement was demonstrated in degradation of the organic pollutant, compared to the primary SnO2-based nanofibers (NFs) and bare ZnO. Furthermore, it was found that the H2 evolution from water splitting was achieved by photocatalysis of heterostructured nanocomposites after sulfurization treatment. This synthetic methodology described herein promises to be an effective approach for fabricating variety of nanostructures for enhanced catalytic applications. The heterostructured nanomaterials have considerable potential to address the environmental and energy issues via degradation of pollutant and generation of clean H2 fuel.

Coaxial crystalline nanowires have been synthesized by chemical vapor deposition. Recrystallization of a copper substrate provided a natural template for the self-assembled growth of nanowires. The core of the wires is made up of numerous faceted SiC nanowires typically 20−50 nm in diameter, encapsulated by larger hollow wires typically 0.2−1.0 μm in diameter. The nanowires are crystalline and catalyst free. A vapor−solid growth mechanism is proposed based on detailed morphology and structural characterization.

Several techniques have already been developed for synthesizing silicon carbide (SiC) material in the form of nanospheres and nanowires/rods. Here, we report the synthesis of a distinctly different kind of SiC nanostructure in the form of three-dimensional crystalline nanowire-based flower-like structures. Interest in such structures centres around the combination of a simple growth process based on SiC nanowire formation, with a resultant structure having potentially complex mechanical and optical properties, the latter a consequence of the wide band gap of bulk SiC. The synthesis of these SiC nanowire flowers is via a vapour–liquid–solid (VLS) process, on which a detailed study of both the chemical and structural composition has been carried out.

A piezoelectric power generator based on ZnO nanowire arrays (NWAs) is proposed for scavenging energy from low-frequency ambient vibration. A low-temperature and low-cost hydrothermal method is employed to grow the uniform ZnO nanowires with the diameters of ~ 70 nm and lengths of ~2.5 . A theoretical model is derived to better understand piezoelectric-energy harvesting and to predict the output performance of cylindrical ZnO NWAs. The open-circuit output voltages of the resonant generators at normal and shear modes are 1.1 and 3.59 mV, respectively.

Large-area, 2D, anisotropic, direct growth of nanostructures is considered an effective and straightforward way to readily fulfill transparent, flexible technology requirements. In addition, formation of thin hybrid structures by combining with another 2D material brings about dimensional advantages, such as intimate heterostructure functionalities, large specific area, and optical transparency. Here, we demonstrate 2D planar growth of thin Ni(OH)2 nanosheets on arbitrary rigid and soft supports, by exploiting the growth strategies of oriented attachment induced by interfacial chemistry and the intrinsic driving force of layered structure constitution. Moreover, large-scale 2D heterohybrids have successfully been prepared by direct conformal growth of Ni(OH)2 nanosheets overlying MoO3 nanobelts. Unlike the exfoliation and transfer of 2D materials technique, this approach minimizes multiple process contamination and physical-handling structural defects. Accordingly, proof-of-concept flexible electrochromism is demonstrated in view of its prerequisite to the access of a large homogeneous material coating. The as-synthesized 2D layered structure affirms its optical and electrochemical superiority through the display of wide optical modulation, high coloration efficiency, good cyclic stability, and flexibility.

In this paper, we demonstrate a facile design of ZnS-based heterostructures tailored by versatile glucose-derived carbon ensembles, including carbon dots (CDs) and thin carbon shells, via hydrothermal synthesis. Tuning the content of glucose allows interesting and simple conversion from CDs to carbon shells on the surfaces of ZnS nanospheres. The as-formed ZnS/carbon nanocomposites exhibit an enhanced hydrogen evolution rate, up to 4.9 times over bare ZnS nanospheres, from sacrificial photocatalytic water splitting under solar light. The upconverted photoluminescence properties of the carbon nanomaterials, coupled with favorable electron transfer ability, are responsible for the improved photocatalytic behavior. Additionally, the difference in the hydrogen rates between CDs and the carbon shell was discussed. The inexpensive and convenient strategy may offer new prospects in the engineering of desirable nanostructures with better performance.

Silicon nanoparticles at different doping concentrations are investigated for tuning their optical nonlinear performance. The silicon nanoparticles are synthesized from doped silicon wafers by pulsed laser ablation. Their dispersions in water are studied for both nonlinear absorption and nonlinear refraction properties. It is found that the optical nonlinear performance can be modified by the doping concentration. Nanoparticles at a higher doping concentration exhibit better saturable absorption performance for femtosecond laser pulse, which is ascribed to the free carrier absorption mechanism.

Well-aligned multiwalled nanotubes (MWNTs) have been deposited by plasma-enhanced chemical vapor deposition of acetylene (C2H2) on nickel-coated quartz glass at 650°C. The growth reaction of the carbon nanotubes was found to be dependent on the morphology of the metal catalyst, which was related to the thickness of the Ni catalyst film. The flow rate of the hydrocarbon gases was observed to be crucial for the growth of high density carbon nanotubes. Well-aligned and dense carbon nanotubes were grown uniformly on 15-nm thick Ni film with a flow rate of 15 and 30 sccm for C2H2 and NH3, respectively. Transmission electron microscopy confirmed the structures to be hollow with Ni particles encapsulated by the multi-walls at the tip of the nanotube.

This work focused on the development of a hybrid organic–inorganic TiO2 nanocomposite, which demonstrates the first ever report on harmful volatile organic compound (VOC) sensing and photocatalytic degradation–H2 production. The sensing and photocatalytic properties are enhanced by the synergetic effects of well-structured TiO2 nanotubes, metal nanoparticles and reduced graphene oxide loading for enhanced light absorption and charge-transfer kinetics. Hybridization of a functionalized TiO2 nanocomposite with a polyvinylidene fluoride (PVDF) matrix induced strong cross-linking networks between the inorganic–organic components, which promote mechanical reinforcement-flexibility and highly porous asymmetric structures. The developed solution processable nanocomposite has immense potential to remedy the global environmental and energy issues by producing clean water/air and energy from organic compound waste.

Flexible palladium-based H2 sensors have a great potential in advanced sensing applications, as they offer advantages such as light weight, space conservation, and mechanical durability. Despite these advantages, the paucity of such sensors is due to the fact that they are difficult to fabricate while maintaining excellent sensing performance. Here, we demonstrate, using direct nanoimprint lithography of palladium, the fabrication of a flexible, durable, and fast responsive H2 sensor that is capable of detecting H2 gas concentration as low as 50 ppm. High resolution and high throughput patterning of palladium gratings over a 2 cm × 1 cm area on a rigid substrate was achieved by heat-treating nanoimprinted palladium benzyl mercaptide at 250 °C for 1 h. The flexible and robust H2 sensing device was fabricated by subsequent transfer nanoimprinting of these gratings into a polycarbonate film at its glass transition temperature. This technique produces flexible H2 sensors with improved durability, sensitivity, and response time in comparison to palladium thin films. At ambient pressure and temperature, the device showed a fast response time of 18 s at a H2 concentration of 3500 ppm. At 50 ppm concentration, the response time was found to be 57 s. The flexibility of the sensor does not appear to compromise its performance.

Here we have demonstrated the preparation of high-quality, monodispersed and tunable phases of Cu nanoparticles. Structural and chemical composition studies depict the evolution of Cu-Cu(2)O-CuO nanoparticles at various process stages. The loading of Cu and Cu oxide nanoparticles on TiO(2) catalyst has enhanced the photocatalytic H(2) production. Comparatively, H(2) treatment produces well-dispersed Cu nanoparticles with thin oxide shells that show the highest H(2) production amongst the samples. The relatively higher photocatalytic performance is deemed to result from reduced structural defects, higher surface area and dispersivity as well as favorable charge transfer, which inhibits recombination. The Cu nanoparticles are shown to be a promising alternative to noble metal-loaded TiO(2) catalyst systems due to their low cost and high performance in photocatalytic applications.

In this work, enhancement of ionic conductivity and long-term stability through the addition of diphenylamine (DPA) in poly(ethylene oxide) (PEO) is demonstrated. Potassium iodide (KI) is adopted as the crystal growth inhibitor, and DPA is used as a charge transport enhancer in the electrolyte. The modified electrolyte is used with titanium dioxide (TiO2) nanoparticles, which is systematically tuned to obtain high surface area. The dye-sensitized solar cell (DSSC) showed a photocurrent of 14 mAcm2 with a total conversion efficiency of 5.8% under one sun irradiation. DPA enhances the interaction of the TiO2 nanoparticle film and the I-/I3- electrolyte leading to high ionic conductivity (3.5 × 10-3 Scm-1), without compromising on the electrochemical and mechanical stability. Electrochemical impedance spectroscopy (EIS) studies show that electron transport and electron lifetime are enhanced in the DPA added electrolyte due to reduced sublimation of iodine. The most promising feature of the electrolyte is increased device stability with 89% of the overall efficiency preserved even after 40 days.

A facile large-scale synthesis approach for producing intrinsically p-type nanowires with uniform coverage of nanocrystals to form a highly interconnected porous nanowire network is of great demand for p-type sensing. Here, we have demonstrated synthesis of a very high aspect ratio (10(2)-10(5)) open network of interconnected hybrid nanocrystals-nanowire copper and copper oxide nanomaterials. The copper nanowire scaffold is employed to realize a porous and highly interconnected network of hybrid metal-metal oxide nanocrystal-nanowire structures. The structural and composition tunability of the hybrid nanomaterials is demonstrated. The hybrid copper-copper oxide nanowires exhibit enhanced gas/light sensing properties without any operating temperature. This may be attributed to enhanced medium diffusion due to the porous network of highly interconnected nanocrystal-nanowire structures.

Electronic structures, magnetic properties, and spin-dependent electron transport characteristics of C-doped ZnO nanowires have been investigated via first-principles method based on density functional theory and nonequilibrium techniques of Green's functions. Our calculations show that the doping of carbon atoms in a ZnO nanowire could induce strong magnetic moments in the wire, and the electronic structures as well as the magnetic properties of the system sensitively depend on partial hydrogenation. Based on these findings, we proposed a quasi-1d tunneling magnetic junction made of a partially hydrogenated C-doped ZnO nanowire, which shows a high tunneling magnetoresistance ratio, and could be the building block of a new class of spintronic devices.

Dye sensitized solar cells (DSSC) are attractive because they hold promise for devices that are easy to fabricate and inexpensive. In the present work, highly crystalline mesoporous TiO2 has been synthesized by evaporation induced self assembly (EISA) method using triblock copolymer Pluronic P123 as the organic template. The synthesized TiO2 is anatase in nature with a pore size of 10-15 nm. DSSC made from mesoporous TiO2 demonstrated solar conversion efficiency of ∼7%. This comes from the benefits of increased surface roughness, surface area and uniform porosity. In addition, well ordered and crystalline pores provided good sunlight absorption and low recombination path for charge carriers. To further enhance the efficiency of the DSSCs, light scattering centers were introduced in the mesoporous TiO2 film. Nanoparticles light scatterers are introduced to scatter the incoming light and hence to increase the light harvesting capability of the device. A 26 % increase in DSSC efficiency was observed with the implementation of scattering centers.

A maskless method of employing polymer growth inhibitor layers is used to modulate the conflicting parameters of density and alignment of multi-junction nanowires via large-scale low temperature chemical route. This low temperature chemical route is shown to synthesize multi-junction nanostructures without compromising the crystal quality at the interfaces. The final morphology of an optimized multi-junctions nanowire arrays can be demonstrated on various substrates due to substrate independence and low temperature processing. Here, we also follow-up on device demonstrations whereby p-n junction are created by exposure of secondary nanowires to ammonia plasma, converting them to p-type characteristics and also the density modulated multi-junction nanowires were tuned to infiltrate nanoparticles to create a hybrid hierarchically-structured nanowire/nanoparticles solar cell. The fabrication of hierarchically-structured nanowire/nanoparticles composites presents an advantageous structure, one that allow nanoparticles to provide large surface areas for the dye adsorption, whilst the nanowires can enhance the light harvesting, electron transport rate, and also the mechanical properties of the films. This work can be of great scientific and commercial interest since the technique employed is of low temperature (< 90 °C) and economical for large-scale solution processing, much valued in today’s flexible display and photovoltaic industries. In addition, ZnO nanostructures for gas sensing will be presented.

We present experimental evidence of nanojunction structures explicitly observed after application of high electric fields on multiwall carbon nanotube arrays. The electric field as well as thermal effects result in carbon–carbon bond breaking and redeposition leading to nanojunction formation. The growth mechanism of the nanojunction is believed to be open-ended topological defect growth in which carbon atoms at two adjacent nanotube tips chemically react and fuse forming an array of nanojunctions.

We describe the growth of gallium nitride nanoneedles synthesized via a self-catalytic process. Transmission electron microscopy studies confirmed the gallium nitride nanoneedles to be single-crystalline with a predominant (10–10) growth direction. The nanoneedles are facetted and no catalyst particles are observed at their tips. We propose that the nanowires formed from nanosized gallium droplets supersaturated with nitrogen, but under Garich conditions, the nanowires tapered to form nanoneedles. Excess Ga in the metallic droplets then reacted to form gallium nitride microcrystals.

A zinc oxide (ZnO) nanowire field effect transistor having the highest mobility and lowest subthreshold slope obtained to date (from ZnO) is reported. The device consists of a single nanowire with self-aligned gate electrodes having well defined nanoscale spacing, independent of lithographic definition. The fabricated device exhibits a transconductance of 3.06 /spl mu/S, a mobility of 450 cm/sup 2//Vs and a subthreshold swing of 129 mV/decade. The transistor also shows an on/off current ratio of 10/sup 6/.

The mean inner potentials of wurtzite GaN nanowires are measured using off-axis electron holography in the transmission electron microscope (TEM). The nanowires have a circular cross-section and are suspended across holes in a holey carbon film, resulting in an accurate knowledge of their thickness profiles and orientations. They are also free of the implantation and damage that is present in mechanically-polished ion-milled TEM specimens. The effect of a thin amorphous coating, which is present on the surfaces of the nanowires, on measurements of their mean inner potential is assessed. A value for the mean inner potential of GaN of (16.7 ± 0.3) V is obtained from these samples.

After the cost of ownership of tool, the next significant cost involved in nanoimprint lithography is that of mold fabrication. The cost of mold fabrication is proportional to the area of pattern and follows an inverse relationship with the pattern resolution. In this work, the authors demonstrate proof-of-concept fabrication of Si and SiO2 grating molds of variable feature sizes, spacings, densities, and aspect ratios that can be generated from a single Si master mold of 2 μm line and space features. This process utilizes “SiO2 resin,” which can be imprinted via in situ thermal free radical polymerization. Heat-treatment of the patterned resin resulted in loss of organics, formation of SiOx and gave rise to known feature size reduction (∼65%). After the pattern transfer using SiOx as the etch mask, a Si daughter mold containing 0.7 μm wide gratings with 3.3 μm spacing was generated. The process of imprinting and heat-treatment was repeated using the daughter mold, which regenerated a mold that approximates the master mold feature profile. Our technique demonstrates that submicron-sized features can be achieved from Si molds containing micron-sized features and vice versa. Such flexibility may lead to substantial reduction in the cost of mold fabrication.

In this paper, we demonstrate a series of metal-free and inexpensive TiO2/carbon dot (CD) nanocomposites via facile hydrothermal synthesis from bidentate complexes of a green carbon source, vitamin C (VC). Other than the importance of deriving CDs from alternate carbon materials instead of graphitic precursors, the in situ transformed CDs from VC ensure the formation of chemically coupled heterostructures, TiO2/CDs, which serve as efficient photocatalysts exhibiting a higher H2 evolution rate from photocatalytic reactions up to 9.7 times than that of bare TiO2. Interestingly, the H2 evolution rate can effectively be tuned by VC amounts, hydrothermal temperatures and reaction durations. The mechanism of the enhanced H2 evolution rate was also discussed, in which the synergetic effects of the hydrothermal treatment along with the favourable electron transfer ability and upconverted photoluminescence of CDs contribute to the improved photocatalytic behaviour.

One-dimensional TiO2 nanostructures of different structural phases with graphene composites were employed as photocatalysts for photocatalytic H2 production. Two strategies have been explored for enhancement of photocatalytic reactivity. The first is demonstrated through the use of one-dimensional nanostructures, which feature good vectorial electron transport due to decreased grain boundaries. The second strategy is to form a composite/network with two-dimensional reduced graphene oxide (RGO), which features visible light photosensitization and is an efficient charge transporter and separator. It is noted that other than structural design, it is crucial to attain anatase phase structures and superior interfacial contact between GO and TiO2 nanostructures to enable optimal synergy between one-dimensional TiO2 nanostructures and graphene for enhanced photocatalytic H2 production performance. In this work, hydrothermal synthesis and an in situ solution-based photoreduction method are used owing to their scalability, low temperature, high yield and ease of temperature and reactant concentration control characteristics.

We have demonstrated an environmentally friendly and template-free aqueous synthesis of hierarchically assembled 3D ZnO nanoflakes. The ZnO nanoflakes self-assembled to expose highly interconnected networks of well-defined catalytic active {0001} facets. Well dispersed Pt, Ag and Au metal nanoparticles were loaded to form hybrid ZnO nanoflakes for enhanced photocatalytic activity. The enhanced photocatalytic activity may be attributed to the synergetic effects of well-structured ZnO crystal facets, high metal nanoparticles dispersity, enhanced light absorption and charge-transfer kinetics which leads to high photocatalytic degradation.

In this work, we devised a simple optical technique that allowed the nucleation and growth of Ga:ZnO films grown via aqueous synthesis at 90 °C to be studied in situ. Our two fold objective was to study the nucleation processes and to acquire real-time information of the film thickness. In doing so, the growth parameters (e.g. temperature, precursor concentration, and time) could be optimized to give the maximum yield, coupled with the ability to control the film thickness with a greater measure of precision and accuracy. We further demonstrated that such a degree of control could be used to fabricate transparent conducting electrodes of low sheet resistance (

In this work, we have developed a nanocomposite graphene hydrogel (NGH) based on green chemistry, employing vitamin C (VC) to attain a supramolecular 3D network of hybrid nanostructured materials. Here, it is shown that the hydrogel is an appropriate and robust host for stable a TiO2 semiconductor catalyst sensitized with visible light responsive nanostructured particles. The NGH is tailored with well-defined nano-mesopores, a large surface area, a highly dispersive nanosheet–nanorods–nanoparticle composite, and enhance visible light absorption. Finally, we demonstrate practical applications of utilizing the NGH with water containing pores for photocatalytic H2 production. An important pragmatic consideration of using a NGH is the ease of separation and recovery of the nanosized catalyst after the photoreaction which would otherwise require extensive and expensive nanofiltration.

We present a versatile technique to create three dimensional graphene oxide (GO)-reduced GO (rGO) stacked-layered structure with the added attribute that micropatterns could be defined in each layer. We used focused laser beam to convert GO to rGO and create micropatterns of rGO on a heated substrate with GO spin-coated on it. The sample was then sonicated. Either the (1) micropatterned rGO (laser scanned region) or (2) micropatterned GO (unscanned region) could be preferentially removed depending on laser power and temperature of the substrate. A new layer of GO was then spin-coated and thus achieving 3D multilayered and patterned structure.

Problems associated with the costly production of Ga doped ZnO (Ga:ZnO) related to high-quality epitaxial films, which can only be grown on a lattice-matched single-crystal substrate using a vacuum system, have limited its wide-scale commercial applications. Moreover, for many practical applications, large-area devices must be fabricated on non-epitaxial glass, metal and other substrates. Here, we demonstrate a cost effective, low temperature aqueous synthesis, doping and transfer of high quality epitaxial Ga:ZnO on a non-epitaxial substrate. The capability of transferring epitaxial Ga:ZnO films may promote quick deployment of these high quality films for various electronic applications. We conclude the work with the demonstration of the Ga:ZnO films for gas sensing and dye-sensitized solar cell (DSSC) applications.

Despite the attractiveness of low temperature hydrothermal processes, the synthesis of vertical ZnO nanostructures has mostly been limited to rigid substrates. Moreover, patterned growth of nanostructures is also commonly carried out on rigid substrates, since conventional optical lithography is not easily applied to polymeric substrates, as focusing and reaction of the substrate with the organic solvent used in the lithography process prove to be a challenge. Here, we demonstrate the limited work on laser writing lithography patterned growth instead of the commonly used soft lithography patterned growth of nanorods on the transparent flexible substrate polyethylene terephthalate (PET) with a practical device demonstration. The visibly-transparent nanorods on the PET platform constitute a superior structural integrity with ohmic electro-conductivity even in a highly bent state. Accordingly, this can pave the way towards integration of vertically-aligned 1D nanostructures on a flexible platform for a transparent, conformable, shock-proof and lightweight product.

Transparent conducting Ga : ZnO films were synthesized directly on glass substrates via a low-temperature aqueous route for application in dye-sensitized solar cells. Preliminary electrical and optical characterization of the films showed that 85% transparency across the optical range with sheet resistances as low as 15 Ω sq−1 were achievable, making them comparable to commercial transparent conducting oxides. Novel non-planar transparent conducting electrodes consisting of pillars, cross-hatched trenches and pit structures were fabricated to produce films with increased surface roughness and enhanced light scattering capabilities which are essential for photovoltaic applications. The work concludes with proof of concepts demonstrating the feasibility of large-scale fabrication and the compatibility of the electrodes for dye-sensitized solar cells.

In this work, we demonstrate that graphene oxide (GO) can be reversibly converted to reduced-graphene-oxide (rGO) through the use of electric current. Strong electric field could cause ionization of water molecules in air to generate H+ ions at cathode, causing GO to be reduced. When the bias is reversed, the same electrode becomes positive and OH− ions are produced. According to Le Chatelier Principle, it then favors the reverse reaction, converting rGO back to GO, GO+2H++2e−=>rGO+H2O. X-ray spectroscopy and Raman spectroscopy were carried to verify the conversion reversibility in the reversed process.

Though the fabrication of ZnO nanostructures is economical and low temperature, the lack of a facile, reliable and low temperature methodology to tune its electrical conductivity has prevented it from competing with other semiconductors. Here, we carried out surface modification of ZnO nanowires using ammonia plasma with no heat treatment, and studied their electrical properties over an extended time frame of more than a year. The fabrication of flexible devices was demonstrated via various methods of transferring and aligning as-synthesized ZnO nanowires onto plastic substrates. Hall measurements of the plasma modified ZnO nanowires revealed p-type conductivity. The N1s peak was present in the X-ray photoelectron spectrum of the surface modified ZnO, showing the presence of ammonia complexes. Low temperature photoluminescence showed evidence of acceptor-bound exciton emission. The resulting electrical devices, a chemical sensor and p-n homojunction, show the tunable electrical response of the surface modified ZnO nanowires.

A maskless method of employing polymer growth inhibitor layers is used to modulate the conflicting parameters of density and alignment of multi-junction nanowires via large-scale low temperature chemical route. This low temperature chemical route is shown to synthesize multi-junction nanostructures without compromising the crystal quality at the interfaces. The final morphology of optimized multi-junctions nanowire arrays can be demonstrated on various substrates due to substrate independence and low temperature processing. Here, we also fabricated devices based on density modulated multi-junction nanowires tuned to infiltrate nanoparticles. The fabrication of hierarchically structured nanowire/nanoparticles composites presents an advantageous structure, one that allows nanoparticles to provide large surface areas for dye adsorption, whilst the nanowires can enhance the light harvesting, electron transport rate, and also the mechanical properties of the films. This work can be of great scientific and commercial interest since the technique employed is of low temperature (90 degrees C) and economical for large-scale solution processing, much valued in today's flexible display and photovoltaic industries.

One-dimensional titanate and titania nanostructures are prepared by hydrothermal method from titania nanoparticles precursor via hydrolysis and ion exchange processes. The formation mechanism and the reaction process of the nanobelts are elucidated. The effects of the NaOH concentration, HCl leaching duration and the calcination temperature on the morphology and chemical composition of the produced nanobelts are investigated. Na+ ions of the titanate nanobelts can be effectively removed by longer acid leaching and neutralization process and transformed into metastable hydrogen titanate compound. A hybrid hydrogen titanate and anatase titania nanobelts can be obtained under dehydration process of 500 °C. The nanobelts are produced in gram quantities and easily made into nanostructure paper for the bulk study on their electrical and sensing properties. The sensing properties of the nanobelts sheet are tested and exhibited response to H2 gas.

The microstructure of β-FeSi 2 films grown on Si using magnetron sputtering has been examined using various electron microscopy techniques. After annealing, the differences in interfacial roughness and grain size with different target materials are investigated using secondary electron and transmission electron microscopy techniques. Here, we study the variation in microstructures with sputtered materials. We observed, for Fe sputtered onto Si followed by rapid thermal anneal, the formation of nanosized FeSi 2 grains (∼120 nm) with a rough surface and film/Si interface. These morphologies and microstructure are very different when FeSi 2 is sputtered onto Si and annealed; instead, the formation of micrometer FeSi 2 grains (∼1 to 5 μm) with sharp surfaces and interfaces is observed. In addition, the effect of oxygen on the growth of FeSi 2 has also been studied. Our results show that oxygen impurities in the films result in the formation of Si x O y nanoparticles in the FeSi 2 matrix upon anneal.

Several important synthetic parameters such as precursor concentration, rate of evaporation and reaction time are found to determine the growth of ZnO nanostructures. These reaction parameters can be tailored and tuned to produce a variety of nanostructures ranging from nanoparticles, nanorods and nanospheres. The nanorods are structurally uniform made up of crystallographically oriented attached nanoparticles while the nanospheres are made up of several closely packed and randomly aligned nanocrystallites. XRD spectra of both the nanoparticles and nanorods exhibit typical diffraction peaks of a well-crystalline wurtzite ZnO structure. Finally, solar cells made up of ZnO nanoparticles and nanorods electrodes with absorbed ruthenium dye (N3) were measured to have a power conversion efficiency of 0.87% and 1.32%, respectively.

We describe the formation of a ferromagnetic Fe-rich germanide layer by a two-step process involving magnetron sputtering and annealling. A thin epitaxial iron (epi-Fe) film is deposited on the Ge (001) substrate and then annealed at 275 ◦ C in nitrogen inducing germanide formation. Surprisingly, we observe an enhancement in saturation magnetization in germanide films. Secondary ion mass spectroscopy and x-ray diffraction confirm the formation of a thin Fe-rich germanide layer whilst high resolution transmission electron imaging suggests it to be Fe3Ge. (Some figures in this article are in colour only in the electronic version)

A high-yield synthesis of SnO(2) nanoparticles via a facile, economical and easily scalable solid-state molten salt synthesis method has been demonstrated. The inorganic additive, molar ratios of chemicals and annealing temperature were found to control the size and porosity of the SnO(2) nanoparticles. The synthesized SnO(2) nanostructures were uniform, well dispersed and exhibited high crystallinity. Hydrogen sensors made from the SnO(2) nanoparticles were found to possess high sensitivity and stability. Other than tailoring the material's structure in terms of size and porosity, another potential method of enhancing the gas sensitivity is functionalization with noble Pd metal.

A field effect transistor (FET) using a zinc oxide nanowire with significantly enhanced performance is demonstrated. The device consists of single nanowire and self-aligned gate electrodes with well defined nanosize gaps separating them from the suspended nanowire. The fabricated FET exhibits excellent performance with a transconductance of 3.06μS, a field effect mobility of 928cm2∕Vs, and an on/off current ratio of 106. The electrical characteristics are the best obtained to date for a ZnO transistor. The FET has a n-type channel and operates in enhancement mode. The results are close to those reported previously for p-type carbon nanotube (CNT) FETs. This raises the possibility of using ZnO as the n-type FET with a CNT as the p-type FET in nanoscale complementary logic circuits.

TiO 2 hierarchical spheres synthesized via solvothermal method were decorated with Ag 2 S nanoparticles as co-catalyst at room temperature. The Ag 2 S nanoparticles improved the charge separation efficiency, thereby reducing recombination and enhancing the photocatalytic performance. The optimized Ag 2 S loading on TiO 2 could produce hydrogen (H 2 ) gas at an evolution rate of 707.6 μmol h -1 g -1 and degrade methyl orange with a rate constant of 0.018 min -1 . The composite material presents properties which are highly promising for environmental clean up and clean energy generation applications.