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High density Mn-doped ZnO nanorod arrays were vertically grown on ITO substrate via hydrothermal reaction at relatively low temperature of 95 °C. The microstructure and magnetism of the arrays have been examined. Field emission scanning electron microscopy shows that the nanorods of 100 nm diameter and 1 μm length grow along the [001] direction. X-ray photoemission spectroscopy demonstrates that Mn is successfully doped into the nanorods. Meanwhile, all the Mn-doped ZnO nanorod arrays are ferromagnetic at room temperature. It is also found that the value of the saturation magnetization (Ms) of the ZnO nanorod arrays firstly increases with increasing the Mn concentration and then decreases. The higher Ms value is 0.11emu/g, which is obtained in the 5 at.% Mn-doped ZnO nanorod arrays. The ferromagnetism comes from the ferromagnetic interaction between the Mn ions, which partly replace Zn ions.

The highly ordered TiO2 thin films are prepared by anodic oxidation and calcined at 300, 400, 500 and 600 °C, respectively. X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) are employed to analyze the structure and the morphology of the TiO2 films. We design a novel sensor to investigate the humidity sensing behaviours of the samples. The samples calcined at 600 °C show high sensitivity with nearly two orders change in the resistance and short response and recovery time (

The BaMgAl 10 O 17 :Eu 2+ (BAM) as an efficient blue-emission phosphor has been used in tricolor fluorescent lamps (FLs) and plasma display panels (PDPs) because it has a deep blue color and a short decay time, but in the process of FL manufacturing, BAM, which spreads on the insides of a glass tub, is heated at 700–750 °C in air. The PDP manufacturing process also heats phosphor at 500–600 °C to make phosphor layers. These heat-treatments result in the luminance decrease. In this work, the BAM phosphors are covered with uniform and continuous MgO coatings via a precipitation route, which is expected to inhibit their surface oxidation. The results indicated that thermal stability was largely improved.

A facile and low-cost synthesis route was used to synthesize inorganic fullerene-like (IF) MoS 2 nanoparticles by reaction of sulfur powder and ammonium molybdate in a hydrogen atmosphere at 600 °C. As-synthesized IF-MoS 2 nanoparticles are of a closed hollow cage structure with size of 10–20 nm. Nanowires and nanotubes were also obtained at the same annealing temperature. The composition, structure, and morphology of the products were characterized by XRD, Raman, and TEM and the possible growth mechanism is proposed.

Large-scale uniform dumbbell-like ZnO microcrystals were successfully synthesized via a facile solution method under mild conditions. The as-prepared dumbbells, with lengths of 3.5-5.4 microm and diameters of 1.3-1.8 microm, possess a single-crystal hexagonal structure and grow along the [0001] direction. The influence of the reactant concentration on the size and shapes of the ZnO samples had been studied, and the results revealed that the reactant concentration plays a crucial role in determining final morphologies of the samples. Moreover, the evolution process of the dumbbell-like ZnO microcrystals was viewed by field-emission scanning electron microscopy (FE-SEM) characterization, and a possible formation mechanism was proposed. In addition, optical properties of the ZnO samples prepared at different reaction times were also investigated by photoluminescence (PL) spectroscopy. The room-temperature PL spectrum of the dumbbell-like ZnO microcrystals shows a strong UV emission peak. The UV emission is further identified to originate from the radiative free-exciton recombination by the temperature-dependent PL.

Monodispersed single-crystalline SnO2 nanocubes with exposed a large percentage of high-energy surfaces have been synthesized by a simple solvothermal process at low temperature without any templates and catalysts. The as-prepared samples have been characterized by X-ray diffraction and transmission electron microscopy. Many outstanding characters of the final products have been shown, such as uniform particle size, high purity, and monodispersity. In property, superior gas-sensing properties such as high response, rapid response-recovery time, and good selectivity have also been shown to ethanol at an optimal working temperature of as low as 280 °C. It indicates that the as-prepared SnO2 nanocubes are promising for gas sensors.

Metal–semiconductor composite microstructures have recently been demonstrated to possess potential applications due to their unique structures. Ag–Cu2O composite microstructures (Ag–Cu2O CMSs) with tunable silver content have been synthesized with a facile in situ method. Ag contents on the surface of Cu2O can be tuned through the variation of the concentration of AgNO3, which further greatly affected the surface-enhanced (resonance) Raman scattering (SE(R)RS) performance. The Ag–Cu2O CMSs prepared with 0.4 mM AgNO3 show the optimum SE(R)RS properties, better than pure Ag NPs. Furthermore, the enhancement mechanism and uniformity of Ag–Cu2O CMSs are investigated in detail.

Semiconductor/metal composite nanomaterials have been used as surface-enhanced Raman scattering (SERS) active substrates and have attracted increasing attention due to their widespread applications in both optical and material fields. Here, we report a facile strategy to prepare highly sensitive SERS substrates with excellent reproducibility and stability based on uniform and well-controlled Ag nanoparticle (NP) decorated Cu2O nanoframes. Our strategy is a unique one-pot procedure. Simply, hollow Cu2O/Ag composite nanoframes (Cu2O/Ag CNFs) with tunable silver content have been successfully designed and constructed by reduction of Ag+ with sodium citrate in a 14 day old Cu2O-containing mother solution, and then a second component (Ag) was directly deposited onto primary nanomaterials (Cu2O nanoframes). There is an optimum amount of Ag NPs. When 0.40 mM AgNO3 is used, the prepared Cu2O/Ag CNFs show significantly improved SERS properties with an enhancement factor of ~105. Furthermore, the enhancement mechanism, reproducibility and stability of Cu2O/Ag CNFs are investigated in detail. The excellent properties of the prepared Cu2O/Ag CNFs suggest that this substrate has a potential application in SERS detection.

In this work, [110] oriented ZnO nanosheet (ZnONS) array films with a large percentage of high-energy {0001} surfaces were prepared for the first time with the assistance of sodium citrate. ZnONS array films possess prominent UV–visible absorption with an absorption edge at ~405 nm, indicating that the optical property of the semiconductor is dependent on a specific crystal structure and crystal plane. CdS and CdSe quantum dots (QDs) were assembled onto ZnONS array films to form a cascade structure of ZnONS/CdS/CdSe by the successive ionic layer adsorption and reaction method. The as-fabricated photoanode exhibits strong absorption in the visible spectrum up to 735 nm. With light illumination, the optimum photoanode yields a photocurrent of ~4.40 mA cm−2 at 0 V versus SCE, which is about 4.6 times of that of pure ZnONS samples. The excellent photoelectrochemical (PEC) properties of our photoanodes suggest that the QDs sensitized ZnONS array films with a large percentage of high-energy surfaces have potential applications in PEC solar cells.

Oriented and high-density n-type CdS nanorod arrays were successfully embedded in p-type PbS absorber layers by a facile and low-cost hydrothermal method and a chemical bath deposition method. The structural, optical and electrical properties of these samples were examined, and the results demonstrated that the high quality three-dimensional heterostructure was obtained. Further investigation revealed that the three-dimensional heterostructure possessed superior optical absorption property due to the optical scattering from the nanorod array. In addition, photovoltaic property measurements demonstrated that the energy conversion efficiency of the novel three-dimensional heterojunction solar cell was increasing by 35% in comparison with the standard planar heterojunction solar cell. The observed improvement is mostly attributed to the three-dimensional heterostructure enabling increased heterojunction area, improved charge carrier collection and enhanced optical absorption ability. This study demonstrates that the three-dimensional heterostructure has potential application in thin film solar cells, and the solution process represents a promising technique for large-scale fabrication of these novel solar cells.

A novel perpendicularly aligned CdTe array with cauliflower-like morphology was fabricated on a Ni substrate using a simple electrochemical synthesis method. The samples were characterized by XRD, EDX and FESEM, and the results demonstrate that a high-purity, uniform cauliflower-like CdTe array was obtained. Rod lengths can reach to 3.0 μm, with nanoparticles stacking along the rod growth direction, keeping the diameter at 1.5 μm. A schematic diagram of the possible growth process and evolution from CdTe seed nuclei to the cauliflower-like CdTe array was proposed. The device based on the aligned array-on-Ni configuration demonstrates excellent photoelectrical properties, which is ascribed to the large absorption coefficient of the material and also suggests good electronic structure quality of the cauliflower-like rods. The technique described is applicable to fabricate highly aligned cauliflower-like semiconductor arrays on other conductive substrates.

A TiO2 nanotubes array film with nanowires directly formed on top (denoted as TiO2 NTWs) was prepared by an anodization method (potentiostatic anodization growth). Bi2S3 QDs were sensitized on the CdS/TiO2 NTWs array by a simple successive ionic layer adsorption and reaction (S-SILAR). A short-circuit photocurrent density of 2.16 mA cm−2 was obtained under an illumination of AM 1.5 G. The data of the photoelectrochemical performance test show that Bi2S3/CdS co-modification can boost the photocurrent density of the bare TiO2 NTWs by up to 308%. The photocatalytic activity was tested by treating rhodamine B (RhB) and methyl orange (MO) solutions, which were degraded completely after 240 min and 210 min, respectively. The present study shows the Bi2S3/CdS/TiO2 NTWs array can be applied in photocatalytic devices, and the greatest advantages are low-cost, easy reuse and recyclability.

It is reported here that a wheat-like CdSe array on an ITO substrate has been developed by a simple electrochemical synthesis method. These samples were characterized by XRD, EDX and FESEM, whose results demonstrate that a high-purity, uniform hexagonal wheat-like CdSe array was obtained. Photoelectrochemical solar cells are constructed using the wheat-like CdSe array as the photoanode in a polysulphide electrolyte and their power output characteristics are studied. The photoelectric conversion efficiency of the photoelectrochemical solar cells based on the wheat-like CdSe array on an ITO substrate, which are prepared in electrolyte solution containing CdSO4 (0.01 M) + Na2SeO3 (0.01 M) + H2SO4 (0.208 M), can reach a value of 1.15%.

A novel ZnO nanorod array (NR)/CuAlO2 nanofiber (NF) heterojunction nanostructure was grown on a substrate of Ni plates using sol–gel synthesis for the NFs and hydrothermal reaction for the NRs. Compared with a traditional ZnO/CuAlO2 laminar film nanostructure, the photocurrent of this fibrous network heterojunction is significantly increased. A significant blue-shift of the absorption edge and a favorable forward current to reverse current ratio at applied voltages of − 2t o+2 V were observed in this heterojunction with the increase of Zn 2+ ion concentration in the hydrothermal reaction. Furthermore, the photoelectrochemical properties were investigated and the highest photocurrent of 3.1 mA cm −2 was obtained under AM 1.5 illumination with 100 mW cm −2 light intensity at 0.71 V (versus Ag/AgCl). This novel 3D fibrous network nanostructure plays an important role in the optoelectronic field and can be extended to other binary or ternary oxide compositions for various applications. (Some figures in this article are in colour only in the electronic version)

Cuprous oxide (Cu2O), with various morphologies including nanosphere, quasi-cubic, type-I Cu2O, type-II Cu2O (as illustrated in the Experimental section), cube, and type-I nanoframe, has been synthesized selectively in high-yield by a simple solution-phase method. Among them type-I and type-II Cu2O with novel shapes are first reported. The synthesis procedure variables such as the amount of sodium mixture solution and reaction time are observed to influence the resultant shape of Cu2O nano/microstructures. The structures and morphologies of the obtained products are characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and high-resolution transmission electron microscopy (HRTEM) techniques. On the basis of the time-dependent experimental data, a possible formation mechanism is presented. Furthermore, compared to our previous work, type-I nanoframes are also obtained in a shorter time by stirring the resulting solution in air at room temperature, and the condition/theory for synthesis of Cu2O nanoframes and nanocages is supplemented too.

Well-defined cuprous oxide (Cu2O) thin film electrodes were electrodeposited on indium-doped tin oxide (ITO) substrates from a slightly acidic Cu(II) acetate solution. The morphologies of Cu2O film were tunable by altering the deposition potential, reaction time, solution temperature and the NaCl concentration. In particular, the Cu2O morphologies evolved from dendritic branching to cube-like with the increasing of the NaCl concentration. A growth mechanism was proposed according to the experimental results. In addition, a photocurrent of 0.06 mA cm−2, an open-circuit photovoltage (Voc) of 0.38 V, and a significant energy conversation efficiency of 0.01% were obtained under 100 mW cm−2 UV-visible illumination of the dendritic Cu2O thin film.

Seaweed-like titanium dioxide (TiO2) nanoarrays (STNAs) were grown on the surface of a titanium (Ti) sheet by hydrogen peroxide sculpture at low temperature. After calcination, the STNA transformed to highly crystalline anatase phase and exhibited a vertically standing structure, with an average length of 1.35–2.12 μm, leaves breadth of about 30–80 nm, and leaves thickness of about 10–15 nm. STNA-electrode dye-sensitized solar cells (DSCs) fabricated with dye C106 achieved an efficiency of 3.2% under irradiation of 100 mWcm‒2 air mass 1.5 global (AM1.5G) sunlight. Further research showed that the STNA-electrode DSC has much lower recombination rate (Kr) and longer electron life time (τn), thus making this STNA a potential candidate of electrode for fabricating high performance DSC.

One dimensional (1D), self-organized TiO2 nanotube arrays are known to have excellent charge transport properties and a NiO/TiO2 junction is efficient in separating electron–hole pairs. This paper describes the synthesis of a NiO/TiO2 junction electrode constructed using self-organized TiO2 nanotube arrays combining the above two properties. The self-organized TiO2 nanotube arrays used in this study were prepared by anodizing titanium films, which resulted in closely packed n-type TiO2 tubes with an inner pore diameter of 60–90 nm, a wall thickness of approximately 15 nm and a length of 600 nm. The NiO/TiO2 junction was synthesized by electroless plating and annealing which resulted in TiO2 nanotube arrays coated with a layer (about 200 nm in thickness) of NiO particles (20–40 nm). The resulting NiO/TiO2 junction electrode enabled us to obtain an enhanced photocurrent (3.05 mA cm−2) as compared with a TiO2 electrode based on TiO2 nanotube arrays (0.92 mA cm−2) under AM 1.5 G (100 mw cm−2) at a bias of 0.65 V.

Large-scale aggregative flowerlike ZnO nanostructures, consisting of many bunches of nanorods at different orientations with a diameter of about 60 nm and a length of 1 µm, have been synthesized through a simple hydrothermal process at a lower temperature. The x-ray power diffraction pattern indicates that the novel flowerlike ZnO nanostructures are hexagonal, and the selected area electron diffraction reveals that the ZnO nanorods are single crystal in nature and preferentially grow along [0 0 1]. Raman spectrum, room-temperature photoluminescence and UV–vis absorption spectra are also discussed. Furthermore, the influence of the reaction time on the morphology of the ZnO nanostructures is investigated, and a possible growth model is proposed. Finally, the gas sensor based on the ZnO nanostructures exhibits high sensitivity for ethanol as well as quick response and recovery time due to the high surface-to-volume ratio.

In this paper, Fe-doped TiO2 photocatalyst supported on hollow glass microbeads (Fe-TiO2/beads) is prepared by dip-coating method, which uses hollow glass microbeads as the carriers and tetrabutylorthotitanate [Ti(OC4H9)4] as the raw material. The phase structure, ingredient, morphologies, particle size and shell thickness of the products are characterized by X-ray powder diffraction (XRD), energy-dispersive spectroscopy (EDS) and field emission scanning electron microscope (FESEM). The feasibility of photocatylic degradation of Rhodamine B (RhB) under illumination of UV-vis light is studied. The results show that the core-shell structure catalyst is composed of Fe-doped anatase TiO2 and hollow glass microbeads, and the catalytic activity of the TiO2 is markedly enhanced by Fe ion doping. The optimum concentration of Fe ion is 0.1% (molecular fraction) in the precursor and the photocatalytic activity can be increased to 98% compared with that of the undoped one. The presence of ferrum elements neither influences the transformation of anatase to rutile, nor creates new crystal phases. The possible mechanism of photocatalytic oxidation is also discussed.