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TiO2 nanotubes (TNTs) have been extensively applied in many fields owing to their excellent porous structure and surface properties. Herein, a series of CuO-ZnO-CeO2/TNTs catalysts are synthesized through a deposition-precipitation method. The effects of TNTs content and support morphology on the catalyst physicochemical properties and catalytic performance are investigated. The incorporation of TNTs support into CuO-ZnO-CeO2 catalysts not only promotes CuO reducibility and improves the metallic Cu dispersion and specific surface area, but also enhances CO2 adsorption and increases the proportion of basic sites γ, thereby resulting in high CO2 conversion and CH3OH selectivity. It is also shown that CO2 conversion is positively correlated with the Cu specific surface area and that CH3OH selectivity is related to the proportion of basic sites γ. Due to the excellent reducibility, high metallic Cu surface area, superior CO2 adsorption and large proportion of basic sites γ, CuO-ZnO-CeO2/10 wt.% TNTs gives excellent catalytic performance and possesses a great potential as catalyst for methanol synthesis.

In this paper we have presented a power conversion efficiency (PCE) enhanced Pb-chalcogenide/CdS quantum dots (QDs) solar cells with novel tandem absorption layers synthesized by using chemical bath deposition (CBD) method. The tandem absorption layer is assembled by orderly stacking PbS-QDs layer, PbS-QDiM layer and PbSe-QDiM layer. Compared to single layer PbS-QDs/CdS solar cells, the solar cell with double-tandem layers (PbS-QDiM/QDs) shows the highest short current density ( J sc ) of 47.5 mA/cm 2 due to smoothing of the photo-generated carrier transportation and enhancing the absorption in the visible region 530–800 nm. However, the decreased open circuit voltage (V oc ) of 0.14 eV results in a low power conversion efficiency (PCE) of 2.2%. The triple-tandem absorber (PbSe-QDiM/PbS-QDiM/QDs) enhances the spectra absorption both in the visible (500–800 nm) and near-infrared (1000–1700 nm) regions, resulting in a higher short current density ( J sc ) of 40 mA/cm 2 , while keeping a relatively large open circuit voltage (V oc ) of 0.28 eV. Through an architectural modification, an enhancement of power conversion efficiency (PCE) of 4.2% has been achieved.

Photoconductive thin films on the basis of PbSe have been used as functional materials for infrared (IR) detectors. High quality PbSe thin films were grown on glass substrates by chemical bath deposition (CBD) yielding a peak detectivity of 2.8 × 10 10 cm Hz 1/2 W −1 at room temperature. The photoconductive sensor function is established by a sensitization process by annealing PbSe films in oxygen and iodine rich atmospheres. By studying such sensitized PbSe layers we discovered that new, quaternary phases are formed at the top of the layered structure. We could show that after annealing the following layer structure had formed: a bottom layer of PbSe (1 μm) and a top layer of Pb-Se-O-I (400 nm), containing (i) a poly-crystalline and (ii) a nano-crystalline phase. The poly-crystalline phase was found to be a solid solution of Se and I and yielded an average Pb/I mole fraction ratio of 3.1 and Pb/Se of 3.9, respectively. It contained the largest iodine mole fraction of ∼20 at.% while the nano-crystalline phase yielded less iodine (

TiO 2 nanoparticles functionalized with Cu x S (Cu x S-TiO 2 , x = 1 or 2) photocatalysts were synthesized via a facile precipitation method at room temperature. The resulting products were well characterized by XRD, TEM, EDS, XRF, BET, XPS, UV–vis and PL. The performance of H 2 production by photocatalytic water decomposition for the Cu x S-TiO 2 nanocomposite was examined in methanol aqueous solution using a 300 W Xe lamp as light source. Results showed that the activities of the CuS and Cu 2 S dual-cocatalysts co-loaded samples exhibited highly efficient water splitting capabilities for H 2 evolution, and 5.62 mmol h −1 g −1 of H 2 production was achieved with the composition-optimized Cu x S-TiO 2 , which was more efficient than those of single cocatalyst deposited samples and TiO 2 alone. It is proposed that the co-deposition of CuS and Cu 2 S onto TiO 2 nanoparticle surface could efficiently extend light absorption toward visible light range, facilitate the separation of photoinduced charge carriers and consequently enhance the photocatalytic H 2 production activity. The present work not only shows the possibility for the simultaneous utilization of Cu x S mixtures as efficient cocatalysts and photosensitizers to significantly facilitate the photoactivity of H 2 evolution, but also offers a general, feasible strategy for constructing ternary hybrid photocatalysts with other multivalent non-noble metal compounds as cocatalysts for target applications in solar energy conversion.

Novel red phosphorus-CdS (P-CdS) composite photocatalysts were successfully prepared through a facile and fast precipitation method. The samples were then characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET), ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRS) and photoluminescence emission spectroscopy (PL). The photocatalytic activity was evaluated by H2 generation in the aqueous solution containing Na2S/Na2SO3 as hole scavengers under visible light irradiation (λ ≥ 400 nm). The results show the optimal P molar ratio was 10 mol% and the corresponding H2 production rate reached 923 umol h−1 g−1, which is about 2.53 times higher than that of CdS sample. Meanwhile, the composite photocatalysts show favorable photostability. The enhanced photocatalytic activity can be attributed to the highly effective charge separation on P-CdS hybrids as confirmed by PL result. Also, a possible photocatalytic mechanism of the P-CdS composites is proposed and discussed in detail.

TiO2 nanotubes (TNTs) with nickel sulfide (NiS) co-catalyst were prepared by a simple solvothermal method and characterized by X-ray diffraction, transmission electron microscope, N2-physisorption, UV–vis diffuse reflectance spectroscopy and photoluminescence spectroscopy. Loading NiS nano-clusters can significantly enhance the photocatalytic H2 evolution performance of TNTs. The optimum NiS loading content was found to be 8 wt% and the corresponding hydrogen production rate is ca. 7486 µmol/h/g, being about 79 times higher than that of pure TNTs. This enhancement of photocatalytic H2 evolution was attributed to the synergistic effect between NiS and TNTs.

A new method of surface passivation of PbSe epitaxial layers by growing a thin epitaxial CaF2 layer is proposed. Improvement in photoluminescence (PL) intensity is observed when the PbSe layer is passivated. The minority carrier lifetime (?), measured by photo-current decay method corroborates PL measurements and shows a consistent, albeit not considerable, improvement in the lifetime of PbSe samples after surface passivation. The positive effect of surface passivation, especially at low heat-sink temperature, offered by a new passivating material is critically important for IV-VI material-based infrared detector and sensor applications.

PbSe thin film was grown on a patterned Si substrate with (1 1 1)-orientation by molecular-beam epitaxy (MBE). On the mesa, a low dislocation density of 9×105 cm−2 was confirmed by the etch-pits density (EPD) wet-etching technique. The photoluminescence (PL) intensity at room temperature from the low dislocation PbSe film was much higher than that from the PbSe film grown on the planar area, which further indicated the high-quality of PbSe thin film grown on patterned Si substrate.

The continual improvement of IV–VI materials grown by molecular beam epitaxy (MBE) is a key step in the development of IV–VI infrared semiconductor devices on silicon substrates. This study presents a novel surface-treatment method which is carried out during MBE growth of monocrystalline PbSe on Si(1 1 1)-oriented substrates. Details of the experimental procedures are described and supported by reflection high-energy electron diffraction (RHEED) patterns. The effect of the in-situ surface-treatment method is exhibited in the forms of improved electrical and morphological properties of PbSe thin films. Specially, the carrier mobility increases almost three-fold at 77 K and nearly two-fold at 300 K. The density of the growth pits undergoes almost three-fold reduction, whereas the density of the threading dislocations decreases around four-fold.

Fabrication of microrods from multi-quantum well (MQW) PbSe-PbSrSe structure grown in molecular beam epitaxy (MBE) followed by its morphological as well as optical characterizations are described. Pulsed PL intensity is increased by 64 times per unit surface area from a free-standing MQW microrod mounted on copper heat sink compared with the bulk sample. Enhancement in side emission power due to the higher optical confinement effect during pulsed photoluminescence (PL) from MQW semiconductor microtube inserted in hollow quartz optical fiber signifies that these microstructures are robust in nature and crucial contenders for portable mid-infrared optoelectronic devices to be used in the field of industrial trace-gas sensing.

Micropillars were fabricated on multiple quantum-well structure of PbSe/PbSrSe grown on top of BaF"2 substrate in molecular beam epitaxy (MBE). The photoluminescence spectra from the pillar structure, having a diameter of 5@mm and inter-pillar distance of 8@mm, was studied at various temperature starting from 77 to 300K. There had been an approximately consistent red-shift of photoluminescence peak of ~3.62cm^-^1 for unit K change in ambient temperature. The prominent and repeatable emission from the micropillars at various temperatures signified high crystalline nature of the fabricated micro-objects. This type of micropillar structure is one of the magnificent contenders of future opto-electronic micro-features.

PbSe thin film and PbSe/PbSrSe multiple quantum well (MQW) structures were successfully grown on (1 1 0) BaF2 substrates by molecular beam epitaxy. The average linewidth of the rocking curve from high-resolution X-ray diffraction measurements of the (2 2 0) reflection for the PbSe thin film was 60 arcsec, which indicates high crystalline quality. The dislocation density estimated from the rocking curve was 1×107 cm−2. Strong photoluminescence (PL) of the MQW structure at room temperature was observed. This PL signal was two times larger than those measured from a duplicate structure grown at the same time on a (1 1 1) BaF2 substrate. The energy bandgap of (1 1 0) PbSe follows the same temperature dependence as [1 0 0]- and [1 1 1]-orientated PbSe.

Epitaxial wide band gap Pb 1− x Sr x Se ( x >0.9) layers have been successfully grown by molecular beam epitaxy on Si(1 1 1) and BaF 2 (1 1 1) substrates. Reflection high-energy electron diffraction (RHEED) showed that layers on both substrates were single crystal and oriented to the substrate. X-ray diffraction showed that layers on Si(1 1 1) were high quality as indicated by full-width at half-maximum (FWHM) values of less than 300 arcsec. These results provide a foundation for the eventual fabrications of ultraviolet detector arrays and high power-integrated circuits on silicon substrates.