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A synthesis and characterization of luminescent nano‐heterostructures consisting of CdSe nanorod (NR) cores and a ZnO shell with up to three monolayers of ZnO is reported. The core/shell heterostructures show a tunable, dual photoluminescence (PL) in visible and Near Infrared (NIR) spectral ranges. Upon shelling the visible PL band attributed to the carrier recombination within the CdSe core shifts to lower energy by ≈0.05 to 0.15 eV relative to the bare CdSe NRs, due to a reduced quantum confinement. A NIR band, observed ≈0.4 – 0.5 eV below the PL energy of the CdSe core, is attributed to a type‐II carrier recombination across the CdSe/ZnO interface. The total PL quantum yield (PLQY) in the brightest heterostructures reaches ≈20%, increasing ≈100‐fold over the PLQY of the corresponding bare CdSe NRs. The average lifetimes of the visible PL in some heterostructures exceeds 100 ns, compared to ≈5 ns lifetime typical for bare CdSe NRs. The average PL lifetimes attributed to the type‐II charge separated states exceed one microsecond. Strong NIR PL, tunable in the 800–900 nm spectral range and the long‐lived charge separated state make the CdSe/ZnO core‐shell NRs appealing materials for exploitation in applications such as bioimaging, photocatalysis and optoelectronics. [ABSTRACT FROM AUTHOR]

The data on electron levels induced by defects in In(Ga)As/(In)GaAs nanostructures, their localization, activation energy and identification have been systematically reviewed. Point defects inherent to GaAs and found in the (In)GaAs-based nanostructures have been listed, and their classification has been clarified, including EB3, EL2, EL3, EL4 (M4), EL5, EL6 (M3), EL7, EL8, EL9 (M2), EL10 (M1), EL11 (M0) and M00. The effect of the interfaces on the formation of different types of extended defects has been described. All the levels of electron traps found in heterostructures with quantum wells, wires and dots by deep level spectroscopies have been collected in a table with indication of the detection technique, object, location in the structure and their origin assumed. This overview can be useful as a reference material for researchers who study these nanostructures. [ABSTRACT FROM AUTHOR]

This study proposed a technique to enhance the photocatalytic properties of TiO2 using graphene oxide (GO) and modified Montmorillonite (M-MMT). TiO2/GO/M-MMT nano-heterostructured composites were prepared via hydrothermal and co-precipitation. The photocatalytic performance was evaluated by investigating the photodegradation rate and absorption behavior of methyl orange (MO) under visible light irradiation. The results showed that TiO2/GO/M-MMT heterojunction exhibited excellent photocatalytic degradation performance, as the degradation rate of MO was observed to be 99.3% within 150 min. The density of adsorbed MO decreased by 62.1% after 210 min of dark adsorption using the TiO2/GO/M-MMT composite, which was significantly higher than that achieved using M-MMT, GO/M-MMT, and TiO2/M-MMT. The nano-heterostructure increased the effective interface between TiO2, GO, and MMT, which increased the charge transfer ability and prolonged the electron-hole separation time. Therefore, the results of this study can be used to design novel photocatalysts to eradicate environmental pollutants.

Titania is very famous photocatalyst for decomposition of organic pollutants. Its photocatalytic properties significantly depend on the morphology and chemical composition of the samples. Herein, the TiO2 nanotubes/CuxO nanoheterostructures have been synthesized and the effect of heat treatment performed in molecular atmospheres of air and argon on their photoelectrochemical and photocatalytic properties has been studied. The prepared samples have a higher reaction rate constant compared to TiO2 nanotubes in the decomposition reaction of methylene blue molecules. It is established that in argon treated nanoheterostructures, the copper oxide is present in two phases, CuO and Cu2O, while in air treated ones there is only CuO. In the TiO2 nanotubes/CuxO samples, Cu2+ ions and molecular O2− radicals were detected while in TiO2 nanotubes only carbon dangling bond defects are present. The dynamics of O2− radicals under illumination are discussed. It was shown that the TiO2 nanotubes do not exhibit photocatalytic activity under visible light. The mechanism of the photocatalytic reaction on the surface of the TiO2 nanotubes/CuxO samples was proposed. It is assumed that a photocatalytic decomposition of organic molecules under visible light at the surface of the nanoheterostructures under investigation is realized mainly by the reaction of these molecules with photogenerated O2− radicals. The results obtained are completely original and indicate the high promise of the prepared photocatalysts. [ABSTRACT FROM AUTHOR]

The results of an experimental study of the effect of thermal annealing on the structure, surface morphology and optical properties of thin films of aluminum nitride on sapphire are presented. Thin films of aluminum nitride on sapphire with a thickness of 200 nm were annealed in air and in a nitrogen atmosphere at a residual gas pressure in the vacuum chamber of the ion-beam deposition unit of no less than 100 Pa at a temperature of 850°C. It was found that thermal annealing of aluminum nitride films on sapphire in a nitrogen atmosphere leads to a decrease in the root mean square roughness of the films to 0,8 nm, an increase in the transmittance in the wavelength range of 300 — 1000 nm up to 96%, and an increase in the stoichiometry of the films. It is shown that for aluminum nitride films annealed in air on sapphire, aluminum nitride is oxidized to form amorphous aluminum oxide at a temperature of 850 °C. The results of energy dispersive analysis showed the complete absence of nitrogen on the surface of these films. A decrease in the transmittance over the entire wavelength range for films AlN annealed in air makes them unsuitable for use in optoelectronics. The surface morphology of these films is an array of pointed formations with a maximum height 190,7 nm and an arithmetic mean surface roughness 3,7 nm.

1D solid solutions Zn1-xCuxO and composites Zn1-xCuxO / CuO with spherical morphology of aggregates from formate glycolate complexes Zn1-xCux (HCOO)(OCH2CH2O)1/2 (0 ≤ x ≤ 0,15) were obtained. All materials have been tested in the reaction of As(III) photooxidation upon exposure to ultraviolet and visible radiation. It was found that copper is an effective doping impurity in the composition of the solid solution Zn1-xCuxO (0 ≤ x ≤ 0,1). Its presence in the shell of the Zn1-xCuxO / CuO composite negatively affects the photoactivity of the material up to suppression of photocatalysis in the visible light range. The sorption efficiency of materials for arsenic is also shown, regardless of the composition and morphology of the material. According to x-ray photoelectron spectroscopy data, the surface of the samples after sorption contains arsenic mainly in the form of As(III).

For obtaining multicomponent III–V solid solutions, the vapor-phase methods such as the chloride–hydride epitaxy, the epitaxy from organometallic compounds, and the molecular-beam epitaxy are mainly used. The development of optimal technological modes of multicomponent layers and structures, as a rule, requires a lot of time and material costs. In the study, the method of modeling the growth processes of multicomponent solid solutions based on the key physicochemical laws of crystallization of materials and the properties of III–V compounds is proposed. The processes of obtaining four-component In1 – yGayAs1 – xPx solid solutions isoperiodic with GaAs and three-component GaAs0.8P0.2 and GaAs0.6P0.4 solid solutions are analyzed and predicted. The calculated modes are experimentally implemented, and materials are obtained, which correspond to the modern level in quality. [ABSTRACT FROM AUTHOR]

For obtaining multicomponent III–V solid solutions, the vapor-phase methods such as the chloride–hydride epitaxy, the epitaxy from organometallic compounds, and the molecular-beam epitaxy are mainly used. The development of optimal technological modes of multicomponent layers and structures, as a rule, requires a lot of time and material costs. In the study, the method of modeling the growth processes of multicomponent solid solutions based on the key physicochemical laws of crystallization of materials and the properties of III–V compounds is proposed. The processes of obtaining four-component In1 – yGayAs1 – xPx solid solutions isoperiodic with GaAs and three-component GaAs0.8P0.2 and GaAs0.6P0.4 solid solutions are analyzed and predicted. The calculated modes are experimentally implemented, and materials are obtained, which correspond to the modern level in quality. [ABSTRACT FROM AUTHOR]

Titania is very famous photocatalyst for decomposition of organic pollutants. Its photocatalytic properties significantly depend on the morphology and chemical composition of the samples. Herein, the TiO2 nanotubes/CuxO nanoheterostructures have been synthesized and the effect of heat treatment performed in molecular atmospheres of air and argon on their photoelectrochemical and photocatalytic properties has been studied. The prepared samples have a higher reaction rate constant compared to TiO2 nanotubes in the decomposition reaction of methylene blue molecules. It is established that in argon treated nanoheterostructures, the copper oxide is present in two phases, CuO and Cu2O, while in air treated ones there is only CuO. In the TiO2 nanotubes/CuxO samples, Cu2+ ions and molecular O2− radicals were detected while in TiO2 nanotubes only carbon dangling bond defects are present. The dynamics of O2− radicals under illumination are discussed. It was shown that the TiO2 nanotubes do not exhibit photocatalytic activity under visible light. The mechanism of the photocatalytic reaction on the surface of the TiO2 nanotubes/CuxO samples was proposed. It is assumed that a photocatalytic decomposition of organic molecules under visible light at the surface of the nanoheterostructures under investigation is realized mainly by the reaction of these molecules with photogenerated O2− radicals. The results obtained are completely original and indicate the high promise of the prepared photocatalysts.

Nanoheterostructures based on titanium dioxide synthesized by the sol–gel technique are studied. Microscopy, X-ray diffraction, optical spectroscopy, and electron-spin resonance techniques are used. All the investigated samples are characterized by a large specific surface area (~100 m2 per 1 g substance). It is established that the main types of radicals in the obtained structures are N•, Ti3+, Мо5+, V 4+, and W 5+, depending on the composition of the samples. It is shown that nanoheterostructures consisting of several metal oxides have a high photocatalytic activity in the visible spectral region and the ability to accumulate photogenerated charge carriers. As a result, catalytic reactions in the samples continue even after illumination is turned off. A correlation is found between the rate of photocatalysis, the absorption spectra in the visible region, and the concentration of radicals in the studied structures. The results can be used to develop energy-efficient catalytic devices based on nanoheterostructures consisting of titanium, molybdenum, tungsten, and vanadium nanooxides in various combinations which operate under periodic illumination in the visible spectral range. [ABSTRACT FROM AUTHOR]

This work reports on an experimental investigation of the influence of vertical stacking of quantum dots, the thickness of GaAs potential barriers, and their isovalent doping with bismuth on the photoluminescence properties of InAs/GaAs heterostructures. The experimental samples were grown by ion-beam deposition. We showed that using three vertically stacked layers of InAs quantum dots separated by thin GaAs barrier layers was accompanied by a red-shift of the photoluminescence peak of InAs/GaAs heterostructures. An increase in the thickness of the GaAs barrier layers was accompanied by a blue shift of the photoluminescence peak. The effect of isovalent Bi doping of the GaAs barrier layers on the structural and optical properties of the InAs/GaAs heterostructures was investigated. It was found that the Bi content up to 4.96 atom % in GaAs decreases the density of InAs quantum dots from 1.53 × 1010 to 0.93 × 1010 cm−2. In addition, the average lateral size of the InAs quantum dots increased from 14 to 20 nm, due to an increase in the surface diffusion of In. It is shown that isovalent doping of GaAs potential barriers by bismuth was accompanied by a red-shift of the photoluminescence peak of InAs quantum dots of 121 meV.

Epitaxial growth of germanium quantum dots on an oxidized silicon surface is considered. A kinetic model of the nucleation and growth of three-dimensional islands by the Volmer–Weber mechanism in this system is proposed. The dependences of the average size and surface density of quantum dots on the parameters of their synthesis are obtained. The proposed theoretical model can easily be extended to other material systems in which island growth by the Volmer–Weber mechanism is realized. [ABSTRACT FROM AUTHOR]

Mixed cobalt and nickel oxides MTiO3/TiO2 (M = Co2+, Ni2+) are synthesized. Organometallic complexes of titanium tetrabutylate Ti(OBu)4 with 1,2-dihydroxybenzene and nitrate hydrates of corresponding metals (M) synthesized under conditions of the modified sol-gel process are used as precursors. The synthesized samples are characterized by field-emission scanning electron microscopy, energy-dispersive X-ray analysis, diffuse reflectance spectroscopy, dispersive X-ray radiation analysis, X-ray diffraction, and low-temperature nitrogen adsorption. The photocatalytic activity of the samples is tested in the ultraviolet spectral range (200 nm < λ < 400 nm) in the photodegradation of 1,2-dihydroxybenzene (catechol) in aqueous solutions. [ABSTRACT FROM AUTHOR]

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Nanoheterostructures based on titanium, molybdenum, tungsten, and vanadium nanooxides with symmetric crystal structures, morphologies and high photocatalytic activity in under illumination by visible light, have been synthesized and studied. Microscopy, optical spectroscopy, and electron-spin resonance techniques were used. The asymmetric separation of photo-generated holes and electrons between different nanooxides in their nanoheterostructures suppresses their recombination. Using the method developed by the authors and based on ESR spectroscopy, the energy levels of the active centers inside the band gaps of the studied samples were found. We have shown, for the first time, that under illumination of nanoheterostructures under asymmetric conditions with adsorbed rhodamine dye at the dye-absorption wavelength (500 nm), photocatalytic reactions are mainly determined by light absorption by the nanostructures themselves, and not by energy transfer from the dye. This important result shows that high photocatalytic activity of materials with symmetric crystal structures is the primary criterion for creating energy-efficient photocatalysts. The results will be useful for the development of energy-efficient catalytic devices based on various combinations of metal nanooxides.

The BiFeO 3 /V 2 O 5 has been successfully synthesized by simple annealing of BiFeO 3 nanoplates and V 2 O 5 nanoflower. The phase, structural, optical properties and chemical state of the BiFeO 3 , V 2 O 5 and different composition of BiFeO 3 /V 2 O 5 samples were comparatively characterized by various spectroscopic and microscopic techniques. The prepared catalyst exhibits unique photo catalytic and post-oxidation/reduction ability for removal of various (MB, Phenol, CV, RhB) water organic pollutants. Compared to pure BiFeO 3 and V 2 O 5 , the different Wt % of BiFeO 3 /V 2 O 5 composition exhibited higher photo catalytic activity. The fortunate BiFeO 3 /V 2 O 5 interface hybrid photo catalyst makes a significant impact in the enhancement of photo catalytic reaction. This remarkable efficiency could be ascribed to the synergistic effect between the V 2 O 5 petals and BiFeO 3 plates. The exceptional morphology, increased surface area, uniformity, less-agglomerated spreading could increase the ability of visible light response, which lead the improved electron transport ability and the higher charge separation. The enhanced rate of photo generated charge carriers separations were evinced by the EIS and PL spectrum measurements. The allowed radical trapping experiment divulge that the hole (h+), and super oxide radical (O 2 -) are the minimized effect in degradation, on the other hand hydroxyl radical (OH) is plays the foremost role and act as the active radicals in the catalytic organism. In relations of above investigation, a probable photo degradation mechanism of the as-synthesized photo catalyst is carefully explicated. This effort delivers an effective approach to design and fabricate the efficient photo catalyst through integrating of materials, which has a potential for industrial waste water purification. Image 1 • The BiFeO 3 /V 2 O 5 Nano heterostructure successfully prepared by effective methods. • The synthesized BiFeO 3 /V 2 O 5 material displayed a better physicochemical properties. • The BiFeO 3 /V 2 O 5 was thoroughly investigated for diverse organic pollutants removal. • The synergistic effect in BiFeO 3 /V 2 O 5 played important role in photo degradation. • A systematic investigation of photo catalytic removal mechanism is proposed. [ABSTRACT FROM AUTHOR]

GexSi1 – x/Si nanoheterostructures are synthesized via ion-beam deposition. The crystal structure, surface morphology, and chemical composition are investigated using X-ray diffraction, Raman spectroscopy, scanning probe microscopy, and Auger electron spectroscopy methods. The germanium content is shown to affect the structural perfection and surface morphology of the GexS1 – x/Si layer. Finally, GexSi1 – x/Si nanoheterostructures are established to serve as cheap synthetic substrates for high efficiency cascade solar cells based on III—V compounds. [ABSTRACT FROM AUTHOR]

A metal-free C60/CNTs/g-C3N4 nanoheterostructure with excellent visible-light photocatalysis for rhodamine B (Rh B) degradation has been reported. Via a convenient low-temperature solution-phase method, g-C3N4 nanosheets can serve as substrate for dispersion of C60/CNTs. The loading of C60/CNTs onto g-C3N4 nanosheets surfaces significantly enhanced visible-light-driven photocatalytic activity of g-C3N4 catalyst, for oxidation of organic pollutant (Rh B, 100%). Excellent photocatalytic properties of C60/CNTs/g-C3N4 can be predominantly attributed to the intimate interfacial contact among constructing compounds, increased specific surface area and enhanced light adsorption efficiency resulted from C60/CNTs carbon materials. Particularly, the synergistic heterostructure interaction remarkably hinders the electron–hole pairs recombination, giving rise to significantly enhanced photocatalytic performance of C60/CNTs/g-C3N4 in comparison with other counterparts.

In this work, a novel NiO/Co 3 O 4 nanoheterostructure was fabricated via a simple pyrolysis treatment of nickelocene (NiCp2) filled ZIF-67. With remarkable structural features, the obtained NiO/Co 3 O 4 hybrids exhibit high specific capacitance of 405 F g -1  at 1 A g −1 and high cycling stability (97.4% after 1000 cycles at 15 A g −1 ). Asymmetric supercapacitors (ASCs) were fabricated using the NiO/Co 3 O 4 heterostructure as the positive electrode and active carbon as negative electrode. The operation voltage of ASCs is expanded to 1.5 V in aqueous electrolyte, revealing high energy density (23.8 Wh kg −1 at a power density of 0.75 kW kg −1 ) and high capacitance retention (97.9% after 1000 cycles). The excellent electrochemical performance of the NiO/Co 3 O 4 nanoheterostructure was attributed to its special hierarchical nanoarchitecture, in which the synergistic effect of Co 3 O 4 and NiO to supply more pathways for accelerating fast electron and ion transfer. This functionalized MOF-driven strategy pave the way to the preparation of various metal oxide nanoheterostructures by varying the type of MOFs and fillers. [ABSTRACT FROM AUTHOR]

Low photocatalytic efficiency, rapid charge recombination and limited light absorption in wide band gap materials like ZnO severely hinder their practical applications. In order to overcome the above mentioned drawbacks and improve the photocatalytic efficiency, we have developed a series of Pt loaded ZnO-reduced graphene oxide (RGO) nanoheterostructures. The photocatalytic activity of these nanoheterostructures in different compositions, under sunlight irradiation, towards the reduction of 4-nitrophenol has been investigated. The prepared nanoheterostructures showed superior photocatalytic activity and composition having 5 wt% of RGO and 2 wt% of Pt in ZnO (ZPG5) was found to exhibit the highest activity. Control experiments were performed on ZnO-RGO (ZG) nanocomposites without Pt to determine the role of Pt loading. The rate constant of 4-nitrophenol reduction reaction obtained using ZPG5 nanoheterostructure was 0.4203 min −1 , which is about 30 folds higher than the rate constant catalyzed using bare ZnO NR (0.0142 min −1 ) and 6 folds higher than ZG5. Strong enhancement in the photocatalytic activity could be evidenced for the Pt loaded ZnO-RGO nanoheterostructures under sunlight irradiation, which could be attributed to improved charge separation, enhanced charge transfer across the Schottky barrier between ZnO and Pt and the high ability of RGO to adsorb 4-nitrophenol. The developed nanoheterostructures can be used as highly efficient sunlight activated heterogeneous photocatalysts for several real life applications. [ABSTRACT FROM AUTHOR]

The p-Si/n-ZnO nanoheterostructures were prepared by the sol-gel and hydrothermal method. The structural characterization carried out by the x-ray diffraction and field emission scanning electron microscope confirms the growth of ZnO nanorods on p-type silicon substrate. The current-voltage (I-V) characteristics of the junction show a rectifying diode-like behavior. The analysis indicates the presence of a high value of series resistance (3.2 KΩ) at the interface. The barrier height extracted from the temperature variation study using the thermionic emission model was of the order of 167.7 meV and the Richardson constant value was of the order of 1.1096E−6 A cm−2 K−2 which is much lower than the standard value, i.e., 32 A cm−2 K−2 for ZnO. Such a discrepancy has been resolved and explained using the Gaussian distribution of barrier heights. The refined value of the barrier height and Richardson constant as calculated from the modified Richardson plot was 1.24 eV and 35.16 A cm−2 K−2, respectively. These are in agreement with the standard reported values. [ABSTRACT FROM AUTHOR]

Co 0.3 Zn 0.7 Fe 2 O 4 nanoparticles prepared by co-precipitation method were characterized by X-ray diffraction (XRD). Reduced graphene oxide (rGO) was prepared by modified Hummer's route and then characterized by UV–Visible and XRD techniques. Nano-heterostructures of Co 0.3 Zn 0.7 Fe 2 O 4 with rGO were prepared using ultra-sonication technique. XRD analysis of Co 0.3 Zn 0.7 Fe 2 O 4 nanoparticles and Co 0.3 Zn 0.7 Fe 2 O 4 -rGO confirmed the cubic structure of ferrite nanoparticles. Cyclic voltammetry experiments showed that Co 0.3 Zn 0.7 Fe 2 O 4 -rGO nano-heterostructures exhibit the greater value of specific capacitance (151.33 Fg −1 ) as compared to Co 0.30 Zn 0.70 Fe 2 O 4 nanoparticles (91.20 Fg −1 ). These values of specific capacitance were observed at 10 mV s −1 . Moreover, electrochemical impedance spectroscopy showed that Co 0.3 Zn 0.7 Fe 2 O 4 -rGO nano-heterostructures have lower charge transfer resistance than the bare Co 0.3 Zn 0.7 Fe 2 O 4 nanoparticles. Electrochemical experiments illustrated that Co 0.3 Zn 0.7 Fe 2 O 4 -rGO nano-heterostructures have efficient energy storage properties and can be utilized for electrode's fabrication in supercapacitors. [ABSTRACT FROM AUTHOR]

A comparative analysis is carried out of the growth peculiarities under molecular-beam epitaxy of germanium quantum dots on the silicon surfaces with different crystallographic orientations Si(100) and Si(111), including the case of the presence of tin surfactant on the surface. The free energy change, activation barrier of nucleation, critical thickness of the transition from two-dimensional growth to three-dimensional one, as well as the surface density and size distribution function of quantum dots in these systems are calculated. [ABSTRACT FROM AUTHOR]

Hybrid semiconductor-metallic nanostructures play an important role in a wide range of applications and are key components in photocatalysis. Here we reveal that the nature of a nanojunction formed between a semiconductor nanorod and metal nanoparticle is sensitive to the size of the metal component. This is reflected in the activity toward hydrogen production, emission quantum yields, and the efficiency of charge separation which is determined by transient absorption spectroscopy. A set of Ni decorated CdSe@CdS nanorods with different tip size were examined, and an optimal metal domain size of 5.2 nm was obtained. Remarkably, charge separation time constants were found to be nonvariant with metal tip size. It is proposed that electron transfer mechanism encompasses two consecutive but separate processes: slow charge migration along the rod toward the interface, followed by fast interface crossing of the electron from the semiconductor into the metal phase. The first migration step dominates the time constant for the charge separation process and is not affected by the metal size. The efficiency of charge separation on the other hand was found to be sensitive to metal size. It is suggested that Coulomb blockade charging energy and a size-dependent Schottky barrier contribute to the metal size effect on charge transfer probability across the semiconductor-metal nanojunction. These two opposing trends result in an optimal metal size domain for the cocatalyst. This work is expected to benefit a broad range of applications utilizing semiconductor-metal nanocomposites. [ABSTRACT FROM AUTHOR]

Inorganic nanoparticles have great potential for application in many fields, including nanomedicine. Within this class of materials, inorganic nanoheterostructures (NHS) look particularly promising as they can be formulated as the combination of different domains; this can lead to nanosystems with different functional properties, which, therefore, can perform different functions at the same time. This review reports on the latest development in the synthesis of advanced NHS for biomedicine and on the tests of their functional properties in in vivo studies. The literature discussed here focuses on the diagnostic and therapeutic applications with special emphasis on cancer. Considering the diagnostics, a description of the NHS for cancer imaging and multimodal imaging is reported; more specifically, NHS for magnetic resonance, computed tomography and luminescence imaging are considered. As for the therapeutics, NHS employed in magnetic hyperthermia or photothermal therapies are reported. Examples of NHS for cancer theranostics are also presented, emphasizing their dual usability in vivo, as imaging and therapeutic tools. Overall, NHS show a great potential for biomedicine application; further studies, however, are necessary regarding the safety associated to their use.

Nanoheterostructures based on metal oxide semiconductors have emerged as promising materials for the conversion of sunlight into chemical energy. In the present study, ZnO-based nanocomposites have been developed by a hybrid vapor phase route, consisting in the chemical vapor deposition of ZnO systems on fluorine-doped tin oxide substrates, followed by the functionalization with Fe2O3 or WO3 via radio frequency-sputtering. The target systems are subjected to thermal treatment in air both prior and after sputtering, and their properties, including structure, chemical composition, morphology, and optical absorption, are investigated by a variety of characterization methods. The obtained results evidence the formation of highly porous ZnO nanocrystal arrays, conformally covered by an ultrathin Fe2O3 or WO3 overlayer. Photocurrent density measurements for solar-triggered water splitting reveal in both cases a performance improvement with respect to bare zinc oxide, that is mainly traced back to an enhanced separation of photogenerated charge carriers thanks to the intimate contact between the two oxides. This achievement can be regarded as a valuable result in view of future optimization of similar nanoheterostructured photoanodes. [ABSTRACT FROM AUTHOR]

Gas sensors based on titanium dioxide (TiO2) have attracted much public attention during the past decades due to their excellent potential for applications in environmental pollution remediation, transportation industries, personal safety, biology, and medicine. Numerous efforts have therefore been devoted to improving the sensing performance of TiO2. In those effects, the construct of nanoheterostructures is a promising tactic in gas sensing modification, which shows superior sensing performance to that of the single component-based sensors. In this review, we briefly summarize and highlight the development of TiO2-based heterostructure gas sensing materials with diverse models, including semiconductor/semiconductor nanoheterostructures, noble metal/semiconductor nanoheterostructures, carbon-group-materials/semiconductor nanoheterostructures, and organic/inorganic nanoheterostructures, which have been investigated for effective enhancement of gas sensing properties through the increase of sensitivity, selectivity, and stability, decrease of optimal work temperature and response/recovery time, and minimization of detectable levels. [ABSTRACT FROM AUTHOR]

We report a new approach for the synthesis of multifunctional Au core@Prussian Blue analogous (PBA) shell nanoheterostructures that involves PBA shell growth on the surface of cyanide-stabilized gold nanoparticles. It permits the assembly of Au@KNiII[FeII(CN)6] core@shell and Au@KNiII[FeII(CN)6]@KNiII[CrIII(CN)6] core@shell@shell heterostructures with well-defined and size-controlled gold cores and PBA shells. These heterostructures exhibit tunable size- and shape-dependent magnetic and optical properties: (i) the surface plasmon resonance band position and intensity mainly depend on the PBA shell thickness, and (ii) the magnetic properties (the transition temperature, the coercivity, and magnetic regime) depend in a complex manner on the thickness as well as the particular morphology of the magnetic shell. [ABSTRACT FROM AUTHOR]

Thermoelectric materials, which can convert waste heat into electricity, have received increasing research interest in recent years. This paper describes the recent progress in thermoelectric nanocomposites based on solution-synthesized nanoheterostructures. We start our discussion with the strategies of improving the power factor of a given material by using nanoheterostructures. Then we discuss the methods of decreasing thermal conductivity. Finally, we highlight a way of decoupling power factor and thermal conductivity, namely, incorporating phase-transition materials into a nanowire heterostructure. We have explored the lead telluride-copper telluride thermoelectric nanowire heterostructure in this work. Future possible ways to improve the figure of merit are discussed at the end of this paper. [ABSTRACT FROM AUTHOR]

Feasibility was demonstrated for the use of low-dimensional CdSe@CdS particles with core@shell structure and 1.8-2.0 nm mean core diameter as a component in the FTO/TiO/CdSe@CdS photoanode in photoelectrochemical solar cells with aqueous polysulfide electrolyte and copper sulfide-based counter-electrode. An average light conversion efficiency of 6.3% was achieved (at excitation intensity of 30 mW/cm) in cells with the FTO/TiO/CdSe@CdS photoanode and an FTO/TiO/CuS counter-electrode produced by sulfidation of copper particles photochemically deposited onto the titanium dioxide surface. [ABSTRACT FROM AUTHOR]

NaYF 4 :Yb 3+ ,Tm 3+ /CdSe nanoheterostructures were synthesized by an improved two-step wet-chemical route. Upon the excitation from a 980-nm near-infrared (NIR) laser, an intense 797 nm NIR emission from Tm 3+ ions was observed in the nanoheterostructures while neither ultraviolet (UV) nor blue emissions of Tm 3+ ions appeared in the upconversion (UC) spectrum. It indicated that the energy transfer (ET) occurred between NaYF 4 :Yb 3+ ,Tm 3+ and CdSe. Under 980 nm irradiation, the excitation energy absorbed by Yb 3+ ions transferred to Tm 3+ ions successively, then transferred to CdSe partially from the 1 G 4 state of Tm 3+ ions, and finally the excited CdSe returns the energy back to the 3 F 2,3 levels of Tm 3+ ions. Both the excitation (980 nm) and the emission (797 nm) are located in the NIR spectral range (700–1100 nm) that is referred as the “optical window” of biological tissues. Therefore, the nanoheterostructures could have great potential in applications of biology and biomedicine. [ABSTRACT FROM AUTHOR]

Ag2Mo3O10 nanorods decorated with Ag2S nanoparticles have been synthesized by an anion-exchange route. With thiourea as the sulfur source, sulfur ions replace [Mo3O10]2- units of active sites on the surface of Ag2Mo3O10 nanorods, forming Ag2Mo3O10 nanorods decorated with Ag2S nanoparticles. This induces enhanced absorption in the visible- light region. Ag2S nanoparticles decorate the surface of Ag2Mo3O10 nanorods uniformly with a suitable amount of thiourea. The Ag2S/Ag2Mo3O10 nanoheterostructure enhances the photocatalytic activity on the degradations of Rhodamine B and glyphosate under visible light. This enhancement is attributed to the improved absorption of visible light and effective separation of charge carriers in the nanoheterostructure. Meanwhile, the Ag2S/Ag2Mo3O10 nanoheterostructure displays good photocatalytic stability based on cyclic photocatalytic experiments. [ABSTRACT FROM AUTHOR]

Gas sensors based on titanium dioxide (TiO2) have attracted much public attention during the past decades due to their excellent potential for applications in environmental pollution remediation, transportation industries, personal safety, biology, and medicine. Numerous efforts have therefore been devoted to improving the sensing performance of TiO2. In those effects, the construct of nanoheterostructures is a promising tactic in gas sensing modification, which shows superior sensing performance to that of the single component-based sensors. In this review, we briefly summarize and highlight the development of TiO2-based heterostructure gas sensing materials with diverse models, including semiconductor/semiconductor nanoheterostructures, noble metal/semiconductor nanoheterostructures, carbon-group-materials/semiconductor nano- heterostructures, and organic/inorganic nanoheterostructures, which have been investigated for effective enhancement of gas sensing properties through the increase of sensitivity, selectivity, and stability, decrease of optimal work temperature and response/recovery time, and minimization of detectable levels.

Novel Bi 2 S 3 /Bi 2 MoO 6 hollow microsphere composites with oxygen vacancies were successfully synthesized through in-situ anion exchange and hydrothermal method. After introducing sulfur into the Bi 2 MoO 6 substrate with oxygen vacancies, Bi 2 S 3 was close distributed on the surface of the Bi 2 MoO 6 hollow microsphere to form Bi 2 S 3 /Bi 2 MoO 6 heterojunctions and led to inducing the more oxygen vacancies. Compared to pristine Bi 2 MoO 6 and Bi 2 S 3 , the Bi 2 S 3 /Bi 2 MoO 6 -0.03 exhibited higher photocatalytic efficiency toward Rhodamine B (RB) degradation under the full-spectrum (visible and near-infrared) light illumination. Meanwhile, it showed high near-infrared photocatalytic activity for antibiotics. The enhanced catalytic performance was attributed to the synergetic effect of heterojunction and the oxygen vacancies between Bi 2 MoO 6 and Bi 2 S 3. Meanwhile, the active species were carefully investigated by the active species capture tests and the electron spin resonance technique. Finally, the reasons for the improved photocatalytic performance and reaction mechanism were also uncovered in detail, and degradation products obtained by N-de-ethylation by the cleavage of C N of RB were demonstrated. The findings in this work provide insight into the potential applications in treating wastewater. [Display omitted] • Bi 2 S 3 distributed on the surface of Bi 2 MoO 6 hollow sphere with oxygen vacancies. • Formation of Bi 2 S 3 /Bi 2 MoO 6 heterojunctions led to inducing more oxygen vacancies. • Bi 2 S 3 /Bi 2 MoO 6 showed excellent full-spectrum (Vis and NIR) photocatalytic activity. • Boosted activity ascribed to synergic effect of heterojunction and oxygen vacancies. [ABSTRACT FROM AUTHOR]

Results of investigations into the time characteristics of photosensitive layers based on Ge/Si nanoheterostructures excited by femtosecond laser pulses with a wavelength of 1.55 μm are given. It is demonstrated that the leading front duration of the photoresponse pulse for the examined specimens excited by laser pulses of 120 fs duration does not exceed 30-40 пs. [ABSTRACT FROM AUTHOR]

[Display omitted] • β-Fe 2 O 3 /CuO and β-Fe 2 O 3 /WO 3 nanoheterostructures are developed via a two-step vapor-phase route. • The fabricated materials are tested as De-NO x photocatalysts. • The target heterostructures show an enhanced NO photochemical removal with negligible release of toxic intermediates. • The performances higher than those of single oxides are attributed to O defectivity and enhanced charge carrier separation. • •O 2 − radicals are the main species contributing to NO x oxidation. The increasing release and accumulation of harmful nitrogen oxides (NO x with x = 1,2) in industrial and urban environments renders the efficient removal of these atmospheric pollutants an urgent and obligatory issue. In this regard, the advantages yielded by photocatalytic oxidation processes have triggered the search for eco-friendly catalysts featuring an improved efficiency. In this work, we propose the use of heterostructures based on β-Fe 2 O 3 , a scarcely investigated iron(III) oxide polymorph, as viable De-NO x photocatalysts with appealing functional performances. The present materials were fabricated in supported form by chemical vapor deposition (CVD) of Fe 2 O 3. A proof-of-principle investigation on the modulation of material performances by heterostructure formation is explored through Fe 2 O 3 functionalization with CuO or WO 3 by radio frequency (RF)-sputtering. The obtained results reveal a controllable dispersion of CuO or WO 3 in close contact with β-Fe 2 O 3 , a crucial issue to profitably exploit their mutual interplay for De-NO x applications. A preliminary analysis in this regard evidenced very encouraging conversion efficiency and selectivity towards nitrate formation, outstanding among non-titania oxide-based De-NO x photocatalysts. The improved photoactivity with respect to bare Fe 2 O 3 , CuO and WO 3 was related to a higher oxygen defectivity and an enhanced separation of photogenerated charge carriers, enabled by the matched band edges in the target heterostructures. [ABSTRACT FROM AUTHOR]

Nanoheterostructures based on titanium, molybdenum, tungsten, and vanadium nanooxides with symmetric crystal structures, morphologies and high photocatalytic activity in under illumination by visible light, have been synthesized and studied. Microscopy, optical spectroscopy, and electron-spin resonance techniques were used. The asymmetric separation of photo-generated holes and electrons between different nanooxides in their nanoheterostructures suppresses their recombination. Using the method developed by the authors and based on ESR spectroscopy, the energy levels of the active centers inside the band gaps of the studied samples were found. We have shown, for the first time, that under illumination of nanoheterostructures under asymmetric conditions with adsorbed rhodamine dye at the dye-absorption wavelength (500 nm), photocatalytic reactions are mainly determined by light absorption by the nanostructures themselves, and not by energy transfer from the dye. This important result shows that high photocatalytic activity of materials with symmetric crystal structures is the primary criterion for creating energy-efficient photocatalysts. The results will be useful for the development of energy-efficient catalytic devices based on various combinations of metal nanooxides. [ABSTRACT FROM AUTHOR]