Efficiently reclaiming the utilization of solar light in a photocatalysis system remains very challenging. By integrating full advantage of upconversion material, plasmonic metals, and narrow bandgap semiconductors, β-NaYF4:18%Yb3+ and 2%Tm3+@SnO2@Ag nanoparticles (denoted as NaYF4@SnO2@Ag NPs) are designed and successfully synthesized as a wide-spectral (UV–vis-NIR) responsive upconversion and plasmonic-enhanced photocatalyst. The as-obtained NaYF4@SnO2@Ag NPs present broadband optical absorption dimension, excellent photocatalytic efficiency, and good stability for the degradation of organic dyes. The enhanced photocatalytic performance of NaYF4@SnO2@Ag NPs can be attributed to the synergistic effects of the components composed in this core/shell architecture that result in higher photocarriers yield and favor the efficient transfer of photocarriers and energy. This work gives insight to guidance of fabricating efficient, multicomponent upconversion catalysts and proposes a potential in the field of high-efficiency environmental and energy-related applications.Keywords: Core/shell structure; Energy transfer; FDTD calculation; Plasmonic photocatalyst; Upconversion materials;

We produce the p-n heterostructure of BiOBr/BiPO4 sheets with retained two-dimensional (2D) morphology through a simple solvothermal process. Comparatively, the BiOBr/BiPO4 sheets present enhanced photocatalytic performance of formaldehyde oxidation due to effective separation and migration of the photoinduced electron–hole pairs. Notably, the increasing number of grown BiPO4 particles on the surface of BiOBr sheets without isolated homogeneous BiPO4 particles are significant factors in the promotion of photocatalytic performance. Hence, the BiOBr/BiPO4 composite sheets with loading of 30% BiPO4 exhibit superior photocatalytic performance. This outstanding performance suggests that the p-n heterostructure of BiOBr/BiPO4 sheets has potential in purification of gaseous pollutants.Keywords: BiOBr/BiPO4 sheets; Formaldehyde oxidation; Homogeneous growth; p-n heterostructure; Photocatalytic performance;

Rare-earth ion (RE3+) doped up-conversion (UC) fluorescent materials and novel fluorescent carbon quantum dots (CDs) have been widely used as traditional anti-counterfeiting materials owing to their excellent optical properties. The drawbacks of these materials are being exposed gradually with the widespread occurrence of counterfeit products in the market because of their single fluorescence mode and easy replication. In this work, we propose a novel strategy to combine both luminescent materials with different modes via a facile solvothermal method. Interesting, the composite materials show unalterable down-conversion (DC) blue light under a 365 nm ultraviolet (UV) analyzer, except for adjustable UC luminescence properties. The UC and DC optical properties are measured and the probable mechanism is proposed, indicating that the dual-mode fluorescence processes are separate and do not interference with each other. Moreover, we use a mixture containing a small number of UCMPs/CDs and poly(acrylic acid) (PAA) aqueous solution as a colorless anti-counterfeiting ink, and successfully print a variety of dual-mode fluorescence patterns through the screen printing technique, including QR codes, the logo of Wuhan University, and clover patterns. The composite materials show good dispersion and outstanding dual-mode fluorescence properties, suggesting that they are promising luminescent materials in the anti-counterfeiting field.

The development of photocatalysts with superior photoactivity and stability for the degradation of organic dyes is very important for environmental remediation. In this study, we have presented a multidimensional (1D and 2D) structured CdS/ZnIn2S4/RGO photocatalyst with superior photocatalytic performance. The CdS/ZnIn2S4 helical dimensional heterostructures (DHS) were prepared via a facile solvothermal synthesis method to facilitate the epitaxial growth of 2D ZnIn2S4 nanosheets on 1D CdS nanowires. Ultrathin 2D ZnIn2S4 nanosheets have grown uniformly and perpendicular to the surface of 1D CdS nanowires. The as-obtained 1D/2D CdS/ZnIn2S4 helical DHS show good photocatalytic properties for malachite green (MG). Subsequently, 2D reduced graphene oxide (RGO) was introduced into the 1D/2D CdS/ZnIn2S4 helical DHS as a co-catalyst. The photoactivity and stability of the CdS/ZnIn2S4/RGO composites are significantly improved after 6 cycles. The enhanced photoactivity can be attributed to the high surface area of RGO, the improved adsorption of organic dyes and the efficient spatial separation of photo-induced charge carriers. The transfer of photo-generated electrons from the interface of CdS and ZnIn2S4 to RGO also restricted the photocorrosion of metal sulfide, suggesting an improved stability of the reused CdS/ZnIn2S4/RGO composited photocatalyst.

The development of efficient full-spectrum-activated photocatalysts has become a research topic of intense interest in environmental remediation or solar energy conversion applications. Herein, newly Z-scheme UV-vis-NIR-activated photocatalysts consisting of β-NaYF4:18% Yb3+, 2% Er3+@TiO2–Ag6Si2O7 (denoted as NaYF4@T–ASO) were designed and used as full-spectrum response photocatalysts. For tailoring NaYF4@T–ASO, the size of in situ deposited ASO nanoparticles on the surface of NaYF4@T microplates was determined by the pumping rate of the AgNO3 precursor, which played indirect roles in the photocatalytic activity with different carrier migration distances. Especially, NaYF4@T–ASO (S10) with the smallest and well distributed ASO nanoparticles showed superior photocatalytic activity than the commercial P25 TiO2 by 15 fold under the stimulated solar light irradiation. The enhanced photocatalytic performance of NaYF4@T–ASO could be ascribed to the synergic effect of the upconversion material and the direct Z-scheme heterojunction formed between TiO2/ASO, where the Z-scheme heterojunction induced efficient separation of photogenerated carriers and highly oxidative species (h+ and ˙O2−). Alternative mechanisms of carriers and energy transfer under various light sources have been proposed and discussed in detail.

Advanced anti-counterfeiting labels have aroused an intensive interest in packaging industry to avoid the serious issue of counterfeit. However, the preparation and cost of the existing labels associated with the drawbacks, including the complex and high-cost equipment, limit the protection of the authenticity of goods. Herein, we developed a series of anti-counterfeiting labels based on multicolor upconversion micro-particles (UCMPs) inks via straightforward and low-cost solutions, including spin-coating, stamping and screen printing. The UCMPs were synthesized through a facile hydrothermal process and displayed tunable red (R), green (G) and blue (B) color by doping different lanthanide ions, which are Er3+/Tm3+, Yb3+/Er3+ and Yb3+/Tm3+ in NaYF4 hosts, respectively. The optimal UCMPs inks were deposited on a flexible polyethylene terephthalate (PET) substrate to obtain transparent anti-counterfeiting labels possessing higher transmittance, stronger upconversion fluorescence intensity and good photostability. Under ambient conditions, the patterns and films were transparent, but could exhibit multicolor light under 980 nm laser excitation. They can be used as anti-counterfeiting labels for die-cutting packages to further elevate the security of goods. The tunable and designable transparent anti-counterfeiting labels based on RGB UCMPs inks exhibit the merits of low-cost, easy-manufacture and versatility, underlying the practical application in the field of anti-counterfeiting.

•The amorphous FeOOH/MnO2 composites are prepared by a facile method.•This material shows 350.2 F g−1 and 95.6% capacitance retention after 104 cycles.•All-printed flexible supercapacitors are fabricated on PET, paper and textile.•The device is capable to light up a 1.9 V LED, even after bending and stretching.More convenience and intelligence life lead by flexible/wearable electronics requires innovation and hommization of power sources. Here, amorphous FeOOH/MnO2 composite as screen-printed electrode materials for supercapacitors (SCs) is synthesized by a facile method, and solid-state flexible SCs with aesthetic design are fabricated by fully screen-printed process on different substrates, including PET, paper and textile. The amorphous FeOOH/MnO2 composite shows a high specific capacitance and a good rate capability (350.2 F g−1 at a current density of 0.5 A g−1 and 159.5 F g−1 at 20 A g−1). It also possesses 95.6% capacitance retention even after 10 000 cycles. Moreover, the all-printed solid-state flexible SC device exhibits a high area specific capacitance of 5.7 mF cm−2 and 80% capacitance retention even after 2000 cycles. It also shows high mechanical flexibility. Simultaneously, these printed SCs on different substrates in series are capable to light up a 1.9 V yellow light emitting diode (LED), even after bending and stretching.Download high-res image (238KB)Download full-size image

•g-C3N4/Ag/Ag3PO4 were synthesized by in situ deposition and reduction routes.•Photocatalytic activity of S1 is 24.7 times higher than P25 under visible light.•The g-C3N4/Ag/Ag3PO4 (S1) show a stable photodegradation after 6 times cycle.Trinary g-C3N4/Ag/Ag3PO4 heterostructures with different Ag content were designed and synthesized by in situ deposition and reduction routes. The photocatalytic performances of these heterostructures were investigated under visible light (λ > 450 nm) and simulated sunlight. Moreover, the influence of Ag content and ratio of each component on the photocatalytic performance of g-C3N4/Ag/Ag3PO4 was also studied. As a result, the photocatalytic activities of all these g-C3N4/Ag/Ag3PO4 samples were higher than commercial P25 (TiO2). Moreover, sample S1 (the ratio of g-C3N4, Ag3PO4 and Ag is 1: 2.52: 0.12) showed the better photocatalytic activities than other g-C3N4/Ag/Ag3PO4 samples (S2 and S3) and g-C3N4/Ag3PO4 (1: 3) under the same light irradiation. It indicated that small amount of Ag nanoparticles could improve the photocatalytic performances by compared with g-C3N4/Ag3PO4 sample. And S1 showed a stable photodegradation after 6 times of cycle experiments under simulated sunlight. The stable and significant superior photocatalytic performance of g-C3N4/Ag/Ag3PO4 could be attributed to the fast charge separation among g-C3N4, Ag and Ag3PO4 during the Z-scheme charge transfer and recombination process.Trinary g-C3N4/Ag/Ag3PO4 heterostructures with different Ag content were designed and synthesized for stable and superior photocatalytic application.Download high-res image (196KB)Download full-size image

Inorganic materials with controllable shapes have been an intensely studied subject in nanoscience over the past decades. Control over novel and anisotropic shapes of inorganic nanomaterials differing from those of bulk materials leads to unique and tunable properties for widespread applications such as biomedicine, catalysis, fuels or solar cells and magnetic data storage. This review presents a comprehensive overview of shape-controlled inorganic nanomaterials via nucleation and growth theory and the control of experimental conditions (including supersaturation, temperature, surfactants and secondary nucleation), providing a brief account of the shape control of inorganic nanoparticles during wet-chemistry synthetic processes. Subsequently, typical mechanisms for shape-controlled inorganic nanoparticles and the general shape of the nanoparticles formed by each mechanism are also expounded. Furthermore, the differences between similar mechanisms for the shape control of inorganic nanoparticles are also clearly described. The authors envision that this review will provide valuable guidance on experimental conditions and process control for the synthesis of inorganic nanoparticles with tunable shapes in the solution state.

Up-conversion materials can be applied in anti-counterfeit fields because of their high concealment and high up-conversion fluorescence efficiency. Herein, different lanthanide ions-doped β-NaYF4 up-conversion micro-particles (UCMPs) with uniform hexagonal morphology were synthesized on a large-scale (more than 0.5 g) via a facile hydrothermal method. It is very interesting to find out the fluorescence intensity and the eventual morphology of the UCMPs were highly dependent on the reaction conditions. Then, the optimal UCMPs with uniform morphology and strong fluorescence intensity were selected as promising candidates for preparing ink. Eventually, we successfully printed designable and multicolor fluorescent patterns on flexible substrates (common paper and polyethylene terephthalate, PET) using the as-prepared β-NaYF4:Yb3+,Tm3+/Er3+/Eu3+ UCMPs inks. Under ambient conditions, the printed patterns on conventional paper are invisible, while such printed patterns on PET are white. However, all the patterns could display blue, yellow-green and green fluorescence patterns under the irradiation of a 980 nm laser when using the β-NaYF4:Yb3+,Tm3+/Er3+/Eu3+ UCMPs inks. We envision that the UCMPs fluorescent inks-based flexible and rapid screen printing patterns have enormous potential for anti-counterfeit and security applications.

In this work, the novel dumbbell-like α-Fe2O3/Ag/AgX (X = Cl, Br, I) heterostructures were successfully synthesized via an in situ oxidation reaction and self-assembly process by using the α-Fe2O3/Ag core–shell nanoparticles (NPs). The as-obtained dumbbell-like α-Fe2O3/Ag/AgX heterostructure contains an individual spindle-like α-Fe2O3 nanoparticle and a single near-spherical Ag/AgX nanoparticle. The morphology, microstructure, component and optical property of as-synthesized α-Fe2O3/Ag/AgX heterostructures were characterized by various analytical techniques. The great changing of morphology and component in such synthesis route make great effect on the final photocatalytic performance. The dumbbell-like α-Fe2O3/Ag/AgX heterostructures exhibit excellent photocatalytic activity for the degradation of RhB dye under simulated sunlight irradiation. In particular, the α-Fe2O3/Ag/AgCl can completely degrade RhB molecules within only 20 min under simulated sunlight irradiation, which is superior to the pure α-Fe2O3, α-Fe2O3/Ag NPs, and commercial P25. The enhanced activity is attributed to the efficient interfacial charge rectification and faster carrier migration in the α-Fe2O3/Ag/AgX heterostructures. Furthermore, the degradation rate of as-synthesized dumbbell-like α-Fe2O3/Ag/AgX (X = Cl, Br, I) heterostructures follows this order: α-Fe2O3/Ag/AgCl > α-Fe2O3/Ag/AgBr > α-Fe2O3/Ag/AgI. The results can be owing to that the oxidation capability of Cl0 is stronger than Br0 and I0. This unique synthetic work can provide physical insight into prepare novel nanomaterials with special structures and properties, which can apply in photocatalysis, photosplitting of water and solar cell, etc.Keywords: Dumbbell-like structure; Noble metal; Photocatalytic activity; Silver halides

Coupling two different semiconductors to form composite photocatalysts is the most significant method for environmental remediation. In this regard, tube-like α-Fe2O3/Ag6Si2O7 heterostructures are synthesized via anchoring p-type Ag6Si2O7 nanoparticles (NPs) on the surface of n-type α-Fe2O3 short nanotubes (SNTs) by conventional wet-chemical routes. α-Fe2O3 SNTs are firstly fabricated by a hydrothermal method with the assistance of dihydrogen phosphate and sulphate. Then, Ag6Si2O7 NPs are anchored on α-Fe2O3 SNTs by an in situ deposition method, and the α-Fe2O3/Ag6Si2O7 p–n heterostructures are finally obtained. The morphologies, crystal structure, photocatalytic performance and photocurrent properties of as-synthesized α-Fe2O3/Ag6Si2O7 heterostructures are investigated. Six organic dyes are used for determining the high-efficiency Z-scheme photocatalytic activities of the as-obtained photocatalysts under ultraviolet and visible light (mercury lamp, 300 W). Compared with pure α-Fe2O3 SNTs, the photocurrent intensity of the α-Fe2O3/Ag6Si2O7 heterostructures is improved 62 times. The enhanced significant photocatalytic performance of α-Fe2O3/Ag6Si2O7 heterostructures could be attributed to charge transfer between Ag6Si2O7 NPs and the charge separation between Ag6Si2O7 NPs and α-Fe2O3 SNTs. These composite heterostructures are proposed to be an example for the preparation of other composite silicate photocatalysts for practical application in environmental remediation issues.

Iron oxide nanocrystals (IONCs) with various geometric morphologies show excellent physical and chemical properties and have received extensive attention in recent years. The various shape-induced magnetic and electrochemical properties of the IONCs make them suitable for diverse applications. Understanding the correlation between the physicochemical properties and morphology of IONCs is a prerequisite for their widespread applications. Hence, this review focuses on current research progress regarding shape-controlled IONCs in different dimensions, and the corresponding shape-dependent magnetic, catalytic and gas-sensor properties are discussed. Furthermore, the general preparation methods, shape-guided growth mechanisms and energy conversion applications in photoelectrochemical water splitting, dye-sensitized solar cells (DSSCs) and lithium-ion batteries (LIBs) of these IONCs (α-Fe2O3, γ-Fe2O3, Fe3O4) are also discussed. Finally, the perspectives of IONCs in promising research directions are proposed.

Characteristics of crystal quality, including crystal size distribution, size, morphology, polymorphism and chirality, have been established as important indicators of crystalline materials. There have been many attempts at controlling crystal quality during crystallization. Herein, this study summarizes crystal quality control by using temperature cycling during solution state crystallization. During crystallization, the temperature cycling is implemented through successive heating–cooling cycles for dissolution and recrystallization in crystal suspension. Therefore, the fines crystals or one species are expected to dissolve out completely during the heating period, and the remaining crystals or dominant species continuously grow or nucleate during the cooling period. When such temperature cycling is facilitated during crystallization, the characteristics of crystal quality, including crystal size distribution, size, morphology, polymorphism and chirality, are well managed. Furthermore, based on the basic principle of temperature cycling, the key parameters for controlling each characteristic of crystal quality are clearly elucidated during the process. Thus, this review provides qualitative insight into the general operation strategies and the principle of temperature cycling for crystal quality control during crystallization.

The p–n heterojunction is an effective structure to suppress the recombination of photogenerated charge carriers due to the built-in internal electric field. Herein, we successfully synthesize a spindle-like α-Fe2O3/Bi2O3 core–shell heterostructure, in which α-Fe2O3 is an n-type semiconductor and Bi2O3 is a p-type semiconductor. In comparison with pure α-Fe2O3 seeds, the α-Fe2O3/Bi2O3p–n heterojunction photocatalyst exhibits tremendous photocatalytic performance on the degradation of Rhodamine B (RhB) under illumination of visible light. In addition, we insert an interlayer between p–n heterostructure, similar to p–i–n heterostructure. The silicon oxide and carbon are selected as the interlayer due to its different conductivity. The as-obtained α-Fe2O3/C/Bi2O3 exhibits higher degradation rate than α-Fe2O3/SiO2/Bi2O3. The reason is attributed to the mesoporous structure of carbon layer and its high conductivity so that the photogenerated electrons can be easily transferred from the conduction band of α-Fe2O3 to the conduction band of Bi2O3 thereby promoting an effective separation of photogenerated electrons and holes. However, the introduction of interlayer reduces the photocatalytic activity due to the alteration of internal built-in electric field in the heterojunction. We envision that these results have potential applications for designing the heterostructural photocatalysts.The spindle-like α-Fe2O3/Bi2O3 core–shell p–n heterojunction has been prepared and it exhibits excellent photocatalytic performance for the degradation of Rhodamine B (RhB) under illumination of visible light. To further understand the mechanism of this p–n heterostructure, carbon and silica are introduced as an interlayer between the p-type and n-type semiconductor.

•Two different tetragonal α-Fe2O3 are synthesized via hydrothermal approach.•Different metal ions induced different exposed facets and shapes for α-Fe2O3.•Tetragonal α-Fe2O3 single crystals exhibit good cycling and rate performance.•Cubic α-Fe2O3 products significantly improved Li-storage cycling performance.Understanding the correlation between the desired morphology of nanostructures and its electrochemical properties is a prerequisite for widespread application of advanced energy materials. Herein, two types of tetragonal α-Fe2O3 single crystals with a mean size of ca. 200 nm, including cubic and thorhombic shapes, have been synthesized via a facile hydrothermal approach. The as-obtained shape of α-Fe2O3 nanocrystals depends on the addition of the metal ions precursor, the Zn2+ ions result in the cubic shape and the Cu2+ ions result in the thorhombic shape, respectively. These two different tetragonal α-Fe2O3 single crystals are used as anode materials for lithium ion batteries (LIBs), and the results reveal that cubic α-Fe2O3 single crystal exhibits a better performance than thorhombic α-Fe2O3 single crystal. The discharge capacity of cubic α-Fe2O3 single crystal is up to 1028 mAh/g, and the current density is up to 1000 mA/g (1C) after 222 cycles. Clearly, the α-Fe2O3 single crystal with controlled shapes would improve the electrochemical performance of LIBs as superior anode materials, and this approach could pave a way to develop high performance LIBs.

The 3D flowerlike α-Fe2O3@TiO2 core–shell nanocrystals with thorhombic, cubic, and discal morphologies are synthesized for photocatalytic application. α-Fe2O3 nanocrystals were prepared via a Cu2+, Zn2+, and Al3+ ion-mediated hydrothermal route. The α-Fe2O3@TiO2 core–shell nanocrystals are obtained via a hydrothermal and annealing process. The shape-dependent photocatalytic activities of these as-obtained α-Fe2O3@TiO2 core–shell nanocrystals are measured. The results reveal that the discal α-Fe2O3@TiO2 nanocrystals exhibit the best photocatalytic activity relative to the other two core–shell nanocrystals because the discal α-Fe2O3 nanocrystals possess more rough surface and surface defects. The fast interfacial charge-transfer process and the wide spectral response could be the driving force for the enhanced photocatalytic performance. These core–shell architectures provide a positive example for synthesis of novel composite nanomaterial.Keywords: Core−shell structure; Heterostructures; Iron oxide; Photocatalyst; Titanium dioxide;

Monodisperse silver nanoparticles (NPs) have been synthesized on a large scale by oxidation–reduction reactions in water by adding triethylamine to the aqueous solutions of AgNO3, glucose and poly(vinyl pyrrolidone). Different anions, including –SO42−, –PO43−, –CO32− and –Br−, are introduced to the abovementioned mixture to form slightly soluble silver compounds, which are used as the precursor to synthesize silver NPs. The effects of silver nitrate–glucose ratio and reaction temperature are investigated. The electrical performance of the as-obtained Ag NPs has been studied, and the results reveal that the –CO32− mediated-synthesized Ag NPs possess the lowest resistivity. Note that silver NPs can be well-dispersed in ethanol and generated as inks, which can be screen printed onto flexible polyester (PET) and paper substrates and form conductive patterns after a low-temperature sintering treatment. An optimal electrical resistivity can be reached at 5.72 μΩ cm, which is much closer to the value of bulk silver (1.6 μΩ cm). Evidently, the synthesized silver NPs could be considered as low-cost and effective materials that have a great potential application for flexible printed electronics.

Rational designing and controlling of nanostructures is a key factor in realizing appropriate properties required for the high-performance energy fields. In the present study, hollow SnO2@C nanoparticles (NPs) with a mean size of 50 nm have been synthesized in large-scale via a facile hydrothermal approach. The morphology and composition of as-obtained products were studied by various characterized techniques. As an anode material for lithium ion batteries (LIBs), the as-prepared hollow SnO2@C NPs exhibit significant improvement in cycle performances. The discharge capacity of lithium battery is as high as 370 mAh g−1, and the current density is 3910 mA g−1 (5 C) after 573 cycles. Furthermore, the capacity recovers up to 1100 mAh g−1 at the rate performances in which the current density is recovered to 156.4 mA g−1 (0.2 C). Undoubtedly, sub-100 nm SnO2@C NPs provide significant improvement to the electrochemical performance of LIBs as superior-anode nanomaterials, and this carbon coating strategy can pave the way for developing high-performance LIBs.SnO2@C nanoparticles have been synthesized in large-scale via a facile hydrothermal approach, and characterized by the various techniques, which exhibits significant improvement in cycle performance as an anode material for lithium ion batteries.

•The SiO2 particles as template are used to prepare hollow SnO2 particles.•Au and Ag nanoparticles have been coated on the surface of SnO2.•Direct Schottky contact (Au/SnO2) shows better photocatalytic activity than that of ohmic contact (Ag/SnO2).•The enhanced photocatalysis has been quantitatively interpreted by the FDTD simulations.According to relative energy band positions between noble metals of Au, Ag, and wide bandgap semiconductor SnO2, Au, and Ag nanoparticles (NPs) modified hollow SnO2 NPs were designed. Firstly, the hollow SnO2 NPs have been synthesized by employing the silica template-assisted hydrothermal methods, then Au and Ag were coated on the surface of SnO2 to form the core–shell structures, respectively. The morphology, composition, and optical properties of as-prepared samples have been investigated by various analytic methods. Subsequently, the photocatalytic reaction to Rhodamine B (RhB) dye under simulated-sunlight irradiation was employed to investigate their photocatalytic performance, the results demonstrate the metal–semiconductor with direct Schottky contact exhibited remarkable photocatalytic activity. The finite difference time domain (FDTD) calculation results illustrate the introduced and decorated Au and Ag NPs could enhance the harvesting abilities for visible light. We envision the aforementioned synthesized strategy and catalytic results are used to the designing and application of other metal–semiconductor system.

Heterogeneous photocatalysis is of great interest for environmental remediation applications. However, fast recombination of photogenerated electron–hole pair and a low utilization rate of sunlight hinder the commercialization of currently available semiconductor photocatalysts. In this regard, we developed a unique ternary single core-double shell heterostructure that consists of α-Fe2O3@SnO2@Cu2O. This heterostructure exhibits a tube-like morphology possessing broad spectral response for the sunlight due to the combination of narrow bandgap and wide bandgap semiconductors forming a p–n heterojunction. To fabricate such a short nanotube (SNT), we used an anion-assisted hydrothermal route for deposition of α-Fe2O3, a seed-mediated deposition strategy for SnO2, and finally an aging process to deposit a Cu2O layer to complete the tube-like ternary α-Fe2O3@SnO2@Cu2O single core-double shell heterostructures. The morphology, composition, and photocatalytic properties of those ternary core–shell–shell heterostructures were characterized by various analytical techniques. These ternary heterostructures exhibited enhanced photocatalytic properties on the photodegradation of the organic dye of Rhodamine B (RhB) under simulated sunlight irradiation. The origin of enhanced photocatalytic activity is due to the synergistic effect of broad spectral response by combining narrow bandgap and wide bandgap semiconductors and, hence, an efficient charge separation of photogenerated electron–hole pairs facilitated through the p–n heterojunction. Furthermore, our unique structure provides an insight on the fabrication and controlled preparation of multilayer heterostructural photocatalysts that have intriguing properties.Keywords: iron oxide; multilayer heterostructure; photocatalytic activity; p−n heterojunction

Our study reports a novel iron oxide/noble metal/semiconductor ternary multilayer hybrid structure that was synthesized through template synthesis and layer-by-layer deposition. Three different morphologies of α-Fe2O3/Ag/SiO2/SnO2 hybrid architectures were obtained with different thicknesses of the SiO2 interlayer which was introduced for tailoring and controlling the coupling of noble metal Ag nanoparticles (NPs) with the SnO2 semiconductor. The resulting samples were characterized in terms of morphology, composition, and optical property by various analytical techniques. The as-obtained α-Fe2O3/Ag/SiO2/SnO2 nanocomposites exhibit enhanced visible light or UV photocatalytic abilities, remarkably superior to commercial pure SnO2 products, bare α-Fe2O3 seeds, and α-Fe2O3/SnO2 nanocomposites. Moreover, the sample of α-Fe2O3/Ag/SiO2/SnO2 also exhibits good chemical stability and recyclability because it has higher photocatalytic activity even after eight cycles. The origin of enhanced photocatalytic activity on the multilayer core–shell α-Fe2O3/Ag/SiO2/SnO2 nanocomposites was primarily ascribed to the coupling between noble metal Ag and the two semiconductors Fe2O3 and SnO2, which are proven to be applied in recyclable photocatalysis.Keywords: heterostructures; iron oxide; noble metal; photocatalytic activity; SiO2 interlayer;

•We present a facile approach to the gram-scale production of the carbon–core/Ag–shell (C@Ag) nanoparticles.•A controllable Ag shell thickness from 10 to 40 nm can be tailored by simple adjustments of repeat coating times.•The conductive ink of C@Ag nanoparticles was printed on paper by screen printing.•The conductivity of printing antenna depends on the Ag coating thickness.The large-scale synthesis and characterization of carbon–core/Ag–shell (C@Ag) nanoparticles by the successive reduction of silver ammonia are described. The resultant C@Ag nanoparticles had a mean core diameter of 360 nm and a controllable shell thickness from 10 to 40 nm by simple adjustments of repeat coating times. Various analysis techniques confirmed that the carbon cores were fully covered by Ag nanoshells. The results also show that C/Ag composite nanomaterials-based conductive inks, which can be easily produced on a large scale and possess outstanding electronic properties, have great potential for the convenient fabrication of flexible and low-cost carbon-based electronic devices and replace the traditional pure silver paste, by using a simple screen printing technique.Graphical abstract

Mesoporous spindlelike iron oxide/ZnO core–shell heterostructures are successfully fabricated by a low-cost, surfactant-free, and environmentally friendly seed-mediate strategy with the help of postannealing treatment. The material composition and stoichiometry, as well as these magnetic and optical properties, have been examined and verified by means of high-resolution transmission electron microscopy and X-ray diffraction, the thickness of ZnO layer can be simply tailored by the concentration of zinc precursor. Considering that both α-Fe2O3 and ZnO are good photocatalytic materials, we have investigated the photodegradation performances of the core–shell heterostructures using organic dyes Rhodamin B (RhB). It is interesting to find that the as-obtained iron oxides/ZnO core–shell heterostructures exhibited enhanced visible light or UV photocatalytic abilities, remarkably superior to the as-used α-Fe2O3 seeds and commercial TiO2 products (P25), mainly owing to the synergistic effect between the narrow and wide bandgap semiconductors and effective electron–hole separation at the interfaces of iron oxides/ZnO.Keywords: heterostructure; magnetic properties; mesoporous structure; photocatalyst; semiconductors;

Rare-earth ion (RE3+) doped up-conversion (UC) fluorescent materials and novel fluorescent carbon quantum dots (CDs) have been widely used as traditional anti-counterfeiting materials owing to their excellent optical properties. The drawbacks of these materials are being exposed gradually with the widespread occurrence of counterfeit products in the market because of their single fluorescence mode and easy replication. In this work, we propose a novel strategy to combine both luminescent materials with different modes via a facile solvothermal method. Interesting, the composite materials show unalterable down-conversion (DC) blue light under a 365 nm ultraviolet (UV) analyzer, except for adjustable UC luminescence properties. The UC and DC optical properties are measured and the probable mechanism is proposed, indicating that the dual-mode fluorescence processes are separate and do not interference with each other. Moreover, we use a mixture containing a small number of UCMPs/CDs and poly(acrylic acid) (PAA) aqueous solution as a colorless anti-counterfeiting ink, and successfully print a variety of dual-mode fluorescence patterns through the screen printing technique, including QR codes, the logo of Wuhan University, and clover patterns. The composite materials show good dispersion and outstanding dual-mode fluorescence properties, suggesting that they are promising luminescent materials in the anti-counterfeiting field.

The development of photocatalysts with superior photoactivity and stability for the degradation of organic dyes is very important for environmental remediation. In this study, we have presented a multidimensional (1D and 2D) structured CdS/ZnIn2S4/RGO photocatalyst with superior photocatalytic performance. The CdS/ZnIn2S4 helical dimensional heterostructures (DHS) were prepared via a facile solvothermal synthesis method to facilitate the epitaxial growth of 2D ZnIn2S4 nanosheets on 1D CdS nanowires. Ultrathin 2D ZnIn2S4 nanosheets have grown uniformly and perpendicular to the surface of 1D CdS nanowires. The as-obtained 1D/2D CdS/ZnIn2S4 helical DHS show good photocatalytic properties for malachite green (MG). Subsequently, 2D reduced graphene oxide (RGO) was introduced into the 1D/2D CdS/ZnIn2S4 helical DHS as a co-catalyst. The photoactivity and stability of the CdS/ZnIn2S4/RGO composites are significantly improved after 6 cycles. The enhanced photoactivity can be attributed to the high surface area of RGO, the improved adsorption of organic dyes and the efficient spatial separation of photo-induced charge carriers. The transfer of photo-generated electrons from the interface of CdS and ZnIn2S4 to RGO also restricted the photocorrosion of metal sulfide, suggesting an improved stability of the reused CdS/ZnIn2S4/RGO composited photocatalyst.

Up-conversion materials can be applied in anti-counterfeit fields because of their high concealment and high up-conversion fluorescence efficiency. Herein, different lanthanide ions-doped β-NaYF4 up-conversion micro-particles (UCMPs) with uniform hexagonal morphology were synthesized on a large-scale (more than 0.5 g) via a facile hydrothermal method. It is very interesting to find out the fluorescence intensity and the eventual morphology of the UCMPs were highly dependent on the reaction conditions. Then, the optimal UCMPs with uniform morphology and strong fluorescence intensity were selected as promising candidates for preparing ink. Eventually, we successfully printed designable and multicolor fluorescent patterns on flexible substrates (common paper and polyethylene terephthalate, PET) using the as-prepared β-NaYF4:Yb3+,Tm3+/Er3+/Eu3+ UCMPs inks. Under ambient conditions, the printed patterns on conventional paper are invisible, while such printed patterns on PET are white. However, all the patterns could display blue, yellow-green and green fluorescence patterns under the irradiation of a 980 nm laser when using the β-NaYF4:Yb3+,Tm3+/Er3+/Eu3+ UCMPs inks. We envision that the UCMPs fluorescent inks-based flexible and rapid screen printing patterns have enormous potential for anti-counterfeit and security applications.

Coupling two different semiconductors to form composite photocatalysts is the most significant method for environmental remediation. In this regard, tube-like α-Fe2O3/Ag6Si2O7 heterostructures are synthesized via anchoring p-type Ag6Si2O7 nanoparticles (NPs) on the surface of n-type α-Fe2O3 short nanotubes (SNTs) by conventional wet-chemical routes. α-Fe2O3 SNTs are firstly fabricated by a hydrothermal method with the assistance of dihydrogen phosphate and sulphate. Then, Ag6Si2O7 NPs are anchored on α-Fe2O3 SNTs by an in situ deposition method, and the α-Fe2O3/Ag6Si2O7 p–n heterostructures are finally obtained. The morphologies, crystal structure, photocatalytic performance and photocurrent properties of as-synthesized α-Fe2O3/Ag6Si2O7 heterostructures are investigated. Six organic dyes are used for determining the high-efficiency Z-scheme photocatalytic activities of the as-obtained photocatalysts under ultraviolet and visible light (mercury lamp, 300 W). Compared with pure α-Fe2O3 SNTs, the photocurrent intensity of the α-Fe2O3/Ag6Si2O7 heterostructures is improved 62 times. The enhanced significant photocatalytic performance of α-Fe2O3/Ag6Si2O7 heterostructures could be attributed to charge transfer between Ag6Si2O7 NPs and the charge separation between Ag6Si2O7 NPs and α-Fe2O3 SNTs. These composite heterostructures are proposed to be an example for the preparation of other composite silicate photocatalysts for practical application in environmental remediation issues.