In this work, a new design of ternary core–shell nanostructures of Au@ZnO–Pd was demonstrated to realize the synergetic utilization of a plasmonic effect and an electron-trapping co-catalyst for enhanced photocatalytic performance. In the ternary hybrid nanostructures, ZnO provides photo-generated carriers with higher redox ability, under UV-visible light, and Au nanocrystals perform the plasmonic hot electron injection as well as the local electromagnetic field enhancement of ZnO photoexcitation. Meanwhile, the Pd NPs can efficiently trap the generated electrons to govern the directional separation of the charge carriers. The efficient charge carrier separation in the ternary hybrid nanostructures was confirmed by steady-state PL spectra, time-resolved PL decay spectra, and transient photocurrent responses. The photocatalytic activity of the Au@ZnO–Pd nanostructures was evaluated by photodegrading phenol and methylene blue, respectively, under simulated sunlight (λ = 360–780 nm), and the results showed that the Au@ZnO–Pd nanostructures gained a great enhancement of photocatalysis compared with ZnO, ZnO–Pd and Au@ZnO. Moreover, the effect of Pd loading content in the Au@ZnO–Pd nanostructures on the photocatalytic efficiency was studied within a certain range, indicating that the Au@ZnO–Pd photocatalyst with ∼1.8 wt% Pd loading exhibited the best photocatalytic activities for photodegrading both phenol and methylene blue. The generation and effect of active species in the photocatalytic process were investigated using ESR testing and radical scavenging experiments. As a consequence, the integration of the ternary Au@ZnO–Pd core–shell nanostructures could achieve collective effects to greatly increase the photocatalytic efficiency.

Investigating the dependence of the catalysis on the size and structure of materials is of great significance for exploiting catalysts with characteristics of high activity, low cost, and new property. Non-precious metal catalysts bear high hope to meet the increasing demands of industrial applications in a cost-effective and environmentally friendly way. In this work, we take size-controlled BiOCl nanosheets as examples, which are synthesized via a hydrothermal method by changing the reaction conditions. The BiOCl nanosheets were characterized in details to understand their size–property relationships, and were found to exhibit a series of thickness-dependent physicochemical properties, including specific surface area, light absorption, and the separation efficiency of photo-generated charge carriers. Moreover, this work demonstrates the first example that BiOCl nanostructures have very high catalytic activity for the reduction of nitrophenols by sodium borohydride, without any light irradiation. The high catalytic activity of BiOCl nanosheets was proved to be due to the metallic Bi0 clusters that were produced by surface Bi (III) reduction. The catalytic activity increased greatly with a decrease in the average thickness from 106.42 nm of BiOCl(H2O) to 3.47 nm of ultrathin BiOCl, because the increased specific surface area provided more active sites for catalytic reactions. As a result, this work provides evidences for the size–property relationships of nanostructured catalysts as well as some inspirations for exploiting novel heterogeneous catalysis of BiOCl nanomaterials.Download high-res image (190KB)Download full-size image

Transition metal oxides with hollow or mesoporous microstructures represent a unique class of heterogeneous catalysts or catalyst supports with many fascinating features such as the large surface areas, tunable pore sizes and volumes, multitude of compositions, and ease of functionalization. In this work, we demonstrated a general ultrasonic-spray-assisted synthesis of various transition metal oxide hollow/mesoporous microspheres, using only low-cost commercial metal chlorides as precursors and water as solvent. As typical examples, five mono-component metal oxides (CeO2, α-Fe2O3, Co3O4, SnO2 and TiO2) hollow or mesoporous microspheres were prepared and their formation mechanisms were discussed. The catalytic carbon monoxide (CO) oxidation indicated that these metal oxide products exhibited improved catalytic activities than some of those reported previously, due to their tiny crystalline grains, large pore volume and specific surface area. The universality of this synthetic method was also demonstrated in producing multi-component and multi-functional metal oxides with hollow/mesoporous structures. This work therefore provides an industrial level producing method for the scalable preparation of various metal oxide hollow/mesoporous microspheres which are expected to be used as high-performance catalysts or catalyst supports in more chemical reactions.

•Porous MgO material with ultrahigh surface area was synthesized.•A composite PCM was prepared from PEG-1000 and the porous MgO.•The phase change temperatures and enthalpy of the composite were measured.•The composite PCM performed good shape-stabilized property.Mesoporous magnesium oxide (MgO) material was synthesized using an integration of the evaporation-induced surfactant assembly and magnesium nitrate pyrolysis. The as-prepared MgO material is well crystalline, and possesses three-dimensional interconnected mesopores and a surface area as high as 596 m2/g. Using the porous MgO as a matrix and polyethylene glycol (PEG-1000) as the functional phase for heat energy storage, a shape-stabilized phase change composite of PEG/MgO was fabricated by an easy impregnation method. In the composite, mesoporous MgO material provides structural strength and prevents the leakage of the molten PEG during the phase change process. The compositions and microstructures of the PEG/MgO composite were determined by Fourier transformation infrared spectroscope (FT-IR), X-ray diffractometer (XRD), scanning electronic microscope (SEM) and thermogravimetric analyzer (TGA), respectively. The phase change properties of the PEG/MgO composite were determined by differential scanning calorimeter (DSC). The high heat-energy storage capability and good thermal stability of the composite enable it extensive applications in the future.

•TiO2 micro/nanostructures were chemically deposited on glass substrates.•Excellent superhydrophobicity with low roll-off angle and good rebound property.•The double control over roughness and transparency of the coatings are achieved.•The coatings remain superhydrophobic even heated at temperatures up to 200 °C.Superhydrophobic surfaces generally require a combination of surface topography and low surface energy, where a thick surface coating on the substrate usually leads to loss of its transparency or color. We demonstrated a convenient and controllable strategy for fabricating the superhydrophobic TiO2 coatings with improved transparency on glass substrates. The TiO2 coating possesses hierarchical morphology assembled by radial nanowires, which effectively constructed a rough surface topography and sufficiently captured air pockets. After thermal annealing and modification with stearic acid, the as-prepared TiO2 coating on glass exhibited excellent superhydrophobicity with a water contact angle (WCA) as high as 157°, low roll-off angle of 2° and good bounce performance. The growth process of the hierarchical TiO2 coating was studied. The double control over roughness and transparency of the superhydrophobic coatings on the glass substrate are achieved by adjusting the original concentration of titanium source. Moreover, the coatings remain superhydrophobic even heated at temperatures up to 200 °C for 30 min.

In this work, a novel microencapsulated phase change composite of paraffin@SiO2 was prepared by in situ emulsion interfacial hydrolysis and polycondensation of tetraethyl orthosilicate (TEOS). The as-prepared paraffin@SiO2 composite was determined by Fourier transformation infrared spectroscope (FT-IR), X-ray diffractometer (XRD), scanning electronic microscope (SEM), and transmission electron microscopy (TEM), respectively. The results showed that the paraffin@SiO2 composite is composed of quasi-spherical particles with diameters of 200–500 nm. The paraffin is encapsulated in a SiO2 shell, and there is no chemical reaction between them. The DSC results indicate that the melting temperature and latent heat of the composite are 56.5 °C and 45.5 J/g, respectively. The encapsulation ratio of paraffin was calculated to be 31.7% from the results of the DSC measurements, slightly lower than the loading content (32.5%) of paraffin in the microencapsulated composite from the TGA measurements. The as-prepared paraffin@SiO2 composite could maintain its phase transition perfectly after 30 melting–freezing cycles, and no leakage of paraffin was observed at 70 °C for 20 min. Moreover, the high heat storage capability and good thermal stability of the composite enable it to be a potential material to store thermal energy in practical applications.Keywords: Chemical synthesis; Composite; Microencapsulation; Phase change material; Thermal energy storage

Gathering the photocatalysis of semiconductors and the superduper electron transmittability of graphene, graphene-based semiconductor photocatalytic composites are attracting increasing interest of researchers. In this paper, a Cu2O/reduced-graphene-oxide (Cu2O/RGO) nanocomposite was prepared via a facile wet-reduction process, for removal of organic pollutants. The samples were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, and UV–vis spectrophotometry. The nanocomposite is composed of Cu2O nanoparticles with sizes of 100–500 nm attached to the RGO sheets. For photodegradation of methylene blue (MB) under visible light, the Cu2O/RGO nanocomposites exhibited greatly enhanced photocatalytic efficiency compared to the pure Cu2O nanoparticles. The enhanced photocatalytic performance was mainly ascribed to the increased adsorptivity to organic dye as well as the efficient charge transportation and separation from Cu2O to RGO.Highlights► Cu2O/reduced-graphene-oxide (Cu2O/RGO) nanocomposite was synthesized via a mild one-pot wet-reduced route. ► The Cu2O/RGO nanocomposite exhibited greatly enhanced visible-light-driven photocatalytic performance. ► The mechanism for the enhanced photocatalytic activity of Cu2O/RGO nanocomposite was discussed.

A char forming agent and silica-gel microencapsulated APP were selected to form novel intumescent flame-retardant system (IFR) to prepare flame-retardant low-density polyethylene (LDPE) composites, and then the influence of zeolites on the thermal and flame-retardant properties of flame-retardant LDPE composites were studied. With the addition of 1 wt% zeolites to LDPE/IFR system, the LOI value increases from 29.0 to 34.0 %. The results of cone calorimetry show that the heat release rate peak and total heat release of the intumescent flame-retardant LDPE composite with 1 wt% zeolites decreases remarkably compared with that of without zeolites. The scanning electron microscopy indicates zeolites with suitable content can improve the quality of the char layer of flame-retardant LDPE composite which is more coherent and dense. The zeolites with the appropriate content can remarkably improve the flame-retardant properties of the LDPE composites.

ZnO/CdS nano-heterostructure with flower-like morphology is fabricated by a facile two-step precipitation method for use in photocatalytic degradation of organic dyes. The as-prepared samples were characterized by X-ray diffraction, scanning electron microscopy, and UV–vis spectroscopy, demonstrating that the microstructure of the ZnO/CdS nano-heterostructure is composed of flower-like ZnO modified by CdS nanoparticles. The photocatalytic performance of ZnO/CdS nano-heterostructure is evaluated by the photodegradation of rhodamine B under the simulated sunlight, and the result indicates that the ZnO/CdS nano-heterostructure exhibits an appreciable photocatalytic property, which can be attributed to the extended photo-response range and the increased charge separation rate in the heterostructure.Highlights► ZnO/CdS nano-heterostructure was fabricated by a facile method. ► Microstructures of the samples were characterized. ► ZnO/CdS nano-heterostructure exhibited an improved photocatalytic property. ► Possible photocatalytic mechanism was proposed.

This paper presents a facile, low-cost and pollution-free route to prepare porous metal oxide nanomaterials. Hierarchically assembled ZnO microstructures with multi-scaled porosity were obtained by calcining the flower-like assembly of a basic zinc carbonate (BZC) precursor which was synthesized by a facile low-temperature (100 ∘C) homogenous precipitation without using any organic solvent or surfactant. A gas sensor based on the porous ZnO sample exhibited higher response to ethanol and formaldehyde gases than commercial ZnO powder. The facile preparation method and the improved property derived from the hierarchically porous microstructure are of great significance in the synthesis and application of nanomaterials.

Nanostructured ZnO–CuO composite with an open and porous surface was successfully prepared through a simple one-step homogeneous coprecipitation method under low temperature (80 °C), without using any organic solvent or surfactant. The as-prepared samples were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, and UV–vis spectroscopy. The results demonstrated that the ZnO–CuO nanocomposite presented a hierarchical 3D morphology composed of flower-like ZnO microstructures adorned with leaf-like CuO nanopatches. The photocatalytic activity of ZnO–CuO nanocomposite was evaluated by the photodegradation of rhodamine B under the simulated sunlight irradiation, and compared with those of the monocomponent oxides synthesized by the identical synthetic route and their physical mixture in the approximate molar ratio as that of the nanocomposite. The results indicated that the ZnO–CuO nanocomposite exhibited an appreciable photocatalytic activity, which was mainly attributed to the extended photo-responding range and the increased charge separation rate in the nanocomposite.

•Au/CeO2 hybrid nanofibers with different Au loadings were synthesized.•Au/CeO2 exhibited improved photocatalysis for benzyl alcohol oxidation.•Various factors influencing the photocatalytic activity were analyzed.•The photocatalytic mechanism was discussed.Exploiting photocatalysts with improved properties for solar-driven chemical reactions is of great significance in developing green chemistry. Here, a series of Au/CeO2 hybrid nanofibers with different Au loadings have been fabricated by a simple method of electrospinning followed by calcination in air. The particle size and plasmonic absorption of Au nanoparticles (NPs) loaded in the nanofibers were analyzed and found to vary with the dosage of chloroauric acid in the precursor solution. The Au/CeO2 hybrid nanofibers were used as photocatalysts for selective oxidation of benzyl alcohol to benzaldehyde with O2 under simulated sunlight and visible light (>420 nm), respectively. The results showed that introducing Au NPs into CeO2 nanofibers induced a great improvement in photocatalysis. The degree of improvement increased first and then decreased with the increase in Au loading, reaching an optimal level over 0.5 wt.% Au-loaded CeO2 nanofibers. The photocatalytic reaction presents a very high selectivity of 100% for benzaldehyde, which is important for organic synthesis. The transient photocurrent responses of the Au/CeO2 catalysts were also tested for corroborative evidence. After detailed discussion of various factors including plasmonic absorption, charge transfer, and surface activity of the photocatalyst, a possible mechanism for the photocatalytic oxidation of benzyl alcohol occurring at the Au–CeO2 interface was proposed.Download high-res image (71KB)Download full-size image

Constructing a core–shell nanostructured photocatalyst by integration of plasmonic metal nanocrystals and a semiconductor can offer large active metal/semiconductor interfacial areas and avoid aggregation of the metal nanocrystals. Herein, well-defined Au@ZnO core–shell nanostructures were prepared by coating ZnO on cetyltrimethylammonium bromide (CTAB) stabilized Au nanospheres in aqueous solution. The resultant core–shell nanostructures have Au-nanosphere cores with a diameter of ∼55 nm and ZnO shells with a thickness of ∼50 nm. After calcination at 350 °C in air, the mesoporous ZnO shell with higher crystallinity and a larger surface area was obtained without any significant change in the morphology or plasmon band of Au@ZnO. The specific surface plasmon resonance of the Au-nanosphere cores endows the Au@ZnO nanostructures with strong visible light absorption around 550 nm. The photocatalytic degradation of an organic pollutant was performed under simulated sunlight and monochromatic LED light with three different wavelengths (365 nm, 520 nm, 660 nm), demonstrating the enhanced photocatalysis of the Au@ZnO nanostructures. Furthermore, the Au@ZnO as a photoelectrode material presents a higher photocurrent density than that of pure ZnO nanoparticles under simulated sunlight. The electrochemical impedance spectra (EIS) Nyquist plots also confirm the higher charge transfer efficiency of the Au@ZnO nanostructures. Such plasmonic metal–semiconductor core–shell nanostructures would provide a desirable platform for studying plasmon-induced/enhanced processes and have great potential in light-harvesting applications.