Mechanistic Investigations of PEG-Directed Assembly of One-Dimensional ZnO Nanostructures

Apple-like Zinc-Oxide Mesocrystals as Robust and Versatile Photocatalysts for Efficient Degradation of Eight Different Organic Dyes

The discovery of efficient photocatalysts is a promising key approach to solve the environmental crisis caused by hazardous organic dyes. Herein, we have for the first time created ZnO mesocrystals with a novel apple-like morphology. We have developed a one-pot biomineralization route to synthesize ZnO nanostructures at room temperature by using the rod-like protein collagen as the template. The shape of ZnO mesocrystals can be conveniently tuned from fusiform-like and kiwi-like to orange-like, apple-like, and snack-like structures. The apple-like ZnO mesocrystals show a significantly better photodegradation efficiency than the commercial ZnO powder as well as other nanostructured ZnO materials for both rhodamine B (RhB) and methyl orange (MO). Furthermore, the apple-like zinc-oxide mesocrystals can degrade all of the tested eight different types of organic dyes (RhB, rhodamine 6G, methylene blue, Coomassie brilliant blue R250, BPB, MO, Li Chunhong S, and carmine) simply under the exposure of sunlight, demonstrating their superior photodegradation prowess, environmental amiability, and energy-saving features. The novel robust and versatile photocatalyst has greatly advanced our abilities for the elimination of organic dyes. The green, one-pot strategy provides a convenient method for the construction of novel metal-oxide nanostructures with promising applications in environmental protection.

Facile, high yield ultrasound mediated protocol for ZnO hierarchical structures synthesis: Formation mechanism, optical and photocatalytic properties

Hierarchical flowers-like zinc oxide structures have been successfully obtained by a simple and fast ultrasound-assisted method performed in a ordinary ultrasonic bath using an ammonia solution and zinc acetate, in the absence of any surfactant or template. The composition, structure, crystallinity, morphology and optical properties of the materials obtained at different ultrasound irradiation times were characterized by infrared, UV-Vis and photoluminescence spectroscopy, X-ray diffraction, scanning and transmission electron microscopy investigations. It was proved that the ultrasound irradiation time manipulates both the defect content (implicit the photoluminescent properties) and morphology of the ZnO materials: shorter irradiation times leads to the synthesis of high-defected ZnO structures of flower morphology with triangular-shaped petals, while higher irradiation times favours the formation of low-defected ZnO structures with tipped rod-like petals. A plausible growth mechanism of the architectures that implies aggregation via oriented attachment followed by an Ostwald ripening is advanced based on these results. The ZnO flower-like structures present high photocatalytic activities, a total phenol mineralization being registered in the case of visible light experiments. Electron-spin resonance measurements demonstrate the generation of reactive oxygen species, namely hydroxyl radicals but also C centred radicals adducts derived most probable from the residual acetate adsorbed on ZnO surface.

Surfactant Effects on the Morphology and Pseudocapacitive Behavior of V2 O5 ⋅H2 O

To overcome the drawback of low electrical conductivity within supercapacitor applications, several surfactants are used for nanoscale V2 O5 to enhance the specific surface area. Polyethylene glycol 6000 (PEG-6000), sodium dodecylbenzene sulfonate (SDBS), and Pluronic P-123 (P123) controllers, if used as soft templates, easily form large specific surface area crystals. However, the specific mechanism through which this occurs and the influence of these surfactants is not clear for V2 O5 ⋅H2 O. In the present study, we aimed to investigate the mechanism of crystal growth through hydrothermal processes and the pseudocapacitive behavior of these crystals formed by using diverse surfactants, including PEG-6000, SDBS, and P123. Our results show that different surfactants can dramatically influence the morphology and capacitive behavior of V2 O5 ⋅H2 O powders. Linear nanowires, flower-like flakes, and curly bundled nanowires can be obtained because of electrostatic interactions in the presence of PEG-6000, SDBS, and P123, respectively. Furthermore, the electrochemical performance of these powders shows that the nanowires, which are electrodes mediated by PEG-6000, exhibit the highest capacitance of 349 F g(-1) at a scan rate of 5 mV s(-1) of all the surfactants studied. However, a symmetric P123 electrode comprising curly bundled nanowires with numerous nanopores showed an excellent and stable specific capacitance of 127 F g(-1) after 200 cycles. This work is beneficial to understanding the fundamental role of the surfactant in the assisted growth of V2 O5 ⋅H2 O and the resulting electrochemical properties of the pseudocapacitors, which could be useful for the future design of appropriate materials.

A general, eco-friendly synthesis procedure of self-assembled ZnO-based materials with multifunctional properties

One way of getting green: saccharides in cooperation with triethanolamine are proposed as green and versatile tools for the synthesis of ZnO-based materials.

PEG-assisted hydrothermal synthesis and electrochemical performance of ZnO/Ketjenblack nanocomposite for lithium ion batteries

A ZnO/Ketjenblack(KB) composite, exhibiting a special porous structure with ZnO particles embedded in the mesopores of KB, was fabricated. The combined KB acts as a conducting buffering matrix during the lithiation/delithiation process, improving electrochemical performance.

ZnO nano reactor on textiles and polymers: ex situ and in situ synthesis, application, and characterization

Zinc oxide consumption has increased in today's world. It is one of the most popular nanoparticles with photocatalytic activity under light illumination utilized in different industries, especially in textiles and polymers. Lately, textiles and polymers with new features have been produced through utilization of ZnO nanoparticles to create photocatalytic characteristics, UV absorption, self-cleaning, and antimicrobial properties. Various approaches have been introduced to synthesize and apply nanoparticles on the textile and polymer surfaces such as cotton, polyester, wool, and others. This review presents diverse aspects of nano zinc oxide application in textile and polymer industry and approaches used for in situ and ex situ synthesis and application of nano zinc oxide on different textiles and polymers. This also brings a brief overview on the several studies accomplished in this area.

Fabrication and photoluminescence properties of TiO2:Eu3+ microspheres with tunable structure from solid to core–shell

The structure of TiO₂:Eu³⁺ microspheres can be tuned from solid to core–shell only by changing the amount of ethanol. In addition, the PL intensity of Eu³⁺ ions is related to the structure of the microspheres.

Synergistic manipulation of micro-nanostructures and composition: anatase/rutile mixed-phase TiO2 hollow micro-nanospheres with hierarchical mesopores for photovoltaic and photocatalytic applications

The construction of nanocrystals with controllable composition and desirable micro-nanostructures is a well-known challenge. A combination of favorable composition and optimized micro-nanostructures can enhance the performance of a material significantly. Using TiO(2) as an example, we demonstrate here a facile approach to prepare anatase/rutile mixed-phase TiO(2) hollow micro-nanospheres with hierarchical mesopores. Our strategy relies on polymer-assisted assembly of ∼ 5 nm nano-building blocks into three-dimensional hierarchical hollow micro-nanospheres in a mixed alcohol-water solution. This superior micro-nanostructure endows the sample with hierarchical mesopores and a high surface area of 106 m(2) g(-1). We also show that, due to the synergetic effects of the mixed-phase composition and the micro-nanostructures, the sample exhibited significantly improved photovoltaic performance and similar photocatalytic performance compared with the commercial Degussa P25. These results suggested that our sample has great potential for future photovoltaic and photocatalytic applications.

Three-dimensional type II ZnO/ZnSe heterostructures and their visible light photocatalytic activities

We report a method for synthesizing three distinct type II 3D ZnO/ZnSe heterostructures through simple solution-based surface modification reactions in which polycrystalline ZnSe nanoparticles formed on the surfaces of single-crystalline ZnO building blocks of 3D superstructures. The experimental results suggested a possible formation mechanism for these heterostructures. The formation of the ZnO/ZnSe heterostructures was assumed to result from a dissolution-recrystallization mechanism. The optical properties of the 3D ZnO/ZnSe heterostructures were probed by UV-vis diffuse reflectance spectroscopy. The 3D ZnO/ZnSe heterostructures exhibited absorption in the visible spectral region. The visible photocatalytic activities of 3D ZnO/ZnSe heterostructures were much higher than those of the 3D pure ZnO structures. The activities of the 3D ZnO/ZnSe heterostructures varied according to the structures under visible light. The morphologies and exposed crystal faces of pure ZnO building blocks prior to surface modification had a significant effect on the visible light photocatalytic processes of ZnO/ZnSe heterostructures after surface modification.

Exposed crystal face controlled synthesis of 3D ZnO superstructures

We report a method for synthesizing exposed crystal face controlled 3D ZnO superstructures under mild conditions (at room temperature or 90 degrees C under 1 atm) without organic additives. The exposed crystal faces of the building blocks of the 3D structures were controlled by varying the reactant concentrations and the reaction temperatures. On the basis of the experimental results, we speculated a possible mechanism for the formation of the four distinct 3D ZnO superstructures (structures I, II, III, and IV) under the different growth conditions. The optical properties of the 3D ZnO superstructures were probed by UV-vis diffuse reflectance spectroscopy. The spectra were shifted depending on the dimensions and sizes of the building blocks of the 3D superstructures. The photocatalytic activities of the 3D superstructures varied according to the exposed crystal faces, which could be controlled by this method (structure I > structure IV > structure III > structure II).

Synthesis of ZnO hexagonal single-crystal slices with predominant (0001) and (0001) facets by poly(ethylene glycol)-assisted chemical bath deposition

ZnO hexagonal single-crystal slices with predominant (0001) and (0001) facets have been fabricated by poly(ethylene glycol)-assisted chemical bath deposition.

Zn(II)-PEG 300 globules as soft template for the synthesis of hexagonal ZnO micronuts by the hydrothermal reaction method

Hexagonal ZnO micronuts (HZMNs) have been successfully synthesized with the assistance of poly(ethylene glycol) (PEG) 300 via a hydrothermal method. The structure and morphology of the HZMNs were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and selected area electron diffraction (SAED). An individual ZnO micronut is revealed as twinned crystals. Time-dependent investigation shows that the growth of HZMNs involves a dissolution-recrystallization process followed by Ostwald ripening, in which is the first formed solid ZnO particles dissolve and transform to HZMNs with hollow structure. PEG 300 has been found to play a crucial role in the growth of this unique hollow structure. TEM observations show that the PEG chains aggregate to globules in water, which then have interaction with the dissolved zinc species to form the globules in a coiled state under hydrothermal conditions. These Zn(II)-PEG 300 globules act as soft template for the growth of HZMNs, and the possible growth mechanism is proposed. The room-temperature photoluminescence (PL) spectrum shows red emission around 612 nm with a full width at half-maximum (fwhm) only about 13 nm.