Macroporous ZnO Research Articles

Nanoporous ZnO Photoelectrode for Dye‐Sensitized Solar Cell

Nanoporous and macroporous structures were prepared by using self‐assembled monolayer (SAM) onto ZnO thin films in order to investigate the efficiency of dye‐sensitized solar cells (DSSCs) produced using these films. Using SAM on ZnO thin films, it is obtained successfully assembled large‐area, highly ordered porous ZnO thin films. Varying nanoporous radius is observed between 20 and 50 nm sizes, while it is 500–800 nm for macroporous radius. The solar conversion efficiency of 2.75% and IPCE of 29% was obtained using ZnO nanoporous/N719 dye/I−/ electrolyte, while macroporous ZnO given solar conversion efficiency of 2.22% and IPCE of 18%.

Macroporous ZnO Nanofilms and its Electrochemical Hydrogen Storage Ability

Macroporous ZnO nanofilms were synthesized by a simple hydrothermal reaction. The products exhibit noticable hydrogen storage capacity and big BET surface area. The present work shows that the nanostructures of products are important to their electrochemical hydrogen storage performances. On the other hand, the low cost, convenient process, good reproducibility, high yield, and clean reactions of the present synthetic method make it possible to scale it up to industrial production.

Macroporous ZnO Nanofilms and its Electrochemical Hydrogen Storage Ability

Macroporous ZnO nanofilms were synthesized by a simple hydrothermal reaction. The products exhibit noticable hydrogen storage capacity and big BET surface area. The present work shows that the nanostructures of products are important to their electrochemical hydrogen storage performances. On the other hand, the low cost, convenient process, good reproducibility, high yield, and clean reactions of the present synthetic method make it possible to scale it up to industrial production.

Bubble-Assisted Nanofabrication of Macroporous ZnO Foams

Bubble-Assisted Nanofabrication of Macroporous ZnO Foams

Dye-sensitized biosystem sensing using macroporous semiconducting metal oxide films

Transparent semiconducting oxide (TiO2, SnO2 and ZnO) films having highly interconnected pores in the range of 30–200 nm were fabricated in one-pot using polystyrene-block-poly(ethylene oxide) (PS-b-PEO) diblock copolymer. Such porous structures were helpful for efficient transport of bulky guest species such as proteins. Biosensing protocols were constructed in the films by using bulky biomolecules, namely, adsorbed DNA, adsorbed antibody and adsorbed antigen–antibody (immunoassay). In the DNA-based system, the macroporous TiO2 film was the most useful among porous anatase films such as mesoporous and mesoporous/PS beads derived macroporous ones, leading to significant detection of 125 times higher photocurrent generated from a dye (Cy5) attached to DNA than those observed for the others. Macroporous SnO2 and ZnO films were also available for the construction of similar biomolecule immobilized electrodes. Extremely complicated immunoassay reactions involving bulky proteins (antigen, antibody, etc.) were also established using the macroporous TiO2 and SnO2 films. Especially photocurrent for electron transfer from Cy5 attached to the second antibody was successfully detected by using the SnO2 film for exceptionally selective sensing applications.

Electrodeposition of ZnO nanorods on opaline replica as hierarchically structured systems

We present a new method to prepare hierarchical structures by using ZnO replica and ZnO-coated PMMA opals as electrodes in an electrodeposition process of ZnO nanorods. Depending on the approach the nanorods can be either grown exclusively on top of the replica or inside the replica structures. Therefore two types of systems are accessible: 3D photonic crystals with a hierarchically structured surface consisting of nanorods and macroporous ZnO structures with an increased surface area.

Nanostructural control of ZnO photoelectrodes for enhancing solar energy conversion efficiency in dye-sensitised solar cells

Dye-sensitised solar cells (DSSCs) are one of the promising photovoltaic devices based on nanosized metal oxide semiconductors. We have focused on ZnO photoelectrodes and their nanostructural control in terms of nanomaterials processing. Since significant photophysical and electrochemical reactions take place around electrodes in the operation of DSSCs, their performance depends greatly on nanostructure of photoelectrodes. In this review article, we introduce our series of studies on nanostructural control of ZnO photoelectrodes to enhance the cell performance. It is shown that the introduction of macroporous ZnO particles as light scattering layers is effective to improve the light harvesting efficiency. Formation of silica nanolayers on ZnO electrodes is also proven to be beneficial to suppress the recombination of photogenerated electrons and enhance the charge collection efficiency. In both cases, short-circuit photocurrent density and open-circuit photovoltage were increased and hence, light-to-electricity conversion efficiency could be enhanced up to 4.80% only by controlling the photoelectrode structures.

Shape-controlled synthesis and photocatalytic properties of three-dimensional and porous zinc oxide

In this study, we reported a method for growing macroporous ZnO on a large scale via a facile solution-based method using citrate as crystal growth modifier. The microstructures were studied by X-ray diffraction, scanning electron microscopy, FT-IR, UV–visible spectrometer and N2-physisorption techniques. Influencing factors on the morphology of ZnO were discussed, including anion species of Zn2+ precursor, adding sequence of sodium citrate, sodium citrate concentration and reaction time. On the basis of the investigation on the growth process, citrate ion–ZnO interaction was vital to the formation of complex structure, which was accompanied by acetate ion induction to form the high-quality macroporous spheres. UV–Vis results exhibited a blue-shift when compared with conventional-sized zinc oxide. The large specific surface area of porous ZnO resulted in enhanced absorption of Rhodamine B and improved photocatalytic activity.

Two-dimensional ZnO–NiO macroporous arrays: Fabrication, structure and electrical properties

Colloidal templating and pulsed laser deposition were combined to fabricate arrays of ordered two-dimensional macroporous ZnO–NiO thin films. The underlying principles involved in the formation of colloidal templates were investigated using Fourier transformations and radial distribution functions. The macroporous thin film consists of hollow half-spheres of nanocrystalline wurtzite ZnO and rock salt NiO. The electrical properties of macroporous ZnO–NiO thin films were investigated by impedance and DC current–voltage measurements. The electrical properties are controlled by the interfaces between oxide grains. The potential applications such as gas sensors and optics are discussed.

Effect of temperature on the formation of macroporous ZnO bundles and its application in photocatalysis

In this article, the effects of temperature on the formation of macroporous zinc oxide bundles and its photocatalytic activity under a variety of experimental conditions were reported. Thermal decomposition of zinc oxalate dihydrate yields hexagonal wurtzite-type ZnO bundles. Increased the decomposition temperatures resulted in decreased time required for bundle formation, with a corresponding increase in nanoparticles agglomeration. ZnO bundle formation was facilitated up to 200 °C after complete decomposition of zinc oxalate into ZnO at 400 °C in 15 min. However, low temperature (such as 100 °C) was not facilitated nanobundle formation, suggesting the importance of temperature on ZnO bundles formation. In addition, nitrogen adsorption experiments confirmed the presence of macroporous structure in the bundles. The photocatalytic decolorization and adsorption of methylene blue dye (MB) on ZnO bundles were investigated under UV light irradiation. The adsorption and decolorization efficiency of macroporous bundles were higher than the fused bundles. In conclusion, ZnO bundles are efficient and easily recyclable photocatalyst.

Low-temperature ZnO atomic layer deposition on biotemplates: flexible photocatalytic ZnO structures from eggshell membranes

Macroporous ZnO membranes with a strong photocatalytic effect and high mechanical flexibility were prepared from inner shell membranes (ISM) of avian eggshells as templates after performing low-temperature ZnO atomic layer deposition (ALD). In order to evaluate the potential merits and general applicability of the ZnO structures, a comparative study of two membranes with coatings of either TiO2 or ZnO, processed under similar conditions, was performed. The study includes crystallographic features, mechanical and thermal stability and bactericidal efficiency. Both, the ZnO and the TiO2 coated membranes clearly exhibited bactericidal effects as well as mechanical flexibility and thermal stability even at relatively high temperatures. The ZnO membranes, even though prepared at fairly low temperatures (approximately 100 degrees C), exhibited polycrystalline phases and showed a good bactericidal efficiency as well as higher mechanical flexibility than the TiO2 coated membranes. This study shows the benefits of low-temperature ZnO ALD i.e., the thermally non-destructive nature, which preserves the mechanical stability and the native morphology of the templates used, together with an added functionality, i.e. the bactericidal effect.

Hydrothermal synthesis of 2D ordered macroporous ZnO films

The ZnO films with two-dimensional ordered macroporous structure were successfully fabricated through hydrothermal crystal growth of ZnO on the ZnO substrate covered with a monolayer of polystyrene (PS) spheres as template. The precursor solution of hydrothermal crystal growth of ZnO were prepared by equimolar solution of Zn(NO3)2·6H2O and hexamethylenetramine (HMT). The confinement effect of the PS spheres template on the growth of ZnO nanorods and the influence of sodium citrate on the crystal growth of ZnO had been studied. The film surface morphology and the preferential growth of ZnO crystal were investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. Also, the photoluminescence spectrum of ZnO films had been measured, and the corresponding mechanism was discussed.

Two Growth Modes of Metal Oxide in the Colloidal Crystal Template Leading to the Formation of Two Different Macroporous Materials

The experimental results show that there are two growth modes of crystalline metal oxide in the colloidal crystal template, which depend on the quality of the colloidal crystal. In well-ordered colloidal crystal templates, the metal oxide growth follows the structure of the colloidal crystal; and high quality three-dimensional ordered macroporous (3DOM) Cu2O or ZnO are formed. In contrast, in less-ordered colloidal crystal templates, metal oxide is grown according to its own capital structure, and cubic-shaped macroporous Cu2O or sheetlike macroporous ZnO are formed. Our method provides an easy and convenient way to prepare three-dimensional ordered macroporous materials or shaped macroporous materials via adjusting the level of ordered arrangement of the colloidal crystal templates.

Preparation and Characterization of Ordered Macroporous ZnO Films for Photonic Application

Wide band-gap semiconductor ZnO film with ordered face-centered cubic (FCC) structure air holes was prepared by electrochemical process. The porous ZnO film was prepared in zinc nitrate aqueous solution, using the indium tin oxide (ITO) substrate covered with synthetic opals as cathode by potentiostatic method. In order to improve the filling ratio of ZnO in the opal interstices, various potentials were applied to control the deposition speeds. The porous ZnO film was characterized by X-ray diffraction and Scanning Electron Microscope and a photonic band gap at about 568nm was observed by micro-region reflection spectrometer in ZnO inverse opals.

Macroporous ZnO Films Electrochemically Prepared by Templating of Opal Films

Abstract Highly ordered macroporous ZnO films were electrodeposited using polystyrene colloidal crystals as templates. The films prepared at −1.0 V vs Ag/AgCl had the long-range order of pores reflecting the templates.