Aqueous Solution Deposition Research Articles

Synthesis and Electrochemical Characteristics of Flowerlike Hierarchically Nanostructured ZnO Film

Multilayer ZnO films fabricated by the combination of sol-gel and aqueous solution deposition routes exhibit many flowerlike clusters with the diameter of on their top layer. Each flowerlike cluster is an assembly of nanoparticles in diameter. The investigation of electrochemical properties, phase, and composition of the ZnO film before and after cyclic voltammetric measurement revealed that the reaction mechanism of lithium with ZnO in our growth method differs from those from the literature. The proposed reversible electrochemical reactions would potentially cause the improvement of capacity retention and the enhancement of cycling performance, which might break the reported negative conclusions such as poor cycling on lithium storage in ZnO.

One-step growth of structured ZnO thin films by chemical bath deposition in aqueous ammonia solution

Structured ZnO films have been fabricated on soda-lime glass slides at a low temperature (80–85 °C) by a chemical bath deposition method in one step without seed layers. Mixed aqueous solutions of zinc sulfate, ammonia and thiourea were used at alkaline conditions. The influence of the ammonia concentration in the initial solution on the property of the deposited film was investigated systematically. The morphology, structural and optical properties of the deposited films were examined and characterized by x-ray diffraction (XRD), energy-dispersive spectroscopy x-ray diffraction (EDX), scanning electron microscopy (SEM), Raman spectroscopy and photoluminescence (PL) spectroscopy. Structural analyses with XRD, EDX and SEM revealed that the formed films exhibit a wurtzite hexagonal phase. The deposited film was more preferentially oriented in the (0 0 2) direction with an increase in the ammonia concentration from 0.75 to 2 mol l−1. The optical-phonon E2 mode at 437 cm−1 in the Raman spectrum, together with the XRD and EDX analyses, showed that flower-like and columnar crystalline ZnO films were formed in two ammonia concentration ranges, 0.75–1.4 mol l−1 and 1.6–2.0 mol l−1, respectively. Furthermore, PL spectra showed strong and high intensity peaks of UV emission with suppressed green emission for these deposited ZnO films. ZnS films were formed with a high ammonia concentration of 3.0 M. The formation mechanisms of ZnO, Zn(OH)2 and ZnS phases were discussed.

Fabrication of Ga2O3 thin films by aqueous solution deposition

Ga2O3 thin films were fabricated using the Ga nitrate and GaOOH aqueous solutions. The films were crystallized as β-Ga2O3 phase by heating at 700°C and the band gap of resultant films was about 4.9 eV. The films were uniform and the film from Ga nitrate solution was dense with porosity of about 3%. The resistivity of the blank film was about 107 Ω cm. The doped films with Ti and Zr exhibited rectifying properties on ITO sputtered glass substrate.

Cobalt oxide supported on alumina catalysts prepared by various methods for use in catalytic afterburner of PEM fuel cell

In the present work we have investigated the influence of the preparation method on the physicochemical and activity features of CoO x /γ-Al 2O 3 catalysts used for the combustion of anode tail gas produced in a proton-exchange membrane (PEM) fuel cell. The catalysts prepared contain 21% (w/w) Co and have been calcined at 850 °C. Three different impregnation methodologies have been followed: incipient wetness impregnation (IWI) using a cobalt nitrate aqueous solution, incipient wetness impregnation using a mixed cobalt nitrate–nitrilotriacetic acid (IWI-nta) aqueous solution and equilibrium deposition filtration (EDF) using a cobalt nitrate aqueous solution. The catalysts were characterized using nitrogen adsorption for determining the specific surface area, the pore volume and the mean pore diameter as well as using X-ray powder diffraction (XRD), diffuse reflectance spectroscopy (DRS; UV–vis), LRS, X-ray photoelectron spectroscopy (XPS) and temperature-programmed reduction (TPR). Catalytic activity measurements were performed in the temperature range 250–850 °C using a continuous flow fixed-bed micro-reactor working under atmospheric pressure and fed with a reaction mixture consisted of 15% H 2/3% CO/1.1% CH 4/20% O 2 balanced in He. The EDF methodology imposed interfacial deposition and resulted to the formation of an almost bi-dimensional surface precipitate. Upon calcination, this surface precipitate provided a very well-dispersed CoO x amorphous species strongly interacted with the support surface and thus hardly reducible as well as relatively small Co 3O 4 supported nanocrystals (14.3 nm). The first phase is the predominant one. Therefore, EDF resulted to a catalyst with the highest cobalt surface and specific surface area. The conventional IWI imposed bulk (solution) precipitation and thus induced relatively large supported crystallites which upon calcination provided relatively large supported Co 3O 4 nanocrystals (19.8 nm) and CoAl 2O 4 as well. The formation of the relatively large nanocrystals and the insertion of cobalt inside the γ-alumina lattice to form CoAl 2O 4 may be responsible for the lowest cobalt surface obtained in this catalyst. The presence of the nitrilotriacetic acid in the impregnating solution induced the exchange of the water ligands of the Co(II) aqua complex present in the cobalt nitrate solution with organic ligands and thus the bulk precipitation of an organometallic complex. The more bulky organic ligands decreased the cobalt-support interactions. Thus, the insertion of cobalt inside the γ-alumina lattice and the formation of CoAl 2O 4 are inhibited upon calcination of the IWI-nta sample. This may be responsible for the relatively higher cobalt surface obtained with respect to that achieved in the IWI sample though the size of the Co 3O 4 nanocrystals is larger in the IWI-nta sample (25.8 nm). At relatively high reaction temperatures all catalysts exhibited almost the same activity for oxidation reactions. In contrast, at low reaction temperatures the EDF catalyst proved to be more active for the CH 4 production as well as for the oxidation of H 2 and CO. This behaviour may be attributed to the favourable physicochemical characteristics of this catalyst.

Tuning the architectures of lead deposits on metal substrates by electrodeposition

Different morphologies of lead (Pb) deposited on different metal substrates have been prepared via electrochemical deposition in aqueous solution. The morphologies of as-deposited lead were determined by scanning electron microscope (SEM). It is found that the various morphologies of the products are dependent on the electrodeposition conditions, including the deposition current densities, concentration of additives, substrates and deposition time. X-ray diffraction (XRD) and transmission electron microscope (TEM) results reveal that all these lead deposits with different morphologies can be assigned to the space group Fm-3 m (2 2 5).

Poly(d,l-lactide-co-glycolide) Dispersions Containing Pluronics: from Particle Preparation to Temperature-Triggered Aggregation

In this work the preparation mechanism, properties and temperature-triggered aggregation of poly(D, L-lactide- co-glycolide) (PLGA) dispersions are investigated. The dispersions were prepared by interfacial deposition in aqueous solution containing Pluronic L62 (EO(6)PO(30)EO(6)) or F127NF (EO(101)PO(56)EO(101)), where EO and PO are ethylene oxide and propylene oxide, respectively. PLGA dispersions were also prepared in the absence of added Pluronic for comparison. The PLGA particles were characterized using SEM, photon correlation spectroscopy and electrophoretic mobility measurements. It was found that the hydrodynamic diameter (d) increased with PLGA concentration used in the organic solvent phase ( C PLGA(o) ). The value for d was proportional to C(PLGA)(o) (1/3). The value for d increased upon addition of 0.04 M NaNO(3) which demonstrated the importance of electrostatic interactions during particle formation. Electrophoretic mobility measurements were conducted as a function of pH and the data used to estimate the Pluronic layer thicknesses on the PLGA particles. The layer thickness was greatest for the PLGA particles prepared in the presence of Pluronic F127NF. PLGA dispersions containing Pluronic L62 exhibited temperature-triggered aggregation in the presence of 0.15 M NaNO(3). It was found that the critical temperature for dispersion aggregation (T(crit)) was comparable to the cloud point temperature ( T(cp)) for the parent Pluronic L62 solution. Conditions were established for achieving temperature-triggered aggregation at body temperature for PLGA particle/Pluronic L62 dispersions under physiological ionic strength and pH conditions. The PLGA/Pluronic L62 mixtures studied may have potential for use as injectable biodegradable implants for controlled release applications.

High Density Silver Nanowire Arrays using Self-ordered Anodic Aluminum Oxide(AAO) Membrane

Highly ordered silver nanowire with a diameter of 10 ㎚ was arrayed by electroless deposition in a porous anodic aluminum oxide (AAO) membrane. The AAO membrane was fabricated electrochemically in an oxalic acid solution via a two-step anodization process, while growth of the silver nanowire was initiated by using electroless deposition at the long-range-ordered nanochannels of the AAO membrane followed by thermal reduction of a silver nitrate aqueous solution by increasing the temperature up to 350℃ for an hour. An additional electro-chemical procedure was applied after the two-step anodization to control the pore size and channel density of AAO, which enabled us to fabricate highly-ordered silver nanowire on a large scale. Electroless deposition of silver nitrate aqueous solution into the AAO membrane and thermal reduction of silver nanowires was performed by increasing the temperature up to 350℃ for 1 h. The morphologies of silver nanowires arrayed in the AAO membrane were investigated using SEM. The chemical composition and crystalline structure were confirmed by XRD and EDX. The electrolessdeposited silver nanowires in AAO revealed a well-crystallized self-ordered array with a width of 10 ㎚.

Fabrication of polydimethylsiloxane shadow masks for chemical solution deposition of CdS thin-film transistors

PDMS (polydimethylsiloxane) shadow masks were fabricated by replica molding using laser-patterned metal shadow masks as primary templates, which were applied to solution as well as vapor deposition to prepare patterned thin films on solid substrates. We demonstrated a method of fabricating cadmium sulfide (CdS) thin-film transistors (TFTs) using the prepared PDMS shadow masks thanks to their solution-tight, free-standing and elastic characteristics. The patterned CdS thin films were deposited by chemical solution deposition in aqueous solution and aluminum metal electrodes were deposited by thermal evaporation. The electrical characteristics of the CdS/SiO 2/n-Si transistors consisted of a field effect mobility of ~ 0.5 cm 2/Vs, a threshold voltage of ~ 14 V and an on/off ratio of ~ 10 7.

Tin oxide nanocrystals embedded in silica aerogel: Photoluminescence and photocatalysis

Tin oxide nanocrystals were successfully introduced into the mesoporous network of silica aerogels with an aqueous solution deposition process. The success of the tin oxide introduction was evidenced by the drastic reduction in the specific surface area, over 400 m 2/g, and pore volume of the resulted SiO 2–SnO 2 composite aerogels and a shift in nitrogen adsorption–desorption characteristics from type H3 to type H2 hysteresis loop of the type IV isotherm. The crystallinity of the tin oxide nanoparticles was improved and grain size was increased, from 5.5 to 8.5 nm, with increasing the post-reaction thermal treatment temperature. Characterizations of photoluminescence and photocatalysis were performed, and rich photoluminescence emissions were observed. The composite aerogel showed a near band edge emission of the tin oxide nanocrystals at 349 nm and two emission peaks, 318 and 475 nm, attributable to the oxygen deficiency of the silica backbone. Three more emission peaks, 390, 433, 548 nm, were observed, with the 390 nm peak contributed by the oxygen vacancies V O + + , the 433 nm peak by the Sn interstitials, and the 548 nm peak by the oxygen vacancies V O + . Photocatalysis performance of the composite aerogel was conducted for photo-degradation of methylene blue and was found achieved by the embedded tin oxide nanocrystals but not by the silica backbone. Products from three thermal treatment temperatures, 400, 500, and 700 °C, were investigated, with those from thermal treatment at or above 500 °C showing better performance in photocatalysis, 73% vs. 62% in conversion, attributable to the better crystallinity realized at or above 500 °C.

Direct Fabrication of ZnO Whiskers Bridging Between Micron-gap Electrodes in Aqueous Solution for Highly Gas Sensing

AbstractA simple but convenient method for fabricating ZnO micro-sized structure selectively and artificially between two micron-gap electrodes was proposed and investigated. The technique is based on electrolytic deposition in aqueous solution of zinc nitrate or zinc acetate, which selectively occurs between the electrodes being enhanced by electric field. The deposition characteristics were investigated in terms of the deposition conditions, and under the optimized condition ZnO micro-sized structure was obtained with bridging between the electrodes. The gas sensing characteristics of the structure was investigated by exposing to a 500 ppm H2 gas, resulting in 23% variation of the resistance at room temperature. The device dimensions can be downsized to nanometer scale by applying nano-gap electrodes, and therefore this technique is promising for fabrication of highly functional nano-sized sensors at low cost, contributing to mass applications.

Study of the initial stage of electroless Ni deposition on Si (100) substrates in aqueous alkaline solution

We investigated electroless nickel deposition in aqueous alkaline solution with and without conventional palladium catalyzation and found that nickel deposition was initiated and sustained on silicon substrates even without the palladium nuclei activation of the surface. But the resulting quality of the nickel film was not as good as the one with the prior activation. The reason was observably directed to the initial stage of the deposition processes. Nickel deposits nucleation on silicon surface was considered crucial for subsequent achievement of a well adhered, least damage influenced film. Effects of ammonia fluoride, nickel ion concentration and bath temperature in the aqueous nickel bath without reducing agent were studied over the nucleation results. The existence of fluorine ions in the solution increased the density of nickel nuclei particles and refined nickel particle sizes to the most extent, while concentrated nickel bath enhanced the nucleation as well. Consequently the improved quality of nickel film that was obtained from the electroless baths can be attributed to the fine and dense nickel particles formed in the initial stage by virtue of the fluorine ion, concentrated nickel ion and elevated temperature.

Aqueous solution deposition of indium hydroxide and indium oxide columnar type thin films

Abstract Crystalline In(OH)3 and UV-emitting In2O3 thin films with a unique columnar morphology have been successfully prepared for the first time via a simple aqueous solution deposition method. In the present study, sulfonate-terminated self-assembled monolayers on single-crystal Si wafers were used as substrates for the film deposition. Uniform In(OH)3 thin films formed on self-assembled monolayers in aqueous solutions of InCl3.4H2O at 60°C. These films, containing columnar In(OH)3 crystals, showed preferential growth orientation along the [100] direction. The current understanding of the film formation mechanism was discussed. After annealing in air at 400°C, these films were converted to nanocrystalline In2O3 films without modification of the morphology. Photoluminescence emission from In2O3 films was reported at approximately 3.4eV, which was ascribed to the near-band-edge emission.

Weathering of Valle Ricca stiff and jointed clay

The study proposes a weathering model of Pliocene–Pleistocene stiff and jointed blue-grey clay transforming into yellow clay. Physical, mineralogical, chemical and textural changes, as well as the weathering profile were investigated in a quarry of central Italy. Based on geological records and inferences, these changes are likely to have occurred within a time-span of about 50,000 years BP, upon overburden stress unloading and in a stress regime that is locally controlled by suction. Weathering propagated into the clay at a rate of about 0.3 mm/year and was enhanced by the enlargement of the pre-existing tectonic discontinuities and by the formation of new joints. A mass loss of about 22–25 wt.% was calculated. Considering Fe and P as immobile elements, the individual oxides contribute to mass loss in the following order: SiO 2 > CaO = CO 2 > Al 2O 3 > MgO > K 2O > S > Na 2O > TiO 2 > MnO. The Fe 2O 3 / (Fe 2O 3 + FeO) ratio varies from 9–29% in the blue-grey clay to 75–82% in the yellow one. Oxidation and/or dissolution of 7 Å-Fe 2+-bearing clay minerals, mica-like minerals and calcite and parallel increase of smectite and Fe-hydroxides play a critical role in the chemical changes and explain the higher plasticity of the yellow clay with respect to the blue-grey one. The role of water during the weathering process was inferred to occur in cyclical steps: 1) seepage of meteoric water; 2) dissemination of highly oxidizing meteoric water; 3) triggering of oxidation and dissolution of minerals; 4) water evaporation; 5) partial migration of the elements contained in the aqueous solution and consequent deposition of minerals in the joints.

Self-organization of porphyrin structures on Si

The system produced by deposition of aqueous solution (10 − 3 –10 − 6 M) of mesotetra(4-sulfonatophenyl)porphine (TPPS 4) on Si was studied. The morphology of self-organized structures of TPPS 4 was investigated by atomic force microscopy (AFM). The rod- and fiber-like structures of 250–1000 nm width and 30–200 nm height have been found on glass substrates and crystalline Si (c-Si). The aggregation state of TPPS 4 was determined by analysis of optical absorption of aqueous solutions in a visible spectral range and spectroscopic ellipsometry of TPPS/Si samples in the region 1–5 eV. The deposition of aqueous solution of metal-free TPPS 4 and Fe-TPPS 4 was examined. The difference in the adsorption of TPPS 4 on c-Si, porous Si and glass substrates was discussed. The self-ordered ring effect caused inhomogeneous distribution of Fe-TPPS 4 on the c-Si surface. From optical studies, it was found that in TPPS/Si samples formed from aqueous solution of TPPS 4 of high acidity the optical response of J-aggregates was dominant. In contrast, the fine structure in the optical spectra of the samples Fe- TPPS 4/Si corresponded to the excitation of monomers in aqueous solution independently on the pH-value of deposited aqueous solutions. The dependence of spectra for TPPS/Si samples on substrate type, orientation of c-Si, and acidity of aqueous solution was discussed in order to clarify the mechanism of porphyrin adsorption on Si.

Characteristics and Electrochemical Performance of Supercapacitors with Manganese Oxide-Carbon Nanotube Nanocomposite Electrodes

Supercapacitor characteristics of manganese oxide/nickel and manganese oxide/carbon nanotubes/nickel nanocomposite electrodes were investigated in this study. The CNTs were deposited on the Ni substrate by electrophoresis in a dimethylformamide solution, whereas the were synthesized by anodic deposition in a manganese sulfate pentahydrate aqueous solution on substrates. The crystallinity and surface morphology of these electrodes were determined by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The capacitive properties of these electrodes were demonstrated by cyclic voltammetry with scan rates ranging from . The specific capacitances of the nanocomposite electrode were 415 and with scan rates of 5 and , respectively. After of operation, this electrode can maintain 79% of its original capacitance. These nanocomposite electrodes possessing good electrochemical reversibility and high capacitance may be appropriate for supercapacitor application in the future.

Suppression of the green photoluminescence band in ZnO embedded into porous opal by spray pyrolysis

The photoluminescence (PL) and transmittance characteristics of the zinc oxide embedded into voids of FCC sub-micron packed silicon dioxide spheres by using technologically simple and inexpensive spray pyrolysis are reported. The uniform formation of ZnO nanocrystalline particles inside of the porous opal takes place after deposition in aqueous solution with zinc nitrite hexahydride precursor followed by thermal annealing. The decrease of green PL is observed due to the inhibition of spontaneous emission through oxygen vacancies in ZnO. The strong red shift of the transmittance characteristics signifies the essential filling of voids in the opal matrix.

Aqueous solution fabrication of large-scale arrayed obelisk-like zinc oxide nanorods with high efficiency

Two-dimensional (2D) arrays of obelisk-like zinc oxide nanorods were successfully synthesized with high efficiency on quartz and glass substrate on a large scale through a simple aqueous solution deposition method with zinc nitrate, ammonia, and ammonium chloride as the precursors. Characterized by XRD, EDS, TEM and SEM, the as-grown zinc oxide rods had a single crystalline obelisk-like hexagonal wurtzite structure with diameters of about 300–400 nm and length up to 5 μm. Both XRD and SEM studies revealed the orientation of ZnO rods, and the orientation of ZnO rods can be controlled easily by temperature, pH of the reaction system and the concentration of reactants.

Suppression of the green photoluminescence band in ZnO embedded into porous opal by spray pyrolysis

The photoluminescence (PL) and transmittance characteristics of the zinc oxide embedded into voids of FCC sub-micron packed silicon dioxide spheres by using technologically simple and inexpensive spray pyrolysis are reported. The uniform formation of ZnO nanocrystalline particles inside of the porous opal takes place after deposition in aqueous solution with zinc nitrite hexahydride precursor followed by thermal annealing. The decrease of green PL is observed due to the inhibition of spontaneous emission through oxygen vacancies in ZnO. The strong red shift of the transmittance characteristics signifies the essential filling of voids in the opal matrix.

Aqueous solution fabrication of large-scale arrayed obelisk-like zinc oxide nanorods with high efficiency

Two-dimensional (2D) arrays of obelisk-like zinc oxide nanorods were successfully synthesized with high efficiency on quartz and glass substrate on a large scale through a simple aqueous solution deposition method with zinc nitrate, ammonia, and ammonium chloride as the precursors. Characterized by XRD, EDS, TEM and SEM, the as-grown zinc oxide rods had a single crystalline obelisk-like hexagonal wurtzite structure with diameters of about 300–400 nm and length up to 5 μm. Both XRD and SEM studies revealed the orientation of ZnO rods, and the orientation of ZnO rods can be controlled easily by temperature, pH of the reaction system and the concentration of reactants.

Preparation of LiMn 2O 4 thin films by aqueous solution deposition

Cathode material LiMn 2O 4 thin films were prepared by aqueous solution deposition using lithium acetate and manganese acetate as starting materials. The structures, morphologies, and the first discharge specific capacity of the thin films were investigated as a function of annealing temperature and time. The cycling properties of the thin films were also examined. The results show that LiMn 2O 4 thin films prepared by this method are homogenous and crack-free. The thin film annealed at 750°C for 30 min has good rechargeability. The capacity loss per cycle is about 0.05% after being cycled 100 times.