Akihiko Kajinami

Preparation and characterization of polymer thin films containing silver and silver sulfide nanoparticles

Abstract Composite thin films consisting of nano-sized Ag particles dispersed in nylon 11 thin films have been prepared by using a thermal relaxation technique. The films obtained were characterized by transmission electron microscopy (TEM), electron diffraction (ED), energy-dispersive X-ray (EDX) microanalysis, and optical absorption spectroscopy. The Ag nanoparticles with 4.5–9.1 nm in diameter were found to be isolated individually and dispersed uniformly in the nylon 11 matrix. The volume fraction and the mean size of Ag nanoparticles in the film could be controlled by varying the initial amount of Ag deposition. Optical absorption peak due to the surface plasmon resonance of the Ag particles were observed around 430 nm and shifted to a longer wavelength with increasing the mean size of Ag nanoparticles, and absorbance increased simultaneously. We have also prepared Ag 2 S nanoparticles with 4.7–11.2 nm in diameter in nylon 11 films from exposing the Ag/nylon 11 films to H 2 S/O 2 mixed gas. ED patterns of the particles formed after the reaction with H 2 S were completely indexed as those of β -Ag 2 S with a monoclinic structure. The onset of the optical absorption spectra is similar to that of bulk β -Ag 2 S, suggesting that Ag 2 S nanoparticles with diameter of ca. 5nm preserve the band structure of bulk Ag 2 S.

Preparation and characterization of iron oxyhydroxide and iron oxide thin films by liquid-phase deposition

Iron oxyhydroxide thin films have been prepared from the aqueous solution system of FeOOH–NH 4 F·HF (aq.) with added boric acid by a novel liquid-phase deposition (LPD) method and is the first attempt to preparate iron oxide thin films by this method. A crystalline β-FeOOH thin film was formed directly on the substrate upon immersion into a mixed solution of FeOOH–NH 4 F·HF and H 3 BO 3 . The orientation of the deposited film differed according to the concentration of H 3 BO 3 in the solution. When the concentration of H 3 BO 3 was >0.30 mol dm -3 , the β-FeOOH thin film was preferentially oriented in the [211] direction. The β-FeOOH thin film formed was transformed into α-Fe 2 O 3 upon heat treatment in air flow. The α-Fe 2 O 3 thin films obtained were oriented in the [110] direction. The F content of the as-deposited β-FeOOH film was ca. 15% F/Fe and was reduced to 0.19% upon heat treatment.

Preparation and characterization of copper(I) oxide nanoparticles dispersed in a polymer matrix

Nano-sized copper(i) oxide particles dispersed in nylon 11 thin films have been prepared by a thermal relaxation technique. The obtained composite films were characterized by XRD, HRTEM, XPS, AES and UV-VIS absorption spectroscopy. Upon heat treatment under air, metallic copper initially deposited on the nylon 11 surface penetrates into the bulk phase of the nylon 11 as Cu2O particles. The mean size of the Cu2O particles increased from 3.2 to 6.3nm in diameter upon increasing the amount of Cu deposition. UV-VIS spectroscopy revealed that the absorption increased from as low as 600nm with increasing the size and the concentration of the dispersed Cu2O particles.

Studies on PVdF-based gel polymer electrolytes

Abstract A complex of polymer, plasticizer and lithium salts can be used as a solid gel polymer electrolyte in lightweight and rechargeable lithium batteries. Considerable research has been directed towards the development of a gel polymer with high conductivity at room temperature. In this work, a gel polymer electrolyte using polyvinylidene fluoride (PVdF)-1000 (KF), a plasticizer of 1:1 ethylene carbonate (EC) and propylene carbonate (PC), and LiBF 4 salt is optimized. Gel electrolytes have high ionic conductivity, good mechanical stability, a wide electrochemical stable window, and a stable lithium interface. The results of preliminary charge–discharge of cells are discussed in detail.

Novel wet process for preparation of vanadium oxide thin film

Abstract Vanadium oxide thin film has been prepared from an aqueous solution system of (V 2 O 5 -HF) with addition of aluminum metal by a novel wet preparation method called Liquid Phase Deposition (LPD). The as-deposited film was amorphous and consisted of reduced-state vanadium ion. By heat treatment under air flow, the film was crystallized and oxidized to V 2 O 5 . Electrochemical properties of the deposited films were observed. Crystallized film showed reversible color change when lithium was electrochemically intercalated and deintercalated.

Preparation and characterization of Au-dispersed TiO2 thin films by a liquid-phase deposition method

Au-dispersed TiO2(anatase) thin films have been prepared by a novel method, liquid-phase deposition (LPD). The deposited films were characterized by XRD, XPS, TEM and UV–VIS absorption spectroscopy. The results showed that the titanium oxide thin film containing AuIII ions was formed from a mixed solution of ammonium hexafluorotitanate, boric acid and tetrachloroauric acid. Heat treatment above 200 °C of the deposited film under flowing air produced dispersed Au metal particles, accompanied by the crystallization of titanium oxide as a matrix. The mean particle size of the dispersed Au particles was ca. 15 nm. The optical absorption band due to the surface plasmon resonance of the dispersed Au particles shifted toward longer wavelengths with increasing heat-treatment temperature.

Growth of metal oxide thin films from aqueous solution by liquid phase deposition method

Abstract The deposition process of iron oxyhydroxide (β-FeOOH) from aqueous solution system of FeOOH–NH 4 F·HF (aq.) with H 3 BO 3 by the liquid phase deposition (LPD) method has been investigated. The effect of initial concentration in the treatment solution and reaction time on microstructure and orientation of the deposited films were studied by means of scanning electron microscope (SEM), X-ray diffraction (XRD) and transmission electron microscope (TEM) observation. The films deposited were constructed by small particles having a crown-like and columnar structure, depending on the concentration range in the treatment solution. XRD measurements revealed that the deposited film preferred the specific direction normal to (211) plane and the dimension of the crystallites varied with the initial concentration of the solution. The deposition process and structure of the films appeared to be strongly affected by the hydrolysis reaction of Fe 3+ ions coordinated by F − and/or partial OH − ions by adding boric acid.

Synthesis and characterization of nano-sized gold-palladium bimetallic particles dispersed in polymer thin film matrix

We have prepared nano-sized Au/Pd bimetallic particles with various compositions dispersed in nylon 11 thin films by thermal relaxation technique. The films obtained were characterized by TEM, EDX, XPS and visible absorption spectroscopy. The Au/Pd molar ratio in the bimetallic particles could be varied over the entire composition range by controlling the initial deposition amount of constituent metals. It was found that the mean size of the dispersed particles decreased from 5.3 to 3.2 nm in diameter with increasing the Pd content in the bimetallic particles. Optical absorption due to surface plasmon resonance absorption of the Au particles decreased with decreasing the Au/Pd ratio, which can be caused by the changes in the band structure of the Au particles due to alloying with Pd.

Monitoring the growth of titanium oxide thin films by the liquid-phase deposition method with a quartz crystal microbalance

The quartz crystal microbalance (QCM) technique has been applied to investigate the formation of titanium oxide thin films by the liquid-phase deposition (LPD) method. A linear relationship was observed between the thickness measured by the QCM technique and that measured by direct observation with a scanning electron microscope, indicating that it is possible to monitor the growth of thin films from aqueous solution systems by the LPD method with the QCM technique. The concentration effects of free F - , H 3 BO 3 and (NH 4 ) 2 TiF 6 on the film deposition rate are discussed.

An electrochemical investigation on polyvinylidene fluoride-based gel polymer electrolytes

Abstract Many types of polymer electrolytes have been developed and characterized in the past few years. Recently special attention has been focussed on the development of gel polymer electrolytes consisting of host polymers such as PAN, PVC, PVP, PVS, PMMA, PEGDA and PVdF etc., as they may find unique applications in consumer electronic and electric vehicle products. In the present study, gel polymer electrolytes have been prepared using the solvent casting technique in the presence of PVdF-1015 (SOLEF), EC+PC as a plasticizer, and LiBF 4 salt. The influence of the amount of polymer, plasticizer and LiBF 4 on the gel electrolytes has been studied using XRD, DSC, AC impedance and charge–discharge studies.