Tomoyasu Hiramatsu

X-ray photoemission spectroscopy and Fourier transform infrared studies of electrochemical doping of copper phthalocyanine molecule in conducting polymer

A conducting polymer polythiophene (PT) film incorporated with copper phthalocyanine (CuPc), which was a highly functional molecule, was synthesized and characterized by Fourier transform infrared (FTIR) spectroscopy and x-ray photoemission spectroscopy (XPS). Electrochemical and casting processes were developed as a doping method of CuPc molecules in a PT film. In the XPS measurements of the CuPc doped PT, CuPc-origin peaks on the higher energy side appeared in the C 1s spectrum. The C 1s spectral profiles between electrochemically doped and cast samples were different in the higher binding energy region. S 2p and N 1s core-level spectra of CuPc doped compounds also showed the difference of the spectral profile between electrochemically doped and cast samples, which suggested the dopant-polymer interaction. A split of Cu 2p spectra indicates the charge transfer between CuPc and the polymer chains. In the FTIR measurements, characteristic vibrational modes to CuPc, in-plane, out-of-plane, and ring stretch...

X-ray photoemission spectroscopy characterization of electrochemical growth of conducting polymer on oxidized Si surface

Electrochemical growth of conducting polymer polythiophene (PT) film on an oxidized Si(100) wafer was closely investigated by x-ray photoemission spectroscopy (XPS). The initial stage of polymer growth was investigated by analyzing the core-level energies and spectral profiles of the atomic components. The oxidized Si surface was also closely characterized by XPS using curve fitting of Si 2p and Si 2s core-level spectra to determine precisely covalent states of Si at surface layers. The XPS spectra of Si 2p and Si 2s of the oxidized substrate surface was composed of five peaks which correspond with Si valence values, such as Si, Si+, Si2+, Si3+, and SiO2. The core-level energy positions of those different states were determined by XPS. The Si wafer was prepared through several stages of a wet cleansing process. Scanning tunneling microscopy image of nanoscale ordered native oxide surface was obtained. The native SiO2 layers remained and was probed by Fourier transform infrared spectroscopy reflection abso...

Topographical studies of electrochemical anodized metal surfaces

An electrochemical anodization technique associated with wet surface cleansing processes was applied for fabrication of surface nanoscale structures on Al plates. Dynamic force microscopy (DFM) measurements clarifies that different wet cleansing processes create different initial surface structures on Al such as a linked-crater pattern and a groove-pattern on Al surfaces and induce finer and well-ordered characteristic surface nanoscale patterns. Based upon those structures, anodization proceeds in the fabrication of well-ordered characteristic nanoscale patterns on Al surface such as a well-oriented row-aligned pattern and a well-fined lattice pattern. Deposition of copper phthalocyanine (CuPc) molecules upon anodized craterarrayed Al surface is conducted by casting CuPc resolved toluene. DFM and X-ray photoemission spectroscopy (XPS) measurements clarify that an organic-inorganic nanoscale patterned material is fabricated.

X-ray photoemission spectroscopy and Fourier transform infrared characterizations of C60 states in C60 doped conducting polymersa)

Conducting polymer polythiophene (PT) film incorporated with C60 was prepared by electrochemical doping and diffusing injection methods. Charge transfer and the molecule-chain interaction were investigated by x-ray photoemission spectroscopy (XPS). Vibration states of the doped C60 and polymer backbone in the hybrid films were also investigated by fourier transform infrared (FTIR) reflaction absorption spectroscopy and FTIR transmission. The XPS spectral profile of the electrochemically doped sample was different from that of the casting sample, which reflects the different dopant-chain interactions in polymer films. The higher binding peaks appearing in the C 1s spectra correspond to C60 and its charged states doped in the polymer, which are closely connected with threefold t1u lowest unoccupied molecular orbital and fivefold hu higest occupied molecular orbital. FTIR transmission measurements clarified that C60 molecules were doped in the polymer film using both electrochemical doping and casting, as ch...

Photoluminescence characterization of polythiophene films incorporated with highly functional molecules such as metallophthalocyanine

The photoluminescence (PL) of conducting polymer polythiophene (PT) films incorporated with metallophthalocyanines (PcMs) such as CuPc, MgPc, FePc, Li2Pc, and CoPc was studied by PL and time-correlated single photon counting (TCSPC) measurements. Polymer films were prepared by electrochemical polymerization and PcMs migrated into the polymer films by a diffusion method using acetonitrile or toluene as a solvent to dissolve the PcMs. The wavelength of PL emission peaks changed significantly depending on the solvent used in the doping process. Using acetonitrile, the observed PL emission peaks originated from the Q band, whereas they were assigned to the Soret band in the case of toluene. TCSPC measurements showed that PL emission took place through a ligand-ligand transition process when using acetonitrile because the average lifetimes were comparable and independent of the central metal ions for CoPc-, Li2Pc-, and MgPc-doped polymer films. Conversely, using toluene, it was found that ligand-ligand emission occurred for Li2Pc-, MgPc-, and FePc-doped films. To identify the cause of the drastic change in PL emission pattern, x-ray photoelectron spectroscopy measurements were obtained. A lower binding energy component appeared in the C 1s core-level spectra of acetonitrile-processed PcM-doped PT films, whereas this component shifted to higher energy and overlapped with the main peak for toluene-processed PcM-doped PT films. The lower binding energy component corresponded to photoelectrons due to the C atoms in the benzene rings of the ligand. Lower binding energy components also appeared in the N 1s core-level spectra of acetonitrile-processed PcM-doped PT films, and this component shifted to higher energy for toluene-processed PcM-doped PT films. These lower energy components were assigned to the core-level peaks due to the N atoms at the meso position bridging between pyrrole rings. This suggests that the electron charge at the N sites of the meso positions in toluene-processed films was smaller than in acetonitrile-processed ones. The changes in energy at benzene C sites and meso N sites suggest that the electronic states of the phthalocyanine in the toluene-processed films were porphyrin-like, so the Soret band became dominant in the PL emission spectrum.

Photoluminescence characterization of polythiophene films doped with highly functional molecules

Conducting polymer polythiophene (PT) films incorporated with copper phthalocyanine (CuPc) or fullerene C60 or both molecules together were synthesized and characterized by photoluminescence measurements. The hybrid materials were also modified by electrochemically applying positive or negative voltage or by adding the donor molecule tetrathiafulvalene (TTF) or acceptor molecule tetracyanoquinodimethane (TCNQ) into the hybrid films and were investigated by photoluminescence measurements in order to obtain fundamental photoluminescence properties of the hybrid materials. The molecule was injected by electrochemical and diffusion methods. A photoluminescence emission peak was observed at 594 nm in the case of a PT sample doped with CuPc by the diffusion method. Adding C60 molecules to the CuPc diffused PT sample by the diffusion method made the emission peak shift to the higher wavelength at 730 nm, suggesting the molecular interaction between the polymer chain and C60 in the photoluminescence emission proc...

Conducting polymer nanofilm growth on a nanoscale linked-crater pattern fabricated on an Al surface

A linked-crater structure was fabricated on an Al surface by chemical and electrochemical combination processes. The surface of an Al plate was treated with semiClean and was successively processed in anodization in H2SO4. Dynamic force microscopy image showed that a linked-crater structure was formed on the Al surface. The crater size ranged from 80to200nm. It turned out that a lot of pores with 9nm in diameter were created inside each crater. The depth of each crater was approximately 7–17nm. At the next stage, the thin film growth of polythiophene on the linked-crater structured Al surface was conducted by an electrochemical synthetic method. The electrochemical polymerization on the Al surface was performed in acetonitrile containing thiophene monomer and (Et)4NBF4 as a supporting electrolyte. After being electrochemically processed, the contour image of each crater was still recognized implying that the polymer nanofilm was grown on the nanoscale structured Al surface. The cross section analysis demo...

Study of dye molecule orientation and configuration in dye molecule doped polythiophene films

Dye molecules doped polythiophene (PT) films prepared by electrochemical doping were investigated by Fourier transform infrared spectroscopy (FTIR) reflection absorption spectroscopy (RAS) and transmission in order to investigate whether the presence of an electric field could control the ordering of the dye molecule assembly in the polymer. The present work focuses on organic dye molecules, which contain three benzene rings in plane with a high symmetry such as crystal violet (CV) and brilliant green (BG) as a dopant. In the case of CV doped PT by applying triangle-shaped negative voltage, the orderings of CV molecules were found by FTIR measurements. Since the ring stretching mode due to the componential benzene ring around 1585 cm−1 was observed only in the FTIR transmission spectra while not observed in the spectrum of FTIR RAS spectra, this result shows that CV molecules are doped in the polymer so that the ring plane of CV is inclined to be parallel to the polymer film plane. In the case of CV doped...

Topographical studies of nanoscale secondary structure of electrochemical anodized aluminum surface

An electrochemical anodization technique associated with wet surface cleansing processes was applied for fabrication of surface nanoscale structures on Al plates. Dynamic force microscopy (DFM) measurements clarifies that different wet cleansing processes create different initial surface structures on Al such as a linked-crater pattern and a groove pattern on Al surfaces and induce finer and well-ordered characteristic surface nanoscale patterns. Based on those structures, anodization proceeds in the fabrication of well-ordered characteristic nanoscale patterns with quite unique secondary structures on Al surface. One is a crater-array structure with small pores in each crater. The other is a hut-shaped structure with a well-oriented line structure in each hut structure. Further anodization assists in fabrication of more ordered finer nanoscale structures such as well-oriented row-aligned pattern and a well-defined lattice pattern. Deposition of copper phthalocyanine (CuPc) molecules on anodized crater-ar...

Fabrication of a highly oriented line structure on an aluminum surface and the nanoscale patterning on the nanoscale structure using highly functional molecules

The surface of an Al plate was treated with a combination of chemical and electrochemical processes for fabrication of surface nanoscale structures on Al plates. Chemical treatments by using acetone and pure water under supersonic waves were conducted on an Al surface. Additional electrochemical process in H2SO4 solution created a finer and oriented nanoscale structure on the Al surface. Dynamic force microscopy (DFM) measurement clarified that the nanoscale highly oriented line structure was successfully created on the Al surface. The line distance was estimated approximately 30–40nm. At the next stage, molecular patterning on the highly oriented line structure by functional molecules such as copper phthalocyanine (CuPc) and fullerene C60 was also conducted. CuPc or C60 molecules were deposited on the highly oriented line structure on Al. A toluene droplet containing CuPc molecules was cast on the nanostructured Al plate and was extended on the surface. CuPc or C60 deposition on the nanostructured Al sur...