Optical and Electrical Properties of Polyimide Thin Films Grown by Vapor Deposition Polymerization

Using pyromellitic dianhydride (PMDA) and 4,4’ diaminodiphenyl ether (ODA) as monomer materials, polyimide thin films have been prepared onto glass substrate by vapor deposition polymerization under a vacuum of 2.666×10 -3 Pa and thermal curing of polyamic acid film in a vacuum at temperature of 150～200 ℃ for 60 min. In this process, the polymerization can be carried out through controlling the stoichiometric ratio, heating time and deposition ratio of the two monomers. The composition, the structure and properties of the polyimide films are investigated with IR spectrum, XRD, and SEM methods. The results show that the polyimide films by vapor deposition polymerization have good electrical properties and thermal stability. Therefore, the vapor deposition polymerization process is considered as a possible method of polymerization for other polymers.

Optical and Electrical Properties of Polyimide Thin Films Doped-Cu-phthalocyanine Polymerized by Vapor Phase Deposition

Using Cu-phthalocyanine（CuPc）,4,4’-diaminodiphenyl ether and pyromellitic dianhydride as monomer materials, polyimide（PI） thin films doped-CuPc have been prepared onto glass substrate by vapor phase co-deposition polymerization under a vacuum of 2×10-3Pa and thermal curing of polyamic acid film in at temperature of 150-200℃ for 60min. In this process, the polymerization can be carried out through controlling the stoichiometric ratio, heating time and deposition rates of the three monomers. IR spectrum identifies the designed chemical structure of the polymer. The absorption of polyimide doped-CuPc is very intense in vis-range and near-infrared by UV-Vis spectrum. And, the PI films doped-CuPc polymerized by vapor phase deposition have uniformity, fine thermal stability and good nonlinear optical properties, and the third-order optical nonlinear susceptibility χ（3） with degenerate four-wave mixing can be 1.984×10-9ESU.

Atomic layer deposition of ultrathin layered TiO_2 on Pt/C cathode catalyst for extended durability in polymer electrolyte fuel cells

This study shows the preparation of a TiO2 coated Pt/C（TiO2/Pt/C） by atomic layer deposition（ALD）,and the examination of the possibility for TiO2/Pt/C to be used as a durable cathode catalyst in polymer electrolyte fuel cells（PEFCs）. Cyclic voltammetry results revealed that TiO2/Pt/C catalyst which has 2 nm protective layer showed similar activity for the oxygen reduction reaction compared to Pt/C catalysts and they also had good durability. TiO2/Pt/C prepared by 10 ALD cycles degraded 70% after 2000 Accelerated degradation test, while Pt/C corroded 92% in the same conditions. TiO2 ultrathin layer by ALD is able to achieve a good balance between the durability and activity, leading to TiO2/Pt/C as a promising cathode catalyst for PEFCs. The mechanism of the TiO2 protective layer used to prevent the degradation of Pt/C is discussed.

Optimized growth and dielectric properties of barium titanate thin films on polycrystalline Ni foils

Barium titanate（BTO） thin films were deposited on polycrystalline Ni foils by using the polymer assisted deposition（PAD） technique.The growth conditions including ambient and annealing temperatures were carefully optimized based on thermal dynamic analysis to control the oxidation processing and interdiffusion.Crystal structures,surface morphologies,and dielectric performance were examined and compared for BTO thin films annealed under different temperatures.Correlations between the fabrication conditions,microstructures,and dielectric properties were discussed.BTO thin films fabricated under the optimized conditions show good crystalline structure and promising dielectric properties with εr～ 400 and tan δ 〈 0.025 at 100 kHz.The data demonstrate that BTO films grown on polycrystalline Ni substrates by PAD are promising in device applications.

Substrate Effect on the Structural and Electrical Properties of LaNiO_(3) Thin Films

Epitaxial LaNiO_(3)(LNO)thin films prepared from the sols modified with polyethyleneimine(PEI)were grown on single-crystal LaAlO_(3),(LaAlO_(3))_(0.3)(SrAlTaO_(6))_(0.7),and SrTiO_(3) substrates,respectively,using a simple polymer assisted deposition(PAD).The epitaxial structure,surface morphologies and transport of the LNO films were studied by X-ray diffraction(θ/2θ symmetric scan,ω-scan,and in-planeφ-scan),the field emission scanning electron microscopy,and a standard dc four-probe method.It is found that,compared with that of LNO bulk,the c-axis parameter of the LNO film increases under compressive strain and decreases under tensile strain.All the LNO films exhibit metal properties in the temperature-dependent resistivity.The resistivity of the LNO films shows an increasing trend with the lattice mismatch strain changing from compressive to tensile.It is suggested that the oxygen vacancy compensated by more Ni^(2+)changed from Ni^(3+)in the film increases with the strain changing from compressive to tensile,which results in the increase of the resistivity.

Fe-doped TiO_2/SiO_2 nanofibrous membranes with surface molecular imprinted modification for selective photodegradation of 4-nitrophenol

In this study, Fe-doped TiO2/SiO2 （Fe@TS） nanofibrous membranes with molecular imprinted modification, were fabricated by a combination of sol-gel process, electrospinning, calcination and liquid phase deposition techniques, The precursor sol was prepared from one-pot condensation of poly （vinylpyrrolidone）, ferric chloride hexahydrate, tetraethyl orthosilicate and titanium n-butoxide in the mixture solvents of N,N-dimethylformamide and ethyl alcohol. Fibrous membrane wasthen fabricated by electrospinning, followed by calcination to form the Fe@TS composite. The physicochemical properties of Fe@TS were characterized. Thereafter, 4-nitrophenol （4NP） was used as the template to deposit onto nanofibrous Fe@TS membranes, with a thin layer of molecular imprinted polymer in liquid phase. The photodegradation capabilities of 4NP and methyl orange wereexamined in both single and binary systems. The results demonstrated that molecular imprinted Fe@TS membranes exhibited excellent selectivity for photodegradation of 4NP.

Precursor synthesis strategy for polycyclic aromatic conjugated polymers on the application of supercapacitors

Polycyclic aromatics (PCAs) possess excellent photoelectric properties, but the construction of such compounds has been a quite challenging subject of study, mainly due to very low solubility. Herein we report a precursor synthesis strategy for polycyclic aromatic conjugated polymers. A soluble precursor polymer, that containing fusible "double U-shaped aromatic"(DUA) and perylenetetracarboxydiimide (PDI) units, was firstly synthesized by Suzuki coupling. The stereo aromatic units in polymer backbone were found to be converted into polycyclic aromatic units, i.e. hexa-peri-hexabenzocoronene (HBC), by chemical or electrochemical oxidation, which resulted in a formation of insoluble polycyclic aromatic conjugated polymers. The electrochemical oxidations that occurred at the interface of electrode and solution exhibited higher cyclization reactivity and leads to the formation of high quality films on the electrode surface. Characterization by Raman and UV-visible (UV-Vis) spectroscopy validated the successful formation of this HBC structure. Some potential applications of such thin films are being explored, and here we focus on the characteristics of supercapacitors based on their excellent electrochemical properties.