We investigated the insulation performance of sub-micrometer parylene C films over time using electrochemical impedance spectroscopy (EIS). For this, interdigitated electrodes were fabricated and completely encapsulated with parylene C in thicknesses of 50, 100, 200, and 500 nm. The EIS was measured in phosphate buffered saline (PBS) solution under an accelerated aging condition at 90 °C over 45 days. To analyze the EIS data, the equivalent circuit models of coating at different stages of coating degradation were used and the lumped circuit parameters of the best fitted equivalent circuit model were extracted by curve fitting. The analysis of impedance using the equivalent circuit model and the FTIR measurements suggest that sub-micrometer parylene C coatings exhibited delamination resulting from water diffusion from the top surface as soon as being immersed in PBS solution, although the degree of delamination varied depending on the film thickness. The penetration of water through sub-micrometers thick parylene C films can occur as quickly as the film is in contact with solution, unlike for thicker coatings in several micrometers where water diffusion would be saturated before water reaches the bottom surface of the coating. 相似文献
Homogeneous NaBH_4-reduced Co_O_4 thin film electrodes with enhanced oxygen evolution electrocatalysis were obtained via a controlled-synthesis route.Firstly CoOx colloids were synthesized via ethylene glycol solvothermal method and cast on conductive glass substrates.The oxygen evolution reaction(OER) electrocatalysis of these asprepared Co_3O_4 thin films were then significantly enhanced via a simple surface reduction by NaBH_4 solution.The OER catalytic performance of the NaBH_4-reduced thin films was strongly dependent on the NaBH_4 concentration.The use of NaBH_4-reduced thin film electrodes for OER in alkaline solution supported higher current density and consequently negative shifts of the onset potential compared to that of the pristine.The optimal B_(12.5,20)-Co_3O_4 thin films exhibited excellent OER catalytic performances:At the current density of 10 mA·cm~(-2),a low overpotential of 365 mV and a small Tafel slope of 59.0 mV·dec~(-1) were observed.In addition,these B_(12.5,20)-Co_3O_4 thin film electrodes possessed good stability that can well recover its OER performance in a 24-h chronoamperometric stability test. 相似文献
A thin layer of polypyrrole was formed on sintered CdSe electrodes. The photoelectrochemical properties of bare CdSe and P-Py/CdSe electrodes were studied in electrolyte with the redox couple [K3Fe(CN)6]. The results were explained by assuming that a p-n junction is formed on CdSe electrodes with polypyrrole working as a p-type semiconductor. 相似文献
Dense TiO2 and TiO2/CdSe coupled nanocrystalline thin films were synthesized onto ITO coated glass substrate by chemical route at relatively low temperature (≤100 °C). TiO2 films were nanocrystalline and crystallinity disappears after CdSe deposition as evidenced by X-ray powder diffraction. Surface morphology and physical appearance of films were studied from SEM and actual photo-images, reveals dense nature of TiO2 (10-12 nm spherical grains, faint violet) and CdSe (80-90 nm spherical grains, deep brown), respectively. Presence of two absorption edges in UV spectra implies existence of separate phases rather than composite formation. TiO2 film was found to have higher water contact angle (71°) than TiO2/CdSe (61°) and CdSe (56°). I-V and stability tests of photo-electrochemical cells were performed with TiO2 and TiO2/CdSe film electrodes (under light of illumination intensity 80 mW/cm2) in lithium iodide as an electrolyte using two-electrode system. 相似文献
The fabrication and characterization of a hybrid polymer p‐n junction‐type thin film via electropolymerization of NPs and a precursor polymer is described. Blends of TiO2 NPs, CdSe NCs, Cbz‐COOH, and PVK were utilized to enable electrochemical deposition on ITO glass substrates. Spectroscopic, microscopic, and wetting measurements confirmed thin film fabrication. CV yielded a CPN nanocomposite with electropolymerized (i.e., crosslinked) carbazole units embedding CdSe NCs. Absorption and emission measurements confirmed a charge transfer mechanism between the crosslinked carbazole and the NCs resulting in a p‐n junction‐type thin film on ITO; with the observed quenching of CdSe NC emission. Several possible applications of such thin films are also discussed.
Vertically aligned single crystalline ZnO nanorod arrays, approximately 3 μm in length and 50-450 nm in diameter are grown by a simple solution approach on a Zn foil substrate. CdS and CdSe colloidal quantum dots are assembled onto ZnO nanorods array using water-soluble nanocrystals capped as-synthesized with a short-chain bifuncional linker thioglycolic acid. The solar cells co-sensitized with both CdS and CdSe quantum dots demonstrate superior efficiency compared with the cells using only one type of quantum dots. A thin Al2O3 layer deposited prior to quantum dot anchoring successfully acts as a barrier inhibiting electron recombination at the Zn/ZnO/electrolyte interface, resulting in power conversion efficiency of approximately 1% with an improved fill factor of 0.55. The in situ growth of ZnO nanorod arrays in a solution containing CdSe quantum dots provides better contact between two materials resulting in enhanced open circuit voltage. 相似文献