ABSTRACT
Superhydrophilicity performs well in anti-fog and self-cleaning applications. In this study, polycarbonate substrate was used as the modification object because of the low surface energy characteristics of plastics. Procedures that employ plasma bombardment, such as etching and high surface free energy coating, are applied to improve the hydrophilicity. An organic amino silane that contains terminal amine group is introduced as the monomer to perform plasma polymerization to ensure that hydrophilic radicals can be efficiently deposited on substrates. Different levels of hydrophilicity can be reached by modulating the parameters of plasma bombardment and polymerization, such as plasma current, voltage of the ion source, and bombardment time. The surface of a substrate that is subjected to plasma bombarding at 150 V, 4 A for 5 min remained superhydrophilic for 17 days. After 40 min of Ar/O2 plasma bombardment, which resulted in a substrate surface roughness of 51.6 nm, the plasma polymerization of organic amino silane was performed by tuning the anode voltage and operating time of the ion source, and a water contact angle < 10° and durability up to 34 days can be obtained.
ABSTRACT
SiOxCy thin films were deposited by plasma polymerization. The stress of the deposited SiOxCy thin films can be modified by adjusting the beam current, the anode voltage, and the flow rate of hexamethyldisiloxane (HMDSO) gas and oxygen. Reducing the beam current or increasing the flow rate of HMDSO gas increased the linear/cage structure ratio and turned the stress of the SiOxCy thin films from compressive to tensile. The linear/cage structure ratio can be adjusted by changing the composite parameter, W[FM]c/[FM]m, to control the stress of the deposited plasma polymer films. Multilayers of TiO2/SiO2/TiO2 were coated on a SiOxCy plasma polymer film herein, reducing their stress by 70% from 0.06 to 0.018 GPa. The refractive index is 1.55, and the absorption coefficient is less than 10-4 at 550 nm of the SiOxCy films. Superior optical performances of SiOxCy thin films make their use in optical thin films.
ABSTRACT
An approximate growth model was employed to predict the time required to grow a graphene film by chemical vapor deposition (CVD). Monolayer graphene films were synthesized on Cu foil at various hydrogen flow rates from 10 to 50 sccm. The sheet resistance of the graphene film was 310Ω/â¡ and the optical transmittance was 97.7%. The Raman intensity ratio of the G-peak to the 2D peak of the graphene film was as high as ~4 when the hydrogen flow rate was 30 sccm. The fitting curve obtained by the deviation equation of growth model closely matches the data. We believe that under the same conditions and with the same setup, the presented growth model can help manufacturers and academics to predict graphene growth time more accurately.
ABSTRACT
Cyanine dye J-aggregate films are a class of absorbing and luminescent materials which have been extensively applied in the polariton-based research. Here we systematically study the DEDOC cyanine dyes J-aggregate films made by layer-by-layer assembly and spin-coating processes to establish a clear correlation between the film structure and the absorption and luminescence properties. From detailed analyses of morphology, optical spectra, and light-emitting diode characteristics, we demonstrate that layer-by-layer assembled film has higher degrees of homogeneity and molecular packing quality than spin-coated film, leading to a higher absorption coefficient, more uniform luminescence, and a greater electroluminescence quantum efficiency with maximized thickness.
Subject(s)
Absorption, Radiation , Carbocyanines/chemistry , Coloring Agents/chemistry , Electricity , Luminescence , Electronics , Glass/chemistry , Microscopy, Atomic Force , Spectrum AnalysisABSTRACT
Developing of highly absorbing thin films is essential for exploration of light-matter interaction and polariton-based applications. We demonstrate here layer-by-layer assembled J-aggregate thin films of (DEDOC) cyanine dyes that have high absorption coefficient and controlled thicknesses, leading to adjustable exciton-photon coupling and Rabi splitting exceeding 400 meV at room temperature in all-metal mirror microcavities.
ABSTRACT
We proposed a novel technique to fabricate colloidal crystals by using monodisperse SiO(2) coated magnetic Fe(3)O(4)(SiO(2)/Fe(3)O(4)) microspheres. The magnetic SiO(2)/Fe(3)O(4) microspheres with a diameter of 700 nm were synthesized in the basic condition with ferric sulfate, ferrous sulfate, tartaric acid and tetraethyl orthosilicate (TEOS) in the reaction system. Monodisperse SiO(2)/Fe(3)O(4) superparamagnetic microspheres have been successfully used to fabricate colloidal crystals under the existing magnetic field.
ABSTRACT
Preparation of inorganic molecularly imprinted polymers (IMIPs) with higher adsorption and selectivity has been developed on caffeine as model compound by sol-gel processes. In our study, by introducing pore-forming agent, lactic acid, into sol-gel process, the porosity of IMIPs was enhanced and the performance of IMIPs was thus improved. And, by introducing base catalyst in the sol-gel process, large pore volume was obtainable, and the caffeine adsorption of IMIPs was increased. Competition adsorption experiments between caffeine (CAF) and structure analogous molecule, theophylline (TH), were determined by HPLC analysis. It was found that adding pore-forming agent method produced better caffeine adsorption (ca. 20 micromol/g) than by adding base catalyst. But adding base catalyst method was found to yield better selectivity (ca. 4) (Selectivity (alpha) is the ratio of CAF bound to TH bound.) In addition, caffeine adsorption of IMIPs with template removed by calcination is two times that by extraction without sacrificing the selectivity of IMIPs.
