In the fabrication of polymeric electroluminescent devices with indium-tin oxide (ITO) as anode, indium contamination of the polymers can greatly degrade the device performance. In the present study, we have used x-ray photoelectron spectroscopy to measure indium incorporation in poly(3,4-ethylene dioxythiophene):poly(styrene sulphonate), referred to as PEDOT:PSS, which were spincast on bare ITO and encapsulated ITO. We found that the deposition of a self-assembled monolayer of alkylsiloxanes on ITO prior to spincasting PEDOT:PSS was effective and practical in blocking the reactions between ITO and PEDOT:PSS.
Biomorphic CaCO3 with different hierarchically ordered micro- and nanostructures was fabricated with natural cellulose substances as the host templates. The fabrication involves two mild sonication processes in which calcium and carbonate ions are sequentially added to the template, together with subsequent calcination in air. The specific pseudo-1D and pseudo-2D structures of the resultant crystalline calcite can be tailored by mimicking both natural and artificially woven cellulosic substances, with the former following the ribbon/tube form of cellulose fiber and the latter following the netlike architectures of the woven cotton cloth. The building block of these structures is a layer of CaCO3 grains grown on the surfaces of each cellulose fiber. By choosing Ca2+, CO32-, or HCO3- ions as the first adsorption species on the cellulose template, we show that the resultant CaCO3 grain size can be fine-tuned in a nanoscopic scale, most probably due to the differences in the nature of ion adsorption on the cellulose molecules and the resultant CaCO3 nucleation and growth. The impact of this new route is that we can precisely predict the morphologies of the final CaCO3 products that were not realized in other chemical approaches.
We have successfully chemically functionalized the multi-walled carbon nanotubes (MWCNTs) with COOH group by the method of oxidation and used AC electrophoresis to formed these bundles MWCNTs between Au electrodes on the Si substrate. We then demonstrated that these resistive elements are capable of detecting alcohol vapor using an ultra-low input power of only ∼0.01μW. The sensors exhibit fast, repeatable, highly sensitive, and reversible response. Our results show that the resistances of the sensors vary linearly with alcohol vapor concentration from 5ppth to 100ppth (ppth = part per thousand). We can also easily reverse the initial resistance of the sensors by annealing them in real time at 100-250μA current within 1-6 minutes. We have experimental proof that the functionalized MWCNTs have a much higher sensitivity towards the alcohol vapor than the bare MWCNTs. Based on our experimental results, we prove that MWCNTs sensors, especially for those with proper functionalized groups, are sensitive to a wide range of alcohol vapor and potentially other volatile organic compounds, and are very attractive for commercialization due to their extreme low-power requirements for activation.
Textured diamond films have been grown on silicon (111) substrate by using hot filament chemical vapor deposition. A graphite plate immersed in hydrogen was used as the carbon source rather than the conventional gaseous methane source. During the nucleation period, a negative bias relative to the filaments was applied to the substrate. An epitaxial β-SiC layer was deposited during the bias treatment. Textured diamond film was subsequently grown on the β-SiC layer from the mixture of hydrogen and hydrocarbon species etched from the graphite.
Phase synchronization of chaotic systems with both weak and strong couplings has recently been investigated extensively. Similar to complete synchronization, this type of synchronization can also be applied in secure communications. We develop a digital secure communication scheme that utilizes the instantaneous phase as the signal transmitted from the drive to the response subsystems. Simulation results show that the scheme is difficult to be broken by some traditional attacks. Moreover, it operates with a weak positive conditional Lyapunov exponent in the response subsystem.
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