A novel approach to fabricate supercapacitors (SCs) via vapor printing, specifically oxidative chemical vapor deposition (oCVD), is demonstrated. Compared to stacking multiple layers into a SC, this method enables the monolithic integration of all components into a single-sheet substrate, minimizing the inactive materials and eliminating the possibility of multilayer delamination. Electrodes comprised of pseudocapacitive material, poly(3,4-ethylenedioxythiophene) (PEDOT), are deposited into both sides of a sheet of flexible porous substrate. The film deposition and patterning are achieved in a single step. The oCVD PEDOT penetrates partially into the porous substrate from both surfaces, while leaving the interior of the substrate serving as a separator. Near the surface, the PEDOT coating conforms to the substrate's structure without blocking the pores, resembling the substrate's intrinsic morphology with high surface area. The porously structured PEDOT coating, paired with in situ ion gel electrolyte synthesis, gives enhanced electrode-electrolyte interfaces. The monolithic device demonstrates high volumetric capacitance (11.3 F cm ), energy density (2.98 mWh cm ), and power density (0.42 W cm ). These outstanding performance metrics are attributed to the large loading of active materials, minimization of inactive materials, and good electrode-electrolyte interfaces. SC arrays can be printed on a single substrate without the use of wire interconnects.

Room temperature resistive volatile organic compound (VOC) sensing materials fabricated with vertically aligned-carbon nanotubes (VA-CNT) demonstrated 10-fold improved sensitivity upon application of a thin conformal layer of the conducting polymer coating ((poly­(3,4-ethylenedioxythiophene) (PEDOT)). The PEDOT was directly synthesized on the VA-CNTs via oxidative chemical vapor deposition (oCVD). Conformal PEDOT coatings with thickness of 8 and 17 nm were easily achievable by oCVD. The hybrid VA-CNT/oCVD PEDOT sensing materials exhibited excellent response to low concentrations of analyte gases of different polarity. The projected detection limit for n-pentane is as low as ∼50 ppm. A second polymer layer, nonconducting polystyrene (PS, ∼6 nm), was further conformally coated on the VA-CNT/PEDOT via initiative chemical vapor deposition (iCVD) to enhance the gas selectivity. The iCVD PS enhanced the selectivity of n-pentane over methanol by 2.7-fold and toluene by 4.4-fold. Several unique advantages of these sensing materials include the following: (1) detection of nonpolar hydrocarbon molecule n-pentane at room temperature; (2) high signal quality (signal-to-noise ratio typically ∼30 dB); (3) solvent-free facile fabrication method that preserves the accessible high-surface-area morphology of the VA-CNTs; (4) good reversibility and short response time (∼400 s). Our results indicate that both the polarity of the analyte molecule and the carrier transport regime of the PEDOT layer are important in sensing behavior. Furthermore, this versatile selective layer design is potentially useful for selectivity enhancement for other important target analytes.

Tuning the optoelectronic properties and the density of hydroxyl pendant groups of 3-thiopheneethanol-co-ethylenedioxythiohene produced via an oxidative chemical vapor deposition technique.

The synthesis and characterization of poly(3,4-ethylenedioxythiophene) (PEDOT) using water-assisted vapor phase polymerization (VPP) and oxidative chemical vapor deposition (oCVD) are reported. For the VPP PEDOT, the oxidant, FeCl3 , is sublimated onto the substrate from a heated crucible in the reactor chamber and subsequently exposed to 3,4-ethylenedioxythiophene (EDOT) monomer and water vapor in the same reactor. The oCVD PEDOT was produced by introducing the oxidant, EDOT monomer, and water vapor simultaneously to the reactor. The enhancement of doping and crystallinity is observed in the water-assisted oCVD thin films. The high doping level observed at UV-vis-NIR spectra for the oCVD PEDOT, suggests that water acts as a solubilizing agent for oxidant and its byproducts. Although the VPP produced PEDOT thin films are fully amorphous, their conductivities are comparable with that of the oCVD produced ones.

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We report a novel room temperature methanol sensor comprised of gold nanoparticles covalently attached to the surface of conducting copolymer films. The copolymer films are synthesized by oxidative chemical vapor deposition (oCVD), allowing substrate-independent deposition, good polymer conductivity and stability. Two different oCVD copolymers are examined: poly(3,4-ethylenedioxythiophene-co-thiophene-3-aceticacid)[poly(EDOT-co-TAA)] and poly(3,4-ehylenedioxythiophene-co-thiophene-3-ethanol)[poly(EDOT-co-3-TE)]. Covalent attachment of gold nanoparticles to the functional groups of the oCVD films results in a hybrid system with efficient sensing response to methanol. The response of the poly(EDOT-co-TAA)/Au devices is found to be superior to that of the other copolymer, confirming the importance of the linker molecules (4-aminothiophenol) in the sensing behavior. Selectivity of the sensor to methanol over n-pentane, acetone, and toluene is demonstrated. Direct fabrication on a printed circuit board (PCB) is achieved, resulting in an improved electrical contact of the organic resistor to the metal circuitry and thus enhanced sensing properties. The simplicity and low fabrication cost of the resistive element, mild working temperature, together with its compatibility with PCB substrates pave the way for its straightforward integration into electronic devices, such as wireless sensor networks.

a b s t r a c tWithin this article, we report the characterization and organic vapor sensing properties of Langmuir-Blodgett (LB) thin films of calix[8]arenes. Surface pressure-area isotherms show that very stable monolayers are formed at the air-water interface. The LB film could be deposited onto different substrates which allowed the films to be characterized by UV, quartz crystal microbalance (QCM), surface plasmon resonance (SPR) and atomic force microscopy (AFM). The results indicate that good quality, uniform LB films can be prepared with transfer ratios of over 0.95. QCM results showed that the deposited mass of calix[8]arene monolayer onto a quartz crystal decreased from 693 to 204 ng as the number of layers is increased. AFM studies showed a smooth, and void free surface morphology with a rms value of 1.202 nm. The sensing abilities of this LB film towards the development of room temperature organic vapor sensing devices are also studied. Responses of the LB films to various vapors are fast, large, and reversible. It was found that the obtained LB film is significantly more sensitive to chloroform than other vapors. It can be concluded that this molecule could have a potential application in the research area of room temperature vapor sensing devices.

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