Search

A facile and effective catalyst deposition process for carbon nanotube (CNT) array growth via chemical vapor deposition using a resistively heated thermal evaporation technique to sublimate FeCl3 onto the substrate is demonstrated. The catalytic activity of the sublimated FeCl3 catalyst precursor is shown to be comparable to the well-studied e-beam evaporated Fe catalyst, and the resulting vertically aligned CNTs (VA-CNTs) have a similar diameter, walls, and defects, as well as improved bulk electrical conductivity. In contrast to standard e-beam-deposited Fe, which yields base-growth CNTs, scanning and transmission electron microscopy and X-ray photoelectron spectroscopy characterizations reveal a tip-growth mechanism for the FeCl3-derived VA-CNT arrays/forests. The FeCl3-derived forests have a lower (∼1/3 less) longitudinal indentation modulus, but higher longitudinal electrical conductivity (greater than twice) than that of the e-beam Fe-grown CNT arrays. The sublimation process to grow high-quality VA-CNTs is a highly facile and scalable process (extensive substrate shape and size, and moderate vacuum and temperatures) that provides a new route to synthesizing aligned CNT forests for numerous applications.

Sustainable processes for purifying water, capturing carbon, producing biofuels, operating fuel cells, and performing energy-efficient industrial separations will require next-generation membranes. Solvent-less fabrication for membranes not only eliminates potential environmental issues with organic solvents, but also solves the swelling problems that occur with delicate polymer substrates. Furthermore, the activation procedures often required for synthesizing microporous materials such as metal–organic frameworks (MOFs) can be reduced when solvent-less vapor-phase approaches are employed. This perspective covers several vacuum deposition processes, including initiated chemical vapor deposition (iCVD), initiated plasma-enhanced chemical vapor deposition (iPECVD), solvent-less vapor deposition followed by in situ polymerization (SLIP), atomic layer deposition (ALD), and molecular layer deposition (MLD). These solvent-less vapor-phase methods are powerful in creating ultrathin selective layers for thin-film composite membranes and advantageous in conformally coating nanoscale pores for the precise modification of pore size and internal functionalities. The resulting membranes have shown promising performance for gas separation, nanofiltration, desalination, and water/oil separation. Further development of novel membrane materials and the scaling up of high-throughput reactors for solvent-less vapor-phase processes are necessary in order to make a real impact on the chemical industry in the future.

The combination of inorganic semiconductors with organic thin films promises new strategies for the realization of complex hybrid optoelectronic devices. Oxidative chemical vapor deposition (oCVD) of conductive polymers offers a flexible and scalable path towards high-quality three-dimensional inorganic/organic optoelectronic structures. Here, hole-conductive poly(3,4-ethylenedioxythiophene) (PEDOT) grown by oxidative chemical vapor deposition is used to fabricate transparent and conformal wrap-around p-type contacts on three-dimensional microLEDs with large aspect ratios, a yet unsolved challenge in three-dimensional gallium nitride technology. The electrical characteristics of two-dimensional reference structures confirm the quasi-metallic state of the polymer, show high rectification ratios, and exhibit excellent thermal and temporal stability. We analyze the electroluminescence from a three-dimensional hybrid microrod/polymer LED array and demonstrate its improved optical properties compared with a purely inorganic microrod LED. The findings highlight a way towards the fabrication of hybrid three-dimensional optoelectronics on the sub-micron scale., Though integrating functional organic materials with semiconductor nanostructures is attractive for 3D chip processing, realizing these hybrids remains a challenge. Here, the authors report an oxidative chemical vapor deposition-based process for designing novel 3D hybrid optoelectronic structures.

Chemical vapour deposition (CVD) enables nanoscale control for the synthesis of high-purity polymer thin films. Ultrathin (

Printing of ultrathin layers of polymeric and colloidal inks is critical for the manufacturing of electronics on nonconventional substrates such as paper and polymer films. Recently, we found that nanoporous stamps overcome key limitations of traditional polymer stamps in flexographic printing, namely, enabling the printing of ultrathin nanoparticle films with micron-scale lateral precision. Here, we study the dynamics of liquid transfer between nanoporous stamps and solid substrates. The stamps comprise forests of polymer-coated carbon nanotubes, and the surface mechanics and wettability of the stamps are engineered to imbibe colloidal inks and transfer the ink upon contact with the target substrate. By high-speed imaging during printing, we observe the dynamics of liquid spreading, which is mediated by progressing contact between the nanostructured stamp surface and by the substrate and imbibition within the stamp-substrate gap. From the final contact area, the volume of ink transfer is mediated by rupture of a capillary bridge; and, after rupture, liquid spreads to fill the area defined by a precursor film matching the stamp geometry with high precision. Via modeling of the liquid dynamics, and comparison with data, we elucidate the scale- and rate-limiting aspects of the process. Specifically, we find that the printed ink volume and resulting layer thickness are independent of contact pressure; and that printed layer thickness decreases with retraction speed. Under these conditions, nanoparticle films with controlled thickness in the

Blockage of pipelines due to accretion of salt particles is detrimental in desalination and water-harvesting industries as they compromise productivity, while increasing maintenance costs. We present a micro-/nanoscale approach to study fundamentals of scale formation, deposition, and adhesion to engineered surfaces with a wide range of surface energies fabricated using the initiated chemical vapor deposition method. Silicon wafers and steel substrates are coated with poly(1H,1H,2H,2H-perfluorodecylacrylate) or pPFDA, poly(tetravinyl-tetramethylcyclotetrasilohexane) or pV4D4, poly(divinylbenzene) or pDVB, poly(1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasilohexane) or pV3D3, and cross-linked copolymers of poly(2-hydroxyethylmethacrylate) and poly(ethylene glycol) diacrylate or p(PHEMA-co-EGDA). Particles of salt (CaSO4·2H2O) are formed and shaped with a focused ion beam and adhered to a tipless cantilever beam using a micromanipulator setup to study their adhesion strength with a molecular force probe...

Tuning heterogeneous nucleation of CaCO3 could enable new bio-mimic structures and address inorganic fouling in desalination and petroleum industries. However, few fundamental principles exist to guide surface modification for controlling this complex nucleation process. Additionally, industrial applications often require high stability for harsh operational conditions and nanoscale thickness for low heat transfer resistance. Such robust nanoscale coating materials have not yet been reported, motivating the current study of durable ultrathin (≤100 nm) organic covalent networks synthesized by initiated chemical vapor deposition (iCVD). The low surface energy of the iCVD films results in a high energy barrier for CaCO3 heterogeneous nucleation, leading to slow kinetics with extended induction periods. We also found the dominant role of electrochemical oxidation on Cu/Ni surfaces in affecting heterogeneous nucleation of CaCO3 in a hot aqueous environment. With excellent stability and passivation capability, our iCVD coatings effectively inhibit corrosion-induced heterogeneous nucleation, thus reducing the amount of CaCO3 fouling by up to 14 times at 110 °C.

Chemical vapour deposition (CVD) is a powerful technology for producing high-quality solid thin films and coatings. Although widely used in modern industries, it is continuously being developed as it is adapted to new materials. Today, CVD synthesis is being pushed to new heights with the precise manufacturing of both inorganic thin films of 2D materials and high-purity polymeric thin films that can be conformally deposited on various substrates. In this Primer, an overview of the CVD technique, including instrument construction, process control, material characterization and reproducibility issues, is provided. By taking graphene, 2D transition metal dichalcogenides (TMDs) and polymeric thin films as typical examples, the best practices for experimentation involving substrate pretreatment, high-temperature growth and post-growth processes are presented. Recent advances and scaling-up challenges are also highlighted. By analysing current limitations and optimizations, we also provide insight into possible future directions for the method, including reactor design for high-throughput and low-temperature growth of thin films. This Primer on chemical vapour deposition summarizes current and emerging experimental set-ups as well as common characterization approaches used to determine thin film formation and quality as applied to graphene and other novel 2D materials.

Controlling the permeation of molecules and ions enables numerous technologies, including sensing, actuation, membrane separations, controlled drug release, and electrochemical energy storage. Rapid transport requires using ultrathin layers. Selective and switchable permeation entails the precise design of film architecture at the molecular level. Additionally, the permeation control layers must conform to the micro- and nanostructured topologies utilized to increase the surface area for permeation. This work will review the utility of highly conformal chemical vapor deposited (CVD) polymer nanolayers for permeation control. Using CVD polymerization couples the versatility of organic chemistry with the high-purity and systematic process control of all-dry vacuum processing. The full retention of organic functional groups by polymerization is essential for the fabrication of smart layers capable of switching permeation behavior in response to variations in light, pH, or temperature. Additionally, precise mechanistic control over chain formation and morphology is also essential for engineering the ionic conduction of vapor deposited polymer nanolayers.Controlling the permeation of molecules and ions enables numerous technologies, including sensing, actuation, membrane separations, controlled drug release, and electrochemical energy storage. Rapid transport requires using ultrathin layers. Selective and switchable permeation entails the precise design of film architecture at the molecular level. Additionally, the permeation control layers must conform to the micro- and nanostructured topologies utilized to increase the surface area for permeation. This work will review the utility of highly conformal chemical vapor deposited (CVD) polymer nanolayers for permeation control. Using CVD polymerization couples the versatility of organic chemistry with the high-purity and systematic process control of all-dry vacuum processing. The full retention of organic functional groups by polymerization is essential for the fabrication of smart layers capable of switching permeation behavior in response to variations in light, pH, or temperature. Additionally, precise m...

Starting from low-molecular weight reactants in the vapor phase, initiated Chemical Vapor Deposition (iCVD) synthesizes fluoropolymer chains and forms thin films in a single step. Copolymerization results from simply flowing more than one type of monomer into the iCVD vacuum chamber. If any of the monomers has more than one vinyl bond, a crosslinked film is directly obtained without the need for a post-treatment step. Additionally, a pretreatment step with in the iCVD reactor chamber can be used for in situ grafting without the need to break vacuum before commencing film growth.

Poly(ethylene 3,4-dioxythiophene (PEDOT) films synthesized by oxidative chemical vapor deposition (oCVD) display strong electrochemical activity in the region from 2 to 4.2 V vs Li/Li+. By contrast, the more commonly studied PEDOT:polystyrenesulfonate (PSS) films have negligible electrochemical activity in this region. For the oCVD films, its small dopant anions (Cl–) that can easily enter and exit the polymer structure allow exchange with the Li+ counterion in solution, while for PEDOT:PSS, the poly(styrenesulfonate) dopant is a large macromolecule having substantially lower mobility. Here, we seek to elucidate the relationship between the structural characteristics of oCVD PEDOT thin films and their electrochemical properties, particularly in Li-ion electrolyte systems. Specifically, we seek to rationally design the thin-film properties of oCVD PEDOT for high-rate performance and cycle life by varying the film growth temperature. We observe that the dominant effect of increasing growth temperature is an...

The formation of solid inorganic salts from solutions is of fundamental importance for industrial, geological, and biological processes. Here, we review the literature on the fundamentals of inorganic scaling with the goal of elucidating the underlying phenomena observed during thermal desalination processes, mainly multi-stage flash (MSF). We will focus on one of the most common foulants, CaCO3, recognizing that similar phenomena occur for other salts and that behaviors in mixtures with other salts and organic molecules will impact the real world situation. This review will cover a wide range of dimensions, providing views from molecular level to plant scale. In addition to the mechanism and kinetics of scale formation in MSF, we will also review current strategies to control scaling in MSF and highlight directions for future development.

Directed self-assembly (DSA) of block copolymer (BCP) thin films is a promising approach to enable next-generation patterning at increasingly smaller length scales. DSA utilizes interfacial wetting layers to force the BCP domains to self-assemble with the desired orientation with respect to the substrate. Here, we demonstrate that initiated chemical-vapor-deposited (iCVD) polydivinylbenzene (pDVB) ultrathin films can direct the self-assembly of poly(styrene- block-methylmethacrylate). We found that the methyl radicals formed at increased filament temperatures during the iCVD process result in the backbone methylation of pDVB. By tuning the degree of backbone methylation, we systematically changed the wetting properties of the iCVD pDVB from a slight poly(methylmethacrylate) preference to complete poly(styrene) preference. Additionally, we utilize the conformal nature of the iCVD to form a wetting layer over a topographical line and space pattern, which is subsequently used to produce self-assembled BCP films with both perpendicular orientation and long-range alignment.

Molecular adsorption—the process in which small molecules adhere to a surface—typically considers homogeneous, atomistically continuous, flat geometries. In this issue of Matter, Reimer and colleagues tackle a much more complex situation of volatile organic compounds and carbon dioxide on hierarchical nanoporous carbon with multiscale pores, resolving and characterizing phase-dependent site-specific dynamics via nuclear magnetic resonance (NMR).

In this article, we report effect of surface coatings on organic fouling in reverse osmosis (RO) desalination membranes at the two operating pressure extremes of 20.7 and 55.2 bar. The surface of commercial RO membranes was modified by depositing surface-enriched zwitterionic films in order to achieve enhanced organic fouling resistance. Antifouling performance of both the surface-modified and bare (uncoated) RO membranes was evaluated under cross-flow filtration conditions in the presence of sodium alginate (SA). Filtration studies of the model organic foulant solution showed that both reversible and irreversible flux declines were significantly lower and, as a result, considerably higher flux recovery was achieved after simple hydraulic flushing in the surface-modified membranes when compared to virgin RO membranes. The FE-SEM analysis revealed that foulant deposition on the surface of the modified membranes was patchy/irregular and porous in structure at both lower and higher pressures as opposed to dense and continuous foulant deposition with full coverage of bare membranes with SA at both low and high operating pressures. FTIR scans also qualitatively confirmed a higher amount of SA deposition and revealed that the foulant deposition is further enhanced at higher operating pressure of 55.2 bar on the surface of bare membranes.

Directed self-assembly (DSA) of the domain structure in block copolymer (BCP) thin films is a promising approach for sub-10-nm surface patterning. DSA requires the control of interfacial properties on both interfaces of a BCP film to induce the formation of domains that traverse the entire film with a perpendicular orientation. Here we show a methodology to control the interfacial properties of BCP films that uses a polymer topcoat deposited by initiated chemical vapour deposition (iCVD). The iCVD topcoat forms a crosslinked network that grafts to and immobilizes BCP chains to create an interface that is equally attractive to both blocks of the underlying copolymer. The topcoat, in conjunction with a chemically patterned substrate, directs the assembly of the grating structures in BCP films with a half-pitch dimension of 9.3 nm. As the iCVD topcoat can be as thin as 7 nm, it is amenable to pattern transfer without removal. The ease of vapour-phase deposition, applicability to high-resolution BCP systems and integration with pattern-transfer schemes are attractive properties of iCVD topcoats for industrial applications. A thin topcoat that grafts directly to block copolymer films does not need to be removed prior to further fabrication steps.

Membranes possessing high permeability to water vapor and high liquid entry pressure (LEP) are necessary for efficient membrane distillation (MD) desalination. A common technique to prepare specialized MD membranes consists of coating a hydrophilic or hydrophobic base membrane with a low surface-energy material. This increases its liquid entry pressure, making the membrane suitable for MD. However, in addition to increasing LEP, the surface-coating may also decrease permeability of the membrane by reducing its average pore size. In this study, we quantify the effects of initiated chemical vapor deposition (iCVD) polymer coatings on membrane permeability and LEP. We consider whether the iCVD films should have minimized thickness or maximized non-conformality, in order to maximize the permeability achieved for a given value of LEP. We determined theoretically that permeability of a single pore is maximized with a highly non-conformal iCVD coating. However, the overall permeability of a membrane consisting of many pores is maximized when iCVD film thickness is minimized. We applied the findings experimentally, preparing an iCVD-treated track-etched polycarbonate (PCTE) membrane and testing it in a permeate gap membrane distillation (PCMD) system. This study focuses on membranes with clearly defined, cylindrical pores. However, we believe that the principles we discuss will extend to membranes with more complex pore architectures. Overall, this work indicates that the focus of surface-coating development should be on minimizing film thickness, not on increasing their non-conformality., MIT & Masdar Institute Cooperative Program (02/MI/MI/CP/11/07633/GEN/G/00), Massachusetts Institute of Technology. Institute for Soldier Nanotechnologies (W911NF-13-d-0001)

In this work, we demonstrate a solvent-free, low temperature ( 2 ms) compared to bare silicon (~30 μs), and remained stable in air for over 200 h. These values approach that of SiN x films deposited at significantly higher temperatures. The polymer passivation processes and materials are shown to significantly reduce surface recombination rates: chemically by reducing density of surface states and electrostatically by altering band bending at the silicon interface. Passivation quality also improved on grafting using aliphatic monomers compared to aromatic ones suggesting a reduction in steric effects in the former, helping us posit design rules for polymer based surface passivation of silicon. Finally, the ability to use an electrically conducting polymer for passivation creates a direct interface between traditional silicon microelectronics and organic electronics. Beyond microelectronics and photovoltaics, these processes can enable the fabrication of hybrid or multifunctional devices, such as biosensors and light emitting diodes.

Polymeric membranes have been applied in industrial gas separations for decades. Competing technologies, such as cryogenic distillation and sorption processes, require the gases to be either condensed or thermally regenerated from the sorbents. In contrast, membrane gas separation does not involve phase transition, representing the potential for a more energy efficient and eco-friendly separation process. However, the overall energy consumption by membrane gas separation is highly dependent on the quality of the membrane employed for the separation process. With the goal of reducing the energy input needed for creating the transmembrane pressure difference, numerous bulk polymers have been investigated. However, less effort has been devoted to processing polymers into ultrathin membranes and investigating their gas permeation properties, which can be quite different from their bulk counterparts. This review summarizes recent advances in fabricating ultrathin gas-selective polymeric membranes. Several classes of ultrathin polymeric membranes are highlighted: microporous polymers, facilitated transport polymeric membranes, Langmuir–Blodgett (LB) films and Layer-by-Layer (LbL) deposited polyelectrolyte multilayers (PEMs), polyamides and other commercial polymers. The application of gas-selective polymeric membranes beyond gas separation is also included as a meaningful extension to this review.

In membrane distillation desalination (MD), a hydrophobic membrane acts as a barrier between feed and distillate solutions. MD membranes are often fabricated using a composite method: a hydrophilic or mildly hydrophobic base membrane is coated with a highly hydrophobic material to produce a membrane with adequate water liquid entry pressure (LEPw) for MD. This composite method increases the range of materials that can be used for MD membranes. However, environmental safety concerns about the hydrophobic coating materials persist. In this study we systematically quantify the relationship between the hydrophobicity of the coating material (its contact angle with water) and the LEPw of the coated MD membrane. This relationship determines the conditions when lower-hydrophobicity, more environmentally-friendly coating chemistries can be used to prepare successful MD membranes. For the membranes in this study, we found that for coating materials with intrinsic advancing contact angles (ACA) not much greater than 90°, water liquid entry pressure (LEPw) was in a range suitable for MD. We explained this result with a new model for liquid entry pressure (LEP). This work predicted that the hydrocarbon, poly(divinyl benzene) (pDVB), an environmentally-friendly but low-hydrophobicity polymer, could be a successful coating chemistry for MD membranes. We thus fabricated a nylon-pDVB composite membrane and demonstrated it in an MD desalination system.

Optimizing PEDOT crystallite texture and lattice constants improves conductivity and enhances perovskite solar cell stability., For semicrystalline poly(3,4-ethylene dioxythiophene) (PEDOT), oxidative chemical vapor deposition (oCVD) enables systematic control over the b-axis lattice parameter (π-π stacking distance). Decreasing the b-axis lattice parameter increases the charge transfer integral, thus enhancing intracrystallite mobility. To reduce the barrier to intercrystallite transport, oCVD conditions were tailored to produce pure face-on crystallite orientation rather than the more common edge-on orientation. The face-on oriented oCVD PEDOT with the lowest b-axis lattice parameter displayed the highest in-plane electrical conductivity (σdc = 2800 S/cm), largest optical bandgap (2.9 eV), and lowest degree of disorder as characterized by the Urbach band edge energy. With the single step oCVD process at growth conditions compatible with direct deposition onto flexible plastic substrates, the ratio σdc/σop reached 50. As compared to spun-cast PEDOT:polystyrene sulfonate, integration of oCVD PEDOT as a hole transport layer (HTL) improved both the power conversion efficiency (PCE) and shelf-life stability of inverted perovskite solar cells (PSC).

Nanocarbon electronic conductors combined with pseudocapacitive materials, such as conducting polymers, display outstanding electrochemical properties and mechanical flexibility. These characteristics enable the fabrication of flexible electrodes for energy-storage devices; that is, supercapacitors that are wearable or can be formed into shapes that are easily integrated into vehicle parts. To date, most nanocarbon materials such as nanofibers are randomly dispersed as a network in a flexible matrix. This morphology inhibits ion transport, particularly under the high current density necessary for devices requiring high power density. Novel flexible densified horizontally aligned carbon nanotube arrays (HACNTs) with controlled nanomorphology for improved ion transport are introduced and combined with conformally coated poly(3-methylthiophene) (P3MT) conducting polymer to impart pseudocapacitance. The resulting P3MT/HACNT nanocomposite electrodes exhibit high areal capacitance of 3.1 F cm-2 at 5 mA cm-2 , with areal capacitance remaining at 1.8 F cm-2 even at a current density of 200 mA cm-2 . The asymmetric supercapacitor cell also delivers more than 1-2 orders of magnitude improvement in both areal energy and power density over state-of-the-art cells. Furthermore, little change in cell performance is observed under high strain, demonstrating the mechanical and electrochemical stability of the electrodes.

Bulk polytetrafluoroethylene (PTFE) possesses excellent chemical stability and dielectric properties. Indeed, thin films with these same characteristics would be ideal for electret applications. Previously, the electret properties of PTFE-like thin films produced by rf sputtering or plasma enhanced chemical vapor deposition were found to deteriorate due to structural changes and surface oxidation. In this article, the technique of initiated chemical vapor deposition (iCVD) is evaluated for electret applications for the first time. The iCVD method is known for its solvent-free deposition of conformal, pinhole-free polymer thin films in mild process conditions. It is shown that PTFE thin films prepared in this way, show excellent agreement to commercial bulk PTFE with regard to chemical properties and dielectric dissipation factors. After ion irradiation in a corona discharge the iCVD PTFE thin films exhibit stable electret properties, which can be tailored by the process parameters. Due to the mild deposition conditions, the iCVD technique is suitable for deposition on flexible organic substrates for the next-generation electret devices. It is also compatible with state-of-the-art microelectronic processing lines due to the characteristics of conformal growth and easy scaling up to larger size substrates.

Coronavirus The evidence has become clear that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is transmitted by aerosols, so enclosed spaces such as automobiles are thus high risk. Mathai et al. numerically calculated the flow patterns of aerosol droplets inside the cabin of a four-windowed car. Having the windows closed and the air-conditioner on results in considerable transfer of air and aerosols between occupants. However, having all the windows fully open separates the airflows on the right and left sides of the cabin and thus best reduces disease transmission if the passenger is seated in the back, on the opposite side from the driver. Sci. Adv. 10.1126/sciadv.abe0166 (2020).

Conducting polymers have attracted tremendous attention because of their unique characteristics, such as metal-like conductivity, ionic conductivity, optical transparency, and mechanical flexibility. Texture and nanostructural engineering of conjugated conducting polymers provide an outstanding pathway to facilitate their adoption in a variety of technological applications, including energy storage and harvesting devices, flexible optoelectronic devices, and wearable electronic devices. Generally, obtaining high carrier mobility in the presence of high carrier density is challenging and requires precise control of the texture and nanostructure of conducting polymers to avoid the charge localization. Preferential semicrystalline orientation, π–π stacking distances, crystallite size, intra- and interchain couplings, intra- and intercrystallite connections, and grain boundaries are the key parameters that influence the charge carrier mobility and needs to be controlled by the synthesis parameters. This article provides a comprehensive overview of the recent texture and nanostructural engineering development of conducting polymers. In addition, this work describes the fundamental of charge carrier transport mechanisms in conducting polymers; and the latest progress on the optoelectronic characteristics of flexible transparent conductive electrodes based on conducting polymers is reported.

The chemical vapor deposition (CVD) polymerization of metalloporphyrin building units is demonstrated to provide an easily up-scalable one-step method toward the deposition of a new class of dense and defect-free metal–organic covalent network (MOCN) layers. The resulting hyper-thin and flexible MOCN layers exhibit outstanding gas-separation performances for multiple gas pairs., United States. Army Research Office. Institute for Soldier Nanotechnologies (Contract DAAD-19-02D-0002), Luxembourg National Research Fund

Oxidative chemical-vapor-deposition (oCVD) provides a facile route to polymerize and deposit insoluble monomers in thin film form. Here, we report on oCVD polythiophene (PT)-based organic thin film transistors (OTFTs) that present both high mobility and excellent stability over time in air. The measured field effect mobility (μFE) is ∼0.02 cm2/V sec with the low threshold voltage between −1 V and 0.3 V. Additionally the PT OTFTs show no evidence of performance degradation after 3 months exposure in air. The transmission line model (TLM) enables the determination of the specific contact resistance (ρC) of oCVD PT channel/metallization interface and reveals that ρC is improved with increasing gate bias. The oCVD PT channel conductivity (σch) and carrier density (p) were evaluated from more than 100 devices using TLM measurements and the relation of σch = qpμFE. Carrier transport analysis suggests that the charge screening effect governs hole carrier mobility in the carrier density regime below approximately 1018/cm3 where an increase in carrier density leads to higher mobility. We also demonstrate photo-conductivity of oCVD PT through an increase in device on-state current and the field effect mobility when the PT OTFT is illuminated. Strategies to further enhance the performance of the materials and devices are also suggested.

In previous studies of the desalination technology membrane distillation (MD), superhydrophobicity of the membrane has been shown to dramatically decrease fouling in adverse conditions, but the mechanism for this is not well understood. Additionally, air layers present on submerged solid superhydrophobic surfaces have been shown to dramatically reduce biofouling, and air-bubbling has been used to reducing fouling and increase flux and efficiency in MD. The present work studies the effect of maintaining air layers on the membrane surface and superhydrophobicity as a new method for preventing fouling of MD membranes by salts, particulates, and organic particles. Superhydrophobic MD membranes were prepared using initiated chemical vapor deposition (iCVD) of perfluorodecyl acrylate (PFDA) on poly(vinyldene fluoride) PVDF membranes and used to study the effects of surface energy on fouling. A static MD setup with evaporation through an MD membrane but no condensing of permeate was used to examine the effect of air exposure on fouling, by measuring the increase in weight of the membrane caused by scale deposition. Theory was derived for the reduction of fouling on superhydrophobic surfaces, and a review of related theory was included. Air layers may displace fouling gels, reduce the area of feed in contact with the membrane, reduce foulant adhesion, and enhance superhydrophobicity in a Cassie–Baxter state. The study shows that the presence of air on the membrane surface significantly reduces biological fouling, but in some cases had mildly exacerbating effects by increasing crystal formation of salts, especially when the air was not saturated with water vapor. Air recharging combined with superhydrophobicity reduced fouling in several cases where hydrophobic membranes alone did little., National Science Foundation (U.S.). Materials Research Science and Engineering Centers (Program) (DMR-1120296), Masdar Institute of Science and Technology/MIT/UAE (Cooperative agreement, Reference no.02/MI/MI/ CP/11/07633/GEN/G/00)

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...