No abstract

Despite recognition of the possible role of biological nitrogen removal (BNR) processes in nitrous oxide (N(2)O) emission, a measured database of N(2)O emissions from these processes at the national scale does not currently exist. This study focused on the quantification of N(2)O emissions at 12 wastewater treatment plants (WWTPs) across the United States using a newly developed U.S. Environmental Protection Agency (USEPA) reviewed protocol. A high degree of variability in field-scale measurements of N(2)O was observed, both across the WWTPs sampled and within each WWTP. Additionally, aerobic zones, which have hitherto not been considered in the USEPA approach of estimating N(2)O emissions, generally contributed more to N(2)O fluxes than anoxic zones from BNR reactors. These results severely qualify the conventional use of a single emission factor to "estimate" N(2)O emissions from BNR processes, solely by virtue of denitrification. Upon subjecting the nationwide data set to multivariate regression data mining, high nitrite, ammonium, and dissolved oxygen concentrations were positively correlated with N(2)O emissions from aerobic zones of activated sludge reactors. On the other hand, high nitrite and dissolved oxygen concentrations were positively correlated with N(2)O emissions from anoxic zones. Based on these results, it can be argued that activated sludge processes that minimize transient or permanent build up of ammonium or nitrite, especially in the presence of dissolved oxygen, are expected to have low N(2)O emissions.

A series of high-k, ultrathin copolymer gate dielectrics were synthesized from 2-cyanoethyl acrylate (CEA) and di(ethylene glycol) divinyl ether (DEGDVE) monomers by a free radical polymerization via a one-step, vapor-phase, initiated chemical vapor deposition (iCVD) method. The chemical composition of the copolymers was systematically optimized by tuning the input ratio of the vaporized CEA and DEGDVE monomers to achieve a high dielectric constant (k) as well as excellent dielectric strength. Interestingly, DEGDVE was nonhomopolymerizable but it was able to form a copolymer with other kinds of monomers. Utilizing this interesting property of the DEGDVE cross-linker, the dielectric constant of the copolymer film could be maximized with minimum incorporation of the cross-linker moiety. To our knowledge, this is the first report on the synthesis of a cyanide-containing polymer in the vapor phase, where a high-purity polymer film with a maximized dielectric constant was achieved. The dielectric film with the optimized composition showed a dielectric constant greater than 6 and extremely low leakage current densities (<3 × 10 A/cm in the range of ±2 MV/cm), with a thickness of only 20 nm, which is an outstanding thickness for down-scalable cyanide polymer dielectrics. With this high-k dielectric layer, organic thin-film transistors (OTFTs) and oxide TFTs were fabricated, which showed hysteresis-free transfer characteristics with an operating voltage of less than 3 V. Furthermore, the flexible OTFTs retained their low gate leakage current and ideal TFT characteristics even under 2% applied tensile strain, which makes them some of the most flexible OTFTs reported to date. We believe that these ultrathin, high-k organic dielectric films with excellent mechanical flexibility will play a crucial role in future soft electronics.

Advances in device technology have been accompanied by the development of new types of materials and device fabrication methods. Considering device design, initiated chemical vapor deposition (iCVD) inspires innovation as a platform technology that extends the application range of a material or device. iCVD serves as a versatile tool for surface modification using functional thin film. The building of polymeric thin films from vapor phase monomers is highly desirable for the surface modification of thermally sensitive substrates. The precise control of thin film thicknesses can be achieved using iCVD, creating a conformal coating on nano-, and microstructured substrates such as membranes and microfluidics. iCVD allows for the deposition of polymer thin films of high chemical functionality, and thus, substrate surfaces can be functionalized directly from the iCVD polymer film or can selectively gain functionality through chemical reactions between functional groups on the substrate and other reactive molecules. These beneficial aspects of iCVD can spur breakthroughs in device fabrication based on the deposition of robust and functional polymer thin films. This review describes significant implications of and recent progress made in iCVD-based technologies in three fields: electronic devices, surface engineering, and biomedical applications.