There exists a tremendous interest in metallic polymers as they combine facile processing, high conductivity and transparency. However, to date no straightforward method has been found to engineer a system that unites high doping and high order. [1][2][3][4][5][6] The apparent conflict lies in the nature of doping of a conducting polymer, which occurs through a distinct mechanism compared to inorganic semiconductors. Severe lattice distortions arise in the doping of conducting polymers as a result of the penetration of ions into the system. Consequently, the solid-state order becomes disrupted-it transforms from a former homogeneous organic vander-Waals crystal into a disordered salt. To form a substantial degree of order, growth methods have to consider the effect of ion penetration. [7][8][9][10][11][12][13][14][15][16] Small molecular systems have the advantage that they can be dissolved in polar solvents. Thus they can be grown in the doped form as a salt dissolved from Conductive polymers represent a rare case in which free-carrier absorption is shifted to the far-infrared-an attractive advantage in light of the requirement of highly transparent conductors across the visible and near-infrared. Unfortunately, prior approaches to doping these polymers-imperative for high conductance-have consistently led to strong localization arising from fluctuating band alignment among polymer chains. Here, this study overcomes this problem of doping-induced Anderson localization for the first time in polymers by developing a new conductive polymer synthesis strategy. This study achieves polymerization and doping simultaneously, thereby using an alternative nonmetal oxidant and thereby avoiding the introduction of excess energy that normally arises from exergonic polymerization. The resulting conductive polymer is the first to provide electron coherence in a metallic polymer thin film. The conductivity reaches a remarkable 3300 S cm −1 at 1.8 K and the mean electron scattering length a record 330 Å. This enhancement drives the glassy metal transition in the vicinity of the Mott-Ioffe-Regel (MIR) limit. The new metallic polymer achieves 10 −2 Ω −1 figure of merit, making it a contender for transparent conductive contacts previously only accessible using inorganics. The new material offers a uniquely broad transparency window spanning the UV to the mid-infrared. The ORCID identification number(s) for the author(s) of this article can be found under http://dx
Weak localization describes a metallic system, where due to the presence of disorder the electrical transport is governed by inelastic electron relaxation. Thereby the theory defines a threshold of spatial and of energetic disorder, at which a metal-insulator transition takes place. To achieve a metallic state in an inherently disordered system such as a conductive polymer, one has to overcome the threshold of localization. In this work we show that the effective suppression of disorder is possible in solution-processible poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate). We grow polymer films under optimized conditions allowing self-organization in solution. Interestingly, we find the requisite threshold, at which the system becomes finally metallic. We characterize the transition using a complementary morphology and magneto-electrical transport study and find coherent electron interactions, which emerge as soon as local order exceeds the macromolecular dimensions. These insights can be used for discrete improvement in the electrical performance, in particular for tailoring conductive polymers to alternative metal-like conductors.
The optimum activity for glucose electrocatalytic oxidation was found by screening along a large spread cosputtered combinatorial copper-palladium library (2.6 at.% to 39.2 at.% Pd) in neutral media using flow-type scanning droplet cell microscopy (FT-SDCM). The elemental composition and the surface topography were characterized along the compositional spread using energy dispersive X-ray spectroscopy (EDX), as well as atomic force microscopy (AFM). The study proves that the entire range of alloys can be implemented in glucose detection. The highest catalytic effect was obtained at a Pd content of 8.2 at.% (E SHE = 0.58 V) with a current density value of 7.33 mA cm , normalized to the stepwise increase of 1 mM glucose. Also, a good longterm stability, reproducibility (relative standard deviatioñ 5%), as well as the selective sensitivity to glucose oxidation were demonstrated by performing measurements in the presence of other compounds found in blood (e.g., ascorbic acid and uric acid).
Co-evaporation of Cu and Pd was used for the deposition of a relatively small gradient concentration thin film combinatorial library with Pd amounts between 4 and 14 atomic percent (at%). Screening for electrocatalytic oxidation of formaldehyde was performed by scanning droplet cell microscopy along the Cu-Pd compositional spread in alkaline solution and a best material performance for this process was identified for 7.5 at% Pd in Cu confirming results from co-sputtering studies. However, the microstructure and crystallographic analysis of Cu-Pd thin film alloys showed a compositionally induced gradual change of properties without any significant discontinuity. This indicates that the Cu-Pd atomic ratio is the main factor defining the electrocatalytic activity of the investigated alloys. This finding is also confirmed for bulk Cu-Pd alloys where the reproducibility of significant formaldehyde oxidation electrocatalytic activity when using Cu-7.5 at% Pd was demonstrated. An amperometric formaldehyde sensor was fabricated and its reproducibility, repeatability and stability were assessed. During successive anodic formaldehyde current oxidation peak observations a standard deviation value of 8% was measured. Multiple efficient successive use of the same sensor (5 to 10 times) were demonstrated and a maximum of 5% decrease in the current density was observed after 21 days of normal environment storage during a shelf-lifetime evaluation of the sensor. Overall, the study reveals inexpensive approaches for fabrication of multiple use formaldehyde sensors via thermal evaporation or bulk alloy casting, as well as the transfer of the main feature (i.e. maximum current density for formaldehyde oxidation) from a thin film combinatorial library to bulk samples.
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