The fabrication of electronic devices based on organic materials, known as 'printed electronics', is an emerging technology due to its unprecedented advantages involving fl exibility, light weight, and portability, which will ultimately lead to future ubiquitous applications. [ 1 ] The solution processability of semiconducting and metallic polymers enables the cost-effective fabrication of optoelectronic devices via high-throughput printing techniques. [ 2 ] These techniques require high-performance fl exible and transparent electrodes (FTEs) fabricated on plastic substrates, but currently, they depend on indium tin oxide (ITO) coated on plastic substrates. However, its intrinsic mechanical brittleness and inferior physical properties arising from lowtemperature ( T ) processing below the melting T of the plastic substrates (i.e., typically below 150 °C) have increased the demand for alternative FTE materials. [ 3 ] Conducting polymers (CPs) have been considered a promising candidate for FTEs due to their mechanical fl exibility and solution processability. The high transparency of CPs originates from the charge carrier density ( n ) of approximately 10 21 cm −3 because both the refl ectance and absorption are confi ned in the IR region below the plasma frequency ( ω P , ω P 2 = 4 π e 2 n / m * where m * is the effective mass of the charge carrier) at approximately hω P ≈ 1 eV. [ 2 ] A complex of poly(3,4-ethylenedioxythiophene) (PEDOT) and poly(4-styrenesulfonate) (PSS), in which PSS acts as both a counter-ion and a soluble template for PEDOT, is a successful CP due to its high electrical conductivity ( σ dc ) and excellent transparency in the visible range. [ 4 ] The conducting fi lms, which were coated from PEDOT:PSS solution in an aqueous dispersion, consist of hydrophobic and conducting PEDOT-rich grains encapsulated by hydrophilic and insulating PSS-rich shells. [ 5 ] These morphological features involve an excess amount of PSS as well as low chain alignment, resulting in a low σ dc of approximately 1 S cm −1 . Over the past decade, pre-and/or post-treatment with various organic solvents, surfactants, salts, and acids have been found to enhance the σ dc of PEDOT:PSS by two to three orders of magnitude. [6][7][8] Recently, the high σ dc (≈3065 S cm −1 ) was achieved using a treatment of dropping a 1.0 M H 2 SO 4 solution onto the PEDOT:PSS fi lms. [ 8 ] Although numerous studies suggested that the σ dc enhancement could be attributed to morphological changes in the PEDOT:PSS complex, such as grain growth, polymer chain expansion, and phase separation, a clear understanding of the mechanism of the σ dc enhancement is still required for both the basic material studies on CPs and developing high-performance FTEs. [6][7][8] Herein, we report the solution-processed crystalline formation in PEDOT:PSS via H 2 SO 4 post-treatment. By rigorously controlling the post-treatment conditions (i.e., the H 2 SO 4 concentration, treatment T , and processing details), we obtained insight into how the H 2 SO 4 solution proce...

A precise control of the size, density, and distribution of metal nanoparticles dispersed on functional oxide supports is critical for promoting catalytic activity and stability in renewable energy and catalysis devices. Here, we measure the growth kinetics of individual Co particles ex-solved on SrTi0.75Co0.25O3‑δ polycrystalline thin films under a high vacuum, and at various temperatures and grain sizes using in situ transmission electron microscopy. The ex-solution preferentially occurs at grain boundaries and corners which appear essential for controlling particle density and distribution, and enabling low temperature ex-solution. The particle reaches a saturated size after a few minutes, and the size depends on temperature. Quantitative measurements with a kinetic model determine the rate limiting step, vacancy formation enthalpy, ex-solution enthalpy, and activation energy for particle growth. The ex-solved particles are tightly socketed, preventing interactions among them over 800 °C. Furthermore, we obtain the first direct clarification of the active reaction site for CO oxidationthe Co-oxide interface, agreeing well with density functional theory calculations.

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Catalysis with single-atom catalysts (SACs) exhibits outstanding reactivity and selectivity. However, fabrication of supports for the single atoms with structural versatility remains a challenge to be overcome, for further steps toward catalytic activity augmentation. Here, we demonstrate an effective synthetic approach for a Pt SAC stabilized on a controllable one-dimensional (1D) metal oxide nano-heterostructure support, by trapping the single atoms at heterojunctions of a carbon nitride/SnO2 heterostructure. With the ultrahigh specific surface area (54.29 m2 g–1) of the nanostructure, we obtained maximized catalytic active sites, as well as further catalytic enhancement achieved with the heterojunction between carbon nitride and SnO2. X-ray absorption fine structure analysis and HAADF-STEM analysis reveal a homogeneous atomic dispersion of Pt species between carbon nitride and SnO2 nanograins. This Pt SAC system with the 1D nano-heterostructure support exhibits high sensitivity and selectivity toward detection of formaldehyde gas among state-of-the-art gas sensors. Further ex situ TEM analysis confirms excellent thermal stability and sinter resistance of the heterojunction-immobilized Pt single atoms.

Tuning of the cation–oxygen bond strength effectively promotes B-site ex-solution in a perovskite, thereby boosting the catalytic activity of CO oxidation.