In this study, the surface morphology of electrospun polycaprolactone (PCL) fibers was investigated. PCL was dissolved in various solvent/nonsolvent systems (acetone/dimethylformamide (DMF), tetrahydrofuran (THF)/DMF, dichloromethane (DCM)/DMF, chloroform (CF)/DMF, acetone/dimethyl sulfoxide (DMSO), THF/DMSO, DCM/DMSO, CF/DMSO) at a fixed ratio of 80/20 v/v. PCL solutions from these solvent systems were electrospun under varying high relative humidity (60–90%), and also room humidity. Characterization of fibers was evaluated by a scanning electron microscope, an atomic force microscope, water contact angle measurements, the Brunauer–Emmett–Teller method, and a strain–stress test. Results revealed that the surface texture of individual fibers changed with the presence of different types of pores and surface roughness depending on both humidity and solvent/nonsolvent properties. Miscibility with water was another factor to be taken into account for understanding mechanisms that contributed to the formation of surface defects. Fibrous materials having such a surface architecture, especially the porous ones, are potential candidates for various applications such as tissue engineering, drug delivery, catalysis, and filtration.

Piezoelectric single crystals based on the perovskite ferroelectric system (K,Na)NbO3 have been widely investigated over the past 20 years due to large piezoelectric coefficients, high transition temperatures, low density, and the nontoxic chemical composition. Various crystal growth methods were examined, including high-temperature solution growth, solid-state crystal growth, Bridgman–Stockbarger method, and the floating zone method. Increased understanding of the crystal growth process and post-growth treatments resulted in improved crystal quality and larger sizes. Recently, crystals with high piezoelectric and electromechanical coupling coefficients exceeding 1000 pC/N and 0.90, respectively, were reported. Moreover, their large potential for high-frequency ultrasonic medical imaging was demonstrated. This work provides a review of the development of piezoelectric (K,Na)NbO3-based single crystals, including their growth, defect chemistry, domain structures, electromechanical properties, and applications. Approaches for reducing growth defects, controlling point defects, and domain engineering are discussed. The remaining open issues are presented and an outlook on the future is provided.

Epitaxial SnSxSe2−x films with tunable band gap energies (1.0–2.2 eV) are of growing interest for photodetectors and 2D heterostructures for nanoscale electronics. In this study, powder vapor transport growth of SnSxSe2−x was investigated on c-plane sapphire and epitaxial graphene (EG)/6H–SiC substrates using tin, sulfur, and selenium powder sources in a heated tube furnace. The SnSxSe2−x composition was controlled by varying the sulfur and selenium source temperatures and the corresponding chalcogen vapor pressure ratio. Raman spectroscopy was used to determine the alloy composition of the films, and the optical properties were characterized using UV-Vis-NIR spectroscopy. SnSxSe2−x grown on sapphire consisted of vertically oriented platelets. By contrast, large-area, planar coalesced SnSxSe2−x films grew on EG with low surface roughness indicative of a van der Waals growth mode. High-resolution X-ray diffraction θ–2θ scans and pole figure analysis confirm that the SnSxSe2−x films are c-axis oriented with epitaxial relation being $\left[ {11\bar{2}0} \right]$ SnSxSe2−x‖$\left[ {10\bar{1}0} \right]$ 6H–SiC.

Electrochemical reduction of CO2 to formic acid is a good strategy to address both environmental and energy issues. However, some drawbacks including low activity, selectivity, and stability of electrocatalysts must be overcome. We propose a method for tailoring Bi2O2CO3-coated carbon fiber electrodes with higher selectivity and stability for electrochemical CO2 reduction to formic acid. We evaluated the effect of Bi2O2CO3 and Nafion contents on the electrocatalysts performance for CO2 reduction reaction (CO2RR). All electrodes produced only HCOO− in the liquid phase with a maximum faradaic efficiency (FE) of 69%. The electrocatalysts were stable under 24 h of continuous CO2RR operation. The FE increased with the increasing electrolyte concentration and cation radius size, which indicates that the anion stabilization in solution is critical for adequate formate generation. The CO2RR mechanism was proposed with basis on the literature. The structural carbonate of Bi2O2CO3 acts as an intermediate species in the formate production from CO2.