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In situ small angle X-ray scattering (SAXS) measurements of ion track etching in polycarbonate foils are used to directly monitor the selective dissolution of ion tracks with high precision, including the early stages of etching. Detailed information about the track etching kinetics and size, shape, and size distribution of an ensemble of nanopores is obtained. Time resolved measurements as a function of temperature and etchant concentration show that the pore radius increases almost linearly with time for all conditions and the etching process can be described by an Arrhenius law. The radial etching shows a power law dependency on the etchant concentration. An increase in the etch rate with increasing temperature or concentration of the etchant reduces the penetration of the etchant into the polymer but does not affect the pore size distribution. The in situ measurements provide an estimate for the track etch rate, which is found to be approximately three orders of magnitude higher than the radial etch rate. The measurement methodology enables new experiments studying membrane fabrication and performance in liquid environments.

The development of nanomaterials with multifunctional properties presents a viable business case for potential scale-up of nanomaterial fabrication. Hence, the design and engineering of structures as well as tuning of active sites are crucial in generating multifunctional properties in nanomaterials. In this regard, we demonstrate a three-dimensional (3D) fractal structure of Au–Bi2O3 with a fractal dimension (Df) of ≈ 1.80, which is obtained from the small-angle X-ray scattering (SAXS) measurement and through the box counting algorithm. The fractal structures, fabricated via a one-step direct synthesis, gives a homogeneous distribution of catalytically active nanocrystals Au and Bi2O3 on a 3D platform with a large active surface area, resulting in a strong enhancement of its localized electric field. Therefore, when applied as a catalyst for electrochemical CO2 reduction reactions (CO2RR) and optical gas sensing, the material displays an excellent performance. Specifically, the fractal structure exhibits a high selectivity towards the formation of formate, achieving a very high faradaic efficiency of 97% and high mass-specific formate current density of −54 mA mg−1 at −1.1 V vs. a reversible hydrogen electrode (RHE). Similarly, this structure displayed a plasmonic shift as high as ∼5 nm for 4 vol% acetone sensing with a detection limit of 100 ppm towards different volatile organic compounds (VOCs).

Mobile applications are suitable as a structural possibility for students beginning their studies. Using the app Reflect.UP, students are encouraged to reflect on the organization, contents, and objectives of their studies. This article focuses on how students can acquire the academic ability to consider their own actions, which is an intrinsic component of academic professionalization. The work examines how a competency framework is derived through study regulations and module descriptions, and how subsequent questions for students’ reflection are systematically created using this framework. Next, the hybrid mobile application Reflect.UP and its underlying software components are introduced, stimulating students’ reflections on study content and objectives. The data gathered through the practical use of Reflect.UP is evaluated, and then the ensuing conclusions drawn from students’ problems and learning processes for organizing the course of studies are explored. In addition, this paper reflects on the strengths and weaknesses of a mobile application as a sociological and technological compound for structural support of the introductory phase of education.

Advance of photonics media is restrained by the lack of structuring techniques for the 3D fabrication of active materials with long-range periodicity. A methodology is reported for the engineering of tunable resonant photonic media with thickness exceeding the plasmonic near-field enhancement region by more than two orders of magnitude. The media architecture consists of a stochastically ordered distribution of plasmonic nanocrystals in a fractal scaffold of high-index semiconductors. This plasmonic-semiconductor fractal media supports the propagation of surface plasmons with drastically enhanced intensity over multiple length scales, overcoming the 2D limitations of established metasurface technologies. The fractal media are used for the fabrication of plasmonic optical gas sensors, achieving a limit of detection of 0.01 vol% at room temperature and sensitivity up to 1.9 nm vol%-1 , demonstrating almost a fivefold increase with respect to an optimized planar geometry. Beneficially to their implementation, the self-assembly mechanism of this fractal architecture allows fabrication of micrometer-thick media over surfaces of several square centimeters in a few seconds. The designable optical features and intrinsic scalability of these photonic fractal metamaterials provide ample opportunities for applications, bridging across transformation optics, sensing, and light harvesting.