Enrico Nichelatti

Optically-transparent LiF film radiation imaging detectors of three different thicknesses, grown by thermal evaporation on Si(100) substrates and irradiated with monochromatic 7 keV X-rays at several doses in the range between 13 and 4.5×10³ Gy, were investigated by fluorescence microscopy to evaluate their visible photoluminescence response of X-ray induced colour centres and their spatial resolution. By edge-enhancement imaging experiments, performed by irradiating LiF film detectors with an Au mesh in front of them, a spatial resolution of ∼0.3 μm was estimated. This high spatial resolution, combined with the large field of view and the wide dynamic range offered by LiF detectors, encourages their use in X-ray imaging and for high-energy density experiments in synchrotron facilities.

In certain experimental setups used for proton irradiations at the TOP-IMPLART linear accelerator at the ENEA Frascati Center, the energy spectrum of the proton beam is measured at the end of a propagation path, which includes transmission through different materials, such as air, windows, slabs, etc. In this paper, we develop and test an approximate mathematical method to calculate the energy spectrum at the accelerator exit from such a measured transmitted spectrum. In the first experimental test application, the spectrum measurement exploits the visible photoluminescence of F2 and F3+ color centers generated in lithium fluoride crystals by the interaction of the crystal lattice with protons. In the second test application, a simulated measurement of a propagated energy spectrum along a transport line is considered. In principle, the proposed method is applicable to the energy spectra of proton beams measured in any manner.

Stimuli-responsive microgels have attracted great interest in recent years as building blocks for fabricating smart surfaces with many technological applications. In particular, PNIPAM microgels are promising candidates for creating thermo-responsive scaffolds to control cell growth and detachment via temperature stimuli. In this framework, understanding the influence of the solid substrate is critical for tailoring microgel coatings to specific applications. The surface modification of the substrate is a winning strategy used to manage microgel–substrate interactions. To control the spreading of microgel particles on a solid surface, glass substrates are coated with a PEI or an APTES layer to improve surface hydrophobicity and add positive charges on the interface. A systematic investigation of PNIPAM microgels spin-coated through a double-step deposition protocol on pristine glass and on functionalised glasses was performed by combining wettability measurements and Atomic Force Microscopy. The greater flattening of microgel particles on less hydrophilic substrates can be explained as a consequence of the reduced shielding of the water–substrate interactions that favors electrostatic interactions between microgels and the substrate. This approach allows the yielding of effective control on microgel coatings that will help to unlock new possibilities for their application in biomedical devices, sensors, or responsive surfaces.