EXECUTIVE SUMMARY OF ACTIVITIES CARRIED OUT DURING THE IMPLEMENTATION PERIOD
In the first stage of the PhotoActComp project (year 2025), the planned activities were fully accomplished, aiming at the scientific and technological foundation necessary for the development of hybrid photocatalytic materials based on photosensitized ZnO nanoparticles and hydrogel matrices.
· Stage 1/2025 included three main directions: synthesis and characterization of ZnO–xanthene photocatalysts (O1), development and investigation of photocatalytic composites in Xn–PVA hydrogels (O2) and training, dissemination and publication activities (O4). All objectives were fully achieved (100%).
· To achieve objective O1, the extensive synthesis and optimization of ZnO nanoparticles was carried out by varying the precursors (Zn(Ac)₂, ZnSO₄, Zn(NO₃)₂), precipitating agents (NaOH, NH₄OH, PEI), OH⁻/Zn²⁺ ratio, reagent introduction method, stirring speed and heat treatment. The 13 samples obtained allowed the identification of optimal conditions for particles with small dimensions, good dispersion and high crystallinity. FTIR, SEM, STEM, TEM, XRD, DLS and Zeta potential characterizations confirmed the determining influence of the precursor and nucleation processes on morphology, colloidal stability and crystalline purity.
· Next, the nanoparticles were photosensitized with rose bengal (RB) by two strategies – physical adsorption and chemical modification. Four series of hybrid materials (Z2–RB, Z3–RB, Z3–RB/2, Z4–NH₂–RB) were obtained, which facilitated the evaluation of the effect of the immobilization method on the photocatalytic stability and efficiency. Kinetic and dose studies showed a rapid adsorption of RB, reaching equilibrium in 30–60 min, and nanoparticles derived from the sulfate precursor showed the highest capacity. Chemical functionalization led to good dye binding, confirmed by FTIR and by the decrease in XRD diffraction intensities, without modifying the crystalline structure of ZnO.
· UV-Vis and fluorescence characterization revealed specific optical properties of nanometric ZnO, with Eg values between 3.29–3.52 eV and emissions characteristic of lattice defects, relevant for photocatalytic applications. Calcination reduced the band gap and enhanced the visible emission, improving electron transfer in photoinduced processes.
· Within the O2 objective, xanthan and PVA-based hydrogels were prepared by chemical crosslinking and cryogelation, followed by the incorporation of unmodified ZnO or RB-modified ZnO materials. SEM analysis confirmed the homogeneous integration of nanoparticles into the hydrogel networks, and swelling studies highlighted the structural stability of the composites.
· Activities related to O4 included the elaboration of a bibliographic study, the development of the project website, the preparation and submission of an article to Q1/Q2 journals, and participation in scientific conferences. Team members also participated in training activities specific to the field.
· Stage 1/2025 was successfully completed, providing the scientific and experimental basis necessary for the following stages, dedicated to the optimization of photocatalytic composites and the validation of their performances in depollution processes.
· Dissemination of results: 2 published papers, 3 participations in international conferences (1 oral communication and 2 posters). | 
