Facile Formation of Sulfurized Nanorod-Like ZnO/Zn(OH)2 and Hierarchical Flower-Like γ-Zn(OH)2 /ϵ-Zn(OH)2 from a Green Synthesis and Application as Luminescent Solar Concentrator.

This research endeavors to overcome the significant challenge of developing materials that simultaneously possess photostability and photosensitivity to UV-visible irradiation. Sulfurized nanorod (NR)-like ZnO/Zn(OH)2 and hierarchical flower-like γ-Zn(OH)2 /ϵ-Zn(OH)2 were identified from XRD diffraction patterns and Raman vibrational modes. The sulfurized material, observed by FEG-SEM and TEM, showed diameters ranging from 10 and 40 nm and lengths exceeding 200 nm. The S2- ions intercalated Zn2+ , modulating NRs to dumbbell-like microrods. SAED and HRTEM illustrated the atomic structure in (101) crystal plane. Its direct band gap of 3.0 eV was attributed to the oxygen vacancies, which also contribute to the deep-level emissions at 422 and 485 nm. BET indicated specific surface area of 4.4 m2 g-1 and pore size as mesoporosity, which are higher compared to the non-sulfurized analogue. These findings were consistent with the observed photocurrent, photostability and photoluminescence (PL), further supporting the suitability of sulfurized NR-like ZnO/Zn(OH)2 as a promising candidate for Luminescent solar concentrators (LSC)-photovoltaic (PV) system.

Facile Ionic Liquid-Assisted Strategy for Direct Precipitation of Eu2+ -Activated Nanophosphors under Ambient Conditions.

This work describes a novel ionic liquid (IL)-assisted synthesis strategy for a direct and easy production of Eu2+ -doped nanoparticles (NPs), where ILs are also used as fluoride sources to avoid the use of elemental fluorine or toxic hydrofluoric acid. Up to now, the direct synthesis of Eu2+ -doped nanophosphors consisted of an enormous challenge, due to the oxidation to Eu3+ observed in hydrous solution, which is commonly used for the preparation of NPs, generating lattice defects and undesired particle growth or agglomeration by additional reducing steps at high temperatures. In contrast, ILs, unless containing ClO4- or NO3- anions, do not present an oxidizing character, allowing the direct precipitation of NPs, e.g., using Eu2+ containing starting materials. Here, the undoped and Eu2+ -doped BaFCl NPs have been prepared under atmospheric conditions for the first time using ILs as solvents and also as fluoride source, applying sonochemical and microwave-assisted approaches. In general, this method bears an enormous potential for an easy synthesis of fluoride materials compared to inconvenient solid-state methods. In addition, the IL plays the role of a strongly attached protecting shell which represents ≈7-8% of the total NPs weight.