Modulating trap properties by Nd3+- Eu3+ co-doping in Sr2SnO4 host for optical information storage.

We report a novel Nd3+ and Eu3+ co-doped Sr2SnO4 (SSONE) phosphor showing the capability of "write-in" and "read-out" in optical information storage. As-prepared phosphors exhibit a dominant emission (PL) band centered at 596 nm under UV excitation, closely identical with its photo-stimulated luminescence (PSL) spectrum center (595 nm) upon near-infrared (NIR) light and thermal-stimulated luminescence (TSL) spectrum center (595 nm) under heat source. Remarkably, compared with Eu3+ single-doped phosphors, the co-doping strategy enhances the deep traps and also separates the deep traps with shallow traps, which are very crucial factors for optical information storage in electron trapping materials. Further, a demonstration confirmed the optical information storage capacity by photo- and thermal-stimulating the prepared phosphors filled in the designed patterns.

Crystal Field Engineering of Pr-Activated Gehlenite with Near Golden Ultraviolet C Emission for 100% Sterilization Efficiency.

Ultraviolet C (UVC) sterilization has the advantages of high efficiency, broad spectrum, and no secondary pollution. However, the emission wavelength of UVC phosphors still suffers from a large deviation from the golden sterilization wavelength of 265 nm and a low luminescence intensity. Herein, we report UVC emission near the golden sterilization wavelength as well as a long afterglow through crystal field engineering, which can lead to 100% sterilization efficiency. Combined with theoretical calculation and experimental studies, substitution of Ca2+ with large-sized Sr2+ could obtain slight expansion and distortion of cationic sites, resulting in a decrease in crystal field intensity and blue shift of Ca1.5Sr0.5Al2SiO7:1%Pr3+, and produce near golden UVC emission. Ca1.5Sr0.5Al2SiO7:1%Pr3+ phosphor can effectively inactivate Staphylococcus aureus within 10 min, showing more efficiency than the traditional mercury lamp. This work provides an effective solution for the design and preparation of UVC phosphors using crystal field engineering toward near golden UVC emission.

Bismuth Vacancy-Induced Enhancement of Luminescence Intensity and Irradiation Resistance for Bi4Ge3O12.

Bi4Ge3O12 (BGO) is a traditional scintillator, widely used in high-energy physics and nuclear medicine. However, it not only suffers from low scintillation intensity but also tends to be damaged by high-energy rays. Herein, we prepare pure-phase BGO materials enriched with Bi vacancies by rationally reduced Bi content, showing significantly enhanced luminescence intensity and irradiation resistance ability. The optimized Bi3.6Ge3O12 shows 178% of luminescence intensity compared to BGO. After 50 h of ultraviolet irradiation, Bi3.6Ge3O12 possesses ∼80% of original luminescence intensity, much superior to the 60% for BGO. The existence of the Bi vacancy is identified by advanced experimental and theoretical studies. The mechanism studies show the Bi vacancies could cause the symmetry destruction of the local field around the Bi3+ ion. It enhances scintillation luminescence by increasing the probability of radiative transition while resisting nonradiative relaxation caused by irradiation damage. This study initiates vacancy-induced performance enhancement for inorganic scintillators.

Dual-ion substituted (MeY)3(AlSi)5O12:Eu garnet phosphors: combinatorial screening, reductive annealing, and luminescence property.

In recent years, the efficiency of combinatorial methods has been utilized to accelerate the finding or screening of inorganic materials. In this work, based on the double substitution strategy of the cation ions Me2+/Si4+, a series of Me y Y3-y Al5-y Si y O12:Eu x garnet phosphors (MeYASG:Eu, Me = Mg, Ca, Sr, Ba) were rapidly prepared and screened by a combinatorial method in microreactor arrays. Through parallel experiments of solid-state synthesis, the reliability of the combinatorial screening was verified and an optimal composition of CaY2Al4SiO12:Eu0.03 (CYASG:Eu) with advanced luminous intensity was obtained. Annealing experiments under air and reductive atmospheres were performed and demonstrated the controllability and reversibility of the Eu3+ ↔ Eu2+ valence transition process, thus realizing the tuning of the dominant emission from divalent Eu2+ or trivalent Eu3+. The optimal CYASG:Eu sample showed excellent thermal quenching resistance after annealing at 800 °C for 1 h in a reducing atmosphere. The abnormal intensity of PL increased by 10% in the 50-100 °C region, and retained 63% of the initial value at 250 °C. With the assistance of thermoluminescence characterization, the complementary effect of the release of captured electrons or charge carriers in trap levels on the abnormal increase of PL intensity during the high-temperature luminescence process was revealed. By combination of the double substitution strategy of cations and annealing, a new approach is proposed to creating the coexistence of activator Eu ions with a mixed-valence state. Also, the prepared CYASG:Eu phosphors have promising applications in fields such as plant light supplements in greenhouses and plant factories and as luminescent materials for energy-saving light sources.

Multi-channel fiber optical spectrometer for high-throughput characterization of photoluminescence properties.

High-throughput experiment can significantly accelerate the materials research efficiency. Thanks to national efforts, the Materials Genome Initiative further promotes the development of high-throughput experimental technology. A multi-channel fiber optical spectrometer has been designed and developed by us for high-throughput characterization of photoluminescence (PL) properties. It can quickly and automatically detect the PL spectrum, Commission International de l'Eclairage chromaticity, and PL intensity over time for luminescent materials under a given condition. The multi-channel fiber optical spectrometer synergistically combines a sample library holder, multiple modular excitation sources, multiple spectrometers, and Coral software, so it can measure and analyze multiple samples simultaneously. The number of channels in the multi-channel fiber optical spectrometer can be added or subtracted as required. Various modular light-emitting diode or laser diode excitation sources with the wavelength from 370 nm to 980 nm and corresponding filters can be provided according to the measurement need of different luminescent materials. The monitoring wavelength of the currently used fiber optical spectrometer is from 300 nm to 1000 nm. For example, the PL spectral measurement of 54 samples in a {6 × 9} array is completed in only about 30 min by using a representative triple-channel fiber optical spectrometer. The designed multi-channel fiber optical spectrometer facility not only makes PL measurements faster and more intuitive but is also easy to popularize for wide users.