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Upconversion (UC) luminescence modulation is quite important in controlling and processing light for active components of light sources, photoswitches, optical memories, and optical sensing devices. In this work, we reported one kind of novel phosphor, Ho3+/Yb3+‐doped SrBi4Ti4O15 ceramics, which displayed both strong UC luminescence and obvious photochromic (PC) reaction. The UC luminescence, PC effect, and the modulation of UC performance based on PC behavior were investigated in detail. By alternating visible light irradiation and thermal stimulus, the UC luminescence could be reversibly regulated. Meanwhile, the modulation was unveiled to tightly rely on the irradiation time and thermal treatment processes. Excellent reproducibility was also achieved. In addition, as an alternative method to thermal treatment, the manipulation of luminescence by electric field was also explored. Finally, the mechanism related to the UC luminescence manipulation was illustrated. The results indicate that these samples could be potentially utilized in optical data storage and anti‐counterfeiting security fields. [ABSTRACT FROM AUTHOR]

• A class of smart SrBi 8 Ti 7 O 27 based phosphor was developed. • UC reversible regulation was achieved accompanying with photochromic process. • Polarization treatment was an effective way to improve UC modulation performance. • SrBi 8 Ti 7 O 27 based phosphor has promising application in optical switching field. The various applications of luminescence materials were generally based on the effective modulation of luminescence spectra. However, the research on reversible spectral regulation of up-conversion (UC) luminescence materials was still in its infancy stage. In this work, a class of smart phosphor, Er3+ and Yb3+-codoped SrBi 8 Ti 7 O 27 (SBYT: xEr3+) intergrowth bismuth layer-structured ferroelectric, possessing fast sensitivity to visible light irradiation, was reported based on visible light driven photochromic effect. Through the alternate stimuli of light irradiation and heating treatment, the reversible regulation of UC luminescence was achieved accompanying with the switching of coloration and decoloration processes. The luminescence modulation degree tightly relied on the irradiation time and thermal treatment modes. The reversibility and stability properties were also revealed. Moreover, it is found that polarization treatment was an effective approach which can be adopted to improve the UC luminescence contrast. The maximum luminescence modulation ability of SBYT: xEr3+ reached up to 81.3% which was 131% of that un-polarized sample. It is believed that SBYT: xEr3+ ceramics can act as a promising candidate for optical data storage and anti-counterfeiting applications. [ABSTRACT FROM AUTHOR]

Up-conversion nanoparticles (UCNPs) stimulated by near-infrared (NIR) light have received immense interest for their potential applications in many fields. In this work, Nd3+- and Yb3+-sensitized Bi 4 Ti 3 O 12 (BiT x :Nd3+/Yb3+, 0.005 ≤ x ≤ 0.3) UCNPs with thermometric and photo-thermal (PT) functions were successfully synthesized by a convenient co-precipitation approach, and the phase and morphologies were characterized. Under 980 nm excitation, BiT x :Nd3+/Yb3+ UCNPs exhibited remarkable multiple emissions in the region from 450 to 900 nm. The visible and NIR emissions were tightly dependent on the Nd3+ concentration and the strongest NIR emissions were obtained in sample BiT0.3:Nd3+/Yb3+. The possible UC mechanisms and processes were proposed. Furthermore, the capability of the UCNPs as thermometers was probed based on the thermo-responsive fluorescence intensity ratio technique in the temperature range 303–573 K. The maximum sensitivity (S max) of BiT0.3:Nd3+/Yb3+ was determined to be as high as 0.032 K-1. Meanwhile, PT effect was evaluated by monitoring the variation of surface temperature of the sample as functions of irradiation time and power density. Conspicuous PT effect was confirmed and the maximum temperature induced by laser was about 91 °C. These results reveal that BiT0.3:Nd3+/Yb3+ UCNPs has promising potential applications as optical thermometer and heater. • BiTx:Nd3+/Yb3+ UCNPs were synthesized by a facile co-precipitation method. • UC properties were investigated and the corresponding mechanism was discussed. • Relying on FIR technique, thermometric properties were studied. • Sensor sensitivity as high as 0.032 K−1 was achieved. • Prominent PT effect was obtained and the induced temperature was about 91 °C. [ABSTRACT FROM AUTHOR]

The manipulation of luminescence properties of upconversion (UC) materials from micro to macro aspects is of vital importance for disclosing new physical phenomena and expanding the range of applications. In this work, a novel class of SrBi 2 Nb 2 O 9 (SBN)-based inorganic photochromic (PC) phosphors was synthesized, which exhibited intense susceptibility to visible light irradiation. Large reversible UC modulation ability upon PC effect was realized. Besides, the regulation of UC luminescence was discovered to strongly rely on the irradiation time and heating processes. The mechanisms connected to the UC luminescence, PC effect, and UC manipulation were illustrated. These results demonstrated that SBN-based samples owing high reversible manipulation ratio, fast response, low heating temperature, and excellent reproducibility can be employed as a type of ideal optical medium for future information storage device. In addition, based on the reversible behavior of photochromism, the application of the SBN-based ceramic as an anti-counterfeiting agent was also depicted. [ABSTRACT FROM AUTHOR]

The upconversion (UC) luminescence tuning of phosphors has attracted increasing interest as optical switches, optical sensing, and high-density optical data storage devices. However, the design and synthesis of photo-switchable inorganic luminescent materials were still at primary stage. In this work, a new type of UC luminescence regulation materials, Er3+-activated tetragonal tungsten bronze Ba 0.7 Sr 0.3 Nb 2 O 6 ferroelectrics, showing strong susceptibility to visible light irradiation, was reported based on non-photochromic (N-PC) effect. Under visible light irradiation, the maximum luminescent modulation ability reached up to 79.4%. The tuning of UC luminescence was disclosed to tightly rely on the irradiation time and thermal treatment processes. Meanwhile, excellent reproducibility was also demonstrated. Besides, the luminescent readout almost had no any influence on the UC emission, indicating the extremely low destruction to the stored luminescent states. The mechanisms related to the UC luminescence and manipulation were also discussed. In contrast to the previous tuning way based on PC reaction, it is believed that this work shed new light for the understanding of UC modulation fundamentals. Graphical abstract of our paper "A new class of upconversion luminescence tuning materials based on non-photochromic reaction: Er-activated Ba 0.7 Sr 0.3 Nb 2 O 6 ferroelectrics" is as follow. UC spectra and photographs of BSN: xEr3+ (x=0.2) sample before and after LD irradiation. Image, graphical abstract [ABSTRACT FROM AUTHOR]