Fluorescent materials generally show diverse light emission, simple manufacturing processes, long service life, and long-term reliability properties, and they have gradually become a hotspot in the field of anti-counterfeiting. Phosphors with multi-functions for the realization of dual-mode anti-counterfeiting designs are still subject to the tailoring difficulty, readout order restriction, detection complexity, etc. To solve these problems, we propose a new flexible dual-mode anti-counterfeiting design by using a series of phosphors MAl₁₂O₁₉:Cr³⁺ (M = Ca and Sr) based on their both deep red/NIR dual emissions and afterglow. By tailoring the concentration of dopants, a similar deep red but strong NIR intensity comparison has been realized. In the fluorescent mode, the intense NIR emission that represents the effective information can be pictured by filtering the deep red encryption light under white LED. In addition, the persistent luminescence in the afterglow mode, which has been tuned by Ti⁴⁺ co-dopants, can be pictured after UV irradiation. The dual-mode information can be designed separately and detected independently without interference or readout order restriction. Such a dual-mode system with flexibility and simplicity properties is a good choice not only for anti-counterfeiting but also for the multi-layer information encryption.

Ferroelectrics have recently attracted attention as a candidate class of materials for use in photovoltaic devices due to their abnormal photovoltaic effect. However, the current reported efficiency is still low. Hence, it is urgent to develop narrow-band gap ferroelectric materials with strong ferroelectricity by low-temperature synthesis. In this paper, the perovskite bismuth ferrite BiFeO₃ (BFO) thin films were fabricated on SnO₂: F (FTO) substrates by the sol–gel method and they were rapidly annealed at 450, 500 and 550 °C, respectively. The microstructure and the chemical state’s evolution with annealing temperature were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS), and the relationship between the microstructure and electric, optical and photovoltaic properties were studied. The XRD, SEM and Raman results show that a pure phase BFO film with good crystallinity is obtained at a low annealing temperature of 450 °C. As the annealing temperature increases, the film becomes more uniform and has an improved crystallinity. The XPS results show that the Fe³⁺/Fe²⁺ ratio increases and the ratio of oxygen vacancies/lattice oxygen decreases with increasing annealing temperature, which results in the leakage current gradually being reduced. The band gap is reduced from 2.68 to 2.51 eV due to better crystallinity. An enhanced photovoltaic effect is observed in a 550 °C annealed BFO film with a short circuit current of 4.58 mA/cm² and an open circuit voltage of 0.15 V, respectively.

Circular dichroism (CD) is required in the applications of biological detection, analytical chemistry, etc. Here, we numerically demonstrated large-range switchable CD by controlling the phase change of Ge₂Sb₂Te₅ (GST) in a zigzag array. At the amorphous state of GST (a-GST), the strong and dual-waveband CD effects are realized via the selective excitations of electric, magnetic, and toroidal resonances. With the transition from a-GST to crystalline state GST, CD strengths are tailored dynamically in large ranges. In detail, the CD magnitudes change by about 0.93 and the modulation depths exceed 94% at dual wavebands. The strong CD effects and large-range switch capability in the GST-based metasurfaces will boost the development of active chiroptical devices.

Understanding an efficient blue-emitting phosphor NaBaBO₃:Ce³⁺ for UV pumped warm white LEDs through experimental and computational methods.

A comprehensive study of a highly distorted garnet Ca ₄ HfGe ₃ O ₁₂ :Cr ³⁺ phosphor with desired and undesired properties.