Green emitting long afterglow phosphor SrAl₂O₄: Eu²⁺, Dy³⁺ was synthesized via the combustion method. The physical phase analysis was carried out by X-ray diffraction, the results show that the introduction of Eu²⁺ into the lattice of the matrix resulted in a broad green emission centered at 508 nm, which is ascribed to the characteristic 4f⁶5d¹ to 4f⁷ electronic dipole allowed transition of Eu²⁺ ions. The doping of Eu²⁺ and Dy³⁺ did not change the physical phase of the crystals. Dy³⁺, as a coactivator, does not emit light itself, but can generate holes to form a trap energy level, which acts as an electron trap center to capture some of the electrons generated by the excitation of Eu²⁺. After excitation has ceased, let them gradually to transfer to the ground state for long afterglow luminescence. Then, we investigate the optical characterizations of different samples excited by X-ray. We found that SrAl₂O₄: Eu²⁺, 0.5% Dy³⁺ has this higher luminous intensity and afterglow. Its fluorescence lifetime is about 720 ns, and its quantum yield can reach 15.18%. Through search engine marketing (SEM) and energy dispersive X-ray spectroscopy (EDX), it has been proved that the sample has been successfully synthesized and its component content has been confirmed. The Eg value calculated from the diffuse reflectance spectrum is 4.61eV. The prepared SrAl₂O₄: Eu²⁺, Dy³⁺ luminescent powder is combined with Polydimethylsiloxane substrate for anticounterfeiting application, which provides a novel idea and method for the development of the anticounterfeiting field.

A series of long-afterglow luminescent materials (SrAl₂O₄: Eu²⁺ (SAOE), SrAl₂O₄: Eu²⁺, Dy³⁺ (SAOED) and SrAl₂O₄: Eu²⁺, Dy³⁺, Gd³⁺ (SAOEDG)) was synthesized via the combustion method. Temperature and concentration control experiments were conducted on these materials to determine the optimal reaction temperature and ion doping concentration for each sample. The crystal structure and luminescent properties were analyzed via X-ray diffraction (XRD), photoluminescence (PL), and afterglow attenuation curves. The outcomes demonstrate that the kind of crystal structure and the location of the emission peak were unaffected by the addition of ions. The addition of Eu²⁺ to the matrix’s lattice caused a broad green emission with a central wavelength of 508 nm, which was attributed to the characteristic 4f⁶5d¹ to 4f⁷ electronic dipole, which allowed the transition of Eu²⁺ ions. While acting as sensitizers, Dy³⁺ and Gd³⁺ could produce holes to create a trap energy level, which served as an electron trap center to catch some of the electrons produced by the excitation of Eu²⁺ but did not itself emit light. After excitation ceased, this allowed them to gently transition to the ground state to produce long-afterglow luminescence. It was observed that with the addition of sensitizer ions, the luminous intensity of the sample increased, and the afterglow duration lengthened. The elemental structure and valence states of the doped ions were determined with an X-ray photoelectron spectrometer (XPS). Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) were used to characterize the samples. The results show that the sample was synthesized successfully, and the type and content of ions in the fluorescent powder could be determined. The fluorescence lifetime, quantum yield, bandgap value, afterglow decay time, and coordinate position in the coherent infrared energy (CIE) diagram of the three best sample groups were then analyzed and compared. Combining the prepared phosphor with ink provides a new idea and method for the field of anti-counterfeiting through screen printing.

This manuscript describes the synthesis of green long afterglow nanophosphors SrAl₂O₄:Eu²⁺, Nd³⁺ using the combustion process. The study encompassed the photoluminescence behavior, elemental composition, chemical valence, morphology, and phase purity of SrAl₂O₄:Eu²⁺, Nd³⁺ nanoparticles. The results demonstrate that after introducing Eu²⁺ into the matrix lattice, it exhibits an emission band centered at 508 nm when excited by 365 nm ultraviolet light, which is induced by the 4f⁶5d¹→4f⁷ transition of Eu²⁺ ions. The optimal doping concentrations of Eu²⁺ and Nd³⁺ were determined to be 2% and 1%, respectively. Based on X-ray diffraction (XRD) analysis, we have found that the physical phase was not altered by the doping of Eu²⁺ and Nd³⁺. Then, we analyzed and compared the quantum yield, fluorescence lifetime, and afterglow decay time of the samples; the co-doped ion Nd³⁺ itself does not emit light, but it can serve as an electron trap center to collect a portion of the electrons produced by the excitation of Eu²⁺, which gradually returns to the ground state after the excitation stops, generating an afterglow luminescence of about 15 s. The quantum yields of SrAl₂O₄:Eu²⁺ and SrAl₂O₄:Eu²⁺, Nd³⁺ phosphors were 41.59% and 10.10% and the fluorescence lifetimes were 404 ns and 76 ns, respectively. In addition, the E_g value of 4.98 eV was determined based on the diffuse reflectance spectra of the material, which closely matches the calculated bandgap value of SrAl₂O₄. The material can be combined with polyacrylic acid to create optical anti-counterfeiting ink, and the butterfly and ladybug patterns were effectively printed through screen printing; this demonstrates the potential use of phosphor in the realm of anti-counterfeiting printing.

Herein, a series of novel long afterglow nanophosphors BaYAl₃O₇:Eu²⁺, Nd³⁺ was synthesized by the combustion method. The investigation encompassed the characterization of X-ray diffraction, morphology, chemical valence, elemental composition, and photoluminescence behavior of BaYAl₃O₇:Eu²+ and BaYAl₃O₇:Eu²⁺, Nd³⁺ nanoparticles. Under 365 nm excitation, BaYAl₃O₇:Eu²⁺ and BaYAl₃O₇:Eu²⁺, Nd³⁺ show emission bands centered at 497 nm and 492 nm, which are attributed to the 4f⁶5d→4f⁷ transition of Eu²⁺ ions. The optimal samples of BaYAl₃O₇:0.03Eu²⁺ and BaYAl₃O₇:0.03Eu²⁺, 0.02Nd³⁺ have average fluorescence lifetimes of 850 ns and 1149 ns, respectively. The co-doping of Nd³+ ions as the trap centers produced long afterglow luminescence properties, and the afterglow time could reach up to 8 min. Furthermore, the fluorescent powder can be mixed with polyacrylic acid to prepare anti-counterfeiting inks; a clover pattern and snowflake pattern have been successfully printed using screen printing technology, proving its potential application in the field of anti-counterfeiting.

In recent years, the incidence of bone defects has been increasing year by year. Bone transplantation has become the most needed surgery after a blood transfusion and shows a rising trend. Three-dimensional-printed implants can be arbitrarily shaped according to the defects of tissues and organs to achieve perfect morphological repair, opening a new way for non-traumatic repair and functional reconstruction. In this paper, strontium-doped mineralized collagen was first prepared by an in vitro biomimetic mineralization method and then polylactic acid was homogeneously blended with the mineralized collagen to produce a comprehensive bone repair scaffold by a gas extrusion 3D printing method. Characterization through scanning electron microscopy, X-ray diffraction, and mechanical testing revealed that the strontium-functionalized composite scaffold exhibits an inorganic composition and nanostructure akin to those of human bone tissue. The scaffold possesses uniformly distributed and interconnected pores, with a compressive strength reaching 21.04 MPa. The strontium doping in the mineralized collagen improved the biocompatibility of the scaffold and inhibited the differentiation of osteoclasts to promote bone regeneration. This innovative composite scaffold holds significant promise in the field of bone tissue engineering, providing a forward-thinking solution for prospective bone injury repair.

Solution combustion-synthesized BaAl₂O₄: Eu²⁺, Nd³⁺, and Pr³⁺ blue–green long-afterglow phosphors are prepared and systematically investigated. First, XRD confirms the BaAl₂O₄ host and screens for trace residual features. SEM reveals the agglomerated granular morphology typical of combustion products. XPS verifies the valence states (Eu²⁺, Nd³⁺, Pr³⁺) and the chemical environment of the host lattice. UV-Vis diffuse reflectance spectra, transformed via the Kubelka–Munk function and analyzed using Tauc plots (indirect-allowed), indicate a wide band gap of the BaAl₂O₄ host with small, systematic shifts upon Nd³⁺/Pr³⁺ co-doping. PL measurements show Eu²⁺ 4f–5d emission and co-dopant-assisted excitation/defect pathways without altering the Eu²⁺ emission band shape. Afterglow lifetime and decay analyses correlate trap depth/distribution with the extended persistence. Finally, we demonstrate anti-counterfeiting by (i) snowflake printing and (ii) a binary 3 × 3 grid printed with two afterglow inks of different lifetimes to realize multi-level authentication. The sequential evidence links structure, chemistry, optical absorption, carrier trapping, and practical readout, providing a coherent basis for performance enhancement and application.