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While numerous approaches have been devised to optimize the luminescence properties of Eu2+-activated phosphors, the quest for a simple design strategy to achieve color-tunable Eu2+ emission remains a significant challenge. Here, we present a straightforward, doping-free method to tailor the site occupation of Eu2+ and modify its luminescence properties. In the pristine sample, the NaBaB9O15 (NBB) host featuring two cation sites (Na+ and Ba2+), Eu2+ exclusively occupies the Ba2+ site, resulting in blue emission when the NBB:Eu2+ phosphor is synthesized in a H2 reducing atmosphere. When we use CO instead of a H2 reducing atmosphere, impressively, the formation energy required for heterovalent substitution of Na+ by Eu2+ is lowered, leading to the emergence of a distinct green emission band. Significantly, the resultant phosphor NBB:Eu2+@CO exhibits not only a high internal quantum yield of 85.1% and zero-thermal-quenching behavior within the temperature range of 25–200 °C but also wavelength-tunable emission. Benefitting from the multi-color luminescence of the NBB:Eu2+@CO phosphor, its optical applications will no longer be confined to general lighting but extend to anti-counterfeiting and encryption. This study provides a novel design methodology for optimizing the optical properties of Eu2+-activated phosphors. [ABSTRACT FROM AUTHOR]

Near-infrared (NIR) phosphors with high thermal stability are significant for NIR light-emitting diodes (LEDs). For a decade, Debye temperature has been a successful indicator of structural rigidity and thermal stability for phosphors, but some exceptions exist due to its dependence on atomic mass. Inspired by the Debye temperature model that relates the elastic properties of solids, our density functional theory calculations revealed that the Vickers hardness of Cr3+-doped NIR phosphors was negatively correlated with Stokes shifts (Pearson's R = −0.81) and positively correlated with thermal stabilities (Pearson's R = 0.85) within a set of 13 distinct material types. Highlighting the predictive power of Vickers hardness, two new NIR phosphors were investigated: KMg(PO3)3:Cr3+ showed low thermal stability, correlating with its lower Vickers hardness, in contrast to the high thermal stability and correspondingly higher Vickers hardness of La2MgSnO6:Cr3+. Vickers hardness can be used to screen potential hosts for Cr3+-doped NIR phosphors with high thermal stabilities, due to the advantages of the predictable feature by density functional theory calculation and low independence on atomic mass. [ABSTRACT FROM AUTHOR]

To develop novel luminescent materials for optical temperature measurement, a series of Yb3+- and Er3+-doped Ca3Sc2Si3O12 (CSS) upconversion (UC) phosphors were synthesized by the sol–gel combustion method. The crystal structure, phase purity, and element distribution of the samples were characterized by powder X-ray diffraction and a transmission electron microscope (TEM). The detailed study of the photoluminescence emission spectra of the samples shows that the addition of Yb3+ can greatly enhance the emission of Er3+ by effective energy transfer. The prepared Yb3+ and Er3+ co-doped CSS phosphors exhibit green emission bands near 522 and 555 nm and red emission bands near 658 nm, which correspond to the 2H11/2→4I15/2, 4S3/2→4I15/2, and 4F9/2→4I15/2 transitions of Er3+, respectively. The temperature-dependent behavior of the CSS:0.2Yb3+,0.02Er3+ sample was carefully studied by the fluorescence intensity ratio (FIR) technique. The results indicate the excellent sensitivity of the sample, with a maximum absolute sensitivity of 0.67% K−1 at 500 K and a relative sensitivity of 1.34% K−1 at 300 K. We demonstrate here that the temperature measurement performance of FIR technology using the CSS:Yb3+,Er3+ phosphor is not inferior to that of infrared thermal imaging thermometers. Therefore, CSS:Yb3+,Er3+ phosphors have great potential applications in the field of optical thermometry. [ABSTRACT FROM AUTHOR]

Artificial light fishing technology has been used in marine fisheries for thousands of years. The light source with multi‐color adjustable output is expected to become a new generation of fish‐attracting lamps. Herein, a new method of crystal‐site engineering through reducing atmospheres is proposed for the development of Eu2+ doped single‐phase phosphor with multi‐excitation and multi‐emission properties. Following this approach, the distribution ratio of Eu2+ at Ca2+ and Sr2+ sites in CaSrSiO4 (CSO) can be modulated. Importantly, Eu2+ at both lattice sites exhibit non‐interfering optical properties, CSO:Eu2+ phosphor realizes multi‐color output from green to yellow and then to red when Eu2+ occupies the Sr2+ and Ca2+ sites in a relatively balanced ratio. Benefitting from the tunable color range covering the spectral sensitivity regions of most marine fishes, this phosphor may eventually be applied in futuristic innovative fish‐attracting lamps. [ABSTRACT FROM AUTHOR]

A Sm3+-doped YGa1.5Al1.5(BO3)4 (abbreviated as YGAB) phosphor was synthesized via a solid-state reaction with mechanical activation assistance in a high-energy density stirred bead mill. The samples were characterized by laser particle size analysis, specific surface area analysis, powder X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and fluorescence spectroscopy. In addition, the photoluminescence characteristics, luminescence decay, thermal stability, and LED application of the phosphors were also investigated. The results show that the mechanical activation of mixed raw materials before calcination can reduce the particle size and the activation energy of crystallization, resulting in the formation of the YGAB crystal phase at a lower calcination temperature. The mechanical activation in grinding can accelerate the subsequent solid-phase reaction, make Sm3+ ions more easily diffuse into the YGAB lattice, and improve the crystal structure of the synthesized phosphor, thus enhancing the optical properties of the phosphor. According to the photoluminescence emission (PL) and excitation (PLE) spectra, Sm3+ doped in the YGAB lattice can provide an efficient emission under 405 nm excitation. The optimum doping concentration of Sm3+ ions is 0.03 mol%. The optimum photoluminescence intensity, quantum yield, and fluorescence lifetime of the phosphor synthesized from mixed raw materials ground for 45 min can be obtained. The temperature-dependent PL spectra show that the emission intensity of the YGAB:0.03Sm3+ phosphor at 425 K is 84.7% of its initial intensity at room temperature. It is indicated that the YGAB:0.03Sm3+ phosphor synthesized could be used as one of the promising LED lighting materials. [ABSTRACT FROM AUTHOR]

Au nanoparticles (NPs) attached to various TiO2 supports are widely studied as plasmonic catalysts for driving chemical reactions under visible light irradiation. However, plasmonic catalysis still suffers from unsatisfactory efficiencies due to limited light-harvesting abilities. Here we reported a new tactic to enhance the light-harvesting ability of plasmonic Au NPs by utilizing a light reflection-promoted model – a vertically <001> oriented anatase mesocrystal (meso-TiO2) rooted on Ti foil as the support, and thus achieving efficient photocatalytic sulfur-containing volatile organic compound elimination and hydrogen evolution from water. Experimental evidence and theoretical simulations confirm that the Au NPs in this architecture more effectively harvest visible light because of the simultaneous absorption of both the incident and the back-reflected photons from the meso-TiO2/Ti foil surface, where Ti foil serves as the reflective substrate. The enhanced light absorption of Au NPs in this light reflection-promoted model excited strong localized surface plasmon resonance to yield more reactive species that drive the redox reactions. This research could inspire a new paradigm to improve the photocatalytic performance of plasmonic metals by utilizing the light reflection model. [ABSTRACT FROM AUTHOR]

Red-light-emitting materials, as pivotal components of warm white light-emitting diodes (WLEDs), have drawn increasing public focus. Among these, Mn4+-doped red light-emitting fluorides have drawn considerable attention when combined with an InGaN chip; however, they suffer from poor water stability under humid conditions. In this work, a novel fluoride red phosphor, Cs30(Nb2O2F9)9(OH)3·H2O:xMn4+ (CNOFM), with good water resistance was synthesized for the first time using a facile co-precipitation method at ambient temperature. Experiments were implemented for the precise analysis of its crystal structure, optical properties, micro-morphology, thermal behavior, and waterproof properties. 6.66% Mn4+-doped CNOFM maintained a stable crystal structure and possessed strong PL intensity located at 633 nm with high color purity of 96%. CNOFM showed better thermal and waterproof stability compared with the commercial K2SiF6:Mn4+ red phosphor. Without any surface modifications, the PL intensity remained at about 83% of the initial value after immersion in water for 60 min, and the mechanism was investigated. Finally, a warm WLED with a CRI of 92.3 and CCT of 3271 K was fabricated using the CNOFM red phosphor. [ABSTRACT FROM AUTHOR]