Search

Near‐infrared (NIR) emitting phosphors draw much attention because they show great applicability and development prospects in many fields. Herein, a series of inverse spinel‐type structured LiGa5O8 phosphors with a high concentration of Cr3+ activators is reported with a dual emission band covering NIR‐I and II regions. Except for strong ionic exchange interactions such as Cr3+−Cr3+ and Cr3+ clusters, an intervalence charge transfer (IVCT) process between aggregated Cr ion pairs is proposed as the mechanism for the ~1210 nm NIR‐II emission. Comprehensive structural and luminescence characterization points to IVCT between two Cr3+ being induced by structural distortion and further enhanced by irradiation. Construction of the configurational energy level diagram enabled elucidation of this transition within the IVCT process. Therefore, this work provides insight into the emission mechanism within the high Cr3+ concentration system, revealing a new design strategy for NIR‐II emitting phosphors to promote its response. [ABSTRACT FROM AUTHOR]

Near‐infrared‐II (NIR‐II) phosphors are extensively used as NIR phosphor‐converted light‐emitting diodes across various applications. Nonetheless, their application in fiber communication remains underexplored. Furthermore, efficiency challenges persist in developing broadband NIR crystal fiber amplifiers. A series of the Y3−yAl5−xO12:xCr,yCa2+ phosphors with boosted Cr4+ concentration via calcium charge compensation is synthesized, and the optimized sample is fabricated to crystal fibers to reveal the application of the NIR‐II phosphors to fiber communication. The fabricated Cr4+‐doped crystal fiber, exhibiting broadband Cr4+ emission within 1100–1600 nm, effectively covers the high‐transmission loss region caused by water absorption in the telecommunication band. Comprehensive characterization and analyses of the Cr4+ are discussed. Y2.84Al4.9O12:0.1Cr,0.16Ca2+ crystal fiber, fabricated through phosphor synthesis, pellets' production, and the laser‐heated pedestal growth method, exhibits superior photoluminescence compared to the commercial Cr4+‐doped Y3Al5O12 crystal fiber. Here the potential of NIR‐II phosphors is highlighted in enhancing fiber communication and valuable insights for their future application are provided. [ABSTRACT FROM AUTHOR]

The growing production and use of plastics significantly contribute to microplastics (MPs) contamination in the environment. Humans are exposed to MPs primarily through the gastrointestinal route, as these particles are present in beverages and food, e.g., sugar. Effective isolation and identification of MPs from food is essential for their elimination. This study aimed to evaluate factors influencing the isolation of MPs from sucrose solutions to determine optimal conditions for the process. Polyethylene particles were used to test separation methods involving chemical digestion with acids and filtration through membrane filters made of nylon, mixed cellulose ester, and cellulose acetate with pore sizes of 0.8 and 10 µm. The effects of temperature and acid type and its concentration on plastic particles were examined using scanning electron microscopy and µ-Raman spectroscopy. The results indicate that increased temperature reduces solution viscosity and sucrose adherence to MPs' particles, while higher acid concentrations accelerate sucrose hydrolysis. The optimal conditions for MPs' isolation were found to be 5% HCl at 70 °C for 5 min, followed by filtration using an efficient membrane system. These conditions ensure a high recovery and fast filtration without altering MPs' surface properties, providing a reliable basis for further analysis of MPs in food. [ABSTRACT FROM AUTHOR]

The increasing demand for second near‐infrared (NIR‐II) region materials, which retain the advantage of minimal scattering and immense applications in the medical and NIR spectroscopy field, has led to considerable research in this region. A mini light‐emitting diode (mini‐LED) is essential for backlighting liquid crystal displays, indicating the need for the small size of phosphors. However, current market phosphors must be more significant to be a viable option for mini‐LEDs. This scenario necessitates the synthesis of small‐sized phosphors to be used in mini‐LEDs. In this work, a mesoporous silica nanoparticle (MSN) and incorporated the Mg1−yGa2−xO4:xCr3+,yNi2+ system is fabricated. The structural investigation confirmed the single phase of MgGa2O4 with a pore size of 2.73 nm for the MSN. The results showed a steady NIR‐II signal at 1270 nm and an enhanced energy transfer with a high quantum yield of 79.2% for a nanophosphor. The mini‐LED package revealed a 1000–1600 nm signal, qualifying the nanophosphor for realistic applications. This work can make provisions for various NIR‐II nanophosphors in the LED industry. [ABSTRACT FROM AUTHOR]

In modern technology devices, an energy‐saving miniature near‐infrared (NIR) light source plays a critical role in non‐destructive, non‐invasive sensing applications and further advancement of technology. This paper reports the broadband NIR luminescence of Cr3+ clusters for designing phosphor‐converted NIR light‐emitting diodes as an alternative to typical isolated Cr3+ centers and Cr3+ ion pairs. Here, Cr3+ clusters form in the intermediate spinel structure of MgGa2O4 by utilizing the long‐chain edge‐shared octahedral dimers with the shortest bond distance between Cr3+ cations. Electron paramagnetic and magnetometry measurements confirm the isolated Cr3+ and Cr3+ clusters, resulting in NIR luminescence with three distinct emission centers. The formation of Cr3+ clusters in MgGa2O4 ensures stable internal quantum efficiency (≈94%), full‐width‐half‐maximum (248 nm), thermal stability (87%), and a radiant flux of ≈17.66 mW. This work offers a promising approach to NIR phosphor design and enhances the understanding of luminescence mechanisms in spinel and related structures. [ABSTRACT FROM AUTHOR]

This paper analyzes the influence of pressure on electron–lattice interactions in the 5d excited states of Ce3+ and Eu2+ in the AlN host based on pressure-dependent photoluminescence and photoluminescence excitation spectra. High-pressure measurements on AlN samples doped with Eu2+ and Ce3+ ions reveal that the Stokes shift increases with pressure for Eu2+ dopants and decreases for Ce3+ dopants. Within the interstitial sites of AlN occupied by lanthanide dopants, the effect of crystal field strength on the behavior of luminescent ions can be strongly reduced. Therefore, the observed changes in optical properties under pressure can be interpreted as occurring mainly due to electron–lattice interactions. Based on the experimental data, one can conclude that the barycenter energy of Eu2+ exhibits virtually no pressure-induced shift (within the experimental error), unlike Ce3+, which shows a pressure-dependent redshift. Our findings demonstrate the significance of the specific central ion in the lattice relaxation process. [ABSTRACT FROM AUTHOR]

CuLaO2 is a rare-earth and dopant-free inorganic compound able to emit green light upon blue excitation. Its absorption amounts to 90% but its internal quantum efficiency is poor (<17%). The origin of this deleterious radiationless behavior is addressed by investigating the spectroscopic properties of this compound under the action of temperature and hydrostatic pressure in the 15–400 K and 1 bar–40 kbar intervals, and by combining the spectroscopic data with earlier results of DFT calculations. A two-step radiationless process is demonstrated, involving radiative re-absorption and cross-over to excitonic states. [ABSTRACT FROM AUTHOR]

In the biomedical field, the use of fluorescence imaging in the second near‐infrared (NIR‐II) region is growing rapidly because it imparts the advantages of reduced autofluorescence and low photon scattering. The advantage of reduced scattering is that it increases penetration depth in vivo and improves imaging clarity. Herein, this work uses mesoporous silica, a biocompatible template that can be easily modified, functionalized, and loaded with drugs for use in several bioapplications. The ZnGa2O4 spinel oxide system is integrated into mesoporous silica and different concentrations of Cr3+ and Ni2+ are loaded in octahedral sites to obtain the highest emission intensity in the NIR‐II region at 1285 nm via energy transfer from Cr3+ to Ni2+. Given that only a few nanophosphor systems with emission in the NIR‐II region are available, this work attempts to establish emission in the NIR‐II and NIR‐I regions to obtain images in vivo with an increased penetration depth to 5 mm and improved clarity for bioimaging purposes. This system will open the door for biomedical research on other NIR‐II nanophosphors. [ABSTRACT FROM AUTHOR]