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In this investigation, the incorporation of Gd3+ ions into ZMF-spinel ferrites through the citrate sol-gel auto-combustion method significantly modified their structural, magneto-optical, and gamma-ray attenuation properties. Doping levels were varied across samples labeled ZMF0 to ZMF4 with Gd3+ concentrations ranging from 0.000 to 0.100. Advanced characterization techniques such as XRD, SEM, TEM, FT-IR, Raman spectroscopy, and XPS, alongside UV-vis spectroscopy and VSM measurements, highlighted the profound impact of Gd3+ doping. Notably, the incorporation of Gd3+ led to nano-sized cubic structures with an optimized crystallite size of 19.82 nm in the ZMF4 sample, and a notable reduction in the band gap from 3.21 eV to 2.99 eV was observed, indicative of enhanced electronic properties. Magnetic analysis revealed a transition towards superparamagnetic behavior, with a decrease in coercivity and squareness ratios, suggesting applications in areas such as data storage and optical waveguides. Furthermore, the study leveraged FLUKA Monte Carlo simulations to assess the gamma-ray shielding efficiency of these materials. It was found that increasing Gd3+ concentration or sample thickness markedly improved radiation attenuation, highlighting the material's enhanced shielding capabilities against a range of photon energies. The most significant findings included the optimized sample (ZMF4) displaying superior magneto-optical characteristics and outstanding gamma-ray shielding performance, especially at higher Gd3+ levels. This investigation underlines the critical role of Gd3+ doping in advancing the functional properties of ZMF-spinel ferrites for technological and radiation protection applications, showcasing the potential of tailored nanomaterials in addressing complex challenges in material science. Highlights: Gd3+ ion doping in ZMF-spinel ferrites reduced crystallite sizes to an optimal 19.82 nm, significantly enhancing their magneto-optical properties. Spectral analysis showed a noticeable blue shift in band edge absorption, with optical band gaps narrowing from 3.21 eV to 2.99 eV, indicating improved electronic properties. Magnetic assessments revealed a transition to soft magnetic behavior and identified superparamagnetic regions, broadening potential technological applications. FLUKA Monte Carlo simulations demonstrated that increased Gd3+ concentration and sample thickness significantly boost the material's gamma-ray shielding efficiency. The study's comprehensive analysis establishes ZMF-spinel ferrites doped with Gd3+ ions as promising candidates for advanced applications, including radiation protection and energy systems. [ABSTRACT FROM AUTHOR]

Abstract The multiplexing capacity of conventional fluorescence materials are significantly limited by spectral overlap and background interference, mainly due to their short-lived fluorescence lifetimes. Here, we adopt a novel Gd3+ doping strategy in NaYF4 host materials, realized tuning of upconversion photoluminescence (UCPL) lifetimes at selective emissions. Time-correlated single-photon counting (TCSPC), was applied to measure the photoluminescence lifetimes accurately. We demonstrated the large dynamic range of lifetimes of upconversion nanoparticles with good upconversion quantum yields, mainly owing to the dominance of high efficient energy transfer upconversion mechanism. The exceptional tunable properties of upconversion materials allow great potential for them to be utilized in biotechnology and life sciences.

Phosphors that exhibit tunable broadband emissions are highly desired in multi-functional LEDs, including pc-WLEDs and pc-NIR LEDs. In this work, broadband emissions were obtained and modulated in the unexpectedly wide spectral range of 517–609 nm for (Lu0.99−xGdxBi0.01)2WO6 phosphors by tuning the Gd3+ content (x = 0–0.99). The effects of Gd3+ doping on phase constituents, particle morphology, crystal structure, and photoluminescence were systematically investigated. Broadband green emission was obtained from Gd3+-free (Lu0.99Bi0.01)2WO6 phosphors (x = 0), whose emission intensity was enhanced by 50% with 5 at% Gd3+ (x = 0.05). The phase transition happened when x > 0.50 and the broadband red-NIR emission was obtained when x = 0.75–0.99. Three luminescence centers were proved to be responsible for the broadband green emissions via crystal structure, spectral fitting and fluorescence decay analysis. A pc-WLED with a high color rendering index (Ra = 91.3), a stable emission color, and a low color temperature (3951 K) was fabricated from the (Lu0.94Gd0.05Bi0.01)2WO6 broadband green phosphor, and an LED device that simultaneously emits high color rendering index white light and NIR light was obtained with the (Gd0.99Bi0.01)2WO6 broadband red-NIR phosphor. Night vision and noninvasive imaging were also demonstrated using the latter LED device. [ABSTRACT FROM AUTHOR]