Optimizing optical thermometry with tri-doped Ba2GdV3O11 phosphors: Ratiometric and fluorescence lifetime analysis.

Optical sensor technology has undergone a transformative evolution with the advent of fluorescence ratio techniques (FIR) and fluorescence lifetime (FL) strategies, revolutionizing precision, performance, and reliability. This study delves into the synthesis of Ba2GdV3O11 phosphors doped with Ho3+/Nd3+, Er3+, and Yb3+, employing the sol-gel method for upconverting material fabrication. A thorough investigation into the structural, morphological, and optical properties of the synthesized phosphors is conducted. Excitation at 980 nm unveils upconversion (UC) emissions across green and red spectra. The intensities of the observed emission bands for Ho3+, Nd3+, and Er3+ demonstrate significant sensitivity to fluctuations in temperature. Temperature sensing relies on the 4S3/2 and 2H11/2 upconversion emissions bands, in addition to the emission lifetimes at 4S3/2. Enhanced thermal sensitivity values are attained, reaching up to 1.03 % K-1 and 1.07 % K-1 using the FIR strategy, and up to 0.146 % K-1 and 0.47 % K-1 with the FL strategy for Ho3+/Er3+/Yb3+ and Nd3+/Er3+/Yb3+ tri-doped Ba2GdV3O11 phosphors, respectively. Furthermore, the studied phosphors exhibit remarkable precision in detecting minute temperature changes (0.3 K), positioning them as promising candidates for precise temperature sensing. This study pioneers innovative methodologies to advance optical thermometry techniques, offering promising prospects for scientific and industrial applications reliant on precise optical temperature sensing.

Advanced temperature sensing with Er3+/Yb3+ co-doped Ba2GdV3O11 phosphors through upconversion luminescence.

Optical thermometry is a non-contact temperature sensing technique with widespread applications. It offers precise measurements without physical contact, making it ideal for situations where contact-based methods are impractical. However, improving the accuracy of optical thermometry remains an ongoing challenge. Herein, enhancing the thermometric properties of luminescent thermometers through novel materials or strategies is crucial for developing more precise sensors. Hence, the present study focuses on the application of four-mode luminescence thermometric techniques in sol-gel synthesized Er3+/Yb3+ co-doped Ba2GdV3O11 phosphors for optical temperature sensing in the temperature range of 298-573 K. The upconversion (UC) luminescence is achieved under excitations of 980 nm or 1550 nm, resulting in bright yellow-green emission in the visible spectral range. Temperature sensing is realized by exploiting the UC emissions of 4S3/2, 2H11/2 and 4F7/2 bands, which represent intensity ratios of thermally coupled levels (TCELs) and non-thermally coupled levels (NTCELs) of Er3+/Yb3+, along with the emission lifetimes at 4S3/2. The relative sensitivity (Sr) values for TCELs exhibit a gradual decrease with rising temperature, reaching a maximum of 1.1% K-1 for 980 nm excitation and 0.86% K-1 for 1550 nm excitation at 298 K. Conversely, for NTCELs, the highest Sr value observed is 0.9% K-1 at 298 K for 1550 nm excitation. Moreover, the emission lifetimes at 4S3/2 yield notably high Sr values of up to 5.0% µs K-1 (at 425 K). Furthermore, the studied phosphors have a sub-degree thermal resolution, making them excellent materials for accurate temperature sensing. Overall, this study provides a promising new direction for the development of more precise and reliable optical thermometry techniques, which could have important implications for a range of scientific and industrial optical temperature sensing applications.

Glass-based LED system for indoor horticulture: enhanced plant growth through Sm3+ and Tm3+ co-doped luminescent glasses.

This study addresses the challenges of sustainable and efficient agricultural practices in the face of climate change and the destruction of agricultural lands by presenting the development of a novel plant growth LED based on Sm3+ and Tm3+ co-doped luminescent glasses with color-converting properties that emit blue and red light, resulting in an increased rate of photosynthesis and density of photosynthetically active radiation reaching the harvesting pigments. The developed LED exhibits photoluminescence (PL) peak positions ranging from 454 to 648 nm, with a spectral coverage of 50% and 39% of the absorption regions of chlorophyll a and chlorophyll b, respectively, resulting in an impressive 56% photoluminescence quantum yield (PLQY). Furthermore, the developed plant growth LED demonstrates robust performance, remaining unaffected by temperature cycles and extended operation periods. Using Romaine lettuce cultivated under identical conditions, a comparative study between the developed LED and commercially available plant growth LED is conducted, with the designed LED showing significant improvements in plant growth characteristics, including increased plant height, weight, number of leaves, and enhanced levels of chlorophyll a, chlorophyll b, and carotenoid content, while the root diameter is reduced, and the shoot-to-root ratio is diminished in comparison to the commercially available plant growth LED. The paper also compares the performance of Sm3+ and Tm3+ co-doped luminescent glass-based plant growth LED with other reported plant growth LED designs using different luminescent materials, exploring the impact of PLQY, PL position, and plant growing conditions. The results suggest that the developed LED system offers a more efficient and sustainable way of lighting for indoor horticulture and has significant implications for meeting the increasing food demands of the growing world population.