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1. Metal surface effects on single upconverting nanoparticle luminescence and thermometry signals

   https://doi.org/10.1039/D4TC03911D  

   Ye, Ziyang; Signor, Laura; Cohan, Molly; Pickel, Andrea D (December 2024, Journal of Materials Chemistry C)

   Metal surfaces can alter the luminescence emitted by nanoparticles through a variety of effects including quenching, plasmonic enhancement, and optical interference-, reflection-, and absorption-related phenomena. While many of these effects are well-established, multiple such effects typically occur in parallel in realistic measurement scenarios, making the relative importance of each effect difficult to discern. As imaging and sensing applications in which luminescent nanoparticles are placed on metal surfaces continue to grow, a detailed understanding of how metal surfaces modify nanoparticle luminescence is increasingly important for optimizing and ensuring correct interpretation of the measurement results. Here, we systematically investigate how metal surfaces affect the luminescence emitted by individual NaYF₄:Yb³⁺,Er³⁺ upconverting nanoparticles (UCNPs) ∼27 nm in diameter using a judiciously selected set of five different metal coatings with varying optical and thermal properties. We find that the average single-UCNP emission intensity is determined by an interplay between quenching and reflection effects. Consequently, the average single-UCNP emission intensity is correlated with the reflectance of the underlying metal coating, but non-radiative decay rate changes also play an important role, leading to different average single-UCNP emission intensities for metal coatings with near-identical reflectances. We also evaluate metal surface effects on the common ratiometric thermometry signal of NaYF₄:Yb³⁺,Er³⁺ UCNPs and find that the intrinsic temperature dependence of the luminescence intensity ratio is unaffected by the underlying material. The only differences observed are the result of laser-induced heating for sufficiently absorbing metal coatings on low thermal conductivity substrates, in accordance with the predictions of an analytical heat transfer model. 

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2. Selective enhancement of upconversion luminescence for enhanced ratiometric sensing

   https://doi.org/10.1039/d1ra01396c  

   Bae, Kyuyoung; Xu, Bo; Das, Ananda; Wolenski, Connor; Rappeport, Eric; Park, Wounjhang (May 2021, RSC Advances)

   null (Ed.)

   Lanthanide-doped upconversion nanoparticles (UCNPs) have attracted widespread interest in bioimaging and sensing due to their photostability, low excitation energy, and good tissue penetration. Plasmonic nanostructures, on the other hand, can enhance the luminescence of UCNPs by concentrating electric fields into a nanoscale volume. While the enhanced luminescence intensity is in principle beneficial to sensing, intensity-based sensing has limitations in absolute measurements. This deficiency can be overcome by employing ratiometric sensing in which intensity ratio, rather than intensity itself, is used to quantitatively determine the presence of analytes. The ratiometric sensing is advantageous because the intensity ratio is much less sensitive to the variations in the environment and the number of probe materials in the sensing volume. Here, we demonstrate a plasmonic nanostructure with upconversion nanoparticles for an enhanced ratiometric sensing platform. The plasmonic nanostructure is composed of UCNPs, an indium tin oxide (ITO) spacer layer and an Au nanodisk. The nanostructure is designed such that the plasmon resonance selectively enhances the red luminescence of NaYGdF 4 :Yb 3+ , Er 3+ UCNPs while leaving the green luminescence unaffected, thereby increasing the dynamic range and achievable sensitivity of the red-to-green (R/G) intensity ratio. We observed a 4-fold enhancement in the R/G ratio and also a drastic reduction in the signal uncertainty. This work advances our knowledge of the optical interaction between UCNPs and plasmonic nanostructures and also provides a foundation for improved ratiometric sensing in biomedical applications. 

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3. Evaluating mid-IR laser potential of Er ³⁺ vs. Dy ³⁺ in low-maximum-phonon-energy hosts for 4.1-4.8 µm applications

   https://doi.org/10.1364/OME.572481  

   Brown, Ei_Ei; Fleischman, Zackery_D; Merkle, Larry; Hommerich, Uwe; McKay, Jason; Palosz, Witold; Trivedi, Sudhir; Dubinskii, Mark (August 2025, Optical Materials Express)

   A comparative spectroscopic investigation was conducted to evaluate the potential of Dy³⁺and Er³⁺doped Ga₂Ge₅S₁₃chalcogenide glass and CsCdCl3 crystal for suitability as gain media for mid-infrared lasers operating within the 4.1-4.8 (m spectral range. Both rare-earth ions exhibited broad mid-IR emissions at room temperature centered at ∼4.4-4.5 µm, attributed to the Dy³⁺:⁶H_11/2→⁶H_13/2and Er³⁺:⁴I_9/2→⁴I_11/2transitions. The fluorescence lifetimes of these mid-IR transitions varied significantly between these two host materials. Dy³⁺and Er³⁺doped CsCdCl₃crystals exhibited long lifetimes of ∼9-12 ms, while the same ions in Ga₂Ge₅S₁₃glass yielded lifetimes in the range of ∼1 ms. Temperature-dependent lifetime measurements further confirmed the role of multiphonon relaxation in Dy³⁺: Ga₂Ge₅S₁₃, although fitting with the temperature dependence of the multiphonon energy-gap law indicated the presence of additional nonradiative decay channels, likely involving impurity interactions. In contrast, Er³⁺emissions exhibited minimal temperature dependence across both hosts, with measured lifetimes closely matching calculated radiative values. Judd-Ofelt analyses revealed radiative properties and transition probabilities comparable to other low-maximum-phonon-energy rare-earth-doped hosts, with the studied Dy³⁺doped host materials standing out by offering sigma-tau products several times higher than those of Er³⁺in the same hosts. 

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4. Pyrene‐Based Polyimide Covalent Organic Framework with Temperature‐Dependent Fluorescence

   https://doi.org/10.1002/adom.202300412  

   Zadehnazari, Amin; Khosropour, Ahmadreza; Altaf, Ataf_Ali; Amirjalayer, Saeed; Abbaspourrad, Alireza (April 2023, Advanced Optical Materials)

   Abstract The synthesis of a fluorescent covalent organic framework (COF) using perylene and pyrene building blocks (PEPy‐COF), via a one‐pot condensation reaction is reported. PEPy‐COF is crystallized into 2D nanosheets with a cubic and prismatic crystalline morphology and demonstrates structural stability at temperatures up to 500 °C. The structural morphology is confirmed using X‐ray diffraction and atomic‐level simulations. These 2D porous polymer sheets form a tetragonal framework that is found to have a high specific surface area of 772 m²g⁻¹. Based on the definition of porous materials, the network is mesoporous with an observed pore size of 3.03 nm, which is in good agreement with the material's calculated pore size. The experimentally obtained HOMO‐LUMO band gap is 2.62 eV, confirming the semiconducting nature of PEPy‐COF. PEPy‐COF emits a shiny blue luminescence under UV and visible light. This luminescence intensity is temperature‐dependent in solvents with different polarities and dielectric constants demonstrating that the PEPy‐COF has potential use in a wide range of temperature‐sensing devices. The fluorescence intensity ratio is similar for different temperatures under ultra‐sound conditions and varying solvents. 

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5. A deficiency screen of the 3rd chromosome for dominant modifiers of the Drosophila ER integral membrane protein, Jagunal

   https://doi.org/10.1093/g3journal/jkad059  

   Ascencio, Gerson; de Cruz, Matthew A.; Abuel, Judy; Alvarado, Sydney; Arriaga, Yuma; Conrad, Emily; Castro, Alonso; Eichelberger, Katharine; Galvan, Laura; Gundy, Grace; et al (March 2023, G3: Genes, Genomes, Genetics)

   Abstract The mechanism surrounding chromosome inheritance during cell division has been well documented, however, organelle inheritance during mitosis is less understood. Recently, the endoplasmic reticulum (ER) has been shown to reorganize during mitosis, dividing asymmetrically in proneuronal cells prior to cell fate selection, indicating a programmed mechanism of inheritance. ER asymmetric partitioning in proneural cells relies on the highly conserved ER integral membrane protein, Jagunal (Jagn). Knockdown of Jagn in the compound Drosophila eye displays a pleotropic rough eye phenotype in 48% of the progeny. To identify genes involved in Jagn dependent ER partitioning pathway, we performed a dominant modifier screen of the 3rd chromosome for enhancers and suppressors of this Jagn-RNAi-induced rough eye phenotype. We screened through 181 deficiency lines covering the 3L and 3R chromosomes and identified 12 suppressors and 10 enhancers of the Jagn-RNAi phenotype. Based on the functions of the genes covered by the deficiencies, we identified genes that displayed a suppression or enhancement of the Jagn-RNAi phenotype. These include Division Abnormally Delayed (Dally), a heparan sulfate proteoglycan, the γ-secretase subunit Presenilin, and the ER resident protein Sec63. Based on our understanding of the function of these targets, there is a connection between Jagn and the Notch signaling pathway. Further studies will elucidate the role of Jagn and identified interactors within the mechanisms of ER partitioning during mitosis. 

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