Exploring the potential of lanthanide-doped oxyfluoride materials for bright green upconversion and their promising applications towards temperature sensing and drug delivery.

The most efficient upconversion (UC) materials reported to date are based on fluoride hosts with low phonon energies, which reduce the amount of nonradiative transitions. In particular, NaYF4 doped with Yb3+ and Er3+ at appropriate ratios is known as one of the most efficient UC phosphors. However, its low thermal stability limits its use for certain applications. On the other hand, oxide hosts exhibit better thermal stability, yet they have higher phonon energies and are thus prone to lower UC efficiencies. As a result, developing host nanomaterials that combine the robustness of oxides with the high upconversion efficiencies of fluorides remains an intriguing prospect. Herein, we demonstrate the formation of ytrrium doped oxyfluoride (YOF:Yb3+,Er3+) particles, which are prepared by growing a NaYF4:Yb3+,Er3+ layer around SiO2 spherical particles and consecutively applying a high-temperature annealing step followed by the removal of SiO2 template. Our interest lies in employing these materials as Boltzmann type physiological range luminescence thermometers, but their weak green emission is a drawback. To overcome this issue, and engineer materials suitable for Boltzmann type thermometry, we have studied the effect of introducing different metal ion co-dopants (Gd3+, Li+ or Mn2+) into the YOF:Yb3+,Er3+ particles, focusing on the overall emission intensity, as well as the green to red ratio, upon 975 nm laser excitation. These materials are explored for their use as ratiometric thermometers, and further also as drug carriers, including their simultaneous use for these two applications. The investigation also includes examining their level of toxicity towards specific human cells - normal human dermal fibroblasts (NHDFs) - to evaluate their potential use for biological applications.

Engineering Porosity and Functionality in a Robust Twofold Interpenetrated Bismuth-Based MOF: Toward a Porous, Stable, and Photoactive Material.

Defect engineering in metal-organic frameworks (MOFs) has gained worldwide research traction, as it offers tools to tune the properties of MOFs. Herein, we report a novel 2-fold interpenetrated Bi-based MOF made of a tritopic flexible organic linker, followed by missing-linker defect engineering. This procedure creates a gradually augmented micro- and mesoporosity in the parent (originally nonporous) network. The resulting MOFs can tolerate a remarkable extent of linker vacancy (with absence of up to 60% of linkers per Bi node) created by altering the crystal-growth rate as a function of synthesis temperature and duration. Owing to the enhanced porosity and availability of the uncoordinated Lewis acidic Bi sites, the defect-engineered MOFs manifested improved surface areas, augmented CO2 and water vapor uptake, and catalytic activity. Parallel to this, the impact of defect engineering on the optoelectronic properties of these MOFs has also been studied, offering avenues for new applications.

Ratiometric dual-emitting thermometers based on rhodamine B dye-incorporated (nano) curcumin periodic mesoporous organosilicas for bioapplications.

This study explores the potential of combining periodic mesoporous organosilicas (PMOs) with a fluorescent dye to develop a ratiometric thermometry system with enhanced stability, sensitivity, and biocompatibility. PMOs, ordered porous materials known for their stability and versatility, serve as an ideal platform. Curcumin, a natural polyphenol and fluorescent dye, is incorporated into PMOs to develop curcumin-functionalized PMOs (C-PMO) and curcumin-pyrazole-functionalized PMOs (CP-PMO) via hydrolysis and co-condensation. These PMOs exhibit temperature-dependent fluorescence properties. The next step involves encapsulating rhodamine B (RhB) dye within the PMO pores to create dual-emitting PMO@dye nanocomposites, followed by a lipid bilayer (LB) coating to enhance biocompatibility and dye retention. Remarkably, within the physiological temperature range, C-PMO@RhB@LB and CP-PMO@RhB@LB demonstrate noteworthy maximum relative sensitivity (Sr) values of up to 1.69 and 2.60% K-1, respectively. This approach offers versatile means to create various ratiometric thermometers by incorporating different fluorescent dyes, holding promise for future temperature sensing applications.

Single-Crystal-to-Single-Crystal Photosynthesis of Supramolecular Organoboron Polymers with Dynamic Effects.

The solid-state synthesis of single-crystalline organic polymers, having functional properties, remains an attractive and developing research area in polymer chemistry and materials science. However, light-triggered topochemical synthesis of crystalline polymers comprising an organoboron backbone has not yet been reported. Here, we describe an intriguing example of single-crystal-to-single-crystal (SCSC) rapid photosynthesis (occurs on a seconds-scale) of two structurally different linear organoboron polymers, driven by environmentally sustainable visible/sun light, obtained from the same monomer molecule. A newly designed Lewis acid-base type molecular B ← N organoboron adduct (consisting of an organoboron core and naphthylvinylpyridine ligands) crystallizes in two solid-state forms featuring the same chemical structure but different 3D structural topologies, namely, monomers 1 and 2. The solvate molecule-free crystals of 1 undergo topochemical photopolymerization via an unusual olefin-naphthyl ring [2 + 2] cyclization to yield the single crystalline [3]-ladderane polymer 1P growing along the B ← N linkages, accompanied by instantaneous and violent macroscopic mechanical motions or photosalient effects (such as bending-reshaping and jumping motions). In contrast, visible light-harvesting single crystals of 2 quantitatively polymerize to a B ← N bond-stabilized polymer 2P in a SCSC fashion owing to the rapid [2 + 2] cycloaddition reaction among olefin double bonds. Such olefin bonds in the crystals of 2 are suitably preorganized for photoreaction due to the presence of solvate molecules in the crystal packing. Single crystals of 2 also show photodynamic jumping motions - in response to visible light but in a relatively slower fashion than the crystals of 1. In addition to SCSC topochemical polymerization and dynamic motions, both monomer crystals and their single-crystalline polymers feature green emissive and short-lived room-temperature phosphorescence properties upon excitation with visible-light wavelength.

Versatile Palladium-catalyzed intramolecular cyclization to access new luminescent azaphosphaphenalene motifs.

Using a straightforward sequence of diphosphonylation and a Pd-catalysed concerted-metalation-deprotonation (CMD), a synthetic strategy towards polyaromatic phosphorus containing heterocycles was developed. Herein, we report the synthesis and characterization of new azaphosphaphenalenes, using easily accessible palladium catalysts and starting materials. The key tetrahydroquinoline intermediates of the reaction were synthesised via a fast and effective procedure and could be isolated as such, or further reacted towards the target polyaromatic structures. The obtained products showed interesting luminescent properties and their emission, excitation and quantum yields were evaluated.