The true atomistic structure of a disordered crystal: a computational study on the photon upconverting material β-NaYF and its Er-, Tm-, and Yb-doped derivates.

Hexagonal (β-) NaYF and LiYF doped with trivalent lanthanide ions (Ln, , Er, Tm, and Yb) are well-known photon upconverting materials. This property is crucially determined by the precise location of the Ln dopant ions and their closest neighbouring ions in the host material. However, due to the inherent disorder of the crystal structures the atomistic structure of a disordered crystal such as β-NaYF is not unambiguously provided by X-ray diffraction techniques.

Nano-bio interactions of Gum Arabic-stabilized lanthanide-based upconverting nanoparticles: and study.

Lanthanide-based nanoparticles (Ln-NPs) are highly valued for their unique optical and magnetic properties, making them useful in various scientific fields, including materials science and biomedicine. This study investigated the use of Gum Arabic (GA), a natural, non-toxic biopolymer, as capping agent for Ln-NPs to enhance their biocompatibility and chemical and colloidal stability. Specifically, Er/Yb co-doped NaGdF Ln-NPs were modified with GA, followed by their characterization with respect to upconversion properties and as well as toxicity.

Synthesis, Characterization and Photophysical Properties of a New Family of Rare-Earth Cluster-Based Metal-Organic Frameworks.

In this work, nine new rare-earth metal-organic frameworks (RE-MOFs, where RE=Lu(III), Yb(III), Tm(III), Er(III), Ho(III), Dy(III), Tb(III), Gd(III), and Eu(III)) isostructural to Zr-MOF-808 are synthesized, characterized, and studied regarding their photophysical properties. Materials with high crystallinity and surface area are obtained from a reproducible synthetic procedure that involves the use of two fluorinated modulators. At the same time, these new RE-MOFs display tunable photoluminescent properties due to efficient linker-to-metal energy transfer promoted by the antenna effect, resulting in a series of RE-MOFs displaying lanthanoid-based emissions spanning the visible and near-infrared regions of the electromagnetic spectrum.

Confining single Er ions in sub-3 nm NaYF nanoparticles to induce slow relaxation of the magnetisation.

Molecular systems known as single-molecule magnets (SMMs) exhibit magnet-like behaviour of slow relaxation of the magnetisation and magnetic hysteresis and have potential application in high-density memory storage or quantum computing. Often, their intrinsic magnetic properties are plagued by low-energy molecular vibrations that lead to phonon-induced relaxation processes, however, there is no straightforward synthetic approach for molecular systems that would lead to a small amount of low-energy vibrations and low phonon density of states at the spin-resonance energies. In this work, we apply knowledge accumulated over the last decade in molecular magnetism to nanoparticles, incorporating Er ions in an ultrasmall sub-3 nm diamagnetic NaYF nanoparticle (NP) and probing the slow relaxation dynamics intrinsic to the Er ion.

Introduction to fundamental processes in optical nanomaterials.

An introduction to the joint and themed collection focused on fundamental processes in optical nanomaterials that features a series of articles describing the properties of this versatile class of materials while highlighting some of their potential applications.

Lanthanide-based nanomaterials for temperature sensing in the near-infrared spectral region: illuminating progress and challenges.

Being first proposed as a method to overcome limitations associated with conventional contact thermometers, luminescence thermometry has been extensively studied over the past two decades as a sensitive and fast approach to remote and minimally invasive thermal sensing. Herein, lanthanide (Ln)-doped nanoparticles (Ln-NPs) have been identified as particularly promising candidates, given their outstanding optical properties. Known primarily for their upconversion emission, Ln-NPs have also been recognized for their ability to be excited with and emit in the near-infrared (NIR) regions matching the NIR transparency windows.

Core-multi-shell design: unlocking multimodal capabilities in lanthanide-based nanoparticles as upconverting, -weighted MRI and CT probes.

Multimodal bioimaging probes merging optical imaging, magnetic resonance imaging (MRI), and X-ray computed tomography (CT) capabilities have attracted considerable attention due to their potential biomedical applications. Lanthanide-based nanoparticles are promising candidates for multimodal imaging because of their optical, magnetic and X-ray attenuation properties. We prepared a set of hexagonal-phase (β)-NaGdF:Yb,Er/NaGdF/NaDyF core/shell/shell nanoparticles (Dy-CSS NPs) and demonstrated their optical/-weighted MRI/CT multimodal capabilities.

Entrapped Molecule-Like Europium-Oxide Clusters in Zinc Oxide with Nearly Unaffected Host Structure.

Nanocrystalline ZnO sponges doped with 5 mol% EuO are obtained by heating metal-salt complex based precursor pastes at 200-900 °C for 3 min. X-ray diffraction, transmission electron microscopy, and extended X-ray absorption fine structure (EXAFS) show that phase separation into ZnO:Eu and c-Eu O takes place upon heating at 700 °C or higher. The unit cell of the clean oxide made at 600 °C shows only ≈0.

Phytoglycogen Encapsulation of Lanthanide-Based Nanoparticles as an Optical Imaging Platform with Therapeutic Potential.

Lanthanide-based upconverting nanoparticles (UCNPs) are largely sought-after for biomedical applications ranging from bioimaging to therapy. A straightforward strategy is proposed here using the naturally sourced polymer phytoglycogen to coencapsulate UCNPs with hydrophobic photosensitizers as an optical imaging platform and light-induced therapeutic agents. The resulting multifunctional sub-micrometer-sized luminescent beads are shown to be cytocompatible as carrier materials, which encourages the assessment of their potential in biomedical applications.

Metabolic Consequences of Developmental Exposure to Polystyrene Nanoplastics, the Flame Retardant BDE-47 and Their Combination in Zebrafish.

Single-use plastic production is higher now than ever before. Much of this plastic is released into aquatic environments, where it is eventually weathered into smaller nanoscale plastics. In addition to potential direct biological effects, nanoplastics may also modulate the biological effects of hydrophobic persistent organic legacy contaminants (POPs) that absorb to their surfaces.

Trends in hyperspectral imaging: from environmental and health sensing to structure-property and nano-bio interaction studies.

Hyperspectral imaging (HSI) is a technique that allows for the simultaneous acquisition of both spatial and spectral information. While HSI has been known for years in the field of remote sensing, for instance in geology, cultural heritage, or food industries, it recently emerged in the fields of nano- and micromaterials as well as bioimaging and -sensing. Herein, the attractiveness of HSI arises from the suitability for generating knowledge about environment-specific optical properties, such as photoluminescence of optical probes in a biological sample or at a single-crystal/particle level, to be leveraged into better understanding of structure-property relationships and nano-bio interactions, respectively.

Cubic hexagonal - phase, size and morphology effects on the photoluminescence quantum yield of NaGdF:Er/Yb upconverting nanoparticles.

Upconverting nanoparticles (UCNPs) are well-known for their capacity to convert near-infrared light into UV/visible light, benefitting various applications where light triggering is required. At the nanoscale, loss of luminescence intensity is observed and thus, a decrease in photoluminescence quantum yield (PLQY), usually ascribed to surface quenching. We evaluate this by measuring the PLQY of NaGdF:Er,Yb UCNPs as a function of size ( 15 to 100 nm) and shape (spheres, cubes, hexagons).

Microwave-assisted synthesis of NaMnF particles with tuneable morphologies.

Here, the synthesis of sub-micron MMnF (M = Na or K) particles by a rapid microwave-assisted approach is reported. Adjustment of the Na-to-Mn ratio in the reaction mixture yielded tuneable morphologies, , rods, ribbons, and plates. Relaxometric results indicated that poly(acrylic acid)-capped MMnF particles exhibited characteristic magnetic properties, which endows them with potential -weighted contrast agent capabilities.

Effect of light scattering on upconversion photoluminescence quantum yield in microscale-to-nanoscale materials.

Scattering affects excitation power density, penetration depth and upconversion emission self-absorption, resulting in particle size -dependent modifications of the external photoluminescence quantum yield (ePLQY) and net emission. Micron-size NaYF:Yb, Er encapsulated phosphors (∼4.2 µm) showed ePLQY enhancements of >402%, with particle-media refractive index disparity (Δn): 0.

Fast, Low-Cost Synthesis of ZnO:Eu Nanosponges and the Nature of Ln Doping in ZnO.

A low-cost template-free solution chemical route to highly porous nanocrystalline sponges of ZnO-EuO with 0-5 mol % Eu is presented. The process uses Zn- and Eu-acetate-nitrate and triethanolamine as precursors in methanol. After evaporation of the solvent and heating at 200 °C for 3 min, crystalline ZnO:Eu sponges with minor amounts of organic residues were obtained.

Hyperspectral Imaging as a Tool to Study Optical Anisotropy in Lanthanide-Based Molecular Single Crystals.

In this work, we describe a protocol for a novel application of hyperspectral imaging (HSI) in the analysis of luminescent lanthanide (Ln)-based molecular single crystals. As representative example, we chose a single crystal of the heterodinuclear Ln-based complex [TbEu(bpm)(tfaa)6] (bpm=2,2'-bipyrimidine, tfaa =1,1,1-trifluoroacetylacetonate) exhibiting bright visible emission under UV excitation. HSI is an emerging technique that combines 2-dimensional spatial imaging of a luminescent structure with spectral information from each pixel of the obtained image.

Water dispersible ligand-free rare earth fluoride nanoparticles: water transfer NaREF-to-REF phase transformation.

The chemical stability of oleate-capped sub-10 nm α- and β-NaREF4 NPs (RE = Y, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, Lu for α- and RE = Pr, Nd, Sm, Eu, Gd, Tb, Dy for β-phase NPs) was evaluated under the acidic conditions used for ligand removal towards water dispersibility. It was found that for such small NPs, a pH lower than 3 was necessary for the water transfer to be efficient and to yield well-dispersed ligand-free NPs. In stark contrast to the generally considered good chemical stability of NaREF4, these conditions were observed to pose a risk to phase transformation of the NaREF4 NPs into much larger, hexagonal- or orthorhombic-phase REF3, depending on the NP composition.

Triplet-State Position and Crystal-Field Tuning in Opto-Magnetic Lanthanide Complexes: Two Sides of the Same Coin.

Lanthanide-complex-based luminescence thermometry and single-molecule magnetism are two effervescent fields of research, owing to the great promise they hold from an application standpoint. The high thermal sensitivity achievable, their contactless nature, along with sub-micrometric spatial resolution make these luminescent thermometers appealing for accurate temperature probing in miniaturised electronics. To that end, single-molecule magnets (SMMs) are expected to revolutionise the field of spintronics, thanks to the improvements made in terms of their working temperature-now surpassing that of liquid nitrogen-and manipulation of their spin state.

A Luminescent Thermometer Exhibiting Slow Relaxation of the Magnetization: Toward Self-Monitored Building Blocks for Next-Generation Optomagnetic Devices.

The development and integration of Single-Molecule Magnets (SMMs) into molecular electronic devices continue to be an exciting challenge. In such potential devices, heat generation due to the electric current is a critical issue that has to be considered upon device fabrication. To read out accurately the temperature at the submicrometer spatial range, new multifunctional SMMs need to be developed.

Exploring the dual functionality of an ytterbium complex for luminescence thermometry and slow magnetic relaxation.

We present a comprehensive investigation of the magnetic and optical properties of an ytterbium complex, which combines two desirable and practical features into a single molecular system. Based upon Yb ions that promote near-infrared optical activity and a chemical backbone that is ideal for an in-depth understanding of the magnetic behaviour, we have designed a multifunctional opto-magnetic species that operates as a luminescent thermometer and as a single-molecule magnet (SMM). Our magnetic investigations, in conjunction with calculations, reveal one of the highest energy barriers reported for an Yb-based complex.

Cubic versus hexagonal - effect of host crystallinity on the T shortening behaviour of NaGdF nanoparticles.

Sodium gadolinium fluoride (NaGdF4) nanoparticles are promising candidates as T1 shortening magnetic resonance imaging (MRI) contrast agents due to the paramagnetic properties of the Gd3+ ion. Effects of size and surface modification of these nanoparticles on proton relaxation times have been widely studied. However, to date, there has been no report on how T1 relaxivity (r1) is affected by the different polymorphs in which NaGdF4 crystallizes: cubic (α) and hexagonal (β).

Microwave-Assisted Solvothermal Synthesis of Upconverting and Downshifting Rare-Earth-Doped LiYF Microparticles.

Growing attention toward optically active materials has prompted the development of novel synthesis methods for a more reliable and efficient access to these systems. In this regard, microwave-assisted approaches provide unique advantages over traditional solvothermal methods reliant on convectional heating: namely, significantly shorter reaction durations, more rigid reaction conditions, and thus a higher degree of reproducibility. Reported herein for the first time is a rapid synthesis of rare-earth (RE)-doped LiYF upconverting and downshifting microparticles with well-defined bipyramidal morphology and good size dispersion via a microwave-assisted solvothermal process.

Probing Optical Anisotropy and Polymorph-Dependent Photoluminescence in [Ln ] Complexes by Hyperspectral Imaging on Single Crystals.

Two homodinuclear and one heterodinuclear lanthanide (Ln)-based complexes of the general formula [Ln (bpm)(tfaa) ] (Ln=Eu (1), Tb (2), Eu-Tb (3), bpm=2,2'-bipyrimidine, tfaa =1,1,1-trifluoroacetylacetonate) were synthesized and characterized by single-crystal photoluminescence spectroscopy and hyperspectral imaging. Complexes 1 and 2 crystallize in two polymorphic structures, while three polymorphs were isolated for 3, namely having needle-, plate-, and block-like morphologies. Single-crystal photoluminescence spectroscopy and imaging on Eu -containing 1 and 3 revealed polymorph-dependent J-splitting of the hypersensitive D → F Eu transition as well as electric-to-magnetic dipole emission intensity ratios.