Excitation-Dependent Anti-Thermal Quenching in Zero-Dimensional Manganese Bromides for Photoluminescence and X-Ray Scintillation.

One of the most significant challenges of luminescent materials is the thermal quenching (TQ) at high temperature. Understanding the correlation between crystal structure variation and photoluminescence (PL) quenching is significant to achieve anti-thermal quenching (anti-TQ) phosphors. Herein, we unveil a universal principle governing switchable TQ and anti-TQ behaviors in zero-dimensional (0D) organic-inorganic hybrid manganese bromides.

Mechanism of action and evaluation of ratiometric probes for uric acid using lanthanide complexes with tetraazatriphenylene sensitisers.

A series of new ligands has been prepared that incorporate electron-poor aromatic moieties (dpqMe and dpqPh chromophores) into tetraazacyclododecane or triazacyclononane based complex structures, and the time-dependent photophysical properties of their Eu(iii) and Tb(iii) complexes evaluated for the selective and rapid ratiometric analysis of urate in diluted serum solution, together with mechanistic studies probing the nature of the intermediate exciplex and the excited state dynamics using transient absorption spectroscopy.

Mechanistic Investigation of Sensitized Europium Luminescence: Excited State Dynamics and Luminescence Lifetime Thermometry.

Fluorescent nanothermometers based on thermal-dependent lifetime have a significant advantage in biological imaging owing to their immunity toward scattering, absorption, and autofluorescence. In this study, we present the first example of a water-soluble europium complex () that exhibits high sensitivity (1.2% K at 298 K) based on a temperature-dependent lifetime in the millisecond time range.

Organic Excitonic State Management by Surface Metallic Coupling of Inorganic Lanthanide Nanocrystals.

The ability to harness charges and spins for control of organic excitonic states is critical in developing high-performance organic luminophores and optoelectronic devices. Here we report a facile strategy to efficiently manipulate the electronic energy states of various organic phosphors by coupling them with inorganic lanthanide nanocrystals. We show that the metallic atoms exposed on the nanocrystal surface can introduce strong coupling effects to 9-(4-ethoxy-6-phenyl-1,3,5-triazin-2-yl)-9H-carbazole (OCzT) and some organic chromophores with carbazole functional groups when the organics are approaching the nanocrystals.

Antioxidant hepatic lipid metabolism can be promoted by orally administered inorganic nanoparticles.

Accumulation of inorganic nanoparticles in living organisms can cause an increase in cellular reactive oxygen species (ROS) in a dose-dependent manner. Low doses of nanoparticles have shown possibilities to induce moderate ROS increases and lead to adaptive responses of biological systems, but beneficial effects of such responses on metabolic health remain elusive. Here, we report that repeated oral administrations of various inorganic nanoparticles, including TiO, Au, and NaYF nanoparticles at low doses, can promote lipid degradation and alleviate steatosis in the liver of male mice.

Elemental-Migration-Assisted Full-Color-Tunable Upconversion Nanoparticles for Video-Rate Three-Dimensional Volumetric Displays.

Herein, we demonstrate video-rate color three-dimensional (3D) volumetric displays using elemental-migration-assisted full-color-tunable upconversion nanoparticles (UCNPs). In the heavily doped NaErF:Tm-based core@multishell UCNPs, erbium migration was observed. By tailoring this migration through adjustment of the intermediate shell thickness between the core and the sensitizer-doped second shell, red-green orthogonal upconversion luminescence (UCL) was achieved.

Mammary Leukocyte-Assisted Nanoparticle Transport Enhances Targeted Milk Trace Mineral Delivery.

Nanoparticles are applied as versatile platforms for drug/gene delivery in many applications owing to their long-retention and specific targeting properties in living bodies. However, the delivery mechanism and the beneficial effect of nanoparticle-retention in many organisms remain largely uncertain. Here, the transport and metabolism of mineral nanoparticles in mammary gland during lactation are explored.

Time-Gated Imaging of Latent Fingerprints with Level 3 Details Achieved by Persistent Luminescent Fluoride Nanoparticles.

The discovery of X-ray-charged persistent luminescence (PersL) in fluoride nanoparticles enables these materials to emit photons without real-time excitation, which provides a great possibility for the development of new luminescent nanotechnologies. In this work, we developed NaLuF:Mn nanoparticles with intense green PersL and functionalized surfaces and accordingly achieved time-gated imaging of latent fingerprints (LFPs) with Level 3 details. These surface-modified NaLuF:Mn nanoparticles exhibited near-spherical morphology, long-lasting emission for several hours, appropriate trap depth distribution, and tight chemical bonding with amino acids from fingerprints, thus greatly improving the accuracy of LFP imaging in a variety of environments.

NIR light-triggered peroxynitrite anion production direct lanthanide-triplet photosensitization for enhanced photodynamic therapy.

Peroxynitrite anion (ONOO), a product derived from reaction between reactive oxygen species (ROS) and nitric oxide (NO), is considered to be a more toxic reactive species than most ROS for cancer photodynamic therapy (PDT). To promote the PDT effect, a viable method is to develop rational strategies for efficient ONOO generation at targeted tumor sites. Herein, a heterostructure nanocomposite containing ZnO-coated lanthanide nanoparticles (LnNPs) is reported for ONOO-based PDT.

Rare-Earth Doping in Nanostructured Inorganic Materials.

Impurity doping is a promising method to impart new properties to various materials. Due to their unique optical, magnetic, and electrical properties, rare-earth ions have been extensively explored as active dopants in inorganic crystal lattices since the 18th century. Rare-earth doping can alter the crystallographic phase, morphology, and size, leading to tunable optical responses of doped nanomaterials.

Lanthanide-doping enables kinetically controlled growth of deep-blue two-monolayer halide perovskite nanoplatelets.

Impurity doping has been widely applied in nanomaterial synthesis for modulating the crystallographic phase, morphology, and size of nanocrystalline materials, but mostly by altering thermodynamic equilibria of final products. Here, we report the use of lanthanide dopants to manipulate the growing kinetics of halide perovskite nanocrystals to enable the preparation of highly anisotropic two-dimensional (2D) CsPbBr3-based nanoplatelets with precisely controlled thickness. We demonstrate that the incorporation of trivalent lanthanides increases the energy barrier in growing three-monolayer (3 ML) CsPbBr3 from a 2 ML intermediate.

X-ray-charged bright persistent luminescence in NaYF:Ln@NaYF nanoparticles for multidimensional optical information storage.

NaYF:Ln, due to its outstanding upconversion characteristics, has become one of the most important luminescent nanomaterials in biological imaging, optical information storage, and anticounterfeiting applications. However, the large specific surface area of NaYF:Ln nanoparticles generally leads to serious nonradiative transitions, which may greatly hinder the discovery of new optical functionality with promising applications. In this paper, we report that monodispersed nanoscale NaYF:Ln, unexpectedly, can also be an excellent persistent luminescent (PersL) material.

Nonvolatile electrical control of 2D CrGeTe and intrinsic half metallicity in multiferroic hetero-structures.

The electrical control of two-dimensional (2D) van der Waals ferromagnets is a step forward for the realization of spintronic devices. However, using this approach for practical applications remains challenging due to its volatile memory. Herein, we adopt an alternative strategy, where the bistable ferroelectric switches (P↑ and P↓) of ScCO (SCO) assist the ferromagnetic states of CrGeTe (CGT) in order to achieve non-volatile memories.

Lanthanide-doped inorganic nanoparticles turn molecular triplet excitons bright.

The generation, control and transfer of triplet excitons in molecular and hybrid systems is of great interest owing to their long lifetime and diffusion length in both solid-state and solution phase systems, and to their applications in light emission, optoelectronics, photon frequency conversion and photocatalysis. Molecular triplet excitons (bound electron-hole pairs) are 'dark states' because of the forbidden nature of the direct optical transition between the spin-zero ground state and the spin-one triplet levels. Hence, triplet dynamics are conventionally controlled through heavy-metal-based spin-orbit coupling or tuning of the singlet-triplet energy splitting via molecular design.

Single-molecule photoreaction quantitation through intraparticle-surface energy transfer (i-SET) spectroscopy.

Quantification of nanoparticle-molecule interaction at a single-molecule level remains a daunting challenge, mainly due to ultra-weak emission from single molecules and the perturbation of the local environment. Here we report the rational design of an intraparticle-surface energy transfer (i-SET) process, analogous to high doping concentration-induced surface quenching effects, to realize single-molecule sensing by nanoparticle probes. This design, based on a Tb-activator-rich core-shell upconversion nanoparticle, enables a much-improved spectral response to fluorescent molecules at single-molecule levels through enhanced non-radiative energy transfer with a rate over an order of magnitude faster than conventional counterparts.

Ferric Hydroxide-Modified Upconversion Nanoparticles for 808 nm NIR-Triggered Synergetic Tumor Therapy with Hypoxia Modulation.

The efficacy of dynamic therapy for solid tumors suffers daunting challenges induced by tumor hypoxia. Herein, we report a biocompatible nanosystem containing Fe(OH)-modified upconversion nanoparticles (UCNPs) for promoting synergetic chemo- and photodynamic therapy with the modulation of tumor hypoxia. In this system, UCNPs convert 808 nm near-infrared excitation to visible photon energy, which stimulates chlorin-e6 photosensitizers to generate toxic reactive oxygen species (ROS) by consumption of dissolved oxygen in cancer cells.

Energy Transfer in Dye-Coupled Lanthanide-Doped Nanoparticles: From Design to Application.

Surface modification with organic dye molecules is a useful strategy to manipulate the optical properties of lanthanide-doped nanoparticles (LnNPs). It enables energy transfer between dyes and LnNPs, which provides unprecedented possibilities to gain new optical phenomena from the dye-LnNPs composite systems. This has led to a wide range of emerging applications, such as biosensing, drug delivery, gene targeting, information storage, and photon energy conversion.

Binary temporal upconversion codes of Mn-activated nanoparticles for multilevel anti-counterfeiting.

Optical characteristics of luminescent materials, such as emission profile and lifetime, play an important role in their applications in optical data storage, document security, diagnostics, and therapeutics. Lanthanide-doped upconversion nanoparticles are particularly suitable for such applications due to their inherent optical properties, including large anti-Stokes shift, distinguishable spectroscopic fingerprint, and long luminescence lifetime. However, conventional upconversion nanoparticles have a limited capacity for information storage or complexity to prevent counterfeiting.

Enabling Förster Resonance Energy Transfer from Large Nanocrystals through Energy Migration.

The stringent distance dependence of Förster resonance energy transfer (FRET) has limited the ability of an energy donor to donate excitation energy to an acceptor over a Förster critical distance (R) of 2-6 nm. This poses a fundamental size constraint (<8 nm or ∼4R) for experimentation requiring particle-based energy donors. Here, we describe a spatial distribution function model and theoretically validate that the particle size constraint can be mitigated through coupling FRET with a resonant energy migration process.

Nonlinear spectral and lifetime management in upconversion nanoparticles by controlling energy distribution.

Optical tuning of lanthanide-doped upconversion nanoparticles has attracted considerable attention over the past decade because this development allows the advance of new frontiers in energy conversion, materials science, and biological imaging. Here we present a rational approach to manipulating the spectral profile and lifetime of lanthanide emission in upconversion nanoparticles by tailoring their nonlinear optical properties. We demonstrate that the incorporation of energy distributors, such as surface defects or an extra amount of dopants, into a rare-earth-based host lattice alters the decay behavior of excited sensitizers, thus markedly improving the emitters' sensitivity to excitation power.

Stabilizing triplet excited states for ultralong organic phosphorescence.

The control of the emission properties of synthetic organic molecules through molecular design has led to the development of high-performance optoelectronic devices with tunable emission colours, high quantum efficiencies and efficient energy/charge transfer processes. However, the task of generating excited states with long lifetimes has been met with limited success, owing to the ultrafast deactivation of the highly active excited states. Here, we present a design rule that can be used to tune the emission lifetime of a wide range of luminescent organic molecules, based on effective stabilization of triplet excited states through strong coupling in H-aggregated molecules.

Probing the nature of upconversion nanocrystals: instrumentation matters.

Probing the nature of nanocrystalline materials such as the surface state, crystal structure, morphology, composition, optical and magnetic characteristics is a crucial step in understanding their chemical and physical performance and in exploring their potential applications. Upconversion nanocrystals have recently attracted remarkable interest due to their unique nonlinear optical properties capable of converting incident near-infrared photons to visible and even ultraviolet emissions. These optical nanomaterials also hold great promise for a broad range of applications spanning from biolabeling to optoelectronic devices.

Temporal full-colour tuning through non-steady-state upconversion.

Developing light-harvesting materials with tunable emission colours has always been at the forefront of colour display technologies. The variation in materials composition, phase and structure can provide a useful tool for producing a wide range of emission colours, but controlling the colour gamut in a material with a fixed composition remains a daunting challenge. Here, we demonstrate a convenient, versatile approach to dynamically fine-tuning emission in the full colour range from a new class of core-shell upconversion nanocrystals by adjusting the pulse width of infrared laser beams.