Development of fast 2.5 MeV neutron detectors for high-intensity stray magnetic field environments.

Several small to medium-scale magnetic confinement fusion devices operate using deuterium as fuel. These low neutron rate (108-1010 n/s) devices rely on 2.45 MeV neutron measurements to validate physical models and to assess their performance.

On the Origin of the Light Yield Enhancement in Polymeric Composite Scintillators Loaded with Dense Nanoparticles.

Fast emitting polymeric scintillators are requested in advanced applications where high speed detectors with a large signal-to-noise ratio are needed. However, their low density implies a weak stopping power of high energy radiation and thus a limited light output and sensitivity. To enhance their performance, polymeric scintillators can be loaded with dense nanoparticles (NPs).

Sensitized Triplet-Triplet Annihilation in Nanostructured Polymeric Scintillators Allows for Pulse Shape Discrimination.

Scintillating materials emit light when exposed to ionizing radiation or particles and are used for the detection of nuclear threats, medical imaging, high-energy physics, and other usages. For some of these applications, it is vital to distinguish neutrons and charged particles from γ-rays. This is achievable by pulse shape discrimination (PSD), a time-gated technique, which exploits that the scintillation kinetics can depend on the nature of the incident radiation.

Scintillation Properties of CsPbBr Nanocrystals Prepared by Ligand-Assisted Reprecipitation and Dual Effect of Polyacrylate Encapsulation toward Scalable Ultrafast Radiation Detectors.

Lead halide perovskite nanocrystals (LHP-NCs) embedded in polymeric hosts are gaining attention as scalable and low-cost scintillation detectors for technologically relevant applications. Despite rapid progress, little is currently known about the scintillation properties and stability of LHP-NCs prepared by the ligand assisted reprecipitation (LARP) method, which allows mass scalability at room temperature unmatched by any other type of nanostructure, and the implications of incorporating LHP-NCs into polyacrylate hosts are still largely debated. Here, we show that LARP-synthesized CsPbBr NCs are comparable to particles from hot-injection routes and unravel the dual effect of polyacrylate incorporation, where the partial degradation of LHP-NCs luminescence is counterbalanced by the passivation of electron-poor defects by the host acrylic groups.

Noninvasive Treatment of Alzheimer's Disease with Scintillating Nanotubes.

Effective and accessible treatments for Alzheimer's disease (AD) are urgently needed. Soluble Aβ oligomers are identified as neurotoxic species in AD and targeted in antibody-based drug development to mitigate cognitive decline. However, controversy exists concerning their efficacy and safety.

Energy Partitioning in Multicomponent Nanoscintillators for Enhanced Localized Radiotherapy.

Multicomponent nanomaterials consisting of dense scintillating particles functionalized by or embedding optically active conjugated photosensitizers (PSs) for cytotoxic reactive oxygen species (ROS) have been proposed in the last decade as coadjuvant agents for radiotherapy of cancer. They have been designed to make scintillation-activated sensitizers for ROS production in an aqueous environment under exposure to ionizing radiations. However, a detailed understanding of the global energy partitioning process occurring during the scintillation is still missing, in particular regarding the role of the non-radiative energy transfer between the nanoscintillator and the conjugated moieties which is usually considered crucial for the activation of PSs and therefore pivotal to enhance the therapeutic effect.

Light-accelerated depolymerization catalyzed by Eosin Y.

Retrieving the starting monomers from polymers synthesized by reversible deactivation radical polymerization has recently emerged as an efficient way to increase the recyclability of such materials and potentially enable their industrial implementation. To date, most methods have primarily focused on utilizing high temperatures (typically from 120 °C to 180 °C) to trigger an efficient depolymerization reaction. In this work, we show that, in the presence of Eosin Y under light irradiation, a much faster depolymerization of polymers made by reversible addition-fragmentation chain-transfer (RAFT) polymerization can be triggered even at a lower temperature ( 100 °C).

Design Principles of Hybrid Nanomaterials for Radiotherapy Enhanced by Photodynamic Therapy.

Radiation (RT) remains the most frequently used treatment against cancer. The main limitation of RT is its lack of specificity for cancer tissues and the limited maximum radiation dose that can be safely delivered without damaging the surrounding healthy tissues. A step forward in the development of better RT is achieved by coupling it with other treatments, such as photodynamic therapy (PDT).

Highly luminescent scintillating hetero-ligand MOF nanocrystals with engineered Stokes shift for photonic applications.

Large Stokes shift fast emitters show a negligible reabsorption of their luminescence, a feature highly desirable for several applications such as fluorescence imaging, solar-light managing, and fabricating sensitive scintillating detectors for medical imaging and high-rate high-energy physics experiments. Here we obtain high efficiency luminescence with significant Stokes shift by exploiting fluorescent conjugated acene building blocks arranged in nanocrystals. Two ligands of equal molecular length and connectivity, yet complementary electronic properties, are co-assembled by zirconium oxy-hydroxy clusters, generating crystalline hetero-ligand metal-organic framework (MOF) nanocrystals.

Bypassing the statistical limit of singlet generation in sensitized upconversion using fluorinated conjugated systems.

The photon upconversion based on triplet-triplet annihilation (TTA) is a mechanism that converts the absorbed low-energy electromagnetic radiation into higher energy photons also at extremely low excitation intensities, but its use in actual technologies is still hindered by the limited availability of efficient annihilator moieties. We present here the results obtained by the synthesis and application of two new fluorinated chromophores based on phenazine and acridine structures, respectively. Both compounds show upconverted emission demonstrating their ability as TTA annihilator.

Block Copolymer Stabilized Liquid Nanodroplets Facilitate Efficient Triplet Fusion-Based Photon Upconversion in Solid Polymer Matrices.

Sensitized triplet-triplet annihilation-based photon upconversion is a photophysical process that affords anti-Stokes-shifted emission after annihilation of two metastable triplet excitons of an emitter dye and the formation of a fluorescent singlet state. While this process readily occurs in solutions under conditions where the mobility of the dye molecules is high, particular architectures are required to facilitate efficient energy transfers in solid polymers. One possibility is to incorporate liquid upconverting domains into solid polymer matrices.

Treatment with ROS detoxifying gold quantum clusters alleviates the functional decline in a mouse model of Friedreich ataxia.

Friedreich ataxia (FRDA) is caused by the reduced expression of the mitochondrial protein frataxin (FXN) due to an intronic GAA trinucleotide repeat expansion in the gene. Although FRDA has no cure and few treatment options, there is research dedicated to finding an agent that can curb disease progression and address symptoms as neurobehavioral deficits, muscle endurance, and heart contractile dysfunctions. Because oxidative stress and mitochondrial dysfunctions are implicated in FRDA, we demonstrated the systemic delivery of catalysts activity of gold cluster superstructures (Au-pXs) to improve cell response to mitochondrial reactive oxygen species and thereby alleviate FRDA-related pathology in mesenchymal stem cells from patients with FRDA.

Functionalized Scintillating Nanotubes for Simultaneous Radio- and Photodynamic Therapy of Cancer.

As a model radio-photodynamic therapy (RPDT) agent, we developed a multicomponent nanomaterial by anchoring conjugated chromophores on the surface of scintillating chrysotile nanotubes. Its ultimate composition makes the system a scintillation-activated photosensitizer for the singlet oxygen production. This nanomaterial shows a remarkable ability to enhance the production of singlet oxygen in an aqueous environment, under X-ray irradiation, boosting its production by almost 1 order of magnitude.

Photon upconversion in multicomponent systems: Role of back energy transfer.

Photon upconversion based on sensitized triplet-triplet annihilation in bi-component systems is a multistep process that involves a triplet-triplet energy transfer (ET) from a donor to an acceptor moiety. This is aimed at sensitizing the population of annihilating optically dark triplets that generates the high energy photoluminescence. A large resonance between the involved triplets is usually recommended because it increases the energy gain between absorbed and emitted upconverted photons.

High Photon Upconversion Efficiency with Hybrid Triplet Sensitizers by Ultrafast Hole-Routing in Electronic-Doped Nanocrystals.

Low-power photon upconversion (UC) based on sensitized triplet-triplet annihilation (sTTA) is considered as the most promising upward wavelength-shifting technique to enhance the light-harvesting capability of solar devices. Colloidal nanocrystals (NCs) with conjugated organic ligands have been recently proposed to extend the limited light-harvesting capability of molecular absorbers. Key to their functioning is efficient energy transfer (ET) from the NC to the triplet state of the ligands that sensitize free annihilator moieties responsible for the upconverted luminescence.

Engineering Porous Emitting Framework Nanoparticles with Integrated Sensitizers for Low-Power Photon Upconversion by Triplet Fusion.

The conversion of low-energy light into photons of higher energy based on sensitized triplet-triplet annihilation (sTTA) upconversion is emerging as the most promising wavelength-shifting methodology because it operates efficiently at excitation powers as low as the solar irradiance. However, the production of solid-state upconverters suited for direct integration in devices is still an ongoing challenge owing to the difficulties concerning the organization of two complementary moieties, the triplet sensitizer, and the annihilator, which must interact efficiently. This problem is solved by fabricating porous fluorescent nanoparticles wherein the emitters are integrated into robust covalent architectures.

Triplet-triplet annihilation based photon up-conversion in hybrid molecule-semiconductor nanocrystal systems.

Photon up-conversion based on triplet-triplet annihilation (TTA) exploits the annihilation of optically dark triplets of an organic emitter to produce high-energy singlets that generate high energy emission. In recently proposed hybrid systems, the annihilating triplets are indirectly sensitized by light-harvesting semiconductor colloidal nanocrystals via energy transfer from their capping ligands (h-sTTA). Here, we discuss quantitatively the performance of the h-sTTA up-conversion mechanism in a reference nanocrystal/organic emitter pair, by introducing a kinetic model that points out the relationship between the up-conversion yield and the excitation intensity.

Quasi-thresholdless Photon Upconversion in Metal-Organic Framework Nanocrystals.

Photon upconversion based on sensitized triplet-triplet annihilation ( sTTA) is considered as a promising strategy for the development of light-managing materials aimed to enhance the performance of solar devices by recovering unused low-energy photons. Here, we demonstrate that, thanks to the fast diffusion of excitons, the creation of triplet pairs in metal-organic framework nanocrystals ( nMOFs) with size smaller than the exciton diffusion length implies a 100% TTA yield regardless of the illumination condition. This makes each nMOF a thresholdless, single-unit annihilator.

Bottom-up Synthesis and Self-Assembly of Copper Clusters into Permanent Excimer Supramolecular Nanostructures.

Metal clusters with appropriate molecular ligands have been shown to be suitable subnanometer building blocks for supramolecular architectures with controlled secondary interactions, providing access to physical regimes not achievable with conventional intermolecular motifs. An example is the excimer photophysics exhibited by individual cluster-based superstructures produced by top-down etching of gold nanoparticles. Now, a supramolecular architecture of copper clusters is presented with controlled optical properties and efficient non-resonant luminescence produced via a novel bottom-up synthesis using mild green reductants followed by a ligand exchange reaction and spontaneous supramolecular assembly.

Demonstration of cellular imaging by using luminescent and anti-cytotoxic europium-doped hafnia nanocrystals.

Luminescent nanoparticles are researched for their potential impact in medical science, but no materials approved for parenteral use have been available so far. To overcome this issue, we demonstrate that Eu3+-doped hafnium dioxide nanocrystals can be used as non-toxic, highly stable probes for cellular optical imaging and as radiosensitive materials for clinical treatment. Furthermore, viability and biocompatibility tests on artificially stressed cell cultures reveal their ability to buffer reactive oxygen species, proposing an anti-cytotoxic feature interesting for biomedical applications.

Cascade sensitization of triplet-triplet annihilation based photon upconversion at sub-solar irradiance.

In triplet-triplet annihilation based upconversion, high-energy photons are generated through the annihilation of fluorophore triplets, populated via energy transfer from a light-harvesting sensitizer. However, the absorption band of common sensitizers is narrow, limiting the fraction of recoverable photons. We overcome this issue using a third chromophore as an additional light-harvester in the transparency window between the upconverted luminescence and the sensitizer absorption.

Highly Fluorescent Metal-Organic-Framework Nanocomposites for Photonic Applications.

Metal-organic frameworks (MOFs) are porous hybrid materials built up from organic ligands coordinated to metal ions or clusters by means of self-assembly strategies. The peculiarity of these materials is the possibility, according to specific synthetic routes, to manipulate both the composition and ligands arrangement in order to control their optical and energy-transport properties. Therefore, optimized MOFs nanocrystals (nano-MOFs) can potentially represent the next generation of luminescent materials with features similar to those of their inorganic predecessors, that is, the colloidal semiconductor quantum dots.