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Fast photoluminescence and scintillation with a Stokes shift larger than 1 eV is achieved in hetero-ligand metal–organic framework (MOF) crystals comprising inorganic linking nodes and fluorescent conjugated ligands. By finely engineering the MOF composition with the use of ligands with strictly complementary emission and absorption properties and highly delocalized molecular electronic orbitals, the singlet excitons diffusion is enhanced through the ligand framework, fully exploiting both Förster and Dexter energy transfer mechanisms. This allows for the sensitization of energy acceptor ligand fluorescence by ultrafast non-radiative energy transfer with a rate up to the THz range. This efficient antenna effect instantly activates the MOF scintillation with a Stokes shift as large as 1.3 eV in the blue spectral range, matching the highest sensitivity spectral window of the best photodetector available. This is obtained using a minimal doping level of the energy acceptor species, with a consequent elimination of emission re-absorption that allows the achievement of a 500% increment of the MOFs scintillation efficiency and the detection of the radioactive krypton isotope 85Kr from the gas phase with an improved sensitivity compared with the reference material.

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). We investigate the properties of a series of polymeric scintillators by means of photoluminescence and scintillation spectroscopy, comparing standard scintillators with a composite system loaded with dense hafnium dioxide (HfO2) NPs. The nanocomposite shows a scintillation yield enhancement of +100% with an unchanged time response. We provide for the first time an interpretation of this effect, pointing out the local effect of NPs in the generation of emissive states upon interaction with ionizing radiation. The obtained results indicate that coupling fast conjugated emitters with optically inert dense NPs could lead to surpassing the actual limits of pure polymeric scintillators.

I radionuclidi gassosi naturali e antropogenici come il radon, lo xeno, il trizio e gli isotopi del kripton devono essere monitorati per essere gestiti come agenti patogeni, agenti diagnostici radioattivi o indicatori di attività nucleare. I rivelatori di ultima generazione basati su scintillatori liquidi soffrono di una preparazione laboriosa e di una solubilità limitata per i gas, che influiscono sull'accuratezza delle misurazioni. La sfida attuale consiste nel trovare materiali scintillanti solidi in grado di concentrare i gas radioattivi e, contemporaneamente, produrre in modo efficiente luce visibile rivelata con elevata sensibilità. L'elevata porosità, combinata con l'uso di blocchi di costruzione scintillanti in strutture metallo-organiche (MOF), offre la possibilità di soddisfare questi requisiti. Qui viene dimostrata la capacità di un MOF a base di afnio, incorporante dicarbossi-9,10-difenilantracene (DPA) come ligando coniugato scintillante, di rilevare radionuclidi gassosi. Queste strutture metallo-organiche mostrano una scintillazione rapida, una resa di fluorescenza del ∼40% e una porosità accessibile adatta a ospitare atomi e ioni di gas nobili. L'adsorbimento e la rivelazione di radionuclidi 85Kr, 222Rn e 3H sono testati attraverso un dispositivo di nuova concezione basato su una tecnica di coincidenza temporale. La polvere cristallina di MOF a base di afnio ha dimostrato una migliore sensibilità, mostrando una risposta lineare fino a un valore di radioattività inferiore a 1 kBq m-3 per 85Kr, che supera i dispositivi commerciali. Inoltre, è stata anche studiata la possibilità dell’occorrenza di meccanismi di trasferimento di energia all'interno dei cristalli MOFs. In particolare, sono stati sintetizzati MOF etero-ligandi a base di zirconio incorporando una specifica diade di cromofori. In particolare, il colorante terfenile (Tp), che emette raggi UV, è utilizzato come fluoro primario (donore) nell'architettura MOF ed è accoppiato con il D, Natural and anthropogenic gas radionuclides such as radon, xenon, tritium and krypton isotopes must be monitored to be managed as pathogenic agents, radioactive diagnostic agents or nuclear activity indicators. State-of-the-art detectors based on liquid scintillators suffer from laborious preparation and limited solubility for gases, which affect the accuracy of the measurements. The actual challenge is to find solid scintillating materials simultaneously capable of concentrating radioactive gases and efficiently producing visible light revealed with high sensitivity. The high porosity, combined with the use of scintillating building blocks in metal–organic frameworks (MOFs), offers the possibility to satisfy these requisites. Here is demonstrated the capability of a hafnium-based MOF incorporating dicarboxy- 9,10- diphenylanthracene (DPA) as a scintillating conjugated ligand to detect gas radionuclides. Metal–organic frameworks show fast scintillation, a fluorescence yield of ∼40%, and accessible porosity suitable for hosting noble gas atoms and ions. Adsorption and detection of 85Kr, 222Rn and 3H radionuclides are explored through a newly developed device that is based on a time coincidence technique. Hafnium-based Metal–organic framework crystalline powder demonstrated an improved sensitivity, showing a linear response down to a radioactivity value below 1 kBq m−3 for 85Kr, which outperforms commercial devices. Furthermore, here is also analysed the possibility of the occurrence of energy transfer mechanisms inside MOFs crystals. In particular, zirconium-based hetero-ligand MOFs were synthesised by incorporating a specific chromophores dyad. Specifically, the UV emitting terphenyl (Tp) dye is used as primary fluor (i.e. donor) in the MOF architecture and it is coupled with the DPA that acts as wavelength shifter (i.e. acceptor). This strategy has been formulated to drastically reduce the self-absorption phenomenon, leading to higher outputs, better transparency a

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 (i.e. 100 °C). For instance, green light, in conjunction with ppm amounts of Eosin Y, resulted in the accelerated depolymerization of poly(methyl methacrylate) from 16% (thermal depolymerization at 100 °C) to 37% within 1 hour, and finally 80% depolymerization after 8 hours, as confirmed by both 1H-NMR and SEC analyses. The enhanced depolymerization rate was attributed to the activation of a macroCTA by Eosin Y, thus resulting in a faster macroradical generation. Notably, this method was found to be compatible with different wavelengths (e.g. blue, red and white light irradiation), solvents, and RAFT agents, thus highlighting the potential of light to significantly improve current depolymerization approaches.

Natural and anthropogenic gas radionuclides such as radon, xenon, hydrogen and krypton isotopes must be monitored to be managed as pathogenic agents, radioactive diagnostic agents or nuclear activity indicators. State-of-the-art detectors based on liquid scintillators suffer from laborious preparation and limited solubility for gases, which affect the accuracy of the measurements. The actual challenge is to find solid scintillating materials simultaneously capable of concentrating radioactive gases and efficiently producing visible light revealed with high sensitivity. The high porosity, combined with the use of scintillating building blocks in metal–organic frameworks (MOFs), offers the possibility to satisfy these requisites. We demonstrate the capability of a hafnium-based MOF incorporating dicarboxy-9,10-diphenylanthracene as a scintillating conjugated ligand to detect gas radionuclides. Metal–organic frameworks show fast scintillation, a fluorescence yield of ∼40%, and accessible porosity suitable for hosting noble gas atoms and ions. Adsorption and detection of 85Kr, 222Rn and 3H radionuclides are explored through a newly developed device that is based on a time coincidence technique. Metal–organic framework crystalline powder demonstrated an improved sensitivity, showing a linear response down to a radioactivity value below 1 kBq m−3 for 85Kr, which outperforms commercial devices. These results support the possible use of scintillating porous MOFs to fabricate sensitive detectors of natural and anthropogenic radionuclides.

The precise spatial assembly of chromophores inside MOF allows for the rational fabrication of photonic materials with unique photophysical properties. We propose an innovative radioactive gas detector based on highly porous luminescent MOFs.[1] Hf-based MOFs containing diphenyl anthracene (DPA) moieties display high porosity (SBET = 2550 m2 g-1), fast and reversible adsorption of noble gases (proven by combined experimental adsorption and simulation methods) and high photoluminescence and scintillating properties. After exposure to radioactive gases, Hf-DPA displays fast and bright scintillation sensitized by the decay of the radioactive nuclei that allows for their effective detection at ultra-low concentrations. Indeed, 85Kr isotope was detected even at activity as low as 0.3 kBq⋅m3, below the minimum value declared for commercial devices, strongly supporting the development of MOFbased scintillators for radioactive gas detection. Fast composite scintillators were engineered by embedding nanocrystalline Zr-MOFs containing highly luminescent DPA moieties in a continuous polymer matrix.[2] The hybrid bulk scintillators display good light yield, fast time response and an ultrafast scintillation rise time of ~ 50 ps, making them promising materials for time resolved applications. Moreover, nanocrystalline hetero-ligand Zr-based MOFs with high luminescent quantum yield and large Stokes shift emission were engineered by coassembly donor and acceptor chromophores, diphenyl anthracene (DPA) and diphenyl tetracene (DPT) moieties, respectively, to generate reabsorption-free emitters with potential applications in bioimaging, solar luminescent concentrators and bulk scintillators.[3] The two luminescent ligands, with similar molecular length and topology, were homogeneously inserted inside the MOF nanocrystals as proven by 129Xe hyperpolarized NMR experiments. The overlap between the emission frequency of DPA molecule and the absorption spectrum of DPT, and the precise spat

The sensitization of scintillation was investigated in crosslinked polymeric composite materials loaded with luminescent gold clusters aggregates acting as sensitizers, and with organic dye rhodamine 6G as the emitting species. The evolution in time of the excited states population in the systems is described by a set of coupled rate equations, in which steady state solution allowed obtainment of an expression of the sensitization efficacy as a function of the characteristic parameters of the employed luminescent systems. The results obtained indicate that the realization of sensitizer/emitter scintillating complexes is the strategy that must be pursued to maximize the sensitization effect in composite materials.