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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 CsPbBr3 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. Experiments on NCs with tailored surface defects show that the balance between such antithetical effects of polymer embedding is determined by the surface defect density of the NCs and provide guidelines for further material optimization.

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 CsPbBr3 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. Experiments on NCs with tailored surface defects show that the balance between such antithetical effects of polymer embedding is determined by the surface defect density of the NCs and provide guidelines for further material optimization.

The use of scintillators for the detection of ionizing radiation is a critical aspect in many fields, including medicine, nuclear monitoring, and homeland security. Recently, lead halide perovskite nanocrystals (LHP-NCs) have emerged as promising scintillator materials. However, the difficulty of affordably upscaling synthesis to the multigram level and embedding NCs in optical-grade nanocomposites without compromising their optical properties still limits their widespread use. In addition, fundamental aspects of the scintillation mechanisms are not fully understood, leaving the scientific community without suitable fabrication protocols and rational guidelines for the full exploitation of their potential. In this work, we realize large polyacrylate nanocomposite scintillators based on CsPbBr3 NCs, which are synthesized via a novel room temperature, low waste turbo-emulsification approach, followed by their in situ transformation during the mass polymerization process. The interaction between NCs and polymer chains strengthens the scintillator structure, homogenizes the particle size distribution and passivates NC defects, resulting in nanocomposite prototypes with luminescence efficiency >90%, exceptional radiation hardness, 4800 ph/MeV scintillation yield even at low NC loading, and ultrafast response time, with over 30% of scintillation occurring in the first 80 ps, promising for fast-time applications in precision medicine and high-energy physics. Ultrafast radioluminescence and optical spectroscopy experiments using pulsed synchrotron light further disambiguate the origin of the scintillation kinetics as the result of charged-exciton and multiexciton recombination formed under ionizing excitation. This highlights the role of nonradiative Auger decay, whose potential impact on fast timing applications we anticipate via a kinetic model.

The use of scintillators for the detection of ionizing radiation is a critical aspect in many fields, including medicine, nuclear monitoring, and homeland security. Recently, lead halide perovskite nanocrystals (LHP-NCs) have emerged as promising scintillator materials. However, the difficulty of affordably upscaling synthesis to the multigram level and embedding NCs in optical-grade nanocomposites without compromising their optical properties still limits their widespread use. In addition, fundamental aspects of the scintillation mechanisms are not fully understood, leaving the scientific community without suitable fabrication protocols and rational guidelines for the full exploitation of their potential. In this work, we realize large polyacrylate nanocomposite scintillators based on CsPbBr3 NCs, which are synthesized via a novel room temperature, low waste turbo-emulsification approach, followed by their in situ transformation during the mass polymerization process. The interaction between NCs and polymer chains strengthens the scintillator structure, homogenizes the particle size distribution and passivates NC defects, resulting in nanocomposite prototypes with luminescence efficiency >90%, exceptional radiation hardness, 4800 ph/MeV scintillation yield even at low NC loading, and ultrafast response time, with over 30% of scintillation occurring in the first 80 ps, promising for fast-time applications in precision medicine and high-energy physics. Ultrafast radioluminescence and optical spectroscopy experiments using pulsed synchrotron light further disambiguate the origin of the scintillation kinetics as the result of charged-exciton and multiexciton recombination formed under ionizing excitation. This highlights the role of nonradiative Auger decay, whose potential impact on fast timing applications we anticipate via a kinetic model.

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 supramolecular capacity of calixarenes towards guests is largely consolidated; in contrast, the synthesis of porous calixarene-based frameworks by covalent bond formation is still a challenge. Our target was to yield 3D polymers and copolymers based on calixarenes for selective gas-capture, endowed with easy pore accessibility and specific sites, and builtviaa straightforward synthetic route. The covalent calixarene frameworks (CXFs) were prepared by the Yamamoto coupling reaction starting from tetrabromo calixarene propoxy- and methoxy-monomers of three stable calixarene (partial cone, effective cone, and 1,3-alternate) conformers and complete post-synthetic deprotection to achieve polar phenolic calixarene derivatives. Moreover, the copolymer of calixarene-based monomers with tetrabromo-tetraphenylmethane exhibited remarkable surface area up to about 3000 m2g−1. Smart architectures endowed with hierarchical porosity from micro- to meso-porosity showed notable sponge-like swellability by CO2, which was captured effectively at room temperature, even in competition with N2, yielding CO2removal in column breakthrough experiments. Indeed, CXFs displayed excellent CO2and CH4energy binding of 35 and 24 kJ mol−1, respectively. Ultramicropore sites were highlighted by Xe capture andin situdetection after a xenon diffusion time of a few milliseconds, by laser-assisted hyperpolarized129Xe NMR, revealing the accessibility of calixarene capsules and the available space. This synthetic route demonstrated the possibility to modulate at will the pore capacity and selectivity, displaying porous frameworks with two distinct pore families, wherein calixarene moieties play the role of small and selective sites. A contractile behavior of the frameworks was observed upon deprotection which produced more polar sites, due to the formation of hydrogen bond networks.

Rotors, motors and switches in the solid state find a favorable playground in porous materials, such as Metal Organic Frameworks (MOFs), thanks to their large free volume, which allows for fast dynamics. We fabricated MOFs with reorientable linkers and benchmark mobility also at very low temperature, to reduce the energy demand for motion-activation and light stimulus-response. In particular, we have realized a fast molecular rotor in the solid state whose rotation speed approaches that of unhindered rotations in organic moieties even at very low temperatures (2 K). The rotors were hosted within the struts of a low-density porous crystalline MOF and energetically decoupled from their surroundings. A key point was the unusual crossed conformation adopted by the carboxylates around the pivotal bond on the rotor axle, generating geometrical frustration and very shallow wells along the circular trajectory. Continuos, unidirectional hyperfast rotation with an energy barrier of 6.2 cal/mol and a high frequency persistent for several turns is achieved (10 GHz below 2 K).[1] Responsive porous switchable framework materials endowed with light-responsive overcrowded olefins, took advantage of both the quantitative photoisomerization in the solid state and the porosity of the framework to reversibly modulate the gas adsorption in response to light. [2] Motors were inserted into metal-organic frameworks wherein two linkers with complementary absorption-emission properties were integrated into the same materials. Therefore, unidirectional motion was achieved by simple exposure to sun-light of the solid particles, which thus behave as autonomous nanodevices.[3] MOF nanocrystals comprising high-Z linking nodes interacting with the ionizing radiation, arranged in an orderly fashion at a nanometric distance from diphenylanthracene ligand emitters showed ultrafast sensitization of the ligand fluorescence, thus supporting the development of new engineered scintillators.[4] References

Using muon-spin spectroscopy, we study the exceptional dynamical properties of rotating molecular struts engineered within a Zn-based metal-organic framework at cryogenic temperatures, where the internal motions of almost any other organic substance are quenched. Muon-spin spectroscopy is particularly suited for this aim, as the experimental evidence suggests several implantation sites for the muons, among which at least one directly onto the rotating moiety. The dynamics of the molecular rotors are characterized by the exceptionally low activation energy EA ∼ 30 cal mol-1. At the same time, we evidence a highly unusual temperature dependence of the dipolar interaction of muons with nuclear magnetic moments on the rotors, suggesting a complex influence of the rotations on the muon implantation and diffusion.

L'attività di ricerca si è occupata della progettazione, sintesi e caratterizzazione di materiali porosi. Diverse linee di ricerca sono state perseguite. Materiali porosi per l'assorbimento selettivo e lo stoccaggio di gas. Le proprietà di una serie di polimeri porosi organici sono state studiate attraverso misure di assorbimento di gas e misure di risonanza magnetica nucleare dello stato solido in presenza di una fase gassosa per comprendere la natura delle interazioni tra le molecole ospiti e le pareti dei canali. In particolare, si è verificata l'elevata energia di interazione tra le molecole di anidride carbonica e gruppi amminici alifatici che genera un'efficiente trasferimento di magnetizzazione tra gli idrogeni del gruppo amminico e il carbonio dell'anidride carbonica. Polimeri iper-reticolati porosi e polimeri organici porosi sono stati studiati mediante assorbimento di metano ad alta pressione (fino a 180 bar) per possibili applicazioni per lo stoccaggio di gas naturale in presenza di reticoli porosi (ANG). Durante il periodo all'estero presso il Bernal Institute sotto la supervisione del Prof. M.J. Zaworotko mi sono occupato dello sviluppo di una serie di framework metallo-organici che presentano flessibilità strutturale. In presenza di un opportuno gas o vapore i reticoli sintetizzati danno luogo a una transizione di fase tra una fase compatta e una fase porosa in maniera repentina. Questo meccanismo è attualmente molto studiato per le possibili applicazioni nell'ambito dello stoccaggio e separazione dei gas. Reticoli metallo-organici contenenti rotori molecolari. Due nuovi reticoli porosi metallo-organici sono stati sviluppati e le loro proprietà di assorbimento e termiche sono state caratterizzate. Inoltre, i due sistemi contengono un rotore molecolare molto mobile anche alle basse temperature come dimostrato da esperimenti di risonanza magnetica nucleare dello stato solido. Materiali porosi per applicazioni nella fotonica. Sono stati sintetizzat, The research activity focused on the design, synthesis and characterization of porous organic and hybrid materials. Porous materials for selective gas adsorption and storage. Tailored porous organic frameworks bearing different functional groups have been investigated via gas adsorption analyses and in situ spectroscopic techniques to understand the interaction between the guest phase and the primary adsorption sites installed on pore walls. Specifically, aliphatic amines interact strongly with carbon dioxide molecules resulting in an isosteric heat of adsorption as high as 54 kJ/mol at low loading and this close-contact interaction has been characterized with 2D heterocorrelated NMR sppectroscopy. Hyper.crosslinked polymers and porous organic frameworks have been synthetized and their performance towards high pressure (up to 180 bar) methane adsorption have been evaluated to assess their potential applications in adsorbed natural gas technology (ANG). During a period at Bernal institute (Limerick, Ireland) under the supervision of Prof. M. J. Zaworotko, I developed novel switching metal-organic frameworks that display guest-induced phase transitions between close phases and a porous open phase. During the close to open phase transitions the coordination sphere of the zinc cations inside the structures changes from a square pyramidal to a tetrahedral geometry. Moreover, the threshold pressure for gas adsorption can be manipulated through a mixed-linker approach. These materials are currently investigated for applications in gas storage and separation. Metal-organic frameworks with intrinsic dynamics. Metal organic frameworks built up with rigid aliphatic linkers have been developed and their adsorptive and thermal properties fully characterized. These materials display ultra-fast rotational dynamic even at very low temperature. An in-depth solid state NMR study has been conducted to understand the fast rotation of the organic strut and the influence of guest species