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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.

Cesium lead halide perovskite nanocrystals of general formula CsPbX3 are having tremendous impact on a vast array of technologies requiring strong and tunable luminescence across the visible range and solutions processing. The development of plastic scintillators is just one of the many relevant applications. The syntheses are relatively simple but generally unsuitable to produce a large amount of material of reproducible quality required when moving from proof-of-concept scale to industrial applications. Wastes, particularly large amounts of lead-contaminated toxic and flammable organic solvents, are also an open issue. We describe a simple and reproducible procedure enabling the synthesis of luminescent CsPbX3 nanobricks of constant quality on a scale going from 0.12 to 8 g in a single batch. We also show complete recycling of the reaction wastes, leading to dramatically improved efficiency and sustainability.

Il mio Progetto di dottorato si è incentrato sul potenziamento di strategie sintetiche in soluzione per la produzione di colloidi con applicazioni come materiali colloidali. Esso si è strutturato in due linee di ricerca all’apparenza differenti ma concettualmente interconnesse tra loro. In primo luogo, lo sviluppo di una procedura sintetica di nanocristalli colloidali CsPbBr3 che fosse intrinsecamente scalabile, versatile e affidabile ad ogni scala. L’aspetto fondamentale su cui verte è stata l’introduzione di un turbo-emulsore, il cui utilizzo non è mai stato riportato nel campo dei nanocristalli. Per prima cosa, abbiamo corroborato il suo contributo innovative rispetto all’agitazione magnetica generalmente utilizzata, dimostrando che per volumi superiori al litro, il suo utilizzo diventa indispensabile. Successivamente, abbiamo approfonditamente studiato l’impatto di differenti parametri sintetici sulle proprietà delle risultanti dispersioni colloidali, acquisendo un punto di vista completo e controllabile a nostro favore sul meccanismo con cui avviene il processo: incremento della viscosità del mezzo di reazione, effetto della temperature, sostituzione dei leganti acidi e amminici. Abbiamo inoltre ottimizzato un processo di recupero degli scarti di sintesi che permette di riutilizzarli quasi direttamente per riprodurre la sintesi, senza diminuire la qualità dei materiali ottenuti. Infine, abbiamo testato preliminarmente I materiali in celle solari, evidenziando una maggiore compatibilità con il campo dell’indoor, e abbiamo depositato una domanda di brevetto per scintillatori nanocompositi ultraveloci che preservano le loro proprietà sotto irradiazione da raggi gamma fino ad 1 MGy. La seconda linea di ricerca parallela consiste nello sviluppo di un approccio fotochimico per la trasformazione di micelle formate da surfattanti commerciali in oggetti nanometrici stabilizzati core-shell che possono essere applicati in rilascio controllato di farmaci, catalisi, My research was centred on the enhancement of synthetic strategies via wet methods intended for production of colloids having applications as functional materials. The overall project is composed by two distinct but conceptually connected research lines. Firstly, the development of unprecedentedly scalable, versatile and reliable synthetic strategy for high quality colloidal CsPbBr3 nanocrystals. The key advantage of the method is the original introduction of a high shear homogenizer. We firstly corroborated the improvement with respect to generally used magnetic stirring, showcasing its requirement when working with volumes that exceed 1 L. Successively, we deeply studied the impact of processing parameters on the properties of colloidal dispersions to gain a full insight and completely rule over the synthetic mechanism: increased medium viscosity, temperature, acid and amine ligands substitution during synthesis. We also optimized a waste recovery process that allows to almost directly reuse unreacted species remaining after the synthesis to perform the reaction again and without decreasing output nanocrystals properties. Finally we preliminary tested these materials in solar cells, deducing better compatibility with indoor target and patented a new type of nanocomposite scintillator able to preserve its properties to gamma irradiation doses up to 1 MGy. The second research line deals with the development of photochemical approaches for the transformation of micelles of commercially available surfactants into crosslinked core-shell amphiphilic nano-hosts, intended for applications in controlled release, catalysis and imaging. We exploited the formation of a semi-interpenetrated network between the branched, cheap, commercial tween 80 and the photopolymerized co-surfactant APE-4 (2-(tetrahydropyranyl)oxy tetraethylene glycol methacrylate) to freeze the specific association colloid formed. We firstly optimized efficiency of photopolymerization process under 365 nm i

The photon upconversion based on sensitized triplet–triplet annihilation (sTTA-UC) is a spin-flip mechanism exploited to recover the energy stored on dark triplet states in conjugated systems. In this process, a high-energy fluorescent singlet is created through the collision and fusion of two low-energy triplets belonging to different diffusing molecules. Its high yield in solution under low excitation intensity and noncoherent light highlighted the huge potential of sTTA-UC to provide a breakthrough in solar technologies. However, its diffusion-limited nature restrains its efficiency in the solid state. To overcome this issue, we propose a single-molecule system that is able to host simultaneously more than one triplet, thus enabling a diffusion-free intramolecular TTA. We obtain the first direct demonstration of intramolecular triplet fusion by tailored photoluminescence spectroscopy experiments, thus opening the way to realize a new family of single-molecule upconverters with huge potential in solar and lighting technologies by accessing the natural triplets’ energy reservoir.

Perovskite solar cells (PSCs) are experiencing tremendous interest due to compatibility with solution processing on a wide range of substrates and very high efficiency. The hole transport layer (HTL) plays a fundamental role in such multistack cells. We propose new branched and polymeric organic HTL derivatives with sustainable synthesis and performances exceeding those of Spiro-OMeTAD, the standard in the field.

Perovskite solar cells (PSCs) are experiencing tremendous interest due to compatibility with solution processing on a wide range of substrates and very high efficiency. The hole transport layer (HTL) plays a fundamental role in such multistack cells. We propose new branched and polymeric organic HTL derivatives with sustainable synthesis and performances exceeding those of Spiro-OMeTAD, the standard in the field.

The photon upconversion based on sensitized triplet-triplet annihilation (sTTA-UC) is a spin-flip mechanism exploited to recover the energy stored on dark triplet states in conjugated systems. In this process, a high-energy fluorescent singlet is created through the collision and fusion of two low-energy triplets belonging to different diffusing molecules. Its high yield in solution under low excitation intensity and noncoherent light highlighted the huge potential of sTTA-UC to provide a breakthrough in solar technologies. However, its diffusion-limited nature restrains its efficiency in the solid state. To overcome this issue, we propose a single-molecule system that is able to host simultaneously more than one triplet, thus enabling a diffusion-free intramolecular TTA. We obtain the first direct demonstration of intramolecular triplet fusion by tailored photoluminescence spectroscopy experiments, thus opening the way to realize a new family of single-molecule upconverters with huge potential in solar and lighting technologies by accessing the natural triplets' energy reservoir.