Opto-thermal properties of plasmonic metal nanostructures in solution and in polymer matrix for optical limiting protection against cw laser

The development of nanotechnology has provided a variety of noble metal nanostructures with unique optical properties that are useful for different application fields. Metal nanoparticles present strongly enhanced optical properties associated with localized surface plasmon resonance (LSPR): here, the effect on the optical properties of metal nanostructures is investigated by different techniques. The large AuNPs absorption cross section coupled with fast nonradiative decay rate and low radiative decay efficiency make them perfect converter of light into heat: the high temperatures reached can be used for photothermal terapy, light conversion in thermal and photovoltaic devices, but our interest has been focused on optical limiting application against cw laser. The study of the thermal conversion of incoming light could be useful for the protection of the human eye from accidental or intentional damage. A good protection device should be a “smart material” able to activate the protection at high energy with a large dynamic range and in a wide wavelength interval. The last property is especially required in the case of military use, for protection against laser pointing devices or blinding weapons of unpredictable emission wavelength. In this case, passive filters, commonly used for specific wavelengths, are useless because of their selectivity and lack of tuning properties. The irradiation of an optical limiting material with a focused cw laser beam induces energy absorption rapidly converted into a local heating and a temperature gradient corresponding to a refractivity index variation across the sample. In this way, even a flat sample acts as a focusing or defocusing lens and spreads the laser beam. We have studied different aspects of the phenomenon, as described below, to achieve the application in a solid state device with a broadband range of activity and a fast response time. In the first experimental part of this thesis different nanostructures have been synthesized, starting from gold nanoparticles, nanoshells and nanorods with different aspect ratio, in order to obtain plasmonic resonances in a wide range of the visible spectrum. Nanostructures has been then manipulated for the functionalization with a thiolated-fulleropyrrolidine (FULP-SH) to combine the thermal relaxation process with a faster one. A useful material for protection devices should preferably be in the solid state, so a thorough study has been centered on polycarbonate (PC) as matrix because of its good optical qualities. Film production and nanoparticles embedding require a specific study of the functionalization and transfer of nanostructures synthesized in aqueous solvent. We characterized the morphology and their linear optical properties with conventional techniques: transmission electron microscopy (TEM) gives information about the dimension of nanostructures to implement the synthesis, UV-Vis spectroscopy correlates structures with extinction properties and surface enhanced Raman spectroscopy (SERS) of the nanosystems defines the correct functionalization with organic molecules. In the second part of the project we studied and tried to improve the nonlinear optical response of these promising systems in order to obtain different characteristics. Using z-scan technique we define the nature of the defocusing mechanism, confirming the self-defocusing behavior and giving nonlinear efficiency parameters to compare different systems. Optical power limiting measurements give direct information on the protection ability of these systems. Thanks to the easy functionalization of nanostructures we figured out promising properties for a solid state protection device. First we have studied the optical limiting properties of gold nanoparticle solutions identifying a thermal response as the main mechanism. We have then compared these results with those obtained by coupling gold nanoparticles with a thiolated-fulleropyrrolidine. In this way we wanted to combine the thermal process with a faster one, to permit a stronger reduction of transmittance and a better limiting efficiency. Such a strategy has been proved to be effective for improving OL through a quite different mechanism that is activated in a much shorter time. Optical limiting measurements have been conducted on gold nanoparticles embedded in polycarbonate with good results that have been compared to the colloidal solutions. The study of a different matrix for optical limiting studies has been attempt: silk fibroin. This matrix has been selected because of the easier nanoparticles embedding. Furthermore it can be applied for instance in controlled release of drugs, thanks to the biocompatibility and gradual solubility of silk matrix. Preliminary studies discourage the use of this system for optical limiting but different application could be considered. The fibroin-nanoparticles solution can be easily transform to obtain a porous structure: the idea is to employ this matrix as a sensor for liquid samples with SERS characterization, taking advantage of the high porosity and the presence of plasmonic structures. In the last part we tried to compare thermal properties revealed by our systems through cw laser excitation to nonlinear optical properties classically expressed by pulsed laser excitation. Optical limiting related to photoacoustic measurements allow us to discriminate the contribution of the absorption and to choose the best system with higher linear transmittance and lower threshold for nonlinear behavio

Freeze-drying of pharmaceuticals in vials nested in a rack system

The distribution of biopharmaceuticals often requires lyophilisation. The drug product is first frozen and potentially exposed to stress conditions that can be detrimental to its quality. These stresses are also encountered when a drug product has to be distributed under ultra-cold conditions. Adjusting the formulation and/or freezing conditions allows for limiting the impact of these stresses on the final product. This paper investigates two loading configurations, vials directly resting on the shelf and nested in a rack system, and their impact on the freezing and drying behaviour of a sucrose-based formulation. First, two key freezing parameters, i.e., ice nucleation temperature and cooling rate, were studied as they can affect the product behaviour during drying. The product freezing rate and the ice nucleation temperature distribution were affected by the loading configuration, resulting in larger ice crystals in the case of vials nested in a rack system. The analysis was also extended to the drying phase, showing that the loading configuration impacted the product temperature during drying and the overall heat transfer coefficient between the equipment and the product

Klimageographische Inhalte des Geographieunterrichts erfahrungsbasiert verstehen : eine didaktische Rekonstruktion der Passatzirkulation

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Opto-thermal properties of plasmonic metal nanostructures in solution and in polymer matrix for optical limiting protection against cw laser

The development of nanotechnology has provided a variety of noble metal nanostructures with unique optical properties that are useful for different application fields. Metal nanoparticles present strongly enhanced optical properties associated with localized surface plasmon resonance (LSPR): here, the effect on the optical properties of metal nanostructures is investigated by different techniques. The large AuNPs absorption cross section coupled with fast nonradiative decay rate and low radiative decay efficiency make them perfect converter of light into heat: the high temperatures reached can be used for photothermal terapy, light conversion in thermal and photovoltaic devices, but our interest has been focused on optical limiting application against cw laser. The study of the thermal conversion of incoming light could be useful for the protection of the human eye from accidental or intentional damage. A good protection device should be a “smart material” able to activate the protection at high energy with a large dynamic range and in a wide wavelength interval. The last property is especially required in the case of military use, for protection against laser pointing devices or blinding weapons of unpredictable emission wavelength. In this case, passive filters, commonly used for specific wavelengths, are useless because of their selectivity and lack of tuning properties. The irradiation of an optical limiting material with a focused cw laser beam induces energy absorption rapidly converted into a local heating and a temperature gradient corresponding to a refractivity index variation across the sample. In this way, even a flat sample acts as a focusing or defocusing lens and spreads the laser beam. We have studied different aspects of the phenomenon, as described below, to achieve the application in a solid state device with a broadband range of activity and a fast response time. In the first experimental part of this thesis different nanostructures have been synthesized, starting from gold nanoparticles, nanoshells and nanorods with different aspect ratio, in order to obtain plasmonic resonances in a wide range of the visible spectrum. Nanostructures has been then manipulated for the functionalization with a thiolated-fulleropyrrolidine (FULP-SH) to combine the thermal relaxation process with a faster one. A useful material for protection devices should preferably be in the solid state, so a thorough study has been centered on polycarbonate (PC) as matrix because of its good optical qualities. Film production and nanoparticles embedding require a specific study of the functionalization and transfer of nanostructures synthesized in aqueous solvent. We characterized the morphology and their linear optical properties with conventional techniques: transmission electron microscopy (TEM) gives information about the dimension of nanostructures to implement the synthesis, UV-Vis spectroscopy correlates structures with extinction properties and surface enhanced Raman spectroscopy (SERS) of the nanosystems defines the correct functionalization with organic molecules. In the second part of the project we studied and tried to improve the nonlinear optical response of these promising systems in order to obtain different characteristics. Using z-scan technique we define the nature of the defocusing mechanism, confirming the self-defocusing behavior and giving nonlinear efficiency parameters to compare different systems. Optical power limiting measurements give direct information on the protection ability of these systems. Thanks to the easy functionalization of nanostructures we figured out promising properties for a solid state protection device. First we have studied the optical limiting properties of gold nanoparticle solutions identifying a thermal response as the main mechanism. We have then compared these results with those obtained by coupling gold nanoparticles with a thiolated-fulleropyrrolidine. In this way we wanted to combine the thermal process with a faster one, to permit a stronger reduction of transmittance and a better limiting efficiency. Such a strategy has been proved to be effective for improving OL through a quite different mechanism that is activated in a much shorter time. Optical limiting measurements have been conducted on gold nanoparticles embedded in polycarbonate with good results that have been compared to the colloidal solutions. The study of a different matrix for optical limiting studies has been attempt: silk fibroin. This matrix has been selected because of the easier nanoparticles embedding. Furthermore it can be applied for instance in controlled release of drugs, thanks to the biocompatibility and gradual solubility of silk matrix. Preliminary studies discourage the use of this system for optical limiting but different application could be considered. The fibroin-nanoparticles solution can be easily transform to obtain a porous structure: the idea is to employ this matrix as a sensor for liquid samples with SERS characterization, taking advantage of the high porosity and the presence of plasmonic structures. In the last part we tried to compare thermal properties revealed by our systems through cw laser excitation to nonlinear optical properties classically expressed by pulsed laser excitation. Optical limiting related to photoacoustic measurements allow us to discriminate the contribution of the absorption and to choose the best system with higher linear transmittance and lower threshold for nonlinear behaviorLo sviluppo delle nanotecnologie ha fornito una varietà di nanostrutture metalliche con proprietà ottiche uniche utili per diverse applicazioni. Le nanoparticelle metalliche presentano una forte amplificazione delle proprietà ottiche associate al plasmone di risonanza superficiali (LSPR): in questo lavoro abbiamo studiato le proprietà ottiche di nanoparticelle d’oro (AuNPs) con diverse tecniche. La grande cross section di assorbimento delle AuNPs accoppiata con la rapido decadimento non radiativo e la scarsa efficienza di decadimento rendono efficace la conversione di luce in calore: le alte temperature raggiunte possono essere utilizzate per terapia fototermica, conversione luminosa in dispositivi fotovoltaici, ma il nostro interesse si è focalizzato sull’applicazione nella limitazione ottica contro laser in continuo (cw). Lo studio della conversione termica della luce incidente può essere utilizzato per la realizzazione di dispositivi per la protezione dell’occhio contro danni accidentali o intenzionali. Un buon dispositivo di protezione dovrebbe essere un materiale intelligente in grado di attivarsi sopra una certa soglia di intensità, con un ampio intervallo di attività e a diverse lunghezze d’onda. Quest’ultima proprietà è di particolare interesse in ambito militare per la protezione contro dispositivi laser di puntamento o armi accecanti di lunghezze d’onda non note a priori. In questo caso sono i filtri passivi per specifiche lunghezze d’onda attualmente utilizzati risultano inefficaci data la loro alta selettività e scarsa versatilità. L’irraggiamento di un limitatore ottico con un raggio laser cw focalizzato induce un assorbimento dell’energia che viene rapidamente convertito in un riscaldamento locale e la formazione di un gradiente di temperatura che corrisponde ad una variazione di indice di rifrazione attraverso il campione. In questo modo anche un campione piatto agisce come una lente focalizzante o defocalizzante e diffonde la luce. Abbiamo studiato diversi aspetti del fenomeno, come descritto in seguito, per ottenere un dispositivo a stato solido con un ampio intervallo di attività e una risposta rapida. Nella prima parte sperimentale di questa tesi sono state sintetizzate diverse nanostrutture, a partire da nanoparticelle d’oro, nanoshells e nanorods con aspect ratio differenti, al fine di ottenere risonanze plasmoniche in un ampio intervallo dello spettro visibile. Le nanostrutture sono state in seguito funzionalizzate con molecole di fulleropirrolidina tiolata (FULP-SH) per combinare il processo di rilassamento termico con uno più rapido. Un limitatore ottico per un dispositivo di protezione deve essere preferibilmente solido, e quindi lo studio delle proprietà ottiche è stato effettuato anche in matrice, in particolare in polycarbonato (PC), scelto per le sue ottime qualità ottiche. La produzione dei film e l’inglobamento delle nanoparticelle ha richiesto degli studi sulla funzionalizzazione e la stabilizzazione delle nanostrutture sintetizzate in solvente acquoso. Abbiamo caratterizzato la morfologia e le proprietà ottiche lineari con tecniche convenzionali: microscopia a trasmissione elettronica (TEM), che fornisce informazioni sulle dimensioni e la forma delle nanostrutture al fine di implementarne la sintesi, spettroscopia UV-Visibile che correla le strutture con le proprietà di estinzione, e la spettroscopia Raman che ha verificato l’effettiva funzionalizzazione dei sistemi con le molecole organiche. Nella seconda parte del progetto abbiamo studiato le risposte ottiche non lineari di questi promettenti sistemi per poterne modulare le proprietà. Attraverso la tecnica Z-scan siamo stati in grado di definire la natura del meccanismo di defocalizzazione e di ottenere i parametri non lineari che ci hanno permesso di confrontare i nostri risultati con quelli attualmente presenti in letteratura. Misure di limitazione ottica hanno dato informazioni sull’efficacia di protezione dei nostri sistemi. Grazie alla semplicità di funzionalizzazione delle nanoparticelle abbiamo individuato delle nuove e promettenti proprietà per un dispositivo di protezione a stato solido. In primo luogo abbiamo studiato le proprietà di limitazione ottica di nanoparticelle in soluzione per identificare la tipologia di funzionamento. In seguito i risultati sono stati confrontati con quelli ottenuti con nanoparticelle funzionalizzate con FULP-SH. In questo modo abbiamo tentato di associare al processo di rilassamento termico un meccanismo più rapido, in modo da ridurre maggiormente la trasmittanza e migliorare l’efficienza di limitazione. Abbiamo quindi verificato l’efficacia della strategia utilizzata evidenziando un miglioramento della limitazione ottica in un tempo inferiore. Le misure di limitazione ottica eseguite su nanoparticelle in matrice di PC hanno dato ottimi risultati, paragonabili a quelli ottenuti in soluzione. Un primo di studio di matrici differenti si è concentrato sulla fibroina della seta, scelta per la semplicità di inglobamento delle nanoparticelle. Inoltre questo sistema AuNPs-fibroina potrebbe trovare sbocco anche in diverse applicazioni: grazie alla biocompatibilità della matrice ed alla sua solubilità graduale in acqua potrebbe essere usato per il rilascio controllato di farmaci. Studi preliminari scoraggerebbero l’utilizzo di questo sistema nella limitazione ottica ma possono essere comunque considerate altre applicazioni. Le nanoparticelle in fibroina possono infatti essere facilmente trasformate in strutture porose: un’idea potrebbe essere quella di utilizzarle come sensori per campioni in soluzione con caratterizzazione Raman amplificata (SERS), combinando l’alta porosità e la presenza di strutture plasmoniche. Nell’ultima parte abbiamo confrontato le proprietà termiche dei nostri sistemi attraverso studi di fotoacustica che ci hanno permesso di discriminare il contributo assorbitivo dall’estinzione totale e di scegliere il sistema migliore con alta trasmittanza lineare e basse soglie di attivazione nonlinear

Freeze-Drying of Pharmaceuticals in Vials Nested in a Rack System—Part I: Freezing Behaviour

The distribution of biopharmaceuticals often requires either ultra-cold conditions or lyophilisation. In both cases, the drug product is frozen and, thus, exposed to similar stress conditions, which can be detrimental to its quality. However, these stresses can be inhibited or mitigated by a suitable formulation and/or an appropriate freezing design. This paper addresses how the key freezing parameters, i.e., ice nucleation temperature and cooling rate, impact the freezing behaviour of a sucrose-based formulation. The analysis included two loading configurations, vials directly resting on the shelf and nested in a rack system. The loading configuration affected the product freezing rate and the ice nucleation temperature distribution, resulting in larger ice crystals in the case of vials nested in a rack system. SEM micrographs and specific surface area measurements confirmed the different product morphology. Eventually, the different product morphology impacted the bioactivity recovery of lactate dehydrogenase