In recent years, organic semiconductors are gaining more attention as a new class of materials for multifunctional applications. Their distinctive optoelectronic properties allow their use in photovoltaic, photodetection, light emission and photo-electrochemical devices. Newly, conjugated polymers are replacing the common inorganic semiconductor materials also in the biotechnology field, thanks to the high biocompatibility and peculiar mechanical properties. Furthermore, the possibility to exploit their optoelectronic properties makes conjugated polymers ideal exogenous materials for optical modulation of living cells activity. Moreover, the structure of these kinds of polymer is closely alike the chemical structure of retinal, a chromophore molecule contained in rhodopsin proteins, explaining their use in the field of artificial vision. An organic artificial retinal prosthesis using poly(3-hexylthiophene) (P3HT) as the light-absorbing layer has successfully been produced. It has been implanted in the sub-retinal space of blind rats, and it has been well-tolerated over several months. This new device can partially restore visual acuity. The mechanisms involved in the interaction between the polymer and the retina are still not clear. It is believed that the polymer may induce an acidification of the surrounding areas upon photon absorption. Due to the small dimensions in which these peculiar modifications happen, any changes have been difficult to be detected using standard techniques. Plasmonics can offer an innovative probing platform to address the characterization of the polymer/electrolyte solution interface, thanks to the high localization of the light field and the high sensitivity. For this reason, in this work, gold nanorods were functionalized with a molecule sensitive to the pH of the environment. A calibration of this sensor was successfully made. The P3HT/water interface was studied. The results obtained may suggest an increase in the acidity.
I semiconduttori organici hanno recentemente iniziato a sostituire i comuni materiali inorganici nel campo della biotecnologia, grazie all'elevata biocompatibilità e alle peculiari proprietà meccaniche. I polimeri coniugati, inizialmente, sono stati utilizzati come materiali esogeni per la modulazione ottica dell'attività delle cellule. È stato in seguito provato che la struttura chimica di questi polimeri è strettamente correlata a quella del retinale, un cromoforo polienico contenuto nelle proteine della rodopsina, ciò ha suggerito il loro utilizzo anche per applicazioni nel campo della visione artificiale. È stata infatti prodotta con successo una protesi retinica organica usando Poly(3-hexylthiophene) (P3HT) come fotorecettore. Nonostante il suo provato funzionamento in vivo, i meccanismi coinvolti nell'interazione tra il polimero e la retina non sono ancora chiari. Si ritiene però che il polimero possa indurre un’acidificazione delle aree circostanti in seguito all'assorbimento dei fotoni. A causa della zona limitata in cui tale fenomeno può accadere, l’utilizzo di tecniche standard non ha portato risultati sufficienti a provare l’abbassamento locale del pH. La plasmonica è in grado di superare le limitazioni delle tecniche fino ad ora utilizzate grazie all'elevata localizzazione del campo luminoso e sensibilità: nanorods d'oro sono stati per questo motivo funzionalizzati con una molecola sensibile al pH. Una calibrazione di questo sensore è stata eseguita ed è stata studiata l'interfaccia P3HT/acqua. I risultati ottenuti possono suggerire un aumento dell'acidità, nonostante sia richiesto un numero maggiore di misure.
P3HT/water interface pH sensing using functionalized gold nanorods
WAGNER, ALESSANDRO
2018/2019
Abstract
In recent years, organic semiconductors are gaining more attention as a new class of materials for multifunctional applications. Their distinctive optoelectronic properties allow their use in photovoltaic, photodetection, light emission and photo-electrochemical devices. Newly, conjugated polymers are replacing the common inorganic semiconductor materials also in the biotechnology field, thanks to the high biocompatibility and peculiar mechanical properties. Furthermore, the possibility to exploit their optoelectronic properties makes conjugated polymers ideal exogenous materials for optical modulation of living cells activity. Moreover, the structure of these kinds of polymer is closely alike the chemical structure of retinal, a chromophore molecule contained in rhodopsin proteins, explaining their use in the field of artificial vision. An organic artificial retinal prosthesis using poly(3-hexylthiophene) (P3HT) as the light-absorbing layer has successfully been produced. It has been implanted in the sub-retinal space of blind rats, and it has been well-tolerated over several months. This new device can partially restore visual acuity. The mechanisms involved in the interaction between the polymer and the retina are still not clear. It is believed that the polymer may induce an acidification of the surrounding areas upon photon absorption. Due to the small dimensions in which these peculiar modifications happen, any changes have been difficult to be detected using standard techniques. Plasmonics can offer an innovative probing platform to address the characterization of the polymer/electrolyte solution interface, thanks to the high localization of the light field and the high sensitivity. For this reason, in this work, gold nanorods were functionalized with a molecule sensitive to the pH of the environment. A calibration of this sensor was successfully made. The P3HT/water interface was studied. The results obtained may suggest an increase in the acidity.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/152074