La récente découverte des carbon dots (CDs) et de leurs propriétés physico-chimiques exceptionnelles (stabilité chimique, solubilité en milieu aqueux, faible toxicité, biocompatibilité, photoluminescescence et résistance au photoblanchiment) permet d’envisager l’utilisation de ces matériaux carbonés de taille nanométrique dans de nouvelles approches en imagerie biomédicale (fluorescence, IRM...), pour la vectorisation d’acides nucléiques (ADN, siARN) et la délivrance d’actifs thérapeutiques. Dans ce contexte, les objectifs de ce travail de thèse s’articulent autour de deux thématiques bien précises : échantillonnage de nanoparticules carbonées et développement de plateformes théranostiques. Une première partie a ainsi été consacrée à la préparation de carbon dots diversement fonctionnalisés de façon à pouvoir explorer l’espace structural et mener des études de relation structure-toxicité sur différentes lignées de cellules en culture. La seconde partie a été centrée sur l’élaboration d’une plateforme théranostique à base de carbon dots visant, d’une part, à délivrer un acide nucléique de façon intracellulaire et, d’autre part, à permettre un suivi des particules par différentes techniques d’imagerie. / The recent discovery of carbon dots (CDs) and their very interesting phsico-chemical properties (chemical stability, water solubility, low toxicity, biocompatibility, photoluminescence and resistance to photobleaching) make these carbon nanoparticles a powerfull platform for biomedical imaging (fluorescence, MRI...), nucleic acids vectorization (DNA, siRNA) and drug delivery. In this context, the objectives of the thesis work are divided into two different thematics: carbon nanoparticles sampling and development of theranostic platforms. The first part is devoted to the preparation of various functionalized carbon dots to explore the structural space and to manage structure-toxicity relationship studies on different cell lines. The second part is focused on the development of a theranostic platform based on carbon dots in order to promote simultaneously nucleic acids delivery into cells and to monitor them by different imaging techniques.

Disponibiliza??o do conte?do parcial, conforme Termo de Autoriza??o no trabalho. / Submitted by Jos? Henrique Henrique (jose.neves@ufvjm.edu.br) on 2017-02-07T17:34:06Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) larissa_almeida_alves_parcial.pdf: 127946 bytes, checksum: d9a934a0580a850c74fd0e5efc19ebe6 (MD5) / Approved for entry into archive by Rodrigo Martins Cruz (rodrigo.cruz@ufvjm.edu.br) on 2017-03-06T11:41:19Z (GMT) No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) larissa_almeida_alves_parcial.pdf: 127946 bytes, checksum: d9a934a0580a850c74fd0e5efc19ebe6 (MD5) / Made available in DSpace on 2017-03-06T11:41:19Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) larissa_almeida_alves_parcial.pdf: 127946 bytes, checksum: d9a934a0580a850c74fd0e5efc19ebe6 (MD5) Previous issue date: 2016 / Carbon Dots (CDs) sol?veis em ?gua preparados a partir da desidrata??o ?cida da celulose foram utilizados como fotossensibilizadores na polimeriza??o da acrilamida na presen?a do co-iniciador trietanolamina. Os materiais preparados foram caracterizados por diferentes t?cnicas, incluindo MET, IVFT, espectroscopia UV-Vis e fotoluminesc?ncia, voltametria c?clica, TG-MS, titula??o potenciom?trica, entre outras. Os Carbon Dots preparados apresentaram tamanho de part?culas de aproximadamente 2,7 ?0,5nm, com uma superf?cie altamente funcionalizada com grupos funcionais oxigenados (carbox?licos, fen?licos, pironas, etc.) dos quais 65% s?o carbox?licos. Uma vez que estes grupos apresentam pKa ao redor de 4, potenciais zeta negativos foram observados em pHs ?cidos maiores que 4. Por outro lado, as caracteriza??es das suas propriedades ?pticas mostraram que os Carbon Dots apresentam uma absortividade molar (?) de 20,1 Lg-1cm-1 em ?= 254nm e 7,6 Lg-1cm-1 em ?= 360 com fotoluminesc?ncia dependente do comprimento de onda de excita??o e rendimento qu?ntico de 0,6%. Devido ?s suas propriedades, os Carbon Dots foram usados como fotossensibilizadores na polimeriza??o da acrilamida. A cin?tica da rea??o de polimeriza??o foi realizada em pHs 3, 6, 8 e 10, sendo que em pH 8 foi verificada uma maior taxa de convers?o. Neste pH as nanoestruturas possuem um pequeno excesso de carga negativa e a estrutura da trietanolamina est? predominantemente desprotonada (pKa = 7,86) o que facilita a intera??o das duas esp?cies promovendo a forma??o de radicais iniciadores da rea??o. O material fotopolimerizado foi caracterizado e os resultados obtidos s?o t?picos de poliacrilamida. Em adi??o, o material polim?rico obtido foi sol?vel em ?gua sugerindo que o pol?mero seja linear (n?o apresenta reticula??es) com uma massa molar viscosim?trica de at? 3,1x106 Da. A partir dos resultados experimentais obtidos e c?lculos te?ricos da estrutura de ambos, fotossensibilizador e co-iniciador, foi sugerido que devido ? capacidade dos Carbon Dots em receber el?trons em sua estrutura de bandas, sua alta absortividade molar e fotoestabilidade, as nanoestruturas quando excitadas foram capazes de gerar radicais amino, respons?veis pela inicia??o da polimeriza??o, devido ao acoplamento entre seus orbitais de fronteira com os orbitais HOMO-LUMO da trietanolamina. Por fim, os resultados apresentados demonstram uma nova e promissora aplica??o para estas nanopart?culas, com um grande potencial para o desenvolvimento futuro das tecnologias relacionadas ? fotopolimeriza??o. / Disserta??o (Mestrado) ? Programa de P?s-Gradua??o em Qu?mica, Universidade Federal dos Vales do Jequitinhonha e Mucuri, 2016. / Water soluble Carbon Dots (CDs) prepared from the acid dehydration of cellulose were used as photosensitizers in the polymerization of the acrylamide in the presence of co-initiator triethanolamine. The prepared materials were characterized by different techniques, including TEM, FTIR, UV-Vis spectroscopy and photoluminescence, cyclic voltammetry, TG-MS, potentiometric titration, among others. The Carbon Dots prepared showed the particle size of approximately 2.7 ? 0.5nm and a highly functionalized surface with oxygenated functional groups (carboxylic, phenolic, pyrones, etc.) 65% of them carboxylic. Since these groups have pKa around 4, negative zeta potentials were observed uawes of pH hifher than 4. Furthermore, the characterization of their optical properties showed that Carbon Dots exhibit a molar absorptivity (?) de 20.1 Lg-1cm-1 in ?= 254nm e 7.6 Lg-1cm-1 in ?= 360 with photoluminescence dependent of the excitation wavelength and quantum efficiency of 0.6%. Because their properties, the carbon dots were used as photosensitizers in the polymerization of the acrylamide. The kinetics of the polymerization reaction was carried out at pH 3,6,8 and 10, whereas at pH 8 was observed a higher conversion rate. At this pH the nanostructures have a small excess of negative charge and the structure of triethanolamine are predominantly deprotonated ( pKa = 7.86) that facilitates the interaction of the two species promoting the formation of radical reaction initiators. The polymeric material was characterized and the obtained results are typical of polyacrylamide. In addition, the polymerized material was water soluble and suggests that the polymer is linear (no presents crosslinks) and has a molecular weight of approximately 3.1x106 Da. The experimental results and theoretical calculations of the band structure of both, photosensitizer and co-initiator, suggest that due to the ability of Carbon Dots to receive electrons in its band structure, their high molar absorptivity and photostability, these nanostructures when excited were able to generate amine radicals, responsible for initiating polymerization, due to the coupling between their frontier orbitals with the HOMO-LUMO of triethanolamine. Finally, the results show a promising new application for carbon nanostructures in all areas related to photopolymerization.

Data de aprova??o retirada da vers?o impressa do trabalho. / Submitted by Jos? Henrique Henrique (jose.neves@ufvjm.edu.br) on 2018-01-04T19:50:32Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) edgard_ronny_delgado_huamani.pdf: 5898825 bytes, checksum: 78eee370de5fed297b3181e82d98f63d (MD5) / Approved for entry into archive by Rodrigo Martins Cruz (rodrigo.cruz@ufvjm.edu.br) on 2018-01-17T18:40:25Z (GMT) No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) edgard_ronny_delgado_huamani.pdf: 5898825 bytes, checksum: 78eee370de5fed297b3181e82d98f63d (MD5) / Made available in DSpace on 2018-01-17T18:40:25Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) edgard_ronny_delgado_huamani.pdf: 5898825 bytes, checksum: 78eee370de5fed297b3181e82d98f63d (MD5) Previous issue date: 2017 / Neste trabalho, Carbon Dots (CD) oxidados foram preparados a partir de rea??es de desidrata??o/oxida??o ?cida da celulose, e posteriormente desoxigenados em meio alcalino e rea??o com sulfato de hidrazina. As caracteriza??es dos CD foram feitas com Microscopia eletr?nica de Transmiss?o, FTIR, titula??o potenciom?trica, Resson?ncia Magn?tica Nuclear de 13C e espectroscopia UV-Vis e fluoresc?ncia. Os resultados obtidos com estas caracteriza??es mostraram que a amostra oxidada apresenta um tamanho m?dio aproximadamente de 2,7 nm com uma significativa quantidade de grupos funcionais oxigenados ?cidos, dos quais 63% s?o ?cidos carbox?licos. Ap?s as rea??es de modifica??o superficial foi verificado que em meio alcalino ocorre somente uma elimina??o de nanoestruturas mais oxidadas, enquanto que na rea??o com hidrazina ocorre a redu??o de alguns grupos carbox?licos e ep?xidos com forma??o de grupos funcionais hidrazonas. Como consequ?ncia da modifica??o superficial, as propriedades ?pticas dos CD s?o alteradas significativamente. Com a redu??o, o band gap diminui e a energia da emiss?o aumenta, deslocando-se para a regi?o azul do espectro eletromagn?tico. Uma vez caracterizados, a parti??o de todos os CD preparados foi investigada em diferentes Sistemas Aquosos Bif?sicos (SAB), nos quais foram avaliados os efeitos dos c?tions e ?nions dos sais, dos pol?meros e do pH inicial do sistema no coeficiente de parti??o (K). Em adi??o foi avaliado o efeito da modifica??o superficial das nanopart?culas. A rela??o do K com comprimento da linha de amarra??o (CLA), o par?metro termodin?mico dos SAB foi estudado para todos os sistemas. Os resultados obtidos mostraram que a melhor separa??o ocorreu com o sistema PEO1500+sulfato de l?tio+?gua em pH=3 e usando os Carbon Dots reduzidos com hidrazina. O valor do K para este sistema foi de 64,4. Por outro lado, o menor valor de K foi 0,79, foi obtido para o sistema PEG1500+tartarato de s?dio+?gua em pH=6 e usando Carbon Dots oxidados. As an?lises detalhadas das fases superior e inferior de alguns destes sistemas com espectroscopia de fluoresc?ncia mostraram que os SAB s?o capazes, al?m de particionar, separar as nanopart?culas com diferentes propriedades ?pticas, as quais est?o diretamente associadas ?s propriedades superficiais e tamanho de part?culas. Por fim, n?s avaliamos a atividade catal?tica foto-Fentom dos CD na degrada??o do corante ani?nico ?ndigo de carmim e os resultados mostraram que os CD apresentam atividade fotocatal?tica neste sistema. Devido ? alta parti??o verificada para o sistema PEG1500+ sulfato de l?tio+?gua, este foi usado para avaliar a potencialidade de seu uso em cat?lise de transfer?ncia de fase usando CD como fotocatalisador e o corante ?ndigo de carmim como mol?cula modelo. Apesar da complexidade e da dificuldade de caracteriza??o dos produtos da foto-oxida??o no SAB, os resultados obtidos indicam que o sistema testado pode ser usado em rea??es de transfer?ncia de fase fotocatalisadas. Como conclus?o final, acredita-se que os resultados apresentados, em especial, a parti??o/sele??o das nanopart?culas com distintas propriedades ?pticas s?o de extrema import?ncia para o desenvolvimento de novas e eficazes aplica??es dos CD. / Disserta??o (Mestrado) ? Programa de P?s-Gradua??o em Qu?mica, Universidade Federal dos Vales do Jequitinhonha e Mucuri, 2017. / In this work, oxidized Carbon Dots (CD) were prepared by a dehydration/oxidation reaction of cellulose and subsequently deoxygenated in alkaline medium and reaction with hydrazine sulfate. The CD characterizations were made with Transmission Electron Microscopy, FTIR, potentiometric titration. 13C Nuclear Magnetic Resonance, UV-Vis and fluorescence spectroscopy. The results obtained with these characterizations showed that the oxidized sample has an average size of 2.7 nm with a significant amount of acid oxygenated functional groups, of which 63% are carboxylic acids. After the superficial modification reactions, it was verified that in alkaline conditions only one elimination of more oxidized nanostructures occurs, whereas in the reaction with hydrazine the reduction of some carboxylic groups and epoxides with formation of hydrazones functional groups. As a consequence of the surface modification, the optical properties of the CD are significantly changed. The band gap decreases and the emission energy increases, shifting to the blue region of the electromagnetic spectrum. Once characterized, the partitioning of all CD prepared was investigated in differente Aqueous two-phase systems (ATPS), in which the effects of the cations and anions of salts, of the polymers and the initial pH of the system in the partition coefficient (K) were evaluated. In addition, the surface modification effect of the nanoparticles was evaluated. The relationship of K with Tie Line Length (TLL), the thermodynamic parameter of the ATPS was studied for all systems. The results showed that the best separation occurred with the system PEO1500 + lithium sulfate + water at pH = 3 and using the reduced carbon dots with hydrazine. The K value for this system was 64,4. On the other hand, the lowest K value was 0,79, it was obtained for the system PEG1500 + sodium tartrate + water at pH = 6 and using oxidized carbon dots. The detailed analysis of the upper and lower phases of some of these systems with fluorescence spectroscopy showed that the ATPS are capable, in addition to partition, to separate the nanoparticles with different optical properties, which are associated directly to the surface properties and particle size. Finally, we evaluated the photo-Fentom catalytic activity of the CD in the degradation of the anionic anion dye indigo carmine and the results showed that the CD present photocatalytic activity in this system. Due to the high partition found for the PEG1500 + lithium + water sulfate system, it was used to evaluate the potentiality of its use in phase transfer catalysis using CD as a photocatalyst and the indigo carmine dye as a model molecule. Despite the complexity and difficulty of characterizing the photo-oxidation products in ATPS the results indicate that the system tested can be used in photocatalysed phase transfer reactions. As a final conclusion, we believe that the results presented, in particular, the partitioning / selection of nanoparticles with different optical properties are of extreme importance for the new and effective applications of CD.

Carbon dots (CDs) have attracted much attention as an excellent gene/drug delivery and biological imaging agent for early cancer theranostics. In this study, we prepared two series of nanoparticles (NPs), which are composed of (CDs) with a targeting agent, folic acid (FA), and a chemotherapeutic agent Doxorubicin (Dox). All the NPs and their intermediates were characterized using ultraviolet-visible spectroscopy (UV-vis), fluorescence spectroscopy, and Fourier transform-infrared spectroscopy (FT-IR). The drug loading capacity (DLC) and drug loading efficiency (DLE) of two series of FA-CDs-Dox were assessed using UV-vis absorption spectroscopy at the wavelength of 485 nm. Both showed good DLE and DLC results when compared to literature data. In addition, the cumulative release property of Dox from the FA-CDs-Dox complexes were investigated in a pH solution of 7.4.

This study aims to prepare theranostic nanoparticles (NPs) that are expected to increase cancer diagnostics and therapeutic efficacy. We prepared the NPs constituting carbon dots (CDs) as an imaging agent, folic acid as a targeting agent, doxorubicin (DOX), or gemcitabine (GEM) as chemotherapy agents. The NPs include noncovalent FA-CDs-DOX, covalent CDs-FA-DOX, and covalent FA-CDs-GEM. Through ultraviolet-visible spectroscopy, fluorescence spectroscopy, and Fourier transform-infrared spectroscopy, the fabrication of these NPs was confirmed. It was discovered that the high drug loading efficiency is the noncovalent series while the high drug loading capacity is the covalent series The in-vitro pH-dependent drug release data indicate the NPs release more drugs at around pH 5.0 than at pH 7.4. The NPs sizes are between 2-5 nm. The Cell viability was investigated using the Alamar Blue assay and the three NPs complexes exhibited strong therapeutic efficacy against MDA-MB-468 breast cancer cells as compared with CDs-drug.

The main aim of this study is to synthesize theranostic nanoparticles (NPs) that will drastically increase the diagnostics and therapeutic efficacy for cancer. In this research, we had prepared the NPs which constitute carbon dots (CDs), the imaging agent, Folic acid, the targeting agent, and Doxorubicin (DOX) or Gemcitabine (GEM) as the chemotherapy agents. The prepared NPs include noncovalent FA-CDs-DOX, covalent CDs-FA-DOX, and covalent FA-CDs-GEM. The spectroscopy, ultraviolet-visible spectroscopy (UV-vis), fluorescence spectroscopy, and Fourier transform-infrared spectroscopy (FT-IR), were used to confirm the successful fabrication of these complexes. Through UV-vis analysis, the drug loading capacity (DLC) and drug loading efficiency (DLE) of the complexes were determined. The noncovalent series had a higher DLE of about 83% while the covalent series showed higher DLC, 70% on average indicating high drug content. The in-vitro pH-dependent drug release shows that the noncovalent FA-CDs-DOX and the covalent FA-CDs-GEM series release more drugs into the cancer cells (pH of 5.0) than into healthy normal (pH of 7.4). The sizes of NPs were measure around 2-5 nm with Dynamic light Scattering (DLS). The toxicity of CDs, CDs-drug, and FA-CDs-drug on MDA-MB468 breast cancer cell was tested through the methylthiazolytetrazolium (MTT) assay and found that the FA bonded NPs exhibited strong therapeutic efficacy. More pharmaceutical data towards the cancer cells are investigated by our research collaborators – the pharmaceutical department at ETSU and Xavier University at Louisiana.

Despite the recent advances in cancer therapy, the successful detections and treatments of cancer still remains a challenge. The existing strategies for early cancer detection are often limited due to their poor sensitivity and specificity. Also, the non-selective action of therapeutic interventions hinders treatment success. Our research was therefore directed towards the engineering of excellent bi-functionalized nanoparticles (NPs) based on carbon dots (CDs) that would improve early cancer detection and overcome the limitations of chemotherapy. With the actively targeting agent, these new NPs are expected to effectively deliver pharmacological agents directly to cancer cells. CDs are carbon-based NPs that are utilized as bioimaging agents and drug delivery systems (DDS) due to their excellent biocompatibility, non-toxicity, unique imaging, and facile surface modification. Using folic acid (FA) as targeting agent, the prepared novel CDs will carry doxorubicin (DOX) covalently and non-covalently to the cancer cells with overexpressed folate receptors. The CDs were first synthesized via the hydrothermal bottom-up approach using citric acid and ethylenediamine as precursors. The prepared CDs were then functionalized by FA via a non-cleavable peptide bond followed by complexation with DOX covalently or non-covalently to obtain the desired FA-CD-DOX NPs. All the NPs and intermediates were characterized using ultraviolet-visible spectroscopy (UV-vis), fluorescence spectroscopy (FL), and Fourier transform infrared spectroscopy (FTIR). Assessment of the drug loading capacity (DLC) and drug loading efficiency (DLE) with UV-vis indicated that the non-covalent NPs have low DLC but high DLE compared to the relatively low DLE and high DLC of covalent NPs. In vitro drug release studies were also carried out in phosphate buffered saline (PBS) systems with various pH. It was found that even though both non-covalent and covalent complexes released more DOX at pH 5.0 than at pH 7.0, the DOX release rate was faster in the non-covalent FA-CD-DOX NPs compared to the covalent FA-CD-DOX. Based on these results, we project increased accumulation of drugs in the more acidic (pH 4.5-5.0) microenvironment of cancer cells compared to that of normal healthy cells under physiological pH (7.4). This new FA-CD-DOX NPs could work as efficient theranostic systems to detect and treat cancer.

This work focused on engineering bi-functionalized nanoparticles (NPs) based on carbon dots (CDs) to improve early cancer detection and treatment. Therefore, using folic acid (FA) as a targeting agent, the CDs were prepared to deliver high concentrations (HC) of doxorubicin (DOX) and gemcitabine (GEM) covalently and non-covalently to cancer cells. The prepared FA-CDs-DOX/GEM-HC NPs were characterized using ultraviolet-visible spectroscopy, fluorescence spectroscopy, and Fourier transform infrared spectroscopy. Assessment of the drug loading capacity (DLC) and drug loading efficiency (DLE) indicated that the non-covalent NPs have low DLC but high DLE compared to the relatively low DLE and high DLC of covalent NPs. In vitro drug release studies showed that the DOX/GEM release rate was faster at pH 5.0 in the non-covalent FA-CDs-DOX/GEM-HC NPs than covalent. Also, the non-covalent FA-CDs-DOX-HC NPs showed greater percentage cumulative drug release and lower cell viability in the MDA-MB-231 breast cancer cell line compared to covalent.

Η παρούσα εργασία περιλαμβάνει την μελέτη της μη γραμμικής οπτικής απόκρισης διμεταλλικών κραμάτων ευγενών μετάλλων και άλλων μεταλλικών συστημάτων νανοσωματιδίων, είτε περιβεβλημένα με πολυμερή, είτε εγκιβωτισμένα σε μικυλιακά συστήματα συμπολυμερών κατά συστάδες. Τα μέταλλα τα οποία επιλέχθηκαν για την παρασκευή των νανοσωματιδίων ήταν ο χρυσός (Au), ο άργυρος (Ag) και το παλλάδιο (Pd). Τα δύο πρώτα έχουν αποτελέσει τα τελευταία χρόνια αντικείμενο έρευνας σε μορφή κυρίως κολλοειδών διαλυμάτων ή μέσα σε άμορφες μήτρες (π.χ. υάλους) και πολυμερικές μήτρες, καθώς λόγω των εξαιρετικών μη γραμμικοτήτων τους βρίσκουν εφαρμογή σε πληθώρα εφαρμογών της φωτονικής και της οπτο-ηλεκτρονικής. Όσον αφορά τα νανοσωματίδια Pd, οι μη-γραμμικές οπτικές ιδιότητες τους έχουν μελετηθεί ελάχιστα (μόλις μερικές εργασίες στη διεθνή βιβλιογραφία), ενώ είναι η πρώτη φορά που μελετώνται εγκιβωτισμένα σε αμφι-φιλικά συμπολυμερή κατά συστάδες. Στα πλαίσια της παρούσας εργασίας, διερευνήθηκε ο ρόλος του επιφανειακού πλασμονίου στην γραμμική και μη-γραμμική οπτική απόκριση νανοσωματιδίων Au, Ag και Pd, όταν αυτά διεγείρονται με ακτινοβολίες λέιζερ γύρω από την συχνότητα συντονισμού του πλασμονίου, καθώς αναμένεται σημαντική ενίσχυση. Στη συνέχεια αυτής της εργασίας, παρουσιάζονται οι μη γραμμικές οπτικές ιδιότητες άλλων χαμηλοδιάστατων νανοδομών, όπως κβαντικών και ανθρακικών ψηφίδων. Στη περίπτωση αυτών, οι μη γραμμικοί μηχανισμοί που προκαλούν την ενίσχυση της απόκρισης τους είναι διαφορετικοί από αυτούς των μεταλλικών νανοδομών. Η δομή της εργασίας έχει ως ακολούθως: Στα δυο πρώτα κεφάλαια αναφέρονται οι βασικές έννοιες της μη γραμμικής οπτικής και φυσικές διεργασίες που σχετίζονται με αυτή, καθώς και οι πειραματικές τεχνικές Z-scan και Οπτικού Φαινομένου Kerr, που χρησιμοποιήθηκαν για τον χαρακτηρισμό των μη γραμμικών οπτικών ιδιοτήτων των νανοσυστημάτων. Τα επόμενα κεφάλαια είναι αφιερωμένα στα πειραματικά αποτελέσματα που προέκυψαν από την μελέτη των μεταλλικών, ημιαγώγιμων και ανθρακικών νανοϋλικών. Συγκεκριμένα, στο κεφάλαιο 3 γίνεται αναφορά στα πειραματικά αποτελέσματα των νανοσωματιδίων μεταλλικών κραμάτων, τα οποία παρασκευάσθηκαν στο Πανεπιστήμιο του Μόντρεαλ από την ερευνητική ομάδα του καθηγητή κ. Μ. Μeunier. Τα νανοσωματίδια χρυσού-αργύρου είχαν διαφορετικές περιεκτικότητες των δύο μετάλλων (δηλ. ΑuxAg(1-x)), ενώ ανάλογα με τη σύσταση τους παρουσίασαν μεταβλητές οπτικές ιδιότητες, συμπεριλαμβανομένου και της θέση του επιφανειακού πλασμονίου. Η μελέτη των διαλυμάτων πραγματοποιήθηκε για μήκος κύματος διέγερσης στην ορατή φασματική περιοχή (δηλ. 532 nm), πολύ κοντά στο επιφανειακό πλασμόνιο του χρυσού. Η επίδραση του επιφανειακού πλασμονίου στην απόκριση των δυο μετάλλων αλλά και των διαφόρων κραμάτων που μελετήθηκαν ήταν εμφανής, προκαλώντας ενίσχυση με αύξηση της περιεκτικότητας σε χρυσό, ενώ ιδιαίτερο ενδιαφέρον παρουσίασε η συμπεριφορά των κραμάτων υπό διέγερση ns παλμών, καθώς βρέθηκαν να έχουν θεμελιωδώς διαφορετικές ιδιότητες από αυτές του χρυσού και του αργύρου. Στο κεφάλαιο 4, παρουσιάζονται οι μη γραμμικές οπτικές ιδιότητες συστημάτων πολυμερών/παλλαδίου. Μελετήθηκαν δυο ειδών συστήματα, τα υβριδικά μικυλιακά CbzEMAx-b-AEMAy/Pd και τα PVP/Pd, τα οποία παρασκευάσθηκαν στο τμήμα Μηχανολικών Μηχανολογίας και Κατασκευαστικής του Πανεπιστημίου Κύπρου υπό την επίβλεψη της Επ. καθηγήτριας κ. Κρασιά-Χριστοφόρου. Όπως αποδείχθηκε από τα αποτελέσματα της μελέτης, η απόκριση των συστημάτων δεν επηρεάζεται από το πολυμερικό περιβάλλον, ενώ καθορίζεται αποκλειστικά από το μέταλλο. Τέλος, σημαντικό ρόλο φάνηκε να παίζει το μέγεθος των σωματιδίων ή του μεταλλικού πυρήνα αντίστοιχα. Έπειτα, στο κεφάλαιο 5 μελετώνται χαμηλοδιάστατα υβριδικά συστήματα ιωδιούχου μολύβδου. Η σύνθεση των δειγμάτων πραγματοποιήθηκε στο εργαστήριο του Επ. καθηγητή του τμήματος Επιστήμης των Υλικών του Πανεπιστημίου της Πάτρας, κ. Κούτσελα. Η μελέτη πραγματοποιήθηκε για διαλύματα μονοδιάστατων κβαντικών ψηφίδων των οκταεδρικών νανοδομών PbI6 και για αιωρήματα της διδιάστατης δομής (FpAH)2PbI4, η οποία απαρτίζεται από μονοστρωματικά φύλλα των δομικών μονάδων (PbI6)4-. Σε όλες τις πειραματικές συνθήκες, το διδιάστατο σύστημα παρουσίασε μια γιγαντιαία ενίσχυση της μη γραμμικότητας συγκριτικά με το μονοδιάστατο, φτάνοντας τις πέντε τάξεις μεγέθους. Τέλος, στο κεφάλαιο 6 παρουσιάζεται η μη γραμμική οπτική απόκριση και ο οπτικός περιορισμός διαφόρων συστημάτων ανθρακικών ψηφίδων, φέροντας διαφορετικές οργανικές αλυσίδες στην επιφάνεια τους. Η σύνθεση των συστημάτων πραγματοποιήθηκε στο τμήμα Φυσικής του Πανεπιστημίου Ιωαννίνων από τον Επ. Καθηγητή κ. Μπουρλίνο. Οι διαφορές που εντοπίστηκαν μεταξύ των διαφόρων νανοϋλικών ήταν ουσιώδεις, υποδηλώνοντας τη δυνατότητα προσαρμογής και ελέγχου των μη γραμμικών οπτικών ιδιοτήτων, με κατάλληλη τροποποίηση της επιφάνειας των σωματιδίων. / In the present thesis, the third-order nonlinear optical (NLO) properties of metallic nanoparticles, either encapsulated in polymers or in block copolymers, as well as bimetallic nanoparticles are investigated. Among the purposes of this work is to examine metallic nanostructures based on palladium (Pd), which is one of the least studied metals regarding their nonlinear optical response. In this view, single Pd nanoparticles are compared with another class of recently synthesized Pd-based nanomaterials, i.e., Pd micellar nanohybrids. In addition, gold-silver alloyed nanoparticles are examined and compared with their monometallic counterparts, exhibiting substantial differences and potential application in optoelectronic devices and photonic applications. In all cases, the main motivation of this work is to take advantage of the surface plasmon resonance (SPR), located in the ultraviolet or visible spectral area, to enhance/tailor the NLO properties of the metallic/hybrid nanostructures. As a continuation of the low dimensional metallic structures, the NLO response of some carbon-dots and quantum-dots are investigated, aiming to examine the correlation of their optical nonlinearities with their structure and the origin of the NLO enhancement. Therefore, the structure of this thesis is as follows: Initially the basic concepts of nonlinear optics, the physical processes related with it, as well as the physical mechanisms related to the nonlinear refractive index will be presented. Moreover the equations, which describe the nonlinear optical susceptibilities (linear and nonlinear) will be derived. Then, reference will be made to the optical parameters related to the third order optical nonlinearity and to the experimental techniques which were employed for the determination of the nonlinearity, as well as to the procedure followed to derive the nonlinear optical parameters from the acquired experimental data. Moreover, in the beginning of chapter 3 the theory of SPR in metals will be explicitly presented, followed by the experimental results obtained by the Au-Ag nanoalloys. More in detail, AuxAg(1-x) nanoparticles with varying metallic content and optical properties (i.e., SPR) were excited with resonant irradiation conditions (i.e., close to the SPR maximum) both of ps and ns pulse duration. The results demonstrate a straightforward dependence of the NLO response on the gold molar fraction of the alloys, this being attributed to the different band structures of the systems, thus suggesting a mean of tailoring the NLO properties of bimetallic nanostructures. Also, it is shown that under ns laser excitation the nano-alloys exhibit fundamentally different behavior than pure Au and Ag nanoparticles. The samples were produced by fs laser ablation in the University of Montreal by the research group of Prof. Michel Meunier. In chapter 4, the NLO properties of various polymer/Pd systems will be presented. Two different type of materials were investigated: the hybrid micellar CbzeMAx-bAEMAy/Pd and PVP/Pd, which were synthesized in University of Cyprus under the supervision of Prof. Theodora Krasia-Christoforou. As shown, the polymeric environment does not affect the total NLO response, however it can be effectively used to define the size, shape and SPR properties of the nanohybrids. On the contrary, the size of Pd nanoparticles or the micellar core size was found to be determinative for the NLO behavior of the systems. Then, in chapter 5, some low-dimensional hybrid lead-iodide systems are investigated. Specifically, the PbI6 octahedral quantum dots and the two-dimensional (FpAH)2PbI4 structure, consisting of monolayers of (PbI6)4- corner sharing structural units are synthesized in University of Patras, by Prof. Ioannis Koutselas. Under all excitation conditions, the quantum wells were found to exhibit gigantic NLO response in comparison with the quantum dots, reaching even 5 orders of magnitude. Finally, in the last chapter, the NLO response and optical limiting action of a series of carbon-dots, bearing various organic chains attached on their surfaces, will be presented. The carbon-based materials were prepared in the University of Ioannina, by Prof. Athanasios Bourlinos. By comparing the various studied systems, it is shown that the surface passivation is the key to control the NLO behavior of these nanostructures. In this case, of great importance is the sp2/sp3 ratio and consequently the modification of the band structure of carbon-dots, since it can significantly affect their NLO properties.

A new rising star in the carbon nanomaterial family is carbon dots. Carbon dots have received great attention due to their excellent luminescence and low toxicity. In this project, a new carbon dot derived from birch leaves is studied and characterized. The birch leaf carbon dot (BL-CD) exhibits narrow red photoluminescence (peak = 670 nm, full width at half maximum = 23 nm) with a photoluminescence quantum yield of 26% in dilute methanol solution.  The presence of the characteristic peaks of the pigment pheophytin-a in the absorption spectrum and the photoluminescence spectrum of the BL-CD and the absence of a crystal structure together with the narrow and excitation-independent photoluminescence indicate a carbon dot with a non-emissive amorphous structure with emissive molecular sites consisting of the pigment. The photoluminescence quenching of the BL-CDs in solid-state is reduced by the introduction of a hostmaterial. The use of a host enabled the employment of BL-CDs as the emitter in a light-emitting electrochemical cell (LEC). This project paves the way for further development of the environmentally friendly and sustainable BL-CD LEC.