Layer-by-Layer Assembly of Clay-Carbon Nanotube Hybrid Superstructures

Much of the research effort concerning layered materials is directed toward their use as building blocks for the development of hybrid nanostructures with well-defined dimensions and behavior. Here, we report the fabrication through layer-by-layer deposition and intercalation chemistry of a new type of clay-based hybrid film, where functionalized carbon nanotubes are sandwiched between nanometer-sized smectite clay platelets. Single-walled carbon nanotubes (SWCNTs) were covalently functionalized in a single step with phenol groups, via 1,3-dipolar cycloaddition, to allow for stable dispersion in polar solvents. For the production of hybrid thin films, a bottom-up approach combining self-assembly with Langmuir-Schaefer deposition was applied. Smectite clay nanoplatelets act as a structure-directing interface and reaction media for grafting functionalized carbon nanotubes in a bidimensional array, allowing for a controllable layer-by-layer growth at a nanoscale. Hybrid clay/SWCNT multilayer films deposited on various substrates were characterized by X-ray reflectivity, Raman, and X-ray photoelectron spectroscopies, as well as atomic force microscopy

Nanosized hybrid superstructures: synthesis, characterization, and study of properties

The main subject of this doctoral thesis was focused on the design and development of novel nanostructured hybrid materials. The research work was divided into four sections, each of which represents a part of the most important categories of structures and properties. The as prepared superparamagnetic iron oxide nanoparticles were firstly converted into hydrophilic and chemically active through a novel and unconventional process by “trimming” the surface organic coating. The study of their biological activity revealed interesting results for their selective toxic properties against cancer cells. Hydrophilic nanoparticles were also used to develop hybrid superstructures by conjugating boronic acid molecules on the surface. The hybrid nanomaterial was used to bind, via boronic acid, and magnetically remove glucose from aqueous dispersions. The popular family of carbon nanomaterials was represented in this work by three nanostructures with different geometry. Nanodiscs, nanotubes and graphene were chemically activated through covalent surface functionalization and subsequently were used as substrates for lysozyme immobilization. The as produced superstructures displayed nanobiocatalytic properties as well as the biological activity of the enzyme was affected by nanomaterials morphology.Exfoliation of graphene by using fuming nitric acid was also proceeded. According to this simple method, the intercalated nitrate compounds do not interact with the aromatic system. Thus, high-quality, microcrystalline graphene structure, especially after thermal stabilization, remained unaffected and demonstrated extremely high electrical conductivity.Porous carbons with three-dimensional hierarchical porous network were studied at the last section of this work. The hierarchical porous materials were developed by using sucrose as carbon precursor through hard template and ice template strategies. Variation in precursor: template ratio and different combinations of hard templates led to a wide range of hierarchical porous structures with non-identical porous properties.Αντικείμενο της Διδακτορικής Διατριβής αποτέλεσε ο σχεδιασμός και η ανάπτυξη νέων νανοδομημένων υβριδικών υλικών. Οι τέσσερις ενότητες, στις οποίες διαμερίστηκε η έρευνα, συμπεριέλαβαν νανοϋλικά που καλύπτουν μεγάλο εύρος από τις πιο σημαντικές ομάδες δομών και ιδιοτήτων. Τα υπερπαραμαγνητικά νανοσωματίδια κατασκευασμένα από οξείδιο του σιδήρου, τροποποιήθηκαν επιφανειακά με μία καινοτόμο και ανατρεπτική μέθοδο «ψαλιδίσματο» των επιφανειακών μορίων προκειμένου να μετατραπούν σε υδρόφιλα και χημικά δραστικά. Η μελέτη της βιολογικής τους δράσης αποκάλυψε ενδιαφέροντα αποτελέσματα για τον επιλεκτικά τοξικό χαρακτήρα τους απέναντι σε καρκινικά κύτταρα. Τα υδρόφιλα νανοσωματίδια χρησιμοποιήθηκαν, επίσης, για την ανάπτυξη υβριδικής υπερδομής με την επιφανειακή ακινητοποίηση βορονικού οξέος. Το υβριδικό νανοϋλικό χρησιμοποιήθηκε για την δέσμευση, μέσω του βορονικού οξέος, και απομάκρυνση γλυκόζης από υδατικό διάλυμα. Η δημοφιλής οικογένεια των νανοϋλικών άνθρακα εκπροσωπήθηκε σε αυτή την εργασία από τρεις νανοδομές με διαφορετικά γεωμετρικά χαρακτηριστικά. Οι νανοδίσκοι, οι νανοσωλήνες και το γραφένιο ενεργοποιήθηκαν χημικά με επιφανειακή τροποποίηση και στη συνέχεα, λειτούργησαν ως υπόστρωμα για την ακινητοποίηση λυσοζύμης. Οι υπερδομές, που αναπτύχθηκαν, λειτουργούν ως νανοβιοκαταλύτες ενώ οι βιολογικές ιδιότητες του ενζύμου στις υπερδομές συσχετίζονται με το σχήμα του νανοϋλικού. Ακόμα, αναπτύχθηκε αποφυλλοποιημένο γραφένιο με ένθεση νιτρικών ιόντων από ατμίζον νιτρικό οξύ. Αυτή η συνθετική πορεία αφήνει ανεπηρέαστη την αρωματική δομή των γραφενικών φυλλών και σταθερά αποφυλλοποιημένη με την απομάκρυνση των ιόντων. Ως εκ τούτου, το θερμικά σταθεροποιημένο υβριδικό γραφένιο παρουσιάζει εξαιρετικά υψηλή τιμή ηλεκτρικής αγωγιμότητας. Τέλος, μελετήθηκε η ανάπτυξη υλικών άνθρακα με τρισδιάστατο ιεραρχημένο δίκτυο πόρων. Τα υλικά κατασκευάστηκαν από σακχαρόζη ως πρόδρομη ένωση άνθρακα, και συνδυασμό των μεθόδων σκληρού εκμαγείου και εκμαγείου πάγου. Η εφαρμογή των σκληρών εκμαγείων σε διαφορετικές αναλογίες και συνδυασμούς αποκάλυψε τον καθοριστικό ρόλο του συνδυασμού μεγέθους του σκληρού εκμαγείου και της αναλογίας στη δημιουργία μικρο-, μεσο- και μακρο- πόρων. Έτσι, προέκυψε εύρος ιεραρχημένων δομών με διαφορετικά πορώδη χαρακτηριστικά

The Role of Diamines in the Formation of Graphene Aerogels

Aliphatic or aromatic diamines undergo nucleophilic attack on the epoxy groups of graphene oxide under hydrothermal conditions resulting in partial functionalization and partial reduction of the graphenic surface. The overall reaction decreases the solubility of graphene oxide and yields a hydrogel that can be dried to a 3D porous structure classified as an aerogel. This article compares the graphene aerogels derived from different aliphatic and aromatic diamines

L-Cysteine Modified Chitosan Nanoparticles and Carbon-Based Nanostructures for the Intranasal Delivery of Galantamine

The present study evaluates the use of thiolized chitosan conjugates (CS) in combination with two fundamental carbon nanoforms (carbon dots (CDs) and Hierarchical Porous Carbons (HPC)) for the preparation of intranasally (IN) administrated galantamine (GAL) nanoparticles (NPs). Initially, the modification of CS with L-cysteine (Cys) was performed, and the successful formation of a Cys-CS conjugates was verified via 1H-NMR, FTIR, and pXRD. The new Cys-CS conjugate showed a significant solubility enhancement in neutral and alkaline pH, improving CS’s utility as a matrix-carrier for IN drug administration. In a further step, drug-loaded NPs were prepared via solid-oil–water double emulsification, and thoroughly analyzed by SEM, DLS, FTIR and pXRD. The results showed the formation of spherical NPs with a smooth surface, while the drug was amorphously dispersed within most of the prepared NPs, with the exemption of those systems contianing the CDs. Finally, in vitro dissolution release studies revealed that the prepared NPs could prolong GAL’s release for up to 12 days. In sum, regarding the most promising system, the results of the present study clearly suggest that the preparation of NPs using both Cys-CS and CDs results in a more thermodynamically stable drug dispersion, while a zero-order release profile was achieved, which is essential to attain a stable in vivo pharmacokinetic behavior

Hierarchical Porous Carbon—PLLA and PLGA Hybrid Nanoparticles for Intranasal Delivery of Galantamine for Alzheimer’s Disease Therapy

In the present study, poly(l-lactic acid) (PLLA) and poly(lactide-co-glycolide) (PLGA) hybrid nanoparticles were developed for intranasal delivery of galantamine, a drug used in severe to moderate cases of Alzheimer’s disease. Galantamine (GAL) was adsorbed first in hierarchical porous carbon (HPC). Formulations were characterized by FT-IR, which showed hydrogen bond formation between GAL and HPC. Furthermore, GAL became amorphous after adsorption, as confirmed by XRD and differential scanning calorimetry (DSC) studies. GAL was quantified to be 21.5% w/w by TGA study. Adsorbed GAL was nanoencapsulated in PLLA and PLGA, and prepared nanoparticles were characterized by several techniques. Their sizes varied between 182 and 394 nm, with an exception that was observed in nanoparticles that were prepared by PLLA and adsorbed GAL that was found to be 1302 nm in size. DSC thermographs showed that GAL was present in its crystalline state in nanoparticles before its adsorption to HPC, while it remained in its amorphous phase after its adsorption in the prepared nanoparticles. It was found that the polymers controlled the release of GAL both when it was encapsulated alone and when it was adsorbed on HPC. Lastly, PLGA hybrid nanoparticles were intranasally-administered in healthy, adult, male Wistar rats. Administration led to successful delivery to the hippocampus, the brain area that is primarily and severely harmed in Alzheimer’s disease, just a few hours after a single dose