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Author:Järvinen, Päivi
Title:Nacre-Mimetic Nanocomposites via the Self-Assembly of Hydrophobin Proteins and Reduced Graphene Oxide
Hydrofobiini-proteiinien ja redusoidun grafeenioksidin itsejärjestyminen reittinä kohti helmiäismimeettisiä komposiittimateriaaleja
Publication type:Master's thesis
Publication year:2013
Pages:[1] + 38      Language:   eng
Department/School:Teknillisen fysiikan laitos
Main subject:Optiikka ja molekyylimateriaalit   (Tfy-125)
Supervisor:Ikkala, Olli
Instructor:Walther, Andeas
OEVS:
Electronic archive copy is available via Aalto Thesis Database.
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Location:P1 Ark Aalto  182   | Archive
Keywords:nanocomposite
reduced graphene oxide
hydrophobin
self-assembly
nanokomposiitti
pelkistetty grafeenioksidi
hydrofobiini
itsejärjestyminen
Abstract (eng): Today's engineering applications require materials that are ever stronger, stiffer, tougher, lighter, cheaper and laden with new, functional properties.
Composite materials are a way of incorporating contrasting properties, such as ductility and mechanical strength, into a single material.
The limited success of traditional composites has made researchers turn to the superb natural composites for inspiration.
One such material is nacre, which demonstrates a rare combination of toughness and strength.
These properties are largely due to the delicate interplay between the reinforcing calcium carbonate platelets and the soft protein layer between them.

The aim of this work was to prepare an ordered nanocomposite with reinforcing particles embedded in a soft protein matrix.
Hydrophobin proteins were chosen as the matrix protein due to their inherent Janus-like character.
Because of a hydrophobic patch formed by eight cysteine groups, hydrophobins adsorb on hydrophobic surfaces in aqueous solutions.
Moreover, the genetic engineering of hydrophobins further increases the tenability of interactions within the protein layer.

Graphene has lately attracted considerable research interest due to its exceptional properties.
Graphene's exceptional mechanical properties make it an excellent candidate for nanocomposite reinforcement.
However, the attempts to transfer these remarkable qualities to composites have yet to reach their full potential.
Here, we investigated the self-assembly of class II hydrophobins and graphene as a pathway to nacre-mimetic composites.

The first challenge of the project was producing a sufficiently large amount of grapheme for composite film preparation.
We settled on the reduction of oxidised graphene sheets via colloidal chemistry.
The reduction process was studied by atomic force microscopy, X-ray photoelectron spectroscopy and X-ray diffraction.
After the reduction, hydrophobin proteins were able to adsorb on the newly hydrophobic reduced graphene oxide sheets.
This process was studied with atomic force microscopy, X-ray photoelectron spectroscopy and X-ray diffraction.

The hydrophobin/reduced graphene oxide composite films were prepared by vacuum filtration.
This way, ordered composite films were obtained.
Film structure was studied by X-ray diffraction, scanning electron microscopy and transmission electron microscopy
Abstract (fin): Entistäkin vahvempia, jäykempiä, sitkeämpiä, kevyempiä ja halvempia materiaaleja kaivataan uudenlaisten sovellutusten toteuttamiseksi.
Eräs tapa yhdistää erilaisia ominaisuuksia samaan materiaaliin ovat komposiittimateriaalit.
Luonnon komposiittimateriaaleissa yhdistyvät taidokkaasti erilaiset, jopa ristiriitaiset ominaisuudet, kuten sitkeys ja vahvuus.
Helmiäisessä näiden kahden harvinaisen ominaisuuden yhdistelmä on pehmeän proteiinimatriisin ja vahvistavien kalsiumkarbonaattihiukkasten vuorovaikutuksen ansiota.

Tämän työn tarkoituksena oli valmistaa järjestynyt nanokomposiittimateriaali, jossa vahvistavat hiukkaset ovat pehmeässä proteiinimatriisissa.
Hydrofobiini-proteiinit valittiin matriisiproteiineiksi niiden amfifiilisen luonteen ansiosta.
Niiden hydrofobinen alue hakeutuu hydrofobisille pinnoille vesiympäristössä, minkä lisäksi hydrofobiinien geneettinen muokkaus voi mahdollistaa proteiinikerroksen sisäisten vuorovaikutusten hienosäädön.

Grafeeni on viime aikoina herättänyt laajaa kiinnostusta tiedemaailmassa.
Erinomaisten mekaanisten ominaisuuksiensa ansiosta sitä on tutkittu nanokomposiittien vahvistavana rakenneosana.
Tässä työssä tutkimme hydrofobiiniproteiinien ja grafeenin itsejärjestymistä tapana valmistaa helmiäismimeettisiä komposiittimateriaaleja.

Projektin ensimmäiseksi haasteeksi muodostui grafeenin tuottaminen riittävän suuressa mittakaavassa.
Päädyimme grafeenioksidin pelkistämiseen kolloidisen kemian keinoin.
Pelkistämisprosessia tutkittiin atomivoimamikroskopialla, röntgenfotoelektronispektroskopialla ja röntgendiffraktiolla.
Pelkistäminen muuttaa hydrofiilisen grafeenioksidin hydrofobiseksi, jolloin hydrofobiinit voivat hakeutua sen pinnalle.
Hydrofobiinien adsorbtiota tutkittiin atomivoimamikroskopialla, röntgenfotoelektronispektroskopialla ja röntgendiffraktiolla.
Hydrofobiini/pelkistetty grafeenioksidi -komposiittikalvot valmistettiin vakuumisuodatuksella.
Tällä tavoin onnistuttiin valmistamaan järjestyneitä komposiittikalvoja.
Kalvojen rakennetta tutkittiin röntgendiffraktiolla, pyyhkäisyelektronimikroskopialla ja läpäisyelektronimikroskopialla.
ED:2013-06-17
INSSI record number: 46889
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