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Evaluation of Amyloid Fibrils as Templates for Photon Upconversion by Sensitized Triplet-Triplet Annihilation
KTH, School of Chemical Science and Engineering (CHE).
KTH, School of Chemical Science and Engineering (CHE).
KTH, School of Chemical Science and Engineering (CHE).
2017 (English)Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesisAlternative title
Utvärdering av Amyloidfibriller som Stödmaterial för Photon Upconversion via Sensitized   Triplet-Triplet Annihilation (Swedish)
Abstract [en]

In the face of global warming and shrinking resources of fossil fuels

the interest in solar energy has increased in recent years. However,

the low energy and cost efficiency of current solar cells has up to

this date hindered solar energy from playing a major role on the

energy market. Photon upconversion is the process in which light

of low energy is converted to high energy photons. Lately, this

phenomenon has attracted renewed interest and ongoing research

in this field mainly focuses on solar energy applications, solar cells

in particular. The aim of this study was to investigate and evaluate

amyloid fibrils as nanotemplates for an upconversion system

based on the dyes platinum octaetylporphyrin (PtOEP) and 9,10-

diphenylanthracene (DPA). This well-known pair of organic dyes

upconverts light in the visible spectrum through a mechanism

known as sensitized triplet-triplet annihilation. Amyloid fibrils

are β-sheet rich protein fibril structures, formed by self-assembly

of peptides.

Amyloid fibrils were prepared from whey protein isolate using heat

and acidic solutions. Dyes were incorporated according to a wellestablished

technique, in which dyes are grinded together with the

protein in solid state prior to fibrillization. Photophysical properties

of pure fibrils and dye-incorporated fibrils were studied using

UV-VIS spectroscopy and fluorescence spectroscopy. Atomic force

microscopy was further employed to confirm the presence of amyloid

fibrils as well as to study fibril structure. Results indicate

that amyloid fibrils may not be the optimal host material for the

upconversion system PtOEP/DPA. It was found that the absorption

and emission spectra of this system overlap to a great deal

with that of the fibrils. Though no upconverted emission clearly

generated by the dye system was recorded, anti-Stokes emission

was indeed observed. Interestingly, this emission appears to be

strongly enhanced by the presence of dyes. It is suggested that

this emission may be attributed to the protein residues rather than

the amyloid structure. Future studies are encouraged to further

investigate these remarkable findings.

Abstract [sv]

Intresset för solceller har ökat under de senaste åren, till stor del

tillföljd av den globala uppvärmningen och de sinande oljeresurserna.

Dagens solceller har dock problem med låg energi- och kostnadseffektivitet,

vilket gör att solenergin än så länge har svårt

att hävda sig på energimarknaden. Photon upconversion är ett

fotofysikaliskt fenomen där fotoner med låg energi omvandlas till

fotoner med hög energi. Den senaste tiden har denna process

fått förnyat intresse och forskningen inom området har ökat, inte

minst med sikte på att integrera processen i solceller och därmed

öka dess effektivitet. Målet med denna studie var att undersöka

huruvida amyloidfibriller kan användas som stomme för ett photon

upconversion-system baserat på platinum-oktaetylporfyrin

(PtOEP) och 9,10-difenylantracen (DPA). Dessa två organiska

färgämnen är ett välkänt par som konverterar synligt ljus med

låg frekvens till mer hög frekvent ljus i det synliga spektrumet,

via en mekanism som kallas sensitized triplet-triplet annihilation.

Amyloidfibriller är proteinbaserade fiberstrukturer med hög andel

β-flak, vilka bildas genom självassociation av peptider.

I denna studie skapades amyloidfibriller av vassleprotein genom

upphettning i sur lösning. Färgämnena inkorporerades enligt

en välbeprövad metod där proteinet mortlas tillsammans med

färgämnena i fast tillstånd, innan fibrilleringsprocessen påbörjas.

De fotofysikaliska egenskaperna hos fibriller med och

utan färgämnen analyserade med UV-VIS samt fluorescensspektroskopi.

Atomkraftsmikroskopi användes för att bekräfta att

fibriller fanns i proven, samt för att studera dess struktur. De

erhållna resultaten antyder att amyloidfibriller inte är ett optimalt

material för systemet PtOEP/DPA, delvis på grund av

att absorptions- och emissionsspektrumet för systemet överlappar

med fibrillernas egna spektrum. Anti-Stokes emission detekterades,

men denna är med stor sannolikhet inte orsakad av färgämnena.

Dock noterades, intressant nog, att denna emission ökar

betydligt i närvaro av färgämnena. En möjlighet är att denna

emission är kopplad till monomerer i proteinet snarare än till fibrillstrukturen,

eftersom emission observerades hos både nativt och

fibrillerat protein. Framtida studier uppmuntras att vidare undersöka

dessa effekter.

Place, publisher, year, edition, pages
2017.
Keywords [en]
photon upconversion, sensitized triplet-triplet annihilation, anti-stokes emission, amyloid fibrils, whey protein
National Category
Physical Chemistry
Identifiers
URN: urn:nbn:se:kth:diva-215658OAI: oai:DiVA.org:kth-215658DiVA, id: diva2:1148715
Available from: 2017-10-12 Created: 2017-10-12 Last updated: 2017-10-12Bibliographically approved

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