University of Twente Student Theses


Rapid exfoliation of layered metal-oxides

Timmerman, M. (2015) Rapid exfoliation of layered metal-oxides.

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Abstract:Nanosheets have potential applications in a wide range of fields. Besides the well-known graphene nanosheets, metal-oxide nanosheets are very promising as well. The nanosheets are obtained via exfoliation of their corresponding layered parent-compounds. The exfoliation process is considered to be slow (weeks), but recent studies in the IMS group suggest that the exfoliation process is driven by an acid-base reaction and is a fast process (minutes) for layered metal oxides. The effect of the reaction time on the morphology and degree of exfoliation is studied of the layered metal-oxide K0.8Ti1.2Fe0.8O4 (KFTO). KFTO is protonated and H0.8Ti1.2Fe0.8O4 (HFTO) is formed. Reaction times with tetrabutylammonium hydroxide (TBAOH, an exfoliating agent) ranging from 30 seconds to 2 weeks are used. The exfoliated nanosheets are deposited on silicon substrates using Langmuir-Blodgett deposition. AFM images are used to determine the morphology and UV-vis spectroscopy is used to determine relations between absorbance and reaction time. XRD spectra and SEM images confirmed the successful synthesis of KFTO and, its protonated form, HFTO. The exfoliation of 30 seconds to two weeks reaction times all yielded densely packed nanosheets, with a height of ~1.1nm. Increasing reaction time led to a decrease in nanosheets size from 6.9μm2 to 3.75μm2 (reaction time of 30 seconds to two weeks). This is explained by the breaking of the nanosheets due to mechanical shaking. The trough area at which the deposition took place decreased from 46cm2 to 31cm2 and the lift-up point decreased from 77cm2 46cm2. This suggests a decrease in concentration of nanosheets, which is explained by restacking of nanosheets into a hybrid state happening at longer reaction times. The absorbance at 253nm wavelength increased from 0,096 to 0,21. Indicating that there is a higher concentration of nanosheets.
Item Type:Essay (Bachelor)
Faculty:TNW: Science and Technology
Subject:58 process technology
Programme:Chemical Engineering BSc (56960)
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