In recent years photocatalysis moved into the focus of attention due to its potential application in a broad variety of fields, for example the production of hydrogen and organic compounds like carbohydrates(Nakata & Fujishima, 2012; Wenderich & Mul, 2016). Some of the most common photocatalysts are metal oxides, like the extensively studied TiO2(Guo et al., 2016). Nevertheless, these photoactive metal oxides are limited to a narrow range of wavelengths which can be absorbed and used for photo-electrochemical conversions. In order to broaden the range of the usable light spectra and thereby improving the yield, different pigments which act as photosensitizers can be used.
Goal of the project is to increase the efficiency of photocatalytic agents like TiO2 or WO3. Therefore, we aim to pack photoactive pigments into liposomes built of certain lipids, TELs (“tetraether lipids”), together with electron shuttles, so called quinones. These special lipids as well as electron shuttles are derived from the extremophile archaea Sulfolobus acidocaldarius and they exhibit a high resistance against oxidative stress and extreme pH(Rastädter et al., 2020). By encapsulating pigments together with quinones into TELs and coating the catalysator with these “coloursomes”, the project aims to not only broaden the absorption spectra but also to ensure an efficient transfer of the absorbed energy to the photocatalytic agents.
After the identification of suitable light sensitive pigments, studies testing the solubility and compatibility with subsequent encapsulation experiments are performed. Necessary requirements for the photoactive pigments are a high solubility in solvents which enable optimal requisites for the embedment into liposomes and a high chemical stability. Furthermore, up-to-date analytical methods are developed for an easy and fast quantification and qualification of the chosen pigments, for example HPLC methods (“high pressure liquid chromatography”).
Figure 1: Examples of photoactive pigments as well as illustration of a potential usage of “coloursomes”.
The most promising candidates are used for formulation experiments, the encapsulation into liposomes, “Coloursomes”. Different parameters are tested, for example commonly used lipids, like POPC (“1-palmitoyl-2-oleioyl-glycero-3-phosphocholine”), versus special lipids, TELs, which are highly resistant against oxidative stress and extreme pH.
Finally, the coloursomes are used to coat electrodes made from TiO2 and their potential for photo catalytical redox reaction is evaluated.
Guo, Q., Zhou, C., Ma, Z., Ren, Z., Fan, H., & Yang, X. (2016). Elementary photocatalytic chemistry on TiO 2 surfaces. Chemical Society Reviews, 45(13), 3701–3730. doi.org/10.1039/C5CS00448A, opens an external URL in a new window
Nakata, K., & Fujishima, A. (2012). TiO2 photocatalysis: Design and applications. Journal of Photochemistry and Photobiology C: Photochemistry Reviews, 13(3), 169–189. doi.org/10.1016/j.jphotochemrev.2012.06.001, opens an external URL in a new window
Rastädter, K., Wurm, D. J., Spadiut, O., & Quehenberger, J. (2020). The Cell Membrane of Sulfolobus spp.—Homeoviscous Adaption and Biotechnological Applications. International Journal of Molecular Sciences, 21(11), 3935. doi.org/10.3390/ijms21113935, opens an external URL in a new window
Wenderich, K., & Mul, G. (2016). Methods, Mechanism, and Applications of Photodeposition in Photocatalysis: A Review. Chemical Reviews, 116(23), 14587–14619. doi.org/10.1021/acs.chemrev.6b00327, opens an external URL in a new window