Having completed my MPhys degree in Chemical Physics at Heriot-Watt University, I moved to Warwick University to begin working on my PhD at the new Warwick Centre for Ultrafast Spectroscopy (WCUS). My research focusses on the photostability of molecular systems with applications to sunscreens. I study these systems through transient electronic absorption spectroscopy to understand how they dissipate excess energy within a solvent environment, in a hope to engineer the next generation of photoprotective species for use in commercial applications.
Away from the laboratory I enjoy weekends away hillwalking and rock climbing in the National Parks.
J. M. Woolley, V.G. Stavros. Science Progress., 2019.
Mycosporine-like amino acids have long been known as a natural form of photoprotection for fungi and cyanobacteria. This review will highlight the key time-resolved experimental and theoretical techniques unravelling their photochemistry and photophysics, and directly link this to their use in commercial skin-care products, namely as sunscreen filters. Three case studies have been selected, each having aided advancement in this burgeoning field of research. We discuss these studies in the context of photoprotection and conclude by evaluating the necessary future steps towards translating the photochemistry and photophysics insight of these nature derived sunscreen filters to commercial application.
J.M. Woolley, J.S. Peters, M.A.P. Turner, G.J. Clarkson, M.D. Horbury, V.G. Stavros. Phys. Chem. Chem. Phys., 2019.
Photoisomerisation has been shown to be an efficient excited-state relaxation mechanism for a variety of nature-based and artificial-based molecular systems. Here we report on the excited-state relaxation dynamics and consequent photostability of a symmetrically functionalised cinnamate by transient electronic absorption spectroscopy, along with complementary computational and steady-state spectroscopy methods. The findings are then discussed in comparison to 2-ethylhexyl-E-4-methoxycinnamate, a structurally related ‘off the shelf’ chemical filter present in commercial sunscreens with a similar absorption profile. The present study allows for a like-for-like comparison between 2-ethylhexyl-E-4-methoxycinnamate and the functionalised cinnamate, driven by the need to enhance solar protection across both the UVA and UVB regions of the electromagnetic spectrum.
J.M. Woolley, M Staniforth, M.D Horbury, G.W. Richings, M.Wills, and V.G.Stavros. J. Phys. Chem. Lett., 2018.
Photoprotection from harmful ultraviolet (UV) radiation exposure is a key problem in modern society. Mycosporine-like amino acids found in fungi, cyanobacteria, macroalgae, phytoplankton, and animals are already presenting a promising form of natural photoprotection in sunscreen formulations. Using time-resolved transient electronic absorption spectroscopy and guided by complementary ab initio calculations, we help to unravel how the core structures of these molecules perform under UV irradiation. Through such detailed insight into the relaxation mechanisms of these ubiquitous molecules, we hope to inspire new thinking in developing next-generation photoprotective molecules.
Efficient intraband hot carrier relaxation in Sn and Pb perovskite semiconductors mediated by strong electron-phonon coupling
M Monti, J.M. Woolley, M Staniforth, A Wijesekara, SX Tao, RMI Bandara, I Jayawardena, A Crocker, E Griffin, SRP Silva, RA Hatton, J Lloyd-Hughes Proc. SPIE 10916
The dynamic increase in terahertz photoconductivity resulting from energetic intraband relaxation was used to track the formation of highly mobile charges in thin films of the tin iodide perovskite Cs1-xRbxSnI3 and compared to the lead based Cs0:05(FA0:83MA0:17)0:95Pb(I0:83Br0:17)3. Energy relaxation times were found to be around 500 fs, comparable to those in GaAs and longer than the ones of the lead-based perovskite (around 300 fs). At low excess energies the efficient intraband relaxation can be understood within the context of the Frohlich electron-phonon interaction. For higher excess energies the photoconductivity rise time lengthens in accordance with carrier injection higher in the bands, or into multiple bands. The findings contribute to the development of design rules for photovoltaic devices capable of extracting hot carriers from perovskite semiconductors.
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