It has been a busy summer for the Oliver group with multiple contributions to several symposia and conferences covering a wide range of topics. Victoria and Tom both presented at INASCON 2017, an international student led nanoscience conference. Marta and Victoria presented their research at the Southern Universities Spectroscopy and Dynamics Group Meeting. Marta detailed her work investigating charge transfer between a model dinucleotide of guanine and thymine using time-resolved infrared spectroscopy, and Victoria presented her 2DIR studies of lead-halide perovskite thin films. Marta also presented and attended the RSC’s Photochemistry Group Meeting in Birmingham. Finally Aditi will be presenting some of her transient X-ray absorption measurements from her work at UC Berkeley and LBNL as part of the Emerging Techniques in Chemical Dynamics Mini-Symposium.
We are happy to welcome Dr. Aditi Bhattacherjee to the Oliver group. Aditi received her PhD from the Tata Institute for Fundamental Research (Mumbai) in 2014, before postdoctoral research with Prof. Steve Leone at UC Berkeley. In the Leone group, Aditi used pioneering extreme-UV and X-ray transient spectroscopies to study photoinitiated non-adiabatic dynamics, including studies of an electrocyclic ring opening reaction (published in Science) and the transition state dynamics of C-I bond fission in allyl iodide. Aditi will be working on multidimensional optical spectroscopies to investigate electronic and vibrational couplings in biological and molecular systems.
Plant photonic bionics: Combining natural photonic structures with carbon nanoparticles to enhance photosynthesis
The project is jointly supervised by Dr Heather Whitney (Life Sciences) and Dr Tom Oliver (Chemistry), with associated academics Dr Carmen Galan, Dr Henkjan Gersen and Dr Ruth Oulton. For more details contact Heather or Tom
|The ability of photosynthetic organisms such as plants and algae to harvest energy sun light through photosynthesis is not only one of the fundamental processes of life on Earth, but can provide inspiration for solar energy capture in artificial light harvesting. Photosynthetic organisms have highly evolved and efficient machineries to capture the incident solar flux. One of the more unexpected mechanisms by which plants interact with light, that may have implications for solar energy transduction, is the presence of structures that lead to plants becoming iridescent– a form of structural colour that changes hue depending on the viewing angle.
The iridescence is produced by materials that are micro-structured on a comparable scale to the wavelength of incident light, and very similar to man-made “photonic crystals”. While iridescence produced by animals such as peacocks and butterflies has been widely studied, iridescence in plants has largely been ignored. Yet, not only do these biological microstructures have properties not seen in “photonic crystals”, but we have also found that they can function to enhance the light harvesting quantum yield in photosynthesis (Jacobs et al., 2016 Nature Plants). Chloroplasts in species of Begonia that grow under extremely low light conditions develop in a unique way and form a photonic crystal. This structure enhances the light harvesting quantum efficiency of the chloroplast – which could be advantageous, as usually only 25% of available light is even initially captured by chlorophyll in the photosynthetic proteins.
However, the advantages that iridescence provides appears to come at a significant cost – the operating efficiency, i.e. final yield of sugars and carbohydrates, of these photonic chloroplasts is lower than that of normal chloroplasts under standard light conditions. The underlying reason for the lower yield of carbon fixation is unclear, but we hypothesize is due to enhanced non-photochemical quenching (NPQ) mechanisms in the iridescent chloroplasts. NPQ is a suite of rapidly reversible processes that allow plants to dissipate excess energy and avoid damage arising from over-exposure to sunlight.
Evolution has therefore not been able to couple the higher initial light harvesting yields afforded by the photonic crystal like properties of iridescent chloroplasts (the plants that evolved these structures only require the slow photosynthesis of deep shade conditions), with a concomitant increased carbon fixation yield, however, studies in a second area of nanomaterials science (bionics) might provide a solution. Plants that take up fluorescent nanoparticles such as carbon dots have been found to have increased photosynthetic rates, potentially due both the enhanced light capture in regions of the solar spectrum not covered by native chlorophyll and carotenoid pigments and/or enhanced rates of electron transport.
Initially this project will use established protocols to quantify the higher quantum efficiency and operating efficiency in photonic chloroplasts that incorporate carbon dots. The molecular structure of these iridescent chloroplasts will be probed using fluorescence lifetime measurements. This latter step will require integration of time-correlated single photon counting detection hardware with a newly established ultrafast laser system.
If successful this could lead to both increases in crop and photobioreactor yield, and provide inspiration for the design of bioinspired solar energy capture devices
|The objectives of this project will be achieved by a multidisciplinary approach, with work taking place in several leading laboratories at the University of Bristol. These include:
| H. Whitney et al., Science 323: 130-133  Giraldo et al., Nature Materials 13: 400-408.  M. Jacobs et al., Nat Plants. 2, 16162 (2016).  S. A. Hill et al., Nanoscale. 8, 18630–18634 (2016).|
We welcome Gary and Venki to the Oliver research group. Gary and Venki will be investigating the excitonic properties of J-aggregate films using transient absorption spectroscopy as part of a Bristol Centre for Nanomaterials theta project. The research is jointly supervised by Dr Sara Núñez-Sánchez in the faculty of Engineering.
Victoria was interviewed by BBC Radio Bristol for the Laura Rawlings show as part of their ‘Cabinet of Curiosities’ segment curated by the Bristol Centre for Functional Nanomaterials. Victoria gave a splendid overview of her PhD research project that involves investigating the molecular mechanisms of photosynthesis. The interview can be found on BBC iPlayer here and starts at 26:20.
Ashley Beckstead from Montana State University and the laboratory of Professor Bern Kohler, is visiting our group for two weeks to investigate the non-adiabatic relaxation dynamics of violacein molecules in various solutions.