Online Seminar Announcement: Thursday 2 July 2020

Dr Nathaniel Davis
Victoria University of Wellington

Luminescent light harvesting chromophores have the potential to improve many optoelectronic technologies, such as photovoltaics, LEDS, lasers and luminescent solar concentrators. Our research into the creation of artificial light-harvesting antenna complexes aims to disrupt the current chromophore technology. The current state of the art chromophores can be split into two types: 1) Organics, which suffer heavily from instability and reabsorption; and 2) Inorganics, which solved many of the problems inherent with organic emitters in terms of stability and reabsorption but require complex surface treatments to improve their luminescent efficiency (LE). We aim to combine the beneficial properties of both these systems into a single hybrid chromophore. This will act to improve the LE of the hybrid particle and reduce reabsorption losses.
The science behind attaching chromophores to nanocrystals and studying the subsequent photophysics is in its infancy. We envision two options forward, that would promote the field, both based on the replacement of ligands on a nanocrystal that offer colloidal stability with ones that add additional optoelectronic properties. 1) Energy transfer from the ligand into the nanocrystal, which will have potential applications for increased solar absorption, efficient transport of excitations, and singlet fission. 2) Coupling a highly luminescent molecule to a nanocrystal, avoids the complex surface passivations (treatments) required by current state-the-art nontoxic emitters and offers the potential for upconversion of light.This talk will look at our recent success with caesium lead halide nanocrystals.

Dr. Guanran Zhang
University of Queensland

Food wastage due to spoiling is a global economic issue and contributes to over-farming and overfishing with real environmental consequences. Smart food packaging is a promising solution to this problem, the idea of which is to utilize responsive sensors that allow direct monitoring of the gasses released from food as it spoils and provides a visual indicator to the consumer. Here we report two dicyanovinyl-fluorene-benzothiadiazole-based fluorescent compounds, K12 and K12b, both of which showed rapid response to biogenic amines via two independent mechanisms. When primary alkyl amines were present in solution, they underwent Michael addition with the dicyanovinyl group of the sensing material, resulting in rapid color change. The reaction products of K12 and K12b with primary amines also showed a decrease and increase in the fluorescence quantum yield, respectively, enabling a unique dual-sensor array with turn-off/turn-on response. In addition, fluorescence quenching via photoinduced hole transfer was observed in the solid-state sensor films with a wide range of primary, secondary and tertiary amines, enabling rapid and sensitive detection of amine vapors. Finally, as a proof-of-concept integrated packaging sensor, soft membranes incorporating K12 and K12b were prepared and showed rapid response to primary amine vapor.