Understanding an efficient light harvesting material

When we fill porous materials with dye molecules of the right size, we obtain useful compounds for solar energy technology. These compounds can transfer solar energy efficiently because pores and channels fit to the dyes “like a glove”. In this way, molecules are forced to stay in line, and energy can easily pass from a molecule to the next one in the line. If we knew in detail the structure of the dye arrays, we’d have better chances to improve these compounds.

Unfortunately, the precise positioning of the molecules inside the pores is very hard to determine.  Recently, we solved this problem for a class of particularly efficient dyes filling the channels of zeolite L.  Key to success was diversity within the team, which favored the combination of multiple techniques involving both experiments and calculations.

The useful properties of these materials arise from the arrangement of dye molecules inside the porous host, which depends on the interactions among molecules and with the porous host. After this work, now it seems we understand a little better these complex materials. Indeed, our dyes are linear, symmetric and fit to the zeolite channels. Yet they adopt a slightly asymmetric positioning to maximize the interactions with the zeolite cations, which stabilize the compound.

Perylene-bisimide dye (cyan) in zeolite L (gray). The purple spheres represent the zeolite potassium cations

This work also suggests some possible ideas to improve these compounds by modifying either the porous container (the “host”) or the dye molecule (the “guest”). In my view, this is also a good example of how computational modeling may help to rationalize experimental results in apparent contrast with each other, yielding a consistent picture of a useful and intriguing material.


Gigli et al. (2018)  “Structure and Host–Guest Interactions of Perylene–Diimide Dyes in Zeolite L Nanochannels”  J. Phys. Chem. C 122, 6, 3401-3418

RSC Twitter conference 2018

The Twitter Poster Conference is an annual event organized by the Royal Society of Chemistry, which consists of sharing chemical research using tweets. You may take part either by tweeting an image of your poster or by commenting on other poster (doing both is better, in my view). As in a traditional conference, you see great research, are asked interesting questions, meet old friends, and come in contact with new colleagues or potential collaborators. Only, at the twitter conference this happens 24 hours non-stop  on global scale; so, it’s a good idea to get there prepared!

I enjoyed so much my 2017 participation that I couldn’t miss the 2018 edition.  Of course, it was awesome, and I am grateful to the organizers, the sessions’ chairs, and all participants, particularly those with whom I interacted.  Indeed, I have learnt new stuff, seen exciting science, been inspired, without moving from my office and paying any conference fees. Really cannot ask for more. Many thanks to all of you!

Tweeting posters is not trivial. For optimal readability,  you should keep into account, for example,  that mobile phones have small screens, and that Twitter images are resized and cropped down – so, it would be better to prepare the poster in landscape format. These and other useful tips can be found in this excellent post. I came across it when the event was over, but it would surely be useful in the future.

Below you can find my poster, illustrating the fruitful collaboration between calculations and diffraction experiments at high-pressure conditions.

Besides water and ethanol in ferrierite (discussed in this post), the poster shows our new work on a host-guest compound of zeolite L and fluorenone dye under high pressure. These host-guest materials have excellent optical properties, useful for many applications, from solar cells to sensing in medical technology. Knowing their structure and working principles could help improve their performances – that’s why we try so hard to understand dye-zeolite composites at molecular level.

Basically fluorenone inside the channels of zeolite L forms a molecular ladder, which is very stable at room conditions because the carbonyl groups of the dye interact very strongly with the potassium cations of the zeolite.

Is this peculiar structure also stable under GPa pressures?

According to experiments and simulations, the answer is apparently yes!  Our composite  maintains its structure, and the interactions between the dye and the zeolite cations become stronger. The exceptional resilience of this material to compression highlights its outstanding mechanical properties. These are important to extend the application of dye-zeolite composites beyond room-pressure conditions.

More about this research can be found in this recently published paper (“Unravelling the High-Pressure Behaviour of Dye-Zeolite L Hybrid Materials”) – which is open access. The high-resolution poster and the green open access version of the ferrierite paper can be downloaded at figshare.