Penny Brothers: Exploring surface patterning

13 July, 2015

Story by Kate Hannah

Professor Penny Brothers is as proud and enthusiastic talking about her family as she is her science – her screensaver is a beautiful shot of her climbing Mt Aspiring with her son Tristan. She tells me, with some pleasure, that she’s delighted to be the incoming President of both the New Zealand Institute of Chemistry and the New Zealand Alpine Club in 2016. Similarly, she’s pleased when describing the various projects she has on the go – with colleagues and students – many of which have been facilitated via her involvement with the MacDiarmid Institute.

“In the 3 or 4 years that I’ve been an investigator I think I’ve had more discussions with more scientists from different fields in New Zealand that ever before.” Penny’s vocal in her support for the centre of research excellence model – enabling the “spark that lights things up” through face-to-face, personal engagement with colleagues and collaborators.

She’s an experimental chemist, describing the spectrum of science from fundamental to applied as being “like a piece of string”: while laypeople, government, funders etc. might only see the useful end, if you shorten the string – leaving the basic research behind – you lose out on the length. So for Penny, involvement in the MacDiarmid Institute provides a chance to connect those two ends of the piece of string, linking fundamental synthesis and materials chemistry with potential applications.

She’s working with David Williams on a MBIE-funded project that’s testing the use of magnetic metal complexes as pH sensors, in an attempt to replace the glass electrodes that are currently used in the food and beverage industries with all the attendant risks associated with broken glass. Her face lights up as she describes work she and students are exploring, looking into surface patterning.

Penrose Tiling

The work they’re attempting expands upon the Nobel-winning work of Dan Shechtman, who was awarded the prize in 2011 for his discovery of quasicrystals – crystalline materials with fivefold symmetry. Shechtman’s discovery utterly changed the way in which chemists understand solid matter – “the paradigm, up until then, had been that you could have 2, 3, 4, or 6 fold symmetry.”

Penny wants to explore the aesthetic qualities of molecules, creating pentagonal molecules that will order themselves. “We want to programme them to deposit on a surface to order in Penrose tiling –order, but in an aperiodic pattern.” The beauty of the mathematics that underlies this work is inspiring – “it’s aesthetically really, really pleasing” and draws on fundamental mathematical principles such as the Golden Ratio.

Wooden door on the Blue Mosque

This principle is observed in art and architecture, and reflected in nature – both Shechtman and Penny use classical Islamic architecture and other patterns to illustrate the beauty of fivefold symmetry.  What Penny and her group are doing is developing pentagonal molecules that are programmed to deposit on a surface and self-arrange in Penrose tiling orders, with specified edge-sharing rules that allow the programmed molecules to recognise which other molecules they need to buddy up with to create ordered but aperiodic patterns.

This neat patterning extends to life outside the lab – Penny is gratified at the way in which, some days now, all her family will be at work in the same building at the University of Auckland – her husband Dr David Ware is also in the School of Chemical Sciences, and both their children, Hayley and Tristan Ware, are engineers working in the Photon Factory.

Door from Topkapi Palace, Istanbul, Turkey

Her delight in sharing her research, and explaining it through metaphor permeate a conversation with Penny Brothers; describing her work on porphyrins – “donut-shaped organic compounds”, like heme, the pigment in red blood cells – gives a quick, clear picture of the highly visual, tactile nature of Penny’s relationship with her work.

This set of projects seeks to explore the potential utility of porphyrins and related molecules in surface chemistry, modulating the electronic properties of oxides, or programmed to be sensitive to the presence of small gases, and thus able to modify the oxide surface electronic states to detect air quality changes. 

Before I leave her office, I’m shown a wee vial of beautiful purple, glittery porphyrin crystals.  Penny is also exploring related boron-dipyrromethene (BODIPY) molecules, for use to attach to sugars for human health and polysaccharide materials applications. It’s a wonderful long piece of string – from conceptual, “aesthetically really, really pleasing” chemistry to practical synthetic and materials chemistry for modern applications.