ISACS2revised399_tcm18-165163

Well, after last night’s veritable feast of fine dining, today it was time to get down to the feast of fine chemistry – and I certainly wasn’t disappointed. Here are just a few of the highlights:

Moungi Bawendi from the Massachussetts Institute of Technology, US, and Hongkun Park from Harvard University, US, kicked off proceedings with a pair of talks about how light interacts with matter.

QuantumOptoelectronics

Bawendi was looking at the real fundamentals of how quantum dots turn light into excitons (separated electrons and positively charged ‘holes’) and back again, whereas Park’s talk was looking at channelling light in the form of surface plasmons through silver nanowires to form the basic building blocks of optical circuits. If they excite the quantum dot with a green laser, the red fluorescence appears not only at the dot but at the far end of the nanowire as well.

lukas_novotny

The last talk of the day was also related to the way electromagnetic radiation interacts with matter, but this time Lukas Novotny from the University of Rochester, US, was thinking a little more generally. He highlighted the way antennas have been used for years at radio and microwave frequencies, and how the same ideas can be applied to light. An example that he gave was bringing Raman scattering spectroscopy and fluorescence microscopy into nanometre resolution – it is well known that gold nanoparticles can be used to boost Raman signals (techniques like surface enhanced Raman spectroscopy, or SERS, rely on this fact. See here for a recent Chemistry World feature article), but what Novotny’s team has done is to take a gold nanoparticle ‘antenna’ attached to a scanning tip that allows them to get a very localised enhancement and really boost the resolution almost to single molecule levels.

From the poster hall
The poster sessions here at ISACS2 are split into two, and today’s concentrated mostly on nanoscience and nanotechnology. The highlight for me was talking to Lynsey Aitken, a PhD student at the University of Strathclyde in Scotland. Her work is aimed at colour-changing sensors for protease enzymes, starting with elastase, which breaks down one of the body’s structural proteins, elastin, and turns up in things like bedsores and diabetic ulcers, preventing the wounds from healing properly.

The idea is pretty straightforward – gold nanoparticles are covered with organic molecules that have three parts: a sulfur containing ring to stick them to the gold surface; an alanine-alanine peptide link, which is the target for the elastase; and an aromatic end group. In this case the group used fluorenylmethyloxycarbonyl (Fmoc) – a common protecting group in peptide synthesis. When the whole thing is assembled, the Fmoc groups should pi-stack with each other, making the nanoparticles aggregate together and giving them a blue colour. But if there’s any elastase around, it will chew up the peptide linkers, releasing the Fmoc groups and allowing the nanoparticles to disperse and turn red, giving a simple visual indication that extra treatment is required.

That about wraps it up for today, tune in tomorrow for another instalment.

Phillip Broadwith

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