Molecules at Surfaces: What do we really know?

MolSurf_1.png

MatsI’m writing this on the Liverpool Lime Street to Norwich train1, heading back after attending an inspiring and entertaining symposium at the University of Liverpool over the past couple of days. As the title of this post suggests, the symposium had molecules at surfaces as its theme. More than that, however, it was a celebration of the work – and often, the life and times — of Prof. Mats Persson (pictured right), a formidably talented, influential, and yet humble and unimposing theorist who has played a leading role in shaping and defining the research fields in which I work: surface science, nanoscience, and, in particular, scanning probe microscopy. The words “A true gentleman” were repeated regularly through the symposium by Mats’ former PhD students researchers, postdocs, and co-workers, for very good reason.

Organised by George Darling, Matthew Dyer, Jackie Parkinson, and Rasmita Raval, the symposium was one of the best meetings I’ve attended not just recently but throughout my career to date. Ras, a leading light in the UK surface science community who has worked closely with Mats since he arrived in Liverpool in 2006 (and with whom I had the pleasure of collaborating on the Giants Of The Infinitesimal project2), kicked off the symposium with an engaging overview of not just surface science at Liverpool but of the city itself, including, of course, mention of the age-old rivalry between the two primary religious factions: the Reds and the Blues3.

What I particularly enjoyed about the meeting was the blend of world-leading science – an accolade that is often thrown around with wild abandon regardless of the quality of the work, but in this case its usage is absolutely justified —  with personal anecdotes about Mats’ career and those of his (very many) collaborators. It brought home to me yet again just how important social dynamics are to the evolution of science, no matter what howls of outrage this suggestion might provoke in certain quarters. Yes, of course, we do our utmost to be as rigorous, objective, and systematic in our research as possible – well, most of us – but the direction of a field is influenced not just by the science but by the “many-body interactions” of those who do the science. (For those interested in finding out more about the extent to which developments in science are influenced by the sociology of scientists, I thoroughly recommend Harry CollinsGravity’s Kiss; it’s that rarity among science and technology studies (STS) books: a page-turner. Harry is going to be visiting Nottingham in a couple of months to give an invited seminar for The Politics, Perception, and Philosophy of Physics module and I’ll post a lot more about his work then (including this fascinating “Spot The Physicist” experiment.))

A great example of just why the “who” can be as important as the “what” was this morning’s thoroughly entertaining retrospective from Stephen Holloway, erstwhile Head of Chemistry at Liverpool. Stephen covered not just his memories of working with Mats but included fascinating anecdotes about the political landscape, the interpersonal conflicts, and the “Big Names” who influenced the evolution of surface science through his career from the seventies onwards. I’ll spare Stephen’s (and others’) blushes by not revealing the names he mentioned, but his stories of scientists not quite being able to put personal grudges behind them when reviewing or assessing the work of their rivals/nemeses is just one aspect of where the personal and the professional are blurred. (This post from the popular blogger Neuroskeptic emphasises just how entwined these dual aspects can be.)

A running gag throughout the symposium was that many of those presenting owed their tenure/academic positions, either directly or indirectly, to working with Mats. And, indeed, the line-up of presenters read like a “Who’s Who?” of the most respected and influential groups in experimental and theoretical surface science/nanoscience today. Highlights are too many to mention but in addition to Stephen Holloway’s opening act this morning, I particularly enjoyed Wilson Ho’s compelling overview of his pioneering inelastic tunnelling spectroscopy work4 which opened the scientific symposium yesterday afternoon; Leonhard Grill’s always-fascinating insights into the reactions, switching and dynamics of single molecules at surfaces (the “ask Mats” image that opens this post is taken from Leonhard’s presentation);  Richard Palmer’s characteristically absorbing overview of his group’s STM and STEM research; Takashi Kumagi’s next-generation nanoplasmonics using sculpted probes…

molsurf_2-e1568397370242.png

…and Jascha Repp’s engrossing presentation of his group’s exceptionally impressive work on combining ultrafast optics with probe microscopy, enabling an unprecedented increase (by very, very many orders of magnitude) in the temporal resolution of the tunnelling microscope. This is Jascha presenting the working principle of the THz-STM:

MolSurf_3.png

…and one of the stand-out moments of the symposium for me was a video of the internal vibrational dynamics of a single adsorbed molecule, captured with ~ 100 femtosecond temporal resolution using the THz-STM technique. There is no question that the exciting results Jascha presented represent a truly ground-breaking step forward in our ability to probe matter at not just the sub-molecular but the sub-Angstrom scale — perhaps not quite as seismic as the Nobel-winning gravitational wave discovery but, nonetheless, an achievement that will certainly cause considerable ripples across the surface science, nanoscience, and scanning probe communities for many years to come.

Two other talks particularly piqued my interest, due to both the fascinating insights into single molecule behaviour and the alignment with my particular research interests right now. Cyrus Hirjibehedin – formerly of UCL and now at Lincoln Lab, MIT (Cyrus’ move back to the other side of the pond is a major loss to the UK scanning probe/nano/surface/magnetism communities) — gave a typically energetic and compelling presentation on his work on probing and tuning magnetic behaviour in phthalocyanine molecules, while Nicolas Lorente, who manages to combine razor-sharp scientific insights with razor-sharp wit in his presentations, discussed fascinating work on the Jahn-Teller effect (I’ll discuss this in a future post), again in phthalocyanine molecules. We are eagerly awaiting delivery and installation of a Unisoku high magnetic field STM/AFM, kindly funded by EPSRC, and so spin will be a major focus of our group’s research at Nottingham in the coming years. We’ve got such a lot of catching up to do…

Finally, it would be remiss of me to close this overlong post without mentioning a prevailing and exceptionally important theme throughout the symposium: the very close interplay between experiment and theory. Almost every speaker highlighted the “feedback loop” between experimental and theoretical data, but it was David Bird of the University of Bath whose — once again, thoroughly engaging — perspective hammered this point home time and again…

MolSurf_4.png

“Experiments Lead The Way”

MolSurf_5.png

“You learn more when theory doesn’t agree with experiment than when it does”, and…

MolSurf_6.png

“Simple models are best.”

This strong and very healthy experiment-theory interplay contrasts somewhat with other fields of physics, where sometimes experimental data seems to be almost an afterthought, at best, in the generation of new theories

A big thank-you to George, Matthew, Ras, and Jackie for organising such a great meeting. And, of course, enjoy your retirement, Mats!


A service that usually runs via Nottingham — cancellations, strikes, and acts of god/God/gods permitting — and with which I’m exceptionally familiar following very many fun, and occasionally somewhat gruelling, beamtime experiments at the now sadly defunct Daresbury Synchrotron Radiation Source. Daresbury is beside Warrington, which in turn is roughly midway between Liverpool and Manchester. I spent a lot of time (up to three months per year) at Daresbury in the late(-ish) nineties to early noughties, with very many hours whiled away sodden and/or freezing on the Warrington station platform, eyeing the announcement board and waiting for trains to collapse from a delayed-cancelled superposition into a more defined state…

2 Our friend and colleague Tom Grimsey, the powerhouse behind the Giants… project, sadly passed away almost five years ago. He was a wonderful man — full of enthusiasm for, and a hunger to learn about, all things nano, molecular, and atomic. I think that Ras would agree that Giants was such a fun project to work on because of the unique perspective Tom and Theo brought to our science. I couldn’t help but wonder a number of times during the symposium what Tom would have made of the incredible single molecule images presented during the talks.

3 Not being a football fan, I can’t comment further. (My dad was a lifelong Sunderland fanatic and my lack of interest in football may possibly not be entirely unrelated to this fact…)

4 …although I don’t quite yet share Wilson’s confidence in scanning probe microscopy’s ability to “see” intermolecular bonds.

Are the Nanobots Nigh?

The annual Pint Of Science festival, about which I’ve blogged previously and enthusiastically, is taking place this year from May 20 – 22 not only across the UK but in 24 countries worldwide. This, if I remember correctly, is the fourth consecutive year that I’ve done a Pint of Science talk, and I am looking forward immensely to speaking in the Scratching The Surface of Material Science session tonight in Parliament Bar in town, alongside my University of Nottingham colleagues Morgan Alexander and Nesma Aboulkhair. (Encouragingly, all of the Pint of Science events in Nottingham have sold out!)

The title of the talk I’ll give is “Artifical Intelligence at the Nanoscale (or Is The Nanopocalypse Nigh?“, and I’ll focus on recent developments in machine-learning-enabled scanning probe microscopy, of the type described in this Computerphile video put together by Sean Riley last year…

The PoS talk will, however, also roundly criticise the breathless enthusiasm of certain futurist pundits for a nano-enabled future. (OK, I’ll name names. I mean Ray Kurzweil.  We’re going to become immortal by 2045 according to Ray. Because nano.) I had a long, but ultimately exceptionally productive, exchange all the way back in 2004 about the considerable stumbling blocks that stand in the way of the molecular manufacturing nanotech that is a key enabling component of Kurzweil’s “vision”. At the time I didn’t have a blog but Richard Jones very kindly posted the exchange at his Soft Machines blog, and I was rather pleased to find that the debate is still available there.

Soft Machines is an exceptionally good read on everything from nanoscience to R&D policy to general economics and politics. Richard has also written an incisive and compelling critique of Kurzweil and others’ stance on transhumanism. You should give both the blog and the book, “Against Transhumanism: The Delusion of Technological Transcendence“, a read at the earliest opportunity. You won’t regret it.