Thursday, November 06, 2008

Two new papers in Nano Letters

Two recent papers in Nano Letters caught my eye.

Kuemmeth et al., "Measurement of Discrete Energy-Level Spectra in Individual Chemically Synthesized Gold Nanoparticles"
One of the first things that I try to teach student in my nano courses is the influence of nanoscale confinement on the electronic properties of metals. We learn in high school chemistry about the discrete orbitals in atoms and small molecules, and how we can think about filling up those orbitals. The same basic idea works reasonably well in larger systems, but the energy difference between subsequent levels becomes much smaller as system size increases. In bulk metals the single-particle levels are so close together as to be almost continuous. In nanoparticles at low temperatures, however, the spacing is reasonably large compared to the available thermal energy that one can do experiments which probe this discrete spectrum. Now, in principle the detailed spectrum depends on the exact arrangement of metal atoms, but in practice one can look at the statistical distribution of levels and compare that distribution with a theory (in this case, "random matrix theory") that averages in some way over possible configurations. This paper is a beautiful example of fabrication skill and measurement technique. There are no big physics surprises here, but the data are extremely pretty.

Xiao et al., "Flexible, stretchable, transparent carbon nanotube thin film loudspeakers"
This is just damned cool. The authors take very thin films of carbon nanotubes and are able to use them as speakers even without making the films vibrate directly. The idea is very simple: convert the acoustic signal into current (just as you would to send it through an ordinary speaker) and run that current through the film. Because of the electrical resistance of the film (low, but nonzero), the film gets hot when the current is at a maximum. Because the film is so impressively low-mass, it has a tiny heat capacity, meaning that small energy inputs result in whopping big temperature changes. The film locally heats the air adjacent to the film surface, launching acoustic waves. Voila. A speaker with no moving parts. This is so simple it may well have real practical implementation. Very clever.

6 comments:

Uncle Al said...

If it transparent and it locally heats air or other fluid it is also an optical modulator through change of refractive index wtih temp. Consider a nanotube membrane disk ringed with electrodes or patterned with ITO.

Anonymous said...

I share the opinion of Doug that the fabrication and the data in the paper of Kuemmeth et al. are nice but that there is no really new physics in the paper. For this reason, I am a bit surprised that the work has been published in Nano Letters.

I do not know what to think about Nano Letters. On one side, the impact factor is high (about 10) and many researchers read the journal. I have the feeling that a paper in Nano Letters is better for a CV than a paper in PRL. On the other side, publishing experimental work on nanoelectronics in PRL has become very difficult in my opinion. Probably, the work of Kuemmeth et al. would not have been accepted in PRL.

Is it better to have a paper on nanoelectronics in PRL or Nano Letters? Do you have an opinion?

Doug Natelson said...

Anon. - My sense is, PRL submissions need to be physics-focused. That's the main reason why my student and I didn't submit our recent paper on simultaneous single-molecule transport + Raman to PRL. As cool and important as (we think) the result was, it really wasn't a physics result. I was concerned that it would languish for months at PRL in the review process and then get bounced because it was "not appropriate". Conversely, my postdoc just submitted a nano-related paper to PRL because the nano is used as a means of doing physics. I do think that PRL has lost some of these kinds of papers to NL in part because NL has tended to be much faster.

In the end the best place to put a paper is somewhere with the appropriate target audience. Having a paper in, e.g., PNAS is a nice achievement, but if people in your field never read it or cite it, the long-term impact isn't there.

DanM said...

Yep, agreed, it's all about citations. Even citations in conference abstracts count, now. Ain't that great?

lzhu said...

Concerning about the comparison between PRL and Nano Letters, my 2-cents worth is Nano Letters is getting far better than PRL now. Personally I have 6 PRLs and 3 Nano Letters, but recently I have the feeling PRL is too political and some referee are way too unreasonable.

Anonymous said...

Nano Letters is also very political, particularly for plasmonics research related articles. We found that in a few occasions, our papers were simply turned down calling them inappropriate, while very similar plasmonic research papers appear in Nano Letters, with much lesser data than we had. I just think the nanooptics related work is just gaurded for publication by a previleged few already a part of the editorial board or their close friends...