Researcher uses vibrations to identify materials’ composition - it's better than tunneling electron

[Bill USA]

http://www.ethanolproducer.com/articles/12543/researcher-uses-vibrations-to-identify-materialsundefined-composition

A researcher now at the University of Central Florida has developed a new method for identifying materials’ unique chemical “fingerprints” and mapping their chemical properties at a much higher spatial resolution than ever before.

It’s a discovery that could have promising implications for fields as varied as biofuel production, solar energy, opto-electronic devices, pharmaceuticals and medical research.

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For more than two decades, scientists have used atomic force microscopy—a probe that acts like an ultra-sensitive needle on a record player—to determine the surface characteristics of samples at the microscopic scale. A “needle” that comes to an atoms-thin point traces a path over a sample, mapping the surface features at a sub-cellular level.

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A team led by Tetard has come up with a hybrid form of that technology that produces a much clearer chemical image. As described Monday in the journal Nature Nanotechnology, Hybrid Photonic-Nanomechanical Force Microscopy can discern a sample’s topographic characteristics together with the chemical properties at a much finer scale.
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abstract: Opto-nanomechanical spectroscopic material characterization in Nature: Nanotechnology

The non-destructive, simultaneous chemical and physical characterization of materials at the nanoscale is an essential and highly sought-after capability. However, a combination of limitations imposed by Abbe diffraction, diffuse scattering, unknown subsurface, electromagnetic fluctuations and Brownian noise, for example, have made achieving this goal challenging. Here, we report a hybrid approach for nanoscale material characterization based on generalized nanomechanical force microscopy in conjunction with infrared photoacoustic spectroscopy. As an application, we tackle the outstanding problem of spatially and spectrally resolving plant cell walls. Nanoscale characterization of plant cell walls and the effect of complex phenotype treatments on biomass are challenging but necessary in the search for sustainable and renewable bioenergy. We present results that reveal both the morphological and compositional substructures of the cell walls. The measured biomolecular traits are in agreement with the lower-resolution chemical maps obtained with infrared and confocal Raman micro-spectroscopies of the same samples. These results should prove relevant in other fields such as cancer research, nanotoxicity, and energy storage and production, where morphological, chemical and subsurface studies of nanocomposites, nanoparticle uptake by cells and nanoscale quality control are in demand.

[div class="excerpt" style="width:390px;"]Figure 2: Experimental set-up of HPFM



Various photon sources (via the photoacoustic channel) and multiple waveform generators (via the PZT, lead zirconate titante) supply mechanical energy to the sample and the probe to generate a time (t) domain signal S(t) that can be detected by the position-sensitive detector (PSD) and analysed in the frequency (?) domain. S(t) will carry the amplitude modulation of period T (frequency ?) imposed by the external cavity (EC) QCL or the interferometric amplitude modulation imposed by the pulses (labelled I₁, I₂) from the broadband source through the ZnSe.

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