Biological systems emerge from evolved sophisticated processes developed by Nature. Understanding of how the biological materials function can help us to synthesize, control and manipulate materials at an atomic scale. Biological nanotechnology aims at the design and synthesis of novel artificial materials and devices for electronic, optical, biomedical, and spintronic applications. One of the examples of a nanoscale biological system is a plant virus (see Figure 1). Plant viruses have recently attracted attention as biological templates for assembly of nanostructures and nanoelectronic circuits.

Figure 1. Vibrations in the rod-shaped TMV viruses immersed in air and water.
After A.A. Balandin and V.A. Fonoberov, J. of Biomedical Nanotechnology.

Plant viruses can be coated with metals, silica or semiconductor materials and form end-to-end nano-rod assemblies (see Figure 2). Such virus as tobacco mosaic virus (TMV) has appropriate cylindrical shape and particularly suitable dimensions: TMV is 300 nm long, 18 nm in diameter and with a 4 nm in diameter axial channel. The knowledge of vibrational, i.e. phonon, modes of these viruses is important for materials and structural characterization of the virus-based nano-templates and for in-situ monitoring of the virus-assisted nanostructure self-assembly. NDL team has recently reported on the application of Raman spectroscopy for investigation of properties of hybrid virus-inorganic nanotubes.

Figure 2. TEM micrograph of pure TMV and platinum coated TMV assembly. NDL, 2004.

Professor Balandin's Nano-Device Laboratory (NDL) research group carries out theoretical and experimental research on bio-inspired materials and development of novel characterization techniques for such hybrid materials. NDL researchers focus on the characterization of properties and investigation of vibrational modes in the plant viruses and plant virus-based assemblies (see Figure 3). Recent results on the subject can be found in W.L. Liu, et al., Appl. Phys. Lett. (2005). Some thrusts of this biological nanotechnology research in NDL are performed under the framework of the DARPA-SRC funded MARCO Center on Functional Engineered Nano Artichectonics (FENA) . The bio-nano-tech modeling and computer simulation work in NDL is closely corellated with the group's experimental activities described HERE, particularly micro-Raman spectroscopic investigation of phonons in hybrid nanostructures. More information on Raman spectroscopy in NDL can be found HERE.

Figure 3. Dispersion of the lowest vibrational frequencies for cylindrical viruses.
Solid (dashed) lines correspond to radial-axial vibrations of the virus in air (water).

In our recent paper we reported on calculation of the dispersion relations for the lowest vibrational frequencies of TMV immersed in air and water (see Figure 3). In this work we analysed the damping of vibrations in water and discuss application of micros-Raman spectroscopy for monitoring and control of the virus-based self-assembly processes (see Figure 4). For details see the rapid research note in physica status solidi (2004) by V.A. Fonoberov and A.A. Balandin.

Figure 4. Raman spectra of TMV virus under visible laser excitation. NDL, 2004.

The signatures of the unique vibrational modes observed in Raman (Brillouin) spectra (see Figure 3) can be used to monitor the process of virus functionalization, i.e. coating with different materials, and self-assembly, i.e. attachment to other objects such as quantum dots, carbon nanotubes, etc., or forming end-to-end superstructures (see Figure 5). Information, which can be obtained with the help of Raman spectroscopy, is particularly valuable since other direct characterization techniques, such as transmission electron microscopy (TEM), are difficult to carry out and require special treatment of the samples. For details see A.A. Balandin and V.A. Fonoberov, Vibrational Modes of Nano-Template Viruses published in the Journal of Biomedical Nanotechnology.

Figure 5. Radial vibrational modes for TMV virus in air (a-c) and in water (d-f).
The length or arrows is proportional to the magnitude of the displacement.

Finally, talking about nanostructure growth, Figure 6 shows the growth of the tobacco mosaic viruses on (what else...) tobacco plants. The growth is carried out at the facilities of the UCR College of Natural and Agricultural Sciences. As one can guess the method is not as expensive as molecular beam epitaxy (MBE). It is also a parallel process allowing mass production of TMV nano-templates. At the same time, do not try it at your backyard.

Figure 6. Growth of tobacco mosaic viruses on tobacco plants. UCR, 2004.

More information on the BIOLOGICAL NANOTECHNOLOGY and other projects currently under way in the Nano-Device Laboratory (NDL) can be found HERE. To join NDL as a graduate student or postdoctoral research visit the web-page HERE. To learn more about course offering in the field of Materials, Devices and Circuits visit the web-page HERE.