IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Biomaterials Monday Sessions
       Session BI+SS-MoA

Invited Paper BI+SS-MoA3
Local Solvation Shell Measurement in Water using a Carbon Nanotube Probe

Monday, October 29, 2001, 2:40 pm, Room 102

Session: Role of Water in Biological Systems
Presenter: S.P. Jarvis, Nanotechnology Research Institute, AIST, Japan
Authors: S.P. Jarvis, Nanotechnology Research Institute, AIST, Japan
T. Ishida, Institute for Mechanical System Engineering, AIST, Japan
C.C. Liew, Research Institute for Computational Sciences, AIST, Japan
H. Tokumoto, Nanotechnology Research Institute, AIST, Japan.
Y. Nakayama, Osaka Prefecture University, Japan
Correspondent: Click to Email
Using a multiwalled carbon nanotube as an atomic force microscope (AFM) probe tip we have directly measured localised structuring in aqueous environments at small tip-sample separations and have combined this with nanometer resolution images of the surface. By diversifying beyond the simple surfaces of graphite and mica, to self-assembled monolayers with varying end groups, we have been able to investigate the role of local surface chemistry and morphology on the measured water structure. Directly measuring solvation shells with a mechanical probe of lateral dimensions comparable to that of a single molecule provides an invaluable insight into the processes controlling if and how a molecule approaches another molecule or a membrane. In the immediate vicinity of the molecule, continuum models break down and the aqueous environment will often form a discrete layered structure depending on the nature of the molecule. The absence or presence of such structure may be fundamental in influencing the promotion or inhibition of protein adsorption, biological function and membrane recognition. In order to perform such measurements it has been necessary to combine a number of innovative techniques with a standard AFM. For high-resolution imaging we use a highly sensitive frequency modulation detection scheme. To do this effectively in liquid involves the implementation of magnetically activated dynamic mode (MAD-mode!) where a small magnetic particle is attached to the end of the cantilever and an external magnetic field applied via a current carrying coil. To increase the sensitivity of the measurement to the interaction local to the tip apex we have used a high aspect ratio multiwalled carbon nanotube probe. This reduces the hydrodynamic squeeze damping between the surface and the bulk of the tip. The nanotube is attached in a specially designed field emission scanning electron microscope, which permits us some control over both the length and direction of the probe.