Biogeochemical Processes at the Mineral-Water Interface
Dissolution of Rhodochrosite using SECM with Au/Hg Microelectrodes
(S. Neuhuber, M. Taillefert, C. Kranz, B. Mizaikoff)
In this project, the dissolution of rhodochrosite is monitored in three
dimensions using Scanning ElectroChemical Microscopy (SECM) with a Au/Hg
microelectrode of 25 mm. The manganese
carbonate sample is precipitated on a glass slide (see specimen on micrograph)
and redissolved using a mild solution of hydrochloric acid. The Au/Hg microelectrode
is scanned over a 500 x 500 mm substrate and
Mn2+ is detected simultaneously using an amperometric technique.
SECM images generated using this technique provide information on the release
and diffusion of Mn2+ just above the mineral surface. The objective
of this project is to learn more about the mechanisms of dissolution of
minerals.
Multifunctional Scanning Nanoprobes for In Situ Analysis of Chemical Processes
at Microbe/Mineral
Interfaces (B. Mizaikoff, C. Kranz, T. J. DiChristina, A.
G. Fedorov, P. J. Hesketh, M. Taillefert)
Multifunctional scanning nanoprobes integrating scanning electrochemical
microscopy (SECM), atomic force microscopy (AFM), and scanning nearfield
optical microscopy (SNOM) are developed using microfabrication technology.
Novel strategies for the development of a new generation of multifunctional
scanning probe tips will extend the application of scanning probe techniques
to complex environmental and biological systems at the molecular level.
In addition to
multiple electrode systems and tip arrays the main focus of this project
is aimed at integrating multiple smart electrochemical sensing systems
for the in-situ
analysis of chemical and biochemical processes at the interface between
Fe(III)-reducing microorganisms and Fe(III)-containing mineral surfaces.
Instead of performing sequential analysis of complex processes between
microorganisms and mineral surfaces, we examine these processes
simultaneously in space and in time with the newly developed, multifunctional
scanning nanoprobes. Attractive energies and electrochemical signals generated
by Fe(III)-reducing bacterial cells and specific Fe(III)-reducing enzymes
attached to nanoprobe tips are detected via simultaneous confocal microscopy
and scanning probe measurements at the Fe(III) mineral surface. This
new technology enable us to investigate electron transfer mechanisms at
the
nanometer scale and correlate in-situ measurements with computational
simulations of these dynamic processes in the probed volume between the
nanoprobe tip and sample surface.