nanotehnoloogia, nanoteknologia, nanotechnologija, nanotehnologijas, nanoteknologija,
nanotechnologii, nanotecnologia, nanotehnologijo, nanoteknik
components must continue to get smaller: Miniaturization
has now reached the nanometer scale (10 -9 m). In
this tiny world, classic semiconductor technology
is reaching its limits. We now need switches and
other devices whose dimensions are on the scale of
individual molecules. The difficulty with this is
in the addressability and compatibility of molecular
systems with the available nanoelectronic components.
Until now, all molecular systems require at least
one step in which a solution must be injected into
the system and then rinsed out again, which is time-consuming.
L. Furtado, K. Araki, H. E. Toma, and co-workers at the University of São
Paulo in Brazil describe for the first time an optoelectronic molecular gate
that directly absorbs light and gives off electrical impulses.
The gate consists of a glass electrode onto which a thin, nanocrystalline film
of TiO2 is deposited. A dye, in this case a cluster of three ruthenium–pyrazinecarboxylate
complexes, is adsorbed to this surface. A platinum counter electrode is used,
and the space between the electrodes is filled by an electrolyte solution of
I 3-/I2 in CH3CN.
When this gate is irradiated with light, electrons are excited, which leads
to charge separation and a flow of current. The direction of the current changes
depending on the wavelength of the light irradiating the system: at 350 nm,
the electrons flow from the Pt electrode to the glass electrode; at 420 nm,
they flow the other way.
At 350 nm, the TiO2 layer absorbs the light and gives off electrons to the
underlying glass electrode. To compensate, the corresponding number of electrons
is removed from the ruthenium cluster, which replaces them with electrons from
the Pt electrode. At 420 nm, however, the ruthenium complexes are induced to
give off electrons to the Pt electrode, which are re-supplied from the TiO2
The result is a switch that is not only turned on and off by light, but whose
signal can change direction on the basis of the wavelength of light used.
Author: Koiti Araki, Universidade de São Paulo
Title: TiO2-Based Light-Driven XOR/INH Logic Gates
Angewandte Chemie International Edition , 2006, 45 , No. 19,
3143–3146, doi: 10.1002/anie.200600076
or David Greenberg (US)
or Julia Lampam (UK)