New materials for electrochemiluminescence
Creators: name: Zanarini, Simone <1975>
Publisher: name: Alma Mater Studiorum - Università di Bologna
Year: 2007
Subjects: CHIM/02 Chimica fisica

description: The study of electrochemiluminescence (ECL) involves photophysical and
electrochemical aspects. Excited states are populated by an electrical stimulus.
The most important applications are in the diagnostic field where a number of
different biologically-relevant molecules (e.g. proteins and nucleic acids) can
be recognized and quantified with a sensitivity and specificity previously not
reachable. As a matter of fact the electrochemistry, differently to the classic
techniques as fluorescence and chemiluminescence, allows to control the
excited state generation spatially and temporally. The two research visits into
A. J. Bard electrochemistry laboratories were priceless. Dr. Bard has been one
of ECL pioneers, the first to introduce the technique and the one who
discovered in 1972 the surprising emission of Ru(bpy)3
2+. I consider necessary
to thank by now my supervisors Massimo and Francesco for their help and for
giving me the great opportunity to know this unique science man that made me
feel enthusiastic. I will never be grateful enough…
Considering that the experimental techniques of ECL did not changed
significantly in these last years the most convenient research direction has
been the developing of materials with new or improved properties.
In Chapter I the basics concepts and mechanisms of ECL are introduced so
that the successive experiments can be easily understood. In the final
paragraph the scopes of the thesis are briefly described.
In Chapter II by starting from ECL experimental apparatus of Dr. Bard’s
laboratories the design, assembly and preliminary tests of the new Bologna
instrument are carefully described. The instrument assembly required to work
hard but resulted in the introduction of the new technique in our labs by
allowing the continuation of the ECL studies began in Texas.
In Chapter III are described the results of electrochemical and ECL studies
performed on new synthesized Ru(II) complexes containing tetrazolate based
ligands. ECL emission has been investigated in solution and in solid thin films.
The effect of the chemical protonation of the tetrazolate ring on ECL emission
has been also investigated evidencing the possibility of a catalytic effect
(generation of molecular hydrogen) of one of the complexes in organic media.
Finally, after a series of preliminary studies on ECL emission in acqueous
buffers, the direct interaction with calf thymus DNA of some complexes has
been tested by ECL and photoluminescence (PL) titration.
In Chapter IV different Ir(III) complexes have been characterized
electrochemically and photophysically (ECL and PL). Some complexes were
already well-known in literature for their high quantum efficiency whereas the
remaining were new synthesized compounds containing tetrazolate based
ligands analogous to those investigated in Chapt. III. During the tests on a
halogenated complex was unexpectedly evidenced the possibility to follow
the kinetics of an electro-induced chemical reaction by using ECL signal.
In the last chapter (V) the possibility to use mono-use silicon chips
electrodes as ECL analitycal devices is under investigation. The chapter begins
by describing the chip structure and materials then a signal reproducibility
study and geometry optimization is carried on by using two different
complexes. In the following paragraphs is reported in detail the synthesis of an
ECL label based on Ru(bpy)3
2+ and the chip functionalization by using a lipoic
acid SAM and the same label. After some preliminary characterizations (mass
spectroscopy TOF) has been demonstrated that by mean of a simple and fast
ECL measurement it’s possible to confirm the presence of the coupling
product SAM-label into the chip with a very high sensitivity. No signal was
detected from the same system by using photoluminescence.