by a complete quenching of the emission of monomers. It was found that a
quenching mechanism related to the amplification of the energy transfer from dye
monomers to dimers and larger aggregates. Without this enhancement, the
J-aggregates were weakly emitting species with a luminescence that was difficult
to detect and measure [105]. A few materials combining quantum dots and layered
nanoparticles have also been constructed. A few examples include LbL assemblies
based on quantum dots attached to the LDH particles [106, 107].
4.2.12 Chemiluminescence Resonance Energy Transfer
Chemiluminescence resonance energy transfer (CRET) has not been investigated as
frequently as the basic types of FRET [108]. Unlike FRET, CRET is initiated
without an external source of excitation. It is initiated by specific reactions, such
as the oxidation of chemiluminescent substrates. Chemiluminescence has many
advantages, as to some extent, it minimizes nonspecific signals and light backgrounds and avoids the bleaching of dyes caused by external light excitation
[109]. Highly effective CRET can be achieved when the molecules of interacting
substances are fixed to the surface of layered nanoparticles [109]. An example is
fluorescein dianions fixed onto the LDH surface. Under optimal conditions using
peroxynitronium dianions as the ED, high CRET efficiency was achieved due to the
improvement in the molecular orientation in the LDH matrix and the flatness of the
molecules. This led to a remarkable increase in the fluorescence lifetime and
quantum yield. This complex material was used for the construction of a device
that was able to detect very low concentrations of the analyte, exhibiting operational
stability, high reproducibility, and long service life. A flow column was constructed
and successfully applied to determine nitrite ions in salami samples [109]. In another
study, chemiluminescence was observed after the electrophilic attack of OH radicals
on RB molecules adsorbed onto the montmorillonite surface [110]. Increased emissions were attributed to the H-aggregates of RB molecules, leading to an increased
electron density on the aromatic rings. High electron density facilitated using the
electrophilic reaction with OH radicals as a selective probe to determine these
species. Inorganic layered particles can be used to prevent chemiluminescence
quenching [111]. For example, the inhibition of chemiluminescence by halide ions
in micelles was demonstrated by the fact that micelles formed from cetyltrimethylammonium hydroxide exhibited much higher emissions than those formed
with the bromide salt. An elegant solution was to use organoclays based on
alkylammonium-exchanged montmorillonite (without halide anions), leading to a
large improvement in its chemiluminescence in a peroxynitrous acid (ONOOH)
system [111].
Resonance Energy Transfer in Hybrid Systems of Photoactive Dye Molecules and. . .
237
quenching mechanism related to the amplification of the energy transfer from dye
monomers to dimers and larger aggregates. Without this enhancement, the
J-aggregates were weakly emitting species with a luminescence that was difficult
to detect and measure [105]. A few materials combining quantum dots and layered
nanoparticles have also been constructed. A few examples include LbL assemblies
based on quantum dots attached to the LDH particles [106, 107].
4.2.12 Chemiluminescence Resonance Energy Transfer
Chemiluminescence resonance energy transfer (CRET) has not been investigated as
frequently as the basic types of FRET [108]. Unlike FRET, CRET is initiated
without an external source of excitation. It is initiated by specific reactions, such
as the oxidation of chemiluminescent substrates. Chemiluminescence has many
advantages, as to some extent, it minimizes nonspecific signals and light backgrounds and avoids the bleaching of dyes caused by external light excitation
[109]. Highly effective CRET can be achieved when the molecules of interacting
substances are fixed to the surface of layered nanoparticles [109]. An example is
fluorescein dianions fixed onto the LDH surface. Under optimal conditions using
peroxynitronium dianions as the ED, high CRET efficiency was achieved due to the
improvement in the molecular orientation in the LDH matrix and the flatness of the
molecules. This led to a remarkable increase in the fluorescence lifetime and
quantum yield. This complex material was used for the construction of a device
that was able to detect very low concentrations of the analyte, exhibiting operational
stability, high reproducibility, and long service life. A flow column was constructed
and successfully applied to determine nitrite ions in salami samples [109]. In another
study, chemiluminescence was observed after the electrophilic attack of OH radicals
on RB molecules adsorbed onto the montmorillonite surface [110]. Increased emissions were attributed to the H-aggregates of RB molecules, leading to an increased
electron density on the aromatic rings. High electron density facilitated using the
electrophilic reaction with OH radicals as a selective probe to determine these
species. Inorganic layered particles can be used to prevent chemiluminescence
quenching [111]. For example, the inhibition of chemiluminescence by halide ions
in micelles was demonstrated by the fact that micelles formed from cetyltrimethylammonium hydroxide exhibited much higher emissions than those formed
with the bromide salt. An elegant solution was to use organoclays based on
alkylammonium-exchanged montmorillonite (without halide anions), leading to a
large improvement in its chemiluminescence in a peroxynitrous acid (ONOOH)
system [111].
Resonance Energy Transfer in Hybrid Systems of Photoactive Dye Molecules and. . .
237