5 Applications
5.1 Control of Photodegradation of Pesticides by FRET
One of the first types of applications that utilized the FRET phenomenon in a
combination of hybrid materials, especially clay minerals, was agriculture. This
was connected with controlling the photochemical degradation of pesticides. With
FRET, it was possible to either stabilize or accelerate the decomposition of the
pesticides. The stabilization was based on the quenching of the pesticides using a
substance that interacted via the FRET mechanism. Or, on the contrary, the photosensitizer could be a source of energy to photochemically promote the decomposition of agrochemicals or to accelerate their decomposition. One example was the
photochemical degradation of a thiazine-type insecticide adsorbed onto montmorillonite, nontronite, and hectorite [112]. The photodegradation was slower due to
significant photostabilization compared to the pesticide in its free form. This was
probably due to a charge transfer from the excited state of the pesticide to the Fe
3+
ions. Further stabilization was achieved when the cationic dye, 3,6-diamino-10methyl-acridinium, was co-adsorbed with the insecticide. The deactivation of the
photodecomposition was carried out by FRET between the two organic molecules
adsorbed onto the surface of the mineral [112]. Various mechanisms have been
described for the photostabilization of agrochemicals, such as pesticides, using clay
minerals modified with organic dyes. The phenomenon of energy transfer often
played a dominant role. This was also the case in the stabilization of the photolabile
insecticide bioresmethrin in a system of montmorillonite with the cationic dye
methyl green [113]. The pesticide was stabilized due to the energy transfer from
excited pesticide molecules to the methyl green. Energy transfer processes can also
occur from the pesticide to the inorganic host, and the presence of transition metal
ions in the structure can be effective energy or electron acceptors. Such a mechanism
was observed during the photostabilization of the insecticide tetrahydro-2(nitromethylene)-2H-1,3-thiazine [113]. Alternatively, photostabilization was
achieved by the addition of a cationic dye – acriflavine – when a stereochemical
factor played an important role in preventing or slowing down certain photochemical
reactions. An example is the photostabilization of the herbicide trifluralin. Energy
transfer has also been proven in photostabilizing microbial insecticides such as a
toxin isolated from Bacillus thuringiensis [113].
5.2 FRET for Sensing
The most frequent applications of FRET are related to sensors. The spectral overlap
integral can be altered by the effect of the molecular environment in various ways, in
particular by changing the molar absorption coefficient of the ED. As analyzed in
Sect. 4.2.10, the absorption spectra of rhodamine dyes are significantly changed by
238
J. Bujdák
5.1 Control of Photodegradation of Pesticides by FRET
One of the first types of applications that utilized the FRET phenomenon in a
combination of hybrid materials, especially clay minerals, was agriculture. This
was connected with controlling the photochemical degradation of pesticides. With
FRET, it was possible to either stabilize or accelerate the decomposition of the
pesticides. The stabilization was based on the quenching of the pesticides using a
substance that interacted via the FRET mechanism. Or, on the contrary, the photosensitizer could be a source of energy to photochemically promote the decomposition of agrochemicals or to accelerate their decomposition. One example was the
photochemical degradation of a thiazine-type insecticide adsorbed onto montmorillonite, nontronite, and hectorite [112]. The photodegradation was slower due to
significant photostabilization compared to the pesticide in its free form. This was
probably due to a charge transfer from the excited state of the pesticide to the Fe
3+
ions. Further stabilization was achieved when the cationic dye, 3,6-diamino-10methyl-acridinium, was co-adsorbed with the insecticide. The deactivation of the
photodecomposition was carried out by FRET between the two organic molecules
adsorbed onto the surface of the mineral [112]. Various mechanisms have been
described for the photostabilization of agrochemicals, such as pesticides, using clay
minerals modified with organic dyes. The phenomenon of energy transfer often
played a dominant role. This was also the case in the stabilization of the photolabile
insecticide bioresmethrin in a system of montmorillonite with the cationic dye
methyl green [113]. The pesticide was stabilized due to the energy transfer from
excited pesticide molecules to the methyl green. Energy transfer processes can also
occur from the pesticide to the inorganic host, and the presence of transition metal
ions in the structure can be effective energy or electron acceptors. Such a mechanism
was observed during the photostabilization of the insecticide tetrahydro-2(nitromethylene)-2H-1,3-thiazine [113]. Alternatively, photostabilization was
achieved by the addition of a cationic dye – acriflavine – when a stereochemical
factor played an important role in preventing or slowing down certain photochemical
reactions. An example is the photostabilization of the herbicide trifluralin. Energy
transfer has also been proven in photostabilizing microbial insecticides such as a
toxin isolated from Bacillus thuringiensis [113].
5.2 FRET for Sensing
The most frequent applications of FRET are related to sensors. The spectral overlap
integral can be altered by the effect of the molecular environment in various ways, in
particular by changing the molar absorption coefficient of the ED. As analyzed in
Sect. 4.2.10, the absorption spectra of rhodamine dyes are significantly changed by
238
J. Bujdák