knowledge of the localization and role of biomolecules in living systems [4]. The
simplest types of fluorescence probes are organic dyes that specifically interact with
the target site; this interaction is detected as a change in fluorescence properties. The
evolution of fluorescence probes continues to advance due to progress in the
synthesis of new types of luminophores [4]. The development of FRET probes
significantly expands the possibilities of using optical microscopy.
The objective of this chapter is to analyze the most important results and trends in
the research of hybrid materials of organic dyes and two-dimensional inorganic
hosts, focusing on the phenomenon of FRET and in part on other related
photophysical processes and phenomena. The chapter partly follows the author’s
previous reviews and chapters on the analysis of the general properties of such
systems [5–7]. It analyzes several aspects related to FRET in these systems. The first
sections briefly describe the theoretical basis of FRET, basic knowledge on the
properties of layered nanomaterials, and the nature of their interaction with organic
dyes. Based on the essential criteria for efficient energy transfer, the chapter focuses
on the problem of the distribution of photoactive molecules in such systems and its
crucial effect on FRET. The later sections deal with the analysis of the properties of
materials of various types including very complex systems, and some examples and
possibilities for their application are discussed.
2 Theoretical Basics of Resonance Energy Transfer
FRET is a phenomenon representing the transfer of the energy from excited dye
molecules in a non-radiative way. The first step that is required for the energy
transfer to occur is the excitation of a dye molecule, playing the role of an energy
donor (ED). The excitation is realized by absorbing a photon, but in principle also
other sources of energy could be applied (electrical energy, chemical reaction, etc.).
The excited molecule is unstable and rapidly relaxes back to its ground state via
several mechanisms, either by emitting a photon or by transferring its energy to
nearby molecules. The simplest system to be described is represented by a
one-photon event: FRET from the excited ED molecule (ED
à ) to an energy acceptor
(EA). The energy transfer between the ED
à and EA leads to the formation of an ED
EA
à pair:
ED* þ EA ! ED þ EA*
ð1Þ
where the symbol à denotes a molecule in an excited state. The interaction energy β
is expressed by the Coulombic U and the exchange E ex interactions:
β ¼ U À E ex
ð2Þ
At shorter distances, Dexter energy transfer (DET) can occur, representing a
quenching mechanism based on the transfer of an excited electron. In contrast to
208
J. Bujdák
simplest types of fluorescence probes are organic dyes that specifically interact with
the target site; this interaction is detected as a change in fluorescence properties. The
evolution of fluorescence probes continues to advance due to progress in the
synthesis of new types of luminophores [4]. The development of FRET probes
significantly expands the possibilities of using optical microscopy.
The objective of this chapter is to analyze the most important results and trends in
the research of hybrid materials of organic dyes and two-dimensional inorganic
hosts, focusing on the phenomenon of FRET and in part on other related
photophysical processes and phenomena. The chapter partly follows the author’s
previous reviews and chapters on the analysis of the general properties of such
systems [5–7]. It analyzes several aspects related to FRET in these systems. The first
sections briefly describe the theoretical basis of FRET, basic knowledge on the
properties of layered nanomaterials, and the nature of their interaction with organic
dyes. Based on the essential criteria for efficient energy transfer, the chapter focuses
on the problem of the distribution of photoactive molecules in such systems and its
crucial effect on FRET. The later sections deal with the analysis of the properties of
materials of various types including very complex systems, and some examples and
possibilities for their application are discussed.
2 Theoretical Basics of Resonance Energy Transfer
FRET is a phenomenon representing the transfer of the energy from excited dye
molecules in a non-radiative way. The first step that is required for the energy
transfer to occur is the excitation of a dye molecule, playing the role of an energy
donor (ED). The excitation is realized by absorbing a photon, but in principle also
other sources of energy could be applied (electrical energy, chemical reaction, etc.).
The excited molecule is unstable and rapidly relaxes back to its ground state via
several mechanisms, either by emitting a photon or by transferring its energy to
nearby molecules. The simplest system to be described is represented by a
one-photon event: FRET from the excited ED molecule (ED
à ) to an energy acceptor
(EA). The energy transfer between the ED
à and EA leads to the formation of an ED
EA
à pair:
ED* þ EA ! ED þ EA*
ð1Þ
where the symbol à denotes a molecule in an excited state. The interaction energy β
is expressed by the Coulombic U and the exchange E ex interactions:
β ¼ U À E ex
ð2Þ
At shorter distances, Dexter energy transfer (DET) can occur, representing a
quenching mechanism based on the transfer of an excited electron. In contrast to
208
J. Bujdák