in a similar way as are achieved with Dyads and Triads. Of note are the types of
hybrid materials that are based on an inorganic host which is photochemically
inactive but can incorporate photoactive organic molecules into its skeleton. For
example, zeolite L has proven to be a suitable host material that allows for the
controlled intercalation of dye molecules into internal channels suitable for this
purpose. Basic knowledge is summarized, e.g., in the work of Calzaferri [1]. In
several hybrid materials of this type, efficient FRET over relatively large distances
has been confirmed, in which energy migration between dye molecules of the same
type was effectively involved. Efficient FRET along a zeolite crystal is only possible
if the dye molecules are suitably ordered, arranged, and oriented in the channels [1–
3]. Besides the host materials with a 3D structure, inorganic hosts composed of
two-dimensional particles also need to be considered as templates for photoactive
hybrid systems exhibiting efficient FRET (see reviews [5, 7, 12–14]). A detailed
analysis of such systems is provided in the sections below.
4 Layered Inorganic Compounds as Hosts for Efficient
Energy Transfer
4.1 Layered Inorganic Compounds: Structure and Properties
There are several reviews and book chapters devoted to the chemistry of layered
nanoparticles [15–18]. Several types of inorganic compounds are composed of
layered particles with thicknesses at the sub-nanometer or nanometer level. There
are many types of layered inorganic compounds, and their chemistry is relatively
variable. They include graphene, graphene oxide (GO), oxides, hydroxides, LDH,
layered chalcogenides, carbonates, metal phosphates, vanadates, niobates, titanates,
layered perovskites, and layered silicates. The structure, properties, and their hybrid
materials have been reviewed [17, 19, 20]. Nanosheets composed of atoms of one
type are structurally the simplest platelet-like particles (graphene). Their atoms are
often partially functionalized GO. Some types of nanosheets are composed of
polyhedrons. Nanosheets of layered double hydroxides (LDHs) built from octahedrons are a typical example. More complex nanolayered particles can be composed
of covalently linked sheets of different polyhedrons [17]. Complex layers are the
case of layered silicates of 2:1 type, represented by smectites (naturally occurring
clay minerals) or synthetic expandable layered silicates. The structure of an individual layer is based on a sheet of octahedrons ([MO 4 (OH) 2 ]
z- ) covalently bound and
sandwiched between the two sheets of tetrahedrons ([SiO 4 ]
4À ). One of the most
important properties of these materials is the layer charge, which plays a key role in
the stability of the colloidal systems. The layer charge affects many important
properties and plays a dominant role in the interaction with ionic organic substances.
Layered particles can bear either a positive or negative charge. For example,
particles of layered silicates of the 2:1 type bear a permanent negative charge caused
Resonance Energy Transfer in Hybrid Systems of Photoactive Dye Molecules and. . .
215
hybrid materials that are based on an inorganic host which is photochemically
inactive but can incorporate photoactive organic molecules into its skeleton. For
example, zeolite L has proven to be a suitable host material that allows for the
controlled intercalation of dye molecules into internal channels suitable for this
purpose. Basic knowledge is summarized, e.g., in the work of Calzaferri [1]. In
several hybrid materials of this type, efficient FRET over relatively large distances
has been confirmed, in which energy migration between dye molecules of the same
type was effectively involved. Efficient FRET along a zeolite crystal is only possible
if the dye molecules are suitably ordered, arranged, and oriented in the channels [1–
3]. Besides the host materials with a 3D structure, inorganic hosts composed of
two-dimensional particles also need to be considered as templates for photoactive
hybrid systems exhibiting efficient FRET (see reviews [5, 7, 12–14]). A detailed
analysis of such systems is provided in the sections below.
4 Layered Inorganic Compounds as Hosts for Efficient
Energy Transfer
4.1 Layered Inorganic Compounds: Structure and Properties
There are several reviews and book chapters devoted to the chemistry of layered
nanoparticles [15–18]. Several types of inorganic compounds are composed of
layered particles with thicknesses at the sub-nanometer or nanometer level. There
are many types of layered inorganic compounds, and their chemistry is relatively
variable. They include graphene, graphene oxide (GO), oxides, hydroxides, LDH,
layered chalcogenides, carbonates, metal phosphates, vanadates, niobates, titanates,
layered perovskites, and layered silicates. The structure, properties, and their hybrid
materials have been reviewed [17, 19, 20]. Nanosheets composed of atoms of one
type are structurally the simplest platelet-like particles (graphene). Their atoms are
often partially functionalized GO. Some types of nanosheets are composed of
polyhedrons. Nanosheets of layered double hydroxides (LDHs) built from octahedrons are a typical example. More complex nanolayered particles can be composed
of covalently linked sheets of different polyhedrons [17]. Complex layers are the
case of layered silicates of 2:1 type, represented by smectites (naturally occurring
clay minerals) or synthetic expandable layered silicates. The structure of an individual layer is based on a sheet of octahedrons ([MO 4 (OH) 2 ]
z- ) covalently bound and
sandwiched between the two sheets of tetrahedrons ([SiO 4 ]
4À ). One of the most
important properties of these materials is the layer charge, which plays a key role in
the stability of the colloidal systems. The layer charge affects many important
properties and plays a dominant role in the interaction with ionic organic substances.
Layered particles can bear either a positive or negative charge. For example,
particles of layered silicates of the 2:1 type bear a permanent negative charge caused
Resonance Energy Transfer in Hybrid Systems of Photoactive Dye Molecules and. . .
215