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Research paper thumbnail of Playing with dye molecules at the inner and outer surface of zeolite L

Solid State Sciences, 2000

Plants are masters of transforming sunlight into chemical energy. In the ingenious antenna system... more Plants are masters of transforming sunlight into chemical energy. In the ingenious antenna system of the leaf, the energy of the sunlight is transported by chlorophyll molecules for the purpose of energy transformation. We have succeeded in reproducing a similar light transport in an artificial system on a nano scale. In this artificial system, zeolite L cylinders adopt the antenna function. The light transport is made possible by specifically organized dye molecules, which mimic the natural function of chlorophyll. Zeolites are crystalline materials with different cavity structures. Some of them occur in nature as a component of the soil. We are using zeolite L crystals of cylindrical morphology which consist of a continuous one-dimensional tube system and we have succeeded in filling each individual tube with chains of joined but noninteracting dye molecules. Light shining on the cylinder is first absorbed and the energy is then transported by the dye molecules inside the tubes to the cylinder ends. We expect that our system can contribute to a better understanding of the important light harvesting process which plants use for the photochemical transformation and storage of solar energy. We have synthesized nanocrystalline zeolite L cylinders ranging in length from 300 to 3000 nm. A cylinder of 800 nm diameter, e.g. consists of about 150 000 parallel tubes. Single red emitting dye molecules (oxonine) were put at each end of the tubes filled with a green emitting dye (pyronine). This arrangement made the experimental proof of efficient light transport possible. Light of appropriate wavelength shining on the cylinder is only absorbed by the pyronine and the energy moves along these molecules until it reaches the oxonine. The oxonine absorbs the energy by a radiationless energy transfer process, but it is not able to send it back to the pyronine. Instead it emits the energy in the form of red light. The artificial light harvesting system makes it possible to realize a device in which different dye molecules inside the tubes are arranged in such a way that the whole visible spectrum can be used by conducting light from blue to green to red without significant loss. Such a material could conceivably be used in a dye laser of extremely small size. The light harvesting nanocrystals are also investigated as probes in near-field microscopy, as materials for new imaging techniques and as luminescent probes in biological systems. The extremely fast energy migration, the pronounced anisotropy, the geometrical constraints and the high concentration of monomers which can be realized, have great potential in leading to new photophysical phenomena. Attempts are being made to use the efficient zeolite-based light harvesting system for the development of a new type of thin-layer solar cell in which the absorption of light and the creation of an electron-hole pair are spatially separated as in the natural antenna system of green plants. Synthesis, characterization and applications of an artificial antenna for light harvesting within a certain volume and transport of the electronic excitation energy to a specific place of molecular dimension has been the target of research in many laboratories in which different approaches have been followed. To our knowledge, the system developed by us is the first artificial antenna which works well enough to deserve this name. Many other highly organized dye-zeolite materials of this type can be prepared by similar methods and are expected to show a wide variety of remarkable properties. The largely improved chemical and photochemical stability of dye molecules inserted

Research paper thumbnail of Supramolecularly organized luminescent dye molecules in the channels of zeolite L

Research paper thumbnail of Cover Picture: Electronic Excitation Energy Migration in a Photonic Dye-Zeolite Antenna (ChemPhysChem 6/2003)

ChemPhysChem, 2003

The cover picture shows a zeolite L crystal containing organized dye molecules that act as donors... more The cover picture shows a zeolite L crystal containing organized dye molecules that act as donors (green) and acceptors (red). The confocal fluorescence microscopy images of a cylindrical crystal, seen after selective excitation of the green dyes, visualize the organization of the donors and acceptors. These crystals behave as photonic antenna, in which excitation energy is transported by a Fˆrster-type mechanism until it reaches the acceptor, where the energy is emitted as red luminescence. The intensity decrease is faster in the presence of acceptors (solid green curve) than in their absence (dashed). But the main characteristic of the time evolution of the crystals is that the acceptor intensity is first built up before it starts to decay. Find out more in the article by Calzaferri et al. on pages 567 ± 587.

Research paper thumbnail of Playing with dye molecules at the inner and outer surface of zeolite L

Solid State Sciences, 2000

Plants are masters of transforming sunlight into chemical energy. In the ingenious antenna system... more Plants are masters of transforming sunlight into chemical energy. In the ingenious antenna system of the leaf, the energy of the sunlight is transported by chlorophyll molecules for the purpose of energy transformation. We have succeeded in reproducing a similar light transport in an artificial system on a nano scale. In this artificial system, zeolite L cylinders adopt the antenna function. The light transport is made possible by specifically organized dye molecules, which mimic the natural function of chlorophyll. Zeolites are crystalline materials with different cavity structures. Some of them occur in nature as a component of the soil. We are using zeolite L crystals of cylindrical morphology which consist of a continuous one-dimensional tube system and we have succeeded in filling each individual tube with chains of joined but noninteracting dye molecules. Light shining on the cylinder is first absorbed and the energy is then transported by the dye molecules inside the tubes to the cylinder ends. We expect that our system can contribute to a better understanding of the important light harvesting process which plants use for the photochemical transformation and storage of solar energy. We have synthesized nanocrystalline zeolite L cylinders ranging in length from 300 to 3000 nm. A cylinder of 800 nm diameter, e.g. consists of about 150 000 parallel tubes. Single red emitting dye molecules (oxonine) were put at each end of the tubes filled with a green emitting dye (pyronine). This arrangement made the experimental proof of efficient light transport possible. Light of appropriate wavelength shining on the cylinder is only absorbed by the pyronine and the energy moves along these molecules until it reaches the oxonine. The oxonine absorbs the energy by a radiationless energy transfer process, but it is not able to send it back to the pyronine. Instead it emits the energy in the form of red light. The artificial light harvesting system makes it possible to realize a device in which different dye molecules inside the tubes are arranged in such a way that the whole visible spectrum can be used by conducting light from blue to green to red without significant loss. Such a material could conceivably be used in a dye laser of extremely small size. The light harvesting nanocrystals are also investigated as probes in near-field microscopy, as materials for new imaging techniques and as luminescent probes in biological systems. The extremely fast energy migration, the pronounced anisotropy, the geometrical constraints and the high concentration of monomers which can be realized, have great potential in leading to new photophysical phenomena. Attempts are being made to use the efficient zeolite-based light harvesting system for the development of a new type of thin-layer solar cell in which the absorption of light and the creation of an electron-hole pair are spatially separated as in the natural antenna system of green plants. Synthesis, characterization and applications of an artificial antenna for light harvesting within a certain volume and transport of the electronic excitation energy to a specific place of molecular dimension has been the target of research in many laboratories in which different approaches have been followed. To our knowledge, the system developed by us is the first artificial antenna which works well enough to deserve this name. Many other highly organized dye-zeolite materials of this type can be prepared by similar methods and are expected to show a wide variety of remarkable properties. The largely improved chemical and photochemical stability of dye molecules inserted : S 1 2 9 3 -2 5 5 8 ( 0 0 ) 0 0 1 2 9 -1 G. Calzaferri et al. / Solid State Sciences 2 (2000) 421-447 422 in an appropriate zeolite framework allows us to work with dyes which otherwise would be considered uninteresting because of their lack of stability. We have developed two methods for preparing well-defined dye -zeolite materials, one of them working at the solid-liquid and the other at the solid -gas interface. Different approaches for preparing similar materials are in situ synthesis (ship in a bottle) or different types of crystallization inclusion synthesis.

Research paper thumbnail of Excitation Energy Migration in a Photonic Dye-Zeolite Antenna: Computational Techniques

Journal of Computational Methods in Sciences and Engineering

Excitation energy migration between dyes embedded in hexagonal crystals of cylinder morphology is... more Excitation energy migration between dyes embedded in hexagonal crystals of cylinder morphology is an attractive phenomenon for the construction of photonic anten- nae (1, 2). Detailed knowledge of the zeolite structure, the organization and the spectro- scopic properties of the dyes and the nature and strength of the host-guest interactions is required to optimize energy migration (EnM). Whether a dye-zeolite antenna efficiently transports excitation energy is mainly determined by the mechanism and rate of energy transfer (EnT) between the dyes embedded in the zeolite channels. The decay of the lumi- nescence of these dyes, which reveals information about the EnT, is measured indirectly using Multi-Frequency Phase Fluorimetry (MFPF). Subsequently a fit of the measured data to a multiexponential decay is performed. A new, user-friendly Windows software has been developed which performs this fit, allowing full control over all fit parameters and providing useful information about the ...

Research paper thumbnail of Playing with dye molecules at the inner and outer surface of zeolite L

Solid State Sciences, 2000

Plants are masters of transforming sunlight into chemical energy. In the ingenious antenna system... more Plants are masters of transforming sunlight into chemical energy. In the ingenious antenna system of the leaf, the energy of the sunlight is transported by chlorophyll molecules for the purpose of energy transformation. We have succeeded in reproducing a similar light transport in an artificial system on a nano scale. In this artificial system, zeolite L cylinders adopt the antenna function. The light transport is made possible by specifically organized dye molecules, which mimic the natural function of chlorophyll. Zeolites are crystalline materials with different cavity structures. Some of them occur in nature as a component of the soil. We are using zeolite L crystals of cylindrical morphology which consist of a continuous one-dimensional tube system and we have succeeded in filling each individual tube with chains of joined but noninteracting dye molecules. Light shining on the cylinder is first absorbed and the energy is then transported by the dye molecules inside the tubes to the cylinder ends. We expect that our system can contribute to a better understanding of the important light harvesting process which plants use for the photochemical transformation and storage of solar energy. We have synthesized nanocrystalline zeolite L cylinders ranging in length from 300 to 3000 nm. A cylinder of 800 nm diameter, e.g. consists of about 150 000 parallel tubes. Single red emitting dye molecules (oxonine) were put at each end of the tubes filled with a green emitting dye (pyronine). This arrangement made the experimental proof of efficient light transport possible. Light of appropriate wavelength shining on the cylinder is only absorbed by the pyronine and the energy moves along these molecules until it reaches the oxonine. The oxonine absorbs the energy by a radiationless energy transfer process, but it is not able to send it back to the pyronine. Instead it emits the energy in the form of red light. The artificial light harvesting system makes it possible to realize a device in which different dye molecules inside the tubes are arranged in such a way that the whole visible spectrum can be used by conducting light from blue to green to red without significant loss. Such a material could conceivably be used in a dye laser of extremely small size. The light harvesting nanocrystals are also investigated as probes in near-field microscopy, as materials for new imaging techniques and as luminescent probes in biological systems. The extremely fast energy migration, the pronounced anisotropy, the geometrical constraints and the high concentration of monomers which can be realized, have great potential in leading to new photophysical phenomena. Attempts are being made to use the efficient zeolite-based light harvesting system for the development of a new type of thin-layer solar cell in which the absorption of light and the creation of an electron-hole pair are spatially separated as in the natural antenna system of green plants. Synthesis, characterization and applications of an artificial antenna for light harvesting within a certain volume and transport of the electronic excitation energy to a specific place of molecular dimension has been the target of research in many laboratories in which different approaches have been followed. To our knowledge, the system developed by us is the first artificial antenna which works well enough to deserve this name. Many other highly organized dye-zeolite materials of this type can be prepared by similar methods and are expected to show a wide variety of remarkable properties. The largely improved chemical and photochemical stability of dye molecules inserted : S 1 2 9 3 -2 5 5 8 ( 0 0 ) 0 0 1 2 9 -1 G. Calzaferri et al. / Solid State Sciences 2 (2000) 421-447 422 in an appropriate zeolite framework allows us to work with dyes which otherwise would be considered uninteresting because of their lack of stability. We have developed two methods for preparing well-defined dye -zeolite materials, one of them working at the solid-liquid and the other at the solid -gas interface. Different approaches for preparing similar materials are in situ synthesis (ship in a bottle) or different types of crystallization inclusion synthesis.

Research paper thumbnail of Intrazeolite Diffusion Kinetics of Dye Molecules in the Nanochannels of Zeolite L, Monitored by Energy Transfer

ChemPhysChem, 2000

Intracrystalline diffusion kinetics of two cationic dyes in an aqueous medium were studied by mea... more Intracrystalline diffusion kinetics of two cationic dyes in an aqueous medium were studied by means of energy transfer from an electronically excited donor to an acceptor located in one-dimensional crystalline channels. Different stages of the diffusion processes were visualized by using fluorescence microscopy. The picture illustrates the counter diffusion of the dye (hatched block) and water molecules (circles) in such a one-dimensional channel; the diffusion of the water molecules past the dye (1 → 2) is the rate-determining step rather than the period between encountering different dyes (2 → 3).

Research paper thumbnail of Electronic Excitation Energy Migration in a Photonic Dye-Zeolite Antenna

ChemPhysChem, 2003

Electronic excitation energy migration in a photonic antenna host ± guest material has been inves... more Electronic excitation energy migration in a photonic antenna host ± guest material has been investigated by time-resolved fluorescence experiments and by Monte Carlo calculations. The host consists of a linear channel system (zeolite L). The channels are filled with energy transporting dyes (donors) in their middle section and by one or several monolayers of a strongly luminescent trapping dye (acceptors) at each end of the channels. Excitation energy is transported among the donors in a series of steps until it reaches an acceptor at one end of the channels, or it is somehow trapped on its way, or it escapes by spontaneous emission. We describe the organization of dyes in the channels by means of Monte Carlo simulation and we report time-resolved data on a variety of pyronine-, oxonine-, and oxonine,pyronine ± zeolite L materials. In the latter, the pyronine acts as donor and oxonine as acceptor. We find that the luminescence decay of crystals containing only one kind of dye is single exponential for moderate loading if measured under oxygen-free conditions, but biexponential otherwise. The main characteristic of the time evolution of oxonine,pyronine ± zeolite L crystals is that the acceptor intensity is first built up before it starts to decay. This intensity increase becomes faster with increasing donor loading, a fact that beautifully supports the interpretation that the crystals behave as photonic antenna in which excitation energy is transported preferentially along the channels by a Fˆrster-type mechanism until it reaches the acceptor, where it is emitted as red luminescence.

Research paper thumbnail of Supramolecularly Organized Luminescent Dye Molecules in the Channels of Zeolite L

Advances in Photochemistry, Volume 27, 2002

Research paper thumbnail of Playing with dye molecules at the inner and outer surface of zeolite L

Solid State Sciences, 2000

Plants are masters of transforming sunlight into chemical energy. In the ingenious antenna system... more Plants are masters of transforming sunlight into chemical energy. In the ingenious antenna system of the leaf, the energy of the sunlight is transported by chlorophyll molecules for the purpose of energy transformation. We have succeeded in reproducing a similar light transport in an artificial system on a nano scale. In this artificial system, zeolite L cylinders adopt the antenna function. The light transport is made possible by specifically organized dye molecules, which mimic the natural function of chlorophyll. Zeolites are crystalline materials with different cavity structures. Some of them occur in nature as a component of the soil. We are using zeolite L crystals of cylindrical morphology which consist of a continuous one-dimensional tube system and we have succeeded in filling each individual tube with chains of joined but noninteracting dye molecules. Light shining on the cylinder is first absorbed and the energy is then transported by the dye molecules inside the tubes to the cylinder ends. We expect that our system can contribute to a better understanding of the important light harvesting process which plants use for the photochemical transformation and storage of solar energy. We have synthesized nanocrystalline zeolite L cylinders ranging in length from 300 to 3000 nm. A cylinder of 800 nm diameter, e.g. consists of about 150 000 parallel tubes. Single red emitting dye molecules (oxonine) were put at each end of the tubes filled with a green emitting dye (pyronine). This arrangement made the experimental proof of efficient light transport possible. Light of appropriate wavelength shining on the cylinder is only absorbed by the pyronine and the energy moves along these molecules until it reaches the oxonine. The oxonine absorbs the energy by a radiationless energy transfer process, but it is not able to send it back to the pyronine. Instead it emits the energy in the form of red light. The artificial light harvesting system makes it possible to realize a device in which different dye molecules inside the tubes are arranged in such a way that the whole visible spectrum can be used by conducting light from blue to green to red without significant loss. Such a material could conceivably be used in a dye laser of extremely small size. The light harvesting nanocrystals are also investigated as probes in near-field microscopy, as materials for new imaging techniques and as luminescent probes in biological systems. The extremely fast energy migration, the pronounced anisotropy, the geometrical constraints and the high concentration of monomers which can be realized, have great potential in leading to new photophysical phenomena. Attempts are being made to use the efficient zeolite-based light harvesting system for the development of a new type of thin-layer solar cell in which the absorption of light and the creation of an electron-hole pair are spatially separated as in the natural antenna system of green plants. Synthesis, characterization and applications of an artificial antenna for light harvesting within a certain volume and transport of the electronic excitation energy to a specific place of molecular dimension has been the target of research in many laboratories in which different approaches have been followed. To our knowledge, the system developed by us is the first artificial antenna which works well enough to deserve this name. Many other highly organized dye-zeolite materials of this type can be prepared by similar methods and are expected to show a wide variety of remarkable properties. The largely improved chemical and photochemical stability of dye molecules inserted

Research paper thumbnail of Supramolecularly organized luminescent dye molecules in the channels of zeolite L

Research paper thumbnail of Cover Picture: Electronic Excitation Energy Migration in a Photonic Dye-Zeolite Antenna (ChemPhysChem 6/2003)

ChemPhysChem, 2003

The cover picture shows a zeolite L crystal containing organized dye molecules that act as donors... more The cover picture shows a zeolite L crystal containing organized dye molecules that act as donors (green) and acceptors (red). The confocal fluorescence microscopy images of a cylindrical crystal, seen after selective excitation of the green dyes, visualize the organization of the donors and acceptors. These crystals behave as photonic antenna, in which excitation energy is transported by a Fˆrster-type mechanism until it reaches the acceptor, where the energy is emitted as red luminescence. The intensity decrease is faster in the presence of acceptors (solid green curve) than in their absence (dashed). But the main characteristic of the time evolution of the crystals is that the acceptor intensity is first built up before it starts to decay. Find out more in the article by Calzaferri et al. on pages 567 ± 587.

Research paper thumbnail of Playing with dye molecules at the inner and outer surface of zeolite L

Solid State Sciences, 2000

Plants are masters of transforming sunlight into chemical energy. In the ingenious antenna system... more Plants are masters of transforming sunlight into chemical energy. In the ingenious antenna system of the leaf, the energy of the sunlight is transported by chlorophyll molecules for the purpose of energy transformation. We have succeeded in reproducing a similar light transport in an artificial system on a nano scale. In this artificial system, zeolite L cylinders adopt the antenna function. The light transport is made possible by specifically organized dye molecules, which mimic the natural function of chlorophyll. Zeolites are crystalline materials with different cavity structures. Some of them occur in nature as a component of the soil. We are using zeolite L crystals of cylindrical morphology which consist of a continuous one-dimensional tube system and we have succeeded in filling each individual tube with chains of joined but noninteracting dye molecules. Light shining on the cylinder is first absorbed and the energy is then transported by the dye molecules inside the tubes to the cylinder ends. We expect that our system can contribute to a better understanding of the important light harvesting process which plants use for the photochemical transformation and storage of solar energy. We have synthesized nanocrystalline zeolite L cylinders ranging in length from 300 to 3000 nm. A cylinder of 800 nm diameter, e.g. consists of about 150 000 parallel tubes. Single red emitting dye molecules (oxonine) were put at each end of the tubes filled with a green emitting dye (pyronine). This arrangement made the experimental proof of efficient light transport possible. Light of appropriate wavelength shining on the cylinder is only absorbed by the pyronine and the energy moves along these molecules until it reaches the oxonine. The oxonine absorbs the energy by a radiationless energy transfer process, but it is not able to send it back to the pyronine. Instead it emits the energy in the form of red light. The artificial light harvesting system makes it possible to realize a device in which different dye molecules inside the tubes are arranged in such a way that the whole visible spectrum can be used by conducting light from blue to green to red without significant loss. Such a material could conceivably be used in a dye laser of extremely small size. The light harvesting nanocrystals are also investigated as probes in near-field microscopy, as materials for new imaging techniques and as luminescent probes in biological systems. The extremely fast energy migration, the pronounced anisotropy, the geometrical constraints and the high concentration of monomers which can be realized, have great potential in leading to new photophysical phenomena. Attempts are being made to use the efficient zeolite-based light harvesting system for the development of a new type of thin-layer solar cell in which the absorption of light and the creation of an electron-hole pair are spatially separated as in the natural antenna system of green plants. Synthesis, characterization and applications of an artificial antenna for light harvesting within a certain volume and transport of the electronic excitation energy to a specific place of molecular dimension has been the target of research in many laboratories in which different approaches have been followed. To our knowledge, the system developed by us is the first artificial antenna which works well enough to deserve this name. Many other highly organized dye-zeolite materials of this type can be prepared by similar methods and are expected to show a wide variety of remarkable properties. The largely improved chemical and photochemical stability of dye molecules inserted : S 1 2 9 3 -2 5 5 8 ( 0 0 ) 0 0 1 2 9 -1 G. Calzaferri et al. / Solid State Sciences 2 (2000) 421-447 422 in an appropriate zeolite framework allows us to work with dyes which otherwise would be considered uninteresting because of their lack of stability. We have developed two methods for preparing well-defined dye -zeolite materials, one of them working at the solid-liquid and the other at the solid -gas interface. Different approaches for preparing similar materials are in situ synthesis (ship in a bottle) or different types of crystallization inclusion synthesis.

Research paper thumbnail of Excitation Energy Migration in a Photonic Dye-Zeolite Antenna: Computational Techniques

Journal of Computational Methods in Sciences and Engineering

Excitation energy migration between dyes embedded in hexagonal crystals of cylinder morphology is... more Excitation energy migration between dyes embedded in hexagonal crystals of cylinder morphology is an attractive phenomenon for the construction of photonic anten- nae (1, 2). Detailed knowledge of the zeolite structure, the organization and the spectro- scopic properties of the dyes and the nature and strength of the host-guest interactions is required to optimize energy migration (EnM). Whether a dye-zeolite antenna efficiently transports excitation energy is mainly determined by the mechanism and rate of energy transfer (EnT) between the dyes embedded in the zeolite channels. The decay of the lumi- nescence of these dyes, which reveals information about the EnT, is measured indirectly using Multi-Frequency Phase Fluorimetry (MFPF). Subsequently a fit of the measured data to a multiexponential decay is performed. A new, user-friendly Windows software has been developed which performs this fit, allowing full control over all fit parameters and providing useful information about the ...

Research paper thumbnail of Playing with dye molecules at the inner and outer surface of zeolite L

Solid State Sciences, 2000

Plants are masters of transforming sunlight into chemical energy. In the ingenious antenna system... more Plants are masters of transforming sunlight into chemical energy. In the ingenious antenna system of the leaf, the energy of the sunlight is transported by chlorophyll molecules for the purpose of energy transformation. We have succeeded in reproducing a similar light transport in an artificial system on a nano scale. In this artificial system, zeolite L cylinders adopt the antenna function. The light transport is made possible by specifically organized dye molecules, which mimic the natural function of chlorophyll. Zeolites are crystalline materials with different cavity structures. Some of them occur in nature as a component of the soil. We are using zeolite L crystals of cylindrical morphology which consist of a continuous one-dimensional tube system and we have succeeded in filling each individual tube with chains of joined but noninteracting dye molecules. Light shining on the cylinder is first absorbed and the energy is then transported by the dye molecules inside the tubes to the cylinder ends. We expect that our system can contribute to a better understanding of the important light harvesting process which plants use for the photochemical transformation and storage of solar energy. We have synthesized nanocrystalline zeolite L cylinders ranging in length from 300 to 3000 nm. A cylinder of 800 nm diameter, e.g. consists of about 150 000 parallel tubes. Single red emitting dye molecules (oxonine) were put at each end of the tubes filled with a green emitting dye (pyronine). This arrangement made the experimental proof of efficient light transport possible. Light of appropriate wavelength shining on the cylinder is only absorbed by the pyronine and the energy moves along these molecules until it reaches the oxonine. The oxonine absorbs the energy by a radiationless energy transfer process, but it is not able to send it back to the pyronine. Instead it emits the energy in the form of red light. The artificial light harvesting system makes it possible to realize a device in which different dye molecules inside the tubes are arranged in such a way that the whole visible spectrum can be used by conducting light from blue to green to red without significant loss. Such a material could conceivably be used in a dye laser of extremely small size. The light harvesting nanocrystals are also investigated as probes in near-field microscopy, as materials for new imaging techniques and as luminescent probes in biological systems. The extremely fast energy migration, the pronounced anisotropy, the geometrical constraints and the high concentration of monomers which can be realized, have great potential in leading to new photophysical phenomena. Attempts are being made to use the efficient zeolite-based light harvesting system for the development of a new type of thin-layer solar cell in which the absorption of light and the creation of an electron-hole pair are spatially separated as in the natural antenna system of green plants. Synthesis, characterization and applications of an artificial antenna for light harvesting within a certain volume and transport of the electronic excitation energy to a specific place of molecular dimension has been the target of research in many laboratories in which different approaches have been followed. To our knowledge, the system developed by us is the first artificial antenna which works well enough to deserve this name. Many other highly organized dye-zeolite materials of this type can be prepared by similar methods and are expected to show a wide variety of remarkable properties. The largely improved chemical and photochemical stability of dye molecules inserted : S 1 2 9 3 -2 5 5 8 ( 0 0 ) 0 0 1 2 9 -1 G. Calzaferri et al. / Solid State Sciences 2 (2000) 421-447 422 in an appropriate zeolite framework allows us to work with dyes which otherwise would be considered uninteresting because of their lack of stability. We have developed two methods for preparing well-defined dye -zeolite materials, one of them working at the solid-liquid and the other at the solid -gas interface. Different approaches for preparing similar materials are in situ synthesis (ship in a bottle) or different types of crystallization inclusion synthesis.

Research paper thumbnail of Intrazeolite Diffusion Kinetics of Dye Molecules in the Nanochannels of Zeolite L, Monitored by Energy Transfer

ChemPhysChem, 2000

Intracrystalline diffusion kinetics of two cationic dyes in an aqueous medium were studied by mea... more Intracrystalline diffusion kinetics of two cationic dyes in an aqueous medium were studied by means of energy transfer from an electronically excited donor to an acceptor located in one-dimensional crystalline channels. Different stages of the diffusion processes were visualized by using fluorescence microscopy. The picture illustrates the counter diffusion of the dye (hatched block) and water molecules (circles) in such a one-dimensional channel; the diffusion of the water molecules past the dye (1 → 2) is the rate-determining step rather than the period between encountering different dyes (2 → 3).

Research paper thumbnail of Electronic Excitation Energy Migration in a Photonic Dye-Zeolite Antenna

ChemPhysChem, 2003

Electronic excitation energy migration in a photonic antenna host ± guest material has been inves... more Electronic excitation energy migration in a photonic antenna host ± guest material has been investigated by time-resolved fluorescence experiments and by Monte Carlo calculations. The host consists of a linear channel system (zeolite L). The channels are filled with energy transporting dyes (donors) in their middle section and by one or several monolayers of a strongly luminescent trapping dye (acceptors) at each end of the channels. Excitation energy is transported among the donors in a series of steps until it reaches an acceptor at one end of the channels, or it is somehow trapped on its way, or it escapes by spontaneous emission. We describe the organization of dyes in the channels by means of Monte Carlo simulation and we report time-resolved data on a variety of pyronine-, oxonine-, and oxonine,pyronine ± zeolite L materials. In the latter, the pyronine acts as donor and oxonine as acceptor. We find that the luminescence decay of crystals containing only one kind of dye is single exponential for moderate loading if measured under oxygen-free conditions, but biexponential otherwise. The main characteristic of the time evolution of oxonine,pyronine ± zeolite L crystals is that the acceptor intensity is first built up before it starts to decay. This intensity increase becomes faster with increasing donor loading, a fact that beautifully supports the interpretation that the crystals behave as photonic antenna in which excitation energy is transported preferentially along the channels by a Fˆrster-type mechanism until it reaches the acceptor, where it is emitted as red luminescence.

Research paper thumbnail of Supramolecularly Organized Luminescent Dye Molecules in the Channels of Zeolite L

Advances in Photochemistry, Volume 27, 2002