Time, Space, and Spectrally Resolved Studies on J-Aggregate Interactions in Zeolite L Nanochannels

Physikalisches Institut and Center for Nanotechnology, CeNTech, University of Münster, Mendelstrasse 7, 48149 Münster, Germany.
Journal of the American Chemical Society (Impact Factor: 12.11). 08/2008; 130(33):10970-6. DOI: 10.1021/ja801178p
Source: PubMed


Temporally and spectrally resolved confocal microscopy has been used to explore the behavior of pyronine intercalated zeolite L crystals at different loadings. The low pyronine loading of 0.6% exhibits photophysical behavior similar to that of the free molecule in solution, indicating molecules are isolated from each other in the crystal channels. The higher loading of 20% results in a dye gradient along the channel axis, and the presence of an additional red-shifted spectroscopic transition, with shorter lifetimes. The new band is assigned to an inline arrangement of the molecules undergoing a J-aggregate-type coupling, a process so far not observed in subnanometer channels.

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    • "J-aggregates are characterized by head to tail alignments of transition dipole moments of the dyes and are featured by a red-shifted absorption with respect to the monomer electronic transition. These two-dimensional stacks of aggregates have many applications in photography, molecular photonics, and microelectronic devices [16] [17] [18] [19] [20] [21]. In particular, stilbene derivatives are known to form well-defined two-dimensional aggregates [22] [23] [24] [25] [26] with potential properties in different areas [27], such as organic fluorescent nanowires [28] or two-photon chemosensors [29] [30]. "
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    ABSTRACT: Langmuir and Langmuir–Blodgett films of a pyridine-terminated stilbene derivative, namely 4-hexyloxy-4′-[N-(4-pyridilmethylene)amine] stilbene (abbreviated as HPAS), have been fabricated and characterized at various surface pressures, with surface pressure and Brewster Angle Microscopy being used to map the different phases of the stilbene monolayer at the air–water interface. UV–vis reflection spectroscopy showed a strong blue shift of 48 and 93nm of the reflection spectrum of the Langmuir film with respect to the spectrum of a solution of HPAS, which indicates that two dimensional H-aggregates are formed at the air–water interface. These structures represent a minimum free energy conformation for the system, as they are observed even before the compression process starts. The sequential transfer of monolayers of HPAS onto solid substrates results in a Y-type deposition. Single layer LB films transferred at several surface pressures onto mica substrates have been analyzed by means of atomic force microscopy, from which it can be concluded that 20mN/m is an optimum surface pressure of transfer, giving well-ordered homogeneous films without three dimensional defects and a low surface roughness. The optical properties of the LB films have been determined, with significant blue-shifted absorption spectra suggesting that the two dimensional H-aggregates at the air–water interface are transferred undisturbed onto the solid substrates. In addition, absorption and emission spectra are indicative of a strongly coupled excitonic interaction between the HPAS H-aggregates. X-ray reflectivity (XRR) experiments yielded a film thickness consistent with one monolayer in which the molecules are tilted 73° with respect to the solid substrate.
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    • "We have used multimode imaging to demonstrate J-aggregate coupling between pyronine dye molecules inside the sub-nanometre one-dimensional nanochannels of zeolite L (Busby et al. 2008). Organizing molecules in a defined manner holds great promise to realize highly structured systems that exploit properties that only arise due to the defined molecular geometry. "
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    ABSTRACT: Multimode microscopy exploits the measurement of multiple spectroscopic parameters to yield a wealth of spatially resolved spectroscopic detail about the sample under study. Here, we describe the realization of a multimode microscope capable of wide-field transmission, reflectivity and emission imaging. The instrument also incorporates confocal spectral and lifetime imaging enabling convenient high-content imaging of complex samples, allowing the direct correlation of the data obtained from the different modes. We demonstrate the versatility of this imaging platform by reviewing applications to the modulation of fluorescent protein emission by inverse opal photonic crystals, to the detection and visualization of J-aggregate coupling of small molecule dyes intercalated into nanochannels in zeolites and to the visualization of fluorescent proteins micropatterned onto surfaces. In all cases, the combination of different microspectroscopic modes is essential for the resolution of specific photophysical details of the complex systems in question.
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