Zeolite-dye micro lasers

We present a new class of micro lasers based on nanoporous molecular sieve host-guest systems. Organic dye guest molecules of 1-Ethyl-4-(4-(p-Dimethylaminophenyl)-1,3-butadienyl)-pyridinium Perchlorat were inserted into the 0.73-nm-wide channel pores of a zeolite AlPO$_4$-5 host. The zeolitic micro crystal compounds where hydrothermally synthesized according to a particular host-guest chemical process. The dye molecules are found not only to be aligned along the host channel axis, but to be oriented as well. Single mode laser emission at 687 nm was obtained from a whispering gallery mode oscillating in a 8-$\mu$m-diameter monolithic micro resonator, in which the field is confined by total internal reflection at the natural hexagonal boundaries inside the zeolitic microcrystals.Comment: Accepted for publication in Phys. Rev. Let

Synthesis of millimeter-sized perfect AlPO₄-5 crystals

Large, perfect hexagonally shaped AlPO4-5 crystals with maximum length up to 1.4 mm have been crystallized in hydrothermal syntheses carried out at 453 K with a crystallization period of 20 h. The improved length growth is attributed to the replacement of triethylamine (TEA) with tripropylamine (TPA) and to higher dilution of the gel. Better crystal quality is achieved by using ultra-purified water. Insolubility of the template in the absence of alcohol induces deep pits in the surface of the crystals, although the length is retained and reaches up to 1.0 mm. During these experiments a new by-product for AlPO4-5 syntheses has been identified and structurally classified as AlPO4-36. This is in contrast to previously used synthesis systems with triethylamine, in which only dense aluminumphosphate phases were identified as by-products

Alignment of a Laser Dye in the Channels of the AlPO₄-5 Molecular Sieve

Solid-state laser systems based on molecular sieves may not be far away. Here, the incorporation and linear alignment of a pyridine-based laser dye in the channels of AlPO4-5 is reported and the spectroscopic properties of the composite are investigated. A first indication that AlPO4-5–laser dye composite crystals show laser action is demonstrated for microcrystals with a highly intergrown shap

Ordered porous materials as media for the organization of matter on the nanoscale

Ordered porous inorganic compounds can now be synthesized with pore sizes between 0.3 nm and several tens of nanometers. The sharp pore size distribution of such materials and the ordered pore arrangement open possibilities for using them to organize matter on the nanometer scale. This overview highlights different aspects of this topic, using four selected examples: the spatial organization of molecules with high molecular hyperpolarizability to create a frequency-doubling element; the encapsulation of a laser dye which results in a new class of solid-state lasers; the encapsulation of small metal clusters in mesoporous ordered oxides; and the encapsulation of semiconductor clusters in such oxides

Molecular dynamics in zeolitic host systems

Broadband dielectric spectroscopy (10-2Hz - 109Hz) is employed to study the molecular dynamics of the simple glassforming liquid ethylene glycol (EG) being confined to zeolites of varying size and topology. A sharp transition is observed from a single molecule dynamics (with an Arrhenius-type temperature dependence) to that of a liquid (with a temperature dependence of the mean relaxation rate according to a Vogel-Fulcher-Tammann-law (VFT-law)): While EG in silicalite and H-ZSM-5 (showing a single-molecule relaxation) has a coordination number of four, EG in zeolite beta or AIPO4-5 has a coordination number of five and behaves like a bulk liquid

Glass Transition in Sub-nanometer Confinement

Broadband dielectric spectroscopy (10−2 Hz - 109Hz) is employed to study the molecular dynamics of low-molecular-weight glassforming liquids being confined to nanopores. For the H-bond forming liquid propylene glycol being confined to (uncoated and silanized) nanopores (pore size: 2.5 nm, 5.0 nm and 7.5 nm) a molecular dynamics is observed which is comparable to that of the bulk liquid. Due to surface effects in uncoated nanopores the relaxation time distribution is broadened on the long term side and the mean relaxation rate is decreased by about half a decade. This effect can be counterbalanced by lubricating the inner surfaces of the pores resulting in a relaxation rate which is slightly faster compared to the bulk liquid. For the H-bonded liquid ethylene glycol (EG) embedded in zeolites of different pore size and topology one observes a sharp transition from a single-molecule dynamics to that of a liquid depending on the coordination number of the confined molecules. While EG in silicalite (showing a single molecule relaxation) has four neighboring molecules, EG in zeolite beta or AIPO4-5 has a coordination number of five and behaves like a bulk liquid