title: Probing Zeolite Crystal Architecture and Structural Imperfections using Differently Sized Fluorescent Organic Probe Molecules.
abstract: A micro-spectroscopic method has been developed to probe the accessibility of zeolite crystals using a series of fluorescent 4-(4-diethylaminostyryl)-1-methylpyridinium iodide (DAMPI) probes of increasing molecular size. Staining large zeolite crystals with MFI (ZSM-5) topology and subsequent mapping of the resulting fluorescence using confocal fluorescence microscopy reveal differences in structural integrity: the 90° intergrowth sections of MFI crystals are prone to develop structural imperfections, which act as entrance routes for the probes into the zeolite crystal. Polarization-dependent measurements provide evidence for the probe molecule's alignment within the MFI zeolite pore system. The developed method was extended to BEA (Beta) crystals, showing that the previously observed hourglass pattern is a general feature of BEA crystals with this morphology. Furthermore, the probes can accurately identify at which crystal faces of BEA straight or sinusoidal pores open to the surface. The results show this method can spatially resolve the architecture-dependent internal pore structure of microporous materials, which is difficult to assess using other characterization techniques such as X-ray diffraction.
authors.affiliation: Inorganic Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University, Universiteitsweg 99, 3584CG, Utrecht, The Netherlands.
authors.forename: Frank C
authors.identifier: http://orcid.org/0000-0001-8810-6966
authors.initials: FC
authors.lastname: Hendriks
authors.affiliation: Inorganic Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University, Universiteitsweg 99, 3584CG, Utrecht, The Netherlands.
authors.forename: Joel E
authors.identifier: http://orcid.org/0000-0002-0039-2863
authors.initials: JE
authors.lastname: Schmidt
authors.affiliation: Department of Chemistry and Pharmaceutical Sciences, VU University Amsterdam, De Boelelaan 1083, 1081 HV A, msterdam, The Netherlands.
authors.forename: Jeroen A
authors.identifier: http://orcid.org/0000-0003-1550-6330
authors.initials: JA
authors.lastname: Rombouts
authors.affiliation: Department of Chemistry and Pharmaceutical Sciences, VU University Amsterdam, De Boelelaan 1083, 1081 HV A, msterdam, The Netherlands.
authors.forename: Koop
authors.identifier: http://orcid.org/0000-0001-9162-5783
authors.initials: K
authors.lastname: Lammertsma
authors.affiliation: Inorganic Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University, Universiteitsweg 99, 3584CG, Utrecht, The Netherlands.
authors.forename: Pieter C A
authors.identifier: http://orcid.org/0000-0001-8134-0530
authors.initials: PCA
authors.lastname: Bruijnincx
authors.affiliation: Inorganic Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University, Universiteitsweg 99, 3584CG, Utrecht, The Netherlands.
authors.forename: Bert M
authors.identifier: http://orcid.org/0000-0001-5245-1426
authors.initials: BM
authors.lastname: Weckhuysen
keywords: confocal fluorescence microscopy; crystal growth; fluorescent probes; polarization dependence; zeolites