Molecular Imprinting Through van der Waals Interactions: Fluorescence Detection of PAHs in Water

Abstract

17] The maximum loading of 1 into the MCM-41 was determined by making several samples of MCM-41 with increasing loadings of monomer until an excess of monomer was present. This occurred at approx. 74 wt.-% (estimated standard deviation (esd) 5 %) 1 in calcined MCM-41. All samples prepared with larger quantities of 1 had an excess of 1 that was removed by sublimation. Given an estimated porosity of 1±1.2 cm 3 g ±1 for MCM-41, this seems to be a reasonable loading. The ca. 45 % loaded sample contains approximately 45 % of the determined maximum loading. See the Experimental section for details of how the ca. 45 % loaded and the fully loaded samples were prepared.[18] These NMR assignments at low loadings are consistent with those published by O'Hare and coworkers for the surface derivatization of MCM-41 using a pentane solution of 1 (see [16b]).Chemical sensors [1] are successfully used to monitor air quality, for example, for emission control. Consequently, air pollution is continuously being reduced, but the toxic agents intercepted are increasingly being deposited elsewhere. After deposition, the pollutants contaminate ground water. Therefore the monitoring of harmful substances in liquid media, for example, in seepage water, is becoming more and more important in environmental analysis. This is especially true of the toxic and carcinogenic polycyclic aromatic hydrocarbons (PAHs) [2] that form in incomplete combustion processes, for example, in diesel engines.Because of its high sensitivity, fluorescence spectroscopy [3,4] is a suitable technique for the detection of PAHs.Online measurements in the range of maximum permissible values are favorable and are achieved by improved sensitivity through the use of laser fluorescence and chemical sensor layers. The sensitive coatings can enrich the concentration of the analyte and both sensitivity and selectivity are optimized by chemical recognition. Pyrene and anthracene are used here as test analytes for the evaluation of the potential of this method. Supramolecular compounds, for example, molecular cavities, [5] are promising materials in sensor design in combination with both microelectronic devices and optical detection principles. However, complex synthesis is necessary to generate these host molecules. The technique of molecular imprinting [6±8] opens up new prospects as these materials can be directly generated on the transducer by polymerization in the presence of the analyte, which is efficiently extracted even from complex matrices. [9] After completion of this on-chip polymerization reaction, the template molecules are removed by dissolution. Diffusion pathways and adapted cavities ideally suited to the analyte's reinclusion are left behind. Improved properties as regards mechanical stability, insolubility, and chemical inertness in the case of in-liquid-sensing are accomplished. In the the case of PAHs no pronounced functionality exists and therefore the imprinting process is performed through all kinds of noncovalent interactions, summarized as van der W...

Simple method for the fabrication of 1-hydroxypyrene-imprinted TiO2 gel nanofilms

“…The matrix for imprinting has mostly been cross-linked polymers, and the imprinting effect was enhanced by the spatial fixation of functional monomer units that interact with template molecules. Various approaches to develop PAH-imprinted polymer matrices, such as polyurethane films, styrene-co-devinylbenzene imprinted polymer, and pyrene-imprinted microspheres, have been proposed over the last decade [8][9][10][11]. However, imprinted polymer matrices have some drawbacks, such as low binding efficiency and a slow binding process.…”

The development of a MIP-optosensor for the detection of monoamine naphthalenes in drinking water

“…It indicates that the pore size of a polymer is specifically adapted to the size of the compounds even if no covalent bonding between template and monomer is used. Even weak interactions such as Van der Waals forces or -interactions are sufficient to induce specific orientations of the reacting compounds during polymerization, thus enabling the design of sterically adapted cavities suitable for reversible inclusion of the analytes (Dickert et al, 1998).…”

Solid‐state Sensors for Field Measurements of Gases and Vapors

“…A possibility of their direct detection via fluorescence spectrometry using molecularly imprinted polymers has been described. (128) The sensors produced provide both good selectivity between different PAHs and low detection limits, as can be seen in Figures 35 and 36. Concentration limits for the fluorimetric measurements are down to 1 μg L −1 and even lower.…”