Bioanalogous Recognition with Sol-Gel Thin Films and Nanoparticles in Harsh Environments
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1094-DD05-08
Bioanalogous Recognition with Sol-Gel Thin Films and Nanoparticles in Harsh Environments Peter A. Lieberzeit, Adeel Afzal, Adnan Mujahid, and Franz Dickert Department of Analytical Chemistry and Food Chemistry, University of Vienna, Waehringer Strasse 38, Vienna, 1090, Austria ABSTRACT Sol-gel thin films and nanoparticles can be functionalized by imprinting strategies based on self-organization of the polymer precursors around a template compound. The resulting rugged layers are highly suitable for operating as sensor layers in harsh environments, such as engine oils. By adding e.g. dimethyl formamide or polyethylene glycol to titanate sols, the resulting layers show substantially increased sensitivity due to higher porosity and accessibility of the recognition sites. The same is true for nanoparticles, where the sensor effects are directly correlated to particle dimensions. Furthermore, also imprinted ZrO2 nanoparticles show very appreciable selectivity. INTRODUCTION Biology increasingly inspires materials science to implement the exceptional functionality of natural compounds within rugged, artificial matrices. One example for this is bioanalogous recognition, which can e.g. be achieved by molecular imprinting [1] as shown in Figure 1 depicting the synthesis of functional (nano)particles: here a template is used for
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Figure 1: Principle of generating molecularly imprinted particles directing the growth of a highly cross-linked polymer backbone. After removing it, the polymer retains interaction centers being capable of reversibly incorporating it again. The strategy e.g. leads to biomimetic sensor layers that can operate for extended periods of time in environments
being too harsh for biomaterials and has proven highly useful both in the detection of molecules, where e.g. solvents can be distinguished by as little as a single methyl group [2, 3], or also biological entities, such as entire cells [4], proteins [5] and viruses [6]. This is one of the application examples clearly showing the advantage of artificial layers, as no natural receptor would retain its functionality when subjected to the elevated temperatures and the demanding chemical environment within an oil pan. Aside of the outstandingly straightforward approach, imprinting also allows for an exceptional flexibility in tuning the material according to the properties desired. Within this paper, we present the influence of how different synthetic approaches lead to optimized interaction properties within sol-gel based inorganic molecularly imprinted polymers (MIP) optimized for engine oil degradation sensing. EXPERIMENT We prepared TiO2 sol-gel layers by dissolving 10mg of the template (e.g. capric acid) in 970µL of iso-propanol. Then we added 67µL of Ti(OBu)4 as monomer to the solution. To initiate and propagate hydrolysis and condensation of the titanates, 10µL of TiCl4 were added. The mixture was allowed to polymerize at 60°C for an hour while stirring. The water necessary for hydrolysis came from the iso-propanol that contained
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