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The fast identification and quantification of analytes in the field of food safety or environmental analysis is difficult. Surface enhanced Raman scattering (SERS) is an analytical method which can be used simultaneously for the rapid identification and concentration determination of trace analytes,[1,2] usually covering a large dynamic range from nanomolar up to molar concentrations. The identification of the molecules is accomplished through the specific fingerprint of a molecule’s Raman spectrum.
For facile and straightforward SERS measurements, we present here a combination of paper-based SERS test strips with microfluidic systems on paper as a microfluidic paper-based analytical device (μPAD). The SERS μPAD is thus principally suited for cheap, fast, non-destructive, label-free and portable detection of analytes. In this system basically, the use of the microfluidic structured paper increases the sensitivity and suppresses background signals of the SERS assay.
Deposition of the SERS substrate on the test strips is simple and relies on an inkjet printer. For the optimization of the reproducibility and intensity of the SERS signal, we tested different nanoparticles, different numbers of print cycles and different paper types. The nanoparticle solutions used in the μPAD preparation were gold and silver nanoparticle solutions. The paper types were cellulose and glass fiber. SERS arrays were prepared by printing and compared to arrays prepared by spraying. The optimized μPAD was used for the identification and quantification of pure analyte solutions (e.g., adenine) and mixtures of compounds, the concentration series following Langmuir isotherms.
Relevant analytes in the field of food safety are antibiotics and pesticides. We apply the SERS microfluidic paper-based analytical devices for the detection of antibiotics (enoxacin, enrofloxacin) and pesticides.
The aim of the lecture is to present the productive interplay of connoisseurs and material analysis using the example of selected drawings from the Rembrandt collection of the Klassik Stiftung Weimar. We try to determine the point at which the question of the materiality of the drawings makes sense in the traditional discourse of connoisseurship. On the one hand, this involves the question of authorship – Rembrandt – or not? – and the locating of attributed drawings in the context of the work. On the other hand, it is about making drawing processes visible, characterizing ways of drawing and workshop practices as well as distinguishing different forms of reworking and copying within the Rembrandt workshop. The material analyses culminate in the question of whether Rembrandt’s inks can be distinguished at all.
It becomes apparent that the newly gained knowledge about the materiality of the drawing no longer reveals itself to the “mere” view of the connoisseur. Rather, it is only generated by the digital image. The rhetoric of connoisseurs must therefore be contrasted with the necessity of a hermeneutics of the digital image. The envisaged “material turn” of drawing science is thus simultaneously able to take up the critique of the question of authorship, which has been growing ever more recently, and to transfer it to a more comprehensive perspective of aesthetics of production.