Martin Strobl

NIR optical carbon dioxide sensors based on highly photostable dihydroxy-aza-BODIPY dyes

A new class of pH-sensitive indicator dyes for optical carbon dioxide sensors based on di-OH-aza-BODIPYs is presented. These colorimetric indicators show absorption maxima in the near infrared range (λmax 670–700 nm for the neutral form, λmax 725–760 nm for the mono-anionic form, λmax 785–830 nm for the di-anionic form), high molar absorption coefficients of up to 77 000 M−1 cm−1 and unmatched photostability. Depending on the electron-withdrawing or electron-donating effect of the substituents the pKa values are tunable (8.7–10.7). Therefore, optical carbon dioxide sensors based on the presented dyes cover diverse dynamic ranges (0.007–2 kPa; 0.18–20 kPa and 0.2–100 kPa), which enables different applications varying from marine science and environmental monitoring to food packaging. The sensors are outstandingly photostable in the absence and presence of carbon dioxide and can be read out via absorption or via the luminescence-based ratiometric scheme using the absorption-modulated inner-filter effect. Monitoring of the carbon dioxide production/consumption of a Hebe plant is demonstrated.

Fast pesticide detection inside microfluidic device with integrated optical pH, oxygen sensors and algal fluorescence

The necessities of developing fast, portable, cheap and easy to handle pesticide detection platforms are getting attention of scientific and industrial communities. Although there are some approaches to develop microchip based pesticide detection platforms, there is no compact microfluidic device for the complementary, fast, cheap, reusable and reliable analysis of different pesticides. In this work, a microfluidic device is developed for in-situ analysis of pesticide concentration detected via metabolism/photosynthesis of Chlamydomonas reinhardtii algal cells (algae) in tap water. Algae are grown in glass based microfluidic chip, which contains integrated optical pH and oxygen sensors in a portable system for on-site detection. In addition, intrinsic algal fluorescence is detected to analyze the pesticide concentration in parallel to pH and oxygen sensors with integrated fluorescence detectors. The response of the algae under the effect of different concentrations of pesticides is evaluated and complementary inhibition effects depending on the pesticide concentration are demonstrated. The three different sensors allow the determination of various pesticide concentrations in the nanomolar concentration range. The miniaturized system provides the fast quantification of pesticides in less than 10min and enables the study of toxic effects of different pesticides on Chlamydomonas reinhardtii green algae. Consequently, the microfluidic device described here provides fast and complementary detection of different pesticides with algae in a novel glass based microfluidic device with integrated optical pH, oxygen sensors and algal fluorescence.

Trace Ammonia Sensors Based on Fluorescent Near-Infrared-Emitting aza-BODIPY Dyes

Highly sensitive ammonia sensors for environmental monitoring are presented. The sensing materials are based on fluorescent BF2-chelated tetraarylazadipyrromethene dyes (aza-BODIPYs) dyes physically entrapped in polyurethane hydrogels and dispersed in silicone rubber. This layer is covered by a hydrophobic porous Teflon membrane used as an additional proton barrier and light scattering layer. The dual-lifetime referenced (DLR) sensors make use of near-infrared (NIR)-emitting Egyptian blue as a reference material and in combination with optical fibers are read-out via a compact phase-fluorometer. The detectable concentration range can be tuned by the choice of aza-BODIPY dye or/and the hydrogel matrix. The most sensitive sensor has a limit of detection (LOD) of 0.11 μg/L and the upper detectable concentration of 300 μg/L. No cross-sensitivity toward pH is observed. The sensors show remarkable operational stability with no noticeable drift over a period of 2 weeks.

Modeling procedural knowledge: a generative modeler for cultural heritage

Within the last few years generative modeling techniques have gained attention especially in the context of cultural heritage. As a generative model describes a rather ideal object than a real one, generative techniques are a basis for object description and classification. This procedural knowledge differs from other kinds of knowledge, such as declarative knowledge, in a significant way. It can be applied to a task. This similarity to algorithms is reflected in the way generative models are designed: they are programmed. In order to make generative modeling accessible to cultural heritage experts, we created a generative modeling framework which accounts for their special needs. The result is a generative modeler (http://www.cgv.tugraz.at/euclides) based on an easy-to-use scripting language (JavaScript). The generative model meets the demands on documentation standards and fulfils sustainability conditions. Its integrated meta-modeler approach makes it independent from hardware, software and platforms.

Highly Sensitive Poisoning-Resistant Optical Carbon Dioxide Sensors for Environmental Monitoring

A new optical carbon dioxide sensor for environmental monitoring is presented. It combines a robust and long-term stable sensing material with a compact read-out device. The sensing material relies on a NIR pH indicator immobilized into ethyl cellulose along with a quaternary ammonium base. The perfluorinated polymer Hyflon AD 60 used as a protection layer significantly enhances the long-term and mechanical stability of the sensor foils, as well as the robustness against poisoning gases, e.g. hydrogen sulfide. The sensor can be stored under ambient conditions for more than six weeks, whereas sensors covered with silicone rubber deteriorate within one week under the same conditions. The complete sensor device is applicable after a three-point (re)calibration without a preconditioning step. The carbon dioxide production and consumption of the water plant Egeria densa was measured in the laboratory. Furthermore, results of profiling carbon dioxide measurements during a research cruise on the Baltic Sea at water depths up to 225 m are presented.

Publishing 3D content as PDF in cultural heritage

Sharing 3D models with embedded annotations and additional information in a generally accessible way still is a major challange. Using 3D technology must become much easier, in particular in areas such as Cultural Heritage, where archeologists, art historians, and museum curators rely on robust, easy to use solutions. Sustainable exchange standards are vital since unlike in industry, no sophisticated PLM or PDM solutions are common in CH. To solve this problem we have examined the PDF file format and developed concepts and software for the exchange of annotated 3D models in a way that is not just comfortable but also sustainable. We show typical use cases for authoring and using PDF documents containing annotated 3D geometry. The resulting workflow is efficient and suitable for experienced users as well as for users working only with standard word processing tools and e-mail clients (plus, currently, Acrobat Pro Extended).