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- 2020 (7) (entfernen)
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- Additive manufacturing (2)
- Analytical chemistry (2)
- Pyrethroids (2)
- Spectroscopy (2)
- Ammunition (1)
- Antibodies (1)
- Biosensors (1)
- Cocaine detection (1)
- Fuel adulteration (1)
- Gated delivery systems (1)
Organisationseinheit der BAM
- 1.9 Chemische und optische Sensorik (7) (entfernen)
Additive Manufacturing (AM) becomes widespread in many technological fields including the precise machining of steel. To assure quality of final products, thorough monitoring of online process is required. We test several monitoring techniques during the AM printing to quickly detect and possibly correct flaws while building a workpiece. Here we show how optical emission spectroscopy can be used to recognize defects that are artificially introduced on a steel printing substrate.
The globe's seas were used as dumping ground after the world wars and those millions of ammunition, most of all containing 2,4,6-trinitrotoluene (TNT), represent a pressing danger for fishermen, dredging operations, submarine cable installations and tourism. We developed an extremely selective indication method for TNT based on a specific reaction that produces a highly fluorescent compound. The indication system was integrated into a microfluidic PDMS chip for the solid-liquid extraction of TNT from water samples, offering environmental monitoring possibilities. Combining the advantages of a light-up indicator, microfluidics and a smartphone as detector, the embedded sensor allows for the remote and rapid detection of TNT down to ng in surface and sea waters.
Sensors are the scientific and technological extension of human senses and enormously expand human capabilities. Despite the fact that scientific and technological advances are usually seen in a positive light, the name of this conference, Sensors for Good, put me in a bit of a trouble, because in general science does not operate in ethical categories, but instead it just tells how far from the truth one is. In this respect, sensors help us in recognizing states and events beyond our immediate reach. Fortunately, sensors are used for many applications, such as environmental monitoring, food control, and alike, which unequivocally benefit society.
I will focus on a particular type of sensors, those that rely on microfluidics for operation and which are typically realized in lab-on-a-chip (LOC) devices. In this domain, where at least one of the dimensions through which a fluid flows is submillimetric, our natural senses fail, because the phenomena are too small to be detected either by eye, smell, touch, and even the common sense explanation that we learn for many years in school is not applicable, because the phenomena are dominated by different parameters. To give one simple example, in general the direction of flow in microfluidic channels does not depend on the up-down direction of the channel, because gravitational force or the weight of the fluid is negligible compared to the viscous forces present on the chip.
This presentation consists of three parts: initially, two sensors produced in our lab are presented, followed by a simulation oriented discussion on microfluidics and biosensors, and finally a project in progress that we are involved in is presented, concluding with a list of open issues raised during the presentation.
Type-I pyrethroids are frequently used for disinfection purposes on airplanes from and to tropical areas as a preventive health measure to control or kill the insect vectors of human diseases including dengue, yellow fever and malaria. The aim of the presented work was the development of such a simple, rapid and effective method for pyrethroid analysis
The urgent necessity to carry out reliable and relevant analytical measurements directly at a point-of-need is one of the current drivers for the development of miniaturised analytical systems, quick tests and wearables. Despite their simplicity, this type of tests must guarantee analytical relevance and reliability like laboratory-based analysis, e.g., in terms of sensitivity, selectivity, immunity against false positives and false negatives as well as robustness and repeatability. Keeping in mind the high sensitivity offered by gated indicator-releasing micro- and nanoparticles due to their inherent features of signal amplification, we performed several optimisations to develop a potential biosensor platform for use in rapid tests. Conceptually, these gated materials are closely related to drug delivery systems, consisting of high porous materials usually closed with macromolecular “caps” and loaded with indicator molecules that are released in presence of a target analyte. However, the key difference between the two types of functional materials is that many drug delivery systems should deliver their cargo over a longer period, often many hours, whereas the gated materials prepared for sensing should show fast release kinetics, on the order of <5 min.
With the aim to optimise and adapt gated materials for sensing purposes, we prepared in this work several antibody-gated materials for small-molecule sensing. The materials consisted of porous silica particles containing indicator molecules in the pores and certain hapten molecules grafted to the particle surface close to the pore openings. The pores were then capped with antibodies binding to these haptens, thus inhibiting the escape of the indicators from inside of the pores. In presence of the corresponding analyte, the antibody is displaced from the surface of the material, allowing the escape of the indicators. This allows the detection of the analyte indirectly through an inherent signal amplification. In this work, the insecticide permethrin, a type-I pyrethroid, was selected as target model, because type-I pyrethroids play an important role in airplane disinfection. A first in-depth study of the various chemical tuning options of such antibody gated systems was performed. Different mesoporous silica supports, different functionalisation routes and different loading sequences were assessed. The materials’ performances were evaluated by studying their temporal response behaviour and detection sensitivity, including the tightness of pore closure (through the amount of blank release in absence of analyte) and the release kinetics. Our results indicate that the better the paratope-accommodating Fab region of the antibody “cap” fits into the host material’s pore openings, the better the closing/opening mechanism can be controlled. Because such materials can be used in various different formats from suspension assays[1] via microfluidic chips[2] to test strip-based lateral flow assays,[3] such materials present a powerful analytical particle platform for the sensitive analytics and diagnostics outside of a laboratory, realising sensitivities down to the µg kg–1 range in less analysis times of less than 5 min as we have recently demonstrated.[4]
Combined Raman and LIBS using Spatial Heterodyne Spectrometer with High Repetition Rate Laser
(2020)
Spatial heterodyne spectroscopy is used for Raman and laser-induced breakdown spectroscopy of six rocks with various mineral content, using high repetition rate diode-pumped solid state lasers. While LIBS data are obtained for all samples, Raman signal was determined only for half of those. This work shows that it is possible to combine LIBS and Raman spectrometry into a single instrument consisting of a DPSS laser for excitation and SHS for spectral recording. For better results and gain from complementary spectrochemical information that the system provides, it is necessary to optimize light collection.