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Franz L Dickert

Publications and source records attributed to Franz L Dickert.

8 recordsLinked to original sources
PubMed2006

Sensor technology and its application in environmental analysis.

Environmental analysis is one of the fundamental applications of chemical sensors. In this review we describe different sensor systems for the gas and liquid phases that have been tested either with real-life samples or in the field during the last five years. Most field sensors rely either on electrochemical or optical transducers. In the gas phase, systems have been proposed for analysis of oxides of nitrogen, carbon, and sulfur in air, and volatile organic compounds. In the liquid phase, most detection systems used for real-life samples detect heavy-metal ions or organic contamination, for example pesticides, organic solvents and polycyclic aromatic hydrocarbons.

Journal Article↗
PubMed2006

Cavities generated by self-organised monolayers as sensitive coatings for surface acoustic wave resonators.

Silanisation of quartz substrate surfaces with a mixture of two chlorosilanes, namely trimethylchlorosilane and 7-octenyldimethylchlorosilane, leads to sensitive coatings for volatile organic compounds (VOC) on surface acoustic wave (SAW) devices. In this way we created monolayers of molecular cavities engulfing the analytes according to host-guest chemistry directly on the device surfaces, and also confirmed the occurrence of such cavities by molecular modelling. We monitored the binding process of the silanes by using Fourier transform infrared (FTIR) spectrometry and atomic force microscopy (AFM). In order to increase the stiffness of the cavities, we crosslinked the terminal double bonds of the long spacers by heating the surface in the presence of a radical initiator. Compared to SAW delay lines silanised with trimethylchlorosilane, devices modified with the binary silane mixture lead to substantially higher frequency shifts when exposed to solvent vapour streams. Nearly instantaneous responses can be observed, which e.g. allows xylene detection down to a few ppm.

Journal Article↗
PubMed2006

Surface imprinting strategies for the detection of trypsin.

Self-organized receptor layers are synthesized by molecular imprinting methods directly on pre-coated 10 MHz quartz-crystal microbalances (QCMs). The surface-imprinting is performed by three methods using amorphous, crystalline and solubilized trypsin, respectively, as templates. These attempts allowed us to compare imprinting results obtained with templating proteins in the dry state as well as in aqueous solution. All methods are generally applicable for surface imprinting of thin films. The biomimetic sensor layers allow selective enzyme enrichment on the imprinted electrode with detection limits as low as 100 ng ml(-1) and response times of a few minutes. Solution-based polymer imprinting with native trypsin as template resulted in the highest specific enzyme recognition, which even allowed us to distinguish denatured trypsin from the native form.

Animals↗
PubMed2004

Synthetic receptors for chemical sensors--subnano- and micrometre patterning by imprinting techniques.

Antibody-like selectivities are introduced into man-made polymeric systems by means of molecular imprinting. On the molecular scale, organic contaminants in water were analysed by 10 MHz QCM sensors coated both with affinity layers and with selective imprinted polymers. Affinity layers, polystyrene/silicone, yield sensor effects for aromatic hydrocarbons according to, e.g., molecular weight and solubilities, a prediction by molecular modelling is proposed. Imprinted layers, however, recognise molecular shapes: the lean toluene is favoured by factor of six to the more bulky o-xylene; even the three xylenes can be distinguished from each other. On the micrometre scale, erythrocytes of different blood groups are differentiated, although their geometrical shape is identical. In this case, the recognition is accomplished by a predefined hydrogen bonding network between excess OH groups of the polyurethane layer and the sugar molecules on the cell surface defining the blood group.

Biomimetic Materials↗
PubMed2004

QCM array for on-line-monitoring of composting procedures.

Six QCM resonators forming a sensor array were coated with different molecularly imprinted polymers for the on-line monitoring of composting procedures. Four key analytes are traced, namely water, 1-propanol, ethyl acetate and limonene. Trendlines obtained on-line by the sensor during measurements in a commercial composter give a distinct pattern: the signal for the alcohols first decreases according to an increase in ethyl acetate concentration, and increases again, when obviously no more acetic acid is formed. Limonene is detected in later stages of composting. Similar trends could also be observed by GC-MS. Additionally, chromatographic and sensor data for limonene could be correlated with each other.

Electrochemistry↗
PubMed2004

Bioimprinted QCM sensors for virus detection-screening of plant sap.

Surface imprinting techniques on polymer-coated quartz-crystal microbalances (QCM) have been used to detect tobacco mosaic viruses (TMV) in aqueous media. Molecularly imprinted polymers (MIP), tailor-made by self organisation of monomers around a template (TMV), were generated directly on the gold electrodes. Imprinted trenches on the polymer surface mimicking the shape and surface functionality of the virus serve as recognition sites for re-adsorption after washing out of the template. The sensors are applicable to TMV detection ranging from 100 ng mL(-1) to 1 mg mL(-1) within minutes. Furthermore, direct measurements without time-consuming sample preparation are possible in complex matrices such as tobacco plant sap.

Biosensing Techniques↗