Furthermore, the amount of template is very decisive. Only a few number of template molecules will generate less interaction centers in the coating, thus a diminished sensor effect will result. A high amount of imprinted molecules causes a dilution of the monomers and an effective polymerization is hindered. The sensor properties of the coatings are tailored according to these ideas [16]. We used different layer heights of polymers in the range of 1�C6 kHz, where 1 kHz corresponds to a thickness of 40 nm. This variation of sensor signal is demonstrated in Figure 2 and an optimum layer height is observed. Obviously this finding can be attributed to a bulk behavior since the response increases in parallel to layer height.
At a layer height of approximately 4�C5 kHz a plateau formation is followed by some hint for a slight decrease in frequency response.
This behavior is easily understood by analyte diffusion in the interior of the layer. Thin layers incorporate analytes easily due to the pores which are generated additionally by the templates. An increasing layer height will statistically block the excess to the diffusion channels and thus the behavior in Figure 2 is explained.Figure 2.Variation of sensor response with changing layer heights of terpinene MIP at 50 ppm.Table 1.Sensor responses to limonene and eucalyptol as function of MIP composition.2.2. Selectivity Pattern of the E-noseFigure 3 shows the selectivity pattern of all polymer layers at 50 ppm concentration of each analyte.
The sensor array is alternatively exposed to different analytes with the same concentration and normalized according to layer height.
The astonishing observation is the capability of the sensor array to distinguish isomeric compounds as ��-pinene and ��-pinene. Similarly all other layers showed maximum selectivity towards their corresponding GSK-3 templates. Thus the designed sensor array proved to be sensitive and selective for online monitoring of terpenes emanated from fresh and dried herbs. In addition, a sensing ability of sensor for analytes with similar structures is beneficial in regard of analyzing complex mixtures. Such problems are best addressed by multivariate analysis and the collected data should be analyzed through modern data analysis tools which are important part of today��s electronic bio-mimetic instruments.
Figure Brefeldin_A 3.Selectivity profile of e-nose at 50 ppm.2.3. Sensitivity Profile Established from Fresh and Dried HerbsThis s
Recently, there has been much research on the Global Navigation Satellite System (GNSS) and its applications are spread over many areas. Location-based services are a good example of GNSS applications.