This review paper discusses the influence of morphology and crystallographic structure on gas-sensing characteristics of metal oxide conductometric-type sensors. The effects of parameters such as film thickness, grain size, agglomeration, porosity, faceting, grain network, surface geometry, and film texture on the main analytical characteristics (absolute magnitude and selectivity of sensor response (S), response time (τres), recovery time (τrec), and temporal stability) of the gas sensor have been analyzed. A comparison of standard polycrystalline sensors and sensors based on one-dimension structures was conducted. It was concluded that the structural parameters of metal oxides are important factors for controlling response parameters of resistive type gas sensors. For example, it was shown that the decrease of thickness, grain size and degree of texture is the best way to decrease time constants of metal oxide sensors. However, it was concluded that there is not universal decision for simultaneous optimization all gas-sensing characteristics. We have to search for a compromise between various engineering approaches because adjusting one design feature may improve one performance metric but considerably degrade another.

The role of morphology and crystallographic structure of metal oxides in response of conductometric-type gas sensors

6.2. Orthogonality versus Independence 584 6.3. Cross-sensitivity and Diversity 585 6.4. Multiple Roles of Redundancy 585 7. Data Preprocessing 586 7.1. Baseline Correction 586 7.2. Scaling 587 7.2.1. Global Techniques 588 7.2.2. Local Techniques 588 7.2.3. Nonlinear Transforms 588 8. Drift Compensation 588 8.1. Univariate Drift Compensation 589 8.2. Multivariate Drift Compensation 589 9. Feature Extraction from Sensor Dynamics 591 9.1. Transient Analysis 591 9.1.1. Oversampling Procedures 592 9.1.2. Ad hoc Transient Parameters 593 9.1.3. Model-Based Parameters 593 9.1.4. Comparative Studies 595 9.2. Temperature-Modulation Analysis 596 10. Multivariate Calibration 599 10.1. Multiway Analysis 599 10.2. Dynamical Models 602 11. Array Optimization 604 11.1. Sensor Selection 604 11.2. Feature Selection 605 11.3. Optimization of Excitation Profiles 607 12. Conclusion and Outlook 608 13. References 609

Higher-order chemical sensing.

Several metal-organic framework (MOF) materials were under investigated to test their applicability as sensor materials for impedimetric gas sensors. The materials were tested in a temperature range of 120 °C - 240 °C with varying concentrations of O2, CO2, C3H8, NO, H2, ethanol and methanol in the gas atmosphere and under different test gas humidity conditions. Different sensor configurations were studied in a frequency range of 1 Hz -1 MHz and time-continuous measurements were performed at 1 Hz. The materials did not show any impedance response to O2, CO2, C3H8, NO, or H2 in the gas atmospheres, although for some materials a significant impedance decrease was induced by a change of the ethanol or methanol concentration in the gas phase. Moreover, pronounced promising and reversible changes in the electric properties of a special MOF material were monitored under varying humidity, with a linear response curve at 120 °C. Further investigations were carried out with differently doped MOF materials of this class, to evaluate the influence of special dopants on the sensor effect.

Metal-Organic Frameworks for Sensing Applications in the Gas Phase

Single-walled carbon nanotubes coated with crystalline tin oxide by a simple chemical-solution route are reported. The room-temperature chemical treatment results in a nominally complete and unifor...

Coating Single-Walled Carbon Nanotubes with Tin Oxide

Transition metal oxides – Thermoelectric properties

This review deals with gas sensors combining a metal oxide based sensing layer and a substrate realized by using micromachining. It starts by giving an overview of the design principles and technology involved in the fabrication of micromachined substrates examining thermal and mechanical aspects. Both kinds of micromachined substrates, closed-membrane-type and the suspended-membrane-type, are discussed. The deposition of the sensing layer is complicated by the mechanical fragility of the micromachined substrates. Different approaches used for the formation of the sensing layer such as thin film and thick film deposition techniques are reviewed. Finally, the gas sensing function of the sensitive layer is analyzed and various ways for extracting the information are presented with respect to the improvement of sensor performance brought by this new approach.

Micromachined metal oxide gas sensors: opportunities to improve sensor performance

https://febs.onlinelibrary.wiley.com/doi/pdf/10.1016/0014-5793%2892%2981211-4

ATP binding to bovine serum albumin.

Die Erfindung betrifft ein Verfahren zum Ermitteln eines Korrekturwertes fur eine Kraftstoffzumessung eines Kraftstoffinjektors (130) einer Brennkraftmaschine (100), bei der mittels des Kraftstoffinjektors (130) Kraftstoff aus einem Hochdruckspeicher (120) in einen Brennraum (105) eingespritzt wird, wobei ein fur eine statische Durchflussrate durch den Kraftstoffinjektor (130) reprasentativer Wert ermittelt wird, indem bei wenigstens einem Einspritzvorgang des Kraftstoffinjektors (130) ein Verhaltnis einer im Hochdruckspeicher (120) aufgrund des Einspritzvorgangs auftretender Druckdifferenz und einer zugehorigen, fur den Einspritzvorgang charakteristischen Dauer ermittelt wird, und wobei anhand eines Vergleichs des reprasentativen Wertes mit einem Vergleichswert der Korrekturwert ermittelt wird.

Verfahren zum Ermitteln eines Korrekturwertes für eine Kraftstoffzumessung eines Kraftstoffinjektors

A sensor module having a heating structure and a sensor element is described. The heating structure surrounds the sensor element so that heat dissipation through a frame is largely prevented. This yields a greater measuring accuracy of the sensor module. In particular, interfering influences due to a temperature dissipation through the mount frame are thereby prevented.

Michael Bauer

Papers

Micromachined metal oxide gas sensors: opportunities to improve sensor performance

ATP binding to bovine serum albumin.

Verfahren zum Ermitteln eines Korrekturwertes für eine Kraftstoffzumessung eines Kraftstoffinjektors

Sensor module having a sensor element surrounded by a heating element

Chemical Sensors for CO/NOx-Detection in Automotive Climate Control Systems