Calorimetric gas sensors for monitoring the H 2 O 2 concentration at elevated temperatures in industrial sterilisation processes have been presented in previous works. These sensors are built up in form of a differential set-up of a catalytically active and passive temperature-sensitive structure. Although, various types of catalytically active dispersions have been studied, the passivation layer has to be established and therefore, chemically as well as physically characterised. In the present work, fluorinated ethylene propylene (FEP), perfluoralkoxy (PFA) and epoxy-based SU-8 photoresist as temperature-stable polymeric materials have been investigated for sensor passiva-tion in terms of their chemical inertness against H 2 O 2 , their hygroscopic properties as well as their morphology. The polymeric materials were deposited via spin-coating on the temperature-sensitive structure, wherein spin-coated FEP and PFA show slight agglomerates. However, they possess a low absorption of humidity due to their hydrophobic surface, whereas the SU-8 layer has a closed surface but shows a slightly higher absorption of water. All of them were inert against gaseous H 2 O 2 during the characterisation in H 2 O 2 atmosphere that demonstrates their suitability as passivation layer for calorimetric H 2 O 2 gas sensors.

In this work, a multi-sensor chip for the investigation of the sensing properties of different types of metal oxides towards hydrogen peroxide in the ppm range is presented. The fabrication process and physical characterization of the multisensor chip are described. Pure SnO 2 and WO 3 as well as Pdand Pt-doped SnO 2 films are characterized in terms of their sensitivity to H 2 O 2 . The sensing films have been prepared by drop-coating of water-dispensed nano-powders. A physical characterization, including scanning electron microscopy and X-ray diffraction analysis of the deposited metal-oxide films, was done. From the measurements in hydrogen peroxide atmosphere, it could be shown, that all of the tested metal oxide films are suitable for the detection of H 2 O 2 in the ppm range. The highest sensitivity and reproducibility was achieved using Pt-doped SnO 2 .Calibration plot of a SnO 2 , WO 3 , Pt-, and Pd-doped SnO 2 gas sensor for H 2 O 2 concentrations in the ppm range.

The presented work focuses on the development of a multisensor system for the evaluation of aseptic processes employing hydrogen peroxide vapour. In a first step, selected commercially available gas sensors have been investigated on crosssensitivity towards hydrogen peroxide vapour and humidity. An MOX (TGS 816, Figaro) and a solid-electrolyte gas sensor (SO-A0-250, Electrovac) (l-probe) have shown good characteristics in terms of sensitivity towards HPV, considering also reproducibility, long-term drift and stability. Further, the sterilization effect of HPV has been investigated by means of the microbial reduction test. A correlation between the microbial reduction of Bacillus subtilis spores and the sensor response in hydrogen peroxide atmosphere has been established. Based on this correlation the microbial reduction may be estimated by means of the sensor output over a wide range of parameters.

241 6009 53235 A handheld sensor system for the online measurement of hydrogen peroxide (H 2 O 2 ) in aseptic sterilisation processes has been developed. It is based on a calorimetric-type gas sensor that consists of a differential set-up of two temperature sensors, of which one is catalytically activated and the second one is passivated and used as reference. The sensor principle relies in detecting a rise in temperature on the active sensor due to the exothermic reaction of H 2 O 2 on the catalytic surface. To characterise the sensor system towards H 2 O 2 sensitivity and other influencing factors, measurements have been carried out both at an experimental set-up and a manufacturer's sterilisation machine. Physical sensor characterisation was done by means of the optical microscopy.

We present a sensor concept based on copper(II)oxide (CuO) nanofibres for the detection of hydrogen peroxide (H 2 O 2 ) vapour in the percent per volume (% v/v) range. The fibres were produced by using the electrospinning technique. To avoid water condensation in the pores, the fibres were initially modified by an exposure to H 2 S to get an enclosed surface. By a thermal treatment at 350 8C the fibres were oxidised back to CuO. Thereby, the visible pores disappear which was verified by SEM analysis. The fibres show a decrease of resistance with increasing H 2 O 2 concentration which is due to the fact that hydrogen peroxide is an oxidising gas and CuO a p-type semiconductor. The sensor shows a change of resistance within the minute range to the exposure until the maximum concentration of 6.9% v/v H 2 O 2 . At operating temperatures below 450 8C the corresponding sensor response to a concentration of 4.1% v/v increases. The sensor shows a good reproducibility of the signal at different measurements. CuO seems to be a suitable candidate for the detection of H 2 O 2 vapour at high concentrations.Resistance behaviour of the sensor under exposure to H 2 O 2 vapours between 2.3 and 6.9% v/v at an operating temperature of 450 8C.