Cu2O@PNIPAM core–shell microgels as novel inkjet materials for the preparation of CuO hollow porous nanocubes gas sensing layers

There has been long-standing interest in developing metal oxide-based sensors with high sensitivity, selectivity, fast response and low material consumption. Here we report for the first time the utilization of Cu2O@PNIPAM core–shell microgels with a nanocube-shaped core structure for construction of novel CuO gas sensing layers. The hybrid microgels show significant improvement in colloidal stability as compared to native Cu2O nanocubes. Consequently, a homogeneous thin film of Cu2O@PNIPAM nanoparticles can be engineered in a quite low solid content (1.5 wt%) by inkjet printing of the dispersion at an optimized viscosity and surface tension. Most importantly, thermal treatment of the Cu2O@PNIPAM microgels forms porous CuO nanocubes, which show much faster response to relevant trace NO2 gases than sensors produced from bare Cu2O nanocubes. This outcome is due to the fact that the PNIPAM shell can successfully hinder the aggregation of CuO nanoparticles during pyrolysis, which enables full utilization of the sensor layers and better access of the gas to active sites. These results point out great potential of such an innovative system as gas sensors with low cost, fast response and high sensitivitH. J. gratefully acknowledges financial support of the CSC scholarship. S. P. acknowledges funding from the Community of Madrid under grant number 2016-T1/AMB-1695

Copper(II)Oxide for Hydrogen Sulfide Detection

During the generation of biogas, various contaminant gases occur beside the desired methane. Hydrogen sulfide (H2S) and volatile siloxanes (VMS) are two main contaminants causing severe damage to facility parts and attached cogeneration units. Different filtering techniques are established, but operated in inefficient overdosing mode because current detection systems are measuring discontinuously or having no detection unit for contaminants at all. Scope of the thesis is the development of a sensor concept, which is able to continuously and selectively measure contaminant gases for dynamic control system to improve filtering techniques and prevent frequent maintenance or failure. For the mentioned gases possible approaches for the detection of H2S, being a reducing gas, are for example the resistive read-out of polymer ion-sensitive layers or copper oxide/tin oxide hetero junctions. Molecules of the VMS family are comparably unreactive. This requires research on specifically adsorbing layers and mass- or surface sensitive detection principles

Odor-Sensing System to Support Social Participation of People Suffering from Incontinence

This manuscript describes the design considerations, implementation, and laboratory validation of an odor sensing module whose purpose is to support people that suffer from incontinence. Because of the requirements expressed by the affected end-users the odor sensing unit is realized as a portable accessory that may be connected to any pre-existing smart device. We have opted for a low-cost, low-power consuming metal oxide based gas detection approach to highlight the viability of developing an inexpensive yet helpful odor recognition technology. The system consists of a hotplate employing, inkjet-printed p-type semiconducting layers of copper(II) oxide, and chromium titanium oxide. Both functional layers are characterized with respect to their gas-sensitive behavior towards humidity, ammonia, methylmercaptan, and dimethylsulfide and we demonstrate detection limits in the parts-per-billion range for the two latter gases. Employing a temperature variation scheme that reads out the layer’s resistivity in a steady-state, we use each sensor chip as a virtual array. With this setup, we demonstrate the feasibility of detecting odors associated with incontinence