Cu2O Nanoparticles for Application in Printed and Flexible Electronics

This work reports the synthesis of cuprous oxide (Cu2O) nanoparticles (NP) and further application in conductive inks and resistive switching memory devices. A study was conducted on the used method to synthetize the NPs, to identify the influence of each parameter in the final morphology of the NPs. Also, two other studies focused on the stability of the NPs were conducted. In a first approach, non-volatile memories with MIM (Metal-Insulator-Metal) structure were produced on glass substrates. Contacts were made from gold deposited by e-beam and the insulator layer was made of organic compounds with NPs dispersed, deposited by spin-coating. The devices exhibited a unipolar switching, with an ON/OFF current ratio of approximately 103 and working voltages below 30V. Later, similar devices were produced on paper substrates, with intention to replicate the devices using flexible substrates. In this case, pen-writing printing was used method to deposit the newly optimized insulator layer of organic compounds and NPs. The new devices showed an ON/OFF current ratio of 104 and working voltages below 7V. Also 20 cycles were achieved into the opposing 5 achieved on glass produced devices, showing an improved stability and endurance. It was also demonstrated the formation of conductive copper films through reduction of the Cu2O NPs when dispersed in solvents containing glycerol, and recurring to annealing temperatures around 300ºC

Effects of Operating Temperature on Droplet Casting of Flexible Polymer/Multi-Walled Carbon Nanotube Composite Gas Sensors

This study examined the performance of a flexible polymer/multi-walled carbon nanotube (MWCNT) composite sensor array as a function of operating temperature. The response magnitudes of a cost-effective flexible gas sensor array equipped with a heater were measured with respect to five different operating temperatures (room temperature, 40 °C, 50 °C, 60 °C, and 70 °C) via impedance spectrum measurement and sensing response experiments. The selected polymers that were droplet cast to coat a MWCNT conductive layer to form two-layer polymer/MWCNT composite sensing films included ethyl cellulose (EC), polyethylene oxide (PEO), and polyvinylpyrrolidone (PVP). Electrical characterization of impedance, sensing response magnitude, and scanning electron microscope (SEM) morphology of each type of polymer/MWCNT composite film was performed at different operating temperatures. With respect to ethanol, the response magnitude of the sensor decreased with increasing operating temperatures. The results indicated that the higher operating temperature could reduce the response and influence the sensitivity of the polymer/MWCNT gas sensor array. The morphology of polymer/MWCNT composite films revealed that there were changes in the porous film after volatile organic compound (VOC) testing