Highly Sensitive Humidity Sensors Based on Polyethylene Oxide/CuO/Multi Walled Carbon Nanotubes Composite Nanofibers.

Polymer composites are favorite materials for sensing applications due to their low cost and easy fabrication. In the current study, composite nanofibers consisting of polyethylene oxide (PEO), oxidized multi-walled carbon nanotubes (MWCNT) and copper oxide (CuO) nanoparticles with 1% and 3% of fillers (i.e., PEO-CuO-MWCNT: 1%, and PEO-CuO-MWCNT: 3%) were successfully developed through electrospinning for humidity sensing applications. The composite nanofibers were characterized by FTIR, XRD, SEM and EDX analysis. Firstly, they were loaded on an interdigitated electrode (IDE), and then the humidity sensing efficiency was investigated through a digital LCR meter (E4980) at different frequencies (100 Hz-1 MHz), as well as the percentage of relative humidity (RH). The results indicated that the composite nanofibers containing 1% and 3% MWCNT, combined with CuO in PEO polymer matrix, showed potent resistive and capacitive response along with high sensitivity to humidity at room temperature in an RH range of 30-90%. More specifically, the PEO-CuO-MWCNT: 1% nanocomposite displayed a resistive rapid response time within 3 s and a long recovery time of 22 s, while the PEO-CuO-MWCNT: 3% one exhibited 20 s and 11 s between the same RH range, respectively.

Achieving a High Thermoelectric Performance of Tetrahedrites by Adjusting the Electronic Density of States and Enhancing Phonon Scattering.

Recently, many researchers have focused on tetrahedrite-based compounds due to their intrinsic low thermal conductivity; however, their thermoelectric performance is limited by the lower power factor. In this case, using Ge doping on Sb sites, the power factor is obviously enhanced due to an increment in carrier concentration and density of states; simultaneously, the thermal conductivity is substantially suppressed by atomic defects. Also, ZnO nanoparticles are introduced in the Ge-doped compounds to further weaken the thermal conductivity. As a result, the maximum dimensionless figure of merit (ZT) of ∼1.0 is obtained for the Cu12Sb3.96Ge0.04S13-0.5 wt % ZnO sample at 750 K, which is ∼72% larger than that of Cu12Sb4S13. All results indicate that suitable elemental doping combined with the incorporation of the nanophase is a very promising approach for Cu12Sb4S13 tetrahedrites to improve the thermoelectric performance.