Due to its limiting factor of the cycle-life on Zn-polyaniline (PANI) rechargeable battery, the surface morphology and electrochemical properties have been extensively investigated. However, there are no studies that found on the chemical structure of PANI electrode before and after used in the battery with spectroscopy. Here, the Zn-PANI Battery was tested through a 60-cycle discharging process using 10 mA fixed current. The Open Circuit Voltage (OCV) at this condition was ± 1.3 V. The Raman spectra at 488 nm on PANI discharge showed increasing intensity at 1495 cm -1 υ(C=N). Furthermore, the new peak appeared on the band at 1212 cm -1 υ(N=Q=N) and 1166 cm -1 υ(C-H), related to mode on the benzenoid ring. This investigation indicated the formation of Emerald in Bases (EB), caused by the consumption of protons by Zn metal during the filling process.

Magnetic freeze-out experiments under hydrostatic pressure have been performed in the temperature range 4.2-77 K on direct-band-gap Si-doped AlGaAs samples. Successive illuminations have been used to monitor the concentrations of the metastable shallow states arising from the DX centres. With increasing concentrations of those states, evidence is given for an insulator-metal transition confirming the r character of these shallow impurity states. Moreover a shallow-deep transition is shown to hold at x = 0.32 as a result of the appearance in the gap at x = 0.30 of a localized level also originating from t h e DX centre but with no potential barrier for carrier capture.

The invention of formalin gas sensors based on polyaniline (PANI) has been developed which arranged by PANI|graphite composite form. The reaction between amine and formaldehyde produced a Schiff base that alters the resistance of PANI film as a function of formaldehyde concentration. The response of the sensor was measured in variations of graphite composition with 3%, 10%, and 25%. The results showed similar patterns in all concentrations of formalin. However, the sensor response at 10% and 25% graphite decreased dramatically. The formalin with concentration 400 ppm shown the response with 3% graphite was 1.62 times greater than 25%. Addition of too much graphite makes the absorption area on the PANI surface becomes less because the graphite covered it. In this case, the sensor performance was still stable and functional, but the measured resistance seems smaller because the sensor conductivity level more dominated by graphite. Therefore, composites of polyaniline and graphite can be used as sensors to detect the presence of formaldehyde gas.                     KEY WORDS: Formalin, Graphite, Polyaniline, Resistance, Sensors   Bull. Chem. Soc. Ethiop. 2020, 34(3), 597-604.  DOI: https://dx.doi.org/10.4314/bcse.v34i3.14

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