Results Latencies on the tail withdrawal test were significantly

Pure SnO2 and Sb2O3 doped SnO2 powders were prepared by sol–gel preparation route as described in Refs. [38] and [39]. For SnO2 powder preparation, pure SnCl4 was dropped slowly in de-ionized water (3 ml/min) and for 0.1% Sb2O3 doped SnO2 preparation, pure SnCl4 and SbCl3 were slowly dissolved in ethanol and later diluted by HCl. The obtained sols in both cases were precipitated by adding ammonia solution. After aging for 2–3 weeks, ASA 404 gel was washed several times with deionized water and ammonium nitrate, and later with ethanol to reduce the concentration of the chloride ions. The gel in liquid form was grounded for 6 h at 200 rpm by ball milling in zirconia vessels, then dried and sintered at 450 °C for 5 h to get fine pale yellow SnO2 powder. 2.5 wt.% of La2O3 and CuO were admixed with certain amount of SnO2 powder by dissolving La(NO3)3·6H2O and Cu(NO3)2·3H2O, respectively in ethanol. The mixture was milled for 12 h to get homogenous distribution of the brachiopods fine powders with the dissolved salt. After drying, the powder was mixed with organic carriers before micro-dispensing. After dispensing on the electrodes, the layers were subjected to sintering process at 700 °C. Substantial experiments (weight analysis and EDX (SI Fig. 1)) were carried out so as to assert the absence of residual organic compounds.