{'fraction_non_alphanumeric': 0.02702702702702703, 'fraction_numerical': 0.035035035035035036, 'mean_word_length': 5.369426751592357, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Effect of calcination temperature on the physicochemical properties of zinc oxide nanoparticles synthesized by coprecipitation

In this study, an intermediate zinc oxalate phase was synthesized by the coprecipitation of an oxalate from a nearly saturated solution of zinc acetate and a 2-propanol solution of oxalic acid. A highly crystalline pure phase of ZnO nanoparticles was successfully obtained after calcination at 400 °C–600 °C for 4 h. A unimodal, narrow size distribution of ZnO nanoparticles with average particle sizes of 3, 28, and 25 nm was observed at 400 °C, 500 °C, and 600 °C, respectively. Moreover, field-emission scanning electron microscopy and transmission electron microscopy images revealed different surface structures and morphologies for ZnO nanoparticles obtained at different calcination temperatures. With the increase in the calcination temperature from 400 °C to 600 °C, the specific surface area of ZnO nanoparticles significantly decreased from 22.9 to 2.6 m2 g−1.