Annealing effects on zinc oxide-silica films prepared by sol–gel technique for chemical sensing applications

• The nanoparticles size increased from 5 to 15 nm with the annealing temperatures.
• Two optical band gaps located at 3.0 eV and 4.2 eV are observed.
• ZnO:SiO2 showed good sensitivity and lower limit of detection.
• Cycling test indicated ZnO:SiO2 was stable during liquid–solid chemical sensing.

ZnO:SiO2 films are prepared by sol–gel technique on Si substrates. The effect of annealing temperatures (Ta) on the structure, surface morphology, and optical and photoluminescence (PL) properties of these films is studied. The X-ray diffraction analysis revealed that the c-axis orientation and the grain size of ZnO:SiO2 films increased at high Ta. High-resolution transmission electron microscopy results showed that the ZnO nanoparticles are spherical in shape with their size increasing from 5 to 15 nm with Ta while PL spectroscopy showed few separated PL bands. In addition, two optical band gaps located at 3.0 eV and 4.2 eV are observed and showed a redshift with Ta up to 600 °C, and then a blueshift is observed at 800 °C. ZnO:SiO2 film was tested as sensors for the detection and quantification of phenyl hydrazine. It is found that ZnO:SiO2 films showed good sensitivity of 390 μA mM− 1 cm− 2 and a lower limit of detection of 3 mM with linear dynamic range of 0.05 mM to 3 mM and rapid reaction kinetics (in the order of seconds). The cycling tests indicated that the ZnO:SiO2 films are quite stable since no significant decrease in sensitivity was observed even after being used repetitively for 3 times, showing a good potential for practical applications.