Controllable and enhanced HCHO sensing performances of different-shelled ZnO hollow microspheres

Hollow ZnO microspheres with tunable interior architecture are successfully synthesized by a simple green chemistry routes at low temperature. This process is environmentally friendly processing, which based on without using solvents, employing carbon microspheres as template and reaction at low temperature. The layer-control of hollow ZnO microspheres can be easily adjusted by varying the concentration of the zinc precursor added. To demonstrate the usage of such hollow ZnO microspheres, gas sensors have been fabricated from the as-synthesized hollow ZnO microspheres with different shelled and investigated for formaldehyde (HCHO) detection. Interestingly, the response of hollow ZnO microspheres increased with increasing the number of shell structures. These results indicate that three-shelled ZnO sensor displays about 1.5 and 3–4 fold enhancement in response compared to double and single-shelled one, respectively. The mechanism of enhanced sensor performances is also proposed.