Preparation of ZnO-carbon quantum dot composite thin films with superhydrophilic surface

ABSTRACT

Carbon quantum dots (CQDs)-ZnO composite thin films were prepared via ultrasonic mist vapour deposition (UMVD) method. The effect of different CQDs concentrations (C), substrate temperatures (T_s), nozzle-substrate distances and also post-annealing process on the thin film structure were considered and examined systematically. The effects of these parameters on optical, morphological and surface properties of the layers as well as their wettability were carefully investigated and discussed. It was found that for low T_s and short ‘d’, CQDs diffuse inside the layer during deposition and then were evaporated after annealing process making drastic changes in layer morphology and optical transmittance. On the other hand, for high T_s and long ‘d’, most of CQDs inside mist vapour drops are evaporated during deposition process. Therefore, the layer transmittance and morphology did not change notably after annealing. Interestingly, the layer prepared with C = 5 volume %, T_s = 470 °C and d = 9 cm was turned to super-hydrophilic surface after annealing process with contact angle of ⁓ 3º. Such a super-hydrophilic CQDS-ZnO thin film is highly beneficial for a wide range of applications which high wettability is required.

KEYWORDS:

• Carbon quantum dots
• Zno thin film
• mist vapour deposition
• super-hydrophilic

Acknowledgments

Financial support of Research and Technology Council of the Hakim Sabzevari University is highly acknowledged.

Disclosure statement

No potential conflict of interest was reported by the authors.