Transparent, Adherent, and Photocatalytic SiO2-TiO2 Coatings on Polycarbonate for Self-Cleaning Applications

Sanjay Latthe,Kazuya Nakata,Chiaki Terashima,Shanhu Liu,Akira Fujishima

doi:10.3390/coatings4030497

Abstract

Photocatalytic TiO2 coatings are famously known for their excellent self-cleaning behavior, where very thin water layer formed on the superhydrophilic surface can easily wash-off the dirt particles while flowing. Here we report the preparation of the optically transparent, adherent, highly wettable towards water and photocatalytic SiO2-TiO2 coatings on polycarbonate (PC) substrate for self-cleaning applications. The silica barrier layer was applied on UV-treated PC substrate before spin coating the SiO2-TiO2 coatings. The effect of different vol% of SiO2 in TiO2 and its influence on the surface morphology, mechanical stability, wettability, and photocatalytic properties of the coatings were studied in detail. The coatings prepared from 7 vol% of SiO2 in TiO2 showed smooth, crack-free surface morphology and low surface roughness compared to the coatings prepared from the higher vol% of SiO2 in TiO2. The water drops on this coating acquires a contact angle less than 10° after UV irradiation for 30 min. All the coatings prepared from different vol% (7 to 20) of SiO2 in TiO2 showed high transparency in the visible range.

Highlights

TiO2 is one of the most widely researched photocatalytic semiconductor materials to date
The SiO2-TiO2 coating prepared with 7 vol% of SiO2 in TiO2 showed uniform, crack-free and smooth morphology (Figure 2a)
We studied the photocatalytic degradation of the ODS monolayers after UV light illumination (365 nm, 2 mW/cm2) by means of water contact angle measurements

Summary

Introduction

TiO2 is one of the most widely researched photocatalytic semiconductor materials to date. Hwang and coworkers [8] have prepared mechanically durable and optically transparent organic-inorganic SiO2-TiO2 nanocomposite coatings on PC by simple spray coating. Reported the comparative study on the influence of NaOH etching and UVC irradiation on the mechanical stability of the TiO2 thin films prepared on PC. The strong hydrophilic, antifogging, photocatalytic and self-cleaning properties were observed on the TiO2 film coated on NaOH treated PC. Razan Fateh et al have prepared optically transparent, highly hydrophilic, mechanically stable and photocatalytic TiO2/SiO2 [7,10], and. Transparent, adherent, highly wettable and self-cleaning SiO2-TiO2 coating on PC by simple spin coating. The effect of different vol% of SiO2 sol in TiO2 and its influence on the surface morphology, mechanical stability, wettability, and photocatalytic properties of the coatings were studied in detail

Results and Discussion

Mechanical Properties of the Coatings

Materials

Self-Cleaning Coating on PC Substrates

Characterization Techniques

Conclusions