Photocatalytic Reactivity of Carbon–Nitrogen–Sulfur-Doped TiO2 Upconversion Phosphor Composites

Seong-Rak Eun,Shielah Mavengere,Bumrae Cho,Jung-Sik Kim

doi:10.3390/catal10101188

Seong-Rak Eun, Shielah Mavengere + Show 2 more

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https://doi.org/10.3390/catal10101188

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Abstract

Sol–gel synthesized N-doped and carbon–nitrogen–sulfur (CNS)-doped TiO2 solutions were deposited on upconversion phosphor using a dip coating method. Scanning electron microscopy (SEM) imaging showed that there was a change in the morphology of TiO2 coated on NaYF4:Yb,Er from spherical to nanorods caused by additional urea and thiourea doping reagents. Fourier transform infrared (FTIR) spectroscopy further verified the existence of nitrate–hyponitrite, carboxylate, and SO42− because of the doping effect. NaYF4:Yb,Er composites coated with N- and CNS-doped TiO2 exhibited a slight shift of UV-Vis spectra towards the visible light region. Photodecomposition of methylene blue (MB) was evaluated under 254 nm germicidal lamps and a 300 W Xe lamp with UV/Vis cut off filters. The photodegradation of toluene was evaluated on TiO2/NaYF4:Yb,Er and CNS-doped TiO2/NaYF4:Yb,Er samples under UV light illumination. The photocatalytic reactivity with CNS-doped TiO2/NaYF4:Yb,Er surpassed that of the undoped TiO2/NaYF4:Yb,Er for the MB solution and toluene. Photocatalytic activity is increased by CNS doping of TiO2, which improves light sensitization as a result of band gap narrowing due to impurity sites.

Highlights

The photocatalytic reactivity with CNS-doped TiO2 /NaYF4 :Yb,Er surpassed that of the undoped TiO2 /NaYF4 :Yb,Er for the methylene blue (MB)
Titanium dioxide (TiO2 ) inorganic semiconductors have emerged as trending materials for photocatalysis applications [1,2,3]
This study focuses on investigating the effects of N doping and CNS doping of TiO2 and coupling with NaYF4 :Yb,Er upconversion phosphor

Summary

Introduction

Titanium dioxide (TiO2 ) inorganic semiconductors have emerged as trending materials for photocatalysis applications [1,2,3]. The band gap of 3.2 eV necessitates ultraviolet (UV) light absorption to cause electron movement from the valence band to the conduction band to progress the photocatalytic reaction. These photoreactions only proceed within the UV portion of the solar spectrum, which leaves the broad portions of visible and near infrared (NIR) spectra undetected. The methods for improving spectral absorbance include doping with metals and non-metals [4,5,6,7] and coupling with other compounds to form nanocomposites [8,9]. Non-metallic doping is advantageous because of the smaller ionic radii that can occupy the interstitial sites of TiO2 [15,16,17]

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