Enhanced near-infrared photocatalysis of NaYF4:Yb, Tm/CdS/TiO2 composites

• Published in: Dalton transactions : an international journal of inorganic chemistry Vol. 43; no. 3; pp. 148 - 154
• Main Authors: Guo, Xingyuan, Di, Weihua, Chen, Changfeng, Liu, Chunxu, Wang, Xue, Qin, Weiping
• Format: Journal Article
• Language: English
• Published: England 21.01.2014
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c3dt52288a

The previous works by our group ( Chem. Commun. , 2010, 46 , 2304-2306; ACS Catal. , 2013, 3 , 405-412; Phys. Chem. Chem. Phys. , 2013, 15 , 14681-14688) have reported the near-infrared-driven photocatalysis of broadband semiconductor TiO 2 or ZnO that was combined with upconverting luminescence particles to form a core-shell structure. However, the photocatalytic efficiency is low for this new type of photocatalysts. In this work, NaYF 4 :Yb,Tm/CdS/TiO 2 composites for NIR photocatalysis were prepared by linking CdS and TiO 2 nanocrystals on the NaYF 4 :Yb,Tm microcrystal surfaces. CdS and TiO 2 were well interacted to form a heterojunction structure. The energy transfer between NaYF 4 :Yb,Tm and the semiconductors CdS and TiO 2 was investigated by steady-state and dynamic fluorescence spectroscopy. The photocatalytic activities of the as-prepared composites were evaluated by the degradation of methylene blue in aqueous solution upon NIR irradiation. Significantly, it was found that the united adhesions of CdS and TiO 2 on the NaYF 4 :Yb,Tm particle surfaces showed much higher catalytic activities than the individual adhesion of CdS or TiO 2 on the NaYF 4 :Yb,Tm surfaces. This was attributed mainly to the effective separation of the photogenerated electron-hole pairs due to the charge transfer across the CdS-TiO 2 interface driven by the band potential difference between them. The presented composite structure of upconverting luminescence materials coupled with narrow/wide semiconductor heterojunctions provides a new model for improved NIR photocatalysis. NaYF 4 :Yb,Tm/CdS/TiO 2 composites show an improved photocatalytic performance due to the formation of the heterojunction structure of CdS and TiO 2 .