Enhanced Plasmonic Electron Transfer from Gold Nanoparticles to TiO 2 Nanorods via Electrochemical Surface Reduction
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Enhanced Plasmonic Electron Transfer from Gold Nanoparticles to TiO2 Nanorods via Electrochemical Surface Reduction Jong-Won Yun, Tri Khoa Nguyen, Sunghan Lee, Sungdo Kim and Yong Soo Kim∗ Department of Physics and Energy Harvest-Storage Research Center, University of Ulsan, Ulsan 44610, Korea
Tri Khoa Nguyen NTT Hi-Tech Institute, Nguyen Tat Thanh University, Ho Chi Minh City 70000, Viet Nam
Cao Khang Nguyen Center of Nano Science and Technology, Hanoi National University of Education, Hanoi 122000, Vietnam
Yang Ha Faculty of Electrical and Electric Engineering, Ulsan College, Ulsan 44610, Korea (Received 6 December 2019; revised 26 January 2020; accepted 3 February 2020) The transport of charge carriers across the heterojunction of an optoelectronic device plays a crucial role in the performance of the device. This issue is particularly important in the area of heterogeneous metal-semiconducting photocatalysis in terms of harvesting the hot carriers generated under plasmonic resonance. This paper presents the results of a case study on the impact of electrochemical surface reduction on the transport properties of plasmonic electrons, which are generated on gold nanoparticles (Au NPs) under visible light irradiation to TiO2 nanorods (TiO2 NRs). Based on microscopic and spectroscopic characterizations, this study examined the subtle changes in the structural and the optical properties of the Au NPs/TiO2 NRs upon surface reduction of the oxygen layer which is ubiquitous on TiO2 NRs. These results suggest that the oxygen layer works as a blocking layer that limits the charge transfer efficiency of plasmonic electrons from Au to TiO2 and, consequently, reduces the device performance. The main thesis was verified directly by comparing the photocatalytic activities of pristine Au NPs/TiO2 NRs and Au NPs/reduced TiO2 NRs with methylene blue as a reference. The photocatalytic performance of the Au NPs/reduced TiO2 NRs was two times higher than that of the pristine one owing to the efficient charge transfer across the Au/TiO2 interface. This simple surface treatment can be employed widely to enhance the charge transport efficiency of various optoelectronic materials and devices derived from metalsemiconducting heterostructures. Keywords: Electrochemical reduction, Surface reduction, Plasmonic electrons, Tansfer efficiency, Photocurrent, Photocatalytic activities DOI: 10.3938/jkps.77.853
I. INTRODUCTION Chemically stable, non-toxic and abundant titanium dioxide (TiO2 ) is an ideal material for investigating the photocatalytic activity [1, 2]. In a photocatalytic process, in addition to light absorption and charge separation, charge transfer plays a critical role in determining the photocatalytic efficiency. Generally, a junction between two dissimilar materials, or even between different structural phases of a single material, can improve the charge separation process significantly provided their energy bands are aligned in such a way that drifts the oppo∗ E-mail:
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pISSN:0374-4884/eISSN:1976-8524
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