Effect of N-rGO Decoration on the Structure and Optical Properties of WO 3 Nanoplates
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https://doi.org/10.1007/s11664-020-08578-w Ó 2020 The Minerals, Metals & Materials Society
ORIGINAL RESEARCH ARTICLE
Effect of N-rGO Decoration on the Structure and Optical Properties of WO3 Nanoplates FARZANEH BADIEZADEH,1 SALIMEH KIMIAGAR,2 and NASSER ZARE-DEHNAVI 1,3 1.—Department of Physics, Central Tehran Branch, Islamic Azad University, Tehran, Iran. 2.—Nano Research Lab (NRL) Department of Physics, Central Tehran Branch, Islamic Azad University, Tehran, Iran. 3.—e-mail: [email protected]
In this research, tungsten trioxide (WO3 ) nanoplates and WO3 /N-doped reduced graphene oxide (WO3 /N-rGO) nanocomposites were synthesized with various amounts of N-rGO using the hydrothermal method. X-ray diffraction analysis showed that WO3 /N-rGO nanocomposites (with 3%, 6%, and 9% of NrGO) had a hexagonal structure with (200) preferential radial of the crystal plane. According to transmission electron microscopy images, WO3 has a nanoplate structure with a width within the range of 20–40 nm and length of 500 nm. The result of bandgap energy calculation was 3.69 eV for WO3 , while for WO3 /N-rGO 3%, WO3 /N-rGO 6%, and WO3 /N-rGO 9%, it was 2.65 eV, 2.84 eV, and 2.61 eV, respectively. Dynamic light scattering confirmed particle sizes 86.7 nm, 56.9 nm, and 76.9 nm for the samples with 3%, 6%, and 9% N-rGO, respectively. The minimum of particle size was for WO3/N-rGO nanocomposites. Photoluminescence spectra revealed that there were a few transitions in which the intensity in WO3/N-rGO 3% was stronger than in the samples with 6% and 9% N-rGO. The origin of these emissions is associated with oxygen vacancies, defects, near-band edge transition, and band-to-band transition. The effective control of bandgap has a clear advantage for use in optical devices and makes the samples more applicable in electrical, photo-electrochemical, and photocatalytic applications. Key words: WO3, nanocomposites, hydrothermal, N-rGO
INTRODUCTION Among transition metal oxide semiconductors, tungsten trioxide (WO3 ) as a nanoparticle, thin-film or quantum dot, is a promising material thanks to its various novel properties including small bandgap energy, excellent thermal stability, and photocorrosion resistance.1 Furthermore, it is suitable as a photo-catalyst due to widely tunable bandgap energy (2.5–3.7 eV) at room temperature, thus making it suitable for absorbing blue light just as TiO2 is suitable for absorbing UV light.2–10 WO3 is among promising electrochromic materials due to
(Received June 14, 2020; accepted October 20, 2020)
its high coloration efficiency (50 c/m2 ), quick response time (0.5 s), and long life (107 cycles).11 Thus, owing to electrochromic,12,13 photochromic14 and gaschromic properties,15 WO3 is suitable for some applications such as variable reflection mirrors, dazzle-free mirrors in automobiles, smart windows (variable transmittance) and surfaces with a tunable emittance of thermal control of satellites, non-emissive displays, and optical recording devices. Nanostructured tungsten oxides have been used for
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