Silver Molybdate and Silver Tungstate Nanocomposites with Enhanced Photoluminescence

Author(s)

De Santana, Yuri V. B. ^[1] ; Cardoso Gomes, Jose Ernane ^[2] ; Matos, Leandro ^[2] ; Cruvinel, Guilherme Henrique ^[2] ; Perrin, Andre ^[3] ; Perrin, Christiane ^[3] ; Andres, Juan ^[4] ; Varela, Jose A. ^[2] ; Longo, Elson ^[1]

Affiliation

^[1] Univ Estadual Paulista, UNESP, CDMF INCTMN, Araraquara, SP - Brazil

^[2] Univ Fed Sao Carlos, UFSCar, CDMF INCTMN, BR-13560 Sao Carlos, SP - Brazil

^[3] Univ Rennes 1, Rennes - France

^[4] Univ Jaume 1, Dept Expt Sci, Castellon de La Plana - Spain

• Document type: Journal article
• Source: NANOMATERIALS AND NANOTECHNOLOGY; v. 4, AUG 1 2014.
• Web of Science Citations: 43

Abstract

Silver molybdate (Ag2MoO4) and silver tungstate (Ag2WO4) nanomaterials were prepared using two complementary methods, microwave assisted hydrothermal synthesis (MAH) (pH 7, 140 degrees C) and co-precipitation (pH 4, 70 degrees C), and were then used to prepare two core/shell composites, namely alpha-Ag2WO4/beta-Ag2MoO4 (MAH, pH 4, 140 degrees C) and beta-Ag2MoO4/beta-Ag2WO4 (co-precipitation, pH 4, 70 degrees C). The shape and size of the microcrystals were observed by field emission scanning electron microscopy (FE-SEM), different morphologies such as balls and nanorods. These powders were characterized by X-ray powder diffraction and UV-vis (diffuse reflectance and photoluminescence). X-ray diffraction patterns showed that the Ag2MoO4 samples obtained by the two methods were single-phased and belonged to the beta-Ag2MoO4 structure (spinel type). In contrast, the Ag2WO4 obtained in the two syntheses were structurally different: MAH exhibited the well-known tetrameric stable structure alpha-Ag2WO4, while co-precipitation afforded the metastable beta-Ag2WO4 allotrope, coexisting with a weak amount of the alpha-phase. The optical gap of beta-Ag2WO4 (3.3 eV) was evaluated for the first time. In contrast to beta-Ag2MoO4/beta-Ag2WO4, the alpha-Ag2WO4/beta-Ag2MoO4 exhibited strongly-enhanced photoluminescence in the low-energy band (650 nm), tentatively explained by the creation of a large density of local defects (distortions) at the core-shell interface, due to the presence of two different types of MOx polyhedra in the two structures. (AU)

• FAPESP's process: 13/07296-2 - CDMF - Center for the Development of Functional Materials
• Grantee: Elson Longo da Silva
• Support Opportunities: Research Grants - Research, Innovation and Dissemination Centers - RIDC
• FAPESP's process: 08/57872-1 - National Institute for Materials Science in Nanotechnology
• Grantee: Elson Longo da Silva
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 12/22823-6 - Nanocrystalline metal sulphides obtained by synthesis at the interface of two solvents assisted by microwave
• Grantee: Yuri Vinicius Bruschi de Santana
• Support Opportunities: Scholarships in Brazil - Post-Doctoral