Structural evolution in crystalline MoO{sub 3} nanoparticles with tunable size

• Published in: Journal of solid state chemistry Vol. 190
• Main Authors: Barros Santos, Elias de, Aparecido Sigoli, Fernando, Odone Mazali, Italo
• Format: Journal Article
• Language: English
• Published: United States 15-06-2012
• Subjects: DECOMPOSITION; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; MOLYBDENUM; MOLYBDENUM OXIDES; NANOSTRUCTURES; OPTICAL PROPERTIES; ORTHORHOMBIC LATTICES; PARTICLE SIZE; PARTICLES; POROUS MATERIALS; RAMAN SPECTRA; RAMAN SPECTROSCOPY; RED SHIFT; TRANSMISSION ELECTRON MICROSCOPY; X-RAY DIFFRACTION
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1016/J.JSSC.2012.02.012

In this study MoO{sub 3} nanoparticles were prepared in porous Vycor glass by impregnation-decomposition cycles (IDC) with molybdenum(VI) 2-ethylhexanoate. X-ray diffraction data show that the nanoparticles are crystalline and are in the orthorhombic {alpha}-MoO{sub 3} phase. Raman spectroscopy data also indicate the formation of this phase. The profiles in the Raman spectra changed with the number of IDC, indicating a structural evolution of the MoO{sub 3} nanoparticles. The IDC methodology promoted a linear mass increase and allowed tuning the nanoparticle size. Analysis of HRTEM images revealed that for 3, 5 and 7 IDC, the MoO{sub 3} nanoparticle average diameters are 3.2, 3.6 and 4.2 nm. Diffuse reflectance spectroscopy indicates a consistent red shift in the band gap from 3.35 to 3.29 eV as the size increases from 3.2 to 4.2 nm. This observed red shift in the band gap of the MoO{sub 3} nanoparticles is presumably due to quantum confinement effects. - Graphical abstract: Modification of profile Raman spectra for crystalline MoO{sub 3} nanoparticles in function of the particle size. Highlights: Black-Right-Pointing-Pointer Structural evolution of the MoO{sub 3} nanoparticles as a function of the crystallite size. Black-Right-Pointing-Pointer Tunable optical properties by controlling the MoO{sub 3} nanoparticle size. Black-Right-Pointing-Pointer The impregnation-decomposition methodology allowed tuning the nanoparticle size. Black-Right-Pointing-Pointer The red shift in the band gap of the MoO{sub 3} nanoparticles is due to quantum size effect. Black-Right-Pointing-Pointer The short-distance order in MoO{sub 3} nanoparticle is function to area/volume ratio.