Abstract
A method to produce pure VSH-1 in large quantities (similar to 20 g) was developed. The reagents were silica sol, V2O5, H2SO4, KOH, and ethanol. The crystals adopted distorted octahedral shapes. The total surface area of the pristine VSH-1 with the general formula of K-2(VO)(Si4O10)center dot H2O was 76 m(2)/g, indicating that a significant portion of the pores are occupied by K+ ions. Analyses of the diffuse-reflectance UV-Vis spectra of Mn+-VSH-1 (Mn+ = K+, Na+, Ca2+, Pb2+, and Zn2+) revealed that the bands that appear in the 200-400 nm region arise due to the D-A-A triad charge-transfer (CT) interaction among the V4+, O2-, and Mn+, and the 447, 590, and 879 nm bands arise due to the d-d transition of V4+. The measured atomic magnetic moment (mu) was 1.73 BM, indicating that all the V atoms exist in V4+. The ESR spectrum of VSH-1 showed a strong signal due to V4+ with the g value of 1.959 with Delta H-pp value of 131 G. The Raman spectra of Mn+-VSH-1 revealed the existence of strong V=O stretching at 955 cm(-1), and other peaks at 373 (weak), 453 (weak), 534 (weak), 620 (medium), 800 (weak), and 1072 (weak) cm(-1). The V=O stretching band shifted to a higher energy region upon increasing the Sanderson's electronegativity of Mn+. The thermogravimetric (TGA) analysis showed that VSH-1 is thermally stable up to 550 degrees C and above which the oxidation of V4+ occurs and the structure collapse. (C) 2011 Elsevier Inc. All rights reserved.