Structural and spectroscopic properties of poly(vinyl alcohol)-borax hydrogels co-/doped with holmium and erbium

Abstract

Holmium and Erbium nitrates, singly and together, have been incorporated in a Poly(vinyl alcohol)-borax hydrogel matrix and studied with XRD, FTIR, DTA, swelling tests, UV-visible spectroscopy and photoluminescence. FTIR data show that the basic network structure undergoes only minor modification due to doping. X-ray diffraction shows structural correlations in the 2 angstrom to 6 angstrom, and 15 angstrom regions. Glass transition temperature and solvent uptake undergo significant changes in the doped samples. Excitation in the ultraviolet region causes photo-luminescent emission in the visible region, while absorption in the visible region leads to photo-luminescent emission in the near infra-red region. The spectral intensities of the emission bands may be varied by choosing appropriate relative ratios of the dopant rare-earth species.