Re-dispersible Tb(3+) doped LaPO(4) nanorods have been prepared using ethylene glycol (EG) as a capping agent as well as reaction medium at a relatively low temperature of 150 °C. The X-ray diffraction study reveals that all the doped samples are well crystalline with a monoclinic structure of the LaPO(4) phase. The luminescence intensity of (5)D(4)→(7)F(5) transition at 543 nm (green) is more prominent than that of (5)D(4)→(7)F(6) transition at 487 nm (blue) for all the samples. This is related to the polarizing effect from [PO(4)](3-) to the Tb(3+) site. Concentration dependent luminescence study shows that the luminescence intensity of Tb(3+) increases up to 10 at.% and decreases above this. This is due to the concentration quenching effect arising from cross relaxation among Tb(3+)-Tb(3+) ions. The results show that nanoparticles prepared in EG medium gives an enhanced luminescence compared to that prepared in water. This is attributed to the multiphonon relaxation effect from O-H groups surrounding over nanoparticles as well as the extent of increase of agglomeration among particles for samples prepared in water. Significant enhancement in the emission of Tb(3+) is also observed when Ce(3+) is used as the sensitizer in LaPO(4):Tb(3+)nanorods. The optimum concentration of Ce(3+) for maximum luminescence is found to be 7 at.% in Ce(3+) sensitized LaPO(4):Tb(3+) (5 at.%). Based on the energy transfer process from Ce(3+) to Tb(3+), the luminescence of Tb(3+) can be switched OFF and ON by performing oxidation and reduction of Ce(3+)↔Ce(4+) using KMnO(4) and ascorbic acid, respectively. The samples are re-dispersible in water, methanol and can be incorporated into polyvinyl alcohol (PVA) films. They show a dark green emission under ultraviolet radiation.

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This article discusses the potential applications of natural polysaccharide-based graphene oxide nanomaterials in the field of wastewater remediation through the removal of organic and synthetic dyes. Being highly toxic, carcinogenic, and nonbiodegradable, dyes disposed from textile, paper, and printing industries etc. pose a serious threat to various life forms on earth. Recently, there has been an increased interest in the amalgamation of biopolymers, such as polysaccharides, with the high adsorption efficiency of graphene oxide. Polysaccharides, apart from being nontoxic, low cost, and eco-friendly, possess a variety of functional groups enabling them to be easily tuned for the desired applications. When grafted with GO nanosheets, they give rise to unique nanomaterials possessing diverse applications, especially in the eradication of harmful contaminants from wastewater. This review is an attempt to give consolidated and detailed information on different aspects of the adsorption behavior of various potentially low-cost polysaccharide-based GO nanoadsorbents toward lethal dyes. The characterization techniques used, adsorption isotherms, kinetics, thermodynamic behavior, recyclability, and swelling properties as well as the adsorption mechanism have been outlined in this article. The whole anthology of literature reports excellent dye removal efficiency with significant regeneration performance making these nanoadsorbents promising candidates for practical applications. In view of all aspects, this review recommends the use of such sustainable adsorbents with a further search toward obtaining the polysaccharides from natural wastes.

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