Crystal growth and optical characterization of chromium-doped l-arginine phosphate monohydrate

Abstract l -arginine phosphate monohydrate single crystals doped with Cr 3+ ions (LAP:Cr) were grown by slow cooling method, with dimensions up to 10 × 10 × 8 mm 3 . Chromium ions induce a drastic reduction of overall growth rate and produce a drastic change in LAP growth morphology. The functional groups of LAP:Cr crystals were confirmed by FTIR analysis and compared with pure LAP. The optical band gap of LAP:Cr was determined from UV-VIS-NIR transmittance spectrum. Optical absorption spectrum at room temperature and 10 K was measured consisting of two large bands due to the 4 A 2 → 4 T 2 and 4 A 2 → 4 T 1 transitions and a narrower band attributed to the 4 A 2 → 2 E spin-forbidden transition, characteristic of Cr 3+ ions. Luminescence spectra of pure and Cr 3+ -doped samples were collected with excitation at wavelength of 350 nm and 335 nm. Emissions from host LAP matrix and Cr 3+ ions were observed. Excited with 350 nm the spectra reveal a broad intense band from 21000 to 26000 cm −1 region due to electronic transition from LAP ligand. The emission spectra of doped sample present two broad bands centered at 12346 cm −1 and 13412 cm −1 from 2 E → 4 A 2 and 4 T 2 → 4 A 2 transitions, characteristics of luminescence from Cr 3+ ions. From these results the Racah and crystal-field Cr 3+ parameters were evaluated and comparing with those obtained in similar systems.