High pressure induced local ordering and tunable luminescence of La2Hf2O7:Eu3+ nanoparticles. (26th March 2020)

• Record Type: Journal Article
• Authors: Gupta, Santosh K.; Zuniga, Jose P.; Pokhrel, Madhab; Mao, Yuanbing
• Is Part Of: New journal of chemistry. Volume 44:Number 14(2020)
• Page Start: 5463
• Page End: 5472
• Publication Date: 2020-03-26
• Subjects: Chemistry -- Periodicals; Chimie -- Périodiques; 540
• DOI: 10.1039/d0nj00585a
• Languages: English
• ISSNs: 1144-0546

Abstract

Abstract : This work highlights the high-pressure induced site swapping and improved ordering of Eu 3+ in La2 Hf2 O7 :Eu 3+ nanocrystals which leads to red-orange-yellow tunable emission at low-moderate-high pressure regime and enhanced correlated color temperature. Abstract : High pressure spectroscopy is of immense importance in understanding materials with respect to their high pressure phases, structural phase transitions, designing pressure sensors, etc. With this objective in mind, we have carried out time resolved photoluminescence and Raman spectroscopy on La2 Hf2 O7 :Eu 3+ (LHOE) nanoparticles (NPs) under applied high pressure. High pressure Raman spectra of the LHOE NPs suggest enhanced disordering at high pressure and shifting of the most intense F2g Raman band to higher wavenumber. High pressure excitation photoluminescence spectra of the LHOE NPs demonstrate that the O 2− → Eu 3+ charge transfer band quenches beyond 2.7 GPa whereas not many changes could be observed from the intra-configurational f–f excitation bands of Eu 3+ ion. High pressure emission photoluminescence spectra of the LHOE NPs show gradual lowering of asymmetry ratio value, reduced Stark component in magnetic dipole transition, and the disappearance of the 5 D0 → 7 F0 transition of Eu 3+ ion at high pressure. These observations suggest significant improvement in Eu 3+ symmetry. These results are further corroborated with lifetime spectroscopy, which indicates high pressure induced tunneling of Eu 3+ ion from La 3+ to Hf 4+ sites. These changes are visualized by beautiful color tunability of the LHOE NPs from red to orange to yellow and correlated color temperature from 1900 to 2600 K. This work demonstrates a new mode of designing optically tunable luminescent nanomaterials and understanding high pressure induced changes in photonic materials.