title: Tuning the Energy Transfer Efficiency between Ce3+and Ln3+Ions (Ln=Tm, Sm, Tb, Dy) by Controlling the Crystal Phase of NaYF4Nanocrystals.
abstract: NaYF4is a superior host matrix to study the luminescence properties of lanthanide (Ln3+) ions. Ln3+ions in hexagonal-phase NaYF4(β-phase) nanocrystals (NCs) exhibit strong luminescence via an upconversion process compared to cubic NaYF4(α-phase) NCs. However, in Ce3+/Ln3+-doped NaYF4NCs (Ln=Tm, Tb, Sm, Dy) the α-phase NaYF4NCs shows strong luminescence compared to their counterpart β-phase NCs despite the latter being much larger in size. This is attributed to comparatively large overlap between Ce3+ions emission band with excited energy levels of those Ln3+ions in α-phase compared to β-phase NCs. This difference is attributed to different crystal-field splitting of Ce3+ions 4f-5d band in different crystal environments of the α-phase (cubic crystal field environment) and β-phase (trigonal prismatic with equatorials crystal field environment) NaYF4NCs with respect to their barycenter. The enhanced luminescence from α-phase NaYF4NCs is advantageous as they are prepared at a relatively lower temperature and shorter reaction times compared to β-NaYF4NCs.
authors.affiliation: Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER), Kolkata, Mohanpur, West Bengal, 741252, India.
authors.forename: Venkata N K B
authors.initials: VN
authors.lastname: Adusumalli
authors.affiliation: Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER), Kolkata, Mohanpur, West Bengal, 741252, India.
authors.forename: Heramba V S R M
authors.initials: HV
authors.lastname: Koppisetti
authors.affiliation: Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER), Kolkata, Mohanpur, West Bengal, 741252, India.
authors.forename: Sagar
authors.initials: S
authors.lastname: Ganguli
authors.affiliation: Department of Chemistry, Ananda Mohan College 102/1, Raja Rammohan Sarani, Kolkata, 700009, W.B., India.
authors.forename: Shyam
authors.initials: S
authors.lastname: Sarkar
authors.affiliation: Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER), Kolkata, Mohanpur, West Bengal, 741252, India.
authors.forename: Venkataramanan
authors.initials: V
authors.lastname: Mahalingam
keywords: energy transfer; lanthanides; luminescence; phase change; upconversion