Enhanced frequency upconversion in Ho3+/Yb3+/Li+:YMoO4 nanophosphors for photonic and security ink applications

Mondal, Manisha and Rai, Vineet Kumar and Srivastava, Chandan and Sarkar, Suman and Akash, R (2016) Enhanced frequency upconversion in Ho3+/Yb3+/Li+:YMoO4 nanophosphors for photonic and security ink applications. In: JOURNAL OF APPLIED PHYSICS, 120 (23).

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Abstract

The YMoO4 nanophosphors codoped with Ho3+/Yb3+/Li+ ions synthesized by the chemical coprecipitation method have been structurally characterized by using X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), and Transmission Electron Microscopy (TEM) techniques. The TEM bright field imaging shows that the developed nanophosphors are crystalline in nature with particle size similar to 45 nm. The upconversion (UC) emission spectra upon excitation at 980 nm of the nanophosphors at low pump power (<900 mW) show the emission peaks in the UV, green, and red regions, whereas at high pump power (>= 900 mW) an intense broad band ranging from 400-900 nm along with a UV band has been observed. The enhancement of about similar to 104 times corresponding to the green band in the Ho3+-Yb3+-Li+ codoped nanophosphors compared to that of the Ho3+ singly doped nanophosphors has been observed. This enhancement is caused by the energy transfer from the Yb3+ to Ho3+ ions and modified the local crystal field developed around the rare earth ions. A higher value of the slope (i.e., n similar to 6.38) for broad band emission within the 944 mW-1200 mW pump power region in the Ho3+-Yb3+-Li+ codoped nanophosphors is found to be due to the involvement of the photon avalanche population process but it is not related to the black body radiation. The intense peak at similar to 564 nm and similar to 648 nm for the broad band emission is attributed to the charge transfer luminescence of codoped nanophosphors, which is related to the oxygen ion present in the MoO4 group and Yb3+ ion. The observations described in this paper may be of significant interest for developing the visible upconverters, security ink, and novel devices for displays in the low and high pump power region. Published by AIP Publishing.

Item Type:	Journal Article
Publication:	JOURNAL OF APPLIED PHYSICS
Additional Information:	Copy right for this article belongs to the AMER INST PHYSICS, 1305 WALT WHITMAN RD, STE 300, MELVILLE, NY 11747-4501 USA
Department/Centre:	Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Date Deposited:	17 Feb 2017 04:48
Last Modified:	17 Feb 2017 04:48
URI:	http://eprints.iisc.ac.in/id/eprint/56250

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