fulltext36 - Preparation and Characterization of...

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Preparation and Characterization of Nanocrystalline ZrO 2 :Yb 3 + ,Er 3 + Up-conversion Phosphors I KO H YPP ¨ ANEN , a J ORMA OLS ¨ A , a J OUKO K ANKARE , a M IKA L ASTUSAARI , a AND L AURA P IHLGREN a , b , c a University of Turku, Department of Chemistry, Turku, Finland b University of Turku, Department of Biotechnology, Turku, Finland c Graduate School of Materials Research, Turku, Finland Nanocrystalline up-converting phosphors with zirconium oxide (ZrO 2 ) as the host lattice were prepared with combustion and sol–gel methods. Impurities were analyzed with Fourier transform infrared (FT-IR) spectroscopy. Yb 3 + absorption was studied in the wave number region 10,000– 11,500cm 1 at room temperature and at 10 K. The whole-blood absorption was measured in the region 9100–41,600cm 1 at room temperature. Up-conversion luminescence was excited at room temperature with an IR-laser at 977 nm. The up-conversion luminescence spectra showed red (650– 685 nm)andgreenemission(520–560nm)duetothe 4 F 9 / 2 4 I 15 / 2 and( 2 H 11 / 2 , 4 S 3 / 2 ) 4 I 15 / 2 transitions of Er 3 + , respectively. The materials prepared with combustion synthesis were found to yield the most efficient up-conversion intensity and the longest luminescence decay. Key words: zirconium oxide; nanocrystals; combustion; sol–gel; up-conversion luminescence Introduction The field of up-conversion luminescence, wherein the absorption of two or more low energy photons is followed by the emission of a higher energy photon, has witnessed numerous breakthroughs during the past decades. Up-converting phosphors have a variety of proven applications as lasers, displays, and inks for se- curity printing (bank notes, bonds). 1–3 Up-conversion luminescence materials are also increasingly used in clinical diagnostic assays. 4 For coupling to biological compounds, nanometer- sized up-converting phosphor particles with high lu- minescent efficiency are required. The up-converting nanophosphors are needed in the development of novel homogeneous label technology for quantitative all-in- one whole-blood immunoassay which uses low-cost measurement devices. 5–7 Biological materials, including whole blood, have no capability for up-conversion. 6 In biological materi- als, there is neither autoluminescence nor scattered Address for correspondence: Laura Pihlgren, University of Turku, De- partment of Chemistry, FI-20014 Turku, Finland. Voice: + 358-2-333 6788; fax: + 358-2-333 6700. laerle@utu.fi radiation in the region of red luminescence (635– 710 nm). This enables immunoassays with low back- ground luminescence signals. Very simple whole-blood immunoassays, suitable for point-of-care applications, are needed in resource-limited areas and when the pretreatment of blood samples would be inconvenient. The local environment, the dopant concentration,
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This note was uploaded on 07/11/2010 for the course SPECTOGRAP 545 taught by Professor Gdf during the Spring '10 term at AIB College of Business.

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fulltext36 - Preparation and Characterization of...

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