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Synthesis and Characterization of host-guest materials with charge transfer complexes of Coumarin:TCNQ inserted into hydrotalcite for LED applications. |
Sumeet Kumar , Leonardo Marchese , Marco Milanesio , Enrico Boccaleri |
Università degli Studi del Piemonte Orientale and NANO-Sistemi Interdisciplinary Centre (DISTA), Via V. Bellini 25/G, Alessandria 15100, Italy |
Abstract |
Recent study of charge transfer (CT) effects on hole injection and device stability in an Organic thin film transistor (OTFT)1and its stability supposedly by the complex formation of poly(9,9-dioctylfluorene-alt-bithiophene) doped with an 8 % of electron-acceptor 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane, study of photo-physical features2 and further organization of chromophores into layered double hydrotalcite (LDH) like materials3 motivated us to follow a similar approach.The possible interactions between CT pairs with the LDH host have been investigated. We present the work done in synthesizing luminescent materials based on coumarin-3-carboxylic acid (3CCA) and 7,7,8,8-tetracyanoquinodimethane (TCNQ). An in situ hydrothermal synthesis is carried out to intercalate the 3CCA alone at first and then the CT complex into the LDH Hydrotalcite, following a one-pot synthesis approach. In fact the organic-inorganic hybrid materials have been obtained by dissolving 5 mmol each of 3CCA and TCNQ with 10 mmol of hydrated Aluminium nitrate and 20 mmol of (Zn/Mg) nitrate hydrate salts with at a controlled pH of 7.5±0.5 and CO2 free water solvent. A LDH sample with empirical composition:
[M(II)0.65 M(III)0.35 (OH)2](A-)0.175.nH20], where MII = (Mg2+or Zn2+), MIII = Al3+, and A-= anionic CT complex was obtained. The effect of the M(II) cations was studied by synthesizing Mg/Al HTLc and Zn/AlHTLc [M(II)/M(III) = 2.0]. Finally the samples were washed with decarbonised water, dried at 60 °C and characterized by XRPD/FTIR/IR/FT Raman/UV Vis/TGA techniques. A clear absorption edge with DR-UV-Vis Lambda 900 is observed for the Mg/Al HTLc with 3CCA and with its CT complex with TCNQ (See figure). The [Mg/Al HTLc + CT complex/or 3CCA alone] also shows luminescence in the visible.
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Presentation: Oral at E-MRS Fall Meeting 2008, Symposium B, by Sumeet KumarSee On-line Journal of E-MRS Fall Meeting 2008 Submitted: 2008-05-17 23:23 Revised: 2009-06-07 00:48 |