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Thermal and Optical Properties of CdS Nanoparticles in Thermotropic Liquid Crystal Monomers
Nanoscience Research Laboratory, School of Chemical Sciences, University Sains Malaysia, 11800 Penang, Malaysia
School of Industrial Technology, University Sains Malaysia, 11800 Penang, Malaysia
Institut Jean Lamour, UMR 7198 CNRS, Nancy Université, Université P. Verlaine Metz, Faculté des Sciences et Techniques B.P. 239 F-54506 Vandoeuvre les Nancy Cedex, France
* Authors to whom correspondence should be addressed.
Received: 10 December 2009; in revised form: 15 February 2010 / Accepted: 17 March 2010 / Published: 19 March 2010
Abstract: Two new mesogenic monomers, namely 3,3’-dimethoxy-4,4’-di(hydroxyhexoxy)-N-benzylidene-o-Tolidine (Ia) and 4,4’-di(6-hydroxyhexoxy)-N-benzylidene-o-Tolidine (IIa), were reacted with cadmium sulfide (CdS) via an in situ chemical precipitation method in ethanol to produce CdS nanocomposites. A series of different mass compositions of CdS with Ia and IIa ranging from 0.1:1.0 to 1.0:1.0 (w/w) were prepared and characterized using X-ray Diffraction (XRD), Raman spectroscopy, Fourier Transform Infrared Spectroscopy (FT-IR), Transmission Electron Microscopy (TEM), Polarizing Optical Microscopy (POM) and Differential Scanning Calorimetry (DSC), X-ray Photoelectron Spectroscopy (XPS) and Photoluminescence Spectroscopy (PL). XRD showed that the broad peaks are ascribed to the formation of cubic CdS nanoparticles in both Ia and IIa. The average particle size for both nanocomposites was less than 5 nm with a narrower size distribution when compared with pure CdS nanoparticles. The analyses from POM and DSC demonstrated that mass composition from 0.1:1.0 up to 0.5:1.0 of CdS:Ia nanocomposites showed their enantiotropic nematic phase. On the other hand, polarizing optical microscopy (POM) for IIa nanocomposites showed that the liquid crystal property vanished completely when the mass composition was at 0.2:1.0. PL emissions for CdS: Ia or IIa nanocomposites indicated deep trap defects occurred in these both samples. The PL results revealed that addition of CdS to Ia monomers suppressed the photoluminescence intensity of Ia. However, the introduction of CdS to IIa monomers increased the photoluminescence and was at a maximum when the mass composition was 0.3:1.0, then decreased in intensity as more CdS was added. The XPS results also showed that the stoichiometric ratios of S/Cd were close to 1.0:1.0 for both types of nanocomposites for a mass composition of 1.0:1.0 (CdS:matrix).
Keywords: chalcogenides; nanomaterials; composite materials; liquid crystals; optical properties; in situ methods
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Lee, H.L.; Mohammed, I.A.; Belmahi, M.; Assouar, M.B.; Rinnert, H.; Alnot, M. Thermal and Optical Properties of CdS Nanoparticles in Thermotropic Liquid Crystal Monomers. Materials 2010, 3, 2069-2086.
Lee HL, Mohammed IA, Belmahi M, Assouar MB, Rinnert H, Alnot M. Thermal and Optical Properties of CdS Nanoparticles in Thermotropic Liquid Crystal Monomers. Materials. 2010; 3(3):2069-2086.
Lee, Hooi Ling; Mohammed, Issam Ahmed; Belmahi, Mohammed; Assouar, Mohamed Badreddine; Rinnert, Hervé; Alnot, Marc. 2010. "Thermal and Optical Properties of CdS Nanoparticles in Thermotropic Liquid Crystal Monomers." Materials 3, no. 3: 2069-2086.