Synthesis and Characterization of Mn Doped CdS Quantum Dots from a Single Source Precursor
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133 Mat. Res. Soc. Symp. Proc. Vol. 581 ©2000 Materials Research Society
EXPERIMENTAL Chemicals Tri -n- octylphosphine oxide (TOPO), tri-n-octylphosphine (TOP), n-methylhexylamine, carbon disulfide and manganese(II) chloride were purchased from Aldrich Chemical Company Ltd and methanol, toluene from BDH.. TOPO was purified by vacuum distillation at ca. 250 C ( 0.1 torr). The solvents used for air sensitive chemistry were distilled, deoxygenated under a nitrogen flow and stored over molecular sieves (type 4 A, BDH) before use. Instrumentation UV/VIS Absorption Spectroscopy: A Philips PU 8710 spectrophotometer was used to carry out the optical measurements of the semiconductor nanoparticles. The samples were placed
in silica cuvettes ( 1 cm path length). Photoluminescence Spectroscopy: A Spex FluoroMax instrument with a xenon lamp (150W) and a 152 P photomultiplier tube as a detector was used to measure the photoluminescence of the particles. Good spectral data was recorded with the slits set at 2nm and an integration time of 1 second. The samples were quantitatively prepared by dissolving 25 mg in 10 ml toluene. The samples were placed in quartz cuvettes (1 cm path length) used as blank for all measurements. The wavelength of excitation was set at a lower value than onset of absorption of a particular sample. X-Ray Diffraction (XRD): X- Ray diffraction patterns were measured using a Philips PW 1700 series automated powder diffractometer using Cu- K( radiation at 40kV/4OmA with a secondary graphite crystal monochromator. Samples were prepared on glass slides (5 cm). A concentrated toluene solution was slowly evaporated at room temperature on a glass slide to obtain a sample for analysis. Electron microscopy: A Joel 2000 FX MK I operated at 200KV electron microscope with an Oxford Instrument AN 10000 EDS Analyser was used for the conventional TEM (transmission electron microscopy) images. Selected area electron diffraction (SAED) patterns were obtained using a Jeol 2000FX MK 2 electron microscope operated at 200kV. The samples for TEM and SAED were prepared by placing a drop of a dilute solution of sample in toluene on a copper grid (400 mesh, agar). The excess solvent was wicked away with a paper tip and completely dried at room temperature. Electron spin resonance (ESR): Measurements were made on a Bruker 200D X-band spectrometer employing 100 kHz modulation, magnetic field markers from an NMR gaussmeter and an external microwave frequency counter. Synthesis All experiments were carried out by using dry solvents and standard Schlenck techniques. Glassware was dried in the oven before use and TOPO (tri-n-octylphosphineoxide) was used after purification by vacuum distillation Preparation of Cd(S 2CNMe(CHex)) 2 Cd(S 2CNMe(nHex)) 2 was synthesised according to the literature method. 8 A mixture of Cd(OH) 2 2H 20 (8.43g, 46.2 mmol), CS 2 (4.6 cm 3, 77.2 mmol) and N-methyl-hexylamine (11.6 cm 3, 76.3 mmol) in ethanol (50 cm 3) was refluxed for 1 h. The mixture was filtered to remove the solid impurities and the clear f
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