Analysis of a C 6 O/Twelve Solvent Survey for Red Shifting of Spectra
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Experimental All solvents used in this study were obtained in the highest purity available and used as received from Aldrich. Solvents were chosen from the literature1 to have a wide range of dielectric constants. C60 was obtained in 99.99% purity from MER Corp. and used as received. Samples were desired at the solubility limit in each solvent since the fluorescence signal of C60 is very small. Each sample was weighed in the literature solubility limit amount on a six place balance into a preweighed precleaned vial with a teflon lined cap. Solvents were measured with a glass syringe into the vial which was then sealed to prevent random evaporation of the solvent. The samples were sonicated four times with an ultrasonic bath for five minutes, with five minute rest intervals to avoid overheating the samples. The mixtures were sealed in foil to protect them from light and then allowed to sit for 48 hours at room temperature. To avoid floating agglomerates in the solution and to remove any inert column material, each sample was filtered with a preweighed .2 4tm pore size PTFE filter and loaded into precleaned lcm quartz cuvettes. By drying and reweighing the filter and original vial with the undissolved C60 and inert material, the actual amount of dissolved C60 was determined. From this value the molarity at saturation was obtained. Table 1 lists the solvents, calculated molarity, measured mg/ml at saturation, and the molar extinctions of the solutions at 694 nm.The calculated mg/ml solubility limit obtained is, in all cases, less than that obtained from the literature. 1 Correlation to literature values ranges from 23 to 97%. Sources of error include the weighing error in the vial and filter, inert column packing material from the purification of C60 and the syringe measurement error. Possible sources of the lower values include differences in the method of measurement and error bars on the 523 Mat. Res. Soc. Symp. Proc. Vol. 359 ©1995 Materials Research Society
material from the purification of C60 and the syringe measurement error. Possible sources of the lower values include differences in the method of measurement and error bars on the measurements. Reference 1 samples were filtered with a .45 gim filter and diluted several times to meet the test range of the HPLC column. Their measured solubilites were within 10% error. The dilutions may have introduced solvent evaporation. Concentrated solutions may contain agglomerates which will vary the concentration of each HPLC sample. Table I. Molar Extinctions and Molarity of C60 Solvent Solutions at Saturation Solvent
tetrachloroethane (TCE) trichloroethylene (TCE1) decalins (DEC) toluene TOL) chlorobenzene (CB) dichlorobenzene (DCB) 1-chloro-naphthalene (CHN)
Dielectric Molarity of Constant C 60 (d) IM] 2.46 3.40 2.20 2.44 5.71 9.93 5.00
N,N-diethylaniline (DEA) benzonitrile (BZN) 25.60 nitrobenzene (NB) 35.74 N-methyl-pyrrolidone --(NMP) pyridine (PY) 12.30 * These solutions are not at saturation.
2.64 x 10-3 1.88 x 10-3 4.48 x 10-3 2.21 x 10-3 _.46 x 10-3 6.52 x
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