UV-vis spectra were obtained using a Jasco V-530 spectrophotometer scanning in the 400 to 700 nm range. Left to Right: 1,1’-Diethyl-4,4’-cyanine iodide, 1,1’-Diethyl-4,4’-carbocyanine iodide, 1,1’-Diethyl-4,4’-dicarbocyanine iodide, 1,1’-Diethyl-2,2’-carbocyanine iodideĬdSe quantum dots embedded in glass slides were obtained that had been heated to 700☌ for varying amounts of time (0.5 to 4 hours). Color of dye solutions when diluted to 100 mL. The conjugated dyes studied in this experiment with their structure, molecular weight, CAS and amount used to make each solution. UV-Vis spectra for each dye were obtained using a Jasco V-530 spectrophotometer scanning in the 450 to 800 nm range. The resulting solutions were further diluted by adding 1 mL solution to a 10 mL flask and diluting to the line with methanol with a final concentration that ranged from 1×10 -5 to 8×10 -5 M. Varying amounts of dye (0.001-0.008 mmol) were added to a 100 mL flask and then diluted with methanol. Particle size increased with prolonged heating but slowed after 2 hours. Crystal size was determined from the corrected absorption spectra by fitting the curves to a parabola using Origin and changing wavelength to energy (eV). CdSe nanoparticles embedded in glass plates were heated to 700☌ between 0.5 and 4 hours causing crystal size to vary. The CdSe nanoparticles are represented by the quantum dot model which are crystal semiconductors that confine excitons to three spatial directions. The 1,1’-diethyl-2,2’-carbocyanine iodide dye was also investigated with a carbon chain of 5 and a of 604 nm, which had a longer wavelength than 1,1’-diethyl-4,4’-cyanine iodide although it had a shorter carbon chain. The free electron model was used to calculate theoretical at 579, 706, and 832 nm for cyanine, carbocyanine, and dicarbocyanine, which had a 1.87, 0.06, and 2.47% difference to observed. The wavelength increased with length of the conjugated carbon chain due to the resonating electronic transition along the □ bonds which is related to the particle in a box model. The family of 1,1’-diethyl-4,4’ dyes are compared with varying length of conjugated carbon chains of 7, 9, and 11 carbons long for cyanine, carbocyanine, and dicarbocyanine at, of 590, 706, and 812 nm respectively. In this experiment conjugated polymethine dyes and cadmium selenide (CdSe) nanoparticles are excited to their lowest excited energy state are investigated by ultraviolet-visible (UV-Vis) Spectroscopy. There are several different properties that molecules can possess to display color.
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