![]() ![]() 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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