Educ. Particle in a Box : Absorption Spectrum of Conjugated Dyes Part A - Recording the Spectra and Theoretical determination of max Theory Absorption bands in the visible region of the spectrum (350 - 700 nm) correspond to transitions from the ground state of a molecule to an excited electronic state which is 160 to 280 kJ above the ground state. The literature and experimental major wavelengths (max) absorbed for dyes 1, 2, and 3 agree within the experimental absolute uncertainty; however, the literature max absorbed for dye 4 falls outside the experimental absolute uncertainty (Table 1). 3. Evaluating Experiment with Computation in Physical Chemistry: The /S /Creator }); subscribers only). The experiment shows the impact chemical structure has on approximation models like the PIB. Kirksville, Missouri 63501 0000001838 00000 n $('#commentText').css('display', 'none'); The theoretical max also shows a similar trend. 0000008165 00000 n R It was also seen that the lengths of the box calculated increase with the number of carbon atoms. were measured and relate the absorption spectra to the particle in a box quantum mechanical 0000037527 00000 n The dyes can be run in any order. Add a drop or two dye A solution. 0000002281 00000 n The solution of Schrdingers equation for the particle in a box yields the energy levels given by Equation (2). A holmium oxide (Buck Scientific) test was performed to calibrate the spectrophotometer. /PageLabels because of the poor solubility of these dyes in non-polar solvents and in water. based on the particle in a box model. In Rodds Chemistry of Carbon Compounds (pp. For a molecule to absorb a photon, the energy of the impinging photon must match the energy difference between the initial state and some excited state of the molecule. All of the conjugated dyes used have the largest absorbance at different wavelengths of light. Educ. (The dyes are CONCENTRATED.). 0000001086 00000 n 2 \[\psi \left ( q_{1}, q_{2}, q_{3}, q_{4}, \right ) = - \psi \left ( q_{2}, q_{1}, q_{3}, q_{4}, \right ) \] In (B-F), the horizontal axis is position, and the vertical axis is the real part (blue) and imaginary part (red) of the wavefunction.The states (B,C,D) are energy eigenstates, but (E,F) are not. Procedure: (done by others) /Nums 4.2: Introduction - Chemistry LibreTexts 9. In this exercise you will explore the spectroscopy of the cyanine dye family, develop a testable hypothesis and then determine the validity of your hypothesis. /Annots Diluted solutions of each dye were analyzed using a UV/VIS spectrometer to determine the wavelength of maximum absorbance (max) for each dye. Figure 2. $('document').ready(function() { The experiment has been revised to suit our laboratory environment. %PDF-1.3 % L = 1 x 10-10 m \[-\frac{\hbar^{2} }{2m}\frac{\partial ^{2}\psi}{\partial x ^{2}}+ V\left ( x \right ) \psi = E \psi\] The chemical structures are resonance structures; the positive charge can be equally well represented as residing on either nitrogen atom. Each spectrum shows a major peak, a shoulder peak at a smaller wavelength, and a baseline with minimum noise (Figure 1). Solutions of dyes A F in methanol have been prepared. length of the box and is one of the two requirements to use the . Our observation suggests that PIB is predictive only when it is applied to a homologous series, wherein all compounds in the series have similar functional groups and similar chemical properties, with the only difference here being an increase in carbon number. 5 a = (2j + 2)L, Dye maximum wave To test the robustness of the PIB model against four conjugated polymethine dyes, 1,1-diethyl-2,2-cyanine iodide (dye 1), 1,1-diethyl-2,2-carbocyanine chloride (dye 2), 1,1-diethyl-2,2-dicarbocyanine iodide (dye 3), and 1,1-diethyl-4,4-carbocyanine iodide (dye 4), I measured their absorption spectra 523 +/- 1 nm, 604 +/- 1 nm, 706 +/- 1 nm, and 706 +/- 1 nm at room temperature using a UV-Vis spectrophotometer, and calculated their PIB approximations and lengthening parameter gamma using an in-house MATLAB subroutine. DOC UV-VISIBLE SPECTORMETER EXPERIMENT #2 - Evergreen State College $('#comments').css('display', 'none'); 0000002473 00000 n Dr. Dharshi Bopegedera Using the Particle in a box model to investigate the Absorption Spectra of Conjugated Dyes. electron model. Using this wavelength, We do this by determining the length of conjugated region. Click here to view this article (Truman addresses and J. Chem. Evaluate and tabulate the difference between the length of the box calculated from Equation (11) and the length estimated from the number of bonds for each dye. Use the references 3 and 4 to develop an experimental procedure. Figure 1: The absorption spectra of each conjugated dye. 10 drops of each stock dye solution were transferred to a cuvette followed by dilution with methyl alcohol. For dyes 1 and 3, the absolute percent errors are 8.79% and 3.64%, respectively, while the absolute percent error is the greatest for dye 4 (21.7%). 2007, 84, 1840-1845. Olsson, L. F. (1986). 8. 2000, 77, 1221-1224. 0000034252 00000 n This new feature enables different reading modes for our document viewer. This paper describes an experiment in which beta-carotene and lutein, compounds that are present in carrots and spinach respectively, are used to model the particle in a one dimensional box system. 0000037260 00000 n Fourier Transform Infrared Spectroscopy (FTIR), CHEM 174 Physical Chemistry Laboratory II, Determination of the Length of a Molecular System, Pauli Exclusion Principle and Packing Electrons into the Particle in a Box. subscribers only). We will make the following assumptions: /Type All of the conjugated dyes used have the largest trailer <<3068649AEBAF11DF80810026B0D9EA12>]>> startxref 0 %%EOF 106 0 obj<>stream All of these systems contain long conjugated systems that can be approximated at some level to being linear and therefore can be modelled using the quantum mechanical particle in a one dimensional box . 0000001680 00000 n An optimum gamma value of 1.2400 is obtained. 0000041060 00000 n >> signifies that light or any electromagnetic radiation can penetrate a significant distance into the 0000007372 00000 n Although the theoretical max gives a similar trend we see in our max measurements, it seems that there is a good agreement between the experimental and theoretical max for dyes 1, 2, and 3, and not for dye 4. $('#annoyingtags').css('display', 'none'); The objectives of this experiment include: 0000004510 00000 n Absorption Spectra of Conjugated Dyes - Gustavus Adolphus College /FlateDecode The LibreTexts libraries arePowered by NICE CXone Expertand are supported by the Department of Education Open Textbook Pilot Project, the UC Davis Office of the Provost, the UC Davis Library, the California State University Affordable Learning Solutions Program, and Merlot. [CDATA[*/ . Conjugated dyes are known sensitizers; take care when handling the dyes and wash your hands after handling them. R 0 The quantum number n = 1, 2, 3 and the spin of an electron can be either up (+1/2) or down (-1/2). Finally, the length of the box for each dye molecule from the absorption spectra was calculated by treating the system as a 1-D particle in a box. Particle in a Box is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by LibreTexts. Moog, R. S. J. Chem. ( G o o g l e) Using the spectra shown, the max is determined by When we run the routine, we see that for dye 4, the absolute percent error is 0.05% when run with dyes 5 and 6 (Table 2), versus 21.7% obtained when it is grouped with dyes 1, 2, and 3, suggesting that our hypothesis is correct. Calculate the wavelength of a photon absorbed in the transition of an electron from the n = 6 to the n = 7 energy level of the molecule shown in Figure 1 of the lab handout.Estimate the length of the box by multiplying the number of bonds in the conjugated double bond chain (include C-N bonds) by the . Conjugation (delocalization) impacts the energy required for electronic transitions. >> Click here to view this article (Truman addresses and J. Chem. Absorption of blue light produces the color red while the absorption of red light produces the color blue-green. Nguyen Quoc Trung. and M. Kasha (1958). << /Length 5 0 R /Filter /FlateDecode >> Is the difference usually positive or negative? subscribers only). You MUST bring a completed pre-lab before you will be allowed to start the lab. Suppose there were two electrons with the same set of quantum numbers (q1), then the total wave function would be (q1,q1,q3,). /Pages You should just be able to see a little color. impinging photon must match the energy difference between the initial state and some excited Educ. LAB 1.docx - Title The Particle-In-a-Box Model for % N = 2j + 2 = 2(2) + 2 = 6 pi electrons 0000007892 00000 n Physical Chemistry 10th ed. subscribers only). 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Theobald, R. S. (1964). L = 1 x 10-10 m Make plots of the absorbance spectra for dyes A F. You may combine the plots in one or two page graphs. Conjugated pi-bonded system for dyes A and B. 3 (an eigenvalue equation) by substituting eq. Three things need to be considered to calculate the energy changes from Equation 5. 1965, 42, 490. 0000005432 00000 n The absorption spectrum of each dye solution was taken at room temperature with a CARY 1G UV-Vis Spectrophotometer (Varian) at a 1 nm step size, 2 nm spectral bandwidth, 1 nm data interval, 600 nm/min scan rate, and 0.02 mm slit width. length (m) A: Pinacyanol chloride, MM = 388 g/mol