An introduction to the Pigment Research ProjectLight, Color and PigmentsChemistry 123Spring 2008Dr. Woodward

Ohio REEL ProjectResearch Experiences to Enhance Learning

Partner Institutions

University of Akron (UA)Bowling Green State University (BGSU)Capital University (CU)Central State University (CtlSU)University of Cincinnati (UC)Cleveland State University (CSU)Columbus State Community College (CSCC)University of Dayton (UD)Kent State University (KSU)Miami University of Ohio (MU)Ohio University (OU)University of Toledo (UT)Wright State University (WSU)Youngstown State University (YSU)The Ohio State University (OSU)

http://ohio-reel.osu.edu/Supported by the National Science Foundation

How does a research module differ from a normal labResearch explorationOutcome is not known in advanceInvolves all phases of the research processForm a hypothesisConduct experiments to test hypothesisInterpret & report resultsModify hypothesisTackles problems of societal interestChemistry plays a central role in many challenges facing society Builds on previous experimentsThe details of the experiment evolve from year to year

Research TimelineREEL-I: Use X-ray fluorescence (XRF) and X-ray powder diffraction (XRPD) to identify an unknown saltREEL-II: Use UV-Visible (UV-Vis) spectroscopy to probe the electronic structures of transition metal complexes in solutionREEL-III: Use solid state reactions to prepare pigments, characterize the composition, crystal structure and electronic structure of the pigments using XRF, XRPD and UV-Vis methods.REEL-IV: Build on the ideas developed in REEL-III to prepare and characterize inorganic pigments of your own design.

LogisticsResearch will be conducted in teamsStudents will work in teams (~4 students per team)Research will be pursued collaborativelyDr. Woodward & Dr. StoltzfusREEL Lab Coordinator (Harry Seibel)Teaching AssistantsPeer MentorsResearch presentationEach research group will present their results at one of three REEL poster presentations (May 20,21,22) Research documentation and reportingEach student will prepare a report in the form of a scientific paper to describe their research findings

Peer MentorsBack Row: Lana Alghotani, Sachin Sharma, Jen Scherer, Alex Paraskos, Eric Smith, Sarah Watson, Ashley Doles, Derek Heimlich, David Albani, Front Row: Jalpa Patel, Sam Karnitis, Gina Aloisio, Stephen Smith, Brittany Thompson, Ravi Rajmohon, Ken Verdell, Amy Ullman, Amy Tucker, and Kristen Brandt

Experimental MethodsSynthesisDirect solid state reactionsCharacterizationX-ray powder diffractionX-ray fluorescenceUV-Visible SpectroscopyX-ray Powder Diffractometer (~$65,000)Ocean Optics UV-Visible Spectrometer (~$7,000)

PigmentsPigment: Coloring matter used to make paint.

Pigments work by selectively absorbing a portion of the visible light while the remaining visible light is reflected.

For more info see http://webexhibits.org/pigments/

Causes of ColorEmitted LightBlackbody Radiation, Incandesence (light bulb, flame)Gas Discharges/Excitations (neon lights, aurora borealis)Luminescence (LEDs, fluoresecent lights, chemluminescence)Steering and/or Interference EffectsDispersive Refraction (rainbows, prisms)Scattering (blue sky)Interference & Diffraction (butterflies, beetles, opals, CDs)Absorbed LightIntra-atomic excitations (Complex ions, gemstones)Molecular Orbital Excitations (Chlorophyll, organic dyes)Band to Band Transitions in Semiconductors (CdS, SnS2, HgS)Interatomic (charge transfer) excitationsOxoanions (i.e. CrO42, MnO4), Pigments (Prussian blue, chrome yellow), gemstones (sapphire)

For more info see http://webexhibits.org/causesofcolor/

The Electromagnetic SpectrumVioletBlueGreenYellowOrangeRed

Properties of Electromagnetic Radiation (Light)

QuantityUnitsEnergy, EJoulesFrequency, n1/s or HzWavelength, metersSpeed of Light, c2.998 108 m/sPlancks constant, h6.626 1034 Js

The Color WheelUV 100-400 nm12.4 - 3.10 eVViolet 400-425 nm3.10 - 2.92 eVBlue 425-492 nm2.92 - 2.52 eVGreen 492-575 nm2.52 - 2.15 eVYellow 575-585 nm2.15 - 2.12 eVOrange 585-647 nm2.12 - 1.92 eVRed 647-700 nm1.92 - 1.77 eVNear IR 10,000-700 nm1.77 - 0.12 eV

1 eV = 1.602 1019 J

Absorption of Light & Color

If absorbance occurs in one region of the color wheel the material appears with the opposite (complimentary color). a material absorbs violet light Color = Yellow

a material absorbs green light Color = Red

Absorption of Light & Color

If absorbance occurs in multiple regions of the color wheel the material generally takes on a color in the middle of the colors that are not absorbed. a material absorbs violet, blue and green light Color = Orange

a material absorbs violet and red light Color = Yellow-Green

UV-Visible SpectroscopyMonochromatic light (light of a single wavelength) is passed through the sample and the amount of light absorbed by the sample is measured.

Color and Cu2+ complexes[Cu(H2O)4]2+[Cu(NH3)4]2+