QuantumDotResearch2

QuantumDotResearch2 - Fluorescence Photons absorbed to...

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Quantum Dot Research: Spectroscopy S117 Fall 2011
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Overview Post-Lab Discussion of Synthesis Pre-lab: Quantum Dot Spectroscopy Band gap theory review Determination of band gap energy Determination of quantum dot size Fluorescence Application to materials
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Small Molecules and Bulk Materials From J. Chem. Ed. Vol 84 pp709-710
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Particle in a Box! Tune the energy of band gap through size of quantum dot Measure band gap energy—use theory to determine size How do we measure? Absorbance spectroscopy
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Gap Energy Electronic transition in molecule is broad due to multiple vibrational states in addition to condensed phase considerations Need the gap energy
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Wavelength Cutoff 400 420 440 460 480 500 520 540 560 580 600 -0.1 0.4 0.9 1.4 1.9
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Quantum Dot Size From cutoff wavelength, calculate the nanoscale material band gap (Egnano) All constant values given in handout
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Unformatted text preview: Fluorescence Photons absorbed to promote electron into various vibrational modes in electronic excited state Partial relaxation of electron through loss of vibrational energy (heat-during collisions) to ground vibrational Fluorescence Spectrum Application: Fluorescent Lights Stokes shift Application to Materials Conductors, Insulators, and Semi-conductors Metals Sea of electrons model MO model Electrons and holes Carbon: Conductor or Insulator? Semiconductor More difficult, but still possible, to transfer valence electrons into the conduction band Free electrons and holes have energy difference Recombination releases energy in form of light Not very efficient Doping: More efficient Semiconductors Two Distinct Materials Light Emitting Diodes...
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This note was uploaded on 01/17/2012 for the course S 117 taught by Professor Stephenjacobson during the Fall '11 term at Indiana.

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QuantumDotResearch2 - Fluorescence Photons absorbed to...

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