Quantum/Classical Modelling of Au/Dye Absorption LUMO Au E NP - - PowerPoint PPT Presentation

Quantum/Classical Modelling of Au/Dye Absorption

Jelaine Cunanan LSU CHEM CCT REU S’16

Mentor: Dr. Kenneth Lopata/Holden Smith

HOMO LUMO ∆ E

Au NP

Importance

• 1. Bio / Chemical Sensors
• 2. Catalysis (Photochemistry)

○ Chemical Rxns at Surface

• 3. Light Harvestry

Optical Absorption

HOMO LUMO ∆E ∆E = hv Light In Light Out

Energy where light is absorbed

Computer Simulations of Light Absorption in Au nanoparticle coated with dye molecules 100nm

Light energy D y e m

• l

e c u l e

NP

Metal + Molecule Absorption

Challenges

• 1. Dye molecules require

Quantum Mechanics (QM)

• 2. Au NP is too large for QM

Requires QM 106 atoms

Too large for QM!

D y e m

• l

e c u l e

Au NP

Overall Goals

• 1. Develop tools for

Quantum/Classical Simulations

• 2. Model Coupled

excitements of Au nanoparticles & dyes

106 atoms

Au NP

Classical Electrodynamics (electric & magnetic fields) Quantum Mechanics

My Objectives

1. Develop code for 2-level QM molecule 2. Parameterize model using Time-Dependent Density Functional Theory (TDDFT) eg: HOMO-LUMO gap 3. Integrate into electrodynamic code using finite-difference time domain (FDTD)

HOMO LUMO ∆E

Results (FDTD)

Gridpoint Grid spacing

Gold Nanoparticle

Results (FDTD)

Dye Molecule

Malachite Green

Results (FDTD)

Gold Nanoparticle/Dye Molecule Coupled Simulations Distance ~2.5nm

Results (FDTD)

Gold Nanoparticle/Dye Molecule Coupled Simulations

Results (FDTD)

Gold Nanoparticle/Dye Molecule Coupled Simulations

Acknowledgments

➔ Dr. Kenneth Lopata ➔ Holden Smith ➔ Adam Bruner ➔ NSF REU ➔ CCT