Optical Filter Using Graphene/Graphene Oxide Thin Films Abhay Varghese Thomas Graduate Student Department of Mechanical, Aerospace and Nuclear Engineering Rensselaer Polytechnic Institute, Troy, NY, USA Advisor Dr. Nikhil Koratkar John A. Clark and Edward T. Crossan Chair Professor In collaboration with Dr. Anna Dyson Director, Center for Architecture Science and Ecology (CASE) 2013 Rensselaer Nanotechnology Center Research Symposium Wednesday, November 6, 2013
Outline Dynamic Glazing Dynamic Window Technologies Graphene/Graphene Oxide Introduction and Synthesis Wrinkling of GO thin films Uniaxial vs. Biaxial wrinkling Effect of GO film thickness Wrinkled graphene thin films
Dynamic Glazing Primary energy benefits Reduce cooling loads Reduce electric lighting use by managing daylight Summer & hot climates minimize solar heat gain with adequate daylight Winter & colder climates admission of both solar heat gain and daylight Selkowitz, S. E. et. al (1994). A review of electrochromic window performance factors. SPE International Symposium on Optical Materials Technology for Energy Efficiency and Solar Energy Conversion XIII
Dynamic Window Technologies 1. Electrochromics 2. Photochromics 3. Thermochromics 4. Gasochromics 5. Liquid Crystal 6. Suspended Particle Switching sequence of an electrochromic laminated glass [2] Electrochromics Optical range ( ~ 67%) Dynamic - but slow (5-80 min) temporal response Low material and power consumption (0.5 W/m2) Endurance (30 yrs.) and stable cycling (10 5 ) 1. Andow, B. C., Krietemeyer, B., Stark, P. R., & Dyson, A. H. (2013, April). Performance criteria for dynamic window systems using nanostructured behaviors for energy harvesting and environmental comfort. In SPIE Smart Structures and Materials+ Nondestructive Evaluation and Health Monitoring (pp. 86923V-86923V). International Society for Optics and Photonics. 2. Gesimat, www.gesimat.de
Graphene Single atom thick sheet of sp 2 carbon atoms. GRAPHENE Basic building block of carbon nanomaterials [1]. Extremely good mechanical and electrical properties in-plane. FULLERENE CARBON NANOTUBE GRAPHITE Geim, A. K., and K. S. Novoselov, 2007, Nature Materials, 6, 183
Graphene/Graphene Oxide Synthesis Bottom up Chemical Vapor Deposition High quality single layer graphene (1 to 10µm domains, low # defects) Suitable for single to few layer architectures Top down Exfoliation of graphite Oxidise graphite and exfoliate into graphene oxide (GO) sheets Bulk liquid processing Suitable for bulk assembly of sheets
Graphene Oxide Wrinkling Principle Drop coat GO solution Substrate: O 2 plasma treated silicone rubber Thin films: 20-200 nm Compressive strain (~ 400%) on GO thin films uniform wrinkling Uniaxial Biaxial Uniaxial (linear) strain Biaxial (areal) strain
Uniaxial vs. Biaxial: Morphology Flat GO Biaxial (areal) strain uniform wrinkles with no cracks Uniaxial (linear) strain uniform wrinkles along with cracks
Uniaxial vs. Biaxial: Optical Transmission 100 90 550 nm GO Uniaxial 104 nm Transmission (%) 80 70 60 50 40 30 20 10 0 200 300 400 500 600 700 800 Wavlength (nm) Optical Range 45% GO Biaxial 104 nm Optical Range 70%
80 nm Effect of GO thickness on wrinkle morphology 40 nm 25 nm As film thickness inc. wrinkles more well defined (AFM to determine wrinkle height)
Graphene Wrinkling Reduce GO to Gr before/after wrinkling Hydrazine/HI Silicone Rubber Advantage conductive optical filter Combine with photoactive material for energy harvesting Disadvantage Unwrinkled transparency is low
Future Work Short term increase optical range: 80-90% Cyclability of graphene oxide optical filter Explore role of filter beyond optical wavelengths
Acknowledgement Rensselaer Nanotechnology Center Funding Grant from John A. Clark and Edward T. Crossan Chair Professorship Advisor Dr. Nikhil Koratkar Collaborator Dr. Anna Dyson and Brandon Andow at CASE, NY