Core-Shell Nanoparticle Generation
Using Laser Ablation
Vanessa Coronado, Westside High School, Houston ISD
Dr. Sy-Bor Wen/ Assistant Professor and YoungKyong Jo/ Ph.D. student Dept. of Mechanical Engineering
http://www.istm.cnr.it/~ponti/NJC06.html
Dr. Sy-Bor Wen, Department of Mechanical Engineering
• Ph.D. in Mechanical Engineering
@ University of California at Berkeley, CA
• M.S. and B.S. in Mechanical Engineering
@ National Taiwan University, Taipei, Taiwan
• Working on using lasers to ablate germanium and copper and condense them together to form a nanoparticle core-shell material that has superior optical and electromagnetic properties.
What is nano?
• Very small!
• 1nm, is a nanometer = 10-9m.
• Essentially, a billionth.
• It takes up to 150,000 nanoparticles to be as wide as a human hair.
Lasers being used• Excimer laser – class IV laser (short for 'excited dimer‘)
193 nm = UV light
• Nd: YAG laser – class IV laser (neodymium-doped yttrium aluminum garnet)
532 nm= green light
en.wikipedia.org/wiki/Nd-YAG_laser
• The laser light is fed through a series of mirrors and lenses to a closed chamber that has the samples of copper and germanium inside.
Two pulsed laser ablation
• Courtesy of YoungKyong Jo
*Sample alignment
*Copper Fiber0.25 mm
*Optical Fiber
Excimer Laser
Nd:YAG laser
*different materials used in current lab set-up.
• The excimer laser is triggered first to ablate the germanium and a fraction of a second later the Nd: YAG laser will be triggered to ablate the copper sample.
Courtesy of YoungKyong Jo
• A plume of germanium is first created then the copper is ablated to create a larger second plume that will condense onto the first.
• This is all captured by an ICCD camera. An ICCD camera captures light as sensitive as a single photon….much better than my camera…
Courtesy of YoungKyong Jo
• Once the particles have condensed and formed, they deposit on the inside of the chamber onto a collection plate strategically placed inside of the chamber. This occurs over a period of time that varies up to 2 hours.
http://www.canemco.com/catalog/grids/Quantifoils.htm http://www.gatan.com/resources/answers/Answer-10.php
• The particles are then taken for imaging using a SEM- scanning electron microscope and a TEM- transmission electron microscope to see if core-shell nanoparticles were created.
http://www.nims.go.jp/htm21/MA/tem.jpg
scanning electron microscopy
transmission electron microscope
Possible applications of nanoparticles
• Biomedical uses – cancer cell eradication that targets only malignant cells
• Better catalyst
• Creates stronger magnetic field for use in electronics
• Makes stronger, lighter composite materials
• ? ….we don’t know what else….
Variables being tested
• the position within the chamber that the sample is being collected from.
• the gas that is within the chamber is variably argon or helium.
in air in argon
Variables being tested
• the time that the sample deposits on the collection
grid
• the time between the lasers being triggered
What are we doing?
•Learning about experiment
•Studying procedures
•Running experiments using different variables
In summary….• 2 lasers ablate germanium and copper a
fraction of a second apart
• Second material condenses onto first to form core-shell particle
• Particles deposit over time and are sent to a SEM and/or a TEM
• If the particle is a core-shell particle…party…. then determine the properties of it.
How will this translate to the physics classroom?
Not sure yet…but somewhere along the lines of…(get it…it’s a little laser joke)…
• Supporting TEK 8: “The student knows the characteristics and behavior of waves.”
and/or• Supporting TEK 9b: “the student is
expected to explain the line spectra from different gas-discharge tubes.”
What might this look like?
• Using classroom grade lasers coupled with mirrors and lenses to discover properties of light and waves
• Use spectrum tubes to discover the differences between colors of light and what makes them unique.
http://webapps.lsa.umich.edu/physics/demolab/controls/imagedemosm.aspx?picid=600
Acknowledgements
• Texas A&M
• National Science Foundation
• E3 RET Program coordinators
• Mechanical Engineering Dept
• Dr Sy-Bor Wen and his team
• And viewers like you