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.

Ablation: \a-’blā-shən\

• Using a laser to vaporize material.

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

Variables being tested

• the laser energy being used

• the amount of gas flowing into the chamber

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

Any questions?