Optical Spectroscopy: Measurement Demonstration

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Del curso dictado por Duke University

Nanotechnology: A Maker’s Course

382 calificaciones

Duke University

Nanotechnology: A Maker’s Course

382 calificaciones

How can we create nano-structures that are 10,000 times smaller than the diameter of a human hair? How can we “see” at the nano-scale? Through instruction and lab demonstrations, in this course you will obtain a rich understanding of the capabilities of nanotechnology tools, and how to use this equipment for nano-scale fabrication and characterization. The nanoscale is the next frontier of the Maker culture, where designs become reality. To become a Nanotechnology Maker pioneer, we will introduce you to the practical knowledge, skills, and tools that can turn your nanotechnology ideas into physical form and that enable you to image objects at the nano-scale. This course has been developed by faculty and staff experts in nano-fabrication, electron beam microscopy, and nano-characterization through the Research Triangle Nanotechnology Network (RTNN). The RTNN offers training and use of the tools demonstrated in this course to schools and industry through the United States National Nanotechnology Coordinated Infrastructure program. The tools demonstrated in this course are available to the public through the RTNN.

De la lección

Nano Measurement and Characterization Tools: X-ray and Optical Characterization

In this module, we will see demonstrations of micro-computed tomography, X-ray photoelectron spectroscopy, and optical spectroscopy. You will learn the basic function of the equipment and how samples are prepared and measured.

Optical Spectroscopy: Basic Function7:04

Optical Spectroscopy: Sample Preparation Demonstration3:25

Optical Spectroscopy: Measurement Demonstration3:38

Conoce a los instructores

Nan M. Jokerst
J. A. Jones Professor of Electrical and Computer Engineering
Electrical and Computer Engineering, Duke University
Carrie Donley
Director of CHANL (Chapel Hill Analytical and Nanofabrication Laboratory)
Applied Physical Sciences, UNC Chapel Hill
James Cahoon
Assistant Professor
Chemistry, UNC Chapel Hill
Jacob Jones
Professor
Materials Science and Engineering, North Carolina State University

Welcome, my name is Carrie Donley and I'm

the director of the Chapel Hill Analytical and Nanofabrication Lab or CHANL at UNC.

Joining me today is Kaci Kuntz a graduate student here at UNC.

Thank you, Carrie. Today, I will be demonstrating

how to measure the scatterings spectrum of gold nanoparticles.

The system we will use to take this data is

a combination of a light microscope and a spectrometer,

we call it a microspectrophotometer.

First, I will place one of my samples onto the microscope stage.

This is a sample with 200 nanometer gold nanoparticles.

Then I will focus on the sample in brightfield reflection mode.

In this mode, I see a lot of light reflected off of

the shiny silicon wafer and it is difficult to

see any of the scattered light from the nanoparticles.

The features we see at the top of the image are chips on the edge of the silicon wafer.

And if you look closely,

you can see some small dots on the wafer.

Those are the nanoparticles.

Now, I'll switch to darkfield reflection mode.

In this mode only light that has been scattered will be collected by

the objective and it will be much easier to see the nanoparticle scattering.

I can see individual nanoparticles using this technique and I can also

tell that they are not clustered together in aggregates but separated from one another.

This is exactly what I was hoping to see in this image.

At the 50X magnification,

I can compare the images from the different sized particles.

The particles look to be different sizes and they also appear to be different colors.

This is because nanoparticles of different sizes will scatter different colors of light.

I can now take some spectra of the samples.

On this instrument, the area inside the red square in

the center of the image is the area from which we will collect our spectrum.

I'll place it in a location with a lot of particles.

Because there are only about 10 nanoparticles within

the square and the amount of light that they each scatter is pretty low,

it takes a minute or two to collect enough light for one spectrum.

But after I collect spectra for each sample,

I can see that the scattering peak shift to

higher wavelengths as the size of the nanoparticle increases.

Now, let's consider the scattering by nanorods.

The spectra for these samples are a bit more complicated.

The nanoparticles were spheres with

just one diameter but the nanorods have two dimensions.

Sometimes the spectra for nanorods contain more than one peak.

You can see that here in the spectra for the 50 by 110 nanometer nanorods.

This is due to the large difference in length scales in the nanorod.

Many applications such as solar cells and chemical sensors use nanoparticles like these.

And scientists need to measure the reflectance spectra of

the nanoparticles to make better solar cells and sensors.

I hope this demonstration of nanoparticle scattering helps you understand this process.

Thank you for joining me.

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