Quantum Dot Detective

December 5, 2017

by Megan Litwhiler

Recently, QSTORM communications team member Karine Thate posted about our newest QSTORM prop here at the Museum of Science - a shiny new batch of super-bright, super-safe quantum dots. We’ve been showing off our new quantum dots during our QSTORM stage presentations, but we also wanted to figure out a way to get our visitors up close and personal with these cool little nanocrystals. 

Showing off our QDot kit during
NanoDays 2017 at the Museum of Science

One of the exciting ways we facilitate learning at the Museum of Science is by letting people discover new ideas themselves through hands-on exploration. So, we figured the next step should be to design an interactive, hands-on activity using quantum dots! All we needed now was an idea.

Luckily, we were working with some talented graduate students from MIT who came up with a fantastic idea for a quantum dot activity - Quantum Dot Detective. In this activity, visitors at the Museum of Science become the “detectives”. Their assignment is to figure out which colors are in a “mystery vial” containing a mix of two or three different colored quantum dots. To accomplish the task, the visitors are given tools, like diffraction grating glasses (glasses that split light into separate colors) and a spectrophotometer (a device used to measure wavelengths of light). Using the spectrophotometer lets the visitors feel like real scientists, while they learn about light by matching different colors to their respective wavelengths. Our graduate students tested the Quantum Dot Detective activity out at the Museum of Science back in April 2017 during our annual NanoDays event, and it was a big hit with our visitors!

Left: QSTORM Communications Team member Karine Thate works
with graduate students from MIT to develop Quantum Dot Detective
Right: MIT PhD student Cole Perkinson tests out Quantum Dot
with visitors at the Museum of Science

We definitely wanted to use this activity regularly at the Museum. It’s a lot of fun and a great way to introduce people to quantum dots and their applications - like QSTORM! Our graduate students had borrowed equipment from their own lab to make Quantum Dot Detective, so we needed to build our own copy of it. With some guidance from the grad students, we purchased all the necessary equipment -  Logger Pro software and a spectrophotometer with an optical fiber probe from Vernier, and a UV light from Thomas Scientific that the quantum dots could sit on top of to illuminate them from below.  

But there was a problem - our new spectrophotometer wasn't detecting the light from our quantum dots! When we held the probe of the spectrophotometer up to the quantum dots and looked at the Logger Pro graph of fluorescence vs. wavelength, nothing happened.

Testing out our new set-up for Quantum Dot Detective on
a cuvette of blue quantum dots. The QDots sat nicely on top of
the flat UV light (left), but the spectrophotometer probe
was not detecting any light, so we saw no peak on the Logger Pro
graph (right).

In order for our visitors at the Museum to understand what is going on, they need to be able to see a peak on graph that corresponds to the wavelength of light emitted by the quantum dots. After some trouble shooting, we realized the problem was our UV light. It was just too dim. We had an extra-bright UV flashlight lying around, so we tested that out and it did the trick! We were able to record nice peaks at the right wavelengths for each different colored quantum dot. And we could even see multiple peaks for the “mystery vials” containing a mix of colors.  

When we used a much brighter UV flashlight, the QDots were much brighter too.
Here we're testing out blue QDots (top left). We saw a nice peak at the right
wavelength on the graph (top right). We could even see multiple peaks
(bottom right) in the "mystery vials" (bottom left) containing a few different colors. 

But in order to easily hold the probe of the spectrophotometer up to the quantum dots, we need them to sit on or near a stable light that won’t roll around, so the flashlight, although nice and bright, is not ideal. We're working on solving this last final lighting issue and we hope to have Quantum Dot Detective up and running at the Museum of Science soon. Stay tuned!