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A Methods for finding properties of quantum dots?

  1. May 16, 2016 #1
    What are some good methods to determine properties such as light quality/intensity, pH, and water solubility of quantum dots? Other properties are welcome, as well. I do not have a college lab available, so some equipment may not be possible to get. This is for my science fair project next year.

    Thank you!
  2. jcsd
  3. May 16, 2016 #2
    Maybe we need to be a little more specific, first are you trying to model these properties theoretically or measure them by experiment, second what kind of quantum dots? What material are they made of, how small are they? By the sounds of it you're interested in quantum dots immersed in a liquid medium: In that case the best place to start might be reading about Cadmium Selenide QDs?

    If you have access to scientific literature I would look there as for CdSeQDs things have come a long way (it's a reliable QD). If you could describe the system and what you want exactly I could be a little more specific?
  4. May 16, 2016 #3
    Hello! Sorry for not being more specific. My project is Production Methods in Graphene Quantum Dots. I'll be using previously developed procedures to fabricate graphene quantum dots and then I'll compare the different properties from the resulting QDs in each procedure. Currently, I'm trying to find procedures with a realistic cost and equipment. Here's two I plan on using:

    For the first procedure, quantum dots were synthesized by a microwave assisted pyrolysis method. 1g of aspartic acid and 2g of NH4HCO were added to 20 mL of ionized water in a beaker. Then, this mixture was heated using microwave irradiation for 10 minutes in a microwave reactor operating at a power of 560 W. Finally, the obtained graphene quantum dots (GQDs) were purified by dialyzing and deionized water using a dialysis membrane (molecular weight cut-off=500) for 7 hours.

    For the second procedure, 0.2g carbon black was put into 50 mL L⁻¹ HNO₃ followed by refluxing for 24 hours. After cooling to room temperature, the suspension was centrifuged (2770 g) for 10 minutes to obtain a supernatant and a sediment. The supernatant was heated at 200 ℃ to evaporate the water and nitric acid and a reddish-brown solid (ca. 0.089 g, 44.5%) was obtained, labeled as GQDs1. The sediment was washed with 1 M HCl followed by centrifuging three times and subsequently drying under a vacuum. The dried sample was dissolved in 50 mL H₂O and further adjusted to about pH 8 with 10 mM ammonium water. The solution was ultrafiltered through a centrifugal filter device with a 100 kDa molecular weight cutoff membrane. The filtrate was collected, dried, and labeled as GQDs2 (ca. 0.018 g, 9.0%).

    And I think I found a possible way to measure the toxicity with luminous bacteria and a way to determine the size of the QDs with dynamic light scattering (this was my physics teacher's idea). I want to be able to find quite a few properties so I can compare the different procedures and determine which would be best for certain applications.
  5. May 16, 2016 #4
    Cool sounds fun! First of all I would say focus on one major objective at a time, do you need the properties of your graphene QDs to be highly specific? I assume if you fabricate the QDs in right way you will have a chance at measuring the toxicity?

    I am not sure about the toxicity part and luminous bacteria but I'm guessing that's not important right now, you want to demonstrate you can make graphene QDs that are fit for a specific purpose? In this case focus on the most important properties you want to measure, for instance their size/concentration will likely determine most of the other properties of interest that have to do with light and chemical reactivity..
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