We have synthesized carbon based nanoparticles and have found that it has fluorescent property under UV. Using Malvern particle size analyzer we have found the presence of particles of 3 different size. The report is attached. One of the particles which has the maximum intensity is less than 1 nm and another particle is around 220 nm. What can be the cause of the fluorescence and is there any reference of particles less than 1 nm.
Muralidharan Sir,
Thank you for your reply.
What about the particles which are in the range of 230 nm? What can be the reason for fluorescence? Does atomic clusters give fluorescence?
I agree with Volodymyr. firs you should use an other method to be sure you have clasters that smaller than 1nm. If you have, and you work with carbon, it could be something like carbon dots but of course mach smaller. Carbon dots contains graphitic carbon, sp3 carbon, oxidized groups cumulated bonds etc which have fluorescence.
RAMAN could help. If you have graphene, you probably see it with raman....
The report you attached states "Refer to quality" report and this will give you some indication of possible issues. Your attenuator position of 10 shows virtually no scattering in the sample - small size, too low concentration, too low optical contrast are the possible reasons. You have evidence of contamination in the sample - large peak in the microns region and a z-average of 185 nm with high PDI (~ 0.2). Did you filter all solutions to < 20 nm or better? For such small systems the quartz cuvette has better optical quality that the polystyrene disposable cuvettes that you have used. The quartz cuvette is recommended
In certain cases the rotational mode of diffusion (not the translational as is inherent in the Stokes-Einstein) can be observed in a DLS experiment. Here's a webinar on that:
https://www.brainshark.com/malvern/vu?pi=zFAz11CZD6z5chz0&tx=preview
This mode will be lower in size, calculable based on the top size mode, and can be demonstrated to occur by inserting a polarizer in the system. DLS can measure particle sizes below 1 nm and this has been shown many times for materials such as sucrose and Vitamin B1. See for example:
http://www.malvern.com/en/support/resource-center/technical-notes/TN101104ZetasizerAPSSpecificationsMinSize.aspx
http://www.malvern.com/en/support/resource-center/application-notes/AN101104CharacterizationVitaminB1.aspx
The sucrose results have been published in J Nanopart Res and I attach. See
http://www.malvern.com/Assets/AR071217_MRK1034-01.pdf
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