I have been making my own graphene quantum dots (GQDs) as of late, and have to say they certainly do have some amazing noteworthy properties.
Here is one sample I created and photographed showing the natural appearance and color of the nanoparticle suspension in white light (a), the Tyndall Effect demonstrated using a 532 nm green laser (b), and band bending phenomenon (c), which arises from quantum confinement effects (due to plasmonic resonance). This particular batch illustrates a blue-shift in near-UV light at 435.8 nm suggesting the sample has a unique band structure similar to some antidot arrays, and the sample is not like typical GQDs which posses narrow red-shifting that gives rise to photoluminescence (fluorescence). This particular colloidal nanosuspension is also exhibiting an extremely low water evaporation rate which was not expected. Minute droplets resist evaporation in ambient conditions remaining totally stable for several days at RT.
I'm hoping to know whether the narrow band shift I observed occurs in normal GQDs (sizes), or does functionalising GQDs do this, as some have reported. Also, could my nanoplatelets have holes in them (like antidots)? Yet to have it analysed with Raman spectroscopy, TEM. I was wondering if I can use the spectrum shift alone to arrive at a preliminary conclusion.
Has anyone here seen studied or seen this blue-shift before? Any suggestions or comments would be appreciated greatly. Thanks.
Dear Jonathan.
Sorry, my english is poor. Maybe I cannot understand your question well.
But I think two letters will help you about PL of GQDs. (2 links)
I hope it helps.
p.s. I don't know whether red & blue shift are same meaning or not.
http://pubs.acs.org/doi/abs/10.1021/nn302878r
http://onlinelibrary.wiley.com/doi/10.1002/adma.201300233/abstract
I guesses this behavior is due to upconversion fluorescence.
http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=B715402J
Thanks for the above references. I have concluded that my observations were in part due to the dicarboxylic acid medium I had the GQDs in. The effect is not a direct photoluminescence (PL), but rather the sol acted as a optical converter. I however been fine-tuning the PL response in subsequent batches.
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