In recent years Graphene quantum dots with very high Luminescence (Quantum yield) are reported. These QDs are generally dispersed in DI water (some time organic solvents as well). PL of GQDs in 400-500 nm (absorption 300-400 nm ) is credited to Surface functional groups (-OH,-COOH,-NH2).
But is it even possible to retain these optical properties if we try to obtain there GQDs in powder form or if we want to coat them on some substrate?
If yes then how to do it?
Yes.. it is absolutely possible. GQDs have inherent PL, they easily not get affected to drying. since, it is depend on what material you are coating them.
Rahul Tade Generally For N-GQDs there are three types of excitation leading to the PL. one is intrinsic (below 300nm), related to -COOH type surface functional groups(absorption peak around 330-350nm), and -NH2 type surface functional groups(absorption peak around 370-390nm).
on Drying the intrinsic emission may not change but I am confused (lack knowledge) about the effect on surface functional groups, as in my pursuits of drying GQDs I face Aggregation of QGDs (PL is no more there).
if its possible to retain the PL, then can you please guide me for the way to do it.
Also you mentioned about the Substrate, can you mention what type of material are favorable, or how to conclude that.
Firstly, clear that, above mentioned values are for Fluorescence Intensity or UV- Absorption values?
although you have done best literature but we have to confirm it on our own basis. the first point of any good research is "dont relay on previous opinions". you have to confirm it by FT-IR. since you have drying issue. i have make GQDs from graphene. it get dried in off-white color solid. you have to sonicate (do not probe sonicate) them after dispersing in solvent. further to avoid the functional group loss (as you mentioned) add some methanol or ethanol in 10:1 proportion in dispersion medium.
Yes, you can.
I attached my published papers which are based on GQDs. Please have a look. They might be useful for you...
Rahul Tade those values are For Florescence intensity ( PLE).
Does you Dried GQDs ( off-white color solid ) shows florescence on illuminating UV on them?
Since I want the GQDs in a thin film (uniformly distributed on a substrate) I have to dry them, that's my requirement. BUT as you mention that you need to sonicate them,does that mean that GQDs in solid from are not same (optical properties) as that in solution (if yes then what changes occur).
which is unlike the other semiconductor QDs (CdS) which can be retain their optical properties in solid form.
In some literature it is said that" GQDs undergo self‐quenching in the solid state, like organic molecules ascribed to excessive resonance energy transfer (RET) or direct π–π interactions "
Yes..!
"GQDs undergo self‐quenching in the solid state, like organic molecules ascribed to excessive resonance energy transfer (RET) or direct π–π interactions"
it correct.
U can use any inert Film former for it.
Rahul Tade since I want a highly transparent film (for wavelength >400 nm) , and you suggest any " inert Film former " for my highly hydrophilic GQDs
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