Dear colleagues!
A few days in a row I'm trying to obtain PbTe quantum dots in water and ethanol using laser ablation technique. I put a PbTe target in water (or ethanol) and used a 1064 and 532 pulsed laser. As a result I see that the solution gets darker but when I try to measure luminescence (awaiting a luminescence peak to be somewhere in between 1.3 to 2 um that corresponds to the PbTe QDs with size around 5-10 nm) I don't see one. I didn't use any stabilizer so I think that particles grow too big and behave like bulk. What should I use to make them of the desired size?
Regards!
Hi man,
Laser ablation in organic liquids is considered a contamination-free green synthesis method.
Initial solutions/solvents are very important.
In your case, the product can be obtained include: PdTe, metals, oxides, complexes. Moreover, the distribution of the particles is heterogeneous (a few nanometers to micrometers).
A little experience:
Firstly, Reduce the laser power (e.g 5-mJ pulse energy) (reducing metal phases).
- Change the initial solvent instead of water (alcohol) (e.g. Chloroform, or Toluene).
Secondly, the post-treatment procedure as second stage to obtain small-sizes.
The products were covered by the mixture of methanol and alcohol (ISO-propanol) with specific concentrations in ultrasonic bath.
This technique will separate the hydrophilic (oxides, complexes) and hydrophobic phase (PdTe). Furthermore, reducing size, increasing homogeneity.
Good luck! :)
Dear Minh Tan Man!
Thank you for your reply! I'll try your method.
I didn't get very well the second part of the procedure. If I use Toluene as a solvent and get a big QDs, what exactly should happen on the second stage? I didn't get why QDs will be covered by mixture of methanol or/and isopropanol? I'm not really strong in chemical part yet.
I already seen one Chinees article saying that to produce PbTe QD by laser ablation you should do it in two stages: 1-st is to make big size QDs, 2-nd is to deminish them by small fluences to the desired size (of order of a few nm).
Probably you can suggest some articles that describe in detailes the mechanism?
Regards!
Dear Victor Ermakov,
There is a confusion in the previous email.
The solution used for the second process is mixed Chloroform and ISO-propanol (e.g. 1:1).
In second Process, ultrasonic treatment was applied for 30 min (or longer).
Then we add water into the solution. These suspensions are separated into two phases.
Quantum dots (QDs) will lie in chloroform-phase, other components move into the remaining phase.
About the mechanism, you can refer to several articles on related QDs (CdSe, CdTe, Silicon..) synthesized by this method. [e.g. J. Phys. Chem. C 2011, 115, 5147–5151]
Yours sincerely,
Dear Minh Tan Man,
I tried your method. I did the laser ablation in Chloroform of PbTe target with pulse energy of 5 mJ (532 nm) and around 24000 pulses during 20 min. As a result the color of solution slightly changed. Then I added Isopropanol (1:1) and put in ultrasonic bath for 30 min. When added DI water, solution separated into two phases. The lower one was Chloroform phase that I analized on luminescence. I used different lasers (514nm and continuously changed wavelength from 600 to 900nm) to exite photoluminescense and tried to find any responce in the 1 to 2.5 um range. Unfortunately I see nothing.
By your experience should I see a photoluminescent response on PbTe QDs fabricated by this method or the quantum yield is too low? And if you would change the pulse energy what would you prefer: to rise it or to diminish it? Or it is better to change some other parameters?
Regards,
Victor.
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