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Reply to Comment on “Carbon Dots with Continuously Tunable FullColor Emission and Their Application in Ratiometric pH Sensing”
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variety of conditions, such as under inert atmosphere using thoroughly dehydrated reactants, in the presence of solvents including ethanol, using different C and N sources, and so on, but we are not yet in a position to provide well-defined insights into the mechanism. Since we are unable to explain the reaction mechanism clearly at present, we felt that it was productive to publish the work first to attract more participation from the scientific community to collectively solve this question. Regarding whether the full-color emission arises from a mixture of different C dots or a single C dot that can give excitation-dependent emission colors, we are hopeful that single particle imaging and colocalization techniques can provide us with these results. These experiments are underway, and the results will be published when ready.
e are very thankful to Dr. Chandross for his interest in our work on full-color carbon dots (C dots)1 and his pertinent comments.2 In his commentary, he points out that the description regarding the preparation of C dots is brief and lacking sufficient details. First, we agree that we should have included more specifics in the experimental section, and therefore we provide the following additional experimental details to readers. Second, we would like to offer the C dots to readers who are interested but do not have the facility to prepare and purify them. The synthesis and purification details: For blue fluorescent C dots (B-C dots), CHCl3 and diethylamine with a volume ratio of 10:1 were added in this sequence to a round-bottomed flask equipped with an Allihn condenser, cooled by running tap water. The volume of this CHCl3 solution can be varied from hundreds of milliliters to tens of milliliters, to enable scaling of the reaction size; typically, 100 mL of CHCl3 and 10 mL of diethylamine are used. The mixture was refluxed in an oil bath under vigorous stirring with a magnetic stir bar for 1 h. The temperature of the oil bath was set to 70 °C, and the temperature inside the flask was measured to be ∼62 °C. This temperature resulted in about 2−4 drops per second during reflux. After 1 h, a yellow transparent solution was obtained. Upon completion of the reaction, the reactor was removed from the oil bath and allowed to cool to room temperature. The unreacted CHCl3 and diethylamine were removed via rotary evaporation, and the resulting yellow solid was dissolved in about 5 mL of ethanol and sealed in a dialysis tube (regenerated cellulose, molecular weight cutoff of 3500, Union Carbide Corporation). The dialysis tube was placed into a water beaker and allowed to sit for 24 h and then transferred to absolute ethanol for about 6 h. The obtained solution was then dried under vacuum to obtain the B−C dot powder. The yield of B−C dots was about 1 mg/100 mL of CHCl3. For full-color fluorescent C dots (F-C dots), a similar procedure was followed, except that the reflux time was extended to 60 h, resulting in a transparent reddish-black solution. The unreacted CHCl3 and diethylamine were removed via rotary evaporation, and the obtained solid was dissolved in ethanol and purified by dialysis (same type of dialysis tube as above) against water for 48 h and then ethanol for 12 h, to remove small residuals; the product was a mixture of F-C and B-C dots. The B-C and F-C dots were separated by column chromatography using silica gel; CH2Cl2-MeOH (10:1, v/v) resulted in elution of the B-C dots, which was followed by elution of F-C dots with ethanol. The above solution was then dried under vacuum to obtain the powder of F-C dots. The yield of F-C dots was about 2.7 mg/100 mL of CHCl3. As for the second issue regarding the origin of oxygen within the C dots and their mechanism of formation, we are continuing this line of research, although it must be stated that this pursuit is very challenging due to the dozens of byproducts generated during the reaction. Just as Dr. Chandross suggested, we have carried out the synthesis in a © 2014 American Chemical Society
Minjie Li* Sean Xiao-An Zhang*
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State Key Lab of Supramolecular Structure and Materials, Jilin University, 2699 Qianjin Avenue, Changchun, 130012, China
AUTHOR INFORMATION
Corresponding Authors
*(M.L.) E-mail:
[email protected]. *(S.X.-A.Z.) E-mail:
[email protected]. Notes
The authors declare no competing financial interest.
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REFERENCES
(1) Nie, H.; Li, M.; Li, Q.; Liang, S.; Tan, Y.; Sheng, L.; Shi, W.; Zhang, S. X.-A. Chem. Mater. 2014, 26, 3104−3112. (2) Chandross, E. A. Chem. Mater. 2014, DOI: 10.1021/cm5028157.
Received: September 4, 2014 Revised: September 5, 2014 Published: October 1, 2014 6084
dx.doi.org/10.1021/cm503256m | Chem. Mater. 2014, 26, 6084−6084
