The hydrothermal method involves heating and pressurizing a reaction system within an autoclave to achieve high temperature and pressure conditions. The hydrothermal technique creates conditions that dissolve substances which usually remain insoluble or poorly soluble and thus leads to supersaturation followed by crystal formation. The hydrothermal method prevents physical defects which happen during crystal phase transitions unlike melt methods and others which results in a final product with fewer defects. The hydrothermal method excels at preparing crystalline powders which produce consistently small particles with uniform sizes and minimal agglomeration. Researchers can maintain precise stoichiometry and crystal morphology while utilizing low-cost raw materials with this method. The hydrothermal method's advantages make it the preferred choice for producing high-performance powder materials.
High-Quality Carbon Quantum Dots We Offer
| Product Name | CAS Number | Inquiry |
| Carbon Quantum Dots | 7440-44-0 | Inquiry |
| Carbon Quantum Dots (C-dots) | -- | Inquiry |
Carbon quantum dots (CQDs) represent a newly developed fluorescent nanomaterial with extensive potential for various applications. The synthesis of fluorescent carbon dots using surface passivation was first reported by Professor Ya-Ping Sun from Clemson University in 2006 which sparked intense research interest in CQDs because of their biocompatibility related to carbon abundance in human tissue, high fluorescence quantum yield and outstanding photostability. CQDs demonstrate excellent performance for biomedical imaging purposes and researchers have utilized them in live fluorescence imaging of bacteria, cells, and animals. Fluorescence sensing widely uses them to detect heavy metal ions as well as DNA and enzymes. CQDs demonstrate significant potential in photocatalysis because they catalyze CO₂ to formic acid using visible light and support hydrogen production through water splitting. Carbon quantum dots demonstrate potential applications as sensitizers in solar cells through photoelectric conversion. The research and production advancements of CQDs will lead to their integration as significant fluorescent materials in everyday life.
The two primary approaches for creating CQDs are through top-down and bottom-up methods. The standard top-down technique uses nitric acid to oxidize carbon particles until they reach nanoscale dimensions (1-5 nm) and then applies defect passivation to induce fluorescence. The hydrothermal method stands out as the most versatile option among bottom-up approaches. Figure 1 shows how hydrothermal dehydration and carbonization processes transform small carbon-containing molecules or polymers into carbon particles measuring between 1 and 5 nanometers. Residual molecules function to passivate defects which results in the activation of fluorescence emission from the particles. The hydrothermal method allows researchers to dope the carbon core which results in various fluorescent properties. The researchers used citric acid to generate carbon for this experiment while doping it with nitrogen through ethylenediamine and formamide to create water-soluble red-emitting CQDs which respond to pH changes.
Figure 1. Schematic of hydrothermal synthesis of fluorescent carbon quantum dots.
Instruments and Reagents
- Instruments: Fluorescence spectrometer, 100 mL autoclave, centrifuge, graduated cylinder, mortar and pestle, forced-air drying oven, dropper.
- Reagents: Citric acid, ethylenediamine, formamide, ethanol, acetone, hydrochloric acid, sodium hydroxide.
Experimental Procedure
(1) Hydrothermal Reaction
① Take off the polytetrafluoroethylene (PTFE) liner from the 100 mL autoclave by opening it. Clean it thoroughly.
② Insert 1.2 g of citric acid with 2.1 mL of ethylenediamine and 80 mL of formamide into the PTFE liner and mix until completely dissolved.
③ Put the liner inside the stainless-steel autoclave shell before securing the lid and placing the container into the oven. Maintain the temperature at 180 °C for a duration of 4 hours.
(2) Product Purification
① Let the autoclave cool down to room temperature following the reaction before removing it.
② After removing the lid from the autoclave, collect the reaction mixture. Filter to collect the clear solution.
③ The clear solution requires 200 mL of acetone to precipitate the desired product. Wash the precipitate with an ethanol: Use an ethanol:acetone ratio of 1:5 for washing and then separate the content by centrifuging before air-drying.
(3) Fluorescence Property Testing
① Take 0.1 g of CQDs and dissolve them in 50 mL of water. Split the solution into three separate 10 mL portions and modify each one to have pH levels of 5, 7, and 9.
② Subject CQD solutions to UV light exposure and check the appearance of red fluorescence.
③ Transfer the solution that exhibits the highest fluorescence intensity into a quartz cuvette to perform fluorescence spectroscopy analysis.
