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The synthesis method of PbSe colloidal quantum dots usually involves a series of complex chemical reaction steps, among which the thermal injection method is a commonly used approach. During the synthesis process, the selection of raw materials, the control of reaction conditions, and the subsequent processing steps all have a significant impact on the properties of the final product, including solubility.
Synthesis method of PbSe colloidal quantum dots
The general steps for synthesizing PbSe colloidal quantum dots by the thermal injection method are as follows:
Preparation of selenium source: Mix selenium powder with organic sulfur source (such as TOP) and heat it to synthesize the selenium source (such as TOPSe).
Preparation of lead source: Mix lead oxide (or triethyl acetate lead), oleic acid, TOP and diphenyl ether (or octadecene) and heat them to obtain lead source oleic acid lead.
Growth of quantum dots: Inject the selenium source into the lead source at a high temperature of approximately 180℃ and grow PbSe quantum dots through reaction. The surface of the quantum dots is passivated by oleic acid, thus stabilizing and dispersing in organic solvents.
Reasons for low solubility and improvement methods
The low solubility of PbSe colloidal quantum dots in solvents such as toluene, n-hexane, n-octane, and chloroform, as you mentioned, may be caused by the following factors:
Surface properties of quantum dots: The interaction between the ligands (such as oleic acid) on the surface of quantum dots and the solvent may not be strong enough, resulting in poor dispersion of quantum dots in the solvent.
Size and shape of quantum dots: The size and shape of quantum dots also affect their solubility in the solvent. Larger quantum dots or those with irregular shapes may be more difficult to be uniformly dispersed in the solvent.
Polarity of the solvent: The polarity of the solvent is also an important factor affecting solubility. Different solvents may have different solubilities for quantum dots.
To increase the solubility of PbSe colloidal quantum dots in octane, you can try the following methods:
Optimizing the surface ligands of quantum dots: By changing the type or quantity of ligands on the surface of quantum dots, the interaction between quantum dots and the solvent can be enhanced, thereby improving the solubility. For example, one can try to replace oleic acid with ligands that have better compatibility with octane.
Adjusting the size and shape of quantum dots: By optimizing the synthesis conditions, the size and shape of quantum dots can be controlled to be more conducive to dispersion in the solvent. Smaller quantum dots usually have a higher specific surface area and are easier to disperse in the solvent.
Selecting the appropriate solvent: Although you have already tried various solvents, it may still be necessary to further screen solvents with better compatibility with PbSe colloidal quantum dots. Additionally, one can also try mixed solvent systems to find the best dissolution effect.
Ultrasonic treatment: Before dispersing quantum dots into octane, ultrasonic treatment can help break the aggregation of quantum dots and improve their dispersion in the solvent.
Temperature control: Properly controlling the temperature during the dispersion process can also help increase the solubility of quantum dots in the solvent.
Please note that these methods may need to be combined and through experiments to find the best synthesis and dispersion conditions. At the same time, due to the influence of various factors on the properties of quantum dots, careful control of each step is required in actual operation to obtain high-quality PbSe colloidal quantum dots.
