The negligence of laboratory personnel four years ago led to an accidental discovery that eventually led to a world-first craft. Recently, the quantum dot material and device research group of Tianjin University’s School of Materials has developed a new environmentally friendly and efficient process for the synthesis of monodispersed quantum dots. The results were published in the journal Nature Communications, the first report in the world. Physical methods for the synthesis of monodispersed quantum dots are more efficient than chemical methods. Du Xiwen, a professor of materials at the Tianjin University’s School of Materials and the author of the paper, said that when semiconductor materials are several nanometers in diameter, they can exhibit many unique physical properties. As is well-known in silicon, the highest efficiency of converting solar energy into electricity is 33% under normal volume, but when the volume of silicon is about 4 nanometers, the efficiency can be increased to 66%. Some materials can emit special light. If nano-level luminescent materials are carried on antibody products of tumors, the position of the tumor can be marked very accurately, which will help doctors to judge the condition and find lesions. It is precisely because these quantum dots (also known as semiconductor nanocrystals) have such magical capabilities that they are currently research and development hotspots by researchers in various countries. Du Xiwen said that traditional mechanical processes can crush semiconductor materials up to the micron level, which is thousands of times larger than the nanometer level. Quantum dot materials have been made in the past by wet chemical methods using the reactions between concentrated chemicals. However, this method takes a long time, from as little as a few hours to several days, but also produces a large amount of pollutants, causing a burden on the environment. Four years ago, a student in Prof. Du Xiwen’s laboratory experimented with lasers to break metal targets into metal particles. The experiment usually only uses a laser to irradiate the metal target for about 3 minutes, but the students leave halfway and let the laser irradiate the metal target for more than 4 hours. The team then discovered that the metal target was made into metal particles of a few nanometers in size, which is more desirable than before. They turned to this "strange" phenomenon as a research focus and explored how to use lasers to "knock out" semiconductor materials into nanometer-sized uniform particles. In the final 4 years, a physical method for synthesizing monodispersed quantum dots was explored in this field. Using lasers as a "hammer," scientists can "change" their strength according to actual needs and precisely control the specific dimensions of semiconductor materials. Compared to the wet chemical method, this world-first method takes only a short time, it takes only 20 minutes at a time, and the obtained quantum dots are more uniform in size, and the surface is free of chemical drugs and is very clean. Du Xiwen said that in the future this process can help to obtain cheaper quantum dots, which will play a more prominent role in disease diagnosis, water pollution detection, and photoelectric conversion.
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