Chemistry creates a wonderful trick that crops can do with photosynthesis, using light energy to drive chemical processes that run inadequately or do not spontaneously erupt. This necessitates the use of photocatalysts, which catch light energy and provide it to the process.
A Chinese research team has recently presented multilayer core/shell quantum dots that successfully drive complex chemical transformations in the journal Angewandte Chemie. Its low toxicity is an added benefit.
Quantum dots are nanoscopic crystals of inorganic semiconductors that are finely scattered. They absorb significantly in a variable spectral range and are simple to recycle, as per Nano Magazine. Until recently, photocatalytic quantum dots were nearly entirely based on the exceedingly hazardous metals cadmium and lead. Such, together with their poor efficiency, has been the principal impediment to their widespread usage.
Distinct Quantum Dots with Low Toxicity
As reported by Phys, the team of scientists led by Kaifeng Wu (Chinese Academy of Sciences) recently developed unique quantum dots with extremely low toxicity and great performance. They are triggered by commercially available commercially blue LEDs, rather than the UV radiation that is normally required. Their success is due to the core/shell design and the changeable coatings that may be employed to "store" light energy.
The quantum dots have a width of only a few nanometers. Their core is formed of zinc selenide (ZnSe), which is covered by a thin shell of zinc sulfide (ZnS). Blue light excites the zinc selenide, allowing it to quickly give off electrons. The ring inhibits electrons from being instantly trapped by so-called defects.
The scientists coated the shell's exterior with unique benzophenone ligands which "suck up" electrons from quantum dots, retain them, then make them accessible for organic processes. For example, the team was able to perform reductive dehalogenation of aryl chlorides as well as additive-free polymerizations with acrylates-important processes that are performed poorly or not at all by typical photocatalysts.
Reactions That Result in 4-Membered Rings
A second version was created by the surface being coated with biphenyl ligands, which may directly absorb the energy from excited quantum dots. This causes them to enter a long-lived, extremely energetic triplet state. The triplet energy "stored" in this manner may be transferred to certain organic molecules, which then enter a triplet state. Particles can perform chemical reactions in this state that they cannot in their initial state.
The Master Chemistry report states as an example as the researchers performed [2+2] homo-cycloadditions of styrene plus carbonyl cycloadditions with alkenes. These reactions result in four-membered compounds (cyclobutanes or oxetanes, respectively), which seem to be essential starting chemicals in areas such as pharmaceutical research.
The Chinese Academy of Sciences is the driving force behind China's efforts to investigate and use high technology and biological sciences for the advantage of China and the rest of the world, as stated on the academy's website. The institution also serves as the home of the Chinese Ecosystem Research Network (CERN), which has 50 core field stations and 100 additional stations spread around the country. CERN monitors and performs research on the ecological environment and its systems.
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