Latest Research on Quantum Dots

Quantum dot characteristics

• Quantum dots have a wide excitation spectrum and a narrow emission spectrum. The same excitation light source can be used to synchronously detect quantum dots with different particle sizes, so it can be used for multicolor labeling, and the narrower emission spectrum can largely avoid spectral overlap when multicolor quantum dots are used simultaneously.
• Quantum dots have good photostability. It has better stability than ordinary organic dyes and can be used for long-term observation of research objects.
• Good biocompatibility. After a variety of chemical modifications, quantum dots can make specific connections, which have low cytotoxicity and little harm to organisms, and can be used for living organism labeling and detection.
• The emission spectrum of quantum dots can be controlled by changing the size of the dots. By changing the size and chemical composition of a quantum dot, its emission spectrum can cover the entire visible region.
• Quantum dots have a large Stokes shift, which can avoid the overlap of emission spectrum and excitation spectrum.

Latest news

Due to the excellent photoelectric characteristics of quantum dots, they have received extensive attention and research. The latest research trends of quantum dots in three fields are introduced below for reference.

• Photocatalytic degradation of dyes ^[1]

  As organic dyes are widely used in textile, printing, leather and other industries, the problem of dye pollution should not be underestimated. Research shows that even if the concentration of dye in water is less than 1mg/L, it will cause serious harm to water quality. What's more, long-term exposure to methyl orange, methylene blue, and rhodamine B dyes can cause rapid heartbeat, cyanosis, tumors, liver disease, and human skin irritation.

  In the study of photocatalytic dye removal, metal oxides such as zinc oxide and titanium oxide have been proved to be an effective way. However, there are still some limitations, such as low surface area, fast electron hole recombination, low response to light, long time to achieve the desired efficiency, and limited by the conditions of use. In order to overcome these limitations, we developed a cheap, fast/rapid and environmentally friendly photocatalyst based on carbon dot modified zinc oxide (C _Dots /ZnO2). It has the advantages of higher efficiency, high recovery rate, high light stability and high recycling rate. Large numbers of dye molecules can be removed in many industries. In addition, the (C _Dots /ZnO2) system has high operational stability without any loss of initial efficiency. It is expected to be a high value method to eliminate environmental pollution using photocatalysis.

  Fig.1 Photocatalysis mechanism of the C _Dots/ZnO2 catalyst

• Circulating tumor cell tracking detection ^[2]

  Circulating tumor cell (CTC) detection technology has become a research hotspot. Circulating tumor cells refer to all kinds of residual cells existing in peripheral blood. Under normal circumstances, the detached CTCs will undergo apoptosis or phagocytosis after entering the peripheral blood, and a few cells will escape and develop into metastases, leading to the deterioration of the patient's condition. Therefore, detection of CTCs plays an important role in patient prognosis, recurrence risk assessment, efficacy evaluation and individualized treatment. Recently, by changing the stoichiometric ratio of Se/In, Wei. and colleagues have developed a kind of NIL-II semiconductor nanobiological probe based on copper indium Selenide quantum dots, and its luminescence performance and photostability have been greatly improved. At 808 nm excitation, CISe@ZnS QDS were used as a high-efficiency Nanoir II luminescent nanobiological probe for the detection of rare breast cancer in whole blood samples. CTC also realized real-time tumor-targeting bioimaging using CISe@ZnS nanobiological probe. In addition, CISe@ZnS nanoprobes show good biocompatibility and rapid clearance through liver and kidney pathways, demonstrating their great potential for a wide range of biomedical applications.

  Fig.2 Schematic illustration showing the proposed broadband excitable CISe@ZnS NIR-II luminescent nanoprobes for CTCs bioassay and tumor-targeted bioimaging.

• Photocatalytic decomposition of water ^[3]

  With the continuous growth of global energy demand, people pay more and more attention to the search for new energy. Hydrogen, as a secondary energy, has the advantages of cleanliness, efficiency, safety, storage and transportation, and is generally considered as the most ideal green energy. Photodissociation of water to produce hydrogen provides an effective means for hydrogen production. At present, hydrogen and oxygen are generally obtained by photohydrolysis of water, followed by a step of gas separation.

  Recently, researchers have developed a simple method to prepare water cracking photocatalyst, and successfully obtained graphene@Au photocatalyst. Studies show that the prepared graphene@Au catalyst can effectively split water into hydrogen and hydrogen peroxide, and the activity is effectively improved, providing an important idea for the development of hydrogen energy.

  Fig.3 illustration of the overall water splitting mechanism of graphene@Au under light irradiation

References

• El-Shamy A.; et al, New carbon quantum dots nano-particles decorated zinc peroxide (Cdots/ZnO2) nano-composite with superior photocatalytic efficiency for removal of different dyes under UV-A light. Synthetic Metals, 2020, 267: 116472.
• Lian W, et al, Broadband excitable NIR-II luminescent nano-bioprobes based on CuInSe2 quantum dots for the detection of circulating tumor cells. Nano Today, 2020, 35: 100943.
• Liang J., et al, Graphene quantum dots piecing together into graphene on nano Au for overall water splitting. Carbon, 2021, 178: 265-272.