Quantum dots (QDs) are modern nanoparticles with a wide potential for use in medicine, bioanalysis, as well as in optics and energetics. Different types of QDs can be produced depending on their synthesis method. QDs formed by semiconductor components able to mutual solid-solution formation named alloyed. This type of QDs has a high quantum yield and narrow emission peak but less chemical stability relative to core-shell type QDs. Better core-shell QDs stability explains by the additional surface shell covering. This approach can be applied to the alloyed QDs also. One-step hightemperature organometallic procedure is excellent in this regard due to its simplicity and consistency in the synthesis. However, QDs which obtained in this way are hydrophobic and do not dissolve in polar solutions such as water. Hydrophilization is used to convert QDs from a hydrophobic to a hydrophilic state. It was found that when hydrophilizing with β-mercaptoethanol, the quantum yield (QY) significantly increases, although when hydrophilizing with other ligands, it is just a decrease in the quantum yield that appears. This article investigates the process of hydrophilization of core-shell alloyed QDs in which an increase in QY is observed. For this, the effect on the optical properties of the amount of the hydrophilizing agent, long-term storage at room and low temperatures, and the effect of pH on hydrophilized QDs are considered.
In this paper, we report the synthesis of hydrophilic luminescent quantum dots (QDs) of the core/shell structure using two approaches: high-temperature organic synthesis of CdZnSeS/ZnS and aqueous synthesis of AgInS/ZnS. Dihydrolipoic and thioglycolic acids have been used as surface ligands to impart hydrophilic properties. The influence of whole blood and serum on the optical properties of both types of QDs was evaluated for their application in blood analysis. It has been shown that AgInS/ZnS QDs with emission in the red spectral region (λPL = 638 nm) remained the most stable in whole blood samples and its optimal dilutions (up to 1:100, inclusive). Whereas CdZnSeS/ZnS fluorescent in the green region of the spectrum (λPL = 530 nm) showed the best signal of fluorescence (PL) intensity in blood serum samples.
Alloyed quantum dots (QDs) are luminescent semiconductor nanocrystals, which are promising materials in various fields of science and technology, including in bioanalysis. The key requirement for alloyed QDs in polar solutions analysis is hydrophilicity. The modification with dihydrolipoic acid (DHLA) makes it possible to increase the alloyed QDs colloidal stability in a polar medium while retaining the advantages of nanoparticles of this structure, and also allows further electrostatic self-assembly of alloyed QDs with antibodies. The article describes the DHLA-modification of the alloyed QDs composition CdxZn1-xSeyS1-y / ZnS using 2-mercaptoethanol (BME) as an additional hydrophilizing agent. The effect of hydrophilization conditions on the following modified properties alloyed QDs was studied: photoluminescence quantum yield (PLQY), width peak at half maximum (FWHM), luminescence peak position, colloidal stability during long-term storage. The search for the optimal ratio of hydrophilizing agents DHLA:BME was carried out, at which the advantages of the biligand shell would be maximally realized. The methods presented in this work make it possible to obtain alloyed QDs with a high PLQY (about 65%) and a long stability period (more than 3 months).
Alloyed quantum dots (QDs) are the popular material for the fabrication of the light-emitting diodes because of their optical parameters advantages. One of the most interesting features peculiar to this QDs class is the ability to controlled size-independent emission peak tuning via compound amounts changing. The same advantages can be valuable in bioanalytical methods and sensor systems development. Facile one-pot synthesis of the bright quaternary alloyed QDs made by CdxZn1-xSeyS1-y/ZnS semiconductor composition with narrow (FWHM < 26 nm) emission peak (548 nm) and photoluminescence quantum yield (PLQY) up to 50% was described. Obtained QDs were stabilized in water by the dihydrolipoic acid (DHLA) ligand exchange approach with insignificant PLQY loss relative initial (16%) and great colloidal stability period (6 months). This article summarizes the easiest ways of the alloyed QDs synthesis and subsequent hydrophilization for the potential simplification of their large-amounts manufacturing procedure.
We demonstrate a one-pot synthesis of CdSeZnS/ZnS alloyed blue (482 nm) and green (526 nm) quantum dots in organic solvents. During the formation of core/shell quantum dots (QDs), a blue-shift was observed after coating with ZnS shell. A wavelength tuning of alloyed QDs emission is obtained by the different ratios of Se-precursor in the cores. Silica surface was formed to make water-soluble alloyed QDs. The alloyed QDs were characterized by absorbance and photoluminescence (PL) spectroscopy and PL quantum yield.
Nowadays semiconductor quantum dots (QDs) is a popular luminescent material for different kinds of bioapplications. Core-shell CdSe/ZnS QDs obtained by the high-temperature synthesis are traditional luminescent nanocrystals with high quantum yield and narrow emission peak. But this type of QDs must be hydrophilized before their use in a water or biological environment. The goal of our work was the comparison of hydrophilized QDs properties, obtained from one initial sample using two different hydrophilization methods. Core-shell type QDs with CdSe/ZnS semiconductors composition was synthesized and hydrophilized by two ligand exchange methods: silanization and coating with dihydrolipoic acid (DHLA). Quantum yield, size and colloidal stability of the nanoparticles obtained via both methods were investigated. The collected data allows making the conclusions about perspectives to use the described methods in different bioapplications.
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