Multicolored silica coated CdSe core/shell quantum dots

Silanization is a convenient route to provide water-solubility to the quantum dots (QDs) with different structure. Green, orange and red emitting CdSe-based QDs were synthesized by varying of number and material of wider-band gap shells and fluorescent properties of QDs were characterized before and after silanization. It was shown that structure of the QD influences on the quantum yield of the silanized QDs: the better CdSe core is protected with wider-band gap semiconductor shells, the more fluorescence properties remain after silica coated QD possess. Hence silica coated QDs have a great perspectives for the multiplex analysis

Molecular nature of breakdown of the folic acid under hydrothermal treatment: a combined experimental and DFT study

Using a combination of experimental Raman, FTIR, UV–VIS absorption and emission data, together with the corresponding DFT calculations we propose the mechanism of modification of the folic acid specifically under the hydrothermal treatment at 200 °C. We established that folic acid breaks down into fragments while the pteridine moiety remains intact likely evolving into 6-formylpterin with the latter responsible for the increase in fluorescence emission at 450 nm. The results suggest that hydrothermal approach can be used for production of other purpose-engineered fluorophores

Thermal carbonization in nanoscale reactors: controlled formation of carbon nanodots inside porous CaCO3 microparticles

This work has been supported by the Russian Science Foundation grant number 16-13-10195. TEM work has been supported by the Biological Sciences Research Council grant BB/J001473/1

Gel electrophoresis separation and origins of light emission in fluorophores prepared from citric acid and ethylenediamine

We investigated light emission of hydrothermally treated citric acid and ethylenediamine (EDA) with various precursor ratios using gel-electrophoresis. We show that this relatively simple approach can deliver significant insights into the origins of photoluminescence. We found that products of the synthesis consist of both positively and negatively charged species and exhibit large dispersion in electrophoretic mobility (i.e. charge-to-size ratio). We observed that despite the large dispersion of the reaction products the blue light emission is confined to discrete bands clearly identifiable in the gel. We demonstrate clear evidence that this emission originates from the negatively charged light molecular fraction with the highest mobility which shows no excitation-dependent light emission. This molecular fluorophore exhibits spectral characteristics similar to previously reported 1,2,3,5-tetrahydro-5-oxo-imidazo[1,2-a]pyridine-7-carboxylic acid (IPCA). Secondary gel electrophoresis run performed on the bands extracted from the first run indicates that no further separation takes place. On the basis of our experimental results, we conclude that relatively stable binding exists between IPCA and EDA-derived product. Thus, the products of the reaction contain IPCA both in molecular form and in complexes with EDA-derived products. We conclude that excitation-dependent emission is related to the fluorophore binding to the positively charged EDA-derived products with a positive charge

Carbon nanodots: Mechanisms of photoluminescence and principles of application

The work was supported by Russian Science foundation (project 16-13-10195)

Luminescent quantum dots as labels for multiparametric immunoassay

Use of quantum dots as highly sensitive labels in immunochemical assay for simultaneous screening of multiple analytes is described

High-fluorescent product of folic acid photodegradation: Optical properties and cell effect

Folic acid (FA) is a natural body component essential for normal cell growth and division. Uptake of FA into cells is mediated by the folate receptors with particularly large amount of folate receptors found on the surface of cancer cells. This feature traditionally is used for selective drug delivery systems targeting in cancer cells or visualization of the border between healthy and tumor tissue based on FA-modified fluorescent labels. However, preparation of FA-conjugates can be an elaborate procedure, while FA itself shows low photostability under illumination. Here we use photodegradation of FA colloid to produce high fluorescent product and compare its effects on the cells grows and division with the ones of FA. It was found UV-irradiation of FA colloid for 60 min allows obtaining water soluble fluorophore with quantum yield 30 ± 2 %. We also show that the resulting fluorescent product retained FA biological activity in relation to cell growth and division, comparable to native FA