Russian scientists have created a nanocomposite is controlled by light

A team of scientists from Moscow State University of Fine Chemical Technology. MV Lomonosov, Institute of Biochemical Physics. NM Emanuel Academy of Sciences, Institute of Problems of Chemical Physics, Russian Academy of Sciences, taking as a basis the photochromic ligands and cadmium selenide, synthesized composite whose properties can be changed by irradiation with light of a specific wavelength. The resulting hybrid material can be used in photocontrollable "smart" devices.

Purposeful change in the properties of photochromic materials by light exposure — an extremely popular area of research. As a general rule, the successful results of such work are the basis for the prototype of so-called smart devices (smart-devices): molecular optical switches, photocontrollable logic modules, sensor devices for the detection of ions. They are used in bioinformatics, nano-medicine, and other fields of applied science and technology. To make these developments more perfect form, further studies and experiments on the properties of materials management.

In the latest issue of the journal "Russian Nanotechnology" published an article devoted to the results of work on the topic of the research team of three Russian institutions of science and education — Moscow State University of Fine Chemical Technology. MV University, Institute of Biochemical Physics. NM Emanuel Academy of Sciences, Institute of Problems of Chemical Physics, Russian Academy of Sciences. Scientists have synthesized photocontrollable composite, based on the organic material — photochromic ligands and inorganic — nanoparticles of cadmium salt.

The authors of the study failed to ensure that the ligand molecule can be fixed on the surface of nanoparticles of cadmium selenide, thus forming, composite connection.

For what purpose the scientists combined in one material organic molecules and inorganic salt? The essence as follows.

Inorganic nanocrystals of cadmium selenide (scientists call them even quantum dots) is inherent in such a property as controlled fluorescence. Fluorescence — the ability of some atoms and molecules absorb photons at first a certain energy (wavelength) and then emit photons of lower energy (longer wavelength). This effect, for example, have a fluorescent paints. They are able to absorb the invisible ultraviolet radiation of the solar spectrum and emit in the visible wavelength region. Due to this, the color is very saturated. With the effect of fluorescence familiar clubbers who can watch the tonic glows in ultraviolet rays.

Fluorescent properties of cadmium selenide quantum dots stand out from those of organic fluorescent molecules, and it is the latter are widely used in biology and medicine. For example, the wavelength, which will emit quantum dots depends on the size of the nanoparticles. By changing the size of the nanoparticles can be specified region of the spectrum, in which they will emit. These and other features allow you to get the system for visualization of single molecules with good sensitivity and brightness of the image, making the prospective use of inorganic quantum dots in nanosensorike.

In this paper, the researchers used a cadmium selenide particles with a diameter of 3.7 nm. Nanoparticles characterized by a size range of a visible absorption maximum at 585 nm.

Photochromic ligand is capable of under the action of light to change their configuration, and thereby change the amount and the fluorescence spectrum of CdSe quantum dots. Initially, the composite shows an intense fluorescence quantum dots at 598 nm. When short-wavelength light irradiation ligand alters its configuration and composite fluoresces at 670 nm. If the composite is placed at some time in the dark or irradiated with visible light, the ligand molecule returns to the original state, and composite — to the initial fluorescence.

Thus, a group of authors managed to get composite, properties which can be directionally changed by irradiation with light of a particular wavelength. And this change is reversible, and the composite can be easily returned to its original state. It turns out a kind of optical switch. These results open up good prospects for the use of similar systems for prototyping photocontrollable smart-devices.

This work was supported by RFBR (grant number 09-03-00565a, 09-04-01003a), the Federal Program "Research and scientific-pedagogical personnel of innovative Russia" for 2009-2013 (State Contract № 16.740.11.0177), a grant from the President of the Russian Federation for the support of research young PhD number MK-6877.2012.4.

Source: Zvezdin KV, Belikov NE, Laptev AV, Lukin A., Demin OV New hybrid and other photochromic materials c switchable fluorescence. "Russian Nanotechnology», № 5-6.


Alex Shabelski

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