Nikita Belko

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• PhD in Optics
• Researcher at University of Eastern Finland

“Blinking” behavior of fluorophores, being harmful for the majority of super-resolved techniques, turns into a key property for stochastic optical fluctuation imaging and its modifications, allowing one to look at the fluorophores already used in conventional microscopy, such as graphene quantum dots, from a completely new perspective. Here we disc...

Spirocyclic rhodamine derivatives have great potential to be used as fluorescent sensors. Rhodamine B hydrazide (RBH) and its derivatives have been employed to detect various analytes. The interactions of a sensor with an analyte might result in the protonation or hydrolysis of the sensor. Understanding these processes is useful for developing new...

Photodynamic therapy is an effective and minimally invasive treatment method for cancer. A deeper understanding of the photocytotoxicity mechanism of cyanine dyes is necessary for the development of more efficient photosensitizers. We combine electrochemistry, optical and ESR spectroscopy, and quantum chemical calculations to study indotricarbocyan...

Here we discuss fluorescent properties of graphene quantum dots (GQDs) interacting with the membranes of red blood cells. We report the results of spectroscopic, microscopic, and photon-counting measurements of the GQDs in different surroundings for uncovering specific features of the GQD fluorescence, and describe two observed phenomena important...

Rhodamine B hydrazide and rhodamine B acylhydrazone are spirocyclic compounds that provide a versatile framework for developing chemical and electrochemical sensors with turn-on optical response. Herein, we explore how a simple conversion of rhodamine B hydrazide into rhodamine B acylhydrazone can change its electrochemical behavior. Non-aqueous el...

Zn-BTC (H3BTC refers to 1, 3, 5-benzoic acid) MOF was used as a self-template and a zinc source to prepare ZnS/NiS2 with a layered heterogeneous structure as a promising electrode material using cation exchange and solid-phase vulcanization processes. The synergistic effect of the two metal sulfides enhances the application of ZnS/NiS2. And the hig...

Charge-transfer organic-inorganic complexes have demonstrated great potential in optoelectronic applications. Herein, a drop-casting processed photodetector based on thick composite films made of multi-layered MoS2 nanosheets chemically bonded to linear molecules of aromatic thiols has been developed. Composites based on multilayered nanosheets all...

Spirocyclic rhodamines are promising sensors that exhibit turn-on fluorescence response to different stimuli including electric potential. Although rhodamine B hydrazide is often used as a building block for chemical and electrochemical sensors, the electrochemistry of this compound has not been reported. Herein, the electrochemical transformations...

Thick ZnO/ZnAl2O4 coatings were synthesized on zinc alloy Z1 substrates through plasma electrolytic oxidation (PEO) for different anodization times. The prepared coatings were characterized by scanning SEM, XRD, diffuse reflectance and photoluminescence spectroscopy in order to establish the relationship between their structural and optical propert...

Cyclic voltammetry, UV–Vis absorption spectroscopy, and electron spin resonance are applied to study the properties of indotricarbocyanine dyes and their radicals formed during electrooxidation. We use electrochemistry to generate relatively stable free radicals of the dyes under controlled conditions. The dyes undergo electrooxidation during the c...

In living organisms, redox reactions play a crucial role in the progression of disorders accompanied by the overproduction of reactive oxygen and reactive chlorine species, such as hydrogen peroxide and hypochlorous acid, respectively. We demonstrate that green fluorescence graphene quantum dots (GQDs) can be employed for revealing the presence of...

The effect of the molecular structure of indotricarbocyanine dyes on their luminescence spectral and redox properties was studied. The introduction of a chlorine-substituted bridge into the polymethine chain leads to a significant hypsochromic shift of the absorption and fluorescence spectra, whereas change in the structure of substituents at the i...

The dynamics of the transient absorption spectra of H*- and J-aggregates of an indotricarbocyanine dye was studied using femtosecond pump-probe spectroscopy. Relaxation of the induced transmission of the H*-aggregates occurs with time constants of ~3 and ~30 ps with radiation pumping at λmax = 400 nm and ~30 ps with pumping at λmax = 800 nm. For J...

The express method for esting purity and stability of an indotricarbocyanine dye based photosensitizer for photo-dynamic therapy was developed. Storage of the hydrophilic photosensitizer under unfavorable conditions resulted in contamination with a hydrophobic dye. The absorption spectrum of the hydrophobic dye was characterized by a new band at 51...

Spectral properties of an indotricarbocyanine dye upon complexation with nanodiamonds in aqueous solutions were studied. Complexation was accompanied by disappearance of the H*-aggregate absorption band at 514 nm and a bathochromic shift of long-wavelength absorption maxima from 706 to 718 nm. The dye emission spectrum was almost unchanged. The flu...

Aggregation process of a symmetrical cationic indotricarbocyanine dye in aqueous medium was studied. It was shown that self-assembled H*-aggregates with an absorption peak at 514 nm as well as J-aggregates with an absorption peak at 777 nm can be obtained. Both of the aggregate types are non-fluorescent. High concentration of a desired aggregate ty...

Spectral and luminescent properties of an indotricarbocyanine dye are studied in solutions and after deposition on quartz or silicon substrates. It is found that the dye molecules self-assemble in aqueous EtOH solutions to form H*-aggregates. The absorption band of the H*-aggregates shows a hypsochromic shift of 192 nm (5291 cm–1) relative to the a...

Photodynamic therapy is an evolving technique for treatment of various oncological diseases. This method employs photosensitizers - species that lead to death of tumor cells after the photoactivation. For further development and novel applications of photodynamic therapy new photosensitizers are required. After synthesis of a new photosensitizer it...