The interaction of indotricarbocyanine dyes with lipid-transfer protein Ns-LTP1 in Dulbecco's phosphate-buffered saline (PBS) was studied. An orthophenylene bridge with a chlorine in the meso-position of the dye was shown to be ineffective as a linker for protein macromolecules without a free cysteine residue. The indotricarbocyanine dye was modified into the N-hydroxysuccinimide ester to obtain a complex of the indotricarbocyanine dye with the Ns-LTP1 protein. A complex of dye molecules with the Ns-LTP1 protein was obtained by mixing a two-phase system of the protein in PBS and the dye activated ester in 1,2-dichloroethane. The half-width of the absorption spectrum increased from 56 to 61 nm; the fluorescence decay time, from 0.3 to 0.5 ns; and the degree of polarization, from 27 to 31

Developing new materials for efficient fluorescent detection of metal corrosion is a highly relevant task. One challenge is that highly sensitive sensors might lose functionality after exposure to certain coating formulations. In this work, silica nanocontainers are used to encapsulate rhodamine B acylhydrazone, an efficient pH sensor. The resulting nanomaterial is then used in water-based epoxy and acrylic coatings for early-stage detection of steel corrosion. Coatings with as little as 0.01 wt% rhodamine B acylhydrazone show a marked increase in fluorescence intensity that correlates with the onset of steel corrosion. Coatings containing the dye encapsulated in silica nanocontainers demonstrate a significantly stronger response (4 times) compared to coatings containing the dye without an encapsulating agent. Furthermore, encapsulating rhodamine B acylhydrazone improves the dispersion of this hydrophobic dye in epoxy and acrylic coating formulations without requiring an organic solvent. The ability of the resulting coatings to detect corrosion by changes in fluorescence is validated by fluorescence spectroscopy and microscopy. Impedance spectroscopy investigations indicate that silica nanocontainers improve the barrier properties of the composite epoxy coatings on steel. The encapsulation of highly sensitive and hydrophobic molecules in silica nanocontainers can be an effective method for preparing smart coatings with desired characteristics.

Photoelectrochemical, structural, and electrocatalytic properties of titanium dioxide (TiO 2 ) nanotubes obtained by the anodization of titanium with subsequent thermal treatment in air or hydrogen were studied. The heat treatment of TiO 2 nanotubes in hydrogen was found to have no effect on the morphology and phase composition of the resultant TiO 2 electrodes. However, such treatment led to a high concentration of defect states in the TiO 2 crystal lattice due to reductive doping accompanied by the conversion of Ti 4+ to Ti 3+ . The rise in the defectivity diminished the overpotential for oxygen electroreduction at an electrode made from titanium dioxide nanotubes annealed in hydrogen compared to such an electrode annealed in air. In addition, annealing in hydrogen led to a significant increase in the long-wavelength photocurrent generated under visible light irradiation.

One of the most significant limitations of photodynamic therapy is its reduced efficacy in hypoxic microenvironments, which are typical of the majority of tumors. This work demonstrates that indolenine heptamethine cyanines with different substituents in the polymethine chain and at the terminal heterocycles are effective superoxide generators that can be activated in the near-infrared range. The introduction of an indene moiety into the polymethine chain results in a significant enhancement in photostability compared to dyes with a cyclohexene moiety or an unsubstituted polymethine chain. A hydrophilic indene-bearing heptamethine cyanine dye is shown to be efficiently internalized by Vero E6 cells and to give bright intracellular fluorescence in the 700-850 nm range. Furthermore, the dye generates superoxide anion radicals and induces severe oxidative stress in cells upon activation in the near-infrared range (similar to 750 nm), ultimately resulting in cell death. The capacity of heptamethine cyanines to generate a superoxide anion radical may prove advantageous for enhancing the efficacy of photodynamic therapy under hypoxic conditions. A heptamethine cyanine dye with an indene moiety and 4-meso-chloride generates superoxide inside cells upon near-infrared photoactivation, inducing cell death.

The spread of multidrug-resistant mycobacterium strains requires the development of new approaches to combat diseases caused by these pathogens. For that, photodynamic inactivation (PDI) is a promising approach. In this study, a tricarbocyanine (TCC) is used for the first time as a near-infrared (740 nm) activatable PDI photosensitizer to kill mycobacteria with deep light penetration. For better targeting, a novel tricarbocyanine dye functionalized with two trehalose units (TCC2Tre) is developed. The photodynamic effect of the conjugates against mycobacteria, including Mycobacterium tuberculosis, is evaluated. Under irradiation, TCC2Tre causes more effective killing of mycobacteria compared to the photosensitizer without trehalose conjugation, with 99.99% dead vegetative cells of M. tuberculosis and M. smegmatis. In addition, effective photoinactivation of dormant forms of M. smegmatis is observed after incubation with TCC2Tre. Mycobacteria treated with TCC2Tre are more sensitive to 740 nm light than the Gram-positive Micrococcus luteus and the Gram-negative Escherichia coli. For the first time, this study demonstrates the proof of principle of in vitro PDI of mycobacteria including the fast-growing M. smegmatis and the slow-growing M. tuberculosis using near-infrared activatable photosensitizers conjugated with trehalose. These findings are useful for the development of new efficient alternatives to antibiotic therapy.

Herein, a heterostructured design strategy involving Ag nanoparticles (Ag NPs) stabilized with 5-(2-mercaptoethyl)tetrazole and immobilized on titania nanotubes for the oxygen reduction reaction (ORR) is reported. Bare titania nanotubular layers were annealed in air (TNT) or in a hydrogen atmosphere (hTNT), and their composites with tetrazole-stabilized Ag NPs (tz-Ag NPs) were evaluated for their ORR performance in alkaline media. The activity of the tz-Ag NP/TNT composites was shown to correlate with TNT doping level, which can be controlled by varying the annealing conditions. In all cases, the tz-Ag NP/hTNT composite shows more positive ORR onset and half-wave potentials (E1/2) than the tz-Ag NP/TNT composite. An increase in tz-Ag NP loading onto the TNT and hTNT matrix leads to a decrease in the overpotential of O2 reduction. The hTNT electrocatalyst loaded with a high amount of tz-Ag NPs (24 mu g cm-2) exhibits superior ORR activity over a bare Ag electrode in terms of ORR onset and half-wave potentials. Ag NPs stabilized with tetrazole demonstrate an improved ORR performance in alkaline media compared to Ag NPs capped with citrate. The TNT electrodes loaded with tz-Ag NPs have shown high electrocatalytic activity toward the ORR indicating their suitability as cathode materials in alkaline fuel cells.

Electrooxidation of rhodamine B acylhydrazone in MeCN involves free radical intermediates and yields diverse products.

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 high specific surface area and abundant active sites further promote the mass/charge transfer and redox reaction kinetics. In the three-electrode system, the specific capacitance was as high as 1547 F/g at a current density of 1 A/g, along with satisfactory rate capability (1214 F/g at 6 A/g) and cycling performance. Coupled with activated carbon (AC), the prepared hybrid device (ZnS/NiS2 as the positive electrode and AC as the negative electrode) (ZnS/NiS2/AC) can be operated under a potential window of 1.6 V and provides a high energy density of 26.3 Wh/kg at a power density of 794 W/kg. Notably, the assembled ZnS/NiS2//AC showed little capacity degradation after 5000 charge/discharge cycles.

Photodynamic therapy is an effective and minimally invasive treatment method for cancer. A deeper under-standing 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 calcula-tions to study indotricarbocyanine dyes relevant for photodynamic therapy. The incorporation of 4-meso-chloride and a 3,5-o-phenylene bridge into the polymethine chain results in a hypsochromic shift of the absorption spectrum by ca. 30 nm and in a downward shift of the frontier orbitals energy levels by 0.1-0.3 eV. In addition, such substitution imparts stability to the electrogenerated radical dications of the dyes. The presence of 4-meso- chloride and a 3,5-trimethylene bridge in the polymethine chain causes the absorption spectrum to shift bath-ochromically by almost 40 nm and the HOMO-LUMO energy gap to decrease by ca. 0.1 eV. The radical dication of the dye with such substitution is particularly stable and exhibits improved electron delocalization. The radical dication of the dye with an unsubstituted polymethine chain is unstable due to its propensity to form dimers. The substituents at the nitrogen atoms are shown to have almost no influence on the optical and electrochemical properties of the indotricarbocyanine dyes. The radical dications of the dyes with an o-phenylene bridge can oxidize bromide ions, unlike the radical dications of the dyes with an unsubstituted polymethine chain or with a trimethylene bridge. The reported data can be used to develop new indotricarbocyanine dyes with desired characteristics.

Spirocyclic rhodamine derivatives have great potential to be used as fluorescent sensors. Rho- damine 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 sensors with improved characteristics. In this work, the performance of rhodamine B acylhydrazone (RBA) as a sensor for Fe3+ and Cu2+ ions is evaluated. In the presence of these ions, RBA undergoes protonation and the spirolactam ring opening. The ring opening renders the dye colored and fluorescent. RBA is then hydrolyzed to RBH leading to the decay of the absorbance in the visible range. The protonation and hydrolysis of RBA are acid-catalyzed, and metal ions contribute to these processes by lowering pH. Metal ions, unlike hydrogen ions, catalyze the transformation of RBH into rhodamine B and a phenanthrenone derivative. These products exhibit emission bands in the visible and near-infrared ranges, respectively. The obtained results can be applied to a variety of sensors based on rhodamines and Schiff bases. RBA can be employed for bioimaging. RBA quickly penetrates into cells, localizes in the organelles with acidic pH, probably in lysosomes, persists there for a long time, and gives bright fluorescence in the visible range. Cell incubation with Cu2+ ions produces fluorescence in the near-infrared range. RBA can be used as a multifunctional fluorescent biosensor to visualize cell compartments with acidic pH and detect Cu2+ ions in living cells.

The electrooxidation of rhodamine B hydrazide is shown to produce rhodamine B, a phenanthrenone derivative, and a phtalazinone derivative.

A study was carried out on the spectral-luminescence and phosphorescence properties of an indotricarbocyanine dye with an ortho-phenylene bridge in the conjugation chain as well as two 300-Da polyethylene glycol (PEG) substituents (PD1) and its analog without PEG (PD2). The presence of the bulky PEG300 substituents in the dye structures was shown to alter the efficiency of singlet oxygen generation. The yield of singlet oxygen in ethanol for both dyes in the concentration range from 5∙10–8 to 10–5 M has a constant value γΔ = 0.031 ± 0.005 for PD1 and 0.050 ± 0.008 for PD2. An increasing value of γΔ from 0.022 ± 0.004 when Cdye = 2.6·10–7 M to 0.104 ± 0.016 when Cdye = 5.8·10–5 M was found in the concentration range from 10–7 to 10–5 M in low-polarity chloroform for PD2, whereas the quantum yield for PD1 with bulky substituents is invariant in this concentration range (0.032 ± 0.003). The increase in the singlet oxygen formation quantum yield with increasing concentration of PD2 in low-polarity chloroform is attributed to an increase in the fraction of contact ion pairs in solution and a heavy atom effect related to the Br– anion. The presence of two PEG300 chains in the structure of the cationic indotricarbocyanine dye ( 770 Da) prevents the counterion from moving away from the cation of dye PD1 in low-polarity chloroform. Furthermore, the dye molecules are in the form of contact ion pairs at any concentration and it is hence difficult for the chromophore to interact with dissolved oxygen due to steric hindrance.

The results from studying the time characteristics (counting, amplitude distributions of single-electron pulses, spread of the signal propagation time (jitter) when exposed to radiation from picosecond diode lasers in the spectral range 405–780 nm) of high-speed photomultipliers FEU-175 and FEU-186 manufactured by AO Central Research Institute Electron (St. Petersburg). FEU-175 and FEU-186, respectively, are equipped with bialkali and multialkali photocathodes; their operating spectral range is 250–650 and 250–800 nm, respectively. Signal amplification is provided by a 14-dynode multiplication system, while the rise time of the PMT impulse response does not exceed 1.5 ns and the jitter is approximately 0.4 ns. PMT data can be used as photodetectors in single-quantum kinetic spectrometers with subnanosecond resolution and in other high-speed optoelectronic recorders.

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 properties and PEO processing parameters. Under different PEO processing conditions (anodization time—1–10 min and applied voltage—370 and 450 V) ceramic coatings with a mean thickness of 2–12 μm were prepared. XRD analysis explored the coating structure composed of zinc oxide (wurtzite) and zinc aluminate spinel. The content of ZnAl2O4 in the coatings grows with increasing the applied voltage and anodization time. Photoluminescence (PL) measurements showed that the PEO coatings have several bands in the visible and near-infrared regions associated with their composite structure. The PL spectra significantly depend on the PEO processing parameters due to varying ZnO and ZnAl2O4 content in the coatings. The insight in the relationship between the ZnAl2O4 structure and the photoluminescent properties of ZnO/ZnAl2O4 coatings has been provided using the combination of XRD and luminescence spectroscopy.

The photophysical properties of indotricarbocyanine dyes upon complexation with serum albumin were studied. The technique using electrophoresis to detect their formation was optimized. The area in which the studied dye was localized on the surface of the gel plate was searched for by recording the fluorescence spectra of the dye before protein fixation and visualization followed by completion of the protocol for obtaining the electrophoregrams because the dye was degraded by acids. Excitation used radiation of a semiconductor laser with a wavelength of 684 nm, which excited fluorescence of the studied dyes, to minimize the possible influence of luminescence of the gel components. It was established that the position of the maxima and the half-width of the fluorescence spectra of dyes with an o-phenylene bridge in the conjugation chain in the regions of the electrophoregram corresponding to the location of albumin coincided with the characteristic emission of the dyes in the initial solutions with albumin, which revealed that covalently bonded complexes of the dyes with albumin formed.

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 chronoamperometric electrolysis at 1.1 V (versus saturated calomel electrode) yielding radical dications. The radicals exhibit an absorption band that is blue-shifted relative to the parent dye (561 nm versus 714 nm). In acetonitrile solutions, the radicals are characterized by a lifetime of ca. 20 min and a g factor of 2.002. The oxidation potential of the dyes is slightly greater than that of bromide ions allowing the radicals of the dyes to interact with bromide ions. The ability of the indotricarbocyanine dyes to sensitize generation of highly reactive bromine radicals might play an important role in their photodynamic activity.

The interaction of indotricarbocyanine dyes with human blood serum proteins was studied. The spectral and fluorescent properties of dyes in butanol, Dulbecco’s sodium and potassium phosphate buffer (0.14 mol/L) with pH 7.4, and human blood serum solutions were determined. It was shown that the spectral properties of dyes in butanol differ significantly from the spectral properties in solutions of Dulbecco’s sodium and potassium phosphate buffer and human blood serum, and that butanol effectively extracts the molecules of the studied dyes that do not form covalently bound complexes with blood serum components. By analysing the extraction products, the proportion of covalent complexes of dyes with protein molecules was determined. It has been established that indotricarbocyanine dyes with a chlorine-substituted orthophenylene bridge in the conjugation chain are partially passes into butanol, the degree of extraction depends on the ratio of dye and protein concentrations. Thus, at a concentration of 10 mmol/L in 5 % human serum, the degree of extraction of these dyes is ~50 – 60 % respectively, the proportion of dye molecules in strong covalently bound complexes with blood serum components is ~ 40 –50 %. On the contrary, the dye with a free polymethine chain is extracted almost completely (91.4 % extraction rate). The indotricarbocyanine dyes are promising for use as a photosensitisers for photodynamic therapy.

This article presents the electrical circuit, a description of the design, and results of measurements of the radiative watt–ampere and time characteristics of compact inexpensive emitters based on commercial laser diodes with wavelengths from 405 to 850 nm, which operate in the picosecond (70–180 ps) and nanosecond (0.69–1.2 ns) modes. The optical emitter includes a master crystal oscillator based on a microcontroller (frequencies of 76 Hz–20/80 MHz), a synchronization circuit, a low-voltage (9–12 V) subnanosecond electric pulse shaper that operates according to the method of double differentiation, a pump circuit with an adjustable direct current source, and a laser diode. The average light power at a frequency of 80 MHz varies in pico mode from 0.6 to 1.6 mW and in nano mode from 6 to 18 mW. The lasers are powered by a 220 V/12 V, 0.25 A serial power supply, with a power consumption of 3 W and a weight of 0.2 kg.

H*-aggregates are a rarely observed type of molecular aggregates, with many of their properties yet to be investigated. The indotricarbocyanine dye under study is the first known compound able to produce both H*- and J-aggregates. Steady-state spectral properties, morphology, photoelectrochemical response, and excited-state dynamics of the H*-aggregates are investigated for the first time. Under 400 nm pumping, the deactivation of electronic excitations in the H*-aggregates follows two paths involving the top and bottom of the exciton band. This is consistent with the presence of a fast 3 ps and a slow 33 ps component in the decay trace of the ground-state bleaching. Under 800 nm pumping, the H*-aggregates are promoted to the bottom of the exciton band. Consequently, only the slow component is present in the decay trace of the ground-state bleaching. For the J-aggregates, the ground-state bleaching follows biexponential decay with the time constants of 1 and 20 ps under both 400 and 800 nm pumping. The relaxation involves only the bottom of the exciton band. The faster deactivation of electronic excitations in the J-aggregates is probably due to greater exciton delocalization: 9 molecules in the J-aggregates versus 4 molecules in the H*-aggregates. The obtained results can be used to create photonic devices containing the H*-aggregates.