Luminescent properties of natural substances in solutions under low-dose radiation exposure

Humic substances or natural organic materials recently have they attracted steady attention as promising biologically active substances. These compounds are widely distributed in natural waters and soils, and have a wide range of chemical and physical properties. Their structure includes a large number of diverse functional groups, which determines their complex-forming, surface-active and redox properties, as well as contributes to their biological activity and possess detoxifying properties. Using humic substances, it is possible to reduce the toxicity of an important class of toxicants - radionuclides. Technogenic pollution by radioactive elements is a consequence of the extraction and processing of radioactive materials, the operation of nuclear power stations, the placement of radioactive waste, accidents at nuclear enterprises, etc. In most cases, technogenic radioactive contamination is caused by isotopes of uranium, thorium, etc., as well as tritium, which is one of the most common decay products of radioisotopes used in the nuclear industry. As a rule, enterprises control discharges, conduct wastewater treatment, reducing the content of radionuclides to an acceptable limit. Moreover, even residual radioactivity can lead to disruption of the physiological functions of aquatic microorganisms, which are the initial link in the food chain for all organisms. The influence of biologically active nanostructures is able to correct the state of aquatic microorganisms. In the presence of humic substances under the influence of radiation, organic molecules are transformed by the mechanisms of direct and indirect photolysis. However, experiments show that the addition of a humic fraction containing both humic and fulvic acids to an aqueous solution of phenol leads to a decrease in the efficiency of phenol decomposition. We managed to find the conditions and fix the effective decomposition of phenol in an aqueous solution when exposed to radiation with a wavelength of 222 nm from an excilamp in the presence of fulvic acid

Induced absorption spectra of crystal violet in various solvents

The study of short-lived induced (singlet-singlet) and long-lived induced (in particular, triplet-triplet) absorption capacity of crystal violet (CV) in various solvents was carried out by the pump-probe method. Water, dimethyl sulfoxide, isopropyl alcohol, and ethyl alcohol were selected as solvents. The formation of triplet states in various CV solvents was revealed upon excitation by nanosecond radiation of the 4th harmonic of a Nd: YAG laser (wavelength 266 nm, average power –25.5 mV, repetition frequency –3Hz, pulse duration –10 ns, peak power –10-12 MW/cm2). It is shown that the spectrum of the induced CV absorption in ethanol contains two closely spaced bands at 400 and 485 nm. Short-lived and long-lived induced CV absorption in isopropanol at room temperature (λmax=400 nm) was recorded

Photonics of halogenated zinc(II) and cadmium(II) dipyrromethene complexes

This article compares spectroscopic properties of the series of dipyrromethene dyes, namely their complexes of boron (III), zinc(II) and cadmium(II) with the halogenated ligands of the same structure. Absorption and emission spectra, lifetimes of long-lived emission and quantum yields of luminescence were studied as the functions of molecular structure of dipyrromethene complexes. The role of the position and nature of a substituent in a ligand, polarity of a solvent and temperature of media were also investigated. The studies demonstrate that replacing the central atom boron(III) by zinc(II) decreases the fluorescence quantum yield, indicating the increased role of non-radiative processes in excitation energy deactivations such as intersystem crossings. In addition, according to the heavy atom effect, the efficiency of intersystem crossings in halogen-substituted zinc(II) and cadmium(II) dipyrromethene complexes is higher than in the corresponding boron fluoride dipyrromethenes (BODIPY), which leads to increase in phosphorescence at low temperatures (frozen solutions). The obtained results make it possible to carry out further investigations of potential sensory properties that are required for systematic use of halogenated dipyrromethene complexes for the creation of modern optical oxygen sensors and singlet oxygen photosensitizers for photodynamic therapy or photocatalytic oxidative reactions

Optical spectra and laser induced fluorescence of bisphenol A

Bisphenol A (BPA) is a known disruptor of the human endocrine system. Our research has been carried out aimed at identifying the features of laser induced fluorescence of BPA at different pH and the properties of the solvent for the development of a method for the detection of a toxicant in biological systems. The spectral characteristics of BPA are very sensitive to the excitation wavelength. We used excitation wavelengths at 266, 355, and 532 nm from a YAG–Nd3 + laser LQ 529

Induced absorption spectra of Crystal Violet at various solvents

The study of short-lived induced (singlet-singlet) and long-lived induced (in particular, triplet-triplet) absorption capacity of crystal violet (CV) in various solvents was carried out by the pump-probe method. Water, dimethyl sulfoxide, isopropyl alcohol, and ethyl alcohol were selected as solvents. The formation of triplet states in various CV solvents was revealed upon excitation by nanosecond radiation of the 4th harmonic of a Nd: YAG laser (wavelength 266 nm, average power –25.5 mV, repetition frequency –3Hz, pulse duration –10 ns, peak power –10-12 MW/cm2). It is shown that the spectrum of the induced CV absorption in ethanol contains two closely spaced bands at 400 and 485 nm. Short-lived and long-lived induced CV absorption in isopropanol at room temperature (λmax=400 nm) was recorded

Solvent effect on the spectra of methylene green and methylene blue

This investigation focuses on dyes that differ only in the nitro substituent. The NO2 group leads to a strong hardening of the fluorescence at 298 K. In methylene green (MG) the excitation energy migrates to the system of triplet states. This nonradiative process causes the MG fuorescence absent or too low compared to methylene blue (MB). Moreover, laser-induced fluorescence is completely absent for MG in the investigated solvents. However, at liquid nitrogen temperature, we recorded fluorescence for MG in ethanol 250 times higher than at room temperature and phosphorescence too. The intensity of the MB fluorescence band in ethanol at 77 K is 6 times higher than at room temperature. According to the results of this study, the lifetime in the excited state decreases in the following order: isopropanol > acetonitrile≈ethanol≈dimethyl sulfoxide > > water for MG and chloroform > acetonitrile≈ethanol≈dimethyl sulfoxide > > water≈isopropanol for MB. In addition, MG has phosphorescence in ethanol at 780 nm and in chloroform at 810 nm