Spectral and luminescent properties of some porphyrin compounds in different electronic states

The spectral and luminescent properties of some derivatives of tetraphenylporphyrin are studied at different concentrations of these compounds; the spectra of neutral and ionic forms are interpreted; and the quantum yields of ordinary and, in some cases, short-wavelength fluorescence from highly excited states are determined. The spectra of transient absorption from excited states, existing in the time range of tens of nanoseconds, are measured, and the quantum yields of formation of triplet molecules are estimated. Hypotheses regarding the mechanism of phototransformations of some porphyrins in chloroform are put forth.     

Studying the coordination geometry of 3d transition-metal ions in complexes of crown-substituted porphyrins by EXAFS spectroscopy with allowance for multiple scattering

The structure of a series of complexes of 3d metals (Co, Ni, and Cu) with substituted porphyrins is studied by X-ray EXAFS spectroscopy. Together with complexes based on tetraphenylporphyrin and octaethylporphyrin with known crystalline structures, new complexes of asymmetrically substituted tetraphenylporphyrin, 5-(4-(((4′-hydroxy-benzo-15-crown-5)-5′-yl)diazo)phenyl)-10,15,20-triphenylporphyrin, are studied. Based on an analysis of experimental spectra with allowance for the contributions of multiple scattering, the coordination parameters of metal atoms at the center of the porphyrin ring are determined: the bond distances and valence angles between them for the first four coordination spheres around metal atoms. The EXAFS spectra are shown to be sensitive to the angular parameters. Differences in the geometric parameters in the series of studied metal-porphyrin complexes are analyzed.     

Comparative X-Ray Absorption Analysis of the Spectrum of Vacant Electronic States in Cobalt and Nickel Tetraphenylporphyrin Complexes

Physics of the Solid State - The energy distributions and the properties of the lower vacant electronic states in cobalt and nickel tetraphenylporphyrin complexes CoTPP and NiTPP are studied by...     

SEM-EDS probing of morphological and physiological changes produced by a porphyrin photosensitizer in Psammobatis extenta electrocytes

Morphological and physiological changes produced by the intracellular localization of an alkyl long-chain tetraphenylporphyrin photosensitizer in Psammobatis extenta electrocytes were studied by means of SEM-EDS. Immediately after photosensitizer penetration, electrocytes swell and their convex faces lose all invaginations. This effect is due to chloride and sodium ion flux into electrocytes, in accordance with energy dispersive X-ray microanalysis.     

船舶噪声激励夜光虫发光特性实验研究

对船舶噪声刺激下的生物发光特性展开研究,发光生物为夜光虫。利用声学换能器模拟船舶辐射噪声,在含有发光生物夜光虫的实验水槽中进行生物发光实验。声学换能器发出不同频率,对夜光虫受不同频率噪声激励下的发光特性进行记录。通过对不同激励频率下夜光虫发光图像的分析处理,得到不同频率激发下生物发光点图像,经统计分析得到了夜光虫在船舶噪声激励下的发光特性,得出夜光虫发光点数随频率和声源级的增加而增加的结论。     

Photo- and electroluminescence of mixed-ligand Eu(III) complexes

Spectral and luminescent properties of mixed-ligand Eu(III) complexes were studied in solutions and in polyvinylcarbazole (PVC) thin films. Trends in their variations were found depending on the complex structure and excitation mode. The electroluminescence was observed in ITO/PEDOT/Eu complex:PVC/CaMg/Al devices. Their current-voltage and voltage-brightness characteristics were investigated.     

Development of novel formulations for photodynamic therapy on the basis of amphiphilic polymers and porphyrin photosensitizers. Pluronic influence on photocatalytic activity of porphyrins

Effect of ethylene and propylene oxide tri-block copolymers (Pluronics) on the photocatalytic activity of tree porphyrins differing by their hydrophobicity was studied. It was shown that Pluronics induce considerable increase in the photocatalytic activity of the tetraphenylporphyrin, hematoporphyrin disodium salt (Dimegine) and relatively hydrophilic N-methyl-bis-glucamine salt of chlorine e₆ (Photoditazine) in the reaction of photooxidation of tryptophan in water solution. This effect was maximal for Pluronics F127 and P85 with intermediate hydrophobicity, while more hydrophilic F68 and more hydrophobic L61 were less effective. Pluronic effect on the photocatalytic activity of tetraphenylporphyrin and dimegine is attributed to their disaggregation in water solution, while PD activity is elevated due to the local concentrating of the photocatalyst and the substrate within micellar volume. It was found by AFM that the structure of Pluronic F127 thin films prepared by water solution evaporation on mica surface significantly changed in the presence of porphyrin. This effect can be attributed to the interaction of Pluronics with porphyrins in water solution.     

Luminescent and photosensitive properties of nanocomposites based on tris(diimine) Ru<Superscript>2+</Superscript> complexes chemically bound to a silica matrix

The photosensitive and luminescent properties of composites in the system organic Ru²⁺ complex-SiO₂ are studied. The effect exerted by specific interactions of Ru²⁺ complexes with the silica matrix and by different ligands on the spectral characteristics of the complexes is studied.     

Bactericidal action of single-walled carbon nanotubes

The action of single-walled carbon nanotubes (SWCNTs) on cells of the genetically engineered K12 TG1 strain of Escherichia coli, which have a luminescent phenotype generated by the cloning of the lux operon of the native luminescent marine bacterium Photobacterium leiognathi into the strain, is studied in this work. The survival rate of the bacterial cells and their morphological changes are studied by means of atomic force microscopy as a function of their exposure to SWCNTs.     

The influence of perchloric acid on the spectral and luminescent properties of cyclopalladated complexes

The influence of perchloric acid in ethanol on the spectral and luminescent characteristics of cyclopalladated amine complexes with 4-phenylpyrimidine, 1,7-phenanthroline, and coumarin-6 is studied. A protonation mechanism is proposed.     

Effect of the molecular structure of films of tetrapyrrole compounds on their photoelectrochemical characteristics for different types of sensitization

It was examined how the photoelectrochemical properties of thin films (50 nm) prepared from metal derivatives of tetrapyrrole compounds with various central atoms depend on the character of sensitization. It was demonstrated that the treatment of pigment films with oxygen and iodine vapor increases their photoactivity two- to threefold. A more pronounced effect is produced by deposition onto the films of layers of electron acceptors (o-chloranil, tetracyanoquinodimethane, etc.) or organic semiconductors (phenylselenodiimide) with a thickness of one to three monolayers. For tetrapyrrole compounds with the same structure of the macrocycle but with different central atoms, the sensitization effect may differ severalfold. For example, treatment of zinc tetraphenylporphyrin with iodine vapor increases the photocurrent by a factor of 14, with only a 1.5-fold increase being observed for cobalt tetraphenylporphyrin. The parameters of phthalocyanine metallocomplexes are less sensitive to sensitization compared to those of tetraphenylporphyrin metallocomplexes. The sequence of variation of the photoactivity of tetrapyrrole compounds according to the type of the central atom is not affected by the nature of the sensitizer, but the extent of change in the photoactivity is dependent on its properties, in particular, electron affinity.     

IR luminescence of bismuth-containing centers in materials prepared by impregnation and thermal treatment of porous glasses

The properties of bismuth-containing luminescent materials prepared by impregnating a porous glass with an aqueous solution of bismuth and aluminum salts followed by thermal treatment are studied. The formation of a variety of bismuth-containing centers luminescent in the near infrared range of the spectrum is revealed, one of which is the Bi⁺ monocation. At high temperatures, along with it, bismuth-containing cluster-type luminescent centers are apparently formed.     

Characteristics of Organic Photo- and Electro-Luminescent Devices with Double Mirrors

The luminescent characteristics of organic thin films sandwiched between two mirrors were measured. The optical length between the two mirrors was set according to the scale of the luminescent wavelength in order to compose a microcavity structure. Photoluminescence (PL) and electroluminescence (EL) from tris(8-hydroxyquinoline)aluminum (ALQ) were enhanced at distinct resonating wavelengths, and suppressed in other regions. Then, narrow and enhanced luminescent peaks were observed from the devices with the microcavity structure. Based on their injection current dependence, the primary cause of these spectra was speculated to be spontaneous emission. An EL sample with the microcavity structure for multicolor emissions was fabricated.     

发光搪瓷釉料研究

铕激活的铝酸锶系列超长余辉发粉具有起始亮度高、余辉时间长、无放射性毒害等突出优点,成为当前一类极具发展前途的发光材料,本项目采用该系列发光材料,研究了蓄能发光搪瓷釉料,并制备了性能稳定的发光搪瓷制品。     

The influence of perchloric acid on spectral and luminescent characteristics of 4-phenylpyrimidine and 1,7-phenanthroline

The influence of perchloric acid on the spectral and luminescent characteristics of 4-phenylpyrimidine and 1,7-phenanthroline is studied. Stepwise protonation of both nitrogen atoms is established.     

Fluorescence quenching of 9-cyanoanthracene in presence of zinc tetraphenylporphyrin in a polar liquid medium

Steady-state and time-resolved techniques are used to study photoinduced electron and/or excitational energy transfer processes involved within a novel donor (zinc tetraphenylporphyrin)-acceptor (9-cyanoanthracene) system in a polar liquid medium (acetonitrile) at the ambient temperature (300 K). After photoexcitation of 9-cyanoanthracene, its fluorescence emission as well as lifetime are found to be quenched in presence of zinc tetraphenylporphyrin. The fluorescence quenching is ascribed to be due to the combined effect of electron transfer from zinc tetraphenylporphyrin to 9-cyanoanthracene and energy transfer (radiative as well as non-radiative) from 9-cyanoanthracene to zinc tetraphenylporphyrin. The highly exergonic values of Gibbs free energy change for both forward electron transfer reaction (−1.15 eV) and charge recombination reaction (−1.94 eV) indicate the possibilities of occurrences of these two processes in the Marcus inverted region. The fluorescence quenching rate due to photoinduced electron transfer reaction is found to be close to the diffusion-controlled limit within the present donor-acceptor system upon excitation of the acceptor molecules.     

用转移函数方法研究铒离子上转换发光与抽运功率的关系

用转移函数方法分析了铒离子上转换发光与抽运功率的关系.对单掺铒离子的发光材料,对比分析了铒离子为高浓度和低浓度掺杂时上转换发光强度与抽运功率的关系.对稀土离子共掺杂系统,分析了Er3+在铒镱共掺杂的氟氧化物玻璃陶瓷中的上转换发光过程,认为Er3+绿色辐射的上转换发光强度与抽运激光功率的非平方关系是由于Er3+和Yb3+之间的强交叉弛豫过程引起的.讨论了在稀土离子共掺杂的氟氧化物玻璃陶瓷中提高Er3+的上转换发光强度的几种方法. 关键词： 转移函数方法 上转换发光 氟氧化物玻璃陶瓷     

水热法制备不同形貌的GdVO_4:Eu~(3+)纳米发光材料

采用水热法制备了不同形貌的GdVO4:Eu3+纳米晶样品,对其结构以及发光性质进行了表征。XRD结果表明:水热前驱体和经过灼烧之后样品均为四方晶系,具有锆石结构。TEM照片表明:通过改变表面活性剂分别得到了分散性良好的米粒状、六角形和球形的GdVO4:Eu3+纳米晶粒子。发光光谱表明:在288nm的紫外光激发下,不同形貌的GdVO4:Eu3+纳米晶材料均在617nm处产生特征红光发射,归属为Eu3+离子的5D0→7F2跃迁,不同形貌粒子的发光光谱的相对强度有所不同。     

Synthesis and study of the luminescent properties of europium-doped yttrium niobate

A method of synthesis of single-phase europium-doped yttrium niobate powders without using additional fluxes is developed. Using this method, a series of samples with different europium concentrations are synthesized. The phase composition, grain size, and luminescent properties of the synthesized powders are studied. The optimal dopant concentration corresponding to the maximum luminescence intensity is determined. It is shown that the decay time of the most intense luminescence line of europium decreases with increasing europium concentration. Comparative analysis of the luminescent properties of calcium tungstate and the luminescent properties of a synthesized sample with the highest luminescence intensity is performed.     

Luminescence Spectroscopy and Decay Kinetics of Pr3+ Ions in K3LuSi2O7:Pr3+

Physics of the Solid State - The luminescent characteristics of K3LuSi2O7:Pr3+ (1%), which is a promising optical material for the use as a scintillator, have been studied using a set of...