Intense Absorption Band Research Articles

Polypyridyl CoII -Curcumin Complexes as Photoactivated Anticancer and Antibacterial Agents.

Four new CoII complexes, [Co(bpy)2 (acac)]Cl (1), [Co(phen)2 (acac)]Cl (2), [Co(bpy)2 (cur)]Cl (3), [Co(phen)2 (cur)]Cl (4), where bpy=2,2'-bipyridine (1 and 3), phen=1,10-phenanthroline (2 and 4), acac=acetylacetonate (1 and 2), cur=curcumin monoanion (3 and 4) have been designed, synthesized and fully characterized. The X-ray crystal structures of 1 and 2 indicated that the CoN4 O2 core has a distorted octahedral geometry. The photoactivity of these complexes was tuned by varying the π conjugation in the ligands. Curcumin complexes 3 and 4 had an intense absorption band near 435 nm, which made them useful as visible-light photodynamic therapy agents; they also showed fluorescence with λem ≈565 nm. This fluorescence was useful for studying their intracellular uptake and localization in MCF-7 breast cancer cells. The acetylacetonate complexes (1 and 2) were used as control complexes to understand the role of curcumin. The white-light-triggered anticancer profiles of the cytosol targeting complexes 3 and 4 were investigated in detail. These non-dark toxic complexes displayed significant apoptotic photo-cytotoxicity (under visible light) against MCF-7 cells through ROS generation. The control complexes 1 and 2 did not induce significant cell death in the light or dark. Interestingly, 1-4 produced a remarkable antibacterial response upon light exposure. Overall, the reported results here can increase the boundary of the CoII -based anticancer and antibacterial drug development.

Influence of Permanent Crops and Fallow on the Thermal and Optical Properties of Typical Chernozem

Using the thermal method and IR spectroscopy, a typical chernozem (Haplic Chernozem (Loamic, Pachic)) of various land uses was studied. According to the data obtained, the organic matter of the chernozem mainly consists of weakly thermally stable aliphatic compounds such as polysaccharides. This is evidenced by the mass loss in the low-temperature region, which varies within 68.15–71.54%, and the intense absorption band at 1083 cm-1, which determines the shape of the IR spectra of the chernozem. Under the influence of extensive agricultural use, the mineralization of labile aliphatic compounds and an increase in stable cyclic structures in the composition of the organic matter of chernozem occurred. This is indicated by a decrease in the Chernikov–Konchits Z coefficient from 3.16 to 2.47–2.73 and the intensity of most absorption bands in the IR spectra. The most noticeable negative impact on the organic matter of a typical chernozem was caused by bare fallow.

Studies of Thyroid Hormones (Propylthiouracil and L-Thyroxine) Interaction with Human Serum Albumin-Spectroscopic Approach

In this work, UV-absorption, fluorescence spectroscopy and Fourier transform infrared (FTIR) spectroscopy were used to investigate the relationship between Propylthiouracil and L-Thyroxine with human serum albumin. The binding constants of propylthiouracil and L-Thyroxine have been determined of both UV-absorption and fluorescence spectroscopy. The binding Constants values measured at 293k are 1.659×10³ M^-1 for propylthiouracil and 1.013×10⁴ M^-1 for L-Thyroxine. The constant values of the Stern–Volmer quenching were determined to be 2.144×10³ L mol^-1 for propylthiouracil and 1.937×10³ L mol^-1 L-for Thyroxine. The UV-absorption intensity of HSA- hormones complexes has increased with increasing of propylthiouracil and L-Thyroxine concentration. With the rise in propylthiouracil and L-thyroxine concentrations, the fluorescence results indicate a decrease in HSA- hormone emission intensity. To determine the effects of protein secondary structure and hormone binding mechanisms, we have used FTIR spectroscopy with Fourier self-deconvolution technique and second derivative resolution enhancement, as well as curve-fitting methods for the investigation of the amide I, II, and III regions. The peak positions within the three amide regions (amide I, amide II and amide III) were allocated and any results were explored due to changes in concentration. Due to variations in hormone concentrations, the measurements of the FTIR spectra indicate a difference in the intensity of absorption bands.. FTIR Spectra measurements reflect a difference in the strength of the absorption bands due to changes in hormone concentrations.

Microwave treatment effect on the enhanced basicity of porous clay heterostructured composites derived from Laponite

Porous clay heterostructured composites (PCH) derived from layered hydrous magnesium silicate, Laponite, were functionalized by Fe(NO3)3x9H2O with the use of mechano-chemical impregnation followed by microwave irradiation or hydrothermal treatment to evoke new base properties, active in CO2 sorption. It resulted in the progressive leaching of the Mg2+ from the octahedral sheets of the Laponite structure and their capture on the surface of PCH composites increasing the Mg/Si ratio. The increase of Mg/Si ratio was accompanied by the decline of the (Mg3OH) absorption bands intensity attributed to Laponite and discussed regarding the formation of dispersed nanostructured MgO moieties capable of adsorbing CO2. CO2-TPD temperature-programmed desorption technique revealed that sorption and stabilization of CO2 molecules are related to the coordination of oxygen sites in the formed MgO lattice and that edge and corner sites facilitate the interaction of CO2 molecules with O2− sites on MgO. Doping of PCH resulted also in the nucleation of nanocrystalline α-Fe2O3 able to capture CO2 with strength and stability higher than MgO. Microwave irradiation resulted in significant development of the surface basicity as part of the transformation of clay structure. This study confirms the importance of clay minerals in the uptake and retention of CO2.

A Switchable Near‐Infrared‐Absorbing Dye Based on Redox‐Bistable Benzitetraazaporphyrin

AbstractActivatable near‐infrared (NIR) dyes responsive to external stimuli are used in medical and other applications. Here, we describe the design and synthesis of bench‐stable 18π‐ and 20π‐electron benzitetraazaporphyrins (BzTAPs) possessing redox‐switchable NIR properties. X‐Ray, NMR, and UV/Visible‐NIR analyses revealed that 20π‐electron BzTAP 1 exhibits NIR absorption and antiaromaticity with a paratropic ring‐current, while 18π‐electron BzTAP 2 shows weakly aromatic character with NIR inertness. Notably, the NIR‐silent BzTAP 2 was readily converted to the NIR‐active BzTAP 1 in the presence of mild reducing agents such as amine. The intense NIR absorption band of BzTAP 1 is in sharp contrast to the very weak absorption bands of previously reported antiaromatic porphyrinoids. Molecular orbital analysis revealed that symmetry‐lowering perturbation of the 20π‐electron porphyrinoid skeleton enables the HOMO–LUMO transition of 1 to be electric‐dipole‐allowed. BzTAPs are expected to be useful for constructing activatable NIR probes working in reductive environments.

A Switchable Near-Infrared-Absorbing Dye Based on Redox-Bistable Benzitetraazaporphyrin.

Activatable near-infrared (NIR) dyes responsive to external stimuli are used in medical and other applications. Here, we describe the design and synthesis of bench-stable 18π- and 20π-electron benzitetraazaporphyrins (BzTAPs) possessing redox-switchable NIR properties. X-Ray, NMR, and UV/Visible-NIR analyses revealed that 20π-electron BzTAP 1 exhibits NIR absorption and antiaromaticity with a paratropic ring-current, while 18π-electron BzTAP 2 shows weakly aromatic character with NIR inertness. Notably, the NIR-silent BzTAP 2 was readily converted to the NIR-active BzTAP 1 in the presence of mild reducing agents such as amine. The intense NIR absorption band of BzTAP 1 is in sharp contrast to the very weak absorption bands of previously reported antiaromatic porphyrinoids. Molecular orbital analysis revealed that symmetry-lowering perturbation of the 20π-electron porphyrinoid skeleton enables the HOMO-LUMO transition of 1 to be electric-dipole-allowed. BzTAPs are expected to be useful for constructing activatable NIR probes working in reductive environments.

The impact of puff frequency on respirable particulate matter in mainstream cigarette smoke.

Inhalation of particulate matter (PM) from cigarette smoke is hazardous to smokers and non-smokers. This contribution simulates the deposition of cigarette PM on the lung surface by trapping tobacco smoke particulates on Croton megalocarpus biochar. This study investigated one commercial cigarette (MM) and one local cigarette (RR). Biochar was incorporated into the filters of MM and RR cigarettes in order to adsorb PM from mainstream cigarette smoke. A weighed 5mg of biochar with adsorbed cigarette PM was analyzed using a scanning electron microscope and a Fourier transform infrared spectrometer. The size distribution of cigarette smoke particulates was processed using ImageJ software. At 15 s puff time, the mean particulate diameters for the commercial and the local cigarettes, respectively, can be classified as coarse ≈PM10 . Conversely, the mean particulate diameter at 2s puff time for the commercial cigarette falls under the ultrafine classification of ≤PM2.5 , whereas at the same puff time, the mean particulate diameter for the local cigarette was approximately PM2.5 . Data from Fourier transform infrared spectroscopy indicate the PM in the two model cigarettes contains aromatic structures that feature the C=C bond characterized by an intense absorption band at δs (1600 cm-1 ). This study found that PM in mainstream cigarette smoke depends on puff time. Although cigarette smoking was conducted for two model cigarettes, this study can be extended to any other form of cigarette. Moreover, this study emphasizes the need for comprehensive studies on real-world cigarette smoking conditions, taking into account cigarette smokers who use larger puff volumes.

Porphyrins Acting as Photosensitizers in the Photocatalytic CO2 Reduction Reaction

The success of the photocatalytic CO2 reduction using sunlight depends on how visible light is captured and utilized. Zn porphyrins, which are synthetic analogues of chlorophyll and bacteriochlorophyll, have very intense absorption bands in the visible region and are high potential candidates as photosensitizers for CO2 reduction. However, the use of zinc porphyrins had been limited due to their poor stability under the photocatalytic reduction conditions. We found that the durability of porphyrin during the photocatalytic CO2 reduction reaction is dramatically improved by combining a metal complex catalyst with the porphyrin so that two or more electrons are not accumulated on the porphyrin. In this perspective, we describe the molecular design of systems that combine Re complexes and porphyrins in detail and their unique reaction mechanisms in the photocatalytic CO2 reduction.

Polaritons in a Polycrystalline Layer of Non-fullerene Acceptor.

Non-fullerene acceptor molecules developed for organic solar cells feature a very intense absorption band in the near-infrared. In the solid phase, the strong interaction between light and the transition dipole moment for molecular excitation should induce formation of polaritons. The reflection spectra for polycrystalline films of a non-fullerene acceptor with a thienothienopyrrolo-thienothienoindole core of the so-called Y6 type indeed show a signature of polaritons. A local minimum in the middle of the reflection band is associated with the allowed molecular transition. The minimum in reflection allows efficient entry of light into the solid, resulting in a local maximum in external quantum efficiency of a photovoltaic cell made of the pure acceptor.

Chemical bath deposition synthesis of Dy2(CO3)3, and their evolution to Dy2O3 transition

Dy2(CO3)3 (dysprosium carbonate) nanocrystals, are successfully prepared at 60 °C, applying Chemical Bath Deposition technique. The powders are thermal annealing temperature (TAT) of 300 °C, 500 °C, 700 °C and 900 °C in air atmosphere. By XRD patterns, Dy2(CO3)3 where identified in the orthorhombic-phase. Structural evolution is observed for Dy2(CO3)3→Dy2O3 transition by correlating interplanar distance and grain size and Urbach energy tails, is applied to extract information on crystalline defects. The DSC experimental curve, shows a weight loss and a slight weight loss before ∼450 ◦C, indicating the absence of absorbed water or other polutants. The optical study in the %T, %R, Absorbance and d(D.O)/dE are investigated, the following optical responses are recorded: The non-hypersensitive 4F9/2→6H15/2 electronic intra-transitions (4fs→4fs) in Dy3+ cation being a magnetic dipole transition is insensitive to environment. Intense absorption band: 6H15/2, 6H11/2→6H9/2 is recorded at UV-region. Dy2O3(s) show absorption bands located at ∼457 nm (∼2.71 eV), assigned to Dy3+ cation of 4F9/2⟶6H15/2 electronic intra-transition. The dOD/dE vs. Energy (eV) spectra shows absorption bands situated at ∼324 nm (∼3.82 eV), ∼348 nm (∼3.56 eV), ∼363 nm (∼3.41 eV), ∼386 nm (∼3.21 eV) and ∼399 nm (∼3.10 eV) to 6H15/2→4M17/2, 6H15/2→6P7/2, 6H15/2→6P5/2, 6H15/2→4K17/2 to 4fs→4fs electronic intra-transitions of Dy3+ cation. The PL emission band located at UV-Vis region, are overlapped with the 4fs→4fs electronic intratransitions, typical of the Dy3+ cation, which are deconvoluted and associated with intrinsic crystalline defects.

Получение и анализ первичной смолы пиролиза углей разного генетического типа по восстановленности

Combining the methods of thermal destruction and physicochemical analysis, the primary pyrolysis tar obtained from coals of different genetic restorability types (GRT) in the series Cdaf = 76,2-86,1 %) was analyzed. The pyrolysis carried out at a temperature of Tmax (derivatography, DTG-curve) showed that restored coals of the “b” type differ from coals of slightly reduced “a” type in an increased tar yield and have more intense absorption bands at 2900 cm-1 (Сal–Н bond) and at 810 cm-1 (Сar–Н bond). It has been established that Har/Hal relation in tar increases in the coal rank (Cdaf) and is higher for type “a” coals. Using the Brown-Ladner equation, the main structural parameters of the studied coals were calculated.

Расчет структуры и инфракрасных спектров поглощения водородно связанных комплексов метилформиата с фтористым водородом

Equilibrium nuclear configurations of three dimers formed by the most stable conformer of a methyl formate molecule with a hydrogen fluoride molecule are calculated using the MP2/aug-cc-pVTZ quantum–chemical method and taking the basis set superposition error into account. The frequencies and intensities for the IR absorption bands of dimers are determined both in the harmonic and anharmonic approximations with the use of the second-order perturbation theory. The calculation method was tested in a calculation of the spectrum of an isolated methyl formate molecule and by comparison with experimental data. The changes in the geometrical parameters of monomers and the charges on atoms under the action of hydrogen bonds were analyzed. The shifts of vibrational frequencies of the monomers upon formation of dimers were calculated. The strongest absorption bands of dimers that can be used in detection of these complexes in spectroscopic experiments were determined.

Исследование различий ИК-спектров дождевых червей как возможный способ их таксономической идентификации

IR spectrometry is successfully used for the taxonomic identification of various groups of invertebrates: butterflies, flies, grasshoppers, mosquitoes, weevils, and termites. Therefore, the purpose of this study was to assess the fundamental possibility of taxonomic identification of earthworms based on the study of the functional-group composition of their bodies by the method of IR-Fourier spectroscopy. Seven species of earthworms from five genera were the objects of the study: Aporrectodea caliginosa, Eisenia fetida, Eisenia nordenskioldi, Lumbricus rubellus, Rhiphaeodrilus diplotetrathecus, Octolasion lacteum, Eisenia ventripapillata. IR absorption spectra were registered on an FT-801 IR-Fourier spectrometer in the range of 500–4000 cm–1. The position, intensity, and area of the absorption bands were determined on all spectra. The maximum differences between individual species in intensity and position of protein and nucleic acid absorption bands were established. Using the principal component method, it was shown that the classification was based on the characteristics of the absorption bands of stretching and bending vibrations of methyl and methylene groups, as well as amide groups in the structure of worms. At the same time, the division of earthworms into subgroups with similar spectral characteristics could be explained by several reasons: their origin, kinship, and the influence of the environment. The data obtained during the study confirm the possibility of using IR spectrometry for the identification of earthworms.

Biofabrication of Silver Nanoparticles for Selective and Sensitive Colorimetric Detection of Hg(II) Ions

The current study explored a green, simple, selective and cost-effective method for the detection of Hg2+ ions in the aqueous medium using silver nanoparticles (AgNPs) synthesized from marine macroalgae Sargassum duplicatum. The biosynthesized AgNPs were further characterized by using UV-visible spectroscopy, FTIR, HR-TEM, SAED and XRD techniques. The synthesized AgNPs were almost spherical in shape and polydisperse in nature. Due to the intense SPR absorption band, the biosynthesized AgNPs solution is seen as dark brown colour. In the presence of Hg2+, the brown coloured AgNPs solution becomes colourless coupled with the disappearance of absorption maxima at 419 nm. The selectivity and sensitivity of AgNPs towards Hg2+ were also investigated and the minimum detection limit was found to be 0.1 μM. Furthermore, a test strip technique for the rapid detection of Hg2+ was also devised. Thus, the biogenic AgNPs are expected to be a promising candidate for developing low-cost Hg2+ sensors.

Effect of meso-substituent and solvent nature on spectral properties, pH-stability and affinity to blood transport proteins of BODIPY dyes

The paper is focused on a comparative analysis of the structural and solvation factors on the spectral properties, pH-stability and lipophilicity of BODIPY biomarkers containing in meso-position methyl group, carboxylic acid residues and their esters. The affinity of meso-BODIPYs to blood transport proteins was studied. Dyes intensely absorb (ε ∼ 45000–90000) and fluoresce (to φ ∼ 100 %) in the range of 493–504 and 508–520 nm, respectively. meso-substitution causes a hypsochromic shift (by ∼4–11 nm) of the maximum of the intense absorption band and a noticeable increase of the Stokes shift (up to ∼1.7–2.6 times) of BODIPYs compared to the meso-unsubstituted analog. It has been shown that the introduction of a carboxyl group into the BODIPY meso-position significantly (by a factor of ∼2) increases the hydrophilicity of the compounds, and the presence of ester groups in the structure leads to an increase of the hydrophobicity of the luminophores by a factor of ∼1.3 compared to the meso-unsubstituted dye. It has been demonstrated that compounds are stable in a wide pH range and exhibit intense fluorescence (to φ ∼ 80 %), while carboxyl BODIPYs can be considered as pH sensors for alkaline media. Introducing carboxylic acid residues and their esters into the meso-position of BODIPY is an excellent way to increase affinity dyes to biostructures, including blood transport proteins.

Investigation of semimetallic properties of GdSb and TbSb compounds: A first-principle and optical study

The electronic and optical properties of binary semimetals GdSb and TbSb in the rocksalt cubic structure have been investigated. The spin-polarized band structure calculations were performed within GGA + U method accounting for strong electron correlations in rare-earth ions. The effect of spin-orbit interaction for the band structure is investigated. The resulting band features near the Fermi energy are found in a good agreement with the previous ARPES experimental data. Our first-principle calculations have shown that isostructural compounds GdSb and TbSb are electron-hole compensated semimetals with qualitatively similar electronic structures. A small pseudogap is observed in their densities of states. The energy dependencies of the real and imaginary parts of the complex dielectric permittivity of both materials are investigated by the spectroscopic ellipsometry in the range 0.078–5.6 eV. The experimental optical conductivity spectra are compared with the calculated ones. There is a reasonable agreement between experiment and theory on a number of spectral features formed by quantum transitions and related to the specifics of the electronic structures. The nature of the occurrence of intense absorption bands in the optical conductivity spectra of both compounds has been identified. The anomalous behavior of optical characteristics in the infrared region is associated with the semi-metallic properties of these materials.

Diketopyrrolopyrrole Derivatives as Photosensitizing Agents against Staphylococcus aureus.

Diketopyrrolopyrrole (DPP) derivatives containing sulfonamide (Sulfonamide-DPP), pyridyl (Dipyridyl-DPP) and N-methylpyridyl (MePyridyl-DPP) substituents were assessed as antibacterial photosensitizers. Non-charged DPPs showed an intense absorption band centered at about 480 nm and green fluorescence emission (ΦF ~ 0.7) in acetonitrile. The absorption of MePyridyl-DPP was bathochromically shifted at 510 nm, with decreased fluorescence emission. Sulfonamide-DPP and Dipyridyl-DPP photosensitized the formation of O2 (1 Δg ) (ΦΔ ~ 0.15-0.17), while the production induced by MePyridyl-DPP was at least 10 times lower. Furthermore, these DPPs produced a photoreduction of NBT similar to that of the control. Photodynamic inactivation induced by DPPs was first investigated at the single-bacterium level of Staphylococcus aureus attached to a surface. After 30 min irradiation, MePyridyl-DPP produced a complete eradication of the bacteria. In bacterial cell suspensions, dicationic DPP induced more than 7 log10 decrease in S. aureus cell survival after 30 min irradiation. Potentiation with iodide anions allowed a complete elimination of bacteria after 15 min therapy. This compound was also effective to eliminate S. aureus cells on biofilms. The results show that MePyridyl-DPP bearing two positive groups provides an amphiphilic character to the structure that improves the interaction with the cell envelop. This effect enhances the photocytotoxic activity of MePyridyl-DPP against bacteria.

Synthesis of Trifluoromethyl-Substituted [14]Triphyrin(2.1.1), Its Selective Reduction to Triphachlorin, and Stable Isomeric Triphabacteriochlorins via Direct Detrifluoromethylation.

Two novel classes of reduced triphyrin(2.1.1), namely, triphachlorin and triphabacteriochlorin, are realized via selective reduction of the newly synthesized 7,12-bis(trifluoromethyl)triphyrin(2.1.1) 1 using p-tosylhydrazide. Triphachlorin 2 displayed red-shifted absorption (580 nm). Harsher conditions, however, led to a unique direct detrifluoromethylation of one CF3 moiety to form two isomeric triphabacteriochlorins 3 and 4, which exhibit blue-shifted intense lowest-energy absorption bands and intense emission (ϕf = 0.52 and 0.36, respectively) while generating singlet oxygen very efficiently (ϕΔ = 0.88 and 0.86, respectively). These reduced porphyrinoids show very high oxidative stability as they remain unchanged upon refluxing with 2,3-dichloro-5,6-dicyanobenzoquinone in toluene.

Spectroscopic Properties of Er3+ Doped in Zinc Lithium Calcium Potassiumniobate Phosphate Glasses

Abstract: Zinc lithium calcium potassiumniobate phosphate glasses containing Er3+ in (45-x): P2O5:10ZnO:10Li2O:10CaO:10K2O:15Nb2O5:xEr2O3. (where x=1, 1.5,2 mol %) have been prepared by melt-quenching method. The amorphous nature of the glasses was confirmed by x-ray diffraction studies. Optical absorption, Excitation, and fluorescence spectra were recorded at room temperature for all glass samples. Judd-Ofelt intensity parameters Ωλ (λ=2, 4, 6) are evaluated from the intensities of various absorption bands of optical absorption spectra. Using these intensity parameters various radiative properties like spontaneous emission probability, branching ratio, radiative life time and stimulated emission cross– section of various emission lines have been evaluated.

Spectral and FTIR Analysis of Tm3+ Doped in Zinc Lithium Tungsten Sodalime Borotellurite Glasses

Abstract: Glass sample of Zinc Lithium Tungsten Sodalime Borotellurite: (35-x) TeO2:10ZnO:10Li2O:10WO3:10CaO:10Na2O:15B2O3:xTm2O3. (where x=1,1.5 and 2 mol%) have been prepared by meltquenching technique. The amorphous nature of the prepared glass samples was confirmed by X-ray diffraction. Optical absorption ,fluorescence and FTIR spectra were recorded at room temperature for all glass samples. Judd-Ofelt intensity parameters Ωλ (λ=2, 4 and 6) are evaluated from the intensities of various absorption bands of optical absorption spectra. Using these intensity parameters various radiative properties like spontaneous emission probability, branching ratio, radiative life time and stimulated emission cross– section of various emission lines have been evaluated