Shift Of Absorption Band Research Articles

Proton motive force in plant photosynthesis dominated by ΔpH in both low and high light.

The proton motive force (pmf) across the thylakoid membrane couples photosynthetic electron transport and ATP synthesis. In recent years, the electrochromic carotenoid and chlorophyll absorption band shift (ECS), peaking ∼515 nm, has become a widely used probe to measure pmf in leaves. However, the use of this technique to calculate the parsing of the pmf between the proton gradient (ΔpH) and electric potential (Δψ) components remains controversial. Interpretation of the ECS signal is complicated by overlapping absorption changes associated with violaxanthin de-epoxidation to zeaxanthin (ΔA505) and energy-dependent nonphotochemical quenching (qE; ΔA535). In this study, we used Arabidopsis (Arabidopsis thaliana) plants with altered xanthophyll cycle activity and photosystem II subunit S (PsbS) content to disentangle these overlapping contributions. In plants where overlap among ΔA505, ΔA535, and ECS is diminished, such as npq4 (lacking ΔA535) and npq1npq4 (also lacking ΔA505), the parsing method implies the Δψ contribution is virtually absent and pmf is solely composed of ΔpH. Conversely, in plants where ΔA535 and ECS overlap is enhanced, such as L17 (a PsbS overexpressor) and npq1 (where ΔA535 is blue-shifted to 525 nm) the parsing method implies a dominant contribution of Δψ to the total pmf. These results demonstrate the vast majority of the pmf attributed by the ECS parsing method to Δψ is caused by ΔA505 and ΔA535 overlap, confirming pmf is dominated by ΔpH following the first 60 s of continuous illumination under both low and high light conditions. Further implications of these findings for the regulation of photosynthesis are discussed.

NIR absorbing dimeric aza-BODIPY dye with J-type aggregation and photothermal properties

A novel amphiphilic dimeric aza-BODIPY dye was synthesized by oxidative coupling and characterized by 1H NMR, 13C NMR, MS, and UV/Vis absorption and fluorescence spectroscopy. In comparison with its precursor, the dimeric dye displayed a bathochromically shifted absorption band with maximum at 731 nm and an emission maximum at 768 nm. In addition, the dimeric dye formed stable J-type aggregates in DMSO/H2O. The morphology of nanowire was observed for the aggregates by AFM and TEM. Furthermore, the J-type aggregates of the dimeric aza-BODIPY exhibited promising photothermal conversion efficiency (38.7%).

Conjugated-linker dependence of the photophysical properties and electronic structure of chlorin dyads

The synthesis, photophysical properties and electronic structure of seven new chlorin dyads and associated benchmark monomers are described. Each dyad contains two identical chlorins linked at the macrocycle [Formula: see text]-pyrrole 13-position. The extent of electronic communication between chlorin constituents depends on the nature of the conjugated linker. The communication is assessed by modification of prominent ground-state absorption and redox properties, rate constants and yields of excited-state decay processes, and molecular-orbital characteristics. Relative to the benchmark monomers, the chlorin dyads in toluene exhibit a substantial bathochromic shift of the long-wavelength absorption band (30 nm average), two-fold increased radiative rate constant [average (10 ns)[Formula: see text] vs. (22 ns)[Formula: see text]], reduced singlet excited-state lifetimes (average 5.0 ns vs. 8.2 ns), and increased fluorescence quantum yields (average 0.56 vs. 0.42). The excited-state lifetime and fluorescence yield for the chlorin dyad with a benzothiadiazole linker are reduced substantially in benzonitrile vs. toluene due largely to [Formula: see text]25-fold accelerated internal conversion. The results aid design strategies for molecular architectures that may find utility in solar-energy conversion and photomedicine.

Red‐to‐NIR Iridium(III) Emitters: Synthesis, Photophysical and Computational Study, the Effects of Cyclometallating and β‐Diketonate Ligands

AbstractIn this work nine novel heteroleptic Ir(III) complexes of general formulae [Ir( #)2( #)] containing four different cyclometallating and four β‐diketonate ligands were synthesized and fully characterized. Six of them display phosphorescence in the deep red and NIR regions with quantum yields reaching 24.6 % in degassed solution for one of the NIR emitters. Variation in the nature of orthometalating ligands results in dramatic changes in photophysical behavior: the compounds containing 2‐phenylpyridine ( 1) and 2‐(benzo[b]thiophen‐2‐yl)pyridine ( 2) ligands give non‐emissive complexes, whereas those with methyl 2‐phenylquinoline‐4‐carboxylate ( 3) and 6‐(benzo[b]thiophen‐2‐yl)phenanthridine) ( 4) are luminescent, but display different character of electronic transitions responsible for absorption and emission. Complexes with the 3 ligand luminesce from 3LC excited state and do not change their emission characteristics upon variations in the nature of β‐diketonates. On the contrary, the compounds based on the 4 cyclometalating ligand emit from the excited state with considerable contribution of 3MLCT character and show systematic bathochromic shift of absorption and emission bands upon increase in electron donicity of # ligands. This conclusion was supported by DFT and TD‐DFT calculations and by the analysis of correlations between the 13C chemical shift of the diketonate C(H) carbon and emission maxima of the compounds under study.

Effect of Aegle marmelos on the growth of brushite crystals

BackgroundThe urinary stone formation is a very common health problem due to the prolonged medication. Calcium Hydrogen Phosphate Dihydrate (CaHPO4.2H2O, CHPD and Brushite) is one of the major constituent of urinary stone crystals. The formation and deposition of brushite crystals is the central cause of recurrent kidney stone disease among the global population. The present study aims to investigate the effect of Aegle marmelos leaves on the growth of brushite crystals to explicate the inhibitory effect of urinary stones from a different point of view.MethodsThe CHPD crystals were grown by the Single Diffusion Gel growth technique. In order to inhibit the formation of urinary stones, CHPD crystals are grown in the laboratory in the pure form and by adding the prolonged medicine A. marmelos taken especially by diabetic patients. A comparative study of the pure and A. marmelos leaves added crystals has been carried out using the Growth factor, Powder X-ray diffraction, Microstructural parameters, FTIR and SEM-EDAX.ResultsTotal mass of the grown crystals is found to decrease with increasing concentrations of leaf extract of the A. marmelos. On comparing with undoped, crystalline size of the A. marmelos doped samples is reduced. Disappearance of absorption band and peak shift in the FTIR shows the incorporation of functional groups of A. marmelos. The morphology changes of the treated crystals are assessed in SEM.ConclusionsThe result shows that herbal extracts prepared from A. marmelos have good inhibitory effect on the growth of the brushite urinary stone crystals considered.

Evaluation antioxidant and antibacterial activities of silver nanoparticles synthesized by aqueous extract of Pistacia atlantica

Silver nanoparticles AgNPs were synthesized from an extract of Pistacia atlantica plant. After mixing the silver nitrate solution and extract of P. atlantica leaves, they changed its color to dark brown. UV–vis spectroscopy result showed maximum adsorption at 468 nm, which represents the characteristic surface plasmon resonance of nanosilver. FTIR spectroscopy results recorded a downward shift of absorption bands between 500 and 1700 cm−1 indicting the formation of silver nanoparticles. X-ray crystal analysis showed that the silver nanoparticles are highly crystalline and exhibit a cubic, face-centered lattice with characteristic (111), (200), (220), and (311) orientations. Composition analysis obtained from SEM–EDXA confirmed the presence of elemental signature of silver. Results also showed that biosynthesized AgNPs exhibit remarkable antioxidant activity using DPPH method with IC50 = 0.47 mg/ml. In addition, synthesized AgNPs were also found to control the growth of E. coli, S. aureus and Acinetobacter baumnnii on nutrient medium with 13, 12 and 11 mm mm zone of inhibition, respectively. The main compounds that were identified in the methanolic and the ethanolic extracts of P. atlantica Desf are ascorbic acid, gallic acid, tannic acid, rutin, and quercetin which were performed by HPLC technique. The AgNPs synthesized from the leaf extract of P. atlantica can be a good method for the preparation of various nano formulations.

Synthesis and Properties of Dibenzothiophene Embedded Heteroporphyrins.

A series of new stable dibenzothiophene embedded heteroporphyrins were synthesized in 6-7% yields by condensing 1 equiv of dibenzothiophene-based tripyrrane with 1 equiv of four different diols, 2,5-bis(hydroxymethyl)heterocycles (furan, thiophene, selenophene, and tellurophene), under mild acid-catalyzed conditions in CH2Cl2. The formation of dibenzothiophene embedded heteroporphyrins was confirmed by high-resolution mass spectrometry and thoroughly characterized by 1D and 2D nuclear magnetic resonance (NMR) spectroscopy, absorption, electrochemical, and density functional theory/time-dependent density functional theory (DFT/TD-DFT) studies. The NMR studies indicated that the macrocycles were nonaromatic in nature. The electronic properties of the macrocycles were significantly altered as the heterocycle of the macrocycles was varied from furan to thiophene, selenophene, and tellurophene, as reflected clearly in the spectral and electrochemical properties. The macrocycles exhibited a sharp band in the region of 420-440 nm and a relatively broad absorption band(s) in the higher wavelength region of 550-800 nm. The oxa analogue was considerably blue-shifted as compared to the other macrocycles, whereas the tellura analogue exhibited relatively broadened and red-shifted absorption bands. Upon protonation of these macrocycles, the resulting diprotonated species displayed bathochromically shifted absorption bands, which were extended to the NIR region. DFT studies revealed that the macrocycles were highly distorted and strained and exhibited half chair conformation with restricted π-conjugation and confirmed their nonaromatic nature due to the lack of planarity of the macrocycle. TD-DFT studies were in agreement with the experimental spectral and electrochemical results.

Design of flexible dendritic systems bearing donor-acceptor groups (pyrene-porphyrin) for FRET applications

Herein, we report the synthesis and characterization of a novel series of dendritic compounds, bearing peripheral pyrene groups and a porphyrin core, of zero and first generation with different spacer lengths. These compounds were further metallated with Zn(II) and Mg(II). The optical properties of these dendritic molecules were studied by absorption and fluorescence spectroscopy. After metallation, the dendritic porphyrins exhibited a red shift in the Soret absorption band and a blue shift in the emission band. All compounds exhibited high energy transfer efficiency, reaching values of EFRET above 99%.

Synergistic Recognition-Triggered Charge Transfer Enables Rapid Visual Colorimetric Detection of Fentanyl.

As a new psychoactive substance, abuse of fentanyl (FTN) is currently spreading around the world, resulting in an urgent need of on-site and rapid analytical methods for detection of FTN. Here, we present a synergistic recognition strategy for rapid, cost-effective, selective, sensitive, and visual colorimetric detection of FTN by taking advantage of Rose Bengal (RB) as the specific probe. This assay is based on the halogen- and hydrogen-bonding interactions between them, generating a charge transfer and accompanying a red shift in the RB absorption band as well as color change from red to purple. The utility of the present visual colorimetric assay is demonstrated in aqueous solution, diluted urine, and domestic sewage samples. A detection limit of 0.7 mg·L-1 in aqueous solution is achieved, and the naked-eye detection of FTN is also realized in different real matrices within 6 min. Moreover, this method is insusceptible to interference from various substances (other opioids, cutting agents of street drugs, FTN precursors, amino acids, and small-molecular amines). Additionally, we successfully fabricate a smartphone-based portable device to determine FTN, which is appropriate for field tests. The present work not only provides the first visual assay for FTN but also reveals the molecular structure-property relationship, which will guide the design and development of various probes for recognizing FTN.

The Effect of Alkyl Substitution of Novel Imines on Their Supramolecular Organization, towards Photovoltaic Applications.

Three novel conjugated polyazomethines have been obtained by polycondensation of diamines consisting of the diimine system, with either 2,5-bis(octyloxy)terephthalaldehyde or 9-(2-ethylhexyl)carbazole-3,6-dicarboxaldehyde. Partial replacement of bulky solubilizing substituents with the smaller side groups has allowed to investigate the effect of supramolecular organization. All obtained compounds have been subsequently identified using the NMR and FTIR spectroscopies and characterized by the thermogravimetric analysis, differential scanning calorimetry, cyclic voltammetry, UV–Vis spectroscopy, and X-ray diffraction. Investigated polymers have shown a good thermal stability and high glass transition temperatures. X-ray measurements have proven that partial replacement of octyloxy side chains with smaller methoxy groups induced a better planarization of macromolecule. Such modification has tuned the LUMO level of this molecule and caused a bathochromic shift of the lowest energy absorption band. On the contrary, imines consisting of N-ethylhexyl substituted carbazole units have not been so clearly affected by alkyl chain length modification. Photovoltaic activity of imines (acting as a donor) in bulk-heterojunction systems has been observed for almost all studied compounds, blended with the fullerene derivative (PCBM) in various weight ratios.

Singlet fission in nanoaggregate of bis(phenylethynyl) derivative of benzene (BPEB): High energy triplet exciton generation with >100 % yield

1,4-bis(phenylethynyl)benzene (BPEB) is observed to show a prominent ∼0.17 eV red shift of absorption band due to monomer-aggregate conversion. Along with the absorption band shift it also causes nearly one order reduction in both emission yield and singlet lifetime. The ultrafast transient absorption measurements show annihilation free decay of singlet excitons with ∼40 ps lifetime for this nanoaggregate. Concomitant growth of triplet excitonic absorption and ground state bleach signal with similar time constant ensures presence of singlet fission (SF) process in the present system. Flash photolysis study indicates separated triplet exciton yield of ∼139 % and its decay with ∼4.4 ms lifetime. Observation of triplet-triplet annihilation (TTA) and resultant delayed fluorescence process in this NA also confirms the near-isoergic or endoergic nature of SF process. It also indicates the presence of high energy triplet excitonic state which can be utilized to boost the silicon solar cell efficiency or sensitize other materials having application in photodynamic therapy or near-IR phosphorescence based bio-imaging.

Conjugated Bis(triarylboranes) with Disconnected Conjugation

AbstractA series of methylene‐bridged bis(triarylboranes) has been synthesized via two complementary routes using metal‐free catalytic Si/B exchange condensation under mild conditions. The title compounds comprise two borane moieties that show effective internal π‐conjugation involving the respective boron centers and the adjacent hetaryl groups. Conjugation between both borane units, however, is disrupted by the aliphatic linker. Cyclic voltammetry revealed minimal electronic communication between the boron centers, as evidenced by two closely spaced reduction processes. The UV‐vis spectra showed bathochromic shifted absorption bands compared to related monoboranes, which is attributed to the methylene bridge. A further red‐shift results upon introduction of methyl or SiMe3 groups at the terminal thiophene rings.

1H-indole-based chemosensors for the sequential recognition of Hg2+ and CN− ions

Abstract Сhemosensors based on 1H-indole, 1H-benzo[e]indole, and 1H-benzo[g]indole were synthesized. According to 1H, 13C NMR, X-ray diffraction study and DFT calculations, they exist predominantly in keto form, which absorbs at 371–404 nm and exhibit a low-intensity fluorescence at 454–527 nm. Recognition of Hg2+ cations in acetonitrile results in a bathochromic shift of the long-wave absorption band by ∼20 nm, accompanied by a “naked-eye” effect that causes the colorless solution to turn bright yellow. At the same time, the emission of sensors is completely quenched. The in situ mercury(II) complexes sequentially and selectively detect CN− anions with full restoration of the initial absorption and fluorescence spectra. The fluorescence “on–off–on” cycles generated by the consistent addition of Hg2+ and CN− ions provide the obtained compounds with the properties of ionochromic molecular switch. The values of the limit of detection are 1.8 and 0.83 μМ for Hg2+ and CN− ions, respectively.

Impact of Microwave Irradiation Energy Levels on Molecular Rotation, Structural, Physicochemical, Proximate and Functional Properties of Potato (Ipomoea batatas) Starch

Starch isolated from potato was subjected to microwave treatment at different energy levels (200 - 800 W) to modify the functional, structural and physicochemical properties, as well as induce molecular rotation of the hydroxyl group on the starch polysaccharide. Proximate analyses revealed that moisture content reduced, while ash, protein, fat and fibre increased after modification. Fourier-transform infrared spectroscopy spectra indicated a strong shift in absorption band of OH from 3441 to 3454 cm-1. Optical light microscopy revealed that starch granules were oval and spherical in shape with hyla on some of the granules. Least gelation concentration reduced following microwave treatment. Compared with the native starch, the pasting parameters of the microwave treated starches decreased, with the exception of set­back viscosity for starch modified at 800 W. Onset temperature (TO), peak temperature (TP) and conclusion temperature (TC) of gelatinization increased in microwave treated starches compared with native potato starch. Also, gelatinization enthalpy increased from 8.21 J/g in native starch to 15.39, 16.36, 17.76 and 38.06 J/g in microwave treated starches at 200, 400, 600, and 800 W, respectively. It was concluded that the energy of microwave irradiation can induce and accelerate molecular rotation of the hydroxyl group on the starch polysaccharide.

Shift of CO2-I absorption bands in diamond: A pressure or compositional effect? A FTIR mapping study

Infra-red maps and profiles with high spatial resolution were obtained for two single crystal diamonds with pronounced CO2 IR absorption peaks. Detailed examination allows unambiguous assignment of the spectral features to solid CO2-I phase. It is shown that the distribution of IR band positions, intensities and widths in the sample follows regular patterns and is not chaotic as was suggested in previous works where spectra of a few individual spots were analysed. Consequently, pressure effects alone fail to explain all observed features and shifts of the CO2 bands. Experimental data can be explained by presence of impurities (such as water, N2, etc.) in the trapped CO2. This implies that spectroscopic barometry of CO2 microinclusions in diamond may be subject to poorly controlled bias. However, barometry is still possible if Davydov splitting of the CO2-I ν2 band is unequivocally observed, as this indicates high purity of the CO2 ice.

Theoretical investigations about the effect of electron-withdrawing groups on proprieties of A-π-D-π-A type small molecules donor for organic solar cells.

Taking the reporting donor SM0 as reference, three new A-π-D-π-A type small molecules donors (SM1, SM2, and SM3) were designed via replacing acceptor moieties. The molecular proprieties affecting the cell performance, such as, frontier molecular orbital, open circuit voltage (Voc), absorption spectrum, vertical and adiabatic ionization potential, vertical and adiabatic electronic affinity, and energy driving force ΔEL-L were investigated through the density functional theory (DFT) and the time dependent density functional theory (TD-DFT). All new designed molecules exhibit reduced energy gap, show a red shift absorption band, small energy binding Eb, moderate Voc, and improve the creation of hole and electron as compared to SM0, which demonstrate that these new designed molecules could be used as a promising donors materials for organic solar cell. Additionally, the three new designed molecules present a larger amount charge transfer qCT, a longer length charge transfer DCT than SM0 and have a smaller reorganization energy of hole λ(h) which improve the charge carrier mobilities.

Temperature induced changes in the optical properties of skin in vivo

Knowledge of temperature-induced changes of skin optical properties is required for accurate dosimetry of photothermal treatments. We determined and compared in vivo optical properties of mouse ear skin at different temperatures. The diffuse reflectance, total and diffuse transmittance were measured in the spectral range from 400 to 1650 nm using an integrating sphere spectrometer at the temperatures of 25 °C, 36 °C and 60 °C. Target temperatures were attained and maintained using an automated heater equipped with a sensor for feed-back and control. Temperature and temperature induced morphological changes of skin were monitored using an infrared thermal camera and reflectance confocal microscopy, respectively. An inverse Monte Carlo technique was utilized to determine absorption, scattering, and anisotropy factors from the measured quantities. Our results indicate significant differences between the optical properties of skin at different temperatures. Absorption and scattering coefficients increased, whereas anisotropy factors decreased with increasing temperature. Changes in absorption coefficients indicate deoxygenation of hemoglobin, and a blue shift of water absorption bands. Confocal imaging confirmed that our observations can be explained by temperature induced protein denaturation and blood coagulation. Monitoring spectral responses of treated tissue may become a valuable tool for accurate dosimetry of light treatments.

Structural, dielectric, and magnetic studies based on MWCNTs/NiFe2O4/ZnO nanoparticles dispersed in polymer PVA/PEO for electromagnetic applications

The hydrothermal and the co-precipitation methods were used for the formation of new multifunctional MWCNTs/NiFe2O4/ZnO (MNFZ) hybrid nanostructures. The MNFZ hybrid nanostructure formation was asserted by characterizing it via the X-ray diffraction (XRD) analysis and TEM. Then, the casting technique was used for preparing the MNFZ nanoparticle-doped Poly (vinyl alcohol) (PVA) and poly (ethylene oxide) (PEO) by various concentrations of MNFZ NPs as nanofiller. All polymer blend and nanocomposite films are shown by XRD studies to have a semicrystalline nature with a reduced degree of semi-crystallinity with the dopant. The infrared absorption band shift and the intensity change indicate the interaction or complexation between the blend and nanofiller is confirmed by FTIR studies. The volume percentage variation of the nanoparticles and the ferromagnetic response variation of the nanocomposite were in consistency. The dielectric characteristics and ac conductivity of the film polymer blend were higher upon adding the nanofiller because the charge carrier number was higher. Such features of MNFZ-doped PVA/PEO films prove their appropriateness as materials for electromagnetic applications.

Enhanced removal of organic dye by activated carbon decorated TiO2 nanoparticles from Mentha Aquatica leaves via ultrasonic approach

The development and investigation of environmental-friendly photocatalysts remain a challenge for eco-system remediation concerns. Herein, an ultrasonically-driven, biogenic, green synthesis of titanium dioxide (TiO2) nanoparticles (NPs) utilizing the extract of Mentha Aquatica leaves is reported. The TiO2 nanoparticles were further functionalized with carbon (TiO2@Carbon). The product composition and structure were examined through Raman, BET, and XPS analysis. The XRD studies of the TiO2 NPs confirmed the anatase phase of nanostructures. The TiO2@Carbon NPs displayed enhanced photocatalytic activity(doubled) compared to pristine TiO2 due to their increased surface area, a bathochromic shift in the optical absorption band, and effective charge separation. Significantly, greater than 90% RhB dye was decayed during the photocatalytic oxidation method, which is validated via trapping active species experiment. Carbon is a powerful substrate for the TiO2 hybrid and can be reused over successive five catalytic cycles. The experimental results demonstrated the TiO2@Carbon as a potential candidate for highly-efficient, eco-friendly, reusable, cost-effective photocatalyst.

The effect of the concentration of the stabilizer in the formation of a silver nanoparticle on the phenomenon of Surface Plasmon Resonance (SPR) as an active material for biosensor

It has been successfully synthesized silver nanoparticles by chemical reduction methods. Silver nitrate (AgNO3) is used as a metal precursor and trisodium citrate as a reducing agent with varying concentrations of the stabilizer PVA. The UV-Vis spectrometer shows that increasing the mass concentration of the stabilizer can sharpen the surface plasmon maximum absorption band and there is a shift in the maximum absorption band towards a larger wavelength. This shift occurred from a wavelength of 428.79 nm at a PVA concentration of 0.85 ppm shifted to a wavelength of 429.01 nm, 430.93 nm and 434.13 nm for each PVA concentration of 1.70 ppm, 2.55 ppm and 4.25 ppm. The observation results of the SPR phenomenon showed a shift in the SPR angle when a thin layer of silver as the active ingredient of the sensor was coated with silver nanoparticles. This addition also sharpens the reflectance value. The SPR angle shift and the increase in reflectance value are caused by changes in the surface plasmon wave constant, which becomes a reference that the SPR phenomenon by modifying the sensing surface using an additional layer of silver nanoparticles can increase its sensitivity.