Absorption Spectra Of Solutions Research Articles

Highly sensitive free-base-porphyrin-based thin-film optical waveguide sensor for detection of low concentration NO2 gas at ambient temperature

Meso-5,10,15,20-tetrakis-(4-tertbutyl phenyl) porphyrin was synthesized using Adler–Longo method and was served as sensing material. Electronic absorption spectra of the porphyrin chloroform solution and its thin film were studied comparatively. An optical waveguide sensor based on free-base porphyrin was fabricated by spin coating method. Absorption variation of porphyrin film was studied before and after exposure to NO2, H2S, SO2, and volatile organic gases. XRD patterns of porphyrin film before and after exposure to analytes (NO2, SO2, and H2S) were provided, and light source of the OWG testing system was selected. This facile-prepared sensor exhibited high sensitivity and selectivity to NO2 with fast response time of 3 s and slow recovery time of 10 min or so and was capable of measuring NO2 down to 10 ppb at ambient temperature. Scanning electron microscopy was employed to characterize film morphology before and after contact with NO2. Film thickness was measured before (71.3 nm) and after (76.8 nm) exposure to NO2, and film thickness variation value (5.20 nm) was calculated. The sensing behavior of the studied sensing device was tested through mixture of H2S, SO2, and VOC gases with NO2 and without NO2 for determination of the selectivity of the device. Film stability was probed by UV–Vis spectra, and response values of sensing element to NO2 gas were detected after several days of film preparation, and its RSD value was 1.66%.

Nanotechnologies of the Treatment and Production of Complex Transition Metal Oxides with High Photothermal Effect

The ability to create biofunctional nanoparticles of A х O · BО y complex oxides (A = K, Н, Na; B = Ti, Mo, W; 0 < x < 2; y = 2, 3) produced via self-propagating high-temperature synthesis is considered in the present study. Nanoparticles (5–10 nm) and stable aqueous colloidal solutions on their basis are obtained via fragmentation, nanoparticle size separation, magnetic separation, and functionalization with biocompatible gels (starch and polyvinyl pyrrolidone). The optical methods for controlling nanoparticle sizes in solution are developed as well. The optical absorption spectra of colloidal solutions of K x WO3 nanoparticles are acquired at wavelengths of λ =1.45 and 1.56 μm and the monochromatic absorption coefficients of bronze nanoparticles are measured at colloid concentrations of 10 to 35 mg/mL. Evaluation of photothermal effects reveals that the greatest impact of laser radiation (λ = 1.45 μm) is achieved in K0.4WO3 nanoparticles. Powdered K x TiO2 complex oxide subjected to mechanical treatment is found to gain magnetic properties. The electrical conductivity of K x TiO2 powder is measured versus temperature over a range of 25–270°С and is shown to be an order of magnitude greater with rising temperature to ~200°С. Data gathered in this study can be used for creation of biofunctional nanomaterials with high photothermal effects.

Synthesis of a selective ratiometric fluorescent probe based on Naphthalimide and its application in human cytochrome P450 1A

Cytochrome P450s have brought considerable attention to researchers for their significant correlations with metabolic behaviors of procarcinogenic chemicals. To better understand the roles of CYP1A in biological and physiological systems, we developed a novel ratiometric fluorescence probe N-((2-hydroxyl ethoxy) ethyl)− 4-methoxy-1, 8-naphthalimide (NEMN) allowing for selectively and sensitively monitoring the target enzymes under physiological conditions and living cells. The probe was designed based on substrate predilection of CYP1A and its outstanding O-dealkylation capacity, and 1, 8-naphthalimide was chosen as fluorophore on account of its desirable photophysical properties. Absorption and emission spectra of the probe solution and reacted metabolism showed obvious red-shift with remarkable colour changes, which indicated that NEMN could be a promising ratiometric detector of CYP1A. Additionally, the selectivity assays displayed that NEMN only sensitive to CYP1A1 and CYP1A2 enzymes with scarce interference of other CYPs. Furthermore, the excellent linear relationships between the ratio of fluorescent intensities and incubation time and enzymes concentration signified time- and concentration- dependence of the probe, which were of desire benefit to quantify and monitor the CYP1A-involved biological behaviors in physiological conditions. The assay in real living samples (Human liver microsomes) further proved the analytical utility of the probe. Finally, the cytotoxicity assay and confocal fluorescence imaging demonstrated that this probe was of great promise for detecting the activity of endogenous CYP1A in human living cells.

(D−π−A)3−Type metal-free organic dye for dye-sensitized solar cells application

Three novel (D−π−A)3−type metal-free organic dyes (PTZTC1−3) along with a reference dye (RD−SC) bearing a mono D−π−A unit, comprising 4-positon substituted phenyl coupled with phenothiazine as a donor, thiophene as a π-conjugated linker and cyanoacrylic acid as an acceptor, were synthesized. The UV–Vis absorption spectra in solution and on TiO2 film, electrochemical redox potentials, and the photovoltaic parameters including incident monochromatic photon-to-current conversion efficiency (IPCE), short-circuit current (Jsc), open-circuit voltage (Voc), maximum power conversion efficiency (η), and electrochemical impedance spectroscopy (EIS) of the corresponding dye-sensitized solar cells (DSSCs) were further explored. Among the DSSCs fabricated with these dyes, the PTZTC3 sensitized cell showed a η of 6.09% under standard global AM 1.5 solar condition (100 mW cm−2) owing to its relatively higher IPCE, higher Jsc, higher Voc and longer electron lifetime (τr).

Two wide-bandgap fluorine-substituted benzotriazole based terpolymers for efficient polymer solar cells

In this work, the fluorine substituted benzotriazole (FBTz) unit is introduced into terpolymers for the first time. FBTz as an acceptor unit was added to the terpolymers of PTT-FBTz and PTTz-FBTz, in which the bithiophene (biTh) unit is used as the donor unit and thieno[3,2-b]thiophene (TT) or thiazolo[5,4-d]thiazole (TTz) is adopted as a third component, respectively. Compared to PTT-FBTz with TT as the third component, PTTz-FBTz with TTz showed pronounced aggregated shoulder peaks both in solution and film absorption spectra. Electrochemical cyclic voltammetry (CV) shows PTTz-FBTz possesses both lower HOMO/LUMO level than PTT-FBTz due to the higher electronegativity of nitrogen atoms in TTz unit. Subsequently, the bulk-heterojunction polymer solar cells (PSCs) based on PTTz-FBTz show a higher power conversion efficiency of 7.03%, which is much higher than those of PTT-FBTz based devices (PCE = 2.63%). The enhancement of photovoltaic performance based on PTTz-FBTz is mainly attributed to the deeper highest occupied molecular orbital (HOMO) level, higher carrier transport and better molecular packing.

The role of metals and dithiolate ligands on structural, electronic and optical properties of [M(bipyridine)(dithiolate)] complexes: A theoretical study

A series of [M(diimine)(dithiolate)] complexes of general formula [M(bpy)(dithiolate)] {bpy=2,2′-bipyridine;dithiolate=1,2-benzenedithiolate (bdt2−), 3,4-toluenedithiolate (tdt2−) and 4-cyanobenzene-1,2-dithiolate (cbdt2−); M=Ni(II), Pd(II) and Pt(II)} have been studied by density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations. The geometries, stabilities, electronic structures, optical absorption spectra in different phases as well as thermodynamic parameters are explored. The changes of metal ion center and dithiolate ligands on some molecular properties are also discussed. These calculated results are in good agreement with the experimental data. The bonding analyses show that the MS bond is covalent so that always polarized towards sulfur atom, whereas the MN bond exhibits a considerable amount of electrostatic interaction. Detailed NBO analysis indicates that these complexes can be easily oxidized than reduced, and acts as the reducing agent. The HOMO-LUMO energy gaps of all complexes under study are founded about 2eV and the strong absorption from 400 to 700nm which match with the solar spectra very well. Besides, the simulated absorption spectra are in accordance with the trends of energy gaps. Comparison of the absorption spectra in dichloromethane solution with those in gas phase show that the solvatochromic effect. The order of magnitude for light harvesting efficiencies (LHE) of all complexes is Pt>Pd>Ni and cbdt2−>bdt2−>tdt2−. Our results confirm the effect and role of metals and dithiolate ligands on enhancing the optical properties of these complexes. Thus, the result of this work can serve as a rational tool for the design and synthesis of diimine-dithiolate complexes and broadens the scope for further investigations into potential dyes for use in the field of dye-sensitized solar cells (DSSC).

Unexpected solvent effects on the UV/Vis absorption spectra of o-cresol in toluene and benzene: in contrast with non-aromatic solvents.

Cresol is a prototype molecule in understanding intermolecular interactions in material and biological systems, because it offers different binding sites with various solvents and protonation states under different pH values. It is found that the UV/Vis absorption spectra of o-cresol in aromatic solvents (benzene, toluene) are characterized by a sharp peak, unlike the broad double-peaks in 11 non-aromatic solvents. Both molecular dynamics simulations and electronic structure calculations revealed the formation of intermolecular π-complexation between o-cresol and aromatic solvents. The thermal movements of solvent and solute molecules render the conformations of o-cresol changing between trans and cis isomers. The π-interaction makes the cis configuration a dominant isomer, hence leading to the single keen-edged UV/Vis absorption peak at approximately 283 nm. The free conformation changes between trans and cis in aqueous solution rationalize the broader absorption peaks in the range of 260–280 nm. The pH dependence of the UV/Vis absorption spectra in aqueous solutions is also rationalized by different protonation states of o-cresol. The explicit solvent model with long-ranged interactions is vital to describe the effects of π-complexation and electrostatic interaction on the UV/Vis absorption spectra of o-cresol in toluene and alkaline aqueous (pH > 10.3) solutions, respectively.

Investigation the concentration effect on the absorption and fluorescence properties of Rhodamine 6G dye

Concentration dependence of the optical absorption and fluorescence spectra of Rhodamine 6G dye solution have been investigated. Shift the absorption and the fluorescence peaks with an increase the dye concentration, from 0.1 to 250 μM, is studied. By measuring the absorbed and the fluorescence spectra of Rhodamin 6G dye, enhancement of the absorbance and quenching of the fluorescence intensity are obtained. Observed fluorescence quenching of Rhodamine 6G after 60 μM is caused by the collisional mechanism. From 0.1 to 30 μM, the absorbance obeys the Beer-Lambert law. While, beyond 30 μM, due to contributions of the dimers and aggregation of dye molecules, the absorbance deviates from the Beer-Lambert law.

Kinetics of Crystalline Iodine Dissolution in Ethanol at Room Temperature and at 60°С

The kinetics of crystalline iodine dissolution in ethanol at room temperature and 60°C is studied using the electronic absorption spectra of iodine solutions. Dissolution is shown to proceed for more than three months. It is found that the process begins with the formation of hydroiodic acid HI and is complete with the formation of I 3 − anions.

Tunable Electron Donating and Accepting Properties Achieved by Modulating the Steric Hindrance of Side Chains in A-D-A Small-Molecule Photovoltaic Materials

Modulation of the electron donating and accepting properties of organic semiconductors is an important topic in the field of organic photovoltaics. Although the small-molecule semiconductors (SMs) with an A-D-A structure can act as either electron donor or acceptor in organic photovoltaic (OPV) devices, the reason why molecules with similar conjugated structures play different roles remains unclear. In this work, we designed and synthesized two A-D-A SMs named BTCN-O and BTCN-M, which have an identical backbone and differ in the alkyl substitution position. BTCN-O and BTCN-M demonstrate similar optical absorption spectra in solution and molecular energy levels in a solid film. BTCN-O forms an ordered lamellar packed structure with compact π–π stacking, whereas BTCN-M demonstrates only a weak π–π stacking effect in solid film. We also investigated their photovoltaic properties by blending each with a polymer donor, PBDB-T, and a fullerene acceptor, PC71BM, and found that the electron donating and accepting...

Efficient Calculation of Absorption Spectra in Solution: Approaches for Selecting Representative Solvent Configurations and for Reducing the Number of Explicit Solvent Molecules

Efficient Calculation of Absorption Spectra in Solution: Approaches for Selecting Representative Solvent Configurations and for Reducing the Number of Explicit Solvent Molecules

Theoretical study on the effect of solvents in chlorophyll solution for Dye-Sensitized Solar Cell

Using the density functional theory (DFT) and time-dependent DFT (TD-DFT), we have theoretically studied the electron excitation and absorption spectra of chlorophyll solution with several solvents for Dye-Sensitized Solar Cell (DSSC) application. The solvents were aceton, acetonitrile, DMSO, ethanol, hexane, methanol, THF and water. Also, energy level, oscilator strength, light harvesting efficiency and electron injection have been investigated. The studied dye in the presence of the solvents showed a smaller gap of the highest occupied molecular orbital (HOMO) - the lowest unoccupied molecular orbital (LUMO) and a higher light harvesting, oscillator strength and red shift in the absorption spectra. These changes facilitate the charge transfer phenomena in the nano structure of the chlorophyll as dye and improve the solar cell efficiency.

Multi-scale theoretical approach to X-ray absorption spectra in disordered systems: an application to the study of Zn(ii) in water.

We develop a multi-scale theoretical approach aimed at calculating from first principles X-ray absorption spectra of liquid solutions and disordered systems. We test the method by considering the paradigmatic case of Zn(ii) in water which, besides being relevant in itself, is also of interest for biology. With the help of classical molecular dynamics simulations we start by producing bunches of configurations differing for the Zn(ii)-water coordination mode. Different coordination modes are obtained by making use of the so-called dummy atoms method. From the collected molecular dynamics trajectories, snapshots of a more manageable subsystem encompassing the metal site and two solvation layers are cut out. Density functional theory is used to optimize and relax these reduced system configurations employing a uniform dielectric to mimic the surrounding bulk liquid water. On the resulting structures, fully quantum mechanical X-ray absorption spectra calculations are performed by including core-hole effects and core-level shifts. The proposed approach does not rely on any guessing or fitting of the force field or of the atomic positions of the system. The comparison of the theoretically computed spectrum with the experimental Zn K-edge XANES data unambiguously demonstrates that among the different a priori possible geometries, Zn(ii) in water lives in an octahedral coordination mode.

Detecting order and lateral pressure at biomimetic interfaces using a mechanosensitive second-harmonic-generation probe.

A planarizable push-pull molecular probe with mechanosensitive properties was investigated at several biomimetic interfaces, consisting of different phospholipid monolayers located between dodecane and an aqueous buffer solution, using the interface-specific surface-second-harmonic-generation (SSHG) technique. Whereas the SSHG spectra recorded at liquid-disordered interfaces were similar to the absorption spectra in bulk solutions, those measured at liquid-ordered phases exhibited a remarkable shift towards lower energies to an extent depending on the surface pressure of the phospholipid monolayer. On the basis of quantum-chemical calculations, this effect was accounted for by the planarization of the mechanosensitive probe. Polarization-resolved SSHG measurements revealed that the average orientation of the probe at the interface is an even more sensitive reporter of lateral pressure and order than the spectral shape. Additionally, time-resolved SSHG measurements pointed to slower dynamics upon intercalation inside the phospholipid monolayer, most likely due to the more constrained environment. This study demonstrates that the concept of mechanosensitive optical probes can be further exploited when combined with a surface-selective nonlinear optical technique.

Synthesis and Physicochemical Properties of Nickel-Containing Nanoparticles

Ni and Ni/Pd nanoparticles stable in the liquid phase and in the adsorbed state were prepared by radiation-chemical reduction of metal ions in aqueous-organic inverse micellar solutions. The optical absorption and luminescence spectra of nanoparticle solutions were studied immediately after preparation in the presence of oxygen and without it. Changes in these spectra, resulting from evolution of the nanoparticles in the course of storage and from pH variation, were examined.

Effects of electron donor on luminescence and mechanochromism of D-π-A benzothiazole derivatives

Two benzothiazole derivatives with triphenylamine (CBVD) and phenothiazine (CBVP) moieties as electron donor groups were prepared, and their solid luminescence and mechanofluorochromism (MFC) were investigated and compared. Solvent-dependent fluorescence spectra and quantum chemical calculation indicate that the luminescence of both compounds originates from the intramolecular charge transfer transition. Although the two compounds have similar absorption spectra in solution, CBVP possesses red-shifted fluorescence as compared with CBVD. Similar to that in solution, CBVP in crystal state has longer emission wavelength than CBVD in crystal state. Crystal structures indicate that their molecular stacking models in crystal phases are different. J-aggregate and H-aggregate coexist in CBVD crystal, whereas only H-aggregate was observed in CBVP crystal. Moreover, CBVP exhibits reversible luminescence color change from yellow to orange-red with a spectral shift of 36 nm under mechanical force stimuli, whereas CBVD has a spectral shift of only 20 nm, indicating poor color contrast. UV–Vis absorption spectra show that the mechanical force induces the disappearance of H-aggregate in CBVD crystal and leads to stacking model transition from H-aggregation to J-aggregation in the CBVP system.

Optical limiting of germanium(IV) and tin(IV) phthalocyanines in solution and polymer matrices and comparison to an indium(III) phthalocyanine

A series of peripheral and axial substituted germanium(IV) and tin(IV) phthalocyanines substituted by fluoro, chloro, nitro or phenoxy groups were prepared and characterized by their absorption spectra in solution and in polymer matrices. Multi-layer films of PMMA and PVC containing monomolecular Ge(IV) or Sn(IV) phthalocyanines were obtained by spin-coating from solution on glass plates. Optical limiting properties of these phthalocyanines in solution and in polymer films were investigated using the Z-scan technique at 532 nm. A known indium(III) phthalocyanine was also investigated to compare its optical limiting behavior with the Ge(IV) and Sn(IV) containing compounds. Ge(IV) and Sn(IV) phthalocyanines exhibit a better optical limiting performance in polymer matrices than in solution, which is interesting for practical applications.

In situ Measurement of the pH-dependent Transmission Infrared Spectra of Aqueous Lactic Acid Solutions.

The transmission infrared absorption spectra of an aqueous lactic acid solution was measured over a pH range of 2.66 - 1.59 using a cell with an optical path length of 12 μm. Absorption peaks were then identified by density functional theory (DFT) calculations. The observed pH-dependent changes in the absorbance spectra were consistent with the properties of the assigned functional groups. We therefore believe that the present method can be applied to the contactless and non-invasive quantitative evaluation of pH values in aqueous systems, such as bioprocesses and bioimaging.

Microwave-assisted and conventional synthesis, photophysics and electroluminescence of poly(9,9-dihexadecylfluorene-2,7-diyl-alt-2,2′-bithiophene-5,5′-diyl)

Alternating electroluminescent copolymers, poly(9,9-dihexadecylfluorene-2,7-diyl-alt-2,2′-bithiophene-5,5′-diyl)s (PFC16BTs), were synthesized using two different routes of Suzuki coupling reaction in which either dibromo derivative of fluorene was reacted with diboronic acid ester of bithiophene or vice versa, with microwave-assisted (MA) or conventional (C) heating in high boiling point solvents, chlorobenzene (CB) and xylene (Xy). PFC16BT copolymers with various molecular weights (MW) were obtained depending on the synthetic conditions, and the influence on MW is discussed. The photophysical and electrochemical properties and the electroluminescence (EL) of the PFC16BT copolymers were studied and compared with those of poly(9,9-dioctylfluorene-2,7-diyl-alt-2,2′-bithiophene-5,5′-diyl)s (PFC8BTs) to reveal the impact of MW and the length of side chains on their properties. A slight dependence on the MW was only observed in the absorption spectra in solutions. Photoluminescence (PL) of PFC16BTs solutions emitted green light with a maximum of approximately 500 nm, whereas the PL emission spectra of thin films were redshifted with the maxima at 540 nm. The ionization potential (HOMO level) and electron affinity (LUMO level) values of 5.4 eV and 2.6 eV, respectively, were evaluated for PFC16BTs, which are similar to those for PFC8BTs. The electrochemical bandgap value of 2.8 eV was higher than the value of the optical bandgap of 2.4 eV. The PFC16BT copolymers with various MW were tested as an active layer in light-emitting devices (LEDs), and the results are compared with those of PFC8BT LEDs. The PFC16BT LEDs exhibited a luminance higher than 3500 cd m–2 and low onset voltages of approximately 2 V. The shape of the EL spectra of LEDs is similar to that of PL spectra of the thin films. PL emission of PFC16BT thin films and EL emission were blue shifted compared with those of PFC8BT, indicating a more pronounced aggregation in PFC8BT.

КОЛИЧЕСТВЕННОЕ ОПРЕДЕЛЕНИЕ ЛАМИВУДИНА МЕТОДОМ УФ-СПЕКТРОФОТОМЕТРИИ

HIV infection poses a threat to the existence of humankind as a whole. Currently, lamivudine is widely used in antiretroviral therapy regimens. Modern methods of assessing quality, both in substance and in tablets, are characterized by a number of shortcomings: high cost of equipment, expensive GSO production of the United States. The development of new methods for the analysis of lamivudine, as well as the improvement of existing methods, is an urgent problem. The purpose of this study is to develop a new technique for the quantitative determination of lamivudine by UV spectrophotometric method using a standard sample. The absorption spectrum of lamivudine solutions was studied at different pH values (1.1-14.1) in the wavelength range 200-400 nm. The optimal solvent for the spectrophotometric determination of the test substance was 0.1M HCl (pH 1.1). At pH 1.1, two absorption bands with absorption maxima at wavelengths of 212 ± 1 nm and 279 ± 1 nm are observed in the absorption spectrum of the lamivudine solution. A substance of organic nature, 4,4'-dihydroxyphthalophenone, was chosen as the standard sample for the determination of lamivudine. The maximum absorption of lamivudine (279 nm) is included in the optimal range for 4,4'-dihydroxy-phthalophenone (268-282 nm). The conversion ratio of lamivudine for 4,4'-dihydroxyphthalophenone is 0.1985. The error in determining lamivudine in the substance does not exceed 0.85 %, in tablets -1.6 %. The validation assessment confirmed the compliance of the developed methodology with normative documents and its suitability for analysis.