UV-vis Absorption Measurements Research Articles

Intermolecular Hydrogen Bonding Modulates O-H Photodissociation in Molecular Aggregates of a Catechol Derivative.

The catechol functional group plays a major role in the chemistry of a wide variety of molecules important in biology and technology. In eumelanin, intermolecular hydrogen bonding between these functional groups is thought to contribute to UV photoprotective and radical buffering properties, but the mechanisms are poorly understood. Here, aggregates of 4-t-butylcatechol are used as model systems to study how intermolecular hydrogen bonding influences photochemical pathways that may occur in eumelanin. Ultrafast UV-visible and mid-IR transient absorption measurements are used to identify the photochemical processes of 4-t-butylcatechol monomers and their hydrogen-bonded aggregates in cyclohexane solution. Monomer photoexcitation results in hydrogen atom ejection to the solvent via homolytic O-H bond dissociation with a time constant of 12ps, producing a neutral semiquinone radical with a lifetime greater than 1ns. In contrast, intermolecular hydrogen bonding interactions within aggregates retard O-H bond photodissociation by over an order of magnitude in time. Excited state structural relaxation is proposed to slow O-H dissociation, allowing internal conversion to the ground state to occur in hundreds of picoseconds in competition with this channel. The semiquinone radicals formed in the aggregates exhibit spectral broadening of both their electronic and vibrational transitions.

Anti-cancer study and whey protein complexation of new lanthanum(III) complex with the aim of achieving bioactive anticancer metal-based drugs

In this study, a new lanthanum (III)-amino acid complex utilizing cysteine has been synthesized and characterized. The anticancer activities of the prepared La(III) complex against MCF-7 cell lines were studied. Results of MTT assay showed that at all three incubation times, the cytotoxic effect of prepared La(III) complex on MCF-7 breast cancer cell lines displays a time- and dose-dependent inhibitory effects. The interactions of the La(III) complex with two whey proteins (bovine serum albumin, BSA, and Bovine β-lactoglobulin, βLG) have been explored by using spectroscopic and molecular dicking methods. The obtained results indicated that La(III) complex strongly quenched the fluorescence of two carrier proteins in static quenching mode and also, BSA hah stronger binding affinity toward studied complex than βLG whit binding constant values of KBSA-La Complex ∼ 0.11 × 104 M−1 and KβLG-La Complex ∼ 0.63 × 103 M−1 at 300 K. The thermodynamic parameters revealed the contribution of hydrogen bond and Vander Waals interactions in both systems. The distances of the La(III) complex whit whey proteins were calculated using Förster energy transfer theory and proved existence of the energy transfer between two proteins and prepared La(III) complex with a high probability. FT-IR and UV–Vis absorption measurements indicated that the binding of the La(III) to BSA and βLG may induce conformational and micro-environmental changes of the proteins. The docking results indicate that the La(III) complex bind to residues located in the site II of BSA and second site of βLG.Communicated by Ramaswamy H. Sarma

Elucidation of Electrical and Optical Parameters of Poly(o-anthranilic acid)-poly(o-amino phenol)/Copper Oxide Nanocomposites Thin Films

Copper oxide nanoparticles (CuO-NPs) are prepared based on thermal decomposition method. Polyanthranilic acid (PANA) and poly-o-aminophenol (POAP) are synthesized based on the oxidative polymerization in aqueous medium with potassium dichromate. Thin films are fabricated from PANA/POAP blends and composites of PANA/POAP with 0.25 and 0.40 wt% of CuO-NPs. The resulting thin films are characterized by different techniques such as XRD, SEM and UV–Vis absorption measurements. Surface morphology displays a good level of CuO-NPs distribution in POAP/PANA blends at 0.25 wt%. Initial agglomeration detects at 0.4 wt% concentration of CuO-NPs. It is found that the real dielectric constant (ereal) increases with increasing CuO-NPs content. Transmittance of PANA improves up to 95% in the presence of 50 wt% POAP. I–V characteristics of the PANA/POAP blend and nanocomposite films show a non-ohmic behavior. The obtained results indicate that the poly(o-anthranilic acid)-poly(o-amino phenol)/copper oxide nanocomposites thin film is a good candidate in optoelectronic devices based on its band gap and dispersion parameters.

Synthesis and Characterization of Nickel Oxide Nanostructures by Hydrothermal Method

Nickel oxide (NiO) nanostructures were synthesized by hydrothermal method using ethylene glycol and double distilled water as solvent in 3:2 volume ratio. The synthesized nanostructures were characterized by XRD, FESEM, EDX, FTIR, and UV-visible spectroscopy. XRD result shows that the synthesized nanostructures are polycrystalline in nature. FESEM images show the growth of NiO nanowires. The elemental compositions of the samples were analyzed by EDS. Fourier transform infrared (FTIR) spectroscopy confirms the existence of Ni–O bond in the sample. Optical band gap energy of about 3.71 eV was calculated from the UV-visible absorption measurement.

Fabrication and Photoelectrochemical Performance Optimization of CuInS2 Quantum Dots Sensitized TiO2 Nanonails Array Photoelectrodes

The CuInS2 quantum dots sensitization of TiO2 nanonails (NNs) array was successfully carried out by a successive ionic layer absorption and reaction (SILAR) method using CuCl2 ⋅ 2H2O, InCl3 ⋅ 4H2O and Na2S ⋅ 9H2O as precursors. The morphology, elemental composition and crystalline structure of the CuInS2 quantum dots sensitized TiO2 NNs array heterojunction nanostructures were characterized by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD) and X-ray-photoelectron spectroscopy (XPS). The above characterization results could unanimously reveal that the nanoparticles successfully loaded on the TiO2 NNs array can be assigned as CuInS2 quantum dots. UV-Vis absorption measurements indicated that the CuInS2 quantum dots sensitization extended the visible light absorption. The largest short-circuit photocurrent density of 17.7[Formula: see text]mA/cm2 was obtained, which indicated that the CuInS2 was a promising material in activating visible light functionalities and enhancing photoelectrochemical performance.

Printable MoOx Anode Interlayers for Organic Solar Cells.

Currently, solution-processed MoOx anode interfacial layers (AILs) can only be fabricated by the spin-coating method in organic solar cells (OSCs), which severely limits their use in practical productions where large-area printing techniques are used. Herein, a facile method is demonstrated to prepare highly conductive MoOx (denoted EG:Mo) that can be processed by printing methods such as wire-bar and blade coatings. The EG:Mo films are prepared by depositing an aqueous solution containing ammonium heptamolybdate (VI) tetrahydrate (NMo) and ethylene glycol (EG) and annealing at 200 °C. UV-vis absorption and X-ray photoelectron spectroscopy measurements confirm that Mo (VI) can be reduced to Mo (V) by EG, resulting in the n-doped EG:Mo. Using the EG:Mo as AILs, an OSC based on a PB3T:IT-M active layer exhibits a power conversion efficiency (PCE) of 12.1%, which is comparable to that of the PEDOT:PSS modified devices. More importantly, EG:Mo AILs can be processed by wire-bar and blade-coating methods, and the corresponding devices show PCEs of 11.9% and 11.5%, respectively. Furthermore, the EG:Mo AIL is processed by wire-bar coating to fabricate a large area device (1.0 cm2 ), and a PCE of 10.1% is achieved.

Chitosan hydrogels cross-linked with tris(2-(2-formylphenoxy)ethyl)amine: Swelling and drug delivery

Tris(2-(2-formylphenoxy)ethyl)amine was designed and synthesized by reaction of salicylaldehyde with tris(2-chloroethyl)amine hydrochloride and evaluated as a new multi-functional cross-linker for preparation of new pH- and thermo-responsive chitosan hydrogels through formation of covalent Schiff-base linkage. The structure and properties of the hydrogels were characterized by FT-IR, 1H NMR and scanning electron microscopy (SEM). The swelling behavior of prepared hydrogels at different pHs and temperatures was investigated. Also, in vitro controlled release behavior of the metronidazole model drug was studied with prepared hydrogels. The release profiles of metronidazole from the hydrogels were determined by UV–Vis absorption measurement. The results showed that the new hydrogels exhibit a pH and temperature-responsive swelling ratio. Also, the pH and temperature were found to strongly influence the drug release behavior of these swollen polymers. Due to the concurrent rapid and significant stimuli-response, these smart hydrogels prepared from chitosan as a natural polymer may expand the scope of hydrogel applications in various fields of research such as targeted (cellular or tissue) delivery of drugs. In addition, these new hydrogels can be used to improve bioavailability, sustain release of drugs or solubilize drugs for systemic delivery.

Defect and dopant induced room temperature ferromagnetism in Ni doped ZnO nanoparticles

ZnO nanoparticles were doped with Ni by simple chemical solution deposition method. All the synthesized nanoparticles crystallize in the wurtzite ZnO structure. The UV–Visible absorption measurement shows broad absorption band in the visible range around 440 nm, 618 nm and 660 nm which are d-d transitions characteristic of Ni2+ within the tetrahedral symmetry. Compared to higher doping concentration, 1% Ni doped sample shows higher magnetic moment at room temperature with a saturation magnetization of 0.0123 emu/g. The coercivity of 365 Oe for the 1% doped sample reduces to 217 Oe for 5% Ni doped sample. Fourier Transform Infrared Spectroscopy (FTIR) measurement shows the consistent formation of the characteristic E2 mode in ZnO even after Ni doping and is supported by the Raman measurements. The incorporation of Ni dopant in the ZnO host lattice is further confirmed by X-ray Photoelectron Spectroscopy (XPS) measurement. The prominent visible luminescence in the undoped sample is quenched due to doping as observed from luminescence measurements. Magnetic measurements were also done in the doped samples after annealing. Systematic studies on structural, optical & magnetic measurements reveal that the nature of defects as well as Ni2+ ions are responsible for the magnetic moment obtained at room temperature.

Photoluminescence spectroscopy of CdSe nanoparticles embedded in transparent glass

In this paper we present photoluminescence measurements of CdSe nanoparticles embedded in transparent glass. Sample is prepared using an original technique, which combines both heat treatment and ultraviolet laser irradiation. Photoluminescence spectra displayed one main emission band at 2.14 eV. We identify this bands energy as basic interband transition in CdSe nanoparticle. We calculated energy of basic (1sh–1se) transition in spherical CdSe quantum dot (QD), within infinite potential barrier, in effective-mass approximation. On the basis of this model, average radius of synthesized CdSe QDs is about 3 nm, which is in consistence with AFM measurements and UV–VIS absorption measurements.

An Air-Stable Organoboron Compound, Dithienooxadiborepine: Preparation and Functionalization.

π-Conjugated organoboron molecules, which are easy to prepare, stable against moisture, and easy to functionalize, are scarce. Here, we report a one-pot synthesis of an air-stable organoboron compound, dithienooxadiborepine 1 in 17% yield on a 600 mg scale without separation or handling an air-sensitive intermediate. Dithienooxadiborepine 1 showed excellent stability under ambient conditions, allowing conventional column chromatography purification. Functionalization of 1 was realized via direct bromination using NBS and further Stille coupling reactions, giving access to longer π-conjugated molecules 5A and 5B. Single-crystal structures of compounds 4, 5A, and 5B not only unambiguously verified the chemical identity of dithienooxadiborepine 1 but also revealed that both the seven-member oxadiborepine ring and the 5-7-5 fused dithienooxadiborepine ring system are planar. UV-vis absorption and fluorescence emission measurements of 5A and 5B showed bathochromic shifted absorption and emission relative to 1, evidencing good π-conjugation. Cyclic voltammograms of 5A and 5B displayed two reduction peaks corresponding to two electron-accepting events at two boron atoms. These results proved dithienooxadiborepine 1 a potent π-conjugating building block for electron-accepting materials.

Synthesis and characterization of nano fibrillated cellulose/Cu2O films; micro and nano particle nucleation effects

Cubic, truncated cubic and spherical nano and micro particles of Cu2O, can be selectively deposited onto nano fibrilated cellulose gels by the modulated alkaline reduction of Cu2+ ions aided by the cellulose’s reducing end groups. The role of the cellulose’s reducing end groups and that of externally added carbohydrate reducing agents, towards inducing various Cu2O morphologies, is discussed with respect to the detailed nucleation effects leading to micro and nano Cu2O particle deposition on NFC. When the reducing end groups are provided only by the cellulose’s chain ends, supersaturation effects seem to be affecting the Cu2O nucleation mechanism. However, the Cu2O nucleation considerations were altered when mobile reducing end groups were provided by adding dextrose in the system, promoting additional particle nucleation sites. Furthermore, the effort offered the possibility to quantitatively determine the number of accessible reducing end groups (-CHO) present in NFC, expressed in mmol/g. The optical properties of the created NFC/Cu2O films were examined by UV–vis absorption measurements, revealing band gaps ranging between 2.02–2.25 eV. The accumulated understanding expands the utility window and opens new directions for the novel utilization of nano-fibrillated cellulose, and more specifically toward semiconductor applications.

Photoluminescence properties of SnO2 nanoparticles: Effect of solvents

In the present work, tin oxide nanoparticles were synthesized using chemical co-precipitation method with stannous sulphate and sodium hydroxide as starting materials. The method is simple and quick. The synthesized particles were characterized using powder X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Fourier Transform Infrared spectroscopy (FTIR), UV–Vis optical absorption and fluorescence emission spectroscopy. XRD analysis reveals that the SnO2 sample is in tetragonal structure with crystal size less than 15–20 nm estimated from Scherrer formula. The optical band gap is found to be 4.33 eV from UV–Vis absorption measurements, showing strong quantization. The effect of various solvents on absorption and fluorescence emission is studied. It is found that not only intensity of emission changes with solvent, but emission peak wavelength also changes.

Effects of Annealing Temperature on Structural and Optical Properties Of CIGS Thin Films for Using in Solar Cell Applications

A copper indium0.5gallium0.5selenide2 thin films (CIGS) were deposited at room temperature on glass substrate by thermal evaporation technique. The deposited film were annealed at different annealing temperature (293, 100, 200 and 300)°C. The effect of annealing temperature on structural, optical and electrical properties CIGS films were studied by XRD, UV-Visible absorbance and Hall effect measurements. It is found that the crystallinety enhanced, optical energy gap increases and electrical conductivity decrease with increasing annealing temperature. Three design of solar cells, based on CIGS, were examined to reach the suitable solar cell with higher efficiency.

Bio-synthesis of BiVO4 Nanorods Using Extracts of Callistemon viminalis

AbstractIn this contribution we report on the synthesis of n-type Bismuth vanadate (BiVO4) nanorods prepared via the use of aqueous extracts of Callistemon viminalis. X-ray diffraction analysis confirmed the formation of highly crystalline monoclinic BiVO4 nanorods post annealing of the Bismuth vanadate precursor powder at 500 °C. Scanning Electron Microscopy and High Resolution Transmission Electron Microscopy showed that BiVO4 nanorods have a high aspect ratio. Using UV-Vis absorption measurements the optical band gap of the nanorods is estimated to be 2.4 eV which makes the bio-synthesized BiVO4 powder a good candidate for sunlight driven photocatalysis.

Chemical Events in Oligo(3-methoxythiophene) Coating Solutions and Their Effect on the Goldlike Coating Film Properties.

Metal-free, metal-like lustrous films may find applications in a variety of fields, and a study of the factors affecting their stability is highly desirable. In particular, chemical events occurring in the coating solutions might affect the supramolecular organization of the films and therefore the metal-like luster. Herein, the chemical events occurring in acetonitrile and nitromethane coating solutions of oligo(3-methoxythiophene) and their effect on the optical properties of the films were investigated by X-ray diffraction, UV-vis absorption, and viscosity measurements. In acetonitrile, the oligomers underwent gradual dedoping with time, but only small changes in viscosity were observed. The solution was applied to a glass plate to yield a dark brown film, which turned into a goldlike lustrous film by rubbing. In nitromethane, the supramolecular structure of the oligomers changed with time from the nonaggregated state to π-dimers and then to π-stacks, and the viscosity increased. The properties of the goldlike films prepared from this solution were greatly affected by this chemical event. Remarkably, the π-dimer solution provided the film with the highest specular reflectance, yellowness, greenness, brightness, and crystallinity.

Influence of iron doping on the photocatalytic activity of nanocrystalline TiO2 particles fabricated by ultrasound method for enhanced degradation of organic dye

Synthesis and characterization of Fe doped TiO2 composite with iron concentration varying from 0 to 7% as a photocatalyst in the photodegradation of methylene orange on UV–Vis light irradiation in a closed reactor has been carried out. Synthesis was conducted by the ultrasound method at room temperature using tetrabutyl titanate and iron(III)chloride 6-hydrate as a precursor, followed by thermal treatment at a temperature of 600 °C. The characterizations were performed using X-ray diffraction (XRD), transmission electron microscopy, scanning electron microscopy (SEM), FT-IR spectrometry, thermal analysis, UV–Vis diffuse reflectance spectrophotometer, photoluminescence and Brunauer–Emmett–Teller (BET). XRD spectra revealed that samples crystallized in the anatase phase at 600 °C. The transmission and SEM were used to detect the morphology of synthesized nanoparticles, which sizes changed with the altitude in the doping concentration to 7%. FTIR spectra exhibit broad peaks where anatase phases of TiO2 demonstrate very sharp peaks. In accordance with UV–Vis absorption measurements, this diminution of nanoparticles sizes was followed by a decrease in the band gap value from 3.21 eV, for undoped TiO2, to 2.46 eV, for TiO2 doped at 7%. The TGA showed three mass losses, whereas DTA resulted in three endothermic peaks. The maximum photoconversion efficiency was 2.5%, which was six times the photoconversion efficiency of undoped TiO2. Finally, the prepared materials were used to photocatalyse the decolourization of methylene orange in aqueous medium as a model compound under the illumination of visible light (λ = 420 nm).

Application of Electrochemical Devices to Characterize the Dynamic Actions of Helicases on DNA.

Much remains to be understood about the kinetics and thermodynamics of DNA helicase binding and activity. Here, we utilize probe-modified DNA monolayers on multiplexed gold electrodes as a sensitive recognition element and morphologically responsive transducer of helicase-DNA interactions. The electrochemical signals from these devices are highly sensitive to structural distortion of the DNA produced by the helicases. We used this DNA electrochemistry to distinguish the details of the DNA interactions of three distinct XPB helicases, which belong to the superfamily-2 of helicases. Clear changes in DNA melting temperature and duplex stability were observed upon helicase binding, shifts that could not be observed with conventional UV-visible absorption measurements. Binding dissociation constants were estimated in the range from 10 to 50 nM and correlated with observations of activity. ATP-stimulated DNA unwinding activity was also followed, revealing exponential time scales and distinct time constants associated with conventional and molecular wrench modes of operation further confirmed by crystal structures. These devices thus provide a sensitive measure of the structural thermodynamics and kinetics of helicase-DNA interactions.

RETRACTED ARTICLE: Synthesis and characterization of Ni-doped α-Fe2O3 nanoparticles through co-precipitation method with enhanced photocatalytic activities

In the present study, an attempt has been made for synthesis, characterization and photocatalytic application of pure and Ni-doped α-Fe2O3 (hematite) nanoparticles by chemical co-precipitation method. The synthesized products have been studied by Thermo Gravimetric Analysis (TGA), Differential Thermal Analysis (DTA), X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), Fourier Transform Infra-Red (FT-IR), Raman spectroscopy, Ultraviolet–Visible (UV–Vis) analysis and Vibrating Sample Magnetometer (VSM). The TGA showed three mass losses, whereas DTA resulted in three endothermic peaks. XRD measurements confirm that all the prepared nanocrystals consist only in nanocrystalline hematite phase. TEM and SEM show that the size of the nanoparticles decreases with Ni-doping. FTIR and Raman spectroscopies confirm the phase purity and the phonon modes of the synthesized nanoparticles. The UV–Vis absorption measurements confirm that the decrease of particle size is accompanied by a decrease in the band gap value from 2.02 eV for α-Fe2O3 down to 1.81 eV for 8 mol% Ni-doped α-Fe2O3. Furthermore, the magnetic properties demonstrated that all of the samples exhibited ferromagnetic behavior at room temperature. On the other part, the photocatalytic activity of Ni-doped α-Fe2O3 particles was studied using methylene blue (MB) as model organic pollutants. The 8 mol% Ni-doped α-Fe2O3 nanoparticles disclosed that the discoloration of MB reached 86% after irradiation of 140 min.

Nonmetal element doped g-C3N4with enhanced H2evolution under visible light irradiation

Abstract

New A-D-A type small molecules based on benzodithiophene derivative for organic solar cells

ABSTRACTA synthesized of acceptor-donor-acceptor (A-D-A) type oligomer based on benzodithiophene (BDT) as a donor (D) unit and phenylisoxazol (OX) as an acceptor (A) is to investigate the effect of combination between the strong electron donor and a strong electron acceptor. In addition, we introduce hexylthiophene (HT) ring as a π-bridge to extend the effective conjugation length and increase the solubility. Here we report the performance of 2,6-(4-(thiophen-2-yl)methylene)-3-phenylisoxazol-5(4H)-one)-4,8-bis((2-ethylhexyl)oxy)benzo[1,2-b:4,5-b′]dithiophene) (BDT-HTOX) employing as the electron donor in the inverted organic solar cells and PC71BM as the electron acceptor unit. UV-Vis absorption and electrochemical measurements investigated the optoelectronic properties that revealing the HUMO/LUMO level at −3.72 eV/−5.44 eV with an optical band gap of 1.72 eV for BDT-HTOX. Maximum power conversion efficiency based on BDT-HTOX is showed up to 0.80% with a short-circuit current density (Jsc) of –3.26 mA/cm2, Voc of 0.88 V, and fill factor (FF) of 27.9% using chlorobenzene as a solvent for solution processed organic solar cells.