Ultraviolet Absorption Spectra Research Articles

Quantitative detection of trace H2S based on ultraviolet differential optical absorption spectroscopy

As an important decomposition component of SF6, H2S can provide an important information for the evaluation of insulation state of SF6 gas insulated equipment. Since H2S has obvious absorption in the ultraviolet (UV) range of 190∼230 nm, the UV absorption spectrum detection platform is established to realize its detection. In this paper, SF6 decomposition component detection platform based on UV spectroscopy was built, and the UV absorption spectrum of H2S was obtained. Since the UV absorption spectrum directly obtained by the instrument is susceptible to spectral scattering and high frequency noise, the detection sensitivity is low. Therefore, this paper uses the UV differential algorithm to obtain the UV absorption spectrum of H2S. After experimental tests, the R2 of the fitted line is as high as 0.999. Moreover, the method has good repeatability for detection of H2S, the results show that the absolute error does not exceed 0.2 μL/L. The noise is calculated by randomly collecting 30 sets background spectrum, and the detection limit is 0.590 μL/L when the signal-to-noise ratio is 1. A method for detecting H2S gas concentration based on UV differential absorption spectroscopy is proposed, which is suitable for on-line monitoring of trace H2S in the decomposition components of SF6 gas insulated equipment.

Biosynthesis of Zinc Oxide Nanoparticles Using Biological Polysaccharides for Application in Ceramics

Zinc oxide (ZnO) nanoparticles were synthesized via a polysaccharide-assisted sol-gel process in this work. The nano-sized ZnO was obtained by zinc ions assembled on the biology polysaccharide gel network built of xanthan gum and konjac gum due to the synergistic interaction. Nanostructure studies were carried out using the techniques of thermal gravity, x-ray powder diffraction, transmission electron microscope, Fourier transform infrared, field emission scanning electron microscopy, energy dispersive x-ray spectroscopy, and ultraviolet absorption spectrum (UV–Vis). It can be revealed that the morphology of the sample was nanoparticles with an average diameter of 53.5 nm when the polysaccharide content in the gel solution was optimized to be 0.8 wt.%. FTIR spectrum was adopted to reveal the formation of ZnO nanoparticles involving hydroxyl moieties of gums. The UV–Vis absorption spectrum showed that biosynthesized ZnO with a narrow bandgap of 3.10 eV was a promising material for a visible light absorbing semiconductor. Furthermore, ZnO nanoparticles with optimal polysaccharide content were observed to improve microstructural homogeneity of ZnO-based ceramic and the electrical performance.

Preparative separation of isoquinoline alkaloids from Corydalis impatiens using a middle-pressure chromatogram isolated gel column coupled with two-dimensional liquid chromatography.

We established a two-dimensional strong cation exchange/reversed-phase liquid chromatography protocol to isolate and purify isoquinoline alkaloids from Corydalis impatiens. Isoquinoline alkaloids were first enriched from a C. impatiens extract in which liposoluble components were removed using a medium-pressure chromatographic tower containing middle chromatogram isolated gel. A strong cation exchange column was employed to separate and obtain 30 fractions. We chose fractions 22-29 for reversed-phase liquid chromatography purification using characteristic isoquinoline alkaloid ultraviolet absorption spectra. Several isoquinoline alkaloid fractions (22-29) were further separated, and those of low resolution were isolated via two-dimensional liquid chromatography in the orthogonal plane. A total of eight novel isoquinoline alkaloids with characteristic ultraviolet spectra were obtained from C. impatiens. We thus demonstrate the benefits of off-line two-dimensional strong cation exchange/reversed-phase liquid chromatography to isolate isoquinoline alkaloids from C. impatiens.

Photo-oxidation of an organosulfur for photo-charging of lithium-ion batteries

Polymers of organosulfur with S-S bonds are potential cathode materials for high-capacity lithium-ion batteries, and the photo-oxidation of organosulfurs can be applied in the future to the photo-charging of batteries. Herein, we present the photo-oxidation of dithiobiuret (DTB), a simple organosulfur molecule with two neighbouring tautomeric thiol/thione groups (-SH/>C=S) that can form a disulfide (S-S) bond by reversible intramolecular oxidative cyclization. Aqueous solutions of DTB with different pH values were irradiated by visible light from a halogen lamp. Photo-oxidation was confirmed by ultraviolet (UV) absorption spectroscopy, on comparison of the UV absorption spectra of DTB and chemically oxidized DTB. The rate of photo-oxidation depended on the pH of the DTB solution, and the highest photo-oxidation rate of ∼ 2.8 × 10−3 min.−1 was observed at a pH of ∼ 3.1.

The electronically excited states of cyclooctatetraene-An analysis of the vacuum ultraviolet absorption spectrum by ab initio configuration interaction methods.

A new synchrotron-based study of the vacuum ultraviolet (VUV) absorption spectrum for cyclooctatetraene (COT) shows a series of broad peaks. A significant sharp structure was extracted from the strongest band between 5.9 and 6.3 eV by fitting this range of the spectrum to a polynomial; the regular residuals show a set of sharp peaks. Comparison of this region of the VUV with the photoelectron spectrum demonstrates the presence of several Rydberg states, all based on the lowest observed ionization energy ionic state. The UV onset contains a broad band in the range 4.0 eV-5.3 eV. Theoretical vertical excitation energies, determined by configuration interaction (CI) studies at the multireference multiroot singles and doubles CI level, enabled interpretation of the principal absorption bands of the VUV spectrum. Adiabatic excitation energies (AEEs) for several singlet and triplet valence states (V) were evaluated by multiconfiguration self-consistent field methods. Theoretical Rydberg series AEEs were obtained by use of extremely diffuse Gaussian orbitals in highly correlated wave-functions. The second moments of the charge distribution identify which roots are valence or Rydberg states. A contrast was found between some density functional methods and Hartree-Fock (HF) wave-functions during single-excitation CI, when degenerate orbitals were involved in the leading configurations. The 7a16e* state contained the expected 8-membered ring in the density functional theory calculations. The HF wave-functions led to a 1,5-cross-ring interaction which converged on a singlet excited state of a bicyclo[3,3,0]octatriene; this is reminiscent of the photochemical conversion of COT to semibullvalene.

Effect of methyl methacrylate on the properties of transparent flame retardant unsaturated phosphate ester copolymer

The effect of methyl methacrylate (MMA) on the properties of transparent flame retardant unsaturated phosphate ester copolymer (poly[UPE‐co‐MMA]) prepared by bulk polymerization technique was investigated. Fourier transform infrared spectra, gel fraction (G) test, and dynamic mechanical analysis revealed the structure and crosslinking density of poly(UPE‐co‐MMA) copolymers. The thermal degradation and flame retardancy of copolymers were indicated by thermogravimetric analysis, limiting oxygen index (LOI), and microscale combustion calorimeter (MCC) test. Besides, the mechanical properties and transparency were tested with testing machines and solid ultraviolet absorption spectra. As the MMA content increased to 50%, the copolymer contained 50 wt% MMA showed the maximal G (88.93%) and transmittance was up to 91.72%. From the poly(UPE‐co‐MMA) copolymers, the tensile strength increased from 14.62 to 26.95 MPa, assigned to the increase of crosslinking density of copolymers. The char yield of poly(UPE‐co‐MMA) was up to 21.18 wt%, which was a result of decomposition of phosphate groups, producing a phosphorus‐rich layer that increased the thermal stability of the residues. LOI and MCC results confirm that the introduction of MMA can retain the flame retardancy of copolymer remarkably. POLYM. ENG. SCI., 59:2103–2109, 2019. © 2019 Society of Plastics Engineers

Defect structure and holographic storage properties of LiNbO3:Zr:Fe:Cu crystals with various Li/Nb ratios

A series of LiNbO3:Zr:Fe:Cu single crystals with various Li/Nb ratios ranging from 0.946 to 1.38 were grown in air by the Czochralski method. Both X-ray powder diffraction and ultraviolet absorption spectra have been examined, and are discussed with regard to the defect structure of the as-grown crystals. In addition, the conventional two-wave coupling experiment has been conducted with 532 nm laser to reveal the holographic storage properties. The results have shown the macroscopic photorefractive properties to correspond well to the microscopic defect structure changing with the composition. More specifically, LiNbO3:Zr:Fe:Cu crystals possess at once relatively high sensitivity, fast response time and dynamic range comparable with that of LiNbO3:Zr:Fe crystals, and at the same time maintain high saturation diffraction efficiency (up to 68%) close to that of typical photorefractive LiNbO3:Fe crystals (70%), as such denoting their potential as prominent holographic storage media.

Modulation of membrane properties by DNA in liposomes: A spectroscopic study.

Liposome mediated DNA transport possesses a number of preventing diseases in clinical trials, thus, the study of interaction between DNA and liposomes has become a hot research direction. In this paper, the adsorption behavior of DNA onto two representative lipids had been studied by the fluorescence spectrum measurement, Ultraviolet absorption spectrum and Langmuir-Blodgett technology. The results of fluorescence spectrum measurement indicated that the fluorescence liposomes were quenched statically by DNA at all three temperatures. Thermodynamic analysis displayed that the intermolecular forces between DNA and liposomes were van der Waals forces and Hydrogen bonding. The experimental results of Ultraviolet absorption spectrum and Langmuir-Blodgett technology further verified these mechanisms. This work provides useful theoretical basis for the development of novel DNA delivery materials.

An insight of Mg doped ZnO thin films: A comparative experimental and first-principle investigations

Abstract The aim of this work was to study the structural, electronic and optical properties of Zn1-xMgxO (x = 0, 0.1, 0.3). All theoretical calculations were performed using density functional theory (DFT) and employing the plane-wave pseudopotential method. It was found that the bandgap increased progressively with doping of Mg impurity in pure ZnO thin films. Pure and Mg-doped ZnO thin films (x = 0, 0.1, 0.3) were fabricated using a sol-gel spin coating method and structural characteristics were studied by X-ray diffraction (XRD). The XRD measurements indicated that Mg doping increases the grain size. The products were crystalline with a hexagonal wurtzite phase and the predominant plane was appeared as (001). The optical properties were calculated using ultraviolet (UV) absorption spectra. The blueshift in UV spectra with an increase of Mg concentration confirmed a reasonable increase in the bandgap of ZnO thin films. The bandgap of ZnO thin films was shown to increase progressively with successive increase of Mg concentration in both cases (experimental as well as DFT calculations). Defects in the crystalline structure and their behavior in ZnO thin films were also explored for possible applications in the electronic and optoelectronic industry.

Syntheses, Crystal Structures, Magnetic and Near-infrared Luminescence Properties of 3d−4f Coordination Polymers Cu2Pr2, Cu2Eu2 and Cu4Tb2

Three new 3d−4f heterometallic coordination polymers(CPs), namely, [Pr2(CuL)2(nipt)3(H2O)]·2H2O (Cu2Pr2, 1), [Eu2(CuL)2(nipt)3(H2O)]·2H2O(Cu2Eu2, 2) and [Tb2(CuL)4(nipt)3]·8.3H2O(Cu4Tb2, 3)(CuL, H2L=2,3-dioxo-5,6,14,15-dibenzo-1,4,8,12-tetraazacyclo-pentadeca-7,13-dien; nipt2-=5-nitroisophthalate) were obtained by a solvothermal method and structurally characterized by single-crystal X-ray diffraction analyses, elemental analyses, Fourier transform infrared spectra and ultraviolet visible absorption spectra. In Cu2Pr2 and Cu2Eu2, μ3-bridged and μ5-bridged nipt2- ligands alternately linked three Ln3+ and five metal ions(three Ln3+ and two Cu2+ ions) to generate a 2D heterometallic framework with 3,3,4,5-connected (3.4.5)(32.42.5.63.72)(42.63.8)(42.6) topology. In Cu4Tb2, μ2-bridged and μ4-bridged nipt2- ligands alternately connected two Tb3+ and four metal ions(two Tb3+ and two Cu2+ ions) by carboxylating into a corrugated heterometallic 2D layer with 3-connected (63) topology. The magnetic properties of Cu2Pr2 and Cu2Eu2 were also discussed, the results show that both CPs have a weak antimagnetic interaction. Moreover, the near-infrared luminescence properties of Cu2Pr2 and Cu2Eu2 were also studied.

Real-Time Measurement of Polyvinylpyrrolidone Eluted from Polysulfone Membrane Dialyzers Based on the Ultraviolet Spectrum.

The objective of this study was to develop a new method for measuring polyvinylpyrrolidone (PVP) eluted from polysulfone (PSu) membrane dialyzers. The Müller method is generally used for the measurement of PVP, in which the PVP concentration is determined by measuring the absorbance after a red color is generated by the formation of PVP-iodine complexes when iodine is added to a sample. In contrast, our method does not require any reagents and allows real-time measurement of PVP by the ultraviolet absorption spectrum (UV-s method). In this study, the UV-s method and the Müller method were used to measure PVP eluted from two types of PSu membrane dialyzer (PS-1.6UW sterilized by autoclaving [n = 10] and APS-15SA sterilized by gamma radiation [n = 10]). Polyvinylpyrrolidone concentrations measured by the two methods showed a significant positive correlation (rs = 0.99, p = 0.0006). The PVP concentration (median [25th-75th percentiles]) in PS-1.6UW dialyzer washings obtained by rinsing with physiologic saline was 2.0 (1.18-4.85) mg/L with the Müller method and 3.35 (2.38-4.23) mg/L with the UV-s method, showing no significant difference. However, the PVP concentration in APS-15SA dialyzer washings was 0 (0-0.35) mg/L by the Müller method and 0.95 (0.45-2.58) mg/L by the UV-s method, and there was a significant difference between the two methods. In conclusion, the low concentration of PVP eluted from a PSu dialyzer sterilized by gamma radiation was hardly detected by the Müller method but could be clearly detected by the new UV-s method. These findings suggest that the UV-s method could be used for real-time measurement of PVP eluted from PSu membrane dialyzers.

Basil polysaccharide inhibits hypoxia-induced hepatocellular carcinoma metastasis and progression through suppression of HIF-1α-mediated epithelial-mesenchymal transition

Invasion and metastasis of cancerous cells affects the treatment and prognosis of hepatocellular carcinoma (HCC). HIF-1α-induced epithelial-mesenchymal transition (EMT) is a critical process associated with cancer metastasis. Basil polysaccharide (BPS), one of the major active ingredients isolated from Basil (Ocimum basilicum L.), has been identified to possess an antitumor activity for HCC. In our current study, BPS was obtained by water extraction and ethanol precipitation method and the characterization was analyzed through ultraviolet absorption spectra and Fourier-transform infrared spectrum. A CoCl2-induced hypoxia model and a HCC cell line-derived xenograft (CDX) model were used to explore the anti-metastasis efficacy and the mechanism that underlies the antitumor activity of BPS. The results showed that hypoxia could facilitate EMT and promote HCC cells migration and/or invasion. Conversely, BPS inhibited the progression and metastasis of tumor, as well as reversed EMT by causing cytoskeletal remodeling under hypoxic conditions. Moreover, BPS alleviated tumor hypoxia by targeting HIF1α, and the mesenchymal markers (β-catenin, N-cadherin and vimentin) were down-regulated, while the epithelial markers (E-cadherin, VMP1 and ZO-1) were up-regulated after BPS treatment under hypoxic conditions. Thus, these results suggested that BPS may be a valuable option for use in clinical treatment of HCC and other malignant tumors.

Investigation on the UV spectra of the supermolecular system involving silver nanoparticles–substituted N‐(phenyl‐ethylene)‐anilines

AbstractThe ultraviolet (UV) absorption spectra of the supermolecular system involving silver nanoparticles–substituted N‐(phenyl‐ethylene)‐anilines were investigated. Silver nanoparticles (AgNPs) and 77 kinds of substituted N‐(phenyl‐ethylene)‐anilines ZArC (Me)═NArY (ZPEAY, including 40 compounds 2‐H‐XPEAY without ortho‐hydroxyl and 37 compounds 2‐OH‐XPEAY with ortho‐hydroxyl) were prepared. The size of AgNPs was measured with transmission electron microscopy. To study the effect of substituents X and Y on the UV spectra of the supermolecular system of AgNPs‐ZPEAY, the authors measured the UV absorption spectra of AgNPs, ZPEAY, and AgNPs‐ZPEAY solutions. The experimental results show that (a) the size of AgNPs increases in AgNPs‐ZPEAY solution compared with that in AgNPs solution, due to the absorption of ZPEAY molecules on the surface of AgNPs; (b) the UV absorption wavelength of ZPEAY changes in AgNPs‐ZPEAY solution and there is a limitation for the wavelength shift (λWSL) between ZPEAY and AgNPs‐ZPEAY system; (c) there is a quantitative correlation between the wavenumber ΔνWSL of λWSL and the substituent constants (Hammett constant σ and excited‐state substituent constant ) of substituents X and Y; (d) the intramolecular hydrogen bonding in 2‐OH‐XPEAY makes the ΔνWSL a red shift in AgNPs‐ZPEAY system.

Study on Naphthalene Sulfonic Acid Formaldehyde Condensate by Ultraviolet Absorption Spectrum

Naphthalene sulfonic acid formaldehyde condensate is a kind of surfactant with excellent performance, which is widely used in printing, dyeing, cement, paint and other industries. There are various analytical methods for naphthalene sulfonic acid formaldehyde condensate, such as optical density analysis, electrophoresis, chromatographic analysis and spectral analysis. A series of formaldehyde condensates were synthesized from naphthalene, formaldehyde solution and concentrated sulfuric acid solution. The products were qualitatively analyzed by infrared and ultraviolet absorption spectra.

Induced Quasi-Dynamic Disorder in a Structure of Rhenium Ion-Implanted Quartz Glass

The ultraviolet (UV) absorption spectra were studied in UV–Vis–IR quartz glasses exposed to the rhenium ion irradiation at the energy of 30 keV. An increase in ion fluence (5 × 1015–5 × 1017 cm2) is found to result in a characteristic fan-shaped broadening of the optical absorption edge of glasses. The results were interpreted in the context of the generalized Urbach rule (the approximation of ion radiation induced quasi-dynamic disorder). The effective radiation disorder cross section of a glass matrix was evaluated from the dose dependence of characteristic Urbach energy. This parameter was found to vary between 1.07 × 10–17–1.2 × 10–18 cm2 with increasing fluence. The optical gap width of implanted samples was estimated via the Tautz method for allowed direct interband transitions. The relationship between the second-order deformation potential constants, revealing the correlation between the Urbach energy and the optical gap width in a SiO2 quartz glass matrix was established using the equivalence principle of static and dynamic structural disorder.

A Novel Fluorescent Probe Based on Spiro[chromeno[2,3-c]pyrazole-4,1′-[2]benzofuran]-3′-one for Detecting Copper(II) ions in Aqueous Solution

A novel fluorescent probe, DHMP {7-(dibutylamino)-3-methyl-1H,3′H-spiro[chromeno[2,3-c]pyrazole-4,1′-[2]benzofuran]-3′-one} was designed and synthesized by condensation of 2-[4-(dibutylamino)-2-hydroxybenzoyl]benzoic acid with 5-methyl-2,4-dihydropyrazol-3-one. The ultraviolet absorption and fluorescence emission spectra of DHMP showed a clear pH dependence and highly selective and sensitive response to copper(II) ions in aqueous medium. The detection limit of Cu2+ was estimated at 9.05 × 10−8 M.

Turn-on fluorescence detection of β-glucuronidase using RhB@MOF-5 as an ultrasensitive nanoprobe

β-Glucuronidase (β-GCU) is closely related to the occurrence of multiple diseases, and it has been applied as a biomarker and therapeutic target in clinical diagnosis. However, reliable methods with high selectivity and sensitivity for monitoring β-GCU are still lacked. Herein, we designed a novel fluorescent nanoprobe, rhodamine B encapsulated MOF-5 (RhB@MOF-5) for the first time, to detect β-GCU through the synergistic effect of inner filter effect (IFE) and static quenching effect (SQE) by employing 4-nitrophenyl-β-D-glucuronide (PNPG) as the substrate. After encapsulating into MOF-5, the fluorescence emission of RhB at 550 nm excited by 320 nm was greatly enhanced. The major overlap between the fluorescence excitation spectrum of RhB@MOF-5 (about 320 nm) and the ultraviolet absorption spectrum of PNPG (about 310 nm) lead to PNPG being a good IFE absorber in this sensing system. Under the optimized conditions, the excitation spectrum of the RhB@MOF-5 could be absorbed by PNPG, resulting in the dramatically decrease of fluorescence emission. After adding β-GCU into the system, the substrate of PNPG would be enzymatic hydrolyzed to p-nitrophenol (PNP) and glucose, then the IFE disappearance and the fluorescence recovered. The current sensing platform was interference-free and exhibited a broad linearity relationship for β-GCU range of 0.1–10 U L−1 (R2 = 0.9957) with a limit of detection as low as 0.03 U L−1, which was reduced by more than one orders compared with the reported methods. Moreover, the encapsulation of dyes using porous nanoparticles to achieve some tailor-made characteristics will enrich experimental design inspiration.

Spectroscopic and molecular docking studies on the binding mechanism of Mobic and lipase

Under simulated physiological conditions (pH=7.40), the interaction between non-steroidal anti-inflammatory drug mopicol and lipase was studied by fluorescence spectrum, ultraviolet absorption spectrum, circular dichroism spectrum and computer simulation technique. The experimental results showed that Mobic could quench the fluorescence of lipase by static quenching, and the binding site number is about 1. According to Forster's theory of non-radiation energy transfer, the binding distance between Mobic and lipase was obtained, r 0, indicating that hydrophobic force played a major role in the formation of Mobic and lipase complex. The results of synchronous fluorescence spectra, UV spectra and circular dichroism spectra showed that Mobic changed the conformation of lipase. The molecular docking results showed that the binding position of Mobic was close to the active center, indicating that Mobic could change the microenvironment of amino acid residues at the active center of lipase catalysis. The results of docking showed that there was hydrogen bond between Mobic and lipase, so the interaction between Mobic and lipase was driven by hydrophobic interaction and hydrogen bond.

Exploration on UV-Blocking Performance of Lignin from Palm (Trachycarpus Fortunei) Fiber

ABSTRACT To reveal the ultraviolet (UV) blocking mechanism of palm fiber, alkali lignin was extracted from palm and bamboo fiber and its UV absorption spectrum was tested, followed by some structural characterization. Palm fiber lignin was found to have a higher UV absorbance. Fourier Transform infrared spectroscopy (FTIR) analysis revealed that the ultraviolet absorbing functional groups in palm fibers including phenol OH, aliphatic OH, aromatic ring and triple bond structure. Thermogravimetric Analysis (TG) and elemental analysis indicated high protein content and highly concentrated aromatic structures also contribute to the superior UV absorption properties of palm fibers.

Determining the excited‐state substituent constants of ortho‐substituents from 2,4’‐disubstituted stilbenes

AbstractThere are mainly three kinds of substituent electronic effects derived from aromatic rings: ground‐state, radical‐state, and excited‐state effect. However, excited‐state substituent constants of ortho‐substituents have not been reported up to now. In this paper, a method for extracting the excited‐state substituent constant of ortho‐substituents was provided. Forty‐nine 2,4’‐disubstituted stilbenes were synthesized, and the ultraviolet absorption spectra of the synthesized stilbenes were determined. The values of ortho‐substituents involving MeO, Me, F, Cl, Br, CF3, and CN were quantified by curve fitting method based on the measured ultraviolet absorption spectra. The rationality of the values were further experimentally confirmed by measuring the ultraviolet absorption spectra of other 10 samples of synthesized 2,3’‐disubstituted stilbenes and by applying these values in regression analysis of the ultraviolet absorption spectra for a complicated data set of 284 organic compounds.