Ultraviolet Absorption Spectra Research Articles

Vacuum ultraviolet excited state dynamics of the smallest ring, cyclopropane. I. A reinterpretation of the electronic spectrum and the effect of intensity borrowing.

Cyclopropane, the smallest organic ring compound, exhibits complex spectroscopy and excited state dynamics. In Paper I, we reinterpret the vacuum ultraviolet (VUV) electronic absorption spectrum of cyclopropane via ab initio computation. The first two bands in the VUV spectrum are simulated using wavepacket propagations employing the multiconfigurational time-dependent Hartee method and a newly parameterized linear vibronic coupling Hamiltonian. The parameters of the model Hamiltonian are obtained directly from high level multireference configuration interaction calculations. An analysis of the results, with an emphasis on previously neglected vibronic coupling effects, reveals that these vibronic coupling terms must be included in order to account for strong intensity borrowing effects. This treatment dramatically changes the assignment of much of the VUV spectrum, with intensity borrowing by the optically dark (σ3p x /3p y ) and (σ3p x /3p y ) states from the E'(σ3p x /3p y ) state being found to give rise to almost all the spectral intensities below 8 eV. This is in stark contrast to previous studies, which attributed the first two bands to transitions to the E'(σ3p x /3p y ) state. This highlights the limitations of assigning spectral features based solely on calculated electronic excitation energies and oscillator strengths. Furthermore, we address the significant but infrequently discussed difficulties involved in determining the electronic character of a wavepacket produced in the pump step of ultrafast pump-probe experiments for systems exhibiting strong vibronic coupling.

STANDARDIZATION OF SNOWDROP (GALANTHUS L.) HERBAL PHARMACEUTICAL SUBSTANCES BY UV-SPECTROPHOTOMETRY

Objective: The objective of the present study is to evaluate the electronic ultraviolet (UV) absorption spectra of herbal pharmaceutical substances (70% ethanol extracts) prepared from medicinal plant material of two snowdrop species – Galanthus woronowii Losinsk and Galanthus nivalis L.Methods: The groups of biologically active substances were investigated by UV-spectrophotometry including special sample preparation for flavonoids and alkaloids.Results: In the present study, data were obtained characterizing the composition of the main biologically active compounds of the genus Galanthus L., received its “spectrophotometric profiles.” On the basis of spectral characteristics of G. woronowii and G. nivalis flavonoids and alkaloids, we confirm feasibility for using galantamine, lycorine, quercetin, and its glycosides (hyperoside et al.) state standard samples in standardization analysis.Conclusion: It is shown that this method can be used to assess the quality of herbal pharmaceutical substances, serve to prove their identity in pharmacopoeial monograph.

Preparation of Durable Antibacterial Cellulose with AgCl Nanoparticles

In this study, a facile method was developed to coat AgCl nanoparticles (NPs) onto knitted cotton fabrics. The AgCl NPs were characterized by ultraviolet absorption spectrum, X-ray diffraction (XRD) and dynamic laser light scattering (DLS). The AgCl NPs were coated onto cotton fabrics through a pad-dry-cure process with the assistance of 1,2,3,4- butanetetracarboxylic acid (BTCA). Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), ICP-OES analysis and energy-dispersive X-ray spectroscopy (EDX) confirmed that AgCl NPs were successfully coated onto cotton fabrics. The prepared cotton samples exhibited excellent antimicrobial activity against both Gram-positive S. aureus and Gram-negative K. pneumonia bacteria. Rat skin fibroblast cytotoxicity testing demonstrated the treated cotton fabrics to be non-toxic. The washing durability evaluation showed that the antimicrobial function of cotton fabrics was durable to washing. In addition, the wrinkle resistance of the coated cotton fabrics was improved and there was no obvious change in whiteness.

HPLC characteristic fingerprints of Xinshenghua Keli

Xinshenghua Keli is known as the "preferred prescription of postpartum", with large demand in the field of gynecologic medicine. However, the quality of the preparation is uneven in the market, so its clinical efficacy cannot be guaranteed. In order to improve and establish its quality control standard, high performance liquid chromatography (HPLC) was used to establish the fingerprint of Xinshenghua Keli. The detection was performed on Agilent 5 HC-C₁₈ (2) column(4.6 mm×250 mm, 5 microns) with methanol-0.1% formic acid solution as mobile phase for gradient elution, at a flow rate of 1 mL·min⁻¹ with column temperature of 25 °C. The injection volume was 10 μL and detection wavelength was set at the maximum value between 210.0 nm and 400.0 nm by Photo-Diode Array (PDA) detector. The fingerprint of 12 batches of high-quality Xinshenghua Keli was established and 43 common peaks were identified. The similarities of crowned products, 10 batches of ordinary ones made by Jiangsu Rongyu Pharmaceutical and 10 batches produced by different manufacturers were evaluated. The composition identification and source analysis for the common peaks were performed by comparing the retention time of herbal medicines and ultraviolet absorption spectrum, along with high performance liquid chromatography-mass spectrometry (HPLC-MS) technology. The established fingerprint of Xinshenghua Keli, has proven to have good precision, stability and repeatability through the methodology validation, so it can be used to comprehensively evaluate the quality of Xinshenghua Keli.

Molecular assembly and photoluminescence of lanthanide/silicon[sbnd]oxygen network/poly-vinylphenylboronic functionalized SBA-15 hybrids

Novel organic-inorganic mesoporous luminescent polymeric composite materials containing lanthanide (Eu3+, Tb3+) complexes covalently bonded to mesoporous silica have been prepared in situ, followed by the polymerization reaction of the monomer 4-vinylphenylboronic acid (VPBA) extending along the mesoporous SBA-15 channels. The obtained materials were investigated by Fourier transform infrared spectroscopy (FT-IR), Ultraviolet absorption spectra (UV), X-ray diffraction (SAXRD), N2 adsorption/desorption isotherms, Transmission electron microscopy (TEM), thermogravimetry (TG), and luminescence spectroscopy in detail. These characterizations have proved that composite materials possess high surface area, uniform mesoporous structure, good crystallization and relatively excellent luminescence properties. The terminal ligand phen was used to investigate the difference of photo physical and luminescent properties between binary and ternary composite materials. Furthermore, the results have revealed that the composite material Eu(PVPBA-S15)3phen showed more efficient intramolecular energy transfer between the europium ion and the ligands, and more excellent characteristic emission of the europium ion under UV irradiation with higher 5D0 luminescence quantum efficiency than the composite materials Eu(PVPBA-S15)3 without phen. The excellent luminescence properties and ordered mesoporous structures could give rise to many potential applications in optical and electronic areas.

Bioaccumulation of Arsenic by Engineered Escherichia coli Cells Expressing Rice Metallothionein Isoforms.

Metallothioneins (MTs) are low-molecular weight cysteine (Cys)-rich proteins with high metal-binding capacity. Based on the Cys arrangement in their amino acid sequences, plant MTs are categorized into four classes. This study evaluated the ability of genetically engineered Escherichia coli cells, which express four rice MT isoforms as fusion proteins with glutathione-S-transferase (GST), to remove arsenic. As compared with control strain, the expression of GST-OsMT1, GST-OsMT2, GST-OsMT3, and GST-OsMT4 resulted in 8-, 5.6-, 3-, and 1.1-fold-higher As3+ accumulation. The recombinant GST-OsMT isoforms were purified using affinity chromatography and their apo-forms were prepared. The ability of the GST-OsMT2 isoform to bind with As3+ in vitro was also confirmed by ultraviolet (UV) absorption spectra recorded after the reconstitution of apo-proteins with As3+. However, the formation of complexes of other MT isoforms with arsenic was not observed.

Serological detection of close and distant relationships of an isolated <i>Tobamovirus</i>

A virus causing mosaic and leaf yellowing symptoms on Mucuna pruriens was isolated and purified through its susceptible host Vigna unguiculata var. TVu 76. Yield of the purified virus obtained was 7.2 mg/kg. It had an ultraviolet (UV) absorption spectrum at 260 nm as 1.53±0.00 and at 280 nm as 1.45±0.00, which translated into nucleic acid content of 72.9 %. Determination of the molecular weight of the virus coat protein from a plotted graph gave 27 kiloDaltons. When the purified virus was electrophoresed in agarose gel, no secondary band was observed. Absorbance curve at 260 nm was obtained when the purified virus was measured spectrophotometrically. A volume of 16 000μL antiserum was obtained against the virus with concentration of 0.3 mg/ml. The titre value determined for the antiserum raised against the virus was 1:2000 as there was a wider difference between the readings obtained for the healthy and diseased controls. At this dilution, the titre value was two and a half times greater than that of the healthy control. The heterologous: homologous percentage (%) obtained for the isolated virus and TMV (Muguga strain) was 50.0 % when Protein-A sandwich enzyme linked immunosorbent assay (PAS ELISA) was used to determine its serological relationship with the virus and other Tobamovirus strains.Keywords: PAS ELISA, Tobamovirus, coat protein, molecular weight

Resveratrol Functionalized Carboxymethyl-β-Cyclodextrin: Synthesis, Characterization, and Photostability

The resveratrol functionalized carboxymethyl-β-cyclodextrin conjugate was synthesized by two simple steps. The conjugate was successfully demonstrated by 1H NMR, 13C NMR, UV, and FTIR. The photostability of the conjugate was studied by ultraviolet absorption spectrum. After 360 min of UV light irradiation, the conjugate showed a total loss in absorbance of only 12.54%, while the resveratrol and its CM-β-CD inclusion complex showed a total loss in absorbance of 32.15% and 24.05%, respectively. The results indicate that the conjugate was more stable than resveratrol and its CM-β-CD inclusion complex.

Characterisation and structure analysis of taxanes‐loaded human serum albumin nanoparticles prepared by self‐assembly method

In this work, human serum albumin (HSA) was used to prepare core-shell taxanes-loaded nanoparticle (NP) by self-assembly method. Various experimental technologies were used to character two different taxanes-loaded HSA NPs and analyse the structure of them. The obtained NPs had a spherical morphology and core-shell structure. The data revealed that one paclitaxel (PTX)-loaded HSA NP (∼40 nm) consisted of six HSA molecules and 34 PTX molecules, and one docetaxel (DOC)-loaded HSA NP (∼30 nm) consisted of five HSA molecules and 40 DOC molecules. The infrared, three-dimensional fluorescence and ultraviolet absorption spectra showed that intermolecular hydrogen bond occurred between taxanes and polypeptide chain of HSA and resulted in change of its secondary structure. The fluorescence spectra experiment results suggested that PTX and DOC interacted with tryptophan (Trp)-214, which lie on site I of HSA, and the type of interactions were hydrogen bond and hydrophobic interaction, respectively. It suggested that the binding mode of taxanes with Trp-214 is the primary factor that determined the size and loading capacity of taxanes-loaded HSA NPs. This work indicates that such HSA NP is very promising in the field of nanoscale drug delivery systems research.

Toxic target of trans-crotonaldehyde in mitochondria altered by diallyl disulfides for anti-myocardial ischemia

The purposes of this study were to probe spectral behaviors of the toxic targets in trans-crotonaldehyde (TCA) in mitochondria altered by diallyl disulfides (DADS) derived from garlic. Ultraviolet absorption spectra showed that when ethanol as a solvent, the DADS blue shifted the peak of TCA from 318 nm to 312 nm. In mitochondria, the DADS further blue displaced the peak of TCA from 312 nm to 308 nm. Raman spectra displayed that the SS of DADS directly interacted with the CC toxic target of TCA, then the CCC of DADS interacted with the CHO toxic target of TCA. When DADS to TCA was 1:2, the DADS was the most powerful for the removal of the CC and CHO toxic targets of TCA. Study suggested that the SS of DADS altered the CC toxic target of TCA, while the CCC of DADS eliminated the CHO toxic target of TCA via local electron delocalization. The above two together clearly depicted the spectral behaviors of the toxic targets of TCA in mitochondria altered by DADS. These results are of great significance and value to elucidate the effects of garlic organic polysulfide on myocardial ischemia for the extensive development and use of garlic extracts.

Syntheses and properties of copper hydroxide nanosheets and controlled deposition

In this study, we synthesized copper hydroxide nanosheet and investigated its electrochemical property and how to deposit it with a uniform amount. The precursor of the nanosheet was a layered copper hydroxide synthesized by the ion exchange of dodecylbenzene sulfonate (DBS) with acetate in Cu2(OH)3(CH3COO)⋅H2O. The nanosheet was prepared by delamination of the layered copper hydroxide by dispersion in 1-butanol. Atomic force microscopy (AFM) images of the nanosheets showed lateral dimensions of ca. 2 [Formula: see text]m with the height of ca. 4.5 nm. Cyclic voltammogram of the nanosheet in basic solution showed two cathodic peaks and two anodic peaks similar to the copper oxide electrode. To deposit the nanosheet, a quartz glass slide was dipped in the dispersion of the nanosheet in 1-butanol and dried after washing. This procedure was repeated and the ultraviolet (UV) and visible (Vis) light absorption spectrum of the slide was measured. The absorbance of the slide increased in direct proportion to the number of times of the dip-and-dry procedure. Thus, we confirmed that a controlled amount of nanosheet was deposited on the quartz glass.

Synthesis and photoelectric performance of D-A-A′ type small molecule based on triphenylamine

A kind of novel D-A-A′ type organic small molecule TPA(BT-CNC8)2 based on triphenylamine was designed and synthesized, in which triphenylamine (TPA) was used as central donor (D) core, benzothiadiazole (BT) and i-octyl 2-cyanoacetate (CNC8) were used as main acceptor (A) and secondary acceptor (A′) units, respectively. Its optical physical properties, thermal stability and electrochemical properties were tested and systematically investigated via ultraviolet absorption spectra, thermal gravimetric analysis and cyclic voltammetry measurement, respectively. TPA(BT-CNC8)2 presented a wide absorption profile of 300–750 nm with an optical band gap of 1.65 eV. The highest occupied molecular orbital (HOMO) energy level of TPA(BT-CNC8)2 was calculated to −5.40 eV, which was mainly originated from the strong electron-withdrawing effect of benzothiadiazole and i-octyl 2-cyanoacetate units. The bulk-heterojunction organic solar cells of TPA(BT-CNC8)2-based was fabricated, in which TPA(BT-CNC8)2 was used as donor material while PC71BM as acceptor material, in the absence of optimizing device structure, its power conversion efficiency (PCE) reached to 1.62% together with a short circuit current density (Jsc) of 6.94 mA cm−2 and open circuit voltage (Voc) of 0.81 V. Further improvements of the device efficiency by optimizing the devices structure, using solvent additive or thermal annealing are currently under investigation.

Mechanism Underlying Green Discolouration of Myoglobin Induced by Atmospheric Pressure Plasma

In this study, we elucidated the mechanism underlying atmospheric pressure plasma (APP)-induced green discolouration of myoglobin. Green-coloured pigments are produced upon conversion of myoglobin into sulphmyoglobin, choleglobin, verdoheme, nitrihemin, or nitrimyoglobin. We exposed myoglobin dissolved in phosphate buffer to APP for 20 min and found a decrease in a* value (+redness/−greenness) and increase in b* value (+yellowness/−blueness) (P < 0.05). In the ultraviolet absorption spectrum, myoglobin treated with APP for 20 min showed absorption peaks at 503 and 630 nm, a spectrum different from that of sulphmyoglobin or choleglobin. The secondary structure and molecular weight of myoglobin were unaffected by APP treatment, excluding the possibility of verdoheme or nitrihemin formation. After APP treatment, nitrite was produced in myoglobin solution that provided a positive environment for nitrimyoglobin formation. However, the addition of 0.5% sodium dithionite, a strong reducing agent, to myoglobin solution resulted in the formation of deoxymyoglobin, which was subsequently converted to nitrosomyoglobin upon APP treatment to yield a desirable red colour. Thus, APP-induced green colouration in myoglobin solution is associated with nitrimyoglobin formation. The addition of the antioxidant resulted in the production of red colour in myoglobin solution after APP treatment owing to nitrosomyoglobin formation.

Study on the interaction between surfactin and alkaline protease in aqueous solution

The interaction between surfactin and alkaline protease in aqueous solution has been studied. Ultraviolet visible absorption spectra (UV–vis) show that surfactin causes the extension of peptide chain of the alkaline protease resulting in the weakening of hydrophobic interaction between the hydrophobic groups. Fluorescence spectra indicate that the interaction of surfactin with the tryptophan and tyrosine residues led to a change of conformation of the alkaline protease. Fourier transform infrared spectroscopy (FTIR) proves complex weak interactions between surfactin and alkaline protease, especially hydrogen bonds. Enzyme activity measurements demonstrate that low concentration of surfactin can increase the enzyme activity of alkaline protease, while high concentrations inhibit it. The particle size and Zeta potential measurements confirm that the system particle size and Zeta potential are dependent on the concentration of surfactin, in addition, there is the electrostatic interaction between surfactin and alkaline protease. Surface tension measurements indicate that the binds of surfactin and alkaline protease molecules are spontaneous. Based on experimental results, the composite model of surfactin and alkaline protease in aqueous solution is proposed.

Chemometrics-assisted spectrophotometry for simultaneous determination of sodium benzoate and citric acid in beverage products

The development and validation of chemometrics-assisted spectrophotometry have been successfully performed for determination of sodium benzoate and citric acid that have overlapping of ultra violet absorption spectra. The study aimed to develop, validate, and apply spectrophotometric method with chemometrics approach for determination of both compounds in beverage products simultaneously. The analytical method was performed by making a calibration model using 16 training sets and 10 test sets of mixed solution followed by absorbance measurenment at wavelength of 190 nm up to 400 nm. In addition, the absorbance data was processed by multivariate calibration models of principal component regression (PCR) and partial least square-1 (PLS-1) and validated internally and externally to obtain optimum model. Validation of analytical methods was done by evaluating some parameters such as linearity and ranges, accuracy, precision, detection limits and quantification limits. The results showed that the optimum wavelength was 235 nm to 250 nm for sodium benzoate and 220 nm to 240 nm for citric acid with the selected optimum principal components (PCs) value were 6 (PCR) and 4 (PLS-1) for sodium benzoate and PCs 2 (PCR and PLS-1) for citric acid. The parameters of the analytical method validation developed were suitable and the analytical methods could be applied for the determination of the sodium benzoate and citric acid contents simultaneously in the beverage products.

Optical characteristics of butyl rubber loaded with general purpose furnace (GPF) carbon black

Optical characteristics of butyl rubber/GPF carbon black (BR/GPFCB) composites with carbon black (CB) concentrations 40, 60, 80 and 100 phr (part per hundred part of rubber) were investigated. The structure of the BR/GPFCB composites was analyzed by x-ray diffraction (XRD). All samples with various CB showed diffraction peaks around 2θ = 14°, 25° and 44° which correspond to interlayer spacing of 6.23 Å, 3.62 Å and 2.10 Å respectively. The peaks were shifted toward larger 2θ angles with increasing CB concentration, indicating a decrease in layer spacing. Ultraviolet and visible (UV–vis) absorbance spectra in the range from 200 nm to 800 nm of the BR/GPFCB composites were studied. In the UV range of the spectra, an absorption edge was recorded. Direct and indirect optical band gaps for the composites were evaluated. The direct band gap values were found-as shown to be slightly greater than that of the indirect ones. The reflectance spectra in the UV optical range were demonstrated. Most of the incident UV light was absorbed inside the composites while a very small fraction was reflected and transmitted. This was attributed to the high UV absorption property of the CB filler. The refractive index of the composite was calculated from the reflectance data. The dependence of the real and imaginary parts of the complex dielectric constant on the incident light energy was characterized. The dielectric loss factor was found to decrease with increasing incident photon energy until approximately 5.5 eV (around the absorption edge) and then it increased rapidly.

Synthesis of novel 4,4'-bis(2,4-pyrimidinyl)-diaminostilbene-2,2'-disulfonic acid derivatives and their whitening effect on cotton fiber as fluorescent whitening agents

Some novel 4,4'-bis(2,4-pyrimidinyl)-diamino stilbene-2,2'-disulfonic acid derivatives 4a-d were designed and synthesized. Their structures were confirmed by proton nuclear magnetic resonance, elemental analysis and ultraviolet absorption spectra. All newly synthesized compounds were interrogated on their whitening effect on cotton fiber as fluorescent whitening agents. Their optical properties were evaluated by the degree of whiteness, color index, light fastness, wet rubbing fastness and dry rubbing fastness. The results indicated that compounds 4a-d showed an obvious whitening effect on cotton fiber and higher fastness than that of C186. The reflectivity of cotton fiber treated with compounds 4a-d at the critical concentration was up to 120.76%. In contrast, the reflectivity of untreated cotton fiber was only 87.23%. The ultraviolet absorption properties of compound 4d were tested under diverse pH values. The results showed that the ultraviolet absorption intensity of compound 4d decreased significantly and the absorption curve had blue shift under acidic conditions. Compound 4d was found to be the most effective molecule as a fluorescent whitening agent with a higher degree of whiteness (CIE Whiteness 135.04) compared to untreated cotton fiber (CIE Whiteness 73.02) at the critical concentration (0.1%).

Ultraviolet differential spectroscopy quantitative analysis of SF 6 decomposition component SO 2

SO2 is a symbolic gas that can indicate the insulation status of SF6 insulation electrical equipment. Its accurate quantitative measurement is of the great significance for the judgement of the type and severity of faults inside the insulation equipment. For this reason, a detection system of trace SO2 based on ultraviolet (UV) spectrometry was presented. The measured UV absorption spectra of SO2 were processed using the wavelet analysis to remove useless spectra information and get the UV differential absorption spectra of SO2. The fast Fourier transform (FFT) was used to analyse UV differential spectra in the band of 190–230 and 290–310 nm and extract the feature information. The results show that there is a good linear relationship between the FFT characteristic peak value and the concentration of trace SO2 in the two wave bands. The detection limit in the band of 190–230 nm was even lower than that in the band of 290–310 nm. Besides, the differential absorption cross section of SO2 decreases with the increase of temperature. The study has laid a foundation for the application of the UV differential absorption spectroscopy in the online monitoring and fault diagnosis of SF6 insulation electrical equipment.

Ultraviolet absorption spectrum of the half-filled bilayer graphene

We consider the optical properties of the half-filled AB-stacked bilayer graphene with the excitonic pairing and condensation between the layers. Both intra and interlayer local Coulomb interaction effects have been taken into account and the role of the exact Fermi energy has been discussed in details. We have calculated the absorption coefficient, refractive index, dielectric response functions and the electron energy loss spectrum for different interlayer Coulomb interaction regimes and for different temperatures. Considering the full four-band model for the interacting AB bilayer graphene, a good agreement is achieved with other theoretical and experimental works on the subject, in particular, limiting cases of the theory. The calculations, presented here, permit to estimate accurately the effects of excitonic pairing and condensation on the optical properties of the bilayer graphene. The modifications of the plasmon excitation spectrum are discussed in details for a very large interval of the interlayer interaction parameter.

Quantitative Characterization of the Molecular Absorption Spectra in the Ultraviolet Region by Gas Chromatography

ABSTRACTThe aim of this study was to obtain quantitative characteristics of the ultraviolet absorption spectra as the molecular absorptivity at the wavelength of maximum absorbance. Organic as well as inorganic compounds were explored. A gas chromatography—ultraviolet absorption instrument has been used in the quantitative study of molecular ultraviolet absorption spectra in the vapour phase. The wavelength range studied was between 168 and 330 nm. The absorbance of 170 compounds was determined relative to perchloroethylene and their molecular absorptivities were calculated. For various groups of compounds, these relative absorptivities varied within two to three orders of magnitude. Standard curves were linear within four orders of magnitude from limit of quantification up to an absorption value of 1.5 absorbance units. The noise level was 3 × 10−5 absorbance units peak to peak at a bandwidth of 1.7 nm and a wavelength range from 180 to 330 nm was preferred. The detection limit for mesitylene was calculated to be 2 pg/s and for naphthalene 1 pg/s with 4 s store cycle time.