Foreign gas broadening and shift of the strongly “forbidden” lead line at 1278.9 nm

The collisional broadening and shift rate coefficients of the “forbidden“ 6p^{2 3}P₀ → 6p^{2 3}P₁ transition in lead were determined by diode laser absorption measurements performed simultaneously in two resistively heated hot-pipes. One hot-pipe contained Pb vapor and noble gas (Ar or He) at low pressure, while the other was filled with Pb and noble gas at variable pressure. The measurements were performed at temperatures of 1220 K and 1290 K, i.e., lead number densities of 4.8 × 10¹⁵ cm^− 3 and 1.2 × 10¹⁶ cm^− 3. The broadening rates were obtained by fitting the experimental collisionally broadened absorption line shapes to theoretical Voigt profiles. The shift rates were determined by measuring the difference between the peak absorption positions in the spectra measured simultaneously in the heat pipe filled with noble gas at reference pressure and the one with noble gas at variable pressure. The following data for the broadening and shift rate coefficients due to collisions with Ar and He were obtained: γ_B^Ar = (3.4 ± 0.1) × 10^− 10 cm³ s^− 1, γ_B^He = (3.8 ± 0.1) × 10^− 10 cm³ s^− 1, γ_S^Ar = (− 7.3 ± 0.8) × 10^− 11 cm³ s^− 1, γ_S^He = (− 6.5 ± 0.7) × 10^− 11 cm³ s^− 1.     

Resonantly laser induced plasmas in gases: The role of energy pooling and exothermic collisions in plasma breakdown and heating

The present work is a systematic experimental study of the plasma formation in cesium vapor induced by a continuous laser tuned to the resonance transition 6S_1/2–6P_3/2. Taking into account the measured absolute population densities of Cs ground and excited state atoms as well as the electron densities derived from Stark broadening of the Cs lines, complete local thermodynamic equilibrium in the laser-produced plasma was found for laser power densities ≈ 10 Wcm^− 2 at cesium ground state number densities of about 10¹⁷ cm^− 3. Direct conversion of the excitation energy or parts of the excitation energy in exothermic collisions of laser-excited atoms is concluded to be the major process for atomic vapor heating and subsequent formation of LTE plasmas.     

Photophysical properties of gatifloxacin in aqueous solution by laser flash photolysis and pulse radiolysis

GFX in water, at pH 7.0, shows intense absorption bands with peaks at 284 and 333 nm, (ε=24,670 and 12,670 M⁻¹ cm⁻¹). Both the absorption and emission properties of GFX were pH-dependent; the pK_a values for the protonation equilibria of the ground state (5.7 and 8.9) and excited singlet state (3.6 and 7.5) of GFX were determined spectroscopically. GFX fluoresces weakly, with a maximum quantum yield for fluorescence emission (0.06) at pH 4.7. A series of experiments were performed to characterize the transient species of GFX in aqueous solution using laser flash photolysis and pulse radiolysis. GFX undergoes monophotonic photoionization with a quantum yield of 0.16 on a 355 nm laser excitation. This process leads to the formation of a long-lived cation radical with a maximum absorption at 380 nm. Triplet-triplet absorption had maximum absorption at 510 nm. The reaction of GFX with one-electron oxidant N₃• was investigated and the bimolecular rate constant was determined to be 3.1×10⁹ M⁻¹ s⁻¹.     

IRRS, UV-Vis-NIR absorption and photoluminescence upconversion in Ho-doped oxyfluorophosphate glasses

Infrared reflection spectroscopic (IRRS), ultraviolet-visible-near infrared (UV-Vis-NIR) absorption and photoluminescence upconversion properties with special emphasis on the spectrochemistry of the oxyfluorophosphate (oxide incorporated fluorophosphates) glasses of the Ba(PO₃)₂-AlF₃-CaF₂-SrF₂-MgF₂-Ho₂O₃ system have been studied with different concentrations (0.1, 0.3 and 1.0 mol%) of Ho₂O₃. IRRS spectral band position and intensity of Ho³⁺ ion doped oxyfluorophosphate glasses have been discussed in terms of reduced mass and force constant. UV-Vis-NIR absorption band position has been justified with quantitative calculation of nephelauxetic parameter and covalent bonding characteristics of the host. NIR to visible upconversion has been investigated by exciting at 892 nm at room temperature. Three upconverted bands originated from the ⁵F₃→⁵I₈, (⁵S₂, ⁵F₄)→⁵I₈ and ⁵F₅→⁵I₈ transitions have found to be centered at 491 nm (blue, medium), 543 nm (green, very strong) and 658 nm (red, weak), respectively. These bands have been justified from the evaluation of the absorption, normal (down conversion) fluorescence and excitation spectra. The upconversion processes have been explained by the excited state absorption (ESA), energy transfer (ET) and cross relaxation (CR) mechanisms involving population of the metastable (storage) energy levels by multiphonon deexcitation effect. It is evident from the IRRS study that the upconversion phenomena are expedited by the low multiphonon relaxation rate in oxyfluorophosphate glasses owing to their high intense low phonon energy (∼600 cm⁻¹) which is very close to that of fluoride glasses (500-600 cm⁻¹).     

Binuclear ruthenium and osmium mixed-valence complexes containing fused and flexible polypyridyl bridging ligands

{Os(bpy)₂}²⁺ and {Ru(CN)₄}²⁻ mononuclear and binuclear complexes with ligands 2,3-di-(2-pyridyl)quinoxaline (dpq) and dipyrido[2,3-a:3′,2′-c]phenazine (ppb) have been prepared. For the binuclear complexes a splitting in oxidation potentials is observed consistent with the formation of mixed-valence species with comproportionation constants (K_com) ranging from 2.5 × 10⁴ to 1.8 × 10⁶. The electronic absorption spectra of the mixed-valence species reveal IVCT transitions in the near infrared region. The absorption maximum for the IVCT band ranges from 5800 to 9980 cm⁻¹ and the extinction coefficients from 80 to 6300 M⁻¹ cm⁻¹. In general the {Os(bpy)₂}²⁺ complexes show larger K_com values and more intense IVCT bands than the corresponding {Ru(CN)₄}²⁻ complexes.     

Fast sequential multi-element determination of Ca,Mg, K,Cu, Fe,Mn and Zn for foliar diagnosis using high-resolution continuum source flame atomic absorption spectrometry: Feasibility of secondary lines,side pixel registration and least-squares background correction

The fast sequential multi-element determination of Ca, Mg, K, Cu, Fe, Mn and Zn in plant tissues by high-resolution continuum source flame atomic absorption spectrometry is proposed. For this, the main lines for Cu (324.754 nm), Fe (248.327 nm), Mn (279.482 nm) and Zn (213.857 nm) were selected, and the secondary lines for Ca (239.856 nm), Mg (202.582 nm) and K (404.414 nm) were evaluated. The side pixel registration approach was studied to reduce sensitivity and extend the linear working range for Mg by measuring at wings (202.576 nm; 202.577 nm; 202.578 nm; 202.580 nm; 202.585 nm; 202.586 nm; 202.587 nm; 202.588 nm) of the secondary line. The interference caused by NO bands on Zn at 213.857 nm was removed using the least-squares background correction. Using the main lines for Cu, Fe, Mn and Zn, secondary lines for Ca and K, and line wing at 202.588 nm for Mg, and 5 mL min^− 1 sample flow-rate, calibration curves in the 0.1–0.5 mg L^− 1 Cu, 0.5–4.0 mg L^− 1 Fe, 0.5–4.0 mg L^− 1 Mn, 0.2–1.0 mg L^− 1 Zn, 10.0–100.0 mg L^− 1 Ca, 5.0–40.0 mg L^− 1 Mg and 50.0–250.0 mg L^− 1 K ranges were consistently obtained. Accuracy and precision were evaluated after analysis of five plant standard reference materials. Results were in agreement at a 95% confidence level (paired t-test) with certified values. The proposed method was applied to digests of sugar-cane leaves and results were close to those obtained by line-source flame atomic absorption spectrometry. Recoveries of Ca, Mg, K, Cu, Fe, Mn and Zn in the 89–103%, 84–107%, 87–103%, 85–105%, 92–106%, 91–114%, 96–114% intervals, respectively, were obtained. The limits of detection were 0.6 mg L^− 1 Ca, 0.4 mg L^− 1 Mg, 0.4 mg L^− 1 K, 7.7 µg L^− 1 Cu, 7.7 µg L^− 1 Fe, 1.5 µg L^− 1 Mn and 5.9 µg L^− 1 Zn.     

Organic,inorganic and total mercury determination in fish by chemical vapor generation with collection on a gold gauze and electrothermal atomic absorption spectrometry

A method for organic, inorganic and total mercury determination in fish tissue has been developed using chemical vapor generation and collection of mercury vapor on a gold gauze inside a graphite tube and further atomization by electrothermal atomic absorption spectrometry. After drying and cryogenic grinding, potassium bromide and hydrochloric acid solution (1 mol L^− 1 KBr in 6 mol L^− 1 HCl) was added to the samples. After centrifugation, total mercury was determined in the supernatant. Organomercury compounds were selectively extracted from KBr solution using chloroform and the resultant solution was back extracted with 1% m/v L-cysteine. This solution was used for organic Hg determination. Inorganic Hg remaining in KBr solution was directly determined by chemical vapor generation electrothermal atomic absorption spectrometry. Mercury vapor generation from extracts was performed using 1 mol L^− 1 HCl and 2.5% m/v NaBH₄ solutions and a batch chemical vapor generation system. Mercury vapor was collected on the gold gauze heated resistively at 80 °C and the atomization temperature was set at 650 °C. The selectivity of extraction was evaluated using liquid chromatography coupled to chemical vapor generation and determination by inductively coupled plasma mass spectrometry. The proposed method was applied for mercury analysis in shark, croaker and tuna fish tissues. Certified reference materials were used to check accuracy and the agreement was better than 95%. The characteristic mass was 60 pg and method limits of detection were 5, 1 and 1 ng g^− 1 for organic, inorganic and total mercury, respectively. With the proposed method it was possible to analyze up to 2, 2 and 6 samples per hour for organic, inorganic and total Hg determination, respectively.     

Solvent effects on the ultraviolet absorption spectrum of mercury atom

Absorption spectrum of mercury dissolved in hexane and heptane in the region 280–180 nm was found to consist of three bands. These bands were assigned to the ¹S₀ → ¹P₁ transition (A band, λ = 254 nm), to the ¹S₀ → ³P₂ transition (B band, λ = 226 nm) and to the ¹S₀ → ¹P₁ transition (C band, λ = 190 nm) of a mercury atom placed into a liquid cell. The B and C absorption bands of mercury in liquid solutions were observed for the first time. It was found that the A band and the C band have, respectively, distinct doublet and triplet structure, while the doublet structure of the B band is only slightly seen. The oscillator strengths of all three bands of mercury in solutions were estimated. The structure of the C, A and B bands of mercury in solutions most probably results from the removal of the degeneracy of the excited states ¹P₁, ³P₁ and ³P₂ of a mercury atom, placed into a cell of low symmetry.     

Application of UV–Vis,near-infrared and mid-infrared spectroscopy to the study of Mn-bearing humites

The combination of electronic and vibrational spectra has been applied to correlate the spectral properties, with composition, structure and cation substitutions such as Mn, Fe, Ca and Zn for Mg in humites: norbergite, alleghanyite, leucophoenicite and sonolite with increasing number of silicate layers, 1, 2, 3 and 4. The observation of two broad bands in the visible range, near 550 and 450 nm (18 180 and 22 220 cm⁻¹) and one sharp band around 410 nm (24 390 cm⁻¹) is characteristic of Mn²⁺ in alleghanyite and leucophoenicite. The study of UV–Vis (electronic) spectral features confirms Mn as a major substituent in these two samples. Cation impurities like Zn and Ca as revealed from EDX analysis might be the cause for the absence of Mn-type spectrum in sonolite. The first observation is the near-infrared spectra of all four minerals in the first fundamental overtone OH-stretching mode are different and each mineral is characterized by its NIR spectrum. The feature in the range 7180–6600 cm⁻¹ [1393–1515 nm or 1.39–1.52 μm] corresponds to the overtones of OH stretching vibrational modes of the humite groups observed in their IR spectra over the range, 3680–3320 cm⁻¹. The infrared spectra of the hydrous components of OH and SiO₄ groups in the mineral structure act as an aid to distinguish the minerals of the humite mineral group. A band at 541 cm⁻¹ is assigned to MnO stretching mode.     

Development of novel and sensitive methods for the determination of sulfide in aqueous samples by hydrogen sulfide generation-inductively coupled plasma-atomic emission spectroscopy

Two new, simple and accurate methods for the determination of sulfide (S²⁻) at low levels (μg L⁻¹) in aqueous samples were developed. The generation of hydrogen sulfide (H₂S) took place in a coil where sulfide reacted with hydrochloric acid. The resulting H₂S was then introduced as a vapor into an inductively coupled plasma-atomic emission spectrometer (ICP-AES) and sulfur emission intensity was measured at 180.669 nm. In comparison to when aqueous sulfide was introduced, the introduction of sulfur as H₂S enhanced the sulfur signal emission. By setting a gas separator at the end of the reaction coil, reduced sulfur species in the form of H₂S were removed from the water matrix, thus, interferences could be avoided. Alternatively, the gas separator was replaced by a nebulizer/spray chamber combination to introduce the sample matrix and reagents into the plasma. This methodology allowed the determination of both sulfide and sulfate in aqueous samples. For both methods the linear response was found to range from 5 μg L⁻¹ to 25 mg L⁻¹ of sulfide. Detection limits of 5 μg L⁻¹ and 6 μg L⁻¹ were obtained with and without the gas separator, respectively. These new methods were evaluated by comparison to the standard potentiometric method and were successfully applied to the analysis of reduced sulfur species in environmental waters.     

Sensing hydrogen peroxide involving intramolecular charge transfer pathway: A boronate-functioned styryl dye as a highly selective and sensitive naked-eye sensor

The synthesis, properties and applications of a novel boronate-functioned styryl dye, BSD, as a colorimetric sensor for hydrogen peroxide is presented. The dye displayed remarkable color change from colorless (λ_max = 391 nm) to deep red (λ_max = 522 nm) in the presence of H₂O₂ and the behavior could be rationalized by the chemoselective H₂O₂-mediated transformation of arylboronate to phenolate, resulting in the release of the merocyanine dye which featured with strong intramolecular charge transfer (ICT) absorption band. The absorption increment of merocyanine at λ_max = 522 nm (? = 87000 L mol⁻¹ cm⁻¹) is linear with the concentration of H₂O₂ in the range of 1.0 × 10⁻⁷-2.5 × 10⁻⁵ mol L⁻¹ with the detection limit of 6.8 × 10⁻⁸ mol L⁻¹ under optimum conditions. There is almost no interference by other species that commonly exist due to the specific deprotection of H₂O₂ towards arylboronate group on BSD. The chromogenic sensor has been applied to the detection of trace amounts of hydrogen peroxide in rain water.     

A spectrophotometric assay for quantification of artemisinin

A sensitive and rapid spectrophotometric method for determination of artemisinin concentration is described. The method is based on the measurement of a reaction product of the drug in strong alkali solution. The interaction produces a homogenous electronic transition band from 250 to 330 nm with maximum transition at around 291 nm. The absorption curve shows Gaussian distribution with identical half bandwidth, thus providing information for formation of a possible mono-type reaction product. The 291 nm absorption intensity increases with increasing concentration of artemisinin and obeys Beer's law in the range of 0.44-172 nmol (ml⁻¹). The optimum reaction conditions and other analytical parameters were evaluated including its recovery from human plasma and erythrocyte samples.     

Investigation of ultraviolet photolysis vapor generation with in-atomizer trapping graphite furnace atomic absorption spectrometry for the determination of mercury

Generation of mercury vapor by ultraviolet irradiation of mercury solutions in low molecular weight organic acid solutions prior to measurement by Atomic Absorption Spectrometry is a cheap, simple and green method for determination of trace concentrations of mercury. In this work mercury vapor generated by ultraviolet photolysis was trapped onto a palladium coated graphite furnace significantly improving the detection limit of the method. The system was optimized and a detection limit of 0.12 µg L^− 1 (compared to 2.1 µg L^− 1 for a previously reported system in the absence of trapping) with a precision of 11% for a 10 µg L^− 1 mercury standard (RSD, N = 5).     

A multicommuted flow-system for spectrophotometric determination of tannin exploiting the Cu(I)/BCA complex formation

A flow system exploiting the multicommutation approach is proposed for spectrophotometric determination of tannin in beverages. The procedure is based on the reduction of Cu(II) in the presence of 4,4′-dicarboxy-2,2′-biquinoline, yielding a complex with maximum absorption at 558 nm. Calibration graph was linear (r = 0.999) for tannic acid concentrations up to 5.00 μmol L^− 1. The detection limit and coefficient of variation were estimated as 10 nmol L^− 1 (99.7% confidence level) and 1% (1.78 μmol L^− 1 tannic acid, n = 10), respectively. The sampling rate was 50 determinations per hour. The proposed procedure is more sensitive and selective than the official Folin-Denis method, also minimizing drastically waste generation. Recoveries within 91.8 and 115% were estimated for total tannin determination in tea and wine samples.     

A colorimetric and ratiometric fluorescent turn-on fluoride chemodosimeter and application in live cell imaging: high selectivity via specific SiO cleavage in semi aqueous media and prompt recovery of ESIPT along with the X-ray structures

A ratiometric fluorescent turn-on probe for fluoride ion, based on modulation of the excited-state intramolecular proton transfer (ESIPT) process by chemodosimetric desilylation pathway is reported. The probe SNBT (silyl protected hydroxynaphthalene benzothiazole moiety) shows a significant increase of ratiometric absorption band at 440 nm and emission band at 477 nm by the deprotection of fluoride mediated silyl bond cleavage in CH₃CN–H₂O (8/2, v/v, 25 °C). The test strips based on SNBT and F⁻ are fabricated, which can act as a convenient and efficient F⁻ test kits. Furthermore, the biological application shows that it can be very useful as a selective fluoride probe in the fluorescence imaging of living cells.     

Spectroscopic and structural characterization of Na2[(VO)2(ttha)]·8H2O (ttha = triethylenetetraamine-N,N,N′,N″,N′″,N′″-hexaacetate): Interpreting the results with density functional theory

Na₂[(V^IVO)₂(ttha)]·8 H₂O (ttha = triethylenetetraamine–N,N,N′,N″,N′″,N′″–hexaacetate ion), prepared by treating [VO(H₂O)₅][(VO)₂(ttha)]·4 H₂O with Na₆(ttha), has been characterized by single crystal X-ray diffraction, infrared spectroscopy, UV–Vis absorption spectroscopy, electron spin resonance spectroscopy, and modeled by density functional theory (DFT). The X-ray structure revealed a distorted octahedral geometry around each vanadium center. The electronic absorption spectrum of [(VO)₂(ttha)]²⁻ (aq) features absorptions at ca. 200 nm (ε > 13900 L mol⁻¹ cm⁻¹), 255 nm (ε = 3480 L mol⁻¹ cm⁻¹), 586 nm (ε = 33 L mol⁻¹ cm⁻¹), and 770 nm (ε = 38 L mol⁻¹ cm⁻¹). The time-dependent density functional theory (TDDFT) calculated electronic absorption spectrum was remarkably similar to the actual spectrum, and TDDFT predicts absorption peaks at 297, 330, 458, 656, and 798 nm. TDDFT assigned the peak at 798 nm to be the α spin HOMO → LUMO transition. Hence, the peak at 770 nm in the actual spectrum is most likely the α spin HOMO → LUMO transition. Moreover, the TDDFT calculations revealed that the α spin HOMO and LUMO are partly comprised of d orbitals on both vanadium centers, and the first derivative electron spin resonance spectrum also suggests that the two unpaired electrons in [(VO)₂(ttha)]²⁻ are localized near the vanadium centers.     

FTIR and fluorescence studies on the ground and excited state hydrogen-bonding interactions between 1-methylindole and water in water–triethylamine mixtures

The ground and excited state π-hydrogen-bonding interactions between 1-methylindole, MI, and water have been investigated in water–triethylamine, water–TEA, mixtures. FTIR measurements performed on the OH stretching bands of the water–TEA clusters show that, upon MI addition, the typical bands of the water–TEA system at 3348 cm⁻¹, 3440 cm⁻¹, 3545 cm⁻¹ and 3682 cm⁻¹ diminish, whereas two new absorption bands at 3316 cm⁻¹ and 3654 cm⁻¹ grow up. These spectral changes have been rationalised assuming the formation of only one 1:1 water–MI complex, in which the dangling protons in the water–TEA clusters are hydrogen bonded to the π-cloud of the MI aromatic ring. Steady state and time resolved fluorescence measurements provide additional proofs on the ground state formation of a fluorescent OH ? π hydrogen bonded complex. The relevance that the present and the previously reported results could have on the indole ring photophysics is discussed.     

Photoluminescence of new red phosphor SrZnO2:Eu

SrZnO₂:Eu³⁺ has been synthesized by solid-state reaction and its photoluminescence in ultraviolet (UV)-vacuum ultraviolet (VUV) range was investigated. The broad bands around 254 nm are assigned to CT band of Eu³⁺-O²⁻. With the increasing of Eu³⁺ concentration, Eu³⁺ could occupy different sites, which leads to the broadening of CT band. A sharp band is observed in the region of 110-130 nm, which is related to the host absorption. The phosphors emit red luminescence centered at about 616 nm due to Eu³⁺⁵D₀→⁷F₂ both under 254 and 147 nm, but none of Eu²⁺ blue emission can be observed.     

Determination of Se in biological samples by axial view inductively coupled plasma optical emission spectrometry after digestion with aqua regia and on-line chemical vapor generation

A simple and fast method for the determination of Se in biological samples, including food, by axial view inductively coupled plasma optical emission spectrometry using on-line chemical vapor generation (CVG–ICP OES) is proposed. The concentrations of HCl and NaBH₄, used in the chemical vapor generation were optimized by factorial analysis. Six certified materials (non-fat milk powder, lobster hepatopancreas, human hair, whole egg powder, oyster tissue, and lyophilised pig kidney) were treated with 10 mL of aqua regia in a microwave system under reflux for 15 min followed by additional 15 min in an ultrasonic bath. The solutions were transferred to a 100 mL volumetric flask and the final volume was made up with water. The Se was determined directly in these solutions by CVG–ICP OES, using the analytical line at 196.026 nm. Calibration against aqueous standards in 10% v/v aqua regia in the concentration range of 0.5–10.0 µg L^− 1 Se(IV) was used for the analysis. The quantification limit, considering a 0.5 g sample weight in a final volume of 100 mL^− 1 was 0.10 µg g^− 1. The obtained concentration values were in agreement with the total certified concentrations, according to the t-test for a 95% confidence level.     

Identification of charge transfer (CT) transition in (Gd,Y)BO3:Eu phosphor under 100-300 nm

A broad excitation band in an excitation spectrum of (Gd,Y)BO₃:Eu was observed in the VUV region. It could be considered that this band was composed of two bands at about 160 and 166 nm. The preceding band was assigned to the BO₃ group absorption. The later one at about 166 nm could be assigned to the charge transfer (CT) transition of Gd³⁺-O²⁻. Such an assignment was deduced from the result that broadbands at around 170 nm for GdAlO₃:Eu, and at 183 nm for Gd₂SiO₅:Eu are due to the CT transition of Gd³⁺-O²⁻; this was also identified by CaZr (BO₃)₂:Eu. Since there are no Gd³⁺ ions in it; a weak band in the VUV region in the excitation spectrum of Ca_0.95ZrEu_0.05(BO₃)₂ was observed. The excitation spectra were overlapped between the CT transition of Gd³⁺-O²⁻ and BO₃ group absorption, and it caused the emission of Eu³⁺ effectively in the trivalent europium-doped (Gd,Y)BO₃ host lattice under 147 nm excitation. Intense broad excitation bands were observed at about 155 nm for YBO₃:Eu and at about 153 nm for YAlO₃:Eu; it could be attributed to the CT transition between Y³⁺ and O²⁻. As a result, under the xenon discharge (147 nm) excitation, the intense emission of Eu³⁺ in GdBO₃ was found to be more convenient just because of the partial substitution of Y³⁺ for Gd³⁺.