Ion imaging studies of ClONO2 photodissociation: Primary branching ratios and secondary dissociation

The photodissociation dynamics of ClONO₂ at 235 nm has been reinvestigated using velocity map ion imaging. We report branching ratios for the Cl + NO₃ and ClO + NO₂ channels to be 0.49:0.51 with anisotropy parameters of β = 0.5 ± 0.1 and β = −0.1 ± 0.3 for the Cl and ClO production channels, respectively. Photodissociation at 248 nm and 262 nm results in similar branching ratios and dynamics as observed at 235 nm. Measured O(³P₂) images arising from ClONO₂ dissociation at 226 nm suggest that oxygen atoms result from the spontaneous dissociation of metastable NO₃. The quantum yield of O atoms arising from the spontaneous dissociation of NO₃ varies from 0.09 at 262 to 0.38 at 235 nm based on the derived internal energy distributions of the NO₃ fragments. We also describe a Monte-Carlo forward-convolution fitting of imaging data which permits detailed analysis of both spontaneous secondary dissociation and secondary photodissociation.     

Simulation of equivalent weight dependence of Nafion morphologies and predicted trends regarding water diffusion

Microphase separation within hydrated Nafion^® membranes was simulated using Dissipative Particle Dynamics (DPD). Morphologies were obtained at branching densities corresponding with equivalent weights ranging from 800 to 1400 (g/mole SO₃) and water percentage volume contents ([H₂O]) varying between 10% and 30%. All cases showed pronounced microphase separation involving a hydrophobic Teflon phase and a hydrophilic phase in which water is associated with SO₃ groups that are located near the phase boundaries. Pore morphologies were found to depend strongly on water content and branching density. The average pore radius (R_pore) and the distance between the pores (D_cl-cl) were found to increase with water content obeying the relations R_pore = 1.3 + α[H₂O] (nm), and D_cl-cl = 3.2 + β[H₂O] (nm). The values of the expansion coefficients α and β decrease linearly with branching density with α = 5.3 × 10⁻⁵ × (EW-450) and β = 1.3 × 10⁻⁴ × (EW-450) nm/vol%. For decreasing branching density the pores obtain a more spherical character. The consequence of this on water diffusion is estimated by employing Monte Carlo trajectory calculations in which we assume that water movement is confined within the hydrophilic phase and local water mobility to be equal to that of pure water. The estimated diffusion constants increase linearly with branching density (i.e. linear decrease with equivalent weight). Experimental water diffusion constants obtained from literature for Nafion1100 membrane are in good agreement with our calculations. A counterintuitive picture evolves in which smaller pores lead to enhanced water diffusion.     

Ni + B2H6: Spectroscopic observations on NiB and NiH

An electronic spectrum of the nickel monoboride radical has been observed for the first time, in a reaction between a nickel plasma and diborane. Numerous bands of ⁵⁸Ni¹⁰B and ⁵⁸Ni¹¹B have been recorded between 442 and 503 nm in laser-induced fluorescence (LIF). Dispersed fluorescence experiments have also been performed. The LIF spectrum is dominated by a strong progression of bands of a [19.7]²Σ⁺–X²Σ⁺ transition. Analyses have been carried out to yield the following ⁵⁸Ni¹¹B ground state parameters: r₀ = 0.1698 nm, ω_e = 778 cm⁻¹, ω_ex_e = 4.9 cm⁻¹. Strong signals from NiH have also been observed.     

Emission enhancement using two orthogonal targets in double pulse laser-induced breakdown spectroscopy

The enhancement of emission intensity resulting from the interaction between two laser-induced plasmas on two orthogonal targets was investigated using double pulse laser-induced breakdown spectroscopy (LIBS) at 0.7 Pa, by means of time-resolved spectroscopy and fast photography. The results showed that the interaction between both plasmas improved carbon emission intensity in comparison to a single laser-induced plasma. For all the carbon lines of interest 477.2 nm (CI), 426.7 nm (CII), and 473.4 nm (C₂ Swan band head), the intensity enhancement showed a maximum at a delay between lasers in the range from 2 to 5 μs; moreover it increased with the fluence of the first laser. On the other hand, in the case of C₂ the intensity enhancement reached a maximum at 5 mm from the target; however it decreased with increasing fluence of the second laser. The largest intensity enhancement found was twofold for atomic species and sixfold for molecular species.     

Ground state C2 density measurement in carbon plume using laser-induced fluorescence spectroscopy

The temporal evolution and spatial distribution of C₂ molecules produced by laser ablation of a graphite target is studied using optical emission spectroscopy, dynamic imaging and laser-induced fluorescence (LIF) investigations. We observe peculiar bifurcation of carbon plume into two parts; stationary component close to the target surface and a component moving away from the target surface which splits further in two parts as the plume expands. The two distinct plumes are attributed to recombination of carbon species and formation of nanoparticles. The molecular carbon C₂ moves with a faster velocity and dies out at ~ 800 ns whereas the clusters of nanoparticle move with a slower velocity due to their higher mass and can be observed even after 1600 ns. C₂ molecules in the d³Π_g state were probed for laser-induced fluorescence during ablation of graphite using the Swan (0,0) band at 516.5 nm. The fluorescence spectrum and images of fluorescence d³Π_g − a³Π_u(0,1)(λ = 563.5 nm) are recorded using a spectrograph attached to the ICCD camera. To get absolute ground state C₂ density from fluorescence images, the images are calibrated using complimentary absorption experiment. This study qualitatively helps to get optimum conditions for nanoparticle formation using the laser ablation of graphite target and hence deducing optimum conditions for thin film deposition.     

Doubly ionized ion emission in laser-induced breakdown spectroscopy in air

The emission from doubly ionized species in laser-induced plasmas has not been properly investigated before since most analytical measurements were made at relatively long delays. This work proves that doubly ionized species, such as boron (B) III and iron (Fe) III, can exist during the first 150–200 ns of the plasma lifetime in plasmas produced in air by typical lasers with irradiances of 10⁹–10¹¹ W/cm². The emission from these ions was detected using both the double- and single-pulse excitations. The sum of the second ionization potential and the energy of corresponding excited states is approximately 30 eV. The presence of doubly charged ions in the early plasma was additionally confirmed by computer simulations using a collision-dominated plasma model. The emission from doubly ionized species may be used for analytical purpose. For example, in the spectrum from a B–Fe ore, the B III analytical line at 206.6 nm is free from Fe spectral interference thus enabling the online laser-induced breakdown spectroscopy sorting of ores into three products with high, medium, and low B₂O₃ contents.     

Preparation and catalytic activity of titanium silicalite-1 zeolite membrane with TPABr as template

The preparation of the supported titanium silicalite-1 (TS-1) zeolite membrane with inexpensive tetrapropylammonium bromide (TPABr)/weak base synthesis system was studied by three methods, and the catalytic activity of the obtained TS-1 zeolite membrane was evaluated with the oxidation of 2-propanol (IPA) under pervaporation condition. It was found that TS-1 zeolite membrane could be successfully prepared with “seeding” or “seeding in situ” method, but could not be achieved with “in situ” method. Adding a little amount of promoter ions of PO₄³⁻ into the synthesis gel was of benefit to the catalytic activity of the prepared TS-1 zeolite membrane, but had no obvious effect on the membrane layer formation on the mullite porous support. For “seeding” method, the membrane prepared with the synthesis gel having molar composition of SiO₂:0.1TPABr:0.9Et₂NH:0.03TiO₂:80H₂O:0.06H₃PO₄ at 150 °C for 48 h showed the highest oxidation conversion of IPA of 72% accompanied by a flux of 0.35 kg/m² h. Further more, much higher IPA oxidation conversion of 76% accompanied by a flux of 0.65 kg/m² h was obtained for the TS-1 zeolite membrane prepared with the same synthesis gel by “seeding in situ” method at 150 °C for 72 h.     

Synthesis and reactivity of neodymium(III) amido-tethered N-heterocyclic carbene complexes

The reaction of the heteroleptic Nd(III) iodide, [Nd(L′)(N″)(μ-I)] with the potassium salts of primary aryl amides [KN(H)Ar′] or [KN(H)Ar^*] affords heteroleptic, structurally characterised, low-coordinate neodymium amides [Nd(L′)(N″)(N(H)Ar′)] and [Nd(L′)(N″)(N(H)Ar^*)] cleanly (L′ = t-BuNCH₂CH₂[C{NC(SiMe₃)CHNt-Bu}], N″ = N(SiMe₃)₂, Ar′ = 2,6-Dipp₂C₆H₃, Dipp = 2,6-Prⁱ₂C₆H₃, Ar^* = 2,6-(2,4,6-Prⁱ₃C₆H₂)₂C₆H₃). The potassium terphenyl primary amide [KN(H)Ar^*] is readily prepared and isolated, and structurally characterised. Treatment of these primary amide-containing compounds with alkali metal alkyl salts results in ligand exchange to give alkali metal primary amides and intractable heteroleptic Nd(III) alkyl compounds of the form [Nd(L′)(N″)(R)] (R = CH₂SiMe₃, Me). Attempted deprotonation of the Nd-bound primary amide in [Nd(L′)(N″)(N(H)Ar^*)] with the less nucleophilic phosphazene superbase Bu^tNP{NP(NMe₂)₃}₃ resulted in indiscriminate deprotonations of peripheral ligand CH groups.     

Different Photosynthetic Responses of Pyropia yezoensis to Ultraviolet Radiation Under Changing Temperature and Photosynthetic Active Radiation Regimes

Macroalgae play a crucial role in coastal marine ecosystems, but they are also subject to multiple challenges due to tidal and seasonal alterations. In this work, we investigated the photosynthetic response of Pyropia yezoensis to ultraviolet radiation (PAR: 400–700 nm; PAB: 280–700 nm) under changing temperatures (5, 10 and 15°C) and light intensities (200, 500 and 800 μmol photons m^?2 s^?1). Under low light intensity (200 μmol photons m^?2 s^?1), P. yezoensis showed the lowest sensitivity to ultraviolet radiation, regardless of temperature. However, higher temperatures inhibited the repair rates (r) and damage rates (k) of photosystem II (PSII) in P. yezoensis. However, under higher light intensities (500 and 800 μmol photons m^?2 s^?1), P. yezoensis showed higher sensitivity to UV radiation. Both r and the ratio of repair rate to damage rate (r:k) were significantly inhibited in P. yezoensis by PAB, regardless of temperature. In addition, higher temperatures significantly decreased the relative UV‐inhibition rates, while an increased carbon fixation rate was found. Our study suggested that higher light intensities enhanced the sensitivity to UV radiation, while higher temperatures could relieve the stress caused by high light intensity and UV radiation.     

Vacuum ultraviolet laser-induced breakdown spectroscopy analysis of polymers

Laser-induced breakdown spectroscopy (LIBS) in the vacuum ultraviolet range (VUV, λ < 200 nm) is employed for the detection of trace elements in polyethylene (PE) that are difficult to detect in the UV/VIS range. For effective laser ablation of PE, we use a F₂ laser (wavelength λ = 157 nm) with a laser pulse length of 20 ns, a pulse energy up to 50 mJ, and pulse repetition rate of 10 Hz. The optical radiation of the laser-induced plasma is measured by a VUV spectrometer with detection range down to λ = 115 nm. A gated photon-counting system is used to acquire time-resolved spectra. From LIBS measurements of certified polymer reference materials, we obtained a limit of detection (LOD) of 50 µg/g for sulphur and 215 µg/g for zinc, respectively.The VUV LIBS spectra of PE are dominated by strong emission lines of neutral and ionized carbon atoms. From time-resolved measurements of the carbon line intensities, we determine the temporal evolution of the electronic plasma temperature, T_e. For this, we use Saha–Boltzmann plots with the electron density in the plasma, N_e, derived from the broadening of the hydrogen H-α line. With the parameters T_e and N_e, we calculate the intensity ratio of the atomic sulphur and carbon lines at 180.7 nm and at 175.2 nm, respectively. The calculated intensity ratios are in good agreement with the experimentally measured results.     

Pulsed laser-induced oxygen deficiency at TiO2 surface: Anomalous structure and electrical transport properties

We have studied pulsed laser-induced oxygen deficiencies at rutile TiO₂ surfaces. The crystal surface was successfully reduced by excimer laser irradiation, and an oxygen-deficient TiO_2−δ layer with 160 nm thickness was formed by means of ArF laser irradiation at 140 mJ/cm² for 2000 pulses. The TiO_2−δ layer fundamentally maintained a rutile structure, though this structure was distorted by many stacking faults caused by the large oxygen deficiency. The electrical resistivity of the obtained TiO_2−δ layer exhibited unconventional metallic behavior with hysteresis. A metal–insulator transition occurred at 42 K, and the electrical resistivity exceeded 10⁴ Ω cm below 42 K. This metal–insulator transition could be caused by bipolaronic ordering derived from Ti–Ti pairings that formed along the stacking faults. The constant magnetization behavior observed below 42 K is consistent with the bipolaronic scenario that has been observed previously for Ti₄O₇. These peculiar electrical properties are strongly linked to the oxygen-deficient crystal structure, which contains many stacking faults formed by instantaneous heating during excimer laser irradiation.     

Effects of Light Intensity on the Growth and Lipid Accumulation of Microalga <Emphasis Type="Italic">Scenedesmus</Emphasis> sp. 11-1 Under Nitrogen Limitation

Scenedesmus spp. have been reported as potential microalgal species used for the lipid production. This study investigated the effects of light intensity (at three levels: 50, 250, and 400 μmol photons m⁻² s⁻¹) on the growth and lipid production of Scenedesmus sp. 11-1 under N-limited condition. Carotenoid to chlorophyll ratio was higher when algae 11-1 grew under 250 and 400 μmol photons m⁻² s⁻¹ than that under 50 μmol photons m⁻² s⁻¹, while protein contents was lower. Highest biomass yield (3.88 g L⁻¹), lipid content (41.1 %), and neutral lipid content (32.9 %) were achieved when algae 11-1 grew at 400 μmol photons m⁻² s⁻¹. Lipid production was slight lower at 250 μmol photons m⁻² s⁻¹ level compared to 400 μmol photons m⁻² s⁻¹. The major fatty acids in the neutral lipid of 11-1 were oleic acid (43–52 %), palmitic acid (24–27 %), and linoleic acid (7–11 %). In addition, polyunsaturated fatty acids had a positive correlation with total lipid production, and monounsaturated fatty acids had a negative one.     

Binding of 6-propyl-2-thiouracil to human serum albumin destabilized by chemical denaturants

We compared the binding affinity of 6-propyl-2-thiouracil (PTU) with native and destabilized human serum albumin (HSA) as a model to assess the binding ability of albumin in patients suffering from chronic liver or renal diseases. Urea (U) and guanidine hydrochloride (Gu·HCl) at a concentration of 3.0 M were used as denaturation agents.Increasing the concentration of PTU from 0.8 × 10⁻⁵ to 1.20 × 10⁻⁴ M in the systems with HSA causes a decrease in fluorescence intensity of the protein excited with both 280 and 295 nm wavelengths. The results indicate that urea and Gu·HCl bind to the carbonyl group and then to the NH-group. To determine binding constants we used the Scatchard plots. The presence of two classes of HSA–PTU binding sites was observed. The binding constants (K_b) are equal to 1.99 × 10⁴ M⁻¹ and 1.50 × 10⁴ M⁻¹ at λ_ex = 280 nm, 5.20 × 10⁴ M⁻¹ and 1.65 × 10⁴ M⁻¹ at λ_ex = 295 nm. At λ_ex = 280 nm the number of drug molecules per protein molecule is a_I = 1.45 and a_II = 1.32 for I and II binding sites, respectively. At λ_ex = 295 nm they are a_I = 0.63 and a_II = 1.54 for the I and II binding sites.The estimation of the binding ability of changed albumin in the uremic and diabetic patients suffering from chronic liver or renal diseases is very important for safety and effective therapy.     

Accurate analytic potential energy function and spectroscopic study for CH(XΠ) radical using coupled-cluster theory in combination with the correlation-consistent quintuple basis set

The coupled-cluster singles-doubles-approximate-triples [CCSD(T)] theory in combination with the correlation-consistent quintuple basis set (aug-cc-pV5Z) is used to investigate the spectroscopic properties of the CH(X²Π) radical. The accurate adiabatic potential energy curve is calculated over the internuclear separation ranging from 0.07 to 2.45 nm and is fitted to the analytic Murrell–Sorbie function, which is employed to determine the spectroscopic parameters, ω_eχ_e, α_e and B_e. The present D_e, R_e, ω_e, ω_eχ_e, α_e and B_e values are of 3.6261 eV, 0.11199 nm, 2856.312 cm⁻¹, 64.9321 cm⁻¹, 0.5452 cm⁻¹ and 14.457 cm⁻¹, respectively. Excellent agreement is obtained when they are compared with the available measurements. With the potential obtained at the CCSD(T)/aug-cc-pV5Z level of theory, a total of 18 vibrational states is predicted when J = 0 by numerically solving the radial Schrödinger equation of nuclear motion. The complete vibrational levels, classical turning points, inertial rotation and centrifugal distortion constants are reproduced for the CH(X²Π) radical when J = 0 for the first time, which are in good agreement with the available RKR data.     

Distribution of Co(II) between immiscible phases formed in water + 1-butanol system

Heterogeneous equilibria for the distribution of Co²⁺ between the two layers formed in water + 1-butanol (1-BuOH) system have been investigated at ambient conditions. The study (confined to only 28 °C) reveals an interesting feature of the distribution equilibrium for the system whereby Co²⁺ has been found to exist in both the phases as the same species namely its aqua-complex thus directly demonstrating strong selective solvation of Co²⁺ by the water molecules. Almost constant values of refractive indices and densities were exhibited by the two layers regardless in which ratio the component liquids were mixed together. However, relative volumes of the layers varied smoothly on gradually changing the ratio of the two liquids in the overall “solvent system”. Also the Co²⁺ distribution coefficient (K_D) changed appreciably on going to alcohol-richer “solvent systems” but K_D remained fairly constant on adding different amounts of cobalt dichloride to any given “solvent system”.     

Spectral and temporal luminescent properties of Eu(III) in humic substance solutions from different origins

Although a high heterogeneity of composition is awaited for humic substances, their complexation properties do not seem to greatly depend on their origins. The information on the difference in the structure of these complexes is scarce. To participate in the filling of this lack, a study of the spectral and temporal evolution of the Eu(III) luminescence implied in humic substance (HS) complexes is presented. Seven different extracts, namely Suwannee River fulvic acid (SRFA) and humic acid (SRHA), and Leonardite HA (LHA) from the International Humic Substances Society (USA), humic acid from Gorleben (GohyHA), and from the Kleiner Kranichsee bog (KFA, KHA) from Germany, and purified commercial Aldrich HA (PAHA), were made to contact with Eu(III). Eu(III)-HS time-resolved luminescence properties were compared with aqueous Eu³⁺ at pH 5. Using an excitation wavelength of 394 nm, the typical bi-exponential luminescence decay for Eu(III)-HS complexes is common to all the samples. The components τ₁ and τ₂ are in the same order of magnitude for all the samples, i.e., 40 ≤ τ₁ (μs) ≤ 60, and 145 ≤ τ₂ (μs) ≤ 190, but significantly different. It is shown that different spectra are obtained from the different groups of samples. Terrestrial extract on the one hand, i.e. LHA/GohyHA, plus PAHA, and purely aquatic extracts on the other hand, i.e., SRFA/SRHA/KFA/KHA, induce inner coherent luminescent properties of Eu(III) within each group. The ⁵D₀ → ⁷F₂ transition exhibits the most striking differences. A slight blue shift is observed compared to aqueous Eu³⁺ (λ_max = 615.4 nm), and the humic samples share almost the same λ_max ≈ 614.5 nm. The main differences between the samples reside in a shoulder around λ ≈ 612.5 nm, modelled by a mixed Gaussian–Lorentzian band around λ ≈ 612 nm. SRFA shows the most intense shoulder with an intensity ratio of I_612.5/I_614.7 = 1.1, KFA/KHA/SRHA share almost the same ratio I_612.5/I_614.7 = 1.2–1.3, whilst the LHA/GohyHA/PAHA group has a I_612.5/I_614.5 = 1.5–1.6. This shows that for the two groups of complexes, despite comparable complexing properties, slightly different symmetries are awaited.     

Nitric oxide and singlet oxygen photo-generation by light irradiation in the phototherapeutic window of a nitrosyl ruthenium conjugated with a phthalocyanine rare earth complex

The photochemical, photophysical and photobiological studies of a mixture containing cis-[Ru(H-dcbpy⁻)₂(Cl)(NO)] (H₂-dcbpy = 4,4′-dicarboxy-2,2′-bipyridine) and Na₄[Tb(TsPc)(acac)] (TsPc = tetrasulfonated phthalocyanines; acac = acetylacetone), a system capable of improving photodynamic therapy (PDT), were accomplished. cis-[Ru(H-dcbpy⁻)₂(Cl)(NO)] was obtained from cis-[Ru(H₂-dcbpy)₂Cl₂]·2H₂O, whereas Na₄[Tb(TsPc)(acac)] was obtained by reacting phthalocyanine with terbium acetylacetonate. The UV–Vis spectrum of cis-[Ru(H-dcbpy⁻)₂(Cl)(NO)] displays a band in the region of 305 nm (λ_max in 0.1 mol L⁻¹ HCl)(π–π*) and a shoulder at 323 nm (MLCT), while the UV–Vis spectrum of Na₄[Tb(TsPc)(acac)] presents the typical phthalocyanine bands at 342 nm (Soret λ_max in H₂O) and 642, 682 (Q bands). The cis-[Ru(H-dcbpy⁻)₂(Cl)(NO)] FTIR spectrum displays a band at 1932 cm⁻¹ (Ru–NO⁺). The cyclic voltammogram of the cis-[Ru(H-dcbpy⁻)₂(Cl)(NO)] complex in aqueous solution presented peaks at E = 0.10 V (NO^+/0) and E = −0.50 V (NO^0/−) versus Ag/AgCl. The NO concentration and ¹O₂ quantum yield for light irradiation in the λ > 550 nm region were measured as [NO] = 1.21 ± 0.14 μmol L⁻¹ and ø_OS = 0.41, respectively. The amount of released NO seems to be dependent on oxygen concentration, once the NO concentration measured in aerated condition was 1.51 ± 0.11 μmol L⁻¹ The photochemical pathway of the cis-[Ru(H-dcbpy⁻)₂(Cl)(NO)]/Na₄[Tb(TsPc)(acac)] mixture could be attributed to a photoinduced electron transfer process. The cytotoxic assays of cis-[Ru(H-dcbpy^-)₂(Cl)(NO)] and of the mixture carried out with B16F10 cells show a decrease in cell viability to 80% in the dark and to 20% under light irradiation. Our results document that the simultaneous production of NO and ¹O₂ could improve PDT and be useful in cancer treatment.     

A thermodynamic interpretation of the behavior of higher fatty alcohols and acids upon the chromatographic paper

An idea was presented of treating the chromatographed substance as a “solute,” and the chromatographic system, composed of the stationary and the mobile phase as a “solvent.” Moreover the concept of “local equilibrium” was introduced, allowing to regard a given chromatographic spot as a “binary solution.” Thus a possibility arose to apply the classical thermodynamic approach, normally used for binary solutions, and namely: μ_i = μ_i + RT ln x_iƒ_i, where μ_i—chemical potential of the “i”-th compound in the solution, μ_i—chemical potential of the pure “i”-th compound, x_i-molar fraction of the “i”-th compound, ƒ_i—its activity coefficient, in a modified form, suitable for the chromatographic purpose.     

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.