Applicability of the polyphenylene oxide film dosimeter to high UV exposures in aquatic environments

Previous research has proven that the Poly (2,6-dimethyl-1, 4-phenylene oxide) (PPO) dosimeter is capable of receiving both in-air and underwater UV exposures that are significantly greater than those of the more commonly used polysulphone dosimeter, within a range of accuracy close to what would be expected of dosimetric measurements made in-air provided that the necessary calibrations are completed correctly by factoring in different atmospheric column ozone levels, SZA ranges, varying water turbidity and DOM levels. However, there is yet to be an investigation detailing the performance of the PPO dosimeter and its ability to measure UV in an actual field environment over an extended period of time. This research aims to bridge this gap in the knowledge by presenting a measurement campaign carried out in two real world aquatic environments and a simulated sea water environment using a batch of PPO dosimeters set at different depths and aligned to a range of different angles and geographical directions by means of attachment to a custom built dosimeter submersible float (DSF) unit over the space of a year at a sub-tropical location. Results obtained from this measurement campaign were used to compute a K_d value for the sea water in each particular season. These K_d values where found to be in close agreement to standalone K_d values derived from results taken using a standard calibrated spectrometer in the same sea water.     

The reaction mechanism of p-toluenediamine anodic oxidation: an in situ ESR-UV/Vis/NIR spectroelectrochemical study.

In situ ESR-UV/Vis spectroelectrochemistry is applied to obtain new insights into the intermediates and reaction products of the anodic oxidation of p-toluenediamine in aqueous solution at different pH values. A strong pH dependence of the stability of the cation radical is found. While the absence of a stable radical was proved by ESR spectroscopy at pH 2 and 10, this radical is detected at medium pH values and assigned to the semiquinonediimine structure. The UV/Vis absorption of the radical is observed at these pH values as well. The p-toluenediimine intermediate and the trimeric reaction product were followed during the electrode reaction by UV/Vis spectroscopy at all pH values.     

Controlled aggregation of functionalized gold nanoparticles with a novel conjugated oligomer.

A new route is developed to control the self-assembly of gold nanoparticles (AuNPs) functionalized with a novel pyridyl-ended porphyrin-oligo(p-phenylene vinylene) conjugated oligomer (P-OPV-Py) into branched-rods, chain-networks, uniform fractal-like Au clusters, and larger nanoparticles. The techniques of optical spectroscopy, transmission electron microscopy (TEM) and dynamic light scattering (DLS) are used to characterize the self-assembly in various solvent systems (pure toluene, CHCl(3)/toluene, THF/toluene and n-butanol/toluene). A combination of the ligand/AuNPs molar ratio and relative concentration serves as the driving force to control the size and shape of P-OPV-Py capped AuNPs.     

Electronic absorption spectra of L-ascorbic acid in nonaqueous media

An Electronic spectroscopic study of the self-association of Vitamin C in the nonaqueous phase is reported, pre-sumably for the first time. The oxidation of ascorbic acid in 1,4-dioxane has been studied by UV spectroscopy. The dramatic role of the environment in the stability and identification of the possible intermediates formed in the oxidation of ascorbic acid is shown. Published in Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 2, pp. 263–265, March–April, 2006.     

Measurement of collision broadening of the P1(5) line of (0,0) band of OH AΣ←XΠ transition at high temperatures

Even for the well-studied and ubiquitous species, OH, the current state of theoretical development of broadening theory does not allow extrapolation from low-temperature laboratory measurements to the range of practical combustion devices. We performed a series of experiments at typical combustion conditions to determine the collision broadening of the P₁(5) line of the (0,0) band of OH A²Σ⁺←X²Π transition by Ar in shock-heated H₂-O₂-Ar mixtures and by air in H₂-air flames over a wide range of stoichiometry (φ=0.01-10.0), temperature (T=780-2440 K), and pressure (p=0.7-10.0 atm). The values of the collision width, Δν_C, were acquired by fitting Voigt profiles to the measured spectral line shapes in flames and to the peak absorption coefficients (k_ν0) in shock tube experiments. Collision broadening parameters (2γ_Ar, 2γ_N2, and 2γ_H2O) were then calculated assuming the linear dependence of Δν_C with pressure—the 2γ_N2 and 2γ_H2O values were inferred from 2γ_Air and the equilibrium concentration of N₂ and H₂O of a given flame. The temperature dependences of 2γ_i in our temperature range are, respectively, 1.0, 0.75, and 0.87 for Ar, N₂, and H₂O. The collision broadening cross sections (σ) deduced from 2γ_i values are expressed with an assumed form, σ_i(T)=σ_i,₀(T₀/T)^k, T₀=1000 K: for Ar, σ_Ar,0=63.3 (Ų), k=0.50; for N₂, σ_N2,0=68.0 (Ų), k=0.25; for H₂O, σ_H2O,0=188.8 (Ų), k=0.37.     

Photodegradation of rhodamine B dye using a microwave electrodeless UV lamp (MWUVL)

The photodegradation of organic dye rhodamine B (RhB) in an aqueous solution was studied using a microwave electrodeless UV lamp (MWUVL). The 185 nm vacuum UV (VUV) intensity of the MWUVL amounted to 12% of the total UV output, about 1.7 times as high as that of the con ventional low-pressure mercury lamp. An acidic condition was preferred for the degradation of RhB. Precipitate was generated during RhB degradation when the initial concentration of RhB solution was above 60 mg · L⁻¹. For 100 mg · L⁻¹ RhB at pH 4.0, the mass of precipitate produced was nearly half of the initial amount of RhB in the solution after irradi ation for 75 min. The corresponding degradation ratio of RhB reached up to 99.4% and COD reduced 77.4%. The photo degradation of RhB is mainly achieved by direct photolysis of RhB by 185 nm and OH radical oxidation. __________ Translated from Journal of Fudan University (Natural Science), 2006, 45(6): 726–731 [译自: 复旦学报 (自然科学版)]     

Synthesis and UV absorption properties of 5-sulfosalicylate-intercalated Zn-Al layered double hydroxides

5-sulfosalicylic acid (SSA) anions have been intercalated into layered double hydroxides (LDHs) by an anion-exchange reaction using ZnAl-NO₃-LDHs as a precursor. The samples were characterized by XRD, FT-IR, TG-DTA/MS and UV-visible spectroscopy. The results show that the NO₃⁻ anions in the precursor have been completely replaced by SSA anions to give ZnAl-SSA-LDHs having a high degree of crystallinity. Detailed studies reveal the existence of a supramolecular structure in ZnAl-SSA-LDHs involving electrostatic attraction between opposite charges, hydrogen bonding and other weak chemical bonding interactions between host layers and SSA anions. The thermal stability of ZnAl-SSA-LDHs is considerably enhanced compared with that of a mixture of ZnAl-NO₃-LDHs and SSA. After addition of 2.0 wt% ZnAl-SSA-LDHs to polypropylene (PP), the resistance of the polymer to UV degradation is significantly improved.