Increase In UV Absorption Research Articles

Niobium doping as a pathway for tuning the optical properties of cobalt ferrites

In this work, the effect of niobium pentachloride concentration (NbCl5) and the influence of the pentavalent niobium ion on the structure and optical properties of cobalt ferrites was studied for the first time. The sol-gel method was applied to synthesize the xerogel with a subsequent heat treatment at 550 °C for 2.5h to obtain the nanoparticle. X-ray diffraction showed the expected spinel phase in all samples. Thus, it was possible to observe a shift in the main reflection (311) and a change in the lattice parameter as the niobium content increased. The crystallite size varied between approximately 18 and 34 nm. The Raman spectra showed typical vibrational modes of cobalt ferrite with no indication of secondary phase modes and variation in the A1g(2) and T2g(1) bands related to the octahedral and tetrahedral sites, respectively. Moreover, there is a correlation to an observed redshift, indicating an increase in the degree of inversion. Diffuse reflectance showed that the band gap of the samples varied from 1.99 eV for the pure sample (Co1.0Fe2.0O4) to 1.6 eV for the highest doping content (Co1.0Nb0.1Fe1.90O4). The coercivity was also affected, ranging from 1253 Oe in the pure sample (Co1.0Fe2.0O4) to 745 Oe in the doped sample (Co1.0Nb0.1Fe1.90O4). These results prove that the optimization of properties was successful since there was a marked decrease in the band gap and an increase in UV absorption. This result shows that it is possible to optimize the optical properties by introducing niobium, an effect that has not been possible in other studies with this type of dopant.

Clarification of the Mechanism of Inhibiting the Maillard Reaction between Phosphatidylethanolamine and Sugars by Adding Fatty Acid Calcium Salts.

Lecithin is known to undergo heat induced deterioration by the Maillard reaction between 1 mol of any sugar, except 2-deoxy sugar, and 2 mol of phosphatidylethanolamine (PE). However, we have previously reported that adding fatty acid metal salts can inhibit heat deterioration of soybean lecithin (SL). To clarify the mechanism of inhibition, 1,2-di-O-stearoyl-sn-glycero-3-phosphatidylethanolamine (DSPE), d-glucose, and calcium stearate or calcium decanoate were heated in octane. When DSPE and d-glucose with calcium stearate or calcium decanoate were heated in the octane, the heat deterioration of DSPE was significantly inhibited, and no increase in UV absorption at 350 nm was observed. From these reactant solutions, one compound having a phosphate group and no primary amine was isolated, and NMR spectra confirmed that two molar of stearic acid derived from DSPE were coordinated to the amino group and phosphate group of DSPE. Therefore, we concluded that adding fatty acid metal salts reduced the nucleophilic reactivity of the amino group of PE and inhibited the Maillard reaction with sugars because two molar of fatty acid derived from PE coordinated to the amino group and phosphate group of PE.

Suspended matter filtration causes a counterintuitive increase in UV-absorption.

In water treatment, filtration is often a first step to avoid interference of chemical or UV-disinfection with suspended matter (SPM). Surprisingly, in testing a ballast water filter with 25 and 40μm mesh screens, UV-absorption (A, 254nm) of filtered water increased with the largest increase in the finest screen. The hypothesis that filtration partly removes large particles and partly replaces them with small unfiltered ones, leading to an overall increase in absorption, was tested by measuring particle counts, particle-size distributions (PSD) and by modeling the Mass Normalized Beam Attenuation Coefficient (A/SPM) before and after filtration. An independent model verification was made by measuring and modeling A/SPM of three differently sized Arizona test dust suspensions. It is concluded that filtration is a good pretreatment for chemical disinfection systems because it removes the suspended matter mass, but that the production of smaller particles increases UV-absorption and hence may reduce disinfection performance.

Methoxy-Monobenzoylmethane Protects Human Skin against UV-Induced Damage by Conversion to Avobenzone and Radical Scavenging.

Avobenzone, one of the most commonly used UV filters in topical sunscreens, is susceptible to photodegradation with a consequential reduction of its UV absorbing properties. This loss of function may lead to skin irritation, photodermatosis, and photoallergic reactions caused by photodegradation byproducts. In this work, we aim to address this issue with a substance named methoxy-monobenzoylmethane (MeO-MBM), which is neither a UVB nor a UVA filter, but which converts to avobenzone, a known and approved UVA filter, under mainly UVB light irradiation. The antioxidant and intracellular radical formation properties of MeO-MBM were compared to the ones of avobenzone. The UV irradiation of MeO-MBM led to an increase in UV absorption primarily in the UVA range after conversion, both in vitro and in vivo. HPTLC and UHPLC studies illustrate the conversion of MeO-MBM to avobenzone in vitro after irradiation at 250 kJ/m2, reaching a conversion rate of 48.8%. A stable molecular antioxidant activity was observed, since 100-µM MeO-MBM was measured to be 11.2% in the DPPH assay, with a decrease to 9.7% after irradiation. In comparison, the molecular antioxidant activity of 100-µM avobenzone was determined to be 0.8%. In keratinocytes, MeO-MBM reduces the intracellular ROS by 90% and avobenzone by 75% with tBHP as the inducer and by 53% and 57%, respectively, when induced by pyocyanin, indicating the redox scavenging capacity of both these molecules. These results indicate that MeO-MBM functions initially as an antioxidant material and as a photoantioxidant during its conversion process to avobenzone. This research provides insight into the development of active ingredients for topical applications with dynamic functionalities. Using this approach, we demonstrate the possibility to extend the UV protection offered to skin cells while combating cellular stress in parallel.

Effect of nanoclay on dispersion, thermal stability, optical and burning behavior of sulfonated poly (1,4-phenylene ether ether sulfone)–nanoclay blends

A novel hydrophobic, thermoset film-forming polymer poly (1,4-phenylene ether ether sulfone) (PEES) was sulfonated on its polymer backbone by using conc H2SO4. The nanocomposite of sulfonated PEES (SPEES) was formed by using pretreated nanoclay with different loading labels 2.5%, 5% and 10% and was cast in the form of films. Pure PEES, SPEES, pure nanoclay and SPEES nanocomposites were characterized by using FTIR and UV–visible spectrophotometry. The thermal behavior of pure SPEES and SPEES nanoclay composites was studied by using thermal gravimetric analysis and differential scanning calorimeter. It was found that by using nanoclay as filler, the thermal decomposition of SPEES–nanoclay composite increases compared to that of neat SPEES. The Tg shows wide variations with different loading labels of the nanoclay. Increase in UV absorption with the addition of nanoclay loading level was studied by using UV spectrophotometry.

Zirconium doped TiO2 nano-powder via halide free non-aqueous solvent controlled sol-gel route

Pure and Zr doped TiO2 nano-powder were prepared by economical, halide-free, non-aqueous solvent controlled sol-gel route. XRD, TEM, X-ray photoelectron spectroscopy and Raman spectroscopy results confirmed the crystalline anatase phase, Zr substitution at Ti lattice sites and reduction in crystallite size upto 10at.% nominal Zr doping. A complete amorphous phase is obtained when doping of Zr is increased to 15at.%. Optical band gap, particle size and electron-hole recombination is reduced due to Zr doping upto 10at.%. The resulting increase in UV absorption, generation of electrons and holes, and inhibition of electron-hole recombination are responsible for enhanced photocatalytic properties of Zr doped TiO2 nano-powder. Zr doping of 10at.% resulting in TiO2 nano-powder of size 11nm and energy gap of 3.33eV, yielded maximum enhancement in photocatalytic activity in TiO2. Also, Zr doped TiO2 nano-powder are found to be more efficient photo-catalyst than commercially available Degussa P25 TiO2.

Synthesis of polymer protected AuNPs for silver ions detection

Herein, a novel probe based on poly(N,N′-methylenebisacylamide) protected AuNPs (PDMAM-AuNPs) was developed for determination of silver ions. The thiol-terminated PDMAM was synthesized by the reversible addition fragmentation chain transfer radical polymerization. Then, the PDMAM-AuNPs were prepared by a simple, one-pot and green process. It has been observed that existence of the silver ions evoked a small red-shift to the emission peak of PDMAM-AuNPs and an obvious increase in UV absorption. The detection limit of the present method for silver ions was 0.5 μmol/L, with a linear range of 1.0–1000 μmol/L. Moreover, the possible mechanism for enhanced UV absorption intensity with enlarged diameter of PDMAM-AuNPs was explored and discussed briefly. The results demonstrated that silver ions could be detected by the PDMAM-AuNPs based colorimetric assays, further opening up new ways for the visualization and quantification of silver ions involved in our daily life.

Photocatalytic packed bed reactor design for efficient UV light utilization

In this study, TiO2/SiO2 beads packed bed reactor system in which black light was placed at the center of the reactor was developed for a low cost and environmentally–friendly water treatment process. The reactor was designed to achieve efficient utilization of UV light, large contact area with pollutants as well as easier post separation at the same time. As model pollutants, PNP and DNP were used in this study, and the effects of the initial concentration of those substrates and radial thickness of the packed bed for the decomposition properties were examined. The results showed that the decomposition ratio decreased with the increase of the initial concentration and the packed bed radial thickness. The result suggested that the UV light was absorbed by the solution and TiO2/SiO2 beads. To take into consideration the effect of light absorption toward radial direction of the reactor on the decomposition ratio, simple model called “2-boxes model” was developed. The result of reaction kinetics analysis showed that the 2-boxes model could reasonably explain the experimental data. Finally, by using 2-boxes model, the effective diameter of penetrated UV light was examined. The result confirmed that it decreased with the increase of UV absorption caused by the increase of initial inlet concentration and the increase of the radial thickness of the packed bed. This indicates that the simple 2-boxes model can approximately estimate the effective diameter of packed bed for PNP or DNP decomposition, and it will give a design guideline for an efficient TiO2/SiO2 beads packed bed reactor system for water treatment.

Atmospheric Pressure Plasma Treatment of Fused Silica, Related Surface and Near-Surface Effects and Applications

We report on an atmospheric pressure plasma (APP) treatment of fused silica and its related surface and near-surface effects. Such treatment was performed in order to improve laser micro-structuring of fused silica by a plasma-induced modification of the glass boundary layer. In this context, an APP jet applying a hydrogenous process gas was used. By the plasma treatment, the transmission of the investigated glass samples was significantly decreased. Further, a decrease in the superficial index of refraction of approx. 3.66 % at a wavelength of 636.7 nm was detected ellipsometrically. By surface energy measurements, a decrease of the surface polarity of 30.23 % was identified. These determined modifications confirm a reduction of silicon dioxide to UV-absorbing silicon suboxide as already reported in previous work. Further, a change in reflexion by maximum 0.26 % was detected which is explained by the superposition of constructive and destructive interferences due to a surface wrinkling. With the aid of atomic force microscopy, an increase of the surface root mean squared roughness by a factor of approx. 19 was determined. It was found that both the surface energy and the strength of the fused silica surface were reduced by the plasma treatment. Even though such treatment led to a clustering of carbonaceous contaminants, a surface-cleaning effect was confirmed by secondary ion mass spectroscopy and energy-dispersive X-ray spectroscopy. The increase in UV-absorption allows enhanced laser ablation results as shown in previous work.

Microwave Assisted Synthesis of ZnO Nanoparticles: Effect of Precursor Reagents, Temperature, Irradiation Time, and Additives on Nano-ZnO Morphology Development

The effect of different variables (precursor reagents, temperature, irradiation time, microwave radiation power, and additives addition) on the final morphology of nano-ZnO obtained through the microwave assisted technique has been investigated. The characterization of the samples has been carried out by field emission scanning electron microscopy (FE-SEM) in transmission mode, infrared (FTIR), UV-Vis spectroscopy, and powder X-ray diffraction (XRD). The results showed that all the above-mentioned variables influenced to some extent the shape and/or size of the synthetized nanoparticles. In particular, the addition of an anionic surfactant (sodium di-2-ethylhexyl-sulfosuccinate (AOT)) to the reaction mixture allowed the synthesis of smaller hexagonal prismatic particles (100 nm), which show a significant increase in UV absorption.

Interaction of cationic surfactants with DNA detected by spectroscopic and acoustic wave techniques

Interaction of the cationic surfactants benzalkonium chloride and 1-hexadecylpyridinium chloride, in the concentration range 0.1 microM to 1 mM with calf thymus DNA and with short 19-mer double-stranded DNA has been examined in solution using UV absorption and fluorescent spectroscopies and at the liquid-solution interface by thickness-shear mode acoustic wave sensor. Higher concentrations of surfactant resulted in an increase of UV absorption, and decrease of melting temperature and van't Hoff enthalpy of calf thymus DNA. Both surfactants induce fluorescence quenching of ethidium bromide which is also associated with intercalation of the molecules into the nucleic acid strand. The effect of the pyridinium compound is greater than for the other surfactant likely because of the lower size of polar head group in this molecule. With respect to acoustic wave detection at the device surface, for relatively low surfactant concentrations (below 100 microM), decreases of both series resonant frequency and motional resistance were observed. At higher surfactant concentration both parameters increased. These effects are attributed to acoustic coupling processes that occur at the device-film/liquid boundary.

Heat Deterioration of Phospholipids. V. A New Rearrangement Reaction of Sugars and Phosphatidylethanolamine

Novel four 2,3-dihydro-1H-imidazo[1,2-a]pyridine-4-ylium derivatives were obtained with increase of UV absorption at 350 nm and browning of the solution by heating paste lecithin from soybean (SL) in octane. These four derivatives were formed by reaction of one molar of any sugar except 2-deoxysugars with two molar of phosphatidylethanolamines (PE) in SL. To confirm the reaction mechanism, several (13)C-labeled-sugars were reacted with 1,2-di-O-stearoyl-sn-glycero-3-phosphatidylethanolamine (DSPE), respectively. These reactants clearly showed that five carbons of the pyridinium ring and one carbon of the substituted group were based on those of a sugar and that the formation of the pyridinium derivatives was accompanied with cleaving between the carbons of 1- and 2-positions in the sugar and rearrangement. This reaction is a new rearrangement reaction and we named it "new pseudo Maillard rearrangement reaction".

Identification of Mn2+-binding Aspartates from α, β, and γ Subunits of Human NAD-dependent Isocitrate Dehydrogenase

The human NAD-dependent isocitrate dehydrogenase (IDH), with three types of subunits present in the ratio of 2alpha:1beta:1gamma, requires a divalent metal ion to catalyze the oxidative decarboxylation of isocitrate. With the aim of identifying ligands of the enzyme-bound Mn(2+), we mutated aspartates on the alpha, beta, or gamma subunits. Mutagenesis target sites were based on crystal structures of metal-isocitrate complexes of Escherichia coli and pig mitochondrial NADP-IDH and sequence alignments. Aspartates replaced by asparagine or cysteine were 206, 230, and 234 of the alpha subunit and those corresponding to alpha-Asp-206: 217 of the beta subunit and 215 of the gamma subunit. Each expressed, purified mutant enzyme has two wild-type subunits and one subunit with a single mutation. Specific activities of WT, alpha-D206N, alpha-D230C, alpha-D234C, beta-D217N, and gamma-D215N enzymes are 22, 29, 1.4, 0.2, 7.3 and 3.7 micromol of NADH/min/mg, respectively, whereas alpha-D230N and alpha-D234N enzymes showed no activity. The K(m,Mn(2+)) for alpha-D230C and gamma-D215N are increased 32- and 100-fold, respectively, along with elevations in K(m,isocitrate). The K(m,NAD) of alpha-D230C is increased 16-fold, whereas that of beta-D217N is elevated 10-fold. For all the mutants K(m,isocitrate) is decreased by ADP, indicating that these aspartates are not needed for normal ADP activation. This study demonstrates that alpha-Asp-230 and alpha-Asp-234 are critical for catalytic activity, but alpha-Asp-206 is not needed; alpha-Asp-230 and gamma-Asp-215 may interact directly with the Mn(2+); and alpha-Asp-230 and beta-Asp-217 contribute to the affinity of the enzyme for NAD. These results suggest that the active sites of the human NAD-IDH are shared between alpha and gamma subunits and between alpha and beta subunits.

Heat Deterioration of Phospholipids. III. Thermally Deteriorated Products from Phosphatidylethanolamine and Hexose

Novel four 2,3-dihydro-1H-imidazo[1,2-a]pyridine-4-ylium derivatives were obtained with increase of UV absorption at 350 nm and browning of the solution by heating paste lecithin from soybean (SL) in octane. These four derivatives were characterized the factor based on UV absorption at 350 nm. The SL was separated into the hexane (DSSL fr.) and 60% ethanol in water frs. by liquid- liquid partition method. Even when the DSSL fr. was heated in octane more than 9 h, the four derivatives were not formed and increase of any UV absorption was also not observed but the solution color was slightly yellowing. On the other hand, the formation of four derivatives and increase of UV absorption at 350 nm were observed when DSSL and 60% ethanol in water frs. were combined and, then, heated in octane. From the 60% ethanol in water fr, sucrose, raffinose and stachyose were isolated and identified as compounds which involved the formation of the derivatives with the DSSL fr. When DSPE (1,2-di-O-stearoyl-sn-glycero-3-phosphatidylethanolamine) and any hexose were combined and then heated, two 2,3-dihydro-1H-imidazo[1,2-a]pyridine-4-ylium derivatives generated with increase of UV absorption at 350 nm and browning. From these results, it is concluded that the formation of derivatives, with increase of the UV absorption at 350 nm and browning, are based on the reaction of sugars and phosphatidylethanolamine (PE) in SL.

Heat Deterioration of Phospholipids. IV. Thermally Deteriorated Products from Phosphatidylethanolamine and Several Sugars

Novel four 2,3-dihydro-1H-imidazo[1,2-a]pyridine-4-ylium derivatives were formed by reaction of PE and hexose or oligosaccharides including of hexose moiety in soybean lecithin with increase of UV absorption at 350 nm and browning of the solution. Therefore, several pentoses, a heptose and 2-deoxysugars besides hexoses were examined. When any pentose was reacted with PE in DSSL fr. in octane, two 2,3-dihydro-1H-imidazo[1,2-a]pyridine-4-ylium derivatives without a substitute at 6 position on the aromatic ring were formed with increase of UV absorption at 345nm and browning of the solution. On the other hand, two 2,3-dihydro-1H-imidazo[1,2-a]pyridine-4-ylium derivatives with 1,2-dihydroxyethyl group at 6 position on the ring were formed when a heptose was reacted with PE in DSSL fr. in octane. Contrary to these results, when 2-deoxysugars, regardless hexose or pentose, were reacted with PE in DSSL fr. in octane, the derivatives were not formed at all and change of UV absorption and browning in the solution could not also be observed. From these results, it is concluded that existence of an oxygen atom on 2 position of sugars is essential to brown, change the UV absorption, and form the pyridinium derivatives by heating and that rearrangement of carbon(s) in the sugar might involve the reaction of PE and sugars to form the pyridinium derivatives.

Effect of Changes in TiO2 Dispersion on Its Measured Photocatalytic Activity

This paper reports measurements of photocatalytic oxidation of 2-propanol by dispersions of three different types (a high area rutile, a surface treated rutile, and, the mainly anatase, Degussa P25) of titanium dioxide in 2-propanol. For a fixed loading of any one type of TiO2, the particle dispersion was deliberately modified by milling the suspension to break down the clusters of individual crystals which are usually present in dispersions of all inorganic powders. Sedimentation analysis demonstrated that, as predicted, milling decreased the size of the TiO2 particles and this led to corresponding changes in the optical properties of their dispersions. Measurements of 2-propanol oxidation demonstrated that, for all three forms of titania, milling-times of 30 min led to an 80% decrease in the rate of acetone formation. We propose that the measured decrease is a consequence of the demonstrated increase in UV absorption associated with the reduction of particle size caused by milling. This increased absorp...

UV absorption method should not be applied for determining amoxycillin in acidic dissolution test medium

In order to clarify the suitability of assay method, the stability of amoxycillin (AMX) in the acidic solution at pH 1.2 was determined by two different methods, ultraviolet absorption (UV) and HPLC methods. The determination was simultaneously performed for the same sample solutions. The data from HPLC method indicated that AMX degraded and the concentration of AMX in the acidic solution was decreased. The apparent first-order rate constant ( k obs) for the degradation was 9.83×10 −2 h −1, and the half-life was calculated to be 7.04 h. On the other hand, the data obtained from UV method apparently represented that the concentration of AMX increased with time-course. This phenomena was brought about by the increase of UV absorption at 272 nm, which accompanied with the degradation of AMX. These results clearly indicate that UV method can not be used for determining the samples accompanying the degradation of AMX. In general, the dissolution test (drug release test) has been used for the evaluation of a sustained-release dosage form of AMX. It is impossible to avoid the degradation of AMX in the test under acidic conditions. The results indicated that the UV method should not be used for the determination of AMX in the test.

Fabrication of a waveguiding layer in Teflon AF<sup>®</sup> by ion irradiation

The modification of thin Teflon AF ® films by He 1 ion irradia- tion was investigated. As an integrated optical measurement technique, leaky-mode spectroscopy has been applied, and an increase of Dn58 310 23 for the real part of the refractive index has been found in the irradiated surface region of the film. The irradiated films can be regarded as a bilayer system consisting of a layer with low refractive index and a layer with high refractive index. The latter can be used as an optical waveguide with a substrate of unmodified Teflon AF. In addition, a de- crease of the initial film thickness, an increase in UV absorption, and no significant increase in absorption of near-infrared light were found. © 2001 Society of Photo-Optical Instrumentation Engineers. (DOI: 10.1117/1.1385331) Subject terms: ion irradiation; fluorpolymer; optical waveguide; leaky-mode spec- troscopy.

Effect of UV radiation on photoinhibition of marine macrophytes in culture systems

The present study examined the effect of UV and photosynthetically active radiation (PAR) on photoinhibition and recovery in the phaeophyte Macrocystis pyrifera, the Rhodophyte Chondrus crispusand the chlorophyte Ulva lactuca under outdoor culture conditions. There was an increase in photoinhibition as a consequence of high exposure to UV-B radiation in M. pyrifera, however, high levels of PAR accounted for most of the photoinhibition in C. crispus and U. lactuca .P hotodamage by UV-A, UV-B and PAR was completely repaired within 5ha nd effective quantum yield reached pretreatment values in the three species studied. Species were less susceptible to photoinhibition after being incubated for 5 d under high exposures of natural irradiance suggesting a photoadaptive process. The recovery of the effective quantum yield was impaired by long exposure to high levels of UV-B in C. crispus and UV-A, UV-B and PAR in M. pyrifera. This suggests a different kind of damage by UV-A and PAR radiation, one to the photosynthetic apparatus and another which affects the repair mechanism of some species. There was an increase in UV-absorption ( 330 nm) in M. pyrifera and C. crispus within four days of the initiation of the experiment suggesting that these species photoprotect their photosynthetic system when exposed to elevated UV and PAR levels.

Weak luminescence from cotyledons of Cicer arietinum L. induced by sudden freezing and thawing: The role of superoxide, free radicals and singlet oxygen in the phenomenon

Cotyledons of etiolated seedlings of Cicer arietinum L., when subjected to sudden freezing and thawing, were found to emit luminescence of weak intensity. The presence of oxygen and iron compounds enhanced the intensity of the emission. In contrast, superoxide dismutase, catalase, mannitol, uric acid, vitamin C and t-butyl alcohol inhibited the emission. α-Tocopherol, which is a free radical scavenger, also inhibited the emission. The generation of singlet oxygen in the system was inferred from the suppression of emission by 2,5-dimethyl furan, which is a specific singlet oxygen scavenger. The buffer extracts prepared with D 2O, instead of H 2O, produced enhanced luminescence. These results suggest that singlet oxygen plays a role in the generation of the weak luminescence. Studies on the spectral distribution also revealed the existence of singlet oxygen as the principal emitter. An increase in UV absorption at 233–234 nm was observed with increasing time after the freeze—thaw treatment. This result is indicative of the accumulation of conjugated diene hydroperoxides.