UV Absorption Properties Research Articles

Hydrothermal Synthesis and UV Absorption Property of Firewood-Like CeO2 Nanostructures

In this paper, we reported that firewood-like CeO2nanostructures were synthesized via hydrothermal method in the present of cetyltrimethylammonium bromide (CTAB) for the first time. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) were used to characterize the as-obtained sample. The UV absorption property of the product was investigated by UV-vis spectrophotometry. XRD result shows that the product was a cubic fluorite-type CeO2phase with good crystallinity. FE-SEM and TEM analysis indicate that the firewood-like CeO2nanostructures were composed of CeO2nanoparticles with the average size of about 6-10 nm. The CeO2shows excellent UV absorption for that the transmittance (T %) of the sample in the UV region almost equal to zero.

Thermal and spectral behavior of (Y,Eu)VO4 powder

Thermal analysis of YxEu1−xVO4 powder (used as “phosphor” coating for a high pressure mercury lamp) was done under a non-isothermal linear regime, both in a dynamic air regime and in a nitrogen atmosphere. The heating in air atmosphere gave on TG curve small rate of mass increase due to oxygenation and two endothermic effects are observed on DTA and DSC curves. By contrary, in nitrogen atmosphere a continuous stepped mass loss of powder (around 0.65 %), is recorded in the range of temperatures from room temperatures to 1,200 °C, and only one endothermic effect, to eliminate the gases accumulated on the crystallite surface. The powder was heated for 3 h in a Nabertherm furnace at 350, 800, and 1,100 °C using quite similar rate for heating program followed by a furnace cooling to room temperature. XRD and FTIR analyses showed the sample purification by thermal treatment and a very small increase of nanocrystallite sizes. The time evolution of the optical emission spectra in the range from 186.2 to 877.47 nm were recorded for different lamp powers in two different situations: with the outer bulb coated with YxEu1−xVO4 type “phosphor”, and without it. We observed that UV-Hg lines are absorbed by YxEu1−xVO4 type “phosphor” with different percents (100 % for 253.73 nm, 95 % for 312.65 nm, and 33 % for 365.12 nm) but the heating of the powder do not influence the UV-absorption properties of the powder.

High‐contrast, high‐sensitivity aqueous base‐developable polynorbornene dielectric

AbstractThe impact of multifunctional epoxy‐based additives on the crosslinking, photolithographic properties, and adhesion properties of a tetramethyl ammonium hydroxide developable, polynorbornene (PNB)‐based dielectric was investigated. Three different multifunctional epoxy additives were investigated: di‐functional, tri‐functional, and tetra‐functional epoxy compounds. The tetra‐functional epoxy crosslinker enhanced the UV absorbing properties of the polymer at 365 nm wavelength. It was found that the epoxy photo‐catalyst could be efficiently activated without a photosensitizer when the tetra‐functional epoxy was used. The polymer mixture with additional (3 wt %) tetra‐functional epoxy crosslinker and without a UV sensitizer showed improved sensitivity by a factor of 4.7 as compared to a polymer mixture containing the same number of equivalents of non‐UV sensitive epoxy with a UV sensitizer. The contrast improved from 7.4 for the polymer mixture with non‐UV absorbing epoxy and a UV sensitizer to 33.4 for the new formulation with 3 wt % tetra‐functional epoxy and no UV sensitizer. The addition of the tetra‐functional epoxy crosslinker also improved the polymer‐to‐substrate adhesion, which permitted longer development times, and allowed the fabrication of high‐aspect‐ratio structures. Hollow‐core pillars were fabricated in 96‐µm thick polymer films with a depth‐to‐width aspect‐ratio of 14 : 1. The degree of crosslinking in the cured films was studied by nanoindentation and swelling measurements. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Use of silane coupling agent for surface modification of zinc oxide as inorganic filler and preparation of poly(amide-imide)/zinc oxide nanocomposite containing phenylalanine moieties

A series of novel poly(amide–imide)/ZnO nanocomposites with modified ZnO nanoparticles contents was prepared by ultrasonic irradiation. For this purpose, surface of ZnO nanoparticle was modified with $\boldsymbol\gamma$ -aminopropyltriethoxysilane as a coupling agent. Then the effect of surface modification on dispersion of nanoparticles, thermal stability and UV absorption property of the obtained nanocomposites were investigated. The resulting novel nanocomposites were characterized by several techniques. Field emission scanning electron microscopy and transmission electron microscopy analyses of the nanocomposites were performed in order to study the dispersion of nanofillers in the polymer matrix. According to thermogravimetry analysis results, the addition of ZnO nanoparticles improved thermal stability of the obtained nanocomposites. Since the resulting nanocomposites contain phenylalanine amino acid and ZnO, they are expected to be biocompatible as well as biodegradable.

Synthesis and luminescent properties of block copolymers based on polyfluorene and polytriphenylamine

For the preparation of block copolymers containing polyfluorene (PF) and hole transporting segment, PF homopolymers with diphenylamine terminals were synthesized by Suzuki coupling polymerization. The terminals of PF were converted to polytriphenylamine (PTPA) block by C–N coupling polymerization to give PTPA-block-PF-block-PTPA (PF-PTPA) triblock copolymers with different PTPA chain lengths. These polymers were soluble in common organic solvents and readily formed thin films by solution processing. All of the polymers exhibited similar UV absorption and PL emission properties both in chloroform solution and in film state. PF-PTPA block copolymers showed relatively high HOMO compared with that of PF by cyclic voltammetry. Compared with corresponding PF homopolymers, the EL devices based on PF-PTPA block copolymers showed higher luminance and current efficiency than those of PF homopolymers because of the improvement of hole injection by the introduction of PTPA segment.

Effects of inorganic nanofillers on the thermal degradation and UV-absorbance properties of polyvinyl acetate

The effects of calcium carbonate (CaCO3) and calcium sulfate (CaSO4) nanoparticles on the thermal and UV-absorbing properties of polyvinyl acetate (PVAc) were analyzed in this study. Nanoparticles of CaCO3 and CaSO4 were synthesized by in situ deposition technique. The size and shape of nanoparticles were recognized by X-ray diffraction and scanning electron microscope (SEM) analyses which confirmed that the particle was having a diameter of 25–33 nm. In this technique, the surface modification of nanoparticles was done by non-ionic polymeric surfactant. PVAc/CaCO3 and PVAc/CaSO4 nanocomposites film samples with an average thickness of 30 µm and in the mass ratio of nanoparticles (0–4% (w/w)) were prepared by solution mixing technique. Chemical, structural, and elemental characterizations of nanocomposites were done by, fourier transform infrared, SEM, and energy dispersive X-ray spectroscopy analyses, respectively. Thermal properties of pure polymer and nanocomposites were characterized through differential scanning calorimetric, thermogravimetric, and differential thermogravimetry techniques. The glass transition temperature of nanocomposites increases with increase in content of nanoparticles. It may be due to the interaction between inorganic and organic components. The thermogravimetric analysis results indicate that the thermal degradation temperatures of nanocomposites were enhanced upon the addition of nanosized inorganic fillers. The thermal results show that PVAc/CaSO4 nanocomposites were more thermally stable than PVAc/CaCO3 nanocomposites. The addition of nanoparticles affects degradation mechanism and consequently improves thermal stability of PVAc. The reduction of polymer chain mobility and the tendency of nanoparticles to eliminate free radicals were the principal effects responsible for these enhancements. The ultraviolet–visible (UV–Vis) absorbance spectra of PVAc and its nanocomposites films show that the intensity of absorbance increases with increasing filling content, suggesting that nanocomposites films have greater UV-shielding property.

Synthesis and UV Absorption Properties of Aurintricarboxylic Acid Intercalated Zn–Al Layered Double Hydroxides

Aurintricarboxylic acid (ATA), a UV absorbent, has successfully been intercalated into the interlayer spacing of Zn–Al–NO3-LDHs precursor through an anion-exchange reaction. The structure and the thermal- and photostability of the intercalated product were investigated by various techniques such as powder X-ray diffraction (XRD), infrared spectroscopy (FT-IR), thermogravimetry and differential thermal analysis (TG–DTA), and UV–vis spectroscopy. The increase of the basal spacing from 0.90 to 1.52 nm as observed by XRD suggests that the ATA anions have replaced the NO3– anions in the interlayer region of the precursor LDHs. The results of infrared spectroscopy and thermogravimetry and differential thermal analysis (TG–DTA) also reveal the presence of supramolecular host–guest interactions between the brucite-like sheet and the intercalated ATA anions. The intercalation of the ATA anions into the LDHs markedly enhances the thermal stability of this UV absorbent. After incorporation of 1 wt % ZnAl-ATA-LDHs to...

5,15‐A2B2‐ and 5,15‐A2BC‐Type Porphyrins with Donor and Acceptor Groups for Use in Nonlinear Optics and Photodynamic Therapy (Eur. J. Org. Chem. 29/2011)

AbstractThe cover picture shows the meso functionalization of 5,10‐ and 5,15‐A2‐porphyrins by using a conveyor belt, whereby the porphyrin is functionalized with various substituents (different coloured boxes) and various linkers. When these functionalized porphyrins come together through palladium‐catalyzed coupling reactions they form porphyrin arrays of different shapes, depending on the substitution pattern of the monomeric porphyrin. These arrays are connected through conjugated linkers, and their formation is depicted by an arcade game, “porphyrin arrays”, in the background. These arrays exhibit interesting UV absorption and NLO properties, shown as the “score”. Details are discussed in the articles by M. O. Senge et al. on p. 5797 ff. and p. ????ff.

Effect of R.F Power to the Properties of ZnO Thin Films Deposited by Magnetron Sputtering

The effect of radio frequency (R.F) power to the properties of zinc oxide (ZnO) thin films deposited by magnetron sputtering is presented. This project has been focused on electrical, optical and structural properties of ZnO thin films. The effect of variation R.F power at 100 watt ~ 400 watt on the ZnO thin films has been investigated. The thin films were examined using current-voltage (I-V) measurement, UV-Vis-NIR spectrophotometer, x-ray diffraction (XRD) and atomic force microscope (AFM). ZnO thin films were prepared at room temperature in pure argon atmosphere by a R.F magnetron sputtering using ZnO target. I-V measurement indicates that at 300 watt R.F power show the highest conductivity. All films have showed high UV absorption properties using UV-VIS spectrophotometer (JASCO 670). Highly oriented ZnO thin films [002] direction was obtained by using Rigaku Ultima IV. The root means square (rms) roughness for ZnO thin film were about (<2nm) was measured using AFM (Park System XE-100). Keywords-ZnO thin films, R.F power, electrical properties, optical properties, structural properties

UV/VIS absorption and fluorescence spectroscopic study of some 3‐substituted derivatives of 4‐hydroxycoumarin

PurposeThe purpose of this paper is to test absorption characteristics of some newly synthesised 4‐hidroxycoumarins, containing phenyl‐prop‐2‐enoyl group at the 3‐position. Change in spectral characteristics in solvents of different polarity (chloroform and acetonitrile) was followed in regard to the influence of the substitution at the phenyl ring and influence of concentration H+ ions. Effectiveness of tested substances was compared with well‐known UV absorbers such as benzophenone‐3 and butyl methoxydibenzoylmethane (BMDM).Design/methodology/approachAll the tested substances were dissolved in chloroform and acetonitrile, with 10‐3 mmol concentration range. The pH was adjusted using 0.1 mol/l HCl, glacial acetic acid, 0.1 mol/l NaOH (aqueous solution) and 0.1 mol/l NaOH (methanolic solution). Spectrophotometric measurement was recorded in the range of 200‐800 nm, using 1‐cm quartz cells.FindingsThe tested 4‐hydroxycoumarin derivatives showed good UV absorption properties in the range 280‐380 nm. Substitution on the phenyl ring changes the shape of the absorption maxima. The changes depend on the properties of the substituent as well as the acidity of the solution.Research limitations/implicationsIntroducing an electron‐donating substituent on the phenyl‐prop‐2‐enoyl group can shift absorption maximums to longer wavelength. In addition, the variation in substituents on the synthesised substances and pH of the solution could also be studied.Practical implicationsThe new compounds showed good UV absorption, making them potential candidates for many applications. The practical importance of the tested substances are derived from their stability, relatively easy synthesis and good UV absorption properties.Originality/valueThe paper shows that the tested coumarins derivatives were new compounds with good UV absorption properties, making them good UV absorbers of commercial potential. The tested coumarins showed good UV absorption properties in the range 280‐380 nm, making them potential candidates for many applications.

Conformational Control of Polysilanes: Use of CH(2) Spacers in the Silicon Backbone.

By the reaction of a number of oligosilyl potassium compounds with (trimethylsilyl)chloromethane, derivatives containing the (trimethylsilyl)methyl substituent were prepared. Using X-ray single-crystal structure analysis and UV spectroscopy the conformational properties of some of the compounds were studied. It was found that the (trimethylsilyl)methylated examples exhibit UV absorption properties which correspond to lower energy transitions in comparison to those of analogous trimethylsilylated molecules. The influence of this effect decreases, however, with increasing chain lengths.

Chemical films and monolayers on the water surface and their interactions with ultraviolet radiation: a pilot investigation

Over the past 50 years numerous types of chemical films and monolayers have been deployed on top of a wide variety of water reserves in an endeavour to reduce evaporation. To date very little knowledge has been assimilated on how these chemical films and monolayers, once applied to a water surface, influence the underwater UV light field and, in turn, the delicate ecosystems that exist in aquatic environments. This manuscript presents underwater UV exposure profiles weighted to the DNA damage action spectrum measured under an octadecanol/hexadecanol/lime chemical film mixture, a silicone-based chemical film and an octadecanol monolayer applied to the water surface. UV transmission and absorption properties were also evaluated for each of these chemical films and monolayers. From this it was found that when chemical films/monolayers are applied to surface water they can reduce the penetration of biologically effective UV into the water column by up to 85% at a depth as small as 1 cm. This could have a positive influence on the aquatic ecosystem, as harmful UV radiation may be prevented from reaching and consequently damaging a variety of life forms or it could have a negative effect by potentially stopping aquatic organisms from adapting to solar ultraviolet radiation over extended application intervals. Additionally, there is currently no readily applicable system or technique available to readily detect or visualize chemical films and monolayers on the water surface. To overcome this problem a new method of monolayer and chemical film visualization, using a UV camera system, is detailed and tested and its applicability for usage in both laboratory-based trials and real-world operations is evaluated.

Pure Tetragonal ZrO2 Nanoparticles Synthesized by Pulsed Plasma in Liquid

Pure tetragonal phase ZrO2 (t-ZrO2) nanoparticles of sizes smaller than 5 nm were synthesized by a pulsed plasma in liquid (PPL) method, a one-step synthesis method: in an ammonia solution with no use of dopants or annealing for stabilization. Lattice parameters of the obtained samples refined by the Rietveld method revealed structural differences compared with the nanoparticles obtained by other methods such as the sol–gel method. The intrinsic properties of the pulsed plasma in liquid method and the alkaline environment (OH–) may be responsible for the stabilization of tetragonal zirconia, while the oxygen deficiency level checked by X-ray Absorption Near Edge Structure (XANES) is smaller than 1%, leading to light gray color of samples and a limited stabilization effect on the tetragonal phase. The particles displayed a higher UV absorption property than a commercial stabilized zirconia sample. Also, the emission lines of Zr I atoms and Zr II ions were observed by an optical emission spectrum to gather information on the synthesis mechanism.

The role of natural dyes in the UV protection of fabrics made of vegetable fibres

The safest protection from ultraviolet (UV) radiation exposure is offered by textiles including various apparels, accessories such as hats and shade structures such as umbrellas. Their protectiveness depends on fabric composition, (natural, artificial or synthetic fibres), fabric construction (porosity, weight and thickness) and dyeing (natural or synthetic dyes, dye concentration, UV-absorbing properties, etc.). In this study the UV-protection properties were investigated on fabrics made of vegetable fibres (cotton, flax, hemp and ramie), with different construction parameters (drapery and apparel fabrics), dyed with some of the most common natural dyes. The effect of a tannins-based mordant (the galls of Quercus infectoria) on UV-protection capacity was also tested. UV radiation transmittance of fabrics was measured by two methods: one based on the utilisation of a spectrophotometer equipped with an integrating sphere ( in vitro test), and the other based on outdoor measurements taken by a spectroradiometer. Transmittance measurements were used to calculate the Ultraviolet Protection Factor (UPF). Our results revealed that thick and dense (cover factor, CF > 94%) drapery fabrics made of vegetable fibres usually showed good UV-protection levels even if undyed. The use of the tannins-based mordant increased, even without dyeing, the UV-protection level up to the very good and/or excellent protection categories when fabric construction was suitable. Dyeing did not further increase the protection level. Lighter fabrics, usually used for apparel, even showed high UV-protection level after just dyeing, provided that CF was above 94%. Taking into account the high concentrations of dyes used in the present work and the utilisation of mordants containing tannins, slight differences in UV-protection capacity were detected among natural dyes tested and between the two different methods of transmittance measurement. However, UV-protection category defined from outdoor measurements was often higher than that calculated by the in vitro test, indicating an underestimation of the actual protection level of tested fabrics assessed by the latter.

Antioxidant Content and Ultraviolet Absorption Characteristics of Human Tears

Dry eye syndrome is a common age-related disorder, and decreased antioxidant/ultraviolet (UV) radiation protection in tears may be part of the cause. This study aimed to compare the tear antioxidant content and flow rate in young and older adults. The total antioxidant content and UV absorbing properties of various commercially available ophthalmic solutions used to alleviate dry eye symptoms were also examined. Minimally stimulated tears were collected from 120 healthy Chinese adults with no ocular pathology. Two age groups were studied: 19 to 29 years (n = 58) and 50 to 75 years (n = 62). Tear samples from each subject and 13 ophthalmic solutions were analyzed for total antioxidant content (as the Ferric Reducing/Antioxidant Power value). Tear flow rates were estimated from time taken to collect a fixed volume of tear fluid. UV absorbance spectra of pooled fresh reflex tear fluid and the ophthalmic solutions were determined. Results showed that the antioxidant content of minimally stimulated tears from older subjects (398 ± 160 μmol/l) was not significantly lower than that of younger subjects (348 ± 159 μmol/l; p = 0.0915). However, there was a significant difference in the tear flow rates between the two groups (p < 0.0001), with the younger group having three to four fold higher flow rate. None of the commercial preparations tested had detectable antioxidant content, and none showed the UV absorption characteristics of natural reflex tears. The effect of low flow rate on the dynamic antioxidant supply to the corneal surface indicates that older subjects have poorer overall defense against photooxidative and other oxidative processes. This could predispose older persons to corneal stress and development of dry eye syndrome. The commercially available artificial tears tested lack both the antioxidant content and UV absorbing characteristics of natural tears. Artificial tears formulations that help restore natural antioxidant and UV absorbing properties to the tear film of the aging eye may help prevent or improve dry eye symptoms and promote ocular health.

Fabrication of Colorless Organic Materials Exhibiting White Luminescence Using Normal and Excited-State Intramolecular Proton Transfer Processes

Organic, white luminescent materials were fabricated using a mixture of proton-transfer and nonproton-transfer fluorophores. 2'-Methoxy and 2'-hydroxy derivatives of 2-phenylimidazo[1,2-a]pyridine (PIP) have similar UV-absorption properties; however, they exhibit mechanistically different luminescence respectively ascribable to the normal (∼420 nm) and excited-state intramolecular proton transfer processes (∼530 nm) in the solid state. UV-irradiation of mixed solids excites both components concurrently and results in efficient white luminescence composed of two independent emissions without involving energy transfer process. White luminescent solids are easily transformed into vapor-deposited films under mild conditions, and a colorless and transparent thin film by dissolving in PMMA.

Intercalative Conformations of the 14R (+)- and 14S (−)-trans-anti-DB[a,l]P-N6-dA Adducts: Molecular Modeling and MD Simulations

Among the polycyclic aromatic hydrocarbon class of chemical carcinogens, dibenzo[a,l]pyrene (DB[a,l]P) is the most potent tumorigen that has been identified to date. Structurally, it is bulky with six aromatic rings, and it contains the nonplanar fjord-region. The conformational properties of DB[a,l]P-derived DNA adducts responsible for its extraordinary carcinogenicity are hence of great interest. We have carried out molecular modeling and MD simulations for the 14R (+)- and 14S (-)-trans-anti-DB[a,l]P-N⁶-dA adducts derived from the reactions of the DB[a,l]P diol epoxides with adenine in double-stranded DNA. The structures are based on the classically intercalated NMR solution structures of the analogous fjord-region benzo[c]phenanthrene-derived-N⁶-dA adducts. One objective was to gain insight on the impact of the more bulky DB[a,l]P ring system on the structural characteristics of the intercalative adduct conformations. A further objective was to elucidate the effect of the flexible twist associated with the sterically hindered aromatic ring in the fjord-region on the intercalated conformations, for comparison with the intercalated but planar bay-region benzo[a]pyrene-derived-N⁶-dA adducts. For the DB[a,l]P-N⁶-dA adducts, our results show that the 14R (+)-adduct is more favorably intercalated on the 5'-side of the modified adenine than the stereoisomeric 14S (-)-adduct, intercalated on its 3'-side. The 14R (+)-adduct manifests better van der Waals stacking interactions with flanking base pairs, less perturbed Watson-Crick hydrogen bonding, less local groove enlargement, less unwinding, and a lower solvent exposure than the 14S (-)-adduct. These structural findings are consistent with observed thermodynamic melting data, UV absorption properties, and fluorescence quenching studies. By contrast, the NMR solution structures for the analogous but less bulky B[c]Ph-derived adducts reveal no such stereoisomeric effect, while the planar bay-region benzo[a]pyrene-derived-N⁶-dA adducts do. Differences in nucleotide excision repair susceptibilities of the fjord and bay region adducts stem from distinctions in their intercalative conformations, produced by the intrinsic topological variations in their polycyclic aromatic ring systems.

Synthesis and photoluminescence properties of ZnO powder by solution combustion method

ZnO powder was synthesized by solution combustion method without annealing process. The specimens prepared with different fuel/oxidant ratios were characterized by X-ray diffraction (XRD), scanning electron microscopy, fourier transform infrared spectrometry, ultraviolet spectrometer (UV) and photoluminescence spectra (PL). With the optimal fuel/oxidant ratio of 0.25, relatively pure ZnO powder, showing the highest XRD peak, UV absorption and better luminescence property was obtained. Two peaks at 412 and 468 nm in PL spectra were attributed to the transition from conduction band to some deep acceptor level and the transition from the level of oxygen vacancies to the valence band, respectively.

Synthesis, Characterization and Properties of 1,4-Bis(Naphthalen-1-Ylethynyl)Benzene and Its Derivatives: Monomers of Oligomers or Polymers Based on Linear 1,4-Phenylethynyl or 1,5-Naphthylethynyl Subunits

A series of novel monomers of oligomers or polymers based on linear 1,4-phenylethynyl or 1,5-naphthylethynyl subunits, 1,4-bis(naphthalen-1-ylethynyl)benzene (8a) and its derivatives (8b–8i), has been synthesized and characterized. The UV absorption and fluorescence emission properties of these compounds were analyzed and discussed through the energy gap ( E ) between HOMO and LUMO orbitals, the orbital diagrams and the charge densities of related carbon atoms. It is evident from these results that the introduction of the electron-donating substituent (–OR) to the central phenylene ring of 8a and the introduction of electron-withdrawing substituent (–NO2) to the end of the conjugated system can efficiently improve its solubility, give rise to red-shift of maximum absorption and emission wavelength. But the introduction of electron-withdrawing substituent (–NO2) will lead dramatically decrease in fluorescence efficiency. The novel synthesized compounds 8b–8e have potential prospects as the monomers of oligomers or polymers based on linear 1,4-phenylethynyl or 1,5-naphthylethynyl subunits for their excellent solubility and optical properties.

Synthesis and applications of difluorobenzothiadiazole based conjugated polymers for organic photovoltaics

A new electron deficient building block, difluorobenzothiadiazole (FBT) was designed and synthesized for the first time. Two low band gap polymers containing this unit or benzothiadiazole (BT) and an electron rich unit, benzo[1,2-b:4,5-b′]dithiophene (BDT) were synthesized by Stille coupling reaction. It was found that fluorine substitution significantly lowered the energy levels but did not affect the UV absorption properties of the polymer. Comparatively, the fluorinated polymer showed a higher melting point and a reduced solubility. The electrical and photovoltaic properties of these polymers were studied by fabricating thin film transistors and polymer solar cells. The solar cell based on FBT polymer and PC71BM gives power conversion efficiency up to 3.4% under AM 1.5 G illumination (100 mW cm−2).