Physical-Chemical Study of Anthracene Selective Oxidation by a Fe(III)-Phenylporhyrin Derivative

In this work, we studied the anthracene oxidation by hydroxyl radicals. Hydroxyl radical was generated by reaction of 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin Fe (III) (TPPFe) with hydrogen peroxide under visible radiation at a nitrogen atmosphere. The TPPFe was synthesized by Adler Method followed by metal complexation with Fe (III) chloride hexahydrate. Hydroxyl radical was detected by fluorescence emission spectroscopy and we studied kinetic of anthracene selective oxidation by hydroxyl radicals through the differential method. The TPPFe was characterized by UV-Vis spectrophotometry, Dynamic Light Scattering (DLS) and Scanning Electron Microscopy (SEM) measurements. The results indicated that TPPFE was compound by micro-particles with a size distribution of around 2500 nm. Kinetic results showed that the apparent rate constant for the oxidation of anthracene increased exponentially on as temperature increases, furthermore, the activation energy for the Anthracene oxidation by hydroxyl radicals under visible irradiation was 51.3 kJ/mol. Finally, anthraquinone was the main byproduct generated after oxidation of anthracene by TPP-Fe under visible irradiation.

Exchangeable cations-mediated photodegradation of polycyclic aromatic hydrocarbons (PAHs) on smectite surface under visible light

Clay minerals saturated with different exchangeable cations are expected to play various roles in photodegradation of polycyclic aromatic hydrocarbons (PAHs) via direct and/or indirect pathways on clay surfaces. In the present study, anthracene and phenanthrene were selected as molecule probes to investigate the roles of exchangeable cations on their photodegradation under visible light irradiation. For five types of cation-modified smectite clays, the photodegradation rate of anthracene and phenanthrene follows the order: Fe(3+)>Al(3+)>Cu(2+)>>Ca(2+)>K(+)>Na(+), which is consistent with the binding energy of cation-π interactions between PAHs and exchangeable cations. The result suggests that PAHs photolysis rate depends on cation-π interactions on clay surfaces. Meanwhile, the deposition of anthracene at the Na(+)-smectite and K(+)-smectite surface favors solar light absorption, resulting in enhanced direct photodecomposition of PAHs. On the other hand, smectite clays saturated with Fe(3+), Al(3+), and Cu(2+) are highly photoreactive and can act as potential catalysts giving rise to oxidative radicals such as O2(-) , which initiate the transformation of PAHs. The present work provides valuable insights into understanding the transformation and fate of PAHs in the natural soil environment and sheds light on the development of technologies for contaminated land remediation.

Singlet oxygen mediated apoptosis by anthrone involving lysosomes and mitochondria at ambient UV exposure

Anthrone a tricyclic aromatic hydrocarbon which is toxic environmental pollutant comes in the environment through photooxidation of anthracene. We have studied the photomodification of anthrone under environmental conditions. Anthrone generates reactive oxygen species (ROS) like (1)O2 through Type-II photodynamic reaction. Significant intracellular ROS generation was measured through dichlorohydrofluorescein fluorescence intensity. The generation of (1)O2 was further substantiated by using specific quencher like sodium azide. UV induced photodegradation of 2-deoxyguanosine and photoperoxidation of linoleic acid accorded the involvement of (1)O2 in the manifestation of anthrone phototoxicity. Phototoxicity of anthrone was done on human keratinocytes (HaCaT) through 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide and neutral red uptake assays. Anthrone induced cell cycle arrest (G2/M-phase) and DNA damage in a concentration dependent manner. We found apoptosis as a pattern of cell death which was confirmed through sub-G1 fraction, morphological changes, caspase-3 activation, acridine orange/ethidium bromide staining and phosphatidylserine translocation. Mitochondrial depolarization and lysosomal destabilization was parallel to apoptotic process. Our RT-PCR results strongly supports our view point of apoptotic cell death through up-regulation of pro-apoptotic genes p21 and Bax, and down regulation of anti-apoptotic gene Bcl2. Therefore, much attention should be paid to concomitant exposure of anthrone and UV-R for its total environmental impact.

Preparation, characterization, physical properties, and photoconducting behaviour of anthracene derivative nanowires

Organic nanowires of 9,10-dibromoanthracene (DBA) and 9,10-dicyanoanthracene (DCNA) were obtained by adding the THF solution of DBA/DCNA into water containing P123 surfactants. The as-prepared nanowires were characterized by UV-vis, fluorescence spectra, Field Emission Scanning Electron Microscopy (FESEM), and Transmission Electron Microscopy (TEM). We found that DBA and DCNA nanowires emitted green light rather than blue light for molecules in THF solution. The red-shift UV and fluorescent spectra of DBA and DCNA nanowires implied that these nanowires were formed through J-aggregation. The photoconducting study of DBA/DCNA nanowire-based network on rGO/SiO(2)/Si shows different photocurrent behaviors upon irradiation, which displayed that electron transfer from DCNA nanowire to rGO was stronger than that of DBA nanowires to rGO.

High temperature polyimide containing anthracene moiety and its structure, interface, and nonvolatile memory behavior

A high temperature polyimide bearing anthracene moieties, poly(3,3'-di(9-anthracenemethoxy)-4,4'-biphenylene hexafluoroisopropylidenediphthalimide) (6F-HAB-AM PI) was synthesized. The polymer exhibits excellent thermal stability up to around 410 °C. This polymer is amorphous but orients preferentially in the plane of nanoscale thin films. In device fabrications of its nanoscale thin films with metal top and bottom electrodes, no diffusion of the metal atoms or ions between the polymer and electrodes was found; however, the aluminum bottom electrode had somewhat undergone oxide layer (about 1.2 nm thick) formation at the surface during the post polymer layer formation process, which was confirmed to have no significant influence on the device performance. The polymer thin film exhibited excellent unipolar and bipolar switching behaviors over a very small voltage range, less than ±2 V. Further, the PI films show repeatable writing, reading, and erasing ability with long reliability and high ON/OFF current ratio (up to 10(7)) in air ambient conditions as well as even at temperatures up to 200 °C.

Coupling across a DNA helical turn yields a hybrid DNA/organic catenane doubly tailed with functional termini

We describe the synthesis of a hybrid DNA/organic macrocycle that is prepared by formation of an amide linkage across one full turn of DNA. Formation of a catenane proved that the linkage crossed a turn rather than running along the phosphodiester backbone contour. The product, a doubly tailed catenane, contains 5'- and 3'-termini that can be functionalized further or used to incorporate the catenane structure into other DNA assemblies.

Decomposition of polycyclic aromatic hydrocarbons in atmospheric aqueous droplets through sulfate anion radicals: an experimental and theoretical study

Polycyclic aromatic hydrocarbons (PAHs) are environmental pollutants that have received considerable attention because of their carcinogenic and mutagenic effects. PAHs can be degraded by sulfate anion radicals in atmospheric aqueous droplets. This study was to investigate the mechanism and degradation products of sulfate anion radical reaction with anthracene (ANT) by experimental and quantum chemical approaches. From these observations of the experiments, the sulfate anion radical is capable of oxidizing ANT rapidly and three intermediates anthraquinone (ATQ), 1-hydroxyanthraquinone (1-hATQ), and 1,4-dihydroxyanthraquinone (1,4-dhATQ) were detected as degradation products by GC-MS. The proposed one-electronic transfer mechanism of sulfate anion radical reaction with ANT was modeled using hybrid density function theory (BHandHLYP) methods. Geometry optimization and vibrational frequency analysis calculation were performed for reactants, transition states, intermediates, and products. The potential energy surfaces of these reactions are explored to establish structures and relative energies of reactants, intermediates, transition states, and products. Computational results suggest that initial electron transfer step is predicted to have activation energy of -3.35 kcal/mol in water, indicating that ANT can be oxidized quickly in atmospheric aqueous droplets. The reaction pathways have been proposed on the basis of these experimental and theoretical findings. The results may provide useful information for a better understanding of the sulfate anion radical-initiated reactions in atmospheric aqueous droplets such as clouds, rains or fogs.

Laser-driven acoustic desorption of organic molecules from back-irradiated solid foils

Laser-induced acoustic desorption (LIAD) from thin metal foils is a promising technique for gentle and efficient volatilization of intact organic molecules from surfaces of solid substrates. Using the single-photon ionization method combined with time-of-flight mass spectrometry, we have examined the neutral component of the desorbed flux in LIAD and compared it to that from direct laser desorption. These basic studies of LIAD, conducted for molecules of various organic dyes (rhodamine B, fluorescein, anthracene, coumarin, BBQ), have demonstrated detection of intact parent molecules of the analyte even at its surface concentrations corresponding to a submonolayer coating. In some cases (rhodamine B, fluorescein, BBQ), the parent molecular ion peak was accompanied by a few fragmentation peaks of comparable intensity, whereas for others, only peaks corresponding to intact parent molecules were detected. At all measured desorbing laser intensities (from 100 to 500 MW/cm2), the total amount of desorbed parent molecules depended exponentially on the laser intensity. Translational velocities of the desorbed intact molecules, determined for the first time in this work, were of the order of hundreds of meters per second, less than what has been observed in our experiments for direct laser desorption, but substantially greater than the possible perpendicular velocity of the substrate foil surface due to laser-generated acoustic waves. Moreover, these velocities did not depend on the desorbing laser intensity, which implies the presence of a more sophisticated mechanism of energy transfer than direct mechanical or thermal coupling between the laser pulse and the adsorbed molecules. Also, the total flux of desorbed intact molecules as a function of the total number of desorbing laser pulses, striking the same point on the target, decayed following a power law rather than an exponential function, as would have been predicted by the shake-off model. To summarize, the results of our experiments indicate that the LIAD phenomenon cannot be described in terms of simple mechanical shake-off or direct laser desorption. Rather, they suggest that multistep energy-transfer processes are involved. Two possible (and not mutually exclusive) qualitative mechanisms of LIAD that are based on formation of nonequilibrium energy states in the adsorbate-substrate system are proposed and discussed.

A Highly Fluorescent Anthracene-Containing Hybrid Material Exhibiting Tunable Blue–Green Emission Based on the Formation of an Unusual “T-Shaped” Excimer

A series of flexible bis(9-anthryldiamine) ligands (L1-L3) linked with alkyl spacers of different chain length was synthesized and characterized, in order to investigate the coordination behavior of these diamine ligands with metal ions (Zn2+, etc.) based on fluorescence measurements. The results showed that, in the case of anthryldiamine ligands bearing two- or four-carbon links, the zinc ion induced a chelation-enhanced fluorescence (CHEF) effect in aqueous media, while a trace amount of water could selectively quench the blue emission of the Zn(II) complex with a three-carbon-linked ligand (1). Meanwhile, the introduction of more water (concentration >11 %) resulted in the formation of a new green luminescent species; the luminescence intensity was enhanced stepwise to a maximum with addition of approximately 30 % water in THF solution. The peak position (centered at approximately 500 nm) and the lifetime measurement (tau=19.59 ns) indicated that the green luminescence was attributable to a novel edge-to-face dimeric conformation ("T-shaped" conformation) of anthracene, and not to the more common face-to-face dimeric conformation. Accordingly, 1H NMR spectroscopic studies in nonaqueous or aqueous solution confirmed this T-shaped conformation, which is consistent with the results of single-crystal X-ray structure analysis and solid-state photoluminescence studies.

Synthesis, properties, and photodynamic inactivation of Escherichia coli using a cationic and a noncharged Zn(II) pyridyloxyphthalocyanine derivatives

The photodynamic effect of a cationic Zn(II) N-methylpyridyloxyphthalocyanine (ZnPc 2) and a noncharged Zn(II) pyridyloxyphthalocyanine (ZnPc 1) has been compared in both homogeneous media bearing photooxidizable substrates and in vitro using a typical Gram-negative bacterium Escherichia coli. Absorption and fluorescence spectroscopic studies were analyzed in different media. Fluorescence quantum yields (varphiF) of 0.23 for ZnPc 1 and 0.22 for ZnPc 2 were calculated in N,N-dimethylformamide (DMF). The singlet molecular oxygen, O2(1Deltag), production was evaluated using 9,10-dimethylanthracene (DMA) in DMF yielding values of PhiDelta=0.56 for ZnPc 1 and 0.59 for ZnPc 2. A faster decomposition of L-tryptophan (Trp), which was used as biological substrate model, was obtained using ZnPc 2 as a sensitizer with respect to ZnPc 1. In biological medium, the E. coli cultures were treated with 10 microM of sensitizer for different times at 37 degrees C in the dark. Both ZnPcs 1 and 2 are rapidly bound to E. coli cells in 5 min and the amount of cell-bound sensitizer is not appreciably changed incubating the cultures for longer times. The recovered ZnPc 2 after one washing step is approximately 3 times higher than 1, reaching a value of approximately 3 nmol/10(6) cells. After irradiation with visible light, a higher photoinactivation of cells was found for ZnPc 2. Thus, a approximately 4.5 log (99.997%) decrease of cell survival was obtained after 30 min of irradiation. On the other hand, a very low photodamage was found for cells treated with ZnPc 1 (approximately 0.5 log). Also, these results were established by stopping of growth curves for E. coli. In the structure of ZnPc 2, the cationic centers are isolated from the phthalocyanine ring by an ether bridge, which also provides a higher mobility of the charges facilitating the interaction with the outer membrane of the Gram-negative bacteria. These studies show that cationic ZnPc 2 is an efficient phototherapeutic agent with potential applications in photodynamic inactivation of bacteria.

Complementarity in bimolecular photochromism

Irradiating 2,3,6,7-tetraphenylanthracene in the presence of 9,10-dimethylanthracene leads to exclusive formation of the cross-dimer. No photochemical reaction is observed when either of these chromophores is irradiated in the absence of the other.

Biodegradation of selected UV-irradiated and non-irradiated polycyclic aromatic hydrocarbons (PAHs)

Biodegradation of UV-irradiated anthracene, pyrene, benz[a]anthracene, and dibenz[a,h]anthracene was compared to that of the non-irradiated samples, individually and in synthetic mixtures with enrichment cultures. Combined treatment was repeated for individual anthracene and for the PAH mixture with Sphingomonas sp. strain EPA 505 and Sphingomonas yanoikuyae. Enrichment culture studies were performed on the PAH mixtures in the presence of the main photoproduct of anthracene, pure 9,10-anthracenedione. Photochemically pretreated creosote solutions were also subjected to biodegradation and the results were compared to those of the non-irradiated solutions. The primary interest was on 16 polycyclic aromatic hydrocarbons (PAHs) listed as priority pollutants by European Union (EU) and the United States Environmental Protection Agency (USEPA). Irradiation accelerated the biodegradation onset for anthracene, pyrene, and benz[a]anthracene when they were treated individually. The biodegradation of irradiated pyrene started with no lag phase and was complete by 122 h whereas biodegradation of the non-irradiated sample had a lag of 280 h and resulted in complete degradation by 720 h. Biodegradation of PAHs was accelerated in synthetic mixtures, especially in the presence of pure 9,10-anthracenedione. In general, irradiation had no effect on the biodegradation of PAHs incubated in synthetic mixtures or with pure cultures. Under current experimental conditions, the UV-irradiation invariably reduced the biodegradation of PAHs in creosote. Based on the results of the present and previous photochemical-biological studies of PAHs, the influence of the photochemical pretreatment on the biodegradation is highly dependent on the compounds being treated and other process parameters.

Radiation dosimetry using three-dimensional optical random access memories

Three-dimensional optical random access memories (3D ORAMs) are a new generation of high-density data storage devices. Binary information is stored and retrieved via a light induced reversible transformation of an ensemble of bistable photochromic molecules embedded in a polymer matrix. This paper describes the application of 3D ORAM materials to radiation dosimetry. It is shown both theoretically and experimentally, that ionizing radiation in the form of heavy charged particles is capable of changing the information originally stored on the ORAM material. The magnitude and spatial distribution of these changes are used as a measure of the absorbed dose, particle type and energy. The effects of exposure on 3D ORAM materials have been investigated for a variety of particle types and energies, including protons, alpha particles and 12C ions. The exposed materials are observed to fluoresce when exposed to laser light. The intensity and the depth of the fluorescence is dependent on the type and energy of the particle to which the materials were exposed. It is shown that these effects can be modeled using Monte Carlo calculations. The model provides a better understanding of the properties of these materials. which should prove useful for developing systems for charged particle and neutron dosimetry/detector applications.

Pathway of anthracene modification under simulated solar radiation

Exposure of polycyclic aromatic hydrocarbons (PAHs) to sunlight results in rapid structural photomodification generally via oxidation reactions. These PAH modification products are in many cases more toxic than their parent compounds. In this study, anthracene (ANT), a rapidly photooxidized PAH, was irradiated with simulated solar radiation (SSR, 100 micromol m(-2) s(-1)) in aqueous solution to examine the photomodification pathway. The photoproducts formed were identified by HPLC. The ANT product profile after 9 h in SSR was very complex, with more than 20 compounds detected. The photoproducts formed were anthraquinones, benzoic acids, benzaldehydes and phenols showing the process to be oxidative in nature. Some of the anthraquinones were themselves subject to photooxidation, and were thus intermediates in the product pathway. The kinetics of ANT photooxidation revealed a pseudo first-order reaction with a half-life of 2 h under the SSR source used. The kinetics of product formation allowed deduction of a probable photomodification pathway. This study indicates that PAH photooxidation products are likely to exist as complex, dynamically changing mixtures in PAH contaminated aquatic environments.

Impacts of structural photomodification on the toxicity of environmental contaminants: anthracene photooxidation products

The toxicity of polycyclic aromatic hydrocarbons (PHAs) is known to be enhanced by light via photosensitization reactions (production of active oxygen) and photomodification of the chemicals (e.g., oxidation) to more toxic compounds. Anthracene (ANT) toxicity in particular has been found to increase dramatically following photomodification. The objective of this study was to identify the photooxidation products of ANT and assess the toxicity of selected photoproducts. High performance liquid chromatography (HPLC) analysis of anthracene photooxidation revealed a complex array of oxidation products; prevalent among these were anthraquinone (ATQ) and hydroxy-anthraquinones (hATQs). Eleven of these compounds were tested for toxicity using growth inhibition of the duckweed Lemna gibba L. G-3. All but one of the compounds tested were found to be toxic, and when UV radiation was present in the light source toxicity was generally enhanced. The chemicals were also irradiated under SSR prior to toxicity testing. In about half the cases, the ATQ compounds were rapidly photooxidized and the resultant photoproducts were more toxic than the parent compounds. Interestingly, 2-hydroxyanthraquinone, which was not subject to photooxidation, was the most toxic of the compounds tested. As a light stable compound it presents the risk of a persistent environmental hazard.

Increased polycyclic aromatic hydrocarbon toxicity following their photomodification in natural sunlight: impacts on the duckweed Lemna gibba L. G-3

The authors previously demonstrated that simulated solar radiation (SSR), with a fluence rate of only 40 mumol m-2 sec-1, increased polycyclic aromatic hydrocarbon (PAH) toxicity to the duckweed Lemna gibba and that PAHs photomodified in SSR (generally oxygenation of the ring system) are more toxic than the parent compounds (Huang et al., Environ. Toxicol. Chem., 1993, 12, 1067-1077). It is not known, however, to what extent toxicity of PAHs can increase due to photomodification. Thus, natural sunlight, which has a high fluence rate (approximately 2000 mumol m-2 sec-1), was used to photomodify anthracene, benzo[a]pyrene, fluoranthene, phenanthrene, and pyrene. Toxicity was based on growth inhibition of L. gibba, measured as the rate of production of new leaves over an 8-day period. Initially, the toxicity of the PAHs applied in intact form was probed, with the compounds demonstrating greater toxicity in sunlight than in SSR. Next the PAHs were photomodified in sunlight prior to incubation with the plants. The half-lives of the PAHs in sunlight ranged from 12 min to 30 hr. Although most of the products of PAH photomodification are not yet identified, the degree that PAH toxicity increased following photomodification in sunlight could still be probed. The mixtures of photomodified chemicals that were derived from each PAH in sunlight were applied of L. gibba and growth inhibition under 100 mumol m-2 sec-1 of SSR was determined. The LC50s for the PAH photoproducts generated in sunlight were an order of magnitude lower than the LC50s for the PAHs applied in intact form.

Mutagenicity of photochemical reaction products of polycyclic aromatic hydrocarbons with nitrite

Six kinds of polycyclic aromatic hydrocarbons (PAHs) were subjected to ultraviolet light irradiation with nitrite for 1, 4, 8 and 24 h, and the irradiated samples were tested for mutagenicity towards Salmonella typhimurium TA 98, TA 100 and TA 1538. Irradiated samples of pyrene, fluoranthene and benzo[a]pyrene showed marked mutagen responses towards TA 98 and TA 1538, especially in the absence of S9 mix. The direct-acting mutagenic activity of these samples, showing high activities at 1-8 h, decreased greatly with the development of irradiation. Further, these direct-acting mutagens were mostly present in the neutral fraction. On the other hand, the mutagenicity of the irradiated sample of 5,6-benzoquinoline was high both with and without S9 mix, and was mostly present in the basic fraction because of its authentic characteristic. There was no correlation between the yield of 1-nitropyrene and the mutagenic activity of the photochemical reaction product of pyrene with nitrite. Further studies by TLC separation suggested that a considerable number of direct-acting mutagens formed in this experiment were more polar than nitrated PAH such as 1-nitropyrene.

Radiation damage in electron microscopy of organic materials: effect of low temperatures

As measured by the life-time of their electron diffraction patterns, the radiation sensitivity of anthracene and coronene at 500 kV is reduced by a factor of three to four at liquid helium temperature in comparison to room temperature, For l-valine the ratio is about 1-8 but there is a wide variation in the results, possibly due to differences in crystal thickness. The end-dose at 20 degrees K for valine is equivalent to 13 electrons/A2; for anthracene and coronene it is about 600 electrons/A2 at room temperature. The variation of end-dose with temperature shows that at least two mechanisms must be involved in damage to such compounds, possibly concerning the breaking of intermolecular and intramolecular bonds, respectively.