Different Impact of Suspended Al2O3 Nanoparticles on Microbial Communities: Formation of 2D-Networks (Without Humic Acids) or 3D-Colonies (With Humic Acids).

The use of metal-based and, particularly, Al2O3 nanoparticles (Al2O3-NP) for diverse purposes is exponentially growing. However, the growth of such promissory market is not accompanied by a parallel extensive investigation related to the impact of this pollution on groundwater and biological systems. Pseudomonas species, ubiquitous, environmentally critical microbes, frequently respond to stress conditions with diverse strategies that generally include extracellular polymeric substances (EPS) formation. The aim of this study is to report that changes in the aqueous environment, particularly, the addition of Al2O3-NP without and with humic acids, induce different adaptive strategies of Pseudomonas aeruginosa early biofilms. To this purpose, early biofilms were incubated in diluted culture media without (control) and with Al2O3-NP, and with humic acids (HA-control, HA-Al2O3-NP) for 24 h. 3D colonies with EPS strings and isolated bacteria in their surroundings were detected in the control biofilms. Unlikely, an unusual adaptive behaviour was developed in the presence of Al2O3-NP. Bacteria opt to disassemble the 3D arrangements and to implement a 2D network promoting morphological and size changes of bacterial cells (small coccoid shapes). Remarkably, this strategy allows their temporarily non-EPS-depending survival without decreasing the number of cells. This behaviour was not observed with ZnO-NP, HA-Al2O3-NP, or HA-ZnO-NP. Physicochemical analysis revealed that HA were adsorbed on Al2O3-NP and promoted the Al(III) ions complexation. This supports the hypothesis that the reduction of toxicity of Al ions and the 3D colony formation in the presence of HA-Al2O3-NP is promoted by the complexation of the metal ions with HA components.

Staphylococcus aureus biofilm eradication by the synergistic effect exerted by PEG-coated silicon dots immobilized in silica films and light irradiation.

Immobilization of PEG-covered silicon dots, PEGSiDs, on glass substrates was performed following a simple strategy involving particle embedding by a sol-gel process forming a silica film on glass slides. The obtained films, denoted as fSiO x -PEGSiD, constitute a water-wettable, strongly supported, photoluminescent glass coating. The films showed high capacity for photosensitizing singlet oxygen (1O2) in the UVA when immersed in water. Staphylococcus aureus colonies formed on fSiO x -PEGSiDs modified glasses revealed the inhibition of bacterial adhesion and bacterial growth leading to the formation of loosely-packed and smaller S. aureus colonies. Upon 350 nm light irradiation of the biofilmed fSiO x -PEGSiDs -modified glasses, S. aureus growth was inhibited and bacteria killed reducing the number of living bacteria by three orders of magnitude. Eradication of attached bacteria was achieved by the synergistic effect exerted by a less adherent fSiO x -PEGSiDs surface that inhibits biofilm formation and the ability of the surface to photosensitize 1O2 to kill bacteria.

VUV-photolysis of aqueous solutions of hydroxylamine and nitric oxide. Effect of organic matter: phenol.

VUV-irradiation of aqueous solutions containing hydroxylamine (NH2OH) in its acid form (NH3OH+) and phenol (C6H5OH) results in the simultaneous mineralization of the organic substrate and the almost quantitative reduction of NH3OH+ to ammonium ions (NH4+). Irradiation of aqueous solutions of NH3OH+ in the absence of organic substrates showed the formation of nitrate (NO3-) and nitrite (NO2-) and minor quantities of NH4+. In line with these experiments, VUV-irradiation of aqueous solutions of nitrogen monoxide (NO˙) yields NH4+ only when C6H5OH is simultaneously mineralized. A possible reaction mechanism is discussed, where reactions of NO˙ and NH3OH+ with hydrogen atoms (H˙), hydroxyl radicals (HO˙) and hydrated electrons (e-aq), all generated by the VUV-photochemically initiated homolysis of water, are of great importance to the observed results. In the presence of phenol, competition between phenol and either NO˙ or NH3OH+ for these reactive intermediates in the primary volume of reactions strongly determines the oxidation state and nature of the N-containing products. C-Centered radicals and intermediate products of reactions may also have an important effect on the overall mechanism. The present results are discussed in relation to the actual state of knowledge presented in the literature.

Visible Light Induced Cationic Polymerization of Epoxides by Using Multiwalled Carbon Nanotubes.

The visible light induced cationic polymerization of epoxides can be achieved by means of multiwalled carbon nanotubes (MWCNTs), which act as visible light photoinitiators via a radical-induced cationic photopolymerization process. When MWCNTs are irradiated with longer wavelengths (above 400 nm), they generate carbon radicals, by means of hydrogen abstraction from the epoxy monomer; these radicals are oxidized in the presence of iodonium salt to a carbocation that is sufficiently reactive to start the cationic ring-opening polymerization of an epoxy monomer. These mechanisms have been supported by electron paramagnetic resonance analysis.

Polyethylene glycol-coated blue-emitting silicon dots with improved properties for uses in aqueous and biological environments.

Grafting of polyethylene glycol (PEG) to ultrasmall photoluminescent silicon dots (SiDs) is expected to improve and expand the applications of these particles to aqueous environments and biological systems. Herein we report a novel one-pot synthesis of robust, highly water compatible PEG-coated SiDs (denoted as PEG-SiDs) of (3.3 ± 0.5) nm size. The nanoparticles' synthesis is based on the liquid phase oxidation of magnesium silicide using PEG as reaction media and leading to high PEG density grafting. PEG-SiDs enhanced photophysical, photosensitising, and solution properties in aqueous environments are described and compared to those of 2 nm size PEG-coated SiDs with low PEG density grafting (denoted as PEG-NHSiDs) obtained from a multistep synthesis strategy. PEG-SiDs form highly dispersed suspensions in water showing stable photoluminescence and quantum yields of Φ = 0.13 ± 0.04 at 370 nm excitation in air-saturated suspensions. These particles exhibited the capacity of photosensitising the formation of singlet molecular oxygen, not observed for PEG-NHSiDs. PEG robust shielding of the silicon core luminescent properties is further demonstrated in bio-imaging experiments stressing the strong interaction between PEG-SiDs and Staphylococcus aureus smears by observing the photoluminescence of particles. PEG-SiDs were found to be nontoxic to S. aureus cells at concentrations of 100 mg ml-1, though a bacteriostatic effect on S. aureus biofilms was observed upon UV-A irradiation under conditions where light alone has no effect.

Oxidized silicon nanoparticles for radiosensitization of cancer and tissue cells.

The applicability of ultrasmall uncapped and aminosilanized oxidized silicon nanoparticles (SiNPs and NH2-SiNPs) as radiosensitizer was studied by internalizing these nanoparticles into human breast cancer (MCF-7) and mouse fibroblast cells (3T3) that were exposed to X-rays at a single dose of 3 Gy. While SiNPs did not increase the production of reactive oxygen species (ROS) in X-ray treated cells, the NH2-SiNPs significantly enhanced the ROS formation. This is due to the amino functionality as providing positive surface charges in aqueous environment. The NH2-SiNPs were observed to penetrate into the mitochondrial membrane, wherein these nanoparticles provoked oxidative stress. The NH2-SiNPs induced mitochondrial ROS production was confirmed by the determination of an increased malondialdehyde level as representing a gauge for the extent of membrane lipid peroxidation. X-ray exposure of NH2-SiNPs incubated MCF-7 and 3T3 cells increased the ROS concentration for 180%, and 120%, respectively. Complementary cytotoxicity studies demonstrate that these silicon nanoparticles are more cytotoxic for MCF-7 than for 3T3 cells.

Evaluation of the Hg2+ binding potential of fulvic acids from fluorescence excitation-emission matrices.

The effect of Hg(2+) on the fluorescence intensity of three fulvic acids (Pahokee Peat, Pony Lake and Suwannee River) was studied. The fluorescence intensity decreased in the presence of added Hg(2+), while the fluorescence lifetimes were independent of the concentration of Hg(2+) in solution. These results are indicative of ground-states association between the fulvic acids and Hg(2+) with formation of stable non-fluorescent complexes (static quenching process). The analysis of the excitation-emission matrices with the Singular Value Decomposition (SVD) and Multivariate Curve Resolution-Alternating Least Squares (MCR-ALS) methods provided additional valuable information regarding the binding properties between Hg(2+) ions and specific fluorescence components of the fulvic acids. The three fulvic acids were shown to contain the same three groups of fluorophores characterized by excitation/emission pairs in the following regions: (320-330 nm/425-450 nm), (370-375 nm/465-500 nm), (290-295 nm/370-395 nm). These pairs are almost not affected by the change of pH from 2.0 to 7.0. Ryan-Weber and modified Stern-Volmer methods were used to analyze the static fluorescence quenching of the individual components. Similar conditional stability constants of Hg(2+) binding for the three components were found by both methods. The obtained log K values are in the range of 4.4 to 5.4.

Triplet state of 4-methoxybenzyl alcohol chemisorbed on silica nanoparticles.

The knowledge of photochemical kinetics in colloidal systems is important in understanding environmental photochemistry on dispersed solid surfaces. As model materials for the chemically sorbed organic compounds present in natural environments, modified silica nanoparticles (NPs) were obtained here by condensation of the silanol groups of fumed silica nanoparticles with 4-methoxybenzyl alcohol. These particles were characterized by different techniques. To evaluate their toxicity, the inhibition of the natural luminescence emission of the marine bacterium Vibrio fischeri in suspensions of the particles was measured. Laser flash-photolysis experiments (λ(exc) = 266 nm) performed with NP suspensions in acetonitrile-aqueous phosphate buffer mixtures showed the formation of the lowest triplet excited state of the chemisorbed organic groups (λ(max) = 390 nm). DFT calculations of the absorption spectrum of this radical support the assignment. From the calculated triplet energy, a thermodynamically favorable energy transfer from these triplet states to oxygen to yield singlet molecular oxygen is predicted. A value of 0.09 was measured for the quantum yield of singlet molecular oxygen generation by air-saturated suspensions of the nanoparticles in the mixture of solvents acetonitrile-aqueous phosphate buffer. The quantum yield of singlet molecular oxygen generation by the free 4-methoxybenzyl alcohol in the same solvent is 0.31.

Non-purified commercial multiwalled carbon nanotubes supported on electrospun polyacrylonitrile@polypyrrole nanofibers as photocatalysts for water decontamination.

We present a photoactive composite material for water decontamination consisting of non-purified commercial multiwalled carbon nanotubes (CNT(NP)s) supported on an electrospun polymeric mat made of core-sheath polyacrylonitrile-polypyrrole nanofibers. This is the first system that specifically exploits the superior photocatalytic activity of CNT(NP)s compared with the purified carbon nanotubes usually employed. A CNT(NP) still contains the catalytic metal oxide nanoparticles (NPs) used for its synthesis, embedded in the nanotube structure. Under UV-visible irradiation, these NPs generate highly reactive ˙OH radicals capable of degrading the organic molecules adsorbed on the nanotube. Photocatalytic tests on the composite material show that CNT(NP)s act mostly as a source of photogenerated charge carriers. The adsorption of target substrates occurs preferentially onto the polypyrrole sheath, which shuttles the reactive carriers from CNT(NP)s to the substrates. In addition, UV-visible irradiation of semiconducting polypyrrole generates radical species that directly react with the adsorbed substrates. All synthetic procedures reported are scalable and sustainable. This mechanically resistant and flexible composite overcomes one of the weakest aspects of water treatments that employ suspended nanocatalysts, namely the expensive and poorly scalable recovery of the catalyst through nanofiltration. All these features are required for large-scale photocatalytic treatments of polluted water.

Environmentally Induced Changes of Commercial Carbon Nanotubes in Aqueous Suspensions. Adaptive Behavior of Bacteria in Biofilms.

The effects of environmental factors such as sunlight irradiation and the presence of humic acid (HA) on the physicochemical properties of commercial multiwall carbon nanotubes (MWCNT) suspended in a simulated inorganic matrix (SIM) and their impacts on bacteria growing in biofilms were evaluated. Both solar irradiation and the presence of HA lead to the dissolution of adsorbed metals on the MWCNT, which are residues of synthesis catalysts. Also, preferential adsorption of certain HA components on the MWCNT induces important modifications in the aliphatic/aromatic relationship of HA components in solution and the generation and release of new moieties. Results demonstrated that the variation of such physicochemical parameters strongly affects the interactions of MWCNT with Pseudomonas aeruginosa sessile bacteria. Thus, the number of attached bacteria increased, and stress responses such as decrease in bacterial size were found in the presence of sunlight-irradiated MWCNT with a particular distribution of extracellular polymeric substances (EPS) strands. A shielding effect was observed when HA was added. It was concluded that physicochemical alterations caused by environmental conditions (with/without irradiation, presence/absence of HA) on MWCNT-containing SIM trigger distinctive adaptive behavior of bacteria in biofilms. This information must be taken into account in the development of biologically assisted treatments for organic metal co-contamination of MWCNT-containing media since MWCNT discharge alters the physicochemical properties and composition of the aqueous environment and the response of the biofilms that interact with it.

Magnetic 3D scaffolds for tissue engineering applications: bioactive glass (45S5) coated with iron-loaded hydroxyapatite nanoparticles.

Magnetic 45S5 bioactive glass (BG) based scaffolds covered with iron-loaded hydroxyapatite (Fe-HA-BG) nanoparticles were obtained and its cytotoxicity investigated. Fe-HA nanoparticles were synthesized by a wet chemical method involving the simultaneous addition of Fe2+/Fe3+ions. BG based scaffolds were prepared by the foam replica procedure and covered with Fe-HA by dip-coating. Fe-HA-BG magnetic saturation values of 0.049 emu g-1and a very low remanent magnetization of 0.01 emu g-1were observed. The mineralization assay in simulated body fluid following Kokubo's protocol indicated that Fe-HA-BG scaffolds exhibited improved hydroxyapatite formation in comparison to uncoated scaffolds at shorter immersion times. The biocompatibility of the materialin vitrowas assessed using human osteoblast-like MG-63 cell cultures and mouse bone marrow-derived stroma cell line ST-2. Overall, the results herein discussed suggest that magnetic Fe-HA coatings seem to enhance the biological performance of 45S5 BG based scaffolds. Thus, this magnetic Fe-HA coated scaffold is an interesting system for bone tissue engineering applications and warrant further investigation.

Silicon nanoparticle photophysics and singlet oxygen generation.

The effect of molecular oxygen and water on the blue photoluminescence of silicon nanoparticles synthesized by anodic oxidation of silicon wafers and surface functionalized with 2-methyl 2-propenoic acid methyl ester is investigated. The particles of 3 +/- 1 nm diameter and a surface composition of Si(3)O(6)(C(5)O(2)H(8)) exhibit room-temperature luminescence in the wavelength range 300-600 nm upon excitation with 300-400 nm light. The luminescence shows vibronic resolution and high quantum yields in toluene suspensions, while a vibronically unresolved spectrum and lower emission quantum yields are observed in aqueous suspensions. The luminescence intensity, though not the spectrum features, depends on the presence of dissolved O(2). Strikingly, the luminescence decay time on the order of 1 ns does not depend on the solvent or on the presence of O(2). To determine the mechanisms involved in these processes, time-resolved and steady-state experiments are performed. These include low-temperature luminescence, heavy atom effect, singlet molecular oxygen ((1)O(2)) phosphorescence detection, reaction of specific probes with (1)O(2), and determination of O(2) and N(2) adsorption isotherms at 77 K. The results obtained indicate that physisorbed O(2) is capable of quenching nondiffusively the particle luminescence at room temperature. The most probable mechanism for (1)O(2) generation involves the energy transfer from an exciton singlet state to O(2) to yield an exciton triplet of low energy (<0.98 eV) and (1)O(2). In aqueous solutions, excited silicon nanoparticles are able to reduce methylviologen on its surface.

Reduction of mercury(II) by the carbon dioxide radical anion: a theoretical and experimental investigation.

The laser flash photolysis technique (λ(exc) = 266 nm) was used to investigate the mechanism of the HgCl(2) reduction mediated by CO(2)(·-) radicals in the temperature range 291.7-308.0 K. For this purpose, the CO(2)(·-) radicals were generated by scavenging of sulfate radicals by formic acid. The absorbance of the reduced radical of methyl viologen, a competitive scavenger of CO(2)(·-), was monitored at 390 nm. Moreover, theoretical calculations, including solvent effects, were also performed within the framework of the density functional theory for various chemical species of Hg(I) and Hg(II) to aid in the modeling of the reaction of reduction of HgCl(2) by CO(2)(·-).

BSA-capped gold nanoclusters as potential theragnostic for skin diseases: Photoactivation, skin penetration, in vitro, and in vivo toxicity.

BSA-capped gold nanoclusters are promising theragnostic systems that can be excited to render both fluorescence emission and reactive oxygen species. Although their synthesis and photoluminescence properties are already well described, more accurate information about their use as photosensitizers is required in order to advance towards health applications. In this work, we have obtained BSA-capped gold nanoclusters and characterized their photophysics by different techniques. Singlet oxygen production was detected upon irradiation, which was enough to produce toxicity on two cell lines. Remarkably, an internal energy transfer, probably due to the presence of smaller nanoclusters and the contribution of oxidized residues of BSA in the system, caused fluorescence emission near 640 nm after excitation in the UV range. Additionally, the system was capable of penetrating human skin beyond the stratum corneum, which enhances the potential of these nanoclusters as bifunctional photodynamic therapy effectors and biomarkers with application in a diversity of skin diseases. In the absence of radiation, BSA-capped gold nanoclusters did not cause toxicity in vitro, while their toxic effect on an in vivo model as zebrafish was determined.

Photoinduced degradation of the herbicide clomazone model reactions for natural and technical systems.

The photodegradation of the herbicide clomazone in the presence of S(2)O(8) (2-) or of humic substances of different origin was investigated. A value of (9.4 +/- 0.4) x 10(8) m(-1) s(-1) was measured for the bimolecular rate constant for the reaction of sulfate radicals with clomazone in flash-photolysis experiments. Steady state photolysis of peroxydisulfate, leading to the formation of the sulfate radicals, in the presence of clomazone was shown to be an efficient photodegradation method of the herbicide. This is a relevant result regarding the in situ chemical oxidation procedures involving peroxydisulfate as the oxidant. The main reaction products are 2-chlorobenzylalcohol and 2-chlorobenzaldehyde. The degradation kinetics of clomazone was also studied under steady state conditions induced by photolysis of Aldrich humic acid or a vermicompost extract (VCE). The results indicate that singlet oxygen is the main species responsible for clomazone degradation. The quantum yield of O(2)(a(1)Delta(g)) generation (lambda = 400 nm) for the VCE in D(2)O, Phi(Delta) = (1.3 +/- 0.1) x 10(-3), was determined by measuring the O(2)(a(1)Delta(g)) phosphorescence at 1270 nm. The value of the overall quenching constant of O(2)(a(1)Delta(g)) by clomazone was found to be (5.7 +/- 0.3) x 10(7) m(-1) s(-1) in D(2)O. The bimolecular rate constant for the reaction of clomazone with singlet oxygen was k(r) = (5.4 +/- 0.1) x 10(7) m(-1) s(-1), which means that the quenching process is mainly reactive.

The use of molecular probes for the characterization of dispersions of functionalized silica nanoparticles.

Butoxylated silica nanoparticles (BSN) were prepared by esterification of the silanol groups of fumed silica nanoparticles with butanol and characterized by 13C and 29Si NMR and thermogravimetry. The molecular probes benzophenone (BP) and safranine-T were used to investigate the BSN suspensions in water:acetonitrile. Laser flash-photolysis experiments at lambda(exc)=266 nm performed with BSN suspended in acetonitrile:aqueous phosphate buffer supported previous results of our group obtained by time-resolved phosphorescence experiments and showed that only free and adsorbed excited triplet states of BP and diphenylketyl radicals contribute to the signals. The UV-vis spectroscopic and photophysical properties of safranine-T are strongly solvent-dependent. Thus, the analysis of the emission spectra and fluorescence lifetimes yielded information on the localization of this probe molecule in suspensions of BSN and of the bare silica nanoparticles. The values of the equilibrium constant for the adsorption of the ground-state safranine-T on the particles were found to be (9.2+/-0.8)x10(4), (7.2+/-0.8)x10(5), and (3.0+/-0.1)x10(4) for the BSN in 1:1 acetonitrile:water, SiO2 in 1:1 acetonitrile:water, and SiO2 in acetonitrile, respectively.

Comparative toxicity of PEG and folate-derived blue-emitting silicon nanoparticles: in vitro and in vivo studies.

AIM: Amino functionalization is a first step modification aiming to achieve biomedical applications of silicon nanoparticles, for example, for photodynamic therapy or radiotherapy. Nevertheless, toxicity and low quantum yields due to the positive charge of amino groups emerge as a problem that could be solved with subsequent derivatizations. MATERIALS & METHODS: Folic and PEG-conjugated nanoparticles were obtained from amino-functionalized silicon nanoparticle (NH2SiNP). Cytotoxicity was determined on a tumor cell line at low and high concentrations. Four end points of in vivo toxicity were evaluated on zebrafish (Danio rerio). RESULTS: Folic acid functionalization reduced the cytotoxicity in comparison to amino and PEG-functionalized nanoparticles. In zebrafish, folic functionalization lowered toxicity in general while PEG increased it. CONCLUSION: Functionalization of NH2SiNP with folic acid reduced the toxic effects in vitro and in vivo. This could be useful for therapeutic applications. PEG functionalization did not lower the toxicity.

Bioactive glass (45S5)-based 3D scaffolds coated with magnesium and zinc-loaded hydroxyapatite nanoparticles for tissue engineering applications.

Bioactive glass (BG)-based scaffolds of 45S5 composition covered with hydroxyapatite nanoparticles loaded with Mg2+, Zn2+ and, both Mg2+ and Zn2+ ions, were developed and tested as materials for tissue engineering applications. The scaffolds were prepared by the foam replica technique and mono- and bi-metal loaded and unloaded hydroxyapatite nanoparticles (HA, Zn-HA, Mg-HA and Mg-Zn-HA) were obtained by an adaptation of the wet chemical deposition method. Coating of BG with these nanoparticles was performed by dip-coating to obtain HA-BG, Zn-HA-BG, Mg-HA-BG and Mg-Zn-HA-BG scaffolds. As predictor of the bone bonding ability of the produced scaffolds, in this study we investigated the formation of an apatite layer on the scaffold surfaces in the presence of simulated body fluid. The cytotoxicity and osteogenic properties of the materials in vitro was evaluated using human osteoblast-like MG-63 cell cultures. The mineralization assay following Kokubo's protocol indicated that bi-metal loaded Mg-Zn-HA-BG scaffolds exhibited higher/faster bioactivity than mono-metal loaded scaffolds while mineralization of HA-BG, Zn-HA-BG and Mg-HA-BG was similar to that of uncoated scaffolds. Moreover, an increase of proliferation of MG-63 cells after 48 h and 7 days was measured by BrdU assays for Mg-Zn-HA-BG scaffolds. In agreement with these results, SEM images confirmed increased interaction between these scaffolds and cells, in comparison to that observed for mono-metal-loaded HA-coated scaffolds. Altogether, the obtained results suggest that nanocrystalline Mg-Zn-HA coatings enhance the biological performance of standard scaffolds of 45S5 BG composition. Thus these novel ion doped HA coated scaffolds are attractive systems for bone tissue engineering.

Photodegradation of soil organic matter and its effect on gram-negative bacterial growth.

To learn more about the role of the reactive oxygen species (ROS) in the production of bioavailable products of the dissolved organic matter, we investigate here the effect of the photolysis (lambda(exc) > 320 nm) of a soil extract (SE) on the growth of bacteria isolated from the same soil as used for obtaining the extract. Comparative experiments with Aldrich humic acid (AHA) as substrate were performed. The photodegradation of the SE was evaluated with different techniques-UV-visible absorption spectroscopy, fluorescence excitation emission matrices (EEM) and Fourier transform infrared spectroscopy (FTIR). Known ROS scavengers were employed to study the effect of photochemically produced ROS on the photodegradation of the substrates. To evaluate the effect of irradiation on the bioavailability of the SE and AHA, photolyzed and nonphotolyzed substrates were added to different culture media and the growth of Pseudomonas sp. isolated from the soil and a strain of Escherichia coli were studied. The different results obtained were assigned to the dissimilar metabolisms of both bacteria.

Reaction kinetics and mechanisms of organosilicon fungicide flusilazole with sulfate and hydroxyl radicals.

Flusilazole is an organosilane fungicide used for treatments in agriculture and horticulture for control of diseases. The reaction kinetics and mechanism of flusilazole with sulfate and hydroxyl radicals were studied. The rate constant of the radicals with the fungicide were determined by laser flash photolysis of peroxodisulfate and hydrogen peroxide. The results were 2.0 × 109 s-1M-1 for the reaction of the fungicide with HO and 4.6 × 108 s-1 M-1 for the same reaction with SO4- radicals. The absorption spectra of organic intermediates detected by laser flash photolysis of S2O82- with flusilazole, were identified as α-aminoalkyl and siloxyl radicals and agree very well with those estimated employing the time-dependent density functional theory with explicit account for bulk solvent effects. In the continuous photolysis experiments, performed by photo-Fenton reaction of the fungicide, the main degradation products were: (bis(4-fluorophenyl)-hydroxy-methylsilane) and the non-toxic silicic acid, diethyl bis(trimethylsilyl) ester, in ten and twenty minutes of reaction, respectively.