During the primary steps of photosynthesis, the light-harvesting complexes capture sunlight and transfer the associated energy to reaction centers where charge are separated. Surprisingly, optical spectroscopy has recently revealed manifestations of quantum coherence in the ultrafast dynamics of these natural nanosystems, that would be controlled by the interaction between excitations and the surrounding protein motion. Inspired by the architecture of a natural reaction center, we have designed a generic molecular nanodevice, and simulated the time-dependent photocurrent induced by a femtosecond laser pulse. In this analogue, a time-dependent external voltage is applied to the device in the picosecond timescale via a gate, in order to mimic the effects of protein vibrations. The voltage characteristics are the parameters of this study. The numerical investigation we propose aims at unraveling the conditions in which this external control may increase the photocurrent inside the nanodevice. To this aim, we have developed a combined theoretical/numerical framework to describe and understand the quantum transport of energy and charges, from the nonequilibrium Green's function formalism. Our findings show that such an external control may be beneficial for the integrated (dc) current flowing through the interface. Indeed, this external control enables to prevent the back tunneling oscillations of the timedependent photocurrent, which globally enhances the dc current. This exploratory work paves the way towards smart biologically-inspired optoelectronics.

The widely different effects of Cu-polyester (PES) sputtered by high power impulse magnetron sputtering (HIPIMS) compared to the lower energy direct current magnetron sputtering (DCMS) leading to bacterial inactivation are addressed during the course of this study. The amounts of Ar+ and Cu/Cu-2-ions generated by HIPIMS (20 A) in the plasma was about five times the amounts detected when using for DCMS (0.3 A), but the relative distribution of these three ionic-species was similar. HIPIMS sputtered Cu-polyester (Cu-PES) at 20 A did not release Cu-ions after a few bacterial inactivation cycles but still lead to complete E. coil inactivation. Unambiguous separation of the intracellular Cu-ions effects and of the extracellular surface-contact was possible comparing the inactivation of wild E. coli to the inactivation of genetically modified porinless E. coll. The optical properties and sample microstructure of the Cu-PES samples were determined by diffuse reflectance spectroscopy (DRS) and by scanning transmission electron microscopy (STEM-HAADF). High-density films were obtained by HIPIMS in contrast to the low-density films prepared by DCMS. The DCMS sputtered Cu-PES presented large amounts of O-interstitial voids. A redox mechanism in bacterial inactivation was detected by X-ray photoelectron spectroscopy (XPS) by monitoring the Cu(I)Cu(II) species within the bacterial inactivation time.

This study reports the photosensitizing effect/mechanism of FeOx under visible light irradiation and charge transfer to TiO2 on FeOx–TiO2 cosputtered film.

The fabrication of non-agglomerated nanoparticulate solids with an open structure is a challenging task in the field of nanotechnology and nanomaterials. Such solids would permit conserving specific size-selected physical and chemical properties and highest specific area of the active phase, by avoiding severe health problems related to undesirably nanoparticles inhalation. We report on a successful preparation of Fe-TiO2 and Ag,Au-TiO2 coatings and TiO2-AlO3 ultra-porous monoliths with highly reproducible nanoscale morphology for applications in environmental catalysis.

This article addresses the cell wall damage of Escherichia coli (from now on E. coli) by TiO2 suspensions. The dynamics of TiO2 photocatalysis by thin films layers is described. The films were characterized by FTIR spectroscopy and atomic force microscopy (AFM). The E. coli complete inactivation is shown to be due to the partial damage of the cell-wall components (peroxidation). A small increase in the cell wall disorder concomitant with a decrease of the cell wall functional groups leads to higher cell wall fluidity as the precursor step preceding cell lysis.

Doping of nanocrystalline TiO2 powders with sizes ranging from 9.5 nm up to 19.1 nm was carried out with thiourea (TU) to introduce the C, N and S-species into the TiO2. The crystal size was determined by X-ray diffraction. Doped-TiO2 particles were colored while the undoped TiO2 was white. The edge of the absorption band edge was analyzed to describe the TiO2 band gap according to the indirect transitions theory of semiconductors. In the former analysis the energy distribution of the doped centers is discussed in terms of the Urbach's tail theory (K=K0expσ((hν−Eg)/kT)), being K the absorbance in the Kubelka–Munk equation. Evidence is presented for thiourea doped-TiO2 leading to Urbach's tail associated with the formation of states in the band-gap rather than a narrowing of the band gap. The photocatalytic activity of the doped-TiO2 was tested by the reduction of tetra-nitromethane to nitroform and by the oxidation of I− to I3−. The rate of formation of nitroform (NF) produced under 460 nm light increased for the smaller TiO2 nanoparticles. This suggests the formation of localized centers under 460 nm light. But under 366 nm light, the highest rate of NF formation was observed for samples with the biggest nanocrystal size. Under 366 nm light, the smaller particles show a low rate of nitroform formation due to a more favorable band-gap electron-hole recombination. Lipid phosphatidyl-ethanolcholine (PE) under 460 nm visible light in the presence of doped-TiO2 led to the formation of conjugated of double bonds in PE. This implies the formation of peroxy radicals due to the TiO2 e−cb localized electronic states under visible light irradiation.

An innovative SiO2-PO43−-TiO2 photocatalyst is presented which is able to bond TiO2 to Raschig rings (RR). Evidence for the formation on the catalyst surface of PO stretching bands near 1200–1250cm−1 is presented by FTIR spectroscopy. The TiO2 Degussa P25 on the catalyst surface (RR) was further characterized by high-resolution transmission electron microscopy (HRTEM), and X-ray diffraction showing that the composite catalyst prepared at 500°C does not alter the particle size or crystallographic composition of the TiO2 Degussa P25 particles. The Ti- and P-distribution of the catalyst surface overlayers was obtained by Ar-sputtering eroding up to 100 topmost catalyst layers. By atomic force microscopy (AFM) the root mean square roughness (Rq) or rugosity of ∼771nm and an average height of the catalyst layer of 1.52μm were found on the glass surface. The root mean square roughness Rq varies very little in value before and after the photocatalysis indicating that the sample porosity is conserved during 4-CP photodegradation. The disappearance kinetics of 4-chlorophenol (4-CP) on the SiO2-PO43−-TiO2 composite occurred within 15min and was faster than the 45min needed with suspensions of TiO2 Degussa P25 (1gL−1). The SiO2-PO43−-TiO2 photocatalyst was able to degrade repetitively 4-CP solutions without loss of activity. The effect of the light intensity, oxidant concentration and 4-CP concentration on the photodegradation kinetics was investigated and is reported in this study.

We report on two-photon luminescence of silver nanoparticles grown on non-crystalline mesoporous TiO2 issued of the sol–gel process. The growth is achieved by surface photocatalytic reduction from silver nitrate solution. A structural hierarchy of this particular TiO2 system results in a characteristic distance between nanoparticles ∼10–100nm that is optimal for the electromagnetic field enhancement. The microscope images evidence multiple bright luminescence spots at two-photon near-IR femtosecond laser excitation due to the field enhancement effect. The spectra suggest homogeneous size distribution of emitting silver clusters over the sample area on the scale below 100nm.

This laser kinetics features of the electron decay of TiO2 in the presence of the Escherichia coli (E. coli) phosphatidyl-ethanolcholine (PE) and lipo-polysaccharides (LPS) cell wall components were are reported in this study. The interaction of the biomolecules with the photogenerated charge carriers was determined and the reaction rates were measured. The effect of the variation of ionic strength of the colloidal TiO2 on the electron decay was determined in the presence of PE and E. coli. The ionic strength seems to affect the equilibrium absorption of the biomolecules on TiO2. The e− decay was measured for TiO2 samples having different sizes, charge and isoelectric points (IEP) by laser spectroscopy for different types of TiO2. TiO2 Degussa P-25 mediated the E. coli abatement most effectively compares to other TiO2 samples. The structural features of different TiO2 samples were related to the degradation of E. coli and also related to the fast kinetics results.

Doped TiO2 samples using different preparative procedures were synthesized using either urea or thiourea leading to N- or S-doped TiO2. Photocatalytic peroxidation and oxidation (mineralization) of phosphatidylethanolamine (PE) lipid with doped TiO2 were carried out under light irradiation lambda > 410 nm. The formation of conjugated double bonds in PE molecules was followed to detect the formation of peroxy radicals (peroxidation index) under light excitation (lambda > 410 nm) when doped TiO2 was used. The kinetics of CO2 production was monitored during the mineralization of PE. Colored TiO2 powders were studied in detail by different and complementary physicochemical techniques. The band gap energies of colored TiO2 were determined by diffuse reflectance spectroscopy (DRS). The visible absorption shoulder of TiO2 was observed to follow Urbach's law. The variation of the transient decay after 354 nm laser pulse excitation does not correlate with the different N- and S-TiO2 doping levels introduced by the addition of urea or thiourea. This suggests that the states (recombination centers or traps) introduced by the doping are not effective in varying the decay kinetics within the nanosecond and microsecond time scale. Elemental analysis shows comparable amounts of S- and N-doping of TiO2 when thiourea is used as dopant. X-ray diffraction reveals no rutile in S-TiO2 samples heated to 600 degrees C, suggesting that the addition of sulfur precludes rutilization during sample crystallization. X-ray photoelectron spectroscopy (XPS) of the S-TiO2 samples confirms the preferential localization of S on the 20 topmost layers of S-TiO2 upon calcination at 500 degrees C for 2 h.

The photocatalytic peroxidation of E. coli cell, lipo-polysaccharide (LPS), phosphatidyl-ethanolcholine (PE), and peptidoglycan (PGN) of the E. coli membrane wall has been investigated on TiO2 porous films by ATR-FTIR spectroscopy. The fast reactions of the photogenerated charge carriers in TiO2 with E. coli, LPS, and PE were monitored by laser kinetic spectroscopy. ATR-FTIR spectroscopy allowed the identification of E. coli, LPS, PE, and PGN as photocatalytic peroxidation products. The PGN was observed to be the most resistant membrane wall component. Shorter peroxidation times were observed for LPS and PE. Laser photolysis shows that E. coli, LPS, and PE compete in the scavenging of a surface trapped holes (h+) with the recombination reaction of h+ with the generated electrons (e-) within times > 50 ns. This scavenging leads to the formation of organic radicals initiating the radical chain peroxidation of E. coli, LPS, PE, and PE.

Escherichia coli (E. coli) photokilling due to the TiO2 under light irradiation in a batch reactor was studied by using of attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and atomic force microscopy (AFM). The ATR-FTIR spectral features and AFM images were analyzed in relation to E. coli viability data. ATR-FTIR is shown to be a suitable technique to follow the structural changes of the E. coli cell membranes during TiO2 photocatalysis. Formation of the peroxidation products due to the photocatalysis of E. coli cell is reported by this technique. Time dependent ATR-FTIR experiments provides the evidence for the changes in the E. coli cell wall membranes as the precursor events leading to bacterial lysis. Under the same experimental conditions used by ATR-FTIR spectroscopy, AFM microscopy was carried out to provide direct evidence for the E. coli lysis taking place under light irradiation after about 1h in the presence of TiO2. By transmission electron microscopy (TEM), the aggregated TiO2 Degussa P-25 in aqueous solution is shown to interact with the bacteria surface and partly to remain in the aqueous solution at the concentration of 1mg/ml.

The photocatalytic peroxidation of the bovine brain L-alpha-phosphatidyl-ethanolamine (PE) vesicle was measured and used as a model for phospholipid peroxidation. Synthetic phosphatidyl-ethanolamine, E. coli phosphatidyl-ethanolamine, lipid polysaccharide (LPS), and cardiopilin were used to compare the TiO2 photocatalysis leading to cell wall membrane degradation. During the photocatalytic degradation, the appearance and growth kinetics were followed for (a) conjugated double bond formation, (b) malondialdehyde (MDA), (c) peroxides, and finally (d) the observed CO2 evolution. Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) was measured of PE bilayers cast on TiO2 films and to a lesser extent for other phospholipids during TiO2 photocatalysis. The decay kinetics induced by photocatalysis of the isolated cis C=C-H (3008 cm(-1)), -CH2, and -CH3 groups and of the acyl-ester bond of the fatty acid in the glycerol backbone were followed in detail. The photocatalysis was also observed to induce spectral shifts in the CH2 vibrations and changes in the asymmetric phosphate ester (C-(PO4)(-)-C) stretching vibrations. The ATR-FTIR spectral changes suggest structural changes of the lipid bilayer due to peroxidation. The significant part of the photocatalytic peroxidation seems to take place at the TiO2, surface by heterogeneous mediated processes. But concomitantly, a homogeneous chain radical peroxidation of PE occurs in aqueous solution by a radical chain mechanism.

The bleaching and photobleaching of Orange II due to oxone was observed to proceed within seconds due to the catalytic effect of the Co2+ ions added in solution.

During the last 6 years our laboratory has developed Fenton immobilized catalysts for the partial or total destruction of toxic organic compounds and their mixtures. This paper reports on Fe-supported noncorrosive supported membranes and fabrics like: Nafion, Nafion-glass mats and polyethylene block copolymers. These novel supported catalysts have shown acceptable kinetic rates, resistance to the leaching of Fe3+ into the solution and no corrosion to the highly oxidative radicals generated in the solution during Fenton immobilized photo-assisted catalysis. Nafion-Fe membranes degrade Orange II under visible light only up to pH 4.8. In the case of nafion glass mats supported Fe3+- ions, the initial pH could be raised up to 8 or above. The pH decreased to about 4 during the photodegradation of Orange II due to the formation of intermediate carboxylic acids but the costly initial acidification process necessary in the case of homogeneous Fenton processes is avoided. Carboxylates and carboxylic acids were observed by IR spectroscopy on the surface of the supported catalysts towards the end of the photodegradation process as well as carboxylic acids detected by HPLC. The IR bands are found at 1523 and 1557 cm(-1) in the case of the copolymer-Fe3+ corresponding to two types of iron-carboxylate species. The formation of carboxylates explains the drop of pH during the photodegradation to values between 3 and 4 corresponding to the pK(a) of the carboxylic functional group.

New and up to-date materials have been developed in our laboratory to carry out Fenton photo-assisted processes efficient in the decoloration/degradation of organic pollutants that show: stability against radical attack, do not allow the leaching of Fe-ions into the solution and intervene with suitable kinetics in the degradation processes. These new materials comprise Fe-ions supported on: Nafion membranes, Nafion-glass mats composites, alginate beads, amorphous polycrystalline fused copolymers and silica woven fabrics.

This study presents the detailed nature of iron clusters formed on Fe3+-Nafion membranes. The catalytic nature of these clusters during immobilized Fenton processes was observed to. be a function of the deposition method of Fe ions on the Nafion. The nonbiodegradable azo-dye Orange II and 2-propanol were utilized as convenient organic model compounds in photoassisted Fenton degradation processes. The highest photocatalytic activity was observed when samples were prepared by ion exchange between iron(III) aqua-complexes and H+ or Na+ as counterions of the Nafion SO3- group. Spectroscopic techniques show that iron(III) in the membrane was present mainly as a mononuclear complex of [Fe(H2O)(6)](3+) and binuclear complexes [Fe(H3O2)Fe](5+) and [Fe-O-Fe](4+). If NaOH or ammonia was added to the former samples prepared by ion exchange, Nafion-Fe membranes with low photocatalytic activity were obtained showing alpha-Fe2O3 and [Fe-O-Fe](4+). Detailed high-resolution transmission electron microscopy was carried out for the Nafion-Fe ion-exchariged and also base-treated membranes showing alpha-Fe2O3 nanocrystallites of 3.5-5 nm. Spectral bands were found for iron oxides in the Fe3+-Nafion by femtosecond laser spectroscopy. The alpha-Fe2O3 nanocrystallites in the Nafion exchanged base-treated membranes presented a relaxation dynamics for the excited states close to that observed with alpha-Fe2O3 nanocrystallite colloids taken as reference compounds. Multiexponential transient absorption decay of alpha-Fe2O3 in SO3--water clusters was observed with time constants close to 320 fs, 1.5 ps, and 31 ps after the excitation pulse. Samples of Fe3+-Nafion membranes with-high activity show different transient dynamics relative to the Fe3+-Nafion with low activity. Correlation of the photocatalytic activity of Fe3+-Nafion with UV-vis, Fourier transform infrared, Mossbauer, and X-ray photoelectron spectroscopic results suggests that the photocatalytic activity correlates with the amount of mononuclear [Fe(H2O)(6)](3+), binuclear complexes [Fe(H3O2)Fe](5+) and oxo-bridged [Fe-O-Fe](4+) found in the membranes.

The formation of anthracene ion radicals in the H+-, Na+-, Fe2+-, and Fe3+-Naflon membrane was established by laser kinetic spectroscopy. The formation of ion radicals was observed to be due to (1) the two photon ionization of the anthracene molecule with the formation of the radical cation An(+.) radical and a fast electron scavenging by H+, Na+, Fe2+ and Fe3+ acting as efficient electron traps in solution and (2) the quenching of the excited anthracene by Fe3+ that leads by a redox process to the formation of An(+.) and Fe2+. It is shown that the ensuing kinetics of the ion-radical decay depends on the chemical nature of the traps. The lifetime of (T)An becomes shorter after Fe2+ or Fe3+ is introduced in the Nafion. The steady-state anthracene fluorescence is quenched by Fe3+ or Fe2+ and followed the logarithmic decay law ln(l(0)/I) where the decay in solution was seen to be proportional to the [Fe3+] or [Fe2+]. The counterions of SO3--water clusters as well as of oxygen in the reaction media strongly affect the kinetics of ion-radical reactions occurring in the Nafion membrane. The counterions and oxygen are suggested to be the traps for the generated electrons in solution. The excited state of An was shown to react with Fe3+ through electron transfer. Triplet excited anthracene molecules are quenched by Fe3+ and Fe2+ with rate constants k(q)(Fe3+) = ( 1.9+/-0.19) x 10(8) M(-1)s(-1) and k(q)(Fe2+) (1.4+/-0.11) x 10(9) M(-1)s(-1). Anthracene ion radicals are formed in the reaction with Fe3+ but not with Fe2+ on thermodynamic grounds. Fe2+ or Fe3+ being different chemical species quench with similar rates the An probe inside the Nafion membrane. Treatment of Fe3+ -Nafion with NaOH leads to precipitation of iron particles in the membrane having as consequences (1) the decrease of the observed rate for the triplet excited anthracene quenching with a concomitant decrease in the observed An(+.) yields and (2) a significant decrease of the An(+.) decay time because of the lowering of the mobility of the iron ions in solution.

The NLO properties of the high molecular weight (M-w > 200 000) MEH-PPV films spin casted on BK-7 glass substrates were studied by conventional Z-scan technique in a wide near-infrared region 1100-1700 nm with a measurement step 50 nm. It was shown that the chi (3) value for MEH-PPV in this wavelength range varies from 3.6x10(-10) esu up to the maximum value 1.5x10(-9) esu at 1450 nm. The precision of Z-scan measurements was controlled using standard chi (3) values of BK-7 glass and nitrobenzene.