David García-Fresnadillo - Academia.edu (original) (raw)
Papers by David García-Fresnadillo
Comprehensive Series in Photochemical & Photobiological Sciences, 2000
The Journal of Physical Chemistry B, 2002
The luminescence quenching by electron transfer of a nonintercalating [Ru(TAP) 2 DIP] 2+ complex,... more The luminescence quenching by electron transfer of a nonintercalating [Ru(TAP) 2 DIP] 2+ complex, which is covalently linked to different guanine containing oligonucleotide duplexes, is compared to the sequence dependent ionization potentials of guanines as estimated from Hartree-Fock calculations on regular B-DNA by means of Koopmans theorem. From these experimental and theoretical results, it is demonstrated that the ionization potential of the guanines has a major influence on the efficiency of hole injection by the groove binding [Ru(TAP) 2 DIP] 2+ complex in a type I photooxidation of DNA. Because the photoelectron transfer between the complex and DNA takes place on a nanosecond time scale, nanosecond molecular dynamics simulations were performed for two of the sequences in order to check for the possible influence of the dynamical fluctuations in the DNA structure on the ionization potential. IP fluctuations up to 0.5 eV were observed on a picosecond time scale along the molecular dynamics trajectories. However, these fluctuations scatter statistically around the value calculated for regular B-DNA and are thus not relevant for the slow photoelectron transfer with a nonintercalating [Ru(TAP) 2 DIP] 2+ complex.
Journal of Biological Inorganic Chemistry, 2004
The influence of the distance between the anchoring site of the tethered [Ru(TAP) 2 dip] 2+ compl... more The influence of the distance between the anchoring site of the tethered [Ru(TAP) 2 dip] 2+ complex (TAP=1,4,5,8-tetraazaphenanthrene; dip=4,7-diphenyl-1,10-phenanthroline) on a probe sequence and the guanines of the complementary target strand was studied by (1) the luminescence quenching of the complex (by electron transfer) and (2) the oligodeoxyribonucleotide adduct (ODN adduct) formation which results in photo-crosslinking of the two strands. Moving the guanine moieties away from the complex induces an important decrease of the efficiency of both processes, but clearly affects the ODN adduct formation more specifically than the quenching process. From these results, we determined the positions of the guanine bases in the duplex ODN that are able to form a photo-adduct with the tethered complex. We also examined the possible competition between a long-range hole migration in the duplex ODN and the formation of a photo-adduct by using a sequence labeled with the complex at the 5¢phosphate end. Such a hole migration appears to be inefficient as compared to the ODN adduct formation. Finally, we studied the influence of the photo-crosslinking on the function of two different DNA polymerases. A 17-mer Ru(II)-labeled ODN was hybridized to its complementary sequence located on the 5¢-side of a 40-mer matrix. After illumination, the elongation of a 13-mer DNA primer hybridized to the 3¢-extremity of the same matrix was stopped at a position corresponding to the formation of the ODN adduct.
ABSTRACT The combination of photosensitized production of singlet oxygen (102) and solar energy i... more ABSTRACT The combination of photosensitized production of singlet oxygen (102) and solar energy is gaining increasing interest, as disinfection and water remediation technology. In this work, we have investigated the elimination of three common micropollutants such as, ibuprofen, paracetamol and bisphenol A using a photosensitizing material consisting of tris(4,7-dipheny1-1,10-phenanthroline)ruthenium(II) chloride, immobilized in a porous poly(dimethylsiloxane) inert support. The influence of variables such as, the radiation dose, hydrophobicity, ionization state of the micropollutant and water composition has been discussed. The process has led to effective removal of ibuprofen and bisphenol A in ultra-pure water with conversion rates of 100% and 80%, respectively; whereas elimination of paracetamol was rather limited (35%). Experiments performed in natural water samples have evidenced reduced effectiveness of the O-1(2) photosensitized degradation process, due to water matrix composition. Thus, conversion rates of ibuprofen may decrease until 20% (depending on the water matrix) when other inorganic anions (e.g. bicarbonate, sulphate, etc.) are present in the water samples. On the other hand, identification of the main transformation products of ibuprofen and bisphenol A has been achieved by the use of ultra-high-performance liquid chromatography-time-of-flight mass spectrometry (UHPLC/QTOF-MS). The phototransformation pathway of ibuprofen includes hydroxylation, decarboxylation and demethylation processes, while the degradation of bisphenol A mainly proceeded via fragmentation of the isopropylidene bridge between the two phenyl groups leading to different para substituted phenolic compounds.
Optical Sensors, 2004
CHAPTER 1 3 Environmental and Industrial Optosensing with Tailored Lumi-nescent Ru (ll) Polypyrid... more CHAPTER 1 3 Environmental and Industrial Optosensing with Tailored Lumi-nescent Ru (ll) Polypyridyl Complexes GUILLERMO ORELLANA, DAVID GARCÍA-FRESNADILLO 1 Introduction The sensitivity, specificity and versatility of optical methods for chemical deter -minations ...
Tetrahedron, 2005
In the context of our studies on ruthenium(II) complexes containing polyazaheterocyclic ligands a... more In the context of our studies on ruthenium(II) complexes containing polyazaheterocyclic ligands as functionalised photosensitisers for singlet molecular oxygen generation in heterogeneous phase, we describe the synthesis and spectroscopic characterisation of different amide-...
Solar Energy, 2006
Using Escherichia coli and Enterococcus faecalis as model microorganisms, water disinfection has ... more Using Escherichia coli and Enterococcus faecalis as model microorganisms, water disinfection has been demonstrated with singlet molecular oxygen (a reactive oxygen species) photogenerated by polymer-supported Ru(II) sensitizers and solar light. Both laboratory and sunlight tests were performed. The Ru(II) polypyridyl complex and its insoluble support have been optimized to provide maximum efficiency of singlet oxygen production and contact with the microorganism.
Physical Chemistry Chemical Physics, 2006
Generation of singlet molecular oxygen ((1)O(2)) by photosensitization with methylene blue (MB) s... more Generation of singlet molecular oxygen ((1)O(2)) by photosensitization with methylene blue (MB) supported in Nafion-Na films has been quantified by integration of the (1)O(2) emission decay at 1270 nm. The quantum yield of (1)O(2) production (Phi(Delta)) in the air-equilibrated solid phase is 0.24 +/- 0.03. Information on the (1)O(2) generation environment has been gained from complementary techniques such as UV-Vis absorption and emission spectroscopy, as well as MB fluorescence and triplet-triplet absorption decay. Results are compared with the (1)O(2) generation by MB in methanol solution (Phi(Delta) = 0.51) and in methanol-swollen Nafion films (Phi(Delta) = 0.49 +/- 0.06). Differences and similarities are discussed in terms of the factors that influence Phi(Delta) in solution and in the solid media. The optical and mechanical features of Nafion, ease of dye loading, compatibility with most solvents, homogeneity, reproducibility and stability of the photosensitizing material makes it a convenient reference for (1)O(2) generation quantum yield measurements in transparent (micro)heterogeneous and homogeneous media.
Photochemical & Photobiological Sciences, 2010
Photogeneration of singlet molecular oxygen ((1)O(2)) is applied to organic synthesis (photooxida... more Photogeneration of singlet molecular oxygen ((1)O(2)) is applied to organic synthesis (photooxidations), atmosphere/water treatment (disinfection), antibiofouling materials and in photodynamic therapy of cancer. In this paper, (1)O(2) photosensitizing materials containing the dyes tris(4,4'-diphenyl-2,2'-bipyridine)ruthenium(II) (1, RDB(2+)) or tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) (2, RDP(2+)), immobilized on porous silicone (abbreviated RDB/pSil and RDP/pSil), have been produced and tested for waterborne Enterococcus faecalis inactivation using a laboratory solar simulator and a compound parabolic collector (CPC)-based solar photoreactor. In order to investigate the feasibility of its reuse, the sunlight-exposed RDP/pSil sensitizing material (RDP/pSil-a) has been reloaded with RDP(2+) (RDP/pSil-r). Surprisingly, results for bacteria inactivation with the reloaded material have demonstrated a 4-fold higher efficiency compared to those of either RDP/pSil-a, unused RDB/pSil and the original RDP/pSil. Surface and bulk photochemical characterization of the new material (RDP/pSil-r) has shown that the bactericidal efficiency enhancement is due to aggregation of the silicone-supported photosensitizer on the surface of the polymer, as evidenced by confocal fluorescence lifetime imaging microscopy (FLIM). Photogenerated (1)O(2) lifetimes in the wet sensitizer-doped silicone have been determined to be ten times longer than in water. These facts, together with the water rheology in the solar reactor and the interfacial production of the biocidal species, account for the more effective disinfection observed with the reloaded photosensitizing material. These results extend and improve the operational lifetime of photocatalytic materials for point-of-use (1)O(2)-mediated solar water disinfection.
Photochemical & Photobiological Sciences, 2009
In this study we report on the preparation, photochemical characterisation and evaluation of the ... more In this study we report on the preparation, photochemical characterisation and evaluation of the photodisinfection power of various new types of singlet oxygen photosensitising materials prepared from two homoleptic Ru(ii) complexes with polyazaheterocyclic ligands (abbreviated as RDP(2+) and RSD(4-)) immobilised on anionic and cationic porous silicone polymers (pSil(-) and pSil(+), respectively). Time-resolved emission measurements in the UV-Vis-NIR have confirmed high (1)O(2) production by these materials in water (tau(Delta) = 25-32 micros) due to efficient quenching of the long-lived sensitiser triplet state by dissolved O(2), particularly in those pSil(-) materials with higher sensitiser load (P(O(2))(T)ca. 0.74 and 0.88 for 1.15 and 4.40 g m(-2), abbreviated as "M" and "H", respectively). Photodisinfection tests carried out using both a solar-simulated lab-scale setup and under sunlight have demonstrated the strong bacteria inactivation ability of the RDP/pSil(-) material with the highest sensitiser load. Results of photochemical experiments with aqueous suspensions of Enterococcus faecalis at an initial concentration of 10(4) CFU mL(-1) yield average inactivation rates of 3200 and 24 000 CFU h(-1) for RSD/pSil(+) and H-RDP/pSil(-) films, respectively. The sensitiser charge, its load on the polymer support and the ionic character of the silicone surface play an essential role on the singlet oxygen production in heterogeneous media, the stability of the resulting material, and on the interaction with bacteria, determining the microorganism inactivation efficiency of the ionic silicone-based photosensitising materials.
Photochemical & Photobiological Sciences, 2014
Different photosensitizing materials manufactured by immobilizing (0.5-3.0 g m(-2)) tris(4,7-diph... more Different photosensitizing materials manufactured by immobilizing (0.5-3.0 g m(-2)) tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) (RDP(2+)), [C60]-fullerene, or 1-(4-methyl)-piperazinylfullerene (MPF) on porous neutral (pSil) or surface-modified anionic (pSil(-)) poly(dimethylsiloxane) are compared on the grounds of their singlet molecular oxygen ((1)O2) production and photodynamic solar water disinfection capability. The C60-based sensitizers display a broad weak absorption in the visible and strong absorption in the UV, while absorption of light by RDP(2+) supported on pSil is strong in both the UV and blue regions. The (1)O2 emission lifetimes (τ(Δ)) determined for RDP(2+) and MPF on porous silicone materials under air are similar (40-50 μs) and correspond to the decay of (1)O2 generated by sensitizers dissolved in the polymer support. In contrast, τ(Δ) measured for C60 in pSil is similar to that observed for MPF or RDP(2+) when immobilized at low loading on pSil, but dramatically increases up to 5 ms if C60 aggregates are formed in the porous material as evidenced by microscopy evaluation. The photosensitizing properties of the dyes, together with their electrical charge and the overall charge of the porous silicone-based materials, lead to highly different sunlight-driven bacteria inactivation efficiencies, as tested with waterborne E. faecalis. RDP/pSil provides efficient disinfection by photosensitization unlike MPF/pSil, which leads to reduced bacteria inactivation rates due to poorer (1)O2 production. C60/pSil and MPF/pSil(-) materials, despite their (1)O2 photogeneration, show unsuccessful waterborne bacteria inactivation due to the negative surface charge of fullerene aggregates in contact with water, and to the net negative charge of the pSil(-), respectively.
Mikrochimica Acta, 1995
The spectroscopic features and photoreactivity with oxygen of a novel, highly lipophilic, lumines... more The spectroscopic features and photoreactivity with oxygen of a novel, highly lipophilic, luminescent metal complex Ru(5-odap)~ + (where 5-odap stands for 5-octadecanamide-1,10-phenanthroline), are reported and compared to those of the well-known tris(1,10-phenanthroline) analogue. An array of silicone membranes, containing Ru(5-odap) 2 § or Ru(qSzp) 2 + (where q~2P stands for 4,7-diphenyl-l,10-phenanthroline) as solid-supported luminescent indicators, have been fabricated. Their (non-linear) response to oxygen was evaluated with fibre-optics as a function of their adsorbent nature (silica gel, glass, reverse-phase silica, styrene/divinyl benzene copolymer, or none), surface coverage by the deposited metal complex, and loading of dyed support-into the sensitive layer. The largest oxygen sensitivity (Io/I ca. 6 for a partial pressure of 130 Torr) is achieved with the highest amount of silica gel-or glass-supported Ru(4~2p) 2 + and the highest membrane loading. Ru(5-odap)32 + dissolved directly into silicone yields a linear dose/response plot, but with a small slope (Io/I ca. 1.4 for a partial pressure of 720 Torr). These results are discussed in terms of dynamic surface quenching between the co-adsorbed indicator and oxygen molecules.
Langmuir, 1999
The absorption spectroscopy, photophysics, and dioxygen quenching of [RuL3] 2+ luminescent probes... more The absorption spectroscopy, photophysics, and dioxygen quenching of [RuL3] 2+ luminescent probes, where L stands for 2,2′-bipyridine, 1,10-phenanthroline, 5-octadecanamide-1,10-phenanthroline, and 4,7diphenyl-1,10-phenanthroline (dip), electrostatically loaded onto Nafion ionomer membrane have been investigated in air and in organic solvents and water, with the aim of developing rugged materials for optical sensing of molecular oxygen. The significant differences in size and hydrophobicity of the Ru(II) dyes have been used to probe their location within the perfluorinated ionomer pore network, as well as to gain insight into the oxygen accesibility to its microcrystalline and interfacial domains. While the absorption maximums of the probes (444-458 nm) remain relative unchanged, their emission wavelengths (578-622 nm) are extremely sensitive to the degree of Nafion swelling by the solvent. This feature has been characterized by measuring the density (1.19-2.04 g cm -3 ) of the solvent-saturated ionomer and the mass and volume fractions of solvents (0.0-0.7) uptaken by the original acidic Nafion and Li + -, Na + -, or K + -exchanged films. The excited-state lifetimes of the [RuL3] 2+ complexes (0.03-4.9 µs) reflect important variations of the microenvironment around the luminescent probes, which are rationalized in terms of their location and oxygen accessibility when loaded onto the polysulfonated material. Emission quenching rate constants of 1.7 ( 0.3 M -1 s -1 have been measured for the [Ru(dip)3] 2+ -dyed films dipped in methanol; their oxygen sensitivity turns out to be independent of the Ru(II) loading and counterion of Nafion. Highly oxygen-sensitive luminescent membranes, suitable for continuous monitoring in organic solvents, water, or gas phase, have been prepared by immobilization of [Ru(dip)3] 2+ indicator in 178-µm thick Nafion, with response times below 1.5 min. Nevertheless, a slow evolution of the oxygen response over 1 week has been detected for very solvent-swollen membranes; some ways of minimizing such an effect are also given.
Langmuir, 2008
A comparative study of the chemical functionalization of undoped, n- and p-type GaN layers grown ... more A comparative study of the chemical functionalization of undoped, n- and p-type GaN layers grown on sapphire substrates by metal-organic chemical vapor deposition was carried out. Both types of samples were chemically functionalized with 3-aminopropyltriethoxysilane (APTES) using a well-established silane-based approach for functionalizing hydroxylated surfaces. The untreated surfaces as well as those modified by hydroxylation and APTES deposition were analyzed using angle-resolved X-ray photoelectron spectroscopy. Strong differences were found between the APTES growth modes on n- and p-GaN surfaces that can be associated with the number of available hydroxyl groups on the GaN surface of each sample. Depending on the density of surface hydroxyl groups, different mechanisms of APTES attachment to the GaN surface take place in such a way that the APTES growth mode changes from a monolayer to a multilayer growth mode when the number of surface hydroxyl groups is decreased. Specifically, a monolayer growth mode with a surface coverage of approximately 78% was found on p-GaN, whereas the formation of a dense film, approximately 3 monolayers thick, was observed on n-GaN.
Helvetica Chimica Acta, 2001
Novel anionic [RuL 2 L′] 2− complexes, where L stands for (1,10-phenanthroline-4,7-diyl)bis (benz... more Novel anionic [RuL 2 L′] 2− complexes, where L stands for (1,10-phenanthroline-4,7-diyl)bis (benzenesulfonate) (pbbs; 3a) or (2,2′-bipyridine)-4,4′-disulfonate (bpds; 3b), and L′ is N-(1,10-phenanthrolin-5-yl)tetradecanamide (pta; 2a) or N-(1,10-phenanthrolin-5-yl) ...
Helvetica Chimica Acta, 1996
ABSTRACT
European Journal of Medicinal Chemistry, 2013
About half of the world's population is currently infected with Helicobac... more About half of the world's population is currently infected with Helicobacter pylori, which is involved in the development of several gastro-duodenal pathologies. The increasing number of antibiotic resistance reduces the effectiveness of the first-line therapy, so new strategies to improve the H. pylori eradication rates are needed. Antimicrobial Photodynamic Therapy (APDT) benefits from photogenerated reactive oxygen species, such as singlet oxygen, which inactivate microorganisms by means of photosensitising dyes and visible light. Therefore, it could be a suitable alternative for H. pylori eradication in the gastro-duodenal tract, particularly in patients infected with antibiotic resistant strains. We evaluated APDT against H. pylori, in vitro, using a new photosensitising material (PSM) based on a ruthenium(II) complex covalently bound to micrometric glass beads. Five H. pylori isolates (classified according to cagA genotype, and metronidazole-clarithromycin resistance) were used. Bacteria were mixed with the PSM and incubated in the dark or illuminated by blue light. Aliquots (min 1', 2', 5', 15' and 30') were cultured and colonies were counted after 2-3 days. A 99.99999% decrease was detected in the number of colonies in the irradiated wells where the bacterium was mixed with the PSM, compared to non-illuminated wells or with irradiated wells without PSM. It was also confirmed that DNA is a molecular target for oxidant species released during APDT (evaluated by alkaline gel electrophoresis after endonuclease III incubation, ureC and cagA RT-PCR, and bacterial fingerprint). Results were independent of cagA gene and antibiotic resistances.
Comprehensive Series in Photochemical & Photobiological Sciences, 2000
The Journal of Physical Chemistry B, 2002
The luminescence quenching by electron transfer of a nonintercalating [Ru(TAP) 2 DIP] 2+ complex,... more The luminescence quenching by electron transfer of a nonintercalating [Ru(TAP) 2 DIP] 2+ complex, which is covalently linked to different guanine containing oligonucleotide duplexes, is compared to the sequence dependent ionization potentials of guanines as estimated from Hartree-Fock calculations on regular B-DNA by means of Koopmans theorem. From these experimental and theoretical results, it is demonstrated that the ionization potential of the guanines has a major influence on the efficiency of hole injection by the groove binding [Ru(TAP) 2 DIP] 2+ complex in a type I photooxidation of DNA. Because the photoelectron transfer between the complex and DNA takes place on a nanosecond time scale, nanosecond molecular dynamics simulations were performed for two of the sequences in order to check for the possible influence of the dynamical fluctuations in the DNA structure on the ionization potential. IP fluctuations up to 0.5 eV were observed on a picosecond time scale along the molecular dynamics trajectories. However, these fluctuations scatter statistically around the value calculated for regular B-DNA and are thus not relevant for the slow photoelectron transfer with a nonintercalating [Ru(TAP) 2 DIP] 2+ complex.
Journal of Biological Inorganic Chemistry, 2004
The influence of the distance between the anchoring site of the tethered [Ru(TAP) 2 dip] 2+ compl... more The influence of the distance between the anchoring site of the tethered [Ru(TAP) 2 dip] 2+ complex (TAP=1,4,5,8-tetraazaphenanthrene; dip=4,7-diphenyl-1,10-phenanthroline) on a probe sequence and the guanines of the complementary target strand was studied by (1) the luminescence quenching of the complex (by electron transfer) and (2) the oligodeoxyribonucleotide adduct (ODN adduct) formation which results in photo-crosslinking of the two strands. Moving the guanine moieties away from the complex induces an important decrease of the efficiency of both processes, but clearly affects the ODN adduct formation more specifically than the quenching process. From these results, we determined the positions of the guanine bases in the duplex ODN that are able to form a photo-adduct with the tethered complex. We also examined the possible competition between a long-range hole migration in the duplex ODN and the formation of a photo-adduct by using a sequence labeled with the complex at the 5¢phosphate end. Such a hole migration appears to be inefficient as compared to the ODN adduct formation. Finally, we studied the influence of the photo-crosslinking on the function of two different DNA polymerases. A 17-mer Ru(II)-labeled ODN was hybridized to its complementary sequence located on the 5¢-side of a 40-mer matrix. After illumination, the elongation of a 13-mer DNA primer hybridized to the 3¢-extremity of the same matrix was stopped at a position corresponding to the formation of the ODN adduct.
ABSTRACT The combination of photosensitized production of singlet oxygen (102) and solar energy i... more ABSTRACT The combination of photosensitized production of singlet oxygen (102) and solar energy is gaining increasing interest, as disinfection and water remediation technology. In this work, we have investigated the elimination of three common micropollutants such as, ibuprofen, paracetamol and bisphenol A using a photosensitizing material consisting of tris(4,7-dipheny1-1,10-phenanthroline)ruthenium(II) chloride, immobilized in a porous poly(dimethylsiloxane) inert support. The influence of variables such as, the radiation dose, hydrophobicity, ionization state of the micropollutant and water composition has been discussed. The process has led to effective removal of ibuprofen and bisphenol A in ultra-pure water with conversion rates of 100% and 80%, respectively; whereas elimination of paracetamol was rather limited (35%). Experiments performed in natural water samples have evidenced reduced effectiveness of the O-1(2) photosensitized degradation process, due to water matrix composition. Thus, conversion rates of ibuprofen may decrease until 20% (depending on the water matrix) when other inorganic anions (e.g. bicarbonate, sulphate, etc.) are present in the water samples. On the other hand, identification of the main transformation products of ibuprofen and bisphenol A has been achieved by the use of ultra-high-performance liquid chromatography-time-of-flight mass spectrometry (UHPLC/QTOF-MS). The phototransformation pathway of ibuprofen includes hydroxylation, decarboxylation and demethylation processes, while the degradation of bisphenol A mainly proceeded via fragmentation of the isopropylidene bridge between the two phenyl groups leading to different para substituted phenolic compounds.
Optical Sensors, 2004
CHAPTER 1 3 Environmental and Industrial Optosensing with Tailored Lumi-nescent Ru (ll) Polypyrid... more CHAPTER 1 3 Environmental and Industrial Optosensing with Tailored Lumi-nescent Ru (ll) Polypyridyl Complexes GUILLERMO ORELLANA, DAVID GARCÍA-FRESNADILLO 1 Introduction The sensitivity, specificity and versatility of optical methods for chemical deter -minations ...
Tetrahedron, 2005
In the context of our studies on ruthenium(II) complexes containing polyazaheterocyclic ligands a... more In the context of our studies on ruthenium(II) complexes containing polyazaheterocyclic ligands as functionalised photosensitisers for singlet molecular oxygen generation in heterogeneous phase, we describe the synthesis and spectroscopic characterisation of different amide-...
Solar Energy, 2006
Using Escherichia coli and Enterococcus faecalis as model microorganisms, water disinfection has ... more Using Escherichia coli and Enterococcus faecalis as model microorganisms, water disinfection has been demonstrated with singlet molecular oxygen (a reactive oxygen species) photogenerated by polymer-supported Ru(II) sensitizers and solar light. Both laboratory and sunlight tests were performed. The Ru(II) polypyridyl complex and its insoluble support have been optimized to provide maximum efficiency of singlet oxygen production and contact with the microorganism.
Physical Chemistry Chemical Physics, 2006
Generation of singlet molecular oxygen ((1)O(2)) by photosensitization with methylene blue (MB) s... more Generation of singlet molecular oxygen ((1)O(2)) by photosensitization with methylene blue (MB) supported in Nafion-Na films has been quantified by integration of the (1)O(2) emission decay at 1270 nm. The quantum yield of (1)O(2) production (Phi(Delta)) in the air-equilibrated solid phase is 0.24 +/- 0.03. Information on the (1)O(2) generation environment has been gained from complementary techniques such as UV-Vis absorption and emission spectroscopy, as well as MB fluorescence and triplet-triplet absorption decay. Results are compared with the (1)O(2) generation by MB in methanol solution (Phi(Delta) = 0.51) and in methanol-swollen Nafion films (Phi(Delta) = 0.49 +/- 0.06). Differences and similarities are discussed in terms of the factors that influence Phi(Delta) in solution and in the solid media. The optical and mechanical features of Nafion, ease of dye loading, compatibility with most solvents, homogeneity, reproducibility and stability of the photosensitizing material makes it a convenient reference for (1)O(2) generation quantum yield measurements in transparent (micro)heterogeneous and homogeneous media.
Photochemical & Photobiological Sciences, 2010
Photogeneration of singlet molecular oxygen ((1)O(2)) is applied to organic synthesis (photooxida... more Photogeneration of singlet molecular oxygen ((1)O(2)) is applied to organic synthesis (photooxidations), atmosphere/water treatment (disinfection), antibiofouling materials and in photodynamic therapy of cancer. In this paper, (1)O(2) photosensitizing materials containing the dyes tris(4,4'-diphenyl-2,2'-bipyridine)ruthenium(II) (1, RDB(2+)) or tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) (2, RDP(2+)), immobilized on porous silicone (abbreviated RDB/pSil and RDP/pSil), have been produced and tested for waterborne Enterococcus faecalis inactivation using a laboratory solar simulator and a compound parabolic collector (CPC)-based solar photoreactor. In order to investigate the feasibility of its reuse, the sunlight-exposed RDP/pSil sensitizing material (RDP/pSil-a) has been reloaded with RDP(2+) (RDP/pSil-r). Surprisingly, results for bacteria inactivation with the reloaded material have demonstrated a 4-fold higher efficiency compared to those of either RDP/pSil-a, unused RDB/pSil and the original RDP/pSil. Surface and bulk photochemical characterization of the new material (RDP/pSil-r) has shown that the bactericidal efficiency enhancement is due to aggregation of the silicone-supported photosensitizer on the surface of the polymer, as evidenced by confocal fluorescence lifetime imaging microscopy (FLIM). Photogenerated (1)O(2) lifetimes in the wet sensitizer-doped silicone have been determined to be ten times longer than in water. These facts, together with the water rheology in the solar reactor and the interfacial production of the biocidal species, account for the more effective disinfection observed with the reloaded photosensitizing material. These results extend and improve the operational lifetime of photocatalytic materials for point-of-use (1)O(2)-mediated solar water disinfection.
Photochemical & Photobiological Sciences, 2009
In this study we report on the preparation, photochemical characterisation and evaluation of the ... more In this study we report on the preparation, photochemical characterisation and evaluation of the photodisinfection power of various new types of singlet oxygen photosensitising materials prepared from two homoleptic Ru(ii) complexes with polyazaheterocyclic ligands (abbreviated as RDP(2+) and RSD(4-)) immobilised on anionic and cationic porous silicone polymers (pSil(-) and pSil(+), respectively). Time-resolved emission measurements in the UV-Vis-NIR have confirmed high (1)O(2) production by these materials in water (tau(Delta) = 25-32 micros) due to efficient quenching of the long-lived sensitiser triplet state by dissolved O(2), particularly in those pSil(-) materials with higher sensitiser load (P(O(2))(T)ca. 0.74 and 0.88 for 1.15 and 4.40 g m(-2), abbreviated as "M" and "H", respectively). Photodisinfection tests carried out using both a solar-simulated lab-scale setup and under sunlight have demonstrated the strong bacteria inactivation ability of the RDP/pSil(-) material with the highest sensitiser load. Results of photochemical experiments with aqueous suspensions of Enterococcus faecalis at an initial concentration of 10(4) CFU mL(-1) yield average inactivation rates of 3200 and 24 000 CFU h(-1) for RSD/pSil(+) and H-RDP/pSil(-) films, respectively. The sensitiser charge, its load on the polymer support and the ionic character of the silicone surface play an essential role on the singlet oxygen production in heterogeneous media, the stability of the resulting material, and on the interaction with bacteria, determining the microorganism inactivation efficiency of the ionic silicone-based photosensitising materials.
Photochemical & Photobiological Sciences, 2014
Different photosensitizing materials manufactured by immobilizing (0.5-3.0 g m(-2)) tris(4,7-diph... more Different photosensitizing materials manufactured by immobilizing (0.5-3.0 g m(-2)) tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) (RDP(2+)), [C60]-fullerene, or 1-(4-methyl)-piperazinylfullerene (MPF) on porous neutral (pSil) or surface-modified anionic (pSil(-)) poly(dimethylsiloxane) are compared on the grounds of their singlet molecular oxygen ((1)O2) production and photodynamic solar water disinfection capability. The C60-based sensitizers display a broad weak absorption in the visible and strong absorption in the UV, while absorption of light by RDP(2+) supported on pSil is strong in both the UV and blue regions. The (1)O2 emission lifetimes (τ(Δ)) determined for RDP(2+) and MPF on porous silicone materials under air are similar (40-50 μs) and correspond to the decay of (1)O2 generated by sensitizers dissolved in the polymer support. In contrast, τ(Δ) measured for C60 in pSil is similar to that observed for MPF or RDP(2+) when immobilized at low loading on pSil, but dramatically increases up to 5 ms if C60 aggregates are formed in the porous material as evidenced by microscopy evaluation. The photosensitizing properties of the dyes, together with their electrical charge and the overall charge of the porous silicone-based materials, lead to highly different sunlight-driven bacteria inactivation efficiencies, as tested with waterborne E. faecalis. RDP/pSil provides efficient disinfection by photosensitization unlike MPF/pSil, which leads to reduced bacteria inactivation rates due to poorer (1)O2 production. C60/pSil and MPF/pSil(-) materials, despite their (1)O2 photogeneration, show unsuccessful waterborne bacteria inactivation due to the negative surface charge of fullerene aggregates in contact with water, and to the net negative charge of the pSil(-), respectively.
Mikrochimica Acta, 1995
The spectroscopic features and photoreactivity with oxygen of a novel, highly lipophilic, lumines... more The spectroscopic features and photoreactivity with oxygen of a novel, highly lipophilic, luminescent metal complex Ru(5-odap)~ + (where 5-odap stands for 5-octadecanamide-1,10-phenanthroline), are reported and compared to those of the well-known tris(1,10-phenanthroline) analogue. An array of silicone membranes, containing Ru(5-odap) 2 § or Ru(qSzp) 2 + (where q~2P stands for 4,7-diphenyl-l,10-phenanthroline) as solid-supported luminescent indicators, have been fabricated. Their (non-linear) response to oxygen was evaluated with fibre-optics as a function of their adsorbent nature (silica gel, glass, reverse-phase silica, styrene/divinyl benzene copolymer, or none), surface coverage by the deposited metal complex, and loading of dyed support-into the sensitive layer. The largest oxygen sensitivity (Io/I ca. 6 for a partial pressure of 130 Torr) is achieved with the highest amount of silica gel-or glass-supported Ru(4~2p) 2 + and the highest membrane loading. Ru(5-odap)32 + dissolved directly into silicone yields a linear dose/response plot, but with a small slope (Io/I ca. 1.4 for a partial pressure of 720 Torr). These results are discussed in terms of dynamic surface quenching between the co-adsorbed indicator and oxygen molecules.
Langmuir, 1999
The absorption spectroscopy, photophysics, and dioxygen quenching of [RuL3] 2+ luminescent probes... more The absorption spectroscopy, photophysics, and dioxygen quenching of [RuL3] 2+ luminescent probes, where L stands for 2,2′-bipyridine, 1,10-phenanthroline, 5-octadecanamide-1,10-phenanthroline, and 4,7diphenyl-1,10-phenanthroline (dip), electrostatically loaded onto Nafion ionomer membrane have been investigated in air and in organic solvents and water, with the aim of developing rugged materials for optical sensing of molecular oxygen. The significant differences in size and hydrophobicity of the Ru(II) dyes have been used to probe their location within the perfluorinated ionomer pore network, as well as to gain insight into the oxygen accesibility to its microcrystalline and interfacial domains. While the absorption maximums of the probes (444-458 nm) remain relative unchanged, their emission wavelengths (578-622 nm) are extremely sensitive to the degree of Nafion swelling by the solvent. This feature has been characterized by measuring the density (1.19-2.04 g cm -3 ) of the solvent-saturated ionomer and the mass and volume fractions of solvents (0.0-0.7) uptaken by the original acidic Nafion and Li + -, Na + -, or K + -exchanged films. The excited-state lifetimes of the [RuL3] 2+ complexes (0.03-4.9 µs) reflect important variations of the microenvironment around the luminescent probes, which are rationalized in terms of their location and oxygen accessibility when loaded onto the polysulfonated material. Emission quenching rate constants of 1.7 ( 0.3 M -1 s -1 have been measured for the [Ru(dip)3] 2+ -dyed films dipped in methanol; their oxygen sensitivity turns out to be independent of the Ru(II) loading and counterion of Nafion. Highly oxygen-sensitive luminescent membranes, suitable for continuous monitoring in organic solvents, water, or gas phase, have been prepared by immobilization of [Ru(dip)3] 2+ indicator in 178-µm thick Nafion, with response times below 1.5 min. Nevertheless, a slow evolution of the oxygen response over 1 week has been detected for very solvent-swollen membranes; some ways of minimizing such an effect are also given.
Langmuir, 2008
A comparative study of the chemical functionalization of undoped, n- and p-type GaN layers grown ... more A comparative study of the chemical functionalization of undoped, n- and p-type GaN layers grown on sapphire substrates by metal-organic chemical vapor deposition was carried out. Both types of samples were chemically functionalized with 3-aminopropyltriethoxysilane (APTES) using a well-established silane-based approach for functionalizing hydroxylated surfaces. The untreated surfaces as well as those modified by hydroxylation and APTES deposition were analyzed using angle-resolved X-ray photoelectron spectroscopy. Strong differences were found between the APTES growth modes on n- and p-GaN surfaces that can be associated with the number of available hydroxyl groups on the GaN surface of each sample. Depending on the density of surface hydroxyl groups, different mechanisms of APTES attachment to the GaN surface take place in such a way that the APTES growth mode changes from a monolayer to a multilayer growth mode when the number of surface hydroxyl groups is decreased. Specifically, a monolayer growth mode with a surface coverage of approximately 78% was found on p-GaN, whereas the formation of a dense film, approximately 3 monolayers thick, was observed on n-GaN.
Helvetica Chimica Acta, 2001
Novel anionic [RuL 2 L′] 2− complexes, where L stands for (1,10-phenanthroline-4,7-diyl)bis (benz... more Novel anionic [RuL 2 L′] 2− complexes, where L stands for (1,10-phenanthroline-4,7-diyl)bis (benzenesulfonate) (pbbs; 3a) or (2,2′-bipyridine)-4,4′-disulfonate (bpds; 3b), and L′ is N-(1,10-phenanthrolin-5-yl)tetradecanamide (pta; 2a) or N-(1,10-phenanthrolin-5-yl) ...
Helvetica Chimica Acta, 1996
ABSTRACT
European Journal of Medicinal Chemistry, 2013
About half of the world's population is currently infected with Helicobac... more About half of the world's population is currently infected with Helicobacter pylori, which is involved in the development of several gastro-duodenal pathologies. The increasing number of antibiotic resistance reduces the effectiveness of the first-line therapy, so new strategies to improve the H. pylori eradication rates are needed. Antimicrobial Photodynamic Therapy (APDT) benefits from photogenerated reactive oxygen species, such as singlet oxygen, which inactivate microorganisms by means of photosensitising dyes and visible light. Therefore, it could be a suitable alternative for H. pylori eradication in the gastro-duodenal tract, particularly in patients infected with antibiotic resistant strains. We evaluated APDT against H. pylori, in vitro, using a new photosensitising material (PSM) based on a ruthenium(II) complex covalently bound to micrometric glass beads. Five H. pylori isolates (classified according to cagA genotype, and metronidazole-clarithromycin resistance) were used. Bacteria were mixed with the PSM and incubated in the dark or illuminated by blue light. Aliquots (min 1', 2', 5', 15' and 30') were cultured and colonies were counted after 2-3 days. A 99.99999% decrease was detected in the number of colonies in the irradiated wells where the bacterium was mixed with the PSM, compared to non-illuminated wells or with irradiated wells without PSM. It was also confirmed that DNA is a molecular target for oxidant species released during APDT (evaluated by alkaline gel electrophoresis after endonuclease III incubation, ureC and cagA RT-PCR, and bacterial fingerprint). Results were independent of cagA gene and antibiotic resistances.