ABSTRACT An organic/inorganic nanohybrid, based on the tetranionic mesotetrakis-(4-sulfonatopheny... more ABSTRACT An organic/inorganic nanohybrid, based on the tetranionic mesotetrakis-(4-sulfonatophenyl)porphyrin (TPPS) and on a positively charged polyhedral oligomeric silsesquioxanes (POSS), has been synthesized and fully characterized. Differential scanning calorimetry and thermogravimetric analyses have allowed classifying this compound as a room temperature ionic liquid (RT-IL). The POSS bulky cation is responsible for the observed amorphous waxy solid appearance and for the high solubility in halogenated solvents. The formation of emissive nanosized porphyrin J-aggregates has been detected both in solution and on quartz cuvette surface upon light irradiation on a dichlorometane porphyrin/POSS solution.
AOT/water/decane microemulsions have been used to entrap the water-soluble 5,10,15,20-tetrakis(4-... more AOT/water/decane microemulsions have been used to entrap the water-soluble 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (TPPS4). Quasi-elastic light scattering technique has confirmed the confinement of the porphyrin and its various aggregates into the inner water pool. Various species have been detected as function of the size of the microemulsions, concentration of the porphyrin, pH, and aging of the solutions by using a combination of UV-vis absorption, steady fluorescence emission, fluorescence lifetime measurements, and time-resolved fluorescence anisotropy. Under neutral pH conditions, the porphyrin is present as the free base monomer (S414) in the inner water compartment, and it is free to rotate when the size of the droplet is large enough and the porphyrin concentration is low. On increasing the concentration and/or decreasing the microemulsion size, a H-dimer of the free base (S406) is prevalently formed. Aging both the S414 and S406 species leads to the formation of a new species (S424), which has been postulated as a H-type dimer of the diacid porphyrin. On decreasing the pH, the species S414 and S406 almost instantaneously convert into the diacid porphyrin, which is monomeric (S434). This latter is an intermediate in the eventual formation of J-aggregated TPPS4 (S490). A marked stability has been observed for the S424 species, which do not interconvert on changing the pH of the bulk aqueous phase.
The neutralization reaction between the meso-tetrakis(4-carboxyphenyl)porphyrin (TPPC) and O-(2-a... more The neutralization reaction between the meso-tetrakis(4-carboxyphenyl)porphyrin (TPPC) and O-(2-aminopropyl)-O'-(2-methoxyethyl)poly(propylene glycol) (Jeffamine M-600) in 1:4 stoichiometric ratio affords a stable supramolecular adduct (TPPC@Jeffamine). This species has been ...
CNR-ISMN, Istituto per lo Studio dei Materiali Nanostrutturati, V.le F. Stagno d&am... more CNR-ISMN, Istituto per lo Studio dei Materiali Nanostrutturati, V.le F. Stagno d'Alcontres 31, 98166 Messina, Italy. ... Dipartimento di Chimica Inorganica, Chimica Analitica e Chimica Fisica, and CIRCMSB, Universit di Messina, V.le F. Stagno d'Alcontres 31, 98166, ...
Engineered viruses act as scaffolds to bind porphyrins on their surfaces, exploiting mainly elect... more Engineered viruses act as scaffolds to bind porphyrins on their surfaces, exploiting mainly electrostatic interactions. The close proximity between porphyrins and tryptophan residues, exposed on the solvent-accessible surface, leads to an efficient resonant energy transfer, which makes these systems suitable for developing noncovalent antenna systems.
An acid-base interaction between hemin and PAMAM dendrimers affords supramolecular non-covalent p... more An acid-base interaction between hemin and PAMAM dendrimers affords supramolecular non-covalent peroxidase systems whose catalytic activity is enhanced after spontaneous electrostatic self-assembling onto a solid surface.
Recently, we showed that J-aggregates, formed by the zwitterionic diacid form of the porphyrin 5,... more Recently, we showed that J-aggregates, formed by the zwitterionic diacid form of the porphyrin 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (H 2 TPPS 4 4-) under acidic conditions, can be described in terms of fractal geometry. We have extended the investigation of the ...
Water/decane/AOT microemulsions have been used to obtain J-aggregates of the anionic water solubl... more Water/decane/AOT microemulsions have been used to obtain J-aggregates of the anionic water soluble porphyrin tetrakis(4-sulfonatophenyl)porphyrin (TPPS 4 ), having sizes that are controlled by the dimension of the water pool. The kinetics of aggregation have been investigated ...
A structural change from fractal to nanorod J-aggregates of tetrakis(4-sulfonatophenyl)porphyrin ... more A structural change from fractal to nanorod J-aggregates of tetrakis(4-sulfonatophenyl)porphyrin has been obtained by acting on the intermolecular interaction potential. The size and shape of these self-assembled porphyrin clusters have been monitored under different experimental conditions, by means of polarized and depolarized dynamic light scattering and small and wide angle elastic light scattering. At sufficiently low porphyrin concentration and high ionic strength, the shielded repulsive potential seems to be responsible for the fractal structure of the aggregates. On the contrary, at low ionic strength (nonshielded potential) and high porphyrin concentration, these species self-assemble in a rodlike arrangement. The length of the so-formed rod-shaped aggregates decreases on increasing porphyrin concentration. Moreover, both fractals and rods display a structure-dependent optical activity induced by a chiral template.
UV/vis absorption and time-resolved fluorescence measurements on alcoholic solutions of meso-tetr... more UV/vis absorption and time-resolved fluorescence measurements on alcoholic solutions of meso-tetrakis(4-sulfonatophenyl)porphyrin (TPPS(4)) in neutral and acid form have been performed as a function of the alcohol polarity. These solutions show a peculiar behavior that mimics porphyrin in confined water solutions. In alcohols, TPPS(4) exhibits a metastable phase showing the formation of new species in analogy with the confined water environment of AOT microemulsions. Various species have been detected at different pH values and on aging the solutions. Under neutral pH conditions, the porphyrin is present as free base monomer (S415) with a small amount of H-dimeric species (S400). On aging, the S415 leads to the formation of a new species (S423), which has been assigned as a J-type dimer of the neutral porphyrin. The species S400 and S423 are not present in bulk water solution but are typical of TPPS(4) in confined water. On decreasing pH, the S415 almost immediately converts into the diacid form (S438), which evolves toward red-shifted J-aggregates (S490) and blue-shifted H-aggregates (S420). On decreasing alcohol polarity, the kinetic evolution from fresh to aged solution and from the monomeric diacid species to H- and J-aggregates speeds up. Exploiting the amphiphilic character of short chain alcohols and widely varying their polarity, we were able to enhance in bulk conditions the peculiar behavior observed in close proximity to the microemulsion wall.
AOT/water/decane microemulsions have been used to entrap the water-soluble 5,10,15,20-tetrakis(4-... more AOT/water/decane microemulsions have been used to entrap the water-soluble 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (TPPS4). Quasi-elastic light scattering technique has confirmed the confinement of the porphyrin and its various aggregates into the inner water pool. Various species have been detected as function of the size of the microemulsions, concentration of the porphyrin, pH, and aging of the solutions by using a combination of UV-vis absorption, steady fluorescence emission, fluorescence lifetime measurements, and time-resolved fluorescence anisotropy. Under neutral pH conditions, the porphyrin is present as the free base monomer (S414) in the inner water compartment, and it is free to rotate when the size of the droplet is large enough and the porphyrin concentration is low. On increasing the concentration and/or decreasing the microemulsion size, a H-dimer of the free base (S406) is prevalently formed. Aging both the S414 and S406 species leads to the formation of a new species (S424), which has been postulated as a H-type dimer of the diacid porphyrin. On decreasing the pH, the species S414 and S406 almost instantaneously convert into the diacid porphyrin, which is monomeric (S434). This latter is an intermediate in the eventual formation of J-aggregated TPPS4 (S490). A marked stability has been observed for the S424 species, which do not interconvert on changing the pH of the bulk aqueous phase.
The early stage of fractal porphyrin diffusion-limited aggregation (DLA), induced by addition of ... more The early stage of fractal porphyrin diffusion-limited aggregation (DLA), induced by addition of a polyamine, is observed in aqueous solution by enhanced Raman scattering and fluorescence quenching. The enhancement of Raman scattering is due to nonlinear optical properties typical of fractal composites. Although this early stage (reaction-limited aggregation) has been theoretically predicted (by mean-field theory and molecular dynamics simulation), it is experimentally difficult to observe. During this initial stage, fluorescence quenching gives direct information on the decrease of the concentration of monomeric porphyrins, whereas Raman scattering (through characteristic vibrational modes of the aggregate) reports on the concentration of porphyrins in the aggregated form. These small clusters constitute the seeds for the DLA aggregation process leading to micrometric-sized fractals.
We performed an experimental investigation on the scattering and extinction properties of an aque... more We performed an experimental investigation on the scattering and extinction properties of an aqueous solution of spermine-induced fractal J aggregates, constituted by porphyrin molecules. In analogy with nanostructured particle composites, the dipolar moments of different porphyrins, not belonging to the aggregates J, are coupled and generate a strong light scattering enhancement. Both the enhanced scattered intensity and the imaginary part of the polarizability of the system obey scaling laws with the optical spectral dimension d0=0.3.
Noncovalent adducts (TPPC@PAMAM) between meso-tetrakis(4-carboxyphenyl)porphyrin (TPPC) and polya... more Noncovalent adducts (TPPC@PAMAM) between meso-tetrakis(4-carboxyphenyl)porphyrin (TPPC) and polyamidoamine PAMAM dendrimer (generation 2.0) have been obtained by simply mixing the two components at different stoichiometric amount. The resulting species are readily soluble and stable in aqueous solution up to millimolar concentration. Electrostatic interactions between the anionic carboxylate groups of TPPC and the protonated amino groups of the PAMAM dendrimer play an important role in the stabilization of these adducts. UV/Vis absorption, steady state and time-resolved fluorescence emission and anisotropy measurements suggest the presence of equilibria involving different species as function of the [PAMAM]/[TPPC] ratio. At low ratios the observed spectroscopic behavior evidence the presence of H-aggregates, while at higher ratios well-defined species containing monomeric TPPC strongly interacting with the charged dendrimer are formed. Docking of the binary supramolecular adduct further supports the experimental results showing a favorable interaction with the porphyrin being completely included in the dendrimer. The interaction of the binary TPPC@PAMAM adduct (1/1 ratio) with calf-thymus DNA has been investigated through spectroscopic and photophysical techniques. All the experimental results point to the formation of a ternary complex between the binary adduct and the DNA backbone.
The neutralization reaction between the meso-tetrakis(4-carboxyphenyl)porphyrin (TPPC) and O-(2-a... more The neutralization reaction between the meso-tetrakis(4-carboxyphenyl)porphyrin (TPPC) and O-(2-aminopropyl)-O'-(2-methoxyethyl)poly(propylene glycol) (Jeffamine M-600) in 1:4 stoichiometric ratio affords a stable supramolecular adduct (TPPC@Jeffamine). This species has been ...
ABSTRACT An organic/inorganic nanohybrid, based on the tetranionic mesotetrakis-(4-sulfonatopheny... more ABSTRACT An organic/inorganic nanohybrid, based on the tetranionic mesotetrakis-(4-sulfonatophenyl)porphyrin (TPPS) and on a positively charged polyhedral oligomeric silsesquioxanes (POSS), has been synthesized and fully characterized. Differential scanning calorimetry and thermogravimetric analyses have allowed classifying this compound as a room temperature ionic liquid (RT-IL). The POSS bulky cation is responsible for the observed amorphous waxy solid appearance and for the high solubility in halogenated solvents. The formation of emissive nanosized porphyrin J-aggregates has been detected both in solution and on quartz cuvette surface upon light irradiation on a dichlorometane porphyrin/POSS solution.
AOT/water/decane microemulsions have been used to entrap the water-soluble 5,10,15,20-tetrakis(4-... more AOT/water/decane microemulsions have been used to entrap the water-soluble 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (TPPS4). Quasi-elastic light scattering technique has confirmed the confinement of the porphyrin and its various aggregates into the inner water pool. Various species have been detected as function of the size of the microemulsions, concentration of the porphyrin, pH, and aging of the solutions by using a combination of UV-vis absorption, steady fluorescence emission, fluorescence lifetime measurements, and time-resolved fluorescence anisotropy. Under neutral pH conditions, the porphyrin is present as the free base monomer (S414) in the inner water compartment, and it is free to rotate when the size of the droplet is large enough and the porphyrin concentration is low. On increasing the concentration and/or decreasing the microemulsion size, a H-dimer of the free base (S406) is prevalently formed. Aging both the S414 and S406 species leads to the formation of a new species (S424), which has been postulated as a H-type dimer of the diacid porphyrin. On decreasing the pH, the species S414 and S406 almost instantaneously convert into the diacid porphyrin, which is monomeric (S434). This latter is an intermediate in the eventual formation of J-aggregated TPPS4 (S490). A marked stability has been observed for the S424 species, which do not interconvert on changing the pH of the bulk aqueous phase.
The neutralization reaction between the meso-tetrakis(4-carboxyphenyl)porphyrin (TPPC) and O-(2-a... more The neutralization reaction between the meso-tetrakis(4-carboxyphenyl)porphyrin (TPPC) and O-(2-aminopropyl)-O'-(2-methoxyethyl)poly(propylene glycol) (Jeffamine M-600) in 1:4 stoichiometric ratio affords a stable supramolecular adduct (TPPC@Jeffamine). This species has been ...
CNR-ISMN, Istituto per lo Studio dei Materiali Nanostrutturati, V.le F. Stagno d&am... more CNR-ISMN, Istituto per lo Studio dei Materiali Nanostrutturati, V.le F. Stagno d'Alcontres 31, 98166 Messina, Italy. ... Dipartimento di Chimica Inorganica, Chimica Analitica e Chimica Fisica, and CIRCMSB, Universit di Messina, V.le F. Stagno d'Alcontres 31, 98166, ...
Engineered viruses act as scaffolds to bind porphyrins on their surfaces, exploiting mainly elect... more Engineered viruses act as scaffolds to bind porphyrins on their surfaces, exploiting mainly electrostatic interactions. The close proximity between porphyrins and tryptophan residues, exposed on the solvent-accessible surface, leads to an efficient resonant energy transfer, which makes these systems suitable for developing noncovalent antenna systems.
An acid-base interaction between hemin and PAMAM dendrimers affords supramolecular non-covalent p... more An acid-base interaction between hemin and PAMAM dendrimers affords supramolecular non-covalent peroxidase systems whose catalytic activity is enhanced after spontaneous electrostatic self-assembling onto a solid surface.
Recently, we showed that J-aggregates, formed by the zwitterionic diacid form of the porphyrin 5,... more Recently, we showed that J-aggregates, formed by the zwitterionic diacid form of the porphyrin 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (H 2 TPPS 4 4-) under acidic conditions, can be described in terms of fractal geometry. We have extended the investigation of the ...
Water/decane/AOT microemulsions have been used to obtain J-aggregates of the anionic water solubl... more Water/decane/AOT microemulsions have been used to obtain J-aggregates of the anionic water soluble porphyrin tetrakis(4-sulfonatophenyl)porphyrin (TPPS 4 ), having sizes that are controlled by the dimension of the water pool. The kinetics of aggregation have been investigated ...
A structural change from fractal to nanorod J-aggregates of tetrakis(4-sulfonatophenyl)porphyrin ... more A structural change from fractal to nanorod J-aggregates of tetrakis(4-sulfonatophenyl)porphyrin has been obtained by acting on the intermolecular interaction potential. The size and shape of these self-assembled porphyrin clusters have been monitored under different experimental conditions, by means of polarized and depolarized dynamic light scattering and small and wide angle elastic light scattering. At sufficiently low porphyrin concentration and high ionic strength, the shielded repulsive potential seems to be responsible for the fractal structure of the aggregates. On the contrary, at low ionic strength (nonshielded potential) and high porphyrin concentration, these species self-assemble in a rodlike arrangement. The length of the so-formed rod-shaped aggregates decreases on increasing porphyrin concentration. Moreover, both fractals and rods display a structure-dependent optical activity induced by a chiral template.
UV/vis absorption and time-resolved fluorescence measurements on alcoholic solutions of meso-tetr... more UV/vis absorption and time-resolved fluorescence measurements on alcoholic solutions of meso-tetrakis(4-sulfonatophenyl)porphyrin (TPPS(4)) in neutral and acid form have been performed as a function of the alcohol polarity. These solutions show a peculiar behavior that mimics porphyrin in confined water solutions. In alcohols, TPPS(4) exhibits a metastable phase showing the formation of new species in analogy with the confined water environment of AOT microemulsions. Various species have been detected at different pH values and on aging the solutions. Under neutral pH conditions, the porphyrin is present as free base monomer (S415) with a small amount of H-dimeric species (S400). On aging, the S415 leads to the formation of a new species (S423), which has been assigned as a J-type dimer of the neutral porphyrin. The species S400 and S423 are not present in bulk water solution but are typical of TPPS(4) in confined water. On decreasing pH, the S415 almost immediately converts into the diacid form (S438), which evolves toward red-shifted J-aggregates (S490) and blue-shifted H-aggregates (S420). On decreasing alcohol polarity, the kinetic evolution from fresh to aged solution and from the monomeric diacid species to H- and J-aggregates speeds up. Exploiting the amphiphilic character of short chain alcohols and widely varying their polarity, we were able to enhance in bulk conditions the peculiar behavior observed in close proximity to the microemulsion wall.
AOT/water/decane microemulsions have been used to entrap the water-soluble 5,10,15,20-tetrakis(4-... more AOT/water/decane microemulsions have been used to entrap the water-soluble 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (TPPS4). Quasi-elastic light scattering technique has confirmed the confinement of the porphyrin and its various aggregates into the inner water pool. Various species have been detected as function of the size of the microemulsions, concentration of the porphyrin, pH, and aging of the solutions by using a combination of UV-vis absorption, steady fluorescence emission, fluorescence lifetime measurements, and time-resolved fluorescence anisotropy. Under neutral pH conditions, the porphyrin is present as the free base monomer (S414) in the inner water compartment, and it is free to rotate when the size of the droplet is large enough and the porphyrin concentration is low. On increasing the concentration and/or decreasing the microemulsion size, a H-dimer of the free base (S406) is prevalently formed. Aging both the S414 and S406 species leads to the formation of a new species (S424), which has been postulated as a H-type dimer of the diacid porphyrin. On decreasing the pH, the species S414 and S406 almost instantaneously convert into the diacid porphyrin, which is monomeric (S434). This latter is an intermediate in the eventual formation of J-aggregated TPPS4 (S490). A marked stability has been observed for the S424 species, which do not interconvert on changing the pH of the bulk aqueous phase.
The early stage of fractal porphyrin diffusion-limited aggregation (DLA), induced by addition of ... more The early stage of fractal porphyrin diffusion-limited aggregation (DLA), induced by addition of a polyamine, is observed in aqueous solution by enhanced Raman scattering and fluorescence quenching. The enhancement of Raman scattering is due to nonlinear optical properties typical of fractal composites. Although this early stage (reaction-limited aggregation) has been theoretically predicted (by mean-field theory and molecular dynamics simulation), it is experimentally difficult to observe. During this initial stage, fluorescence quenching gives direct information on the decrease of the concentration of monomeric porphyrins, whereas Raman scattering (through characteristic vibrational modes of the aggregate) reports on the concentration of porphyrins in the aggregated form. These small clusters constitute the seeds for the DLA aggregation process leading to micrometric-sized fractals.
We performed an experimental investigation on the scattering and extinction properties of an aque... more We performed an experimental investigation on the scattering and extinction properties of an aqueous solution of spermine-induced fractal J aggregates, constituted by porphyrin molecules. In analogy with nanostructured particle composites, the dipolar moments of different porphyrins, not belonging to the aggregates J, are coupled and generate a strong light scattering enhancement. Both the enhanced scattered intensity and the imaginary part of the polarizability of the system obey scaling laws with the optical spectral dimension d0=0.3.
Noncovalent adducts (TPPC@PAMAM) between meso-tetrakis(4-carboxyphenyl)porphyrin (TPPC) and polya... more Noncovalent adducts (TPPC@PAMAM) between meso-tetrakis(4-carboxyphenyl)porphyrin (TPPC) and polyamidoamine PAMAM dendrimer (generation 2.0) have been obtained by simply mixing the two components at different stoichiometric amount. The resulting species are readily soluble and stable in aqueous solution up to millimolar concentration. Electrostatic interactions between the anionic carboxylate groups of TPPC and the protonated amino groups of the PAMAM dendrimer play an important role in the stabilization of these adducts. UV/Vis absorption, steady state and time-resolved fluorescence emission and anisotropy measurements suggest the presence of equilibria involving different species as function of the [PAMAM]/[TPPC] ratio. At low ratios the observed spectroscopic behavior evidence the presence of H-aggregates, while at higher ratios well-defined species containing monomeric TPPC strongly interacting with the charged dendrimer are formed. Docking of the binary supramolecular adduct further supports the experimental results showing a favorable interaction with the porphyrin being completely included in the dendrimer. The interaction of the binary TPPC@PAMAM adduct (1/1 ratio) with calf-thymus DNA has been investigated through spectroscopic and photophysical techniques. All the experimental results point to the formation of a ternary complex between the binary adduct and the DNA backbone.
The neutralization reaction between the meso-tetrakis(4-carboxyphenyl)porphyrin (TPPC) and O-(2-a... more The neutralization reaction between the meso-tetrakis(4-carboxyphenyl)porphyrin (TPPC) and O-(2-aminopropyl)-O'-(2-methoxyethyl)poly(propylene glycol) (Jeffamine M-600) in 1:4 stoichiometric ratio affords a stable supramolecular adduct (TPPC@Jeffamine). This species has been ...
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