Thesis (MSc)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: In this thesis the synthesis of a range of model and siloxane functionalized salicylaldimine ligands and [N-(n-propyl)-(2-pyridyl)] diimine ligands are described. The functionalized ligands were obtained by the reaction of salicylaldehyde and 2-pyridinecarboxaldehyde with 3-aminopropyltriethyoxysilane. All ligands were characterized by FT-IR and 1H NMR spectroscopy. The salicylaldimine ligands were reacted with either Cu(II) or Pd(II) salts to form both the model and functionalized Cu(II) and Pd(II) complexes. The Cu(II) complexes were characterized using FT-IR, EPR and UV-VIS spectroscopy while the Pd(II) complexes were characterized using FT-IR, 1H NMR and 13C{1H} NMR spectroscopy. The diimine ligands were reacted with Cu(II) salts to form functionalized pyridinyl complexes which were characterized used FT-IR spectroscopy. Two mesoporous silica supports, MCM-41 and SBA-15 were synthesized. The siloxane functionalized salicylaldimine Cu(II) and Pd(II) complexes were immobilized onto these supports to produce heterogenized catalysts. These catalysts were characterized using a range of solid-state techniques: BET nitrogen adsorption/desorption, scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), ICP-AES, and powder X-ray diffraction (XRD) analysis. The powder XRD and SEM analysis showed that the structural integrity of the catalyst supports was kept intact during the immobilization process. BET analysis and ICP-AES showed that the complexes had been attached to the silica supports. Both the model complexes and heterogenized catalyst systems were tested in the oxidation of benzyl alcohol to benzaldehyde. The model copper catalyst showed high activity in this reaction with molecular oxygen used as oxidant and the (2,2,6,6-tetramethylpiperidin-1-yl)oxyl radical as co-oxidant. The immobilized copper complexes showed low activity in the same reaction. This was attributed to steric hindrance around the active site dye to its entrapment with the silica matrix thus hindering the formation of a key intermediate in the oxidation cycle due to steric hindrance. The palladium complexes were not active in the oxidation reaction when molecular oxygen was used as oxidant, but showed slight activity when hydrogen peroxide was used. / AFRIKAANSE OPSOMMING: In hierdie tesis word die sintese van ‘n reeks model sowel as gefunksioneerde salisielaldemien ligande en [N-(n-propiel)-(2-piridiel)] di-imien ligande beskryf. Die gefunksioneerde ligande is verkry deur die reaksie van salisielaldehied en en 2-piridienaldehied met 3-aminopropieltriëtoksiesilaan. Al die ligande is gekarakteriseer deur FT-IR en 1H-KMR spektroskopie. Die salisielaldimien ligande is met óf Cu(II) óf Pd(II) soute reageer om beide die model en gefunksioneerde Cu(II) en Pd(II) komplekse te vorm. Die Cu(II) komplekse is gekarakteriseer deur FT-IR, EPR en UV-Vis spektroskopie terwyl die Pd(II) komplekse deur FT-IR, 1H-KMR en 13C{1H}-KMR spektroskopie gekarakteriseer is. Die di-imien ligande is met Cu(II) soute reageer om gefunksioneerde piridinielkompekse te vorm wat deur FT-IR spektroskopie gekarakteriseer is. Twee mesoporeuse silika draers, MCM-41 en SBA-15 is gesintetiseer. Die siloksaan-gefunksioneerde salisielaldemien Cu(II) en Pd(II) komplekse is op hierdie draers geimobiliseer om geheterogeniseerde katalisatore te vorm. Hierdie katalisatore is gekarakteriseer deur van ‘n wye reeks vaste toestand tegnieke gebruik te maak: BET stikstof adsorpsie/desorpsie, skandeer elektron mikroskopie (SEM), termiese gravimetriese analise (TGA), ICP-AES en poeier-XRD analise. Die poeier-XRD en SEM analisies het aangetoon dat die strukturele integriteit van die katalisator draers behoue gebly het tydens die immobiliseringsproses. BET analise en ICP-AES het aangetoon dat die komplekse aan die silika draers geheg is. Beide die model komplekse en geimobiliseerde katalisators is getoets in die oksidasie van bensielalkohol na bensaldehied. Die model Cu(II) katalisator het hoë aktiwiteit in hierdie reaksie getoon met molekulêre suurstof as oksideermiddel en die (2,2,6,6-tetrametielpipiridien-1-iel)oksiel radikaal as ko-oksideermiddel. Die geimobiliseerde Cu(II) komplekse het lae aktiwiteit in dieselfde reaksie getoon. Dit is toegeskryf aan steriese hindernis rondom die aktiewe sentrum as gevolg van die verstrikking binne die silika matrys, wat die vorming van ‘n belangrike tussentoestand in die oksidasie-siklus verhinder. Die Pd(II) komplekse was nie aktief in die oksidasie-reaksie in die geval waar molekulêre suurstof as oksideermiddel gebruik is nie, maar het effense aktiwiteit getoon waneer waterstofperoksied gebruik is. / Sasol

Στην παρούσα μεταπτυχιακή εργασία ειδίκευσης περιγράφεται η σύνθεση και ο χαρακτηρισμός νέων μεσοπορωδών βιοενεργών υλικών. Παρουσιάζονται οι συσχετιζόμενες με τα πορώδη/μεσοπορώδη υλικά έννοιες, οι ιδιότητες τους και διάφοροι τρόποι σύνθεσης τους. Εν συνεχεία, αναλύονται θέματα βιουλικών, δίνοντας έμφαση στις βιοϋάλους και τις ιδιότητες τους, και ειδικότερα στη βιονεργότητα, που αποτελεί την πιο χαρακτηριστική ιδιότητα αυτών, ενώ δίνεται έμφαση, επίσης στις διάφορες μεθόδους που χρησιμοποιούνται για την σύνθεση τους. Στην συνέχεια αναλύονται οι τεχνικές που χρησιμοποιήθηκαν για το χαρακτηρισμό των προαναφερθέντων υλικών καθώς και ο τρόπος λειτουργίας της κάθε τεχνικής. Επίσης, γίνεται αναφορά στα διαφορετικά χαρακτηριστικά των υλικών που μπορούν να μελετηθούν για κάθε τεχνική ξεχωριστά. Στο τελευταίο κεφάλαιο παρουσιάζεται αναλυτικά η διαδικασία διεξαγωγής των πειραμάτων, οι διάφοροι τρόποι σύνθεσης που χρησιμοποιήθηκαν, καθώς και σχολιασμός των αποτελεσμάτων. Τέλος, παρουσιάζονται τα συμπεράσματα που προέκυψαν από τα πειραματικά αποτελέσματα για την παρούσα μεταπτυχιακή εργασία. Επίσης γίνεται αναφορά και σε μελλοντικές κατευθύνσεις που περιλαμβάνουν την χρήση αυτών των υλικών σε σύνθετα υλικά για παλμική εναπόθεση με Laser και τεχνικές εναπόθεσης λεπτού υμενίου. / In this master thesis the synthesis and characterization of novel bioactive mesoporous materials is being reported. The notions related to porous/mesoporous materials, their properties and various synthetic methods are being discussed. Subsequently, the notion of “biomaterials” is further analyzed, focusing on bioglasses and their properties. The meaning of bioactivity is also analyzed as the most characteristic feature of bioglasses while various methods used for the synthesis of these are discussed. Following the techniques used to characterize these materials as well as the operating mode of each technique is discussed. In the last chapter, the experimental processes are reported as well as the results are being discussed. Finally, the conclusions of all the experiments and analysis are reported. Also, future directions include the usage of these materials in composite materials for laser ablation and thin film deposition techniques are mentioned.

The use of compressed CO2 processing to alter the pore size, structure and timescale of silica condensation in surfactant templated silica thin films and powders is investigated by systematically varying the template structure and CO2 processing conditions. Tailoring the mesoporous materials increases its potential applications, as demonstrated in catalysis, drug delivery, chromatographic and electrode applications. This work demonstrates for the first time the applicability of fluorinated surfactants as templates for the synthesis of mesoporous silica thin films by dip coating. Well-ordered films with 2D hexagonal close-packed pore structure are synthesized in an acid-catalyzed medium using three cationic fluorinated templates of varied tail length and branching (C6F13C2H4NC5H5Cl, C8F17C2H4NC5H5Cl and (CF3)2CFC5F9C2H4NC5H5Cl). CO2 processing of the fluorinated templated silica results in a significant and controlled increase in pore diameter relative to the unprocessed films. The pore expansion is significantly greater compared to the negligible expansion observed in hydrocarbon (C16H23NC5H5Br) templated silica. The greater swelling of the fluorinated templates is attributed to the favorable penetration of CO2 in the CO2-philic fluorinated tail and the relative solvation of each template is interpreted from their interfacial behavior at the CO2-water interface. The CO2 based pore expansion observed in fluorinated surfactant templated films is extended successfully to base-catalyzed silica powders templated with a fluorinated surfactant (C6F13C2H4NC5H5Cl). Pore expansion in silica powders is significantly less than in acid catalyzed films and demonstrates the effects of pH on surfactant selfassembly in CO2 and increased silica condensation at basic conditions, which inhibits pore expansion. Finally, the use of fluorescence probe molecules is demonstrated for in-situ monitoring of the of CO2 processing of surfactant templated silica films to provide time dependent data on the local environment and dynamics of CO2 penetration. CO2 uptake occurs in surfactant tails even for hydrocarbon templates (C16H23N(CH3)3Br and C16H23NC5H5Br), which display negligible CO2 based swelling of the resulting pores. The timescale of silica condensation increases significantly in the presence of CO2 suggesting opportunities for structure alteration through application of external forces, such as magnetic fields and change in substrate chemistry and system humidity

Self-assembled nonionic alkyl glycoside surfactants are of interest for creating functional adsorption and catalytic sites at the surface of mesoporous metal oxides, but they typically impart poor long-range order when used as pore templates. Improved order and control over the functional site density may be achieved by mixing them with a cationic surfactant. To confirm this hypothesis, we investigate the lyotropic liquid crystalline (LLC) phase behavior of aqueous solutions of the functional nonionic surfactant n-dodecyl β-D-maltoside (C12G2) and cationic cetyltrimethylammonium bromide (C16TAB). A ternary phase diagram of the C16TAB-C12G2-water system is developed at 50 °C. By replacing the volume of water in the phase diagram with an equivalent volume of silica, ordered mesoporous materials are prepared by nanocasting with variable C12G2/C16TAB ratios. Metal oxide mesophases can almost always be predicted from the ternary phase diagram, except that silica prepared with high C12G2/C16TAB ratios are very weakly ordered, perhaps due to differences in hydrogen bonding or rate of assembly. Based on the ternary phase diagram of the system, a systematic approach is taken to the incorporation of titania sites via complexation to the maltoside headgroup of C12G2. Complexation to a saccharide is expected not only to guide titanium to the pore surface, but also to prevent uncontrolled hydrolysis and condensation of the (usually quite reactive) titanium precursor. Tetrahedrally coordinated titanium atoms incorporated into a silica network are believed to be the active oxidation sites required for heterogeneous silica-supported titania oxidation catalysts. To promote well-ordered materials and to allow control over titania site density, the mixed C12G2 / C16TAB system is used for pore templating. Series of Si-Ti mixed oxide thin films and bulk materials are synthesized with different amounts of titanium loading by utilizing pre-complexation between C12G2 and titanium isopropoxide. The degrees of homogeneity (indicated by tetracoordinated Ti) in these films are superior to those of films synthesized with the same loading of titanium but without C12G2 or without pre-complexation. Transition metal-carbohydrate complexation provides highly dispersed, tetrahedrally coordinated titanium atoms rather than the octahedral sites found without saccharide complexation.

Ce travail s'est intéressé à la conception et à l'élaboration de nouveaux agents structurants de silice constitués d'assemblages induits et réversibles de copolymères originaux : les copolymères séquencés doublement hydrophiles (DHBC). Un des systèmes étudiés est constitué d'un DHBC neutre-anionique PAPEO-b-PAA ou poly(acrylate methoxy poly(oxyde d'éthylène))-b-poly(acide acrylique). La séquence PAA est un polyacide faible dont le degré d'ionisation dépend du pH. En solution aqueuse et pour un pH bien choisi, l'association de ce copolymère à une polybase faible, de charge opposée à celle du PAA, (typiquement un oligochitosane) conduit à la formation de micelles complexes de polyions (PIC) sphériques de type cur/couronne. Ces micelles peuvent dans un premier temps conduire à la formation de matériaux mésostructurés hybrides hautement organisés. Dans un second temps, en jouant notamment sur les conditions de pH et de force ionique, il est possible de « contrôler » le taux d'extraction des espèces organiques pour obtenir des matériaux poreux fonctionnels capables de piéger des espèces de charge opposée à la fonctionnalité. Si des matériaux hybrides organisés sont obtenus, c'est parce que les équilibres des interactions mises en jeu entre les espèces organiques et inorganiques y sont favorables. Si une interaction polyamine/silice s'exerce aux dépens de l'interaction polyamine/DHBC, elle peut limiter le processus de mésostructuration par les micelles. Lorsqu'un DHBC neutre-cationique PEO-b-PDMAEMA ou poly(oxyde d'éthylène)-b-poly(méthacrylate de 2-(diméthylamine)éthyle) est utilisé en présence d'un polymère anionique tel que le PVS ou poly(acide sulfonique de vinyle), il joue un double rôle dans la synthèse des matériaux siliciques : une partie gère la croissance des particules de silice en interagissant avec les silicates et l'autre partie qui est complexée par des PVS joue le rôle d'agent structurant en apportant une mésostructuration au matériau. Enfin, une approche très prometteuse a permis d'encapsuler des principes actifs hydrosolubles chargés dans un matériau en les utilisant comme agent complexant du DHBC. / This study focused on the design and development of new structuring agents of silica constituted of induced and reversible assemblies of original copolymers, the double hydrophilic block copolymers (DHBC). The first system studied consists of a neutral-anionic DHBC PAPEO-b-PAA ou poly(acrylate methoxy poly (ethylene oxide))-b-poly (acrylic acid). The PAA block is a weak polyacid with a degree of ionization depending on the pH. In aqueous solution and in a right pH range, the association of this copolymer with a weak polybase, an oppositely charged polyamine, such as an oligochitosan, leads to the formation of polyion complex micelles (PIC) with a core/corona structure. These micelles can direct the structure of highly organized inorganic materials with different types of mesostructures. In a second step, by adjusting the conditions of pH, ionic strength, it is possible to "control" the extraction of organic species to get functional porous materials able to trap species of charge opposite to the functionality. Organized materials are obtained because of a favourable balance of the interactions between organic and inorganic species. If a polyamine/silica interaction occurs at the expense of the interaction polyamine/DHBC, the mesostructuring process by the micelles is limited. A neutral-cationic DHBC PEO-b-PDMAEMA poly(ethylene oxide)-b-poly(2-(dimethylamine)ethyl) associated with an anionic PVS poly(vinyl sulfonic acid) polymer can play a dual role in the synthesis of silica materials: firstly managing the growth of silica particles by interacting with the silicates and secondly acting as a structuring agent in association with PVS, confering a mesostructuration to the material. Finally, a very promising approach allowed to encapsulate water-soluble and charged drugs in a material by using as silica complexing agent a complex between the drug and a DHBC.

The thermochemical process converts almost any kind of biomass to a desired final product, i.e. gaseous or liquid transportation fuels and chemicals. The transportation fuels obtained in this way are renewable biofuels, which are alternatives to fossil fuels. During the last few years, thermochemical plants for the production of bioethanol have been launched and another is under construction. A total of about 290 million liters of ethanol are expected to be processed per year, mostly using municipal solid waste. Considerable efforts have been made in order to find a more selective catalyst for the conversion of biomass-derived syngas to ethanol. The thesis is the summary of five publications. The first two publications (Papers I and II) review the state of the art of ethanol and higher alcohols production from biomass, as well as the current status of synthetic fuels production by other processes such as the Fischer-Tropsch synthesis. Paper III analyses the catalytic performance of a mesoporous Rh/MCM-41 (MCM-41 is a hexagonal mesoporous silica) in the synthesis of ethanol which is compared to a typical Rh/SiO2 catalyst. Exhaustive catalytic testing including the addition of water vapor and modifying the hydrogen partial pressure in the syngas feed-stream which, in addition to the catalyst characterization (XRD, BET, XPS, chemisorption, TEM and TPR) before and after the catalytic testing, have allowed concluding that some water vapor can be concentrated in the pores of the Rh/MCM-41 catalyst. The concentration of water-vapor promotes the occurrence of the water gas shift reaction, which in turn induces some secondary reactions that change the product distribution, as compared to results obtained from the typical Rh/SiO2 catalyst. These results have been verified in a wide range of syngas conversion levels (1-68 %) and for different catalyst activation procedures (catalyst reduction at 200 °C, 500 °C and no-reduction) as shown in Paper IV. Finally, similar insights about the use of mesoporous catalyst have been found over a Cu/MCM-41 catalyst, shown in Paper V. Also in Paper V, the effect of metal promoters (Fe and K) has been studied; a noticeable increase of ethanol reaction rate was found over Cu-Fe-K/MCM-41 catalyst as compared to Cu/MCM-41. / <p>QC 20161125</p>

In today’s drug discovery, the number of candidate drugs based on new molecular entities with poor aqueous solubility is increasing. Since poor aqueous solubility of an active pharmaceutical ingredients (APIs) is associated with low bioavailability and thus limite their therapeutic effect, this is often a great challenge in the development of new drugs when oral administration is the preferred route of administration. A number of different strategies have been developed to circumvent this problem where salt formulations of an API is the most widely employed method. However, new strategies are needed since there is no one solution that solves this issue for all substances. In recent time, the concept of stabilizing poorly soluble APIs in their amorphous form has gained a lot of attention since amorphous compounds exhibit a higher apparent solubility compared to their crystalline counterparts. Amorphous substances are prone to crystallize if left in a non-constricted environment and thus need to be stabilized if the amorphous state is to be conserved until administration. Inorganic mesoporous materials have been proposed as an interesting type of excipients that can conserve the amorphous state of APIs. In this work, the focus was to investigate the possibilities of using a mesoporous type of magnesium carbonate to stabilize the amorphous state of different APIs. Due to the nanometer sized pores in the material, complete conservation of amorphous APIs was obtained. This resulted in both an increase in in vitro release rate and a higher solubility of the substances which may translate to both a faster onset of action and an improved therapeutic effect of the APIs in a clinical situation. The long term stability of formulations was also investigated showing promising results. The results presented in this work show that mesoporous magnesium carbonate represents an interesting type of excipient for oral formulations of APIs with poor aqueous solubility. / <p>Felaktigt ISBN 978-91-554-9702-6 i tryck version.</p>

At the intersection of materials chemistry and biology, biomaterials have been successfully employed in an array of medical applications. From diagnostic tools to targeted drug delivery, the modular physical and chemical properties of these materials provide numerous applications. For example, porous nanoparticles have been widely integrated as vehicles to carry chemotherapeutics to localized tumor sites. By encapsulating these cytotoxic compounds within a porous framework, the commonly associated adverse side effects of conventional chemotherapeutics, such as Doxorubicin, have been greatly reduced. One such material, mesoporous silica, has received widespread attention due to its excellent biocompatibility, high surface area to mass ratio, tunable pore diameters and volumes, and robust surface chemistry. However, recent studies have demonstrated that exposing silica nanoparticles, and other synthetic materials, to biological milieu envelops the particles in layers of proteins and biomolecules. The resulting protein coat, known as the "protein corona", has been shown to have profound effects on bioavailability, cellular targeting, and cytotoxicity. Thus, in order to develop safe and effective particle-based therapies, it is of utmost importance to establish a more thorough understanding of this process. To examine how changes in surface chemistry influence protein adsorption, monodisperse, spherical mesoporous silica nanoparticles, ca. 50 nm, were modified with a variety of surface functionalizations, -NH2, -COOH, and -PEG. Exposing these materials to biological fluid revealed drastically different protein fingerprints, suggesting a strong correlation between the surface chemistry and the identity and composition of the protein corona. Quantification of the protein corona, i.e. mg protein/mg particles, was then achieved by performing thermogravimetric analysis. These values, in concert with spectral counts obtained by shotgun proteomics, illustrates a method for quantifying individual proteins present in the corona. Spherical, silica particles of varying diameters, 70-900 nm, were then synthesized to investigate how particle diameter may affect the biomolecular identity of the protein corona. Applying the previously described methods, it was found that mesoporous particles exhibit a higher affinity for low-molecular weight proteins compared to dense silica particles of similar diameters. Finally, stochastic optical reconstruction microscopy (STORM) was used to map protein adsorption/diffusion throughout as-prepared (pore diameter ~ 30 Å) .and large pore (pore diameter > 60 Å) mesoporous silica particles. By collecting three-dimensional data on the protein-adsorbed materials, a sphere-fitting algorithm could be applied to determine the center and radius of the host particle. This calculation demonstrated that the depth by which specific proteins diffused into the porous framework was a function of both the protein's molecular weight as well as the pore diameter.

Doctor of Philosophy / Department of Chemical Engineering / Keith L. Hohn / The autothermal reforming and partial oxidation of hexadecane via Pt/Ni bimetallic nanoparticles on various ceria-based supports were investigated. Nanoparticles with Pt/Ni molar ratios ranging from 0/100 to 10/90 were loaded on ceria-based supports including cerium oxide, gadolinium-doped cerium oxide and cerium-doped zirconium oxide. The effect of the Pt/Ni molar ratio and the promotional effect of the support were studied by comparing the hydrogen yield. TPR and XPS analysis showed that there was a strong interaction between Ni and the CeO₂-ZrO₂ support, which led to enhancement of catalyst performance when the Pt/Ni ratio was low. The strong interaction between Ni and CeO₂-ZrO₂ support was induced by the formation of a solid solution between NiO and ZrO₂. In the case of bimetallic catalysts loaded on Gd₂O₃-CeO₂, no significant improvement in the catalytic activity of autothermal reforming was achieved until the Pt/Ni ratio reached 10/90. With C-snarf-1 as a pH-sensitive fluorescent probe, the local acidity on the surface of gradient aluminosilicate thin films and in the pore structure of mesoporous silicate films was explored. The single molecule emission ratio (I₅₈₀/I₆₄₀) of C-snarf-1 on the gradient aluminosilicate films showed similar results as previously reported for aluminosilicate mesoporous films. As the Al/Si ratio increases, the emission ratio declines, indicative of increased material acidity. In the case the mesoporous silicate films, much broader distributions of emission ratios were observed and are suggestive of significant heterogeneity in the pore structure of these films. The average emission ratio increased with a rise in pH until pH 6 or 7. A further rise in pH leads to a decline in emission ratio. Molecules with high mobility showed a narrow distribution and slightly lower average emission ratio when compared to data from all detected molecules. This observation implies a reduced heterogeneity for mesopores in which the molecules rapidly diffuse. The narrow distribution and lower average value of emission ratio at low pH, combined with the decrease in emission ratio induced by an increase in ionic strength may further indicate that the interaction between dye molecules and the pore surface impacts the emission ratio of the dye molecules.

L’étude et la compréhension des interactions existantes entre semi-conducteur et nanoparticules métalliques sous irradiation est primordiale pour l’amélioration de leurs performances. Dans cette étude, trois composites oxydes semi-conducteur-métal ont été synthétisés : TiO2-Ag, Fe2O3-Ag et WO3-Ag. La synthèse des films mésoporeux de TiO2, Fe2O3 et WO3 a été effectuée par voie sol gel à l’aide de copolymères à bloc, avec la méthode d’auto-assemblage induit par évaporation (EISA). Les nanoparticules d’argent sont formées dans un deuxième temps par réduction chimique de sels dans la porosité des films. L’étude photo-électrochimique de ces composites a permis de mettre en évidence différents phénomènes : le potentiel d’électroréduction des ions Ag+ dans une matrice de TiO2 mésoporeuse peut être modulé par l’effet de la lumière. Ce phénomène semble résulter d’un effet de passivation des NP Ag par TiO2 qui dépend des conditions d’insolation. Des effets de rechargement de l’électrode poreuse en espèce Ag+ ont aussi été observés, sous l’action simultanée de la chrono-ampérométrie et de l’irradiation / The study and understanding of existing interactions between semiconductor and metal nanoparticles under irradiation is essential for improving their performance. In this study, three semiconductor-metal oxide composites were synthesized: TiO2-Ag, Fe2O3-Ag and WO3-Ag. The synthesis of the mesoporous films of TiO2, Fe2O3 and WO3 was carried out by gel sol method using block copolymers, with the method of self-assembly induced by evaporation (EISA). The silver nanoparticles are formed in a second time by chemical reduction of silver salts in the porosity of the films. The photo-electrochemical study of these composites made it possible to highlight various phenomena: the electroreduction potential of Ag+ ions in a mesoporous TiO2 matrix can be modulated by the effect of light. This phenomenon seems to result from a passivation effect of the NP Ag by TiO2, which depends on the insolation conditions. Charging effects of the porous electrode in Ag+ species have also been observed, under the simultaneous action of chrono-amperometry and irradiation