Leon Payawan - Academia.edu (original) (raw)
Papers by Leon Payawan
Journal of Physical Chemistry A, 1998
Asmp Proceedings of Asian Symposium on Materials and Processing, Nov 8, 2006
J Phys Chem B, 2001
Novel heterogeneous photocatalysts were developed which are able to transfer electrons from excit... more Novel heterogeneous photocatalysts were developed which are able to transfer electrons from excited Ru(II) donors within the zeolite framework to Co(III) acceptor complexes in the exterior. The materials were prepared and characterized by elemental analysis, electrochemical methods, diffuse reflectance, and raster and transmission electron microscopy. The catalysts consist of zeolite Y-encapsulated Ru(bpy) 3 2+ (bpy ) 2,2′bipyridine) sensitizers in close proximity to TiO 2 nanoparticles on the same support. The photophysical properties of Ru(bpy) 3 2+ within the zeolite supercages were investigated at different loadings of Ru(bpy) 3 2+ and TiO 2 . The photoexcited MLCT state of the zeolite-entrapped Ru(bpy) 3 2+ reacts via electron transfer with Co(dpphen) 3 3+ (dpphen ) 4,7-diphenyl-1,10-phenanthroline) in the exterior of the zeolite particles. The relative quenching of Ru(bpy) 3 2+ by external Co(dpphen) 3 3+ increases as the TiO 2 content within the zeolite is increased, where electron transfer from Ru(bpy) 3 2+ complexes within the interior of the zeolite are able to transfer electrons to Co(dpphen) 3 3+ . This observation indicates that electrons can be transported from the interior of the zeolite to the surface in the presence of an appropriate electron relay, such as TiO 2 nanoparticles.
MATEC Web of Conferences, 2015
Self-regulated drug delivery systems (DDS) are potential alternative to the conventional method o... more Self-regulated drug delivery systems (DDS) are potential alternative to the conventional method of introducing insulin to the body due to their controlled drug release mechanism. In this study, Layer-by-Layer technique was utlized to manufacture drug loaded, pH responsive thin films. Insulin was alternated with pH-sensitive, [2-(dimethyl amino) ethyl aminoacrylate] (PDMAEMA) and topped of with polymer/glucose oxidase (GOD) layers. Similarly, films using a different polymer, namely Poly(Acrylic Acid) (PAA) were also fabricated. Exposure of the films to glucose solutions resulted to the production of gluconic acid causing a polymer conformation change due to protonation, thus releasing the embedded insulin. The insulin release was monitored by subjecting the dipping glucose solutions to Bradford Assay. Films exhibited a reversal in drug release profile in the presence of glucose as compared to without glucose. PAA films were also found out to release more insulin compared to that of the PDMAEMA films.The difference in the profile of the two films were due to different polymer-GOD interactions, since both films exhibited almost identical profiles when embedded with Poly(sodium 4-styrenesulfonate) (PSS) instead of GOD.
MATEC Web of Conferences, 2015
Photochemical treatment using ultraviolet radiation was used to prepare fluorescent silver nanopa... more Photochemical treatment using ultraviolet radiation was used to prepare fluorescent silver nanoparticles/nanoclusters from AgNO 3 precursor upon its encapsulation with Poly(Acrylic Acid).
Cozzi/Environmental, 2009
“Ship in a bottle” assemblies of Iridium complexes encapsulated in zeolite Y cages will be synthe... more “Ship in a bottle” assemblies of Iridium complexes encapsulated in zeolite Y cages will be synthesized via a two-step process. These composites will then be tested for their electron transfer property and photocatalytic function when doped with TiO2. Rhodamine B will be employed as a model pollutant and its kinetics of degradation will be monitored via UV-Vis spectrophotometry. Characterization of the synthesized [IrL3]3+/Zeolite Y composites will be done using IR spectroscopy, UV-Vis spectroscopy and SEM-EDX. The absorption and emission spectrum of the [IrL3]3+/Zeolite Y composite both in the solid state and the diffused-state will be evaluated to assess its compatibility with TiO2 in a photocatalytic system. Differential pulse voltammograms of the assembled composite will be used to confirm the encapsulation the Iridium complexes inside the zeolite Y super cages. Molecular modelling and computational methods may also be employed for the assessment of the “ship in a bottle” structu...
Diabetes Mellitus is a chronic condition characterized by high glucose concentration in blood. Th... more Diabetes Mellitus is a chronic condition characterized by high glucose concentration in blood. This is caused by insufficient amount of functional insulin, which is needed by the body to convert glucose into usable energy. Functionalized drug delivery systems (DDS), which are self-regulated, could be a potential alternative to the conventional method of introducing insulin to the body. One advantage of insulin DDS is the controlled release of the drug, which avoids over-dosage and wastage. For the fabrication of the DDS, insulin was incorporated into a layer-by-layer film of pH-sensitive, [2-(dimethyl amino) ethyl aminoacrylate] (PDMAEMA) and glucose oxidase (GOD). Insulin was deposited between the PDMAEMA/GOD bilayers which served as the drug carrier. Exposure of the insulin-PDMAEMA-GOD films to high glucose concentrations results to the production of gluconic acid. Decreasing the pH would cause changes in conformation of the PDMAEMA, as a consequence, releasing the embedded insuli...
Advanced Materials Research, 2015
Adsorption and encapsulation of the nanoparticles in polyelectrolytes impart stability to the nan... more Adsorption and encapsulation of the nanoparticles in polyelectrolytes impart stability to the nanometal by preventing aggregation through electrostatic and steric effects. Poly(acrylic acid) (PAA) was employed as a polymer cap to anatase titania nanoparticles. Cross-linking of the polymer was done via free-radical cross-linking using gamma-irradiation. The size of the nanocomposite produced ranged from 40-120 nm. SEM images showed that excess TiO 2 in solution becomes nucleation sites for aggregation. Film assembly of the synthesized nanocomposite were done by layer-by-layer deposition with PDDA. Films formed with increasing thickness (5, 10, and 15 layers) were analyzed under AFM and shown to have thickness of 0.25 μm, 1.1μm and 3.0 μm respectively. The average film layer thickness obtained ranged from 50-200 nm per TiO 2 /PAA-PDDA layer where as the number of layers deposited increase, the layer thickness increase while the roughness decreases.
Advanced Materials Research, 2015
Layer-by-layer (L-b-L) assembly is a simple method that is useful in immobilizing nanomaterials i... more Layer-by-layer (L-b-L) assembly is a simple method that is useful in immobilizing nanomaterials into thin films. However, the retention of the optical and photogalvanic property of the nanoparticles and the functionalization of these materials are the common issues raised regarding this technique. In this study, L-b-L thin films were prepared from -radiation reduced, silver/poly(acrylic acid) nanocomposites (Ag/PAA). Negatively surface charged nanocomposites were immobilized on different silica surfaces, namely quartz, Indium Tin Oxide-modified glass and ordinary glass. Characterization of the solution and bound form of the nanocomposites were done to evaluate the retention of their novel properties. The size distribution of the solution-phased Ag/PAA was assessed using dynamic light scattering (DLS). The surface morphology, spectroscopic and electronic properties of the multilayer films were characterized using atomic force microscopy (AFM), scanning electron microscopy (SEM), UV-vis spectroscopy, surface plasmon resonance (SPR) and cyclic voltammetry (CV).
Innovations in Chemical Biology, 2009
ABSTRACT The synthetic route followed in the encapsulation of [Ru(bpy)32+ in ZeoliteY is referred... more ABSTRACT The synthetic route followed in the encapsulation of [Ru(bpy)32+ in ZeoliteY is referred to as “ ship-in-a-bottle ” synthesis due to non-extractability of the [Ru(bpy)3]2+ complex, once encapsulation has taken place within the cages of the zeolite Y. Nanoparticles of TiO2 was then introduced through TiCl3 in ethylene glycol mixture under argon, with sintering at 200 ° C. Spectroscopic, surface, and electrochemical characterization confirmed the presence of [Ru(bpy)3]2+ complex within the cages of zeolite Y, and nanoparticles of TiO 2 in its cages. The amount of TiO2 was varied, and the assembly was tested for its photocata-lytic activity using degradation of 2,4-xylidine as test reaction probe. The decrease in the concentration of xylidine and the corresponding increase in oxalate concentration were monitored through HPLC. A pseudo-first order kinetics was observed in the photodegradation process based on the Langmuir-Hinshelwood mechanism. An inverse correlation was observed between the kinetic rate constant and the obtained Light-Induced Optoacoustic Spectroscopy (LIOAS) frequency maxima. Enhanced rate of photodegradation observed with the use of new and efficient photocatalyst such as [Ru(bpy)3]2+TiO2 co-doped Zeolite Y may pave the way for development of large-scale advanced oxidation processes for other pollutant system.
Advanced Materials Research, 2008
... Eduardo R. Magdaluyo, Jr., 1, a , Ian Harvey J. Arellano 2,b , Alvin Karlo G ... 16 (2005), p... more ... Eduardo R. Magdaluyo, Jr., 1, a , Ian Harvey J. Arellano 2,b , Alvin Karlo G ... 16 (2005), p. 2567 [9] N. Mukherjee, P. Bhattacharyya, M. Banerjee, A. Mondal, RTT Gettens, PK Ghosh and H. Saha: Nanotechnology 17 (2006), p. 2665 [10] EC Greyson, Y. Babayan and TW Odom: Adv ...
The Journal of Physical Chemistry B, 2001
Novel heterogeneous photocatalysts were developed which are able to transfer electrons from excit... more Novel heterogeneous photocatalysts were developed which are able to transfer electrons from excited Ru(II) donors within the zeolite framework to Co(III) acceptor complexes in the exterior. The materials were prepared and characterized by elemental analysis, electrochemical methods, diffuse reflectance, and raster and transmission electron microscopy. The catalysts consist of zeolite Y-encapsulated Ru(bpy) 3 2+ (bpy ) 2,2′bipyridine) sensitizers in close proximity to TiO 2 nanoparticles on the same support. The photophysical properties of Ru(bpy) 3 2+ within the zeolite supercages were investigated at different loadings of Ru(bpy) 3 2+ and TiO 2 . The photoexcited MLCT state of the zeolite-entrapped Ru(bpy) 3 2+ reacts via electron transfer with Co(dpphen) 3 3+ (dpphen ) 4,7-diphenyl-1,10-phenanthroline) in the exterior of the zeolite particles. The relative quenching of Ru(bpy) 3 2+ by external Co(dpphen) 3 3+ increases as the TiO 2 content within the zeolite is increased, where electron transfer from Ru(bpy) 3 2+ complexes within the interior of the zeolite are able to transfer electrons to Co(dpphen) 3 3+ . This observation indicates that electrons can be transported from the interior of the zeolite to the surface in the presence of an appropriate electron relay, such as TiO 2 nanoparticles.
The Journal of Physical Chemistry A, 1998
Photochemical & Photobiological Sciences, 2003
A considerably arduous test of a novel class of composite materials consisting of [Ru(bpy) 3 ] 2ϩ... more A considerably arduous test of a novel class of composite materials consisting of [Ru(bpy) 3 ] 2ϩ and TiO 2 codoped zeolites Y is presented here. The [Ru(bpy) 3 ] 2ϩ and TiO 2 codoped zeolites Y served as photocatalysts in the oxidation of the model compounds 2,4-dimethylaniline (2,4-xylidine) by H 2 O 2 in an acidic aqueous medium. Zeolite-embedded TiO 2 (nano)particles play an important role in the degradation mechanism. The first step in this complex mechanism is the photoelectron transfer from photoexcited [Ru(bpy) 3 ] 2ϩ *, located inside the supercage of zeolite Y, to a neighboring TiO 2 nanoparticle. During this electron transfer process, electron injection into the conduction band of TiO 2 is achieved. The second decisive step is the reaction of this electron with H 2 O 2 , which was previously chemisorbed at the surface-region of the TiO 2 nanoparticles. In this reaction, a TiO 2 bound hydroxyl radical (TiO 2 -HO ؒ ) is created. This highly reactive intermediate initiates then the oxidation of 2,4-xylidine, which enters the zeolites framework in its protonated form (Hxyl ϩ ). The formation of 2,4-dimethylphenol as first detectable reaction product indicated that this oxidation proceeds via an electron transfer mechanism. Furthermore, [Ru(bpy) 3 ] 3ϩ , which was created in the initiating photoelectron transfer reaction between [Ru(bpy) 3 ] 2ϩ * and TiO 2 , also takes place in the oxidation of Hxyl ϩ . [Ru(bpy) 3 ] 2ϩ is recycled in that reaction, which also belongs to the group of electron transfer reactions. In addition to the primary steps of this particular Advanced Oxidation Process (AOP), the dependence of the efficiency of the 2,4-xylidine degradation as a function of the [Ru(bpy) 3 ] 2ϩ and TiO 2 loadings of the zeolite Y framework is also reported here. The quenching of [Ru(bpy) 3 ] 2ϩ * by H 2 O 2 as well as the photocatalytic activity of the [Ru(bpy) 3 ] 2ϩ and TiO 2 codoped zeolite Y catalysts both follow a distinct percolation behavior in dependence of their TiO 2 content.
The main objective of this project is to prepare multilayer thin films from nanocomposites of ZnO... more The main objective of this project is to prepare multilayer thin films from nanocomposites of ZnO/Polyacrylic Acid (ZnO/PAA) and Titania/Polyacrylic Acid (TiO2/PAA) that has photogalvanic, photocatalytic and anti-reflective properties. PAA has been selected to control the size of the metal nanoparticles generated by UV-radiation induced free radical-reduction and simultaneously act as stabilizer to prevent particle aggregation. The nanocomposites were immobilized on glass surface using layer-by-layer technique with the polycation poly(diallyldiammonium chloride) (PDDA). The driving force for thin film formation is the electrostatic attraction between the negatively charged polymer shell and PDDA molecules. The surface morphology, spectroscopic, redox and photocatalytic properties of the thin layers will then be evaluated with the view of incorporating functionality to the nanomaterial. The size and shape distribution of nanoparticles in solution and multilayer films was characterize...
Journal of Physical Chemistry A, 1998
Asmp Proceedings of Asian Symposium on Materials and Processing, Nov 8, 2006
J Phys Chem B, 2001
Novel heterogeneous photocatalysts were developed which are able to transfer electrons from excit... more Novel heterogeneous photocatalysts were developed which are able to transfer electrons from excited Ru(II) donors within the zeolite framework to Co(III) acceptor complexes in the exterior. The materials were prepared and characterized by elemental analysis, electrochemical methods, diffuse reflectance, and raster and transmission electron microscopy. The catalysts consist of zeolite Y-encapsulated Ru(bpy) 3 2+ (bpy ) 2,2′bipyridine) sensitizers in close proximity to TiO 2 nanoparticles on the same support. The photophysical properties of Ru(bpy) 3 2+ within the zeolite supercages were investigated at different loadings of Ru(bpy) 3 2+ and TiO 2 . The photoexcited MLCT state of the zeolite-entrapped Ru(bpy) 3 2+ reacts via electron transfer with Co(dpphen) 3 3+ (dpphen ) 4,7-diphenyl-1,10-phenanthroline) in the exterior of the zeolite particles. The relative quenching of Ru(bpy) 3 2+ by external Co(dpphen) 3 3+ increases as the TiO 2 content within the zeolite is increased, where electron transfer from Ru(bpy) 3 2+ complexes within the interior of the zeolite are able to transfer electrons to Co(dpphen) 3 3+ . This observation indicates that electrons can be transported from the interior of the zeolite to the surface in the presence of an appropriate electron relay, such as TiO 2 nanoparticles.
MATEC Web of Conferences, 2015
Self-regulated drug delivery systems (DDS) are potential alternative to the conventional method o... more Self-regulated drug delivery systems (DDS) are potential alternative to the conventional method of introducing insulin to the body due to their controlled drug release mechanism. In this study, Layer-by-Layer technique was utlized to manufacture drug loaded, pH responsive thin films. Insulin was alternated with pH-sensitive, [2-(dimethyl amino) ethyl aminoacrylate] (PDMAEMA) and topped of with polymer/glucose oxidase (GOD) layers. Similarly, films using a different polymer, namely Poly(Acrylic Acid) (PAA) were also fabricated. Exposure of the films to glucose solutions resulted to the production of gluconic acid causing a polymer conformation change due to protonation, thus releasing the embedded insulin. The insulin release was monitored by subjecting the dipping glucose solutions to Bradford Assay. Films exhibited a reversal in drug release profile in the presence of glucose as compared to without glucose. PAA films were also found out to release more insulin compared to that of the PDMAEMA films.The difference in the profile of the two films were due to different polymer-GOD interactions, since both films exhibited almost identical profiles when embedded with Poly(sodium 4-styrenesulfonate) (PSS) instead of GOD.
MATEC Web of Conferences, 2015
Photochemical treatment using ultraviolet radiation was used to prepare fluorescent silver nanopa... more Photochemical treatment using ultraviolet radiation was used to prepare fluorescent silver nanoparticles/nanoclusters from AgNO 3 precursor upon its encapsulation with Poly(Acrylic Acid).
Cozzi/Environmental, 2009
“Ship in a bottle” assemblies of Iridium complexes encapsulated in zeolite Y cages will be synthe... more “Ship in a bottle” assemblies of Iridium complexes encapsulated in zeolite Y cages will be synthesized via a two-step process. These composites will then be tested for their electron transfer property and photocatalytic function when doped with TiO2. Rhodamine B will be employed as a model pollutant and its kinetics of degradation will be monitored via UV-Vis spectrophotometry. Characterization of the synthesized [IrL3]3+/Zeolite Y composites will be done using IR spectroscopy, UV-Vis spectroscopy and SEM-EDX. The absorption and emission spectrum of the [IrL3]3+/Zeolite Y composite both in the solid state and the diffused-state will be evaluated to assess its compatibility with TiO2 in a photocatalytic system. Differential pulse voltammograms of the assembled composite will be used to confirm the encapsulation the Iridium complexes inside the zeolite Y super cages. Molecular modelling and computational methods may also be employed for the assessment of the “ship in a bottle” structu...
Diabetes Mellitus is a chronic condition characterized by high glucose concentration in blood. Th... more Diabetes Mellitus is a chronic condition characterized by high glucose concentration in blood. This is caused by insufficient amount of functional insulin, which is needed by the body to convert glucose into usable energy. Functionalized drug delivery systems (DDS), which are self-regulated, could be a potential alternative to the conventional method of introducing insulin to the body. One advantage of insulin DDS is the controlled release of the drug, which avoids over-dosage and wastage. For the fabrication of the DDS, insulin was incorporated into a layer-by-layer film of pH-sensitive, [2-(dimethyl amino) ethyl aminoacrylate] (PDMAEMA) and glucose oxidase (GOD). Insulin was deposited between the PDMAEMA/GOD bilayers which served as the drug carrier. Exposure of the insulin-PDMAEMA-GOD films to high glucose concentrations results to the production of gluconic acid. Decreasing the pH would cause changes in conformation of the PDMAEMA, as a consequence, releasing the embedded insuli...
Advanced Materials Research, 2015
Adsorption and encapsulation of the nanoparticles in polyelectrolytes impart stability to the nan... more Adsorption and encapsulation of the nanoparticles in polyelectrolytes impart stability to the nanometal by preventing aggregation through electrostatic and steric effects. Poly(acrylic acid) (PAA) was employed as a polymer cap to anatase titania nanoparticles. Cross-linking of the polymer was done via free-radical cross-linking using gamma-irradiation. The size of the nanocomposite produced ranged from 40-120 nm. SEM images showed that excess TiO 2 in solution becomes nucleation sites for aggregation. Film assembly of the synthesized nanocomposite were done by layer-by-layer deposition with PDDA. Films formed with increasing thickness (5, 10, and 15 layers) were analyzed under AFM and shown to have thickness of 0.25 μm, 1.1μm and 3.0 μm respectively. The average film layer thickness obtained ranged from 50-200 nm per TiO 2 /PAA-PDDA layer where as the number of layers deposited increase, the layer thickness increase while the roughness decreases.
Advanced Materials Research, 2015
Layer-by-layer (L-b-L) assembly is a simple method that is useful in immobilizing nanomaterials i... more Layer-by-layer (L-b-L) assembly is a simple method that is useful in immobilizing nanomaterials into thin films. However, the retention of the optical and photogalvanic property of the nanoparticles and the functionalization of these materials are the common issues raised regarding this technique. In this study, L-b-L thin films were prepared from -radiation reduced, silver/poly(acrylic acid) nanocomposites (Ag/PAA). Negatively surface charged nanocomposites were immobilized on different silica surfaces, namely quartz, Indium Tin Oxide-modified glass and ordinary glass. Characterization of the solution and bound form of the nanocomposites were done to evaluate the retention of their novel properties. The size distribution of the solution-phased Ag/PAA was assessed using dynamic light scattering (DLS). The surface morphology, spectroscopic and electronic properties of the multilayer films were characterized using atomic force microscopy (AFM), scanning electron microscopy (SEM), UV-vis spectroscopy, surface plasmon resonance (SPR) and cyclic voltammetry (CV).
Innovations in Chemical Biology, 2009
ABSTRACT The synthetic route followed in the encapsulation of [Ru(bpy)32+ in ZeoliteY is referred... more ABSTRACT The synthetic route followed in the encapsulation of [Ru(bpy)32+ in ZeoliteY is referred to as “ ship-in-a-bottle ” synthesis due to non-extractability of the [Ru(bpy)3]2+ complex, once encapsulation has taken place within the cages of the zeolite Y. Nanoparticles of TiO2 was then introduced through TiCl3 in ethylene glycol mixture under argon, with sintering at 200 ° C. Spectroscopic, surface, and electrochemical characterization confirmed the presence of [Ru(bpy)3]2+ complex within the cages of zeolite Y, and nanoparticles of TiO 2 in its cages. The amount of TiO2 was varied, and the assembly was tested for its photocata-lytic activity using degradation of 2,4-xylidine as test reaction probe. The decrease in the concentration of xylidine and the corresponding increase in oxalate concentration were monitored through HPLC. A pseudo-first order kinetics was observed in the photodegradation process based on the Langmuir-Hinshelwood mechanism. An inverse correlation was observed between the kinetic rate constant and the obtained Light-Induced Optoacoustic Spectroscopy (LIOAS) frequency maxima. Enhanced rate of photodegradation observed with the use of new and efficient photocatalyst such as [Ru(bpy)3]2+TiO2 co-doped Zeolite Y may pave the way for development of large-scale advanced oxidation processes for other pollutant system.
Advanced Materials Research, 2008
... Eduardo R. Magdaluyo, Jr., 1, a , Ian Harvey J. Arellano 2,b , Alvin Karlo G ... 16 (2005), p... more ... Eduardo R. Magdaluyo, Jr., 1, a , Ian Harvey J. Arellano 2,b , Alvin Karlo G ... 16 (2005), p. 2567 [9] N. Mukherjee, P. Bhattacharyya, M. Banerjee, A. Mondal, RTT Gettens, PK Ghosh and H. Saha: Nanotechnology 17 (2006), p. 2665 [10] EC Greyson, Y. Babayan and TW Odom: Adv ...
The Journal of Physical Chemistry B, 2001
Novel heterogeneous photocatalysts were developed which are able to transfer electrons from excit... more Novel heterogeneous photocatalysts were developed which are able to transfer electrons from excited Ru(II) donors within the zeolite framework to Co(III) acceptor complexes in the exterior. The materials were prepared and characterized by elemental analysis, electrochemical methods, diffuse reflectance, and raster and transmission electron microscopy. The catalysts consist of zeolite Y-encapsulated Ru(bpy) 3 2+ (bpy ) 2,2′bipyridine) sensitizers in close proximity to TiO 2 nanoparticles on the same support. The photophysical properties of Ru(bpy) 3 2+ within the zeolite supercages were investigated at different loadings of Ru(bpy) 3 2+ and TiO 2 . The photoexcited MLCT state of the zeolite-entrapped Ru(bpy) 3 2+ reacts via electron transfer with Co(dpphen) 3 3+ (dpphen ) 4,7-diphenyl-1,10-phenanthroline) in the exterior of the zeolite particles. The relative quenching of Ru(bpy) 3 2+ by external Co(dpphen) 3 3+ increases as the TiO 2 content within the zeolite is increased, where electron transfer from Ru(bpy) 3 2+ complexes within the interior of the zeolite are able to transfer electrons to Co(dpphen) 3 3+ . This observation indicates that electrons can be transported from the interior of the zeolite to the surface in the presence of an appropriate electron relay, such as TiO 2 nanoparticles.
The Journal of Physical Chemistry A, 1998
Photochemical & Photobiological Sciences, 2003
A considerably arduous test of a novel class of composite materials consisting of [Ru(bpy) 3 ] 2ϩ... more A considerably arduous test of a novel class of composite materials consisting of [Ru(bpy) 3 ] 2ϩ and TiO 2 codoped zeolites Y is presented here. The [Ru(bpy) 3 ] 2ϩ and TiO 2 codoped zeolites Y served as photocatalysts in the oxidation of the model compounds 2,4-dimethylaniline (2,4-xylidine) by H 2 O 2 in an acidic aqueous medium. Zeolite-embedded TiO 2 (nano)particles play an important role in the degradation mechanism. The first step in this complex mechanism is the photoelectron transfer from photoexcited [Ru(bpy) 3 ] 2ϩ *, located inside the supercage of zeolite Y, to a neighboring TiO 2 nanoparticle. During this electron transfer process, electron injection into the conduction band of TiO 2 is achieved. The second decisive step is the reaction of this electron with H 2 O 2 , which was previously chemisorbed at the surface-region of the TiO 2 nanoparticles. In this reaction, a TiO 2 bound hydroxyl radical (TiO 2 -HO ؒ ) is created. This highly reactive intermediate initiates then the oxidation of 2,4-xylidine, which enters the zeolites framework in its protonated form (Hxyl ϩ ). The formation of 2,4-dimethylphenol as first detectable reaction product indicated that this oxidation proceeds via an electron transfer mechanism. Furthermore, [Ru(bpy) 3 ] 3ϩ , which was created in the initiating photoelectron transfer reaction between [Ru(bpy) 3 ] 2ϩ * and TiO 2 , also takes place in the oxidation of Hxyl ϩ . [Ru(bpy) 3 ] 2ϩ is recycled in that reaction, which also belongs to the group of electron transfer reactions. In addition to the primary steps of this particular Advanced Oxidation Process (AOP), the dependence of the efficiency of the 2,4-xylidine degradation as a function of the [Ru(bpy) 3 ] 2ϩ and TiO 2 loadings of the zeolite Y framework is also reported here. The quenching of [Ru(bpy) 3 ] 2ϩ * by H 2 O 2 as well as the photocatalytic activity of the [Ru(bpy) 3 ] 2ϩ and TiO 2 codoped zeolite Y catalysts both follow a distinct percolation behavior in dependence of their TiO 2 content.
The main objective of this project is to prepare multilayer thin films from nanocomposites of ZnO... more The main objective of this project is to prepare multilayer thin films from nanocomposites of ZnO/Polyacrylic Acid (ZnO/PAA) and Titania/Polyacrylic Acid (TiO2/PAA) that has photogalvanic, photocatalytic and anti-reflective properties. PAA has been selected to control the size of the metal nanoparticles generated by UV-radiation induced free radical-reduction and simultaneously act as stabilizer to prevent particle aggregation. The nanocomposites were immobilized on glass surface using layer-by-layer technique with the polycation poly(diallyldiammonium chloride) (PDDA). The driving force for thin film formation is the electrostatic attraction between the negatively charged polymer shell and PDDA molecules. The surface morphology, spectroscopic, redox and photocatalytic properties of the thin layers will then be evaluated with the view of incorporating functionality to the nanomaterial. The size and shape distribution of nanoparticles in solution and multilayer films was characterize...