Nenhuma / Tem sido demonstrado que as propriedades eletrônicas e ópticas de nanotubos de paredes simples (SWNT) sofrem grande influência do ambiente químico externo. O estudo deste efeito é de grande relevância tanto para o entendimento da estrutura eletrônica de cada nanotubo, quanto para a determinação da concentração de diferentes SWNTs em uma amostra, especialmente nos estudos de separação por tipo, onde o ambiente químico antes e após o processo de separação muda drasticamente. Visando contribuir neste tema, o presente trabalho teve como objetivo estudar os efeitos de diferentes ambientes químicos nos fenômenos de absorção e emissão de luz por SWNTs dispersos em água na forma de tubos individuais. O estudo foi conduzido com nanotubos de pequeno diâmetro produzidos pelo processo comercial HiPco (diâmetros entre 0,7 e 1,2 nm), os quais foram dispersos em soluções aquosas de diferentes agentes dispersantes: i) surfactantes aniônicos dodecilsulfato de sódio (SDS), dodecilbenzenosulfanato de sódio (NaDDBS), colato de sódio (NaC); ii) um oligonucleotídeo de DNA do tipo poli d(GT)10. Algumas dispersões foram preparadas em com diferentes concentrações de SWNTs e agente dispersante. A dispersabilidade dos SWNTs em água for estudada, avaliando-se as propriedades ópticas dos tubos e feixes dispersos nos diferentes ambientes químicos por meio das técnicas de espectroscopia de absorção óptica na região do UV-vis-NIR (AO), fotoluminescência (PL) e fotoexcitação de luminescência (PLE) (photoluminescence excitation spectroscopy). Os valores de energia para os processos de absorção e emissão para os SWNTs nos quatro ambientes químicos estudados foram extraídos dos mapas de PLE e dos dados de absorção óptica. Não foram vistos deslocamentos entre as posições das Eii para os SWNTs dispersos com os três surfactantes aniônicos (SDS, NAC e NaDDBS), indicando que estas substâncias propiciam uma vizinhança química para os tubos bastante semelhante. O mesmo não ocorreu na presença de DNA, onde os valores de Eii para os diferentes SWNTs presentes na amostra, apresentaram um deslocamento batocrômico (para menores energias) de ~ 20 meV em relação aos valores observados para os surfactantes aniônicos. Este deslocamento foi atribuído ao arranjo helicoidal da molécula de DNA em torno do tubo, que expõe a superfície, permitindo maior acesso das moléculas de água e acarretando no aumento da constante dielétrica efetiva nas vicissitudes dos tubos. Foi também investigada a influência do tipo e concentração de agente dispersante, e concentração de SWNT na eficiência de emissão de luz pelos nanotubos suspensos. Neste estudo, a combinação das técnicas de absorção óptica e PLE se mostrou muito útil na investigação do processo de dispersão dos nanotubos. Baseando-se no fato de que o processo de emissão de luz em nanotubos de carbono é altamente sensível ao estado de agregação devido ao efeito de quenching que ocorre quando os SWNTs semicondutores ficam em contato com SWNTs metálicos, enquanto o processo de absorção de luz é pouco afetado, a análise da razão das intensidades dos sinais de PLE e de absorção óptica mostrou ser uma ferramenta poderosa para avaliar a extensão da desagregação dos SWNTs colocados em suspensão. Desta forma, foi possível determinar as melhores condições para maximizar a emissão de luz das dispersões aqui estudadas. Foi verificado que nas condições experimentais usadas, a concentração de SWNTs em solução aumenta na seqüência NaDDBS < NaC < DNA < SDS. Entretanto, embora NaDDBS e NaC produzam dispersões mais diluídas, observou-se pela análise da razão entre os sinais de PL e absorção óptica que a concentração de tubos individuais nestes sistemas é bem maior. Nas dispersões com SDS e o oligonucleotídeo DNA, muitos tubos apresentam-se agregados, provavelmente na forma de feixes estreitos, diminuindo consideravelmente a eficiência de emissão de luz. / It has been demonstrated that the electronic and optical properties of single-wall carbon nanotubes (SWNT) are strongly affected by the environment. This strong environmental effect is very relevant in analyzing the composition of carbon nanotube samples using optical techniques, especially in the case of separation experiments, where the SWNT environments are generally very different before and after the separation process. In this context, this work aimed at studying the effects of different surrounding materials on the absorption and emission of light by the individualized SWNT suspended in water. The study was carried out with small-diameter HiPco SWNT (with diameters between 0.7 and 1.2 nm) which were dispersed in aqueous solutions of different dispersing agents: i) anionic surfactants sodium dodecyl sulfate (SDS), sodium dodecyl benzene sulfonate (NaDDBS) and sodium cholate (NaC); ii) DNA oligonucleotide poly d(GT)10. Samples were prepared with different concentrations of SWNT and surfactants and were analyzed by UV-vis-NIR optical absorption (OA), photoluminescence (PL) and photoluminescence excitation (PLE) spectroscopies. The energies of the emission and absorption peaks for the samples in the four different environments were obtained from PL maps and OA data. The optical transition energies for the nanotubes wrapped by the three surfactants (SDS, NaC and NaDDBS) present basically the same values, thereby indicating that the nanotubes experience a very similar chemical environment. On the other hand, the optical transition energies for DNA-wrapped nanotubes are redshifted by ~ 20 meV as compared to the surfactant-wrapped ones. This shift was associated to the change of dielectric environment because a smaller nanotube coverage by the DNA molecule as compared with those caused by the anionic surfactants. The surfactant molecules cover most of the nanotube surface while the DNA coverage is guided by the self-organization of DNA macromolecule around the nanotube in a helical conformation. The higher exposure of the nanotube surface to the water molecules in DNA system is responsible for the increase in the effective dielectric constant and, consequently, for the redshift in the optical transition energies due to excitonic effects. We have also focused our attention on the role played by the type of surfactant, surfactant concentration, and SWNT concentration on the efficiency of the emission of light by the suspended nanotubes. Based on the fact that the OA intensity is proportional to the concentration of nanotubes in the solution, while the PL signal is quenched when SWNT are aggregated into bundles, it was demonstrated in this work that the ratio between PL and OA intensities gives comparative information on emission efficiency. The PL/OA ratio can be associated, as a first approximation, with the relative amount of isolated nanotubes in the solution, since a nanotube dispersion which presents a high isolated/bundle ratio is expected to maximize the light emission efficiency. SWNT and surfactant concentrations are strongly related to the emission efficiency since different aggregation states are obtained when different concentrations of SWNT and surfactant are used for dispersing SWNT in water. Using this approach, it was possible to determine the best conditions to improve the PL efficiency of SWNT dispersions here investigated. Experimental results have shown that the SWNT concentration follows the sequence: NaDDBS < NaC < DNA < SDS. However, even though NaDDBS and NaC led to dispersions with the lowest net SWNT concentrations, the PL/absorption ratio analysis showed they are the best dispersing agents to obtain the highest concentrations of individually SWNT using the dispersion procedure performed in this work. In DNA and SDS dispersion, most of the SWNT are in the form of ropes or bundles, decreasing the efficiency of light emission.

The interaction of materials with biological systems is of critical importance to a vast number of applications from medical implants, tissue engineering scaffolds, blood-contacting devices, cell-culture products, as well as many other products in industries as diverse as agriculture. This thesis describes a method for the modification of biomaterial surfaces and the generation of tissue engineering scaffolds that utilises the self assembly of poly (styrene)-block-poly (ethylene oxide) (PS-PEO) block copolymers. Block copolymers consist of alternating segments of two or more chemically distinct polymers. The salient feature of these materials is their ability to self organise into a wide range of micro-phase separated structures generating patterned surfaces that have domain sizes in the order of 10-100nm. Further, it is also possible to specifically functionalise only one segment of the block copolymer, providing a means to precisely locate specific biological signals within the 10-100nm domains of a nano-patterned surface, formed via the programmed micro-phase separation of the block copolymer system. The density and spatial location of signalling molecules can be controlled by altering several variables, such as block length, block asymmetry, as well as processing parameters, providing the potential to authentically emulate the cellular micro to nano-environment and thus greatly improving on existing biomaterial and tissue engineering technologies. This thesis achieved several aims as outlined below; Developed methods to control the self-assembly of PS-PEO block copolymers and generate nano-patterned surfaces and scaffolds with utility for biomaterials applications. PS-PEO diblock copolymers were blended with polystyrene (PS) homopolymer and spin cast, resulting in the rapid self-assembly of vertically oriented PEO cylinders in a matrix of PS. Due to the kinetically constrained phase-separation of the system, increasing addition of homopolymer is shown to reduce the diameter of the PEO domains. This outcome provides a simple method that requires the adjustment of a single variable to tune the size of vertically oriented PEO domains between 10-100nm. Polymeric scaffolds for tissue engineering were manufactured via a method that combines macro-scale temperature induced phase separation with micro-phase separation of block copolymers. The phase behaviour of these polymer-solvent systems is described, and potential mechanisms leading to this spectacular structure formation are presented. The result is highly porous scaffolds with surfaces comprised of nano-scale self-assembled block copolymer domains, representing a significant advance in currently available technologies. Characterised the properties of these unique nano-structured materials as well as their interaction with proteinaceous fluids and cells. Nano-patterned PS-PEO self-assembled surfaces showed a significant reduction in protein adsorption compared to control PS surfaces. The adhesion of NIH 3T3 fibroblast cells was shown to be significantly affected by the surface coverage of PEO nano-domains formed by copolymer self-assembly. These nano-islands, when presented at high number density (almost 1000 domains per square micron), were shown to completely prevent cellular attachment, even though small amounts of protein were able to bind to the surface. In order to understand the mechanism by which these surfaces resisted protein and cellular adsorption we utilised neutron reflection to study their solvation and swelling properties. The results indicate that the PEO domains are highly solvated in water; however, the PEO chains do not extend into the solvent but remain in their isolated domains. The data supports growing evidence that the key mechanism by which PEO prevents protein adsorption is the blocking of protein adsorption sites. Control the nano-scale presentation of cellular adhesion and other biological molecules via the self-assembly of functionalised PS-PEO block copolymers Precise control over the nano-scale presentation of adhesion molecules and other biological factors represents a new frontier for biomaterials science. Recently, the control of integrin spacing and cellular shape has been shown to affect fundamental biological processes, including differentiation and apoptosis. We present the self-assembly of maleimide functionalised PS-PEO copolymers as a simple, yet highly precise method for controlling the position of cellular adhesion molecules. By controlling the phase separation of the functional PS-PEO block copolymer we alter the nano-scale (on PEO islands of 8-14 nm in size) presentation of the adhesion peptide, GRGDS, decreasing lateral spacing from 62 nm to 44 nm and increasing the number density from ~ 450 to ~ 900 islands per um2. The results indicate that the spreading of NIH-3T3 fibroblasts increases as the spacing between islands of RGD binding peptides decreases. Further, the same functional PS-PEO surfaces were utilised to immobilise poly-histidine tagged proteins and ECM fragments. The technologies developed in this thesis aim to improve on several weaknesses of existing biomaterials, in particular, directing cellular behaviour on surfaces, and within tissue engineering scaffolds, but also, on the prevention of fouling of biomaterials via non-specific protein adsorption. The application of block copolymer self-assembly for biomaterial and tissue engineering systems described in this thesis has great potential as a platform technology for the investigation of fundamental cell-surface and protein-surface interactions as well as for use in existing and emerging biomedical applications.

The interaction of materials with biological systems is of critical importance to a vast number of applications from medical implants, tissue engineering scaffolds, blood-contacting devices, cell-culture products, as well as many other products in industries as diverse as agriculture. This thesis describes a method for the modification of biomaterial surfaces and the generation of tissue engineering scaffolds that utilises the self assembly of poly (styrene)-block-poly (ethylene oxide) (PS-PEO) block copolymers. Block copolymers consist of alternating segments of two or more chemically distinct polymers. The salient feature of these materials is their ability to self organise into a wide range of micro-phase separated structures generating patterned surfaces that have domain sizes in the order of 10-100nm. Further, it is also possible to specifically functionalise only one segment of the block copolymer, providing a means to precisely locate specific biological signals within the 10-100nm domains of a nano-patterned surface, formed via the programmed micro-phase separation of the block copolymer system. The density and spatial location of signalling molecules can be controlled by altering several variables, such as block length, block asymmetry, as well as processing parameters, providing the potential to authentically emulate the cellular micro to nano-environment and thus greatly improving on existing biomaterial and tissue engineering technologies. This thesis achieved several aims as outlined below; Developed methods to control the self-assembly of PS-PEO block copolymers and generate nano-patterned surfaces and scaffolds with utility for biomaterials applications. PS-PEO diblock copolymers were blended with polystyrene (PS) homopolymer and spin cast, resulting in the rapid self-assembly of vertically oriented PEO cylinders in a matrix of PS. Due to the kinetically constrained phase-separation of the system, increasing addition of homopolymer is shown to reduce the diameter of the PEO domains. This outcome provides a simple method that requires the adjustment of a single variable to tune the size of vertically oriented PEO domains between 10-100nm. Polymeric scaffolds for tissue engineering were manufactured via a method that combines macro-scale temperature induced phase separation with micro-phase separation of block copolymers. The phase behaviour of these polymer-solvent systems is described, and potential mechanisms leading to this spectacular structure formation are presented. The result is highly porous scaffolds with surfaces comprised of nano-scale self-assembled block copolymer domains, representing a significant advance in currently available technologies. Characterised the properties of these unique nano-structured materials as well as their interaction with proteinaceous fluids and cells. Nano-patterned PS-PEO self-assembled surfaces showed a significant reduction in protein adsorption compared to control PS surfaces. The adhesion of NIH 3T3 fibroblast cells was shown to be significantly affected by the surface coverage of PEO nano-domains formed by copolymer self-assembly. These nano-islands, when presented at high number density (almost 1000 domains per square micron), were shown to completely prevent cellular attachment, even though small amounts of protein were able to bind to the surface. In order to understand the mechanism by which these surfaces resisted protein and cellular adsorption we utilised neutron reflection to study their solvation and swelling properties. The results indicate that the PEO domains are highly solvated in water; however, the PEO chains do not extend into the solvent but remain in their isolated domains. The data supports growing evidence that the key mechanism by which PEO prevents protein adsorption is the blocking of protein adsorption sites. Control the nano-scale presentation of cellular adhesion and other biological molecules via the self-assembly of functionalised PS-PEO block copolymers Precise control over the nano-scale presentation of adhesion molecules and other biological factors represents a new frontier for biomaterials science. Recently, the control of integrin spacing and cellular shape has been shown to affect fundamental biological processes, including differentiation and apoptosis. We present the self-assembly of maleimide functionalised PS-PEO copolymers as a simple, yet highly precise method for controlling the position of cellular adhesion molecules. By controlling the phase separation of the functional PS-PEO block copolymer we alter the nano-scale (on PEO islands of 8-14 nm in size) presentation of the adhesion peptide, GRGDS, decreasing lateral spacing from 62 nm to 44 nm and increasing the number density from ~ 450 to ~ 900 islands per um2. The results indicate that the spreading of NIH-3T3 fibroblasts increases as the spacing between islands of RGD binding peptides decreases. Further, the same functional PS-PEO surfaces were utilised to immobilise poly-histidine tagged proteins and ECM fragments. The technologies developed in this thesis aim to improve on several weaknesses of existing biomaterials, in particular, directing cellular behaviour on surfaces, and within tissue engineering scaffolds, but also, on the prevention of fouling of biomaterials via non-specific protein adsorption. The application of block copolymer self-assembly for biomaterial and tissue engineering systems described in this thesis has great potential as a platform technology for the investigation of fundamental cell-surface and protein-surface interactions as well as for use in existing and emerging biomedical applications.

The interaction of materials with biological systems is of critical importance to a vast number of applications from medical implants, tissue engineering scaffolds, blood-contacting devices, cell-culture products, as well as many other products in industries as diverse as agriculture. This thesis describes a method for the modification of biomaterial surfaces and the generation of tissue engineering scaffolds that utilises the self assembly of poly (styrene)-block-poly (ethylene oxide) (PS-PEO) block copolymers. Block copolymers consist of alternating segments of two or more chemically distinct polymers. The salient feature of these materials is their ability to self organise into a wide range of micro-phase separated structures generating patterned surfaces that have domain sizes in the order of 10-100nm. Further, it is also possible to specifically functionalise only one segment of the block copolymer, providing a means to precisely locate specific biological signals within the 10-100nm domains of a nano-patterned surface, formed via the programmed micro-phase separation of the block copolymer system. The density and spatial location of signalling molecules can be controlled by altering several variables, such as block length, block asymmetry, as well as processing parameters, providing the potential to authentically emulate the cellular micro to nano-environment and thus greatly improving on existing biomaterial and tissue engineering technologies. This thesis achieved several aims as outlined below; Developed methods to control the self-assembly of PS-PEO block copolymers and generate nano-patterned surfaces and scaffolds with utility for biomaterials applications. PS-PEO diblock copolymers were blended with polystyrene (PS) homopolymer and spin cast, resulting in the rapid self-assembly of vertically oriented PEO cylinders in a matrix of PS. Due to the kinetically constrained phase-separation of the system, increasing addition of homopolymer is shown to reduce the diameter of the PEO domains. This outcome provides a simple method that requires the adjustment of a single variable to tune the size of vertically oriented PEO domains between 10-100nm. Polymeric scaffolds for tissue engineering were manufactured via a method that combines macro-scale temperature induced phase separation with micro-phase separation of block copolymers. The phase behaviour of these polymer-solvent systems is described, and potential mechanisms leading to this spectacular structure formation are presented. The result is highly porous scaffolds with surfaces comprised of nano-scale self-assembled block copolymer domains, representing a significant advance in currently available technologies. Characterised the properties of these unique nano-structured materials as well as their interaction with proteinaceous fluids and cells. Nano-patterned PS-PEO self-assembled surfaces showed a significant reduction in protein adsorption compared to control PS surfaces. The adhesion of NIH 3T3 fibroblast cells was shown to be significantly affected by the surface coverage of PEO nano-domains formed by copolymer self-assembly. These nano-islands, when presented at high number density (almost 1000 domains per square micron), were shown to completely prevent cellular attachment, even though small amounts of protein were able to bind to the surface. In order to understand the mechanism by which these surfaces resisted protein and cellular adsorption we utilised neutron reflection to study their solvation and swelling properties. The results indicate that the PEO domains are highly solvated in water; however, the PEO chains do not extend into the solvent but remain in their isolated domains. The data supports growing evidence that the key mechanism by which PEO prevents protein adsorption is the blocking of protein adsorption sites. Control the nano-scale presentation of cellular adhesion and other biological molecules via the self-assembly of functionalised PS-PEO block copolymers Precise control over the nano-scale presentation of adhesion molecules and other biological factors represents a new frontier for biomaterials science. Recently, the control of integrin spacing and cellular shape has been shown to affect fundamental biological processes, including differentiation and apoptosis. We present the self-assembly of maleimide functionalised PS-PEO copolymers as a simple, yet highly precise method for controlling the position of cellular adhesion molecules. By controlling the phase separation of the functional PS-PEO block copolymer we alter the nano-scale (on PEO islands of 8-14 nm in size) presentation of the adhesion peptide, GRGDS, decreasing lateral spacing from 62 nm to 44 nm and increasing the number density from ~ 450 to ~ 900 islands per um2. The results indicate that the spreading of NIH-3T3 fibroblasts increases as the spacing between islands of RGD binding peptides decreases. Further, the same functional PS-PEO surfaces were utilised to immobilise poly-histidine tagged proteins and ECM fragments. The technologies developed in this thesis aim to improve on several weaknesses of existing biomaterials, in particular, directing cellular behaviour on surfaces, and within tissue engineering scaffolds, but also, on the prevention of fouling of biomaterials via non-specific protein adsorption. The application of block copolymer self-assembly for biomaterial and tissue engineering systems described in this thesis has great potential as a platform technology for the investigation of fundamental cell-surface and protein-surface interactions as well as for use in existing and emerging biomedical applications.

The interaction of materials with biological systems is of critical importance to a vast number of applications from medical implants, tissue engineering scaffolds, blood-contacting devices, cell-culture products, as well as many other products in industries as diverse as agriculture. This thesis describes a method for the modification of biomaterial surfaces and the generation of tissue engineering scaffolds that utilises the self assembly of poly (styrene)-block-poly (ethylene oxide) (PS-PEO) block copolymers. Block copolymers consist of alternating segments of two or more chemically distinct polymers. The salient feature of these materials is their ability to self organise into a wide range of micro-phase separated structures generating patterned surfaces that have domain sizes in the order of 10-100nm. Further, it is also possible to specifically functionalise only one segment of the block copolymer, providing a means to precisely locate specific biological signals within the 10-100nm domains of a nano-patterned surface, formed via the programmed micro-phase separation of the block copolymer system. The density and spatial location of signalling molecules can be controlled by altering several variables, such as block length, block asymmetry, as well as processing parameters, providing the potential to authentically emulate the cellular micro to nano-environment and thus greatly improving on existing biomaterial and tissue engineering technologies. This thesis achieved several aims as outlined below; Developed methods to control the self-assembly of PS-PEO block copolymers and generate nano-patterned surfaces and scaffolds with utility for biomaterials applications. PS-PEO diblock copolymers were blended with polystyrene (PS) homopolymer and spin cast, resulting in the rapid self-assembly of vertically oriented PEO cylinders in a matrix of PS. Due to the kinetically constrained phase-separation of the system, increasing addition of homopolymer is shown to reduce the diameter of the PEO domains. This outcome provides a simple method that requires the adjustment of a single variable to tune the size of vertically oriented PEO domains between 10-100nm. Polymeric scaffolds for tissue engineering were manufactured via a method that combines macro-scale temperature induced phase separation with micro-phase separation of block copolymers. The phase behaviour of these polymer-solvent systems is described, and potential mechanisms leading to this spectacular structure formation are presented. The result is highly porous scaffolds with surfaces comprised of nano-scale self-assembled block copolymer domains, representing a significant advance in currently available technologies. Characterised the properties of these unique nano-structured materials as well as their interaction with proteinaceous fluids and cells. Nano-patterned PS-PEO self-assembled surfaces showed a significant reduction in protein adsorption compared to control PS surfaces. The adhesion of NIH 3T3 fibroblast cells was shown to be significantly affected by the surface coverage of PEO nano-domains formed by copolymer self-assembly. These nano-islands, when presented at high number density (almost 1000 domains per square micron), were shown to completely prevent cellular attachment, even though small amounts of protein were able to bind to the surface. In order to understand the mechanism by which these surfaces resisted protein and cellular adsorption we utilised neutron reflection to study their solvation and swelling properties. The results indicate that the PEO domains are highly solvated in water; however, the PEO chains do not extend into the solvent but remain in their isolated domains. The data supports growing evidence that the key mechanism by which PEO prevents protein adsorption is the blocking of protein adsorption sites. Control the nano-scale presentation of cellular adhesion and other biological molecules via the self-assembly of functionalised PS-PEO block copolymers Precise control over the nano-scale presentation of adhesion molecules and other biological factors represents a new frontier for biomaterials science. Recently, the control of integrin spacing and cellular shape has been shown to affect fundamental biological processes, including differentiation and apoptosis. We present the self-assembly of maleimide functionalised PS-PEO copolymers as a simple, yet highly precise method for controlling the position of cellular adhesion molecules. By controlling the phase separation of the functional PS-PEO block copolymer we alter the nano-scale (on PEO islands of 8-14 nm in size) presentation of the adhesion peptide, GRGDS, decreasing lateral spacing from 62 nm to 44 nm and increasing the number density from ~ 450 to ~ 900 islands per um2. The results indicate that the spreading of NIH-3T3 fibroblasts increases as the spacing between islands of RGD binding peptides decreases. Further, the same functional PS-PEO surfaces were utilised to immobilise poly-histidine tagged proteins and ECM fragments. The technologies developed in this thesis aim to improve on several weaknesses of existing biomaterials, in particular, directing cellular behaviour on surfaces, and within tissue engineering scaffolds, but also, on the prevention of fouling of biomaterials via non-specific protein adsorption. The application of block copolymer self-assembly for biomaterial and tissue engineering systems described in this thesis has great potential as a platform technology for the investigation of fundamental cell-surface and protein-surface interactions as well as for use in existing and emerging biomedical applications.

The confluence of intriguing size and morphology dependent optical and chemical properties with versatile application in various fields, such as energetic and magnetic makes monometallic nonmaterial of high fundamental scientific interest. However, the challenge that needs to be addressed is to achieve their synthesis with a rational control on their dimensions, morphology and dispersion for the widespread applications of these materials. In addition to synthesis, achieving long-lasting stability of nonmaterial becomes imperative in order to realize their potential applications. Miniaturization in size of particles results in an increased surface to volume ratio, conducing especially reactive metal nanoparticals prone to oxidation. This thesis describes the synthesis of nearly monodiperse colloids of metallic and intermetallic nanoparticles using solvated metal atom dispersion method and digestive ripening facilitated interatomic diffusion process. Our aim is to understand the combinatiorial effects of nanosizing and stability on the functional properties of these nanomaterials. Towards this Direction, we investigated Co, A1 and Mg monometallic, and Au/Ag-In and Au-Sn intermetallic nanoparticle systems. Chapter 2 Describes the synthesis, detailed characterizations and magnetic properties of nearly monodisperse cobolt nanoparticles(<5nm) synthesized using a hydride synthetic protocol, solvated metal atom diserion method. The as-prepared cobalt nanoparticles in this size range exhibit intrinsic instability towards Oxidations. After 30 day of exposure to air, magnetic measurements showed drastic degration in saturation magnetization and complete conversion to antiferromagnetic cobalt oxide was confirmed. In order to achieve their stability, a heat treatment was applied to decompose the organic solvent and capping agent, resulting in carbonization of solvent/ligand around the surface of cobolt nano particles. Controlled and optimized annealing at different temperatures resulted in the formation of hexagonal closed packed (hcp) and fape-centered cubic (fcc) phases of metallic cobalt. Remarkably, the corresponding heat treated samples retained their rich magnetic behavior even after exposure to air for a duration of one year. Compared to un-annealed samples, magnetization values increased two-fold and the corecivity of nanoparticles exhibited strong dependence on the phase transformation of cobolt. Chapter 3 Deal with an exploratory study of the synthesis, characterization, and stabilization of nanometer-sized enegetic material, aluminum. Highly monodisperse colloidal aluminum nanoparticles (3.1‡ 0.6 mm) were prepared by using hexadecy amine (HAD) as the capping agent tetrahydrofurma as a coordinating solvent in the SMAD method. Since such small particles are highly prone to oxidation, a support materials is required for their stabilization. Stability has been achived by carbonization of the capping agent on the surface of A1 nanoparticles by carrying out thermal treatment of A1-HAD nanoparticles at a modest temperature. Presence of corbon was confirmed using Raman spectroscopy and TEM measurements evidencing that annealed A1 nanoparticles are encapsulated in a corbon matrix. The exhibition of robust stability was established using thermal analysis (TGA/DTA) wherein, oxidation of aluminum in air did not occur upto 500 0C. Indirectly, the successful passivation was further exploited in the synthesis and characterization of small sized monodisperse magnesium nanoparticles. The resulting samples were hybrided and nanosized MgH2 released hydrogen at much lower temperature than that of the bulk MgH2 (573 K). The observed hydrogen release was only partially reversible. This partial reversibility could be attributed to the coalescence of small sized Mg nanoparticles upon subsequent charging/discharging hydrogen cycles. In the next step, we exploed the intermetallic systes which are composed of more than one metallic species. Chapter 4 describes the synthesis and characterization of small sized, monodisperse (<10 nm) colloidal AuIn2 and Ag3In intermetallic nanoparticles. The formation of intermetallic nanoparticles could be explained by invoking digestive ripening facilitated atomic diffusion of Au/Ag and In nanoparticles followed simultaneously by their growth in te solution. The course of the reaction was followed using optical spectroscopy where the changes in UV-visible absorption band were correlated to the formation of AuIn/Ag3In intermetallic. Structural characterization, Performed using powder X-ray diffraction, brought out the formation of phase pure AuIn2 and Ag3In intermetallic compounds. Digestive ripening effects were clearly observed using transmission electron microscopy which showed the transformation of polydisperse physical mixture colloid of nanometallic species to uniform sized intermetallic nanoparticles. By invoking the phenomenon of interatomic diffusion at nanoscale favored by feasible thermodynamics ( G being negative) we were successful inrealizing the formation of these intermetallic nanoparticles. Optimization of temperature at which digestive ripening was performed, turned out to be a crucial factor in the successful synthesis of phase pure intermetallic nanoparticles. These promising results inspired us to study further the preparation of Au-Sn intermetallic system which is described in Chapter 5. The potential of such an unprecedented approach has been exploited in the synthesis of homogeneous intermetallic nanaocrystals of Au5Sn and AuSn. The two monometallic collids (Au and Sn), mixed in a stoichiometric amount were subjected to digestive ripening process. 1:1 stichiometry always led to the formation of eutectic mixture (Au5Sn and AUSn), The stoichiometry of monometallic nanocrystals. Therefore, by taking an extra equivalent of Au and Sn in two different experiments, phase pure Au5Sn and AuSn intermatillic nanocrsytals were obtained, respectively. This is the first observation that has been reported regarding the phase pure synthesis if Au5Sn intermetallic nanocrystals using solution based approach. Formation of different phases was established by structural characterization which elicited srystalline nature of the samples. A combination of TEM, HRTEM, and STEM-EDS mapping techniques employed here, brought and tailored phase. In conclusion, the careful selection of solvent, stoichiometry and growth directing agents is an important prerequisite for realizing distinct phases of Au-Sn system with a controlled morphology.