We prepare a series of gold-silver alloy nanoparticles with different Au/Ag mole ratio. The UV/Vis absorption spectra of nanoparticle solutions exhibited one surface plasmon resonance absorption band and the surface plasmon absorption band of the gold-silver alloy nanoparticles is blue-shifted with increase the Ag content. Finally, we produced the nanoparticles capping with alkanethiolate and alkanecarboxylate via place-exchange reaction. The nanoparticles have been characterized by ICP-MS, TEM, 13C-NMR, FT-IR, UV-Vis absorption spectroscopy. We suggest that the carboxylate group is coordinated to the Ag ion as a bridging bidentate.

The application of gold and silver nanoparticles to areas such as medical research is based on unique optical properties exhibited by some metals. These properties are a direct consequence of localised excitations occurring at visible frequencies known as Surface Plasmon Resonances (SPRs). The exact frequency of an SPR induced in a nanoparticle can be 'tuned' in the optical range by, for example, changing the size of gold and silver nanoparticles, or by varying the relative concentrations of gold and silver within an alloy nanoparticle. Whatever the desired frequency, it is critical that the majority of nanoparticles exhibit the frequency within the resolution limit of the imaging system. The research presented here utilises the high resolution imaging and spectroscopy techniques of (Scanning) Transmission Electron Microscopy ((S)TEM) and Electron Energy Loss Spectroscopy (EELS). It is common practice to analyse the optical properties of alloy nanoparticles using techniques that acquire a single spectrum averaged over multiple particles such as Ultraviolet-Visible (UV-Vis) spectroscopy. However, this technique cannot detect any optical variation between the nanoparticles resulting from compositional change. In this research the author demonstrates through the use of EELS that the SPR can be determined for individual gold/silver alloy nanoparticles, for the purpose of determining the extent of their homogeneity. Importantly, the data presented here suggest dramatic variation in SPR frequency between particles and even within the same particle, indicative of large variations in alloy composition. This puts the assumption that alloying can be scaled down to the nanometre-scale to the test. In order to resolve and extract the SPR in both the pure gold and gold and silver alloy nanoparticles, the author has successfully applied multiple post acquisition techniques such as Richardson-Lucy deconvolution and Principle Component Analysis (PCA) to the EELS Spectrum Imaging (SI) acquisition method. Additionally, the valence band EELS data are supported by complementary electron microscopy techniques; Core loss EELS, Energy Dispersive X-Ray Spectroscopy (EDX) and High Angle Annular Dark Field (HAADF) imaging.

The present thesis deals with synthesis of free alloy nanoparticles in immiscible alloy systems by the process of laser ablation under a liquid. In this process the alloy target is submerged in a liquid and the plume formed by the laser beam interaction with the target is confined in the liquid. The nanoparticles formed inside this plume and get quenched by the surrounding liquid yielding suspension of nanoparticles in the liquid. By the addition of suitable surfactants, these nanoparticles can be protected from other reactions and their size can be controlled by preventing further growth. We have selected immiscible alloys for the present study. These alloys tend to phase separate in melt as well as in solid depending on the value of the positive heat of mixing. We have used two binary alloys for the present study. These are alloys in Ag-Cu system and Fe-Cu system. In both these systems, there are reports of formation of extended solid solution due to kinetic factors during nonequilibrium processing like rapid solidification and mechanical alloying. In the present thesis we report synthesis of alloy nanoparticles of different compositions and sizes in these two systems and explore the nature of the phases that form in the small (nano) particles and their evolutionary pathways leading to the final microstructure. Microscopic techniques, especially transmission electron microscope, were used for characterization of these nanoparticles. The phase evolution was further studied using in situ microscopic techniques. After introducing the thesis in the Chapter 1, we describe briefly the relevant literatures in Chapter 2. The experimental details, in particular the experimental set up for laser ablation with targets under liquid are described in chapter 3. This chapter also includes the experimental details of the characterization. Transmission electron microscopy was used as primary characterization tool in the present study. The Chapter 4 presents the result of our study of alloy nanoparticles in Fe-Cu system. This system exhibits a submerged liquid miscibility gap. Although we have studied alloy targets of different compositions, the results of alloy nanoparticles obtained from targets with compositions Cu-40at.%Fe and Cu-60at.%Fe were primarily presented in this chapter. The nanoparticles that were synthesized had a size range of approximately 40nm to more than 100 nm. These particles have spherical morphology. The measurements of local compositions of different locations in the particle indicate the presence of a layer of Fe3O4 oxide at the spherical surface. This layer is devoid of copper. Most of the copper exist in the core of the particle. Fe rich spherical particles of much smaller size (~15 nm) are found to be embedded in the copper rich core. The copper formed solid solution with Fe and a copper concentration gradient exists in the particle below oxide layer due to oxidation of Fe. In contrast the nanoparticles obtained from alloy target with composition Fe-40at.% Cu have a spherical morphology. These have a composite structure with a Fe core in addition to Fe3O4 oxide layer at the surface. We have attempted to explain the phase evolution taking into account under cooling of the melt condensate that forms in the plume and their subsequent solidification through submerged miscibility gap. The chapters 5-7 deals with alloys of Ag-Cu system. In Chapter 5, we have carried out a detailed study of morphological evolution of the nanoparticles of Ag-Cu system. After optimizing the ablation parameters using pure Ag and Cu targets, we have synthesized alloy nanoparticles using different target compositions over the entire range of compositions with sizes having a mode of 25 nm. The evolution of the two phase structure is shown to be composition dependent with particles near equiatomic composition exhibit solid solution with uniformly distributed segregations of composition (Cu & Ag rich) while copper rich alloys exhibit a core shell structure with outer layer being Ag rich. The isothermal experiments again reveal emergence of core-shell morphology at intermediate time for particles with equiatomic composition. In order to compare the results of Ag-Cu nanoparticles with particles produced by other techniques we have synthesized Ag-Cu nanoparticles of near equiatomic composition by chemical route using nitrate salts and NaBH4 as reducing agent. PVP was used as capping agent. The results are presented in chapter 6. Depending on time of reaction, it is possible to synthesis free alloy particles from 2-3 nm to a network of chains. The nanoparticles contain Ag rich and Ag deficient region with Ag tends to segregate near surface. We have also presented mechanism for the formation of chain structure with prolonged reaction. The thermodynamic basis of phase formation in the immiscible system and evolution of phases under nonequilibrium situation have been discussed in chapter 7. This also includes a model to estimate size dependent surface energy. The analysis presented allows a discussion of possible pathways for phase evolution observed in the present work. The thesis ends with a final chapter that discussed the critical issues remains to be addressed and possible future work.

京都大学 / 新制・課程博士 / 博士(理学) / 甲第23026号 / 理博第4703号 / 新制||理||1674(附属図書館) / 京都大学大学院理学研究科化学専攻 / (主査)教授 北川 宏, 教授 吉村 一良, 教授 有賀 哲也 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

The aim of the present thesis is to understand the phase transformation behavior of embedded alloy nanoparticles embedded in immiscible matrices. Embedded alloy inclusions have been dispersed in immiscible matrix via rapid solidification method. The present work deals with synthesis of embedded particles, evolution of microstructure, morphology and crystallographic orientation relation relationships among different phases, phase transformation and phase stability behavior of embedded alloy inclusions in different matrices. In the present investigation the systems chosen are Bi-Sn and Bi-Pb in Zn matrix and Cd-Sn in Al matrix. Chapter 1 gives the brief introduction of present work Chapter 2 gives a brief review of nanoscale materials, various synthesis techniques, microstructure evolution, solidification and melting theories. Chapter 3 discusses the processing and experimental techniques used for characterization of the different samples in the present work. Melt-spinning technique used to synthesize the rapidly solidified ribbons. The structural characterization is carried out using X-ray diffraction and transmission electron microscopy. Chapter 4 illustrates the size dependent solubility and phase transformation behavior of Sn-Cd alloy nanoparticles embedded in aluminum matrix. X-ray diffraction study shows the presence of fcc Al, bct Sn, hcp Cd solid solution and hcp Cd phases. Based on Zen’s law, the amount of Sn present Cd solid solution is estimated. Using overlapped sterograms, the orientational relationships among various phases are found. Microscopy studies reveal that majority of the alloy nano inclusions exhibit a cuboctahedral shape with 111 and 100 facets and they are bicrystalline. STEM-EDS analysis shows that both phases exhibit size dependent solubility behavior and for particles size smaller than 18 nm, single phase solid solution could only be observed. Calorimetric studies reveal a depression in eutectic melting point of bimetallic particles. In situ heating studies show that melting initiates at triple line junction corner and melt first grows into the interior of the Sn rich phase of the particle and then later the melt grows into the interior of the Cd phase of the particle. During cooling first Cd phase solidifies later Sn phase solidifies and on further cooling at low temperatures entire particle transforming into complete solid solution phase particle. Size dependent melting studies show that during heating smaller particles melted first, later bigger particles melted. During cooling first bigger particle solidified later smaller particles solidified. High resolution imaging indicates presence of steps across particle-matrix interface that may get annihilated during heating. During cooling, molten particles in the size range of 16-30 nm solidify as solid solution which for molten particles greater than 30 nm solidify as biphasic particle. Insitu heating studies indicates that for solid particles less than 15 nm get dissolved in the Al matrix at temperatures at around 135°C. Differential scanning calorimetry (DSC) studies show in the first heating cycle most of the particles melt with an onset of melting of at 166.8°C which is close to the bulk eutectic temperature of Sn-Cd alooy. The heating cycle reveals that the melting event is not sharp which can be understood from in-situ microscopy heating studies. In the second and the third cycles, the onset of melting observed at still lower temperatures 164.3°C and 158.5°C .The decrease in onset melting point in subsequent heating cycles is attributed to solid solution formation of all small particles whose size range below 30 nm during cooling. cooling cycles exhibit an undercooling of 90°C with respect to Cd liquidus temperature. Thermal cycling experiments using DSC were carried out by arresting the run at certain pre-determined temperatures during cooling and reheating the sample to observe the change in the melting peak position and area under the peak. The areas of these endothermic peaks give us an estimate of the fraction of the particles solidified upto the temperature when the cycling is reversed. Based on experimental observations, a thermodynamic model is developed, to understand the solubility behavior and to describe the eutectic melting transition of a binary Sn-Cd alloy particle embedded in Al matrix. Chapter 5 discusses the phase stability and phase transformation behavior of nanoscaled Bi-Sn alloys in Zn matrix. Bi-Sn alloys with eutectic composition embedded in Zn matrix using melt spinning technique. X-ray diffraction study shows the presence of rhombohedral Bi, pure BCT Sn and hcp Zn phases. In X-ray diffractogram, there are also other new peaks observed, whose peak positions (interplanar spacings) do not coincide either with rhombohedral Bi or bct Sn or hcp Zn. Assuming these new phase peaks belong to bct Sn rich solid solution(based on earlier work on Bi-Sn rapidly solidified metastable alloys) whole pattern fitting done on x-ray diffractogram using Lebail method. The new phase peaks indicated as bct M1(metastable phase1), bct M2(metastable phase2) phases. The amount of Bi present in M1, M2 solid solution is estimated using Zens law. Two sets of inclusions were found, one contains equilibrium bismuth and tin phases and the other set contains equilibrium bismuth and a metastable phase. In-situ TEM experiments suggest that as temperature increases bismuth diffuses into tin and becomes complete solid solution. Melting intiates along the matrix–particle interface leading to a core shell microstructure. During cooling the entire inclusion solidify as solid solution and decomposes at lower temperatures. High temperature XRD studies show that as temperature increases M1, M2 phases peaks merge with Sn phase peaks and Bi phase peak intensities slowly disappear and on further increasing temperature Sn solid solution phase peaks also disappear. During cooling diffraction studies show that first Sn solid solution phase peaks appear and later Bi phase peaks appear. But, the peaks belong to metstable phases not appeared while cooling. Chapter 6 presents morphology and phase transformation of nanoscaled bismuth-lead alloys with eutectic (Pb44.5-Bi55.5) and peritectic (Pb70-Bi30) compositions embedded in zinc matrix. using melt spinning technique. In alloy1[ Zn-2at%(Pb44.5-Bi55.5)] inclusions were found to be phase separated into two parts one is rhombohedral Bi and the other is hcp Pb7Bi3 phase. X-ray diffraction study shows the presence of rhombohedral Bi, hcp Pb7Bi3 and hcp Zn phases in Zn-2at%(Pb44.5-Bi55.5) melt spun sample. The morphology and orientation relationships among various phases have been found. In-situ microscpy heating studies show that melt initially spreads along the matrix–particle interface leading to a core-shell microstructure. And in the core of the core-sell particles, first Bi phase melts later Pb7Bi3 phase will melt and during cooling the whole particle solidify as biphase particle with large undercooling. In-situ heating studies carried out to study the size dependent melting and solidification behavior of biphase particles. During heating smaller particles melt melt first later bigger particle will melt. In contrast, while cooling smaller particles solidifies first, later bigger particles will solidify. Detailed high temperature x-ray diffraction studies indicate there increases first Bi phase peaks disappear later Pb7Bi3 phase peaks disappear and during cooling first Pb7Bi3 phase peaks appear and later Bi phase peaks appear. In alloy2[ Zn-2at%(Pb70-Bi30)] inclusions were found to be single phase particles. X-ray diffraction study shows the presence of hcp Pb7Bi3 and hcp Zn phases in Zn-2at%(Pb70-Bi30) melt spun sample. The crystallographic orientation relationship between hcp Pb7Bi3 and hcp Zn phases. In-situ microscpy heating studies show that melting initiates across the matrix–particle interface grows gradually into the interior of the particle. Three phase equilibrium at peritectic reaction temperature is not observed during insitu heating TEM studies. Size dependent melting point depression of single phase particles is not observed from in-situ heating studies. Detailed high temperature x-ray diffraction studies show that while heating the Pb7Bi3 phase peak intensities start decreasing after 170°C and become zero at 234°C. And during cooling Pb7Bi3 phase peaks starts appearing at 200°C and on further cooling the Pb7Bi3 phase peak intensities increase upto 150°C, below this temperature peak intensities remain constant.

Alloying is an old trick used to produce new materials by synergistically combining at least two components. New developments in nanoscience have enabled new degrees of freedom, such as size, solubility and concentration of the alloying element to be utilized in the design of the physical properties of alloy nanoparticles (ANPs). ANPs as multi-functional materials have applications in catalysis, biomedical technologies and electronics. Phase diagrams of ANPs are very little known and may not represent that of bulk picture, furthermore, ANPs with different crystallite orientation and compositions could remain far from equilibrium. Here, we studied the synthesis and stability of Au-Sn and Ag-Ni ANPs with chemical reduction method at room temperature. Due to the large difference in the redox potentials of Au and Sn, co-reduction is not a reproducible method. However, two step successive reductions was found to be more reliable to generate Au-Sn ANPs which consists of forming clusters in the first step (either without capping agent or with weakly coordinated surfactant molecules) and then undergoing a second reduction step in the presence of another metal salt. Our observation also showed that capping agents (Cetrimonium bromide or (CTAB)) and Polyacrylic acid (PAA)) play a key role in the alloying process and shorter length capping agent (PAA) may facilitate the diffusion of individual components and thus enabling better alloying. Different molar ratios of Sn and Au precursors were used to study the effect of alloying elements on the melting point and the crystalline structures and melting points were determined by various microscopy and spectroscopy techniques and differential scanning calorimetry (DSC). A significant depression (up to150°C) in the melting transition was observed for the Au-Sn ANPs compared to the bulk eutectic point (T m 280°C) due to the size and shape effect. Au-Sn ANPs offer a unique set of advantages as lead-free solder material which can reflow at lower temperatures leading to lower thermal stresses in adjacent electronic components during the manufacturing process, offering better thermal and mechanical properties suitable for high temperature electronic applications. The second system studied here is Ag-Ni ANPs and electron microscopy and spectroscopy confirm the formation of Ag 0.5 Ni 0.5 ANPs with cubic structure, stable up to125°C. Atomic size and crystalline structure have less effect on the alloy formation process at the nanoscale; therefore, metals with limited solubility in bulk could form solid solutions at the nanoscale. Ag and Ni are immiscible in both solid and liquid states due to the large lattice mismatch and thermodynamically, the formation of core-shell structures is favoured. The effect of capping agents on the alloying was also studied here. Polyvinyl alcohol (PVA) with shorter length shows Ag-Ni ANPs with higher content of Ni compared to sodium citrate; the systems lead to the formation of Ag, Ag 2 O 2 and Ag 0.5 Ni 0.5 ANPs. The study of multi-component nanoparticle systems could shed light into the various parameters that affect stability of structure and phases, which could be quite distinct from their bulk counterparts.

L’émergence de nouveaux matériaux structurés à l’échelle nanométrique, aux propriétés contrôlées, a ouvert de nouvelles perspectives vis-à-vis des matériaux qui nous entourent. C’est notamment le cas des métaux et de leurs alliages et il est crucial d’établir le lien entre leurs propriétés structurales et leurs propriétés chimique et physique pour en permettre une utilisation optimale. Cette thèse s’inscrit dans ce contexte et porte sur la synthèse et la caractérisation en microscopie électronique en transmission de nanoparticules d’alliage bimétallique Au-Cu. En s’appuyant sur le diagramme de phase décrit à l’échelle macroscopique, nous nous sommes particulièrement intéressés aux nanoparticules de compositions nominales Au3Cu, AuCu et AuCu3. Le premier axe de ce travail consiste en l’élaboration de nanoparticules d’alliage Au-Cu. Deux voies de synthèse sont explorées : la voie chimique reposant sur le procédé polyol et la voie physique par ablation par laser pulsé. Le premier mode d’élaboration permet l’obtention de nanoparticules parfaitement cubiques dont la composition est systématiquement riche en Au. Les nanoparticules produites par voie physique présentent en revanche une composition maitrisée et modifiable. D’un point de vue structural, un recuit de ces dernières particules mène à leur mise en ordre chimique et à l’observation de structures L10 et L12. Cependant, nous montrons que cette transition de phase est bloquée dans les nanostructures présentant des défauts structuraux. Enfin, l’évolution du paramètre de maille des nanoparticules synthétisées selon ces deux voies de synthèse, en fonction de leur composition, a été établie et suit exactement la loi de Vegard décrite pour le matériau massif.Dans un second temps, nous avons observé des nanoparticules obtenues par voie physique en microscopie électronique en transmission environnementale, c’est-à-dire dans des conditions proches des environnements d’utilisation habituellement appliqués en catalyse. Les expériences menées en température révèlent que le mécanisme de dissolution de nanoparticules d’Au et d’alliage Au-Cu portées à haute température se fait en deux étapes : il y a fusion des nanoparticules suivi de leur évaporation pour des tailles de nanoparticules centrées autour de 10 nm. Les expériences réalisées en couplant le chauffage des nanoparticules au passage d’un gaz (H2 ou O2), en flux et dans des conditions de pression bien supérieures à celles accessibles jusqu’à maintenant, ont permis d’étudier leur comportement thermodynamique en condition oxydantes et réductrices. Nous avons notamment montré que des cycles d’oxydo-réduction de nanoparticules de taille moyenne supérieure à 20 nm conduisent à un effet Kirkendall menant, de manière réversible, à la formation de nanoparticules creuses (doughnut). Cette thèse interdisciplinaire constitue travail pionnier dans la compréhension du système d’alliage bimétallique Au-Cu à l’échelle nanoscopique / The emergence of new materials, structured at the nanoscale, with controlled properties, has opened new prospects regarding materials around us. In particular for metals and alloys, it seems crucial to connect their structural properties to their chemical and physical properties in order to optimise their use.Within this context, this thesis is focused on the synthesis and the characterisation of Au-Cu bimetallic alloy nanoparticles by transmission electron microscopy. On the basis of the bulk phase diagram, we especially studied particles with nominal compositions Au3Cu, AuCu et AuCu3.The first part of this work is dedicated to the synthesis of nanoparticles in two different ways. The chemical way is based on the polyol process and leads to nanoparticles exhibiting a cubic shape, and a systematically rich Au content. On the other hand, nanoparticles obtained by Pulsed Laser Deposition (PLD), a physical method of synthesis, display a well-controlled and tuneable composition. From a structural point of view, the annealing of the particles leads to chemical order and the stabilisation of L10 and L12 structures. However, we reveal that this phase transition is blocked in nanostructures with crystal defects. Moreover, we establish the evolution of the lattice parameter of the particles as a function of the composition and we demonstrate that, as in the bulk case, it is in agreement with Vegard’s law.In the second part, the nanoparticles synthesised via the physical method are studied using environmental transmission electron microscopy, i.e. in conditions close to those usually applied in catalytic reactors. Experiments performed at high temperature highlight that the dissolution of Au and Au-Cu nanoparticles occurs in a two-step process: fusion occurs first and is followed by evaporation for nanoparticles with a mean diameter of 10 nm.Coupling heating with gas flow (H2 or O2) in higher pressure condition than those usually reached allows us to study the thermodynamic behaviour of the nanoparticles in oxidative or reductive conditions. Most Notably, we show that oxidation-reduction cycles performed on nanoparticles with a diameter larger than 20 nm leads to a Kirkendall effect and the reversible formation of hollow particles (doughnuts).This cross-disciplinary thesis is a pioneering work towards understanding the bimetallic Au-Cu alloy system at atomic scale

Carbon supported PtNi nanoparticles were prepared by hydrazine reduction of Pt and Ni precursor salts under different conditions, namely by conventional heating (PtNi-1), by prolonged reaction at room temperature (PtNi-2) and by microwave assisted reduction (PtNi-3). The nanocomposites were characterized by XRD, EDX, XPS and TEM and used as electrocatalysts in direct methanol fuel cell (DMFC) reactions. Investigations into the mechanism of PtNi nanoparticle formation revealed that platinum nanoparticle seeding was essential for the formation of the bimetallic nanoparticles. The average particle size of PtNi prepared by microwave irradiation was the lowest, in the range of 2.9 – 5.8 nm. The relative rates of electrooxidation of methanol at room temperature as measured by cyclic voltammetry showed an inverse relationship between catalytic activity and particle size in the following order PtNi-1 < PtNi-2 < PtNi-3. / Singapore-MIT Alliance (SMA)

This research is divided into three major parts. In part I, the critical supersaturations required for the homogeneous nucleation of 2,2,2-trifluorothanol (TFE) vapor have been measured over a temperature range (266-296 K) using an upward thermal diffusion cloud chamber (DCC). The measured supersaturations are in agreement with the predictions of both the classical and the scaled theory of nucleation. Moreover, the condensation of supersaturated TFE vapor on laser-vaporized magnesium nanoparticles has been studied under different experimental conditions, such as the supersaturation, the pressure and the electric field. In part II, the laser vaporization controlled condensation (LVCC) technique was used to prepare Au-Ag alloy nanoparticles in the vapor phase using designed targets of compressed Au and Ag micron-sized powder mixtures of selected composition. The results showed that the optical properties of these nanoparticles could be tuned depending on the alloy composition and the laser wavelength. Different intermetallic nanoparticles (FeAl and NiAl) from the vapor phase has also been prepared, using the same approach.In this work, the fraction of the charged particles generated during the laser vaporization process was used to prepare a new class of nanoparticle assemblies in the LVCC chamber under the influence of an electric field. The results showed that the electric field required to induce the formation of these nanoassemblies is material and field dependent. By coupling the LVCC chamber with the differential mobility analyzer, size-selected nanoparticles have been prepared in the vapor phase. The prepared nanoparticles were characterized by different techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV-visible spectroscopy. In part III, new methods were developed to prepare nanoparticle-polymer composites from the vapor phase. In the first method, the LVCC method was used to prepare a carbonaceous cross-linked resin, with different nanoparticles (Ni, Pt and FeAl) embedded inside. In the second method, free radical-thermally initiated polymerization was used to polymerize a monomer vapor of styrene on the surfaces of activated Ni nanoparticles.

The first part of this dissertation deals with the application of a luminescence quenching method to measure diffusion and permeation coefficients of oxygen in polymers. Most luminescence oxygen sensors do not follow linearity of the Stern-Volmer (SV) equation due to heterogeneity of luminophore in the polymer matrix, thus the complexity of data analysis is increased. To circumvent this limitation, inverted fluorescence microscopy is utilized in this work to investigate the SV response of the sensors at the micron-scale. In these diffusion experiments, oxygen concentration is measured by luminescence changes in regions with high SV constants and good linearity. Thus, we avoid numerical complexity of combining nonlinear SV equation with a diffusion model. This technique allows us to measure oxygen diffusion properties in different type of polymers like transparent, opaque, free-standing polymers and polymers that cannot be cast into free standing films and polymer composites. In the second part of this thesis, we have explored the effect of Ag-Cu alloy nanoparticles on the emission intensity of luminophores at their close proximity. Alloy nanoparticles offer additional degrees of freedom for tuning their optical properties by altering atomic composition and atomic arrangement and thus can be an attractive option for manipulating signal of a wide range of luminophores. In this work, surface plasmon resonance spectrum of Ag-Cu alloy nanoparticles deposited by sputtering was easily tuned in wide wavelength range by varying one experimental condition- annealing temperature. Large metal enhanced luminescence for different luminophores viz Alexa Fluor 594 and Alexa Fluor 488 were achieved at the vicinity of Ag-Cu nanoparticles when maximum spectral overlap between SPR spectra of Ag-Cu nanoparticles and the emission and absorption spectra of the luminophores occur. We also studied the effect of composition of Ag-Cu nanoparticles synthesized by the polyol process on the luminescence of low quantum yield dye Cy3. In the third part of this thesis, quenching effect of Cu nanoparticles on CdSe/ZnS nanocrystal quantum dots has been explored. As Cu nanoparticles have comparable dielectric properties with gold nanoparticles, they are expected to show similar quenching effects. It was found that Cu is an efficient quencher of fluorescence from CdSe/ZnS quantum dots and the quenching effect is due to resonance energy transfer from quantum dots to Cu nanoparticles.