Surfaces and interfaces are of fundamental importance from the nucleation to growth of crystals formed under different conditions such as vapor phase, liquid phase including biomineralisation conditions. Recently there is lot of interest in controlling the shape of nanoparticles during the synthesis due to their excellent shape dependent properties. Understanding the role of surfaces and interfaces is vital for such shapecontrolled synthesis of nanomaterials. On the surface, coordination number, structure, density and composition are different from that of bulk and hence the properties are completely different in the surfaces and interfaces of any crystalline material. Especially when the length scale become nanoscale, the surface and interface play a dominant important role and leads to several new and interesting phenomena. In this dissertation, the role of surfaces and interfaces on the synthesis and the properties of inorganic functional nanostructures have been studied. The work primarily relies on basic chemistry to synthesize nanostructures that brings the importance of surfaces/interfaces into the picture. Though several basic characterization techniques have been used, electron microscopy has been the emphasis and has been used extensively through the work to probe and explore the materials for characterizing the structures over a variety of length scales. The entire thesis based on the results and findings obtained from the present investigation are organized as follows: Chapter1 gives a general introduction to the surfaces and interfaces to create a background for the investigation. This emphasizes the role of surfaces and interfaces in several aspects starting from nucleation, growth to the properties of inorganic crystals. It gives some exposure in to the different type of surface phenomenon which is common in nanoscale materials. Chapter 2 deals with the materials and methods which essentially gives the information about the materials used for the synthesis and the techniques utilized to characterize the materials chosen for the investigation. Chapter 3 deals with predicting the morphology of 2D nanostructures by combining the crystal growth theory into chemical thermodynamics. Morphology diagrams have been developed for Au, Ag, Pt and Pd to predict conditions under which two-dimensional nanostructures form as a result of a chemical reaction. In addition, it provides the general understanding of shape control in 2D nanostructures with atomistic mechanism. The validity of the morphology diagram has been tested for various noble metals by carrying out critical experiments. As a result, 2D nanostructures of metals projecting the lowest energy facet resulted in a complete novel way in the absence of any capping/reducing agents. Chapter 4 deals with predicting the formation of 2D nanostructures of inorganic crystals formed as a result of precipitation reaction. Morphology diagram has been developed for the case of hydroxyapatite, an inorganic part of the human bone. This answers some of the long standing question related to the shape of the HA crystals formed in the bone by biomineralisation. The generality of the method has been tested to few other inorganic crystals such as CaCO3, ZnO and CuO formed through precipitation reaction. The key finding of the above two chapter is that the low driving force of the chemical reactions results in two dimensional nanostructures. On contrary, high chemical driving force combined with the optimum zeta potential results in porous aggregate of nanoparticles. Chapter 5 discusses the formation of porous clusters of metals and ceramics at specific conditions. The mechanism behind the formation of monodisperse aggregates are investigated based on the interaction energies of nanoparticles in aqueous medium. This chapter reveals the role of surface charge and the surface energy in controlling the stability of nanoparticles in aqueous medium. In addition, it provides the simple methodology to produce well controlled porous clusters by exploiting the competition between surface charge and surface energy during the aggregation. The application of the porous clusters of Pt has been tested for methanol oxidation which is essential for fuel cell applications. Chapter 6 deals with the development of porous biphasic scaffolds through the morphology transition of nanorods. Rod shape is not stable when subjected to high temperature due to instability and spherodisation takes place to minimize the surface energy. Here in this chapter, by exploiting spherodisation along with the phase transition, highly interconnected porous structure of hydroxyapatite and tricalcium phosphate is achieved. Combined with the morphology transition, by adding naphthalene as a template, the possibility of achieving hierarchical porous structure also presented. The mechanical strength of the biphasic porous scaffold has been tested by microindentation. Mechanical properties of apatite are generally poor and there are lots of efforts to improve the mechanical properties apatite by the composite approach. Chapter 7 deals with the HA-Alumina and HA-TCP composites. In spite of much attention given to the mechanical properties of the composites, the interfacial phenomenon that takes place between the components of the nanocomposite has not been studied in detail. In the present study, interfacial reactions in hydroxyapatite-alumina nanocomposites have been investigated and new reaction mechanism also proposed. The degradation of densification process has been observed for the HATCP composites due to the creation of porous interface between HA crystals and TCP matrix. Mechanical properties of these two composites have been studied using microindentation. The mechanical properties of HA and TCP single crystals are important for developing the biphasic composites with reliable mechanical properties. Chapter8deals with the mechanical behavior of hydroxyapatite and tricalcium phosphate single crystals. The mechanical properties of HA and TCP have been studied by performing nanoand microindentation on specific crystallographic facets. In case of hydroxyapatite, the anisotropy in mechanical properties has been explored by performing indentation on its prism and basal planes. Nanoscale plasticity is observed in both HA and TCP crystals which arise due to the easy movement of surface atoms with lesser coordination compared to the bulk. Nanoindentation has been performed in the calciumdeficient HA platelets provides important clues about the role of calcium deficiency on the mechanical behavior of bone and has implications for the properties of osteoporotic bones.

The ability to encapsulate linear nanoparticle (NP) chains in scrolled nanosheets is an important advance in the formation of nanocomposites.These nanopeapods (NPPs) exhibit interesting properties that may not be achieved by individual entities. Consequently, to fully exploit the potential of NPPs, the fabrication of NPPs must focus on producing composites with unique combinations of morphologically uniform nanomaterials. Various methods can produce NPPs, but expanding these methods to a wide variety of material combinations can be difficult. Recent work in our group has resulted in the in situ formation of peapod-like structures based on chains of cobalt NPs. Building on this initial success, a more versatile approach has been developed that allows for the capture of a series of preformed NPs in NPP composites. In the following chapters, various synthetic approaches for NPPs of various material combinations will be presented and the key roles of various reaction parameters will be discussed. Also, uniform hexaniobate nanoscrolls were fabricated via a solvothermal method induced by heating up a mixture of TBAOH, hexaniobate crystallites, and oleylamine in toluene. The interlayer spacing of the nanoscrolls was easily tuned by varying the relative amount and chain lengths of the primary alkylamines. To fabricate NPPs, as-synthesized NPs were treated with hexaniobate crystallite in organic mixtures via solvothermal method. During solvothermal treatment, exfoliated hexaniobate nanosheets scroll around highly ordered chains of NPs to produce the target NPP structures in high yield. Reaction mixtures were held at an aging temperature for a few hours to fabricate various new NPPs (Fe3O4@hexaniobate, Ag@hexaniobate, Au@hexaniobate, Au-Fe3O4@hexaniobate, TiO2@hexaniobate, CdS@hexaniobate, CdSe@hexaniobate, and ZnS@hexaniobate). This versatile method was first developed for the fabrication of magnetic peapod nanocomposites with preformed nanoparticles (NPs). This approach is effectively demonstrated on a series of ferrite NPs (≤ 14 nm) where Fe3O4@hexaniobate NPPs are rapidly (~ 6 h) generated in high yield. When NP samples with different sizes are reacted, clear evidence for size selectivity is seen. Magnetic dipolar interactions between ferrite NPs within the Fe3O4@hexaniobate samples leads to a significant rise in coercivity, increasing almost four-fold relative to free particles. Other magnetic ferrites NPPs, MFe2O4@hexaniobate (M = Mn, Co, Ni), can also be prepared. This synthetic approach to nanopeapods is quite versatile and should be readily extendable to other, non-ferrite NPs or NP combinations so that cooperative properties can be exploited while the integrity of the NP assemblies is maintained. Further, this approach demonstrated selectivity by encapsulating NPs according to their size. The use of polydispersed NP systems is also possible and in this case, evidence for size and shape selectivity was observed. This behavior is significant in that it could be exploited in the purification of inhomogeneous NP samples. Other composite materials containing silver and gold NPs are accessible. Partially filled Fe3O4@hexaniobate NPPs were used as templates for the in situ growth of gold to produce the bi-functional Au- Fe3O4@hexaniobate NPPs. Encapsulation of Ag and Au NP chains with a hexaniobate nanoscroll was shifted the surface plasmon resonance to higher wavelengths. In these composites NPs can be incorporated to form NPP structures, decorated on nanosheets before scrolling, or attached to the surfaces of the nanoscrolls. The importance of this advancement is the promise it holds for the design and assembly of active nanocomposites. One can create important combinations of nanomaterials for potential applications in a variety of areas including catalysis, solar conversion, thermoelectrics, and multiferroics.

Encapsulation of nanoparticles within hexaniobate nanoscrolls presents interesting advances in the formation of nanocomposites exhibiting unique multi-dimensional properties. Building upon previous successes, facile yet versatile wet-chemical and microwave-irradiation synthetic protocols for the fabrication of a series of hexaniobate composites are presented herein. Solvothermal and, more recently, microwave-assisted methods have been developed that allow for the fabrication of peapod-like structures. During solvothermal treatment, exfoliated hexaniobate nanosheets scroll around highly ordered chains of preformed nanoparticles (NPs) to produce nanopeapods (NPPs). This approach offers versatility and high yields, in addition to the potential for advanced functional device fabrication. For the characterization of these materials, advanced techniques in atomic force microscopy (AFM) were used for investigating the surface of materials at the nanometer scale. Extensive physical, dynamic, and force modulation studies were performed on novel oxide nanocomposites by implementing particular scanning techniques to determine information such as topology, stress-induced behavior at the nanoscale, magnetic behavior, and frictional forces of the nanoscale materials. These composites were then analyzed by topological intermittent contact studies in tapping and contact mode, as well as with derivative techniques of these commonly used scanning probe approaches. In addition to studying surfaces using conventional modes of AFM, the mechanical properties of these nanocomposites were measured via dynamic lateral force modulation (DLFM) and magnetic properties of functionalized magnetic nanosheets were mapped via magnetic sampling modulation (MSM). By utilizing the capabilities of the DLFM imaging mode, elastic properties such as Young’s Modulus were measured from force-distance curves. In addition to this modulation mode, MSM was used to selectively map the vibrating magnetic nanomaterials from a modulated electromagnetic field. The information obtained from these AFM techniques can be helpful in determining the relative structural behavior of these nanocomposites and gauge their use in various applications such as structural engineering of nanoarchitectures as well as studying magnetic characteristics of metal oxide nanocomposites that exhibit characteristics different from their bulk counterparts.

The thesis consists of four parts of which part 1 presents a brief overview of nanomaterials. Parts 2, 3 and 4 contain results of investigations of graphene, nanofilms of noble metal nanoparticles and ZnO nanostructures respectively. Investigations of graphene are described in Part 2 which consists of six chapters. In Chapter 2.1, changes in the electronic structure and properties of graphene induced by molecular charge-transfer have been discussed. Chapter 2.2 deals with the results of a study of the interaction of metal and metal oxide nanoparticles with graphene. Electrical and dielectric properties of graphene-polymer composites are presented in Chapter 2.3. Chapter 2.4 presents photo-thermal effects observed in laser-induced chemical transformations in graphene and other nanocarbons system. Chapter 2.5 describes the mechanical properties of polymer matrix composites reinforced by fewlayer graphene investigated by nano-indentation. The extraordinary synergy found in the mechanical properties of polymer matrix composites reinforced with two nanocarbons of different dimensionalities constitute the subject matter of Chapter 2.6. Investigations of noble metal nanoparticles have been described in Part 3. In Chapter 3.1, ferromagnetism exhibited by nanoparticles of noble metals is discussed in detail while Chapter 3.2 deals with surface-enhanced Raman scattering (SERS) of molecules adsorbed on nanocrystalline Au and Ag films formed at the organic–aqueous interface. Factors affecting laser-excited photoluminescence from ZnO nanostructures are examined in great detail in Part 4.