Cancer continues to be a leading cause of death worldwide despite the increasing research advances into novel treatments. Thermal ablation of tumors is a relatively established method for the destruction of many tumor types, despite inherent shortcomings including incomplete tumor treatment and non-specific treatment. Novel therapies are currently studied including nanoparticle-based therapies to overcome these limitations. One field of research is focused on utilizing non-lethal hyperthermia to enhance carried chemotherapeutic drugs. Additionally a novel field of non-thermal ablations termed Irreversible Electroporation has recently been developed to treat tumors by irreversibly destroying cell membrane function through short electrical pulses. The goal of the present study is to research two novel potential treatments for cancer that do not require thermal destruction of tissue. Firstly, we developed and tested novel ways to load the antineoplastic agent Cisplatin into SWNHs to test the ability to thermally enhance carried drugs with non-lethal, mild hyperthermia. We attached the imaging agent Quantum Dots (QDs) to the particles to understand how hyperthermia affects cellular uptake, minimizing thermal enhancement. Results of this study highlight the need for better biomimetic in vitro models of the tumors to study how hyperthermia affects tissue level transport of nanoparticles. In the second aim we utilized a perfusable 3D collagen in vitro model of the tumor microenvironment, previously developed by our group to study tumor angiogenesis, to study nanoparticle transport. We demonstrated the ability of this model to study key mass transport obstacles nanoparticles face in the tumor including extravasation from a leaky, pro-angiogenic vasculature, diffusion in the extracellular matrix, and cellular uptake in a 3D environment. This model was then utilized in the third aim to study how mild hyperthermia affects transport of SWNHs. Results from this aim were valuable in showing the utility of the 3D in vitro model to controllably test the effects of external stimuli on transport of particles and shows how mild hyperthermia can selectively allow increased permeability of SWNHs in the tumor, increasing selectivity of nanoparticle transport to the targeted tissue. Lastly, we tested the non-thermal ablation, high-frequency irreversible electroporation (H-FIRE) in a 3D tumor platform and in an in vivo swine model to better understand the ability of H-FIRE to produce repeatable destruction of hepatocellular carcinoma, a disease state growing in incidence rate. We then used H-FIRE in an outpatient treatment for infiltrative skin tumors in equines, showcasing the ability to deliver high voltage, short duration pulses in a clinical setting without muscle contractions. Ultimately, the results of this study the engineering studies that must occur to optimize novel treatments utilizing non-lethal hyperthermia, or non-thermal death mechanism to treat cancer. The studies show the usefulness of more complex 3D in vitro models of tumors for early development of novel therapies and the utility of in vivo models to validate studies. / Ph. D.

Acid oxidation of multi-walled carbon nanotubes (MWCNTs) introduced carboxylic acid sites onto the MWCNT surface, which permitted further functionalization. Derivatization of carboxylic acid sites yielded amide-amine and amide-urea functionalized MWCNTs from oxidized precursors. Conventional MWCNT characterization techniques including X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and Raman spectroscopy supported successful MWCNT functionalization. Incorporation of MWCNTs functionalized with hydrogen bonding groups into a segmented polyurethane matrix led to an increase in mechanical properties at optimized MWCNT loadings, in contrast with non-functionalized MWCNTs that resulted in mechanical property decreases across all loadings. Dynamic mechanical analysis (DMA) demonstrated an increase in the polyurethane-MWCNT composite flow temperature with increasing hydrogen bonding MWCNT incorporation, as opposed to non-functionalized MWCNT composites which displayed no significant change in flow temperature. Variable temperature Fourier transform infrared spectroscopy (VT FT-IR) probed temperature-dependent hydrogen bonding in the polyurethane-MWCNT composites and revealed a significant impact on composite hydrogen bonding interactions upon MWCNT incorporation, which was amplified in composites formed using hydrogen bonding functionalized MWCNTs. Acid oxidation of carbon nanohorns (CNHs) yielded carboxylic acid functionalized CNHs, providing sites for further reaction with histamine to afford histamine-functionalized CNHs (His-CNHs). Raman spectroscopy, XPS and TGA confirmed successful functionalization. Transmission electron microscopy (TEM) demonstrated that His-CNHs efficiently complex quantum dots (QDs) through imidazole-Zn interactions. Combination of His-CNHs, QDs, and a poly(oligo-(ethylene glycol9) methyl ether methacrylate)-block-poly(4-vinyl imidazole) copolymer using an interfacial complexation technique afforded stable ternary nanocomplexes with average hydrodynamic diameters under 100 nm. These ternary nanocomplexes represent promising materials for photothermal cancer theranostics due to their size and stability. The efficient reaction of 2-isocyanatoethyl methacrylate with amines afforded urea-containing methacrylic monomers, where the amine-derived pendant groups determined the polymer Tg. Reversible addition-fragmentation chain-transfer (RAFT) polymerization enabled the synthesis of ABA triblock copolymers with urea-containing methacrylic outer blocks and poly(2-ethylhexyl methacrylate) inner blocks. These ABA triblocks copolymers displayed composition dependent phase-separated morphologies and desirable mechanical properties. The urea-containing polymers efficiently complexed gold nanoparticles through urea-gold interactions. Furthermore, urea-containing methacrylic polymers served as a useful matrix for incorporation of silica-coated upconverting nanoparticles, affording upconverting nanoparticle composite films.The novel ionene monomer N1,N2-bis(3-(dimethylamino)propyl)oxalamide permitted synthesis of novel oxalamide-containing ammonium ionenes. The hydrogen bonding, charge density, and counter anion tuned the ionene mechanical properties. The ionene structure also influenced water uptake and conductivity. The differences in physical properties correlated well with the morphology observed in small-angle X-ray scattering. The oxalamide-containing ionenes greatly enhance mechanical properties compared to typical ammonium ionenes, and further expand the library of ionene polymers. / Ph. D.

Magnetic semiconductor nanocrystals are being studied for their potential application in the field of spintronics as spin-injectors for spin-based transistors and spin-based storage elements for nonvolatile memories. They also have a number of biomedical engineering applications including contrast enhancing agents for magnetic resonance imaging (MRI). In this study, we present a synthesis route to grow colloidal II-VI magnetic nanoparticles at room temperature with easily handled, relatively non-toxic source materials. CoSe and CrSe nanocrystals were synthesized in an aqueous solution where gelatin is used to retard the reaction. Characterization of the nanocrystals was done through transmission electron microscope (TEM) imaging and UV-Vis absorption spectroscopy. Spin-carrier relaxation times were determined using a superconducting quantum interference device (SQUID) magnetometer. / Master of Science

No / Lymphocytes have many ion channels. These ion channels contribute to T cell-mediated autoimmune and/or inflammatory responses and therefore are targets for pharmacological immune modulation [1]. Lymphocytes are also suitable surrogate cells for cancer [2] and other diseases states [3] where inflammation is associated with increasing disease incidence. Non-steroidal anti-inflammatory drugs (NSAIDs), such as aspirin, have been associated with anti-tumour effects in cancers [4]. We recently compared DNA damage caused by the nanoparticle forms (NPs) of the NSAIDs, aspirin and ibuprofen and their bulk forms in peripheral blood lymphocytes of patients with respiratory diseases and healthy individuals in the Comet and micronucleus assays [5]. In this present study, we investigate electrophysiological changes from lymphocytes after NP exposure and compare these results with their DNA damage. 10 ml peripheral blood was collected from patients and healthy control individuals. Ethical permission was obtained from the Bradford Ethics Committee REC ref no: 09/H1313/37, ReDA no: 1202, and the University of Bradford ref no: 0405/8. Ibuprofen USP was purchased from Albermarle Europe sprl (Belgium). Pharmcoat 606 (HPMC) was kindly donated by Shinetsu (Japan). Aspirin and sodium lauryl sulphate were purchased from Sigma. Kollidon 30 (PVP K-30) was purchased from BASF (UK). Bulk and nano compound suspensions of aspirin and ibuprofen (IBU) were kindly prepared by Lena Nanoceutics (Bradford, UK). Whole blood collected from healthy individuals and cancer patients were treated for 30 mins with 500µg/ml of IBU bulk and nano forms separately. Whole-cell currents were recorded with normal patch clamping technique. The extracellular solution contained (in mM) the following: NaCl 125; KCl 5; MgCl2 1; CaCl2 2.5; HEPES 10; pH 7.4. The electrode internal solution contained (in mM) the following: KF 120; MgCl2 2; HEPES 10; EGTA 10; and CaCl2 1, pH 7.4. All experiments were carried out at room temperature. Compared with untreated cells, lymphocytes treated with IBU in NP form had lower whole-cell currents and the activities of ion channels were inhibited by 20% compared to those in bulk form. This result is mirrored by the DNA damage which occurred in lymphocytes after exposure to nanoparticles [5]. Although the intracellular biochemical mechanisms and ion channels involved in our nanoparticle toxicity remain to be determined, this study provides direct evidence that 500 μg/ml IBU in nano form can cause membrane damage to lymphocytes after a relatively short exposure. Such cytotoxicity of nanoparticles in lymphocytes may be associated with early membrane damage. Further detailed investigation is needed to explain the changes of lymphocytes in response to different concentrations of NPs in real time. / Poster communications

Yes / Bimetallic nanoparticles are of immense scientific and technological interest given the synergistic properties observed when two different metallic species are mixed at the nanoscale. This is particularly prevalent in catalysis, where bimetallic nanoparticles often exhibit improved catalytic activity and durability over their monometallic counterparts. Yet despite intense research efforts, little is understood regarding how to optimize bimetallic surface composition and structure synthetically using rational design principles. Recently, it has been demonstrated that peptide-enabled routes for nanoparticle synthesis result in materials with sequence-dependent catalytic properties, providing an opportunity for rational design through sequence manipulation. In this study, bimetallic PdAu nanoparticles are synthesized with a small set of peptides containing known Pd and Au binding motifs. The resulting nanoparticles were extensively characterized using high-resolution scanning transmission electron microscopy, X-ray absorption spectroscopy, and high-energy X-ray diffraction coupled to atomic pair distribution function analysis. Structural information obtained from synchrotron radiation methods was then used to generate model nanoparticle configurations using reverse Monte Carlo simulations, which illustrate sequence dependence in both surface structure and surface composition. Replica exchange with solute tempering molecular dynamics simulations were also used to predict the modes of peptide binding on monometallic surfaces, indicating that different sequences bind to the metal interfaces via different mechanisms. As a testbed reaction, electrocatalytic methanol oxidation experiments were performed, wherein differences in catalytic activity are clearly observed in materials with identical bimetallic composition. Taken together, this study indicates that peptides could be used to arrive at bimetallic surfaces with enhanced catalytic properties, which could be leveraged for rational bimetallic nanoparticle design using peptide-enabled approaches. / Air Force Office for Scientific Research (T.R.W., Grant No. FA9550-12-620 1-0226). S.P.E. and E.B.C. gratefully acknowledge financial support from the Army Research Office through a MURI award, W911NF-10-1-0520

Miniaturization of electronic circuits and systems continue to pose great difficulties in meeting the demand and anticipated growth for information services and their associated electronics. Of the several information processing techniques under consideration for devices of the future, optical systems are considered to offer significant advantages in terms of speed and bandwidth. Unfortunately, at the dimensions of contemporary electronics, optical waveguides will fail to assist significantly due to the fact that standard optical waveguides will have dimensions below the diffraction limit and hence optical waveguiding at such scales will be impractical. In order to circumvent this, recent work in the area of using nano-sized protrusions to guide light below the diffraction limit has been receiving a decent amount of attention. Such systems have typically involved using electron beam lithography to create these perturbations on metallic surfaces called plasmonic waveguides. While these waveguides are fairly efficient, in the amounts required to make real circuits this method would be impractically slow and prohibitively expensive. However, such waveguides could be made much more cheaply if means could be found to arrange colloidal nanoparticles on suitable substrates. In this project, nanoscale self-assembly has been investigated with the aim of achieving such ends. Colloidal nanoparticles have been synthesized and self-assembled onto substrates such that they show near field interactions necessary for plasmonic waveguiding without any aggregation. Absorption peak shifts, which were obtained during the experimental phase of this project confirmed that such nanoparticle assemblies can be achieved and that they do demonstrate some plasmonic waveguiding action. With this first step, it is hoped that films like these may find use for quick and cheap plasmonic waveguiding sometime in the near future. / Master of Science

The present work is divided into two sections. The first section deals with the synthesis of regenerable adsorbents for the removal of arsenic from contaminated waters. An adsorbent based on carboxymethylated polyethylenimine grafted agarose gels was synthesized and characterized as a regenerable synthetic ferric oxide adsorbent with high capacity for arsenate ions at pH 3.0. Similarly, four metal ion chelating adsorbents based on dipicolylamine were synthesized and characterized with respect to their Cu(II), Fe(III) and As(V) adsorption capacities. The most efficient adsorbents were Nov-PEI-DPA and Nov-TREN-DPA. Additionally, a commercial ion exchange resin was modified with permanganate to oxidize arsenite into arsenate. A complete oxidation-adsorption system was proposed in which a column packed with the oxidation resin was connected in series with an adsorbent column composed of the polyethylenimine grafted agarose gels.The second section involved work with magnetic nanoparticles. First, composite adsorbents consisting of magnetic particles encapsulated within agarose beads with and without grafted iminodiacetic acid (IDA) chelating groups were synthesized. The adsorption capacity of the adsorbents for Cu(II), Fe(III) and As(V) at different concentrations was investigated. Batch experiments were carried out to determine the Fe(III) and As(V) adsorption isotherms for the magnetic Novarose-IDA. Regenerability of the adsorbent was achieved with a pH change of the inlet solution, without affecting its magnetic or adsorption properties.Magnetic composite particles were synthesized for biomedical applications. First, magnetic nanoparticles were coated with silica and then used for gold nanoshell production. These nanoshells were functionalized with a Brij S10 derivative, containing carboxylic groups, using dodecanethiol as a bridging agent to incorporate a fluorescent biomolecule.Finally, magnetic and gold particles were encapsulated in PLGA nanoparticles. Docetaxel was loaded on these multifunctional nanoparticles and released studies were performed at 37°C. The presence of magnetite, colloidal gold and gold nanoshells in the PLGA nanoparticles was revealed by the coloration acquired by the polymeric nanoparticles. The release of drug from the polymeric nanoparticles showed a biphasic behavior with an initial burst followed by a prolonged slow release. There was no effect of the presence of magnetic or metallic particles on docetaxel release.

Nanoparticles are increasingly incorporated into consumer products because of their unique, size-dependent properties. Although these properties are commercially appealing, data are lacking regarding the fate and reactivity of nanoparticles once incorporated into materials. This information gap prevents accurate assessment of hazards that these materials potentially present to consumers and the environment. To address this concern, new research is needed to investigate the reactivity and transformations of nanoparticles. This dissertation describes the use of an electron transparent characterization platform to observe nanoparticle transformations. Nanoparticles were tethered to the surface of an analysis platform, exposed to a variety of conditions, and evaluated for reactivity and response. The characterization of silver nanoparticles revealed the generation of new daughter nanoparticles on surfaces in ambient humid conditions. Our observations showed that the transport of material is highly dependent on relative humidity and that pH equilibria drives the deposition of new particles and degradation. We discovered, by applying these findings to macro-silver objects, that bulk silver generates new nanoparticles on surfaces. This illuminated the possibility of other, yet undiscovered, naturally occurring nanoparticles. In the second model system, 1.5 nm gold nanoparticles were tethered by a robust metal oxide bond from the terminal group of the stabilizing ligand. This strategy facilitated precise control over thiol ligand removal using a dilute ozone oxidation. Tracking particle oxidation over time allowed us to gain unprecedented control over core exposure, size maintenance, and surface tethering. This platform was also utilized as a proof-of-concept for direct observation of transformations in complex media. Ligand and core transformations were monitored in a variety of biologically relevant conditions using tethered nanoparticles. Morphological and chemical transformations were characterized and correlated to results from solution monitoring. The use of a platform based approach to evaluating the reactivity of nanoparticles in the environment holds promise for evaluations of nanoparticles and their transformation products. The demonstration of monitoring reactivity in systems equilibria, carefully controlled transformations, or complex media shows the versatility of this strategy. Only through the use of this analysis platform was the direct observation of nanoparticle transformations possible. This dissertation includes previously published, unpublished, and co-authored materials. / 10000-01-01

El presente trabajo tiene como objetivo desarrollar en solución acuosa y a tem-peratura ambiente, rutas de síntesis química coloidal de nanopartículas de plata y nano-partículas compuestas estables. Se obtienen nanopartículas de plata reproducibles, con un control morfológico de tamaño y forma durante el proceso de síntesis. Llevamos a cabo el estudio de las propiedades ópticas (espectros de absorción de las resonancias de plasmones superficiales (SPR)) que caracterizan a una determinada forma y tamaño. El análisis incluye estructuras nanométricas de plata de diferentes tamaños, en ambientes diversos y formas diferentes, como esferas, prolates, y prismas de diferente sección transversal, etc Se ha demostrado que la síntesis química produce coloides de nanopartículas de plata esféricas y anisotrópicas estables. La morfología y estabilidad de las nanopartícu-las coloidales son estudiadas mediante técnicas de espectroscopia y microscopía elec-trónica. El rol y concentración necesaria de cada uno de los reactivos para producir co-loides estables mediante síntesis química son determinadas. Se ha demostrado que, con-trariamente a las opiniones actualmente expresadas en la literatura, es posible controlar el tamaño de las nanopartículas de plata y obtener coloides de nanopartículas de plata esféricas y anisotrópicas estables por largo tiempo, utilizando una ruta de síntesis quí-mica sencilla y una baja concentración de reactivos estabilizadores (PVP). Recubrimientos de nanopartículas esféricas de plata estabilizadas con polivinilpirroli-dona (PVP) sobre substratos de vidrio óptico son preparados mediante el proceso de spin-coating y un posterior tratamiento térmico. Diferentes morfologías tipo core-shell de Ag@SiO2 son preparados mediante un método químico simple y rápido, sin necesidad de adicionar reactivos de acoplamiento o modificadores superficiales de la sílice. Proponemos mecanismos de reacción para la preparación de diferentes nano-estructuras tipo core-shell de plata-sílice. Las nanopartí-culas compuestas de sílice-plata muestran unas propiedades de absorción de resonancia plasmónica muy evidentes. El trabajo de éste capítulo ha sido realizado en colaboración con Juan C. Flores, quien desarrolló la ruta de síntesis como parte de sus estudios de doctorado. Por último, una modificación del método sol-gel es empleada para la prepara-ción de nanopartículas de TiO2, y partículas compuestas de Ag@TiO2, SiO2@TiO2-Ag y SiO2@Ag@TiO2. Diferentes morfologías tipo core-shell son preparadas mediante un método químico simple y rápido sobre un substrato óxido, sin necesidad de adicionar agentes de acoplamiento o modificaciones superficiales. Las evidentes propiedades de absorción plasmónica de las nanopartículas de plata mostradas por las partículas com-puestas han demostrado la presencia de plata metálica sobre la titania, sin la posterior oxidación de la capa de plata por el contacto directo con la titania (TiO2). Esta evidencia es confirmada por la técnica de microscopía electrónica de alta resolución. Las propie-dades de absorción plasmónica de las partículas compuestas hacen a estos materiales muy prometedores para aplicaciones foto-catalíticas. / The present work aims to develop chemical synthesis routes of stable colloidal silver nanoparticles and composites nanoparticles in aqueous solution at room tempera-ture. We obtain reproducible morphological control of silver nanoparticles size and shape during synthesis solely by solution chemistry and carry out the study of the opti-cal properties (surface plasmon resonances (RPS) absorption spectra) which character-ize a specific shape and size. The analysis includes silver nanosized bodies of different size, in diverse environments and of various shapes, as spheres, prolates, and prisms of different transversal section, etc. Synthetic wet chemistry routes yielding stable colloids of spherical and aniso-tropic silver nanoparticles are demonstrated, and the morphology and stability of the colloidal nanoparticles studied extensively through spectroscopy and electron micros-copy techniques. The role of each reagent and the concentrations required to obtain sta-ble colloid via these wet chemical routes is determined. It was shown that, contrary to commonly expressed opinions in the literature, it is possible to control the particle size of silver nanoparticles and obtain long-term sable colloids of both spherical and aniso-tropic silver nanoparticles using simple chemical routes and low concentration of stabi-lizing agent (PVP). Films of polyvinylpyrrolidone (PVP) stabilized spherical silver nanoparticles are also prepared, by using spin coating on standard optical glass plates and subsequent thermal processing. Different core-shell type morphologies of Ag@SiO2 are also produced using a simple and rapid chemical method, without using added coupling agents or surface modifications of silica. We propose reaction mechanisms for the formation of the dif-ferent silica-silver core-shell nanostructures. The silica-silver composite nanoparticle display clear plasmonic resonance absorption properties. This chapter work has been done in collaboration with PhD student Juan C. Flores who developed the synthesis route as part of his doctoral studies. Finally, a sol-gel chemistry approach was used to fabricate nanoparticles in the systems TiO2, Ag@TiO2, Ag@TiO2-SiO2 and TiO2@Ag@SiO2. Different core-shell morphologies are produced using a simple and rapid chemical method. without using added coupling agents or surface modifications of the oxide substrate. Clear silver na-noparticle plasmonic absorption properties shown by the composite nanoparticles demonstrate the formation of metallic Ag, without the oxidation of Ag nanoshell in di-rect contact with TiO2, evidence confirmed also by high resolution electron microscopy. The plasmonic absorption properties of the composites nanoparticles make them a promising material for photocatalytic applications.

The present thesis titled “Molecular Modulation of Material Properties: Stud- ies on Nanoparticles, Nanoassemblies and Low Molecular Mass Gelator” deals with the preparation, characterization, and investigations into the properties of gold nanoparticles coated with novel thiols. The coverage of nanoparticle surfaces with these thiols renders them with special characteristics that will be of interest in biological and sensor applications. Also, a novel low molecular mass tetrameric sugar-based hydrogelator was synthesized and its gelation properties were studied in detail. Chapter 1 gives a general introduction and an overview about Nanomaterials, with emphasis towards nanoparticles of gold, which form the basis of this work. It delves with the history of research in noble metal nanoparticles, their interesting electronic and optical properties, the present methods of synthesis of high quality nanoparticles of noble metals, numerous potential applications of these novel materials, as well as the challenges in their real-life applications, and ends with the future outlook of this field of research. Chapter 2 describes the synthesis and characterization of three cationic lipid-like disulfides whose molecular structures are shown in Fig. 2.1. Gold nanoparticles capped with these molecules were then synthesized in small size dispersion by a simple one-phase protocol. These particles exhibited remarkably different solubility properties that were dictated by the molecular structure of the capping agent. The nanoparticles were characterized by a variety of techniques like UV-visible spec- troscopy, Transmission Electron Microscopy (TEM), proton Nuclear Magnetic Resonance (1H NMR), Fourier Transform Infra-red (FTIR) spectroscopy, and Zeta Potential measurements. These nanoparticles were then examined for their interactions (structural formula) Figure 1: Chemical Structures of the cationic lipid-like thiols used for nanoparticle preparation with dipalmitoyl phosphatidyl choline (DPPC) vesicles as model biological membranes. TEM, UV-vis, and Differential Scanning Calorimetry (DSC) were employed to probe the interactions. It was found that the capping agent of the nanoparticle had a strong bearing upon the interactions of the nanoparticles with DPPC vesicles. Chapter 3 describes the assembly of hydrophilic cationic nanoparticles upon elec- trostatic interaction with a variety of anionic surfactants. The chemical structures of some of the anions employed in the study, as well as a schematic of cationic nanopar- ticle are shown in Fig. 2. Upon ion pairing with long-chain anionic surfactants, the hydrophilic cationic nanoparticles were completely hydrophobized. They could then be phase-transferred to organic layer. TEM showed that nanoparticles assemble in to a variety of mesostructures upon ion-pairing with anions. The aggregate formation was found to depend critically upon length of the hydrophobic alkyl chain as well as the head-group of the anion. Isothermal Titration Calorimetry (ITC) was employed to probe the interactions of these nanoparticles with anions. It was found that the anions that resulted in nanoparticle precipitation displayed exothermic interactions with the nanoparticle. Chapter 4 deals with the synthesis of -thiolated metal chelator derivatives whose structures are shown in Fig. 3. The molecules are based on well-known chelators viz. iminodiacetic acid and bis-(2-pyridylmethyl)amine. While the first one is carboxylic acid-based chelator, the second one is pyridine-based. Nanoparticles coated with these chelators were synthesized in a size-controlled manner. These nanoparticles exhibited pH-controlled reversible assembly. However, while S-IDA based nanoparticles aggregated at low pH values, the S-BPA based nanoparticles aggregated in high pH regimes. Mixed monolayer protected gold nanoparticles were synthesized by employing S-BPA and C12H25SH as capping agents. It resulted in the formation of nanoparticles in low size-dispersion. These nanoparticles were characterized by 1H NMR spectroscopy to infer the ratio of the two capping agents on the nanoparticle surface. These nanoparticles demonstrated metal-ion induced aggregation. It was found that the nanoparticles could differentiate Cu2+ ions from other ions, and immediately formed aggregates in presence of Cu2+ ions. Chapter 5 describes the synthesis of novel mono-thiolated “Gemini” surfactants for nanoparticle synthesis. Gemini surfactants with different spacers were prepared. These surfactants had a 12-n-12 kind of molecular structure as shown in the Fig. 4. Upon preparation of nanoparticles with these thiols, the resulting material was soluble in water in the case of rigid thiols like D2S and DBPS Chapter 6 deals with the synthesis and hydrogelation properties of a low molecular mass hydrogelator based on an azobenzene based tetrameric sugar derivative (Fig. 5). The pKa of carboxylic acids in the molecule were determined using 13C NMR. The trans-to-cis isomerization of the compound was probed by time-dependent UV-vis studies. The sugar derivative exhibited pronounced hydrogelation capacity, gelling water at micromolar concentration. The gel formed was characterized extensively (structural formula) Figure 2: Schematic of cationic nanoparticles and molecular structures of the anions employed for nanoparticle assembly (structural formula) Figure 3: Chemical structures of metal-chelator containing thiols employed for the pH-controlled and metal-ion mediated nanoparticle assembly (structural formula) Figure 4: Schematic of cationic nanoparticles and molecular structures of the anions employed for nanoparticle assembly (structural formula) Figure 5: Chemical Structure of azobenzene-based tetrameric sugar derivative exhibit- ing pronounced hydrogelation using melting temperature analysis, UV-vis, FT-IR, circular dichroism spectroscopy and scanning electron microscopy. The resultant gel exhibited impressive tolerance to the pH variation of the aqueous phase and gelated water in the pH range of 4 to 10. While UV-vis and CD spectroscopy indicated that pronounced aggregation of the azobenzene chromophores in the gelator was responsible for gelation, FT-IR studies showed that hydrogen bonding is also a contributing factor in the gelation process. The melting of gel was found to depend upon the pH of the aqueous medium in which gel was formed. The gel showed considerable photostability to UV irradiation indicating tight intermolecular packing inside gelated state that render azobenzene groups in the resultant aggregate refractory to photoisomerization. The electron micrographs of the aqueous gels thus formed showed the existence of spongy globular aggregates in such gelated materials. Addition of salts to the aqueous medium led to a delay in the gelation process and also caused remarkable morphological changes in the microstructure of the gel. Appendix A describes the employment of ligand-free palladium nanoparticles towards efficient catalysis of Heck and Suzuki reactions in aqueous medium. Hexadecyl trimethylammonium bromide was employed as the surfactant to achieve solubilization of organic compounds in aqueous medium. UV-vis and TEM investigations into the formation of nanoparticles in the reaction media were undertaken. These studies indicate that the nanoparticles were formed by reduction of potassium tetrachloropalladinate by methyl acrylate used as one of the reactants. TEM investigation indicated the formation of nanoparticle assemblies upon solvent drying. Efficient and catalytic synthesis of a number of organic compounds could be achieved in high yield.