The electrical properties of metal-molecular nanoparticle networks are studied both theoretically and experimentally. Benzenedithiol-aluminum cluster linear chains, Y-shaped and H-shaped networks are modeled with semi-empirical methods to study the electronic properties of such structures. The HOMO (highest occupied molecular orbital)-LUMO (lowest unoccupied molecular orbital) gaps of the benzenedithiol-Al cluster networks decrease several eV compared to the isolated benzenedithiol molecule. Frontier energy levels become more closely spaced as the size of the molecular networks increase, accompanied with an increased HOMO energy and decreased LUMO energy, indicating a decreased energy barrier to electron transport. Delocalized spatial distribution of the frontier orbitals indicates a high probability for electron transmission and corresponds well with peaks near the HOMO-LUMO gap in the electronic density of states. Self-assembled molecular networks consisting of dithiol/thiol molecules and 30 nm colloidal gold nanoparticles are fabricated with a solution-based method. Electrical measurements performed on these nanostructures show a typically linear current-voltage characteristic while nonlinear I-V curves are also observed for networks built of benzenedithiol or hexane/octanethiol molecules. Further analysis with atomic force microscopy shows that the network’s conductance is determined by the molecule’s conductivity and network dimensions. Circuit model consisting of networked molecular resistors is applied to study the interconnections between the particles within the network and the simulated values of the network’s conductance is consistent with the measured values. Theoretical and experimental study on the electrical properties of metal-molecular nanoparticle networks reveals the influence of molecules and metallic particles on determining the network’s conductivity. Such self-assembled networks can be used to implement several circuit elements, such as resistors, diodes, etc., and more complicated computation components such as nanocells, memristors, etc. The electrical properties of the networks can be tuned by proper choice of molecules, metallic particles and network geometry making them promising for future molecular electronic circuits. / Graduate

With the given information that dendrimers have precisely controlled their sizes and spherical structures in the molecular level, the aim of this study is to show that dendrimer particles can become ordered into a self-assembled regular structure due to the nature of their regular sizes and shapes. For this project, melamine based generation 3 dendrimer was used for solution cast of thin films from the dendrimer-chloroform solutions with different casting conditions, i.e. various solution concentrations, casting temperatures, and substrates. As a result of these experiments, unique phenomena of highly ordered uniform 2-D contraction separations were observed during the solvent evaporation from the dendrimer films. The cast films from the concentration of 0.8 wt% and higher exhibit regular 2-D separation contraction patterns and make well-developed regularly arrayed structures due to the interaction between the contraction stresses and adhesion strength between films and substrates. From the DSC tests, both powder and cast film samples of a dendrimer show similar melting behaviors with different areas under the melting peaks. The results of these tests show that dendrimers, when they are in a descent environment that provides dendrimers with molecular mobility due to surface ionic bonding strength, can make a structural order and regularity in their macroscopic structures.

<p>The particles of the Pt metal were well dispersed on carbon nanotubes when EG was used and in isopropanol poor dispersion was observed and no further investigation was done on them. The platinum wt% on the supports observed from EDS was 21.8, 19.10 and 16.74wt% for Pt/EMWCNT, Pt/LPGCNT and Pt/ commercial CNT respectively. Pt/LPGMWCNT showed high electro-catalytic activity of 2.48 mA and active surface area of 76 m2/g, toward oxygen reduction, observed from cyclic voltammogram in iv sulfuric acid. Pt/LPGMWCNT also showed better tolerance toward methanol, however it was not highly active towards methanol, and hence the methanol oxidation peak current observed between 0.75 and 08 potential was the smallest. In this study a wide range of instruments was used to characterize the properties and behavior of Platinum nanoparticles on multi-wall carbon nanotubes. To add to the already mentioned, Scanning electrochemical microscopy (SEM), proton induced x-ray emission (PIXE), scanning electrochemical microscopy (SECM) and Brunauer-Emmett Tellar (BET) were also used.</p>

Cancer is one of the challenges for today's medicine and therefore a great deal of effort is being put into improving known methods of treatment and developing new ones. A new method that has been proposed is magnetic hyperthermia where magnetic nanoparticles linked to the tumor dissipate heat when subjected to an alternating magnetic field and will thus increase the temperature of the tumor. This method makes the tumor more susceptible to radiation therapy and chemotherapy, or can be used to elevate the temperature of the tumor cells to cause cell death. The particles proposed for this are single core and often have a size in the range of 10 nm to 50 nm. To achieve an effective treatment the particles should have a narrow size distribution and the proper size. In this work, a theoretical model for predicting the heating power generated by magnetic nanoparticles was evaluated. The model was compared with experimental results for magnetite particles of size 15 nm to 35 nm dissolved in water. The properties of the particles were characterized, including measurements of the magnetic saturation, the effective anisotropy constant, average size and size distribution. To evaluate the results from the model the AC susceptibility and heating power were experimentally determined. The model is a two-step model. First the out-of-phase component of the AC susceptibility as a function of frequency is calculated. Then this result is used to calculate the heating power. The model gives a correct prediction of the shape of the out-of-phase component of the susceptibility but overestimates its magnitude. Using the experimentally determined out-of-phase component of the susceptibility, the model estimation of the heating power compares quite well with the measured values.

Polymeric nanoparticles have gained increased popularity for drug delivery as they not only overcome the problem of limited aqueous solubility of many hydrophobic drug molecules, but also have the potential to improve the pharmacologic properties of anticancer drugs by increasing their in vivo half-life. A series of biodegradable poly(D,L-lactide-co-2-methyl-2-carboxytrimethylene carbonate), P(LA-co-TMCC), was first synthesized by Sn(Oct)2 catalyzed bulk polymerization. In order to obtain the polymer product with a better-defined composition, the polymer synthesis was improved by using organo-catalytic ring-opening copolymerization. The copolymer molar mass and composition were controlled by varying the monomer to initiator ratio and the monomer feed ratio. By grafting amine-terminated polyethylene glycol (PEG-NH2) to the carboxylate groups on the copolymer backbone, amphiphilic copolymers were formed and self-assembled to form nanoparticles with narrow size distribution. The nanoparticle size was observed to be influenced by the polymer composition and the self-assembly conditions. To gain greater insight into the stability of these nanoparticles in blood, they were tested in both fetal bovine serum and individual serum protein solutions. By encapsulating Förster resonance energy transfer (FRET) pairs and following their release by fluorescence, these micelles demonstrated strong thermodynamic and kinetic stability in the presence of serum. By incorporating functional groups (azide or furan) on the PEG chains, either cell adhesive peptides (i.e. alkyne-functionalized GRGDS) or targeting antibodies (i.e. maleimide-modified trastuzumab) were coupled to the surface of the nanoparticles through Huisgen 1,3-dipolar cycloaddition reaction or Diels-Alder chemistry, respectively. The GRGDS modified nanoparticles showed specific binding affinity to rabbit corneal epithelial cells that express αvβ1 integrin receptors.

Polymeric nanoparticles have gained increased popularity for drug delivery as they not only overcome the problem of limited aqueous solubility of many hydrophobic drug molecules, but also have the potential to improve the pharmacologic properties of anticancer drugs by increasing their in vivo half-life. A series of biodegradable poly(D,L-lactide-co-2-methyl-2-carboxytrimethylene carbonate), P(LA-co-TMCC), was first synthesized by Sn(Oct)2 catalyzed bulk polymerization. In order to obtain the polymer product with a better-defined composition, the polymer synthesis was improved by using organo-catalytic ring-opening copolymerization. The copolymer molar mass and composition were controlled by varying the monomer to initiator ratio and the monomer feed ratio. By grafting amine-terminated polyethylene glycol (PEG-NH2) to the carboxylate groups on the copolymer backbone, amphiphilic copolymers were formed and self-assembled to form nanoparticles with narrow size distribution. The nanoparticle size was observed to be influenced by the polymer composition and the self-assembly conditions. To gain greater insight into the stability of these nanoparticles in blood, they were tested in both fetal bovine serum and individual serum protein solutions. By encapsulating Förster resonance energy transfer (FRET) pairs and following their release by fluorescence, these micelles demonstrated strong thermodynamic and kinetic stability in the presence of serum. By incorporating functional groups (azide or furan) on the PEG chains, either cell adhesive peptides (i.e. alkyne-functionalized GRGDS) or targeting antibodies (i.e. maleimide-modified trastuzumab) were coupled to the surface of the nanoparticles through Huisgen 1,3-dipolar cycloaddition reaction or Diels-Alder chemistry, respectively. The GRGDS modified nanoparticles showed specific binding affinity to rabbit corneal epithelial cells that express αvβ1 integrin receptors.

Almost a decade has passed ever since the first time nanoparticles were proposed to be used for tumor/cancer diagnosis and treatment. For tumor/cancer treatments, nanoparticles are usually engineered to be the photo-thermal agent to promote the selectivity of the photo-thermal therapy while the most promising diagnostic applica- tion for nanoparticles might be being used as the exogenous optical contrast agent for optical imaging technique. This study is targeted at developing numerical modeling & simulation to be a subsidiary tool of experimental investigation of diagnostic & therapeutic applications of nanoparticles, particularly, gold-silica nanoshells. Around this goal, the present study is comprised with four sub-projects, each would be presented as an independent chapter. Firstly, an alternative method for calculating the spatial distribution of interstitial fluence rate in laser-induced interstitial thermo-therapy is introduced. The method originates from the un-simplified integral-differential radiant transport equa- tion, which is then solved by the radial basis function collocation technique. Validation of the method against the stochastic Monte Carlo and the numerical finite volume method has been done. Secondly, the nanoparticle assisted laser-induced interstitial thermo-therapy for tumor/cancer treatments is numerically investigated, which was targeted at exploring the therapeutic effects of a variety of treatment conditions including laser wavelength, power, exposure time, concentrations of tailored nanoparticles, and optical/thermal properties of the tissue that is under the treatment. Thirdly, the feasibility of extending nanoparticle assisted photo-thermal therapy from treating subcutaneous tumors to treating organ tumors, particularly, tumors growing in the clearance organ liver has been investigated. For organ tumors, nanoparticles could not recognize tumors from the surrounding normal organ tissue very well, as what has been for subcutaneous tumors. And last, how gold-silica nanoshells alter the diffuse reflectance signature of tissue phantoms has been numerically investigated, for the purpose of exploring how to engineering nanoshells to be good exogenous optical contrast agent for early-staged cancer diagnostic imaging.

Transition metal nanomaterials are used to catalyze many chemical reactions, including those key to environmental, medicinal, and petrochemical fields. Improving their catalytic properties and lifetime would have significant economic and environmental rewards. Potentially expedient options to make such advancements are to alter the shape, size, or composition of transition metal nanocatalysts. This work investigates the relationships between structure and catalytic properties of synthesized Au, Pd-on-Au, and Au-enzyme model transition metal nanocatalysts. Au and Pd-on-Au nanomaterials were studied due to their wide-spread application and structure-dependent electronic and geometric properties. The goal of this thesis is to contribute design procedures and synthesis methods that enable the preparation of more efficient transition metal nanocatalysts. The influence of the size and composition of Pd-on-Au nanoparticles (NPs) was systematically investigated and each was found to affect the catalyst’s surface structure and catalytic properties. The catalytic hydrodechlorination of trichloroethene and reduction of 4-nitrophenol by Pd-on-Au nanoparticles were investigated as these reactions are useful for environmental and pharmaceutical synthesis applications, respectively. Structural characterization revealed that the dispersion and oxidation state of surface Pd atoms are controlled by the Au particle size and concentration of Pd. These structural changes are correlated with observed Pd-on-Au NP activities for both probe reactions, providing new insight into the structure-activity relationships of bimetallic nanocatalysts. Using the structure-dependent electronic properties of Au NPs, a new type of light-triggered biocatalyst was prepared and used to remotely control a model biochemical reaction. This biocatalyst consists of a model thermophilic glucokinase enzyme covalently attached to the surface of Au nanorods. The rod-like shape of the Au nanoparticles made the thermophilic-enzyme complexes responsive to near infrared electromagnetic radiation, which is absorbed minimally by biological tissues. When enzyme-Au nanorod complexes are illuminated with a near-infrared laser, thermal energy is generated which activates the thermophilic enzyme. Enzyme-Au nanorod complexes encapsulated in calcium alginate are reusable and stable for several days, making them viable for industrial applications. Lastly, highly versatile Au nanoparticles with diameters of ~3-12 nm were prepared using carbon monoxide (CO) to reduce a Au salt precursor onto preformed catalytic Au particles. Compared to other reducing agents used to generate metallic NPs, CO can be used at room temperature and its oxidized form does not interfere with the colloidal stability of NPs suspended in water. Controlled synthesis of different sized particles was verified through detailed ultraviolet-visible spectroscopy, small angle X-ray scattering, and transmission electron microscopy measurements. This synthesis method should be extendable to other monometallic and multimetallic compositions and shapes, and can be improved by using preformed particles with a narrower size distribution.

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In this study, the molecular dynamics simulation method was used to investigate the mechanical properties of non-crystalline PEEK mixed with SiO2 nanoparticle. It is found the SiO2/PEEK nano-composite has higher mechanical properties in comparison with pure PEEK composite. Therefore, we wish to obtain the reason. The radial distribution function was used to explain the conformation of the change of microstructure and mechanical properties. The parametric study of different SiO2 particle size was discussed, such on the effects on the structure of PEEK and the strength of the structure.