The wet chemical synthesis of energy and sensor relevant nanomaterials often requires large amounts of high boiling point solvents, grams of reactants, solvent-based purification, and the use of oxygen free atmospheres. These synthetic routes are also prone to poor scalability due to requirements of precise control of high temperatures. Because of this, the potential use of metallic nanoparticles and semiconductive quantum dots (q-dots) in energy transfer and real time biosensor applications is labor intensive and expensive. We have explored a green alternative route that involves the colloidal synthesis of CdSe and CdTe quantum dots under well-controlled hydrothermal conditions (100-200°C) using simple inorganic precursors. The resulting nanomaterials are of high quality, and are easily processed depending upon application, and their synthesis is scalable. Temperature control, and synthetic scalability is provided by the use of a synthetic microwave reactor, which employs computer-controlled dielectric heating for the rapid and controllable heating.

This paper reports the preliminary results of an investigation of the synthesis of monolayer-capped GaAs nanoparticles using different surface capping molecules. Our approach focuses on the surface encapsulation using alkanethiolates. The organic shell can effectively block the aggregation during nanoparticle synthesis, providing molecular-level control of the core-shell structure. The results have demonstrated the effect of surface alkanethiolate modification on the interparticle spatial properties and particle sizes, which upon further refinement could lead to the ability in controlling the size of GaAs nanoparticles.

This paper describes the results of an investigation of modified synthetic protocols to produce monodispersed magnetic ferrite nanoparticles, γ-Fe2O3 and Fe3O4, and their magnetic properties. The synthesis involved thermal decomposition of organometallic precursors followed by oxidation or reduction. In the synthesis of γ-Fe2O3, iron pentacarbonyl was used as the precursor and trimethylamine oxide as the oxidant. In the synthesis of Fe3O4, iron (III) acetylacetonate was reduced by 1, 2-hexadecanediol. The particle sizes ranged from 5–15 nm with high monodispersity. Results from TEM, XPS, and SQUID characterizations of these iron oxide nanoparticles are discussed.

The application of molecularly-capped gold nanoparticles (1–5 nm) in catalysis (e.g., electrocatalytic oxidation of CO and methanol) requires a thorough understanding of the surface composition and structural properties. Gold nanoparticles consisting of metallic or alloy cores and organic encapsulating shells serve as an intriguing model system. One of the challenges for the catalytic application is the ability to manipulate the core and the shell properties in controllable ways. There is a need to understand the relative core-shell composition and the ability to remove the shell component under thermal treatment conditions. In this paper, we report results of a thermogravimetric analysis of the alkanethiolate monolayer-capped gold nanoparticles. This investigation is aimed at enhancing our understanding of the relative core-shell composition and thermal profiles.

This paper describes the results of an investigation of the structure and composition of core-shell gold and alloy nanoparticles as catalytically active nanomaterials for potential fuel cell catalysis. Centered on the electrocatalytic methanol oxidation, we show three sets of results based on electrochemical, surface, and composition characterizations. First, electrochemical studies have revealed that the nanostructured catalysts are active towards the electrooxidation of methanol and carbon monoxide. Second, X-ray photoelectron spectroscopy (XPS) data have shown that the organic encapsulating shells can be effectively removed electrochemically or thermally, which involves the formation of oxides on the nanocrystals. Thirdly, direct current plasma - atomic emission spectrometry (DCP-AES) has revealed insights for the correlation of the composition of alloy nanoparticles with the catalytic activities. Implications of these results to the design of nanostructured catalysts will also be discussed.

This paper reports a study on the assembly of gold nanoparticles via a tetradentate organosulfur ligand, tetra[(methylthio)methyl] silane. We have characterized the evolution of the assembly from individual nanoparticles to spheres (30 ∼ 160 nm) of linked nanoparticles using UV-Visible, TEM, and AFM techniques. We have also demonstrated that the assemblies could be effectively disassembled via manipulating the ligand chemistry. Intriguing assembly-substrate interactions were observed, which could be related to interfacial hydrophobicity. Implications of these findings to the development of abilities in interfacial manipulation of the nanostructures are also discussed.

Thin films derived from nanocrystal cores and functionalized linkers provide large surface-to-volume ratio and three-dimensional ligand framework. This paper describes the results of an investigation of the interfacial ion fluxes associated with redox reactivity and structural properties of such films using cyclic voltammetry, electrochemical quartz-crystal nanobalance, surface infrared reflection spectroscopy, and X-ray photoelectron spectroscopy. Films from gold nanocrystals of 2 nm core sizes and 11-mercaptoundecanoic acid were studied as a model system. First, the film coated on electrode surface displays redox-like voltammetric waves characteristic of the deprotonation-reprotonation of the carboxylic acid groups in the nanostructured network. This process is accompanied by mass changes. Secondly, the film exhibits capability for the complexation of copper ions via the nanostructured carboxylate framework. This process is also accompanied by interfacial fluxes of electrolyte cations across the electrode | film | electrolyte interface which compensate electrostatically the fixed negative charges in the reduction process.

This paper reports results of the characterizations of nanoparticle assembly formed via spontaneous core-shell and shell-shell reactivities at thiolate-capped gold nanoparticles. Gold nanoparticles of two different core sizes and thiols with carboxylic acid terminals are exploited as a model system. The reactivities involve covalent Au-thiolate bonding and non-covalent hydrogen-bonding with anisotropic linking character. We employed infrared reflection spectroscopy (IRS), atomic force microscopy (AFM) and transmission electron microscopy (TEM) for the characterizations. While IRS provides structural assessment, TEM and AFM imaging measurements probe the morphological properties.

The structural, electrical and electrochemical properties of nanoparticle thin films derived by a one-step exchange-crosslinking-precipitation route were characterized by microscopic, spectroscopic and electrochemical techniques. Thiolate-encapsulated gold nanocrystals of 2-nm and 5-nm core sizes and alkyldithiol crosslinkers were studied as a model system. The mixing of the two components in solutions allowed sequential exchanging, crosslinking and precipitation of dithiol-crosslinked nanocrystal thin films. The films were specularly reflecting and electronically continuous, and have potential applications in catalysis and molecular recognition.