Simona E. Hunyadi Murph

AG NANOPARTICLE EMBEDDED TIO2 COMPOSITE NANOROD ARRAYS FABRICATED BY OBLIQUE ANGLE DEPOSITION: TOWARD PLASMONIC PHOTOCATALYSIS

Using a unique oblique angle co-deposition technique, well-aligned arrays of Ag nanoparticle embedded TiO2 composite nanorods have been fabricated with different concentrations of Ag. The structural, optical, and photocatalytic properties of the composite nanostructures are investigated using a variety of experimental techniques and compared with those of pure TiO2 nanorods fabricated similarly. Ag nanoparticles are formed in the composite nanorods, which increase the visible light absorbance due to localized surface plasmon resonance. The Ag concentrations and the annealing conditions are found to affect the size and the density of Ag nanoparticles and their optical properties. The Ag nanoparticle embedded TiO2 nanostructures exhibit enhanced photocatalytic activity compared to pure TiO2 under visible- or UV-light illumination. Ag plays different roles in assisting the photocatalysis with different light sources. Ag can be excited and can inject electrons to TiO2, working as an electron donor under visible light. While under UV illumination, Ag acts as an electron acceptor to trap the photogenerated electrons in TiO2. Due to the opposite electron transfer direction under UV and visible light, the presence of Ag may not result in a greater enhancement in the photocatalytic performance.

Patchy silica-coated silver nanowires as SERS substrates

We report a class of core–shell nanomaterials that can be used as efficient surface-enhancement Raman scattering (SERS) substrates. The core consists of silver nanowires, prepared through a chemical reduction process, that are used to capture 4-mercaptobenzoic acid (4-MBA), a model analyte. The shell was prepared through a modified Stöber method and consists of patchy or full silica coats. The formation of silica coats was monitored via transmission electron microscopy, UV–visible spectroscopy, and phase-analysis light-scattering for measuring effective surface charge. Surprisingly, the patchy silica-coated silver nanowires are better SERS substrate than silver nanowires; nanomolar concentration of 4-MBA can be detected. In addition, “nano-matryoshka” configurations were used to quantitate/explore the effect of the electromagnetic field at the tips of the nanowire (“hot spots”) in the Raman scattering experiment.

Anisotropic Metallic and Metallic Oxide Nanostructures-Correlation Between Their Shape and Properties

In this chapter, we highlight recent innovations from our laboratory by featuring uniquely shaped nanostructures and how their morphology and dimension affect their physico-chemical properties and subsequently their applications. We aim to cover a wide range of applications including optical and plasmonic applications, sensing and imaging , catalytic and photocatalytic applications, bio-medical and environmental implications as well as energy related applications.

Multifunctional Hybrid Fe2O3-Au Nanoparticles for Efficient Plasmonic Heating

One of the most widely used methods for manufacturing colloidal gold nanospherical particles involves the reduction of chloroauric acid (HAuCl4) to neutral gold Au(0) by reducing agents, such as sodium citrate or sodium borohydride. The extension of this method to decorate iron oxide or similar nanoparticles with gold nanoparticles to create multifunctional hybrid Fe2O3-Au nanoparticles is straightforward. This approach yields fairly good control over Au nanoparticle dimensions and loading onto Fe2O3. Additionally, the Au metal size, shape, and loading can easily be tuned by changing experimental parameters (e.g., reactant concentrations, reducing agents, surfactants, etc.). An advantage of this procedure is that the reaction can be done in air or water, and, in principle, is amenable to scaling up. The use of such optically tunable Fe2O3-Au nanoparticles for hyperthermia studies is an attractive option as it capitalizes on plasmonic heating of gold nanoparticles tuned to absorb light strongly in the VIS-NIR region. In addition to its plasmonic effects, nanoscale Au provides a unique surface for interesting chemistries and catalysis. The Fe2O3 material provides additional functionality due to its magnetic property. For example, an external magnetic field could be used to collect and recycle the hybrid Fe2O3-Au nanoparticles after a catalytic experiment, or alternatively, the magnetic Fe2O3 can be used for hyperthermia studies through magnetic heat induction. The photothermal experiment described in this report measures bulk temperature change and nanoparticle solution mass loss as functions of time using infrared thermocouples and a balance, respectively. The ease of sample preparation and the use of readily available equipment are distinct advantages of this technique. A caveat is that these photothermal measurements assess the bulk solution temperature and not the surface of the nanoparticle where the heat is transduced and the temperature is likely to be higher.

Advanced Gas Sensors Using SERS‐Activated Waveguides

This contribution describes progress towards the development and testing of a functionalized capillary that will provide detection of low‐concentration gas‐phase analytes through SERS. Measurement inside a waveguide allows interrogation of a large surface area, potentially overcoming the short distance dependence of the SERS effect.The possible use of Raman spectroscopy for gas detection is attractive for IR‐inactive molecules or scenarios where infrared technology is inconvenient. However, the weakness of Raman scattering limits the use of the technique to situations where low detection limits are not required or large gas pressures are present.With surface‐enhanced Raman spectroscopy (SERS), signal enhancements of 106 are often claimed, and higher values are seen in specific instances. However, most of the examples of SERS analysis are on liquid‐phase samples, where the molecular density is high, usually combined with some sort of sample concentration at the surface. Neither of these factors is present ...

Synthetic Strategies for Anisotropic and Shape-Selective Nanomaterials

This chapter gives an overview of the various approaches that have been taken to create anisotropic nanomaterials. The synthetic mechanisms of nanomaterials are being actively pursued due to the unique size and shape dependent properties that can be exploited for a myriad of applications. Nanomaterials have been synthesized in a gamut of shapes, sizes, and compositions. As their synthetic protocol progresses, scientists are becoming more and more creative in the fabrication of nanomaterials with very interesting architectures to tailor their properties for faster electronics, better resolution imaging, more efficient catalysts, among others.

Anisotropic and Shape-Selective Nanomaterials

Globalization of scientific knowledge and technological advances are sparking innovation and creativity across many fields at an unprecedented rate. Ground-breaking discoveries made in the mid-1980s, namely the development of scanning tunneling microscopy and the discovery of buckminsterfullerene, influenced scientists to envision the world at the atomic level and new paradigms emerged: nanoscience and nanotechnology. Through the manipulation of matter at the atomic level, today scientists can create novel materials with unique properties and functionalities. These new materials enable innovative technologies and applications across many fields from engineering to medicine. Globalization of scientific knowledge and technological advances is sparking innovation and creativity across all fields at an unprecedented rate. Nearly every aspect of science and industry is driven to make advances in the (bio)medical fields, computing and electronics, environmental controls and remediation, transportation, energy production, chemical manufacturing, agriculture, and consumer products. The technological revolution [1] that started decades ago with the introduction of electronic devices and silicon-based integrated circuitry [2] changed humanity forever. The information technology insurgency that emerged with the introduction of internet/broadband, personal computers, mobile phones, and email [3] created a global multi-dimensional world. These technologies re-defined the way we live, communicate, travel and experience the world. This burst of technological developments offered unprecedented opportunities for rapid social and economic progress in our society [4]. S.E. Hunyadi Murph (&) National Security Directorate, Savannah River National Laboratory, Aiken, SC, USA e-mail: Simona.Murph@srnl.doe.gov S.E. Hunyadi Murph Department of Physics and Astronomy, University of Georgia, Athens, GA, USA

An Introduction to Nanotechnology

Globalization of scientific knowledge and technological advances are sparking innovation and creativity across many fields at an unprecedented rate. Ground-breaking discoveries made in the mid-1980s, namely the development of scanning tunneling microscopy and the discovery of buckminsterfullerene, influenced scientists to envision the world at the atomic level and new paradigms emerged: nanoscience and nanotechnology. Through the manipulation of matter at the atomic level, today scientists can create novel materials with unique properties and functionalities. These new materials enable innovative technologies and applications across many fields from engineering to medicine.

Tritium Contamination Prevention Using Sacrificial Materials

Abstract Tritium is produced by irradiating Tritium Producing Burnable Absorber Rods (TPBARs) in a Commercial Light Water Reactor at the Tennessee Valley Authority Watts Bar Reactor 1. The TPBARs are manufactured with strict materials specification for contaminants for all of the components. Despite meeting these requirements, gamma emitting contamination in the form of 65Zn was detected in a glovebox that was designed to contain tritium. A forensic examination of the piping revealed that the zinc was borne from natural zinc. This zinc deposits at an anomalous distance from the extraction furnace based on vapor pressure. A method to capture the zinc was developed that is intended to prevent the further spread of the 65Zn. This method relies on operating filter media at a specific temperature and location. While this approach is acceptable for the facility while it is in limited operation, as the facility undergoes increased utilization, there is a possibility of scheduling conflicts for maintenance and increasing dose to workers. In order to preclude these issues, methods to contain the zinc within the furnace module, an area designed for high radiation dose, were examined and experimental approaches were developed. These approaches used bulk materials and nano-materials deposited on various substrates that are compatible with tritium and the extraction process. These materials were tested to ascertain their zinc capturing capability, capacity, and characteristics. The first generation material was optimized and a process lid has been fabricated for testing.

Tritium Aging of LaNi4.15Al0.85 (LANA.85)

Abstract The Savannah River Tritium Enterprise (SRTE) has used hydride beds to store and process hydrogen isotopes for over two decades. New beds are being designed to use a hydride material – LaNi4.15Al0.85 (LANA.85) – that has a lower plateau pressure than the material previously employed. LANA.85 is expected to have a limited service life due to radiolytic decay of tritium to He-3 within the metal matrix, which will result in degradation of hydride performance. Tritium aging was initiated on a LANA.85 metal hydride sample to look for changes in desorption isotherm performance which occur with aging. Desorption isotherms were collected at 120°C, and 160°C annually. A lower temperature isotherm was collected at 100°C after 2 years of aging. A single absorption isotherm was collected each year at 120°C. After testing, each sample was reloaded with tritium for quiescent aging until the following year. Samples were stored in the beta phase. Results collected on the virgin material and annually for 2 years of tritium exposure are presented and discussed. The results have shown no unexpected behavior of the LANA.85 materials over the course of tritium exposure. As the service life of a the new hydride bed being designed is greater than 8 years, further annual monitoring and evaluation is recommended to track the effects of tritium exposure on isotherm behavior. Continued evaluation of will reduce the likelihood that unanticipated behaviors will be encountered in full scale production beds within the SRTE Tritium Facility.