Geraldine M Purdy

Tetraalkylphosphonium-based ionic liquids for a single-step dye extraction/MALDI MS analysis platform.

Room temperature ionic liquids, or RTILs, based on tetraalkylphosphonium (PR(4)(+)) cations were used as the basis of a platform that enables separation of dyes from textiles, extraction of dyes from aqueous solution, and identification of the dyes by MALDI-MS in a single experimental step for forensic purposes. Ionic liquids were formed with PR(4)(+) cations and ferulate (FA), α-cyano-4-hydroxycinnamate (CHCA), and 2,5-dihydroxybenzoate (DHB) anions. The use of tetraalkylphosphonium-based ionic liquids in MALDI-MS allowed detection of small molecule dyes without addition of a traditional solid MALDI matrix.

Large-scale synthesis of CexLa1−xF3 nanocomposite scintillator materials

Transparent nanocomposites have been developed which consist of nanocrystals embedded in an organic matrix. The materials are comprised of up to 60% by volume of 7–13 nm crystals of the phosphor CexLa1−xF3, and are greater than 70% transparent in the visible region at a thickness of 1 cm. Consistencies of the nanocomposites range from a solid polymer to a wax to a liquid, depending on the workup conditions of the nanoparticle synthesis. These transparent nanophosphor composite materials have potential applications in radiation detection as scintillators, as well as in other areas such as imaging and lighting, and can be produced on large scales up to near-kilogram quantities at near ambient conditions, much lower in temperature than typical nanoparticle syntheses.

Critical role of intercalated water for electrocatalytically active nitrogen-doped graphitic systems

Removal of intercalated water within graphitic sheets is critical to achieving high-performing oxygen reduction reaction catalysts. Graphitic materials are essential in energy conversion and storage because of their excellent chemical and electrical properties. The strategy for obtaining functional graphitic materials involves graphite oxidation and subsequent dissolution in aqueous media, forming graphene-oxide nanosheets (GNs). Restacked GNs contain substantial intercalated water that can react with heteroatom dopants or the graphene lattice during reduction. We demonstrate that removal of intercalated water using simple solvent treatments causes significant structural reorganization, substantially affecting the oxygen reduction reaction (ORR) activity and stability of nitrogen-doped graphitic systems. Amid contrasting reports describing the ORR activity of GN-based catalysts in alkaline electrolytes, we demonstrate superior activity in an acidic electrolyte with an onset potential of ~0.9 V, a half-wave potential (E½) of 0.71 V, and a selectivity for four-electron reduction of >95%. Further, durability testing showed E½ retention >95% in N2- and O2-saturated solutions after 2000 cycles, demonstrating the highest ORR activity and stability reported to date for GN-based electrocatalysts in acidic media.

Physical, structural, and dehydrogenation properties of ammonia borane in ionic liquids

Ionic liquids (ILs) are excellent solvents for the dehydrogenation of ammonia borane (AB); however, the basic properties that allow efficient dehydrogenation are still unclear. In this report, density, viscosity, melting/freezing/glass transition temperature, solubility, and the dehydrogenation properties, including impurity gas quantification, of AB-imidazolium-based IL solutions were studied. Note that ILs can solubilize 32–35 wt% of AB, and the liquid AB–IL solutions have densities of ∼0.9 g cm−3, viscosities similar to motor oil (100–250 cP), and glass transition temperatures below −50 °C. AB–ILs are stable at room temperature for several weeks with minimal hydrogen generation, although some hydrolysis occurs immediately upon mixing as a result of trace water content. Between 80 and 130 °C, more than 2 mol H2/AB are desorbed from AB–ILs with limited impurity emissions. Furthermore, there is no reaction between AB and ILs upon dehydrogenation, and structural analysis reveals a complex solid solution.

Ionic Liquid Polyoxometalates as Light Emitting Materials

The low melting point, negligible vapor pressure, good solubility, and thermal and chemical stability make ionic liquids useful materials for a wide variety of applications. Polyoxometalates are early transition metal oxygen clusters that can be synthesized in many different sizes and with a variety of heterometals. The most attractive feature of POMs is that their physical properties, in particular electrical, magnetic, and optical properties, can be easily modified following known procedures. It has been shown that POMs can exhibit cooperative properties, as superconductivity and energy transfer. POM ionic liquids can be obtained by selecting the appropliate cation. Different alkyl ammonium and alkyl phosphonium salts are being used to produce new POM ionic liquids together with organic or inorganic luminescent centers to design light emitting materials. Ammonium and phosphonium cations with activated, polymerizable groups are being used to further polymerize the ionic liquid into transparent, solid materials with high metal density.

Recycle of scrap plutonium-238 oxide fuel to support future radioisotope applications

The Nuclear Materials Technology (NMT) Division of Los Alamos National Laboratory has initiated a development program to recover & purify plutonium-238 oxide from impure feed sources in a glove box environment. A glove box line has been designed and a chemistry flowsheet developed to perform this recovery task at large scale. The initial demonstration effort focused on purification of 238PuO2 fuel by HNO3/HF dissolution, followed by plutonium(III) oxalate precipitation and calcination to an oxide. Decontamination factors for most impurities of concern in the fuel were very good, producing 238PuO2 fuel significantly better in purity than specified by General Purpose Heat Source (GPHS) fuel powder specifications. A sufficient quantity of purified 238PuO2 fuel was recovered from the process to allow fabrication of a GPHS unit for testing. The results are encouraging for recycle of relatively impure plutonium-238 oxide and scrap residue items into fuel for useful applications. The high specific activity of pl...

A graphite oxide (GO)-based remote readable tamper evident seal

This paper presents a prototype of a remotely readable graphite oxide (GO) paper-based tamper evident seal. The proposed device combines the tunable electrical properties offered by reduced graphite oxide (RGO) with a compressive sampling scheme. The benefit of using RGO as a tamper evident seal material is the sensitivity of its electrical properties to the common mechanisms adopted to defeat tamper-evident seals. RGOs electrical properties vary upon local stress or cracks induced by mechanical action (e.g., produced by shimming or lifting attacks). Further, modification of the seals electrical properties can result from the incidence of other defeat mechanisms, such as temperature changes, solvent treatment and steam application. The electrical tunability of RGO enables the engraving of a circuit on the area of the tamper evident seal intended to be exposed to malicious attacks. The operation of the tamper evident seal, as well as its remote communication functionality, is supervised by a microcontroller unit (MCU). The MCU uses the RGO-engraved circuitry to physically implement a compressive sampling acquisition procedure. The compressive sampling scheme provides the seal with self-authentication and self-state-of-health awareness capabilities. The prototype shows potential for use in low-power, embedded, remote-operation non-proliferation security related applications.

A remote-readable graphite oxide (GO) based tamper-evident seal with self-reporting and self-authentication capabilities

The blossoming of sensing solutions based on the use of carbon materials and the pervasive exploration of compressed sensing (CS) for developing structural health monitoring applications suggest the possibility of combining these two research areas in a novel family of smart structures. Specifically, the authors propose an architecture for security-related applications that leverages the tunable electrical properties of a graphite oxide (GO) paper-based tamper-evident seal with a compressed-sensing (CS) encryption/authentication protocol. The electrical properties of GO are sensitive to the traditional methods that are commonly used to remove and replace paper-based tamper-evident seals (mechanical lifting, solvents, heat/cold temperature changes, steam). The sensitivity of the electro-chemical properties of GO to such malicious insults is exploited in this architecture. This is accomplished by using GO paper to physically realize the measurement matrix required to implement a compressive sampling procedure. The proposed architecture allows the seal to characterize its integrity, while simultaneously providing an encrypted/authentication feature making the seal difficult to counterfeit, spoof, or remove/replace. Traditional digital encryption/authentication techniques are often bit sensitive making them difficult to implement as part of a measurement process. CS is not bit sensitive and can tolerate deviation caused by noise and allows the seal to be robust with respect to environmental changes that can affect the electrical properties of the GO paper during normal operation. Further, the reduced amount of samples that need to be stored and transmitted makes the proposed solution highly attractive for power constrained applications where the seal is interrogated by a remote reader.

Development program for 238Pu aqueous recovery process

Aqueous processing is necessary for the removal of impurities from 238Pu dioxide (238PuO2) scrap due to unacceptable levels of 234U and other non-actinide impurities. 238PuO2 is used to supply the thermal energy in General Purpose Heat Sources (GPHS). Impurities at levels above GPHS fuel specifications may impair the performance of the heat source. Efforts at Los Alamos have focused on developing the bench scale methodology for the aqueous process steps which include comminution, dissolution, ion exchange, precipitation, and calcination. Recently, work has been performed to qualify the bench scale methodology, to show that the developed process produces 238PuO2 that meets GPHS fuel specifications. This work has also enabled us to determine how liquid waste may be minimized during fullscale processing. Results of process qualification for the bench scale aqueous recovery operation and waste minimization efforts will be presented.

Removal of Pu-238 from aqueous process streams using a polymer filtration process

A glovebox facility is under construction at Los Alamos that will recover a significant quantity of the impure Pu-238 that exists in scrap and residues from past production operations. The general flowsheet consists of milling, acid dissolution, ion exchange, precipitation, calcination, oxygen isotope exchange, and waste treatment operations. As part of the waste treatment operations we are using polymer filtration to remove Pu-238 to meet facility discharge limits. Polymer filtration (PF) technology uses water-soluble polymers prepared with selective receptor sites to sequester metal ions, organic molecules, and other species from dilute aqueous solutions. The water-soluble polymers have a sufficiently large molecular size that they can be separated and concentrated using ultrafiltration (UF) methods. Water and small, unbound components of the solution pass freely through the UF membrane while the polymer concentrates in the retentate. The permeate stream is “cleaned” of the components bound to the polym...