Terry E. Phillips

Crystal structure of the radical-cation radical-anion salt from 2,2′-bi-1,3-dithiole and 7,7,8,8-tetracyanoquinodimethane

The three-dimensional structure of the radical-cation radical-anion salt from 2,2′-bi-1,3-dithiole (1) and 7,7,8,8-tetracyanoquinodimethane (2) has been determined by X-ray diffraction methods; the structure is composed of segregated columnar stacks of cations and anions.

Immunoaffinity-based phosphorescent sensor platform for the detection of bacterial spores

Consideration of emergency response plans to an attack with biological weapons such as anthrax spores has spawned renewed interest in the development of inexpensive, rapid, and sensitive field portable sensors for use by non- specialists. The conceptual feasibility of such a device is demonstrated via the immunoaffinity capture of spores of the anthrax simulant B. globigii on a column followed by their washing, elution and phosphorescent detection. Spores are generically detected via the rapid extraction of dipicolinic acid (DPA) followed by its chelation with terbium to yield a phosphorescent complex. Chemical, thermal and mechanical methods of DPA extraction were evaluated. Simple extraction in HNO3 released up to 5 percent of the spore weight as DPA within 60 seconds. Extraction in H2O liberated 7 percent of the spore weight as DPA. Sonication with glass beads in H2O for 45 seconds released up to 4 percent of the spore weight as DPA. It is estimated that implementation of these techniques will permit development of a device requiring 3-5 minutes per analysis with a limit of detection on the order of 500 ng spore/mL. This approach is not intended to replace more specific methods of analysis. However, it is proposed for consideration as an inexpensive, simple and rapid means of spore detection by non-specialists in emergency situations.

X-Ray crystal structure of the organic conductor from 2,2′-bi-(2,4-diselenabicyclo[3.3.0]octylidene) and 7,7,8,8-tetracyano-p-quinodimethane (HMTSF–TCNQ)

The X-ray crystal structure of the organic conductor HMTSF–TCNQ consists of separate stacks of radical cations and radical anions coupled so as to make this the most two-dimensional member of the TTF–TCNQ family of organic metals.

Volatile species from conductive die attach adhesives

An investigation of microelectronic conductive die attach adhesives to determine the volatile species that evolve during cure and after postcure processing, such as preseal bakeout and burn-in, is described, and the results are presented and discussed. Gas chromatography/mass spectrometry was used to measure the volatile species, and complementary thermal analysis measurements were also obtained. The adhesives investigated were Adlebond 84-1LMINB1, Emerson and Cuming C-868-1, and Epo-tek H35-175MP, all silver-loaded epoxies used for electrically conductive component attachment. A comparison with previous mass spectrometry results shows that the sensitivity of the combined method is much higher, especially for higher molecular weight molecules, and that the identification of the outgassing species is simplified. >

Embedded micro-sensor for monitoring pH in concrete structures

Three major causes of corrosion of steel in concrete are chloride ions (Cl-), temperature (T) and acidity (pH). Under normal operating temperatures and with pH above 13, steel does not undergo pitting corrosion. In presence of Cl-, if the pH decreases below 12, the probability of pitting increases. Acid rain and atmospheric carbon dioxide cause the pH to drop in concrete, often leading to corrosion of the structure with the concomitant cost of repair or replacement. Currently, the pH level in concrete is estimated through destructive testing of the structures. Glass ISFET, and other pH sensors that need maintenance and calibration cannot be embedded in concrete. In this paper, we describe an inexpensive solid state pH sensor that can be embedded in concrete, to detect pH changes at the early stages. It employs a chemical reagent, trinitrobenzenesulfonic acid (TNBS) that exhibits changes in optical properties in the 12 - 14 pH range, and is held in a film of a sol-gel/TNBS composite on an optically transparent surface. A simple LED/filter/photodiode transducer monitors pH-induced changes in TNBS. Such a device needs no periodic calibration or maintenance. The optical window, the light-source and sensor can be easily housed and encapsulated in a chemically inert structure, and embedded in concrete.

Thermogravimetric analysis of selected condensed materials on a quartz crystal microbalance

Employing a quartz crystal microbalance and a quadrupole mass spectrometer in a vacuum chamber, thermogravimetric analyses (TGA) and mass spectrometer analyses have been performed at low temperature (90–190 K) on depositions of ammonia, acetone, methanol, toluene, isopropyl alcohol, water, para‐xylene, and selected combinations of these materials. Deposition of a single species yielded a TGA curve characteristic of a pure substance. Homogeneous binary mixtures, like methanol and water, exhibited a desorption curve which contained structure in addition to that observed for the pure materials. Sequential layering of one material on top of another also altered the TGA response, suggesting substantial interlayer interactions, and the TGA curve shape was found to be a function of the top‐layer thickness for the water‐on‐methanol system. Backfilling the chamber with nitrogen or argon at a pressure of 1 Torr increased the apparent desorption temperature of water by about 20 K.

The Organic Metallic State1

Abstract The development of the organic metallic state is traced from our original synthesis and study of TTF-TCNQ to the new conductor HMTSF-TCNQ, the first organic substance which remains metallic as T → 0.

Tiny-TOF-MALDI mass spectrometry for particulate drug and explosives detection

The MALDI (matrix assisted laser desorption/ionization) technique, widely used to desorb and ionize large biomolecules, is applied here to small molecules having low vapor pressure, such as drugs and explosives. Furthermore, we report the coupling of the MALDI technique with a small, highly portable tiny-TOF (fime-of-flight) mass spectrometer developed in our laboratories. This mass spectrometer is a low voltage coaxial reflectron design with a short flight tube that is specifically designed for low molecular weight substances. The reflectron is designed to operate in two different modes that provide an expremely powerful pseudo-tandem mass spectrometry capability that is crucial for field applications. Using this system we have measured mass spectral signatures for cocaine, heroine, and the explosive RDX in the sub- nanogram range. Also reported here are continued developements on advanced MALDI sampling technologies, sensitivity, and mass resolution enhancements of the tiny-TOF, further decreases in system size and weight, and concepts for field operational systems.

Total pressure sensor results from the early operations phase of the MSX mission

The total pressure sensor (TPS) is one of ten contamination sensors aboard the midcourse space experiment (MSX) satellite. The TPS measures both the natural and spacecraft induced pressure environments. This paper presents a first look at the TPS data from the early operations phase of the MSX mission. Flight data are show to be in good agreement with the external contamination model predictions for MSX. TPS fluctuations are shown to be consistent with the venting characteristics of the Spirit III cryogenic cover. Data are presented which characterize and confirm the tumbling nature of the receding Spirit III cover upon its release. Finally, flight data over an orbital period are shown to conform to a bimodal pressure profile.

Vibrational Analysis of a Stearic Acid Adlayer Adsorbed on a Silver Flake Substrate

A surface vibrational study of a stearic acid/silver (Ag) flake system is reported. The chemical nature of this interfacial system was examined with surface enhanced Raman scattering (SERS) as a function of sample temperature. The SERS spectrum from the room temperature flake exhibited vibrational peaks that were attributed to a carboxylate species bound to the Ag substrate through the oxygen atoms in the terminal end group. The surface species remained stable to temperatures up to 150 °C, above which a partial decomposition to an amorphous carbon layer was observed. In addition to the Raman studies, an IR‐visible sum‐frequency (SFG) measurement from a stearic acid/smooth Ag substrate proved a useful probe of the C‐H stretches in the terminal methyl group of the molecule. The SFG signal from the asymmetric C‐H stretch in the methyl group exhibited a temperature dependence that was similar to the SERS response from the surface carboxylate group, namely, a marked and irreversible decrease in signal levels for temperatures above 150 °C.