Charles J. Pearce

Efficient MOF-based degradation of organophosphorus compounds in non-aqueous environments

Decontamination of sensitive electronics exposed to chemical contaminants such as chemical warfare agents (CWA) is incompatible with existing water-based/corrosive methods. The development of new chemistries to tackle this challenge is of great interest. In this paper we investigate the effectiveness of metal–organic frameworks (MOFs) to degrade organophosphorus compounds in non-aqueous environments, via a combined experimental-molecular modeling study. Emphasis is placed on understanding the effect of framework characteristics (metal identity and linker functional group) on the methanolysis of these toxic chemicals, along with identifying reactivity trends for relevant sarin (GB) simulants. Several representative materials based on a hexanuclear metal cluster were judiciously selected, including the well-known catalytically active MOF, UiO-66. Complementary insights into the vibrational and structural properties of these materials were provided by periodic density functional theory (DFT) calculations. Findings indicate that Zr is a more effective metal center to support the degradation of organophosphorus compounds in methanol, as compared to Eu and Y. Detailed investigation into the reactivity of three relevant simulant candidates (diethyl chlorophosphate, DECP, dimethyl 4-nitrophenylphosphate, DMNP, and diisopropyl fluorophosphate, DFP), revealed that nitro- and fluorophosphates are better surrogates to mimic the reactivity of GB in methanol, as compared to chlorophosphate-based molecules. Importantly, experimental results on the MOF based degradation of GB in methanol are reported here for the first time. Additionally, this is the first study that systematically investigates the effectiveness of using MOFs for the solvolysis of organophosphorus compounds, providing valuable insights for materials design and simulant downselection.

Degradation of Superconducting Nb/NbN Films by Atmospheric Oxidation

Niobium and niobium nitride thin films are transitioning from fundamental research toward wafer scale manufacturing with technology drivers that include superconducting circuits and electronics, optical single photon detectors, logic, and memory. Successful microfabrication requires precise control over the properties of sputtered superconducting films, including oxidation. Previous work has demonstrated the mechanism in oxidation of Nb and how film structure could have deleterious effects upon the superconducting properties. This study provides an examination of atmospheric oxidation of NbN films. By examination of the room temperature sheet resistance of NbN bulk oxidation was identified and confirmed by secondary ion mass spectrometry. Meissner magnetic measurements confirmed the bulk oxidation not observed with simple cryogenic resistivity measurements.

Biocompatible MOFs with high absolute quantum yield for bioimaging in the second near infrared window

Here we detail a study highlighting the correlation between particle size and absolute quantum yield (QY) in novel mixed metal near-infrared (NIR) emitting metal–organic frameworks (MOFs) materials. The nanoscale analogue in this series presents a QY of 6.3%, the highest of any NIR emitting MOFs reported to date.

Self-Assembled Array of Tethered Manganese Oxide Nanoparticles for the Next Generation of Energy Storage

Many challenges must be overcome in order to create reliable electrochemical energy storage devices with not only high energy but also high power densities. Gaps exist in both battery and supercapacitor technologies, with neither one satisfying the need for both large power and energy densities in a single device. To begin addressing these challenges (and others), we report a process to create a self-assembled array of electrochemically active nanoparticles bound directly to a current collector using extremely short (2 nm or less) conductive tethers. The tethered array of nanoparticles, MnO in this case, bound directly to a gold current collector via short conducting linkages eliminates the need for fillers, resulting in a material which achieves 99.9% active material by mass (excluding the current collector). This strategy is expected to be both scalable as well as effective for alternative tethers and metal oxide nanoparticles.

Corrections to “Degradation of Superconducting Nb/NbN Films by Atmospheric Oxidation” [Jun 17 Art. no. 1100505]

Presents corrections to the paper, “Degradation of superconducting Nb/NbN films by atmospheric oxidation,” (Henry, M.D., et al), IEEE Trans. Appl. Supercond., vol. 27, no. 4, Jun. 2017, Art. no. 1100505.