Spectral Reconstruction Improvement in a Cycloidal Coded-Aperture Mass Spectrometer.

Spatial aperture coding is a technique used to improve throughput without sacrificing resolution both in optical spectroscopy and sector mass spectrometry (MS). Previous work demonstrated that aperture coding combined with a position-sensitive array detector in a miniature cycloidal mass spectrometer was successful in providing high-throughput, high-resolution measurements. However, due to poor alignment and field nonuniformities, reconstruction artifacts were present.

Proof-of-Concept Vacuum Microelectronic NOR Gate Fabricated Using Microelectromechanical Systems and Carbon Nanotube Field Emitters.

This paper demonstrates a fully integrated vacuum microelectronic NOR logic gate fabricated using microfabricated polysilicon panels oriented perpendicular to the device substrate with integrated carbon nanotube (CNT) field emission cathodes. The vacuum microelectronic NOR logic gate consists of two parallel vacuum tetrodes fabricated using the polysilicon Multi-User MEMS Processes (polyMUMPs). Each tetrode of the vacuum microelectronic NOR gate demonstrated transistor-like performance but with a low transconductance of 7.

A super-resolution proof of concept in a cycloidal coded aperture miniature mass spectrometer.

Rationale: Higher resolution in fieldable mass spectrometers (MS) is desirable in space flight applications to enable resolving isobaric interferences at m/z < 60 u. Resolution in portable cycloidal MS coupled with array detectors could be improved by reducing the slit width and/or by reducing the width of the detector pixels. However, these solutions are expensive and can result in reduced sensitivity.

Design considerations for a cycloidal mass analyzer using a focal plane array detector.

With the advent of technologies such as ion array detectors and high energy permanent magnet materials, there is renewed interest in the unique focusing properties of the cycloidal mass analyzer and its ability to enable small, high-resolution, and high-sensitivity instruments. However, most literature dealing with the design of cycloidal mass analyzers assumes a single channel detector because at the time of those publications, compatible multichannel detectors were not available. This manuscript introduces and discusses considerations and a procedure for designing cycloidal mass analyzers coupled with focal plane ion array detectors.

The Long Neglected Cycloidal Mass Analyzer.

In 1938, Walker Bleakney and John A. Hipple first described the cycloidal mass analyzer as the only mass analyzer configuration capable of "perfect" ion focusing. Why has their geometry been largely neglected for many years and how might it earn a respectable place in the world of modern chemical analysis? This Perspective explores the properties of the cycloidal mass analyzer and identifies the lack of suitable ion array detectors as a significant reason why cycloidal mass analyzers are not widely used.

Improving the Performance of a Cycloidal Coded-Aperture Miniature Mass Spectrometer.

Cycloidal sector mass analyzers have, in principle, perfect focusing due to perpendicularly oriented uniform electric and magnetic fields, making them ideal candidates for incorporation of spatially coded apertures. We have previously demonstrated a proof-of-concept cycloidal-coded aperture miniature mass spectrometer (C-CAMMS) instrument and achieved a greater than 10-fold increase in throughput without sacrificing resolution, compared with a single slit instrument. However, artifacts were observed in the reconstructed mass spectrum due to nonuniformity in the electric field and misalignment of the detector and the ion source with the mass analyzer focal plane.

TiCT MXene-Reduced Graphene Oxide Composite Electrodes for Stretchable Supercapacitors.

The development of stretchable electronics requires the invention of compatible high-performance power sources, such as stretchable supercapacitors and batteries. In this work, two-dimensional (2D) titanium carbide (TiCT) MXene is being explored for flexible and printed energy storage devices by fabrication of a robust, stretchable high-performance supercapacitor with reduced graphene oxide (RGO) to create a composite electrode. The TiCT/RGO composite electrode combines the superior electrochemical and mechanical properties of TiCT and the mechanical robustness of RGO resulting from strong nanosheet interactions, larger nanoflake size, and mechanical flexibility.

Reduction in energy for electrochemical disinfection of in urine simulant.

Abstract: We report the development of novel modes of operation for electrochemical disinfection of in human urine simulant with an aim to minimize the energy required for disinfection. The system employs boron-doped diamond electrodes and will be part of an energy neutral, water and additive free outdoor toilet being developed for use in developing countries. Disinfection had been previously demonstrated with voltage being continuously applied to the electrode until disinfection was achieved.

Effects of Magnetic and Electric Field Uniformity on Coded Aperture Imaging Quality in a Cycloidal Mass Analyzer.

Cycloidal mass analyzers are unique sector mass analyzers as they exhibit perfect double focusing, making them ideal for incorporating spatial aperture coding, which can increase the throughput of a mass analyzer without affecting the resolving power. However, the focusing properties of the cycloidal mass analyzer depend on the uniformity of the electric and magnetic fields. In this paper, finite element simulation and charged particle tracing were used to investigate the effect of field uniformity on imaging performance of a cycloidal mass analyzer.

Proof of Concept Coded Aperture Miniature Mass Spectrometer Using a Cycloidal Sector Mass Analyzer, a Carbon Nanotube (CNT) Field Emission Electron Ionization Source, and an Array Detector.

Despite many potential applications, miniature mass spectrometers have had limited adoption in the field due to the tradeoff between throughput and resolution that limits their performance relative to laboratory instruments. Recently, a solution to this tradeoff has been demonstrated by using spatially coded apertures in magnetic sector mass spectrometers, enabling throughput and signal-to-background improvements of greater than an order of magnitude with no loss of resolution. This paper describes a proof of concept demonstration of a cycloidal coded aperture miniature mass spectrometer (C-CAMMS) demonstrating use of spatially coded apertures in a cycloidal sector mass analyzer for the first time.

Enhanced HO Production at Reductive Potentials from Oxidized Boron-Doped Ultrananocrystalline Diamond Electrodes.

This work investigates the surface chemistry of HO generation on a boron-doped ultrananocrystalline diamond (BD-UNCD) electrode. It is motivated by the need to efficiently disinfect liquid waste in resource constrained environments with limited electrical power. X-ray photoelectron spectroscopy was used to identify functional groups on the BD-UNCD electrode surfaces while the electrochemical potentials of generation for these functional groups were determined via cyclic voltammetry, chronocoulometry, and chronoamperometry.

Coded Apertures in Mass Spectrometry.

The use of coded apertures in mass spectrometry can break the trade-off between throughput and resolution that has historically plagued conventional instruments. Despite their very early stage of development, coded apertures have been shown to increase throughput by more than one order of magnitude, with no loss in resolution in a simple 90-degree magnetic sector. This enhanced throughput can increase the signal level with respect to the underlying noise, thereby significantly improving sensitivity to low concentrations of analyte.

Synthesis and Characterization of an Earth-Abundant CuBaSn(S,Se) Chalcogenide for Photoelectrochemical Cell Application.

CuBaSnSSe films consisting of earth-abundant metals have been examined for photocathode application. Films with different Se contents (i.e.

Compatibility of Spatially Coded Apertures with a Miniature Mattauch-Herzog Mass Spectrograph.

In order to minimize losses in signal intensity often present in mass spectrometry miniaturization efforts, we recently applied the principles of spatially coded apertures to magnetic sector mass spectrometry, thereby achieving increases in signal intensity of greater than 10× with no loss in mass resolution Chen et al. (J. Am.

Achieving Excellence in Graduate Research: A Guide for New Graduate Students.

has been developed to minimize the time spent reiterating general guidance and "norms" that need to be instilled in new graduate students. This allows principal investigators and senior researchers to provide high value, customized coaching for the individual student which is where the real value of the PhD education is expressed.

Correction: Enhanced photoelectrochemical water oxidation via atomic layer deposition of TiO2 on fluorine-doped tin oxide nanoparticle films.

Correction for 'Enhanced photoelectrochemical water oxidation via atomic layer deposition of TiO2 on fluorine-doped tin oxide nanoparticle films' by Isvar A. Cordova, et al., Nanoscale, 2015, 7, 8584-8592.

Chemical ionization mass spectrometry using carbon nanotube field emission electron sources.

A novel chemical ionization (CI) source has been developed based on a carbon nanotube (CNT) field emission electron source. The CNT-based electron source was evaluated and compared with a standard filament thermionic electron source in a commercial explosives trace detection desktop mass spectrometer. This work demonstrates the first reported use of a CNT-based ion source capable of collecting CI mass spectra.

Order of Magnitude Signal Gain in Magnetic Sector Mass Spectrometry Via Aperture Coding.

Miniaturizing instruments for spectroscopic applications requires the designer to confront a tradeoff between instrument resolution and instrument throughput [and associated signal-to-background-ratio (SBR)]. This work demonstrates a solution to this tradeoff in sector mass spectrometry by the first application of one-dimensional (1D) spatially coded apertures, similar to those previously demonstrated in optics. This was accomplished by replacing the input slit of a simple 90° magnetic sector mass spectrometer with a specifically designed coded aperture, deriving the corresponding forward mathematical model and spectral reconstruction algorithm, and then utilizing the resulting system to measure and reconstruct the mass spectra of argon, acetone, and ethanol.

Enhanced photoelectrochemical water oxidation via atomic layer deposition of TiO2 on fluorine-doped tin oxide nanoparticle films.

TiO2 is an exemplary semiconductor anode material for photoelectrochemical (PEC) water-splitting electrodes due to its functionality, long-term stability in corrosive environments, nontoxicity, and low cost. In this study, TiO2 photoanodes with enhanced photocurrent density were synthesized by atomic layer deposition (ALD) of TiO2 onto a porous, transparent, and conductive fluorine-doped tin oxide nanoparticle (nanoFTO) scaffold fabricated by solution processing. The simplicity and disordered nature of the nanoFTO nanostructure combined with the ultrathin conformal ALD TiO2 coatings offers advantages including decoupling charge carrier diffusion length from optical penetration depth, increased photon absorption probability through scattering, complimentary photon absorption, and favorable interfaces for charge separation and transfer across the various junctions.

Two-dimensional aperture coding for magnetic sector mass spectrometry.

In mass spectrometer design, there has been a historic belief that there exists a fundamental trade-off between instrument size, throughput, and resolution. When miniaturizing a traditional system, performance loss in either resolution or throughput would be expected. However, in optical spectroscopy, both one-dimensional (1D) and two-dimensional (2D) aperture coding have been used for many years to break a similar trade-off.

Enhanced electron transfer kinetics through hybrid graphene-carbon nanotube films.

We report the first study of the electrochemical reactivity of a graphenated carbon nanotube (g-CNT) film. The electron transfer kinetics of the ferri-ferrocyanide couple were examined for a g-CNT film and compared to the kinetics to standard carbon nanotubes (CNTs). The g-CNT film exhibited much higher catalytic activity, with a heterogeneous electron-transfer rate constant, k, approximately two orders of magnitude higher than for standard CNTs.

Perspectives on the Growth of High Edge Density Carbon Nanostructures: Transitions from Vertically Oriented Graphene Nanosheets to Graphenated Carbon Nanotubes.

Insights into the growth of high edge density carbon nanostructures were achieved by a systematic parametric study of plasma-enhanced chemical vapor deposition (PECVD). Such structures are important for electrode performance in a variety of applications such as supercapacitors, neural stimulation, and electrocatalysis. A morphological trend was observed as a function of temperature whereby graphenated carbon nanotubes (g-CNTs) emerged as an intermediate structure between carbon nanotubes (CNTs) at lower temperatures and vertically oriented carbon nanosheets (CNS), composed of few-layered graphene, at higher temperatures.

Compressive mass analysis on quadrupole ion trap systems.

Conventionally, quadrupole ion trap mass spectrometers eject ions of different mass-to-charge ratio (m/z) in a sequential fashion by performing a scan of the rf trapping voltage amplitude. Due to the inherent sparsity of most mass spectra, the detector measures no signal for much of the scan time. By exploiting this sparsity property, we propose a new compressive and multiplexed mass analysis approach--multi Resonant Frequency Excitation (mRFE) ejection.

Polyethylenimine-enhanced electrocatalytic reduction of CO₂ to formate at nitrogen-doped carbon nanomaterials.

Nitrogen-doped carbon nanotubes are selective and robust electrocatalysts for CO2 reduction to formate in aqueous media without the use of a metal catalyst. Polyethylenimine (PEI) functions as a co-catalyst by significantly reducing catalytic overpotential and increasing current density and efficiency. The co-catalysis appears to help in stabilizing the singly reduced intermediate CO2(•-) and concentrating CO2 in the PEI overlayer.

Solution-processed, antimony-doped tin oxide colloid films enable high-performance TiO2 photoanodes for water splitting.

Photoelectrochemical (PEC) water splitting and solar fuels hold great promise for harvesting solar energy. TiO2-based photoelectrodes for water splitting have been intensively investigated since 1972. However, solar-to-fuel conversion efficiencies of TiO2 photoelectrodes are still far lower than theoretical values.