Nanostructured carbons offer great promise in numerous electrode applications due to their high surface area and area specific capacitance. With the growing importance of energy applications in ...particular, a need has emerged to characterize the various forms of activated and nanostructured carbons in the context of their electrochemical charge-storage capacity. However, the use of gravimetric or area specific capacitance can be uninformative or even misleading due to the critical role of exposed linear edge density on charge-transfer processes; edges exhibit approximately 20× greater specific capacitance than basal planes. Thus, a more robust normalization is needed for materials that possess this extreme anisotropy. By classifying nanostructures based on linear edge density, a deeper understanding of materials performance can be obtained and a more informed comparison of nanostructures is enabled. This report provides a classification of carbon nanostructures based on the dimensional organization of their edge structures. Morphological benchmarks of the classification are provided, including a novel graphenated CNT hybrid which increases the linear edge density of nanostructured carbons by an order of magnitude. Geometric consideration of the dimensional nature of the edge organization enables quantification of the edge density per unit nominal area.
► Linear edge density (ρL) was approximated for each carbon nano-structure. ► Electron Density of Graphene Edges (EDGE) Triangle maps different nano-structures. ► The EDGE Triangle is organized based on dimensional structure of sp2 bonded edges.
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. Recently, significant progress was made in eliminating most of the reconstruction artifacts with improved field uniformity and alignment. However, artifacts as large as 1/3 of the main peak were still observed at low mass (<17 u). Such artifacts will reduce accuracy in identification and quantification of analytes, reducing the impact of the throughput advantage gained by using a coded aperture. The artifacts were hypothesized to be a result of a mass dependent in curvature of ions in the ion source. Ions with higher mass (m/z > 17 u) and a larger curvature did not pass through all slits in the coded aperture. Therefore, when reconstructing with a system response derived from the aperture image from a higher mass m/z = 32 u ion, reconstruction artifacts appeared for m/z < 17 u. In this work, two methods were implemented to significantly reduce the presence of artifacts in reconstructed data. First, we modified the reconstruction algorithm to incorporate a mass-dependent system response function across the mass range (10–110 u). This method reduced the size of the artifacts by 82%. Second, to validate the hypothesis that the mass-dependent system response function was a result of differences in curvature of ions in the ion source, we modified the design of the ion source by shifting the coded aperture slits relative to the center of the ionization volume. This method resulted in ions of all masses passing through all slits in the coded aperture, a constant system response function across the entire mass range. Artifacts were reduced by 94%.
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. In this paper, we demonstrate high-resolution spectral reconstruction in a cycloidal coded aperture miniature mass spectrometer (C-CAMMS) without changing the slit or detector pixel sizes using a class of signal processing techniques called super-resolution (SR).
We developed an SR reconstruction algorithm using a sampling SR approach whereby a set of spatially shifted low-resolution measurements are reconstructed into a higher-resolution spectrum. This algorithm was applied to experimental data collected using the C-CAMMS prototype. It was then applied to synthetic data with additive noise, system response variation, and spatial shift nonuniformity to investigate the source of reconstruction artifacts in the experimental data.
Experimental results using two ½ pixel shifted spectra resulted in a resolution of ¾ pixel full width at half maximum (FWHM) at m/z = 28 u. This resolution is equivalent to 0.013 u, six times better than the resolution previously published at m/z = 28 for N
using C-CAMMS. However, the reconstructed spectra exhibited some artifacts. The results of the synthetic data study indicate that the artifacts are most likely caused by the system response variation.
This paper demonstrates super-resolution spectral reconstruction in C-CAMMS without changing the slit or detector pixel sizes using a sampling SR approach. With improvements, this technique could be used to resolve isobaric interferences in a portable cycloidal MS for space flight applications.
Stretchable supercapacitors (SCs) have attracted significant attention in developing power‐independent stretchable electronic systems due to their intrinsic energy storage function and unique ...mechanical properties. Most current SCs are generally limited by their low stretchability, complicated fabrication process, and insufficient performance and robustness. This study presents a facile method to fabricate arbitrary‐shaped stretchable electrodes via 4D printing of conductive composite from reduced graphene oxide, carbon nanotube, and poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate. The electrode patterns of an arbitrary shape can be deposited onto prestretched substrates by aerosol‐jet printing, then self‐organized origami (ridge) patterns are generated after releasing the substrates from holding stretchers due to the mismatched strains. The stretchable electrodes demonstrate superior mechanical robustness and stretchability without sacrificing its outstanding electrochemical performance. The symmetric SC prototype possesses a gravimetric capacitance of ≈21.7 F g−1 at a current density of 0.5 A g−1 and a capacitance retention of ≈85.8% from 0.5 to 5 A g−1. A SC array with arbitrary‐shaped electrodes is also fabricated and connected in series to power light‐emitting diode patterns for large‐scale applications. The proposed method paves avenues for scalable manufacturing of future energy‐storage devices with controlled extensibility and high electrochemical performance.
A facile, fast, and low‐cost method for 4D printing of conductive composite via noncontact aerosol‐jet printing is developed to fabricate large‐area, arbitrary‐shaped, high‐performance, stretchable supercapacitors. The printed electrodes with an arbitrary shape onto prestretched substrates can generate self‐organized origami (ridge) patterns due to mechanical instability, enabling the extremely large deformation of the devices.
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. This is partially due to the dilemma of a short minority carrier diffusion length, and long optical penetration depth, as well as inefficient electron collection. We report here the synthesis of TiO2 PEC electrodes by coating solution-processed antimony-doped tin oxide nanoparticle films (nanoATO) on FTO glass with TiO2 through atomic layer deposition. The conductive, porous nanoATO film-supported TiO2 electrodes, yielded a highest photocurrent density of 0.58 mA/cm2 under AM 1.5G simulated sunlight of 100 mW/cm2. This is approximately 3× the maximum photocurrent density of planar TiO2 PEC electrodes on FTO glass. The enhancement is ascribed to the conductive interconnected porous nanoATO film, which decouples the dimensions for light absorption and charge carrier diffusion while maintaining efficient electron collection. Transient photocurrent measurements showed that nanoATO films reduce charge recombination by accelerating transport of photoelectrons through the less defined conductive porous nanoATO network. Owing to the large band gap, scalable solution processed porous nanoATO films are promising as a framework to replace other conductive scaffolds for PEC electrodes.
Hybrid organic–inorganic compounds are receiving increasing attention for photoelectrochemical (PEC) devices due to their high electron transport efficiency and facile synthesis. Biosynthesis is a ...potentially low-cost and eco-friendly method to precipitate transition-metal-based semiconductor nanoparticles (NPs) in an organic matrix. In this work, we examine the structure and composition of bacterially precipitated (BAC) cadmium sulfide (CdS) NPs using electron microscopy, and we determine their PEC properties and the energy band structure by electrochemical measurements. In addition, by taking advantage of the organic matrix, which is residual from the biosynthesis process, we fabricate a prototype photocharged capacitor electrode by incorporating the bacterially precipitated CdS with a reduced graphene oxide (RGO) sheet. Our results show that the hydrophilic groups associated with the organic matrix make BAC CdS NPs a potentially useful component of PEC devices with applications for energy conversion and storage.
The Long Neglected Cycloidal Mass Analyzer Piacentino, Elettra L; Serpa, Rafael Bento; Horvath, Kathleen L ...
Analytical chemistry (Washington),
08/2021, Volume:
93, Issue:
33
Journal Article
Peer reviewed
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. The recent development of capacitive transimpedance amplifier array detectors can enable several techniques using cycloidal mass analyzers including spatially coded apertures and single particle mass analysis with a “virtual-slit”, helping the cycloidal mass analyzer earn a respectable place in chemical analysis.
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 (Ti
C
T
) 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 Ti
C
T
/RGO composite electrode combines the superior electrochemical and mechanical properties of Ti
C
T
and the mechanical robustness of RGO resulting from strong nanosheet interactions, larger nanoflake size, and mechanical flexibility. It is found that the Ti
C
T
/RGO composite electrodes with 50 wt % RGO incorporated prove to mitigate cracks generated under large strains. The composite electrodes exhibit a large capacitance of 49 mF/cm
(∼490 F/cm
and ∼140 F/g) and good electrochemical and mechanical stability when subjected to cyclic uniaxial (300%) or biaxial (200% × 200%) strains. The as-assembled symmetric supercapacitor demonstrates a specific capacitance of 18.6 mF/cm
(∼90 F/cm
and ∼29 F/g) and a stretchability of up to 300%. The developed approach offers an alternative strategy to fabricate stretchable MXene-based energy storage devices and can be extended to other members of the large MXene family.
The bacterium Burkholderia pseudomallei causes melioidosis, a rare but serious illness that can be fatal if untreated or misdiagnosed. Species-specific PCR assays provide a technically simple method ...for differentiating B. pseudomallei from near-neighbor species. However, substantial genetic diversity and high levels of recombination within this species reduce the likelihood that molecular signatures will differentiate all B. pseudomallei from other Burkholderiaceae. Currently available molecular assays for B. pseudomallei detection lack rigorous validation across large in silico datasets and isolate collections to test for specificity, and none have been subjected to stringent quality control criteria (accuracy, precision, selectivity, limit of quantitation (LoQ), limit of detection (LoD), linearity, ruggedness and robustness) to determine their suitability for environmental, clinical or forensic investigations. In this study, we developed two novel B. pseudomallei specific assays, 122018 and 266152, using a dual-probe approach to differentiate B. pseudomallei from B. thailandensis, B. oklahomensis and B. thailandensis-like species; other species failed to amplify. Species specificity was validated across a large DNA panel (>2,300 samples) comprising Burkholderia spp. and non-Burkholderia bacterial and fungal species of clinical and environmental relevance. Comparison of assay specificity to two previously published B. pseudomallei-specific assays, BurkDiff and TTS1, demonstrated comparable performance of all assays, providing between 99.7 and 100% specificity against our isolate panel. Last, we subjected 122018 and 266152 to rigorous quality control analyses, thus providing quantitative limits of assay performance. Using B. pseudomallei as a model, our study provides a framework for comprehensive quantitative validation of molecular assays and provides additional, highly validated B. pseudomallei assays for the scientific research community.
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. To arrive at a set of relevant design considerations, we first review the unique focusing properties of the cycloidal mass analyzer and then present calculations detailing how the dimensions and position of the focal plane array detector relative to the ion source determine the possible mass ranges and resolutions of a cycloidal mass analyzer. We present derivations and calculations used to determine the volume of homogeneous electric and magnetic fields needed to contain the ion trajectories and explore the relationship between electric and magnetic field homogeneity on resolving power using finite element analysis (FEA) simulations. A set of equations relating the electric field homogeneity to the geometry of the electric sector electrodes was developed by fitting homogeneity values from 78 different FEA models. Finally, a sequence of steps is suggested for designing a cycloidal mass analyzer employing an array detector.
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