Three cyclometalated 6-phenyl-4-(p-R-phenyl)-2,2′-bipyridyl (CNN-Ph-R) Pt(II) acetylide complexes, Pt(CNN-Ph-R)(CCPh), where R = Me (1), COOMe (2), and P(O)(OEt)2 (3), have been synthesized and ...studied. Compounds 1 and 3 have been structurally characterized by single crystal X-ray crystallography and are found to exhibit distorted square planar geometries about the Pt(II) ions. The electrochemical properties of the compounds, as determined by cyclic voltammetry, have also been examined. Complexes 1−3 are brightly emissive in fluid CH2Cl2 solution and in the solid state with λem max of ca. 600 nm and lifetimes on the order of ca. 500 ns in fluid solution. The emissions are assigned to a 3MLCT transition. The complexes undergo oxidative quenching by MV2+ with quenching rates near the diffusion-controlled limit (k q ∼ 1.4 × 1010 M−1 s−1) in CH2Cl2 solution. Reductive-quenching experiments of complexes 1−3 by the amine donors N,N,N′,N′-tetramethylphenylenediamine (TMPD), phenothiazine (PTZ), and N,N,N′,N′-tetramethylbenzidine (TMB) follow Stern−Volmer behavior, with very fast quenching rates on the order of 109−1010 M−1 s−1 in CH2Cl2 solution. When the complexes are employed as the sensitizer in multiple component systems containing MV2+, TEOA, and colloidal Pt in aqueous media, approximately one turnover of H2 (TN vs mol of chromophore) is produced per hour upon irradiation with λ > 410 nm but only after at least a 2 h induction period.
A series of luminescent platinum(II) terpyridyl acetylide complexes, (Pt(tpy)(C⋮CPh)ClO4 (1) and Pt(ttpy)(C⋮C-p-C6H4R)ClO4, where tpy = terpyridine, ttpy = 4‘-p-tolylterpyridine, R = H, Cl, Me) (2−4) ...were studied with regard to excited-state quenching by dialkylated bipyridinium cations as electron acceptors and triethanolamine (TEOA) as an electron donor and the photogeneration of hydrogen from systems containing the chromophore, the dialkylated bipyridinium cations, TEOA, and colloidal Pt as a catalyst. The dialkylated bipyridinium cations include methyl viologen (MV2+) and a series of diquats prepared from 2,2‘-bipyridine or 4,4‘-dimethyl-2,2‘-bipyridine. The quenching rates for the diquats for one of the chromophores (2) are close to the diffusion-controlled limit. The most effective electron acceptor and relay for hydrogen evolution has been found to be 4,4‘-dimethyl-1,1‘-trimethylene-2,2‘-bipyridinium (DQ4) which on photoreduction by the chromohore provides the strongest reducing agent of the diquats studied. The rate of hydrogen evolution depends in a complex way on the concentration of the bipyridinium electron relay, increasing with concentration at low concentrations and then decreasing at high concentrations. The rate of H2 photogeneration also increases with TEOA concentration at low values and eventually reaches a plateau. The most effective system examined to date consists of the chromophore 2 (2.2 × 10-5 M), DQ4 (3.1 × 10-4 M), TEOA (2.7 × 10-2 M), and Pt colloid (6.0 × 10-5 M), and has produced 800 turnovers of H2 (67% yield based on TEOA as sacrificial electron donor) after 20 h of photolysis with λ > 410 nm.
The Indian River Lagoon (IRL), located on the east coast of Florida, is a complex estuarine ecosystem that is negatively affected by recurring harmful algal blooms (HABs) from distinct ...taxonomic/functional groups. Enhanced monitoring was established to facilitate rapid quantification of three recurrent bloom taxa,
,
, and
spp., and included corroborating techniques to improve the identification of small-celled nanoplankton (<10 μm in diameter). Identification and enumeration of these target taxa were conducted during 2015-2020 using a combination of light microscopy and species-specific approaches, specifically immunofluorescence flow cytometry as well as a newly developed qPCR assay for
presented here for the first time. An annual bloom index (ABI) was established for each taxon based on occurrence and abundance data. Blooms of
(>2×10
cells L
) were observed in all six years sampled and across multiple seasons. In contrast, abundance of
, largely driven by the annual temperature cycle that moderates life cycle transitions and growth, displayed a strong seasonal pattern with blooms (10
-10
cells L
) generally developing in early summer and subsiding in autumn. However,
bloom development was delayed and abundance was significantly lower in years and locations with sustained
blooms.
spp. were broadly distributed with sporadic bloom concentrations (reaching 10
cells L
), but with minimal concentrations of the toxin domoic acid detected (<0.02 μg L
). In summer 2020, multiple monitoring tools characterized a novel nano-cyanobacterium bloom (reaching 10
cells L
) that coincided with a decline in
and persisted into autumn. Statistical and time-series analyses of this spatiotemporally intensive dataset highlight prominent patterns in variability for some taxa, but also identifies challenges of characterizing mechanisms underlying more episodic yet persistent events. Nevertheless, the intersect of temperature and salinity as environmental proxies proved to be informative in delineating niche partitioning, not only in the case of taxa with long-standing data sets but also for seemingly unprecedented blooms of novel nanoplanktonic taxa.
Bicarbonate ion-containing solutions such as seawater, natural brines, bovine serum and other mineralizing fluids have been found to contain hyperalkaline droplets of a separate, liquid condensed ...phase (LCP), that have higher concentrations of bicarbonate ion (HCO
) relative to the bulk solution in which they reside. The existence and unique composition of the LCP droplets have been characterized by nanoparticle tracking analysis, nuclear magnetic resonance spectroscopy, fourier transform infrared spectroscopy, dissolved inorganic carbon analysis and refractive index measurements. Carbon dioxide can be brought into solution through an aqueous reaction to form LCP droplets that can then be separated by established industrial membrane processes as a means of concentrating HCO
. Reaction of calcium with the LCP droplets results in calcium carbonate precipitation and mineral formation. The LCP phenomenon may bear on native mineralization reactions and has the potential to change fundamental approaches to carbon capture, sequestration and utilization.
In our developing world, carbon dioxide has become one of the most abundant greenhouse gases in the atmosphere. It is a stable, inert, small molecule that continues to present significant challenges ...toward its chemical activation as a useful carbon end product. This
tutorial review
describes one approach to the reduction of carbon dioxide to carbon fuels, using cobalt and nickel molecular catalysts, with particular focus on studying the thermodynamics and kinetics of CO
2
binding to metal catalytic sites.
This tutorial review describes CO
2
reduction with particular focus on studying the thermodynamics and kinetics of CO
2
binding to metal catalysts.
Background Removal of a tumor involving both the intracranial space and the skull presents technical challenges. This is especially so if there is a potential for significant hemorrhage due to a ...hemangioma or a significant attachment to the brain as with a meningioma. Case Description We describe a technique where the tumor attached to the skull is left undisturbed and a second wider concentric craniotomy exposes normal dura. The entire tumor, both intracranial and that involving the skull and dura, can then be removed as one specimen. Conclusion The technique we describe, a concentric craniotomy, transforms a difficult operation with the potential for significant hemorrhage into a more standard removal of a convexity tumor.
Black walnut (
Juglans nigra
L.) nut production stands on the brink of potentially great market expansion that can only be realized with significant genetic and horticultural improvement, such that ...commercial production becomes feasible. The goal of this study was to incorporate microsatellite/simple sequence repeat (SSR) markers to genotype 11 cultivars and selections, and establish a mapping population from a cross of two cultivars, “Football” × “Sparrow.” Morphology of these two cultivars coupled with phylogenetic analysis supports the notion that a cross between them may yield desirable hybrids. Of the 51 SSR markers amplified, 23 were polymorphic and useful for genotyping. A selection mislabeled as “Mintyle” was definitively identified as “Mintle”; therefore, the number of cultivars was reduced to 10. Furthermore, seven of the 23 markers were used to identify 91 intraspecific hybrids (“Football” × “Sparrow”) resulting from open pollination, thereby establishing the first mapping population of black walnut using SSR markers.
A series of cobaloxime complexes(Co(dmgH)2pyCl (1), Co(dmgH)2(4-COOMe-py)Cl (2), Co(dmgH)2(4-Me2N-py)Cl (3), Co(dmgH)(dmgH2)Cl2 (4), Co(dmgH)2(py)2(PF6) (5), Co(dmgH)2(P(n-Bu)3)Cl (6), and ...Co(dmgBF2)2(OH2)2 (7), where dmgH = dimethylglyoximate monoanion, dmgH2 = dimethylglyoxime, dmgBF2 = (difluoroboryl)dimethylglyoximate anion, and py = pyridinewere synthesized and studied as molecular catalysts for the photogeneration of hydrogen from systems containing a Pt terpyridyl acetylide chromophore and triethanolamine (TEOA) as a sacrificial donor in aqueous acetonitrile. All cobaloxime complexes 1−7 are able to quench the luminescence of the Pt(II) chromophore Pt(ttpy)(CCPh)ClO4 (C1) (ttpy = 4′-p-tolyterpyridine). The most effective electron acceptor for hydrogen evolution is found to be complex 2, which provides the fastest luminescence quenching rate constant for C1 of 1.7 × 109 M−1 s−1. The rate of hydrogen evolution depends on many factors, including the stability of the catalysts, the driving force for proton reduction, the relative and absolute concentrations of system components (TEOA, Co molecular catalyst, and sensitizer), and the ratio of MeCN/water in the reaction medium. For example, when the concentration of TEOA increases, the rate of H2 photogeneration is faster and the induction period is shorter. Colloidal cobalt experiments and mercury tests were run to verify that the system is homogeneous and that catalysis does not occur from in situ generated colloidal particles during photolysis. The most effective system examined to date consists of the chromophore C1 (1.1 × 10−5 M), TEOA (0.27 M), and catalyst complex 1 (2.0 × 10−4 M) in a MeCN/water mixture (24:1 v/v, total 25 mL); this system has produced ∼2150 turnovers of H2 after only 10 h of photolysis with λ > 410 nm.
The solid electrolyte interface (SEI) forms from electrolyte decomposition during the initial discharge of half-cell batteries and is affected by the presence of electrolyte additives. Breaking down ...the initial discharge into stages, defined by voltage cut offs, can help discover the role of additives in SEI growth. In this study, X-Ray Photoelectron Spectroscopy (XPS) is used to analyze the SEI formed on electrodeposited, binder free Cu2Sb thin films in sodium ion half-cell batteries. The presence of fluoro-ethylene carbonate (FEC), an electrolyte additive known to enhance battery lifetime, has a significant effect on the carbon 1s XPS spectra. The concentration of oxygenated carbon environments are dramatically decreased when FEC is added to the system. These environments were present in samples without FEC before significant electrochemistry was observed, potentially displaying the reactivity of sodium metal with conventional carbonate electrolytes to form the initial components of the SEI before the battery is cycled. The differences observed when FEC is added are likely the chemical environments of the SEI that have the dramatic effect on battery performance. Interestingly, these results suggest that the critical aspects of SEI formation are determined before the active material is sodiated, with FEC playing an integral role.
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•First use of XPS on binder-free copper antimonide anodes to assess SEI formation.•Use of differential capacity to identify SEI growth in distinct voltage regions.•Unique XPS methodology to identify SEI heterogeneity.•Analysis of the effect of FEC on the SEI formed on the active material.•Elucidation of the effect of FEC on inhibiting SEI formation at different voltages.
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