Thiophene and Pyrrole Derivative Polymers Electro-Synthesized on Stainles Steel. Doping and Morphology Characterization

3,4-ethylenedioxythiophene (EDOT), 3,4-propylenedioxythiophene (PRODOT), 3,4-ethylenedioxypyrrole (PEDOP) and 3,4 propylenedioxypyrrole (PRODOP), thiophene and pyrrole derivatives, were electro-polymerized by potentiodynamic and potentiostatic methods on stainless steel AISI 316 electrodes, using lithium perchlorate as support electrolyte in acetonitrile. In all cases electrodes modified with the respective polymeric deposit (PEDOT, PPRODOT, PPEDOP and PPRODOP) were obtained. One of the most relevant features of these polymers is that their voltammetric responses revealed that all presented p- and n-doping/undoping processes, being both processes reversible. Moreover, nucleation and growth mechanism (NGM) of the polymers was established by deconvolution of the experimental j/t transients recorded during it electropolymerization. PEDOT and PPRODOP showed a single contribution to the overall process, corresponding to instant nucleation with three-dimensional growth, controlled by charge transfer, whereas pyrrole derivatives (PEDOP and PPRODOP) are controlled by the same contribution, but there is also a second one corresponding to progressive nucleation with diffusion-controlled three-dimensional growth. Nuclei shape predicted from these NGM is consistent with the respective morphologies determined by SEM and AFM that, once more, validated the proposed electropolymerization model and the morphology prediction from the NGM of the respective polymers. To sum up, a correlation between the structure of the starting unit, doping, and morphology of the electro-deposited polymers was established

Mercury(II) Extraction Using a Poly(3,4-Ethylenedioxythiophene) Modified Electrode

Poly(3,4-ethylenedioxythiophene), PEDOT, electro-obtention has been widely studied because of its variety of applications. One of its most relevant electrochemical characteristics is its ability of p- and n-doping (an almost unexplored property thus far), consequently in the present survey its potential use for mercury(II) extraction, based on n-doping process, was studied. To this end EDOT was potentiostatically electro-polymerized on steel (AISI 316, 6 cm²) as substrate employing lithium perchlorate as supporting electrolyte and CH3CN as solvent. Each extraction cycle consisted of immersing the PEDOT modified electrode into a solution made of 1 mM Hg(II) and phosphate buffer at physiological pH (PBS). The n-doping potential was then applied for 5 min to incorporate the cation into the polymer matrix. Subsequently, to remove the cation, n-undoping potential was applied for 5 min to the electrode immersed into another cell containing only PBS. In the current survey, the extraction process required 25 successive cycles to achieve 100% yield. XPS spectra confirmed that the metal was always in its +2 oxidation state, confirming that the extraction occurs only through a n-doping/undoping process. Thus, it was verified for the first time that this property of conductive polymers can be utilized to separate (extract or remove) cations (in this case Hg(II)), using a cheap and simple method that, among others, may have great utility in areas of environmental and/or toxicological interest

The Gravity Collective: A Search for the Electromagnetic Counterpart to the Neutron Star-Black Hole Merger GW190814

We present optical follow-up imaging obtained with the Katzman Automatic Imaging Telescope, Las Cumbres Observatory Global Telescope Network, Nickel Telescope, Swope Telescope, and Thacher Telescope of the LIGO/Virgo gravitational wave (GW) signal from the neutron star-black hole (NSBH) merger GW190814. We searched the GW190814 localization region (19 deg$^{2}$ for the 90th percentile best localization), covering a total of 51 deg$^{2}$ and 94.6% of the two-dimensional localization region. Analyzing the properties of 189 transients that we consider as candidate counterparts to the NSBH merger, including their localizations, discovery times from merger, optical spectra, likely host-galaxy redshifts, and photometric evolution, we conclude that none of these objects are likely to be associated with GW190814. Based on this finding, we consider the likely optical properties of an electromagnetic counterpart to GW190814, including possible kilonovae and short gamma-ray burst afterglows. Using the joint limits from our follow-up imaging, we conclude that a counterpart with an $r$-band decline rate of 0.68 mag day$^{-1}$, similar to the kilonova AT 2017gfo, could peak at an absolute magnitude of at most $-17.8$ mag (50% confidence). Our data are not constraining for ''red'' kilonovae and rule out ''blue'' kilonovae with $M>0.5 M_{\odot}$ (30% confidence). We strongly rule out all known types of short gamma-ray burst afterglows with viewing angles $<$17$^{\circ}$ assuming an initial jet opening angle of $\sim$$5.2^{\circ}$ and explosion energies and circumburst densities similar to afterglows explored in the literature. Finally, we explore the possibility that GW190814 merged in the disk of an active galactic nucleus, of which we find four in the localization region, but we do not find any candidate counterparts among these sources.Comment: 86 pages, 9 figure

Nucleation and Growth Mechanism of Electro-synthesized Poly(pyrrole) on Steel

International audiencePolypyrrole was electro-synthetized by potentiodynamic and potentiostatic methods on AISI 316 stainless steel (SS) using lithium perchlorate as supporting electrolyte and acetonitrile as solvent to obtain the respective polymeric coating. One of the most relevant characteristics of this polymer is that its voltammetric response showed the presence of reversible p- and n-doping/undoping processes. Moreover, nucleation and growth mechanisms (NGM) were established by i/t transients deconvolution recorded during the potentiostatic electro-polymerization. It was found that the overall process mechanism involved two contributions, namely an instantaneous nucleation with two-dimensional growth (IN2D) and a three-dimensional progressive nucleation with diffusion-controlled growth (PN3Ddif The nuclei shape predicted by these NGMs are consistent with the respective morphologies obtained by SEM and AFM, which validates, once more, the proposed electro-polymerization model and the predictions from the NGM morphology of the respective electro-deposited polymer. In short, a correlation between the structure of the starting unit, doping and morphology of the electro-deposited polymer was established. At the same time conditions for the electro-obtention of this widely studied polymer were optimized, but this time on SS, a cheap electrodic substrate that makes its potential application more feasible

Influence of inorganic additives on wheat straw composting: Characterization and structural composition of organic matter derived from the process

Metallic oxides and clay minerals have gained increasing interest as additives of composting due to their influence in greenhouse gas emissions reduction and their effectivity in the stabilization of carbon both in compost and soils, leading to a cleaner compost production and potentially C sequestrant amendments. In this study, wheat straw (WS) was co-composted with iron oxide and allophanic soil and their influence on WS composting and composition of the end-products was evaluated. WS compost and their humic like-substances (HS) fraction were characterized by chemical and spectroscopic analyzes. After 126 days of process, the elemental composition showed slight differences of the N content for compost and HS, where the C/N atomic ratio tended to decrease relative to the initial material (WS; similar to 130). This trend was more pronounced in the HS from co-composted treatments (<30). The addition of inorganic materials increased the total acidity and phenolic-OH group contents (similar to 15 and 14 mEq g(-1) respectively, iron oxide treatment) relative to the treatment without inorganic additives. Nevertheless, the FTIR and solid-state (CNMR)-C-13 spectroscopy barely support the wet chemical analysis and revealed a similar final composition between all the studied compost treatments. These results suggest that the incorporation of these materials as compost additives had no major effect on the spectroscopic features of the end-products, however, critical changes of the properties such as the extractability, functionality and composition of HS were revealed by traditional methods. In conclusion, the supply of metal oxides and clays could impact the aerobic composting of WS favorizing the stabilization of certain C pools and adsorptive properties of the endproducts, that is of importance in production of amendments suitable for being used in degraded and contaminated soils. Nevertheless, under the experimental conditions of our research C stabilization apparently depends of other mechanisms that still need to be elucidate

CHLSOC : the Chilean Soil Organic Carbon database, a multi-institutional collaborative effort [Data Paper]

A critical aspect of predicting soil organic carbon (SOC) concentrations is the lack of available soil information; where information on soil characteristics is available, it is usually focused on regions of high agricultural interest. To date, in Chile, a large proportion of the SOC data have been collected in areas of intensive agricultural or forestry use; however, vast areas beyond these forms of land use have few or no soil data available. Here we present a new SOC database for the country, which is the result of an unprecedented national effort under the framework of the Global Soil Partnership. This partnership has helped build the largest database of SOC to date in Chile, named the Chilean Soil Organic Carbon database (CHLSOC), comprising 13 612 data points compiled from numerous sources, including unpublished and difficult-to-access data. The database will allow users to fill spatial gaps where no SOC estimates were publicly available previously. Presented values of SOC range from 6 x 10(-5) % to 83.3 %, reflecting the variety of ecosystems that exist in Chile. The database has the potential to inform and test current models that predict SOC stocks and dynamics at larger spatial scales, thus enabling benefits from the richness of geochemical, topographic and climatic variability in Chile. The database is freely available to registered users a