Control of Spatial Organization of Gold Nanoparticles Using Cylindrical Nanopores of Block Copolymers Films

Abstract In this paper, a sequential process of elaboration of hybrid nanostructured composite films has been proposed. The combination of phase separation in poly(styrene-block-4vinylpyridine) (PS-P4VP) block copolymer leading to the formation of nanopores, and gold nanocolloids synthesis confined in the nanoholes has allowed the facile fabrication of hexagonally arranged gold nanoparticles (NPs) onto silicon wafer. In particular, the nucleation and growth of gold nanoparticles took place within the nanopores, where they are confined in both size and shape the formed Au NPs. The resulting hybrid nanoscomposite has been characterized by Atomic Force Microscopy (AFM) and X-Ray Spectroscopy (XPS). This facile and simple process represents an opened pathway to several technologically important materials fabrication such as hierarchical and ordered crystal architectures. Indeed, the approach based on solvent phase, which is particularly attractive due to its low energy requirement, and the safety and environmentally gentle processing conditions

Mordenite etching in pyridine: textural and chemical properties rationalized by toluene disproportionation and n-hexane cracking

International audienceChemical etching with hydrofluoric acid in pyridine medium has been developed as efficient strategy for the crystal engineering of mordenite zeolites. Contrary to the HF etching in aqueous medium, the etching in pyridine allows to preserves the global composition and acidity of parent mordenites. Zeolites etched in pyridine have a similar distribution of Brønsted acid sites (BAS) as the parent, i.e. 16% in 8-MR channels, 19% at the intersection between side pockets and 12MR channels and 65% in the 12-MR channels. Etching in aqueous HF failed to preserve BAS distribution due to strong dealumination, which further leads to enlargement of side pockets. Mordenites etched with HF in pyridine allow for superior catalytic performance in both n-hexane cracking and toluene disproportionation. It has been evidenced that only the BAS located in the 8-MR side pockets prove active for the toluene disproportionation at 450 °C, while for n-hexane cracking at 541°C BAS in both 12-MR channels and 8-MRs pockets catalyze the reaction, yet BAS in side pockets are more active (1.5 times). Moreover, Lewis acid sites generated during the post-synthetic treatments exalt the strength of the active sites, which multiplies TOFs of the active sites by two

Mono vs. Difunctional Coumarin as Photoinitiators in Photocomposite Synthesis and 3D Printing

This work is devoted to investigate three coumarin derivatives (Coum1, Coum2, and Coum3), proposed as new photoinitiators of polymerization when combined with an additive, i.e., an iodonium salt, and used for the free radical polymerization (FRP) of acrylate monomers under mild irradiation conditions. The different coumarin derivatives can also be employed in three component photoinitiating systems with a Iod/amine (ethyl 4-dimethylaminobenzoate (EDB) or N-phenylglycine (NPG)) couple for FRP upon irradiation with an LED @ 405 nm. These compounds showed excellent photoinitiating abilities, and high polymerization rates and final conversions (FC) were obtained. The originality of this work relies on the comparison of the photoinitiating abilities of monofunctional (Coum1 and Coum2) vs. difunctional (Coum3) compounds. Coum3 is a combined structure of Coum1 and Coum2, leading to a sterically hindered chemical structure with a relatively high molecular weight. As a general rule, a high molecular weight should reduce the migration of initiating molecules and favor photochemical properties such as photobleaching of the final polymer. As attempted, from the efficiency point of view, Coum3 can initiate the FRP, but a low reactivity was observed compared to the monofunctional compound (Coum1 and Coum2). Indeed, to study the photochemical and photophysical properties of these compounds, different parameters were taken into account, e.g., the light absorption and emission properties, steady state photolysis, and fluorescence quenching. To examine these different points, several techniques were used including UV-visible spectroscopy, real-time Fourier Transform Infrared Spectroscopy (RT-FTIR), fluorescence spectroscopy, and cyclic voltammetry. The photochemical mechanism involved in the polymerization process is also detailed. The best coumarins investigated in this work were used for laser writing (3D printing) experiments and also for photocomposite synthesis containing glass fibers

Tropical peatland carbon storage linked to global latitudinal trends in peat recalcitrance

Peatlands represent large terrestrial carbon banks. Given that most peat accumulates in boreal regions, where low temperatures and water saturation preserve organic matter, the existence of peat in (sub)tropical regions remains enigmatic. Here we examined peat and plant chemistry across a latitudinal transect from the Arctic to the tropics. Near-surface low-latitude peat has lower carbohydrate and greater aromatic content than near-surface high-latitude peat, creating a reduced oxidation state and resulting recalcitrance. This recalcitrance allows peat to persist in the (sub)tropics despite warm temperatures. Because we observed similar declines in carbohydrate content with depth in high-latitude peat, our data explain recent field-scale deep peat warming experiments in which catotelm (deeper) peat remained stable despite temperature increases up to 9 °C. We suggest that high-latitude deep peat reservoirs may be stabilized in the face of climate change by their ultimately lower carbohydrate and higher aromatic composition, similar to tropical peats.National Science Foundation (Grant 1114155)National Science Foundation (Grant 1114161)NSF (Award 0628647)US Department of Energy, Office of Science, Office of Biological and Environmental Research (contract DE-SC0012088)US Department of Energy Office of Biological and Environmental Research under the Genomic Science program (Award DE-SC0004632)US Department of Energy Office of Biological and Environmental Research under the Genomic Science program (Award DE-SC0010580)US Department of Energy Office of Biological and Environmental Research under the Genomic Science program (Award DE-SC0016440)NASA Interdisciplinary Studies in Earth Science program (Award NNX17AK10G)US Department of Energy Office of Biological and Environmental Research under the Terrestrial Ecosystem Sciences program (Award DE-SC0012272

Tropical peatland carbon storage linked to global latitudinal trends in peat recalcitrance

Peatlands represent large terrestrial carbon banks. Given that most peat accumulates in boreal regions, where low temperatures and water saturation preserve organic matter, the existence of peat in (sub)tropical regions remains enigmatic. Here we examined peat and plant chemistry across a latitudinal transect from the Arctic to the tropics. Near-surface low-latitude peat has lower carbohydrate and greater aromatic content than near-surface high-latitude peat, creating a reduced oxidation state and resulting recalcitrance. This recalcitrance allows peat to persist in the (sub)tropics despite warm temperatures. Because we observed similar declines in carbohydrate content with depth in high-latitude peat, our data explain recent field-scale deep peat warming experiments in which catotelm (deeper) peat remained stable despite temperature increases up to 9 degrees C. We suggest that high-latitude deep peat reservoirs may be stabilized in the face of climate change by their ultimately lower carbohydrate and higher aromatic composition, similar to tropical peats.US Department of Energy Office of Biological and Environmental Research under the Terrestrial Ecosystem Sciences program [DE-SC0012272]; NASA Interdisciplinary Studies in Earth Science program [NNX17AK10G]; US Department of Energy Office of Biological and Environmental Research under the Genomic Science program [DE-SC0016440, DE-SC0004632, DE-SC0010580]; Geo. X, the Research Network for Geosciences in Berlin and Potsdam; US Department of Energy, Office of Science, Office of Biological and Environmental Research [DE-SC0012088]; NSF [0628647]; Natural Sciences and Engineering Research Council of Canada; National Research Foundation Singapore through the Singapore-MIT Alliance for Research and Technology's Center for Environmental Sensing and Modeling interdisciplinary research program; USA National Science Foundation [1114155, 1114161]; NASA LaRC POWER ProjectOpen access journal.This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]