Formulating Zwitterionic, Responsive Polymers for Designing Smart Soils.

The design of new remediation strategies and materials for treating saline-alkaline soils is of fundamental and practical importantance for many applications. Conventional soil remediation strategies mainly focus on the development of fertilizers or additives for water, nutrient, and heavy metal managements in soils, but they often overlook a soil sensing function for early detection of salinization/alkalization levels toward optimal and timely soil remediation. Here, new smart soils, structurally consisting of the upper signal soil and the bottom hygroscopic bed and chemically including zwitterionic, thermo-responsive poly(NIPAM-co-VPES) and poly(NIPAM-co-SBAA) aerogels in each soil layer are formulated. Upon salinization, the resultant smart soils exhibit multiple superior capacities for reducing the soil salinity and alkalinity through ion exchange, controlling the water cycling, modulating the degradation of pyridine-base ligands into water-soluble, nitrogenous salts-rich ingredients for soil fertility, and real-time monitoring salinized soils via pH-induced allochroic color changes. Further studies of plant growth in smart soils with or without salinization treatments confirm a synergy effect of soil remediation and soil sensing on facilitating the growth of plants and increasing the saline-alkaline tolerance of plants. The esign concept of smart soils can be further expanded for soil remediation and assessment.

Nanoscale InGaSb heterostructure membranes on Si substrates for high hole mobility transistors.

As of yet, III-V p-type field-effect transistors (p-FETs) on Si have not been reported, due partly to materials and processing challenges, presenting an important bottleneck in the development of complementary III-V electronics. Here, we report the first high-mobility III-V p-FET on Si, enabled by the epitaxial layer transfer of InGaSb heterostructures with nanoscale thicknesses. Importantly, the use of ultrathin (thickness, ~2.5 nm) InAs cladding layers results in drastic performance enhancements arising from (i) surface passivation of the InGaSb channel, (ii) mobility enhancement due to the confinement of holes in InGaSb, and (iii) low-resistance, dopant-free contacts due to the type III band alignment of the heterojunction. The fabricated p-FETs display a peak effective mobility of ~820 cm(2)/(V s) for holes with a subthreshold swing of ~130 mV/decade. The results present an important advance in the field of III-V electronics.

Spectroscopic investigation into oxidative degradation of silica-supported amine sorbents for CO(2) capture.

Oxidative degradation characteristics of silica-supported amine sorbents with varying amounts of tetraethylenepentamine (TEPA) and polyethylene glycol (PEG; P(200) or P(600) represents PEG with molecular weights of 200 or 600) have been studied by IR and NMR spectroscopy. Thermal treatment of the sorbents and liquid TEPA at 100 °C for 12 h changed their color from white to yellow. The CO(2) capture capacity of the TEPA/SiO(2) sorbents (i.e., SiO(2)-supported TEPA with a TEPA/SiO(2) ratio of 25:75) decreased by more than 60 %. IR and NMR spectroscopy studies showed that the yellow color of the degraded sorbents resulted from the formation of imide species. The imide species, consisting of NH associated with two C=O functional groups, were produced from the oxidation of methylene groups in TEPA. Imide species on the degraded sorbent are not capable of binding CO(2) due to its weak basicity. The addition of P(200) and P(600) to the supported amine sorbents improved both their CO(2) capture capacities and oxidative degradation resistance. IR spectroscopy results also showed that TEPA was immobilized on the SiO(2) surface through hydrogen bonding between amine groups and the silanol groups of SiO(2). The OH groups of PEG interact with NH(2) /NH of TEPA through hydrogen bonding. Hydrogen bonds disperse TEPA on SiO(2) and block O(2) from accessing TEPA for oxidation. Oxidative degradation resistance and CO(2) capture capacity of the supported amine sorbents can be optimized through adjusting the ratio of hydroxyl to amine groups in the TEPA/PEG mixture.

In situ infrared study of the role of PEG in stabilizing silica-supported amines for CO(2) capture.

The CO(2) capture capacity, adsorption mechanism, and degradation characteristics of two sorbents, silica-supported tetraethylenepentamine (TEPA/SiO(2)) and polyethylene-glycol-modified TEPA/SiO(2) (PEG/TEPA/SiO(2)), are studied by diffuse reflectance infrared Fourier transform spectroscopy and mass spectrometry. The CO(2) capture capacities of TEPA/SiO(2) and PEG/TEPA/SiO(2) are determined to be 2087 and 1110 micromol CO(2) g(-1) sorbent, respectively. Both sorbents adsorb CO(2) as hydrogen-bonding species, NH(2)--O, and carbamate/carboxylate species. The CO(2) adsorption half-time increases with the number of CO(2) capture cycles. Infrared results suggest that the increased adsorption half-time is a result of diffusion limitation, caused by accumulation of TEPA and PEG species on the surface of the sorbent particles. The degradation of TEPA/SiO(2) is found to correlate with the accumulation of carboxylate/carbamic species. The addition of PEG decreases the degradation rate of the sorbent and slows down the formation of carboxylate species. These carboxylate species can block CO(2) capture on amine (NH(2)/NH) sites. The stabilizing role of PEG on TEPA/SiO(2) can be attributed to hydrogen-bonding between TEPA (NH(2)/NH)and PEG (OH).