No abstract

Hydrogels consisting of carboxylic acid groups and N-isopropylacrylamide as pendants on their polymeric network usually exhibit volume expansion upon deprotonation or volume contraction when being heated. Demonstrated here is an anti-intuitive case of a hydrogel containing multiple carboxylic acid groups at each crosslinking point in the polymeric network, which shrinks upon increasing pH from 1 to 7 at 37 °C or expands upon heating from 25 to 37 °C at pH 1. The unexpected volume change originates from the high percentage of the crosslinker in the polymers, as detected by solid-state C NMR spectroscopy. In addition, the volume changes are thermally reversible. As the first example of the use of functional hyper-crosslinkers to control the pH and thermal responses of nanogels, this work illustrates a new way to design soft materials with unusual behaviors.

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No abstract

Ni-doped TiO 2 nanoparticles have been synthesized by a modified sol-gel method. The crystal phase composition, particle size, and magnetic and optical properties of the samples were comprehensively examined using x-ray diffraction analysis, transmission electron microscopy, Brunauer-Emmett-Teller surface area analysis, Raman spectroscopy, magnetization measurements, and ultraviolet-visible (UV-Vis) absorption techniques. The results showed that the prepared Ni-doped TiO 2 samples sintered at 400°C crystallized completely in anatase phase with average particle size in the range from 8 nm to 10 nm and presented broad visible absorption. The bactericidal efficiency of TiO 2 was effectively enhanced by Ni doping, with an optimum Ni doping concentration of 6% (x = 0.06), at which 95% of Escherichia coli were killed after just 90 min of irradiation. Density functional theory (DFT) calculations revealed good agreement with the experimental data. Moreover, the Ni dopant induced magnetic properties in TiO 2 , facilitating its retrieval using a magnetic field after use, which is an important feature for photocatalytic applications.