We report here a unique, simple method for synthesizing polymer film gradients with nanometer thickness through diffusion controlled surface polymerization. Polar solvents, especially water, have previously been shown to increase the rate of atom transfer radical polymerization (ATRP) of numerous monomers. That result made it apparent that the rate of ATRP polymerization could be regulated by the concentration of water in the polymerization solution. On the basis of this observation, we successfully developed a simple method for preparing polymer thin film gradients on substrates by water concentration gradient formed along the surface of substrates. An initiator attached substrate was placed in a two-layer system of water and a polymerization solution in which the diffusion of water into the polymerization solution resulted in a monomer concentration gradient, leading to varied polymerization rates along the substrate, and finally polymer thin film gradients. Poly(ethylene glycol) methacrylate (PEGMA) gradient thin films formed on silica surfaces have thickness ranging from a few of hundreds of angstroms to more than 1000 A ˚.
A novel donor–acceptor emitter exhibiting mechanochromic luminescence was used in light-emitting devices with tunable colors triggered by heat treatment.
A novel
light-emitting material 4-(4-diphenylaminophenyl)-benzo[d,e]benzo[4,5]imidazo[2,1-a]isoquinolin-7-one
(4-TPA-BBI) is synthesized and characterized.
4-TPA-BBI exhibits excellent polymorphism, mechanochromic luminescence
(MCL), and electroluminescence properties. It can form three different
aggregate species: yellow rod-like crystal (Y-crystal), orange needle-like
crystal (O-crystal), and red solid (R-solid). It is observed that
the Y-crystal can be reversibly changed to R-solid upon external stimuli,
while O-crystal can be irreversibly transformed to R-solid via sublimation
under a vacuum. Crystallographic and photophysical studies indicate
that the Y-crystal featuring loose molecular packing demonstrates
a high photoluminescence quantum yield (ΦPL ≈
1) and obvious MCL property, while the compactly packed O-crystal
shows a lower ΦPL of 0.646 with negligible MCL. A
nondoped light-emitting device based on 4-TPA-BBI as an emitter exhibits
bright orange emission with a peak at 588 nm, a high external quantum
efficiency of 4.4%, and a maximum luminance of 22470 cd m–2.
Two glyco-probes, GFP and GFN, which are derived from the condensation of 3-acetyl-5-C-(2,3-dihydroxy-1,4-anhydro-β-D-erythro-tetrofuranosyl)-2-methylfuran with benzaldehyde and 1-naphthaldehyde, respectively, are designed and synthesized. Of these two probes, GFP displays a selective and sensitive switch-on fluorescence response towards bovine serum albumin in phosphate-buffered saline over a wide pH range. Moreover, the fluorescence of this probe displays a good linear relationship with the bovine serum albumin concentration ranging from 0 to 0.8 mg/mL, and has a limit of detection as low as 3.7 nM. The stoichiometric ratio of bovine serum albumin /GFP is 1:1. This research paves the way for the development of glyco-probes for bovine serum albumin sensing.
A novel fluorescent chemosensor containing a coumarin–thiourea unit and a β- N-glycosyl moiety is designed, synthesized, and characterized by 1H NMR, 13C NMR, and elemental analysis. The chemosensor can selectively and efficiently detect Hg2+ in CH3CN with a detection limit of 2.6 μM.
Graphene coupling molybdenum-based nanocomposite structures were synthesized by changing the pyrolytic temperature to implement the molybdenum-based optimized microstructure. The structural and surface properties tests showed that the presence of the most variable species and a high proportion of divalent molybdenum on the surface of the material could effectively expose catalytic sites to improve reduction ability of N2 and inhibited hydrogen evolution reaction. Electrochemical investigations indicated that the Mo-700/rGO nanocomposite exhibited a significantly enhanced electrochemical ammonia synthesis performance. In 0.05[Formula: see text]M H2SO4, the Mo-700/rGO electrode achieved a Faradic efficiency of 12.7% at [Formula: see text]0.15[Formula: see text]V versus reversible hydrogen electrode (RHE), and an ammonia yield of 3.93[Formula: see text][Formula: see text]g[Formula: see text]h[Formula: see text][Formula: see text]cm[Formula: see text] at [Formula: see text]0.2[Formula: see text]V versus RHE.
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