Solvent-Type Passivation Strategy Controls Solid-State Self-Quenching-Resistant Behavior in Sulfur Dots.

Treatment of sulfur dots with polyethylene glycol (PEG) has been an efficient way to achieve a high luminescence quantum yield, and such a PEG-related quantum dot (QD)-synthesis strategy has been well documented. However, the polymeric insulating capping layer acting as the "thick shell" will significantly slow down the electron-transfer efficiency and severely hamper its practical application in an optoelectric field. Especially, the employment of synthetic polymers with long alkyl chains or large molecular weights may lead to structural complexity or even unexpected changes of physical characteristics for QDs. Therefore, in sulfur dot preparation, it is a breakthrough to use short-chain molecular species to replace PEG for better control and reproducibility. In this article, a solvent-type passivation (STP) strategy has been reported, and no PEG or any other capping agent is required. The main role of the solvent, ethanol, is to directly react with NaOH, and the generated sodium ethoxide passivates the surface defects. The afforded STP-enhanced emission sulfur dots (STPEE-SDs) possess not only the self-quenching-resistant feature in the solid state but also the extension of fluorescence band toward the wavelength as long as 645 nm. The realization of sulfur dot emission in the deep-red region with a decent yield (8.7%) has never been reported. Moreover, a super large Stokes shift (300 nm, λex = 345 nm, λem = 645 nm) and a much longer decay lifetime (109 µs) have been found, and such values can facilitate to suppress the negative influence from background signals. Density functional theory demonstrates that the surface passivation via sodium ethoxide is dynamically favorable, and the spectroscopic insights into emission behavior could be derived from the passivation effect of the sulfur vacancy as well as the charge-transfer process dominated by the highly electronegative ethoxide layer.

Study on the Surface Properties and Aggregation Behavior of Quaternary Ammonium Surfactants with Amide Bonds.

A number of techniques, including conductivity, surface tension, dynamic light scattering, transmission electron microscopy, and 1H nuclear magnetic resonance (1H NMR), Fourier transform infrared (FT-IR), and 1H-1H 2D nuclear Overhauser effect spectroscopy (1H-1H 2D NOESY), have been used to investigate the effect of amide bonds on the interfacial and assembly properties of a cationic surfactant, N-anilinoformylmethyl-N-cetyl-N,N-dimethyl ammonium chloride (AMC-C 16 ), in aqueous solutions. The adsorption of AMC-C 16 has been found to be much better than that of the conventional cationic surfactant, benzyl cetyldimethylammonium chloride (BAC-16) at the air/water interface and in solution. The surface tension measurements show the presence of two critical aggregation concentrations (CAC1 and CAC2) for AMC-C 16 . The presence of a strong intermolecular hydrogen bond of AMC-C 16 was confirmed by 1H NMR and FT-TR. The molecular interactions of AMC-C 16 were detected by 1H-1H 2D NOESY. The results show that the rigid group (phenyl) of AMC-C 16 was partially overlapped with its alkyl chain in aqueous solution, and the possible aggregation behavior for AMC-C 16 was proposed. The effects of an inorganic salt (NaCl) and an organic salt (C6H5COONa) to the aggregates of AMC-C 16 have been discussed.

LLSURE: local linear SURE-based edge-preserving image filtering.

In this paper, we propose a novel approach for performing high-quality edge-preserving image filtering. Based on a local linear model and using the principle of Stein's unbiased risk estimate as an estimator for the mean squared error from the noisy image only, we derive a simple explicit image filter which can filter out noise while preserving edges and fine-scale details. Moreover, this filter has a fast and exact linear-time algorithm whose computational complexity is independent of the filtering kernel size; thus, it can be applied to real time image processing tasks. The experimental results demonstrate the effectiveness of the new filter for various computer vision applications, including noise reduction, detail smoothing and enhancement, high dynamic range compression, and flash/no-flash denoising.

[Genetic diversity of Eucommia ulmoides by RAPD analysis].

OBJECTIVE: To determine the genetic diversity of Eucommia ulmoides. METHOD: 260 samples of 20 populations were analyzed through radom amplified polymorphic DHA (RAPD). RESULT: Total polymorphic loci percentage was 96.36 and the average was 38.92. 110 bands were produced with 10 random primers and 106 were polymorphic. Nei's gene diversity (H) was 0.246 1, Shannon's Information index(I) was 0.386 8, Gst was 0.424 4, indicating that 42.44% of the genetic variation was distributed among populations and 57.65% within populations. CONCLUSION: The genetic variation was relatively high in E. ulmoides, so the genetic diversity conservation principle should mainly focus on protection of the populations.