P-block atom modified Sn(200) surface as a promising electrocatalyst for two-electron CO2 reduction: a first-principles study.

Low activity and poor product selectivity of CO2 reduction have seriously hampered its further practical application. Introducing p-block atoms to the catalyst is regarded as a promising strategy due to the versatility of p orbitals and diversity of p-block elements. Here, we systematically studied the influence of p-block atom X (X = C, N, O, S, and Se) on CO2 catalytic properties on a Sn(200) surface by first-principles calculation. Our work shows that all the p-block atoms are relative stable with Ef in the range of -5.11 to -3.59 eV. Further calculation demonstrates that the diversity of the p-block atoms results in unique CO2 electrocatalytic activity and product selectivity. Interestingly, the p-block C atom shows bi-functional activity to form two-electron products HCOOH and CO, with the corresponding energy barriers remarkably low at about 0.19 eV and 0.28 eV. In particular, the p-block S(Se) atom appears to have striking HCOOH selectivity, with the energy barrier to form HCOOH only a quarter of that to form the CO product. This unusual behavior is mainly attributed to the adsorption strength and frontier orbital interaction between the p-block atom and intermediates. These findings can effectively provide a valuable insight into the design of highly efficient CO2 electrocatalyst.

Positive expression of ZNF689 indicates poor prognosis of hepatocellular carcinoma.

The objective of the present study was to investigate the association between zinc finger protein (ZNF) 689 expression and the clinicopathological features and prognosis of hepatocellular carcinoma (HCC). A total of 102 paired HCC and paired non-cancerous tissues, and 16 normal liver tissues were collected. ZNF689 expression was examined in HCC tissues, paired-noncancerous tissues, and normal liver tissues using RT-qPCR and immunohistochemistry analysis, and the association between ZNF689 expression and HCC prognosis was analyzed using the Kaplan-Meier method. ZNF689 expression was not significantly different between HCC tissues and paired-noncancerous tissues (P=0.61). ZNF689 expression in HCC and paired-noncancerous tissues was significantly increased compared with that in normal liver tissues (P<0.01). Positive expression of ZNF689 protein in HCC was significantly associated with a tumor size of ≥10 cm, tumor capsule infiltration, and microvascular invasion (P<0.05). Positive expression of ZNF689 was a prognostic factor for overall survival time [hazard ratio (HR):1.961; P=0.048] and progression-free survival time (HR:1.902; P=0.041). ZNF689 maybe a novel predictor for prognosis of patients with HCC.

Transfer from trap emission to band-edge one in water-soluble CdS nanocrystals.

A simple and rapid route to water-soluble CdS nanocrystals stabilized by citrate was reported, and the transfer of citrate-stabilized CdS NCs from trap emission to band-edge one was studied systematically for the first time. It was found that heating in air, alkaline activation and illumination, all efficiently manipulated surface states of CdS NCs and controlled the emission states, leading to transferring CdS NCs from a broad trap emission (FWHM ~125 nm) to their strong, narrow band-gap emission (FWHM ~25 nm), comparable to that of CdS NCs synthesized by organic routes. Lifetime decay kinetic studies demonstrated that the average lifetimes for CdS NCs before and after transferred were 131.1 and 32.7 ns, respectively. The freshly-synthesized NCs were predominated by trap emission (~94%), while the transferred CdS NCs with well cubic structure dominated by band-edge emission (up to 91%). The tunable emissions of CdS NCs from violet to green could be achieved by controlling emission states of CdS NCs with different Cd/S molar ratios. The transfer mechanisms of CdS NCs from trap to band-edge emission were proposed to be epitaxial growth of a Cd(OH)(2) shell on CdS NCs core. The transition probability of energy states before and after transferred was further investigated.

Synthesis of NAC capped near infrared-emitting CdTeS alloyed quantum dots and application for in vivo early tumor imaging.

The synthesis of water-soluble near-infrared (NIR)-emitting quantum dots (QDs) has recently received extensive attention for non-invasive detection of biological information in living subjects. Highly fluorescent CdTeS alloyed QDs for biological application are introduced in this paper. QDs were synthesized by a hydrothermal method and coated with N-acetyl-l-cysteine (NAC) as both bioactive ligand and sulfur source for biocompatibility and biological stability. The optical properties, morphology and structure of CdTeS alloyed QDs were characterized. The in vitro and in vivo toxicity was intensively investigated. Furthermore, the dynamics and bio-distribution of CdTeS alloyed QDs on living mice were studied. To explore biomedical application, folate-polyethylene glycol (FA-PEG) was used to decorate the CdTeS alloyed QDs (FP-CdTeS QDs) for targeted imaging of tumors over-expressing the folate receptor (FR). The tumor targeting capability of FP-CdTeS QDs on tumor bearing nude mice was demonstrated. The results showed that the prepared CdTeS QDs have excellent optical properties and low toxicity, which makes them an ideal inorganic material for biomedical imaging. In addition, the folate-PEG conjugated NIR-QDs displayed good biocompatibility as well as excellent sensitivity and specificity for optical imaging of tumors which can extend the application of CdTeS QDs.

[Quantitative determination of pazufloxacin using water-soluble quantum dots as fluorescent probes].

The quantum dots (QDs) synthesized in aqueous solution have more advantages than those synthesized in organic solution, for drugs always act on the biological systems. In addition, the CdTe QDs surface-bound TGA molecules can not only enhance the fluorescence intensity, but also improve the stability of quantum dots, which makes the integrate of quantum dots and the organism easier. The present paper studied on the interaction of CdTe quantum dots, which were synthesized in aqueous solution with pazufloxacin, the forth generation of quinoloines drugs by fluorescence spectrum and absorption spectrum. The results showed that the fluorescence intensity of CdTe quantum dots decreased regularly with increasing concentration of pazufloxacin. No absorption band was observed in the 400-700 nm wavelength range for pazufloxacin, so the quenching effect of pazufloxacin on the fluorescence of CdTe QDs was not due to an inner filter resulting from the absorption of the emission wavelength by pazufloxacin. No obvious change was observed for the CdTe QDs absorption spectra before and after adding pazufloxacin, and a blue-shift or red-shift of the fluorescence emission spectra was also not seen when the concentration of pazufloxacin was changed from 10.0 to 850 microg x mL(-1), which also meant that CdTe QDs had not aggregated or become smaller after adding pazufloxacin. And the CdTe QDs, which had a good dispersion characteristic, uniform shape and centralized distribution whether in or out of pazufloxacin solution, were observed by the images of transmission electron microscopy. This indicated that the mechanism of the reaction was likely to be that the changes of surface-bound organic molecules of QDs, the --COOH chemical bond, were induced by pazufloxacin, and the Te-oxygen complex was formed at the Cd surface vacancies. Based on the quenching of the fluorescence of CdTe QDs by pazufloxacin, a rapid, novel and specific method for pazufloxacin determination was proposed. In the optimum conditions, pazufloxacin concentration versus quantum dots fluorescence gave a linear response with an excellent 0. 995 4 correlation coefficient, between 10.0 and 850 micorg x mL(-1). The limit of detection (S/N=3) was 3. 254 x 10(-3) microg x mL. And the quenching constant could be obtained, which was 2.188 x 10(4) L x mol(-1). The RSD value about fluorescence quenching of CdTe QDs by 5 groups of 50 microg x mL(-1) concentration of pazufloxacin was 0.3%. The contents of pazufloxacin in freeze-dried powder injection and sodium chloride injection were determined by the proposed method and the results agreed with the claimed values. The proposed method is much more convenient, rapid, sensitive and has a much broader linear range than other methods, such as HPLC, HPCE and UV etc. It is hopeful to contribute to the development of the studies of pharmacal imaging and the reaction mechanisms of medicines in vivo further.

[Application of wavelet transform to the infrared diffusion reflectance spectrum of rocks].

The infrared diffuse reflectance spectra of hydrocarbon source rocks with different particle sizes were measured. The result indicated that the absorbency of the raw spectrum decreased with the reduction of particle size, but the relationship turned to be reverse after we pretreated the original spectra by using wavelet transform to eliminate the background and calibrate the baseline drift, both of which were caused by scattering. The reversed relations showed that the spectral lines were influenced deeply by the scattering of the samples. So the particle size of the samples to be measured and the particle size of the model samples must be consistent to reduce the error. The low frequency part of the spectrum filtrated by wavelet transform corresponds to the scattering, and the authors used it to set up a model at the latent absorbance wave number (near 2 820 cm(-1)) to forecast the particle size. By comparing this model with the other model based on the original spectrum the authors found that the pertinence of the anterior model is higher than the latter one and the value reaches 0.999 7. So the authors can accurately forecast and control the distribution of the particle size by this model, which can be used to improve the accuracy in the quantitative analysis of the infrared reflectance spectrum. Also the study validated that both scattering and absorption coefficients are inversely correlated with the particle size.

Water-soluble CdSe and CdSe/CdS nanocrystals: a greener synthetic route.

We report a new green synthetic route of CdSe and core-shell CdSe/CdS nanoparticles (NPs) in aqueous solutions. This route is performed under water-bath temperature, using Se powder as a selenium source to prepare CdSe NPs, and H(2)S generated by the reaction of Na(2)SH(2)SO(4) as a sulfur source to synthesize core-shell CdSe/CdS NPs at 25-35 degrees C. The synthesis time of every step is only 20 min. After illumination with ambient natural light, photoluminescence (PL) intensities of CdSe NPs enhanced up to 100 times. The core-shell CdSe/CdS NPs have stronger photoactive luminescence with quantum yields over 20%. The obtained CdSe NPs exhibit a favorable narrow PL band (FWHM: 50-37 nm) with increasing molar ratio of Cd/Se from 4:1 to 10:1 at pH 9.1 in the crude solution, whereas PL band of corresponding CdSe/CdS NPs is slightly narrower. The emission maxima of nanocrystals can be tuned in a wider range from 492 to 592 nm in water by changing synthesis temperature of CdSe core than those reported previously. The resulting new route is of particular interest as it uses readily-available reagents and simple equipment to synthesize high-quality water-soluble CdSe and CdSe/CdS nanocrystals.