Mercury(Ⅱ) detection by water-soluble photoluminescent ultra-small carbon dots synthesized from cherry tomatoes

Mercury ions have been considered highly toxic to human health. What would be great is to develop the ionic probes without any toxicities themselves. Here, we report a friendly, highly sensitive mercury(II) ionic probe, watersoluble photoluminescence carbon dots which were synthesized by simply hydrothermal treatment of fresh cherry tomatoes without adding any other reagents. The ultra-small(\1 nm) carbon dots show robust excitation-depended photoluminescence under a wide p H range(4–10) or a strong ionic strength of up to 1 M, and the detection limit of mercury(II) has been determined as low as 18 n M. We envision such water-soluble, biocompatible carbon dots that could be applied to biolabeling, bio-imaging, and biosensing fields.

First Principle Study on Optical Properties of Tri-Group Doped(6,6) SiC Nanotubes

The optical properties of tri-group（B, Al, Ga, In） doped（6,6） SiC nanotubes（SiCNTs） are studied from first principles. The results show that the main absorption and dispersion of SiCNTs caused by the intrinsic transition appear in the ultraviolet-visible region（below 500 nm）, and the tri-group doping increases the minimum dielectric constant value resulting in enhanced transmittance. In addition, the tri-group doping can introduce a weak absorption and dispersion region in the near-mid-infrared region, and the response peak blue shifts as the diameter of the doping atom increases. Comparative studies of reflectance, absorptivity, and transmittance show that the key factors affecting the transmittance of SiCNTs are reflectance（or refractive index） rather than absorption coefficient.

Effects of substitution of group-V atoms for carbon or silicon atoms on optical properties of silicon carbide nanotubes

Silicon carbide nanotubes(SiCNTs) have broad application prospects in the field of micro-nanodevices due to their excellent physical properties. Based on first-principles, the difference between optical properties of SiCNTs where C atom or Si atom is replaced by group-V element is studied. The results show that the optical absorptions of SiCNTs doped by different elements are significantly different in the band of 600 nm–1500 nm. The differences in photoconductivity, caused by different doping elements, are reflected mainly in the band above 620 nm, the difference in dielectric function and refractive index of SiCNTs are reflected mainly in the band above 500 nm. Further analysis shows that SiCNTs doped with different elements change their band structures, resulting in the differences among their optical properties. The calculation of formation energy shows that SiCNTs are more stable when group-V element replaces Si atom, except N atom. These research results will be beneficial to the applications of SiC nanomaterials in optoelectronic devices and provide a theoretical basis for selecting the SiCNTs' dopants.

Conductance and dielectric properties of hydrogen and hydroxyl passivated SiCNWs

Based on the transport theory and the polarization relaxation model,the effects of hydrogen and hydroxyl passivation on the conductivity and dielectric properties of silicon carbide nanowires(SiCNWs)with different sizes are numerically simulated.The results show that the variation trend of conductivity and band gap of passivated SiCNWs are opposite to the scenario of the size effect of bare SiCNWs.Among the influencing factors of conductivity,the carrier concentration plays a leading role.In the dielectric properties,the bare SiCNWs have a strong dielectric response in the blue light region,while passivated SiCNWs show a more obvious dielectric response in the far ultraviolet-light region.In particular,hydroxyl passivation produces a strong dielectric relaxation in the microwave band,indicating that hydroxyl passivated SiCNWs have a wide range of applications in electromagnetic absorption and shielding.

A facile and precise method for quantifying small–large/light-weighted molecular interaction system

It is significant to quantify the intermolecular physisorption extent in biomedical field.By taking the advantage of a significant difference from either sizes or weights,we introduced a combination of Scatchard equation and either ultracentrifugation or size exclusion chromatography to obtain both the binding constant and the number of binding sites by using bovine serum albumin and eosin B as models.Compared to the photoluminescence quenching-based methods like Stern-Volmer and Hill equations,the introduced method is not only more precise but also simpler and more straightforward for the operation.Moreover,the protein conformational changes and the corresponding theoretical binding mode with an atomic resolution were also studied by using three-dimensional fluorescence spectroscopy and molecular docking method,respectively.These comparative results could help scientists select right methods to study any interactions between two molecules with significant differences from either sizes or weights.

Characterization of the copper-containing amine oxidase from Trifolium pratense seedlings

We studied the kinetic characterizations of the Trifolium pratense seedlings copper-containing amine oxidase(TPAO) by using various amine-containing substrates.The catalyzing rate for all of amine-containing substrates can be ordered as diamines > polyamines > aromatic monoamines,and it shows an apparent trend in each category of substrates such as the longer the carbon chain,the lower the V_(max) is,so does the V_(max)/K_m values but is opposite for the K_m value of TPAO.The distinct differences between the kinetic parameters for different amine-containing substrates indicated that the rate-determining step of the catalytic reaction strongly depends on the substrate's chemical structure.It is concluded that both pH and ionic strength can affect the catalytic activity of TPAO via influencing the coulomb interaction-mediated enzyme-substrate docking processes,which can be attributed to the potential of charged groups from both substrates and the activity sites of TPAO by the regulation of ionic strength.

Comparative study on transport properties of N-, P-, and As-doped SiC nanowires: Calculated based on first principles

According to the one-dimensional quantum state distribution, carrier scattering, and fixed range hopping model, the structural stability and electron transport properties of N-, P-, and As-doped SiC nanowires(N-SiCNWs, P-SiCNWs, and As-SiCNWs) are simulated by using the first principles calculations. The results show that the lattice structure of NSiCNWs is the most stable in the lattice structures of the above three kinds of doped SiCNWs. At room temperature,for unpassivated SiCNWs, the doping effect of P and As are better than that of N. After passivation, the conductivities of all doped SiCNWs increase by approximately two orders of magnitude. The N-SiCNW has the lowest conductivity. In addition, the N-, P-, As-doped SiCNWs before and after passivation have the same conductivity–temperature characteristics,that is, above room temperature, the conductivity values of the doped SiCNWs all increase with temperature increasing.These results contribute to the electronic application of nanodevices.