Ultralow dark current infrared photodetector based on SnTe quantum dots beyond 2 µm at room temperature.

Quantum dots (QDs) are promising materials used for room temperature mid-infrared (MIR) photodetector due to their solution processing, compatibility with silicon and tunability of band structure. Up to now, HgTe QDs is the most widely studied material for MIR detection. However, photodetectors assembled with HgTe QDs usually work under cryogenic cooling to improve photoelectric performance, greatly limiting their application at room temperature. Here, less-toxic SnTe QDs were controllably synthesized with high crystallinity and uniformity. Through proper ligand exchange and annealing treatment, the photoconductive device assembled with SnTe QDs demonstrated ultralow dark current and broadband photo-electric response from visible light to 2 µm at room temperature. In addition, the visible and near infrared photo-electric performance of the SnTe QDs device were well maintained even standing 15 d in air. This excellent performance was due to the effective protection of the ligand on surface of the QDs and the effective transport of photo-carriers between the SnTe interparticles. It would provide a new idea for environmentally friendly mid-IR photodetectors working at room temperature.

Effect of ionic liquid assisted hydrothermal carbonization on the properties and gasification reactivity of hydrochar derived from eucalyptus.

This project studies the relationship between the carbonization temperature and ionic liquid (IL) ([Bmim]Cl and [Bmim]OAC) solution and its impact on the structure, properties and gasification reactivity of the hydrochar obtained from eucalyptus via hydrothermal carbonization (HTC). The structure of hydrochar was analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy while its gasification reactivity with air was measured by thermogravimetric analysis at 340 °C. Results showed that the reactivity of hydrochar prepared in the presence of IL was much higher than that prepared using water. SEM analysis revealed some vesicles on the hydrochar surface during HTC at 220 °C, while Raman and XRD results showed more disordered crystal structure of the hydrochar in the presence of ILs. XPS and Raman results revealed that CO contents on the hydrochar surface increased after adding IL which implied that IL can promote opening the loop of aromatic nucleus of biomass. This study provides important information for the preparation of highly active biochar based on IL assisted HTC of eucalyptus for practical applications.

Membrane structural change of dimyristoylphosphatidylcholine liposome on the interaction with polyethyleneimine.

Polyethyleneimine (PEI) has long been considered as "golden standard" for polymeric gene delivery carriers. To get a better understanding on the molecular basis of PEI cytotoxicity, dynamic light scattering, zeta-potential measurement, fluorescence emission, Fröster resonance energy transfer and anisotropy measurement were conducted to reveal the interaction between PEI and dimyristoylphosphatidylcholine (DMPC) liposome and the influence on the structural properties of the membrane. PEI was found to bind onto the surface of the liposome, inducing an aggregation of the vesicle and an increase in surface potential at low PEI concentration up to 0.05 mg mL-1. A further increase in PEI concentration made little change on the surface potential, however reduced the aggregation of the vesicle due to the repulsion between the adsorbed PEI chains. PEI binding slightly increased the fluidity of lipid in interface region and decreased its packing density, and thus resulted in an enhanced leakage of calcein through the membrane. The polymer size played an important role in PEI-DMPC liposome interaction. PEI of higher molecular weight was more favorable to interact with DMPC and more efficient to perturb the structural properties of the membrane.

Facile synthesis of SrCO3 nanostructures in methanol/water solution without additives.

Highly dispersive strontium carbonate (SrCO3) nanostructures with uniform dumbbell, ellipsoid, and rod-like morphologies were synthesized in methanol solution without any additives. These SrCO3 were characterized by X-ray diffraction, field emission scanning electron microscopy, and N2 adsorption-desorption. The results showed that the reaction temperature and the methanol/water ratio had important effects on the morphologies of SrCO3 particles. The dumbbell-like SrCO3 exhibited a Broader-Emmett-Teller surface area of 14.9 m2 g-1 and an average pore size of about 32 nm with narrow pore size distribution. The formation mechanism of the SrCO3 crystal was preliminary presented.

[Spectroscopic study on the conformational change of silk fibroin in methanol-water mixtures].

A combinational study of circular dichroism, intrinsic fluorescence of protein and exogenous fluorescence probe of ANS was made to investigate the conformational change of silk fibroin in methanol-water mixtures as well as the mechanism. The spectral results showed that small hydrophobic regions were formed in silk fibroin in methanol-water mixtures at the concentration lower than 30% (V/V) via hydrophobic interaction, which was decreased at higher methanol content due to a structural transition of silk fibroin from random coil to beta-sheet. The conformational change of silk fibroin was found to be of a close relationship with the microstructure of the solvent and to be determined by the interaction between the peptide unit of silk fibroin and the cluster of the mixed solvent. Methanol-water mixture at low concentration had little effect on the solvation of the peptide unit and the conformation of silk fibroin, as a consequence of the fact that the inherent water structure was conserved. The transition from the tetrahedral-like water structure to the chain-like methanol structure, due to the increasing concentration of methanol, induced the conformational change of silk fibroin to eliminate the contact of peptide unit with the solvent molecular.