Ultrasensitive triethylamine gas sensors with ZnSe nanospheres/nest-like Cr-doped MoO3.

Developing high-sensitivity TEA sensors has extremely important significance for human health. Design of three-dimensional (3D) nanostructures assembled from one-dimensional nanomaterials can effectively improve sensing performance. In this work, a nest-like structure assembled by Cr-doped MoO3 (Cr-MoO3) nanorods with relatively higher specific surface area was prepared. In order to improve the sensing performance, Cr-MoO3 skeleton was combined with ZnSe nanospheres of different mass ratios as sensing materials (ZnSe/Cr-MoO3), and the successful construction of the heterojunction structure was supported by various spectroscopies and charge density calculation. The prepared composite with an optimal moiety ratio showed very high response values of 371 and 1301 for 10 ppm and 50 ppm for TEA at 200 °C, respectively. Simultaneously, the composite sensor also exhibited a low detection limit (1.7 ppb). The improvement of the sensing performance of ZnSe/Cr-MoO3 was attributed to the formation of oxygen vacancies induced by Cr doping, the 3D nest-like structure provided an efficient network for charge transport/collection and the n-n heterojunctions between Cr-MoO3 nanorods and ZnSe nanospheres. The simulation analysis based on density functional theory (DFT) calculations indicated that the heterojunctions could effectively enhance the adsorption energy of TEA and the more charges transferring from TEA to the Cr-MoO3 nanorods.

Highly sulfonated poly ether ether ketone chelated with Cu2+ as a proton exchange membrane at sub-zero temperatures.

Improving the proton conductivity (σ) of proton exchange membranes at low temperatures is very important for expanding their application areas. Here, sulfonated poly ether ether ketone (SPEEK) membranes were prepared with different sulfonation degrees, and its maximum ion exchange capacity is 3.15 mmol/g for 10 h at 60 °C. Highly sulfonated SPEEK membrane exhibits ultra-high water uptake and excellent proton conductivity of 0.074 S/cm at -25 °C due to its abundant -SO3H. Nevertheless, its high swelling ratio and low mechanical strength are not conducive to the practical application of the membrane. Luckily, by employing the chelation of Cu2+ with -SO3- on the SPEEK chain, Cu2+-coordinated SPEEK membranes were prepared, and they not only retain high -SO3H content but also possess robust mechanical properties and good dimensional stability compared to pristine SPEEK membrane. Meanwhile, the σ of the SPEEK-Cu membrane reaches 0.054 S/cm at -25 °C, and its fuel cell maximum power (Wmax) reaches 0.42 W/cm2 at -10 °C, demonstrating superior low-temperature performance in comparison to other reported materials. Particularly, water states in the prepared membranes are quantified by low-temperature differential scanning calorimetry. Because much more water bound to the plentiful -SO3H and Cu2+ inside the membrane endows it with anti-freezing performance, the decay of the σ and the Wmax for the SPEEK-Cu membrane is retarded at sub-zero temperatures. It is envisioned that composite membranes comprising metal ions such as Cu2+-SPEEK have a high potential for sub-zero fuel cell applications.

Designing novel monolayer and multilayer h-CSe crystals with tunable photoelectric properties.

Using the first-principles method, a new structure of monolayer h-CSe was predicted, exhibiting good dynamical and thermal stability. The geometrical, electronic and optical properties of monolayer h-CSe are examined at the HSE level. Furthermore, the influences of the in-plane strain and layer number on the electric properties of the two dimensional h-CSe material are studied. The results indicate that it possesses an indirect band gap, which exhibits a rich variety of behaviors depending on the small in-plane biaxial strain. The band gap of monolayer h-CSe could be easily tuned in the energy range from 0.82 eV to 2.61 eV under small in-plane biaxial strain (from -3% to 3%). Also, a band gap transition between direct and indirect types is not found. The band gap of the h-CSe materials decreases with the increase of their layer number. In addition, it was found that these h-CSe materials show excellent optical properties, including strong light harvesting ability for the ultra-violet light range of the solar spectrum. The results obtained here indicate that monolayer h-CSe may have significant potential applications in future nanoelectronic fields.

[Basic Research on Therapy of Leukemia with Nanoparticles Drug Delivery System Modified by Transferrin Receptor Monoclonal Antibody].

OBJECTIVE: To investigate the therapeutic effect of targeted drug-loaded nanoparticles modified by transferrin receptor monoclonal antibody (TfR mAb) on acute leukemia and its potential anti-tumor mechanism. METHODS: Nanoparticles drug delivery system, which was composed of poly (lactic-co-glycolic acid), poly-l-lysine, polyethylene glycol, TfR mAb (TfR mAb-PLGA-PLL-PEG)-daunorubicin (DNR), was first synthesized. After drug intervention, the intracellular accumulation in leukemia HL60 cells was observed under a fluorescent microscope and concentration of DNR was determined by flow cytometry (FCM). Meanwhile, cell apoptosis rate was measured by FCM and the expression levels of apoptosis related protein Cleaved-caspase 3 was determined by Western blot. RESULTS: Under an inverted fluorescent microscope, intracellular accumulation of DNR autofluorescence in HL60 cells was observed in both TfR mAb-PLGA-PLL-PEG-DNR group and DNR group. FCM analysis showed that the intracellular concentration of DNR in TfR mAb-PLGA-PLL-PEG-DNR group was higher than that in DNR group（P<0.05）. The apoptotic rate of HL60 cells in TfR mAb-PLGA-PLL-PEG-DNR group was higher than that of DNR group（P<0.05）. Moreover, the expression levels of apoptosis-related protein Cleaved-caspase 3 in TfR mAb-PLGA-PLL-PEG-DNR group was significantly higher than that in DNR group（P<0.05）. CONCLUSION: TfR mAb-PLGA-PLL-PEG nanoparticle drug delivery system can target chemotherapy drugs to leukemia cells and enhance anticancer ability through apoptotic pathway.

Neutron Irradiation Effects on Boron Nitride-Based Ceramics for Use in X-ray Detection.

X-ray detectors based on conventional semiconductors with large atomic numbers are suffering from the poor stability under a high dose rate of ionizing irradiation. In this work, we demonstrate that a wide band gap ceramic-boron nitride with small atomic numbers could be used for sensitive X-ray detection. Boron nitride samples showed excellent resistance to ionizing radiation, which have been systematically studied with the neutron- and electron-aging experiments. Then, we fully analyzed the influence of these aging effects on the fundamental properties of boron nitride. Interestingly, we found that the boron nitride samples could maintain relatively good charge transport properties even after large dose of neutron irradiation. The fabricated X-ray detectors showed decent performance metrics, and the neutron-aged boron nitride even showed improved operational stability under continuous X-ray irradiation, suggesting the great potential for real applications.

Application Progress of PALS in the Correlation of Structure and Properties for Graphene/Polymer Nanocomposites.

Giving a deep insight into the microstructure, and realizing the correlation between microstructure and properties is very important to the precise construction of high-performance graphene/polymer nanocomposites (GPN). For the promising application in microstructure characterization, much attention has been focused on the effective technique of positron annihilation lifetime spectroscopy (PALS). Based on the introduction of the basic principle, this review summarized the application progress of PALS in the correlation of microstructure and properties for GPN, especially for the characterization of free volume and interfacial interaction, and the correlation of these microstructures and properties.

New Aspects of Degradation in Silicone Rubber under UVA and UVB Irradiation: A Gas Chromatography-Mass Spectrometry Study.

In this paper, gas chromatography-mass spectrometry (GC-MS) and positron annihilation lifetime spectroscopy (PALS) were used to probe the changes of oligomers and the polydimethylsiloxane (PDMS) network in silicone rubber, after different durations of UVA/UVB irradiation. At the early stage (<300 h) of UVA/UVB irradiation, the concentration of D4-D9 decreases. The o-Ps intensity of the extracted silicone rubber increases in the stage after UVB irradiation. These results indicate the crosslinking of oligomers into the PDMS network. After a long duration (>300 h) of UVB irradiation, D4 was generated and the lifetime of τ3 also increased, indicating the rupture of the Si-O bond in the PDMS network. These two aging processes were termed the post curing process and the chain session process. The new finding was that UVA could only induce the post curing process; UVB causes the rupture of the chemical bond in silicone rubber. Photons of UVB could break the C-H bond, and then trigger the backbiting decomposition of PDMS, breaking the Si-O bond, while the photons of UVA cannot. The fact that D4 was generated after UVB irradiation can be used to evaluate the UVB stability of silicone rubber in the future.

Numerical investigation of the thermal effect on flow and dispersion of rooftop stack emissions with wind tunnel experimental validations.

The thermal effect on the flow and dispersion of pollutants emitted from a rooftop stack is investigated by means of CFD (computational fluid dynamics) models with wind tunnel experimental validations. The leeward wall and its nearby ground are heated simultaneously to mimic solar radiation. Seventeen Ri (Richardson number) cases with four inflow wind speeds (1, 3, 6, and 9 m/s) and five temperature differences (0, 60, 120, 180, and 240 K) between the heated surface and ambient air are considered to represent the interaction between thermal buoyancy force and inertia force. The results reveal that (1) the steady RANS (Reynolds Averaged Navier-Stokes) computations with Boussinesq approximation can generally reproduce the effect of thermal buoyancy on the wake flow and pollutant distribution in wind tunnel experiments; (2) the wake vortex flow is less affected by the thermal buoyancy force at small Ri (e.g., Ri ≤ 0.26) while an upward flow rather than a clockwise vortex structure is developed in the near wake at Ri ≥ 0.58; (3) it is inappropriate to place fresh air intakes on the leeward wall of the emitting building, but natural ventilation through windows on the leeward wall can be implemented at higher Ri (e.g., Ri = 2.33); (4) at the pedestrian respiration height downstream of the building, the distance between the location of maximum pollutant concentration and the leeward wall increases linearly with Ri while the maximum dimensionless concentration decreases exponentially with increasing Ri; (5) the air temperature is rapidly reduced away from the heated wall/ground and a heat accumulation zone is formed at the ground corner next to the leeward wall. This study can be helpful for determining the strategy for natural ventilation through windows and for evaluating the impacts of rooftop stack exhaust on air quality downstream of emitting buildings.

A reclaimed piezoelectric catalyst of MoS2@TNr composites as high-performance anode materials for supercapacitors.

A piezoelectric catalyst of the MoS2@TNr composite (MoS2 nanosheets composited with TiO2 nanorods) was synthesized by a two-step hydrothermal method, and can be recycled and reused as an advanced anode material for supercapacitors. In the dark, the MoS2@TNr composite exhibited ultra-fast piezoelectric catalytic performance and good cycle stability on dye degradation; within 10 min, nearly all rhodamine B (50 mL, 20 ppm) was removed from the solution with the assistance of magnetic stirring. After the 5 cycle degradation reaction, the catalyst was reclaimed and applied to electrochemical testing, which showed better supercapacitor capacitance properties than the fresh catalyst due to the introduction of oxygen vacancies generated from the piezoelectric degradation process. The reclaimed catalyst demonstrated an excellent specific capacitance of 249 F g-1 at 1 A g-1, and 92% capacitance retention after 10 000 cycles. Furthermore, as the current density increased to 30 A g-1, the capacitance could maintain 58% of the initial value. Thus, it can be concluded that the abandoned catalysts may serve as a potential electrode material for energy storage; simultaneously, the reutilization could eliminate secondary pollution and decrease the energy consumption in efficiency.

Free volume, gas permeation, and proton conductivity in MIL-101-SO3H/Nafion composite membranes.

A series of MIL-101-SO3H/Nafion composite membranes was synthesized. They show an improved proton conductivity, due to the abundance of SO3H groups, which fosters proton conduction by binding the water molecules and enabling a larger number of conducting sites. Gas (including water vapor, hydrogen, and oxygen) permeability, crystallinity, and free volumes of the MIL-101-SO3H/Nafion composite membranes were investigated, as well as their correlation. By increasing the MIL-101-SO3H content, the gas permeability of the membranes significantly decreases, since the crystalline region is larger and the water-bearing MIL-101-SO3H particles are efficient barriers for the gas molecules. The gas permeation in the composite membranes is a very complex process and the results indicate no simple linear relation between the gas permeability and the free volume size (VFV), or between the gas permeability and the crystallinity. Moreover, it is very interesting to observe that the influence of VFV on the gas permeability is closely related to the size of the particular gas molecules: the larger the size of the gas molecules, the larger the free volume needed to achieve their rapid diffusion in the membrane. The results suggest the presence of a threshold value for VFV, which depends on the size of the gas molecules: when VFV is lower than this value, the gas molecules cannot easily jump through neighboring free volumes to a neighboring site, and, as a result, the permeability drops quickly.

Dependence of Dye Molecules Adsorption Behaviors on Pore Characteristics of Mesostructured MOFs Fabricated by Surfactant Template.

In this work, mesostructured metal-organic frameworks (MOFs) of MIL-101-Crs with different specific surface areas were synthesized successfully under solvothermal conditions using cationic surfactant cetyltrimethyl ammonium bromide (CTAB) as a structural template. It was found that crystallinity degrees, specific surface areas, and pore size distributions strongly depended on the loading of CTAB. Nitrogen adsorption and positron annihilation lifetime spectroscopy (PALS) results showed that the mean mesopore size increased with loading more CTAB due to the formation of larger templated mesopores. Although Langmuir adsorption of both methylene blue (MB) and methyl orange (MO) was confirmed in MIL-101-Crs, the experimental results showed different adsorption behaviors for them depending on the dye molecular size, pore structure, and charge properties of dye molecules/MOFs in solution. The MB molecules were found to be mainly adsorbed in the interspaces between grains and the templated mesopores, whereas the MO molecules were adsorbed in the inherent pores as well as the templated ones in MOFs due to the unsaturated metal sites' electrostatic attraction on them. Remarkably, MO adsorption capacity was observed to be proportional to the specific surface area, which allowed one to get a good linear fitting of experimental data. Interestingly, the good consistence between the fitting experimental parameter, that is, the number of adsorbed MO-s per unit specific surface area, and the calculated one according to our rough estimation strongly suggests that MO-s are electrostatically attracted and rotating around the unsaturated metal sites on MOFs' inner surfaces, which exclude other MO-s to be adsorbed around due to the "hindering effect" of the rotating motion.