High-Performance Visible to Mid-Infrared Photodetectors Based on HgTe Colloidal Quantum Dots under Room Temperature.

HgTe colloidal quantum dots (CQDs) are one of few materials that can realize near-to-midwave infrared photodetection. And the quality of HgTe CQD directly affects the performance of photodetection. In this work, we optimize the method of synthesizing HgTe CQDs to reduce the defect concentration, therefore improving the photoelectric properties. The photodetector based on HeTe CQD can respond to the light from the visible to mid-infrared band. Notably, a photoresponse to 4000 nm light at room temperature is realized. The responsivity and detectivity are 90.6 mA W-1 and 6.9 × 107 Jones under 1550 nm light illumination, which are better than these of most reported HgTe CQD photodetectors. The response speed reaches a magnitude of microseconds with a rising time of τr = 1.9 µs and a falling time of τf = 1.5 µs at 10 kHz under 1550 nm light illumination.

[Characteristics and Mechanism of Cd Release and Transport in Soil Contaminated with PE-Cd].

Microplastics （MPs） are a type of emerging contaminants that pose a potential threat to global terrestrial ecosystems. The accumulation of MPs in soil inevitably affects soil physical and chemical properties， both directly and indirectly. Additionally， owing to their small size and surface features， MPs have excellent sorption capacity for both organic and inorganic materials， thus affecting their fate in the environment. However， the influence of MPs on heavy metal sorption and transport in soil is still not fully understood. In this study， polyethylene （PE） and Cd were selected as research objects， and on the basis of clarifying the adsorption mechanism of Cd on PE MPs， the effects of PE concentration and particle size on Cd release and transport behavior in soil under different ionic strengths and types （Ca2+ and Na+） were studied using column leaching experiments. The results of the batch experiments showed that the adsorption capacity of PE MPs for Cd2+ decreased with the increase in particle size. Scanning electron microscopy （SEM）， Fourier transform infrared spectroscopy （FTIR）， and Zeta potential were used to analyze the properties of PE MPs and adsorption behavior of Cd2+ onto MPs. The adsorption was mainly a physical process and was controlled by intra-particle diffusion. The adsorption kinetics could be described well by the quasi-second-order kinetics and Webber-Morris model. The adsorption isotherm conformed to the Langmuir model， indicating monolayer adsorption. The results of leaching experiments showed that the effect of PE MPs on Cd release and transport in soil was related to the CaCl2 concentration. At high ionic strength （0.05 mol·L-1 and 0.1 mol·L-1）， PE promoted the transport of Cd. The effluent concentration of Cd2+ increased from 6.48 mg·L-1 and 16.79 mg·L-1 to 7.12 mg·L-1 and 23.45 mg·L-1， whereas at low ionic strength （0.01 mol·L-1）， Cd transport was inhibited by PE MPs， and the effluent concentration of Cd2+ decreased from 0.66 mg·L-1 to 0.57 mg·L-1. The larger the amount of PE added， the more significant the promoting or inhibiting effect. Additionally， the release and transport of Cd in soil were also affected by the MPs particle size and concentration. When the addition amount was small （1%， 4%）， the large-sized MPs were more conducive to the transport of Cd in soil. When the addition amount was large （7%， 20%）， MPs with small particle sizes promoted Cd2+ transport more significantly. When the leaching solution used was NaCl， soil permeability decreased significantly. PE MPs had no significant effect on Cd release and transport but changed the stability of soil aggregates. In conclusion， PE MPs could change the release and transport behavior of Cd in soil， and the impact results were not only related to the particle size and content of MPs but were also influenced by the chemical properties of the soil solution.

Effect of particle dispersion on electrochemical performance of Prussian blue analogues electrode materials for sodium ion batteries.

Prussian blue analogues (PBAs) have advantages such as high voltage and low cost, making them one kind of the promising positive electrode materials for sodium-ion batteries. Particle dispersion is a key physical parameter of electrode materials, and understanding its impact on electrochemical performance is a prerequisite for obtaining high-performance PBAs. In this article, two PBAs samples with different particle dispersion were synthesized through sodium citrate-assisted co-precipitation method by means of staying and stirring. The influence of particle dispersion on electrochemical performance was investigated through polarization curve and AC impedance tests. It was found that PBAs with well-dispersed particles exhibited excellent rate performance, with a capacity of ~120 mAh g-1 at 1 C rate and a capacity retention of 75 % after 100 cycles. The capacity retention rate could reach 63 % at 5 C rate, far higher than that of PBAs samples with poor particle dispersion. From the perspective of electrochemical kinetics analysis, it has been shown that PBAs with well-dispersed particles exhibit smaller electrochemical polarization and faster Na+ diffusion reaction kinetics, which are key factors in achieving excellent rate performance.

Hot-Injection Synthesis of HgTe Nanoparticles: Shape Control and Growth Mechanisms.

Understanding the growth mechanisms of HgTe nanoparticles (NPs) with varied shapes is crucial for their applications in infrared photodetection. Here, we investigated the growth mechanisms of HgTe NPs with nanorod, sphere, and tetrahedral shapes in depth. The HgTe NPs with a nanorod shape are obtained at low reaction temperatures and formed by breaking tetrapod branches, while HgTe NPs with sphere and tetrahedron shapes have been further achieved at increased reaction temperatures. The systematic crystal analyses demonstrate this effective shape control is related to the synergic effect among the anisotropic passivation of oleylamine, surface free energy, and reaction temperatures. Our findings have deepened the understanding of shape control of the HgTe NPs and inspired a growing passion in the design and engineering of infrared photodetectors using HgTe NPs.

Synthesis of Polyaniline Coating on the Modified Fiber Ball and Application for Cr(VI) Removal.

In this study, polyaniline (PANI) is prepared by means of chemical oxidization polymerization and directly loaded on the modified fiber ball (m-FB) to obtain macroscale polyaniline/modified fiber ball (PANI/m-FB) composite, and then its removal ability of Cr(VI) is investigated. The effects of different parameters such as contact time, pH value and initial concentration on Cr(VI) removal efficiency are discussed. The experimental results illustrate that the favorable pH value is 5.0 and the maximum removal capacity is measured to be 293.13 mg g-1. Besides, PANI/m-FB composites can be regenerated and reused after being treated with strong acid. The kinetic study indicates that the adsorption procedure is mainly controlled by chemical adsorption. More importantly, the macroscale of composites can avoid secondary pollution efficiently. Benefiting from the low cost, easy preparation in large scale, environmentally friendly, excellent recycling performance as well as high removal ability, PANI/m-FB composites exhibit a potential possibility to remove Cr(VI) from industrial waste water. The polyaniline (PANI) was coated on modified fiber ball (m-FB) to remove Cr(VI) in waste water, and this kind of PANI/m-FB composites can avoid secondary pollution efficiently due to its macrostructure. Furthermore, the removal capacity can reach to 291.13 mg/g and can be multiple reused.

[Effects of Copper Pollution on Microbial Communities in Wheat Root Systems].

Wheat is the main food crop in China while at the same time, heavy metals pose a significant threat to crop growth and food security. Many studies indicate that rhizospheric microorganism play an important role in regulating crop development and stress resistance. In this study, the variation in wheat root-associated microbial communities under copper pollution was studied using high-throughput sequencing. The microbial community structure and diversity among different wheat rhizocompartments were compared after sequencing of microbial communities in the bulk soil, rhizosphere, and endosphere of wheat under copper pollution in combination with pot-based experiments. The results showed that the microbial diversity of the endosphere was significantly lower than in the rhizosphere and bulk soil(P<0.001), indicating that root surfaces serve as a gateway for microorganisms to enter into the interior root environment, and play a role in filtering root colonization. Copper pollution significantly reduced the microbial diversity of the rhizosphere (P<0.05). In the bulk soil and endosphere environments, although copper pollution reduced microbial diversity in the corresponding rhizocompartment, the difference was not significant (P>0.05). Proteobacteria and Actinobacteria were the dominant bacteria groups in the rhizosphere and the bulk soil under copper pollution. In addition, microbes such as Bacillus, Pseudoxanthomonas, and Sphingomonas show strong stress resistance and can provide nutrients for plants.

Plasmonic ordered pore array Ag film coated glass: transparent and solar heat reflective material.

In this paper, we fabricate ordered pore array (OPA) Ag film coated glass with the aid of polystyrene sphere (PS) array templates. This kind of OPA Ag coated glass has optical advantages of visible transparency, blue and near-infrared resistance. The average visible transmittance is 68%, including a transmission peak of 78% located at 570 nm, and low average transmittance of 48% in the blue light region that is not damaging to the eyes. The near-infrared light blocking rate is 67%, among which 40% light is reflected directly, indicating the reflection domination.

Preparation of Hollow Polyaniline Micro/Nanospheres and Their Removal Capacity of Cr (VI) from Wastewater.

The hollow polyaniline (PANI) micro/nanospheres are obtained through a simple monomer polymerization in alkaline solution with Triton X-100 Micelles as soft templates. The hollow PANI micro/nanospheres demonstrate rapid and effective removal ability for Chromium (VI) (Cr (VI)) in a wide pH range, and the maximum removal capacity can reach 127.88 mg/g at pH 3. After treated with acid, the used hollow PANI micro/nanospheres have about the similar removal capacity of Cr (VI) from wastewater.

Necklace-like NiO-CuO Heterogeneous Composite Hollow Nanostructure: Preparation, Formation Mechanism and Structure Control.

Composite hollow nanostructure composed by transition metal oxides are promising materials in electrochemistry, catalyst chemistry and material science. In this contribution, necklace-like NiO-CuO heterogeneous composite hollow nanostructures were synthesized by annealing Ni/Cu superlattice nanowires in air. Two kinds of morphologies including CuO nanotube linked core-shell structures and CuO nanotube linked hollow structures were obtained. The structure can be tuned easily by adjusting the relative length of Cu segments in Ni/Cu superlattice nanowires and the annealing temperature. The relative diffusion amount of Cu to Ni segments was proved to be the key factor to influence the annealed sample morphology. The formation mechanism was discussed in detail based on Kirkendal effect and high temperature oxidation of alloy. We demonstrated that hollow structure or core-shell structure is related to whether the oxidation exists only in external sites or co-exists in external and internal sites during annealing.

Noble-metal Ag nanoparticle chains: annealing Ag/Bi superlattice nanowires in vacuum.

One-dimensional noble-metal Ag nanoparticle chains have been prepared by electrodepositing Ag/Bi superlattice nanowires in a porous anodic alumina oxide (AAO) template and following an annealing process in vacuum. It is found that Bi, as a sacrificial metal, can be removed completely after annealing at 450 °C with a vacuum degree of 10(-5) Torr. The regulation of particle size, shape and interparticle spacing of Ag NP chains has been realized by adjusting the segment length of the Ag/Bi superlattice nanowires and the annealing condition. With an extension of the annealing time, it is observed that Ag particles display the transform trend from ellipsoid to sphere. Our findings could inspire further investigation on the design and fabrication of metal nanoparticle chains.

Ultrathin open-ended porous TiO2 membranes for surface nanopatterning in fabricating nanodot arrays.

This communication reports an approach to fabricate large-scale ultrathin open-ended porous TiO2 membranes (UOP-TMs) with ordered straight-through pores. Bi nanodot arrays on Si substrates are obtained by using the UOP-TMs as surface patterning masks.

Fano resonance in anodic aluminum oxide based photonic crystals.

Anodic aluminum oxide based photonic crystals with periodic porous structure have been prepared using voltage compensation method. The as-prepared sample showed an ultra-narrow photonic bandgap. Asymmetric line-shape profiles of the photonic bandgaps have been observed, which is attributed to Fano resonance between the photonic bandgap state of photonic crystal and continuum scattering state of porous structure. And the exhibited Fano resonance shows more clearly when the sample is saturated ethanol gas than air-filled. Further theoretical analysis by transfer matrix method verified these results. These findings provide a better understanding on the nature of photonic bandgaps of photonic crystals made up of porous materials, in which the porous structures not only exist as layers of effective-refractive-index material providing Bragg scattering, but also provide a continuum light scattering state to interact with Bragg scattering state to show an asymmetric line-shape profile.

A facile and universal way to fabricate superlattice nanowire arrays.

A facile and universal synthetic approach for preparing superlattice nanowire (SLNW) arrays is developed. In this method, two kinds of elements are alternately electrodeposited into the holes of the anodic alumina oxide (AAO) template, automatically in separate electrolytes by a programmed device. This method is not restricted by the relative values of the reduction potentials of the elements, and the deposition of each element can be controlled independently. Three kinds of representative SLNW arrays containing noble-metal material (Ag/Ni), thermoelectric material (Bi/Sb) and magnetic material (Ni/Cu) with adjustable segment length are fabricated successfully.

Decolorization of methylene blue by delta-MnO2-coated montmorillonite complexes: emphasizing redox reactivity of Mn-oxide coatings.

Delta-MnO(2) coatings on clay substrates tend to be poorer in crystallinity as compared with their discrete counterparts, which may be of environmental significance for adsorption and oxidation of contaminants. Discrete delta-MnO(2) particles and three delta-MnO(2)-coated montmorillonite complexes with varying MnO(2) loadings (4.8-34.9%) were synthesized, and oxidative decolorization of methylene blue (MB) by the synthetic materials was investigated in batch systems. Results showed that oxidative decolorization of MB increased with increasing loading of Mn-oxide coatings, whereas oxidation capacity of the coatings, on the basis of unit mass of MnO(2), tended to decrease. Initial reaction rate of MB oxidation by both delta-MnO(2) coatings and their discrete counterpart increased linearly with increasing Mn-oxide loadings, but the rate of the former was higher than that of the latter. An increase in humic acid concentration displayed a progressively enhanced promotive effect on MB decolorization, whereas the promotive effect was greatly suppressed at lower pH.

Adsorption of phosphate on hydroxyaluminum- and hydroxyiron-montmorillonite complexes.

One hydroxyaluminum-montmorillonite complex (HyAl-Mt), two hydroxyiron-montmorillonite complexes (HyFe-Mts) with different iron contents, and three hydroxyiron/aluminum-montmorillonite complexes (HyFeAl-Mts) with various Fe:Al molar ratios were synthesized. Behavior and kinetics of phosphate (P) sorption on selected Mt-complexes mentioned above were investigated under acidic conditions. The results indicated that the intercalations of polymeric HyFe and/or HyAl ions in interlayers of Na-saturated montmorillonite (Na-Mt) caused significant changes in surface properties of the Na-Mt, such as cation exchange capacity, specific surface area, pH at zero point of charge. In pH range tested (3.0-6.5), P adsorption on the Mt-complexes decreased with increasing pH, whereas the effect became weaker with increasing Fe contents in the Mt-complexes. The adsorption capacities of the HyFeAl-Mts were greater than those of the HyAl-Mt and HyFe-Mt, which could be attributed to decreasing crystallinity of Fe and Al oxides in the HyFeAl-Mts. The equilibrium adsorption of P on the Mt-complexes could be well described using the Langmuir isotherm, and the kinetics of P adsorption could be well described by both the pseudo-second-order and Elovich models. An increase in Fe contents in the Mt-complexes could enhance the initial kinetic rate of P adsorption, as suggested by the Elovich models. It is inferred that a great number of Fe-related active sorption sites have been located on the outer surfaces of the HyFe-Mt, as indicated by extremely high alpha value in the Elovich model. Previous studies focusing mainly on P sorption on HyAl-Mt complexes might have underestimated the contributions of Mt-complexes to P retention in acidic soils high in Fe contents.