Novel in-situ encapsulation of tin phosphide particles in MXene conductive networks as anode materials of the durable sodium-ion battery.

Sodium-ion battery (SIB) is one of potential alternatives to lithium-ion battery, because of abundant resources and lower price of sodium. High electrical conductivity and long-term durability of MXene are advantageous as the anode material of SIB, but low energy density restricts applications. Tin phosphide possesses high theoretical capacity, low redox potential, and large energy density, but volume expansion reduces its cycling stability. In this study, tin phosphide particles are in-situ encapsulated into MXene conductive networks (SnxPy/MXene) by hydrothermal and phosphorization processes as novel anode materials of SIB. MXene amounts and hydrothermal durations are investigated to evenly distribute SnxPy in MXene. After 100 cycles, SnxPy/MXene reaches high specific capacities of 438.8 and 314.1 mAh/g at 0.2 and 1.0 A/g, respectively. The capacity retentions of 6.0% and 73.6% at 0.2 A/g are respectively obtained by SnxPy and SnxPy/MXene. The better specific capacity and cycling stability of SnxPy/MXene are attributed to less volume expansion of SnxPy during charge/discharge processes and relieved self-stacking of MXene by encapsulating SnxPy particles between MXene layers. Electrochemical impedance spectroscopy and Galvanostatic intermittent titration technique are also applied to analyze the charge storage mechanism in SIB. Higher sodium ion diffusion coefficient and smaller charge-transfer resistance are obtained by SnxPy/MXene.

[Influence of Operating Modes for the Alternating Anoxic/Oxic Process on Biological Nitrogen Removal and Extracellular Polymeric Substances of Activated Sludge].

Nitrogen removal, extracellular polymeric substances (EPS), and the chemical composition (protein (PN), polysaccharide (PS), and DNA) by the aerobic/anoxic (O/A) and the anoxic/aerobic (A/O) modes were studied in a sequencing batch reactor (SBR) fed with domestic wastewater. The results showed that the removal rates of NH4+-N were 97.5% and 98.0% in the two operating modes, respectively, and a removal efficiency of NH4+-N with high efficiency and stability was obtained. The nitrification rate was positively correlated with the nitrogen loading ratio. The influence of operating modes for the alternating anoxic/oxic mode on extracellular polymeric substances of activated sludge was evaluated. The EPS constituent in the A/O mode was slightly higher than the O/A mode. The operating mode had no effect on the contents of PN, PS, and DNA in tightly bound EPS (TB-EPS) and TB-EPS. However, PN and PS in loosely bound EPS (LB-EPS) and LB-EPS in the A/O mode were 1.38 to 1.56 times those of the O/A mode. In the two operating modes, PSs were the main constituents in the TB-EPS and EPS, while PNs were the main constituents in LB-EPS. The EPS content had a good linear correlation with the sludge settling performance.

[Effect of Temperature on Nitrogen Removal Performance and the Extracellular Polymeric Substance (EPS) in a Sequencing Batch Reactor (SBR)].

In this paper, the long-term effects of temperature on the nitrogen removal performance and the extracellular polymeric substance (EPS) in a sequencing batch reactor (SBR) treating synthetic wastewater was investigated under three temperature conditions (15℃, 25℃, 35℃). The results showed that high temperatures (35℃) could promote the establishment of short-cut nitrification processes and improve nitrogen removal performance greatly. Temperature had a significant impact on the EPS and its composition. With an increased temperature, the EPS and tightly bound EPS (TB-EPS) content decreased, while, loosely bound EPS (LB-EPS) increased slowly. TB-EPS became dominant in the EPS (the percentage of TB-EPS/EPS was 69.0%-79.5%), however, the ratio of TB-EPS/LB-EPS decreased from 3.8 (15℃) to 3.6 (25℃), and then to 2.2 (35℃) with a gradual increase in temperature. Moreover, protein (PN) and DNA in the EPS, TB-EPS, and LB-EPS decreased with an increasing temperature. Carbohydrates (PS) in the EPS and LB-EPS increased as temperature increased, nevertheless, PS in TB-EPS decreased. Furthermore, 25℃ was identified as the breaking-point temperature in the variation of PN, DNA and PS concentrations. At 15℃ and 25℃, PN was the main component in TB-EPS and LB-EPS. PS has the second highest concentration and DNA the least. However, PS were the dominant component at 35℃, with PN having the second highest concentration, and DNA having a subtle concentration. Moreover, at 15℃ and 25℃, the EPS content increased in the nitrification process and reduced in the denitrification process.

[Up-conversion luminescence in nanocrystalline zirconia co-doped with Yb3+ and Tm3+ ions].

Nanocrystalline zirconia co-doped with Yb3+ and Tm3+ ions was prepared by co-precipitation. Up-conversion luminescence of the samples doped with different Tm3+ concentrations was investigated under a 980 nm LD excitation. When x = 0.2 and 0.4, the luminescences of the two samples were mostly the same: strong blue up-conversion peaked at 474 nm and very weak red up-conversion were observed, corresponding to the transitions of 1G4 --> 3H6 and 1G4 --> 3F4 respectively. However, there was no luminescence of x = 1. Blue up-conversion luminescence of 0.2 mol% Tm3+-ions-doped nanocrystalline zirconia under different annealing temperatures was investigated. Blue up-conversion emission grew stronger with annealing temperature increasing. With pumping current increasing, blue up-conversion emission grew stronger too. By studying the sources of blue up-conversion, we concluded that it was three-photon process.

Internal structure-mediated ultrafast energy transfer in self-assembled polymer-blend dots.

Applications of polymeric semiconductors in organic electronics and biosensors depend critically on the nature of energy transfer in these materials. Important questions arise as to how this long-range transport degrades in amorphous condensed solids which are most amenable to low-cost optoelectronic devices and how fast energy transfer could occur. Here, we address these in disordered, densely packed nanoparticles made from green-light-harvesting host polymers (PFBT) and deep-red-emitting dopant polymers (PF-DBT5). By femtosecond selective excitation of donor (BT) units, we study in detail the internal structure-mediated energy transfer to uniformly distributed, seldom acceptor (DBT) units. It has been unambiguously demonstrated that the creation of interchain species is responsible for the limitation of bulk exciton diffusion length in polymer materials. This interchain Förster resonance energy transfer (FRET) becomes a preferred and dominant channel, and near 100% energy transfer efficiency could be achieved at high acceptor concentrations (>10 wt%). Side-chain carboxylic acid groups in functionalized polymer-blend dots slightly slow down the FRET rate, but it could not affect the Förster radius and FRET efficiency. These findings imply that a greater understanding of the role of interchain species could be an efficient approach to improve the cell efficiency.