RESUMEN
Thermoelectric (TE) performance of the Janus ZrSSe monolayer under biaxial strain is systematically explored by the first-principles approach and Boltzmann transport theory. Our results show that the Janus ZrSSe monolayer has excellent chemical, dynamical, thermal, and mechanical stabilities, which provide a reliable platform for strain tuning. The electronic structure and TE transport parameters of the Janus ZrSSe monolayer can be obviously tuned by biaxial strain. Under 2% tensile strain, the optimal power factor PF of the n-type-doped Janus ZrSSe monolayer reaches 46.36 m W m-1 K-2 at 300 K. This value is higher than that of the most classical TE materials. Under 6% tensile strain, the maximum ZT values for the p-type- and n-type-doped Janus ZrSSe monolayers are 4.41 and 4.88, respectively, which are about 3.83 and 1.49 times the results of no strain, respectively. Such high TE performance can be attributed to high band degeneracy and short phonon relaxation time under strain, causing simultaneous increase of the Seebeck coefficient and suppression of the phonon thermal transport. Present work demonstrates that the Janus ZrSSe monolayer is a promising candidate as a strain-tunable TE material and stimulates further experimental synthesis.
RESUMEN
In this work, a strategy to boosting thermoelectric (TE) performance of 2D materials is explored. We find that, appropriate chemical adsorption of atoms can effectively increase the TE performance of HfSe2 monolayer. Our results show that the adsorption of Ni atom on HfSe2 monolayer (Ni-HfSe2) can improve the optimal power factor PF and ZT at 300 K, increased by more than â¼67% and â¼340%, respectively. The PF and ZT of Ni-HfSe2 at 300 K can reach 85.06 mW m-1 K-2 and 3.09, respectively. The detailed study reveal that the adsorption of Ni atom can induce additional conductional channels of electrons, enhance the coupling of acoustic-optical phonons and the phonon anharmonicity, resulting in an obvious increment of electrical conductivity (increased by more than â¼89%) in n-type doped system and an ultralow phonon thermal conductivity (1.17 W/mK at 300 K). The high electrical conductivity and ultralow phonon thermal conductivity results in the significant increments of PF and ZT. Our study also shows that, Ni-HfSe2 is a thermal, dynamic and mechanical stable structure, which can be employed in TE application. Our research indicates that selectivity chemical adsorption is a promising way to increase TE performance of 2D materials.
RESUMEN
The van der Waals heterostructures created by stacking two monolayer semiconductors have been rapidly developed experimentally and exhibit various unique physical properties. In this work, we investigate the effects of Se atom substitution and 3d-TM atom doping on the structural, electronic, and magnetic properties of the MoSe2/h-BN heterostructure, by using first-principles calculations based on density functional theory (DFT). It is found that Se atom substitution could considerably enhance the band gaps of MoSe2/h-BN heterostructures. With an increase in the substitution concentration, the energy band changes from an indirect to a direct band gap when the substitution concentration exceeds a critical value. For 3d-TM atom doping, it is shown that V-, Mn-, Fe-, and Co-doped systems exhibit a half-metallic state and magnetic behavior, while there is no spin polarization in the Ni-doped case. The results provide a theoretical basis for the development of diluted magnetic semiconductors and spin devices based on the MoSxSe2-x/h-BN heterostructure.
RESUMEN
This paper studied the variations of glucose concentration in haemolymph and glycogen concentration in hepatopancreas and muscle of Marsupenaeus japonicus under starvation and re-feeding. Groups C, S1, S2 and S3 were deprived of food for 0, 10, 15 and 25 days, respectively, and then re-fed for 10 days. Under starvation, the glucose concentration in haemolymph and glycogen concentration in hepatopancreas decreased rapidly at the beginning, and the glycogen concentration in muscle was the lowest after 10-day fasting. In the following 5 days, the glucose concentration in haemolymph and glycogen concentration in hepatopancreas and muscle recovered to their initial levels due to gluconeogenesis, but the glycogen concentration kept declining with fasting. After refeeding, the glycogen concentration in hepatopancreas and muscle recovered well, and the glucose concentration in haemolymph had a sharper increase in groups S1 and S2 than in group C, but was markedly less in group S3 than in group C. These results indicated that long-term starvation had a greater effect on the glucose concentration in haemolymph.
