[en] The linear and nonlinear refractive index changes (RICs) in a disc-like parabolic quantum dot (QD) with impurity between the ground (L=0) and the first excited state (L=1) have been examined based on the computed energies and wave functions. The parabolic QD without impurity was taken into account for comparison. We found that the linear and total RIC of impurity QD decrease as the charge of the impurity is increased and increase with characteristic dot radius decreasing. The maximum of linear RIC of parabolic QD without impurity remains constant for different confinement strengths.

[en] Dipole-allowed optical absorption in a parabolic quantum dot with two electrons are studied by using the exact diagonalization techniques and the compact density-matrix approach. Numerical results are presented for typical GaAs parabolic quantum dots. The results show that the total optical absorption coefficient of two electrons in quantum dot is about five times smaller than that of one electron in quantum dot

[en] The Hamiltonian equation for positively charged exciton in double-layer harmonic quantum dots is solved numerically by using the exact diagonalization techniques. We find that the correlation energy E_c of positively charged exciton increases with increasing the confinement strength and the binding energy decreases obviously for the heavy hole.

[en] Off-center impurity effects in a spherical quantum dot are theoretically studied by degenerate perturbation method in strong confinement. The energy levels and binding energies are computed for the typical GaAs material as function of the donor position. The numerical results show the quantum size effect. We note that the energy levels and binding energies are not only related to the position of donor and the strength of confinement, but also related to the fold of degenerate states. We can see obviously that gaps will appear among the degenerate states and the splitting of energy levels and binding energies will appear as the position of the impurity is shifted away off the center. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

[en] Highlights: • Ball milling iron-laden biochars produced novel biochar/iron oxide composites • Ball milling increased the exposure of iron oxides on biochar surface • Ball-milled biochar/iron oxide composites showed enhanced removal of Cr(VI) • Iron oxides of the composites are the main sites that can adsorb and reduce Cr(VI) As the first of its kind, a novel biochar/iron oxide composite (BM-Fe-HC) was successfully prepared by simply ball milling iron-laden biochar (Fe-HC). The performance and mechanisms of Cr(VI) removal by BM-Fe-HC were investigated. Ball milling effectively reduced particle size, increased specific surface area, more importantly, enhanced the distribution and increased the exposure of iron oxides on biochar surface. As a result, Cr(VI) removal by BM-Fe-HC showed fast kinetics and large adsorption capacity with the Langmuir maximum capacity of 48.1 mg/g, higher than that of other biochar/iron composites reported in the literature. Acidic pH promoted Cr(VI) removal while competition ions (Cl^-, SO₄^2- and PO₄^3-) inhibited Cr(VI) removal by BM-Fe-HC. Comparison of pre- and post-adsorption samples revealed that iron oxides of the BM-Fe-HC played the dominant role in the adsorption and reduction of Cr(VI) during the removal. After adsorption, part of adsorbed Cr(VI) was reduced by Fe(II) and then stabilized by Fe(III) in the form of amorphous Cr_xFe_1−x(OH)₃ on the composite surface. All the results demonstrate that novel ball-milled biochar/iron oxide composites can be used as an effective adsorbent to remove Cr(VI) from water.

[en] Highlights: • Hydrothermal treatment of biomass with H₃PO₄ produced a novel P-enriched hydrochar. • Weight yield of the P-enriched hydrochar was more than doubled with >20 wt%. • P-enriched hydrochar showed excellent ability to stabilize Pb and reduce its leaching in soils. One-step synthesis of multifunctional materials using biomass waste for environmental remediation is a current research hotspot. In this study, a novel P-enriched hydrochar was obtained by co-hydrothermal treatment of biomass (bamboo or hickory) with concentrated H₃PO₄ (biomass: H₃PO₄ = 1:4) at 200 °C for 7 h. The characteristics of the P-enriched hydrochar were determined and its effect on the stabilization of Pb in soils was investigated. Compared to pristine hydrochar, the weight yield of the P-enriched hydrochar was greater (by over 2 times). This was due to the enrichment of P (over 20% by weight), as the C, N, and H weight content was reduced. Moreover, the aromaticity, thermal stability, and surface functionality of P-enriched hydrochar were all higher than that of pristine hydrochar. Addition of the pristine hydrochar to a simulated 1300 mg·kg⁻¹ Pb-contaminated soil at 3% (w/w) resulted in a 20%–40% reduction in leached Pb only after 4 weeks, compared to the control without hydrochar amendment. However, addition of the P-enriched hydrochar to the spiked Pb-contaminated soil reduced Pb leaching by about 60% after only 1 week and about 90% after 3 weeks. Besides, using a real Pb-contaminated soil (149,000 mg·kg⁻¹ Pb), P-enriched hydrochar addition at 5% (w/w) resulted in a 100% decrease in Pb leaching in the first week and maintained leached Pb levels at −1, meeting U.S.-E.P.A. standards. Thus, P-enriched hydrochar stabilized Pb in both simulated and real Pb-contaminated soil quickly and efficiently. Hence, the potential of one-step co-hydrothermal carbonization of biomass with H₃PO₄ to produce a novel and sustainable P-enriched hydrochar with properties suitable for environmental remediation of cationic metals.

[en] Theranostic nanosystem has been demonstrated great potential in real-timely monitoring drug biodistribution and therapeutic response. It is still a challenge to fabricate a theranostic nanosystem that possesses the properties of good biocompatibility, a high magnetic resonance imaging (MRI) sensitivity, and stimuli-responsive drug release for the diagnosis and treatment of hepatocellular carcinoma. Here, a pH-responsive micelle, which was self-assembled from biodegradable poly(amino acid) block copolymer mPEG-PAsp(DIP)-co-PLLeu, was constructed to load both chemotherapeutic paclitaxel (PTX) and MRI contrast agent superparamagnetic iron oxide nanoparticles (SPIONs). The SPIONs/PTX-coloaded PDPL micelle (SPIONs/PTX-PDPL) had a hydrodynamic particle size of 134.5 ± 11.2 nm. The theranostic SPIONs/PTX-PDPL not only effectively delivered PTX and SPION into Bel-7402 cancer cells but also rapidly released PTX in acidic lysosome to induce cell apoptosis. Meanwhile, in vitro MR imaging sensitively detected the liver cancer cells after co-incubation with SPIONs/PTX-PDPL micelle. The SPIONs/PTX-PDPL micelle is a potential theranostic nanosystem in terms of the simultaneous chemotherapy and MR imaging of hepatocellular carcinoma.