Study of the Phase-Evolution Mechanism of an Fe-Se System at the Nanoscale: Optimization of Synthesis Conditions for the Isolation of Pure Phases and Their Controlled Growth

Semi-Coherent Heterointerface Engineering via In Situ Phase Transition for Enhanced Sodium/Lithium-Ions Storage

To improve ion transport kinetics and electronic conductivity between the different phases in sodium/lithium-ion battery (LIB/SIB) anodes, heterointerface engineering is considered as a promising strategy due to the strong built-in electric field. However, the lattice mismatch and defects in the interphase structure can lead to large grain boundary resistance, reducing the ion transport kinetics and electronic conductivity. Herein, monometallic selenide Fe3Se4-Fe7Se8 semi-coherent heterointerface embedded in 3D connected Nitrogen-doped carbon yolk-shell matrix (Fe3Se4-Fe7Se8@NC) is obtained via an in situ phase transition process. Such semi-coherent heterointerface between Fe3Se4 and Fe7Se8 shows the matched interfacial lattice and strong built-in electric field, resulting in the low interface impedance and fast reaction kinetics. Moreover, the yolk-shell structure is designed to confine all monometallic selenide Fe3Se4-Fe7Se8 semi-coherent heterointerface nanoparticles, improving the structural stability and inhibiting the volume expansion effect. In particular, the 3D carbon bridge between multi-yolks shell structure improves the electronic conductivity and shortens the ion transport path. Therefore, the efficient reversible pseudocapacitance and electrochemical conversion reaction are enabled by the Fe3Se4-Fe7Se8@NC, leading to the high specific capacity of 439 mAh g-1 for SIB and 1010 mAh g-1 for LIB. This work provides a new strategy for constructing heterointerface of the anode for secondary batteries.

Gold-iron selenide nanocomposites for amplified tumor oxidative stress-augmented photo-radiotherapy

The radio-resistance of tumor tissues has been considered a great challenge for cancer radiotherapy (RT).The development of nanoparticle (NP)-based radio-sensitizers can enhance the radio-sensitization of tumor tissues while reducing the side effects to surrounding tissues. However, most of the nano-radiosensitizers show increased radiation deposition with a high-Z element but achieve limited enhancement. Herein, we investigated polyethylene glycol (PEG)-modified gold-iron selenide nanocomposites (Au-FeSe2 NCs) for simultaneously enhancing therapeutic effects in multiple ways. In this study, the high-Z element Au (Z = 79) endows Au-FeSe2 NCs with enhanced X-ray deposition and thus causes more DNA damage. On the other hand, Au-FeSe2 exhibits the ability to produce reactive oxygen species (ROS) by catalyzing endogenous hydrogen peroxide in tumor sites as well as improve the hydrogen peroxide level during ionizing irradiation. Finally, combined with photothermal therapy (PTT), Au-FeSe2 NCs could exhibit a remarkable RT/PTT synergistic effect on tumor treatment.