Cryogenic Exfoliation of 2D Stanene Nanosheets for Cancer Theranostics

Stanene(Sn)-based materials have been extensively applied in industrial production and daily life,but their potential biomedical application remains largely unexplored,which is due to the absence of the appropriate and effective methods for fabricating Sn-based biomaterials.Herein,we explored a new approach combining cryogenic exfoliation and liquid-phase exfoliation to successfully manufacture two-dimensional(2D)Sn nanosheets(SnNSs).The obtained SnNSs exhibited a typical sheet-like structure with an average size of~100 nm and a thickness of~5.1 nm.After PEGylation,the resulting PEGylated SnNSs(SnNSs@PEG)exhibited good stability,superior biocompatibility,and excellent photothermal performance,which could serve as robust photothermal agents for multi-modal imaging(fluorescence/photoacoustic/photothermal imaging)-guided photothermal elimination of cancer.Furthermore,we also used first-principles density functional theory calculations to investigate the photothermal mechanism of SnNSs,revealing that the free electrons in upper and lower layers of SnNSs contribute to the conversion of the photo to thermal.This work not only introduces a new approach to fabricate 2D SnNSs but also establishes the SnNSs-based nanomedicines for photonic cancer theranostics.This new type of SnNSs with great potential in the field of nanomedicines may spur a wave of developing Sn-based biological materials to benefit biomedical applications.

First-Principles Calculation on Geometric,Electronic and Optical Properties of Fully Fluorinated Stanene:a Large-Gap Quantum Spin Hall Insulator

The searches for large-gap quantum spin Hall insulators are important for both practical and fundamental inter- ests. In this work, we present a theoretical observation of the two-dimensional fully fluorinated stanene （SnF） by means of density functional theory. Remarkably, a significant spin-orbit coupling is observed for the SnF monolayer in the valence band at the F point, with a considerable indirect band gap of 278 meV. The direct gap of the SnF monolayer is at the F point, which is slightly larger by as much as 381 meV. In addition, the elastic modulus of the SnF monolayer is about 20J/m^2, which is comparable with the in-plane stiffness of black phos- phorus monolayer along the x-direction （~28.94 J/m^2）. Finally, the optical properties of stanene, SnF monolayer and stanene/SnF bilayer are calculated, in which the stanene/SnF bilayer is supposed to be an attractive sunlight absorber.

Liquid exfoliation of stanene as degradable nanoagents for NIR-II photothermal therapy

Stanene,the two-dimensional form of elemental tin(Sn),is easily oxidized in the ambient environ-ment,significantly hindering its applications in biomedical fields.However,the degradation mechanism of stanene remains unclear.Herein,combined DFT calculations and proof-of-concept experiments were conducted to elucidate the underlying degradation mechanism of stanene.The results reveal that the degradation of stanene in an oxygenated water environment is a water-accelerated oxidation process.H_(2) O molecules could not only facilitate the electron transfer from stanene to O_(2) because of the polarization effect of H_(2) O,but also directly react with the defect sites of stanene due to enhanced absorption energy.Moreover,several protective strategies like alcohol protection were proposed to avoid or mitigate the oxidation of stanene for further applications.Finally,stanene was explored as the second near-infrared(NIR-II)photonic agents for ablation of 4T1 tumor,depicting a tumor-growth inhibition ratio up to 96.7%,much better than that of the first near-infrared(NIR-I)group(65.5%).This work reveals the degradation mechanism of stanene and demonstrates its biomedical applications in the NIR-II region.

Stanene: A good platform for topological insulator and topological superconductor

Two dimenslonal(2D)topological insulators(TIs)and topological superonductors(TSC&)have been intensively studied for recent yars due to their great poterntial for dissipat iouless eloctron transporta-tion and fault-tolerant quantum computing,respectively.Here we focus on stanene,the tin analogue of grapbene,to give a brief review of their development a a candidate for both 2D TI and TSC.Stanene is proposed to bea TI with a large gap of 0.3 eW,and its topological properties are sensitive to various factors,e.g..the lattice constants,chemical functionalization and layer thickness,which offer various methods for phase tunning.Experimentally,the inverted gap and edge states are observed recently,which are strong evidences for TI.In addition,stanene is also predicted to be a time reversal invariant TSC by breaking inversion syumetry,supporting belical Majorana edge modes.The layer dependent superconduetivity of stanene is receatly confirmed by both transport and scauning tumeling microsoopy measurenents.This review givs a detailod introduction to stanene and its topological properties and some proepects are also discussed.

Two-dimensional materials of group-IVA boosting the development of energy storage and conversion

Graphene,an emerging fabric of carbon atoms,has manifested its versatility in all kinds of fields encompassing electronics,optoelectronics,thermoelectrics,taking advantage of its excellent mechanical strength,exceptional electronic and thermal conductivities,high surface specific area,and so forth.The prosperity of graphene never seen before has led the attention to silicene,siloxene,germanene,stanene,and plumbene due to their promising applications in the quantum spin Hall effect,topological insulator,batteries,capacitors,catalysis,and topological superconductivity.Herein,we review the existing production methods,numerous applications of two-dimensional group-IVA materials,and critically discuss the challenges of these materials,providing potential implications to the exploration of uncharted material systems.

2D-layered Sn/Ge anodes for lithium-ion batteries with high capacity and ultra-fast Li ion diffusivity

As a new type of green energy, lithium-ion battery(LIB) has been widely used in various electric portable devices because of its high-voltage, large specific capacity, long cycle life and environmental friendliness [1,2]. However, today’s anode materials of commercial LIBs cannot meet the further development requirements of smart devices and electric car due to the limitations of the electrode capacity(e.g. 372 mAh g-1 for graphite).