Alkali-Ion Intercalation Chemistry and Phase Evolution of Sn4P3.

Despite its high theoretical capacities, Sn4P3 anodes in alkali-ion batteries (AIBs) have been plagued by electrode damage and capacity decay during cycling, mainly rooted in the huge volume changes and irreversible phase segregation. However, few reports endeavor to ascertain whether these causes bear relevance to phase evolution upon cycling. Moreover, the phase evolution mechanism for alkali-ion intercalation remains imprecise. Herein, the structural transformations and detailed mechanisms upon various alkali-ion intercalation processes are systematically revealed, utilizing both experimental techniques and theoretical simulations. The results reveal that the energy storage of Sn4P3 occurs in a two-stage process, starting from an insertion process, followed by a transition process. As the cycle proceeds, the final delithiated/desodiated/depotassiated components gradually trap alkali ions (Li+, Na+, and K+), which is attributed to the incomplete electrochemical transition and difficulty in Sn4P3 regeneration due to the kinetic limitations in removing M (M = Li, Na, and K). Furthermore, Sn4P3 anode obeys the "shrinking core mechanism" in potassium-ion batteries (KIBs), wherein a minor fraction of Sn4P3 in the outer layer of the particles is initially involved in the potassiation/depotassiation processes, followed by a gradual participation of the inner parts until the entire particle is involved. It is worth mentioning that K-Sn alloys are not found to exist during the transition process of KIBs; instead, K-Sn-P phases are found, which makes it differ from that in lithium-ion batteries (LIBs) and sodium-ion batteries (NIBs). These findings are expected to deepen the understanding of the reaction mechanism of Sn4P3 and enlighten the material designs for improved performance.

Bi2S3/Ti3C2-TPP nano-heterostructures induced by near-infrared for photodynamic therapy combined with photothermal therapy on hypoxic tumors.

BACKGROUND: Photodynamic therapy (PDT) efficacy of bismuth sulfide (Bi2S3) semiconductor has been severely restricted by its electron-hole pairs (e--h+) separation inefficiency and oxygen (O2) deficiency in tumors, which greatly hinders reactive oxygen species (ROS) generation and further clinical application of Bi2S3 nanoparticles (NPs) in biomedicine. RESULTS: Herein, novel Bi2S3/titanium carbide (Ti3C2) two-dimensional nano-heterostructures (NHs) are designed to realize multimode PDT of synchronous O2 self-supply and ROS generation combined with highly efficient photothermal tumor elimination for hypoxic tumor therapy. Bi2S3/Ti3C2 NHs were synthesized via the in situ synthesis method starting from Ti3C2 nanosheets (NSs), a classical type of MXene nanostructure. Compared to simple Bi2S3 NPs, Bi2S3/Ti3C2 NHs significantly extend the absorption to the near-infrared (NIR) region and enhance the photocatalytic activity owing to the improved photogenerated carrier separation, where the hole on the valence band (VB) of Bi2S3 can react with water to supply O2 for the electron on the Ti3C2 NSs to generate ·O2- and ·OH through electron transfer. Furthermore, they also achieve 1O2 generation through energy transfer due to O2 self-supply. After the modification of triphenylphosphium bromide (TPP) on Bi2S3/Ti3C2 NHs, systematic in vitro and in vivo evaluations were conducted, revealing that the synergistic-therapeutic outcome of this nanoplatform enables complete eradication of the U251 tumors without recurrence by NIR laser irradiation, and it can be used for computed tomography (CT) imaging because of the strong X-ray attenuation ability. CONCLUSION: This work expands the phototherapeutic effect of Bi2S3-based nanoplatforms, providing a new strategy for hypoxic tumor theranostics.

Tin dioxide-based nanomaterials as anodes for lithium-ion batteries.

The development of new electrode materials for lithium-ion batteries (LIBs) has attracted significant attention because commercial anode materials in LIBs, like graphite, may not be able to meet the increasing energy demand of new electronic devices. Tin dioxide (SnO2) is considered as a promising alternative to graphite due to its high specific capacity. However, the large volume changes of SnO2 during the lithiation/delithiation process lead to capacity fading and poor cycling performance. In this review, we have summarized the synthesis of SnO2-based nanomaterials with various structures and chemical compositions, and their electrochemical performance as LIB anodes. This review addresses pure SnO2 nanomaterials, the composites of SnO2 and carbonaceous materials, the composites of SnO2 and transition metal oxides, and other hybrid SnO2-based materials. By providing a discussion on the synthesis methods and electrochemistry of some representative SnO2-based nanomaterials, we aim to demonstrate that electrochemical properties can be significantly improved by modifying chemical composition and morphology. By analyzing and summarizing the recent progress in SnO2 anode materials, we hope to show that there is still a long way to go for SnO2 to become a commercial LIB electrode and more research has to be focused on how to enhance the cycling stability.

Systematic evaluation of lithium-excess polyanionic compounds as multi-electron reaction cathodes.

Polyanion cathodes with multi-electron redox always facilitate wider application in a metal ion-based battery system because of their high capacity and safety. However, the irreversible phase transformation and interfacial deterioration remain major impediments. Herein, using monoclinic Li3V2(PO4)3 as a model, the impact of excess lithium on its electrochemical properties are demonstrated. It was determined that a maximum of 5% excess lithium could be incorporated into the monoclinic structure, and a further overdose of lithium led to the formation of secondary phase Li3PO4. The excess Li+ ions are located at both octahedral and interstitial sites, which enable enhanced redox kinetics that are mainly attributed to accelerated ionic movement induced by alternate diffusion behavior of Li+ ions in a three-dimensional permeation path. Moreover, Li-excess local configurations can stabilize the lattice oxygen and provide a favorable cathode-electrolyte interface, which synergistically relieves the structural degradation during electrochemical cycling, thus guaranteeing exceptional cycling stability (e.g., 82.5% after 1000 cycles at 1000 mA g-1). These findings provide a comprehensive understanding of defect/electronic structure/ion transport and the intrinsic properties of polyanionic Li3V2(PO4)3 and may help to pave the way for other highly stable electrodes for rechargeable batteries.

Impurity removal with highly selective and efficient methods and the recycling of transition metals from spent lithium-ion batteries.

The use of lithium-ion batteries (LIBs) is skyrocketing since they are widely applied in portable consumer devices and electric vehicles. However, at the end of their lifetime, large amount of spent LIBs will result in a negative environmental impact and aggravate the problem of resource shortage without proper disposal. Therefore, recycling is an effective solution, which will be enforced in the near future. Herein, the purification, recovery and reuse of transition metals from spent LIBs were thoroughly studied. First, the target impurities in a solution were effectively removed individually. Iron(iii) and aluminum(iii) impurities were removed by adjusting the pH value, whereas copper(ii) was purified using highly selective electrodeposition technology and solvent extraction. Second, Ni0.41Co0.21Mn0.38(OH)2 was co-precipitated by adjusting the pH value of the purified metal solution, containing nickel(ii), cobalt(ii) and manganese(ii) ions to 11 with NaOH and a proper amount of NH3·H2O. The comprehensive loss in nickel(ii), cobalt(ii) and manganese(ii) was only 0.37% in the purification and co-precipitation procedures. Finally, LiNi0.41Co0.21Mn0.38O2 (marked as LNCM-R) synthesized with the recycled materials was tested and compared with LiNi0.41Co0.21Mn0.38O2 (marked as LNCM-N) synthesized with new materials as the control group. The XRD, SEM and TEM results indicate that both samples have the same structure and morphology. Furthermore, the charge-discharge tests, initial dQ/dV curves, EIS and GITT results indicate a similar electrochemical performance of the LNCM-R and LNCM-N samples. The purification and recycling strategies in our research have high efficiency and comparatively low cost, which provide great guidance for the industrial recycling of spent Li-ion batteries.

Evaluation of long-term biocompatibility and osteogenic differentiation of graphene nanosheet doped calcium phosphate-chitosan AZ91D composites.

To improve the biodegradable performance and osteoinductivity of magnesium (Mg) alloy, a novel graphene nanosheet (GNS) doped micro-arc oxidized-AZ91D (MAO-AZ91D) based calcium phosphate (CaP)-chitosan (CS) (GNS-CaP-CS/AZ91D) composite was fabricated. Their long-term in vitro biocompatibility, osteoinductivity and the related signaling pathway were evaluated. The electrochemical test, Mg concentration and SEM results showed that the corrosion rate of GNS-CaP-CS/AZ91D became much slower, whose corrosion degree with immersion time being 90 d was similar to that of AZ91D being 16 d. Good biocompatibility and non-cytotoxicity were observed during the whole immersion process of GNS-CaP-CS/AZ91D. Extracts from GNS-CaP-CS/AZ91D especially in the early stage (16 days and before) could significantly enhance alkaline phosphatase (ALP) activity, calcium mineral deposition and osteoblast-related genes expression of human bone marrow mesenchymal stem cells (hBMSCs). GNS released from GNS-CaP-CS/AZ91D composites might serve a critical role to induce osteogenic differentiation through ERK/MAPK pathway in the long-term immersion process, while, PI3K/Akt signaling only significantly in the early stage. Moreover, Mg element could promote osteogenic differentiation through ERK/MAPK pathway and the maximum concentration was about the range between 200 and 500 ppm.

Effect of the addition CNTs on performance of CaP/chitosan/coating deposited on magnesium alloy by electrophoretic deposition.

CaP/chitosan/carbon nanotubes (CNTs) coating on AZ91D magnesium alloy was prepared via electrophoretic deposition (EPD) followed by conversion in a phosphate buffer solution (PBS). The bonding between the layer and the substrate was studied by an automatic scratch instrument. The phase compositions and microstructures of the composite coatings were determined by using X-ray diffraction (XRD), Fourier-transformed infrared spectroscopy (FTIR), Raman spectroscopy and scanning electron microscope (SEM). The element concentration and gentamicin concentration were respectively determined by inductively coupled plasma optical emission spectrometer (ICP-OES) test and ultraviolet spectrophotometer (UV). The cell counting kit (CCK) assay was used to evaluate the cytotoxicity of samples to SaOS-2 cells. The results showed that a few CNTs with their original tubular morphology could be found in the CaP/chitosan coating and they were beneficial for the crystal growth of phosphate and improvement of the coating bonding when the addition amount of CNTs in 500 ml of electrophoretic solution was from 0.05 g to 0.125 g. The loading amount of gentamicin increased and the releasing speed of gentamicin decreased after CNTs was added into the CaP/chitosan coating for immersion loading and EPD loading. The cell viability of Mg based CaP/chitosan/CNTs was higher than that of Mg based CaP/chitosan from 16 days to 90 days.

Saccharomyces boulardii prevention of the hepatic injury induced by Salmonella Enteritidis infection.

Salmonella enterica subsp. enterica serovar Enteritidis (Salmonella Enteritidis) is the predominant cause of serovar-associated food-borne outbreaks in many countries and causes significant clinical symptoms of liver injury, enteritis, and diarrheal diseases. Saccharomyces boulardii is used in clinical application for prophylaxis and the treatment of a variety of diseases caused by bacterial infection. We used a mouse model of Salmonella Enteritidis infection, which included pretreatment with S. boulardii, to reveal the protection mechanisms of S. boulardii against Salmonella Enteritidis infection, including the translocation of Salmonella Enteritidis to the liver 10 days after Salmonella Enteritidis challenge, and the colonisation of Salmonella Enteritidis and the formation of hepatic tissue lesions in mice after Salmonella Enteritidis challenge on the 10th day. Compared with Salmonella Enteritidis infection in mice, S. boulardii decreased Salmonella Enteritidis translocation to the liver by 96%, and 99% of Salmonella Enteritidis colonised the cecum on the 10th day. Saccharomyces boulardii also abated hepatic tissue injury caused by the infiltration of neutrophilic granulocytes, lymphocytes, and plasmocytes by decreasing the translocation of Salmonella to the liver. These findings demonstrated that S. boulardii is an effective agent in the prevention of the hepatic injury induced by Salmonella Enteritidis infection in a mouse model.

Enhancement of the cycling performance of Li3V2(PO4)3/C by stabilizing the crystal structure through Zn²âº doping.

A series of Li3V(2-2/3x)Zn(x)(PO4)3/C phases were synthesized by carbon thermal reduction assisted by the ball-mill process. Scanning electron microscopy (SEM) showed that the irregular morphology of the pristine Li3V2(PO4)3/C could be transformed to spherical upon doping with a suitable amount of zinc. The structural stability of the pristine and the Zn doped Li3V2(PO4)3/C were investigated via X-ray absorption near edge structure (XANES) spectroscopy and X-ray diffraction (XRD). The results revealed that Zn doping not only improves the stability of the VO6 octahedral structures before electrochemical cycling, but also reduces the degree of irreversible expansion of the c axis and the crystal volume upon repeated cycles. Among the Li3V(2-2/3x)Zn(x)(PO4)3/C (0 ≤x≤ 0.15) series, the sample doped with 0.05 Zn atoms per formula unit showed the best electrochemical performance. Excess Zn doping (x > 0.05) didn't result in further improvement in the electrochemical performance due to the segregation effect and the inactive nature of Zn.

A construction of novel iron-foam-based calcium phosphate/chitosan coating biodegradable scaffold material.

Slow corrosion rate and poor bioactivity restrict iron-based implants in biomedical application. In this study, we design a new iron-foam-based calcium phosphate/chitosan coating biodegradable composites offering a priority mechanical and bioactive property for bone tissue engineering through electrophoretic deposition (EPD) followed by a conversion process into a phosphate buffer solution (PBS). Tensile test results showed that the mechanical property of iron foam could be regulated through altering the construction of polyurethane foam. The priority coatings were deposited from 40% nano hydroxyapatite (nHA)/ethanol suspension mixed with 60% nHA/chitosan-acetic acid aqueous solution. In vitro immersion test showed that oxidation-iron foam as the matrix decreased the amount of iron implanted and had not influence on the bioactivity of this implant, obviously. So, this method could also be a promising method for the preparation of a new calcium phosphate/chitosan coating on foam construction.

Degradable behavior and bioactivity of micro-arc oxidized AZ91D Mg alloy with calcium phosphate/chitosan composite coating in m-SBF.

The degradation behavior of a MAO-AZ91D with a calcium phosphate/chitosan composite coating in the modified simulated human body fluid (m-SBF) was investigated by immersion experiments and electrochemical impedance spectroscopy. The compositions of the composite coating soaked in the m-SBF for different time intervals were studied by X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, thermo-gravimetric analysis and differential thermal analysis. The microstructures of the composite coating at different soaking stages were observed by using a scanning electron microscope. Results show that the as-prepared composite coating could slow down the corrosion rate of the AZ91D alloy and it demonstrated good bioactivity in the m-SBF. The coating's morphology changed from a flake-like one into a spherical-shaped one with the increase of immersion time in the m-SBF.

Well-dispersed high-loading pt nanoparticles supported by shell-core nanostructured carbon for methanol electrooxidation.

Shell-core nanostructured carbon materials with a nitrogen-doped graphitic layer as a shell and pristine carbon black particle as a core were synthesized by carbonizing the hybrid materials containing in situ polymerized aniline onto carbon black. In an N-doped carbon layer, the nitrogen atoms substitute carbon atoms at the edge and interior of the graphene structure to form pyridinic N and quaternary N structures, respectively. As a result, the carbon structure becomes more compact, showing curvatures and disorder in the graphene stacking. In comparison with nondoped carbon, the N-doped one was proved to be a suitable supporting material to synthesize high-loading Pt catalysts (up to 60 wt %) with a more uniform size distribution and stronger metal-support interactions due to its high electrochemically accessible surface area, richness of disorder and defects, and high electron density. Moreover, the more rapid charge-transfer rates over the N-doped carbon material are evidenced by the high crystallinity of the graphitic shell layer with nitrogen doping as well as the low charge-transfer resistance at the electrolyte/electrode interface. Beneficial roles of nitrogen doping can be found to enhance the CO tolerance of Pt catalysts. Accordingly, an improved performance in methanol oxidation was achieved on a high-loading Pt catalyst supported by N-doped carbon. The enhanced catalytic properties were extensively discussed based on mass activity (Pt utilization) and intrinsic activity (charge-transfer rate). Therefore, N-doped carbon layers present many advantages over nondoped ones and would emerge as an interesting supporting carbon material for fuel cell electrocatalysts.