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1.
Nanoscale ; 13(34): 14417-14425, 2021 Sep 02.
Artigo em Inglês | MEDLINE | ID: mdl-34473184

RESUMO

The recurrence and metastasis of tumor after surgery is the main cause of death for patients with breast cancer. Systemic chemotherapy suffered from low delivery efficiency to tumors and the side effects of chemo drugs. Localized chemotherapy using drug-containing implants is an alternative, while the reconstruction of breast tissue is generally considered after chemotherapy, resulting in a second surgery for patients. Here, we describe a strategy using implantable drug-containing polymeric scaffolds to deliver chemo drugs directly to the post-resection site, and simultaneously provide mechanical support and regenerative niche for breast tissue reconstruction. When doxorubicin was loaded in mesoporous silica nanoparticles and subsequently incorporated into polycaprolactone scaffolds (DMSN@PCL), a 9-week sustained drug release was achieved post implantation in mice. The local recurrence of residual tumor after surgery was significantly inhibited within 4 weeks in a post-surgical mouse model bearing xenograft MDA-MB-231 tumor. DMSN@PCL scaffolds exhibited good biocompatibility in mice during the treatment. We believe our strategy holds great promise as an adjuvant localized chemotherapy in clinics for combating post-resection breast cancer recurrence.


Assuntos
Antineoplásicos , Neoplasias da Mama , Nanopartículas , Animais , Antineoplásicos/uso terapêutico , Neoplasias da Mama/tratamento farmacológico , Linhagem Celular Tumoral , Doxorrubicina/uso terapêutico , Feminino , Humanos , Camundongos , Poliésteres
2.
ACS Synth Biol ; 10(6): 1417-1428, 2021 06 18.
Artigo em Inglês | MEDLINE | ID: mdl-34003632

RESUMO

1-Octanol has gained interest as a chemical precursor for both high and low value commodities including fuel, solvents, surfactants, and fragrances. By harnessing the power from sunlight and CO2 as carbon source, cyanobacteria has recently been engineered for renewable production of 1-octanol. The productivity, however, remained low. In the present work, we report efforts to further improve the 1-octanol productivity. Different N-terminal truncations were evaluated on three thioesterases from different plant species, resulting in several candidate thioesterases with improved activity and selectivity toward octanoyl-ACP. The structure/function trials suggest that current knowledge and/or state-of-the art computational tools are insufficient to determine the most appropriate cleavage site for thioesterases in Synechocystis. Additionally, by tuning the inducer concentration and light intensity, we further improved the 1-octanol productivity, reaching up to 35% (w/w) carbon partitioning and a titer of 526 ± 5 mg/L 1-octanol in 12 days. Long-term cultivation experiments demonstrated that the improved strain can be stably maintained for at least 30 days and/or over ten times serial dilution. Surprisingly, the improved strain was genetically stable in contrast to earlier strains having lower productivity (and hence a reduced chance of reaching toxic product concentrations). Altogether, improved enzymes and environmental conditions (e.g., inducer concentration and light intensity) substantially increased the 1-octanol productivity. When cultured under continuous conditions, the bioproduction system reached an accumulative titer of >3.5 g/L 1-octanol over close to 180 days.

3.
J Colloid Interface Sci ; 584: 505-519, 2021 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-33129160

RESUMO

Carbon dots (CDs) have a profound effect on elimination of bacteria, fungi, and viruses, but the lack of an exact mechanism to interact with bacterial cells limits their development. Herein, we separated the CDs derived from chlorhexidine gluconate into three groups with uniformly small-scale, middle-scale, and large-scale particle sizes by using different molecular weight cut-off membranes. These positively charged particles exhibit significant antibacterial activity against the Gram-negative bacteria Escherichia coli and the Gram-positive bacteria Staphylococcus aureus; they can cause an increase in bacterial cell permeability, synergistic destabilization, and broken integrity of the plasma membrane. Impressively, we found that antibacterial activity increases as the size of the CDs decreases. This phenomenon may stem from the differences in cellular uptake and distribution of CDs in the plasma membrane or restriction between the polar functional group and DNA molecule. Our study of the size effect as a target may improve the understanding of killing microorganisms by antibacterial CD drugs.


Assuntos
Antibacterianos , Carbono , Antibacterianos/farmacologia , Bactérias Gram-Positivas , Tamanho da Partícula , Staphylococcus aureus
4.
Dev Comp Immunol ; 116: 103923, 2021 03.
Artigo em Inglês | MEDLINE | ID: mdl-33186561

RESUMO

Interferon regulatory factors (IRFs) are a family of transcriptional factors capable of regulating the expression of distinct subsets of interferon (IFN)-stimulated genes by binding to their promoters. IRF1 was the first member identified for its ability to regulate the IFNß gene and has now been revealed to exhibit remarkable functional diversity in the regulation of different cellular responses. In the present study, the IRF1 gene was identified and characterized in Japanese eel, Anguilla japonica (AjIRF1). The open reading frame of AjIRF1 was 804 bp in length, encoding a protein of 267 amino acids (aa) that encompasses a conserved N-terminal DNA binding domain (DBD). Sequence alignment shows the presence of six highly conserved tryptophan (W) residues in the DBD of IRF1, IRF2 and IRF11, while other IRF members have only five tryptophans. Expression analysis showed that AjIRF1 was significantly upregulated in all tested organs/tissues in response to Poly I:C stimulation or Edwardsiella tarda infection. Furthermore, the functional activity of AjIRF1 was confirmed in driving the transcription of AjIFN promoters, which depends on the highly conserved residues within DBD. Subcellular distribution analysis revealed that AjIRF1 was localized exclusively in the nucleus, which is cooperatively regulated by a bipartite NLS embedded within the DBD and a monopartite NLS located immediately downstream of the DBD. Taken together, this study presents the expression profile of AjIRF1 and defines the functional motifs required for its nuclear import and its role in activating IFN promoters, thus providing helpful information for further research on the regulatory mechanisms of teleost IRF1.

5.
Micromachines (Basel) ; 11(12)2020 Nov 26.
Artigo em Inglês | MEDLINE | ID: mdl-33256113

RESUMO

Transport-induced-charge (TIC) phenomena, in which the concentration imbalance between cations and anions occurs when more than two chemical potential gradients coexist within an ultrathin dimension, entail numerous nanofluidic systems. Evidence has indicated that the presence of TIC produces a nonlinear response of electroosmotic flow to the applied voltage, resulting in complex fluid behavior. In this study, we theoretically investigate thermal effects due to Joule heating on TIC phenomena in an ultrathin nanopore by computational fluid dynamics simulation. Our modeling results show that the rise of local temperature inside the nanopore significantly enhances TIC effects and thus has a significant influence on electroosmotic behavior. A local maximum of the solution conductivity occurs near the entrance of the nanopore at the high salt concentration end, resulting in a reversal of TIC across the nanopore. The Joule heating effects increase the reversal of TIC with the synergy of the negatively charged nanopore, and they also enhance the electroosmotic flow regardless of whether the nanopore is charged. These theoretical observations will improve our knowledge of nonclassical electrokinetic phenomena for flow control in nanopore systems.

6.
Chemistry ; 26(72): 17567-17573, 2020 Dec 23.
Artigo em Inglês | MEDLINE | ID: mdl-32965742

RESUMO

Lithium-sulfur (Li-S) batteries are one of the most promising high-energy-density storage systems. However, serious capacity attenuation and poor cycling stability induced by the shuttle effect of polysulfide intermediates can impede the practical application of Li-S batteries. Herein we report a novel sulfur cathode by intertwining multi-walled carbon nanotubes (CNTs) and porous boron nitride fibers (BNFs) for the subsequent loading of sulfur. This structural design enables trapping of active sulfur and serves to localize the soluble polysulfide within the cathode region, leading to low active material loss. Compared with CNTs/S, CNTs/BNFs/S cathodes deliver a high initial capacity of 1222 mAh g-1 at 0.1 C. Upon increasing the current density to 4 C, the cell retained a capacity of 482 mAh g-1 after 500 cycles with a capacity decay of only 0.044 % per cycle. The design of CNTs/BNFs/S gives new insight on how to optimize cathodes for Li-S batteries.

7.
ACS Appl Mater Interfaces ; 12(17): 19530-19538, 2020 Apr 29.
Artigo em Inglês | MEDLINE | ID: mdl-32253908

RESUMO

The nonuniform nucleation of lithium (Li) leads to dendritic behavior and formation of dead Li, which seriously hinders the practical application of Li metal batteries. Here, atomic layer deposition (ALD) is used to deposit uniform and conformal ZnO coating (at a low content of 5.96%) on carbon fibers to form a free-standing framework Li host material without uncontrollable dendrites. Compared with the liquid deposition process, the ALD method can achieve homogeneous and conformal ZnO coating and excellent lithiophilicity of the carbon fiber, guiding molten Li infusion into the carbon fiber skeleton to obtain the Li/C composite electrode with a flat surface, thereby minimizing the effective current density. More importantly, the converted LiZn alloy will serve as uniform and numerous nucleation sites for Li and guide synchronous growth of the Li metal along carbon fibers, displaying a dendrite-free morphology after large-current and long-term deposition/dissolution cycling. Therefore, the ALD ZnO-modified carbon fiber/Li exhibits significantly better cycle and rate performances than the liquid deposition ZnO-modified carbon fiber/Li composite anode. The electrodes display an ultralong lifespan up to 400 cycles at 3.0 mA/cm2, as well as a high rate performance (with a deposition overpotential of 338 mV at 25.0 mA/cm2) at a high Li deposition areal capacity of 5.0 mA h cm-2.

8.
Environ Sci Pollut Res Int ; 27(15): 18729-18742, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32207022

RESUMO

In the paper, the achievements obtained from carrying out the policy of environmental protection price for promoting air pollution control in coal-fired power plants in China during more than a decade were summarized. Based on the situation of current electricity market reform, the role and effectiveness of environmental protection price for controlling the normal air pollutants, such as sulfur dioxide, nitrogen oxides, and dust in China's coal-fired power generation plants, were investigated, including the price structure of electricity environmental protection for coal-fired power generation enterprises in different regions, generating units, and power demands. The policy suggestions were proposed, namely, the reform of electricity environmental protection price would be carried out gradually, the relationship between electricity environmental protection price policy and other environmental protection policies would be matched under the relative overcapacity condition, and the environmental protection price regulation would be integrated into other environmental policies.


Assuntos
Poluentes Atmosféricos/análise , Poluição do Ar/análise , China , Carvão Mineral/análise , Conservação dos Recursos Naturais , Centrais Elétricas
9.
Nanoscale ; 12(6): 3941-3949, 2020 Feb 14.
Artigo em Inglês | MEDLINE | ID: mdl-32009133

RESUMO

As an anode electrode material for lithium-ion batteries, SnS has high specific capacity and has received widespread attention, but its practical application is still hindered by the low reversibility of the conversion reaction and the large irreversible capacity caused by the solid electrolyte interphase (SEI). In this paper, SnS nanoparticles are encapsulated into a sulfur-doped graphene bubble film (SnS@G) by a scalable electrostatic self-assembly of SnS2/graphene oxide and hexadecyl trimethyl ammonium bromide, followed by the thermal decomposition of SnS2 and sulfur doping in graphene. Due to electrostatic attraction, the SnS nanoparticles are tightly wrapped in multilayer graphene sheets to form a flake-graphite-like structure. Compared with the disordered stacked SnS/graphene sheet composite, the closely packed SnS@G shows a much lower specific surface area and smaller irreversible Li+ consumption and surface film resistance after lithiation. The SnS@G composite anode exhibits great initial coulombic efficiency (83.2%), which is the highest value among the chemically synthesized SnS anodes. It also presents unprecedented cycling stability (1462 mA h g-1 after 200 cycles at 0.1 A g-1 and 1020 mA h g-1 after 500 cycles at 1 A g-1) and superior rate capabilities (750 mA h g-1 at 5 A g-1) upon Li storage, which demonstrates its excellent electrochemical performance and great potential as a negative electrode material for lithium-ion batteries.

10.
Nanoscale ; 12(3): 1697-1706, 2020 Jan 23.
Artigo em Inglês | MEDLINE | ID: mdl-31894809

RESUMO

In this work, we demonstrate an interesting structural phase transition from SnS2/reduced graphene oxide to SnS/sulfur-doped graphene at a moderate calcination temperature of 500 °C under an inert atmosphere. It is discovered that SnS2 chemically bound to rGO with a weakened C-S bond is easier to break and decompose into SnS, whereas it is difficult for pure-phase crystalline SnS2 to experience phase transformation at this temperature. Moreover, the thin-layered structure of SnS2 and rGO is an important factor for the effective doping of the dissociated Sx into graphene. Density functional theory calculations also reveal the feasibility of the structural phase transition process. Morphology characterization shows that partial SnS maintains the original nanosheet structure (∼100 nm) and the others are decomposed into tiny nanoparticles (10-20 nm). A high S-doping amount reduces the irreversible lithium storage sites on graphene, and the first coulombic efficiency is as high as 81.7%. In addition, thin-layered and small-sized SnS can alleviate the structural damage caused by volume expansion and shrinkage; therefore, a high specific capacity of 893.9 mA h g-1 is retained after 100 cycles.

11.
Environ Technol ; 41(15): 1980-1991, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-30516089

RESUMO

Cellulose is widely used as an effective sorbent to treat wastewater. Cellulosic sorbents have the advantage of biodegradability, as they are natural plant-based materials, compared with the synthetic materials such as polypropylene (PP) or polyurethane (PU). Among the raw biomass materials used for cellulose production, rice husk is one of the most cost competitive and widely available. In this work, biological treatments are compared to find the most effective treatment method for cellulose fibre production from rice husk. Using biological delignification, cellulose was extracted from raw rice husk and acetylated to acquire hydrophobicity. Delignification was performed using both bacteria and fungi and their results were compared. The white-rot fungi strain using 'Aspergillus flavus CICC 40258' was found to be the most effective treatment method, achieving a modified product with up to 55% w/w cellulose concentration. Acetylation further facilitated the sorption process and the maximum oil uptake capacity using delignification and acetylation treatment was found to be 20 g/g. The as-prepared sorbents exhibited high oil uptake rates and saturation capacity was reached after 5 min of contact with oil. The kinetic study presents a good correlation with the pseudo-second order model. The isothermal studies demonstrated that the oil sorption capacity of rice husk follows the Langmuir model as compared with the Freundlich model.


Assuntos
Oryza , Poluição por Petróleo , Acetilação , Adsorção , Cinética
12.
Langmuir ; 35(47): 15275-15286, 2019 11 26.
Artigo em Inglês | MEDLINE | ID: mdl-31665888

RESUMO

Conventional drug delivery systems for natural clay materials still face critical challenges in their practical application, including multiple bacterial infections, combined infection of bacteria and fungi, and low sterilization efficiency. In this work, we address these challenges using the multifunctional montmorillonite nanosheet-based (MMT-based) drug nanoplatform, which involves the antibiotic 5-fluorocytosine (5-FC), antibacterial metal copper ions, and quaternized chitosan (QCS). Composite material QCS/MMT/5-FCCu can can strongly inhibit Staphylococcus aureus (a typical Gram-positive bacterium), Escherichia coli (a typical Gram-negative bacterium), and Candida albicans (a fungus) because 5-FC coordinates with copper ions in situ and due to the deposition of QCS. The subsequent drug release behavior of 5-FCCu was studied, and the results show an initial high concentration kills microorganisms and long-acting sustained release inhibition. Moreover, in vivo wound experiments and toxicity experiments show the promotion of wound healing and excellent biocompatibility. As a demonstration of the utility of the latter, we have shown that the MMT-based smart platform can be used for the treatment of mixed infections of wounds.


Assuntos
Antibacterianos/uso terapêutico , Bentonita/química , Quitosana/química , Cobre/uso terapêutico , Flucitosina/uso terapêutico , Infecções Cutâneas Estafilocócicas/tratamento farmacológico , Animais , Antibacterianos/farmacologia , Antibacterianos/toxicidade , Antifúngicos/farmacologia , Antifúngicos/toxicidade , Bentonita/toxicidade , Candida albicans/efeitos dos fármacos , Linhagem Celular , Quitosana/toxicidade , Cobre/farmacologia , Cobre/toxicidade , Portadores de Fármacos/química , Portadores de Fármacos/toxicidade , Liberação Controlada de Fármacos , Escherichia coli/efeitos dos fármacos , Flucitosina/farmacologia , Flucitosina/toxicidade , Camundongos , Testes de Sensibilidade Microbiana , Nanocompostos/química , Nanocompostos/toxicidade , Staphylococcus aureus/efeitos dos fármacos
13.
Org Lett ; 21(19): 8018-8021, 2019 Oct 04.
Artigo em Inglês | MEDLINE | ID: mdl-31553198

RESUMO

In the presence of a carboxylic acid directing group, Rh-catalyzed regioselective directed dialkylation of B(4,5)-H bonds in o-carboranes and oxidative coupling with allylic alcohols is reported. This strategy constructs a series of 4,5-dialkylated o-carboranes in good yields with excellent regioselectivity. A possible catalytic cycle is proposed that involves a tandem sequence of Rh-catalyzed cage B-H activation, alkene insertion, selective ß-H elimination, enol isomerization, and decarboxylation.

14.
ACS Nano ; 13(8): 9100-9111, 2019 Aug 27.
Artigo em Inglês | MEDLINE | ID: mdl-31323180

RESUMO

SnS2 materials have attracted broad attention in the field of electrochemical energy storage due to their layered structure with high specific capacity. However, the easy restacking property during charge/discharge cycling leads to electrode structure instability and a severe capacity decrease. In this paper, we report a simple one-step hydrothermal synthesis of SnS2/graphene/SnS2 (SnS2/rGO/SnS2) composite with ultrathin SnS2 nanosheets covalently decorated on both sides of reduced graphene oxide sheets via C-S bonds. Owing to the graphene sandwiched between two SnS2 sheets, the composite presents an enlarged interlayer spacing of ∼8.03 Šfor SnS2, which could facilitate the insertion/extraction of Li+/Na+ ions with rapid transport kinetics as well as inhibit the restacking of SnS2 nanosheets during the charge/discharge cycling. The density functional theory calculation reveals the most stable state of the moderate interlayer spacing for the sandwich-like composite. The diffusion coefficients of Li/Na ions from both molecular simulation and experimental observation also demonstrate that this state is the most suitable for fast ion transport. In addition, numerous ultratiny SnS2 nanoparticles anchored on the graphene sheets can generate dominant pseudocapacitive contribution to the composite especially at large current density, guaranteeing its excellent high-rate performance with 844 and 765 mAh g-1 for Li/Na-ion batteries even at 10 A g-1. No distinct morphology changes occur after 200 cycles, and the SnS2 nanoparticles still recover to a pristine phase without distinct agglomeration, demonstrating that this composite with high-rate capabilities and excellent cycle stability are promising candidates for lithium/sodium storage.

15.
PLoS One ; 14(6): e0217474, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31170178

RESUMO

Hand, foot, and mouth disease (HFMD) is well recognized as one of the major threats to children's health globally. The increasing complexity of the etiology of HFMD still challenges disease control in China. There is little surveillance of the molecular epidemiological characteristics of the enteroviruses (EVs) that cause HFMD in Neijiang city or the Sichuan Basin area in Southwest China. In this study, demographic and epidemiological information for 14,928 probable HFMD cases was extracted and analyzed to describe the epidemic features of HFMD in Neijiang city from Jan 2010 to Dec 2017. The swab samples of select probable HFMD cases from 2012 to 2017 were tested by reverse transcription (RT) real-time PCR to identify the serotype distribution of EVs, and 110 randomly selected RT-real-time PCR positive samples were then amplified and analyzed for the VP1 or VP4 regions of EVs to further analyze the phylogenetic characteristics of the circulating strains in this area. The eight-year average annual incidence was 49.82 per 100,000 in Neijiang. The incidence rates varied between 19.51 and 70.73 per 100,000, demonstrating peaks of incidence in even-number years (2012, 2014 and 2016). The median age of the probable cases was 27 months and the interquartile range (25th to 75th percentile) of ages for the probable HFMD cases was between 14 and 42 months. The male-to-female ratio of the probable HFMD cases was 1.47:1, and scattered children were the major population classification (81.7%). Two epidemic peaks were observed: one major peak between April and July and the other lesser peak between October and December. Of 6513 probable cases tested with RT-real-time PCR, 4015 (61.6%) were positive for enterovirus with the serotype distribution as follows: EV71+, 30.1% (n = 1210); CV-A16+, 28.7% (n = 1154) and a sole pan-enterovirus+, 41.1% (n = 1651). A total of 91 cases (82.7%, 91/110) were successfully amplified and underwent phylogenetic analysis: all EV71+ cases were C4a serotype (n = 23/30); all CV-A16+ cases were B2b serotype (n = 24/30); of 42 sole pan-enterovirus+ samples, 20 were CV-A6, 14 were CV-A10 and the rest within this group were CV-A4 (n = 4), CV-A8 (n = 2), CV-A9 (n = 1) and CV-B3 (n = 1). Our findings provide important evidence that aids the improvement of strategies for vaccination against HFMD and comprehensive disease control in China.


Assuntos
Proteínas do Capsídeo , Enterovirus Humano B/genética , Doença de Mão, Pé e Boca , Filogenia , Sorogrupo , Proteínas Estruturais Virais , Proteínas do Capsídeo/sangue , Proteínas do Capsídeo/genética , Pré-Escolar , China/epidemiologia , Feminino , Doença de Mão, Pé e Boca/sangue , Doença de Mão, Pé e Boca/epidemiologia , Doença de Mão, Pé e Boca/genética , Doença de Mão, Pé e Boca/virologia , Humanos , Incidência , Lactente , Masculino , Estudos Retrospectivos , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Estudos Soroepidemiológicos , Proteínas Estruturais Virais/sangue , Proteínas Estruturais Virais/genética
16.
ACS Appl Mater Interfaces ; 11(23): 21218-21226, 2019 Jun 12.
Artigo em Inglês | MEDLINE | ID: mdl-31099240

RESUMO

Flexible pressure sensors play an important role in electronic skins (E-Skins), which mimic the mechanical forces sensing properties of human skin. A rational design for a pressure sensor with adjustable characteristics is in high demand for different application scenarios. Here, we present tunable, ultrasensitive, and flexible pressure sensors based on compressible wrinkled microstructures. Modifying the morphology of polydimethylsiloxane (PDMS) microstructure enables the device to obtain different sensitivities and pressure ranges for different requirements. Furthermore, by intentionally introducing hollow structures in the PDMS wrinkles, our pressure sensor exhibits an ultrahigh sensitivity of 14.268 kPa-1. The elastic microstructure-based capacitive sensor also possesses a very low detectable pressure limit (1.5 Pa), a fast response time (<50 ms), a wide pressure range, and excellent cycling stability. Implementing respiratory monitoring and vocalization recognition is realized by attaching the flexible pressure sensor onto the chest and throat, respectively, showing its great application potential for disease diagnosis, monitoring, and other advanced clinical/biological wearable technologies.


Assuntos
Técnicas Biossensoriais/métodos , Pressão , Dispositivos Eletrônicos Vestíveis , Humanos
17.
J Clin Lab Anal ; 33(1): e22639, 2019 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-30105783

RESUMO

BACKGROUND: Previous studies have demonstrated both behavioral and neural evidence for the potential mediations of lag length and pre-existing memory representation on repetition priming. However, such mediations on emotional stimuli have not been described. METHODS: The current experiment intended to disentangle lag length from pre-existing memory representation. A lexical decision task was performed, in which different emotional characters (either normal or transposed) were re-presented either immediately or delayed. RESULTS: In immediate repetition, one early and two late (ie, N400 and late positive complex) repetition-related event-related potential (ERP) effects were elicited, but these were not sensitive to pre-existing memory representation. The delayed repetition case merely observed the N400. CONCLUSION: These results suggest that the repetition-related priming effect is neutrally sensitive to lag length. Emotional information potentially exerts early and later influences in the processing underlying stimuli memory.


Assuntos
Emoções/fisiologia , Potenciais Evocados/fisiologia , Priming de Repetição/fisiologia , Adulto , Eletroencefalografia , Feminino , Humanos , Masculino , Fatores de Tempo , Adulto Jovem
18.
Nanoscale ; 10(34): 16116-16126, 2018 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-30117518

RESUMO

Low reversion of lithium oxide (Li2O) and the tin (Sn) coarsening causing irreversible capacity loss is the main reason for the poor cycle performance in tin dioxide (SnO2) based composites. In this research, a novel sandwiched spherical tin dioxide/graphene with a three-dimensional interconnected closed pore structure is synthesized. The microstructural characterization shows that the spherical graphene with submicron sized diameters interconnects with each other forming an interconnected flexible conductive network, whereas a large number of SnO2 nanoparticles (approximately 5 nm) are limited homogeneously in between the interlayers of the sphere-like graphene shell. The sandwich structure of the SnO2/graphene and the closed graphene sphere can provide double protection for the SnO2. When it is used as an anode material for energy storage, the generated Li2O can remain in close contact with Sn to make the conversion reaction (SnO2 + 4Li+ + 2e- ↔ Sn + Li2O) highly reversible in situ and the reversibility even does not diminish markedly after 100 cycles. A high reversible specific capacity of 914.8 mA h g-1 is expressed in the sandwiched spherical SnO2/graphene composite at 100 mA g-1 after 100 cycles, which is significantly higher than that of a SnO2/graphene aerogel with an open pore structure.

19.
Nanoscale ; 9(45): 17922-17932, 2017 Nov 23.
Artigo em Inglês | MEDLINE | ID: mdl-29124272

RESUMO

Low reversion of lithium sulfide and defects causing irreversible capacity loss are the primary causes of low Coulombic efficiency in tin sulfide/graphene-based composites. Herein, we synthesized a SnS/graphene composite via a novel lithiation-assisted exfoliation and reduction method using SnS2, n-butyllithium, and graphene oxide as raw materials. The experimental results reveal that lithium from the insertion agent combine with the oxygen-containing groups on graphene oxide; this can help in the reduction of hexagonal SnS2 to orthorhombic SnS during calcination and simultaneous pre-occupancy of the edge and defect sites of graphene; thus, additional lithium ion consumption during the initial several lithiation processes is diminished. Microstructural characterizations indicate that the exfoliated SnS nanosheets with a dramatically decreased lateral size (50-100 nm) are uniformly decorated on the surface of lithium-integrated graphene sheets. Consequently, the as-prepared SnS/graphene composite exhibits a significantly high SnS ultilization with a 77.5% initial Coulombic efficiency, which is the highest value reported in the current literature. Moreover, an excellent reversibility of conversion reaction (SnS + 2Li+ + 2e- ↔ Sn + Li2S) and a high reversible capacity of 1016.4 mA h g-1 after 100 cycles are expressed in this composite electrode, demonstrating its importance as an anode material for energy storage.

20.
ACS Appl Mater Interfaces ; 9(2): 1407-1415, 2017 Jan 18.
Artigo em Inglês | MEDLINE | ID: mdl-28045243

RESUMO

Three-dimensional (3D) interconnected spherical graphene framework-decorated SnS nanoparticles (3D SnS@SG) is synthesized by self-assembly of graphene oxide nanosheets and positively charged polystyrene/SnO2 nanospheres, followed by a controllable in situ sulfidation reaction during calcination. The SnS nanoparticles with diameters of ∼10-30 nm are anchored to the surface of the spherical graphene wall tightly and uniformly. Benefiting from the 3D interconnected spherical graphene framework and subtle SnS nanoparticles, the generated Li2S could keep in close contact with Sn to make possible the in situ conversion reaction SnS + 2Li+ + 2e- ↔ Sn + Li2S. As a result, the 3D SnS@SG as the anode material for lithium ion batteries shows a high initial Coulombic efficiency of 75.3%. Apart from the irreversible capacity loss of 3D spherical graphene, the initial Coulombic efficiency of SnS in the 3D SnS@SG composite is as high as 99.7%, demonstrating the almost complete reversibility of Li2S in this system. Furthermore, it also exhibits an excellent reversible capacity (800 mAh g-1 after 100 cycles at 0.1 C and 527.1 mAh g-1 after 300 cycles at 1 °C) and outstanding rate capability (380 mAh g-1 at 5 °C).

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