Characterization of the thermal conductivity of La0.95Sr0.05CoO3 thermoelectric oxide nanofibers

Thermoelectric oxide nanofibers prepared by electrospinning are expected to have reduced thermal conductivity when compared to bulk samples. Measurements of nanofibers＇ thermal conductivity is challenging since it involves sophisticated sample preparation methods. In this work, we present a novel method suitable for measurements of thermal conductivity of a single nanofiber. A microelectro- mechanical （MEMS） device has been designed and fabricated to perform thermal conductivity measurements on a single nanofiber. A special Si template was designed to collect and transfer individual nanofibers onto a MEMS device. Pt was deposited by a focused ion beam to reduce the effective length of a prepared nanofiber. La0.95r0.05CoO3 nanofibers with diameters of 140 run and 290 run were studied and characterized using this approach at room temperature. Measured thermal conductivities yielded values of 0.7W-m 1-K-1 and 2.1 W.m-I＇K-1, respectively. Our measurements in La0.95r0.05CoO3 nanofibers confirmed that a decrease of linear dimensions has a profound effect on its thermal conductivity.     

Alumina-coated Ag nanocrystal monolayers as surfaceenhanced Raman spectroscopy platforms for the direct spectroscopic detection of water splitting reaction intermediates

A novel Ag-alumina hybrid surface-enhanced Raman spectroscopy （SERS） platform has been designed for the spectroscopic detection of surface reactions in the steady state. Single crystalline and faceted silver （Ag） nanoparticles with strong light scattering were prepared in large quantity, which enables their reproducible self-assembly into large scale monolayers of Raman sensor arrays by the Langrnuir-Blodgett technique. The close packed sensor film contains high density of sub-nm gaps between sharp edges of Ag nanoparticles, which created large local electromagnetic fields that serve as ＂hot spots＂ for SERS enhancement. The SERS substrate was then coated with a thin layer of alumina by atomic layer deposition to prevent charge transfer between Ag and the reaction system. The photocatalytic water splitting reaction on a monolayer of anatase TiO2 nanoplates decorated with Pt co-catalyst nanoparticles was employed as a model reaction system. Reaction intermediates of water photooxidation were observed at the TiO2/solution interface under UV irradiation. The surface-enhanced Raman vibrations corresponding to peroxo, hydroperoxo and hydroxo surface intermediate species were observed on the TiO2 surface, suggesting that the photo-oxidation of water on these anatase TiO2 nanosheets may be initiated by a nucleophilic attack mechanism.     

Gold nanorod-photosensitizer conjugate with extracellular pH-driven tumor targeting ability for photothermal/photodynamic therapy

Chlorin e6-pHLIPss-AuNRs, a gold nanorod-photosensitizer conjugate containing a pH （low） insertion peptide （pHLIP） with a disulfide bond which imparts extracellular pH （pHe）-driven tumor targeting ability, has been successfully developed for bimodal photodynamic and photothermal therapy. In this bimodal therapy, chlorin e6 （Ce6）, a second-generation photosensitizer （PS）, is used for photodynamic therapy （PDT）. Gold nanorods （AuNRs） are used as a hyperthermia agent for photothermal therapy （PTT） and also as a nanocarrier and quencher of Ce6. pHLIPss is designed as a pile-driven targeting probe to enhance accumulation of Ce6 and AuNRs in cancer cells at low pH. In Ce6- pHLIPss-AuNRs, Ce6 is close to and quenched by AuNRs, causing little PDT effect. When exposed to normal physiological pH 7.4, Ce6-pHLIPs~-AuNRs loosely associate with the cell membrane. However, once exposed to acidic pH 6.2, pHLIP actively inserts into the cell membrane, and the conjugates are translocated into cells. When this occurs, Ce6 separates from the AuNRs as a result of disulfide bond cleavage caused by intracellular glutathione （GSH）, and singlet oxygen is produced for PDT upon light irradiation. In addition, as individual PTT agent, AuNRs can enhance the accumulation of PSs in the tumor by the enhanced permeation and retention （EPR） effect. Therefore, as indicated by our data, when exposed to acidic pH, Ce6-pHLIPss-AuNRs can achieve synergistic PTT/PDT bimodality for cancer treatment.     

Dielectric and Ferroelectric Properties of BaTiO3 Nanofibers Prepared via Electrospinning

BaTiO3 nanofibers of about 400 nm in diameter were synthesized via electrospinning.The evolution of the morphology and phase composition of the BaTiO3 nanofibers was studied by scanning electron microscopy and X-ray diffraction within the annealing temperature of 750-1050 ℃.Higher annealing temperature led to rougher surface and better crystallization of the BaTiO3 nanofibers.Below 1050 ℃,the BaTiO3 nanofibers maintained its large aspect ratios and could still be regarded as individual nanofiber.The dielectric permittivities of the BaTiO3 nanofibers（εr 820） were calculated with the MG equation by considering the porous bulk specimens as composites of BaTiO3 nanofibers and air.The ferroelectric properties of the BaTiO3nanofibers were measured by using a ferroelectric analyzer coupled with an atomic force microscope.P-E loop measured for the BaTiO3 nanofiber exhibits small hysteresis.     

功能化纤维素:PET纤维沸石分子筛复合材料对神经毒剂的解毒性研究(英文)

Presently activated carbon is used as an adsorptive material for chemical and biological warfare agents. It possess excellent surface properties such as large surface area, fire-resistance and plenty availability, but has disadvantages such as its heavy weight, low breathability (after adsorption of moisture) and disposal. In this paper, we propose to utilize novel electrospun polymeric nanostructures having zeolites as catalyst materials. In this respective, the electrospun polymer nanofibers would serve as the best possible substitutes to activated carbon based protective clothing applications. This is the first in the literature that reports the integration of these types of catalysts with nanofiberous membranes. Electrospinning of cellulose/polyethylene terephthalate (PET) blend nanofibers has been carried out. Zeolite catalysts (Linde Type A and Mordenite) for the detoxification of nerve agent stimulant-paraoxon, were prepared due to their relative simplicity of synthesis. The catalysts were then coated onto nanofiber membranes and their morphology was confirmed using SEM. This is the first report on the coating of nanofibers with zeolites and their successful demonstration against nerve agent stimulant. The UV absorption spectra clearly show the detoxification ability of the functionalized fibers and their potential to be used in textiles for protection and decontamination.     

Elevating mitochondrial reactive oxygen species by mitochondria-targeted inhibition of superoxide dismutase with a mesoporous silica nanocarrier for cancer therapy

In the intrinsic pathway of apoptosis, stresses of mitochondrial reactive oxygen species （mitoROS） might be sensed as more effective signals than those in cytosol, as mitochondria are the major sources of reactive oxygen species （ROS） and pivotal components during cell apoptosis. Mitochondrial superoxide dismutase （SOD2） takes the leading role in eliminating mitoROS, and inhibition of SOD2 might induce severe disturbances overwhelming the mitochondrial oxidative equilibrium, which would elevate the intracellular oxidative stresses and drive cells to death. Herein, we report a general strategy to kill cancer cells by targeted inhibition of SOD2 using 2-methoxyestradiol （2-ME, an inhibitor for the SOD family） via a robust mitochondria-targeted mesoporous silica nanocarrier （mtMSN）, with the expected elevation of mitoROS and activation of apoptosis in HeLa cells. Fe304@MSN was employed in the mitochondria-targeted drug delivery and selective inhibition of mitochondrial enzymes, and was shown to be stable with good biocompatibility and high loading capacity. Due to the selective inhibition of SOD2 by 2-ME/mtMSN, enhanced elevation of mitoROS （132% of that with free 2-ME） was obtained, coupled with higher efficiency in initiating cell apoptosis （395% of that with free 2-ME in 4 h）. Finally, the 2-ME/mtMSN exhibited powerful efficacy in targeted killing of HeLa cells by taking advantage of both biological recognition and magnetic guiding, causing 97.0% cell death with only 2 Dg/mL 2-ME/mtMSN, hinting at its great potential in cancer therapy through manipulation of the delicate mitochondrial oxidative balance.     

Eco-friendly and degradable red phosphorus nanoparticles for rapid microbial sterilization under visible light

Pathogens pose a serious challenge to environmental sanitation and a threat to public health.The frequent use of chemicals for sterilization in recent years has not only caused secondary damage to the environment but also increased pathogen resistance to drugs,which further threatens public health.To address this issue,the use of non-chemical antibacterial means has become a new trend for environmental disinfection.In this study,we developed red phosphorus nanoparticles(RPNPs),a safe and degradable photosensitive material with good photocatalytic and photothermal properties.The red phosphorus nanoparticles were prepared using a template method and ultrasonication.Under the irradiation of simulated sunlight for 20 min,the RPNPs exhibited an efficiency of 99.98%in killing Staphylococcus aureus due to their excellent photocatalytic and photothermal abilities.Transmission electron microscopy and ultraviolet–visible spectroscopy revealed that the RPNPs exhibited degradability within eight weeks.Both the RPNPs and their degradation products were nontoxic to fibroblast cells.Therefore,such RPNPs are expected to be used as a new type of low-cost,efficient,degradable,biocompatible,and eco-friendly photosensitive material for environmental disinfection.     

Ultraviolet-accelerated formation of bone-like apatite on oxidized Ti-24Nb-4Zr-7.9Sn alloy

A novel method has been developed to rapidly deposit bone-like apatite with the assistance of ultraviolet （UV） light irradiation on the nanostructured titania in the simulated body fluid （SBF）. The process has three main steps： Ti-24Nb-4Zr-7.9Sn alloy was heated at 650℃ for 3 h, UV-light illumination in air for 4 h and soaking in the SBF for 3 d. A titania coating consisted of main rutile formed on the thermal oxidized Ti-24Nb-4Zr- 7.9Sn alloy. The UV not only converted the futile surface from hydrophilic to hydrophobic but also stimulated high surface activity. After 4 h UV illumination, the contents of Ti3＋ and hydroxyl groups on the oxidized sample were increased, while that of lattice O decreased. After 3 d of soaking in the SBF, a compact and uniform layer of carbonated hydroxyapatite （CHA） particles was formed on the UV-illuminated rutile surface whereas there was a few of HA to be viewed on the surface of as-oxidized Ti-24Nb-4Zr-7.9Sn alloy. Our study demonstrates a simple, fast and cost-effective technique for growing bone-like apatite on titanium alloys.     

Electrospinning of curcumin loaded chitosan/poly （lactic acid） nanofilm and evaluation of its medicinal characteristics

The curcumin loaded chitosanlpoly （lactic acid） （PLA） nanoflbers were produced using electrospinning. Box-Behnken experimental design was used for the optimization of variables （-1, 0, ＋ 1 coded level） like chitosan/PLA strength （% w/v）, curcumin strength （% w/v） and applied voltage （kV） to obtain uniform fiber diameter. The morphology of nanofibers was shown by SEM. Molecular interactions and the presence of each chemical compound of curcumin loaded chitosanlPLA fibers were characterized by FTIR and EDX analysis. Antioxidant, drug release and in vitro cytotoxicity tests were performed to evaluate the suitability of nanofibers that would be used for wound healing. In vivo wound healing studies on excision and incision wounds created on rat model showed significant reduction of wound area when compared to untreated. The better healing efficiency can be attributed to the presence of curcumin and chitosan.     

Gold nanorods with a hematoporphyrin-loaded silica shell for dual-modality photodynamic and photothermal treatment of tumors in vivo

Nanocomposites （NCs） consisting of a gold nanorod core and a mesoporous silica shell doped with hematoporphyrin （HP） have been fabricated in order to improve the efficiency of cancer treatment by combining photothermal and photodynamic therapies （PDT ＋ PTT） in vivo. In addition to the long-wavelength plasmon resonance near 810-830 nm, the fabricated NCs exhibited a 400-nm absorbance peak corresponding to bound HP, generated singlet oxygen under 633-nm excitation near the 632.5-nm Q-band, and produced heat under a 808-nm near-infrared （NIR） laser irradiation. These modalities were used for a combined PDT ＋ PTT treatment of large （about 3 cm3） solid tumors in vivo with a xenorafted tumor rat model. NCs were directly injected into tumors and irradiated simultaneously with 633-nm and 808-nm lasers to stimulate the combined photodynamic and photothermal activities of NCs. The efficiency of the combined therapy was evaluated by optical coherence tomography, histological analysis, and by measurements of the tumor volume growth during a 21-day period. The NC-mediated PDT led to weak changes in tissue histology and to a moderate 20% decrease in the tumor volume. In contrast, the combined PDT ＋ PTT treatment resulted in the large-area tumor necrosis and led to dramatic decrease in the tumor volume.     

A nanoporous oxide interlayer makes a better Pt catalyst on a metallic substrate: Nanoflowers on a nanotube bed

To improve the contact between platinum catalyst and titanium substrate, a layer of TiO2 nanotube arrays has been synthesized before depositing Pt nanoflowers by pulse electrodeposition. Dramatic improvements in electrocatalytic activity （3x） and stability （60x） for methanol oxidation were found, suggesting promising applications in direct methanol fuel cells. The 3x and 60x improvements persist for Pt/Pd catalysts used to overcome the CO poisoning problem.     

Construction of novel TiO_2/Bi_4Ti_3O_(12)/MoS_2 core/shell nanofibers for enhanced visible light photocatalysis

TiO2/Bi4 Ti3 O12 hybrids have been widely prepared as promising photocatalysts for decomposing organic contaminations.However,the insufficient visible light absorption and low charge separation efficiency lead to their poor photocatalytic activity.Herein,a robust methodology to construct novel TiO2/Bi4 Ti3 O12/MoS2 core/shell structures as visible light photocatalysts is presented.Homogeneous bismuth oxyiodide(BiOI) nanoplates were immobilized on electrospun TiO2 nanofiber surface by successive ionic layer adsorption and reaction(SILAR) method.TiO2/Bi4 Ti3 O12 core/shell nanofibers were conveniently prepared by partial conversion of TiO2 to high crystallized Bi4 Ti3 O12 shells through a solid-state reaction with BiOI nanoplates,which is accompanied with certain transition of TiO2 from anatase to rutile phase.Afterwards,MoS2 nanosheets with several layers thick were uniform decorated on the TiO2/Bi4 TiO3 O12 fiber surface resulting in TiO2/Bi4 Ti3 O12/MoS2 structures.Significant enhancement of visible light absorption and photo-generated charge separation of TiO2/Bi4 Ti3 O12 were achieved by introduction of MoS2.As a result,the optimized TiO2/Bi4 Ti3 O12/MoS2-2 presents 60% improvement for photodegrading RhB after 120 min irradiation under visible light and 3 times higher of apparent reaction rate constant in compared with the TiO2/Bi4 Ti3 O12.This synthetic method can also be used to establish other photocatalysts simply at low cost,therefore,is suitable for practical applications.     

Hierarchical TiO2/ZnO Nanostructure as Novel Non-precious Electrocatalyst for Ethanol Electrooxidation

Metal oxides have a higher chemical stability in comparison to metals,so they can be utilized as electrocatalysts if the activity could be enhanced.Besides the composition,the morphology of the nanostructures has a considerable impact on the electrocatalytic activity.In this work,zinc oxide nano branches-attached titanium dioxide nanofibers were investigated as an economic and stable catalyst for ethanol electrooxidation in the alkaline media.The introduced material has been synthesized by electrospinning process followed by hydrothermal technique.Briefly,electrospinning of colloidal solution consisting of titanium isopropoxide,poly(vinyl acetate) and zinc nanoparticles was performed to produce nanofibers embedding solid nanoparticles.In order to produce TiO_2 nanofibers containing ZnO nanoparticles,the obtained electrospun nanofiber mats were calcined in air at 600 °C.The formed ZnO nanoparticles were exploited as seeds to outgrow ZnO branches around the TiO_2 nanofibers using the hydrothermal technique at sub-critical water conditions in the presence of zinc nitrate and bis-hexamethylene triamine.The morphology of the final product,as well as the electrochemical measurements indicated that zinc nanoparticles content in the original electrospun nanofibers has a significant influence on the electrocatalytic activity as the best performance was observed with the nanofibers synthesized from electrospun solution containing 0.1 g Zn,and the corresponding current density was 37 mA/cm~2.Overall,this study paves a way to titanium dioxide to be exploited to synthesize effective and stable metal oxide-based electrocatalysts.     

Cyanobacteria-based near-infrared light-excited self-supplying oxygen system for enhanced photodynamic therapy of hypoxic tumors

Tumor hypoxia has been considered to induce tumor cell resistance to radiotherapy and anticancer chemotherapy,as well as predisposing for increased tumor metastases.Therefore,strategies for the eradication of the hypoxic tumor are highly desirable.Photodynamic therapy(PDT)is a new technique that can be used to treat tumors using laser irradiation to photochemically activate a photosensitizer.Compared to traditional radiotherapy and chemotherapy,photodynamic therapy has many advantages,such as good selectivity,low toxicity,and less trauma and resistance.However,PDT is oxygen-dependent,and the lack of oxygen in hypoxic tumors renders photodynamic therapy ineffective.Cyanobacteria,the earliest photosynthetic oxygen-generating organisms,can utilize water as an electron donor to reduce CO₂ into organic carbon compounds along with continuously releasing oxygen under sunlight.Inspired by this,herein,cyanobacteria were used as a living carrier of photosensitizer conjugated upconversion nanoparticles(UCNP)to construct a self-supplying oxygen PDT system.Improvement in the PDT efficiency for hypoxic tumors can be achieved as a result of in situ oxygen production by cyanobacteria under near-infrared(NIR)light using UCNP as a light harvesting antenna.A successful demonstration of this concept would be of great significance and could open the door to a new generation of carrier systems in the field of hypoxia-targeted drug transport platforms.     

High-performance UV–vis photodetectors based on electrospun ZnO nanofiber-solution processed perovskite hybrid structures

Hybrid organic-inorganic perovskites have been demonstrated as promising candidates for broadband-responsive photodetectors.It is critical to develop perovskite-based photodetectors with excellent photodetection capability and facile fabrication processes for practical application.Herein,we designed and fabricated,for the first time,a hybrid photodetector consisting of electrospun ZnO nanofibers and perovskites.Compared to pristine ZnO or perovskite,the hybrid photodetector showed increased on-off ratio,faster response speed,and higher responsivity and detectivity.The performance of the hybrid devices was significantly enhanced by using quasi-aligned ZnO nanofiber arrays instead of disordered nanofibers,which provide efficient charge transfer between the perovskite and ZnO,shorter transmission paths,and reduced carrier loss at cross-junctions of nanofibers.Our results provide a new and promising route to integrate inorganic functional materials with perovskite for high-performance and low-cost photodetectors.     

Effect of Ni+2-substituted Fe2TiO5 on the H2-reduction and CO2 Catalytic Decomposition Reactions at 500℃

CO2 is a major component of the greenhouse gases, which causes the global warming. To reduce CO2 gas, high activity nanosized Ni＋2 substituted Fe2TiO5 samples were synthesized by conventional ceramic method. The effect of the composition of the synthesized ferrite on the H2-reduction and CO2-catalytic decomposition was investigated. Fe2TiO5 （iron titanate） phase that has a nanocrystallite size of -80 nm is formed as a result of heating Fe2O3 and TiO2 while the addition of NiO leads to the formation of new phases （-80 nm） NiTiO3 and NiFe2O4, but the mixed solid of NiO and Fe2O3 results in the formation of NiFe2O4 only. Samples with Ni^＋2=0 shows the lowest reduction extent （20%）; as the extent of Ni＋2 increases, the extent of reduction increases. The increase in the reduction percent is attributed to the presence of NiTiO3 and NiFe2O4 phases, which are more reducible phases than Fe2TiO5. The CO2 decomposition reactions were monitored by thermogravimetric analysis （TGA） experiments. The oxidation of the H2-reduced Ni＋2 substituted Fe2TiO5 at 500℃ was investigated. As Ni^＋2 increases, the rate of reoxidation increases. Samples with the highest reduction extents gave the highest reoxidation extent, which is attributed to the highly porous nature and deficiency in oxygen due to the presence of metallic Fe, Ni and/or FeNi alloy. X-ray diffraction （XRD） and transmission electron microscopy （TEM） of oxidized samples show also the presence of carbon in the sample containing Ni＋2〉0, which appears in the form of nanotubes （25 nm）.     

Fabrication of periodically aligned vertical single-crystalline anatase TiO2 nanotubes with perfect hexagonal open-ends using chemical capping materials

A vertically aligned anatase TiO2 （A-TiO2） nanotube array has been fabricated by coating a ZnO nanorod （NR） template with a TiO2 precursor solution. After coating, the ZnO NR cores were selectively etched in an acidic environment to form TiO2 nanotubes （NTs）. More specifically, after growing the ZnO NRs via a hydrothermal method, one drop of the TiO2 precursor solution was cast to coat the ZnO NRs, the tops of which were previously covered with chemical capping materials by electrostatic interaction, and then the sample was sintered. Finally, the sample was immersed in an acidic solution resulting in selective etching of the ZnO NR cores. Thus, only TiO2 NTs remained on the substrate. The capping material is effectively used to create a perfect, hexagonal open-ended TiO2 NT array, which interestingly extends onset absorption towards the visible region.     

Nanosized-bismuth-embedded 1D carbon nanofibers as high-performance anodes for lithium-ion and sodium-ion batteries

Bi is a promising candidate for energy storage materials because of its high volumetric capacity,stability in moisture/air,and facile preparation.In this study,the electrochemical performance of nanosized-Bi-embedded one-dimensional (1D) carbon nanofibers (Bi/C nanofibers) as anodes for Li-ion batteries (LIBs) and Na-ion batteries (NIBs) was systematically investigated.The Bi/C nanofibers were prepared using a single-nozzle electrospinning method with a specified Bi source followed by carbothermal reduction.Abundant Bi nanoparticles with diameters of approximately 20 nm were homogeneously dispersed and embedded in the 1D carbon nanofibers,as confirmed by structural and morphological characterization.Electrochemical measurements indicate that the Bi/C nanofiber anodes could deliver a long cycle life for LIBs and a preferable rate performance for NIBs.The superior electrochemical performances of the Bi/C nanofiber anodes are attributed to the 1D carbon nanofiber structure and uniform distribution of Bi nanoparticles embedded in the carbon matrix.This unique embedded structure provides a favorable electron carrier and buffering matrix for the effective release of mechanical stress caused by volume change and prevents the aggregation of Bi nanoparticles.     

Conductive Au nanowires regulated by silk fibroin nanofibers

Conductive Au-biopolymer composites have promising applications in tissue engineering such as nerve tissue regeneration. In this study, silk fibroin nanofibers were formed in aqueous solution by regulating silk self-assembly process and then used as template for Au nanowire fabrication. We performed the synthesis of Au seeds by repeating the seeding cycles for several times in order to increase the density of Au seeds on the nanofibers. After electroless plating, densely decorated Au seeds grew into irregularly shaped particles following silk nanofiber to fill the gaps between particles and finally form uniform continuous nanowires. The conductive property of the Au-silk fibroin nanowires was studied with current-voltage （I-V） measurement. A typical ohmic behavior was observed, which highlighted their potential applications in nerve tissue regeneration.     

Growth of TiO2 Nanorods by Sol-gel Template Process

In this work, TiO2 nanorods with uniform diameter of about 100 nm and a length of several micrometers were successfully prepared by the sol-gel template method. Also the influence of molar ratios of precursor on the morphology and structure of TiO2 nanorods has been investigated. The prepared samples were characterized by Fourier transform infrared spectroscopy （FTIR）, X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The XRD results indicated that the TiO2 nanorods were crystallized in the anatase and rutile phases, after annealing to 400-700℃ up to 2 h.