Preparation and properties of nitrogen-containing hollow carbon nanospheres by pyrolysis of polyaniline-lignosulfonate composites

Polyaniline-lignosulfonate composite hollow spheres were synthesized by using one-step unstirred polymerization of aniline in the presence of lignosulfonate. Novel nitrogen-containing hollow carbon nanospheres were prepared by direct pyrolysis of the polyaniline-lignosulfonate composite spheres at different temperatures under a nitrogen atmosphere. Thermal behavior of the polyaniline-lignosulfonate composite spheres was studied by TG-DTG, FTIR and element analyze instruments. The resultant carbon spheres were characterized by SEM, XRD and nitrogen adsorption-desorption measurement. It was found that the pyrolysis products of the polyaniline-lignosulfonate composite spheres were made up of uniform hollow carbon nanospheres with an average diameter of 135 nm. Furthermore, the hollow carbon nanospheres exhibit high BET surface area range from 381.6 m² g⁻¹ to 700.2 m² g⁻¹. The hollow carbon nanospheres could be used as adsorbents of papain. The papain adsorption capacity for the carbon spheres prepared at 1200 °C was up to 1161 mg g⁻¹ at an initial papain concentration of 10 mg mL⁻¹ at 25 °C.     

Superior cycle performance of Sn@C/graphene nanocomposite as an anode material for lithium-ion batteries

A novel anode material for lithium-ion batteries, tin nanoparticles coated with carbon embedded in graphene (Sn@C/graphene), was fabricated by hydrothermal synthesis and subsequent annealing. The structure and morphology of the nanocomposite were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The size of the Sn@C nanoparticles is about 50-200 nm. The reversible specific capacity of the nanocomposite is ∼662 mAh g⁻¹ at a specific current of 100 mA g⁻¹ after 100 cycles, even ∼417 mAh g⁻¹ at the high current of 1000 mA g⁻¹. These results indicate that Sn@C/graphene possesses superior cycle performance and high rate capability. The enhanced electrochemical performances can be ascribed to the characteristic structure of the nanocomposite with both of the graphene and carbon shells, which buffer the volume change of the metallic tin and prevent the detachment and agglomeration of pulverized tin.     

Preparation and electrochemical performance of monodisperse Li4Ti5O12 hollow spheres

Monodisperse Li₄Ti₅O₁₂ hollow spheres were prepared by using carbon spheres as templates. Scanning electron microscopy images show hollow spheres that have an average outer diameter of 1.0 μm and an average wall thickness of 60 nm. Compared with Li₄Ti₅O₁₂ solids, the hollow spherical Li₄Ti₅O₁₂ exhibit an excellent rate capability and capacity retention and can be charged/discharged at 10 C (1.7 A g⁻¹) with a specific capacity of 100 mA h g⁻¹, and after 200 charge and discharge cycles at 2 C, their specific capacity remain very stable at 150 mA h g⁻¹. It is believed that the hollow structure has a relatively large contact surface between Li₄Ti₅O₁₂ and liquid electrolyte, resulting in a better electrochemical performance at high charge/discharge rate.     

A one-pot synthetic approach to prepare palladium nanoparticles embedded hierarchically porous TiO2 hollow spheres for hydrogen peroxide sensing

A simple one-step method to fabricate hierarchically porous TiO₂/Pd composite hollow spheres without any template was developed by using solvothermal treatment. Pd nanoparticles (2-5 nm) were well dispersed in the mesopores of the TiO₂ hollow spheres via in-situ reduction. In our experiment, polyvinylpyrrolidone played an important role in the synthetic process as the reducing agent and the connective material between TiO₂ and Pd nanoparticles. HF species generated from solvothermal reaction leaded to the formation of TiO₂ hollow spheres and Ostwald ripening was another main factor that affected the size and structure of the hollow spheres. The as-prepared TiO₂/Pd composite hollow spheres exhibited high electrocatalytic activity towards the reduction of H₂O₂. The sensitivity was about 226.72 μA mM⁻¹ cm⁻² with a detection limit of 3.81 μM at a signal-to-noise ratio of 3. These results made the hierarchically porous TiO₂/Pd composite a promising platform for fabricating new nonenzymic biosensors.     

Synthesis of nanospherical Fe3BO6 anode material for lithium-ion battery by the rheological phase reaction method

This paper developed a novel method, the rheological phase reaction method, to synthesize nanospherical Fe₃BO₆. The sizes and morphologies of products vary with the calcination temperatures. Spherical particles with a uniform size about 40 nm in a monodisperse state were obtained at 800 °C, while the spherical particles with a larger size of 100-500 nm were obtained at 900 °C. The electrochemical properties of these Fe₃BO₆ nanospheres were investigated. Sample synthesized at 800 °C delivers a high reversible capacity above 500 mAh g⁻¹. Sample synthesized at 900 °C possesses relatively good cycleability with a capacity retaining of 376 mAh g⁻¹ after 10 cycles. The measurement of electrochemical impedance spectra for the first time indicated that smaller Fe₃BO₆ nanoparticles intend to give higher impedance of solid-electrolyte interface layer and lower charge-transfer impedance after the first discharge. Additionally, it can be speculated that the increase of resistance charge-transfer is the possible reason for the capacity fading during cycling.     

An ultra-clean technique for accurately analysing Pb isotopes and heavy metals at high spatial resolution in ice cores with sub-pg g Pb concentrations

Measurements of Pb isotope ratios in ice containing sub-pg g⁻¹ concentrations are easily compromised by contamination, particularly where limited sample is available. Improved techniques are essential if Antarctic ice cores are to be analysed with sufficient spatial resolution to reveal seasonal variations due to climate. This was achieved here by using stainless steel chisels and saws and strict protocols in an ultra-clean cold room to decontaminate and section ice cores. Artificial ice cores, prepared from high purity water were used to develop and refine the procedures and quantify blanks. Ba and In, two other important elements present at pg g⁻¹ and fg g⁻¹ concentrations in Polar ice, were also measured. The final blank amounted to 0.2 ± 0.2 pg of Pb with ²⁰⁶Pb/²⁰⁷Pb and ²⁰⁸Pb/²⁰⁷Pb ratios of 1.16 ± 0.12 and 2.35 ± 0.16, respectively, 1.5 ± 0.4 pg of Ba and 0.6 ± 2.0 fg of In, most of which probably originates from abrasion of the steel saws by the ice. The procedure was demonstrated on a Holocene Antarctic ice core section and was shown to contribute blanks of only ∼5%, ∼14% and ∼0.8% to monthly resolved samples with respective Pb, Ba and In concentrations of 0.12 pg g⁻¹, 0.3 pg g⁻¹ and 2.3 fg g⁻¹. Uncertainties in the Pb isotopic ratio measurements were degraded by only ∼0.2%.     

Controlled morphology synthesis of β-FeOOH and the phase transition to Fe2O3

The hexagram and arrayed β-FeOOH nanorods were first synthesized free of surfactants through the solvent-thermal method. X-ray powder diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectrum (EDAX) and thermal gravimetric analysis (TGA) were used to characterize the as-prepared products. The TEM and FESEM images showed that hexagram β-FeOOH and arrayed rod-like β-FeOOH with an average diameter of 10-15 nm and an average length of 100 nm (aspect ratio is about 10) were prepared. Electrochemical tests show that these nanorods deliver a large discharge capacity of 277 mA h g⁻¹ versus Li metal at 0.1 mA cm⁻² (voltage at 1.5-4.2 V). Treated the as-synthesized rod-like β-FeOOH by annealing, rhombus hematite was obtained.     

New solid-state synthesis routine and mechanism for LiFePO4 using LiF as lithium precursor

Li₂CO₃ and LiOH·H₂O are widely used as Li-precursors to prepare LiFePO₄ in solid-phase reactions. However, impurities are often found in the final product unless the sintering temperature is increased to 800 °C. Here, we report that lithium fluoride (LiF) can also be used as Li-precursor for solid-phase synthesis of LiFePO₄ and very pure olivine phase was obtained even with sintering at a relatively low temperature (600 °C). Consequently, the product has smaller particle size (about 500 nm), which is beneficial for Li-extraction/insertion in view of kinetics. As for cathode material for Li-ion batteries, LiFePO₄ obtained from LiF shows high Li-storage capacity of 151 mAh g⁻¹ at small current density of 10 mA g⁻¹ (1/15 C) and maintains capacity of 54.8 mAh g⁻¹ at 1500 mA g⁻¹ (10 C). The solid-state reaction mechanisms using LiF and Li₂CO₃ precursors are compared based on XRD and TG-DSC.     

Template‐Free Synthesis of Hierarchical Vanadium‐Glycolate Hollow Microspheres and Their Conversion to V2O5 with Improved Lithium Storage Capability

Nanosheet‐assembled hierarchical V₂O₅ hollow microspheres are successfully obtained from V‐glycolate precursor hollow microspheres, which in turn are synthesized by a simple template‐free solvothermal method. The structural evolution of the V‐glycolate hollow microspheres has been studied and explained by the inside‐out Ostwald‐ripening mechanism. The surface morphologies of the hollow microspheres can be controlled by varying the mixture solution and the solvothermal reaction time. After calcination in air, hierarchical V₂O₅ hollow microspheres with a high surface area of 70 m² g^?1 can be obtained and the structure is well preserved. When evaluated as cathode materials for lithium‐ion batteries, the as‐prepared hierarchical V₂O₅ hollow spheres deliver a specific discharge capacity of 144 mA h g^?1 at a current density of 100 mA g^?1, which is very close to the theoretical capacity (147 mA h g^?1) for one Li⁺ insertion per V₂O₅. In addition, excellent rate capability and cycling stability are observed, suggesting their promising use in lithium‐ion batteries.     

Preparation of NiO/multiwalled carbon nanotube nanocomposite for use as the oxygen cathode catalyst in rechargeable Li–O2 batteries

NiO/multiwalled carbon nanotube (NiO/MWCNT) nanocomposites have been prepared and used for a Li–O₂ battery cathode catalyst. Electrochemical measurements demonstrate that the batteries with NiO/MWCNT catalyst have a discharge capacity of 2,500 mAh g^?1, a charge capacity of 2,100 mAh g^?1, and a rechargeable ability performing better than Ketjenblack (KB) and MWCNTs. KB has the largest discharge capacity (2,700 mAh g^?1) due to the highest surface area and pore volume but the worst charging behavior due to poor mass transport in the small-width pore (2.48 nm). MWCNTs have a much better charging performance owing to a larger pore width (8.93 nm) than carbon black. NiO/MWCNTs have the largest charge capacity because of the facilitated mass transport in the comparatively large pores (7.68 nm) and the increased catalytic ability produced by the NiO nanoparticles. These improvements are also responsible for the best cycle and rate performances of the nanocomposites among the three catalysts.     

Influence of hole mobility on the response characteristics of p-type nickel oxide thin film based glucose biosensor

RF sputtered p-type nickel oxide (NiO) thin film exhibiting tunable semiconductor character which in turns enhanced its functional properties. NiO thin film with high hole mobility is developed as a potential matrix for the realization of glucose biosensor. NiO thin film prepared under the optimized deposition conditions offer good electrical conductivity (1.5 × 10⁻³ Ω⁻¹-cm⁻¹) with high hole mobility (2.8 cm² V⁻¹ s⁻¹). The bioelectrode (GO_x/NiO/ITO/glass) exhibits a low value of Michaelis–Menten constant (K_m = 1.05 mM), indicating high affinity of the immobilized GO_x toward the analyte (glucose). Due to the high surface coverage (2.32 × 10⁻⁷ mol cm⁻²) of the immobilized enzyme on to the NiO matrix and its high electrocatalytic activity, the prepared biosensor exhibits a high sensitivity of 0.1 mA (mM⁻¹-cm⁻²) and a good linearity from 25 to 300 mg dL⁻¹ of glucose concentration with fast response time of 5 s. Various functional properties of the material (mobility, crystallinity and stress) are found to influence the charge communication feature of NiO thin film matrix to a great extent, resulting in enhanced sensing response characteristics.     

Electrospinning preparation and drug delivery properties of Eu/Tb doped mesoporous bioactive glass nanofibers

Luminescent Eu³⁺/Tb³⁺ doped mesoporous bioactive glass nanofibers (MBGNFs) with average diameter of 100-120 nm were fabricated by electrospinning method. Pluronic P123 and N-cetyltrimethylammonium bromide (CTAB) were used as co-surfactants to generate porous structure of the nanofibers. N₂ adsorption-desorption measurement reveals that the MBGNF:Eu³⁺ have a surface area of 188 m² g⁻¹, a pore volume of 0.246 cm³ g⁻¹ and average pore size of 4.17 nm, and the MBGNF:Tb³⁺ have a surface area of 171 m² g⁻¹, a pore volume of 0.186 cm³ g⁻¹ and average pore size of 3.65 nm. Photoluminescence measurements reveal that the MBGNF:Eu³⁺ show strong red emission dominated by the ⁵D₀ → ⁷F₂ transition of Eu³⁺ at 614 nm with a lifetime of 1.356 ms, and MBGNF:Tb³⁺ show strong green emission dominated by the ⁵D₄ → ⁷F₅ transition of Tb³⁺ at 544 nm with a lifetime of 1.982 ms. The biocompatibility tests on L929 fibroblast cells using MTT assay reveal low cytotoxicity of MBGNF. These luminescent nanofibers show sustained release properties for ibuprofen (IBU) in vitro. The emission intensities of Eu³⁺ in the drug delivery system vary with the released amount of IBU, thus making the drug release be easily tracked and monitored by the change of the luminescence intensity.     

A study of the direct determination of Cd, Cr, Cu, Pb and Zn in certified reference materials of soils by solid sampling electrothermal atomic absorption spectrometry

A simple and rapid method for the direct determination of Cd, Cr, Cu, Pb and Zn in soil was developed. The method was developed using three certified reference materials of soil: Eutric Cambisol, Orthic Luvisols and Rendzina, which differed in their matrix composition. Chemical modifiers were essential to achieve reproducible and interference-free signals for the analytes studied. The best results were obtained with a Pd/Mg(NO₃)₂ admixture for the determination of Cd, Pb and Zn and NH₄F for Cu. The combination of W (as a permanent modifier) and Mg(NO₃)₂ provided well-defined signal profiles for Cr. The following spectral lines were used: Cd 228.8 nm, Cr 520.6 nm, Cu 218.2 nm, Pb 205.3 nm and Zn 307.6 nm. The limit of detection was 4.2 ng g^− 1 for Cd, 1.1 μg g^− 1 for Cr, 0.5 μg g^− 1 for Cu, 1.3 μg g^− 1 for Pb and 8.6 μg g^− 1 for Zn for the maximum sample mass used. Under optimized conditions, the analyte and matrix were separated effectively in situ, and aqueous standards could be used for calibration.     

Europium-sensitized luminescence determination of oxytetracycline in catfish muscle

An europium-sensitized time-resolved luminescence (TRL) method was developed to determine oxytetracycline (OTC) in cultivated catfish muscle. Extraction of OTC from fish muscle was performed with pH 4.0 ethylenediaminetetraacetic acid (EDTA)-McIlvaine buffer and clean up with hydrophilic-lipophilic balanced copolymer solid phase extraction (SPE) cartridges. The eluate was used without further concentration for TRL measurement in pH 9.0 micellar tris(hydroxylmethyl)aminomethane (TRIS) buffer. Cetyltrimethylammonium chloride (CTACl) was used as surfactant and EDTA as a co-ligand. The excitation and emission wavelengths were set at 388 and 615 nm, respectively. The linear dynamic range was 0-1000 ng g⁻¹ (R²=0.9995). The recovery was 92-112% in the fortification range of 50-200 ng g⁻¹ and the limits of detection (LOD) ranged from 3 to 7 ng g⁻¹. Incurred catfish samples were used to demonstrate the performance of the method around 100 ng g⁻¹, the European Union maximum residue level.     

Mesoporous TiO2 aerogel for selective enrichment of phosphopeptides in rat liver mitochondria

The enrichment of low abundance phosphopeptides before MS analysis is a critical step for in-depth phosphoproteome research. In this study, mesoporous titanium dioxide (TiO₂) aerogel was prepared by precipitation and supercritical drying. The specific surface area up to 490.7 m² g⁻¹ is achieved by TiO₂ aerogel, much higher than those obtained by commercial TiO₂ nanoparticles and by the latest reported mesoporous TiO₂ spheres. Due to the large specific surface area and the mesoporous structure of the aerogel, the binding capacity for phosphopeptides is six times higher than that of conventional TiO₂ microparticles (173 vs 28 μmol g⁻¹). Because of the good compatibility of enrichment procedure with MALDI-TOF-MS and the large binding capacity of TiO₂ aerogel, a detection limit as low as 30 amol for analyzing phosphopeptides in β-casein digest was achieved. TiO₂ aerogel was further applied to enrich phosphopeptides from rat liver mitochondria, and 266 unique phosphopeptides with 340 phosphorylation sites, corresponding to 216 phosphoprotein groups, were identified by triplicate nanoRPLC-ESI-MS/MS runs, with false-positive rate less than 1% at the peptide level. These results demonstrate that TiO₂ aerogel is a kind of promising material for sample pretreatment in the large-scale phosphoproteome study.     

A Facile synthesis of flower-like Co3O4 porous spheres for the lithium-ion battery electrode

The porous hierarchical spherical Co₃O₄ assembled by nanosheets have been successfully fabricated. The porosity and the particle size of the product can be controlled by simply altering calcination temperature. SEM, TEM and SAED were performed to confirm that mesoporous Co₃O₄ nanostructures are built-up by numerous nanoparticles with random attachment. The BET specific surface area and pore size of the product calcined at 280 °C are 72.5 m² g⁻¹ and 4.6 nm, respectively. Our experiments further demonstrated that electrochemical performances of the synthesized products working as an anode material of lithium-ion battery are strongly dependent on the porosity.     

A comparative analysis of polyurethane hydrogel for immobilization of IgG on chips

Hydrogels are considered an optimum material for protein chip surfaces, since they provide a quasi-liquid environment which allows protein activity to be maintained and shows good spot morphology as well as excellent immobilization capacity. In the following, we present a polyurethane (PU) chip that electrostatically binds IgG. The PU surface is optimized with regard to layer thickness (∼200 nm), hydrogel (2%) and immobilized antibody concentration (0.5 mg mL⁻¹; 0.3 ng spot⁻¹), pH and ionic strength of the print buffer as well as to blocking solution. Evaluation is done in a direct IgG immunoassay using the Nexterion slide H as a reference. It is shown that higher IgG loading is achieved on the PU chip than on slide H, no matter whether 1× PBS (pH 7.2), Sörensen (pH 5.8) or Nexterion buffer was used as a spotting solution. Moreover, the crossreactivity with goat IgG, human IgG and monoclonal anti-CRP spotted in Nexterion buffer was as low as ≤0.74% (slide H: ≤3.34%).     

In situ fabrication of nanostructured titania coating on the surface of titanium wire: A new approach for preparation of solid-phase microextraction fiber

Nanostructured titania-based solid-phase microextraction (SPME) fibers were fabricated through the in situ oxidation of titanium wires with H₂O₂ (30%, w/w) at 80 °C for 24 h. The obtained SPME fibers possess a ∼1.2 μm thick nanostructured coating consisting of ∼100 nm titania walls and 100-200 nm pores. The use of these fibers for headspace SPME coupled with gas chromatography with electron capture detection (GC-ECD) resulted in improved analysis of dichlorodiphenyltrichloroethane (DDT) and its degradation products. The presented method to detect DDT and its degradation products has high sensitivity (0.20-0.98 ng L⁻¹), high precision (relative standard deviation R.S.D. = 9.4-16%, n = 5), a wide linear range (5-5000 ng L⁻¹), and good linearity (coefficient of estimation R² = 0.991-0.998). As the nanostructured titania was in situ formed on the surface of a titanium wire, the coating was uniformly and strongly adhered on the titanium wire. Because of the inherent chemical stability of the titania coating and the mechanical durability of the titanium wire substrate, this new SPME fiber exhibited long life span (over 150 times).     

Template free fabrication of hollow hematite spheres via a one-pot polyoxometalate-assisted hydrolysis process

Uniform hollow hematite (α-Fe₂O₃) spheres with diameter of about 600-700 nm and shell thickness lower than 100 nm are obtained by direct hydrothermal treatment of dilute FeCl₃ and tungstophosphoric acid H₃PW₁₂O₄₀ solution at 180 °C. The hollow spheres are composed of robust shells with small nanoparticles standing out of the surface and present a high-surface area and a weak ferromagnetic behavior at room temperature. The effect of concentration of H₃PW₁₂O₄₀, reaction time and temperature for the formation of the hollow spheres are investigated in series of experiments. The formation of the hollow spheres may be ascribed to a polyoxometalte-assisted forced hydrolysis and dissolution process.     

Synthesis of Highly Uniform Molybdenum–Glycerate Spheres and Their Conversion into Hierarchical MoS2 Hollow Nanospheres for Lithium‐Ion Batteries

Highly uniform Mo–glycerate solid spheres are synthesized for the first time through a solvothermal process. The size of these Mo–glycerate spheres can be easily controlled in the range of 400–1000 nm by varying the water content in the mixed solvent. As a precursor, these Mo–glycerate solid spheres can be converted into hierarchical MoS₂ hollow nanospheres through a subsequent sulfidation reaction. Owing to the unique ultrathin subunits and hollow interior, the as‐prepared MoS₂ hollow nanospheres exhibit appealing performance as the anode material for lithium‐ion batteries. Impressively, these hierarchical structures deliver a high capacity of about 1100 mAh g^?1 at 0.5 A g^?1 with good rate retention and long cycle life.