•Carbon spheres with uniform pore size were prepared by spray-drying assisted method.•Porous carbon acted as sacrificial template for growing carbon modified porous MnO2.•The morphology of the porous MnO2 spheres can be tuned by changing hydrothermal time.•The in-situ formation of carbon modified MnO2 spheres are monitored with microscopy.•Carbon modified porous MnO2 spheres show excellent performance for supercapacitors.Carbon modified MnO2 (CMMO) spheres have been fabricated through a facile low temperature (60 °C) hydrothermal method using mesoporous carbon spheres as reductive agent and sacrificial template and KMnO4 as manganese source. CMMO spheres with novel nanostructures such as flower-like and sea urchin-like are obtained by controlling the reaction time. The roles of mesoporous carbon in directing the growth of the CMMO spheres and controlling their morphologies have been investigated. The CMMO spheres are characterized by XRD, XPS, SEM, TEM, Raman spectra, TGA and N2 adsorption-desorption technique and electrochemical measurement. The resulted samples possess unique morphologies and regular pores, and their properties changed as reaction time proceed. The peseudocapacitive behaviors of the as-prepared samples are tested in two-electrode supercapacitors using 2 mol L−1 KOH aqueous solutions as electrolyte. A high gravimetric capacitance of 344 F g−1 at 1 A g−1 and the capacity retaining of 75% after 5000 cycles are achieved on the electrode prepared with one of the CMMO samples. The other CMMO samples also possess excellent electrochemical performance in comparison with the pristine mesoporous carbon (p-MC). Such superior electrochemical performance makes the porous CMMO spheres to be promising materials in the application of pseudocapacitors.Download high-res image (369KB)Download full-size image

•Spray drying technique was utilized for the preparation of ZnO nanocrystal assemblies using zincoxen cellulose solution as raw materials.•Zincoxen plays both the role as solvent for cellulose and precursor for the ZnO nanocrystals.•Cellulose acts as assembly agent during the spray drying step and sacrificial templates in the calcinations process.•The content of cellulose and the calcination temperature influence the properties of the resulted ZnO nanocrystal assemblies.•The assemblies of ZnO nanocrystals exhibit high photocatalytic activity for methyl orange degradation in aqueous solution.The conventional zincoxen cellulose solution, which was obtained by dissolving cellulose with the zincoxen solvent (tri(ethylenediamine) zinc hydroxide solution, Zn(EDA)32+), has been used as raw materials for the preparation of zincoxen/cellulose complex microspheres via a spray drying technique. The obtained zincoxen/cellulose microspheres are turned into assemblies (or clusters) of ZnO nanocrystals by calcining the complex microspheres at 500 or 700 °C. For the preparation, zincoxen plays both the role as solvent for cellulose and precursor for the ZnO nanocrystals. While, the cellulose acts as assembly agent during the spray drying step and sacrificial templates in the calcinations process. The content of cellulose in the zincoxen cellulose aqueous solution and the calcination temperature show significant impacts on the morphology, porosity, optical properties and photocatalytic activity of the resulted ZnO nanocrystal assemblies. The structures, morphology and porosity have been investigated based on XRD, SEM, TEM and N2 adsorption-desorption technique. The lattice parameters have been fitted by the Rietveld refinement and the strains in the crystals have been studied. Under ultraviolet light irradiation, all the assemblies of ZnO nanocrystals exhibit high photocatalytic activity for methyl orange degradation in aqueous solution and also satisfied reusability and stability of morphology and composition.Download high-res image (184KB)Download full-size imageZincoxen cellulose solution was used as raw materials for the preparation of zincoxen/cellulose complex microspheres via a spray drying process. The obtained zincoxen/cellulose microspheres were turned into assemblies of ZnO nanocrystals upon calcinations at 500 or 700 °C. The assemblies of ZnO nanocrystals exhibit high photocatalytic activity for methyl orange degradation under ultraviolet light irradiation in aqueous solution and also satisfied reusability and stability of morphology and composition.

•LixFe0.2Mn0.8PO4/C composite fibers were synthesized based on the electrospinning method.•The content of lithium of LixFe0.2Mn0.8PO4/C fibers has a strong effect on their electrochemical properties.•The molecular structure of carbon sources plays an important role in determining the electrochemical properties of composite fibers.LixFe0.2Mn0.8PO4/C (LixFMP/C, x = 1.2, 1.1, 1.05) composite fibers were successfully prepared by stabilization and calcination of the electrospun fibers from the precursor solution. The structural and morphological characterizations revealed that the LixFe0.2Mn0.8PO4 with high purity was evenly coated with an amorphous carbon layer. Experimental data testified the well-crystalline structure of composite fibers based on the results of the X-ray diffraction (XRD) and selected area electron diffractions (SAED). The galvanostatic charge–discharge measurements indicated that Li1.2Fe0.2Mn0.8PO4 displayed the highest capacity of 174 mA h g−1 at 0.05 C and the best cycling stability. The charge-transfer impedance of LixFe0.2Mn0.8PO4/C was decreased negatively with the content of lithium. It was found that the molecular structure of carbon sources and calcination procedure played key factor in determining the electrochemical properties of the composite fibers. These results suggested that electrospinning should be a promising method for fabricating crystalline LFMP/C composite fibers as electrode materials for lithium-ion battery.

•Spray drying was applied to the preparation of porous carbon microspheres.•The porous carbon microspheres possess hierarchical pores and controlled porosity.•The porous carbon had been used as support for sulfur with content up to 80 wt%.•A high pressure process was applied to the impregnation of sulfur into the pores.•The obtained Li–S batteries showed excellent electrochemical performance.Mesoporous carbon (MC) spheres with hierarchical pores, controlled pore volume and high specific surface areas have been prepared by a mass-producible spray drying assisted template method using sodium alginate as carbon precursor and commercial colloidal silica particles as hard template. The resulting MC spheres, possessing hierarchical pores in the range of 3–30 nm, are employed as conductive matrices for the preparation of cathode materials for lithium–sulfur batteries. A high pressure induced one-step impregnation of elemental sulfur into the pore of the MC spheres has been exploited. The electrochemical performances of sulfur-impregnated MC spheres (S-MC) derived from MC spheres with different pore volume and specific surface area but with the same sulfur loading ratio of 60 wt% (S-MC-X-60) have been investigated in details. The S-MC-4-60 composite cathode material displayed a high initial discharge capacity of 1388 mAhg−1 and a good cycling stability of 857 mAhg−1 after 100 cycles at 0.2C, and shows also excellent rate capability of 864 mAhg−1 at 2C. More importantly, the sulfur loading content in MC-4 spheres can reach as high as 80%, and it still can deliver a capacity of 569 mAhg−1 after 100 cycles at 0.2C.

Cu particles decorated carbon composite microspheres (CCMs) with a unique sesame ball structure have been prepared by combining the mass-producible spray drying technique with calcinations. The conventional cuprammonium cellulose complex solution obtained by dissolving cellulose in a cuprammonia solution has been applied as raw materials for the preparation of Cu(NH3)42+/cellulose complex microspheres via a spray drying process. The resulted Cu(NH3)42+/cellulose complex microspheres are then transformed into the Cu particles homogeneously decorated porous carbon spheres in situ by calcinations at 450 or 550 °C. The coordination effect between the Cu(NH3)42+ species and the hydroxyl groups of the cellulose macromolecules has been exploited for directing the dispersion of the Cu particles in the resultant composite CCMs. The antimicrobial effects of the CCMs are evaluated by determining the minimum growth inhibitory concentrations using Staphylococcus aureus and Escherichia coli as representatives, respectively. The CCMs show high efficiency catalytic properties to the conversion of 4-nitrophenol to 4-aminophenol using NaBH4 as a reductant in a mild condition. The recyclability and stability of the CCM catalysts have also been studied.Keywords: Antibacterial activity; Chelating effect; Copper particles; Cuprammonium cellulose complex; Porous carbon microspheres; Supported catalyst;

Submicrometer MnFe2O4 colloidal nanocrystal assemblies (CNAs) have been synthesized controllably by using a solvothermal method through simply adjusting synthetic reagents. The size and microstructure of MnFe2O4 CNAs were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Results showed that MnFe2O4 CNAs were well-separated and uniform with the size scales ranging from 230 nm to 950 nm, which were composed of primary crystalline nanoparticles with the sizes ranging from 16 nm to 43 nm. Room-temperature magnetic measurement results showed that MnFe2O4 CNAs were weakly ferromagnetic with small remnant saturation and coercivity values. The magnetization saturation values of CNAs were increased with the increase of the size of primary nanoparticles. Electrochemical measurements showed that the size of primary nanoparticles of MnFe2O4 CNAs had an important effect on the electrochemical reduction of H2O2. However, the electrocatalytic activity of MnFe2O4 CNAs for oxygen reduction reaction closely correlated with both the crystal size and self-assembly of primary nanoparticles. Based on the experimental results, the formation mechanisms of MnFe2O4 CNAs as well as the relationship between their structures and properties have been analyzed and discussed.

•Porous microspheres of cellulose have been prepared by a spray-assisted approach.•Composite microspheres of cellulose can also be fabricated with a similar process.•The spray coagulating process must combine with a spray drying step.•The porous cellulose microspheres can act as a convenient reservoir for drug delivery.•The porous microspheres can be used as precursors for other functional matrices.Porous microspheres of regenerated cellulose with size in range of 1–2 μm and composite microspheres of chitosan coated cellulose with size of 1–3 μm were obtained through a two-step spray-assisted approach. The spray coagulating process must combine with a spray drying step to guarantee the formation of stable microspheres of cellulose. This approach exhibits the following two main virtues. First, the preparation was performed using aqueous solution of cellulose as precursor in the absence of organic solvent and surfactant; Second, neither crosslinking agent nor separated crosslinking process was required for formation of stable microspheres. Moreover, the spray drying step also provided us with the chance to encapsulate guests into the resultant cellulose microspheres. The potential application of the cellulose microspheres acting as drug delivery vector has been studied in two PBS (phosphate-buffered saline) solution with pH values at 4.0 and 7.4 to mimic the environments of stomach and intestine, respectively.

Carbon modified lithium titanate (Li4Ti5O12) anode nanocrystals for Li-ion batteries were synthesized by directly treating the titanium alkoxide and lithium acetate ethanol solution via the Reaction under Autogenic Pressure at Elevated Temperature (abbreviated to RAPET). The mixture of the liquid precursors decomposed during the RAPET process and then reacted in situ and transformed into carbon-modified Li4Ti5O12 anode nanocrystals. The organic moieties in the titanium alkoxide and the lithium salt provided both the oxygen and carbon for the synthesis. The resulting products were characterized by X-ray diffraction (XRD), elemental analysis, scanning electronic microscopy (SEM), high resolution transmission electron microscopy (HR-TEM), nitrogen adsorption–desorption measurements, cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge–discharge testing. The influences of the titanium alkoxide precursors, i.e. the length of the alkoxy group, on the properties of the final products and the presence of the in situ resulting carbon on the electrochemical performance have been investigated.

A one-step high-temperature solvothermal process (can be used up to 400 °C) has been explored for the preparation of Fe3O4/graphene composites. The influence of high temperature (>230 °C) on the structure, morphology and electrochemical properties of the resulting Fe3O4/graphene composites was investigated by XRD, SEM, TEM and N2 adsorption–desorption measurements. Electrochemical performances of the as-prepared Fe3O4/graphene composites at different temperatures were evaluated in coin-type cells as anode materials for lithium-ion batteries. In comparison with the traditional solvothermal method (<240 °C), the high-temperature method does not require an additional calcination process yet it still could result in Fe3O4/graphene composites with pure phase and excellent electrochemical properties. A preferred solvothermal temperature of 280 °C has been deduced based on a series of control experiments. The Fe3O4/graphene composite derived at 280 °C exhibited a high reversible capacity of 907 mA h g−1 at 0.1 C (92.6 mA g−1) even after 65 cycles, showing outstanding cycle stability. It also exhibited a high rate capability of 410 mA h g−1 at 2 C (1852 mA g−1). The role of the graphene substrates in improving the electrochemical properties of the composite is discussed based on the morphology, structure, phase and electrochemical property studies.

•Porous carbon inlaid with Fe3O4 nanoparticles was prepared by a facile approach.•The Fe3O4 encapsulated mesoporous carbon was decorated with Ag nanoparticles.•The porous composite matrices showed flexible magnetic separation property.•The Ag nanoparticles decorated porous matrices exhibited catalytic properties.•The Ag nanoparticles decorated matrices possess high antibacterial effect.Mesoporous composite particles of carbon inlaid with Fe3O4 nanoparticles (designated as Fe3O4@carbon) with a novel bowl structure and magnetic separation property were fabricated by a spray drying assisted template method using chitosan as carbon precursor and silica nanoparticles as pore directing agent. The influence of the contents among Fe3O4 nanoparticles, chitosan and silica nanoparticle on the formation of porous Fe3O4@carbon composite particles has been discussed. Ag nanoparticles were then deposited onto the surface of mesoporous Fe3O4@carbon substrates using silver acetate as precursor with the assistance of ultrasound treatment. The matrices of Ag nanoparticles decorated Fe3O4@carbon composite particles (denoted as Ag–(Fe3O4@carbon)) were derived and characterized with scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier-transform infrared (FT-IR) spectroscopy, nitrogen adsorption–desorption, and magnetic property measurements. The Ag–(Fe3O4@carbon) composites showed efficient antibacterial activities to Escherichia coli and Staphylococcus aureus, high catalytic activity to the reduction of 4-nitrophenol (4-NP) in the presence of NaBH4, strong adsorption ability to organic molecules, and efficient separability under a magnetic field.

Using the surface charged and acid dissolvable melamine formaldehyde (MF) microspheres as sacrificial hard templates, silica coated MF core–shell composite microspheres, denoted as MF@SiO2, were synthesized via a surfactant-assisted sol–gel process by using tetraethyl orthosilicate (TEOS) as silica source. Hollow SiO2 spheres with mesoporous shells were then obtained after selective removal of the MF cores and the pore directing surfactant by hydrochloric acid etching or calcinations in air. Interesting shrinkage phenomena were observed in both the hollow products derived from hydrochloric acid etching and calcinations. The influence of the ratio of MF sphere to TEOS and the removal method of the MF core on the size of the hollow spheres, the shell thickness and the shell surface roughness have been studied. The composition, the thermal stability, the morphology, the surface area and pore size distribution, the wall thickness and adsorption properties of the hollow spheres derived from hydrochloric acid etching and calcinations were also investigated and compared based on the FTIR, SEM, TEM, TGA, Nitrogen adsorption–desorption and spectrophotometer techniques or measurements.

•Size-tunable ZnFe2O4 colloidal nanocrystal assemblies were synthesized solvothermally.•Magnetic properties of ZnFe2O4 assemblies are depended on the size and self-assembly of primary nanoparticles.•Electrocatalytic activity of ZnFe2O4 assemblies is determined by their structure.Three ZnFe2O4 colloidal nanocrystal assemblies (CNAs), namely CNA1, CNA2 and CNA3, have been synthesized solvothermally with the size of 560 nm, 460 nm and 330 nm and are formed by the self-assembly of primary nanocrystals with the crystallite sizes of 19.2 nm, 15.5 nm and 21.8 nm, respectively. It was found that CNA2 performed superparamagnetic behavior with a saturation magnetization value of 36.9 emu g−1 while either CNA1 or CNA3 exhibited weak ferromagnetic with a small hysteresis loop and large saturation magnetization. Electrochemical sensing measurements toward the reduction of hydrogen peroxide showed that the peak currents of the CNAs in cyclic voltammograms showed a linear relationship with the concentration of hydrogen peroxide in the experimental conditions and the peak potentials were increased with the order of CNA3, CNA2 and CNA1. The formation mechanism of ZnFe2O4 CNAs had been discussed based on the experimental data. The magnetism and electrocatalysis of the ZnFe2O4 CNAs were supposed to be dependent on the size of primary nanoparticles and the structure of the CNAs.Download high-res image (141KB)Download full-size image