| Spherical mesoporous carbon possesses symmetrical geometry,good liquidity,adjustable particle size distribution and physicochemical properties,excellent corrosion resistance and thermal stability,good biocompatibility,unique mesoporous structure,high specific surface area,and large pore volume,etc.These characteristics made it extensively researched and applied in various filed such as drug delivery,water treatment,catalytic separation and electrochemical electrode materials.To date,the commonly used synthetic methods for the preparation of the spherical carbon were hard-and soft-template method,hydrothermal route,extended St?ber strategy and so on.However,these synthetic methods and strategies have the corresponding shortcomings including multi-steps,high cost,poor uniformity and dispersibility,low yield and repeatability,and inferior porous structure,which severely limited the large scalable production and practical application of mesoporous carbon spheres.In this study,a one-step aqueous strategy with strong acid-assisted self-assembly was innovatively proposed to realize the controllable synthesis of mesoporous carbon nanospheres and their functionalization,which included magnetic mesoporous carbon microspheres,mesoporous carbon nanospheres and functionalized mesoporous carbon nanospheres.These carbon materials were characterized by scanning electron microscopy,transmission electron microscopy,specific surface area analyzer,X-ray diffractometer,Xray photoelectron spectroscopy,thermogravimetric/differential scanning calorimetry,Raman spectroscopy,Fourier transform infrared spectroscopy etc.The influences of hydrochloric acid,soft template,curing temperature and metal ion on the morphology and structure of polymer and mesoporous carbon were deeply studied.Furthermore,the formation mechanism of mesoporous carbon spheres via a one-step aqueous route was detailedly investigated.It was demonstrated that,under acidic conditions,functionalized mesoporous carbon nanospheres could be easily synthesized such as the fabrication of monodisperse mesoporous carbon nanospheres with ultrafine Fe3O4 nanocrystals(about 2 nm).The typical dyes(methylene blue and methyl orange)and insouble drug(fenofibrate and itraconazole)were selected as model molecules to study the adsorption and release behavior of the model molecular on mesoporous carbon nanotubes and their functional mesoporous materials.At the same time,the cytotoxicity of mesoporous carbon nanospheres and the magnetic separation and recovery mechanism of Fe3O4 modified mesoporous carbon nanospheres were researched.The main fingdings were as follows:In this one-pot aqueous method with acid-assisted self-assembly process,it could be found that the key to the synthesis of spherical mesoporous carbon is to avoid the macroscopic phase separation and to improve the thermal stability of the linear polymer.The macroscopic phase separation was closely related with the interaction force between and the carbon source and the soft template,polymerization rate of carbon precursors,and the molecular weight of the polymer.The curing temperature and the type and concentration of the metal ions have a significant impact on the thermal stability of linear polymer.Firstly,the concentration of hydrochloric acid has a significant influence on the binding force between carbon precursors and template.When the concentration of hydrochloric acid was less than 0.5 M,the low degree of protonation and the weak binding force resulted in macroscopic phase separation and non-spherical polymer.With the increase of the concentration of hydrochloric acid,the binding force was increased and macroscopic phase separation could be successfully suppressed,eventually forming polymer spheres.Secondly,the polymerization rate of the carbon precursors and the molecular weight of the polymer was closely related to the volume ratio of ethanol and water.When the volume ratio of ethanol and water was 5:35,the macroscopic phase separation was avoided,forming polymer nanospheres with uniform diameter;when the volume ratio was larger or smaller than 5:35,rapid polymerization rate and high molecular weight of the polymer,led to the decrease of the miscibility between carbon precursors and template,as well as the formation of the macroscopic phase separation.Thirdly,the curing temperature has a positive effect on the thermal stability of the polymer nanospheres,which could promote the conversion of the linear-chained framework into the 3D network structure with high thermal stability.The morphology of mesoporous carbon materials such as block,polyhedron and spherical structure,which could be easily tuned by utilized the difference of thermal stability of polymer nanospheres.Finally,the metal ions could be chelated with phenolic hydroxyl groups of phenolic resin to form a kind of 3D organic metal framework,thereby solidify the spherical polymer and avoid the agglomeration and fusion of the composite nanospheres during a high-temperature carbonization.The curing effect was dependent on the concentration of metal ions and the binding ability between metal ions and phenolic hydroxyl groups.In addition,the mesoporous carbon spheres as the carrier of the model drug can significantly improve the dissolution rate and the total release of the insoluble drugs,and at the same time it has excellent biocompatibility.In addition,it was different from previous reports,the formation and incorporation of Fe3O4 nanoparticles not only made the mesoporous carbon materials have magnetic properties,but also improved the porosity structure of the spherical composites.Compared with pristine carbon,the Fe3O4 nanoparticles incorporated mesoporous carbon nanospheres with well-developed porous structure and short diffusion length,exhibiting high adsorption capacity,fast magnetic separation and simple repeatability.Furthermore,it was innovatively proposed that the macroscopic phase separation and thermal stability of linear polymer were the technical challenges for the synthesis of mesoporous carbon nanospheres via the aqueous route with acid-assisted self-assembly process.In addition,Fenofibrate,itraconazole,methylene blue and methyl orange were selected as model molecules and then utilized to study the adsorption and release behavior of mesoporous carbon nanospheres and functionalized mesoporous carbon nanomaterials.Meanwhile,the cytotoxicity of mesoporous carbon nanospheres and the magnetic separation and recovery mechanism of Fe3O4 modified mesoporous carbon nanospheres were investigated.The experimental results showed that the mesoporous carbon nanospheres as a carrier of the model drug could significantly enhanced the dissolution rate and cumulative release of the insoluble drug and it has good biocompatibility.It was worth noting that the adsorption capacity of Fe3O4 modified mesoporous carbon nanospheres onto the two dyes was correspondingly higher than that of pure carbon,and the adsorption amount of both adsorbent for methylene blue was higher than methyl orange.Furthermore,Fe3O4 modified mesoporous carbon nanospheres exhibited rapidly magnetic separability and good reproducibility.The overall innovation of the present study lies in: A one-pot,acid-assisted aqueous strategy was first used for the synthesis of spherical mesoporous carbon and functionalized mesoporous carbon nanospheres.Compared with the traditional method,the one-step acidassisted aqueous method solved the key technical problems such as aggregation/ accumulation of spheres,phase separation and uneven size,greatly simplified the synthesis steps and period,as well as expanded the reaction system of the preparation of mesoporous carbon spheres,thereby providing a new technical support and scientific basis for the synthesis of carbon-based mesoporous materials.In addition,this method is easy extended to realize the large-scale synthesis of carbon-based mesoporous nanomaterials with spherical morphology. |
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