Ionic Liquid Assisted Synthesis Of Micro / Nano Materials

Room temperature ionic liquids(RTILs) as a new solvent have received much attention due to their advantageous chemical and physical prosperities,such as negligible vapor pressure,low melting points,wide range of liquid temperatures,high polarity,low toxicity,large electrochemical window,good solvents for many organic and inorganic materials,high ionic conductively and thermal stability,etc.,and significant progress has been made in applications to synthetic-organic chemistry,catalysis,separation and electrochemistry.In contrast to their successful applications in organic and materials chemistry,the use of RTILs in micro-nanostructres synthesis is still in its infancy,but the excellences have brought more attention of scientist.In this paper,we successfully synthesized various micro-nanomatcrials through different routes assisted with ionic liquids.The microwave-assisted RTILs method is a fast and environment-friendly route to the preparation of a variety of nanostructured materials.Heating by microwave can accelerate the reaction evidently,and the polarization of ions under the rapidly changing electric field of the microwave results in anisotropic growth of crystals.The RTILs consist of cations and anions,and the high ionic conductivity and polarizability of cations make it an excellent microwave absorbing agent,thus leading to a high heating rate and a significantly shorten reaction time.By combining the advantages of both RTILs and microwave heating,we have successfully synthesized tin oxide(SnO₂) microspheres with an average 2.5μm in diameters through a rapid hydrothermal process heating by microwave in the presence of an ionic liquid 1-butyl-3-methyl imidazolium tetrafluoroborate.The hydrophilic[Bmim]BF₄ ionic liquid was proved playing an important role in the growth of SnO₂ crystallites and subsequent self-assembly process,which increased greatly the product yield,and make the nucleation occurred at a much faster rate.Recently,the solvothermal technique,which is carried out at low temperature and does not require organometallic precursors,has been developed as a mild and effective route to synthesize novel materials.By combining the advantages of both RTILs and solvothermal technique,we have successfully synthesized copper oxalate nanowires via the reaction of Cu(CH₃COO)₂·4H₂O and oxalic acid in ethanol solution with the aid of 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim]BF₄) ionic liquid under solvothermal conditions at 180℃.The length of the nanowires reaches 5～10μm,and the width～30 nm,giving an aspect-ratio of a few hundreds.The[Bmim]BF₄ ionic liquid plays a unique role in the preparation of copper oxalate nanowires,and may serves as a mineralizing agent to promote crystallization of copper oxalate to nanowires during the solvothermal process.The crystallization follows a novel mechanism based on the reorganization and solid-solid transformation of a copper oxalate solid phase.Upon thermal decomposition at 350℃in air,copper oxalate nanowires can be converted to copper oxide nanowires.