Ionic Liquids-Assisted Synthesis Of Inorganic Nanomaterials

Many chemical processes involve volatile organic solvents that evaporate into the atmosphere with detrimental effects on the environment and human health.As the introduction of "green" technologies has become a major concern throughout both industry and academia,the search for alternatives to the damaging volatile solvents has become a high priority.Room temperature ionic liquids(RTILs)are defined as salts that melt at or below room temperature.As a new kind of environmentally friendly solvents,RTILs are increasingly arousing worldwide interest due to their unique physicochemical properties,such as thermal stabilities, relatively high ionic conductivities,and importantly negligible vapor pressures.They can be actively explored as possible "green" solvents to substitute conventional volatile organic solvents in a variety of processes without negative environmental and safety problems.In addition,RTILs also offer fascinating possibilities for fundamental studies of their effects on chemical reactions and synthetic processes.So far,they have been widely applied in catalysis,analysis,electrochemistry,and separation.By compared,the use of RTILs in inorganic synthesis is still in its infancy.In this article,we report the syntheses of five regular ionic liquids and the ionic liquids-assisted preparations of various nanomaterials, concluding hierarchical copper sulfide(CuS)nanoparticles,bismuth molybdate(Bi₂MoO₆)nanoflakes and calcium molybdate(CaMoO₄) micro-/nano-particles.X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),UV-vis absorption and photoluminescence emission(PL)were used to investigate the phase structures,morphologies and optical properties of as-prepared materials.Hierarchical CuS nanoparticles have been prepared by an ionic liquid-assisted method employing CuCl₂ and thioacetamide(TAA)as the starting materials at room temperature(about 25℃).It was found that hierarchical CuS nanoparticles were of 250～300 nm in size and wellconstructed by numerous nanoflakes with a thickness less than 10 nm. However,the only intermediate complex Cu₃(TAA)₃Cl₃ was obtained without using ionic liquid while keeping other reaction parameters constant.This interesting finding provided a room-temperature approach for hierarchical CuS species,and showed that ionic liquids could facilitate the inorganic polar reactions in water-rich system.An ionic liquid-assisted hydrothermal approach was developed to prepare Bi₂MoO₆ nanostructure with square-laminar morphology.By compared with the morphologies of those samples prepared without adding any ILs,or that with adding PVP,we concluded the approximate ionic liquids coule be used as the excellent directing agent.In addition, we found Bi₂MoO₆ nanoflakes derived from an ionic liquid-assisted process had the stronger absorption in UV light region in addition to that in the visible light region,indicating a good photocatalytic potential.CaMoO₄ hollow microspheres assembled by nanoparticles with a diameter ranged of 10～30 nm were fabricated in ionic liquid/water system at room temperature.The addition of ionic liquid was responsible for the formation of hollow structure,which might be benefit for the optical properties.In a word,we presented a facile and environmentally friendly method for the synthesis of inorganic nanomaterials in this article,and proved that the ionic liquids possessed the extraordinary potential to facilitate the synthesis of inorganic materials with novel or improved properties.This ionic liquids-assisted route may offer a universal pathway towards the synthesis of others nanomaterials.