Templated Synthesis Of A Bifunctional Janus Graphene For Screening Of Chemical Contaminants

Graphene,a two-dimensional carbon nanostructure,has shown great promise in both fundamental and industrial applications.Typically,owing to its ultrahigh surface area and p-electron-rich structure,graphene has been extensively used as an enrichment material in separation chemistry.It has been demonstrated that graphene can capture a great variety of substances including organic pollutants,biopolymers,and metal ions throughp–pinteractions,hydrogen-binding,and electrostatic interactions.However,graphene often suffers from aggregation of material,single target,non-specific adsorption,and less anti-interference,which may greatly reduce its adsorption efficiency and application performance in complex media.Thus,a feasible alternative is to prepare modified graphene or its derivatives through chemosynthesis.Janus graphene can be artificially modified with different functional groups on each side of the surface sheet,endowing it versatility and specificity toward multiple targets.Unfortunately,up to now,the synthesis of Janus graphene is still a very challenging task.Only few papers reported the synthetic methods of Janus graphene.However,these methods suffer from rigorous operation,strict reactive conditions,and low yields.In order to improve the performance of graphene in practical applications,we synthesized Janus graphene with a low-cost method.Furthermore,we carried out its application research.First,we report a novel method for the synthesis of Janus graphene with dual adsorption capabilities toward different types of pollutants with silica microspheres as a template.To test our hypothesis,we used two commonly used adsorption ligands,octadecyl group(C₁₈)and ethylenediamine tetraacetic acid（EDTA）,to functionalize the two sides of graphene sheets.Compared with the previously reported methods,the present synthetic method for Janus graphene is more facile,greener,lower-cost,and free of any laborious procedures or sophisticated devices.Then,we examined the dual adsorption capacities of Janus graphene for organic targets（PFOS）and metal ions（Pb（Ⅱ）and Ni（Ⅱ））.The adsorption amounts on the Janus graphene was significantly higher than that of GO with the maximum adsorption amounts 2.4 times higher than that of graphene oxide for both Pb（Ⅱ）and Ni（Ⅱ）.These results demonstrated that the Janus graphene is a highly efficient adsorbent for toxic heavy metal ions for potential applications in environmental purification fields.The maximum adsorption capacity of PFOS on the Janus graphene was 2.5 times higher than that of graphene oxide.Then we proved that the Janus graphene is an efficient matrix for MALDI-TOF MS.We further tested the performance of Janus graphene as as a SELDI probe in rapid and high-throughput screening of trace amount of toxic compounds in single-drop human whole blood samples.The results indicated that the Janus graphene is a promising probe in enrichment of low-mass toxic organics in complex samples.Finally,in view of the amphiphilic nature of Janus graphene,that is,the EDTA side is polar and the C₁₈ side is non-polar.Therefore,it should behave like surfactants.The performance of Janus graphene for oil-water separation was preliminarily tested.It has been proved that Janus graphene has an obvious effect on the removal of trace oil droplets in water.In conclusion,we studied a novel template-synthesized Janus graphene with dual adsorption capabilities for both organic targets and metal ions.The synthetic process is facile,low-cost,and environmental friendly.Notably,we also show its use as an excellent SELDI-TOF MS probe in rapid and high-throughput screening of trace amount of toxic compounds in single-drop human whole blood samples.This work reveals a new promising route to design and synthesis of multi-functional adsorbents.The dual adsorption capabilities and unique structures of the Janus graphene also make it promising for a great variety of application fields,such as environmental purification and remediation,analytical separation,and medical treatment.