Surface Plasmon Resonance Sensors Based On 2D Materials Franckeite And Ti₂C MXene

Surface plasmon resonance(SPR)refers to the phenomenon that occurs when the wave vector of surface plasmons well-matches with the evanescent wave vector.SPR is extremely sensitive to environmental changes.SPR-based optical sensors have been widely used in biomedical,environmental monitoring,food safety and other fields due to their high sensitivity,label-free,real-time,fast,and online detection.However,improving the sensitivity and detection accuracy of SPR sensors has attracted great attention.In recent years,two-dimensional(2D)materials such as graphene,transition metal dichalcogenides,and MXene have been widely used in transistors,photodetectors,and optical sensors due to their excellent electrical and optical characteristics.Compared with traditional materials,they have excellent properties in many aspects,such as high strength,large surface area ratio,adsorption,and atomic thickness.The introduction of these new two-dimensional materials can directly and effectively improve the performance of SPR sensors.In this paper,two kinds of two-dimensional materials(Franckeite with naturally occurring van der Waals heterostructure and Ti2C MXene)were proposed to improve the sensitivity of SPR sensors,and their applications in heavy metal detection were developed.The innovations are as follows:(1)A surface plasmon resonance(SPR)sensor with 2D Franckeite nanosheets to improve the sensitivity is proposed.Franckeite has the unique advantages of narrow band gap and stable structure compared with the artificial stacking heterostructures.The sensitivity as high as 188°/RIU in theory has been obtained,which is a 62%increasing compared with the conventional SPR biosensor.As an air-stable 2D material,we believe that 2D Franckeite nanosheets could have potential applications in the field of chemical and biological sensors in the future.(2)A wavelength-modulated high sensitivity surface plasmon resonance(SPR)sensor by using 2D Ti₂C MXene nanosheets is proposed.Our experimental results show that the performances of the SPR sensor are closely related to the thickness of 2D Ti₂C nanosheets,and the proposed design gives the wavelength sensitivity of 3579.6 nm/RIU,which are 79%higher than the SPR sensor without Ti₂C overlayer.In addition,the Ti₂C covered SPR biosensor is capable of detecting low concentrations of heavy metal ions owning to their highly active 2D surfaces,and it is shown that the maximum concentrate sensitivities are3.788 nm/?g/L,5.308 nm/?g/L and 3.233 nm/?g/L for Pb²⁺,Cr²⁺and Hg²⁺ions,and the corresponding detection limits are 79.2 ng/L,56.5 ng/L and 92.8 ng/L,which are lower than the international medical standards.