Noble metal nanostructures have attracted much attention recently and have led to a variety of research fields ranging from ultrasensitive ( bio) sensing,nanomedicine to nanophotonics and solar cells for their unique tunable size,shape,composition,and plasmonic optical propertiesl-2.The bimetallic nanoparticles,especially noble metal nanostructures with a core/shell structure,are more flexible tunability in nanometer scale structure and local electric field.which make them exhibit improved physical and chemical properties over their monocomponent counterparts,and make them good candidates for ultrasensitive detection and biosensing applications.Herein.we selected hollow Ag/Au bimetallic nanoshells ( NSs) as platforms for proteins and enzymes immobilization in solution with different pHs and used for detecting their isoelectric point (pI).When the poly ( L-histidine) ( PLH) was electrostatic attached onto the Ag/Au NS surfaces at pH-7.0,the surface plasmon resonance ( SPR) peak of the hollow Ag/Au NSs red-shifted from 578 nm to 589 nm,as shown in Fig.l.After being coated with PLH monolayers,the Ag/Au NSs were positively charged. And the glucose oxidase ( GOx ) can be adsorbed onto the NSs surface through electrostatic interaction at pH =4.5 0r higher( pH = 7.4),for the GOx enzymes were negatively charged[3].The SPR peak of Ag/Au-GOx NSs was at 626 nm.The change of solution pHs would lead to the shift of SPR peaks of GOx-confined Ag/Au bimetallic NSs( Ag/Au-GOx NSs).The SPR peak blue-shifted back to 589 nm when the pH was 4.0 or lower( pH = 3.5).This is because that the Gox enzymes are positively charged when the pH is lower than the isoelectric point,which results in that the enzymes are electrostatically repulsed by positively charged PLH monolayers and peeled off from the NSs surface.It can be inferred that the isoelectric point of Gox was between 4.0 and 4.5,which was agreement with the actual pl value of Gox ( pl 4.2).Therefore,the PLH-coated Ag/Au NSs can be used for detection of proteins and/or enzymes isoelectric point.