Gold Nanoparticle Sorting Based On The Optofluidics

Gold nanoparticles have widespread application in physical,chemical and biological fields due to their unique characters.So the gold nanoparticles,which are too too small to be identified by eyes,attract more and more attentions of researchers in recent years.The special characters have closely relationships with their shapes and sizes.It is a pity that the current way of synthesising homogeneous gold nanoparticles have many difficulties.So it is of great importance to find a way to sort gold nanoparticles with low homogeneous.There are many conventional ways of sorting particles including centrifugation,electrophoresis,size exclusion,sedimentation,diafiltration,and chemical sorting methods.While those ways have their own difficulties making them apply to sorting gold nanoparticles with great hardships.Among all the sorting methods,optical sorting based on optofluidics shows enormous superiority due to its high sorting precise,large throughput and easy integration.This articles study optical sorting chip based on optofluidics.An optofluidics chip is designed,which can sort spherical gold nanoparticles with diameter difference of 30 nm.In the same optical field,gold nanoparticles with different size have enormous different optical force due to their various scattering and absorbing.The optical force of 200-nm gold nanoparticle is 4 times that of the 100-nm gold nanoparticles and the optical force of 100-nm is 13 times that of 50-nm gold nanoparticle.To precise sort nanoparticles in the chip,impinging streams are introduced to slow down the velocity of particles to 30 um/s.At the same time,hydrodynamic focusing has been used to confine the particles in a narrow place to sort and observe easily and conveniently.In the experiment,the particles are successfully confined in about 40 um area in width.In this paper,we integrate the optical force,the hydrodynamic focusing,and the continuous liquid-liquid impinging streams into an optofluidic device and experimentally realize the sorting of gold nanoparticles of 200nm/100nm and 100nm/50nm.The sorting throughput is 300 particles/min.Our method can also be extended to separate nanoparticles of different shapes and compositions,which shows its great promise in the fields of plasmonics and nanophotonics.This article creatively realize sorting of spherical gold nanoparticles in 50 nm difference using optofluidics in fluidic experiment.This work combining hydrodynamic focusing,impinging streams and optical force well sort samples at very low speed in sorting area and the sorting fidelities is higher than 85%.