Luminescence and magnetic properties of bifunctional nanoparticles composited by nitrogen-doped graphene quantum dots and gadolinium

In this paper,nitrogen-doped graphene quantum dots(N-GQDs)were combined with gadolinium ions(Gd^(3+))by a surface modification to obtain magneto-optical dual-functional N-GQDs/Gd^(3+)nanoparticles.The morphology of obtained composite was characterized by field emission scanning electron microscopy and transmission electron microscopy.Luminescence and magnetic properties were measured by a fluorescence spectrophotometer and a vibrating sample magnetometer,respectively.Results indicate that well-dispersed spherical N-GQDs/Gd^(3+)nanoparticles have an average diameter of 7 nm.N-doping significantly increases the luminesce nce of particles with an optimal luminescence intensity at 20℃and pH=9.X-ray photoelectron spectroscopy results indicate that the N-doping introduces pyrrolic N as an electron donor,enhancing fluorescence by increasing the surface electron cloud density of N-GQDs.In addition,density functional theory calculation results reveal that N-doping reduces the band gap of NGQDs/Gd^(3+),enabling electronic transitions to higher energy levels and generating more activation sites,thereby enhancing luminescence.Compared to N-GQDs/Gd^(3+)prepared at 20℃,the saturated magnetization of particles prepared at 40℃is 0.85 emu/g,indicating a better magnetic response.The above results suggest that bifunctional nanomaterials N-GQDs/Gd^(3+)with excellent optical properties and magnetism can be better used for fluorescence and magnetic resonance imaging.

Preparation and properties of bifunctional Gd_(2)O_(3)/GQD composite nanoparticles

Nanocomposites of graphene quantum dots(GQDs)modified gadolinium oxide(Gd_(2)O_(3))particles were successfully synthesized.In addition,the effects of the amount of GQDs and the particle size of Gd_(2)O_(3)on the properties of nanocomposites were investigated.The structures and properties of nanoparticles were characterized by X-ray diffraction,X-ray photoelectron spectroscopy,Fourier transform infrared spectroscopy,field emission scanning electron microscopy,transmission electron microscopy,photoluminescence spectrometry,and magnetic resonance imaging.The results show that the synthesized particles Gd_(2)O_(3)/GQD are spherical with a diameter of approximately 40 nm and have excellent fluorescence and magnetic property,and its relaxation rate(r_(1)=25.18(mmol/L)^(-1)/s)is higher than that of the typical commercial contrast agents Gd-DTPA(r_(1)=4.5(mmol/L)^(-1)/s),The fluorescence property of Gd_(2)O_(3)/GQD is optimized by varying the V_(GQDs):V_(Gd2O3)ratio,and 1:1 ratio of V_(GQDs):V_(Gd2O3)results in the best fluorescence property.The large particles of Gd_(2)O_(3)improve the relaxation property of nanocomposites.Therefore,the nanocomposites Gd_(2)O_(3)/GQD with magnetic and fluorescence characteristics can be used in biological imaging,drug targeting,and in-vivo diagnostic analysis.