Research Of Novel Carbon Dots-based Composites For Drug Carrier And Detection Application

Recently,the requirements for the quality,function,size and structure of drug carrier materials are becoming much higher with the progress of medical technology.So the single-function materials have not satisfied the requirements of scientific research and application.Therefore,multifunctional composite materials have gradually become a new focus in the field of material research,especially the combination of fluorescent materials and inorganic materials.As a kind of emerging fluorescent materials,the carbon dots(CD)and its composite have attracted tremendous attention because of its merits of low toxicity,good water solubility and well stability.These excellent properties make the carbon dot for potential applications in optoelectronic devices,heavy metal testing and cell imaging.For composites of carbon dots and inorganic nanoparticles,there are few studies about their applications as drug carrier and drug detection.Therefore,high-efficient blue-emitting CD and its composites with mesoporous silica(r-CD@MSN)and gadolinium oxide((Gd,Eu)2O3,PEI/CD)were prepared and characterized in these aspects.The results indicate that r-CD@MSN could become a popular drug carrier material with fluorescent signal,while(Gd,Eu)2O3-PEI/CD could act as a potential fluorescent sensor for ratiometric curcumin sensing.The major innovative works are listed as followed:1.High-efficient blue-emitting carbon dots coped with nitrogen and sulfur were synthesized by simple and green hydrothermal method.A systematically characterization of CD structure and fluorescence properties were done.In addition,the effects of temperature,pH,high concentration NaCl solution and metal ions on CD fluorescence were studied.The results show that the CD has good dispersibility with average diameter about 3.6nm,and the quantum yield of CD reaches to 68%.Most of metal ions have no effect on its fluorescence intensity,while Cu2+ and Pb2+lead to obvious fluorescence quenching.In addition,the fluorescence intensity of CD decreases with increasing temperature ranging from 283 K to 343 K.A good linear relationship between fluorescence integral intensity and temperature(R2=0.999).The emission intensity of CD solution was reversible during consecutive heating and cooling cycles,which demonstrated that the CD owns good reversibility and restorability.All results indicate that CDs could be a promising material for use in optical temperature-sensitive devices.2.A facile and effective approach towards high-efficient composite is applied by embedding blue-emitting N-doped carbon dots into spherical SiO2 matrix(CD@SiO2).Mesoporous silica microspheres(r-CD@MSN)with strong luminescence were synthesized by removing CTAB templates from CD@SiO2 using reflux with acetone,and the products were characterized by using X-ray diffraction(XRD),transmission electron microscope(TEM),Fourier transform infrared spectroscopy(FTIR),nitrogen adsorption-desorption analysis(BET),etc.The results show that r-CD@MSN has a spherical morphology with a smooth surface and the average diameter is about 120 n..A blue emission peak with no excitation dependence is observed at 440 nm,and the quantum yield of r-CD@MSN is 21.5%.The BET results show that the surface area SBET of sample is 156.27 m2/g and adsorption total pore volume is 0.682 cm3/g,which is very suitable for drug loading and release.So r-CD@MSN becomes a promising candidate in fluorescent drug career.3.In addition,CD/(Gd,Eu)2O3 composite nanospheres((Gd,Eu)2O3-PEI/CD)were successfully prepared via a facile electrostatic absorption method.The composite was characterized by using X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FTIR),UV-Vis analysis,zeta potential analysis,etc.The size and morphology of product were observed by scanning electron microscopy.Under UV irradiation,the composite simultaneously exhibits both blue CD emission band and red Eu3+ emission peaks.It is found that blue CD emission could be quenched by curcumin,while red Eu3+emission is hardly influenced.Thus,a novel self-referencing fluorescent sensor for curcumin with high sensitivity and superior signal discriminability was designed.The ratio of two emissions(F445/F611)shows good linear relationship with curcumin concentration(R2=0.9973).The limit of detection is determined to be 0.0615?g/mL(S/N = 3).These attractive merits enable this composite in ratiometric sensing for medicines in the future.