Preparation,Characterization And Application Of Nitrogen-doped Carbon Dots/Gold Nanoparticles

Due to the excellent properties,Carbon dots（CDs）have attracted much attention in the fields of chemistry,biology and medicine.In this paper,N-containing polymer—hyperbranched polyethyleneimine（HPEI）was used as the carbon source to synthesize multifunctional carbon dots（HPEI-CDs）that can be used as probes,reducing agents and stabilizers by hydrothermal methods.On the one hamd,based on the fluorescence characteristics of HPEI-CDs,a highly sensitive and selective detection of cadmium ions（Cd2+）can be achieved through the fluorescence enhancement effect.On the other hand,chloroauric acid was reduced by HPEI-CDs to synthesize highly stable gold nanoparticles（AuNPs）.The applications of HPEI-CDs/AuNPs in chemical sensing and catalysis were further explored.The main contents are as follows:1.HPEI-CDs were directly synthesized by a one-step hydrothermal method and further characterized by FTIR,TEM,XPS,and DLS.Due to the increasing of the fluorescence intensity of HPEI-CDs in the presence of cadmium ions（Cd2+）,HPEI-CDs can be applied to the chemical detection of Cd2+.The results showed that Compared with Hg²⁺,Ag⁺,Ni⁺,Sr²⁺,K⁺,Mn²⁺,Mg²⁺,Sr²⁺,Cu²⁺,Ba²⁺,Na⁺,Pb²⁺and Cd²⁺,only Cd²⁺increases the fluorescence intensity of HPEI-CDs.Therefore,HPEI-CDs showed a high selectivity for Cd²⁺detection.HPEI-CDs showed good sensitivity for the Cd2+detection with LOD=0.375μM.In addition,this optical sensor based on fluorescence response also showed good sensitivity and accuracy for the Cd2+detection with the standard recovery rate at 101.03%-102.35%in tap water.Therefore,HPEI-CDs,as a visible probe,plays an important role in the effective monitoring of Cd²⁺in water and timely warning application.2.HPEI-CDs/AuNPs were prepared by in situ reduction of chloroauric acid using HPEI-CDs as reducing agent and stabilizer.And the optimal reaction time and temperature were 90 min and 90℃,respectively.The HPEI-CDs/AuNPs were further characterized to use TEM,XPS,DLS and examined for stability.In comparison of AuNPs prepared by classical sodium citrate,HPEI-CDs/AuNPs showed high stability for heat,pH and salt.Based on the fluorescence properties of HPEI-CDs and the surface plasmon resonance properties of AuNPs,HPEI-CDs/AuNPs are widely used as multifunctional probes:baesd on the multisignal response,HPEI-CDs/AuNPs showed high selectivity and sensitivity toward Cu²⁺and Hg²⁺with a low detection limit of 75.6nM and 0.281μM,respectively.At the same time,this probe can be applied to the visual detection of Cu2+and Hg2+in actual water bodies such as tap water and sea water with a low detection limit of 138.5 nM,96.7 nM and 0.6μM,respectively.3.Based on the unique physical and chemical properties of AuNPs,it has a wide range of applications in the field of catalysis.HPEI-CDs/AuNPs,as a catalyst,can promote the reduction of p-nitrophenol.The effects of temperature,amount of catalyst,and p-nitrophenol concentration on the catalytic reaction were further investigated.The results show that HPEI-CDs/AuNPs have high catalytic efficiency for the treatment of organic phenolic compounds in wastewater.In addition,the temperature-sensitive carbonized polymer dots and AuNPs composites were designed and synthesized.Based on the temperature-sensitive properties,these AuNPs composites can realize recovery,separation and recycling application,which has high application value for the treatment of phenols in wastewater.