Preparation And Modification Of Biomass Based Carbon Quantum Dots And Their Application In The Detection Of Ferric Ions

Ferric ion is one of the most important trace elements in all living organisms and is vital to their health.It participates in the transport and storage of oxygen and has an impact on the human energy metabolism and immune system.Both Fe3+ excessive intake and Fe3+ deficiency could lead to serious diseases and cause dysfunction of biology.it is important to have analytical methods capable to detect and quantify the iron in human body.Among the spectroscopic techniques commonly applied to determine iron and other metal species,the Flame(FAAS),Graphite Furnace Atomic Absorption Spectrometry(GFAAS),Inductively Coupled Plasma Optical(ICP-AES)and Inductively Coupled Plasma-Mass Spectrometry(ICP-MS).Despite of being well-established techniques,they require a minimum of infrastructure and are of highly effective cost,which limits their applications by many laboratories.The UV-VIS spectroscopy can be used as an alternative method to determine metal species in distinct matrices.This well-established technique has low acquisition and maintenance costs;good analytical frequency,precision and accuracy.However,it lacks a sufficient sensitivity to determine trace of metals,such as iron.Thus,in order to increase the sensitivity,it is highly desirable to develop a facile,reusable and robust sensor with high selectivity and sensitivity for Fe3+ detecting.These carbon nanoparticles present some interesting properties such as environmental friendliness,Chemical stability,broadening excitation,fluorescence stability,photobleaching,good biocompatibility and low toxicity.All these properties make them promising materials for applications in different areas such as in optolectronic devices,biosensors,photocatalysis,solar cells,and applications in bioimaging.If CDs only contain-OH and-COOH,quantum yield(QY)is low,which leads to their poor selectivity and low sensitivity in the detection of Fe3+.The QY of CDs could be improved by nitrogen doping,and improved QY contributes to improve the selectivity and sensitivity for the detection of Fe3+,and fluorescence quenching mechanism needs to be further clarified.Specific research contents are as follows:In this paper,wolfberry-based carbon dots(G-CDs)with blue fluorescence was prepared by one step hydrothermal method with wolfberry as carbon source,hydrogen peroxide as oxidant.The fluorescence quantum yield was 24.2%,The average size of the carbon quantum dots was 7 nm,with well dispersed amorphous carbon nanoparticles without apparent aggregation.Hydroxyl,carboxyl/carbonyl moieties are on their surface.which means the good water solubility and easy to modification.Through the fluorescence response for G-CDs to different ions and Fe3+ions with different concertation,the fluorescence of G-CDs was quenched,so that G-CDs can show specific recognition to Fe3+.The degree of fluorescence quenching linear range of G-CDs is 5～60 μmol/L and the detection limit can reach to 1.47μmol/L,Complexing constant was 8.17.The PEI-CDs were modified by one-step hydrothermal method on the basis of the G-CDs with PEI as Amino modifiers.The average size of the carbon quantum dots was declined to 4 nm,FTIR spectra analysis showed that amino was successfully modified on the CDs surface.After optimization,the fluorescence intensity of PEI-CDs could be greatly enhanced,and the fluorescence quantum yield was improved from 24.2%to 30.7%.Besides,the fluorescence emission peak moved to red shift,which could emit bright blue-green light under the ultraviolet light.the detection limit can reach to 1.47 μmol/L,Complexing constant was 44.77.Blueberry slag-based carbon dots(L-CDs)was prepared by one step hydrothermal method with blueberry as carbon source,hydrogen peroxide as oxidant and ethylenediamine as nitrogen dopant.L-CDs,with diameters ranging from 2 to 7 nm.Hydroxyl,carboxyl/carbonyl amino,moieties are on their surface.The fluorescence quantum yield was 34%.Besides,the fluorescence emission peak moved to blue shift,which could emit bright blue light under the ultraviolet light.the detection limit can reach to 2.57 μmol/L,Complexing constant was 125.5 1.