Preparation Of N-doped Long-wave Emission Cds And Its Application In Ion And PH Detection

Carbon dot is a new type of fluorescent nanomaterial with good fluorescence properties.The preparation method of carbon dot is simple and the raw material is easy to obtained.It can be applied in large scale and practical production.The photoluminescence properties of carbon dots can be changed by various methods,such as heteroatom doping,surface passivation and controlling the size of nano particles.The optimized carbon dots can be widely used in various fields,such as biological therapy and imaging,detection,photocatalysis and optical devices etc.Based on the conjugated structure and elemental composition of o-phenylenediamine,O-phenylenediamine was choosed as the only precursor to provide nitrogen and carbon sources.In different reaction media,N-doped fluorescent carbon dots with red emission and orange emission were synthesized by a simple green synthesis method-hydrothermal method.The morphology and size of the carbon spots were observed by transmission electron microscopy.The elemental content and surface functional group composition of the carbon spots were characterized by X-ray diffraction and FTIR spectra.The optical properties of carbon dots were investigated by ultraviolet absorption spectra and fluorescence emission spectra.The results show that the prepared carbon dots have high sensitive response to Fe³⁺and pH,and it can be used as a probe for the detection of Fe³⁺and pH.Using o-phenylenediamine as precursor,r-CDs with red fluorescence emission was prepared in the presence of nitric acid and phosphoric acid.The best synthesis scheme was found by changing the reaction conditions.Using 0.10814 mg o-phenylenediamine,0.8 umol nitric acid and 0.4 umol phosphate,keep the reaction temperature is 200℃,the reaction time is 10 h,is the best preparation condition of carbon dot.The prepared r-CDs show highly selective and sensitive to Fe³⁺,and Fe³⁺can quenched the fluorescence of r-CDs.When Fe³⁺is in a certain concentration range（0-120 umol/L）,the fluorescence intensity decrease of r-CDs has a good linear relationship with the increase of Fe³⁺concentration.O-CDs with orange fluorescence emission were prepared by using o-phenylenediamine as carbon source and nitrogen source in the presence of sodium hydroxide.The optimum synthesis scheme was found by changing the reaction conditions.Using 0.08 mg sodium hydroxide solid and 0.10814 mg o-phenylenediamine.keep the reaction temperature is 185℃,the reaction time is 15 h,is the best preparation condition of carbon dot.The prepared o-CDs has high sensitive response to pH.O-CDs can be used as a sensitive probe for pH detection.The fluorescence intensity of carbon dots varies in the range of pH 1-5.5 and 5.5-9,and show a good linear relationship with pH value.