Preparation Of Biomass Carbon Dots And Checking The Metal Ion Contents In Oils

With the rapid growth of China’s economy,the consumption of lubricating oil is increasing rapidly.Lubricating oil in the process of high temperature induced oil oxidation deterioration,at the same time,friction generated debris-metal particles will also accelerate the deterioration of oil,which may cause various machine faults.In addition,the emission of excessive lubricating oil will also cause serious environmental pollution,so the lubricating oil must be replaced after a certain period of use.Carbon quantum dots（QDS）are widely used in biology,medicine,chemistry and other fields due to their advantages such as low toxicity,stable luminescence,good water solubility,environmental friendliness and low cost.If carbon quantum dots are applied to the detection of heavy metal ions in lubricating oil,it will have important application value in the real-time monitoring of lubricating oil by using the fluorescence characteristics of carbon dots when they meet different metals to detect heavy metal ions in lubricating oil and perceive the status quo of lubricating oil.In this paper with citric acid as raw material was prepared by hydrothermal synthesis method of silane coupling agent modified nitrogen silicon doping carbon quantum dots,the morphology structure of the carbon quantum dots and its fluorescence performance characterization analysis,preparation of carbon blue fluorescence quantum bit,have good amphiphilic,can be evenly dispersed in water and some organic solvents.By particle size analyzer,X-ray diffraction,Fourier infrared transform spectrometer,X-ray photoelectron spectrometer and PL fluorescence spectrum analysis on its characterization indicates that CQDs in 1～6nm size distribution,the average particle size was 2.9 nm,preparation of CQDs is functional,surface with silane and amino groups,containing the elements of the proportion and composition of chemical bonds.The effects of solvent,excitation wavelength,p H and temperature on the fluorescence intensity of quantum dots were studied.The optimal excitation wavelength of carbon quantum dots was 370 nm,and the emission wavelength was450 nm.The fluorescence intensity increased with the increase of p H and decreased with the increase of temperature.Moreover,the fluorescence quantum yield of the prepared carbon points was 46%,and the fluorescence yield also changed with the amount of reactants,reaction time and reaction temperature.Finally,the reaction conditions were determined as KH792 30 m L,anhydrous ethanol 30 m L,citric acid 1g,reaction temperature 140℃,and reaction time 4 h.Carbon quantum dots（QCQDs）were used as fluorescent probes to detect several common metal ions and acid substances in polyethylene glycol base oil.It was found that the fluorescence intensity of QDS showed a tendency of higher slope at low concentration and lower slope at high concentration after the addition of metal ions.After curve fitting,it was found that the carbon quantum dots showed good linear relationship for the detection of Fe³⁺（1μM～1m M）,Mn²⁺（200μM～1 m M）,Cu²⁺（1μM～100μM）,Ni²⁺（200μM～1m M）and acetic acid.Based on the fluorescence quenching principle of carbon quantum dots,an effective method for detecting Fe³⁺,Mn²⁺,Cu²⁺,Ni²⁺and acid substances in lubricating oil was established.