Researches On Accurate Methods To Measure Elemental Impurities In Carbon Nanotubes And Graphene

Carbon nanotubes(CNTs)and graphene(GR)have excellent optical,electrical,and mechanical properties due to their unique microstructure,and they are widely used in materials chemistry,electrochemistry,supercapacitors,nanoelectronic devices,and biomedical applications etc.However,the impurity elements(mainly transition metals and sulfur)introduced during the preparation of CNTs and GR will greatly affect their excellent performance and restrict their development.Therefore,it is of great significance to accurately measure the content of impurity elements in CNTs and GR.In this paper,CNTs and GR were pretreated by microwave digestion(MWAD),dry ashing(DA)and microwave induced combustion(MIC).Using total reflection X-ray fluorescence(TXRF),inductively coupled plasma optiocal emission spectrometry(ICP OES),and inductively coupled plasma mass spectrometry(ICP-MS),several problems in the quantitative analysis of impurity elements were studied.The main conclusions are as follows:(1)The type and amount of digestion solution,digestion temperature and pressure have important influence on the digestion effect when CNTs and GR were digested by MWAD pretreatment methods.By optimizing these conditions,better MWAD conditions are obtained,but it is still difficult to eliminate completely.problem.DA-AD and DA-MWAD are capable of completely dissolving samples,and they are suitable for non-volatile metal elements but not suitable for volatile elements.The MIC pretreatment method can completely eliminate CNTs and GR samples.By optimizing the sample dosage,sample preparation,absorption solution,digestion temperature and pressure conditions,the best MIC pretreatment conditions are obtained.The MIC also has high efficiency,rapid and low pollution and other features.(2)Using TXRF,ICP OES and ICP-MS methods to measure the key impurity elements(S,Fe,Ni,etc.)in CNTs and GR,and systematically optimize measurement conditions such as internal standard elements and spectral line selection,achieving the elemental recovery rate of 95%~100%.It has established an accurate and reliable analysis and measurement method,and the measurement results are basically the same between the three different methods.(3)The pre-processing and measurement methods established in this paper were validated using certified reference materials(CRM)of foreign metrology and research institutes.The measurement results were in good agreement with the certificate values of the standard materials,which showed that the pre-processing and measurement methods established in this paper were accurate.reliable.The CNTs and GR sample preparation methods and accurate measurement methods for key elements studied in this paper are important technical references for accurate measurement of impurity elements in nano-carbon materials,and will provide important technical support for the development and application of carbon nanotubes and graphene.