Colorimetric Performance Of Carbon Dioxide And Metal Ions Based On Water-soluble Perylenimide Radicals

The protons in low barrier hydrogen bond are susceptible to changes in hydrogen bonding geometry due to changes in environmental conditions（e.g.,solvent,p H,etc.）,which can cause changes in optical properties in some systems and possess typical characteristics of responsive stimulus materials with potential applications in the field of colorimetric sensing.Our group had synthesized alkyl primary amine/perylenimine anion radical hydrogen bonding complex using perylenimine anion radicalπ-dimers as raw materials,which have typical low barrier hydrogen bond characteristics and is found to show purple color in acidic and non-polar solvents and green color in basic and polar solvents.Based on the previous work,in this thesis,branched polyethylenimide was used to construct perylene diimide radical anion/branched polyethylenimide hydrogen bond complex（TFPDI-b-PEI）through the low barrier hydrogen bond.The optical response of TFPDI-b-PEI to CO₂ or metal ions in DMF and aqueous solutions was investigated.At the same time,TFPDI-b-PEI/silica gel composite film was prepared,and its colorimetric performance on CO₂ was studied.The results are as follows:The maximum absorption of TFPDI-b-PEI aqueous solution was 776 nm,which was gray,and the absorbance of the 776 nm peak decreased and the absorbance of 561 nm increased after CO₂ charging,so the solution changed color to purple.Based on UV-Vis absorption spectroscopy the detection limit of this aqueous solution for dissolved CO₂ was0.2 ppm,and the naked eye minimum detection concentration for gaseous CO₂ was 0.1%.TFPDI-b-PEI/silica composite film showed a response time of 1 s/3 s at a CO₂/Ar flow rate of 0.017 L/s at a temperature of 30℃and a relative humidity of 20%RH,and demonstrated high sensitivity,response/recovery time and reusability.Under acidic conditions,branched polyethyleneimine（b-PEI）is a cationic polymer containing a large number of NH₂ groups,which can be used as high efficiency adsorbent for some metal ions through coordination interactions.The metal ion detection by TFPDI-b-PEI was achieved by using the complexation reaction between branched polyethyleneimine and metal ions.The detection limits of TFPDI-b-PEI DMF solution were0.525 ppm,3.387 ppm and 9.437 ppm for Al³⁺,Ni²⁺and Cd²⁺respectively,and the detection limits of TFPDI-b-PEI aqueous solutions showed detection limits of 0.090 ppm,0.792 ppm and 1.893 ppm for Al³⁺,Ni²⁺and Cd²⁺respectively.