Nitrogen-doped Nanomaterials And DNAzymes For Detection And Adsorption Of Heavy Metal Ions And Other Pollutants

As is well-known,water is the source of life.Pollutants in the water seriously threaten the survival and safety of all life forms,hindering and restricting the development of economy and society.Heavy metal ions and nitroaromatic compounds?NACs?are common pollutants in water,which cause sustained serious damage to human body.Therefore,the detection and adsorption of these pollutants are of great significance.Novel nanomaterials and DNAzymes exhibit lots of excellent properties,and its applications in environmental chemistry has also been the widely studied in recent years.This thesis focuses on the application of nitrogen doped nanomaterials and DNAzymes in the detection and adsorption of pollutants,mainly including the following:1.A new scheme for the preparation of nitrogen-doped graphene quantum dots?NGQDs?was proposed.The product exhibit excellent fluorescence properties and catalytic performance.The coordination reaction between Cd²⁺and 5,10,15,20-tetrakis?1-methyl-4-pyridinio?-porphyrin tetra?p-toluenesulfonate??TMPyP?can be significantly accelerated by NGQDs.Thus,we proposed a nanomaterials catalyzed mechanism for porphyrin metalization.The porphyrin combined with NGQDs can be used as a new optical probe for sensing Cd²⁺ions.The sensor exhibits rapid,sensitive,and selective responses toward Cd²⁺.This work provides an example of using graphene nanostructures for tuning the interaction between porphyrins and metal ions,which can be extended to other molecules or nanostructures.2.We found that the incorporation rate of the complexation reaction between Mn²⁺and TMPyP is markedly promoted with the coexistence of NGQDs and trace Hg²⁺.Thus,a synergistic effect mechanism was developed,which was discussed in terms of the substitution reaction that Hg²⁺deforms the porphyrin nucleus favorably for the NGQDs carrying the small divalent metal ions attack from the back.Based on this interesting phenomenon,a sensitive,selective,and multisignal method for trace Hg²⁺sensing is proposed.This work provides a good example of utilizing the synergistic effect of graphene nanostructures and large divalent ions for the formation of metalloporphyrin.This work proves that the synergy between nanomaterials and metal ions,which can be extended to study the catalytic activity of nanoenzymes.3.A simple and green approach has been developed for synthesis of boron nitride quantum dots?BNQDs?.The obtained BNQDs are of strong fluorescence and excellent stabilities,including high thermostability,good salt tolerance stability,pH-independence ability,and excellent antiphotobleaching capability.Then,a novel BNQD-based turn-off sensor was constructed for 2,4,6-trinitrophenol?TNP?determination on the basis of the strong inner filter effects?IFE?between TNP and the BNQDs.This sensor has potential application for rapidly and selectively detecting TNP of natural water samples without tedious sample pretreatment processes.It also expanded the preparation and application of new nanomaterial fluorescent probes.4.A facile,scalable,and cost-effective protocol has been proposed to synthesize boron carbon nitride nanosheets?BCN NSs?.Due to the successful introduction of abundant function groups,enhanced specific surface area and hydrophilicity,BCN NSs exhibit excellent adsorption performance toward hearvy metal ions(especially toward Hg²⁺and Pb²⁺).By virtue of the cost-effective and facile production methodology,combined with the excellent adsorption performance,BCN NSs have great potential for practical application in wastewater purification.This work also expande the applications of newly inorganic two-dimensional nanomaterials in pollutant removal.5.We discovered that Pb²⁺can significantly accelerate porphyrin metalation by using the T30695 sequence as a DNAzyme.The catalytic efficiency of the DNAzyme is comparable with the protein-based metalation enzymes,and much better than the DNAzyme coordinated by other metal ions.Based on the variation of the fluorescent spectral,a newly ratiometric Pb²⁺sensor with excellent sensitivity and selectivity was proposed.This work also provides new ideas for the study of new DNAzymes and coenzyme factors.6.We found that the Cu²⁺-catalytic 3,3',5,5'-Tetramethylbenzidine?TMB?oxidation reaction can be markedly accelerated with the presnece of excessed nucleotides or nucleobases.In particular,GMP showed the best acceleration efficiency.Herein,we used a large excess of GMP to boost its binding of Cu²⁺and made the reaction more robust.The GMP-accelerating reaction can be applied for detection of Cu²⁺with excellent sensitivity,selectivity and resistance to interference.The presence of excess ligands in the probes can effectively improve the catalytic efficiency and enhance the stability of the probe in complex environments.