| The chemical and biological sensors possess some advantages of simple design, convenient operation, low cost, high sensitivity, easy to carry, and fast detection. In the present thesis, a preparation method has been developed for the graphene and polydopamine(QG@PDA) composite to be applied for the detection of copper ions. Moreover, a graphene and hemin composite has been prepared with magnetic material for the degradation of environmentally toxic substances. In addition, heme was cross- linked with bovine serum albumin(BSA) toward the mimic enzyme with the catalysis performances investigated in detail.(1) A fluorescence analysis method was developed for the preparation of based on graphene composite material and its application in the detection of copper ions(C hapter 2). The fluorescent QG@PDA nanocomposite materials has been prepared for the one pot synthesis under microwave conditions by using spherical QG nanomaterial as a scaffold to load polydopamine which was oxidized by hydrogen peroxide. The fluorescence intensity of QG@PDA nanocomposites was 1.5 times higher than that of PDA nanoparticles, and the degree of quenching efficiency resulting from copper ions was 2 times higher than that of PDA nanoparticles. By comparing the fluorescence properties of QG@PDA nanocomposites and PDA nanoparticles and the quenching degree resulting from copper ions, the QG@PDA composite material has been selected to detect the copper ions. The selectively and rapidly detection of copper ions in wastewater was realized, and with wide detection range which was 25 nM-50 μM. In addition, QG@PDA nanocomposites can be used for cell imaging, which provides a new idea for the detection of copper ions in vivo.(2) A magnetic composite of enzyme mimic has been prepared by using hemin(Hem), gold nanoclusters(AuNCs), Q-graphene(QG), and Fe3O4 to be applied for the degradation of environmental toxic substances(C hapter 3). First, Hem-AuNCs has been successfully obtained with high stability and catalytic activity by the one-pot reaction via Hem as a stabilizer and reductant, which structure and catalysis activity were studied. Second, a syringe was used to fetch the mixture of Hem-AuNCs, spherical QG, Fe3O4, and sodium alginate, and then dropped them into the calcium chloride solution, forming the magnetic composite of SA-Hem-Au-QG-Fe3O4. The catalysis activity of the resulted compounds was further studied. The results showed that the composite had higher catalytic activity than that of native Hem. In addition, the catalytic degradation activity was systematically investigated in catalytically degrading some organic dyes such as Methylene blue and Rhodamine B. The magnetic enzyme mimic could be recovered and reused by using the magnet field. Particularly, this preparation method is simple and efficient, and the resulting enzyme mimic can promise the wide applications for the catalytic degradation of environmental toxic substances.(3) A new type of enzyme mimic of hemin(Hem) and bovine serum albumin(BSA) was successfully prepared by cross- linking the carboxyl groups of Hem on the amino acid residues of BSA(Chapter 4). The catalytic activity and reaction kinetics of the obtained enzyme mimic has been further studied by using the colorimetric method. The results showed that compared with the native Hem, the prepared Hem- BSA composite could not only have a higher catalytic performance, which the catalytic activity is about 4 times higher than that of native Hem, but also obtained a higher reaction substrate affinity. In addition, the as-prepared enzyme mimic with powerful catalysis activity was applied for the detection of hydrogen peroxide, showing a detection range of 0.015 to 2.5 mM. This preparation route for coupling the catalysis-active core with protein shell paves the new way toward the improvement and synthesis of diverse biological enzymes or mimics for the extensive applications in the fields of enzymatic catalysis.
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