Preparation Of Cu₂MoS₄ Nanozyme And Photothermal Enhancement Of Enzyme Activity For Detection Of Biomolecules

The intrinsic limitations（such as high cost,low stability,and difficulty in storage）of natural enzymes have stimulated the emergence and development of various enzyme mimics.Nanozymes are nanomaterial-based artificial enzymes.By effectively mimicking catalytic sites of natural enzymes or harboring multivalent elements for reactions,nanozyme systems have successfully served as direct surrogates of traditional enzymes for catalysis.Among many nanomaterials,increasing interest has been devoted to ternary layered transition metal chalcogenide（TTMC）nanomaterials which display exceptional catalytic activities,due to both their layered structure and the presence of transition metal d-electrons.Among them,Cu₂MoS₄is a ternary chalcogenide material with an anisotropic structure formed by two-dimensional layers of edge-sharing MoS₄and Cu S₄tetrahedrons.Cu₂MoS₄possesses a strong electron-phonon coupling（EPC）property that lengthens the lifetime of the photoexcited electrons for triggering catalytic reactions.The intrinsic existence of multivalent metal ions(Cu⁺/Cu²⁺、Mo⁴⁺/Mo⁶⁺)and strong absorption in near-infrared（NIR）region lead readily to the hypothesis that Cu₂MoS₄could serve as a potential NIR light-responsive nanozymes.In this thesis,Cu₂MoS₄nanomaterials with peroxidase-mimicking activities have been synthesized by a low-cost solvothermal method.The catalytic efficiency of Cu₂MoS₄nanozymes was improved by two routes including tuning synthetic conditions and laser irradiation,and they were applied to colorimetrically detect biomolecules.The details of the research are as follows:（1）Copper sulfide（Cu S）synthesized from cuprous oxide（Cu₂O）and thioacetamide（C₂H₅NS）was used as the copper source,sodium molybdate dihydrate（Na₂Mo O₄·2H₂O）as the molybdenum source,C₂H₅NS as the sulfur source,ethylene glycol as the reaction solvent,a solvothermal reaction was carried out in a reactor.By adjusting the reaction temperature and reaction time,the regulation of morphology and crystal phase of Cu₂MoS₄nanomaterials was achieved.Thus,the tuning of peroxidase-mimicking activities of Cu₂MoS₄nanomaterials was further realized.The synthesis mechanism and growth process of Cu₂MoS₄nanomaterials were explored according to the experimental results.Meanwhile,the steady-state kinetic analysis was performed on different samples,and the k_m(_<sup>2O2=0.3058)、_<sup>8)=0.2328))values of P phase Cu₂MoS₄nanoparticles（P-Cu₂MoS₄NPs）were all lower than those of other samples and horseradish peroxidase（HRP）,demonstrating its excellent peroxidase-mimicking activities.（2）The strong and broad absorption of P-Cu₂MoS₄NPs at NIR leads to its good photothermal conversion performance,and the corresponding photothermal conversion efficiency was calculated to be 30.29%.The photothermal strategy is an effective way to improve the catalytic effect.Under the synergistic reaction of the photothermal effect,NIR laser irradiation could make P-Cu₂MoS₄NPs catalyze H₂O₂decomposition to generate more hydroxyl radicals（·OH）,further improving its peroxidase-mimicking activities.Herein,P-Cu₂MoS₄NPs were applied for colorimetric detection of H₂O₂,glucose,and ascorbic acid（AA）,and the accurate detection of AA concentration in citron juice beverage was successfully achieved.Due to its photothermally enhanced peroxidase-mimicking activities,the detection limit of the light group is much lower than that of the no-light group,greatly improving the sensitivity of detection.