Synthesis And Application Of Novel AuAg Graphitic Nanocapsules

The tunable plasma properties of gold and silver nanomaterials make them the most widely used metal nanoparticles.However,their limited stability limits their development in biomedical fields.The poor oxidation resistance and potential biological toxicity of silver nanoparticles limit their use.Although gold nanoparticles are chemically inert to a certain extent,they will inevitably agglomerate and deform under high temperature environment.In order to maintain the plasma properties of AuNPs and AgNPs under a harsh external environment,it is of great attraction to develop a protective agent that can stabilize the morphology of the two metal nanoparticles.As an inorganic material,graphene has the characteristics of anti-acid,anti-alkali and anti-oxidation.Combining graphene with AuNPs and AgNPs can improve the stability of AuNPs and AgNPs in complex environments.At the same time,the special surface properties of graphene provide a platform for binding functional molecules.Nanoparticles prepared by combining graphene with AuNPs and AgNPs are powerful composite materials.Among them,metal graphitic nanocapsules are composite nanomaterials with core-shell structures.The graphitic shell has many advantages such as stable chemical properties,large specific surface area and easy functionalization,etc.And the combination of metal nanomaterials endows graphitic nanocapsules with many functions.For example,graphene combines metal with Surface Enhanced Raman Scattering(SERS)activity to improve the detection sensitivity of Raman spectroscopy technology in complex environments;Graphene combines metal with near-infrared light absorption capacity to make it a valuable photothermal therapy reagent.Because metal graphitic nanocapsules can have the dual properties of graphite and metal nanomaterials,they have received extensive attention in the field of nanomedicine.We combined graphene with AuNPs and AgNPs to synthesize Au Ag graphitic nanocapsules,and explored their application potential in biological detection,imaging and treatment.The details are as follows:(1)In Chapter 2,we prepared the Graphene-Isolated-Au AgNanocrystal(GIAAN)by Chemical Vapor Deposition(CVD).This structure was successfully applied to SERS analysis of analytes at the immiscible liquid-liquid interface.We found that GIAAN can generate interfacial self-assembled GIAAN(ISA-GIAAN)film in immiscible two-phase interfaces without any inducer,which was attributed to its poor solubility in both water and organic phases.Meanwhile,dense electromagnetic hotspots were distributed in two-phase interfaces due to the formation of close packed SERS-active ISA-GIAAN film.These outstanding properties can effectively overcome the interference of complex serum environment,and realize sensitive and fast multiphase analysis.In general,ISA-GIAAN can be used as a simple,sensitive SERS substrate that realizes multiphase enrichment detection simultaneously.(2)In Chapter 3,Taking advantage of the inherent D and G peaks of GIAAN as stable Raman tags,we further realized the intracellular Raman imaging by non-covalently functionalized with polyoxyethylenestearyl ether(C18-PEG).Due to the protective effect of graphene,GIAAN@PEG can remain stable in the oxidizing and acidic environment.Good corrosion resistance is the premise of realizing reliable SERS detection in a complex environment.In addition,due to the large specific surface area and ?-? stacking interactions of graphene,GIAAN@PEG can effectively adsorb and quench the fluorescence of dye molecules,reduce the fluorescence background interference of SERS analytes,and improve the analytical ability of GIAAN@PEG for low concentration molecules to be measured.Due to the inherent D and G peaks of graphene,GIAAN@PEG can be used as an ideal SERS probe without the functionalization of Raman reporter molecules.Finally,GIAAN@PEG achieved cellular Raman imaging of MCF-7 cells,and its applications in clinically monitoring drug metabolism and guiding intended drug delivery deserved further exploration.(3)In Chapter 4,we changed the structure of Au Ag graphitic nanocapsules by prolonging the time of methane gas when depositing the carbon layer by the CVD method,and prepared a novel Graphene-Isolated-Au Ag Cavity Nanocrystal(GIAACN),which realizes the application of near-infrared light-mediated high-efficiency bacterial photothermal treatment.GIAACN is a nanocapsule with a cavity structure.We found that the plasmon resonance peak of GIAACN is red-shifted and exhibits a phenomenon of broad-spectrum absorption.It is speculated that the possible cause is the influence of GIAACN's unique cavity structure on the plasma properties of nanomaterials.We studied the unique optical properties of GIAACN and its photothermal properties mediated by near-infrared light.The results showed that GIAACN has excellent photothermal conversion efficiency and its photothermal performance is stable under the protection of graphitic hell.By applying GIAACN to near-infrared light-mediated photothermal antibacterial applications,we confirmed the excellent antibacterial performance of GIAACN.In addition,during the experiment,we also found that the rough graphitic shell of GIAACN also showed a certain inhibitory effect on bacteria.In summary,GIAACN is proven to be a highly effective near-infrared light-mediated photothermal antibacterial reagent.