Synthesis And Applications Of Gold Nanorod And The Hybrid Nanostructures

In the last two decades, owing to the development of the nanomaterials, nanoscience and nanotechnology have achieved significant advancement on the human healthcare, energy and environment field. Among the various nanomaterials, noble metal nanoparticles are attracting lots of attention for their localized surface plamon. The gold nanorod (AuNR) is a typical anisotropic noble metal nanostructure, which have developed a lot applications on the bio-sensing, bio-imaging and biotherapy. Meanwhile, the hybrid nanocomposites synthesized based on AuNR also have promising applications arranging from multimodal bio-imaging to energy field. In this thesis, we have synthesized a series of nanocomposites based on AuNR, and have developed multi applications on sensing, imaging, fluorescence, catalytic, two photon luminescence and so on. The following are the details:The nanoscale core/shell heterostructure is a particularly efficient motif to combine the promising properties of plasmonic materials and rare-earth compounds; however, there remain significant challenges in the synthetic control due to the large interfacial energy between these two intrinsically unmatched materials. Herein, we developed a synthetic route to grow rare-earth vanadate shells onto AuNR cores. After modifying the AuNR surface with oleate through surfactant exchange, well-packaged rare-earth oxide (e.g., Gd2O3:Eu) shells are grown onto the AuNRs ascribed to the multiple roles of oleate. Furthermore, the composition of the shell have been altered from oxide to vanadate (GdVO4:Eu) using an anion exchange method. Attributing to the carefully designed strategy, the AuNR cores maintain the morphology during the synthesis process, thus the final Au/GdVO4:Eu core/shell NRs exhibit strong absorption bands and high photothermal efficiency. In addition, the Au/GdV04:Eu NRs perform bright Eu3+ fluorescence with quantum yield as high as ?17%, and bright Sm3+ and Dy3+ fluorescence can also be obtained by changing the lanthanide doping in the oxide formation. With the attractive integration of the plasmonic and fluorescence properties, such core/shell heterostructures will find particular applications in wide areas from biomedicince to energy.Light-driven physical and chemical processes are attractive to deal with the energy and environmental crisis. We synthesized well-defined ceria (CeO2) coated AuNRs by employing original hexadecyltrimethylammonium bromide (CTAB) as the ligands. The whole process takes only one step for the directly growth of ceria onto AuNRs without any additional ligand-exchange or polyelectrolyte modification. Importantly, the Au/CeO2 core/shell NRs have well maintained the character of tunable longitudinal plasmon resonance in the near-infrared (NIR) region. We demonstrate that this hetero-nanostructure can accelerate the ceria dependent Fenton-like reaction through plasmon-induced hot-electron injection under NIR light illumination. The generation of hot-electron is further revealed by detecting the NIR-light-driven photocurrent of a photoelectrochemical (PEC) cell base on the Au/CeO2 core/shell NRs modified electrode.Early detection of cancer often requires time consuming protocols or expensive instrumentation. To address these limitations, a rose bengal conjugated gold nanorod (RB-AuNR) platform is developed for optical detection of oral cancer cells. The AuNRs are modified by poly(allylamine hydrochloride) and conjugated with RB molecules to produce RB-AuNRs which exhibit strong optical absorption in the near-infrared (NIR) region, low cytotoxicity, and high specificity to oral cancer cells. The label-free sensing assay utilizes RB-AuNRs as the sensing probe and by monitoring the aggregation-induced red-shift in the NIR absorption wavelength, specific and quantitative analysis of the oral cancer cell lysate is accomplished down to a detection limit of 2,000 cells/mL. By employing the RB-AuNRs as an imaging probe, an imaging assay is established on a home-made NIR absorption imaging system. Based on the NIR absorption by the RB-AuNRs specifically conjugated with the oral cancer cells, multi-channel, rapid and quantitative detection of oral cancer cells is demonstrated. The high sensitivity and specificity of the RB-AuNR platform as demonstrated by the two complementary assays provide non-invasive optical diagnostics of oral cancer cells enabling convenient screening and monitoring.Recently, two dimensional materials (like graphene or transition metal dichalcogenides, etc.) is rising for their novel properties different from the bulk. We design two type composites by coupling AuNR with the molybdenum sulfide nanosheets (MoS2) or the reduced graphene oxide (rGO). After modified by the MoS2 or rGO, the plasmon band of AuNR red-shifted a little. The two photon luminescence (TPL) of AuNR and the composites have been measured that TPL intensity of composites is lower than the original AuNR, which means the TPL of AuNR has been quenched. These results demonstrated that there exist energy transfer from AuNR to the two dimensional materials.Nest-like CdS/rGO composites were prepared through a one-pot solvothermal method in which ethylenediamine was used to reduce GO and control the morphology of the CdS, and L-Cysteine was used as sulfur source, reducing agent, and linker between the CdS and rGO. By performing the morphology, structure, and composition of the composites, it could be found that the nest-like CdS particles were decorated on the rGO sheet, and the addition of GO did not influence the crystal structure and shape of the nest-like CdS. Compared with pure CdS, the as-prepared CdS/rGO composites showed enhanced visible light absorption, extended surface area, and facilitated separation of photogenerated charges. Hence, the CdS/rGO composites exhibited improved photocatalytic activity and excellent photostability for the degradation of rhodamine B under visible light irradiation. By combining the good properties of rGO and three-dimensional structured CdS microparticles, the strategy presented in this study is expected to be useful in preparing highly efficient graphene-semiconductor composites for potential applications in various fields.