Synthesis And Optical Response Of Metal Sulfide Semiconductor/Nobel Metal Nanocomposites

With the research of the nanomaterials and nanotechnology,functional nanomaterials have been brought into focus because of the excellent photoelectric properties and good applications.Compared with traditional materials,nanomaterials have played a quite vital role in some respects such as energy crisis,human health andnatural environment problems.In a series of materials,noble metals and semiconductor nanomaterials have more outstanding advantages and unique properties.For instance,composite semiconductor nanomaterials have the photoelectric properties owing to the separation and transfer of the electron-holes;Composite metal/semiconductor nanomaterials promote photocatalytic efficiency due to the thermoelectron effect of surface plasmons.Moreover,the dual plasmonic metal/semiconductor nanostructures have the extremely significant coupling resonance in the near-infrared region between the metal and semiconductor.Bimetallic alloy nanomaterials have unique surface plasmon properties and its extinction spectrum can be tuned from visible to near-infrared by adjusting the size,morphology,proportion and structure of the alloy.In this paper,we have synthesized the metal/semiconductor nanostructures and the double-alloy nanometals,lanched the research of the unique properties of the the surface plasmon resonance and investigated their outstanding performance in catalytic degradation of 4-NP,photoelectrochemical current,hydrogen production and photothermal effect,the following are the details:Firstly,we have grown the TiO2 nanorods arrays on the FTO glass,and grown the MoS2 nanosheets on the TiO2 nanorods arrays.And then the plasmonic Au nanorods are attached to them to form(MoS2-TiO2)/Au compound nanostructure by the hydrothermanl method.The hybrid(MoS2-TiO2)/Au shows different plasmon under the process of preparation.In the photoelectrochemical activity,the photoelectrochemical current density under the visible light and the hydrogen production under full spectrum of MoS2-TiO2 nanostrctures can enhance 2.8 and 2.6 times compared with the TiO2 nanoarrays,due to the electron transfer and separation between the TiO2 nanoarrays and the MoS2 nanosheets.When loading the plasmonic Au nanorods,the results of photoeletrochemical activity have further enhanced the(MoS2-TiO2)/Au hybrids.It is important to promote photocatalytic efficiency because of the effects of the hot-electron injection,extended absorption spectrum,and rapid transfer of electron-hole from the plasmonic Au nanorods.Therefore,the plasmonic noble metal can be used to enhance the photoelectrochemical activity of the two-dimensional nanostructures.Secondly,on the basis of Au nanorods,we have prapered Cu2-xS semiconductors with surface plasmon properties and Au@Cu2-xS core-shell nanostructure with the dual plasmonic properties by a hydrothermal method.The results show that there is a significant surface plasmon coupled resonance effect between the Au core and Cu2-xS shell in the near-infrared region.Meanwhile,we have also prepared Au@Cu2S core-shell nanostructures for comparison.The extinction spectra of Au@Cu2-xS core-shell structures are consist of transverse surface plasmon resonance(TSPR),longitudinal surface plasmon resonance(LSPR)of the Au nanorods and Cu2-xS surface plasmon resonance(SPR)of Cu2-xS shells.Keep the Au nanorods unchanged,by adjusting the thickness of Cu2-xS to adjust the plasmon change,and we find that the TSPR of the Au@Cu2-xS core-shell structure is slightly red-shifted due to the change of the dielectric constant,while the LSPR and SPR shows blue shift mainly depended on the plasmon coupling between the Au nanorods and Cu2-xS shell.Conversely,the TSPR and LSPR of the Au@Cu2S core-shell nanostructures show obvious red-shift with the CU2S shell grown deriveing from the change of refractive index.The spectra composed of the three formants and the electric field distribution at the resonance peak are simulated by finite-difference time-domain(FDTD)theory.We find that the theoretical and experimental spectra of the Au@Cu2-xS core-shell structure are consistent.By adjusting the longitudinal growth of the initial Au nanorods and maintaining a constant thickness of the Cu2-xS shell,we find that the longer the Au nanorods,the stronger the coupling intensity of the Au core and the Cu2-xS shell.Based on the theoretical study of the coupled harmonic oscillator model,we calculate that the coupling strength between LSPR and SPR is 180 meV,which is much higher than the coupling strength of 55 meV between TSPR and SPR.Finally,we perform photothermal measurements on Au,Au@Cu2S and Au@Cu2-xS nanorods under the same conditions.It was found that Au@Cu2-xS has the highest photothermal conversion efficiency.Thirdly,on the basis of Ag nanoplates,we synthesize 2 nm-ultrathin Ag@Au nanorings,6 nm-ultrathin Ag@Au nanorings and porous Ag@Au alloy nanoplates by a hydrothermal method.When Ag nanoplates are synthesized into these three different topographical alloys,the three processes exhibit different surface plasmon properties.We performed 4-NP catalytic degradation on the three final products prepared by redshifting the original Ag nanoplates at the same wavelength.The comparison shows that the 2 nm-ultrathin Ag@Au nanorings have the highest catalytic degradation efficiency.This result indicates that 2 nm-ultrathin Ag@Au nanorings are nanostructures with high efficiency for catalytic degradation of contaminants.