Preparation Of Carbon Nano-composites And Research On Their Optical Detection Properties

The surface plasmonic effect relating to the noble metallic nanostructures,particularly the near field enhancement effect,has become one of the hot-spots in the fields of optoelectronic detection,photovoltaic devices and biosensors due to its great potential applications.Carbon-based nanomaterials,such as fluorescent carbon dots and graphene etc.,have attracted intense attention thanks to their unique optical properties.Therefore,the combination of nano-carbon materials and noble metallic nanostructures is expected to achieve better optical performance and eventually can be employed in the fields of optoelectronic detection,photovoltaic devices and biosensors.This dissertation mainly concerns the silver-carbon nanocomposites.On one hand,silver-carbon nanocomposites were synthesized at room temperature by water-bath and electrochemical deposition methods,respectively.The results reveal that the surface plasmonic decay of silver nanoparticles can be improved by the coupling to the graphene sheet due to two reasons.One is that the coupling results in the electron injection to silver and therefore enhance the luminescent efficiency through exciting the non-radiative plasmon modes to radiative.Another reason is that the existence of graphene could enhance the confinement of the near field and therefore improve the absorption of silver nanoparticles.Furthermore,silver-carbon nanocomposites were employed as surface-enhanced Raman scattering(SERS)substrates.The contacting of silver nanorods and graphene results in more defects and structural changes on the surface of graphene.When the rhodamine molecules were introduced on the SERS substrates,higher Raman signals can be detected due to the interaction between two enhanced local electric fields,which are generated by the silver nanorods due to surface plasmonic near filed effect and the rhodamine molecules because of the electrostatic effect.Eventually,the enhancement factor of 2.58 can be obtained.On the other hand,silver-carbon quantum dots composites were prepared through the hydrothermal route.Photoluminescence properties of such nano-composites were systematically studied to explore their application in field of detection of heavy metallic ions,such as mercury ions.After bonding of silver nanoparticles and carbon quantum dots,an electric field will be built resulting from the difference of the work functions of silver and carbon.This electric filed will bend the energy band of carbon quantum dots and result in higher luminescence intensity.When the mercury ions were introduced into the system,the bending degree will be reduced since the reduction of mercury ions will weaken the intermediate electric field.As a result,the luminescence quenching can be observed.The existence of nano-silver significantly increased the sensibility of carbon quantum dots for mercury ions and the detection limit can be as low as 0.007?M.