Surface charge induced Stark effect on luminescence of quantum dots conjugated on functionalized carbon nanotubes

A significant blue shift of the luminescence of CdSe/ZnS quantum dots (QD) conjugated with functionalized multi-wall carbon nanotubes (CNT) is investigated. The observed Stark shift is due to the local electrostatic field induced by the carboxylic anions on the CNT surface. A theoretical model is developed to evaluate the contribution of the surface charges to the observed spectral shift (up to 0. 59 eV). Based on the present model, the Stark shift provides an effective method for evaluating the density of carboxyl groups on the surface of functionalized CNTs and can be used as a charge detector for QD–nanostructures.