Biophotonics with Nanoparticles

Wolfgang Knolla,b, X. Zhonga,b, M.-Y. Hanb, H. Rochholza, F. Xua, and M. Kreitera

aMax Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany
bInstitute of Materials Research and Engineering, 3 Research Link, Singapore 117602




This contribution summarizes some of our efforts in designing, synthesizing, and characterizing nanoscopic structures for their use in bioaffinity studies and biosensor development.

The first example that will be presented concerns the preparation of semiconducting nanoparticles. These quantum dots can be (bandgap) engineered so as to cover with their photoluminescence emission the full visible spectrum. We developed an alloying protocol (starting from core/ shell particles) that allows for color tuning not only by the size-control of the particles, but offers the possibility for emission tuning by the atomic ratio of the cluster constituents, e.g., CdxZn(1-x)S. These alloyed nanoparticles show excellent photostability superior quantum yields, and very narrow and symmetric emission bands. The application that we will discuss is their use for color multiplexing in parallel multiple detection of surface hybridization reactions of DNA oligonucleotide targets conjugated to different quantum dots.

Another very promising approach is based on Au-nanostructures with their enormous electromagnetic field enhancements at resonant excitation of local surface plasmon modes. In particular, structures with non-spherical shapes offer substantial sensitivity enhancements if used in bioaffinity assays. We document this with C-shaped Au clusters that are prepared by an (oblique) evaporation/sputtering protocol using silica nanospheres at templates. If combined with fluorescence detection schemes by employing chromophore-labeled bio-analytes very promising sensitivities for biosensor applications can be achieved.