AVS 56th International Symposium & Exhibition
    Biomaterial Interfaces Monday Sessions
       Session BI+NS-MoM

Paper BI+NS-MoM6
Size-selective Placement of Nanoparticles on a Single Particle Level

Monday, November 9, 2009, 10:00 am, Room K

Session: Nanoparticles and Self Assembly
Presenter: P. Bhadrachalam, University of Texas at Arlington
Authors: P. Bhadrachalam, University of Texas at Arlington
S.J. Koh, University of Texas at Arlington
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We present a new nanoparticle placement technique in which single nanoparticles of different sizes recognize different target positions on a substrate and exactly one nanoparticle of specific size is placed on each target position in a self-limiting way. We demonstrate this by using ~50nm and ~20nm colloidal Au nanoparticles (AuNPs) as a model system, where the ~50nm particles are first electrostatically guided onto targeted substrate locations and then the ~20nm particles to different target locations on the same substrate. The electrostatic guiding structure was defined using CMOS-compatible fabrication processes and subsequent functionalization of surfaces using self-assembled monolayers (SAMs) of organic molecules. Using appropriate guiding structure, we present >90% success rate of ~50nm AuNPs placement onto substrate locations targeted for ~50nm AuNPs only. Theoretical calculations for ~20nm AuNPs, which was carried out by solving the non-linear Poisson-Boltzmann equation, revealed that the self-limiting single-particle placement is due to an increase of the free energy barrier after the placement of one nanoparticle onto a targeted substrate location, which prevents the approach of other nanoparticles to the already occupied position. The size-selective placement of single nanoparticles can be explained by dependence of the free energy barrier changes upon the sizes of nanoparticles and guiding structures. The same approach may also be useful for size-selective and single-entity-level placement of other nanoscale building blocks such as nanowires, proteins, and DNA.(Supported by NSF CAREER (ECS-0449958), ONR (N00014-05-1-0030), and THECB (003656-0014-2006))