(571g) Molecular Spring Assemblies from Nanowires

The development of micro- and nano-fluidics devices and small scale biosensors demands in-situ measurements of local gradients of solute concentration, temperature, pH and other parameters, which have tremendous importance for the development of lab-on-a-chip applications. The same problem also appears in biomedical fields that require evaluation of local concentrations and other parameters for intricate geometries of 3D cell scaffolds, which affect the development of cells residing on the scaffolds. Both tasks are difficult to accomplish using traditional sensor deployment schemes, which often require substrate and wires. In this presentation, we address these problems by designing a nanoscale sensing device from different types of nanoparticles and nanowires [1] connected by molecular springs made from flexible PEG oligomers [2]. A library of assemblies of nanowires was created using PEG tethers [2]. The polymeric linkers afford continuous and dynamic change of conformations in such structures leading to the variations of the distance between the nanoscale colloids reversibly changes depending on conditions or analyte concentration and can be evaluated by fluorescence measurements (Figure 1). Plasmon-exciton interactions result in tremendous enhancement of luminescence [3] and for some systems in characteristic wavelength shift depending on the analyte concentration. Understanding plasmon-exciton interactions will contribute to the photonics and nanoscale optics and create a knowledge base for other technologies such as lasing in nanomaterials, energy conversion [4], and nanoscale electronics [5].

References. 1. Z. Tang, N. A. Kotov, M. Giersig, Science 2002, 297, 237-240. 2. J. Lee, A. O. Govorov, N. A. Kotov, Angew. Chem. Intern. Ed. 2005, in press. 3. J. Lee, A. O. Govorov, J. Dulka, N. A. Kotov, Nano Lett. 2004, 4, 2323-2330. 4. J. Lee, A. O. Govorov, N. A. Kotov, Nano Lett. 2005, in press. 5. S. Tan, Z. Tang, X. Liang, N. A. Kotov, Nano Lett. 2004, 4, 1637-1641