Isomerization in single molecules of azobenzene probed by Surface-enhanced Raman Scattering

Abstract

Trans↔cis isomerization in single azobenzene molecules were captured by Surface-enhanced Raman Scattering (SERS) using nanoAg-on-Ge substrates. Isomerization was observed to occur more frequently in the presence of 365 nm LED excitation in addition to the 532 nm Raman probe laser. Under these excitation conditions, the trans→cis isomerization frequency (i.e., ~0.1 s -1 ) is observed to be much lower than the theoretical estimate (i.e., ~100 s -1 without the surface enhancement effect). This "slowing down" effect allows us to resolve azobenzene's conformational changes at a time scale of 40 ms. We attribute this dramatic reduction in isomerization frequency to adsorption of azobenzene to silver that restrains its rotational freedom. As deduced from statistical analysis of the single molecule spectra, this restraint is higher for the trans form that we explain its stronger chemisorption due to its planar geometry.

In-vitro nanodiagnostic platform through nanoparticles and DNA-RNA nanotechnology

“…2 a A nanopore reader with chemically functionalized probes (Branton et al 2008); b diagrammatic illustrations of nanowire field effect nanobiosensors. Top, before detection; bottom, during detection (Topal 2011) molecular structure and thus will cause a unique translocation event signal upon passage through a nanopore. Branton et al (2008) have developed a DNA sequencing system that involves the optical detection of specific DNA sequence bases translocating through a nanopore.…”

“…3 a A schematic nIDA-gate MOSFET sensor (Tang et al 2009); b bionanoelectronic devices incorporating lipid-coated SiNWs (Misra et al 2009) current passage through the nanowire allowing for discrete and extremely sensitive detection due to the nanoscale of the system (Fig. 2b) (Topal 2011). Tang et al (2009) developed a protein bionanosensor to detect the binding reactions of typical antibodies antigens at concentrations below 1 ng/ml and demonstrated that the electrical drain current of the bionanosensor is significantly increased with successive binding and that sensitivity can be tuned and optimized by changing the geometrical design of the nIDA-gate MOSFET (Fig.…”