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SUMMARY:Nanostructured-Enhanced Raman Spectroscopy (NERS) for Surface Scie
 nce and Molecular Electronics - Professor Z Q Tian\, Director\, State Key 
 Laboratory for Physical Chemistry of Solid Surfaces\, Xiamen University
DTSTART:20100720T090000Z
DTEND:20100720T100000Z
UID:TALK25552@talks.cam.ac.uk
CONTACT:Duncan Simpson
DESCRIPTION:Surface-enhanced Raman scattering (SERS) stems from surface pl
 asmon resonance (SPR) which takes place on various nanostructures with sui
 table dielectric constant\, shape and scale. It had been very difficult to
  apply conventional SERS to study probed molecules adsorbed at atomically-
 flat single-crystal surfaces and surface components of diverse materials b
 ecause they cannot effectively support SPR. Based on the borrowing SERS ac
 tivity strategy\, we have utilized some nanostructures to expand SERS stud
 ies to Pt and Si single crystal surfaces and various molecules adsorbed on
  surfaces as diverse as those of platinum\, yeast cells or citrus fruits. 
 The latest progress made in our group is a new method named as Shelled-Iso
 lated Nanoparticle-Enhanced Raman Spectroscopy (SHINERS) [1]. We chemicall
 y synthesized Au nanoparticles coated with ultra-thin shells (ca. two to f
 our nanometers) of chemically inert silica and alumina\, respectively. Abo
 ut monolayer of such nanoparticles is spread over the surface that is to b
 e probed. The ultrathin coating keeps the nanoparticles from agglomerating
 \, separates them from direct contact with the probed substance and allows
  the nanoparticles to conform to different contours of substrates. High-qu
 ality Raman spectra were obtained on various molecules adsorbed at Pt and 
 Au single-crystal surfaces and from Si surfaces with hydrogen monolayers. 
 These measurements and our studies on yeast cells and citrus fruits with p
 esticide residues illustrate that our method significantly expands the fle
 xibility of SERS for wide applications in surface\, materials and life sci
 ences\, as well as for the inspection of food safety.\nIn molecular electr
 onics\, individual molecules with unique properties serve as the basic ele
 ctrical components. Various methods have been established to construct ele
 ctron-transport junctions\, which serve as the basic investigative tool in
  molecular electronics\, and to characterise different properties of the a
 ctive region. Very recently we have introduced a “fishing mode” scanni
 ng tunneling microscopy (FM-STM) method which can reliably measure single-
 molecule conductance on the time scale of seconds (currently existing meth
 ods require tens of minutes to hours). We then combine our FM-STM method w
 ith tip-enhanced Raman spectroscopy (TERS) to create a second technique\, 
 one that allows mutually-verifiable single-molecule conductance and single
 -molecule Raman to be acquired simultaneously under ambient conditions. We
  call it “fishing-mode” TERS (FM-TERS). Density functional theory (DFT
 ) calculations reveal a good correlation between the single-molecule condu
 ctance and single-molecule TERS\, and they yield fresh insights into the n
 on-linear nature of voltage-dependent conductance. The correlated data obt
 ained by FM-TERS will allow molecular structure during the electron-transp
 ort process to be understood in a way that has never been possible before:
  by use of vibrational information obtained exclusively from the single mo
 lecule in the junction. Reference: 1. J.F. Li\, et. al.\, Nature 2010\, 46
 4\, 392.
LOCATION:Kapitza Building Seminar Room\, Cavendish Laboratory\, Department
  of Physics
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