Conférence Barré 2 avec le professeur Richard Van Duyne

Titre de la conférence no 2
New Directions in Molecular Plasmonics: Pushing the Sensitivity, Space, and Time Limits

Le Département de chimie a le plaisir et l’honneur d’accueillir le professeur Richard Van Duyne, du Département de chimie de la Northwestern University, dans le cadre des conférences Barré. Il donnera deux conférences différentes en anglais les 12 et 13 septembre 2012.

Résumé de la conférence no 2
In 1997, the startling observation of single molecule surface enhanced Raman spectroscopy (SMSERS) was first reported. Over time the, the evidence for the existence of SMSERS as well as the magnitude of the enhancement factor was called into question. In the first part of this lecture, I will discuss our efforts to provide a robust existence proof for SMSERS employing a frequency-domain approach with two isotopologues of Rhodamine 6G (R6G) that provide unique vibrational signatures. When an average of one molecule is adsorbed per Ag nanoparticle, only one isotopologue is observed in a dry N2 environment. Isotopologues were subsequently used to study the structure of SMSERS active nanoparticle assemblies by HRTEM, perform single molecule excitation spectroscopy measurements, and analyze the SMSERS of crystal violet (CV). This section will conclude with a proof-ofconcept demonstration single molecule LSPR spectroscopy. The concluding section of this lecture will focus on three very recent developments: (1) single molecule tip-enhanced Raman spectroscopy (SMTERS); (2) ultrahigh vacuum tipenhanced Raman spectroscopy (UHV-TERS); and (3) surface-enhanced femtosecond stimulated Raman spectroscopy (SE-FSRS). The isotopologue proof of single molecule specificity in ambient TERS will be demonstrated. A UHV-TERS instrument has been constructed with atomic resolution of the surface and sub-molecular resolution of the adsorbate. The capabilities of this machine are shown with the copper phthalocyanine (CuPc)/Ag(111) system. For the first time, the revolutionary techniques of surface enhanced Raman spectroscopy and femtosecond stimulated Raman spectroscopy (FSRS) have been combined. Thus, plasmonically enhanced broadband Raman spectra using an ultrafast four wave mixing process, which can simultaneously achieve spectral and temporal resolution below the time-energy uncertainty limit, has been achieved! We can now forsee the day when it will be possible to combine UHV-TERS and surface enhanced FSRS to enable single-molecule spectroscopy with simultaneous nanometer spatial resolution and femtosecond time resolution.

À propos des conférences Barré
Ancrées dans une longue tradition qui date de 1979, les conférences Barré rendent hommage à la générosité du regretté professeur Roger Barré, qui a enseigné la chimie à l’Université de Montréal tout au long de sa carrière. En l’honneur de son père, il a créé par testament la Fondation Henri-Barré, dont les revenus permettent au Département de chimie d’inviter des scientifiques de renom à présenter une série de deux conférences devant la communauté de chimie montréalaise.

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