Events Calendar View

• Departmental Colloquium Sep 27, 2012

  ThermoChemical NanoLithography (TCNL)

  

  Guest: Prof. Elisa Riedo, School of Physics, Georgia Institute of Technology
  Thursday, September 27, 2012 4:00 pm - 5:00 pm
  Location: 202

  iCal

  Nanolithography has been recognized as an essential component of future technologies. However, many of the techniques employed today still have significant limitations in terms of resolution, speed of writing, and the chemical diversity of the materials that can be patterned on an arbitrary substrate. Achieving chemical patterning at resolutions of 100 nm and below has been a challenge because of the difficulty in spatially confining reactions and because of the need to control the interactions of the reactant and products with the substrates and stamps. Over the past few years, by using resistively-heated atomic force microscopy (AFM) tips, the ability to thermally activate a chemical reaction at the nm scale at the surface of a material has been demonstrated in our group. Local chemical changes with feature sizes down to 12 nm at scan speeds up to 1 mm/s have been obtained with this new technique, commonly referred to as ThermoChemical NanoLithography (TCNL). In this seminar I will review recent research on TCNL, which includes: i) acid and amine patterning on the surface of copolymers containing thermally labile groups, and subsequent functionalization with proteins and DNA, ii) nanofabricating poly(p-phenylene vinylene) (PPV) nanowires, a typical electroluminescence conjugated polymer, with a clear “turn-on” of luminescence, iii) producing reduced graphene oxide (r-GO) structures by local thermal reduction of insulating GO with a 104 increase in conductivity for features sizes as small as 12 nm, iv) crystallization of Pb(Zr0.52Ti0.48)O3 and PbTiO3 ferro/piezoelectric nanostructures on a variety of substrates including plastic, achieving lines with widths ≥ 30 nm, spheres with diameter  10 nm and densities up to 213 Gb/in2, and v) producing density gradients of functional groups on polymer surfaces with nanoscopic resolution.

• NanoSEC Seminar Sep 28, 2012

  Shed Light on Nanomaterials for Solar Energy Conversion and Cancer Therapy

  

  Guest: Jin Zhong Zhang, Department of Chemistry and Biochemistry, University of California Santa Cruz
  Friday, September 28, 2012 3:00 pm - 4:00 pm
  Location: Riverbend Research South Laboratory Auditorium

  iCal

  Nanomaterials are of strong interest for both fundamental and technological purposes. At the fundamental level, nanomaterials possess novel physical and chemical properties that differ from those of bulk matter due to quantum confinement effects and exceedingly larger surface-to-volume ratio. These novel properties are highly promising for applications in emerging technologies such as solar cells and biomedicine. Our lab has been actively engaged in the study of optical and dynamic properties of nanomaterials for solar energy conversion and biomedical applications. One example is hydrogen generation from water splitting based on novel semiconductor nanostructures with improved properties. We also design and characterize metal nanostructures for chemical sensing based on surface enhanced Raman scattering (SERS) and biomedical imaging and therapy. An example is hollow gold nanospheres that have demonstrated outstanding photophysical properties for photothermal ablation therapy of cancer both in vitro and in vivo, due to their unique structural and optical characteristics.

• Departmental Colloquium Oct 4, 2012

  Who Are the Stars? Where are the Planets?

  

  Guest: Todd Henry, Georgia State University
  Thursday, October 4, 2012 4:00 pm - 5:00 pm
  Location: 202

  iCal

  Since 1994, RECONS (www.recons.org, REsearch Consortium On Nearby Stars) has been discovering and characterizing the Sun's neighbors. Because of their proximity, nearby stars are natural locations to search for other solar systems. The stars provide increased fluxes, larger astrometric perturbations, and higher probabilities for eventual resolution and detailed study of planets than similar stars at larger distances. We have been building a three-dimensional map of stars near the Sun since 1999 using a telescope in the Chilean Andes, and we are now beginning to add planetary companions orbiting the stars. Surprising results include the overwhelming number of red dwarf stars near the Sun ... and the amount of work it will take to search for planets orbiting so many stars. Examination of the nearby stellar sample will reveal the prevalence and structure of solar systems, as well as the balance of Jovian and terrestrial worlds. These are the stars and planets that will ultimately be key in our search for life elsewhere.

• CSP Lunch Seminar Oct 9, 2012

  Effects of the potential width on the folding behavior of flexible polymers

  

  Guest: Jonathan Gross
  Tuesday, October 9, 2012 12:30 pm - 1:30 pm
  Location: CSP Conference Room (322)

  iCal
• Departmental Colloquium Oct 11, 2012

  Science and a Journey of Extremes

  

  Guest: Francis Slakey, Georgetown University
  Thursday, October 11, 2012 4:00 pm - 5:00 pm
  Location: 202

  iCal

  Talk Abstract:
  Physicist and adventurer Francis Slakey describes his decade long journey that led to his becoming the first person to both summit the highest mountain on every continent and surf every ocean. The talk reviews some of the people he encounters and the challenges he endures – a Lama who gives him an amulet etched with “life’s meaning”, an ambush in the jungles of Indonesia, a life-or-death choice atop Everest – that culminate in a recognition that science is the most powerful tool we have to build a better world. He will describe how that perspective now informs his work for the American Physical Society and Georgetown University.
   
  Bio:
  Francis Slakey received his PhD in physics from the University of Illinois, Urbana-Champaign in 1992. He is the Associate Director of Public Affairs for the American Physical Society where he oversees APS legislative activities, specializing in energy and security policy. He is also The Upjohn Lecturer on Physics and Public Policy and the Co-Director of the Program on Science in the Public Interest at Georgetown University. He is a Fellow of the APS, a Fellow of the AAAS, a MacArthur Scholar, and a Lemelson Research Associate of the Smithsonian Institution. In recognition of his adventures, in 2002, he was chosen to run the Olympic Torch from the steps of the US Capitol. He recounts his global journey in his best-selling adventure memoir, To The Last Breath.

• Departmental Colloquium Oct 18, 2012

  Uncovering Molecular Relaxation Processes in Condensed Phases with Nonlinear Optical Spectroscopy

  

  Guest: Andy Moran, University of North Carolina at Chapel Hill
  Thursday, October 18, 2012 4:00 pm - 5:00 pm
  Location: 202

  iCal

  Photoinduced electrocyclic ring opening of cylcoalkene molecules are among the most elementary processes in organic chemistry.  One prototypical light-activated reaction transforms cyclohexadiene into hexatriene.  It is known that a sequence of extremely fast non-radiative transitions precedes bond breaking in cyclohexadiene.  However, these excited state dynamics have never been directly monitored in solution.  We explore such photoinduced relaxation processes in a closely related derivative of cyclohexadiene, α-terpinene, using femtosecond four-wave mixing spectroscopies carried out in the deep UV spectral range.  Of particular interest are the primary molecular geometry changes induced by light absorption.  The importance of these nuclear motions for the ring opening process will be discussed.
  
  Intriguing fundamental physics surround photoinduced relaxation processes in DNA.  Non-radiative transitions deactivate the excited electronic states of the DNA bases in less than 1 picosecond.  Such ultrafast electronic relaxation holds implications for biological photoprotection because all slower excited state chemical reactions are necessarily suppressed.  Following ground state recovery, the nucleobases are left in “hot” quantum states, wherein a subset of vibrational modes possesses a highly non-equilibrium distribution of excitation quanta (i.e., >4 eV in excess energy).  We use laser spectroscopies to follow these dynamics in thymine model systems at temperatures ranging from 100K-300K.  Our data suggest a competition between internal conversion and vibrational cooling processes in this family of molecules. 

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