29 research outputs found
Unveiling Nanometer Scale Extinction and Scattering Phenomena through Combined Electron Energy Loss Spectroscopy and Cathodoluminescence Measurements
Unveiling Nanometer Scale Extinction and Scattering Phenomena through Combined Electron Energy Loss Spectroscopy and Cathodoluminescence Measurements
Plasmon modes of the exact same individual gold nanoprisms are investigated through combined nanometer-resolved electron energy-loss spectroscopy (EELS) and cathodoluminescence (CL) measurements. We show that CL only probes the radiative modes, in contrast to EELS, which additionally reveals dark modes. The combination of both techniques on the same particles thus provides complementary information and also demonstrates that although the radiative modes give rise to very similar spatial distributions when probed by EELS or CL, their resonant energies appear to be different. We trace this phenomenon back to plasmon dissipation, which affects in different ways the plasmon signatures probed by these techniques. Our experiments are in agreement with electromagnetic numerical simulations and can be further interpreted within the framework of a quasistatic analytical model. We therefore demonstrate that CL and EELS are closely related to optical scattering and extinction, respectively, with the addition of nanometer spatial resolution
Imaging the Renner-Teller effect using laser-induced electron diffraction
Structural information on electronically excited neutral molecules can be indirectly retrieved, largely through pump-probe and rotational spectroscopy measurements with the aid of calculations. Here, we demonstrate the direct structural retrieval of neutral carbonyl disulfide (CS) in the BB excited electronic state using laser-induced electron diffraction (LIED). We unambiguously identify the ultrafast symmetric stretching and bending of the field-dressed neutral CS molecule with combined picometer and attosecond resolution using intrapulse pump-probe excitation and measurement. We invoke the Renner-Teller effect to populate the BB excited state in neutral CS, leading to bending and stretching of the molecule. Our results demonstrate the sensitivity of LIED in retrieving the geometric structure of CS, which is known to appear as a two-center scatterer
Ultrastrong coupling between nanoparticle plasmons and cavity photons at ambient conditions
Avaliação da expressão do gene MGMT nos tecidos normal e neoplåsico de doentes com cùncer colorretal
OBJETIVO: Avaliar a expressĂŁo tecidual do gene de reparo MGMT comparando a mucosa cĂłlica normal e neoplĂĄsica em doentes com cĂąncer colorretal. MĂTODOS: Foram estudados 44 portadores de adenocarcinoma colorretal confirmado por estudo histopatolĂłgico. Foram excluĂdos doentes suspeitos de pertencerem a famĂlias com cĂąncer colorretal hereditĂĄrio (HNPCC e PAF) e os portadores de cĂąncer do reto mĂ©dio e inferior submetidos a tratamento quimioradioterĂĄpico neoadjuvante. A expressĂŁo do gene MGMT foi avaliada pela tĂ©cnica da reação de polimerase em cadeia em tempo real (RT-PCR). A comparação dos resultados encontrados para expressĂŁo do gene MGMT entre tecidos normais e neoplĂĄsicos foi feita pelo teste t de Student pareado, adotando-se nĂvel de significĂąncia de 5% (p <0,05). RESULTADOS: A expressĂŁo tecidual do gene MGMT em todos os doentes foi menor no tecido neoplĂĄsico quando comparada a do tecido normal (p=0,002). CONCLUSĂO: O gene de reparo MGMT encontra-se menos expresso no tecido neoplĂĄsico quando comparados aos tecidos normais em portadores de CCR esporĂĄdico
Plasmon Mapping in Au@Ag Nanocube Assemblies
Surface
plasmon modes in metallic nanostructures largely determine their optoelectronic
properties. Such plasmon modes can be manipulated by changing the
morphology of the nanoparticles or by bringing plasmonic nanoparticle
building blocks close to each other within organized assemblies. We
report the EELS mapping of such plasmon modes in pure Ag nanocubes,
Au@Ag coreâshell nanocubes, and arrays of Au@Ag nanocubes.
We show that these arrays enable the creation of interesting plasmonic
structures starting from elementary building blocks. Special attention
will be dedicated to the plasmon modes in a triangular array formed
by three nanocubes. Because of hybridization, a combination of such
nanotriangles is shown to provide an antenna effect, resulting in
strong electrical field enhancement at the narrow gap between the
nanotriangles