Rene A. Nome

Ultrafast dynamics of solvation: the story so far

The presence of solvent molecules in the vicinity of a solute affects a variety of processes in chemistry and biology, and thus one would like to have a physical picture of how solvation works. Although there are many structurally sensitive spectroscopic tools to investigate the role of solvent molecules in chemical processes, real time measurements of the dynamics of solvation had to wait for the development of pulsed laser spectroscopies with femtosecond time-resolution. This review describes applications of ultrafast spectroscopy to the study of solvation dynamics. At third order, we review resonant and non-resonant probes of solvation dynamics, with a focus on the study of simple and complex liquids. Fifth-order Raman spectroscopies are also reviewed, focusing on the insights these techniques give into the role of the solvent in chemical reactions and the anharmonic nature of the liquid state.

Towards in situ fluorescence spectroscopy and microscopy investigations of asphaltene precipitation kinetics

We perform a spectroscopic analysis of asphaltene in solution and in crude oil with the goal of designing an optical probe of asphaltene precipitation inside high-pressure cells. Quantitative analysis of steady-state spectroscopic data is employed to identify fluorescence and Raman contributions to the observed signals. Time-resolved fluorescence spectroscopy indicates that fluorescence lifetime can be used as a spectroscopic probe of asphaltene in crude oil. Quantitative confocal laser-scanning microscopy studies of asphaltene in n-heptane are used to calculate particle-size distributions as a function of time, both at the sample surface and asphaltene interior. The resulting precipitation kinetics is well described by stochastic numerical simulations of diffusion-limited aggregation. Based on these results, we present the design and construction of an apparatus to optically probe the in situ precipitation of asphaltene suitable for studies inside high pressure cells. Design considerations include the use of a spatial light modulator for aberration correction in microscopy measurements, together with the design of epi-fluorescence spectrometer, both fiber-based and for remote sensing fluorescence spectroscopy.

Ultrafast Dynamics of Au Nanopyramid Interfaces Prepared by Nanosphere Lithography: Effect of Substrate Chemical Composition

This work describes ultrafast spectroscopy studies of Au triangular pyramid particle arrays deposited over glass (termed Au/glass), and 190 nm indium tin oxide (ITO) film (termed Au/ITO/glass) prepared by nanosphere lithography. The linear absorption spectra of Au/glass and Au/ITO/glass exhibit surface plasmon resonances at 800 and 870 nm, respectively, in good agreement with discrete dipole approximation simulations. Ultrafast pump-probe measurements at wavelengths below resonance, at resonance, and above the surface plasmon resonance for each of these two systems are presented. The pump-probe measurements on both systems can be well fit with a model accounting for electron-electron scattering, electron-phonon coupling, and acoustic oscillations on top of cooling of the gold lattice. Numerical simulations employing a two-temperature model are consistent with the single-color pump-probe exponential decays. The wavelength-dependent pump-probe results are interpreted in terms of the complex wavelength-dependent refractive index of gold. We show that this interpretation is consistent with diffractive-optic four-wave mixing spectroscopy measurements of absorptive and dispersive parts of the third-order nonlinear polarization at 800 nm.

Enhanced reproducibility of planar perovskite solar cells by fullerene doping with silver nanoparticles

A small cross-section of silver nanoparticles (AgNPs) placed at the rear-part of the solar cell avoids the parasitic absorption of the nanoparticles which is the biggest barrier for plasmonic structures when acting as photocurrent enhancers. Herein, we demonstrate p-i-n planar perovskite solar cells with the structure ITO/PEDOT:PSS/MAPbI3/PCBM/Ni:Au, where the PCBM electron extraction layer (EEL) was intentionally modified with variable amounts of AgNPs. The addition of small amounts of AgNPs (e.g., 5u2009wt. %) into the PCBM improved the overall reproducibility and reliability of the solar cell fabrication process after optimization. Plasmonic simulations suggest that any plasmonic-optical effects are relatively small compared to sample absorbance due to perovskite alone. It has been concluded that plasmonic-electrical effects play a major role in averaged performance improvement. Therefore, the addition of small AgNPs in low concentration to the EEL layer accounts for higher Jsc, Voc and FF as a result of a better perovskite coverage by the EEL and an improved charge carrier collection as evidenced by morphological and electrical analysis.A small cross-section of silver nanoparticles (AgNPs) placed at the rear-part of the solar cell avoids the parasitic absorption of the nanoparticles which is the biggest barrier for plasmonic structures when acting as photocurrent enhancers. Herein, we demonstrate p-i-n planar perovskite solar cells with the structure ITO/PEDOT:PSS/MAPbI3/PCBM/Ni:Au, where the PCBM electron extraction layer (EEL) was intentionally modified with variable amounts of AgNPs. The addition of small amounts of AgNPs (e.g., 5u2009wt. %) into the PCBM improved the overall reproducibility and reliability of the solar cell fabrication process after optimization. Plasmonic simulations suggest that any plasmonic-optical effects are relatively small compared to sample absorbance due to perovskite alone. It has been concluded that plasmonic-electrical effects play a major role in averaged performance improvement. Therefore, the addition of small AgNPs in low concentration to the EEL layer accounts for higher Jsc, Voc and FF as a result of a...

The challenges of characterising nanoparticulate catalysts: general discussion

Rosa Arrigo, Kassim Badmus, Francesca Baletto, Maurits Boeije, Michael Bowker, Katharina Brinkert, Aram Bugaev, Valerii Bukhtiyarov, Michele Carosso, Richard Catlow, Revana Chanerika, Philip R. Davies, Wilke Dononelli, Hans-Joachim Freund, Cynthia Friend, Simone Gallarati, Bruce Gates, Alexander Genest, Emma K. Gibson, Justin Hargreaves, Stig Helveg, Haoliang Huang, Graham Hutchings, Nicola Irvine, Roy Johnston, Stanley Lai, Carlo Lamberti, Joseph Macginley, David Marchant, Toru Murayama, Rene Nome, Yaroslav Odarchenko, Jonathan Quinson, Scott Rogers, Andrea Russell, Said Said, Paul Sermon, Parag Shah, Sabrina Simoncelli, Katerina Soulantica, Federico Spolaore, Bob Tooze, Laura Torrente-Murciano, Annette Trunschke, David Willock and Jiaguang Zhang

Application of new nanoparticle structures as catalysts: general discussion

Baletto, Francesca, Boeije, Maurits, Bordet, Alexis, Brinkert, Katharina, Catlow, C. Richard A., Davies, Josh, Dononelli, Wilke, Freund, Hans-Joachim, Friend, Cynthia, Gates, Bruce, Genest, Alexander, Guan, Shaoliang, Hardacre, Christopher, Hargreaves, Justin, Huang, Haoliang, Hutchings, Graham J., Johnston, Roy, Lai, Stanley, Lamberti, Carlo, Marbaix, Julien, Miranda, Caetano Rodrigues, Nome, Rene, Peron, Jennifer, Quinson, Jonathan, Richards, Nia, Roesch, Notker, Russell, Andrea, Said, Said, Selvam, Parasuraman, Sermon, Paul, Shozi, Mzamo, Skylaris, Chris-Kriton, Spolaore, Federico, Walkerdine, James, Whiston, Keith and Willock, David 2018. Application of new nanoparticle structures as catalysts: general discussion. Faraday Discussions 208 , pp. 575-593. 10.1039/C8FD90016G file

Confocal Fluorescence Microscopy and Kinetics of the Cr 3+-Chromate Ion Oxidation Equilibria at the Solid Liquid Interface

Silica-borax pearl samples impregnated with 0.17 and 0.64% Cr were characterized by specific surface area measurements, UV-Vis spectroscopy, energy-dispersive X-ray fluorescence and laser-scanning confocal microscopy. Pearl stability against oxidizing conditions was tested by adding samples to an aqueous hydrogen peroxide solution. The reaction was examined by UV-Vis spectroscopic measurements of the supernatant and laser-scanning confocal microscopy images of the substrate. Overall, hydrogen peroxide-induced Cr to Cr oxidation across the solid-liquid interface promoted solid matrix cleavage pearl degradation and concomitant formation of multiple scattering centers was observed. A dual-detection scheme was employed in the confocal microscopy measurements allowing us to separate scattering and absorptive contributions to the observed signals. The confocal microscopy images indicate that Cr oxidation induced by hydrogen peroxide solutions occurs throughout the entire pearl sample and indicate that oxidation reactions induce leakage of chromate ion into aqueous solutions.