Institute of Bioengineering IBI

Lausanne, Switzerland

Institute of Bioengineering IBI

Lausanne, Switzerland
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Smolentsev N.,Institute of Bioengineering IBI | Chen Y.,Institute of Bioengineering IBI | Jena K.C.,Institute of Bioengineering IBI | Jena K.C.,Indian Institute of Technology Ropar | And 2 more authors.
Journal of Chemical Physics | Year: 2014

The use of a liquid microjet as a possible source of interest for Second Harmonic Generation (SHG) and Sum Frequency Generation (SFG) spectroscopy is examined. We measured non-resonant SHG scattering patterns from the air/water interface of a microjet of pure water and observe a strong enhancement of the SHG signal for certain scattering angles. These enhancements can be explained by the optical properties and the shape of the liquid microjet. SFG experiments at the surface of a liquid microjet of ethanol in air show that it is also possible to measure the coherent vibrational SFG spectrum of the ethanol/air interface in this way. Our findings are useful for future far-UV or X-ray based nonlinear optical surface experiments on liquid jets. In addition, combined X-ray photoelectron spectroscopy and SHG/SFG measurements are feasible, which will be very useful in improving our understanding of the molecular foundations of electrostatic and chemical surface properties and phenomena. © 2014 AIP Publishing LLC.

Roke S.,Institute of Bioengineering IBI | Roke S.,Max Planck Institute for Intelligent Systems (Stuttgart) | Gonella G.,Temple University
Annual Review of Physical Chemistry | Year: 2012

Nano -and microparticles have optical, structural, and chemical properties that differ from both their building blocks and the bulk materials themselves. These different physical and chemical properties are induced by the high surface-to-volume ratio. As a logical consequence, to understand the properties of nano- and microparticles, it is of fundamental importance to characterize the particle surfaces and their interactions with the surrounding medium. Recent developments of nonlinear light scattering techniques have resulted in a deeper insight of the underlying light-matter interactions. They have shed new light on the molecular mechanism of surface kinetics in solution, properties of interfacial water in contact with hydrophilic and hydrophobic particles and droplets, molecular orientation distribution of molecules at particle surfaces in solution, interfacial structure of surfactants at droplet interfaces, acid-base chemistry on particles in solution, and vesicle structure and transport properties. Copyright © 2012 by Annual Reviews. All rights reserved.

De Aguiar H.B.,Institute of Bioengineering IBI | De Aguiar H.B.,Max Planck Institute for Intelligent Systems (Stuttgart) | Samson J.-S.,Institute of Bioengineering IBI | Samson J.-S.,Max Planck Institute for Intelligent Systems (Stuttgart) | And 2 more authors.
Chemical Physics Letters | Year: 2011

We present a description of sum frequency scattering experiments to probe the interfacial vibrational spectrum of nanoscopic oil droplets dispersed in water. SF scattering measurements as a function of optical path length, infrared (IR) pulse energy and particle density show that for different IR excitation wavelengths a different optimum experimental geometry exists. The optimum optical path length matches roughly the 1/e absorbance length in D2O of the used IR frequency. The intensity depends linearly on the particle density. The SF intensity also scales linearly with the IR pulse energy, whereas no changes are observed in the spectral shape. © 2011 Elsevier B.V. All rights reserved.

De Aguiar H.B.,Institute of Bioengineering IBI | De Beer A.G.F.,Institute of Bioengineering IBI | Roke S.,Institute of Bioengineering IBI
Journal of Physical Chemistry B | Year: 2013

Ultralow densities of crystalline nanospheres have been detected in amorphous polymer microspheres by utilizing the unique sensitivity of second-order nonlinear optical techniques to anisotropy. Vibrational sum frequency scattering (SFS) and X-ray diffraction (XRD) are used to quantify the crystallinity of amorphous poly(d,l-lactic acid) microspheres. While XRD does not display any crystallinity for the microspheres, SFS spectra and patterns are reminiscent of a heterogeneous microsphere that contains small crystalline domains. Nonlinear light scattering theory was used to model the data, and an average domain radius of 147 ± 65 nm was obtained. The degree of crystallinity (0.2%) was estimated by comparing XRD and SFS data obtained from the amorphous microspheres to similar data obtained from crystalline microspheres. We estimate a detection limit of 0.002% for SFS. © 2013 American Chemical Society.

Scheu R.,Institute of Bioengineering IBI | Roke S.,Institute of Bioengineering IBI
Journal of Physical Chemistry B | Year: 2014

Interfacial molecular dynamics are key to understanding many phenomena in technology and life sciences. We demonstrate a first step toward accessing vibrational dynamics at liquid-liquid and nanoscopic (bio)-interfaces using time-resolved sum-frequency scattering to probe the interfaces of a nanodroplet platform. The free induction decay of the vibrational modes of dodecylsulfate amphiphiles from the interface of dispersed nanoscopic oil droplets was measured. We probed the vibrational response of both the functional headgroup and the alkyl tail of the amphiphiles. In the molecular fingerprint region, a beating of vibrational modes was observed. Simultaneous modeling of the time- and frequency-resolved response revealed modes at ∼995 and ∼1065 cm -1 that can be assigned to C-O-S and SO3 stretch vibrations. © 2014 American Chemical Society.

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