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Vibrational sum-frequency generation (SFG) spectroscopy is used to determine the surface p

A simple and fast electrochemical process for gold surface functionalization aimed to immobilize biomolecules is presented here. Raman spectroscopy was used to characterize the complete system starting from surface functionalization to final structure with immobilized proteins.

ICORS, Boston, Massachusetts, USA, paper BThP11, 2010; International audience

Besides nephrite, serpentine is also frequently employed as a jade material in China since the Neolithic period. Translucent or opaque, serpentine presents diverse colors, including yellow‐green, green, dark green, and tan, which are related to its chemical composition and occasionally to its associated sub‐major minerals. Serpentine could be subjected to color change due to secondary alterations or weathering. In this study, we mainly focus on the heating effect on serpentine, as some ancient serpentine jades may have been exposed to heat for some different reasons, such as carving, funeral ceremony or imitating. A series of non‐heated and heat‐treated raw serpentine jades are examined using Raman spectroscopy and other complementary methods. The subtle change of molecular structure and color of serpentine due to the heat treatment is reported in detail.

Using Surface Enhanced Raman Spectroscopy (SERS), we observed Raman enhancements (104–105) for pyridine molecules adsorbed on a II–VI semiconductor CdSe/ZnBeSe sample of uncapped self‐assembled quantum dots produced by molecular beam epitaxy. When a monolayer of pyridine is adsorbed on these structures, excitation at 488 nm produces intense Raman spectra a very large enhancement of the a1, b1 and b2 modes. This indicates the presence of charge‐transfer as a contributor to the enhacement.

International audience; Matrix Metalloproteinases (MMPs) are cell-secreted soluble and membranetethered enzymes that degrade extracellular matrix (ECM) proteins. These proteases play a key role in diverse physiological and pathological processes, including embryonic development, wound repair, inflammatory diseases and cancer [1]. On the other hand, Superoxide Dismutases (SODs) are metalloenzymes that defend biological systems against oxidative damage mediated by the superoxide anion [2]. The vibrational spectra of MMPs and SODs can provide crucial information about conformational changes induced by external factors, e.g. the interaction with metal ions, drugs, others proteins or peptides. On the other side, Raman spectroscopy can be used as a tool for non-invasive and non-ambiguous spectral detection of these proteins at very low concentration (10-8-10-12 M), with potential applications in early diseases diagnosis [3]. At present, there is still insufficient knowledge on the Raman spectral fingerprints of these proteins. Here we present a complete Raman analysis of MMP2 and MnSOD using multiwavelength-excitation at 514, 633, and 785 nm.

The dominant mechanism for the tip-sample interaction in TERS experiment is electromagnetic (EM), with interaction length of the order of a few tens of nanometers. However, due to the presence of metallic layer on the tip, chemical interaction between the sample and the metal on the tip starts to become significant, if the sample is very close to the tip, particularly at molecular distances [1]. Further, if the distance between the sample and the tip is reduced so much that the tip comes in physical contact with the sample, then mechanical interaction also starts to play an important role [2]. In general, the three interactions are simultaneously present in a TERS experiment. However, since they have slightly different interaction ranges, it could be possible to study them individually, if the distance between the tip and the sample in a TERS experiment is precisely regulated with accuracies of the order of sub-nanometer scale. Here, we demonstrate how we can effectively control the tip-sample distance in TERS experiments with extremely high accuracy, even though the AFM tip in our experiment oscillates in tapping mode operation [3]. The chemical as well as the mechanical interaction distinctly shows up in TERS spectra, when the tip is maintained very close to, or pressed against the sample. We achieve this result by time-gating the illumination, so that the sample is selectively illuminated only when the tip is at a certain distance from the sample during the repeated cycles of its tapping-mode oscillation. The measurement precision that we have achieved in this technique is of sub-nanometer order. With this system, we studied two different samples, an isolated single walled carbon nanotube (SWCNT) and an adenine nanocrystal, which were measured with precise control over the tip-sample distance. As the distance between the tip and the sample was decreased, we clearly observed the signatures of EM interaction, chemical interaction and mechanical interaction in different ranges. A precise control over the tip-sample distance does not only provide the subnanometric information in the vertical direction, but can also provide nanometric resolution in the lateral direction. In order to justify our claim, we demonstrated that this technique could provide extremely high spatial resolution in TERS imaging. We scanned the tip under a constant pressure across an isolated SWCNT, and performed a one-dimensional imaging of the sample. An extremely high spatial resolution of about 3 nm was obtained.

Time‐resolved vibrational spectroscopy (TRVS) has many unique features and capabilities for elucidating the structural changes of transient species across the fs to ms time frame. The recently developed 10 KHz, 10W ULTRA laser system represents the very latest technology. ULTRA’s performance and capabilities will be described for the time resolved infrared, 2D infrared and femtosecond stimulated Raman spectroscopy techniques with examples taken from organometallic intermediates, organic excited states and DNA tertiary structure.

Novel materials originating from renowable sources mainly consist of biopolymers and their composites or nanocomposites. A typical material belonging to this group is chitosane (CS), which is a cationic natural polysaccharide that can be produced by alkaline N‐deacetylation of chitine. Chitosane has a variety of applications in biomedical products, cosmetics, and food processing [1, 2].Organic‐inorganic hybrid materials basing on chitosane and nanoclay (montmoryllonite, MMT) were characterized by the vibrational spectrocopy methods (Micro‐Raman spectroscopy and FT‐Raman spectroscopy) and the thermal analysis methods (TG, DSC). It was shown, that small amount on a nanofiller (MMT, 3 wt.%) used to modify the polymer matrix influences the structure of its polymeric chains.

Significant improvement in the detection limits of bioassays have been found from the use of surface enhanced Raman scattering (SERS) detection probes. These probes are constructed from plasmonic nanostructures, including solid gold and silver nanoparticles (colloids) and core-shell structures (metal core-silica shell), taking advantage of the large enhancement in the Raman scattering signal of dyes fixed in close proximity to such surfaces. These dyes come into contact with the surface in a variety of fashions, including electrostatic attraction, direct covalent attachment, or secondary labeling. In order to obtain probes that are SERS active and stable in a variety of biological fluids, these particles often incorporate a mixed monolayer system containing a Raman-active dye and an analyte recognition element. Though there has been much effort in constructing increasingly sensitive dyes, less emphasis has been placed on the method of analyte capture. Many methods use a sandwichassay design that relies on chemistries similar to those used to construct the SERS probes. Often the capture of such analytes requires extremely long incubation times and large volumes of analyte, neither of which is conducive to detection of small quantities of analyte in limited samples of bodily fluids. We have developed a unique analyte capture system for SERS biodetection based on an extension of methods commonly used in Western blotting.

We will demonstrate results from portable stand‐off Raman systems for identification of high energy materials. The first system is a handheld 785 based system with distance capabilities from 0.3 to 3 meters. The second system is a larger tripod mounted system based on 1064 nm laser excitation that measures distances from 3 to 10 meters.

We report on the experimental identification of Raman modes that are enhanced through the chemical effect in surface enhanced Raman spectroscopy of 4-aminothiophenol (also known as p-mercaptoaniline) adsorbed on gold substrate. Introduction of a thin spacer layer between the metal and the sample can prevent any possible chemical bonding between metal atoms and sample molecules, hence such a sample shows only those Raman modes that are enhanced through the electromagnetic effect. Alternatively, a significant increase in the chemical effect could be observed in the presence of halide ions as compared to their absence. This result provides another way to experimentally identify those Raman modes that undergo chemical enhancement. In addition, apart from the electromagnetic-based resonance in SERS, chemical enhancement also shows a resonance with varying wavelength of the excitation light, which provides yet another way to experimentally identify chemically enhanced Raman modes in SERS. Some new chemically en...

International audience