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[en] Full text: This talk will present some of the results of a long-standing, fruitful and still active cooperation with Hans Kuzmany in the field of Raman spectroscopy of carbon nanostructures. We had more than 30 joint publications in the last 20 years about conjugated polymers, fullerenes and carbon nanotubes. I have selected several important joint results to present them at this meeting: the effective conjugation length model for conjugated polymers; the behavior of the radial breathing mode (RBM) and the disorder induced mode (D mode) in the Raman spectrum of single walled carbon nanotubes. (author)
[en] Extensive Raman investigations were conducted on a wide range of diamond films whose structures were dilineated by optical and confocal microscopy. The Raman Spectra from one extreme of this range indicates a very intense 1331 cm-1 line diagnostic of bulk crystalline diamond. Microscopy of the corresponding film shows the presence of many large true diamond crystallite. The 1331 cm-1 Raman line at the other extreme of the range, however, is virtually absent. It is replaced, at this extreme, by a very broad Raman contour whose maxima occur near 1355 cm-1 and 1575 cm-1. Optical microscopy now reveals a complete lack of diamond crystallites. The ratio of the integrated Raman intensity of the 1331 cm-1 diamond line to the integral of the entire broad contour extending from ∼1200 cm-1 to 1800 cm-1, with maxima near 1355 cm-1 and 1575 cm-1, was determined. This ratio rises with increasing diamond crystallite size, and it decreases as true diamond crystallites are replaced by diamond-like, but amorphous, hard carbon, which produces the broad Raman contour. The measured intensity ratio was analyzed in terms of a differential equation related to phonon coupling. The increase of the intensity ratio of the 1331 cm-1 diagnostic diamond peak is due to phono-phonon coupling between the diamond crystallites, as the concentration of the amorphous diamond-like carbon decreases. Confocal microscopy indicates many amorphous-like regions interspersed between diamond crystallites which account for the intensity loss, and agree with the Raman intensity measurements. These Raman measurements crystallinity versus amorphous hard-carbon character of thin diamond film
[en] Nanoparticles with large amounts of surface area and unique characteristics that are distinct from their bulk material provide an interesting application in the enhancement of inelastic scattering signal. Surface Enhanced Raman Spectroscopy (SERS) strives to increase the Raman scattering effect when chemical species of interest are in the close proximity of metallic nnaostructures. Gold nanoparticles of various shapes have been used for sensing applications via SERS as they demonstrate the greatest effect of plasmonic behavior in the visible-near IR region of the spectrum. When coupled with other nanoparticles, namely iron oxide nanoparticles, hybrid structures with increased functionality were produced. Multifunctional iron oxide-gold hybrid nanostructures have been created via solution chemistries and investigated for analyte detection of a model analyte. By exploiting their magnetic properties, nanogaps or “hot spots” were rationally created and evaluated for SERS enhancement studies.
[en] Laser Raman spectroscopy is the powerful tool to investigate the molecular structure. However, the conventional analog signal often causes some problems in many experiments. For high resolution, small signals, or background (solvent) subtraction, the computer interface of the Raman spectroscopy is the essential one. Here the interface work done in our laboratory is described and some results through the softwares developed are displayed. (Author)
[en] The variation of Jahn-Teller (J-T) distortion imposed on various metallo- tetraphenylporphyrins (MTPPs; M = ZnII, PdII, PtII and RhIII) has been investigated by time-resolved resonance Raman spectroscopy. B1g and B2g modes of the triplet (π,π*) states for the heavy-metal porphyrins exhibit the enhancement of their intensities compared with those of 3ZnIITPP, while the enhancement of phenyl internal mode is reduced. These results suggest that the J-T distortion becomes manifest as the metal size increases, and consequently the porphyrin-tophenyl ring charge transfer in the excited triplet state is inhibited
[en] The poster includes sections on the overview and relevance of the project, a project summary, relevance, accomplishments, collaborations, remaining challenges and barriers and. proposed future work.
[en] Colorless quartz is usually exposed to ionizing radiation (gamma rays or high energy electron beams) in order to acquire different colors for jewelry. This is due to the presence of traces of some elements such as aluminum, iron, hydrogen, lithium, or sodium, which are responsible for the extrinsic colors developed after irradiation. Most quartz crystals are extracted colorless from nature and it is necessary to separate those that can develop colors from those that cannot. This can be done through irradiation tests, which take a long time. Other option is to collect the infrared signature of colorless quartz. However, infrared spectroscopic analysis is quite expensive, especially when using portable devices. Raman spectroscopy is now available as an inexpensive and portable technique that could provide identification of the samples of colorless quartz still in the field, facilitating the prediction for their economic exploitation. In addition, Raman spectroscopy usually requires a minimum or no sample preparation. This paper presents an investigation of the feasibility of using Raman spectroscopy as a substitute for infrared spectroscopy to predict the potential for color development of quartz. A band at 3595 cm-1 was observed, only along the c axis of a prasiolite excited by a high power 514 nm laser. This band was nor observed in quartz samples that do not develop color after irradiation, hence requiring further studies. (Author)
[en] The overall objective of this project is to optics procurement and instrumental setup completed in Robert Lascola's laboratory. An Ondax THz-Raman probe was installed in order to obtain Raman terahertz spectra of commercially available Zeolites.
[en] Highlights: • A critical review of tip-enhanced Raman spectroscopy performed in different conditions. • Highlights: including ultrahigh spatial resolution and integration with ultrafast spectroscopy. • Recent advances applied in research areas from electrochemistry to art conservation science. Tip-enhanced Raman spectroscopy (TERS) is a powerful technique that integrates the vibrational fingerprinting of Raman spectroscopy and the sub-nanometer resolution of scanning probe microscopy (SPM). As a result, TERS is capable of obtaining chemical maps of analyzed specimens with exceptional lateral resolution. This is extremely valuable for the study of interactions between molecules and substrates, in addition to structural characterization of biological objects, such as viruses and amyloid fibrils, 2D polymeric materials, and monitoring electrochemical and photo-catalytic processes. In this mini-review, we discuss the most significant advances of TERS, including: super high resolution chemical imaging, monitoring of catalytic processes, incorporation of pulsed-excitation techniques, single-site electrochemistry, biosensing, and art conservation. We begin with a short overview of TERS, comparing it with other surface analytical techniques, followed by an overview of recent developments and future applications in TERS.