We show that the Raman scattering technique can give complete structural information for one-dimensional systems, such as carbon nanotubes. Resonant confocal micro-Raman spectroscopy of an (n,m) individual single-wall nanotube makes it possible to assign its chirality uniquely by measuring one radial breathing mode frequency omega(RBM) and using the theory of resonant transitions. A unique chirality assignment can be made for both metallic and semiconducting nanotubes of diameter d(t), using the parameters gamma(0) = 2.9 eV and omega(RBM) = 248/d(t). For example, the strong RBM intensity observed at 156 cm(-1) for 785 nm laser excitation is assigned to the (13,10) metallic chiral nanotube on a Si/SiO2 surface.

Structural (n,m) determination of isolated single wall carbon nanotubes by resonant Raman scattering

Herein, we report the straightforward synthesis, photoluminescent properties, and cell imaging studies of D-mannose and L-alanine functionalized silicon nanocrystals (SiNCs). Tailoring nanocrystal surface functionalization is essential to interfacing SiNCs with their environment and rendering them stable – surface modification also offers the opportunity to target specific cell types for imaging. A simple and versatile surface modification procedure was developed to tether biomolecules onto the SiNC surfaces and render them water-soluble. The presented approach is precious metal-catalyst free, straightforward, and provides carbohydrate and amino acid functionalized SiNCs. The functionalized SiNCs have been investigated by fluorescence microscopy and our results indicate that they can be internalized by MCF-7 human breast cancer cells as shown in the cell imaging studies. The obtained SiNCs were characterized using FTIR, XPS, PL, and TEM.

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Water-soluble photoluminescent D-mannose and L-alanine functionalized silicon nanocrystals and their application to cancer cell imaging

In this study, tip-enhanced Raman spectroscopy (TERS) is used to characterize graphene-like and graphitic platelets composed of a few layers of graphene. Specifically, gap-mode TERS geometry provides a larger enhancement of the local electromagnetic field at the junction formed by a gold sharp tip and a gold substrate. Graphene-like platelets are deposited onto ultra-flat thin gold nanoplates using a surfactant-assisted method. Au-coated atomic force microscopy (AFM) tips are used to probe specific substrate regions coated by the platelets. TERS spectra are collected on distinctive points on the graphene-like layers and surrounding substrate using radially or linearly polarized light, with an excitation wavelength of 632.8 nm. The position, width and intensity of G, D, and 2D Raman-active modes of graphene are discussed as a function of the incident light polarization and for distinct positions on the graphene layer. We report here on the nature of the collected TERS spectra focusing in particular on the edges of the graphene platelets.

Tip-enhanced Raman spectroscopy of graphene-like and graphitic platelets on ultraflat gold nanoplates

The rise of molecular plasmonics and its application to ultrasensitive spectroscopic measurements has been enabled by the rational design and fabrication of a variety of metallic nanostructures. Advanced nano and microfabrication methods are key to the development of such structures, allowing one to tailor optical fields at the sub-wavelength scale, thereby optimizing excitation conditions for ultrasensitive detection. In this work, the control of both analyte and cell positioning on a plasmonic platform is enabled using nanofabrication methods involving patterning of fluorocarbon (FC) polymer (C4F8) thin films on a plasmonic platform fabricated by nanosphere lithography (NSL). This provides the possibility to probe biomolecules of interest in the vicinity of cells using plasmon-mediated surface enhanced spectroscopies. In this context, we demonstrate the surface enhanced biosensing of glycan expression in different cell lines by surface enhanced Raman spectroscopy (SERS) on these plasmonic platforms functionalized with 4-mercaptophenylboronic acid (4-MPBA) as the Raman reporter. These cell lines include human embryonic kidney (HEK 293), C2C12 mouse myoblasts, and HeLa (Henrietta Lacks) cervical cancer cells. A distinct glycan expression is observed for cancer cells compared to other cell lines by confocal SERS mapping. This suggests the potential application of these versatile SERS platforms for differentiating cancerous from non-cancerous cells.

/pdf/controlled-positioning-of-analytes-and-cells-on-a-plasmonic-1ehv0shhco.pdf

Controlled positioning of analytes and cells on a plasmonic platform for glycan sensing using surface enhanced Raman spectroscopy

Mn(II) removal from aqueous solutions by Co/Mo layered double hydroxide: Kinetics and thermodynamics

The limit of detection of 4-nitrothiophenol adsorbed onto the surface of a platform fabricated by nanosphere lithography is investigated by surface-enhanced Raman spectroscopy. Critical factors suc...

Towards attomolar detection using a surface-enhanced Raman spectroscopy platform fabricated by nanosphere lithography

Bundles of single-walled carbon nanotubes (SWCNTs) prepared by plasma torch method and further purified, are deposited over a glass coverslip to estimate the spatial resolution of tip-enhanced Rama...

Lagugné-LabarthetFrançois

Papers

Towards attomolar detection using a surface-enhanced Raman spectroscopy platform fabricated by nanosphere lithography

High-resolution Raman imaging of bundles of single-walled carbon nanotubes by tip-enhanced Raman spectroscopy