Near-field Raman spectroscopy of biological nanomaterials by in situ laser-induced synthesis of tip-enhanced Raman spectroscopy tips.
ABSTRACT We report a new approach in tip-enhanced Raman spectroscopy (TERS) in which TERS-active tips with enhancement factors of ∼10(-5)× can be rapidly (1-3 min) produced in situ by laser-induced synthesis of silver nanoparticles at the tip apex. The technique minimizes the risks of tip contamination and damage during handling and provides in situ feedback control, which allows the prediction of the tip performance. We show that TERS tips produced by this technique enable the measurement of spatially resolved TERS spectra of self-assembled peptide nanotubes with a spatial resolution of ∼20 nm.
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ABSTRACT: The vibrational modes of molecules provide an intrinsic contrast mechanism for identifying components in cells, tissues and organisms. When excited by a laser, Raman scattered photons can be spatially correlated providing images of biomolecule distributions. The universality (all particles scatter) of Raman scattering enables in vitro and in vivo characterization. A variety of techniques have emerged based on conventional, surface enhanced, and nonlinear Raman methods that are successfully addressing biomedical challenges. Here we review the advances in Raman microscopy relevant to biomedical applications, focusing on research reported in the literature between 2011-2013.Analytical Chemistry 11/2013; · 5.83 Impact Factor
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ABSTRACT: Advances in nanotechnology have opened up a new era of diagnosis, prevention and treatment of diseases and traumatic injuries. Nanomaterials, including those with potential for clinical applications, possess novel physicochemical properties that have an impact on their physiological interactions, from the molecular level to the systemic level. There is a lack of standardized methodologies or regulatory protocols for detection or characterization of nanomaterials. This review summarizes the techniques that are commonly used to study the size, shape, surface properties, composition, purity and stability of nanomaterials, along with their advantages and disadvantages. At present there are no FDA guidelines that have been developed specifically for nanomaterial based formulations for diagnostic or therapeutic use. There is an urgent need for standardized protocols and procedures for the characterization of nanoparticles, especially those that are intended for use as theranostics.Biotechnology advances 11/2013; · 8.91 Impact Factor
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ABSTRACT: A tip-enhanced Raman spectroscopy (TERS) based on plasmonic lens (PL) excitation is proposed in this work. A PL expected to realize a strong longitudinal electric field focus is designed. The focusing performance of the PL is calculated via finite-difference time-domain (FDTD) simulation and experimentally detected by a scattering-type scanning near-field optical microscope. The PL is introduced to a TERS system as a focusing device. Experimental results with carbon nanotube samples indicate that the Raman scatting signal is significantly enhanced. It proves experimentally that the combination of a PL focused excitation field with a metallic tip in a TERS system is a promising method.Optics Express 04/2013; 21(8):9414-21. · 3.53 Impact Factor