Surface-enhanced resonance Raman scattering in optical tweezers using co-axial second harmonic generation

Optics Express (Impact Factor: 3.49). 06/2005; 13(11):4148-53. DOI: 10.1364/OPEX.13.004148
Source: PubMed


Silica particles were partially coated with silver, and a suitable chromophore, such that they could be simultaneously trapped within an optical tweezers system, and emit a surface-enhanced resonance Raman scattering (SERRS) response. A standard 1064 nm TEM00 mode laser was used to trap the bead whilst a frequency doubling crystal inserted into the beam gave several microwatts of 532 nm co-linear light to excite the SERRS emission. The con fi guration has clear applications in providing apparatus that can simultaneously manipulate a particle whilst obtaining surface sensitive sensory information.

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Available from: Miles John Padgett, Oct 03, 2015
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    • "In a similar vein, optical tweezers have often been used to investigate a variety of materials. Examples include the stretching of DNA [8], manipulating sub-cellular organelles [9], accurately placing nanorods across metallic contacts [10], positioning microspheres into photonic crystal template structures [11], measuring the Raman spectra of trapped particles [12] and monitoring mechanotransduction within living cells [13]. One of the key benefits of optical tweezers over many other force measurement techniques is that optical microscopy can be used at the same time as force measurement, ensuring that the desired area of the sample is being investigated. "
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    ABSTRACT: In this paper we demonstrate the optical assembly and control of scanning probe microscopy (SPM)-like probes, using holographic optical tweezers. The probes are formed from cadmium sulphide rods and silica microspheres, the latter providing explicit trapping handles. Calibration of the trap stiffness allows us to use a precise measure of probe displacement to calculate the applied forces. We demonstrate that the optically controlled probe can exert a force in excess of 60 pN, over an area of 1⇥10−13 m2, with a force sensitivity of 50 fN. We believe that probes similar to the ones presented here will have applications as nanotools in probing laser-sensitive cells/materials.
    New Journal of Physics 02/2009; 11:023012. DOI:10.1088/1367-2630/11/2/023012 · 3.56 Impact Factor
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    ABSTRACT: The observation of an unusual light-induced agglomeration phenomenon that occurs besides the trapping of the gold nanoparticles aggregates (GNAs) has been observed. The observed agglomerate has a 60-100 µm donut-shaped metal microstructure with the rate of formation dependent on the laser power used. In this paper, the forces involved and the mechanism of this further agglomeration phenomenon are analyzed in detail. The observed trapping can partially be explained by a model including the optical radiation force and radiometric force. However, the light-induced agglomeration cannot be explained by optical trapping alone as the size of the agglomerate is much greater than the waist of the Gaussion beam used in the optical trapping. Hydrodynamic drag force induced by the laser heating is also considered to play a role. Besides these forces, the mechanism of light-induced agglomeration is attributed to ion detachment from the surface of the nanoparticles/aggregates due to light illumination or heating. This is supported by the observation of reversible conductivity changes in the nanoparticle/aggregate solution upon laser illumination or direct heating. Light-induced agglomeration can be useful in the design and fabrication of microstructures from nanomaterials for various device applications.
    Proceedings of SPIE - The International Society for Optical Engineering 01/2006; 6131. DOI:10.1117/12.646308 · 0.20 Impact Factor
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    ABSTRACT: One of the most promising ways to study the biochemistry of single floating cells is to combine the techniques of optical tweezers and Raman spectroscopy (OTRS). This can reveal the information that is lost when ensemble averages are made over cell populations, like in biochemical assays. However, the interpretation of the acquired data is often ambiguous. Indeed, the trapped living cell continues to move and rotate in the optical trap not only because of the Brownian motion, but also because of its inherent biological motility and the variation of its shape and size. This affects both Rayleigh and Raman light scattering. We propose the use of Rayleigh scattering to monitor the growth of a single optically trapped yeast cell, while OTRS measurements are being performed. For this purpose, we added a quadrant photodiode to our OTRS setup. The cell orientation in the optical trap is shown to vary as the cell growth proceeds, especially when it becomes asymmetrical (budding) or it changes its size or shape considerably (living and growing cell). Control experiments, performed using heat-treated cells and polystyrene beads, confirm that this behavior is a consequence of the cell growth. These measurements have to be taken into account in the interpretation of Raman spectra so as not to incorrectly attribute variations in the spectra to change in the biochemical constituents of the cell if they are in fact due to a change of the orientation of the cell in the trap.
    Proceedings of SPIE - The International Society for Optical Engineering 01/2006; 6326. DOI:10.1117/12.679371 · 0.20 Impact Factor
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