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Design and Fabrication of Fiber-Optic Nanoprobes for Optical Sensing

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ABSTRACT

This paper describes the design and fabrication of fiber-optic nanoprobes developed for optical detection in single living cells. It is critical to fabricate probes with well-controlled nanoapertures for optimized spatial resolution and optical transmission. The detection sensitivity of fiber-optic nanoprobe depends mainly on the extremely small excitation volume that is determined by the aperture sizes and penetration depths. We investigate the angle dependence of the aperture in shadow evaporation of the metal coating onto the tip wall. It was found that nanoaperture diameters of approximately 50 nm can be achieved using a 25° tilt angle. On the other hand, the aperture size is sensitive to the subtle change of the metal evaporation angle and could be blocked by irregular metal grains. Through focused ion beam (FIB) milling, optical nanoprobes with well-defined aperture size as small as 200 nm can be obtained. Finally, we illustrate the use of the nanoprobes by detecting a fluorescent species, benzo[a]pyrene tetrol (BPT), in single living cells. A quantitative estimation of the numbers of BPT molecules detected using fiber-optic nanoprobes for BPT solutions shows that the limit of detection was approximately 100 molecules.

No MeSH data available.


SEM images of a an uncoated nanofiber and b a gold-coated nanofiber.
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Figure 3: SEM images of a an uncoated nanofiber and b a gold-coated nanofiber.

Mentions: A scanning election microscopy (SEM) photograph of one of the nanofibers fabricated by the laser pulling method is shown in Figure 3a. The distal end of the nanofiber is approximately 40 nm. The fiber was pointing away from the evaporation source with an angle of approximately 25°. The tapered end was coated with ~75–100 nm of metal in the thermal evaporator. With the metal coating, the size of the probe tip is approximately 200–250 nm (Figure 3b).


Design and Fabrication of Fiber-Optic Nanoprobes for Optical Sensing
SEM images of a an uncoated nanofiber and b a gold-coated nanofiber.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211233&req=5

Figure 3: SEM images of a an uncoated nanofiber and b a gold-coated nanofiber.
Mentions: A scanning election microscopy (SEM) photograph of one of the nanofibers fabricated by the laser pulling method is shown in Figure 3a. The distal end of the nanofiber is approximately 40 nm. The fiber was pointing away from the evaporation source with an angle of approximately 25°. The tapered end was coated with ~75–100 nm of metal in the thermal evaporator. With the metal coating, the size of the probe tip is approximately 200–250 nm (Figure 3b).

View Article: PubMed Central - HTML - PubMed

ABSTRACT

This paper describes the design and fabrication of fiber-optic nanoprobes developed for optical detection in single living cells. It is critical to fabricate probes with well-controlled nanoapertures for optimized spatial resolution and optical transmission. The detection sensitivity of fiber-optic nanoprobe depends mainly on the extremely small excitation volume that is determined by the aperture sizes and penetration depths. We investigate the angle dependence of the aperture in shadow evaporation of the metal coating onto the tip wall. It was found that nanoaperture diameters of approximately 50 nm can be achieved using a 25° tilt angle. On the other hand, the aperture size is sensitive to the subtle change of the metal evaporation angle and could be blocked by irregular metal grains. Through focused ion beam (FIB) milling, optical nanoprobes with well-defined aperture size as small as 200 nm can be obtained. Finally, we illustrate the use of the nanoprobes by detecting a fluorescent species, benzo[a]pyrene tetrol (BPT), in single living cells. A quantitative estimation of the numbers of BPT molecules detected using fiber-optic nanoprobes for BPT solutions shows that the limit of detection was approximately 100 molecules.

No MeSH data available.