Evaluation of thermal evaporation conditions used in coating aluminum on near-field fiber-optic probes

Hollars, Christopher W.; Dunn, Robert C.

doi:10.1063/1.1148836

Cited by 29 publications

(21 citation statements)

References 45 publications

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“…Aluminum has superior reflectivity properties in the visible region of the spectrum and, thus, requires the least amount of material to confine excitation light (20). This is important as the overall dimensions of the NSOM probe affects how close the probe aperture can approach the sample surface.…”

Section: Methodsmentioning

confidence: 99%

“…Pinholes in the aluminum coating often indicate the presence of contamination on the pulled fiber (20). It is important to decrease the time between pulling the fiber and getting it into vacuum to reduce the chances of dust attaching to the surface.…”

Section: Methodsmentioning

confidence: 99%

“…Figure 4c, d compares AFM measurements from NSOM tips coated at low and high deposition rates. Clearly, higher rates correspond to smaller grains and smoother coatings which translate into higher film reflectivity (20, 26). These results are summarized in Table 1 which tabulates the mean surface roughness of the aluminum coating under various conditions.…”

Section: Methodsmentioning

confidence: 99%

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Near-Field Scanning Optical Microscopy for High-Resolution Membrane Studies

et al. 2012

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The desire to directly probe biological structures on the length scales that they exist has driven the steady development of various high-resolution microscopy techniques. Among these, optical microscopy and, in particular, fluorescence-based approaches continue to occupy dominant roles in biological studies given their favorable attributes. Fluorescence microscopy is both sensitive and specific, is generally noninvasive toward biological samples, has excellent temporal resolution for dynamic studies, and is relatively inexpensive. Light-based microscopies can also exploit a myriad of contrast mechanisms based on spectroscopic signatures, energy transfer, polarization, and lifetimes to further enhance the specificity or information content of a measurement. Historically, however, spatial resolution has been limited to approximately half the wavelength due to the diffraction of light. Near-field scanning optical microscopy (NSOM) is one of several optical approaches currently being developed that combines the favorable attributes of fluorescence microscopy with superior spatial resolution. NSOM is particularly well suited for studies of both model and biological membranes and application to these systems is discussed.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Near-Field Scanning Optical Microscopy for High-Resolution Membrane Studies

et al. 2012

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“…For the visible region of the spectrum, aluminum is the most reflective, with a skin depth of ~13 nm at a wavelength of 500 nm. The high reflectivity enables confinement of light within the taper region of the probe with only 50-100 nm of aluminum [11]. Figure 9.2 shows magnified views of a typical fiber-optic NSOM probe.…”

Section: Near-field Scanning Optical Microscopy (Nsom)mentioning

confidence: 97%

Near-Field Scanning Optical Microscopy: A New Tool for Exploring Structure and Function in Biology

Dickenson

Mooren

Erickson

et al. 2014

Surface Analysis and Techniques in Biology

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Optical microscopy in the biological sciences has proven invaluable for understanding structure and dynamics in these complicated systems. It is a noninvasive tool that is amenable with fragile samples and is easily implemented under physiological conditions. It also benefits from a wide array of contrast mechanisms that can be exploited to gain detailed insight into sample properties. One limitation, however, concerns spatial resolution, which is limited to approximately half the excitation wavelength by the diffraction of light. Overcoming this limitation has motivated the development of near-field scanning optical microscopy (NSOM) or scanning near-field optical microscopy (SNOM). NSOM uses specially fabricated probes to deliver light down to the nanometric dimension, enabling optical microscopy with a spatial resolution of tens of nanometers. For the biological sciences, NSOM can simultaneously map sample fluorescence and topography with high spatial resolution and single-molecule detection limits. This makes NSOM a powerful new tool for understanding biological structure at the nanometric dimension.

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“…Aluminum coated near-field fiber optic probes are fabricated from 125 m single-mode optical fiber ͑Newport Corp.͒ in either the straight geometry or cantilevered design using a micropipette puller ͑Sutter Instruments, P-2000͒ and home-built evaporation chamber. 20,49 For experiments utilizing straight near-field probes, a custom designed near-field head is utilized to implement the shearforce feedback mechanism. For cantilevered probes, a commercial AFM head ͑Digital Instruments, Dimension͒ is utilized to implement a tapping-mode feedback scheme.…”

Section: Methodsmentioning

confidence: 99%

Probing single molecule orientations in model lipid membranes with near-field scanning optical microscopy

Hollars

Dunn

2000

The Journal of Chemical Physics

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Single molecule near-field fluorescence measurements are utilized to characterize the molecular level structure in Langmuir-Blodgett monolayers of L-␣-dipalmitoylphosphatidylcholine ͑DPPC͒. Monolayers incorporating 3ϫ10 Ϫ4 mol % of the fluorescent lipid analog N-͑6-tetramethylrhodaminethiocarbamoyl͒-1,2-dihexadecanoyl-sn-glycero-3-phosphoethanolamine, triethylammonium salt ͑TRITC-DHPE͒ are transferred onto a freshly cleaved mica surface at low ( ϭ8 mN/m) and high ( ϭ30 mN/m) surface pressures. The near-field fluorescence images exhibit shapes in the single molecule images that are indicative of the lipid analog probe orientation within the films. Modeling the fluorescence patterns yields the single molecule tilt angle distribution in the monolayers which indicates that the majority of the molecules are aligned with their absorption dipole moment pointed approximately normal to the membrane plane. Histograms of the data indicate that the average orientation of the absorption dipole moment is 2.2°( ϭ4.8°) in monolayers transferred at ϭ8 mN/m and 2.4°( ϭ5.0°) for monolayers transferred at ϭ30 mN/m. There is no statistical difference in the mean tilt angle or distribution for the two monolayer conditions studied. The insensitivity of tilt angle to film surface pressure may arise from small chromophore doped domains of trapped liquid-expanded lipid phase remaining at high surface pressure. There is no evidence in the near-field fluorescence images for probe molecules oriented with their dipole moment aligned parallel with the membrane plane. We do, however, find a small but significant population of probe molecules ͑ϳ13%͒ with tilt angles greater than 16°. Comparison of the simultaneously collected near-field fluorescence and force images suggests that these large angle orientations are not the result of significant defects in the films. Instead, this small population may represent a secondary insertion geometry for the probe molecule into the lipid monolayer.

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Evaluation of thermal evaporation conditions used in coating aluminum on near-field fiber-optic probes

Cited by 29 publications

References 45 publications

Near-Field Scanning Optical Microscopy for High-Resolution Membrane Studies

Near-Field Scanning Optical Microscopy for High-Resolution Membrane Studies

Near-Field Scanning Optical Microscopy: A New Tool for Exploring Structure and Function in Biology

Probing single molecule orientations in model lipid membranes with near-field scanning optical microscopy

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