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Examines the imaging of silver nanoparticles on graphite basal plane surfaces. Use of electrostatic force microscopy; Determination of the lateral resolution of the images; Accumulation of a positive charge on the silver particles.

Wafer scale (cm2) arrays and networks of nanochannels were created in polydimethylsioxane (PDMS) from a surface pattern of electrodeposited gold nanowires in a master-replica process and characterized with scanning electron microscopy (SEM), atomic force microscopy (AFM), and fluorescence imaging measurements. Patterns of gold nanowires with cross-sectional dimensions as small as 50 nm in hnight and in, tins in width were prepared on silica subsirates using the process of lithographically patterned nanowire electrodeposition (LPNE). Thtie nanowire patterns were then employed at masters for the fabrication of inverse replica nanochannels in a special formulation of PDMS. SEM and AFM measurements verified a linear correlation between the widths and heights of the nanowires and nanochannels over a range of 50 to 500 nm. The PDMS replica was then oxygen plasma-bonded to a glass substrate in order to create a linear array of nanofluidic channels (up to 1 mm in length) filled with solutions of either fluorescent dye or 20 nm diameter fluorescent polymer nanoparticles. Nanochannel continuity and a 99% fill success rate was determined from the fluorescence imaging measurements, and the electrophoretic injection of both dye and nanoparticles in the nanochannel arrays was also demonstrated. Employing a double LPNE fabrication method, this master-replica process was also used to create a large two-dimensional network of crossed nanofluidic channels. [ABSTRACT FROM AUTHOR]

Composite films composed of poly(3,4-ethylenedioxythiophene), PEDOT, and the filamentous virus M13-K07 were prepared by electrooxidation of 3,4-ethylenedioxythiophene (EDOT) in aqueous solutions containing 8 nM of the virus at planar gold electrodes. These films were characterized using atomic force microscopy and scanning electron microscopy. The electrochemical impedance of virus-PEDOT films increases upon exposure to an antibody (p-Ab) that selectively binds to the M13 coat peptide. Exposure to p-Ab causes a shift in both real (ZRE) and imaginary (ZIM) impedance components across a broad range of frequencies from 50 Hz to 10 kHz. Within a narrower frequency range from 250 Hz to 5 kHz, the increase of the total impedance (Ztotal) with p-Ab concentration conforms to a Langmuir adsorption isotherm over the concentration range from from 6 to 66 nM, yielding a value for Kd = 16.9 nM at 1000 Hz. [ABSTRACT FROM AUTHOR]

Surface patterns of single-stranded DNA (ssDNA) consisting of nanoscale lines as thin as 40 nan were fabricated on polymer substrates for nanotechnology and bioaffinity sensing applications. Iarge scale arrays (with areas up to 4 cm2) of ssDNA "nanolines" were created on streptavidin-coated polymer (PDMS) surfaces by transferring biotinylated ssDNA from a master pattern of gold nanowires attached to a glass substrate. The gold nanowires were first formed on the glass substrate by the process of lithographically patterned nanowire electrodeposition (LPNE), and then "inked" with biotinylated ssDNA by hybridization adsorption to a thiolmodified ssDNA monolayer attached to the gold nanowires. The transferred ssDNA nanolines were capable of hybridizing with ssDNA from solution to form double-stranded DNA (dsDNA) patterns; a combination of fluorescence and atomic force microscopy (AFM) measurements were used to characterize the dsDNA nanoline arrays. To demonstrate the utility of these surices for biosensing, optical diffraction measurements of the hybridization adsorption of DNA-coated gold nanoparticles onto the ssDNA nanoline arrays were used to detect a specific target sequence of unlabeled ssDNA in solution. [ABSTRACT FROM AUTHOR]

Electrochemical impedance spectroscopy is used to detect the binding of a 148.2 kDa antibody to a "covalent virus layer" (CVL) immobilized on a gold electrode. The CVL consisted of M13 phage particles covalently anchored to a 3 mm diameter gold disk electrode. The ability of the CVL to distinguish this antibody ("p-Ab") from a second, nonbinding antibody ("n-Ab") was evaluated as a function of the frequency and phase of the measured current relative to the applied voltage. The binding of p-Ab to the CYL was correlated with a change in the resistance, reducing it at low frequency (1-40 Hz) while increasing it at high frequency (2-140 kHz). The capacitance of the CYL was virtually uncorrelated with p-Ab binding. At both low and high frequency, the electrode resistance was linearly dependent on the p-Ab concentration from 20 to 266 nM but noise compromised the reproducibility of the p-Ab measurement at frequencies below 40 Hz. A "signal-to-noise" ratio for antibody detection was computed based upon the ratio between the measured resistance change upon p-Ab binding and the standard deviation of this change obtained from multiple measurements. In spite of the fact that the impedance change upon p-Ab binding in the low frequency domain was more than 100 times larger than that measured at high frequency, the S/N ratio at high frequency was higher and virtually independent of frequency from 4 to 140 kHz. Attempts to release p-Ab from the CVL using 0.05 M HCl, as previously described for mass-based detection, caused a loss of sensitivity that may be associated with a transition of these phage particles within the CVL from a linear to a coiled conformation at low pH. [ABSTRACT FROM AUTHOR]