Nanometer-sized glass-sealed metal ultramicroelectrodes (UMEs) have been prepared using a laser-based micropipet puller. The tip was exposed to solution either by etching away a small portion of glass insulator or by micropolishing. The characterization of the UMEs was carried out by a combination of steady-state voltammetry, scanning electron microscopy (SEM), and scanning electrochemical microscopy (SECM). The cyclic voltammograms obtained have a regular shape with very small capacitive and resistive background. The effective electrode radii obtained from voltammetry were between 2 and 500 nm. From the SEM micrographs, the shape of polished tips appears to be close to a microdisk, while the geometry of etched electrodes is closer to conical. Accordingly, the SECM current-distance curves (i T -d) obtained with polished electrodes fit well the theory for a disk-shaped tip, while a 20-nm-radius etched electrode was shown to be a fairly sharp cone with a height-to-radius ratio of about 2.5. The experimental data were compared to the theory developed for disk-shaped, conical, and recessed tips to demonstrate suitability of the produced electrodes for quantitative electrochemical experiments. The prospects of steady-state measurements of the rates of fast heterogeneous reactions are discussed. Submicrometer-sized ion selective electrodes (ISEs) were prepared by coating etched Ag tips with silver iodide. The concentration response of such ISEs remained stable and linear after coating of the ISEs with protective Nafion film.

Submicrometer-size thermocouples at the tip of gold-coated glass micropipettes containing a platinum core were produced and tested. The response time of such thermocouples measured with different techniques appeared to be not bigger than a few microseconds. The calculations indicate that the spatial selectivity of this new class of thermocouple devices can be less than 2 pm along the pipette and less than 50 nm across the pipette. The suitability of this thermocouple for light intensity measurements with micrometer spatial resolution is demonstrated by measuring the focused beam of an argon-ion laser. In addition, such thermocouples are intrinsically suitable for applications in scanned probe microscopies. All these unique advantages make the pipette thermocouples a new and promising sensor in a variety of applications.

Atomic force microscopy (AFM) with tuning fork feedback is the best method of AFM imaging known today. This presentation will describe the operation of this feedback mechanism in liquid. This allows for live cell AFM and NSOM operation in physiological media with high Q factors and without severe damping effects or any optical or mechanical constraints or interference. The extension of this frequency modulation feedback mechanism to tuning fork based liquid operation allows for scanned probe microscopy (SPM) cellular imaging fully integrated with any optical microscope including upright, 4 pi or standard Raman microprobes. It also will be shown that water immersion objectives can now be used with SPM and that these new directions allow for the first time live cell bioimaging with NSOM in spite of the stiff cantilevers that are generally associated with NSOM probes. The advances reported in this presentation, along with additional innovations in probe and scanner developments, allow for the dream of multiprobe NSOM/SPM to be implemented in physiological media. The results of these efforts portend important advances in the application of SPM in structural and functional bioimaging.