Laser pulling

In order to reduce peak broadening in the nano-ESI needle attached to the nano-LC column, the use of packed needles has been promoted. Gatiin et al. [58] reports the use of 100-pm-ID fused-silica in-needle packed columns (10-pm particles) with a laser-pulled tip with a diameter of -2 pm. Figeys and Aebersold [59] reported the use of such in-needle RPLC columns for the LC-MS analysis of tryptic digests in combination with a nucrofluidic device to generate a nanoflow solvent gradient via electroosmotic flows. 

Fiuther developments of nano-LC comprise further reduction of coltunn inner diameter and the use of smaller particles to enhance the separation efficiency. Some examples of these developments are the use of a 150-pm-ID in-needle coltunn with a 0.3-0.5-pm-ID laser-pulled emitter tip, packed with 1-pm particles, and operated at flow-rates of <50 nl/min [60], and the ttse of long 15-75-pm-ID nano-LC columns, packed with 3-pm particles, and operated at flow-rates as low as -20 nl/min [54]. 

This section discusses the fabrication of microelectrodes with diameters of a few micrometers to tens of nanometers using a laser-pulled technique. The methods discussed focus on the fabrication of platinum (Pt) ultramicroelectrodes (UMEs) sealed in... 

Figure 6.3.3.1 Diagram of the P-2000 laser-puUer setup for the fabrication of Pt laser-pulled UME. The secured quartz capillary is connected via a rubber joint to a machine metal tube that is connected to a vacuum pump with a Y-joint. Two homemade stoppers are added to the sleds of the puller.

This section has described the fabrication of sub 100 nm electrodes based on a laser-pulling technique. Because laser-pulled UMEs with an inlaid disk geometry require a mechanical sharpening step, micrometer to submicrometer dimensions might be the practical limit for electrodes fabricated with this technique. If an inlaid disk is not a requirement, the lower limit of electrode size can be extended to the 10 nm region by using HF-etching techniques to expose a conical surface. 

Mezour, M. A., M. Morin, and J. Manzeroll, Fabrication and characterization of laser pulled platinum microelectrodes with controlled geometry. Anal. Chem., Vol. 83, 2011 pp. 2378-2382. 

When the tension has spread a length (t) along the cylinder, thermal fluctuations over this length have been pulled out. The area stored in these fluctuations scales as Rk T/K. Thus, the membrane is pulled into the trap with a velocity V d(/l /i )/dt ( BT/K)d< /df. The power spent by the laser pulling the membranes is — 2nRl,v. Equating this power with the one dissipated in the fluid, P r v/Rf R - (t), one finds from... 

The possibility of AEM imaging of laser-pulled, polished nanoelectrodes was shown recently. Although a needle-shaped electrode may not look like a suitable AEM substrate (Figure 15.4a), imaging polished Pt and Au electrodes as small as 20 nm radius both in air and in liquids is... 

B. Preparation and electrochemical response of 1-3 mn Pt disk electrodes. Anal. Chem. 2009, 81, 5496-5502. (g) Laforge, F. O., Velmumgan, J., Wang, Y, Mirkin, M. V. Nanoscale imaging of surface topography and reactivity with the scanning electrochemical microscope. Anal. Chem. 2009, 81, 3143-3150. (h) MauzeroU, J., LeSuer, R. J. Laser-pulled ultramicroelectrodes. In Handbook of Electrochemistry,... 

Keywords— nanopipette, laser pulling, living cell, scanning probe microscope (SPM), patch-clamp. 

Fig. 2 Stages of nanopipette shaping by laser pulling. Photos are taken from video shooting the pulling process...

Mauzeroll J, LeSuer RJ (2007) 6.3.3-Laser-pulled uHramicroelectrodes. In Zoski CG (ed) Handbook of electrochemistry. Elsevier, Amsterdam, pp 199-211... 

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