Long Optical Path Length Cell for Thin-Layer Spectroelectrochemistry

Abstract

This paper describes the design and construction of a thinlayer spectroelectrochemical cell with a long optical path length. This cuvette-based cell, which can be reproducibly filled by capillary action, facilitates the use of metal thinfilm electrodes such as those constructed on glass, silicon, and mica substrates. Electrochemical and spectroscopic data are presented that demonstrate the thin-layer behavior of the cell and other important performance characteristics (e.g., optical sensitivity, electrolysis time, and oxygen exclusion capability).Recent studies have exploited the advantages of thin-layer spectroelectrochemistry in explorations of a variety of heterogeneous and homogeneous electrochemical processes. In many instances, optical monitoring is accomplished by irradiating the solution confined in the thin-layer cavity with the propagation axis of the optical beam parallel to the electrode/solution interface. [8][9][10][11][12][21][22][23]25,33,34 The configuration of such long optical path length thin-layer spectroelectrochemical cells (LOPTLCs) yields path lengths of ∼1 cm. These path lengths result in an enhancement in sensitivity of ∼100-fold over that generally achieved using conventional thin-layer cells and optically transparent electrodes that have path lengths of ∼100 µm. A key feature of the LOPTLC is that the long optical path length and large electrode surface area to solution volume ratio provide ample optical sensitivity for the quantitative monitoring of interfacial processes such as adsorption, desorption, and electrocatalysis. [8][9][10][11]14,35 The work described herein stems from interest in applying the LOPTLC to our ongoing investigations of the electrode reactions of monolayers formed by the chemisorption of organosulfur compounds (i.e., alkanethiols, dialkyl disulfides, and dialkyl sulfides) at gold. 35,36 These monolayers are usually adsorbed at thin (200-300 nm) gold films coated onto fragile glass, silicon, and mica substrates by vapor deposition techniques. Many existing LOPTLC designs, however, employ pressure seals between the electrode and the cell for use with vacuum degasfilling procedures, [8][9][10][11][12]14,17,37 requiring mechanically strong electrodes constructed to critical size specifications. The purpose of this paper is to present the design and performance attributes of a LOPTLC that facilitates investigations of electrodes constructed by vapor deposition techniques and can be readily filled without using vacuum procedures. EXPERIMENTAL SECTIONReagents. Potassium ferrocyanide (Fisher), sodium perchlorate (Aldrich), sodium hydroxide (Aldrich), methanol (Fisher, HPLC grade), and ethanol (Quantum, punctilious grade) were used as received. Solutions were prepared using deionized water (Millipore).Electrode Preparation. Glass microscope slides were initially cut into substrates that were 0.99 cm wide and ∼3.5 cm long.

Immunosensing Platforms Using Spontaneously Adsorbed Antibody Fragments on Gold

“…(iv) Thin-Layer Spectroscopy. A long optical path length thin-layer spectroscopy cell was constructed as previously described − Using these cells, experiments were conducted to determine whether the adsorption of Fab‘-SH resulted in an immunosurface with a greater effective epitope density than found with whole molecule antibodies.…”

Rapid Prototyped Optically Transparent Thin‐Layer Electrode Holder for Spectroelectrochemistry in Bench‐Top Spectrophotometers

“…Since the initial OTTLE cell, several cells have been designed based on the conventional cuvette for use with standard spectrophotometers [14][15][16][17][18][19][20][21][22]. A few cells have incorporated an OTTLE into a standard quartz cuvette with the optical beam perpendicular to the electrode [14,15].…”

“…Other designs have positioned the electrode parallel to the optical beam inside a cuvette [17][18][19][20] or a cell of similar dimensions [21]. Orientating the optical beam parallel to the electrode increases the optical path length and therefore improves the optical sensitivity [22].…”

“…Orientating the optical beam parallel to the electrode increases the optical path length and therefore improves the optical sensitivity [22]. The majority of this work involves absorbance based measurements in a long optical path thin-layer cell (LOPTLC) [17][18][19][20][21][22]. However, pseudo-thin-layer, long optical path cells have also been designed for use with standard spectrophotometers, including one designed for both absorbance and fluorescence measurements.…”

Spectroelectrochemistry: In s itu UV ‐visible Spectroscopy

“…15 [190,191]. A cell that was specially designed for studying the adsorption of monolayers (see above) is easy to disassemble and clean [192]. A more sophisticated design has since been published [134].…”