Nanoscale Data Recording on an Organic Monolayer Film

Abstract

The electrochemical measurements were conducted using a three-electrode cell at 25 C. A Pt wire and an Ag/AgCl (in saturated KCl) were used as the counter and reference electrodes, respectively. The carbon working electrode was polished with 1, 0.3, and 0.05 lm Al 2 O 3 paste, and washed ultrasonically in Millipore water (18 MX cm). The working electrode was brushed with a catalyst ink as described previously [14]. Solutions of 0.5 M H 2 SO 4 and 2.0 M CH 3 OH in 0.5 M H 2 SO 4 were stirred constantly and purged with nitrogen gas. All chemicals used in this study were of analytical grade. The electrochemical experiments were performed using an AUTOLAB (Eco Chemie). Voltammetry was performed over the potential range~0.1±0.6 V versus NHE (NHE = normal hydrogen electrode) to identify the properties of the Pt-based catalyst in H 2 SO 4 .For a membrane-electrode assembly (MEA) of DMFC, the anode (supported catalysts prepared using hollow graphitic nanoparticles or commercial catalyst) and cathode (Pt black, Johnson-Matthey) catalyst layers were formed on teflonized carbon paper (TGPH-090) substrates using catalyst inks containing the appropriate weight percent of a Nafion ionomer solution (Aldrich). The MEA for unit cell tests were fabricated by pressing the as-prepared cathode and anode layers onto both sides of a pre-treated Nafion 117 electrolyte membrane at 110 C and 800 psi (= 5.5 MPa) for 3 min. The membrane was pretreated by boiling in 3 wt.-% H 2 O 2 for 1 h followed by 0.5 M H 2 SO 4 for 1 h. The cell performance was evaluated in a DMFC unit cell with a 2 cm 2 cross-sectional area, and was measured using a potentiometer (WMPG-3000), which recorded the cell under a constant current. Both the fuel and oxidant flow paths were machined into graphite block end plates, which also served as the current collectors. The cell temperature was maintained using the heating lines embedded into each cell housing. A 2 M methanol solution with a flow rate of 1 cm 3 min ±1 was supplied using a Maxterflex liquid micropump and a dry O 2 flow was regulated at 500 cm 3 min ±1 using a flow meter. Widely acknowledged as a critical technology in the development of information technology, nanometer-scale data recording has been thoroughly explored.[1±8] Virtually all the factors that may improve the technology have received much attention.[9±13] The choice of medium used when utilizing scanning tunneling microscope (STM) in ultra-high-density information storage is, doubtlessly, a worthy topic; [14] a good medium makes the process cheaper, more predictable, and more easily manipulated. Due to their controllable molecular structures, low price, and abundant supply, organic functional materials have long attracted scientists' attention. Yet, in traditional methods, these materials usually depend on tetracyanoquinodimethane (TCNQ)±metal charge-transfer complexes, [15±17] in which organic molecules are used as electron acceptors and metals are used as electron donors. The problem of these organic± COMMUNICATIONS

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