We report on the use of a novel organometallic precursor for laser-directed chemical vapor deposition of platinum films. We demonstrate their optical transparency and their bulk-platinum-like electrochemical response. The effects of moderate temperature annealing in oxygen and electrochemical cycling in H2SO4 on their electrochemical and optical properties are related. Based on the appearance of scanning electron micrographs and their enhanced transparency, these films would seem to be similar to those produced by photoelectrodeposition.Highly transparent, electrically conducting metal films and microstructures would seem to be ideal for directly using UV-visible (1) and infrared spectroscopy (2) to study and exploit electrochemical, catalytic, charge transfer, photochemical, and mechanical processes at electrode/ metal surfaces. Because it's electrochemical and catalytic properties are well documented, platinum was the metal of choice for our initial studies of light transmitting electrodes. In this paper we describe the preparation of suitable platinum films using laser-directed chemical vapor deposition (LCVD) and their characterization as electrodes for cyclic voltammetry. Our goal with this paper is to demonstrate that we have prepared metal films with properties appropriate for the above studies.Light transmitting platinum films have been prepared previously (3-6) and characterized with respect to various applications. An important study by Heller and coworkers (3) describes films which were prepared by photoelectrodeposition, and their transparency was attributed to microscopic porosity. Deposited from dilute aqueous HC104 solutions of PtO~ onto InP semiconductor substrates, these platinum films would not be generally applicable for spectroelectrochemistry because of the absorption of the substrate. Other workers (4) have utilized RF/dc sputtering to deposit semitransparent platinum films with a thickness of 10 nm and an average surface roughness of 1 nm. No optical data were presented for these sputtered films although cyclic voltammetry studies demonstrated that their electrochemical properties were similar to those of bulk polycrystalline platinum disk electrodes. There have been a number of studies and reviews of evaporated (7-10) and sputtered (11, 12) platinum films on mica. One particular study (11) employs a similar set of characterization methods as is reported here and would seem to suggest that our films are in many respects similar to those produced by sputtering onto mica. While accounts of laserdirected (5, 6) and pyrolytic (13) chemical vapor deposition of platinum exist, none explore the use of such films as optically thin electrodes. Given the possible advantages of photolithographic metal deposition for microelectrode array fabrication, and the possible differences between multiphoton dissocfation/ionization-induced chemistry and thermal chemistry (14), our study was focused on the identification of a convenient LCVD organometallic precursor.Heller and co-workers (3) have calculated the t...
285ChemInform Abstract Pt films are prepared by laser-directed CVD using allyl cyclopentadienyl platinum as a precursor. Film deposition only occurs on the irradiated parts of the substrates. The Pt film electrodes are optical transparent and exhibit bulk-Pt-like electrochemical response. The electrodes produce a quasireversible electrode response which approaches reversibility at low scan rates. The effects of annealing in O2 and cycling in H2SO4 on the electrochemical and optical properties are discussed. It is suggested that the fabrication technique may be used to produce two-dimensional and linear microelectrode arrays by employing direct laser writing techniques.
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