Linker-Enhanced Binding of Metalloporphyrins to Cadmium Selenide and Implications for Oxygen Detection

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• 作者：Albena Ivanisevic ; Arthur B. Ellis ; Gonen Ashkenasy ; Abraham Shanzer ; and Yossi Rosenwaks
• 刊名：Langmuir
• 出版年：2000
• 出版时间：October 3, 2000
• 年：2000
• 卷：16
• 期：20
• 页码：7852 - 7858
• 全文大小：114K
• 年卷期：v.16,no.20(October 3, 2000)
• ISSN：1520-5827

文摘

Adsorption of trivalent metalloporphyrins from nitrogen-saturated chloroform solution onto etched n-CdSecrystals causes a profound reversible quenching of the semiconductor's photoluminescence (PL). The PLresponses due to the presence of M^IIIDMPPCl and M^IIITPPCl (DMPPCl = protoporphyrin IX dimethyl esterchloride; TPP = tetraphenylporphyrin; M = Fe, Mn) exhibit a concentration dependence that can be fitto the Langmuir adsorption isotherm model to yield binding constants of 10^4-10⁵ M^-1. The CdSe surfacemay be modified by adsorption from solution of specifically designed linker ligands (1-4). These ligandsare able to bind to the semiconductor surface through one end and to ligate a heme analogue axially onthe other end. Surfaces derivatized by each of the linkers showed concentration-dependent metalloporphyrin-induced PL changes, corresponding to roughly order-of-magnitude increases in binding constants to 10⁵to 10⁶ M^-1. Films of linker-metalloporphyrin complexes were coated onto the semiconductor substratesand characterized by X-ray photoelectron (XPS) spectroscopy. The linker-metalloporphyrin films can beused as transducers for dioxygen detection. Relative to a nitrogen ambient, the PL of CdSe samples coatedwith 1-3 is reversibly quenched by exposure to oxygen (binding constants of ~1-10 atm^-1; detection limitof ~0.1 atm), while bare CdSe surfaces show no response to dioxygen. These coated CdSe samples werefurther characterized by contact potential difference (CPD) and time-resolved photoluminescence (TRPL),which suggest that oxygen-induced PL changes are due to variations in the electric field present in thesemiconductor substrate.