Electrical Detection of Amine Ligation to a Metalloporphyrin via a Hybrid SOI-MOSFET

Abstract

A close-packed monolayer of zinc 5,10,15,20-tetrakis(3-carboxyphenyl)porphyrin has been prepared and deposited on the thin native oxide covering the surface of an SOI-MOSFET (silicon-on-insulator metal-oxide-semiconductor field effect transistor) using Langmuir-Blodgett techniques. When the device is exposed to amine vapors in a nitrogen atmosphere, the amine coordinates to the zinc atom. The resulting change in electron distribution within the porphyrin leads to a large change in the drain current of the transistor, biased via a back gate. This change is sensitive to both the amount of amine present and the base strength of the amine. Only very small changes in drain current were observed with a monolayer of free base porphyrin or palmitic acid. After exposure to high pyridine concentrations, the device response saturates, but partially recovers after overnight exposure to flowing nitrogen gas. Interestingly, the device response is instantaneously reset by exposure to visible light, suggesting that photode-ligation occurs. An electrical model for the hybrid device that describes its response to ligand binding in terms of a change in the work function of the porphyrin monolayer has been developed. A transistor response to a few hundred attomoles of bound pyridine can be readily detected. This extreme sensitivity, coupled with the ability to reset the device using light, suggests that such systems might be useful as sensors.

Surface chemistry of porphyrins and phthalocyanines

“…Porphyrin derivatives and their metal complexes find widespread applications in science and technology. Fields closely related to surface science include heterogeneous catalysis [78,79] and electrocatalysis [80], sensor systems [81,82], organic electronics [83,84], and various types of lightharvesting systems [85,86] (see details below).…”

“…These sensors mostly rely on the axial coordination of molecules to the coordinated metal centers, for example in multiporphyrin arrays for colorimetric gas sensing [125][126][127][128][129]. An electrical gas sensor was based on a transistor with the gate electrode covered by a Zn porphyrin layer as the active material [81]. A similar approach was used in NO gas sensors on the basis of hemin on InAs planar resistors [130] and graphene field-effect transistors [82].…”

Selective acetylene detection through surface modification of metal–insulator–semiconductor sensors with alkanethiolate monolayers

“…A common approach for enhancing the selectivity of these sensors, and other metal-oxide-semiconductor capacitor or transistor-like devices, is the application of surface coatings to improve the detection of analytes of interest. Monolayer and thin coatings that bind through analyte-specific interactions have been exploited in the detection of amines [1,2] and complex biomolecules such as penicillin and DNA [3]; however, their utility in modifying the performance of small gas sensors has not been widely studied, likely because of an expected lack of specific interactions. Instead, membrane coatings such as polymers [4] and metal oxides [5] have been applied for the specific detection of hydrogen and light gases.…”

A Novel Porphyrin-Containing Polyimide Nanofibrous Membrane for Colorimetric and Fluorometric Detection of Pyridine Vapor

“…This substance is harmful if inhaled, ingested, or absorbed by the skin because of its toxicity and carcinogenicity [17–19], therefore, a sensitive and rapid detection of pyridine vapor is valuable in industrial and environmental monitoring. Zinc porphyrin was chosen for this study because of its strong affinity with nitrogen ligands to form a five-coordinated complex, which results in measurable changes in its photophysical properties [20–24]. Incorporation of zinc porphyrin fluorophore into a polyimide backbone facilitates pyridine vapor detection in harsh environments because of the mechanical stability, as well as the high thermal and chemical resistance, of polyimide.…”