Adsorption of Fluorescently Tagged Self-Assembled Monolayers onto Zinc Selenide Thin Films through Microcontact Printing

Self-assembled monolayers (SAMs) are a spontaneously formed, organized, single layer of organic molecules adsorbed onto a surface. SAMs have many applications, one of which is in the development of biosensors. In the current work, polydimethylsiloxane(PDMS) stamps were utilized to microcontact print fluorescein tagged 11-amino-1-undecanethiol SAMs onto zinc selenide thin films. Initial experiments were run using non-tagged 11-amino-1-undecanethiol hydrochloride to determine an alkanethiol concentration for microcontact printing. A 0.3 mM concentration resulted in successful microcontact printing on both ZnSe and gold thin films and a pattern was visualized using steam imaging at a macroscopic level. The formation of self-assembled monolayers was confirmed by contact angle goniometry, with angles changing from 24.9(±1.8)º to 39.7(±2.1)º for ZnSe films and 46(±4.4)º to 61(±2.6)º for gold films. Microcontact printing using a 0.3 mM concentration of 1:9 fluorescein tagged 11-amino-1-undecanethiol to non-tagged 11-amino-1-undecanethiol resulted in a pattern initially visualized under a fluorescent microscope. After an ethanol rinse, the pattern was no longer observed. Steam imaging was inconclusive due to a poorly visualized pattern and contact angles changed from 19.8(±5.3)º to 48.6(±5.6)º.Additional experiments are required to determine the cause for the observed loss of a fluorescent pattern after rinsing with ethanol. Future work utilizing this procedure will enable the formation of patterned, functionalized SAMs which can be used in developing biosensors for disease detection