An FTIR study of hexamethylenetetrammine in porous silicon

In this work the results of an infrared study of porous silicon (PS) single layers and superstructures exposed at room temperature to air with saturated hexamethylenetetramine (urotropin) vapor for different exposure time are reported. It is shown that significant adsorption is achieved even at very low urotropin concentration (10-7 M). In the case of a PS Fabry-Perot structure an enhancement of the intensities of the infrared absorption bands up to two orders of magnitude has been measured. Besides, the interaction of the urotropin induces also the partial oxidation of PS in air that increases with the exposure time. The rate of oxidation is higher than for exposure to pure air but lower than for exposure to air with saturated vapor of other organic molecules (e.g. pyridine). A possible applications of PS systems to the detection of urotropin vapor is suggested.