Hexamethyldisilazane Modified Paper as an Ultra-sensitive Platform for Visual Detection of Hg2+, Co2+, Zn2+ and the Application to Semi-quantitative Determination of Hg2+ in Wastewater

The present article reports the application of hexamethylsilazane (HMDS) modified filter paper for ultrasensitive detection of Hg2+, Co2+ and Zn7+. By chemical vapor deposition of HMDS, a highly hydrophilic filter paper was fabricated to a low wetting (hydrophobic) substrate. The water contact angle (theta) of modified paper was similar to 128 degrees, whereas scanning electron and atomic force microscopy confirmed the surface modification. Using chromogenic reagents, a one-step assay for aforementioned ions was demonstrated onto pristine as well as hydrophobic paper. The assay was completed in less than 10 min and the end-result was in form of a color change that could be easily read by the naked eye. The limit of detection on modified paper was 0.5 ppb, which was 5-order of magnitude superior to that observed on pristine paper. The proposed method was successfully applied for semi-quantitative determination of Hg2+ ions in real wastewater samples.