טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentKaminski Yelena
SubjectSelective Photocatalysis Based on Molecular Recognition
Sites Located at the Vicinity of Titanium
Dioxide Substrates
DepartmentDepartment of Chemical Engineering
Supervisor Professor Yaron Paz


Abstract

The mechanism of photocatalytic reaction on TiO2 is not selective.  This might be a disadvantage when a mixture containing low concentrations of highly toxic substances together with high concentrations of low-toxic organics has to be treated.   Two approaches for obtaining selectivity are presented hereby: “adsorb and shuttle “ approach and “on-site” approach. These approaches are demonstrated through the enhanced photodegradation of diisopropyl methylphosphonate (DIMP), which is a simulant of the nerve agent Sarin.

The “adsorb and shuttle” approach is based on the construction of molecular recognition sites (MRS) anchored on inert domains in the vicinity of photoactive sites. These MRS are designed to chemisorb target molecules and to “shuttle” them to the photocatalytic sites. Here we present a system demonstrating this approach for enhanced photodegradation of DIMP. 1,1-Mercaptoundecanoic acid (MUA) whose proton was substituted by Cu+2 serves as MRS and DIMP is the target molecule. In the “on-site” approach the MRS are located directly on TiO2 (non-patterned substrates). Here the copper ion is used to increase the adsorption of DIMP.

Faster and selective photodegradation of DIMP was obtained due to the effect of the MRS in both cases. For the “adsorb and shuttle” approach, this improvement was by a factor of approximately 6. The “on-site” approach was more sensitive to deactivation .The enhancive factor was harmed by phosphorous-containing residues that cover the copper during the photodegradation of DIMP. In contrast, patterned substrates, where the DIMP was degraded away from copper and its phosphonate residues did not cover the copper were hardly deactivated.