טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentBen Refael Alon
SubjectTransient Phenomena in the Infrared Spectra of Graphitic
Carbon Nitride Systems
DepartmentDepartment of Chemical Engineering
Supervisor Professor Yaron Paz
Full Thesis textFull thesis text - English Version


Abstract

Graphitic carbon nitride (gCN) has attracted an increasing interest due to its promising photoactive properties that may be potentially applied in the areas of photocatalysis, water splitting and photovoltaics. While its preparation is inexpensive and facile, it was found that minor changes in its preparation scheme might affect its properties considerably.

In this thesis a new method is presented, developed in our group, for studying transient changes in photoactive materials, specifically gCN, following photonic excitation. This method is characterized by the ability to obtain photo-induced changes in the Fourier transform infrared spectroscopy (FTIR) spectrum of the material at a temporal resolution of a few nanoseconds. By performing nanosecond time-scale measurements, one can identify localized phenomena in photoactive samples. The method is quite different from conventional FTIR, where the temporal resolution is in the order of seconds.

Graphitic carbon nitride is an excellent model system to studying the just-developed technique, as it is a photoactive material having well-defined FTIR spectrum and absorbs the excitation light at 355 nm wavelength. Intriguing spectral changes were revealed by introducing gCN to the time resolved-FTIR (TR-FTIR) technique. These include specific spectral changes beginning immediately after excitation which decay within up to 200 nanoseconds. The changes are not only functional-group dependent but also depend upon the preparation scheme (in particular preparation temperature) as well as upon surface treatment.

In this thesis, TR-FTIR measurements, in conjunction with standard analytical methods (such as x-ray diffraction, UV to visible light absorption and reflectance etc.) were performed and the results were compared to photocatalytic activity of the different types of gCN, by performing light induced degradation of p-nitrophenol. In addition, a nanocomposite of gCN with an insulator was procured, of which intriguing semiconductor-insulator interactions were discovered by implementing the TR-FTIR technique.