Band gap effect on the photocatalytic activity of supramolecular structures obtained by entrapping photosensitizers in different inorganic supports

Abstract

Different metallophthalocyanines and 2,4,6-triphenylpyrylium (TP+) ions were entrapped in different inorganic supports such as Y zeolite, mesoporous MCM-41, TiO2-SiO2 and SiO2 following a specific protocol. The resulting supramolecular structures were characterized by chemical analysis and diffuse reflectance UV-vis measurements. The determination of the band gap on the basis of UV-vis measurements showed that the host is not a spectator in this process and an electronic interaction occurs that lowers the band gap of the support. The XPS measurements were performed with an in situ X-ray photoelectron spectrometer, which can be operated at pressures of up to 1 mbar at the sample. They indicated that the formation of the supramolecular structure generates a stable environment, in which the oxidation state of the metal can still be influenced by reaction of the metal center with gas molecules. The photocatalytic tests carried out in photodecomposition of dipropyl sulfide showed a good correlation between the band gap values and the photocatalytic activity for metallophthalocyanine complexes. It is remarkable that the triphenylpyrylium ion follows the same trend observed for metallophthalocyanines, although it is a different type of photosensitizer.

Embedded Phases: A Way to Active and Stable Catalysts

“…The entrapping of photosensitizers (i.e., metallophthalocyanines and triphenylpyrylium ion) in different inorganic supports, such as Y zeolite, mesoporous MCM-41, TiO 2 -SiO 2 , and SiO 2 was recently reported by Cojocaru et al [110] A relevant de- www.chemsuschem.org crease in the band-gap of these supramolecular ensembles was detected, which suggested the existence of a significant electronic interaction of the photosensitizer with the support. Furthermore, the formation of the supramolecular structure generated a stable environment, in which the oxidation state of the photosensitizer's metal can be influenced by reaction of the metal center with gas molecules.…”

Reduced graphene oxide–CuO nanocomposites for photocatalytic conversion of CO2 into methanol under visible light irradiation

“…along with co-catalyst / photo sensitizers have been demonstrated for the photoreduction of CO2 under the light irradiation [9][10][11][12][13][14][15][16][17][18][19][20][21]. Band gap energy of semiconductors plays an important role to control the photocatalytic activity of nanomaterials and it should be in an appropriate range to absorb the visible light [22]. Most of metal oxide semiconductors are unable to absorb visible light because of their wide band gap.…”

Experimental assessment of the phonon confinement in TiO2 anatase nanocrystallites by Raman spectroscopy

“…Aerogels are complex nanostructured materials with extremely porous structure, low density, very large surface area, and large pores . This special class of strong cross‐linked structures drew attention owing to their applications, such as gas sensors, manufacture of thermal isolators with exceptional properties, photodegradation of polluting organic substances, detection of Cherenkov radiation, and electronic devices . Because of the wide range of applications, the interest for studying nanostructures with high porosity is continuously increasing; therefore, the understanding of the structural particularities at nanoscale might enable the improvement of their performances.…”