Graphene Oxide Functionalized with Cationic Porphyrins as Materials for the Photodegradation of Rhodamine B

Abstract

Two noncovalent nanohybrids between cationic porphyrin (free-base TMPyP and zinc(II) ZnTMPyP) bearing cationic ( N -methylpyridyl) groups and graphene oxide (GO) were constructed with the aim of generating a photocatalyst active for rhodamine B (RhB) degradation. The obtained materials were thoroughly characterized by steady-state and time-resolved absorption and emission methods, which indicated that metalation of the porphyrin with Zn(II) increases the affinity of the porphyrin toward the GO surface. Photocurrent experiment together with femtosecond transient absorption spectroscopy clearly showed the existence of electron transfer from the photoexcited porphyrin to GO. Both hybrid materials demonstrated higher photocatalytic activity toward RhB degradation as compared to GO; however, ZnTMPyP–GO exhibited more efficient performance (19% of RhB decomposition after 2 h of irradiation). Our data indicate that the presence of Zn(II) in the core of the porphyrin can promote charge separation in the ZnTMPyP–GO composites. The higher degradation rate seen with ZnTMPyP–GO as compared to the TMPyP–GO assemblies highlights the beneficial role of Zn(II)-metalation of the porphyrin ring.

Lerf–Klinowski-type models of graphene oxide and reduced graphene oxide are robust in analyzing non-covalent functionalization with porphyrins

“…In the latter case, the decrease of the fluorescence is more drastic. Emission quenching for neutral porphyrins TAPP and TPPH with graphene-based materials for which interaction is attributed mainly to - stacking interactions was found to be less efficient in comparison to reported earlier fluorescence quenching of cationic porphyrins by GO 47 , 48 . More efficient emission quenching for cationic porphyrins was evidenced by ca.…”

“…Batochromic shift of the Soret bands together with the decrease of the molar absorption coefficients upon addition of GO was previously reported by us for cationic porphyrins 47 , 48 . Interestingly, the spectral changes occurring upon addition of GO to the aqueous solutions of cationic porphyrins were more pronounced than for TAPP and TPPH since approximately ten times lower concentration of GO was required to achieve detectable spectral changes.…”

“…Based on the analysis of the steady-state and time-resolved emission data we thus conclude that the observed decrease of emission intensity in the presence of graphene materials is solely attributed to static quenching. Static quenching as the reason for the observed decrease of the porphyrins fluorescence in the presence of graphene-type materials has been reported previously by us for the related systems 31 , 47 , 48 .…”

Self-Assembled Nanomaterials Based on Complementary Sn(IV) and Zn(II)-Porphyrins, and Their Photocatalytic Degradation for Rhodamine B Dye

“…The first-order rate constant for the degradation of RhB by triad 3 (0.010 min −1 ) is higher than that for triad 2 (0.009 min −1 ), triad 1 (0.008 min −1 ), triad 4 (0.007 min −1 ), triad 6 (0.006 min −1 ), and triad 5 (0.005 min −1 ). These values are impressive compared to other values in the literature [45]. The recovery of these photocatalysts was very simple; we filtered the reaction mixture after the experiments and then washed it with water, followed by drying in air.…”

“…Rhodamine B was one of the 20 dyes detected most frequently in wastewater, and it causes irritation to the skin, eyes, gastrointestinal tract, and respiratory system. As such, there is an urgent need to remove this dye from wastewater [45]. We have evaluated the photocatalytic activities of these nanostructured materials under visible light irradiation for their ability to degrade RhB dye in an aqueous solution.…”