Photosensitization effect on visible-light-induced photocatalytic performance of $$\hbox {TiO}_{2}$$/chlorophyll and flavonoid nanostructures: kinetic and isotherm studies

Abstract

Preparation and performance of natural dye-sensitized photocatalysts of TiO 2 are described in this study. Such sensitized nanostructures offer visible-light-reactive systems for the photodegradation of organic pollutants. Natural pigments of chlorophyll and flavonoid extracted from parsley leaves and Curcuma longa roots are grated on TiO 2 nanoparticles as photosensitizers using an incipient wetness impregnation method. The as-prepared samples are structurally characterized by combined techniques, such as X-ray diffraction, scanning electron microscopy and Fourier transform infrared. The diffuse reflectance UV-Vis spectra are also used to investigate band-gap energies. The resultant band-gap energies confirm the ability of visible light absorption and thereby the ability of more efficient generation of photoexcited charge-carriers. The photocatalytic performance of dye-sensitized nanoparticles is tested in terms of decolourization efficiency of MB dye as a function of involved operating parameters including reaction time, amount of catalyst, initial MB concentration and pH. Both samples show the excellent photocatalytic efficiencies relevant to the red shift generated and high absorption of photons in the visible region. However, the highest efficiency is obtained for TiO 2 /chlorophyll catalysts (93%) compared to TiO 2 /flavonoid samples (91%), which is perfectly in agreement with their band-gap energies and visible-light absorption ability. Photodegradation process kinetics is investigated by the Langmuir-Hinshelwood model, while the adsorption equilibrium is described based on Langmuir and Freundlich isotherms.

Photocatalytic reduction of Cr(VI) within mesoporous TiO2 templated and confined with chlorophyll

“…It would be interesting to evoke some reasons why the prepared TiO 2 incorporated with chlorophyll exhibited significant activities for the synergistic reduction of Cr(VI) under visible irradiation. A probable mechanism of synergistic reduction of Cr(VI) over TiO 2 incorporated with chlorophyll has been proposes as follows (Figure S7): Firstly, chlorophyll incorporated in TiO 2 acted as a photosensitizer [17,26] and enhanced the absorption of light under visible light irradiation. Chlorophyll majorly absorbs light energy to excite electron from a ground state to an excited state and the electron can be easily released and transferred to TiO 2 .…”

Bifunctional PVA/ZnO/AgI/Chlorophyll Nanocomposite Film: Enhanced Photocatalytic Activity for Degradation of Pollutants and Antimicrobial Property under Visible-Light Irradiation

“…37 It has a strong affinity to the oxygen atom and can be utilized in photodriven synthetic processes. 16,37 To date, there have been several reports about the exploitation of natural plant extracts such as Chl pigments in dye sensitization. 38 Chl pigments have been suggested to shift the photoresponse of semiconductors to the visible-light region of the electromagnetic spectrum.…”

“…Chlorophyll (Chl), with four pyrrole rings in its chemical structure, is a natural photoabsorbent in green plants . It has a strong affinity to the oxygen atom and can be utilized in photodriven synthetic processes. , To date, there have been several reports about the exploitation of natural plant extracts such as Chl pigments in dye sensitization .…”

“…Chlorophyll (Chl), with four pyrrole rings in its chemical structure, is a natural photoabsorbent in green plants . It has a strong affinity to the oxygen atom and can be utilized in photodriven synthetic processes. , To date, there have been several reports about the exploitation of natural plant extracts such as Chl pigments in dye sensitization . Chl pigments have been suggested to shift the photoresponse of semiconductors to the visible-light region of the electromagnetic spectrum. − Accordingly, Chl is employed to enhance the photocatalytic ability of photocatalytic systems for degradation of pollutant molecules.…”

Photosensitive Hybrid Nanostructured Materials: The Big Challenges for Sunlight Capture

“…Recent reports on this kind of dyes as TiO 2 sensitizers include curcumin, a simple conjugated diketone found in turmeric (Curcuma longa) [70], and anthocyanin [71]. In several works, natural dyes are extracted from the species containing them, e.g., chlorophyll and flavonoid from parsley leaves and turmeric roots [72], chlorophyll and other pigments from cyanobacteria [73], anthocyanin-rich mixture from Vaccinium meridionale Swartz (Andean blueberry) [74], extract from Picramnia sellowii tree [75], or Chlorella pyrenoidosa, a green unicellular alga used as both sensitizer and biotemplate for Fe 3 O 4 -TiO 2 composites [76]. Further examples of organic dyes that have been applied in TiO 2 photocatalysis are malachite green (also known as brilliant green) [77] and Sudan black B, a diazo compound [78], for the degradation of polyethylene and phenol, respectively.…”