UV light exposure of aqueous graphene oxide suspensions to promote their direct reduction, formation of graphene–metal nanoparticle hybrids and dye degradation (original) (raw)
Related papers
Applied Sciences
This study presents a novel method for the development of TiO2/reduced graphene oxide (rGO) nanocomposites for photocatalytic degradation of dyes in an aqueous solution. The synergistic integration of rGO and TiO2, through the formation of Ti–O–C bonds, offers an interesting opportunity to design photocatalyst nanocomposite materials with the maximum absorption shift to the visible region of the spectra, where photodegradation can be activated not only with UV but also with the visible part of natural solar irradiation. TiO2@rGO nanocomposites with different content of rGO have been self-assembled by the hydrothermal method followed by calcination treatment. The morphological and structural analysis of the synthesized photocatalysts was performed by FTIR, XRD, XPS, UV-Vis DRS, SEM/EDX, and Raman spectroscopy. The effectiveness of the synthesized nanocomposites as photocatalysts was examined through the photodegradation of methylene blue (MB) and rhodamine B (RhB) dye under artificia...
Eco-Friendly Reduction of Graphene Oxide by Aqueous Extracts for Photocatalysis Applications
Nanomaterials
In the present work, reduced graphene oxide was obtained by green synthesis, using extracts of Larrea tridentata (gobernadora) and Capsicum Chinense (habanero). Graphene oxide was synthesized by the modified Hummers’ method and subsequently reduced using natural extracts to obtain a stable and environmentally friendly graphene precursor. Consequently, the gobernadora aqueous extract was found to have a better reducing power than the habanero aqueous extract. This opportunity for green synthesis allows the application of RGO in photocatalysis for the degradation of the methylene blue dye. Degradation efficiencies of 60% and 90% were obtained with these materials.
Photochemical stability and reactivity of graphene oxide
Journal of Materials Science, 2015
The photoreactivity of graphene oxide (GO) suspensions was investigated with a double aim: i) to give insights into the previously reported photo-reduction process, which allows a partial elimination of the oxygen-containing groups from the 2D graphitic structure; ii) to explore the possible use of GO as photo-activator able to promote the photo-transformation/abatement of organic molecules. To reach these goals and clarify some peculiar aspects of the photochemistry of GO till now obscure or confuse, we synthesized and characterized stable GO suspensions which were then subjected to UV-Vis irradiation for prolonged times. GO underwent partial photoreduction with the release of gaseous molecules and soluble organic species (e.g. carboxylic acid). The mechanisms of photo-reduction occurring under air or N 2 are different, as assessed by the release in solution of diverse soluble molecules. In the presence of oxygen, at long irradiation time, a complete solubilization of the graphenic structures was observed. No difference in the nature and amount of released gases (principally CO 2 and CO) was observed in the oxic or anoxic conditions. The possible use of GO as photo-activator was evaluated by using phenol as probe molecule. GO revealed a double role of photo-activator and reagent in phenol degradation, as competition was assessed between GO self-transformation/reduction and phenol degradation. At prolonged irradiation time a marked reactivity of the photoformed species was observed and the complete degradation was achieved for both organic small molecules formed from GO and the phenol added as probe molecule.
Current Applied Physics, 2011
Novel grapheneeTiO 2 (GReTiO 2 ) composite photocatalysts were synthesized by hydrothermal method. During the hydrothermal process, both the reduction of graphene oxide and loading of TiO 2 nanoparticles on graphene were achieved. The structure, surface morphology, chemical composition and optical properties of composites were studied using XRD, TEM, XPS, DRS and PL spectroscopy. The absorption edge of TiO 2 shifted to visible-light region with increasing amount of graphene in the composite samples. The photocatalytic degradation of methyl orange (MO) was carried out using grapheneeTiO 2 composite catalysts in order to study the photocatalytic efficiency. The results showed that GReTiO 2 composites can efficiently photodegrade MO, showing an enhanced photocatalytic activity over pure TiO 2 under visible-light irradiation. The enhanced photocatalytic activity of the composite catalysts might be attributed to great adsorptivity of dyes, extended light absorption range and efficient charge separation due to giant p-conjugation system and two-dimensional planar structure of graphene.
Journal of King Saud University - Science, 2021
Synthetic dyes are widely used as coloring agents in the textile, food, paper, leather, and printing industries. Sustainable removal of these dye molecules is a challenging task due to their toxic nature to the environment as well as for living organisms. In the present study, a simple hydrothermal method is carried out to synthesize reduced graphene oxide (rGO) using the leaves extract of Murraya koenigii. Further, different characterization techniques such as X-ray diffraction, Raman spectroscopy, UV-vis spectroscopy, and Fourier transform infrared spectroscopy (FT-IR) are used to confirm the physicochemical properties of synthesized rGO. Raman analysis confirms the reduction of graphene oxide by the increase in I D /I G ratio significantly. Field emission scanning electron microscopy (FE-SEM) and Transmission electron microscopy (TEM) analysis show well-exploited rGO morphology. Further, newly synthesized rGO is used as a photocatalyst for the removal of methylene blue (MB) and methyl orange (MO) dyes. UV-vis spectrophotometer is used for monitoring the degradation efficiency. Catalyst MKrGO shows 80% of MO and 77% of MB degradation within 120 min of sunlight exposure. The sustainability of this catalyst is checked by recyclability in five subsequent degradation cycles and noticed a stable and significant degradation activity.
Graphene-based nanostructures for enhanced photocatalytic degradation of industrial dyes
Emergent Materials, 2020
Graphene oxide (GO) is an sp 2-bonded single atomic layer of carbon atoms with plenty of oxy-functional groups at its surface. The occurrence of large surface area (~2630 m 2 /g), surface functionalities, electronic, and mechanical properties make graphene-based compounds favorable for remediation applications. We report the synthesis and comparative dye degradation efficiencies of two titania (TiO 2)-based composites, GO-TiO 2, and reduced GO-TiO 2 (rGO-TiO 2). Both the composites are characterized using SEM-EDX, TEM, FTIR, and XRD. We study the photocatalysis-mediated degradation of anionic dye Eosin Yand cationic dye Methylene blue (MB) in aqueous dispersions under white light and UV irradiation. Our results demonstrate that rGO(10 wt%)-TiO 2 composite shows the maximum degradation (~95%) of both 10 ppm Eosin Y and MB dyes in the aqueous dispersion. The enhanced photocatalytic activity of rGO-TiO 2 composites as compared to TiO 2 and GO-TiO 2 can be credited to the presence of efficient electron shuttling from the conduction band of TiO 2 into the conductive regions of graphene which eventually restricts further recombination of e − /h + pairs. Furthermore, the effects of solution pH and TiO 2 loading are studied on the degradation process.
Catalysts
In this study, a green and facile thermal reduction of graphene oxide using an eco-friendly system of d-(+)-glucose and NH4OH for the preparation of reduced graphene oxide was described. The obtained reduced graphene oxide dispersion was characterized by SEM, Dynamic Light Scattering, Raman and X-Ray Photoelectron Spectroscopy. TiO2 nanoparticles and reduced graphene oxide nanocomposites were successively prepared and used in the preparation of heterogeneous photocatalysts that were characterized by Atomic Force Microscopy and Photoluminescence Spectroscopy and subsequently tested as visible light photocatalysts for the photodegradation of Alizarin Red S in water as target pollutant. Obtained results of photocatalytic tests regarding the visible light photocatalytic degradation of Alizarin Red S demonstrated that the use of reduced graphene oxide in combination with TiO2 led to a significant improvement for both adsorption of Alizarin Red S on the catalyst surface and photodegradati...
Effect of Dissolved Oxygen Content on Photocatalytic Performance of Graphene Oxide
arXiv: Materials Science, 2018
Graphene, a two-dimensional (2D) promising emergent photocatalyst consisting of earth-abundant elements. This study evaluated the potential of graphene oxide (GO) towards photocatalytic degradation of a novel organic dye, Methylene Blue (MB). In this work, photocatalytic activity of graphene oxide (GO), graphene oxide (GO) along with hydrogen peroxide (H2O2) were tested by photodegrading Methylene Blue (MB) in aqueous solution. The resulted GO nanoparticles were characterized by X-ray powder diffraction, Scanning Electron Microscopy, Energy Dispersive Spectroscopy and Fourier Transform Infrared Ray Spectroscopy. The XRD data confirms the sharp peak centered at 2Theta=10.44 degree corresponding to (002) reflection of GO. Based on our results, it was found that the resulted GO nanoparticles along with H2O2 achieved ~92% photodecolorization of MB compared to ~63% for H2O2 under natural sunlight irradiation at pH~7 in 60 min. The influences of oxygen and hydrogen peroxide (H2O2) on the ...
2011
Novel grapheneeTiO 2 (GReTiO 2 ) composite photocatalysts were synthesized by hydrothermal method. During the hydrothermal process, both the reduction of graphene oxide and loading of TiO 2 nanoparticles on graphene were achieved. The structure, surface morphology, chemical composition and optical properties of composites were studied using XRD, TEM, XPS, DRS and PL spectroscopy. The absorption edge of TiO 2 shifted to visible-light region with increasing amount of graphene in the composite samples. The photocatalytic degradation of methyl orange (MO) was carried out using grapheneeTiO 2 composite catalysts in order to study the photocatalytic efficiency. The results showed that GReTiO 2 composites can efficiently photodegrade MO, showing an enhanced photocatalytic activity over pure TiO 2 under visible-light irradiation. The enhanced photocatalytic activity of the composite catalysts might be attributed to great adsorptivity of dyes, extended light absorption range and efficient charge separation due to giant p-conjugation system and two-dimensional planar structure of graphene.
Graphene is a very huge and ultimate material for composite with metals, semiconductors and non metals in recent years, due to its has a unique atom-thick with two-dimensional (2D) structure, excellent physical properties like high conductivity and charge mobility, huge specific surface area, excellent mechanical, thermal and electrical properties. Thus, it has been regarded as an important component for functional materials, especially for developing a variety of catalysts and it has been considered widely as a prominent precursor and a starting material for the synthesis of this processable material. This work describes the synthesis of Graphene oxide (GO) by Modified Hummer’s method and characterization of GO by Ultra violet visible spectroscopy (UV-Vis), UV-visible diffuse reflectance spectroscopy (UV-DRS), X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM) and Energy dispersive spectroscopy (EDX) analysis. The results obtained from the characterization techniques mentioned above is also explained in detailed and evaluation of catalytic application to environmental remedies, such as water purification of degradation of methylene blue under visible light irradiation.