This invention relates to Synthesis of biogenic ZnO and TiO2 integrated graphene oxide-based nanocomposite (GO-ZnO-TiO2) and its photocatalytic performance.
BACKGROUND OF THE INVENTION
US10888845B1 A composite photocatalyst, a method of producing said composite photocatalyst, a method of degrading an organic pollutant using the composite photocatalyst, and a method of producing hydrogen using the composite photocatalyst. The composite photocatalyst includes graphene, tungsten oxide, a metal boride, and a metal hydroxide. The photocatalyst is capable of degrading an organic pollutant when exposed to light. The photocatalyst is also capable of producing hydrogen from water when exposed to light under suitable conditions.
Research Gap : ZnO and TiO2 nanoparticles are used to incorporate in graphene oxide. An environmentally friendly and efficient synthesis of ZnO and TiO2 nanoparticles using Shorea robusta leaves extract. The final nanocomposite (GO-ZnO-TiO2) is used in the degradation of toxic dye (Rhodamine B).
US20180264440A1 a composite photocatalyst, preparation and use thereof are disclosed. The composite photocatalyst is composed of metal oxide and quantum dot material. Based on the photocatalyst, the percentage content of the metal oxide is from 80 to 99.99% by mass, and the percentage content of the quantum dot material is from 0.01 to 20% by mass. The metal oxide is zinc oxide or titanium oxide. The quantum dot material is graphene quantum dot or carbon quantum dot. The preparation is that the metal oxide and quantum dot material are stirred, mixed, ultrasonicated and dried in sequence, and the photocatalyst is obtained. Compared with other photocatalysts, the catalyst has higher catalytic efficiency and faster catalytic rate for Rhodamine B and provides more sufficient and more comprehensive utilization of sunlight.
Research Gap: Graphene oxide is used instead of quantum dots. The final composite is prepared ultrasonically but the constituent nanoparticles are biogenic.
KR101945818B1 discloses A composite comprising a metal component supported on a graphene, a method of making the composite, and the use of the composite. The complex can be usefully used for removing contaminants.
Research Gap: The more efficient and biogenic metal oxides are incorporated in the synthesis of final photo-catalyst.
SUMMARY OF THE INVENTION
Water is a vital resource for life on Earth as well as human growth. Many life-threatening problems result from the introduction of organic and inorganic pollutants into natural water systems. In the degradation of organic contaminants, nanotechnology has received a lot of interest. Organic dyes can be degraded in water or wastewater using graphene and metal oxide based nanomaterials. The human body is harmed by rhodamine B. When it is mixed with food or water, it enters the body and causes oxidative stress in cells and tissues; it may also cause liver malfunction or cancer, and when consumed in large amounts over a short period of time, it causes acute poisoning. The physical or chemical methods used in the synthesis of nanoparticles are suffered with the use of harmful chemicals, poor efficiency and high cost. The use of plant-based extract prepared from leaves, stem, root, floral parts, peels, seed etc in the synthesis of inorganic nanoparticles is an eco-friendly, cost-effective and efficient technique. The introduction of active components into structural system of metal oxides acts as capping, reducing and stabilizing agents. In this work, we have used the leaves extract of Shorea robusta in the synthesis of ZnO and TiO2 nanoparticles. These nanoparticles are ultrasonically mixed with graphene oxide to form GO-ZnO-TiO2 photo-catalyst. GO-ZnO-TiO2 catalyst is used in the degradation of toxic Rhodamine B under ultra-violet light.
DETAILED DESCRIPTION OF THE INVENTION
Synthesis of graphene oxide:
Graphene oxide is synthesized using modified Hummer’s method. In a 1000 mL volumetric flask, graphite flakes (0.5 g) and sodium nitrate (NaNO3) (2 g) were mixed in 23 mL of conc. H2 SO4 under constant shake at temperature below 5OC.
Then the mixture is shaked for 4 h under same temperature and now added 3 g of potassium permanganate (KMnO4). Maintain the temperature of the content below 150C. Mixture is diluted in into 50 ml of double distilled water and stirred for 2 h.
The temperature of the content is increased to 35°C and again stirred for 2 h. For 10-15 minutes, the aforesaid combination is held in a reflux system at 98°C. Change the temperature to 30°C after 10 min for a brown-colored solution.
After 10 min, increase the temperature to 25°C and keep it there for 2 hours. Finally, 10 mL H2 O2 is added to the solution, changing the colour to a yellow. In two separate beakers, 50 mL of water is added, and an equal amount of the produced solution is added and agitated for 1 h.
The mixture is then left undisturbed for 3-4 hours, after which the particles settle to the bottom. The resultant mixture is centrifuged multiple times, first with 10% HCl, then with deionized water, until it forms a gel-like substance. The gel-like substance is vacuum dried for more than 6 hours at 60°C to produce GO powder.
1. Preparation of leaves extract:

2. Synthesis of ZnO nanoparticles

3. Synthesis of TiO2 nanoparticles

4. Synthesis of GO-ZnO-TiO2 photo-catalyst:

5. Photo-catalytic activity of GO-ZnO-TiO2:
The photo-catalytic activity is carried out under ultra-violet radiation (mercury vapour lamp; 175 w) with different paparmeters such time, dosage, concentration, pH and temperature. A definite amount of GO-ZnO-TiO2 is mixed with 100 ml of dye containing solution, and this content placed under suitable ultra-violet radiation shake. After completion the reactions, the concentration of dye is detected in the filtrate using UV-Visible spectrophotometer. The overall photo-catalytic study is shown as below:

Advantages of the Invention
? Efficient, low-cost and eco-friendly synthesis.
? Waste leaves are used in the synthesis of nanoparticles.
? Highly efficient water remediation technique.
? Applicable in large scale operations.

We Claim:

1. A method of Synthesis of biogenic ZnO and TiO2 integrated graphene oxide-based nanocomposite (GO-ZnO-TiO2) comprising the steps of:
Preparing of leaves extract;
Synthesising of ZnO nanoparticles;
Synthesising of TiO2 nanoparticles;
Synthesising of GO-ZnO-TiO2 photo-catalyst; and
Photo-catalytic activity of GO-ZnO-TiO2.
2. The method as claimed in claim 1, wherein In a 1000 mL volumetric flask, graphite flakes (0.5 g) and sodium nitrate (NaNO3) (2 g) were mixed in 23 mL of conc; and H2 SO4 under constant shake at temperature below 5OC.
3. The method as claimed in claim 1, wherein the mixture is shaked for 4 h under same temperature and now added 3 g of potassium permanganate (KMnO4); and Maintain the temperature of the content below 150C; and Mixture is diluted in into 50 ml of double distilled water and stirred for 2 h.
4. The method as claimed in claim 1, wherein the temperature of the content is increased to 35°C and again stirred for 2 h. For 10-15 minutes, the aforesaid combination is held in a reflux system at 98°C; and Change the temperature to 30°C after 10 min for a brown-coloured solution.
5. The method as claimed in claim 1, wherein after 10 min, increase the temperature to 25°C and keep it there for 2 hours. Finally, 10 mL H2 O2 is added to the solution, changing the colour to a yellow; in two separate beakers, 50 mL of water is added, and an equal amount of the produced solution is added and agitated for 1 h.
6. The method as claimed in claim 1, wherein the mixture is then left undisturbed for 3-4 hours, after which the particles settle to the bottom; and the resultant mixture is centrifuged multiple times, first with 10% HCl, then with deionized water, until it forms a gel-like substance; and the gel-like substance is vacuum dried for more than 6 hours at 60°C to produce GO powder.