I hereby declare that the contents in this thesis entitled “Green synthesis of metallic nanoparticles using leaf extract of selected silkworm host plants and their applications” is the result of research carried out by me under the supervision of Professor Utpal Bora and submitted to Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Assam, India for the award of the degree of Doctor of Philosophy in Life Sciences and Bioengineering. It is hereby confirmed that the issue embodied in this thesis entitled “Green synthesis of metallic nanoparticles using leaf extract of selected silkworm host plants and their applications” is the result of research conducted by Ms. In addition, some of the silkworm host plants are also being explored for the synthesis of nanoparticles.
However, some of the primary silkworm host plants are not explored in this context despite their medicinal and indirect economic importance. Northeast India is rich in seri-biodiversity that includes silkworm varieties and their host plants. Silkworms feed on a variety of host plants which are categorized into primary, secondary and tertiary host plants based on silkworm feeding habits.
Therefore, we have selected some primary silkworm host plants of eri and muga silkworms that have not been explored for nanoparticle synthesis. Three selected silkworm host plants include Ricinus communis var carmencita, Heteropanax fragrans and Persea bombycina.
Introduction and Review of Literature
Types of Nanoparticles
Applications of Nanotechnology
Synthesis of Nanoparticles
Characterization of Nanoparticles
Research Gap
Conclusion
Green Synthesis of Silver Nanoparticles using Ricinus communis var
Outline of Research
Experimental Section
Results and Discussions
Conclusion
Green Synthesis of Zinc Oxide Nanoparticles using Heteropanax fragrans
Outline of Research
Experimental Section
Results and Discussions
Conclusion
Green Synthesis of Iron Oxide Nanoparticles using Persea bombycina Leaf
Outline of Research
Experimental Section
Aqueous extract of Persea bombycina leaves was prepared for the synthesis of iron oxide nanoparticles. The standard curve was plotted using the absorbance of gallic acid and the gallic acid equivalent phenolic content of the extract was determined from the linear equation obtained from the standard curve. Three different preparations were made in which the volume of the leaf extract was varied (1 ml, 2 ml and 3 ml) and the total volume of the reaction was kept constant by adding water.
The iron oxide nanoparticles (PbFeONPs) obtained in powder form were stored for further characterization and use. The magnetic properties of iron oxide nanoparticles were evaluated by vibrating sample magnetometer (VSM) analysis. FESEM and TEM studies were performed to analyze the size, morphology and crystallinity of iron oxide nanoparticles.
The lyophilized iron oxide nanoparticles were analyzed for their magnetic properties using a vibrating sample magnetometer (VSM). The samples were accurately weighed on a Teflon tape and then placed on the sample holder of the VSM instrument. FESEM analysis was performed to study the morphology of the iron oxide NPs and TEM analysis was performed to confirm the size and crystallinity of the NPs.
The iron oxide NPs were characterized by X-ray diffractometer studies at 2theta/theta scanning moderately varying from 20-80° (operating voltage 50 kV and current 180 mA, CuKα radiation λ=1.540 A° with 0.05° s−1). High temperature differential scanning calorimetry (DSC)/Thermo Gravimetric (TG) System (make: Netzsch , model: STA449F3A00) was used to assess the thermal stability of the nanoparticles. Biocompatibility of the PbFeONPs was assessed by MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) reduction assay using mouse fibroblastic cell line L929 as mentioned in Sett et al.
Where NT and NC are the absorbance of the treated and negative control cells, respectively. Optimization experiments were performed to study the effects of various parameters such as pH, NP dose, H2O2 concentration, reaction duration and MB concentration. The degradation rate depends on the concentration of the dye, which can be described by the following kinetic model (Taghvaei et al., 2010).
Results and Discussions
VSM analysis was performed to study the magnetic properties of iron oxide nanoparticles synthesized using P. Due to the ferromagnetic properties of the nanoparticles, it is expected that the material can be easily separated and reused for various purposes. The SAED image of PbFeONP in Figure 4.3d shows bright spots with concentric circles, confirming the crystallinity of PbFeONP.
Thus, the XRD spectrum confirms the crystallinity of iron oxide nanoparticles (Wu and Chen, 2012). In Figure 4.7 it is clearly visible that PbFeONPs are less toxic to cells during 24 hours of treatment and become cytotoxic at 48 hours of treatment. In our study, we replaced Fe2+ with iron oxide nanoparticle (PbFeONP) for MB degradation. The reactions that cause MB degradation are mentioned below (Jiang et al., 2011).
The degradation of MB by PbFeONP was performed in different sets of experiments to optimize the iron oxide nanoparticle dosage, H2O2 concentration, solution pH, and duration of dye degradation. Under acidic conditions, the surface of iron oxide nanoparticles corrodes and generates OH radicals, which is the reason for the maximum degradation efficiency at pH 3. The degradation efficiency of MB in the presence of 0.3 mg/ml PbFeONP and different H2O2 concentration is represented in Figure 4.10.
Therefore the concentration of H2O2 was optimized at 0.1 mM, as higher concentration decreased the efficiency of MB degradation. The degradation efficiency increased when the concentration of PbFeONP was increased from 0.1-0.3 mg/ml in the presence of 0.1 mM H2O2 shown in Figure 4.11. The first-order kinetic model is expressed by equation (16), where C and C0 are the initial and apparent MB concentrations, respectively, and K is the kinetic rate constant, which can be calculated from the slope of the straight line (Yang et al., 2009).
A first-order linear relationship was obtained when Ln(C/C0) was plotted against reaction time from the experimental data obtained from the degradation of 20 mg/L MB using 0.3 mg/ml PbFeONP and 0.1 mM H2O2 at pH 3 and 25°C (Figure 4.13). From this it can be interpreted as the rate of the degradation decreased as the number of moles of MB was increased for a constant amount of hydroxyl radicals generated at given time interval. To evaluate the stability of the PbFeONPs, degradation of MB at 20 mg/L concentration was performed using 0.3 mg/ml PbFeONP in the presence of H2O2.
Conclusion
After each cycle, the nanoparticles were separated, dried and used for the next cycle of MB degradation process. The crystallinity and phase unity of the nanoparticles were confirmed by XRD studies and supported by UHRTEM and SAED studies. The presence of functional groups was investigated using FTIR spectroscopy, which insisted on a successful capping of the nanoparticles.
Cell toxicity of the PbFeONPs on mouse fibroblast cell lines L929, was studied by MTT assay and found to be biocompatible at concentrations <50 μg/ml. Effect of pH, initial concentrations, nanoparticle doses, H2O2 concentrations and time were studied for MB removal.
Cadmium removal from aqueous solution by green synthesis of iron oxide nanoparticles with mandarin peel extract. Green synthesis of iron oxide (Fe3O4) nanoparticles using two selected brown seaweeds: characterization and application for lead bioremediation. Green synthesis of magnetic iron nanoparticles coated with olive oil and verification of its efficiency in the extraction of nickel from environmental samples via UV-vis spectrophotometry.
Efficient removal of organic pollutants with magnetic nanoscale BiFeO3 as a reusable heterogeneous Fenton-like catalyst. synthesis, properties and bio-applications. Biogenic synthesis of fe3O4 nanoparticles using Tridax procumbens leaf extract and its antibacterial activity on Pseudomonas aeruginosa. URL:https://www.boundless.com/chemistry/textbooks/virtual-textbook-of-organic- chemistry/spectroscopy-8/infrared-spectroscopy-49/group-frequencies.
H., (2012) Spontaneous synthesis of gold nanoparticles on gum arabic modified iron oxide nanoparticles as a magnetically recoverable nanocatalyst. Decomposition of methylene blue by heterogeneous Fenton reaction using titanomagnetite at neutral pH values: process and influencing factors. Preparation and characterization of magnetic porous carbon microspheres for the removal of methylene blue by a heterogeneous Fenton reaction.
Summary and Future Prospective
Future Prospects
