Photo-luminescence Guided Metal Ion Sensing and Environmental Remediation Applications of Green Synthesized Iron and Iron-based Nanomaterials

Abstract

A rapid growth in the field of industries and academia has resulted in the immense development and amplification of nanomaterials and nanocomposites for environmental remediation application purposes. Over the past few decades, green synthesis has played a major role in nurturing nanoparticle synthesis. The advantages of such nanoparticles are due to their eco-friendly nature, low cost, and higher stability. Green synthesized nanoparticles have been utilized extensively for various environmental-related applications like wastewater treatment, and antimicrobial activities. The need for such nanomaterials in today's world is very crucial since environmental pollution has grasped the world. Greener, safer and effective methods are tomorrow's need for attaining a sustainable environment.

Recent researches have pointed out various sources of green material utilizing which metallic nanoparticles can be synthesized and could be applied towards environmental remediation applications due to their better stability, higher surface area, and antioxidant properties. The present study utilizes a green source to be an effective tool to generate Iron (Fe) nanoparticles with a multipurpose role. Green synthesized Fe NPs towards dye degradation, pollutant removal from wastewater are common applications, but utilizing the photoluminescent activity of green synthesized nanoparticles towards heavy metal sensing ability is a new approach. Moreover synthesizing bimetallic nanocomposites through green synthesis and apart from its fluoride removal efficiency, the heavy metal sensing ability was also investigated in this study and is believed to be a new horizon for future research.

This workaddresses the state of the art, research motivation towards the green synthesis approach.Itprovides a complete description of the methods and experiments involved in green extract preparation, analyzing its total phenolic, flavonoid, tannin content, and investigating its antioxidant properties. The study involves a vivid analysis of selecting suitable green sources among different spices (clove, cardamom, bay-leaf; common name) based on its total phenolic content (TPC), flavonoid content (TFC), tannin content (TTC), and antioxidant property. The selected green source (clove) mediated iron nanoparticles were then utilized for degradation of crystal violet dye, and its efficiency was compared with the other green source mediated iron nanoparticles. Moreover, the work analyzesbetter solvents for extraction of polyphenols, flavonoids, tannins, and their antioxidant property from clove as a green source. Moreover, optimization of maximum phenolic and flavonoid content of the clove extract was carried out by controlling parameters such as time of extraction, extraction temperature, and volume of extraction solvent. The study presents the morphological and chemical property dependency of synthesized Fe NPs with pH. This work also investigates the photoluminescence behavior of synthesized Fe NPs towards the heavy metal ion sensing ability. The Fe NPs were found to act as a better Fe3+ ion detector within a linear range of micromolar concentration, in presence of other heavy metal ions. Its efficiency was studied in presence of real-life water samples collected from the Indian Institute of Technology, Guwahati campus, India. Further,it describes the preparation of the clove extract mediated ZVI NPs embedded pH-responsive polymeric membrane for reducing nitrobenzene to aniline present in wastewater. The nitrobenzene reduction process was maximized by optimizing the controlling parameters such as time, medium pH, iron NPs content. Furthermore, the membrane was also utilized for studying the fluoride rejection behavior. The work focuses on the effectivity of clove extract in preparing iron-aluminum bimetallic nanocomposite and its application towards removing fluoride and enhancing the overall quality of real-life water collected from Northeast regions of India.Finally, it describes the dual activity of such green synthesized iron-aluminum nanocomposite by investigating its heavy metal sensing ability in the real-life water sample. In presence of various heavy metals, the nanocomposite was found to be effective in detecting Fe3+ ion and showed a linear range of applicability for real-life water collected from college campus IIT Guwahati, India. In conclusion, the work contains the inferences drawn from various chapters presented in this thesis and some suggestions towards scope for future work.