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## Meet the editor

Dr. Xiao-Lan Huang is an independent researcher and senior environmental scientist who focuses on the biogeochemistry of soil, water, plant, and solid wastes, including phosphorus. Rachel Carson's Silent Spring inspired him to learn soil science. He holds an MSc in Soil Ecology from Nanjing Agricultural University, China, and a Ph.D. in Environmental Chemistry from the Hebrew University of Jerusalem, Israel. He also

completed a postdoctoral fellowship in Oceanography at the University of Miami, USA. In 2007, Dr. Huang observed the catalytic phenomena of the phosphate ester hydrolysis in aged inorganic iron solutions and iron oxide nanomaterials under the aqueous environment with Michaelis-Menten kinetics behavior and suggested a hypothesis on the inorganic enzyme (University of Miami, 2008; RSC Advance, 2012; Astrobiology, 2018; Iron Oxide Nanoparticles: An Inorganic Phosphatase, 2019). His discovery is not only significant for organic phosphorus transformation in the current environment but also provides clues for biocatalysts and first life evolution. Dr. Huang further stated that all inorganic nanomaterials that have intrinsic enzyme-like properties can be considered inorganic enzymes due to their unique architectural features, which are comparable to the function of known enzymes (proteins) and ribozymes (RNA), in a new discovery catalog of biocatalysts. Dr. Huang is also an active participant in environmental science, as a peer reviewer for twenty international journals.

## Contents


## **Chapter 6 123**

Application of Iron Oxide in Supercapacitor *by Rajan Lakra, Rahul Kumar, Parasanta Kumar Sahoo, Sandeep Kumar and Ankur Soam*

## **Chapter 7 143**

Green Energy Applications of Hematite (α-Fe2O3), Magnetite (Fe3O4), and Maghemite (γ-Fe2O3) Nanoparticles Based Hydroelectric Cell *by Kuldeep Chand Verma and Navdeep Goyal*

## Preface

Iron oxide is one of the most abundant minerals on Earth. It presents in various nanoparticle forms that include several different phases, for example, ferrihydrite (Fh), magnetite (Fe3O4), maghemite (γ-Fe2O3), and wüstite (Fe1−xO). Iron oxide nanoparticles are synthesized due to their innovative functions and applications. Their surface structure, shape, and size dependence make them useful for various functions. This book presents the latest developments in the research on iron oxide nanoparticles, including their synthesis, characteristics (e.g., enzyme-like activity), and applications (e.g., cancer theranostic, green energy applications). Further, the book includes additional references and perspectives in the introduction chapter regarding history, research trends, and the significance of iron architecture in nanoparticles.

Considering the intrinsic enzyme-like properties of inorganic iron oxide nanoparticles, I proposed that all inorganic nanozymes represent a new distinct class of biocatalysts (i.e., inorganic enzymes), owing to the unique architecture of the metal sites embedded in the inorganic nanomaterial. In this sense, they can be comparable to the existing categorization of enzymes (proteins) and ribozymes (RNA). Alternatively, functionalized nanomaterials that display enzyme-like properties may be referred to as "artificial biocatalysts" rather than "artificial enzymes". Metalloenzymes, in essence, are simply functionalized nanomaterials with a metal architecture as the active center, stabilized by amino acids or nucleotides through natural selection and evolution. By drawing inspiration from the understanding of protein structure, scientists may observe more enzyme-like activity in inorganic nanomaterials that have yet to be discovered. It must be emphasized that none of these inorganic nanozymes are artificial enzymes, despite claims made by many scientists. No matter what we observe or imagine, what is certain is that inorganic enzymes continue to play an important role in all the processes occurring on our planet from a biogeochemical perspective.

This book is an invaluable resource for researchers in the field of nanotechnology because it fosters a direct connection among scientists from many different disciplines, including mineralogists, biologists, chemists, engineers, geologists, agronomists, medical professionals, and environmental scientists.

> **Dr. Xiao-Lan Huang** Independent Researcher, Cincinnati, OH, USA

**1**

Section 1

Introduction
