Foreword

I was honored to receive an invitation from Dr. Li Fu to write a foreword for his new book.

The development of nanomaterials within the last few decades has been a very exciting chapter in the history of science. Not only material scientists but also a large number of physicists and chemists are involved in this field. This gives the illusion that nanomaterials are man-made materials and that there is no connection between them and nature. In fact, the development of nanomaterials is inextricably linked to the natural world. Nanotechnology is neither a mystery, nor it is exclusive to humans. Nanomaterials and nanotechnology have existed since the dawn of the universe. In the long evolution of the earth, the natural world, from the pavilion of the lotus, ugly spiders, weird sea snake tail, flying bees, water striders on the surface, shells in the sea, gorgeous butterflies, palm-sized geckos, to bacteria, each of them is a master of nanotechnology. These plants and animals are used to make a living or to defend against enemies through their exquisite nanotechnology skills. Their tenacious survival in nature not only enriches the world around us, but also brings countless inspirations and insights to modern nanotechnologists.

In the 1970s, Barthelot, a botanist at the University of Bonn in Germany, was studying plant foliage and found that smooth leaf surfaces were dusty and had to be cleaned before they could be viewed under a microscope, while leaf surfaces such as lotus leaves were always dry and clean. They used artificial dust particles to contaminate the foliage of eight types of plants, including magnolia, forest beech, lotus, taro, and kale. The condition of the dust particles remaining on the foliage was observed after washing with artificial rain for 2 min. Experiments have found that some plants have up to 40% or more contaminants left on their foliage. The percentage of contaminant residues on the foliage of plants such as lotus is less than 5%. The presence of very complex multiple nano- and micron-scale ultrastructures on the surface of lotus leaves can be observed by electron microscopy. The surface of the lotus leaf has some tiny waxy particles and is covered with numerous protrusions of about 10 microns in size. The surface of each protrusion is covered with even finer villi of only a few hundred nanometers in diameter. The part between the protrusions is filled with air. This forms a layer of air that is only a nanometer thick immediately adjacent to the leaf surface. This makes it possible for dust and rain, which are much larger in size than this structure, to fall on the leaf surface without coming into direct contact with it on a large scale, but with a very thin layer of air. This also makes it possible for them to contact only a number of raised points on the leaf surface. This is the result of the long-term evolution of living organisms in nature. It is this special nanostructure that keeps the surface of lotus leaves clean from water droplets.

However, nanomaterials also pose some challenges for us. The amount of nanoparticles entering the ecosystem and human living environment is increasing, and the number of species is gradually increasing, and all these nanoparticles will have more or less effects on living organisms. In studies on the effects on animals, scientists have found that nanomaterials have certain neurotoxic effects, with different forms of toxicity on different organs, and determined by the dose and duration of action. In addition to the safety risks to animals or humans, nanomaterials also have an impact on plants. Although research on the effects of nanomaterials on plant growth is just beginning, it can be expected that nanoparticles will have varying degrees of impact on plants and even ecosystems. Nanomaterials and plants have a delicate relationship. Sometimes you will find them "mutually beneficial", while at other times, they seem "incompatible".

Initially, people wanted to know how nanomaterials would affect the growth of plants if they entered water bodies and ecological environments. The first concern was the effect on the seed germination rate. For example, moderate concentrations of TiO ₂ nanoparticles were found to promote the germination of some seeds, while having no effect on others. The effect of nanomaterials on seed germination is related to the nature of the nanoparticles. Some scientists have confirmed that Zn nanoparticles and ZnO nanoparticles can significantly inhibit seed germination in rye and rape, and root growth in corn and cucumber. Meanwhile, other scientists have found that TiO ₂ nanoparticles can enhance photosynthesis in spinach, and this has been shown to be closely related to its photocatalytic activity. For example, spraying 0.35% TiO ₂ nanosol on cucumber foliage can significantly reduce the leaf spot area, and promote the synthesis of chlorophyll and carotene.

There are many possibilities for the relationship between nanomaterials and plants. In this book, Dr. Li Fu focuses on the relationship between nanomaterials and plants. In his book, he tells more about the relationship between plants and nanomaterials. For example, plants can be used as effective reducing agents in the synthesis of nanomaterials. Plants can also be carbonized at high temperatures into very useful nanomaterials. Plants can even synthesize nanomaterials in vivo. This is not only an academic book that combines the scientific research results between botany and nanomaterials; it is also an interesting work of science and popularization. I believe that every reader can also feel the fun brought by nature from the book