Synthesis and characterization of new nanocomposites for use in analytical applications

Dissertation for Master degree in Chemistry

Analysis trend

Abstract

Today, nanostructures have attracted the attention of many researchers due to their new features and applications in different fields and branches of science and technology. In the meantime, nanocomposites have directed a significant share of research in the field of nanotechnology due to their unique physical and chemical properties, as well as potential applications in catalytic, electronic, optical, pharmaceutical, medical, and health applications. Therefore, considering that one of the most important aspects of nanotechnology is the advancement of safe and environmentally friendly methods in the synthesis of nanoparticles, without the use of any chemical or toxic substances, in the first part of this research, an easy and fast synthesis route for the preparation of Leonardite nanostructures without the use of any additional surfactants, coating agents, stabilizers or templates is presented. Leonardite nanostructures were successfully synthesized using precipitation method. Morphology, crystal structure, particle size distribution, stability and other characteristics of prepared Leonardite nanostructures were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and FTIR method. Leonardite nanostructure was placed in chitosan-polyvinyl alcohol nanocomposite hydrogel structure and characterized by XRD, SEM and FTIR. Synthesized nanocomposite hydrogel was used as an adsorbent of anionic pollutants to remove nitrate from water. In the second part of this research, mesoporous silica (SBA-15) was synthesized by sol-gel method and the nanostructure characteristics were characterized by SEM and FTIR. Then, in order to improve the properties of mesoporous silica, polythiophene inside its cavities was chemically synthesized. The resulting nanocomposite was characterized by SEM and FTIR, and then it was used as a cover of a rotating absorbent rod for preconcentration and measurement of fatty acids in biodiesel samples. In the third part of this research, iron oxide-polyaniline nanocomposite was synthesized using polystyrene molds. The synthesized nanocomposite was characterized by SEM and FTIR. Iron oxide-polyaniline nanocomposite was used as SPME fiber coating to identify and measure polycyclic aromatic hydrocarbons (PAHs) in water.

Introduction and research background

1-1 Nanotechnology

Nanotechnology is perhaps the leader of modern science in the current world, which is sometimes referred to as "Renaissance of technology [1]". The arrival of products based on this technology will be a huge leap in welfare and quality of life. The discovery of new materials, processes and phenomena at the nanoscale, as well as the development of new experimental and theoretical techniques for research, provide new opportunities for the development of innovative nanosystems and nanostructured materials. Nanosystems have the potential to be used in unique applications. Nanostructured materials can be made with special properties and structures. It is expected that this field will open new positions in science and technology [1,2].

1-1-1 income on nanotechnology

A biological system can be very small. The cells are very small, but very active. They produce different particles, rotate, shake and do all kinds of amazing things, and all this on a small scale. They also store information.An important question is: "Can we make a very small object that does what we want it to do? Can we produce a structure that manifests itself at that level?" The Greek nanos [3] refers to a scale of size in the standard system of measurement. Nano means a billionth (0.0001) of the base unit. When we talk about nano-technology, we are actually talking about a scale of the order of size, quantity or length We are talking about "nanometers". Using this term, it becomes easier to discuss the size of objects that are the main attractions in nanotechnology, i.e. atoms. If we want to express the size of atoms or molecules in units of feet or meters, we should say that a hydrogen atom (the smallest atom) is 10-10 × 7 feet or 10-10 × 2 meters. that hydrogen atom is 0.24 nm. So, the nanoscale used in nanotechnology is the size scale.

A useful and acceptable convention in this regard is that materials must be less than 100 nanometers in at least one of the dimensions (length, width, or depth) in order to be in the nanoscale. In fact, this is a limitation to the nanoscale that the "National Nanotechnology Initiative [4]" (NNI) uses to define nanotechnology: "Nanotechnology is the understanding and control of materials in dimensions of 1 to 100 nanometers, where unique phenomena lead to new applications." For this purpose, it seems necessary to add two more terms to complete the definition. Firstly, nanotechnology includes the construction and use of materials, structures, devices and systems that have unique properties due to their small size. It also includes technologies that are able to control materials at the nano scale.

Even though we know that the word nano in nano technology refers to a specific scale, it is important to have a correct idea of ??what is on this scale and its connection with our daily life. There are various examples that are very common that we can use to understand the size of a nanometer. For example, the width of a human hair is 100,000 nanometers. Another example is the following comparison: a nanometer compared to the size of a meter is about the size of a golf ball compared to the size of a globe. Perhaps the best way to recognize the nanometer scale is to describe the limits of the length scale from the centimeter to the nanoscale. An ant is approximately 5 mm. The head of the pin is 1 to 2 mm. Dust spheres are 200 micrometers. A human hair is about half the size of a dust globe, 100 micrometers. The red blood cells that flow in our veins are about 8 micrometers. Even the smallest cells in our "ATP synthase" are 10 nm in diameter. The size of the two strands of the DNA double helix is ??about 2 nm apart. Finally, the atoms themselves have sizes less than one nanometer, which are often in the angstrom range [3].

While the term nanotechnology is relatively new, the existence of functional devices and structures with nanometer dimensions is not new, and in fact, such structures have existed on Earth since life existed. Albumin is a shell with very strong shells that have iridescent inner surfaces that are held together by the organization of calcium carbonate into rigid brick-like nanostructures, with an adhesive made of a mixture of carbohydrates and proteins. Due to the presence of nanostructured bricks, the cracks created on the outer part are able to move through the shell. Shells represent a natural example that shows that a structure made of nanoparticles can be very strong [4]. Despite such systems in nature, the best efficient and environmentally friendly processes should also be learned from nature itself. When we explore our living environment, we realize the essential role of nanomaterials in biological systems. Architectures built by living organisms are all based on nanoscale assembly. Today, we know that biological processes can also be used to make nanostructures. Products obtained from biological processes may be very complex, but under normal conditions they are very cheap.