Synthesis of gold nanoparticles using willow bark and measurement of cysteine ??by spectroscopy and colorimetry

Dissertation to receive a master's degree in Analytical Chemistry

Abstract

The biosynthesis of gold nanoparticles with small size and biological stability are very important and have various biomedical applications. In this work, an easy and simple method for the green synthesis of gold nanoparticles using willow tree bark extract is reported. The bark of the willow tree contains aspirin, which acts as a reducing agent. In the present method, gold nanoparticles have been synthesized without the need to add any stabilizing agents such as surfactants for stability.

Therefore, the green synthesis of gold nanoparticles with willow tree bark extract is useful from the point of view of biological and medical applications as an alternative to chemical synthesis. Optimum conditions for the synthesis of gold nanoparticles were obtained by checking the pH and amount of willow bark extract solution. The characteristics and morphology of gold nanoparticles were investigated by UV-VIS spectrum and electron microscope images. The interaction between the synthesis of gold nanoparticles and cysteine ??was introduced as a new and potential colorimetric sensor for the selective detection of cysteine ??among other amino acids. The sensitivity and selectivity of gold nanoparticles to cysteine ??were studied in comparison with other amino acids.

Their properties in the nanoscale state are different from their properties in the larger scale (Borisenko V.E. [1], 2005; NASA research by Freita[2])

Throughout human history since the time of ancient Greece, people and especially scientists of that period believed that materials can be divided into small enough parts to reach particles that are indestructible and these particles form the basis of materials. Perhaps the Greek philosopher Democritus[3] can be considered the father of technology and nanoscience because around 400 years before Christ he was the first to use the word atom. which means indivisible in the Greek language, used to describe the constituent particles of materials (website of the Nano Organization [4]; B. Boshan [5], 2003). The starting point and initial development of nanotechnology is not precisely known. It can be said that the first specialists in nanotechnology were medieval glassmakers who used old molds [6] to shape their glasses. Of course, these glaziers did not know why adding gold to the glass changes its color (F. Alhof, 2010)

It seems that the human understanding of the very small world has been formed in recent years. The origin of nanotechnology is the subject of many debates. Nanoparticles are thought to have been used at least in artwork from the Dark Ages. But the correct definition of the conscious manipulation of nanoscale materials was probably used by the American physicist "Richard Feynman[7]" in his famous speech in 292: There is a lot of space down there[8]. For a very long time, nanotechnology seemed to join another conceptual idea that becomes science fiction. But finally, after 1980, this idea became a reality.

Nanotechnology, the science of strange properties of materials

The atom is the fundamental building block of matter, and as a result, atoms are very small. It is difficult to describe and imagine the world at the level of atoms and molecules. This area of ??science is so strange that a special part of physics was dedicated to it, called quantum mechanics. The purpose of this science is to describe events at the atomic level. If you were to throw a tennis ball at a wall and the ball passed through it and went to the other side of the wall, you would be surprised. But this is exactly what happens at the quantum scale. On a very small scale, material properties such as color, magnetism, and the ability to transmit electricity also change unexpectedly (http://www.crnano.org/whatis.htm).

Introduction of nanomaterials

Different definitions are provided in sources for nanomaterials, but two characteristics are included in most of these definitions. First, nanostructured materials or so-called nanomaterials are less than 100 nm in size at least in one dimension.One nanometer is equal to one billionth of a meter (meter), this size is 18,000 times smaller than the diameter of a human hair.

A useful and acceptable convention in this regard is that materials must be less than 100 nanometers in at least one dimension (length, width or depth) to be in the nanoscale. In fact, this is a limitation to the nanoscale that the National Nanotechnology Plan (NNI) uses to define nanotechnology: "Nanotechnology is the understanding and control of materials in dimensions of 1 to 001 nanometers, where unique phenomena lead to new applications." For this purpose, it seems necessary to add two more terms to complete the definition. First, nanotechnology includes the construction and use of materials, structures, devices and systems that have unique properties due to their small size. Also It includes technologies that are able to control materials at the nano scale. Although we know that the word nano refers to a specific scale, it is important to have a proper idea of ??what is in this scale and its connection with our daily life. There are various examples that are very common, which we can use to understand the size of one nanometer. 100,000 nm 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 the Earth. Perhaps the best way to recognize the nanometer scale is to describe the limits from the centimeter length scale to the nanoscale. An ant is approximately 9 mm. The head of the pin is 1 to 2 mm. Dust mites are 200 micrometers. A human hair is about half the size of a dust worm, 100 micrometers. The red blood cells that flow in our veins are about 4 micrometers. Even our smallest cells have ATP synthase 10 nanometers in diameter. The size of two DNA double helix strands is about 2 nm apart. Finally, atoms themselves are less than one nanometer in size, often in the angstrom range (Figure 1-1) (http://www.islandone.org/MMSG/aas).

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[9] is a shellfish with very strong shells that have iridescent inner surfaces that are held together by the organization of calcium carbonate into solid 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 (NASA research by Freita [10]).

With the existence of 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. The architectures built by living organisms are all based on nano-aggregation (J. Koa [11], 2004).

Secondly, nanostructures should have properties related to size and different from the usual state or so-called bulk state. That is, by changing the size to nano dimensions, we can witness the change of material properties.

Nano technology in nature

Not much time has passed since the emergence of nano technology as a scientific discipline. Like many other technologies, a significant part of this technology is also inspired by nature. With the passing of successive years and the development of human technologies and the construction of well-equipped laboratories to test big ideas, nature has been an inspiration for inventions in technology for a very long time. Looking at the designs of Leonardo da Vinci[12], the inspiration from nature for technologies to help humans is quite evident. For example, Da Vinci's studies on the fine details of bird flight helped him a lot to design models for helicopters and gliders. The wings of many of his gliders were based on bat wings.