THE APPLICATIONS OF NANOPARTICLES IN CHEMISTRY

AND RELATED SCIENCESBY

BENEDICT ISEROM ITAPROFESSOR OF PHYSICAL/THEORETICAL CHEMISTRY AND COORDINATOR,

NANOSIENCE AND NANOTECHNOLOGY RESEARCH GROUP CHEMISTRY DEPARTMENT, UNIVERSITY OF CALABAR, CALABAR, NIGERIA AND COVENANT

UNIVERSITY, OTA, OGUN STATE (email: benedict.ita@covenantuniversity.edu.ng; iseromngwuita@unical.edu.ng;

iserom2001@yahoo.com)

Abstract• In this paper, we explore the applications of

nanoparticles in chemistry and other related sciences like technology and medicine. Nanoparticles are defined as tiny objects each of nanometric dimensions 1 – 100nm and exhibit very useful and interesting properties different from their bulk counterpart. Chemistry ingenuity enables them to be applied as catalysts, as magnetic materials, as anti-corrosion agents etc. In technology, they are mainly used in fabrication of equipment parts, as building materials and in electronic devices etc. and in medicine they have very wide applications. The most interesting applications being in the treatments of various diseases, etc. There is hardly any area of human endeavor that has nothing to do with nanoparticles

Introduction

We shall discuss:1) Definition of nanomaterials2) Types of nanomaterials and their dimensions: nanoparticle

nanotubes/nanowires/nanoplatesnanofibresnanofilms

3) Syntheses of nanoparticles4) Applications of nanoparticles in chemistry5) Applications of nanoparticles in technology6) Applications of nanoparticles in biology and medicine7) Advantages of nanotechnology and nanomaterials8) Summary and Conclusion9) References

Continuation

1) Definition of nanomaterialsA material is a substance that things can be made from. For instance, building materials will include things like bricks, sand, glass, metals, etc. A substance is a type of solid, liquid or gas that has particular quantities. A nanomaterial is therefore a substance that has small objects of nanometer (10-9

m) sizes.

Continuation

Nanomaterials have unique properties: They have very high magneto resistance

They have lower melting point, high solid state phase transition pressure, lower Debye temperature and high self diffusion coefficient

They have high catalytic activity and lower ferroelectric phase transition temperature

Continuation

2) Types of nanomaterials and their dimensionsIn the physical sciences, a particle is a small

localized object to which can be ascribed several properties such as volume or mass. In chemistry, a particle is a small object that behaves as a whole unit in terms of its transport and properties. Particles are further classified according to size: in terms of diameter, coarse particles cover a range 2,500nm to 10,000 nm. Fine particles are sized above 100nm to less than 2,500nm and ultrafine particles or nanoparticles are sized between 1nm to 100nm

ContinuationNanomaterials may be zero-dimensional (e.g., nanoparticles), one-dimensional (e.g., nanorods, nanotubes, nanowires, nanoplates, nanoflowers, nanofilms, etc) or two-dimensional (e.g., thin films or stacks of thin films). A zero-dimensional structure is the simplest building block that may be used for nanomaterials design. These materials have dimensions less than 100nm and are synonymously labeled as nanoparticles or nanoclusters. Any nanomaterial that is crystalline should be referred to as a nanocrystal. However, this term is normally reserved for those materials that are single-crystalline. Polycrystalline nanomaterials could be termed nanopolycrystal. A term used by me for the first time, in a paper published in 2000 in Acta Chimica Hungarica-Models in Chemistry.

ContinuationA special case of nanocrystal that is composed of a semiconductor ( a solid substance that conducts electricity better than insulators or non-conductors but not as good as conductors) is known as a quantum dot and has dimension between 1nm to 30nm. Quantum dots are very useful as sensors, lasers, and light emitting diodes (LEDs).

ContinuationTherefore, when the size or dimension of a material is continuously reduced from a large or macroscopic size, such as a metre or centimetre, to a very small size, the properties remain the same at first, then small changes begin to occur, until finally when the size drops below 100 nm, dramatic changes in properties can occur.If one dimension is reduced to the nanorange while the other dimensions remain large, then we obtain a structure known as quantum well. If two dimensions are so reduced and one remains large, the resulting structure is referred to as a quantum wire. The extreme case of this process of size reduction in which all three dimensions reach the low nanometer range is called a quantum dot.

Continuation

Bulk Well Wire Dot

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• The above structures show progressive generation of rectangular structures. Below is the progressive generation of curvilinear structures

Bulk Well Wire Dot

Continuation• The semiconductors like PbS, GaAs, CdS etc.,

can be synthesized in the nanometer level and they are referred to as semiconductor quantum dots. Their properties like band gap, luminescence etc., always differ from their bulk counterpart.

These quantum structures are useful in the fabrication of high efficiency solar cells, infrared detectors, quantum dot lasers etc.

3) Some methods of synthesizing nanomaterials

Although the basic chemistry of the synthesis of nanomaterials is fairly well understood, the synthesis of complex nanomaterials continues to be a problem of importance, since these materials are found to exhibit new phenomena and find novel applications. A variety of methods has been employed for the synthesis of complex metal oxides and many of these methods give the products in form of fine particulates. There are two general approaches to the synthesis of nanomaterials and the fabrication of nanostructures. They are (a) Top-down approach, that is the miniaturization of the components as articulated by Feynman, who stated in the 1959 Nobel lecture that “there is plenty of room at the bottom” and (b) Bottom-top approach akin to that of Jean-Marie Lehn in 1995. It involves the self-assembly of molecular components, where each nanostructured component becomes part of a superstructure. We elaborate on these methods below:

(a)Top-down approach

This involves slicing or successive cutting of a bulk material to get nanosized particle. The advantages are;

1) Mechanical force is used to produce nanosized particles

2)It could be used to produce nanosized particles on large scale

The disadvantages of the method are:

Continuation

1) polydispersity, formation of variable nanosized particles2) surface dislocations occur during attrition/slicing/ball milling3) morphology control of nanoparticles is

very difficult

Continuationb) Bottom-top approach

This approach refers to the build up of a material from the bottom; atom by atom, molecule by molecule or cluster by cluster.Advantages:

1) produces nanostructures with less defects and more homogeneous chemical composition

2) size and shape of nanoparticles can be controlled

3) good quality nanoparticles can be prepared for applications in functional devices

4) Applications of nanoparticles in Chemistry

The knowledge of chemistry is very useful in nanoparticles applications. One important applications of nanoparticles in chemistry is in catalysis. For instance, titanium-doped zirconia, aluminum-doped zirconia and potassium-doped zirconia are used as effective catalysts in nanosized form for the transesterification of soybean with methanol for the production of biodiesel. The list of nanosized particles as catalysts in biodiesel production is inexhaustible

ContinuationThere are also several reports of nanosized particles used as gas sensors for atmospheric pollutants in the literature. In our laboratory, we are exploring the use of iridium-doped indium oxides as gas sensors for atmospheric pollutants due to the absorbing capability of iridium. Titanium oxide nanoparticle coating is being utilized for the corrosion protection of mild steel in high temperature environments. Nickel and iron oxide nanoparticles are recently being used in concrete mixing matrix to increase the compressive strength of cement as well as decrease its setting time.

Continuation• Zirconia-based nanoparticles are attractive for a

variety of applications, such as solid-oxide fuel cells, oxygen sensors etc. We have also found lanthanum oxide capable of enhancing the decomposition of hydrogen peroxide in our laboratory, for effective oxygen production. MgO nanoparticles are also recognized as adsorbent for air purification, toxic waste remediation, etc. Scientists in America are investigating the thermal behavior of metal nanoparticles in geochemical materials in order to obtain a new tool to define the thermal history of nanoparticle-bearing geochemical and planetary materials.

5) Applications of nanoparticles in technology

Technology has a quite different meaning from an apparently similar word, technique. Technique is the method of doing or performing, with skill acquired by experience, something that has already been established. Technology can be defined as the ability of taking advantage of the progress of science to create novel opportunities for practical applications. Technology is the main driving force for the progress of mankind since it provides a wealth of novel materials, devices, and machines capable of improving the quality of life. Unfortunately, however, technology can also be exploited for negative purposes, for example, violence, war, and terrorism. In this paper, we only discuss nanoparticles in positive aspects of technology for the benefit of mankind.

ContinuationNanotechnology could be referred to as the applications of nanoparticles in technology. Thus, nanotechnology pertains to the synthesis, characterization and manipulation of matter on an atomic and molecular scale for the fabrications of useful devices and machines. One of the most important objectives of nanotechnology is a further miniaturization of information processing devices. Present computers are based on the miniaturization of electronic circuits by scientists. Efforts are underway to design and construct “molecular computers’ much smaller and much powerful than the presently used silicon-based computers. In fact, IBM one time announced that it was replacing silicon wafers with nanoparticles of lanthanum strontium manganate as the memory device of its computers. They stated that lanthanum strontium manganate had a better speed and more storage capacity and was cheaper that silicon wafer.

Continuation• Nanotechnology can generate products with many

unique characteristics that can improve the current construction materials: lighter and stronger structural composites, low maintenance coatings, better cementitious materials, lower thermal transfer rate of fire retardant and insulation, better sound absorption of acoustic absorbers and better reflectivity of glass, etc. Concrete is a macro-material strongly influenced by its nano-properties. The addition of nano-silica to cement based materials can control the degradation of calcium-silicate hydrate reaction caused by calcium leaching in water, blocking water penetration and leading to improvements in durability.

Continuation• Also, nano-sensors have a great potential to be used

in concrete structures for quality control and durability monitoring (i.e. to measure concrete density and viscosity, to monitor concrete curing and to measure shrinkage or temperature, moisture, chlorine concentration, pH, carbon dioxide, stresses, reinforcement corrosion or vibration). Carbon nano-tubes increase the compressive strength of cement motar specimens and change their electrical properties which can be used for health monitoring and damage detection.

Continuation• The addition of copper nanoparticles reduces the

surface unevenness of steel, limits the number of stress carriers and hence fatigue cracking, leading to increased safety, less need for monitoring and more efficient materials for construction. Vanadium and molybdenum nanoparticles improve the delay fracture problems associated with high strength bolts, reducing the effects of hydrogen embrittlement and improving the steel micro-structure. The addition of nanoparticles of magnesium and calcium leads to an increase in weld toughness. Wood is composed of nanotubes or “nanofibrils”

Continuation• Lignocellulosic surfaces at the nanoscale could open

new opportunities for such things as self-sterilizing surfaces, internal self-repair, biodiesel production, and electronic lignocellulosic devices, providing feedback for product performance and environmental conditions during service. Highly water repellent coatings incorporating silica and alumina nanoparticles and hydrophobic polymers are proper to be used for wood. Fire-protective glass is obtained using fumed silica nanoparticles as a clear interlayer sandwiched between two glass panels which turns into a rigid and opaque fire shield when heated.

Continuation• Nanotechnology is applied to paints in order to

prevent the corrosion under insulation since it is hydrophobic and repels water from the metal pipe and can also protect metal from salt-water attack. Nanotechnology is now being applied in sports such as soccer, football and baseball. Materials for new athletic shoes may be made from nanoparticles in order to make the shoe lighter ( and the athlete faster). Baseball bats made of carbon nanotubes are already in the market. In agriculture, the applications of nanotechnology have the potential to change the entire agriculture sector and food industry chain from production to conservation, processing, packaging, transportation, and even waste management.

Continuation

• In aerospace industries, nanoparticles have made it possible to create lighter and stronger materials for aircraft manufacture, leading to increased performance. Spacecraft will also benefit, where weight is a major factor. Nanotechnology will help to reduce the size of equipment and thereby decrease fuel consumption required to get it airborne

6) Applications of nanoparticles in biology and medicine

• One area of applications of nanoparticles in biology and medicine is in treatments of various health problems. Malaria, for instance, is a serious menace to countries in the tropics – Africa, Asia, etc. because it is geographically specific, affecting mostly children and pregnant women as well as having greater morbidity and mortality than any other infectious diseases of the world. Currently, the only hope in chemotherapy of malaria lies within the artemisinin class of antimalarial

Continuationdrugs. The widespread resistant malaria parasites (plasmodium spp) to most common antimalarials, and cross-resistance to structurally unrelated drugs, emphasize the need for a new therapeutic targets. Raising the immunocompetence of individuals in malaria endemic areas by vaccination could significantly lower the death tolls due to clinically severe malaria. A viable malaria vaccine could be regarded as the most cost effective and best practical method of reducing the high human and economic toll of this devastating disease. Scientists are now engaged in the use of water-soluble cationic nanoparticle of N, N, N-trimethylchitosan as having a desirable qualities for the intending antigen delivery. Thus, it is regarded as a nanocarrier for malaria vaccine. The biological activities of the nanocarrier is also under investigation. In another development, acinetobacter baumanii (Ab) is found to be a frequent cause of hospital acquired pneumonia and also has increased in incidence as the causative agent of severe disease in troops wounded in Afghanistan and Iraq.

Continuation• Ab clinical isolates are frequently extremely resistant

to antimicrobials, significantly complicating the capacity to treat infections due to this pathogen. Hence, the development of innovative therapeutics targeting mechanisms to which the bacteria are unlikely to evolve resistance becomes urgently needed. Scientists have examined the capacity of nitric oxide-releasing nanoparticle (NO-np) to treat wounds infected with Ab and found it very effective. Foot ulcers are one of the main complications in diabetes mellius, with 15% life time risk in all diabetic patients. Patients with diabetes display aberrant angiogenesis in various organs, with insufficient activity occurring in impaired wound healing including ulcers

ContinuationNanotechnology but is also used in treating diabetic wound. Angiogenesis induced with the peptide DNA nanoparticles helps in the treatment. Also, silver nanoparticles are found to be effective in wound healing in animals and are promising for future applications in human. Silver nanoparticles exert positive effects through their antimicrobial properties, reduction in wound inflammation, and modulation of fibrogenic cytokines. Solid lipid nanopartcles (SLN) are the forefront of the rapidly developing field of nanotechnology with several potential applications in drug delivery and research. Due to their unique size dependent properties, lipid nanoparticles offer exiting possibilities to develop new therapeutics. The ability to incorporate drugs into nanocarriers offers a new prototype in drug delivery that could be used for drug targeting. Hence, SLN hold great promise for reaching the goal of controlled and site specific drug delivery.

Continuation• In the treatment of cancer, scientists have resorted to

nanophotothermolysis with pulsed lasers and absorbing nanoparticles like gold nanospheres, nanorods or carbon nanotubes, attached to specific targets. This technique is a great potential for selective damage to cancer cells, bacteria and viruses. In another development, various nanomaterials such as fullerenes, dendrimers, silver and gold nanoparticles have shown anti-HIV effects in vitro and in vivo. Generally, it has been found that metal nanoparticles can be effective antiviral agents against HIV-1, hepatitis B virus, respiratory syncytial virus, herpes simplex virus type 1, monkeypox virus, influenza virus and Tacaribe virus. Furthermore, laboratory studies in mice have shown that using nanoparticles to target the delivery of clot busting drug can reduce dosage of the drug needed, which may reduce possible side effects, such as internal bleeding

Continuation• The clot busting drug was attached to a cluster

of nanoparticles that break apart in regions of turbulent blood flow. Researchers are developing polymer nanoparticles that get to inflamed tissues such as arterial plaque and then dissolve, releasing drugs, in the presence of hydrogen peroxide that is present in the inflamed tissue. Also, nanoparticles containing iron oxide could be directed by a magnetic field, to stents. This could allow drugs to be delivered directly to stents placed in arteries.

Continuation • In another development, a method being developed by

scientists to tackle autoimmune diseases uses nanoparticles to deliver antigens for a particular disease into the blood stream. The antigens reset the immune system, stopping white blood cells from attacking healthy cells to prevent aging. This method has already been tested in the laboratory on mice with a disease similar to multiple sclerosis with promising result. Another method is being developed to fight aging using mesoporous nanoparticles with coating that releases the contents of the nanoparticles when an enzyme found in aging cell is present. Skin creams that uses proteins derived from stem cells could prevent aging of the skin. These proteins are encapsulated in liposome nanoparticles which merge with the membranes of the skin cells to allow delivery of the proteins

Continuation• Researchers have also developed nanoparticles that

can slip through mucus coating surfaces such as lung tissue. This could provide the capability to coat lung tissue with therapeutic drugs. Medical implants made of porous plastic, coated with carbon nanotubes are also very useful. Therapeutic drugs, which are attached to the nanotubes can be released into the blood stream, for example, when a change in the blood chemistry signals a problem. NASA is developing these implants, called “biocapsule”, to protect astronauts from the effects of radiation, however, the implants may also be useful for releasing insulin for diabetes patients or for delivering chemotherapy drugs directly to tumors

Continuation

• In dentistry, nanofillers used include nanoparticles of aluminosilicate powder. Orthodontic nanorobots are also developed to directly manipulate the periodontal tissues, allowing rapid and painless tooth straightening, rotating and vertical repositioning within minutes. Titanium and silver nanoparticles are being introduced into dental composites, to introduce antimicrobial properties and enhance biocompatibility of the composites

7) Advantages of nanotechnology and nanomaterials

1. IMPROVED TRANSPORTATION Today, most airplanes are made from metal despite the fact that diamond has a strength-to-weight ratio over 50 times that of aerospace aluminum

Diamond is expensive, it is not possible to make it in the required shapes, and it shatters. Nanotechnology will let us inexpensively make shatterproof diamond in exactly the shapes we want. Nanotechnology will dramatically reduce the costs and increase the capabilities of space ships and space flight

The strength-to-weight ratio and the cost of components are absolutely critical to the performance and economy of space ships: with nanotechnology, both of these parameters will be improved Nanotechnology will also provide extremely powerful computers

with which to guide both those ships and a wide range of other activities in space

Continuation2. ATOM COMPUTERS

Today, computer chips are made using lithography -- literally, "stone writing" If the computer hardware revolution is to continue at its current pace, in a decade or so we'll have to move beyond lithography to some new post lithographic manufacturing technology. Ultimately, each logic element will be made from just a few atoms Designs for computer gates with less than 1,000 atoms have already been proposed - but each atom in such a small device has to be in exactly the right place To economically build and interconnect trillions upon trillions of such small and precise devices in a complex three dimensional pattern we'll need a manufacturing technology well beyond today's lithography: we'll need nanotechnology. With it, we should be able to build mass storage devices that can store more than a hundred billion billion bytes in a volume the size of a sugar cube; RAM that can store a mere billion billion bytes in such a volume; and massively parallel computers of the same size that can deliver a billion billion instructions per second will require nanotechnology

Continuation

• 3. SOLAR ENERGY Nanotechnology will cut costs both of the

solar cells and the equipment needed to deploy them, making solar power economical

In this application we need not make new or technically superior solar cells: making inexpensively what we already know how to make expensively would move solar power into the mainstream

Continuation• 4. MEDICAL USES

It is not modern medicine that does the healing, but the cells themselves: we are but onlookers If we had surgical tools that were molecular both in their size and precision, we could develop a medical technology that for the first time would let us directly heal the injuries at the molecular and cellular level that are the root causes of disease and ill health With the precision of drugs combined with the intelligent guidance of the surgeon's scalpel, we can expect a quantum leap in our medical capabilities

Continuation

• 5. Other AdvantagesLess Pollution The problem with past technologies is that they pollute the environment in cases where we humans would die in years. A good example of a bad polluting invention would be the automobile. The automobile runs on gas and the gas fumes destroyes the ozone layer. Nanotechnology can circumvent this problem

Summary• Physics : The construction of specific molecules is

governed by the physical forces between the individual atoms composing them Nanotechnology will involve the continued design of novel molecules for specific purposes

• Researchers need to understand how quantum physics affects the behavior of matter below a certain scale

.

Summary continues• Chemistry : The interaction of different

molecules is governed by chemical forces •

Nanotechnology will involve the controlled interaction of different molecules, often in solution

• Understanding how different materials interact with each other is a crucial part of designing new nanomaterials to achieve a given purpose

Summary continues

• Biology : A major focus of nanotechnology is the creation of small devices capable of processing information and performing tasks on the nanoscale The process by which information encoded in DNA is used to build proteins, which then go on to perform complex tasks including the building of more complex structures, offers one possible template

Summary continues

• Computer Science : Moore’s Law and its corollaries, affect the price performance, speed, and capacity of almost every component of the computer

• Communication industries have improved exponentially in the use of nanotechnology over the last several decades accompanied by steady miniaturization of components

Summary continues• Electrical Engineering : To operate independently,

nanodevices will need a steady supply of power Moving power into and out of devices at that scale represents a unique challenge Within the field of information technology, control of electric signals is also vital to transistor switches and memory storage A great deal of research is also going into developing nanotechnologies that can generate and manage power more efficiently

Summary continues

• Mechanical Engineering : Even at the nanolevel, issues such as load bearing, wear, material fatigue, and lubrication still apply. Detailed knowledge of how to actually build devices that do what we want them to do with an acceptable level of confidence will be a critical component of future research

8) Conclusion• The applications of nanoparticles in chemistry,

technology and medicine can not be exhausted in this lecture. Series of lectures may be required to deal sufficiently with this interesting topic. I have tried my best to define a nanoparticle and will like to mention that nanoparticles are currently being utilized in all fields of human endeavor including their usefulness in clothing, cosmetics, sporting, structural materials, speech recognition, general agricultural sciences, wound healing and dressing, sunglasses, sunscreens, catalysis, biodiesel production, HIV/AIDS treatment, cancer treatment, dentistry, malaria treatment, etc.

Continuation• In biomedical research, nanoparticles (NPs)

can improve solubility, they can be used as carriers for hydrophobic drugs (e.g., Abraxane). NPs also give multifunctional capability, they target tumors, could be used to reduce toxicity of a therapeutic drug, etc. I therefore , call on all researchers to begin focusing their research work on the synthesis, characterization and applications of nanoparticles to solve some unsolved problems

Continuation• To conduct a successful and advanced

research in nanomaterials, a well equipped and functional laboratory is required. Few of the important equipment include (1) X-Ray Diffractometer (XRD) which gives the ‘finger print’ of a material as well as the particle-size of a material using Sherrer’s equation. Also, using appropriate computer programme such as Prozski one can determine the structure of a material from the XRD diffractogram with the d-values and Miller indices indicated. XRD can also tell us whether a material is amorphous or crystalline.

Continuation

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• (2) Scanning Electron Microscope (SEM) attached to Energy Dispersive Analysis of X-rays (EDAX). The SEM provides the morphology of a material. Thus, one can discover the shape of the crystallites in a material. It can also give us information about the range of size of the particles, etc. EDAX gives us information regarding the elemental composition of the material in percentages, etc

Below is the SEM

The ED

EDAX of ZnO nanowire

Continuation

• (3) Transmission Electron Microscope (TEM) coupled with Electron Diffratometer (ED). TEM also gives us the morphology of the material, near exact particle size as well as the crystalline or non-crystalline nature of the material

• (4) Micromerritics Accusorb instrument for nitrogen adsorption in accordance with BET surface area measurement. It gives us specific surface area of the material

TEM images of (a) C nanoparticles, (b) C-Al(OH)3 core-shell nanoparticles, and (c) Al2O3 hollow spherical

nanoparticles are below

Continuation

• (5) Various magnetometers such as Vibrating Sample Magnotometer (VSM), Lewis-Coil Magnetometer (LCM), etc.

• In our department, we have designed a postgraduate programme in Nanoscience and Nanotechnology for approval by the University.

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Continuation

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Continuation

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