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Zinc oxide (ZnO) and Titanium dioxide (TiO₂) nanoparticles are used sunscreen lotions. The chemicals protect the skin against harmful u.v (ultraviolet) rays by absorbing or reflecting the light and prevent the skin from damage.

• Use of safer solvents and auxiliaries – is a principle of green chemistry it states that safer solvent like water, supercritical CO₂ should be used in place of volatile halogenated organic solvents, like CH₂CI_{​​​​​​​2}, CHCI₃, CCI₄ for chemical synthesis and other purposes.
• Solvents dissolve solutes and form solutions, they facilitate many reactions. Water is a safer benign solvent while solvents like dichloromethane (CH₂CI₂), chloroform (CHCI₃) etc are hazardous.
• Use of toxic solvents affect millions of workers every year and have implications for consumers and the environment. A large amount of waste is created by their use and they also have huge environmental and health impacts.
• Finding safer solvents or designing processes which are solvent free is the best way to improve the process and the product.

A substance which speeds up the rate of a reaction without itself being changed chemically in the reaction is called a catalyst. It helps to increase selectivity, minimise waste and reduce reaction time and energy demands. 

For example : Hydrogenation of oil the catalyst used are platinum or palladium, Raney nickel.

Nanoparticles, nanowires and nanotubes can be classified according to dimensions. The nano structured materials may be large organic molecules, inorganic cluster compounds and metallic or semiconductor particles.

Zero-Dimensional Nanostructures : A zero-dimensional structure is one in which all three dimensions are in the nanoscale.

For example : Nanoparticles.

One-Dimensional Nanostructures : A one-dimensional nanostructure is one in which two dimensions are in the nanoscale. 

For example : Nanowires and Nano rods.

Two-Dimensional Nanostructures : A two-dimensional nanostructure is one in which one dimension is in the nanoscale. 

For example : Thin films.

The nanoparticle science is special as at such a small scale, different laws dominate than what we experience in our everyday life.

The characteristic features like optical properties, catalytical activities, have huge surface area and good thermal properties mechanical strength electrical conductivity vary than that of bulk material.

(1) Colour : At nanoscale this optical property behaves differently. Elemental gold has nice shining yellow colour, but nanoparticles of gold show red colour.

(2) Catalytic activity : Since the surface area of nanoparticles is large they show increased catalytic activity. They are usually heterogenous catalyst that means catalysts are solid form and the reactions occur on the surface of the catalyst. These catalysts can be easily separated and recycled. 

For example : Pd, Pt metal nanoparticles used in hydrogenation reactions. Ti02, ZnO are used in photocatalysis. Gold in bulk is unreactive but the nanoparticles of gold behave as very good catalyst for organic reactions.

(3) Surface area : High surface-to-volume ratio is a very important characteristic of nanoparticles. Bulk material if subdivided into a group of individual nanoparticles, the total volume remains the same, but the collective surface area is largely increased. With large surface area for the same volume, these small particles react much faster because more surface area provides more number of reaction sites, leading to more chemical reactivity. Explanation of increase in surface area with decrease in particle size.

(4) Thermal strength : The melting point of nanomaterial changes drastically with size.

For example : Sodium clusters (Nan) of 1000 atoms melts at 288 K, 10000 atoms melt at 303 K and bulk sodium melts at 371 K.

(5) Mechanical strength : The mechanic al strength of nano clusters increase the hardness of the metal.

For example : nanoparticles of copper and palladium clusters with diameter in the range of 5-7 nm have hardness up to 500 r. greater than the bulk metal.

(6) Electrical conductivity : At nanoscale level the electrical conductivity changes. 

For example : Carbon nanotubes behave as a conductor or semiconductor whereas carbon is nonconductor.

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(d) Paul T. Anastas

1 nm = 10⁹ m.

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(d) 500% more than the bulk metal

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(c) TiO₂

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(b) heterogeneous catalyst

Gerd Binning and Heinrich Rohrer. (Nobel prize 1986)

Carbon black is used for tyres of car to increase the life of tyres.

a. XRD-X-ray diffraction 

b. TEM-Tunneling Electron Microscope 

c. STM – Scanning Tunneling Microscope 

d. FTIR-Fourier Transform Infrared Spectroscope 

e. SEM-Scanning Electron Microscope

The colour of gold nanoparticles is red.

Zinc oxide (ZnO) and Titanium dioxide (TiO₂).

The ϒ-isomer of BHC is Lindane.

The analytical tools used for characterization of nanoparticles are

• U.V visible spectroscopy – It gives the preliminary confirmation of formation of nanoparticles.
• X-ray Diffraction (XRD) – The information given by this tool is about particle size, crystal structure and geometry.
• Scanning electron microscopy (SEM) : This is used to study the structure of surface of material that is the morphology of the material.
• Transmission electron microscopy (TEM) gives information about the particles size.
• (FTIR) Fourier transform infrared spectroscopy gives information about absorption of functional groups and binding nature of the nanomaterial.

There is enough evidence that nanomaterials have been produced and used by humans in ancient times. 

For example :

• Gold and silver nanoparticles trapped in the glass matrix gives ruby red colour in some ancient glass paintings.
• The decorative glaze or metallic film known as lustre found on some medieval pottery is due to certain spherical metallic nanoparticles.
• Carbon black is a nanostructured material that is used in tyres of car to increase the life of tyre. (Discovery in 1900). Carbon nanotubes are made up of graphite sheets with nanosized diameter. They have highest strength.
• Fumed silica, a component of silicon rubber, coatings, sealants and adhesives is also a nanostructured material.

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(a) battery cables, brooms, ice scrapers, rakes

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(d) reducing or eliminating the use or generation of hazardous chemicals in chemical products and process

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(c) unique optical, magnetic, electrical properties

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(a) one in which all three dimensions are in the nanoscale

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(b) 1-100 nm

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b. Sustainable development

(i) Green chemistry : Green chemistry is the use of chemistry for pollution prevention and it designs the use of chemical products and processes that reduce or eliminate the use or generation of hazardous substances.

(ii) Sustainable development : Sustainable development is the development that meets the needs of the present, without compromising the ability of future generations to meet their own needs.

Paul T. Anastas

Nanomaterials materials having structural components with at least one dimension in the nanometer scale.

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(b) atom economy

Sustainable development

• There is a need to design safer chemicals to prevent the workers in chemical industries from being exposed to toxic environment.
• Adipic acid is extensively used in polymer industry. In synthesis of adipic acid, benzene is used as the starting material, but benzene is carcinogenic and being volatile organic compound (VOC) it pollutes the air and environment.
• To overcome this health hazard Green technology developed by Drath and Frost, adipic acid is enzymatically synthesised from glucose.

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(c) catalyst

Despite the benefits that nanotechnology offers to the world, it is accompanied by certain disadvantages and potential risks.

The standard of living has been raised by nanotechnology but at the same time it has increased the environmental pollution. The kind of pollution caused by nanotechnology is very dangerous for living organism, it is called nano pollution.

Nanoparticles can be potential health hazard depending on the size, chemical composition and shape. They can be inhaled and can be deposited in the human respiratory tract and in the lungs, causing lung damage.

1. To avoid formation of hazardous waste from chemical processes, the chemical reactions and synthesis routes should be designed to be as safe as possible. 

2. Earlier used insecticide DDT (Dichlorodiphenyltrichloroethanc) was found to be harmful for human beings. So DDT has been replaced by benzenc hexachioride (BHC) as an insecticide, one of the y-isomer (gamma) of BHC is called gammexane or lindane.

Electronics, energy sector and medical fields.

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(b) Greek word meaning dwarf

• There is a dire need to develop improvised analytical methods to allow for real time, in process monitoring and control prior to the formation of hazardous substances.
• It is very much important for the chemical industries and nuclear reactors to develop or modify analytical methodologies so that continuous monitoring of the manufacturing and processing unit is possible.

1. Water purification is an important issue as 1.1 billion people do not have access to improved water supply. Water contains water bom pathogens like viruses, bacteria. 

2. Silver nanoparticles are highly effective bacterial disinfectant to remove E. Coli from water. Hence, filter materials coated with silver nanoparticles is used to clean water. 

3. Silver nanoparticles (AgNps) is a cost effective alternative technology (for e.g. water purifier).

Nano pollution and lung damage.

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(c) silver nanoparticle

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(c) lungs

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(d) All of the above

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(c) Lotus effect

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(b) nano pollution.

• Lotus is an example of self cleansing. 
• Nanostructures on the lotus plant leaves are super hydrophobic, they repel water which carries dirt as it rolls off. 

Thus though lotus plant (Nelumbonucifera) grows in muddy water, its leaves always appear clean.

Atom economy : Atom economy is a measure of the amount of atoms from the starting materials that are present in the final product at the end of chemical process.

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(a) 49.81%