Revision: Std XII >> Green Chemistry and Nanochemistry MAH-MHT CET (PCM/PCB) Green Chemistry and Nanochemistry

Green Chemistry is the use of chemistry for pollution prevention by environmentally conscious design of chemical products and processes that reduce or eliminate the use or generation of hazardous substances.

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

Nanochemistry:

Nanochemistry is the combination of chemistry and nanoscience which deals with designing and synthesis of materials of nanoscale with different sizes and shape, structure and composition, and their organization into functional architectures.

Nanomaterial:

The nanomaterial is a material having structural components with at least one dimension in the nanometer scale, that is, 1-100 nm.

Nanotechnology:

Nanotechnology is the design, characterization, production and application of structures, devices and systems by controlling shape and size at nanometer scale.

Nanoscience is the study of phenomena and manipulation of materials at atomic, molecular, and macromolecular scales where properties differ significantly from those at a larger scale.

% atom economy = `" Formula mass (weight) of the desired product"/"Sum of formula masses (weights) of all the reactants used in the reaction" xx 100`

\[\text{Atom Economy}=\left(\frac{\text{Formula Weight of Desired Product}}{\text{Sum of formula weight of all the reactants used in the reaction}}\right)\times100\]

• Green chemistry focuses on designing chemical processes that reduce or eliminate harmful substances.
• It aims to produce daily-use chemicals without using or releasing toxic chemicals into the environment.
• Nanoparticles have special properties due to their very small size (1–100 nm).
• Silver nanoparticles are widely used as effective antibacterial agents.
• Sustainable development means meeting present needs without harming the ability of future generations to meet their needs.

• Prevention of waste or by-products: It is better to prevent waste than to clean it later.
• Atom economy: Design reactions so that maximum reactants are converted into a useful product.
• Less hazardous chemical synthesis: Use and produce chemicals with minimum toxicity.
• Designing safer chemicals: Develop chemicals that are less harmful.
• Use of safer solvent and auxiliaries: Avoid harmful solvents or use safer ones.
• Design for energy efficiency: Use minimum energy during chemical processes.
• Use of renewable feedstock: Prefer renewable raw materials over non-renewable ones.
• Reduce derivatives: Avoid unnecessary steps that increase waste.
• Use of catalysis: Use catalysts to increase efficiency and reduce energy use.
• Design for degradation: Products should break down safely after use.
• Real-time analysis for pollution prevention: Monitor reactions to prevent harmful substances.
• Safer chemistry for accident prevention: Design processes to reduce the risk of accidents.

• Promotes eco-friendly chemical processes that reduce harmful substances.
• Helps in preventing pollution instead of controlling it later.
• Reduces cost by minimising waste and treatment needs.
• Encourages safe and sustainable manufacturing practices.
• Protects the environment and ozone layer, supporting life on Earth.

• Nanoscience is the study of materials at the atomic and molecular scale, where properties differ from bulk materials.
• Nano-technology involves designing, producing, and using materials and devices at the nanometer scale.
• Nano-materials are materials with at least one dimension in the 1–100 nm range.
• At the nanoscale, materials show unique physical and chemical properties compared to larger-scale materials.

• Colour property: Nanoparticles show different colours at the nanoscale due to size changes (e.g., gold appears red instead of yellow).
• High surface area: Nanoparticles have a high surface area-to-volume ratio, leading to higher chemical reactivity.
• Catalytic activity: Due to large surface area, nanoparticles act as efficient catalysts and can be easily recycled.
• Thermal properties: Melting point changes at the nanoscale and generally decreases with smaller size.
• Mechanical properties: Nanoparticles show greater strength and hardness compared to bulk materials.
• Electrical conductivity: Electrical properties change at the nanoscale; materials can behave as conductors or semiconductors.

Top-Down Approach

• Involves breaking bulk material into smaller particles to form nanoparticles.
• Follows the process: Bulk → Powder → Nanoparticles.
• It is a physical method of synthesis.

Bottom-Up Approach

• Involves building nanoparticles from atoms or molecules.
• Follows the process: Atoms → Clusters → Nanoparticles.
• It is a chemical method with better control over size and structure.

Sol-Gel Method (Wet Chemical Method)

• A widely used method for preparing oxide nanomaterials.
• Involves steps: Hydrolysis → Condensation → Drying → Heating (calcination).
• Forms a gel network through chemical reactions.
• Final products can be thin films, powders, or ceramics.

• Nanomaterials are used to make materials stronger, lighter, cleaner, and smarter.
• They are used in scratch-resistant products like eyeglasses, paints, sunscreen, and transport materials.
• Nanomaterials are used in electronic devices, such as MRAM (Magnetoresistive Random Access Memory).
• They play an important role in water purification, using silver nanoparticles to kill bacteria.
• Silver nanoparticles act as strong antibacterial agents, removing microbes like E. coli from water.
• Self-cleaning materials (like the lotus leaf effect) use nanotechnology to repel water and dirt, applied in self-cleaning windows.

Advantages of Nanotechnology

• Causes a revolution in electronics and computing.
• Makes solar energy cheaper and improves energy storage devices.
• Helps in the medical field by developing smart drugs.
• Useful in treating serious diseases like cancer and diabetes.
• Improves the efficiency and performance of materials and devices.

Disadvantages of Nanotechnology

• Leads to nano-pollution, which is harmful to living organisms.
• Can increase air pollution and environmental problems.
• Nanoparticles may damage the lungs when inhaled.
• Particles can accumulate in the human body, causing health risks.
• Effects depend on the size, shape, and chemical nature of nanoparticles.