Nanochemistry

nano

1. NANOCHEMISTRY

2. BOOKS ON NANOTEHNOLOGY S.NO. TITLE AUTHOR 1. Nanotechnology: Basic Science and Emerging Technologies Mick Wilson 2. Nanotechnology (AIP-Press) Gregory L. Timp 3. Unleashing the Potentials of Nanotechnology Torres Clivia M Sotomayor 4. Nanocomposite Science and Technology Braun Paul V 5. Materials and Processes for Surface and Interface Engineering Pauleau Yves 6. A Journey into the Nanoworld Balzani Vincenzo 7. Nanotechnology and Life Jones Richard A L 8. Nanosystems : Molecular Machinery, Manufacuring and Computation K. Eric Drexler

3. CONTENTS Introduction Principle Methods of preparation Properties Techniques Application Areas

4. Nanoscience A discipline concerning with making, manipulating and imaging materials having at least one spatial dimension in the size range 1–100 nm

5. Nanotechnology A device or machine, product or process based upon individual or multiple integrated nanoscale components

6. Nanochemistry Utilization of synthetic chemistry to make nanoscale building blocks of different: Size and shape Composition Surface structure C harge Functionality.

7. Hierarchical Assembly F eature of self-assembly, where primary building blocks associate into more complex secondary structures that are integrated into the next size level in the hierarchy. This organizational scheme continues until the highest level in the hierarchy is reached. Characteristic of many self-assembling biological structures.

8. Few basic types Nanocrystals Nanotubes Nanowires Nanocomposites

9. Nanocrystals Crystals of nanometer dimensions. Typical dimensions of 1 to 50 nanometers (nm), intermediate in size between molecules and bulk materials. Exhibit intermediate properties. Applications as: Biochemical tags As laser and optical components For the preparation of display devices For chemical catalysis.

10. Nanotubes Hollow carbon tubes of nanometer dimensions. Constitute a new form of carbon, configurationally equivalent to a graphite sheet rolled into a hollow tube. May be synthesized, with sizes ranging from a few microns to a few nanometers and with thicknesses of many carbon layers down to single-walled structures. The unique structure of these nanotubes gives them advantageous behavior relative to properties, such as electrical and thermal conductivity, strength, stiffness and toughness.

11. Nanowires Very small rods of atoms. Solid , dense structures, much like a conventional wire. Offer the potential for creating very small IC components.

12. Nanocomposites Encompass a large variety of systems composed of dissimilar components that are mixed at the nanometer scale. Can be one-, two-, or three-dimensional; organic or inorganic; crystalline or amorphous. Behavior is dependent on not only the properties of the components, but also morphology and interactions between the individual components, which can give rise to novel properties not exhibited by the parent materials. Size reduction from microcomposites to nanocomposites yields an increase in surface area that is important in applications, such as mechanically reinforced components, nonlinear optics, batteries, sensors and catalysts.

13. Methods of Preparation By synthesis strategy By nature of process By medium of synthesis

14. 1. By synthesis strategy a. Bottom-Up Strategy: By the agglomeration of atoms or particles. b. Top-Down Strategy: (Attrition) By breaking the larger particles to the nano size. Generally done by high energy ball milling.

15. 2. By nature of process Physical methods: Only the size of the particles can be reduced mechanically. Physical properties will be changed. No change in chemical properties. Just the increase in chemical reactivity due to increase in surface area. b. Chemical methods: Chemical properties get change according to the chemical route.

16. 3. By medium of synthesis Gas phase synthesis Liquid phase synthesis Solid phase synthesis

17. ( i ) Gas phase synthesis Nanoparticles are formed as a result of reactions among gaseous molecules, gas molecule condensation or decomposition.

18. (ii) Liquid phase synthesis: Precipitation in homogeneous medium. Routes: a. Chemical precipitation b. Hydrothermal synthesis (Thermal hydrolysis) c. Sol-gel synthesis d. Microemulsion synthesis or synthesis in reverse micelles

19. a. Chemical precipitation Fast chemical reaction is required to obtain a high degree of super-saturation of the product to favor homogeneous nucleation.

20. b. Hydrothermal synthesis (Thermal hydrolysis) Aqueous solutions of metal salts or gels are treated at elevated temperatures (100-300˚C) and pressures above 1 atm. Size and shape of nanoparticles can be controlled by changing the conditions of the solutions: pH Concentration Solvent and process conditions (temperature, duration, etc.).

21. c. Sol- Gel synthesis Process involves the alkoxide hydrolysis and a condensation reaction. M(OR) x + yH -OH → M(OR) x-y (OH) y + yROH Partially hydrolysed species are then linked to form M-O-M bonds by condensation via dehydration or dealcoholation . -M-OH + HO-M- → -M-O-M- + H 2 O -M-OH + RO-M- → -M-O-M- + ROH So, the process involving hydrolysis, polymerization, nucleation and growth condenses the molecular units together into small clusters called sols, eventually leading to the formation of an insoluble three dimensional network, the gel.

22. d. Micro-emulsion synthesis or synthesis in reverse micelles Microemulsions : Thermodynamically stable, optically clear dispersions of two immiscible liquids, such as water and oil. They are formed, when a surfactant lowers the oil/water interfacial tension allowing thermal motions to spontaneously disperse the two immiscible phases. Reverse micelles are molecular self assemblies from surfactants which have a spherical shape with a hydrophillic core and a hydrophobic tail on the sphere surface. Most popular method to prepare nanosized inorganic particles as oxides.

23. (iii) Solid phase synthesis Nanoparticles are formed directly from solids or semisolids (viscous liquids). It belongs to top-down approach. Mechanical Milling: Mechanical forces, involved in high energy ball milling, are used to break bulk material down to bring it to nano -level. Mechano -chemical method: Involves the physical reduction in the material size as well as the milling energy is used to initiate the chemical reaction between the materials that are being milled.

24. Properties Surface area: Large. Reactivity: High due to the unsaturated bonds on their pristine surfaces. Basic properties: Properties of materials change as: - their size approaches the nanoscale . - percentage of atoms at the surface of a material becomes significant. Example- Gold nanoparticles melt at much lower temperatures (~300 °C for 2.5 nm size) than the gold slabs (1064°C). Optical properties: Often possess unexpected optical properties as they are small enough to confine their electrons and produce quantum effects. Example- Gold nanoparticles appear deep red to black in solution.

25. Techniques Scanning tunneling microscope ( STM) Atomic force microscope (AFM ) Scanning electron microscopy (SEM) Transmission electron microscopy (TEM) X-ray diffraction (XRD), etc.

26. Application Areas Medicine Diagnosis Drug delivery Tissue engineering Environment Catalysis Filtration Energy Computers Aerospace Refineries Vehicle manufacturing Food packaging Optics Textiles Cosmetics