Part 2. NANOCHEMISTRY - an introduction and potential applications (more details on some of them on separate pages)

Doc Brown's Chemistry Revision Notes  NANOCHEMISTRY

 Nanoscience - Nanotechnology - Nanostructures

Alphabetical keyword index for the nanoscience pages : Index of nanoscience pages : boron nitride * Buckminsterfullerenes-bucky balls * carbon nanotubes * fat nanoparticles * fluorographene * fullerenes * graphene * health and safety issues * liposomes * nanochemistry * nanomaterials * nanoparticles * nanoscale * nanoscience * nanosize-nanosized-particles * nanostructures * nanotechnology * nanotubes * problems in nanomaterial use * silver nanoparticles * safety issues * sunscreens-sunblockers * titanium dioxide

Part 2. NANOCHEMISTRY - Introduction

• What is NANOCHEMISTRY?

• Nanochemistry is a branch of nanoscience, deals with the chemical applications of nanomaterials in nanotechnology.

• Nanochemistry involves the study of the synthesis and characterisation of materials of nanoscale size.

• Nanochemistry is a relatively new branch of chemistry concerned with the unique properties associated with assemblies of atoms or molecules of nanoscale (~1-100 nm), so the size of nanoparticles lies somewhere between individual atoms or molecules (the 'building blocks') and larger assemblies of bulk material which we are more familiar with.

• There are physical and chemical techniques in manipulating atoms to form molecules and nanoscale assemblies.

  • Physical techniques allow atoms to be manipulated and positioned to specific requirements for a prescribed use.

  • Traditional chemical techniques arrange atoms in molecules using well characterised chemical reactions.

• Nanochemistry is the science of tools, technologies, and methodologies for novel chemical synthesis e.g. employing synthetic chemistry to make nanoscale building blocks of desired (prescribed) shape, size, composition and surface structure and possibly the potential to control the actual self-assembly of these building blocks to various desirable size.

• At this extremely small scale level, quantum effects can be significant, fascinating and potentially scientifically very rewarding innovative ways of carrying out chemical reactions are possible.

• The small size of nanoparticles gives these particles 'unusual' structural and optical properties with applications in catalysis, electrooptical devices etc.

• As well as the huge numbers of man-made nanoparticles structures being synthesised, there are naturally occurring nanoparticle assemblies e.g. phospholipid vesicles, polypeptide micelle of the iron storage protein, ferritin.

• Nanoparticles are VERY tiny aggregations of atoms BUT bigger than most molecules.

• There is no strict dividing line between nanoparticles and 'ordinary bulk' particles of a material such as baking powder or grains of sand, BUT particle size matters! ...

• ... BECAUSE nanoparticles can display properties significantly different from the bulk material and these properties can be exploited for many different uses. If you compare the size of nanoparticles to that of conventional industrially produced materials you find they have novel uses such as sunscreens and many present future applications e.g.

  • Nanoparticles have a high surface to volume ratio which has a dramatic effect on their properties compared to non-nanoscale more bulky forms of the same material.

  • Nanoparticles have a very high surface to volume ratio and this gives them special properties different from the bulk material e.g.

    • This difference in surface area / volume ratio for the particles of the material give nanoparticles extra chemical reactivity compared to the bulk material,

    • less of a material like a catalyst is needed in a chemical process, so catalysts based on nanoparticles are more efficient than those based on bulk material catalysts.

  • • See APPENDIX 1 on the introduction page to nanoscience page for more details on this ratio.

  • Pieces of gold are, fairly obviously, gold-coloured, but gold nanoparticles are deep red or even black when mixed with water. use?

  • Titanium dioxide is a white solid used in house paint where plainly it reflects visible light. However, titanium dioxide nanoparticles are so small that they do not reflect visible light, so they cannot be seen and are used in sunblock creams because they block harmful ultraviolet light from the Sun without appearing white on the skin (as in TiO₂ in paint).

  • Silver foil shows virtually no reaction with dilute hydrochloric acid but nanoparticles of silver rapidly react with hydrochloric acid because of the very large surface are to volume ration (think of limestone lumps and very fine powder illustrates this effect at the much larger non-nanoparticle level.

• A summary of some uses of nanoparticles

  • Some are described in more detail on other pages, see index at the end and links here too.

  • New applications for nanoparticle materials are an important area of research.

  • Nanoparticles have many applications in medicine for controlled drug delivery via fullerenes - an example of nanomedicine application.

    • One idea being explored in nanomedicine, is that tiny nanoparticles are more easily absorbed through the skin - an alternative way of delivering a drug directly into the cells where needed.

  • Nanotechnology is being applied to the production of synthetic skin and implant surgery.

  • Nanomaterials that conduct electricity are being used in electronics as minute conductors to produce circuits for microchips.

  • Materials in cosmetics, deodorants and sun creams may be of nanoparticle size and they are used to improve moisturisers without making them too oily.

    • The tiny nanoparticles don't leave white marks on the skin.

  • Nanoscale materials are being developed as new catalysts for fuel cells.

  • Nanoparticle substances are incorporated in fabrics to prevent the growth of bacteria.

  • Fullerene nanoparticles can act as molecular sieves, these allow small molecules to pass through, but larger molecules are trapped on one side.

• Nanotubes (more details of specific examples on other pages), one of the most widespread studied and used nanomaterials, consist of tiny cylinders of carbon (and other materials like boron nitride), no wider than a strand of DNA with a wide range of properties of great use to materials scientists.

  • Nanotubes can be stronger than steel with only ¹/₆th the weight. Some nanotubes are excellent insulators, semiconductors or conduct electricity as well as copper!

  • Incredibly, there are lots of varieties of nanotubes, even for the same element or compound, differing in size and atomic arrangement, which can have very different properties!

  • Therefore a wide range of nanomaterials are being developed for an even wider range of applications and technological uses. See also carbon and boron nitride to illustrate this point.

Applications of Nanoscience - with an emphasis on NANOCHEMISTRY

Detailed examples of uses of nanomaterials in CHEMISTRY are discussed on separate pages (see index below)

• We are talking about the manufacture of new catalysts, coatings, computer components, highly selective sensors, lighter strong materials etc.

  • The large surface to volume ratio will allow the development of new industrial catalysts.

  • Nanomaterials can be used to make sensors that detect specific molecules.

    • These detectors will find applications in detecting and monitoring pollutants in water.

  • Nanotubes can be fabricated into strong and light materials, sometimes as composites with other non-nanomaterials.

    • Such materials can used in such diverse applications as aircraft construction (fuselage, wings etc.) and sports equipment.

  • -

• The increased reactivity and small size of nanoparticles compared to larger ones are two important factors which frequently crop up when studying the function of nanomaterials.

• Nanoparticles have a high surface area to volume ratio, this increases their rate of chemical reaction (greater reactivity) and this also enhances their catalytic effect.

• Nanomaterials can even be used for such mundane-unexciting applications as in self-cleaning ovens and self-cleaning windows!, but not mundane to domestic work in the home, but will it put window cleaners out of business, I doubt it!

  • Nanoparticles are already being used in deodorants, sun blockers (sun tan creams).

• The work on nanochemistry can include colloid chemistry.

WHERE NEXT?

NANOSCIENCE - NANOCHEMISTRY INDEX

Part 1. Introduction to nanoscience, nanoparticles, commonly used terms explained

Part 2. Nanochemistry - introduction, uses & potential applications described

Part 3. Uses of Nanoparticles of titanium(IV) oxide (e.g. sun cream), fat (e.g. cosmetics), silver (e.g. medical applications)

Part 4. From fullerenes & bucky balls to carbon nanotubes - structure, properties, uses

Part 5. Graphene, graphene oxide and fluorographene - structure, properties, uses

Part 6. Cubic and hexagonal boron nitride BN

Part 7. Problems, issues and implications associated with using nanomaterials

see also INDEX of Smart materials pages

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