Doc Brown's Chemistry Revision Notes  NANOCHEMISTRY

 Nanoscience - Nanotechnology - Nanostructures

Part 3. Uses of nanoparticles of titanium(IV) oxide, fat & silver

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 3. Uses of nanoparticles of titanium(IV) oxide (titanium dioxide, TiO2)

  • How does titanium dioxide protect us from uv light? What does titanium dioxide do in sun creams?

  • In the cosmetics industry the use of nanosized particles in creams etc is increasing, because of the small particle size, they can be more easily absorbed through the skin, as in moisturisers.

  • Titanium dioxide, TiO2, is a white powder and a good reflector of visible light and most commonly encountered as a brilliant white pigment in paint.

  • However, it also used in the cosmetic and skincare products industry as a pigment, thickener, moisturiser and used in sunscreens as a uv absorber.

    • Ultraviolet light from the sun impacting on the skin can cause cell damage, e.g. DNA damage, which can lead to skin cancer.

    • Nanoparticles used in sun creams offer better skin protection than traditional uv  sun blocker creams and less is needed to cover the same surface area of skin.

    • In sun creams nanoparticles provide better protection from the harmful effects of ultraviolet radiation (uv rays from the sun) and give better coverage of the skin.

    • Titanium dioxide is a good uv light absorber and is effective as many organic molecules used as uv absorbers in many commercial sun creams.

    • Some of these organic 'sun blocker' molecules can cause skin irritations on sensitive skin. Can the nanoparticles be absorbed by the skin and cause this irritation or other effects?

    • Nanoparticles of titanium dioxide are incorporated into 'sun blockers', though the particles have to be specially coated (*) to avoid skin irritation problems from using such titanium dioxide based sunscreens.

      • (*) Apparently the interaction of uv light and titanium dioxide in the presence of other molecules can produce highly reactive and harmful free radicals.

    • As well as being a good uv absorber (90% absorbed, 10% scattered), nanosized titanium dioxide particles have 2nd another advantage.

      • The TiO2 particles are smaller than the wavelength of light and are therefore too small to see, and when used in sunscreen creams they are transparent to light rather than opaque, so the skin looks a more natural colour (no white creamy marks), so nanochemistry can satisfy aspects of human aesthetics (or vanity!).

      • The wavelength of visible light ranges from 300 to 700 nm.

      • The nanoparticles of TiO2 typically used vary from 20 to 170 nm in size.

    • A good example of where particle size matter, and the tiny size of titanium dioxide particles gives it this commercial advantage.

    • Note in passing that nanoparticles of zinc oxide are also used in sunscreens with the similar properties and effects.

  • Note - titanium dioxide in the form of anatase crystals can be converted into nanotubes 10-20 nm in diameter - but I don't know their potential uses?


Nanoparticles of silver

  • What are nanoparticles of silver? What size are they? What can we do with nanoparticles of silver?

  • Silver has always been used as a catalyst to speed up specific reactions in the chemical industry to improve economic efficiency.

    • By using nanoparticles of silver (35-120 nm in size) the effectiveness of the catalyst is greatly improved because the surface area of nanosized silver is so much greater than the larger particles previously used.

    • Its a good example of the 'surface area' rates-kinetic factor for reactions involving a solid catalyst or reactant and silver nanoparticles are extremely effective in killing bacteria.

      • Larger particles of silver, with a lower surface/volume ratio, have no effect on bacteria.

  • Nanoparticles of silver are being used in anti-bacterial and anti-fungal agents in biotechnology, bioengineering, the textile industry, water treatment and disinfecting surfaces in the home or hospitals etc.

    • Bactericide and fungicide formulations are being developed to include nanoparticles e.g. of silver, because of their powerful ability to kill bacteria and other organisms.

    • Because of their antibacterial and antifungal properties, potential uses of silver nanoparticles include bone cement, surgical instruments, surgical masks and wound dressings.

      • In other words you can fabricate materials e.g. from plastic fibres, with built in silver nanoparticles, to keep them sterile (enhanced antibacterial life) even after application to the patient.

      • A wide variety of fabrics in medical, domestic or outdoor use can be treated with nanoparticles (e.g. of silver) to inhibit the growth of bacteria.

      • You can add antibacterial nanoparticles of silver to polymer fibres used in surgical masks and wound dressings.

      • Nanoparticles of silver can be used in deodorants, but can they do us harm if breathed in?

    • There is an advantage (at least at the moment!) in using nanoparticles of silver in antibacterial agents, because many bacteria are evolving into strains which are resistant to many antibiotics rendering the ineffective in fighting infections, but so far bacteria don't seem to be resistant to nano-silver formulations!

  • Nanoparticles of silver are also used in optics and electronics - important applications but not much, if any, chemistry involved?


Nanoparticles of fat are used in cosmetics

  • Some cosmetics contain 'liposomes', which are fatty nanoparticles.

    • Nanoparticles are used in cosmetics to improve the texture and feel of moisturisers so they don't seem as oily.

  • Nanoparticles of fatty-like molecules have great potential in the pharmaceutical industry to deliver tiny doses of medicines directly into cells.

    • The use of liposome nanoparticles may enable the efficient delivery of chemotherapeutic agents for cancer treatment,


Other examples of the use of nanoparticles and nanowires

  • Hip replacement and dental surgery in nanoscience - examples of nanomedicine

    • Modern surgical techniques are being improved by using ceramic nanowire coatings based on inorganic materials like titanium dioxide and hydroxyapatite.

    • These inorganic nanowires (extremely fine molecular tubes!) create a more effective surface for tissue growth on implants in hip replacement operations and in dental surgery too.

    • In orthopaedic surgery the nanowire coating is applied to the surface of the implanted component where it is actually fitted into the bone.

    • This ceramic nanowire surface layer encourages bone growth on the surfaces of the 'wedges' on the ball and socket that are embedded in the bone in hip replacement operations to hold the ball and socket in place.

    • Nanoparticle materials, to inhibit bacteria growth, are incorporated in materials used in dentistry e.g. fillings.

  • -

WHERE NEXT?

INDEX of NANOSCIENCE-NANOCHEMISTRY pages

Part 1. General introduction to nanoscience and commonly used terms explained

Part 2. NANOCHEMISTRY - an introduction and potential applications

Part 3. Uses of Nanoparticles of titanium(IV) oxide, fat and silver

Part 4. From fullerenes & bucky balls to carbon nanotubes

Part 5. Graphene and Fluorographene

Part 6. Cubic and hexagonal boron nitride BN

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

see also INDEX SMART MATERIALS PAGES


Keywords: uses applications  liposomes fat sunscreens-sunblockers titanium dioxide silver nanoparticles TiO2

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