Tag Archives: TiO2

Canadian research into nanomaterial workplace exposure in the air and on surfaces

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An August 30, 2018 news item on Nanowerk announces the report,

The monitoring of air contamination by engineered nanomaterials (ENM) is a complex process with many uncertainties and limitations owing to the presence of particles of nanometric size that are not ENMs, the lack of validated instruments for breathing zone measurements and the many indicators to be considered.

In addition, some organizations, France’s Institut national de recherche et de sécurité (INRS) and Québec’s Institut de recherche Robert-Sauvé en santé et en sécurité du travail (IRSST) among them, stress the need to also sample surfaces for ENM deposits.

In other words, to get a better picture of the risks of worker exposure, we need to fine-tune the existing methods of sampling and characterizing ENMs and develop new one. Accordingly, the main goal of this project was to develop innovative methodological approaches for detailed qualitative as well as quantitative characterization of workplace exposure to ENMs.

A PDF of the 88-page report is available in English or in French.

An August 30, 2018 (?) abstract of the IRSST report titled An Assessment of Methods of Sampling and Characterizing Engineered Nanomaterials in the Air and on Surfaces in the Workplace (2nd edition) by Maximilien Debia, Gilles L’Espérance, Cyril Catto, Philippe Plamondon, André Dufresne, Claude Ostiguy, which originated the news item, outlines what you can expect from the report,

This research project has two complementary parts: a laboratory investigation and a fieldwork component. The laboratory investigation involved generating titanium dioxide (TiO2) nanoparticles under controlled laboratory conditions and studying different sampling and analysis devices. The fieldwork comprised a series of nine interventions adapted to different workplaces and designed to test a variety of sampling devices and analytical procedures and to measure ENM exposure levels among Québec workers.

The methods for characterizing aerosols and surface deposits that were investigated include: i) measurement by direct-reading instruments (DRI), such as condensation particle counters (CPC), optical particle counters (OPC), laser photometers, aerodynamic diameter spectrometers and electric mobility spectrometer; ii) transmission electron microscopy (TEM) or scanning transmission electron microscopy (STEM) with a variety of sampling devices, including the Mini Particle Sampler® (MPS); iii) measurement of elemental carbon (EC); iv) inductively coupled plasma mass spectrometry (ICP-MS) and (v) Raman spectroscopy.

The workplace investigations covered a variety of industries (e.g., electronics, manufacturing, printing, construction, energy, research and development) and included producers as well as users or integrators of ENMs. In the workplaces investigated, we found nanometals or metal oxides (TiO2, SiO2, zinc oxides, lithium iron phosphate, titanate, copper oxides), nanoclays, nanocellulose and carbonaceous materials, including carbon nanofibers (CNF) and carbon nanotubes (CNT)—single-walled (SWCNT) as well as multiwalled (MWCNT).

The project helped to advance our knowledge of workplace assessments of ENMs by documenting specific tasks and industrial processes (e.g., printing and varnishing) as well as certain as yet little investigated ENMs (nanocellulose, for example).

Based on our investigations, we propose a strategy for more accurate assessment of ENM exposure using methods that require a minimum of preanalytical handling. The recommended strategy is a systematic two-step assessment of workplaces that produce and use ENMs. The first step involves testing with different DRIs (such as a CPC and a laser photometer) as well as sample collection and subsequent microscopic analysis (MPS + TEM/STEM) to clearly identify the work tasks that generate ENMs. The second step, once work exposure is confirmed, is specific quantification of the ENMs detected. The following findings are particularly helpful for detailed characterization of ENM exposure:

  1. The first conclusive tests of a technique using ICP-MS to quantify the metal oxide content of samples collected in the workplace
  2. The possibility of combining different sampling methods recommended by the National Institute for Occupational Safety and Health (NIOSH) to measure elemental carbon as an indicator of NTC/NFC, as well as demonstration of the limitation of this method stemming from observed interference with the black carbon particles required to synthesis carbon materials (for example, Raman spectroscopy showed that less than 6% of the particles deposited on the electron microscopy grid at one site were SWCNTs)
  3. The clear advantages of using an MPS (instead of the standard 37-mm cassettes used as sampling media for electron microscopy), which allows quantification of materials
  4. The major impact of sampling time: a long sampling time overloads electron microscopy grids and can lead to overestimation of average particle agglomerate size and underestimation of particle concentrations
  5. The feasibility and utility of surface sampling, either with sampling pumps or passively by diffusion onto the electron microscopy grids, to assess ENM dispersion in the workplace

These original findings suggest promising avenues for assessing ENM exposure, while also showing their limitations. Improvements to our sampling and analysis methods give us a better understanding of ENM exposure and help in adapting and implementing control measures that can minimize occupational exposure.

You can download the full report in either or both English and French from the ‘Nanomaterials – A Guide to Good Practices Facilitating Risk Management in the Workplace, 2nd Edition‘ webpage.

Astonishing material, multi-use titanium dioxide nanofibres

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The enthusiasm in the Mar. 20, 2013 news release on EurekAlert about Darren Sun’s work with titanium dioxide nanofibres seems boundless,

A new wonder material that can generate hydrogen, produce clean water and even create energy.

Science fiction? Hardly, and there’s more – It can also desalinate water, be used as flexible water filtration membranes, help recover energy from desalination waste brine, be made into flexible solar cells and can also double the lifespan of lithium ion batteries. With its superior bacteria-killing capabilities, it can also be used to develop a new type of antibacterial bandage.

Scientists at Nanyang Technological University (NTU) in Singapore, led by Associate Professor Darren Sun have succeeded in developing a single, revolutionary nanomaterial that can do all the above and at very low cost compared to existing technology.

The Nanyang Technological University Mar. 20, 2013 news release (also posted to EurekAlert) gives details about how Sun created his ‘wonder’ material,

This breakthrough which has taken Prof Sun five years to develop is dubbed the Multi-use Titanium Dioxide (TiO2). It is formed by turning titanium dioxide crystals into patented nanofibres, which can then be easily fabricated into patented flexible filter membranes which include a combination of carbon, copper, zinc or tin, depending on the specific end product needed.

Titanium dioxide is a cheap and abundant material, which has been scientifically proven to have the ability to accelerate a chemical reaction (photocatalytic) and is also able to bond easily with water (hydrophilic).

…

Prof Sun, 52, from NTU’s School of Civil and Environmental Engineering, said such a low-cost and easily produced nanomaterial is expected to have immense potential to help tackle ongoing global challenges in energy and environmental issues.

With the world’s population expected to hit 8.3 billion by 2030, there will be a massive increase in the global demand for energy and food by 50 per cent and 30 per cent for drinking water (Population Institute report, titled 2030: The “Perfect Storm” Scenario).

“While there is no single silver bullet to solving two of the world’s biggest challenges: cheap renewable energy and an abundant supply of clean water; our single multi-use membrane comes close, with its titanium dioxide nanoparticles being a key catalyst in discovering such solutions,” Prof Sun said. “With our unique nanomaterial, we hope to be able to help convert today’s waste into tomorrow’s resources, such as clean water and energy.”

…

Prof Sun had initially used titanium dioxide with iron oxide to make anti-bacterial water filtration membranes to solve biofouling – bacterial growth which clogs up the pores of membranes, obstructing water flow.

While developing the membrane, Prof Sun’s team also discovered that it could act as a photocatalyst, turning wastewater into hydrogen and oxygen under sunlight while still producing clean water. Such a water-splitting effect is usually caused by Platinum, a precious metal that is both expensive and rare.

Here’s a list of what the researchers are claiming multi-use titanium dioxide materials can accomplish, from the news release,

Producing hydrogen and clean water

This discovery, which was published recently in the academic journal, Water Research, showed that a small amount of nanomaterial (0.5 grams of titanium dioxide nanofibres treated with copper oxide), can generate 1.53 millilitre of hydrogen in an hour when immersed in one litre of wastewater. This amount of hydrogen produced is three times more than when Platinum is used in the same situation.

Depending on the type of wastewater, the amount of hydrogen generated can be as much as 200 millilitres in an hour. Also to increase hydrogen production, more nanomaterial can be used in larger amounts of wastewater.

Producing low-cost flexible forward osmosis membranes

Not only can titanium dioxide particles help split water, it can also make water filter membranes hydrophilic – allowing water to flow through it easily, while rejecting foreign contaminants, including those of salt, making it perfect for desalinating water using forward osmosis. Thus a new super high flux (flow rate) forward osmosis membrane is developed.

This discovery was published recently in last month’s journal of Energy and Environmental Science. This is the first such report of TiO2 nanofibres and particles used in forward osmosis membrane system for clean water production and energy generation.

Producing new antibacterial bandages

With its anti-microbial properties and low cost, the membrane can also be used to make breathable anti-bacterial bandages, which would not only prevent infections and tackle infection at open wounds, but also promote healing by allowing oxygen to permeate through the plaster.

The membrane’s material properties are also similar to polymers used to make plastic bandages currently sold on the market.

Producing low-cost flexible solar cells

Prof Sun’s research projects have shown out that when treated with other materials or made into another form such as crystals, titanium dioxide can have other uses, such as in solar cells.

By making a black titanium dioxide polycrystalline sheet, Prof Sun’s team was able to make a flexible solar-cell which can generate electricity from the sun’s rays.

Producing longer lasting lithium ion batteries

Concurrently, Prof Sun has another team working on developing the black titanium dioxide nanomaterial to be used in Lithium ion batteries commonly used in electronic devices.

Preliminary results from thin coin-like lithium ion batteries, have shown that when titanium dioxide sphere-like nanoparticles modified with carbon are used as the anode (negative pole), it can double the capacity of the battery. This gives such batteries a much longer lifespan before it is fully drained. The results were featured prominently in a highly respected Journal of Materials Chemistry on its cover page last year.

As is expected these days, from the news release,

Next step – commercialisation

Prof Sun and his team of 20, which includes 6 undergraduates, 10 PhD students and 4 researchers, are now working to further develop the material while concurrently spinning off a start-up company to commercialise the product.

They are also looking to collaborate with commercial partners to speed up the commercialisation process.

Here’s a citation and a link for the paper,

Novel-Structured Electrospun TiO2/CuO Composite Nanofibers for High Efficient Photocatalytic Cogeneration of Clean Water and Energy from Dye Wastewater by Siew Siang Lee, Hongwei Bai Zhaoyang Liu, & Darren Delai Sun. Water Research Available online 19 March 2013 In Press, Accepted Manuscript http://dx.doi.org/10.1016/j.watres.2012.12.044

This paper is behind a paywall. Good luck to Professor Sun and his colleagues.

Unintended consequences: Australians not using sunscreens to avoid nanoparticles?

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Friends of the Earth (FoE) Australia has waged a campaign against the use of nanosunscreens. It seems to have been somewhat successful but in a way that I imagine is upsetting. From the Feb. 9, 2012 news item on physorg.com,

The Cancer Council of Australia reports that we have one of the highest rates of skin cancer in the world, with over 440,000 people receiving medical treatment for skin cancers each year, and over 1,700 people dying of all types of skin cancer annually.

The survey of public attitudes towards sunscreens with nanoparticles, commissioned by the Australian Department of Industry, Innovation, Science, Research and Tertiary Education and conducted last month, showed that about 17% of people in Australia were so worried about the issue, they would rather risk skin cancer by going without sunscreen than use a product containing nanoparticles. [emphasis mine] [please see correction at the end of this posting]

The survey along with three research papers were presented at the 2012 International Conference on Nanoscience and Nanotechnology (ICONN) in Perth,Feb. 5-9.

One of the research studies indicates that claims of  ‘nano-free’ sunscreen products may be wrong, from the Feb. 9, 2012 news item on Nanowerk,

Scientists from Australia’s National Measurement Institute and overseas collaborators reported on a technique using the scattering of synchrotron light to determine the sizes of particles in sunscreens. They found that some commercial sunscreens that claim to be ‘nano-free’ do in fact contain nanostructured material. The findings highlight the need for clear definitions when describing nanomaterials.

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The Australian Therapeutic Goods Administration has released a statement on safety of sunscreens containing nanoparticles that concluded: “… the current weight of evidence suggests that TiO2 (titanium dioxide) and ZnO (zinc oxide) nanoparticles do not reach viable skin cells, rather, they remain on the surface of the skin and in the outer layer of the skin…”

You can get more information about the studies in either linked news item. The Australian government’s sunscreen use survey is available on this page; the Australian Therapeutic Goods Administration review of the scientific literature on the safety of nanoscale (nanoparticulate) titanium dioxide and zinc oxide in sunscreens is available on this page; and the Cancer Council of Australia has information about sunscreens and nanoparticles on this page.

One can’t lay the blame for *13%* of the population’s hesitance to use any sunscreens at one door but I hope that civil societies like FoEAustralia will give a little thought to the unintended consequences of their campaigns.

The campaign was against nanosunscreens not all sunscreens but presumably coupled with other influences, it seems to have upset a significant percentage of the population to the point that they refuse to use any sunscreens at all for fear of inadvertently being exposed to nanoparticles.

Feb. 10, 2012 update: It’s a very interesting response from FoEAustralia (from the Feb. 10, 2012 article by Simon Lauder for ABC  [Australian Broadcasting Corporation] News),

“We’ve decided to recall the safe sunscreen guides that we have produced this summer until we can revise them based on new information that comes in,” Elena McMaster, the nanotechnology campaigner with Friends of the Earth, said.

“What we see with this research is that in the absence of government regulation, the nanotech industry is able to more or less make up their own rules about what constitutes a nano material,” she said.

“We are obviously probably as shocked as people in the industry about the NMI research results.

“I can’t emphasise enough how urgent we think it is that the Government regulates.”

The best FoEAustralia can offer in the face of the rather shocking information that 17% of the adult population are avoiding sunscreens altogether is a plea for more government regulation of a product that doesn’t seem to be dangerous according to research.

Dexter Johnson in his Feb. 10, 2012 Nanoclast posting noted this about the study which found that sunscreens claiming ‘no nanomaterials/nanoparticles’ did contain some,

“What we see with this research is that in the absence of government regulation, the nanotech industry is able to more or less make up their own rules about what constitutes a nano material,” said Elena McMaster, a FoE spokesperson.

That’s one interpretation, I suppose. But it could also be that traditional sunscreens might contain nanoscale particles even though no attempt had been made to manufacture or add them to the mix. Unintentional nanoparticles, if you will, not unlike those created when the tires of your car drive over the pavement.

I wonder what kind of government regulations the FoE will request. Will each container of sunscreen have to be opened and its contents examined with a scattering of synchrotron light to determine particle size?

In fact, there’s some evidence that nanoparticles are all over the place, some of them created by nature, from the May 11, 2012 article New Evidence for Natural Synthesis of Silver Nanoparticles on Nanowiki,

“this creates the idea that there may be some sort of natural cycle returning some of the ions to nanoparticles.” [said Robert MacCuspie at NIST {US National Institute of Standards and Technology}] It also helps explain the discovery, over the past few years, of silver nanoparticles in locations like old mining regions that are not likely to have been exposed to man-made nanoparticles, but would have significant concentrations of silver ions. [emphasis mine]

My respect for FoEAustralia is seriously damaged by this stance they’ve taken. As far as I’m concerned they should admit they’ve made a mistake by using scare tactics to force some sort of confrontation over nanosunscreens and their strategy to force regulation of nanomaterials has backfired seriously.

Feb.21.12 correction: According to the information in the Feb. 20, 2012 posting on 2020 Science, the percentage of Australians likely to avoid using sunscreens is 13%,

This has just landed in my email in box from Craig Cormick at the Department of Industry, Innovation, Science, Research and Tertiary Education in Australia, and I thought I would pass it on given the string of posts on nanoparticles in sunscreens on 2020 Science over the past few years:
…

“An online poll of 1,000 people, conducted in January this year, shows that one in three Australians had heard or read stories about the risks of using sunscreens with nanoparticles in them,” Dr Cormick said.

“Thirteen percent of this group were concerned or confused enough that they would be less likely to use any sunscreen, whether or not it contained nanoparticles, putting them selves at increased risk of developing potentially deadly skin cancers.

“The study also found that while one in five respondents stated they would go out of their way to avoid using sunscreens with nanoparticles in them, over three in five would need to know more information before deciding.”

*’17%’ corrected to ‘13%’ on Sept. 22, 2016.