Author Archive

Miracle material potential water pollutant

Researchers demonstrate toxic effects of graphene on aquatic life

By looking at the effects of graphene on water fleas, scientists in China have discovered that it may disrupt aquatic ecosystems, suggesting an unfortunate dark side to the wonder material.

Graphene, the poster child of carbon nanomaterials, has been extensively studied in recent years, and has shown great promise in fields ranging from materials chemistry to electronics and medicine. However, until now its toxicity to aquatic organisms has not been a serious concern.

Wenhong Fan and his team at Beihang University suspended a range of carbon nanomaterials in water and observed their effects on daphnids, also called water fleas, a model organism for water pollution tests. At concentrations above 0.5mg/l graphene significantly impaired their growth and reproduction over a period of 21 days. Fan speculates this is caused by adsorption of graphene onto the daphnids’ surface. Other carbon nanomaterials, including buckminsterfullerene, single walled carbon nanotubes and multi-walled carbon nanotubes, proved more benign.

After 21 days in contaminated water, the daphnids were covered in graphene (far right, GN). Other materials (fullerenes/C60, single-walled carbon nanotubes/SWCNT, multi-walled carbon nanotubes/MWCNT) were barely adsorbed. Source: © Royal Society of Chemistry

Read the full article in Chemistry World.


The mechanism of chronic toxicity to Daphnia magna induced by graphene suspended in a water column

Wenhong Fan, Yingying Liu, Zhizhen Xu, Xiangrui Wang, Xiaomin Li and Shenglian Luo

Environ. Sci.: Nano, 2016, Advance Article

DOI: 10.1039/C6EN00361C, Paper

Digg This
Reddit This
Stumble Now!
Share on Facebook
Bookmark this on Delicious
Share on LinkedIn
Bookmark this on Technorati
Post on Twitter
Google Buzz (aka. Google Reader)

The world’s smallest machines as efficient chelation platforms

Jean-Pierre Sauvage, Fraser Stoddart and Ben Feringa have just been awarded the Nobel Prize in Chemistry for the design and synthesis of molecular machines. Ranging from artificial muscles to micromotors, these nanomachines can perform different tasks and present a myriad of applications. In 1983, Sauvage linked two-ring-shaped molecules by a freer mechanical bond. He was then followed by Stoddart who developed, among other things, a molecule-based computer chip, and more recently Ben Feringa who designed a nanocar. These three remarkable scientists were pioneers in the field and many others now benefit from their contributions to science.

Taking advantage of these findings, Uygun and colleagues developed unique micromotors that offer high-speed metal remediation. Microscale machines have been used for accelerated isolation and degradation of toxins and clean-up of oil-contaminated water, among other uses. The continuous autonomous movement of functionalised nanomachines around a contaminated sample leads to enhanced transport of the remediation agent resulting in greatly accelerated decontamination. However, most of these require external fuel, such as hydrogen peroxide, and expensive catalysts, which then prevents their widespread use. Only recently have new fuel-free Mg-based microparticles been developed. They are highly biocompatible as they use water as their sole fuel. Using these new nanomachines, Uygun describes a Mg Janus-micromotor that is functionalised with meso-2,3-dimercaptosuccinic acid (DMSA), which has been recognised as an excellent chelating agent for heavy metals (Figure 1).

Figure 1. Micromotor “on the fly” removing Zn, Cd and Pb.

The micromotors were prepared by half-coating magnesium microparticles with Ti and Au layers and the external gold surface was modified by incubation in DMSA. The removal of its passivation layer will expose the Mg surface allowing an Mg-water redox reaction that generates hydrogen microbubbles leading to an efficient water-propulsion. Moreover, a small number of micromotors can lead to a nearly complete removal of heavy metals within a short period of time and they are not impacted by co-existing metal ions present in complex samples, making these nanomachines an interesting and cost effective option for fast removal of heavy metal pollutants.

By developing these self-propelled water-driven molecular machines, Uygun and colleagues are corroborating the Nobel Prize laureates and spreading the belief of the Swedish Academy of Science: “we are at the dawn of a new industrial revolution of the 21st century and the future will show how molecular machinery can become an integral part of our lives”.

To read the full article for free* click the link below:

D. A. Uygun, B. Jurado-Sánchez, M. Uygun and J. Wang
Environ. Sci.: Nano, 2016,3, 559-566
DOI: 10.1039/C6EN00043F, Paper

—————-

About the webwriter

Luiza Cruz is a PhD student in the Barrett Group at Imperial College London. Her work is towards the development of new medicines, using medicinal and natural products chemistry.

—————-

*Access is free until 20/11/2016 through a registered publishing personal account.

Digg This
Reddit This
Stumble Now!
Share on Facebook
Bookmark this on Delicious
Share on LinkedIn
Bookmark this on Technorati
Post on Twitter
Google Buzz (aka. Google Reader)

What’s your nano poison?

Informatics tool helps researchers visualise complex toxicity datasets

To help predict and avoid designing toxic nanomaterials, researchers have created an informatics tool that can pull out and visualise key information from a large collection of complex nanomaterials research.

Nanomaterials are now common in commercial products such as clothing and cleaning agents, and the amount of research into potential adverse environmental and health effects has increased exponentially. However, there is no comprehensive way to compare, or visualise, this information that could help researchers find correlations between nanomaterial properties and their toxicity. As well as the sheer volume of information, different studies also often consider different experimental conditions and biological material, making it very difficult to compare data directly.

Now, Sandra Karcher at Carnegie Mellon University, US, and her team have designed N4mics, a tool that can visualise nanoparticle toxicity research on zebrafish stored in the Nanomaterial-Biological Interactions Knowledgebase. Karcher says: ‘We developed the tool as a testbed to demonstrate how data that are standardised and shared can be mined to create visual comparisons between nanomaterial types. These visualisations are then used to generate novel hypotheses about how the properties of those materials affect their toxicity potential.’

Read the full article in Chemistry World.


Visualization tool for correlating nanomaterial properties and biological responses in zebrafish

Sandra C. Karcher, Bryan J. Harper, Stacey L. Harper, Christine Ogilvie Hendren, Mark R. Wiesner and Gregory V. Lowry

Environ. Sci.: Nano, 2016, Advance Article

DOI: 10.1039/C6EN00273K, Paper

Digg This
Reddit This
Stumble Now!
Share on Facebook
Bookmark this on Delicious
Share on LinkedIn
Bookmark this on Technorati
Post on Twitter
Google Buzz (aka. Google Reader)

How do iron oxide nanoparticles react?

Iron oxide nanoparticles are not just a laboratory curiosity but a major presence within the whole of the natural world. Ferrihydrite is the predominant iron oxide nanoparticle found under abiotic conditions owing to its very low surface energy. The essential function of iron storage and transport within living organisms is carried out by the protein ferritin, made possible through the incorporation of iron nanoparticles inside the protein’s internal cavity.

The ability of ferritin to template the formation of iron oxide nanoparticles of defined size has been exploited in the production of systems used in targeted drug delivery, magnetic resonance imaging and nano-electronics. The ability of the iron core in ferritin to adsorb phosphate anions has also been put to use in removing this nutrient down to levels which prevent the development of bacteria on water purification membranes.

Understanding nanoparticles

In spite of being recognised for their essential function and with much work dedicated to the development of exciting applications surrounding them, iron oxide nanoparticles have been so far poorly understood at a fundamental level regarding their structure and reactivity models. Their implicitly small size and low symmetry has made imaging difficult using conventional crystallographic techniques. The properties of nanoparticles are generally dependent on their size and any model attempting to quantify the reactivity displayed by the surface must take this into account. The nature of the surface itself is dependent on the chemical properties of the surrounding environment.

Hiemstra and Zhao have conducted both an experimental and a computational study in order to generate a valid reactivity model for the adsorption of phosphate and arsenate by ferrihydrite and by the ferritin core. Ferrihydrite was modelled and essential properties such as surface area, density of surface reactive groups such as O(H), and surface charge were calculated as a function of the particle size.

The experimental study followed the adsorption of phosphate anions onto freshly prepared ferrihydrite and the effect of phosphate concentration on the formation and properties of iron oxide nanoparticles inside ferritin was analysed. Corroboration of theoretical with experimental data allowed for the development of an anion adsorption model with account for surface reactivity and generated new understanding concerning the formation, growth and aggregation of iron oxide nanoparticles under conditions relevant to environmental applications.

The full article is free to access* for a limited time only:

Reactivity of ferrihydrite and ferritin in relation to surface structure, size, and nanoparticle formation studied for phosphate and arsenate

Tjisse Hiemstra and Wei Zhao

Environ. Sci.: Nano, 2016, Advance Article
DOI: 10.1039/C6EN00061D


About the webwriter


Dan Mercea is a PhD student in the Fuchter group at Imperial College London. He is working on developing enantioselective FLP catalysis.

—————-

*Access is free until 11th October 2016 through a registered RSC account – register here

Digg This
Reddit This
Stumble Now!
Share on Facebook
Bookmark this on Delicious
Share on LinkedIn
Bookmark this on Technorati
Post on Twitter
Google Buzz (aka. Google Reader)

Nanomaterial recycling goes for gold

Researchers recover and reuse waste gold nanoparticles

Gold-cyclodextrin complex

The gold–cyclodextrin complex precipitates out of the recycling solution and can easily be filtered. Source: © Royal Society of Chemistry

A group of US chemists has developed a straightforward method to recover and recycle gold nanoparticles from nanomaterials waste.1

The market share for gold nanoparticles is expected to increase exponentially in the next years, as they have applications in areas like medical diagnostics, storage devices and solar cells. Gold is expensive, and researchers have been developing ways to recover gold from waste. However, most methods require toxic chemicals such as mercury or cyanide.

Now, a team led by Peter Vikesland at Virginia Tech in the US has adapted a gold recovery method first developed by recent Nobel prize laureate Sir Fraser Stoddart2 to capture gold nanoparticles from waste.

Read the full article in Chemistry World.


Waste not want not: life cycle implications of gold recovery and recycling from nanowaste

Paramjeet Pati, Sean McGinnis and Peter J. Vikesland

Environ. Sci.: Nano, 2016, 3, 1133-1143

DOI: 10.1039/C6EN00181E, Paper

From themed collection Sustainable Nanotechnology Organization

Digg This
Reddit This
Stumble Now!
Share on Facebook
Bookmark this on Delicious
Share on LinkedIn
Bookmark this on Technorati
Post on Twitter
Google Buzz (aka. Google Reader)

What makes car tires resistant to mechanical and chemical stress?

The answer is nanomaterials. Particularly Carbon Black (CB) and silica nanomaterials which reinforce rubber increasing its durability, road grip and mileage. Other materials, such as carbon nanotubes (CNTs), offer better performance and ecological benefits via fuel savings. However, these are more expensive therefore their use is still very limited.

Nanomaterial fragments are generally released into the environment, constituting a rather uncontrollable source of emission of nanocomposites. In some countries where release quantification is already required, these emissions have been estimated between 4,000 and 7,000 tons of microplastic fragments. In spite of this immense environmental impact, little is known regarding the release from nanocomposites under mechanical and chemical stresses combined. Challenging the hypothesis of release being induced by a synergy of stresses, Wohlleben and co-workers bring a new sequence to test degradation pathways (Figure 1) as well as a fresh look at appropriate analytical techniques.

Figure 1. Synergetic degradation pathways by combined mechanical and chemical stresses.

In both cases shown in Figure 1, only chemical degradation or mechanical shear does not induce appreciable release of fragments. This happens only when the second stress is introduced, showing that synergetic degradation occurs on the diagonal of the scheme shown above.
In the first case, polyurethane (PU) with different single fillers (blue pathway in Figure 1) was first aged under standard conditions then put under mechanical stress simulating rain conditions (immersion, shaking or sonicating). Ultraviolet spectroscopy (UV-Vis), transmission electron microscopy (TEM) and analytical ultracentrifugation (AUC) or field flow fractionation were used to analyse the results. Images from X-ray photoelectron spectroscopy (XPS) showed that nanofillers remain on the surface after UV and rain weathering, accumulated into dense agglomerates as the polymer matrix was removed by the combined photolysis and hydrolysis.

Moreover, by creating an extended, highly reproducible, very low scatter semi-quantitative method to analyse turbidity of the released fragments, Wohlleben and co-workers were able to affirm that the release was reduced when CNTs were used (Figure 2a). Considering fragments below 150 nm diameter, PU filled with CNTs also showed reduced release (Figure 2b). More importantly, fragments coming from PU with CNTs were mostly organic, showing that the release of nanofiller fragments was suppressed.

Figure 2. a) Turbidity assessment of the released fragments from aged PU surfaces after UV and rain, with increasing mechanical shear: 24 h immersion (light grey), 24 h shaking (dark grey) and 1 h sonicating (black). b) Size-selective analysis (AUC) of fragments in the size range of 5 nm to 150 nm released from aged PU surfaces after UV and rain, with increasing mechanical shear: 24 h immersion (light grey), 24 h shaking (dark grey) and 1 h sonicating (black).

In the second case in Figure 1, natural rubber (NR) nanocomposite were filled with 40% CB and 4% CNT representing an innovative reinforced tire tread and it was compared to NR with 40% CB representing a conventionally reinforced tread and also to neat NB. The test focused on a sequence of mechanical-chemical-mechanical stresses, enabling the simulation of dust aging on dry roads and also the direct run-off into surface waters of the secondary fragments using UV irradiation.

During sanding, there was no noticeable difference between the particle concentration of the three rubber specimen. After aging, the structural differences of the fragments were minimal between wet and dry aging. Moreover, being CB and CNT both relatively more inert to UV degradation, they seem to have accumulated on the surface (less oxidised organic structures were quantified).

Fragments could potentially release smaller fragments and even free nanomaterial. Hence, Wohlleben and colleagues also analysed this scenario and indeed, smaller fragments were formed when a second sanding process was introduced, with no significant differences between NB with both fillers and only CB. However, it clearly showed that dry aging induces stronger secondary fragmentation than submersed aging, these results being in contradiction with the expected combined effect of hydrolysis and photolysis being more aggressive than photolysis only.

In summary, regarding analytical techniques, simple UV-Vis was shown to be the most sensitive technique. Qualitative identification by TEM is essential and analysis of XPS images was also important for a plausibility check.

This study is the first to analyse the combined forces of mechanical fragmentation, environmental aging and again mechanical stresses, showing a stepwise sequence that could continue ad infinitum and be tailored to simulate specific scenarios and provide useful estimates of release rates, enabling more reliable modelling and risk assessments.

To read the full article for free* click the link below:

Release from nanomaterials during their use phase: combined mechanical and chemical stresses applied to simple and multi-filler nanocomposites mimicking wear of nano-reinforced tires
Wendel Wohlleben, Jessica Meyer, Julie Muller, Philipp Müller, Klaus Vilsmeier, Burkard Stahlmecke and Thomas A. J. Kuhlbusch

Environ. Sci.: Nano, 2016,3, 1036-1051
DOI: 10.1039/C6EN00094K, Paper


—————-

About the webwriter

Luiza Cruz is a PhD student in the Barrett Group at Imperial College London. Her work is towards the development of new medicines, using medicinal and
natural products chemistry.

—————-

*Access is free until 07/11/2016 through a registered publishing personal account.

Digg This
Reddit This
Stumble Now!
Share on Facebook
Bookmark this on Delicious
Share on LinkedIn
Bookmark this on Technorati
Post on Twitter
Google Buzz (aka. Google Reader)

Introducing our new Associate Editor

We are delighted to introduce Wei-Guo as a new Associate Editor for Environmental Science: Nano.

Wei-Guo joins Greg Lowry, Iseult Lynch and Kristin Schirmer as Associate Editors handling submissions to the journal.

Dr. Wei-Guo Song is a Professor in the Institute of Chemistry at the Chinese Academy of Sciences (ICCAS). He is also a Professor at the University of Chinese Academy of Sciences. He obtained his BSc. from Peking University in 1992, and his PhD from University of Southern California in 2001. He joined ICCAS in 2005, and received National Distinguished Young Scholar award in 2007.

His research group focuses on the design of nano porous materials and their properties. More specifically, he is interested in using nano porous materials as adsorbents for inorganic pollutants, and as heterogeneous catalysts for catalytic degradation of organic pollutants. He is also interested in developing high performance catalysts including noble metal catalysts, solid acid/base catalysts, non-metal catalysts, etc. for fine chemical and pharmaceutical industries.

———-

Please join us in welcoming Wei-Guo to Environmental Science: Nano.

Interested in the latest news, research and events of the Environmental Science journals? Find us on Twitter: @EnvSciRSC

Digg This
Reddit This
Stumble Now!
Share on Facebook
Bookmark this on Delicious
Share on LinkedIn
Bookmark this on Technorati
Post on Twitter
Google Buzz (aka. Google Reader)

Trapping radioactive Technetium with a Tin-containing nanocomposite

Significant quantities of radioactive compounds are contaminating our environment. Due to nuclear weapon production during the Cold War, large quantities of radioactive Technetium-99 (99Tc) has been released into the environment. Although the Cold War ended 25 years ago, the total Tc inventory continues to rise as it is a major product during the generation of nuclear power resulting from the nuclear fission of uranium and plutonium.

Radioactive Tc is long lived and predominantly found in nuclear waste, in the highly mobile form of the water-soluble pertechnetate anion TcO4. The high mobility possessed by TcO4 causes concerns regarding its distribution within the environment and makes storage impracticable within cement-based materials, a widely employed medium for the storage of nuclear waste.

Managing nuclear waste
Reduction of TcO4 from Tc(VII) to Tc(IV)  is one possible solution. This is a challenging solution as Tc(IV) tends to convert back to TcO4 if exposed to oxygen. The reduction process requires a proton source to proceed and is disfavoured under the strongly alkaline conditions found in the waste media. The nuclear waste tanks also contain a large amount of both spectator ions, which make TcO4 more difficult to reduce, and high-valent metal species such as Cr(VI). This can interfere with the reduction process by consuming the available Sn(II) and/or by converting any formed Tc(IV) back to TcO4.

To overcome these obstacles, Eric D. Walter and colleagues have devised a novel Tin(Sn)-based material which displays selective and efficient removal of Tc under conditions similar to those found in nuclear waste tanks. The approach taken relies on the inclusion of both Sn(II) and Sn(IV) within an inert aluminophosphate matrix. The low-valent form of tin is known for its ability of reducing Tc(VII) to Tc(IV), whereas the high-valent Sn(IV) was chosen for its ability to form SnO2 phases capable of accommodating the resulting Tc(IV) and thus facilitate its sequestration.

Representative SEM images of the Sn–Al–PO4 composite (A) before and (B) after exposure to TcO4 − .

The material labelled Sn-Al-PO4 could be easily made from common laboratory chemicals and in this study was characterised by a number of analytical techniques investigating both the bulk and surface properties. It consists of two distinct phases:

  1. An amorphous Sn-based matrix containing the majority of the aluminium.  This material has a large surface area and contains predominantly Sn(II), a combination of properties expected to yield efficient reduction of pertechnetate from the solution medium.
  2. Small embedded fibres of crystalline material with the composition dominated by Sn and phosphate.

The full article is free to access for a limited time only:

Inorganic tin aluminophosphate nanocomposite for reductive separation of pertechnetate Environ. Sci.: Nano, 2016, Advance Article
DOI: 10.1039/C6EN00130K

—————-

About the webwriter

Dan Mercea is a PhD student in the Fuchter group at Imperial College London. He is working on developing enantioselective FLP catalysis.

—————-

*Access is free until 19th October 2016 through a registered RSC account – register here

Digg This
Reddit This
Stumble Now!
Share on Facebook
Bookmark this on Delicious
Share on LinkedIn
Bookmark this on Technorati
Post on Twitter
Google Buzz (aka. Google Reader)

Radioactive technetium waste tinned

Tin nanocomposite mops up nuclear waste contaminant.

Scientists have developed a tin-containing material that captures and stores radioactive technetium.

Scanning electron microscopy images show the tin-aluminophosphate’s structural change after exposure (right) to pertechnetate. Source: © Royal Society of Chemistry

Pertechnetate (99TcO4-) is a splitting product of uranium-235 and plutonium-239 and a radioactive nuclear waste contaminant. Technetium’s 213,000-year-long half-life and pertechnetate’s high solubility in water mean that the radioactive element can contaminate water supplies, enter the food chain and accumulate in animals’ and humans’ vital organs. Cold war activities and the Manhattan Project generated 99Tc in high quantities, and nuclear reactors as well as the Sellafield plant used to release this radioactive contaminant.

Tatiana Levitskaia, Sayandev Chatterjee and their team at the Pacific Northwest National Laboratory, US, have now synthesised a tin-aluminium-phosphate nanocomposite that removes and captures technetium from nuclear waste. The material reduces pertechnetate to the less water soluble Tc(IV), and at the same time changes its structure to capture and retain the reduced technetium.

Read the full article in Chemistry World.


Inorganic tin aluminophosphate nanocomposite for reductive separation of pertechnetate

Tatiana G. Levitskaia, Sayandev Chatterjee, Natasha K. Pence, Jesus Romero, Tamas Varga, Mark H. Engelhard, Yingge Du, Libor Kovarik, Bruce W. Arey, Mark E. Bowden and Eric D. Walter

Environ. Sci.: Nano, 2016, Advance Article

DOI: 10.1039/C6EN00130K, Paper

Digg This
Reddit This
Stumble Now!
Share on Facebook
Bookmark this on Delicious
Share on LinkedIn
Bookmark this on Technorati
Post on Twitter
Google Buzz (aka. Google Reader)

Metal micronutrients get to the root of antifungal defence

Flavoursome tomato varieties could benefit from nanoparticle fertilisers.

heirloom tomato

Tasty heirloom tomato varieties could soon see a return to our plates thanks to the promising antifungal properties of metal oxide nanoparticle fertilisers developed by US scientists.

Centuries of plant breeding mean we’ve grown accustomed to a narrow range of crops bred primarily for their disease resistance. But while we reap the benefits of greater yields and reliability, we’re missing out on a host of different flavours from less disease-hardy varieties.

Now a nanoparticle crop treatment developed by Wade Elmer and Jason White at Connecticut Agricultural Experiment Station, US, could give older tomato varieties – more susceptible to root pathogens such as wilt fungus – a helping hand. Applying copper and manganese oxide nanoparticles to the leaves of tomato plants grown in soil infected with the Verticillium wilt fungus increased fruit yields by up to 33% compared with untreated plants.

Read the full article in Chemistry World.


Wade H. Elmer and Jason C. White
Environ. Sci.: Nano, 2016, Advance Article
DOI: 10.1039/C6EN00146G, Paper
Digg This
Reddit This
Stumble Now!
Share on Facebook
Bookmark this on Delicious
Share on LinkedIn
Bookmark this on Technorati
Post on Twitter
Google Buzz (aka. Google Reader)