Environmental Science: Nano Blog

It is inevitable that nanomaterials will enter the waste stream and be incinerated © Shutterstock

Scientists in the US have begun addressing the question of whether the disposal of nanomaterials could damage the environment, by investigating the fate of nanomaterials in incinerators.

The Royal Society of Chemistry is very good at chemical science. Publishing it, promoting it, encouraging it, supporting it. We are constantly aiming to advance excellence in the chemical sciences.

…but there is also another thing we’re very good at, which is lesser known.

Cake.

We do cake really well.

And so, Environmental Science: Nano demonstrated the RSC love for cake with a celebration of our inaugural issue – in sponge form. Managing Editor Harp Minhas cuts the Environmental Science: Nano cake, featuring our Philip Demokritou front cover, in the picture below.

A huge congratulations to the whole team, and to our excellent authors, for producing such a successful first Issue. We may have had our fill of cake for now, but we certainly haven’t had our fill of nanoscience…

Evaluating the biosafety and environmental fate of carbon nanomaterials can be aided by the use of ¹³C isotopic labelling to improve their in vivo quantification and monitoring. This study conducted at the Chinese Academy of Sciences, Beijing discusses this approach.

The widespread use of carbon nanomaterials (NMs) such as fullerenes in a diverse range of applications such as biomedicine, electronics, and industrial practices will inevitably lead to their interaction with environmental and biological systems. The major barrier to the large-scale production and use of carbon NMs is fully understanding their biosafety and assessing how their unique structure and properties influence their potential effects.

To address this issue will require better knowledge of the exposure, pharmacokinetics, biodistribution and toxicity of carbon NMs. There is currently a lack of simple quantification methods for in vivo carbon NMs. In the past quantification of carbon NMs in blood and body tissue has been achieved by methods based on  high performance liquid chromatography (HPLC) coupled with mass spectrometry (MS). However, other reliable methods are also available.

Isotopic labelling is also a favourable option. This commonly involves use of radioactive isotopes e.g. ¹⁴C, and ¹²⁵I. However, these are subject to a number of drawbacks, as the synthesis and detection of these radioactive isotopes are complicated and this also leads to the creation radioactive wastes. Additionally, most radioactive isotopes can only be used for studying functionalized fullerenes.

The use of stable isotopes for fullerene labelling may avoid these problems. This approach of coupling the use of stable isotope labels with isotope ratio mass spectrometry (IRMS) detection has been used previously to quantify other carbon NMs such as quantum dots and nanotubes. This study by Xue-Ling Chang and co-workers represents the first time this approach of using ¹³C stable isotopic labelling on the carbon skeleton of fullerene has been attempted.

In this study, ¹³C-enriched fullerene (C₆₀) was synthesised by the arc discharge method and purified by HPLC. The labelled fullerenes were dispersed in aqueous solutions assisted by CS₂ and administered to test mice via i.v injection. Blood, tissue and organ samples were then collected and ¹³C enriched C₆₀ content were monitored and quantified using IRMS.

Fig. 1: Schematic of experimental design

The enrichment of the ¹³C on the C₆₀ skeleton was confirmed by assessing the MS and IR spectra data. The pharmacokinetics of the labelled fullerenes was investigated using both one-compartmental and two compartmental models.  C₆₀ was shown to very rapidly clear from blood stream with a blood circulation half-life of 14 minutes calculated. The labelled C₆₀ displayed selective accumulation in the RES organs, particularly, the liver, spleen and lungs with slight decreases noted within 24 hours of exposure.

The study demonstrates the feasibility of using ¹³C stable isotopically labelled fullerenes to trace and quantitatively monitor the bio-behaviour of carbon NMs like fullerenes in vivo. Researchers can therefore better trace the absorption, distribution, metabolism, and excretion of these materials. This approach is preferable as it does not introduce foreign atoms onto, nor does it damage or disrupt, the carbon network. The fullerene therefore retains its intrinsic structure so the labels will reflect the real properties of C₆₀ structures.

This work provides a potential new platform to study the environmental and biological fate of carbon NMs, offering a sensitive, reliable and non-destructive method trace their effects in vivo. The authors also identify further areas of research for which the approach can be used, including the effects of long-term exposure, consequences of surface functionalisation, and potential metabolism mechanisms of carbon NMs.

Read the full paper by following the link below. Your copy is free with registration to an RSC account

Quantification of carbon nanomaterials in vivo: direct stable isotope labeling on the skeleton of fullerene C₆₀, by Xue-Ling Chang et al. DOI: 10.1039/c3en00046j

Graphene nanomaterials have the potential to act as surfaces to rapidly extract persistent organic molecules such as PBDEs, therefore providing potential use in analytical and environmental chemistry applications, according to a new study by Ding and co-workers at Hong Kong University.

Polybrominated diphenyl ethers (PBDEs) are a class of organic compounds widely used as flame retardants in electrical equipment, furniture and textiles. PBDEs are of concern due to possible adverse health effects, including potential toxic and endocrine disrupting behaviour. This has led to the phasing out of their production, import and sale in many countries. However, PBDEs can migrate from existing products and are shown to bioaccumulate in the human body. Therefore, it is essential to find ways to monitor their levels in the environment in order to understand and minimize human exposure, and to develop methods to efficiently remove them from the environment.

Treatment methods for PBDEs have not yet been fully developed for any environmental medium. Recently, however, the low dimensional nanomaterial graphene has emerged as a potentially useful substance in this field. The large surface area to volume ratio, unique chemical and thermal stability and high adsorption capacity of graphene make it suitable for possible use as an adsorbent material for extraction, removal, sensing and degradation of pollutant molecules including aromatic organic compounds like PBDEs. It is important therefore to fully understand the adsorption behaviour of organic pollutants on graphene surfaces to optimise its potential usefulness.

The study by Ding and co workers provides a theoretical investigation of the mechanisms, properties and thermodynamics underlying the adsorption of PBDEs on graphene surfaces. These computer simulations are a preferred way to study this adsorption behaviour, providing a relatively cheap method of obtaining fundamental information that avoids the limitations of using experimental laboratory studies. This is the first study of its kind to attempt this approach.

The method involved investigating adsorption mechanisms of nine PBDEs and DE on graphene in an aqueous environment using density functional theory (DFT) and molecular dynamics (MD) methods. The approach employed both local density approximation (LDA) and generalized gradient approximation (GGA) with the DFT method, corrected to take into account dispersive forces. MD simulations were carried out to supplement the DFT calculations using the COMPASS force field.

The results indicate the adsorption of PBDEs to graphene is very fast, confirming the remarkable performance of graphene in this extraction process. Electronic density of states, charge transfer analysis, and thermodynamic analysis indicate that PBDE adsorption to graphene is primarily controlled by physiosoption. It was shown that interaction strengths between PBDEs and graphene increased with the degree of bromination, due to relatively strong interactions between bromine atoms and the graphene surface.

For compounds without ortho-substitution, adsorption energies exhibited a positive linear correlation between interaction strength of PBDEs and DEs with compound hydrophobicity, while PBDEs with ortho-substitution displayed different adsorption behaviour influenced by steric hindrance. However, adsorption is not simply controlled by the hydrophobicity of the adsorbate. The authors indicate that π-π interactions play a more important role in the PBDE adsorption system and confirm that van der Waals interactions are a dominant factor governing the π-π stacking behaviour.

This study enhances our understanding of adsorption chemistry of aromatic organic pollutants on graphene nanomaterials. This knowledge will help open up the potential use of these materials in analytical and environmental chemistry applications. Therefore, this paper will be of interest to researchers in these broad fields, particularly those interested in laboratory extraction procedures, wastewater treatment processes and contaminated land remediation.

Click on the link below to download your copy of this newly published paper – and remember – it’s FREE TO ACCESS with an RSC publishing account!

Interactions between polybrominated diphenyl ethers and graphene surface: a DFT and MD investigation, Ning Ding, Xiangfeng Chen, and Chi-Man Lawrence Wu. DOI: 10.1039/c3en00037k

The Sustainable Nanotechnology Organization (SNO) is a Professional and international non-profit society, which held its 2nd annual conference on November 3 – 5 2013 at the Fess Parker’s Double Tree Hotel in Santa Barbara, California. The conference was chaired by Dr. Arturo Keller of the University of California at Santa Barbara.

SNO focuses on advancing sustainable nanotechnology around the world through education, research, and the promotion of responsible use of nanotechnology (www.susnano.org). The conference brought together scientists and experts from around the world, both from academia, industry and government agencies, to present and discuss current research findings on the subject of nanotechnology and sustainability. The conference was also attended by members of the press and nongovernmental organizations, and had an increase in attendance by 20% over 2012.

During the meeting it was announced that SNO will partnership with new journal Environmental Science: Nano, published by the Royal Society of Chemistry. Environmental Science: Nano will represent SNO as the Organisation’s official journal and is free to access to all SNO members for two years from launch. It is hoped that members will support this journal with submissions (please see end of post for more details). The journal offers great benefits, including free colour, no page limits and an efficient review process.

As well as this exciting announcement, the SNO conference featured an exciting three days of activities, including outstanding technical programs and cutting-edge research on nanotechnology and sustainability. Presentations included 6 plenary speakers, 154 platform presentations, and 46 poster presentations, which were drawn from early faculty career investigators, postdoctoral fellows, students, and industrial participants. In addition, prior to the Conference, SNO’s first Nanoceria workshop was held, which was led by Robert Yokel in conjunction with the University of Kentucky.

Although SNO is a relatively new organization it has formed an excellent basis to drive it towards a strong and sustainable future. The annual conference provides a place for the formation and advancement of the new community of sustainable nanotechnology. 2013’s conference program was built around providing plenty of time for networking and social interactions; this included the Sunday evening welcome reception and banquet, which allowed for community development.

Attendants at the 2013 Conference represented a vast geographical area, with participants from almost all states of the USA, as well as international participants from Canada, France, Great Britain, India, Korea, Japan and Poland. In addition, approx. 25% of the participants were women, and a sizeable student presence was recorded, indicative of the “recentness” of the field. These young scientists bring fresh appeal to the organization and SNO aims to support and honour them; $500 prizes were awarded to 26 graduate students based on their resumes and the relevance of their research to sustainability and nanotechnology.

If you would like to submit to Environmental Science: Nano, please use the following submission link: http://mc.manuscriptcentral.com/esn

Alternatively, please speak to a member of our Editorial Board at this address esnano-rsc@rsc.org

Associate Editors: Greg Lowry, (Carnegie Mellon University), James Hutchison (University of Oregon), Kristin Schirmer (Eawag, Switzerland)

Chair and Editor-in-Chief: Vicki Grassian (University of Iowa)

Vice-Chair: Christy Haynes (University of Minesota)

Details of our full Editorial Board can be found here: http://rsc.li/19CHl5s

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– Free colour on all figures

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– Simple and effective submission process (http://mc.manuscriptcentral.com/esn)

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Engineered water nanostructures (EWNS), the latest weapons for tackling airborne pathogens, start off as nothing more than atmospheric water vapour.

Despite advances in antibiotics, vaccines and infection control, infectious diseases continue to affect hundreds of millions of people each year and the number of antibiotic resistant bacteria is on the rise. Therefore, there is an urgent need for innovative, effective and low-cost technologies in the battle against airborne infections. Upper-room UV irradiation, air filtration, photocatalysis and biocidal gases are the current methods most commonly used for air disinfection. However, these methods come with a variety of drawbacks such as potential health risks and high costs.

Philip Demokritou and colleagues from the Harvard School of Public Health and the National Institute of Occupational Safety and Health in the US, have designed a system that transforms atmospheric water vapour into EWNS. With a size of only 25nm, the nanostructures are highly mobile and remain in room air for a long time due to their high electric charge. Disinfection of the air is achieved as the nanostructures contain reactive oxygen species, such as hydroxyl and superoxide radicals, which interact with the outer membranes of bacteria, rendering them inactive.

Toxicological studies on mice by Demokritou’s team have shown that the EWNS have minimal toxicological effects. No respiratory tract toxicity was found at exposure levels and times higher and longer than those needed to inactivate the bacteria. Demokritou explains that the radicals are harmless to cell membranes in the lungs of test animals because ‘the organic matter in the lung lining fluid which covers the epithelial cells neutralises the reactive oxygen species, so they never reach the cells.’

‘The proposed method has the potential to transform the way we currently control infectious diseases,’ says Demokritou, ‘if proven effective in practice, it could be used to create “shields” to protect people in their microenvironments.’

Vishal Shah, an expert in microbiology from Dowling College in New York, US, agrees that the research presents ‘a proof-of-concept for an interesting technology that could help improve air quality, particularly in high moisture indoor environments.’ Shah adds that in the future, he would ‘look forward to seeing results describing the efficiency of the technology to inactivate other viruses and gram positive bacteria like streptococci and staphylococcus.’

The team now intend to extend their research to ascertain if EWNS can disinfect fresh produce.

Download the paper for free here, or visit the original Chemistry World post!

A phospholipid component of plants can potentially provide versatile, environmentally benign ligands in the synthesis of asymmetric gold nanoparticles (GNPs). This paper by Benjamin Ayres (Portland State University) and Scott Reed (University of Colorado Denver), demonstrates how this can provide benefits in terms of both possible application and environmental performance of these materials.

Asymmetric GNPs have been utilised for a wide range of applications including biomedical sensors and components of electronic and photonic devices. In order to move towards a large scale production of asymmetric GNPs, a synthetic method is required that is economical and reproducible, as well as displaying suitable green credentials.

The shape and size of GNPs are crucial to governing their electronic and optical properties. There is a need therefore to gain a good understanding of the synthetic process at a molecular level, in order to optimise the process from the perspective of both desired application and environmental impact, creating a method that can be easily controlled and reproduced.

Conventional synthetic methods traditionally involve seed-mediated synthesis using alkyl ammonium salts (e.g. CTAB) as ligands. These methods are unsustainable and non-biocompatible due to the toxic nature of the compounds used, and often require excess ligand and post-synthetic processing e.g. using ligand exchange in order to be used for in vivo applications.

The method described by Ayres and Reed involves reduction of bromoauric acid by ascorbic acid in the presence of ligands derived using biogenic phospholipid extracts from crude soybean lecithin. This provides a cheap, readily available and renewable feedstock for the process, avoiding use of fossil-fuel derived materials.

A key parameter of generated GNPs is their localized surface plasmon resonance (LSPR). In order for GNPs to be suitable for medical applications (e.g. biosensors, in-vivo imaging and phototherapeutic treatments) the LSPR needs to be in the near infrared (NIR) region.

It was shown, using UV-Vis spectroscopy and high resolution transmission electron microscopy (TEM) that the described method produces a mixture of spherical and triangular prismatic GNPs that exhibited an LSPR in the NIR region as well as extended stability with no aggregation.

Furthermore, the method includes chemical identification of the specific molecular component of soy lecithin that is the source of asymmetric growth. Soy lecithin is composed predominantly (~75%) of phosphatidylchorine (PC). However, separation of different GNP shapes using preparatory gel electrophoresis, and analysis of lipid extracts by LC-MS indicated phosphatidic acid (PA) was crucial to GNP asymmetric growth.

Indeed, it was shown that GNPs produced from lower purity PC (30%) showed NIR LPSR and were stable, while higher purity PC (95%) produced only spherical GNPs which aggregated over time and displayed LSPR only in the UV-Vis spectrum. When spiked with PA, the growth solutions of PC₉₅ displayed a second LSPR in the NIR, which shifted further red as more PA was added.

This study presents a biocompatible method for GNP production using environmentally benign ligands. It also demonstrates how gaining molecular level understanding of the synthetic process allows control over the GNP shape and size, based on lipid composition and/or specific plant material used. This therefore provides benefits both from the perspective of the desired application and the environmental impacts.

Environmental Science: Nano is providing free access upon registration* to all content published during 2014 and 2015. To get your free download of this paper, please follow the link below:

A minor lipid component of soy lecithin causes growth of triangular prismatic gold nanoparticles, Benjamin. R. Ayres and Scott. M. Reed, DOI: 10.1039/C3EN00015J

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