Archive for the ‘Nanoscale’ Category

HOT article: Microgel coating of magnetic nanoparticles via bienzyme mediated free-radical polymerization for colorimetric detection of glucose

Researchers from Qigang Wang’s group have developed a new strategy for the fabrication of core shell magnetic microgels for glucose detection, which is one of the most frequently used tests in clinical environments. Magnetic nanoparticles containing carboxylic acid groups on the surface were used as a starting material to covalently bind the enzyme glucose oxidase (GOx). A second enzyme, horseradish peroxidase, was also attached through a bifunctional polyethylene glycol polymer which ensured a working distance between the two immobilised enzymes. The microgels could be formed by adding glucose and acetylacetone (ACAC) with PEGMA and crosslinker PEGDA. One of the by-products of glucose oxidation, hydrogen peroxide, reacts with ACAC to form radicals that polymerise the monomers resulting in a gel-like coating formed around the enzyme containing particles.

The preparation of the magnetic core–shell microgels.

After polymerisation the enzymes retained their reactivity. Even after 7 days storage, 96% catalytic activity was observed with respect to a fresh sample. The high selectivity towards glucose was demonstrated with other sugars e.g. fructose, lactose and maltose. It is thought that this strategy could be extended to the detection of other biomolecules through new oxidase-HRP systems, as well as being easily translatable to clinical fields.

Microgel coating of magnetic nanoparticles via bienzyme-mediated free-radical polymerization for colorimetric detection of glucose
Qing Wu, Xia Wang, Chuanan Liao, Qingcong Wei and Qigang Wang
Nanoscale, 2015,7, 16578-16582. DOI: 10.1039/C5NR05716G

Dr Mike Barrow is a guest web writer for the Nanoscale blog, he currently works as a Postdoctoral Researcher at the University of Liverpool. Twitter: @mikesyb

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Call for Nanotechnology Data Reporting Guidelines

Dr. Mervi Heiskanen

Dr. Stephanie Morris

The authors of this article are both Program Managers based at the US National Cancer Institute’s (NCI) Center for Biomedical Informatics and Information Technology and Office of Cancer Nanotechnology Research, respectively, working towards improving quality of and access to published experimental data.

In recent years, there has been increasing interest in improving how nanomaterials are defined and characterized due to a lack of specific nano-related metadata standards in the Nanotechnology field. The nano-community agrees data reporting guidelines would facilitate data reproducibility and reuse.

The recent collaboration between Elsevier Journals and the NCI cancer Nanotechnology Laboratory (caNanoLab) data portal is an important step towards providing researchers with easy access to high quality nanotechnology data for reproduction and re-use. However, access to data is only useful if information about experimental details is available. Is there something we can do to improve usability of nanotechnology data?

The lack of high quality nanotechnology research data is a known challenge, further complicated by the diversity and growing number of nanomaterials. The OMICs communities (e.g., genomics and proteomics) have pioneered the development of databases such as the Gene Expression Omnibus (GEO) Database and the Worldwide Protein Data Bank (wwPDB), as well as standard guidelines for recording data. These guidelines define the minimum information that must be reported and stored, and facilitate data reproducibility and integration across different datasets to enable further analysis by the research community. Many of these reporting guidelines can be accessed at Biosharing, and are required by journals for data deposition during the manuscript submission process.

Several STM journals already require authors to adhere to minimum characterization requirements, particularly when reporting new chemical compounds, which reviewers are asked to evaluate to ensure reproducibility and reliability of the research. Nature and its sister journals have further enforced this for their life science articles by implementing an initiative which includes the submission of a checklist by authors intended to remind them to provide sufficient experimental details to enable reproducibility. However, we need to agree on a nanotechnology-specific checklist, and extend the reproducibility initiative to include other relevant journals. This needs to be a collaborative effort driven by the research community, editors and publishers, regulatory agencies, and funding organizations in order for this to become common practice and lead to improvements in data reuse.

The nanotechnology community is in the early stages of defining metadata that should be included in data submissions, and recognizes the metadata will differ by research field (e.g., biomedicine, ecological studies, and health and safety). Examples of nanomaterial databases working towards this goal include caNanoLab, which uses MinChar, and the Nanomaterial Registry’s Minimal Information about Nanomaterials (MIAN). However, there is no common minimal information guideline agreed upon by the larger nanotechnology community. The need for the development of a common reporting recommendation has been recognized by the NCI Nanotechnology Working Group (NCI Nano WG). With active participants from federal institutions, academia, and industry, primarily from the US and the NanoSafety Cluster in Europe, the NCI Nano WG can serve as a coordinating body for collecting community input across nanotechnology research fields. A nanotechnology minimal information standard is also of great interest to the US National Nanotechnology Initiative, which has developed a signature initiative on nanoinformatics (Nanotechnology Knowledge Infrastructure) that works with the nanotechnology community to provide resources and tools.

We believe that data submission guidelines combined with better access to data will improve data quality and reproducibility and will ultimately translate to advances in areas such as biomedical research, environmental safety, and nanomanufacturing. Collaboration and coordination among all stakeholders is needed to ensure data submission guidelines benefit all parties.

If everyone is moving forward together, then success takes care of itself.” – Henry Ford

DisclosureViews expressed in this web article are those of the authors and do not necessarily reflect the views or polices of the Department of Health and Human Services, nor does mention of trade names, commercial products, or organizations imply endorsement by the U.S. Government.

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Hybrid nanoparticles: The fight against breast cancer heats up

Gold nanorods with cisplatin-polypeptide wrapping were developed for combinational photothermal therapy and chemotherapy of triple negative breast cancer.

Researchers from China have advanced the fight against breast cancer (BC) by developing a method that targets triple negative breast cancer (TNBC) – a highly aggressive subtype of BC and a form that is challenging to completely eradicate.

Their method consisted of the formation of gold nanorods (GNRs) with a cisplatin-polypeptide wrapping and folic acid (FA) functionalization (FA-GNR@Pt) for the simultaneous targeted photothermal therapy and chemotherapy. These hybrid nanoparticles combine the photothermal conversion properties of GNRs, superior biocompatibility of polypeptide poly(L-glutamic acid) (PGA), chemotoxicity of cisplatin and the tumour targeting ability of FA.  FA-GNR@Pt nanoparticles exhibited temperature increases both in vitro and in vivo using 655 nm NIR laser irradiation and, in combination with systemic administration in mice, were able to inhibit the proliferation and lung metastisis of the 4T1 breast tumour.

The research presented here takes significant steps in furthering the understanding of breast cancer, particularly TNBC, which have increased risk of metastisis.

Near infrared light-actuated gold nanorods with cisplatin–polypeptide wrapping for targeted therapy of triple negative breast cancer
Bing Feng, Zhiai Xu, Fangyuan Zhou, Haijun Yu, Qianqian Sun, Dangge Wang, Zhaohui Tang, Haiyang Yu, Qi Yin, Zhiwen Zhang and Yaping Li
Nanoscale, 2015, 7, 14854-14864.  DOI: 10.1039/C5NR03693C

Dr Lee Barrett is a guest web writer for the Nanoscale blog. Lee is currently a postdoctoral researcher in the Centre for Molecular Nanometrology at the University of Strathclyde. His research is currently focused on the development of nanoparticle-based sensors and surface enhanced Raman scattering (SERS). Follow him on twitter @L_Bargie.

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HOT article: Nanostructured conducting polymer hydrogels for energy storage applications

Future energy storage solutions require a combination of high energy density, high reliability and low manufacturing cost. Conducting polymer hydrogels (CPHs) have emerged in recent years as a viable alternative for energy storage applications, as a Feature article by Shi et al. reports.

CPHs exhibit highly advantageous properties such as a large surface area, tunable mechanical properties and high conductivity compared to other polymers. These materials combine a conductive π–conjugated backbone with a porous structure.

Two synthesis routes are presented: template-guided synthesis (e.g. polymerization of monomers in a non-conductive hydrogel matrix) and direct formation using phytic acid as a gelator and dopant of the polymer.

Independent of synthesis route, CPHs were successfully demonstrated as bulk materials for electrochemical capacitors (also termed “supercaps”), as well as functional binders within Li-ion batteries. By careful modification of the polymer properties, a stable material able to withstand over 10000 charge-discharge cycles was demonstrated. Finally, the current hurdles for mass-market adoption, such as limited mechanical strength, lower conductivity than currently utilized material combinations and a lower capacity are explained, and paths to overcome these are discussed.

Nanostructured conducting polymer hydrogels for energy storage applications
Ye Shi, Lele Peng and Guihua Yu
Nanoscale, 2015, 7, 12796-12806. DOI: 10.1039/C5NR03403E

Sebastian Axmann is a guest web-writer for the Nanoscale blog. His interests comprise manufacturing and metrology of nanostructures as well as their usage in current semiconductor devices. He also posts links to interesting research articles on Twitter: @SebastianAxmann.

Nanoscale, 2015,7, 12796-12806
DOI: 10.1039/C5NR03403E

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HOT article: Bridging the transport pathway of charge carriers in a Ta3N5 nanotube array photoanode for solar water splitting

Besides the wide field of photovoltaics research, additional technologies, such as the direct conversion of H2 via solar water splitting, are currently being researched. A recent article by Zhang et al. presents their findings on improved manufacturing routes for these cells.

For the time being, Ta3N5 is the material of choice as the band gap and structure are both well suited for light absorption. To form a large interfacial area for efficient light conversion within the cells, arrays of hollow nanorods are employed. As the authors describe in their article, earlier attempts of a one-step synthesis route, also evaluated by other researchers, led to weak adhesion of the brittle nanorod film on the substrate. Their new approach utilizes a two-step synthesis route: first, a nanorod layer of Ta2O5 is formed via anodization in a solution with a lower HF concentration compared to that employed by other groups. Next, this weakly adhering layer is removed by sonication and a second layer is formed. The formation of the second layer also employs a low reaction temperature to limit the reaction rate. Finally, this second nanorod layer is nitridated, forming Ta3N5 from the Ta2O5 layer.

(a) Schematic illustration of the synthetic process, (b) top-view SEM image and (c) cross-sectional SEM image of Ta3N5 NTAs.

The resulting layer was found to adhere well on the substrate surface and to exhibit only a few cracks. By further optimization of processing times and the additive material used during nitridation, a maximum current density of 11 mA/cm² at 1.6 V was demonstrated by the authors.

Bridging the transport pathway of charge carriers in a Ta3N5 nanotube array photoanode for solar water splitting
Peng Zhang, Tuo Wang, Jijie Zhang, Xiaoxia Chang and Jinlong Gong
Nanoscale, 2015, Advance Article. DOI: 10.1039/C5NR03013G

Sebastian Axmann is a guest web-writer for the Nanoscale blog. His interests comprise manufacturing and metrology of nanostructures as well as their usage in current semiconductor devices. He also posts links to interesting research articles on Twitter: @SebastianAxmann.

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HOT article: Reversible control of pore size and surface chemistry of mesoporous silica through dynamic covalent chemistry: philicity mediated catalysis

Reversible engineering of the pore size and philicity of mesoporous SBA via dynamic covalent chemistry triggered by changes in pH.

Control of surface chemistry is important for utilisation of mesoporous silicas in many applications such as catalysis, drug delivery and separation sciences. Due to the mostly irreversible nature of covalent functionalisations and lack of rigidity in supramolecular approaches, in this study, dynamic covalent chemistry was used to reversibly alter the chemical coating on the surface of amine functional mesoporous silica SBA-15. This was achieved through the condensation reaction of the primary amine on SBA-15 with 4-decyloxybenzaldehyde (4-DB) to form an imine containing a hydrophobic decyl chain. This step both reduced the pore size and hydrophilicity of the pore surface, however, could be reversed by cleaving the imine at low pH in an ethanol/water mixture.

Dynamic control of the pore properties was demonstrated using the catalytic reduction of p-nitrophenol in aqueous conditions by gold nanoparticles, which were imbedded into both amine and imine/decyl SBA-15 materials. The more porous/hydrophilic amine-based material completely reduced p-nitrophenol to p-aminophenol after 30 minutes, whereas the more hydrophobic imine-based surface exhibited no catalytic activity. The authors suggest that this methodology could be used to generate a host of new covalently functionalised materials with tuneable surface properties.

Reversible control of pore size and surface chemistry of mesoporous silica through dynamic covalent chemistry: philicity mediated catalysis
Dheeraj Kumar Singh, B. V. V. S. Pavan Kumar and M. Eswaramoorthy
Nanoscale, 2015, Advance Article. DOI: 10.1039/C5NR02959G

Dr Mike Barrow is a guest web writer for the Nanoscale blog. He currently works as a Postdoctoral Researcher at the University of Liverpool.

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A SERS biosensor for detecting metal ions in saliva

A gold nanohole array based surface-enhanced Raman scattering biosensor for detection of silver(I) and mercury(II) in human saliva

Researchers from West Virginia University have developed a method for detecting heavy metal ions in human saliva. Silver (I) (Ag) and mercury (II) (Hg) ions form part of dental fillings so it is important to have non-invasive analytical methods to monitor the toxicity of these metal ions should they be accidentally released into saliva.

Here, the authors exploited the strong electromagnetic coupling between gold (Au) nanostars and a Au nanohole array to detect Ag (I) and Hg (II) using surface enhanced Raman scattering (SERS). The Au nanostars and nanohole array were functionalised with mismatched pairs of single-stranded (ssDNA) probes that hybridise to form stable duplexes in the presence of the corresponding metal ions. Hybridisation allows the Au nanostars to come into close proximity with the Au nanohole array, which results in a large amplification of the SERS signal.

In this way, the authors were able to detect Ag (I) and Hg (II) ions in human saliva with limits of detection (LODs) of 0.17 nM and 2.3 pM for Ag (I) and Hg (II), respectively. This demonstrates the applicability of the SERS-based detection platform for on-site, non-invasive detection of analytes in body fluids.

A gold nanohole array based surface-enhanced Raman scattering biosensor for detection of silver(I) and mercury(II) in human saliva
Peng Zheng, Ming Li, Richard Jurevic, Scott K. Cushing, Yuxin Liu and Nianqiang Wu
Nanoscale, 2015, 7, 11005-11012. DOI: 10.1039/C5NR02142A

Dr Lee Barrett is a guest web writer for the Nanoscale blog. Lee is currently a postdoctoral researcher in the Centre for Molecular Nanometrology at the University of Strathclyde. His research is currently focused on the development of nanoparticle-based sensors and surface enhanced Raman scattering (SERS). Follow him on twitter @L_Bargie.

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Poster prize winners at the 10th Sino-US Symposium on Nanoscale Science and Technology

Many congratulations to Chuanbo Gao and Mengyu Yan for winning the Nanoscale and Nanoscale Horizons poster prizes at the 10th Sino-US Symposium on Nanoscale Science and Technology.

Chuanbo, from the Xi’An Jiaotong University, and Mengyu, from Wuhan University, won prizes for their posters entitled “Etching-free epitaxial growth of gold on silver nanostructures for high chemical stability and plasmonic activity” and “Vanadium oxide/graphene nanocomposite for advanced lithium battery”, respectively.

The 10th Sino-US Symposium on Nanoscale Science and Technology took place from 26th to 28th June 2015 at Wuhan University of Technology, China. The conference is organised by the Wuhan University of Technology, University of California, Los Angeles, and Wuhan University, and aims to provide a platform for scholars, experts, research institutes, and companies to share the latest research progress in nanoscience and technology research. This year’s event was the largest symposium ever held in the history of the Forum, with over 1,000 participants. Further details are available on the conference website.

Nanoscale and Nanoscale Horizons will be awarding more prizes throughout the year – keep an eye out to find out about the winners!

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Core–shell InGaN/GaN nanowire light emitting diodes analyzed by electron beam induced current microscopy and cathodoluminescence mapping

Core–shell InGaN/GaN nanowire light emitting diodes analyzed by electron beam induced current microscopy and cathodoluminescence mapping

Blue light emitting diodes (LEDs) have gained wide interest over the last two decades as a foundation of modern solid state lighting technology. Being the basis of many illumination solutions, their development and investigation has not come to a halt. To increase their overall luminous efficiency, new designs such as GaN-based nanowire LEDs are currently being evaluated.
A new article presented by Tchernycheva et al. published in Nanoscale reports on the characterisation of core-shell InGaN/GaN nanowires using electron beam induced current (EBIC) microscopy and cathodoluminescence mapping (CL). Using a combination of both techniques allowed the authors to map the electrical and light emitting properties of the nanostructures both laterally and vertically.
The basic structures used for the experiments were hexagonal nanowires formed by a sequence of 150nm p-GaN / AlGaN / 7 nm InGaN / 200 nm n-GaN / 200 nm GaN. According to the authors, top-view EBIC mapping indicated electrically active regions at the circumference of the nanostructures with an inactive core area. The inactive core is explained by the absence of quantum wells at the m-planes which form the single facet sides at the top of the devices.

By mechanical cleaving, cross-sectional images of the nanostructures were obtained. EBIC mapping was found to indicate the exact position of the p-n-junction within the structures. Furthermore, vertical EBIC signal variations at the junction within the devices were also noted. By employing CL measurements, the drop in electrical activity of the structures was linked to an increase in the optical activity. The authors explain this finding by a variation of the semiconductor layer composition.

Using both findings, the lateral homogeneity of the electrical activity and the vertical variation, further characterisation and optimization of the nanowires are enabled to increase the light output and overall luminous efficiency.

Core–shell InGaN/GaN nanowire light emitting diodes analyzed by electron beam induced current microscopy and cathodoluminescence mapping
M. Tchernycheva, V. Neplokh, H. Zhang, P. Lavenus, L. Rigutti, F. Bayle, F. H. Julien, A. Babichev, G. Jacopin, L. Largeau, R. Ciechonski, G. Vescovi and O. Kryliouk
Nanoscale, 2015, Advance Article. DOI: 10.1039/C5NR00623F

Sebastian Axmann is a guest web-writer for the Nanoscale blog. His interests comprise manufacturing and metrology of nanostructures as well as their usage in current semiconductor devices. He also posts links to interesting research articles on Twitter: @SebastianAxmann.

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HOT article: One-step direct synthesis of layered double hydroxide single-layer nanosheets

Single-layer nanosheets as layered double hydroxides (LDH) are of widespread interest both in research and application as they offer unique advantages for electronic devices. A recent communication in Nanoscale by Yu et al. reports on a new approach to simplify the overall manufacturing process.

Direct growth of single-layer nanosheets with the assistance of layer growth inhibitors

Common techniques yielding LDH nanosheets are based on exfoliation of synthesized multi-layer stacks. Due to the high binding forces in between the single layers, obtaining single layers requires aggressive chemicals and long processing times.

The approach presented by the authors comprises the utilization of formamide during the material growth process to suppress vertical growth for MgAl. Thus, only in-plane layer formation continues, leading to large single-layer LDH nanosheets. The authors demonstrate that only LDH single-layer nanosheets are obtained by means of TEM, XRD and AFM measurement techniques to compare this new method with the standard synthesis procedure.

The underlying mechanism is believed to be based on the weakened layer interaction by formamide. In addition, the same approach was also successfully applied to LDH nanosheets based on Co and Al.

One-step direct synthesis of layered double hydroxide single-layer nanosheets
Jingfang Yu, Benjamin R. Martin, Abraham Clearfield, Zhiping Luo and Luyi Sun
Nanoscale, 2015, 7, 9448-9451. DOI: 10.1039/C5NR01077B

Sebastian Axmann is a guest web-writer for the Nanoscale blog. His interests comprise manufacturing and metrology of nanostructures as well as their usage in current semiconductor devices. He also posts links to interesting research articles on Twitter: @SebastianAxmann.

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