PRESS-NEWS.org - Press Release Distribution
PRESS RELEASES DISTRIBUTION

Almost as sensitive as a dog's nose

New sensor for SERS Raman spectroscopy

2013-08-29
(Press-News.org) Scientists at ETH Zurich and the Lawrence Livermore National Laboratory (LLNL) in California have developed an innovative sensor for surface-enhanced Raman spectroscopy (SERS). Thanks to its unique surface properties at nanoscale, the method can be used to perform analyses that are more reliable, sensitive and cost-effective. In experiments with the new sensor, the researchers were able to detect a certain organic species (1,2bis(4-pyridyl)ethylene, or BPE) in a concentration of a few hundred femtomoles per litre. A 100 femtomolar solution contains around 60 million molecules per litre.

Until now, the detection limit of common SERS systems was in the nanomolar range, i.e. one billionth of a mole. The results of a study conducted by Hyung Gyu Park, Professor of Energy Technology at ETH Zurich, and Tiziana Bond, Capability Leader at LLNL, were published this week as a cover article in the scientific journal Advanced Materials.

Raman spectroscopy takes advantage of the fact that molecules illuminated by fixed-frequency light exhibit 'inelastic' scattering closely related to the vibrational and rotational modes excited in the molecules. Raman scattered light differs from common Rayleigh scattered light in that it has different frequencies than that of the irradiating light and produces a specific frequency pattern for each substance examined, making it possible to use this spectrum information as a fingerprint for detecting and identifying specific substances. To analyse individual molecules, the frequency signals must be amplified, which requires that the molecule in question either be present in a high concentration or located close to a metallic surface that amplifies the signal. Hence the name of the method: surface-enhanced Raman spectroscopy.

Amplified signals for improved reproducibility

"This technology has been around for decades," explains Ali Altun, a doctoral student in the group led by Park at the Institute of Energy Technology. With today's SERS sensors, however, the signal strength is adequate only in isolated cases and yields results with low reproducibility. Altun, Bond and Park therefore set themselves the goal of developing a sensor that massively amplifies the signals of the Raman-scattered light.

The substrate of choice turned out to be vertically arranged, caespitose, densely packed carbon nanotubes (CNT) that guarantee this high density of 'hot spots'. The group developed techniques to grow dense forests of CNTs in a uniform and controlled manner. The availability of this expertise was one of the principal motivations for using nanotubes as the basis for highly sensitive SERS sensors, says Park.

A spaghetti-like surface

The tips of the CNTs are sharply curved, and the researchers coated these tips with gold and hafnium dioxide, a dielectric insulating material. The point of contact between the surface of the sensor and the sample thus resembles a plate of spaghetti topped with sauce. However, between the strands of spaghetti, there are numerous randomly arranged holes that let through scattered light, and the many points of contact -- the 'hot spots' -- amplify the signals.

"One method of making highly sensitive SERS sensors is to take advantage of the contact points of metal nanowires," explains Park. The nano-spaghetti structure with metal-coated CNT tips is perfect for maximising the density of these contact points.

Indeed, Bond explains, the wide distribution of metallic nano-crevices in the nanometre range, well recognised to be responsible for extreme electromagnetic enhancement (or hot spots) and highly pursued by many research groups, has been easily and readily achieved by the team, resulting in the intense and reproducible enhancements.

The sensor differs from other comparable ultra-sensitive SERS sensors not only in terms of its structure, but also because of its relatively inexpensive and simple production process and the very large surface area of the 3D structures producing an intense, uniform signal.

A breakthrough on two levels

Initially, the researchers only coated the tips of the CNTs with gold. The first experiments with the BPE test molecule showed them that they were on the right track, but that the detection limit could not be reduced to quite the degree they had hoped. Eventually, they discovered that the electrons required on the gold layer surface for generating what is referred to as plasmon resonance were flowing out via the conductive carbon nanotubes. The task was then to figure out how to prevent this plasmonic energy leakage.

The researchers coated the CNTs with hafnium oxide, an insulating material, before applying a layer of gold. "This was the breakthrough," says Altun. The insulation layer increased the sensitivity of its sensor substrate by a factor of 100,000 in the molar concentration unit.

"For us as scientists, this was a moment of triumph," agrees Park, "and it showed us that we had made the right hypothesis and a rational design."

The key to the successful development of the sensor was therefore twofold: on the one hand, it was their decision to continue using CNTs, whose morphology is essential for maximising the number of 'hot spots', and on the other hand, it was the fact that these nanotubes were double-coated.

Park and Bond would now like to go one step further and bring their new principle to market, but they are still seeking an industry partner. Next, they want to continue improving the sensitivity of the sensor, and they are also looking for potential areas of application. Park envisions installation of the technology in portable devices, for example to facilitate on-site analysis of chemical impurities such as environmental pollutants or pharmaceutical residues in water. He stresses that invention of a new device is not necessary; it is simple to install the sensor in a suitable way.

Other potential applications include forensic investigations or military applications for early detection of chemical or biological weapons, biomedical application for real-time point-of-care monitoring of physiological levels, and fast screening of drugs and toxins in the area of law enforcement.

###

Reference

Altun AO, Youn SK, Yazdani N, Bond T, Park HG. 'Metal-Dielectric-CNT Nanowires for Femtomolar Chemical Detection by Surface Enhanced Raman Spectroscopy.' Advanced Materials, 2013. DOI: 10.1002/adma.201300571


ELSE PRESS RELEASES FROM THIS DATE:

Researchers develop novel polymer to help oral medications reach the bloodstream

2013-08-28
All too often, when a person takes a pill full of a potent and effective drug, the drug passes straight through the body, not reaching the organ where it is needed — a waste of money and inconvenient if it is a cold medicine, but potentially dire if it is a treatment for a serious illness. Polymer chemists at Virginia Tech and pharmaceutical scientists at Purdue University have teamed up to design a solution. Their research to identify, understand, and create new polymer additives that enhance the ability of orally administered drugs to reach the bloodstream has been ...

Conspiracy theories not to blame for underrepresentation in HIV studies

2013-08-28
Even though most Americans believe some kind of conspiracy theory about HIV care and research, many are willing to take part in vaccine trails, according to a new study1 by Ryan Westergaard of the University of Wisconsin School of Medicine and Public Health, published in Springer's Journal of General Internal Medicine.2 The study found no link between distrust in medical research and willingness to participate in related studies. Westergaard and his team asked 601 Chicago residents at various shopping centers to voluntarily complete a set of 235 questions. The survey ...

Expectant mothers' periodontal health vital to health of her baby

2013-08-28
Chicago, IL – (August 27, 2013) – When a woman becomes pregnant, she knows it is important to maintain a healthy lifestyle to ensure both the health of herself and the health of her baby. New clinical recommendations from the American Academy of Periodontology (AAP) and the Eurpean Federation of Periodontology (EFP) urge pregnant women to maintain periodontal health as well. Research has indicated that women with periodontal disease may be at risk of adverse pregnancy outcomes, such giving birth to a pre-term or low-birth weight baby, reports the AAP and EFP. Periodontal ...

Fukushima radioactive plume to reach US in 3 years

2013-08-28
Tuesday, August 27: The radioactive ocean plume from the 2011 Fukushima nuclear plant disaster will reach the shores of the US within three years from the date of the incident but is likely to be harmless according to new paper in the journal Deep-Sea Research 1. While atmospheric radiation was detected on the US west coast within days of the incident, the radioactive particles in the ocean plume take considerably longer to travel the same distance. In the paper, researchers from the Centre of Excellence for Climate System Science and others used a range of ocean simulations ...

Combating concussions

2013-08-28
SAN DIEGO, Calif. (August 28, 2013) — In the United States there are millions of sports related concussions each year, but many go undiagnosed because for some athletes, the fear of being benched trumps the fear of permanent brain damage, and there is no objective test available to accurately diagnose concussions on the sidelines. Researchers at San Diego State University have set out to change that. A team led by Daniel Goble, an exercise and nutritional sciences professor at SDSU, have developed software and an inexpensive balance board that can measure balance with ...

Parasitic worm genome uncovers potential drug targets

2013-08-28
Researchers have identified five enzymes that are essential to the survival of a parasitic worm that infects livestock worldwide and is a great threat to global food security. Two of these proteins are already being studied as potential drug targets against other pathogens. The team sequenced the genome of Haemonchus contortus, or the barber pole worm, a well-studied parasitic worm that resides in the gut of sheep and other livestock globally. This genome could provide a comprehensive understanding of how treatments against parasitic worms work and point to further new ...

AC or DC? 2 newly described electric fish from the Amazon are wired differently

2013-08-28
Much as human siblings can have vastly different personalities despite their similar resemblance and genetics, two closely related species of electric fish from the Amazon produce very different electric signals. These species, new to science, are described in the open access journal ZooKeys by Drs. John Sullivan of Cornell University in Ithaca, New York, Jansen Zuanon of the National Amazonian Research Institute in Manaus, Brazil and Cristina Cox Fernandes of the University of Massachusetts, Amherst. The two new species are bluntnose knifefish, genus Brachyhypopomus, ...

Specialist nurses as good as doctors in managing rheumatoid arthritis patients

2013-08-28
Patients attending clinical nurse specialist clinics do not get inferior treatment to that offered by consultant rheumatologists, the results of a major new clinical trial have revealed. The results of the multi-centre trial at the University of Leeds, funded by Arthritis Research UK, showed that there may be some clinical benefit to people with rheumatoid arthritis, whose condition is managed in clinics run by rheumatology clinical nurse specialists, especially with respect to their disease activity, pain control, physical function and general satisfaction with their ...

Molecular motors: Power much less than expected?

2013-08-28
An innovative measurement method was used at the Institute of Physical Chemistry of the Polish Academy of Sciences in Warsaw for estimating power generated by motors of single molecule in size, comprising a few dozens of atoms only. The findings of the study are of crucial importance for construction of future nanometer machines – and they do not instil optimism. Nanomachines are devices of the future. Composed of a very little number of atoms, they would be in the range of billionth parts of a meter in size. Construction of efficient nanomachines would lead most likely ...

UK children less likely to be diagnosed with ADHD

2013-08-28
New research suggests that children are far less likely to be diagnosed with Attention deficit hyperactivity disorder (ADHD) in the UK than they are in the USA. However, the same study, led by the University of Exeter Medical School, suggests that autism diagnosis is still rising. The study is published online in the Journal of Autism Developmental Disorders, published by Springer, and was supported by the NIHR Collaboration for Leadership in Applied Health Research and Care in the South West Peninsula (NIHR PenCLAHRC). ADHD is thought to be the most common disorder of ...

LAST 30 PRESS RELEASES:

Scientists unlock secrets behind flowering of the king of fruits

Texas A&M researchers illuminate the mysteries of icy ocean worlds

Prosthetic material could help reduce infections from intravenous catheters

Can the heart heal itself? New study says it can

Microscopic discovery in cancer cells could have a big impact

Rice researchers take ‘significant leap forward’ with quantum simulation of molecular electron transfer

Breakthrough new material brings affordable, sustainable future within grasp

How everyday activities inside your home can generate energy

Inequality weakens local governance and public satisfaction, study finds

Uncovering key molecular factors behind malaria’s deadliest strain

UC Davis researchers help decode the cause of aggressive breast cancer in women of color

Researchers discovered replication hubs for human norovirus

SNU researchers develop the world’s most sensitive flexible strain sensor

Tiny, wireless antennas use light to monitor cellular communication

Neutrality has played a pivotal, but under-examined, role in international relations, new research shows

Study reveals right whales live 130 years — or more

Researchers reveal how human eyelashes promote water drainage

Pollinators most vulnerable to rising global temperatures are flies, study shows

DFG to fund eight new research units

Modern AI systems have achieved Turing's vision, but not exactly how he hoped

Quantum walk computing unlocks new potential in quantum science and technology

Construction materials and household items are a part of a long-term carbon sink called the “technosphere”

First demonstration of quantum teleportation over busy Internet cables

Disparities and gaps in breast cancer screening for women ages 40 to 49

US tobacco 21 policies and potential mortality reductions by state

AI-driven approach reveals hidden hazards of chemical mixtures in rivers

Older age linked to increased complications after breast reconstruction

ESA and NASA satellites deliver first joint picture of Greenland Ice Sheet melting

Early detection model for pancreatic necrosis improves patient outcomes

Poor vascular health accelerates brain ageing

[Press-News.org] Almost as sensitive as a dog's nose
New sensor for SERS Raman spectroscopy