Posts Tagged ‘Nanoparticles’

Nano-particles in skin care & cosmetics ? should we be concerned

Recently, ingredients manufacturer Kobo launched a range of non-nano titanium dioxide and zinc oxide UV filters for use in sunscreens.

The company found many consumers are concerned with the possible health risks of nanoparticles in cosmetics, skin care and sunscreens.

Fears have been expressed from many quarters that this technology is being increasingly used in the products we apply to our skin and is racing ahead of the research that is done to find if there are repercussions.

Some studies have concluded that in healthy skin, these miniscule particles are unlikely to cross the skin barrier and enter the body’s system.

Other researchers have found in their experiments that nanoparticles do, indeed penetrate deeper and have been found to accumulate in organs. Quoted from an article published in The Economist magazine, November, 2007:-

“Research on animals suggests that the nanoparticles can even evade some of the body’s natural defense systems and accumulate in the brain, cells, blood and nerves”

In a study at the University of California, LA, researchers have found a potential risk of cancer and genetic disorders for individuals working with high concentrations of Titanium Dioxide nanoparticles.

Consumers were advised to avoid food colours, vitamins and non-essential drug additives containing this ingredient as well as spray-on sunscreens as these particles can be inhaled.

Further human studies are needed to truly understand the health effects of titanium dioxide nano, according to the scientists. “Some people could be more sensitive to nano exposure than others. I believe the toxicity of these nanoparticles has not been studied enough” said Robert Schiesti, one of the authors of the article published in the Journal of Cancer Research (1)

It appears there are no labeling requirements in most countries, and so consumers are not even informed if the products they use contain nanoparticles.

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In March 2010, the UK Government nanotechnology strategy was released with the aim to develop the technology to benefit the economy and consumers. The strategy plans to address barriers to the growth of the technology and is committed to mandatory labeling of nanoparticles in cosmetic products by 2013.

The British consumer magazine ‘Which?’ has criticized the strategy, claiming the British government “…has dodged some central issues around nanotechnologies, such as the need for a mandatory reporting scheme and plugging research gaps” said Peter Vickery-Smith CEO of ‘Which?’ He went on to say “This strategy was supposed to deliver clear direction to drive this technology forward – instead, the government has rehashed old news and failed act on many concerns”

The consumer magazine believes there should be a pre-market assessment and approval of products developed using nanotechnology as well as a compulsory reporting scheme for companies using nanoparticles as ingredients.

In some countries debate on the safety of nanotechnology has become volatile. French environmental group Pieces et Main d’Oeuvre (PTO) have consistently protested at meetings held to debate the technology. Organized by the Commission of Public Debates held from October 09 until January 10, the PTO has disrupted meetings claiming all important decisions had been made.

German citizens have been warned by Germany’s Federal Environment Agency (UBA) against using products containing nanoparticles while risks to the environment remains unknown.

UBA claims there are significant data gaps that need to be explored concerning human health and the environment even though the German government created a nanotechnology commission. The UBA agency believes the first step for a legal frame work should be compulsory labeling and a register to list all nano containing products. This would provide a transparent development for the technology; there are over 800 companies in Germany producing a large number of consumer products that incorporate nanoparticles. These products include cosmetics and sunscreens.

The agency is far from condemning all nano science. Nano plastics for cars and planes reduce their weight contributing to fuel efficiency.

A research team at EPA will be investigating the use of nano materials, particularly titanium dioxide used in cosmetics.

Recent study at Biomedical Science Institute in Northern Ireland demonstrated a possible link between nanoparticles and brain disorders such as Alzheimer’s and Parkinson’s disease.

Increasing amounts of nanoparticles are finding their way into wastewater streams from personal care and cosmetic products, pharmaceutical and food products as well as industrial waste. It is largely unknown how these tiny particles interact with current waste water treatment systems.

I don’t know about you, but it appears to me that we need to be very concerned about nanotechnology and the obvious lack of checks and balances world wide.

At the very least consumers should be provided with concise labeling of products containing nanoparticles in the ingredients, so informed choices can be made by the individual.

If all the world’s people are agitating, and not just those who are often labeled ‘greenies’ in a derogatory way, but scientists and researchers who’s life work is to test for anomalies then it might be a good idea to stand behind them and pressure our respective

Silica Nanoparticles And Solar Cells

Scientists laptop battery have been working to find better materials and methods to create high-performance solar cells. U.S. scientists, a new study found that in silicon solar cells formed on the surface layer of silicon nanoparticle films can enhance the ability of its energy conversion and reduce the battery’s own heat and prolong life. Relevant papers will be published in “Applied Physics Express” (Applied Physics Letters) on.

The study was conducted by physicists at the University of Illinois Munir Nayfeh leadership, mainly targeted at the ultra-violet absorption and transformation. In terms of traditional solar cells, ultraviolet light leaking out of line either directly or by absorption of silicon devices, but it is converted into heat instead of electricity, which may affect the service life. In 2004, published in the “Photonics Technology Letters” (Photonics Technology Letters) in a study, Nayfeh confirmed that the UV lines with the appropriate nano-scale particles effectively combined to produce electricity.

In order to achieve practical results, Nayfeh and his colleagues conducted a new study. They first use its own developed a proprietary technology to larger silicon switch is made of discrete nano-scale particles, they will be issued in different colors of fluorescence. Then, the researchers of these particles dispersed in isopropyl alcohol and wipe the surface of the solar cell. When the alcohol evaporates, the surface of the battery will eventually form a tight layer of nano-granular films.

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The researchers found that if the solar cells covering the surface is the thickness of 1 nm blue fluorescent nano-particles thin-film, the entire cell will be able to transform more than 60% of the UV lines, but the visible light, the conversion rate of increase less than 3%. However, if the battery is the thickness of the surface covered by 285 nm red fluorescent particle film, then the ultraviolet ray acer battery can increase the conversion rate of 67%, while the enhancement of visible light can reach 10%.

Nayfeh that the performance of solar cells such improvements should be more attributed to the improvement of the battery voltage rather than current. He said, “Our study conclusions indicate that charge transfer within the thin film and nano-particle interface, the importance of the amendment.”

Nayfeh said that the new coating process can easily incorporated into the current solar cell manufacturing process, while the costs are not an additional increase.

Nokia intends to be completed end of this year recovery plan for bad batteries

Nokia Corporation (Nokia Corp.) Spokesman Marianne Holmlund said the company plans to complete its year-end 2007, the battery restoration program. The company currently too much heat is being replaced with 4,600 million cell phone batteries.

According to “Nihon Keizai Shimbun” (Nikkei) reported, Holmlund said, Nokia is working with Matsushita Electric Industrial Co., Ltd. (Matsushita Electric Industrial Co.) Cooperation to ensure that problems with lithium batteries can be repaired as soon as possible. Those batteries from Matsushita Battery Co., Ltd. (Matsushita Battery Industrial Co.) Manufacturing.

The Finnish mobile phone giant has released the battery product advice, because of the problems these batteries overheating while charging the battery itself, leading to deformation. Nokia insists that this is not a serious injury due to battery overheating carried back to the response, but consumers demand the product should be replaced.

Holmlund said that Nokia batteries to fix all problem is very difficult, like the call back to the car and computer parts products, fixed rates are usually 30% or less.

If the battery is low repair rate, Nokia is likely to consider continuing the Dell Latitude D520 Battery in 2007 after the rehabilitation program.

Holmlund did not indicate the cost of replacement batteries. Once the battery is expected to identify the cause of the malfunction, Nokia and Panasonic will be sharing costs.

Antibacterial Silver Nanoparticles

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There are some bacteria that are not effectively killed by the conventional antibiotics including many strains of gram-negative bacteria. However the innovative world of science and the need of developing an effective way to cope with this situation has lead scientist to manage a new technology in this regard.

Rani Pattabi and her colleagues at Mangalore University, explains in the international journal of nanoparticles that an electron beam when blasted on a silver nitrate solution can generate nanoparticles.
These particles are shown to be effective against gram-negative species that are not affected by conventional antibacterial agents.

The researchers in India also pointed that these silver nanoparticles are effective against gram-positive bacteria, such as resistant strains of Staphylococcus aureus and Streptococcus pneumoniae and also effective for treating gram-negative Escherichia coli and Pseudomonas aeruginosa.The problem that is threatening human health is resistance to the existing conventional antibiotics. Therefore the chemists all around the world are desperately trying to develop newer compounds that can easily be bactericidal for strains such as MRSA (methicillin or multiple-resistant Staphylococcus aureus) and E. coli O157.
Since the ancient times, silver has been renowned for its bactericidal activities.

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Therefore a technological advancement in the use of silver means a major step forward and a promise for a wide range of applications of silver as anti bacterial agent in the times where antibiotic resistance is proving to be an obstacle for anti bacterial use. Thus the emergence of silver nanoparticles and other such bacteriostatic agents have become a new industrial revolution.
The experimentation involving the radiations to split the silver compounds to release silver ions that will clump together and form nanoparticles, have been taken as a challenge by the researchers. The target was in fact to get a new approach that avoids the need for costly and hazardous reducing agents and that these can be used to get particles of a controlled size that controls its properties as well.

So Pattabi and colleagues used electron beam technology to irradiate silver nitrate solutions in a biocompatible polymer that was polyvinyl alcohol, to form silver nanoparticles.
The Preliminary tests have shown that silver nanoparticles produced by this straightforward, non-toxic method are indeed highly active against S. aureus, E. coli, and P. aeruginosa.
Now we can imagine that our shoes, socks or even the keyboard we are using may be impregnated with silver nanoparticles that can kill some bacteria and might as well prevent the spread of infection among computer users.

These can be the frontline defenses such as these environmentally benign and cost-effective antibacterial compounds and these can prevent spreading the infections through contact with computer keyboard, phones and other devices.  
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The Cell Damage Caused by Ethanol May Be Alleviated by Silver Nanoparticles

Recently, researchers from the University of Barcelona made a study on the role of silver nanoparticels. The study was carried out by these researchers cooperating with the staff of the Magnetism and Nanotechnology laboratory of the University of Santiago de Compostela. They study they conducted proved that the cell damage caused by ethanol may be alleviated by silver nanoparticles which are composed of a few of silver atoms.

Gustavo Egea is a professor with the Department of Cell Biology, Immunology and Neurosciences of the Faculty of Medicine at the UB and an affiliated researcher for the Institute of Nanosciences and Nanotechnology (IN2UB) and the August Pi i Sunyer Miomedical Research Institute (IDIBAPS). He said that the results of the study completely proved that silver nanoparticels, the clusters of very small numbers of silver atoms could probably accelerate ethanol oxidation. The concentrations of silver nanoparticles are quite similar to those found in the blood of alcoholics. What’s more, the concentrations of silver nanoparticles are basically equal to membrane potential and pH that are compatible with values exhibited by mammalian cells.

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In the study, silver nanoparticles were applied to astrocytes which are in ethanol. All these astrocytes are always being with neurons. In addition, astrocytes are widely used to provide a model which can be imitated to study the physiopathological mechanisms of alcohol in foetal alcohol syndrome. Foetal alcohol syndrome is a kind of disease which has been formed before babies are born. The disease is caused by excessive levels of alcohol consumed by the mother. The result of foetal alcohol syndrome is rather serious, which can result in a wide range of severe neurological disorders.

There are a lot of harms caused by alcohol to nerve cells. In some certain situations, alcohol can even lead to programmed cell-death and a kind of change of the actin cytoskeleton. In the study, after the silver nanoparticles were applied to cells in ethanol, the actin cytoskeleton had obvious improvements. What’s more, the cell-death was stopped. Javier Selva is a lecturer with the Department of Cell Biology, Immunology and Neuroscience and first author of the paper. He explained that the silver nanoparticles played a cytoprotective role in alleviating the harmful effect caused by ethanol to astrosytes.

The study not only analyzed the electrocatalytic properties of silver nanoparticles, but also studied the silver nanoparticles’ potential biological applications. The electrocatalytic properties of silver nanoparticles and their potential biological applications were combined to get a more scientific and systematic result. Gustavo Egea, a professor with the Department of Cell Biology, Immunology and Neurosciences of the Faculty of Medicine at the UB said that there is a bright future for electrochemistry which now is applied to cell biology, as this application can take control of various properties of nanoparticles which are composed of a small amount of silver atoms.

The researchers also found that alterations caused by some other primary alcohols like methanol and butanol could also be stopped by the nanoparticles. But some other alterations caused by such toxins as hydrogen peroxide could probably not be improved by the nanoparticles.

Enhancement of the fluorescence spectra of Rhodamine 101 dye using silver aggregate nanoparticles

I.

I.  Introduction

The most powerful propriety of laser dyes is their tunability band laser emission which gives a varity of applications in many fields. Laser dyes are used efficiently in the isotope separation field. They also have applications in biology such that they modify the DNA by irradiation with ultraviolet light to prevent genetic mutations. The most successful, advanced and widely used application of laser in medicine is certainly eye surgery by photocoagulation, the laser dyes can be also used to coagulate blood vessels in order to obstruct the flow of blood (1). They also can be used in monitoring industrial pollution by means of differential absorption lidar (DIAL) technique (2).

According to these importances there are different methods used for increasing the laser fluorescence intensity with specific wavelength. For example by using the laser induced fluorescence (LIF) technique, the effect of concentration on the laser dye Rhodamine B dissolved in ethanol can be studied such that the fluorescence emission intensity of Rhodamine B gets broad and shifts to higher wavelength with concentration (3). Also a dye fluorescence spectrum shift can be obtained without fluorescence intensity enhancement under the influence of the solvent used (4).

Corresponding authors:

+ Lotfi Z. Ismail: Department of Physics, Faculty of Science, Cairo University.

e-mail: Lotfizaki@hotmail.com

* Mohamed A. El Shaer: Department of Physics and Mathematics, Faculty of Engineering, Zagazig University.

e-mail: Melshaer@link.net

Recently nanoparticles (NPs) have a very interesting role on the laser dyes emission fluorescence such that adding (NPs) to a dye solution enhances the fluorescence emission of the dye. That enhancement of the fluorescence emission of molecules near a metal surface arises from interactions with surface plasmons (sp) resonance in the metal particles; these interactions may also result in shortening of the excited-state lifetime thus improving the photostability of the dye (5).

In the spots, where local fields are concentrated, both linear and nonlinear optical responses of molecules and atoms are gigantically enhanced which will lead to a number of important applications, the most important one is the surface enhanced Raman scattering (SERS) (6) . The presence of the nanoparticles (NPs) will increase the fluorescence quantum efficiency which is expected to have a very important consequence in (SERS) (7).

For example when silver (NPs) are added to the dye solution, dye molecules will be adsorbed on islands and films of the metallic (NPs) and when the surface plasmon resonance (SPR) of the metallic (NPs) coincides with the dye absorption band that will modify the intensity of the electromagnetic field (EMF) around the molecules which will increase the emitted fluorescence intensity (8). That modification of the (EMF) is due to the very high field gradient near the metallic surfaces (9).

Adding Ag (NPs) to the dye solution can cause either an enhancement or a quenching of the fluorescence intensity of the dye depending on the distance between the dye molecules and the metal surfaces. When the metallic (NPs) are in close proximity to the fluorophores, quenching of the luminescence occurs because the non-radiative decay of the excited molecules will increase due to the energy transfer from the dye molecules to silver (NPs), whereas when the metallic (NPs) are located at certain distance, enhancement in the luminescence is observed due to the decrease of the non-radiative decay (10). Silver and gold (NPs) are used in most popular dyes because their plasmon resonance frequency is located in the visible spectrum which matches with the absorption and the emission bands of these dyes. There are important factors affecting the strength of the fluorescence intensity which are the size and shape of the (NPs), the orientation of the dye dipole moments relative to the (NPs) surface normal, the overlap of the absorption and emission bands of the dye with the plasmon band of the metal and the radiative decay rate and the quantum yield (Q) of the fluorescent molecule (5, 11).

 Since Rhodamine dyes are the most and wieldy used dyes in many fields such that they can be used in nonphotochemical hole burning experiments on the mitochondrial dye Rhodamine 800 incubated with two human ovarian surface epithetical cell lines. This dye is believed to be selective for the plasma and inner membranes of the mitochondria (12). Gold nanoparticles can be used as a colorimetric sensor for protein conformational change (13).

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So in this work we study the effect of adding silver (NPs) to Rhodamine 101 dye of concentration 10-4 M/L with different weighting factors between the Ag (NPs) and the dye solution.

II. Experimental samples and setups

Experimentally, we use Rh 101 dye of molecular weight of 591.06 gm, which appears as a green solid with maximum absorption wavelength of 568 nm when it is dissolved in absolute ethanol (99.9 %). The selected concentration of the dye solution is 10-4 M/L.

The aggregated nanoparticles are prepared by vinylpyrrolidone reduction of AgNO3 in ethanol solution. AgNO3 (5 mg) is dissolved in EtOH (100 ml), put in a reflux condenser and heated while stirring for 15 min. Then poly (vinylpyrrolidone) (molecular weight, 40 000; 1.2 g) was added, with stirring, and kept in a reflux condenser for about 10 min. After that NaOH (1 wt%; 0.5 ml) is added and kept at boiling while stirring for 30 min. Then the mixture was kept stirred until it cooled to room temperature. That colloid prepared this way contains mostly isolated Ag particles.

In the preparation of Ag aggregate, ethanol solution of AgNO3 (25 mg in 25 ml of EtOH) is mixed with 25 ml of initial colloid at boiling temperature while stirring. Then, 4 ml of NaOH (1 wt %) is added to the mixture, which was kept stirred at boiling temperature for 30 min and then until it cooled to room temperature. The estimated concentration of Ag particles in the mixture was 8.8*1013  cm-3 (9). Interaction of Rhodamine 101 dye molecule with silver nanoparticles is schematically shown in figure 1.

Fig.1 Schematic representation of the formation of dye-Ag nanoparticles complex

This molecule has two nitrogen atoms with which it can bind to silver nanoparticles. Among these two nitrogen atoms one of them is more electropositive and can bind to silver nanoparticles preferentially to form dye silver nanoparticles complex. Due to the affinity of dye molecule with silver nanoparticles, electron transfer mechanism becomes easier and enhancement is obtained.

The pure dye solution and the dye aggregate mixtures are pumped by argon (Ar) ion laser of output wavelength 488 nm generated from Lexel 95 laser generator and the fluorescence spectrum is detected by SPEX 750M monochromator. An Acquisition card is used to analyze the fluorescence spectra with pc-computer software specially written to scan the wavelength as shown in figure 2.  

Fig.2 Schematic diagram of the spectroscopic system and data acquisition part of the experiment.

III. Results

First, a pure Rh 101 dye solution of concentration 10-4 M/L is pumped with Ar ion laser, and then Ag (NPs) is added to the dye solution with ratios from 1:7 to 1:3 of the Ag (NPs) to the dye in the solution, the fluorescence intensities are recorded as shown in figure 3 which presents a comparison between the fluorescence emission curves of the four cases such that the lowest fluorescence intensity belongs to the pure dye solution (black curve) of concentration 10-4 M/L and equals to 1.32 a.u. and its peak at ? = 627.5 nm, (green curve) the fluorescence intensity of the Ag aggregate to dye solution ratio is 1:7 increases to be 1.55 a.u. and its peak is shifted to be at ? = 617.5 nm, (red curve) the fluorescence intensity of the Ag aggregate to dye solution ratio is 1:3.5  increases to be 1.6 a.u. and its peak is shifted to be at ? = 615 nm, (blue curve) the  fluorescence intensity of the Ag aggregate to dye solution ratio is 1:3 increases to be 2.05 a.u.- the highest value -  and its peak is shifted to be at ? = 614.5 nm.

Fig. 3 A comparison between the fluorescence intensity versus wavelength of different cases (Black) pure dye of concentration 10-4 M/L, (Green) Ag aggregate to dye ratio 1:7, (Red) Ag aggregate to dye ratio 1:3.5, and (Blue) Ag aggregate to dye ratio 1:3.

Figures 4, 5 represent the relation between the dye fluorescence intensity and its peak spectral wavelength shift versus the Ag aggregate percentage in the aggregate-dye solution respectively. They showed that there is a linear relationship between the Ag aggregate percentage in the mixture and the fluorescence intensity and its peak spectral wavelength shift. As the Ag aggregate nanoparticles percentage increased in the mixture, the fluorescence intensity increased and the peak spectral shift also increased.

Fig. 4 The relation between Ag aggregate percentages and the fluorescence intensity.

Fig. 5 The relation between Ag aggregate percentages and the shift of the maximum peak wavelength.

As we dilute the dye solution to be of a concentration of 5×10-5 M/L and pump it with Ar ion laser, and then adding Ag (NPs) to dye solution such that the Ag aggregate to dye ratio in the mixture is 1:7, their fluorescence emission intensities are recorded as shown in figure 6 which represents a comparison between the two cases such that  the pure dye solution (red curve) has the minimum fluorescence intensity with its peak  at ?= 612.5 nm, and the fluorescence intensity of the aggregate dye mixture of ratio 1:7 of the Ag (NPs) to dye (black curve) increases with percentage increase in the fluorescence intensity by only 5% with its maximum peak at ?=610 nm, so we can say that the intensity increased and the shift is obtained but with weak dependence on the Ag aggregate percentage in the solution.

Fig.6 A comparison between the fluorescence intensity of two cases, (red curve) the fluorescence intensity of a pure dye of concentration of 5*10-5 M/L, (black curve) the fluorescence intensity of an Ag aggregate to dye (5*10-5 M/L) mixture of ratio 1:7.

IV. Discussion and Conclusion

In this work, adding silver (NPs) to Rhodamine 101 dye solution is investigated. The measured values reveal that adding Ag (NPs) to the dye solution will enhance the dye fluorescence to significant values accompanied by wavelength shift to higher values as the Ag (NPs) percentage increases in the dye aggregate mixture. The fluorescence enhancement could be due to the field enhancement in metallic nanostructures associated with the surface plasmons, whereas the fluorescence spectrum shift may be obtained due to the overlapping between the electronic transition of the metal nanoparticles and the molecular transition of the dye molecules.

 At the same time adding Ag (NPs) to diluted Rh 101 dye solution of concentration 5*10-5 M/L with ratio 1:7 of the aggregated silver to the dye in the mixture will give an intensity increase in the fluorescence of the dye by only 5%, and a spectrum wavelength shift is obtained by only 2.5 nm which gives a weak dependence on the Ag percentage in the solution because dye dilution decreases fluorophores density  required to make bonds to the Ag nanoparticles to enhance the dye fluorescence intensity as seen in figure 1,  accordingly the intensity enhancement is limited.

V. References

1. F. J. Duaarte, L. W. Hillman, (1990), Academic press.

2. M. L. Paascu, N. Moise, A. Staicu, (2001),  Journal of molecular structure, Vol. 598, pp. 57-64.

3. M. Fikry, M. M. Omar, Lotfi Z. Ismail, (2009) , Journal of Fluorescence, Vol. 19, No. 4, pp. 741-746.

4. B. R. Gayathri, J. R. Mannekutla, S.R. Inamdar, (2008), Journal of molecular structure, Vol. 889, pp. 383-393.

5. O. G. Tovmachenko, C. Graf, D. J. van den Heuvel, (2006) , Advanced materials, Vol. 18, pp. 91-95.

6. S. R. Emory, (2000), the international society of optical engineering, pp. 1-2.

7. A. Santhi, M. Umadevi, V. Ramakrishnan, (2004), Spectrochimica Acta part A, Vol. 60, pp. 1077-1083.

8. M. A. Noginov, G. Zhu, V. P. Drachev, (2006), Physical review B, Vol. 74, No. 18, pp. 184203(1-8).

9. M. A. Noginov, G. Zhu, C. Davison, A. K. Pradhan, (2005), Journal of modern optics, Vol. 52, Issue 16, pp. 2331-2341.

10. S. Kalele, A. C. Deshpande, S. Bhushan Singh, S. K. Kulkarni, (2008), Bull. Mater. Sci., Vol. 31, No. 3, pp. 541-544.

11. R. J. Walsh, T. Reinot, J. M. Hayes, K.  R. Kalli, L. C. Hartmann, G. J. Small, (2002), Journal of Luminescence, Vol. 98, pp. 115-121.

12. S. Chah, M. R. Hammond, R. N. Zare, (2005), Chemistry & Biology, Vol. 12, pp. 323-328.

13.  O. Stranik, R. Nooney, C. McDonagh, B. D. MacCaraith, (2007), Plasmonics, Vol. 2, pp. 15-22.