Turning light energy into heat to fight disease

IMAGE: SENSING THE SIZE-DEPENDENT LIGHT-TO-HEAT CONVERSION EFFICIENCY OF NANOPARTICLES BY TERAHERTZ RADIATION. 

CREDIT: ROBERTO MORANDOTTI

Scientists have developed a method involving terahertz radiation to monitor temperature changes when laser light is focused on tiny gold particles in water

https://www.eurekalert.org/pub_releases/2019-12/aiop-tle121619.php

WASHINGTON, D.C., December 17, 2019 -- An emerging technology involving tiny particles that absorb light and turn it into localized heat sources shows great promise in several fields, including medicine. For example, photothermal therapy, a new type of cancer treatment, involves aiming infrared laser light onto nanoparticles near the treatment site.

Localized heating in these systems must be carefully controlled since living tissue is delicate. Serious burns and tissue damage can result if unwanted heating occurs in the wrong place. The ability to monitor temperature increases is crucial in developing this technology. Several approaches have been tried, but all of them have drawbacks of various kinds, including the need to insert probes or inject additional materials.

In this week's issue of APL Photonics, from AIP Publishing, scientists report the development of a new method to measure temperatures in these systems using a form of light known as terahertz radiation. The study involved suspensions of gold nanorods of various sizes in water in small cuvettes, which were illuminated by a laser focused on a small spot within the cuvette.

The tiny gold rods absorbed the laser light and converted it to heat that spread through the water by convection. "We are able to map out the temperature distribution by scanning the cuvette with terahertz radiation, producing a thermal image," co-author Junliang Dong said.

The study also looked at the way the temperature varied over time. "Using a mathematical model, we are able to calculate the efficiency by which the gold nanorod suspensions converted infrared light to heat," said co-author Holger Breitenborn.

The smallest gold particles, which had a diameter of 10 nanometers, converted laser light to heat with the highest efficiency, approximately 90%. This value is similar to previous reports for these gold particles, indicating the measurements using terahertz radiation were accurate.

Although the smaller gold rods had the highest light-to-heat conversion efficiency, the largest rods -- those with a diameter of 50 nanometers -- displayed the largest molar heating rate. This quantity has been recently introduced to help evaluate the use of nanoparticles in biomedical settings.

"By combining measurements of temperature transients in time and thermal images in space at terahertz frequencies, we have developed a noncontact and noninvasive technique for characterizing these nanoparticles," co-author Roberto Morandotti said. This work offers an appealing alternative to invasive methods and holds promise for biomedical applications.

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The article, "Quantifying the photothermal conversion efficiency of plasmonic nanoparticles by means of terahertz radiation," is authored by H. Breitenborn, J. Dong, R. Piccoli, A. Bruhacs, L.V. Besteiro, A. Skripka, Z. Wang, A.O. Govorov, L. Razzari, F. Vetrone, R. Naccache and R. Morandotti. The article will appear in the journal APL Photonics on Dec. 17, 2019 (DOI: 10.1063/1.5128524). After that date, it can be accessed at https://aip.scitation.org/doi/10.1063/1.5128524.

Abstract-Terahertz optical bistability of graphene-coated cylindrical core–shell nanoparticles

 Tayebeh Naseri, Nader Daneshfar, Milad Moradi-Dangi, Fereshteh Eynipour-Malaee

https://link.springer.com/article/10.1007/s40094-018-0299-7

In this study, we investigate the optical bistability of graphene-coated nanoparticles with cylindrical core–shell structure at terahertz frequency, because graphene displays optical bistability and multistability in a broad range of incident optical intensity. The choice of core–shell system is due to its larger local electric field enhancement, where this characteristic is important for the optical bistable systems. This optical bistability strongly depends on the geometry of the nanoparticle, the fractional volume of the metallic core as well as Fermi energy of graphene. The surrounding medium could also finely affect the optical bistability and induce switching from optical bistability to optical tristability. Since the prosperity of optoelectronics properties of graphene and the importance of core–shell nanoparticles have attracted enormous interest, this model may find potential applications in optical bistable devices such as all-optical switches and biosensors at terahertz communication in near future.

Abstract-Raspberry-like supraparticles from nanoparticle building-blocks as code-objects for hidden signatures readable by terahertz rays

Christopher Stumm, Klaus Szielasko, Tim Granath, Claudia Stauch, Karl Mandel,

https://www.sciencedirect.com/science/article/pii/S2352492818301764

Supraparticles, i.e., raspberry-like microparticles which are composed of nanoparticles (iron oxide), reveal specific interaction properties with terahertz (THz) rays. Depending on the density of the clustering of the nanoparticles within the raspberry-like supraparticle, characteristic THz components are altered upon transmission. The clustering can be adjusted upon supraparticle assembly via modification of the nanoparticles’ surfaces. By employing very densely and very loosely clustered supraparticles, a graphical coding system can be developed which allows creating signatures that are hidden in the bulk of a material (an object) and are easily and unambiguously decodable with THz rays.

Abstract-Terahertz cascades from nanoparticles

K. B. Arnardottir and T. C. H. Liew

https://journals.aps.org/prb/abstract/10.1103/PhysRevB.97.195446

In this article we propose a system capable of terahertz (THz) radiation with quantum yield above unity. The system consists of nanoparticles where the material composition varies along the radial direction of each nanoparticle in such a way that a ladder of equidistant energy levels emerges. By then exciting the highest level of this ladder we produce multiple photons of the same frequency in the THz range. We demonstrate how we can calculate a continuous material composition profile that achieves a high quantum yield and then show that a more experimentally friendly design of a multishell nanoparticle can still result in a high quantum yield.

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Nanoparticle Breakthrough Could Capture Unseen Light for Solar Energy Conversion

Scientists demonstrate how organic dyes work as antennas to help harness, convert light

News Release Glenn Roberts Jr. 

http://newscenter.lbl.gov/2018/04/23/nanoparticle-breakthrough-solar-energy-conversion/

ANIMATION: Energy transfers from a ytterbium atom (blue), which absorbs near-infrared light, to an erbium atom (red). The erbium atom then releases visible, green light. A study led by researchers at Berkeley Lab’s Molecular Foundry found a way to enhance this process, known as “upconversion,” by coating nanoparticles with dyes. Scientists hope to use this process to develop solar cells that capture and convert previously missed sunlight into usable energy. (Credit: Andrew Mueller)

An international team of scientists has demonstrated a breakthrough in the design and function of nanoparticles that could make solar panels more efficient by converting light usually missed by solar cells into usable energy.

The team, led by scientists at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), demonstrated how coating tiny particles with organic dyes greatly enhances their ability to capture near-infrared light and to reemit the light in the visible light spectrum, which could also be useful for biological imaging.

Once they understood the mechanism that enables the dyes on nanoparticles to function as antennas to gather a broad range of light, they successfully reengineered the nanoparticles to further amplify the particles’ light-converting properties. Their study was published online April 23 in Nature Photonics.

“These organic dyes capture broad swaths of near-infrared light,” said Bruce Cohen, a scientist at Berkeley Lab’s Molecular Foundry who helped to lead the study along with Molecular Foundry scientists P. James Schuck (now at Columbia University), and Emory Chan. The Molecular Foundry is a nanoscience research center.

“Since the near-infrared wavelengths of light are often unused in solar technologies that focus on visible light,” Cohen added, “and these dye-sensitized nanoparticles efficiently convert near-infrared light to visible light, they raise the possibility of capturing a good portion of the solar spectrum that otherwise goes to waste, and integrating it into existing solar technologies.”

Researchers found that the dye itself amplifies the brightness of the reemitted light about 33,000-fold, and its interaction with the nanoparticles increases its efficiency in converting light by about 100 times.

An erbium atom (red) in a nanocrystal emits visible, green light via a process known as upconversion that could lead to the development of improved solar cells that capture some previously missed solar energy. Scientists discovered that coating the particles with dyes (blue and purple molecules at right) can greatly enhance this light-converting property. (Credit: Berkeley Lab)

Cohen, Schuck, and Chan had worked for about a decade to design, fabricate, and study the upconverting nanoparticles (UCNPs) used in this study. UCNPs absorb near-infrared light and efficiently convert it to visible light, an unusual property owing to combinations of lanthanide metal ions in the nanocrystals. A 2012 study suggested that dyes on the UCNPs’ surface dramatically enhances the particles’ light-converting properties, but the mechanism remained a mystery.

“There was a lot of excitement and then a lot of confusion,” Cohen said. “It had us scratching our heads.”

Although many researchers had tried to reproduce the study in the following years, “Few people could get the published procedure to work,” added Chan. “The dyes appeared to degrade almost immediately upon exposure to light, and nobody knew exactly how the dyes were interacting with the nanoparticle surface.”

The unique mix of expertise and capabilities at the Molecular Foundry, which included theoretical work and a mix of experiments, chemistry know-how, and well-honed synthetic techniques, made the latest study possible, he noted. “It’s one of those projects that would be difficult to do anywhere else.”

Experiments led by David Garfield, a UC Berkeley Ph.D. student, and Nicholas Borys, a Molecular Foundry project scientist, showed a symbiotic effect between the dye and the lanthanide metals in the nanoparticles.

The proximity of the dyes to the lanthanides in the particles enhances the presence of a dye state known as a “triplet,” which then transfers its energy to the lanthanides more efficiently. The triplet state allowed a more efficient conversion of multiple infrared units of light, known as photons, into single photons of visible light.

The studies showed that a match in the measurements of the dye’s light emission and the particles’ light absorption confirmed the presence of this triplet state, and helped inform the scientists about what was at work.

“The peaks (in dye emission and UCNP absorption) matched almost exactly,” Cohen said.

They then found that by increasing the concentration of lanthanide metals in the nanoparticles, from 22 percent to 52 percent, they could increase this triplet effect to improve the nanoparticles’ light-converting properties.

“The metals are promoting dyes to their triplet states, which helps to explain both the efficiency of energy transfer and the instability of the dyes, since triplets tend to degrade in air,” Cohen said.

The nanoparticles, which measure about 12 nanometers, or billionths of meters, across, could potentially be applied to the surface of solar cells to help them capture more light to convert into electricity, Schuck said.

“The dyes act as molecular-scale solar concentrators, funneling energy from near-infrared photons into the nanoparticles,” Schuck said. Meanwhile, the particles themselves are largely transparent to visible light, so they would allow other usable light to pass through, he noted.

Another potential use is to introduce the nanoparticles into cells to help label cell components for optical microscopy studies. They could be used for deep-tissue imaging, for example, or in optogenetics – a field that uses light to control cell activity.

There are some roadblocks for researchers to overcome to realize these applications, Cohen said, as they are currently unstable and were studied in a nitrogen environment to avoid exposure to air.

More R&D is needed to evaluate possible protective coatings for the particles, such as different polymers that serve to encapsulate the particles. “We have even better designs in mind going forward,” he said.

The Molecular Foundry is a DOE Office of Science User Facility.

Researchers from UC Berkeley, the Korea Research Institute of Chemical Technology, Sungkyunkwan University in South Korea, and the Kavli Energy NanoScience Institute at UC Berkeley also participated in this study. This work was supported by the DOE Office of Science; the National Science Foundation; the China Scholarship Council; and the Ministry of Science, Information and Communication Technology, and Future Planning of South Korea.

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Lawrence Berkeley National Laboratory addresses the world’s most urgent scientific challenges by advancing sustainable energy, protecting human health, creating new materials, and revealing the origin and fate of the universe. Founded in 1931, Berkeley Lab’s scientific expertise has been recognized with 13 Nobel Prizes. The University of California manages Berkeley Lab for the U.S. Department of Energy’s Office of Science. For more, visit www.lbl.gov.

DOE’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.

Abstract-Dewetting during Terahertz Vibrations of Nanoparticles

Ching-Chung Hsueh, Reuven Gordon, Joerg Rottler

http://pubs.acs.org/doi/abs/10.1021/acs.nanolett.7b03984?journalCode=nalefd

We use molecular simulations to demonstrate the formation of a vacuum layer around a vibrating nanoparticle in a liquid. This vacuum layer forms readily for high frequencies with respect to the Einstein frequency of the fluid, even with small amplitude vibrations. The opposite is true for low frequencies, where large amplitudes are required to demonstrate the vacuum layer. With the vacuum layer forming, the quality factor of the oscillations increases substantially. The findings provide an interpretation of our recent experiments that show the onset of high-quality resonances of nanoparticles in water [Xiang et al., Nano Letters 16, 3638 (2016)] in the GHz to THz range.

Abstract-Features of the terahertz spectra of iron oxide nanoparticles in a silicon dioxide shell and of iron oxide and hydroxide nanoparticles

V. Afonin, N. S. Balbekin, G. Z. Gareev, K. G. Gareev, A. N. Gorshkov, D. V. Korolev, V. V. Luchinin, and O. A. Smolyanskaya

https://www.osapublishing.org/jot/abstract.cfm?uri=jot-84-8-515

New methods have been developed for noninvasive monitoring of pathological processes in a living organism by means of terahertz spectroscopy and visualization using contrast agents based on magnetic nanoparticles. The nanoparticles must possess good magnetic characteristics, must be nontoxic and stable against aggregation, and must exhibit chemical stability; therefore, they are enclosed in a biologically inert shell. This paper discusses the spectral features of iron oxide nanoparticles in a biologically inert shell consisting of silicon dioxide and nanoparticles of iron oxide and hydroxide in the terahertz frequency range. It is shown that the crystalline phase of iron oxide can be identified for both types of nanoparticles by means of terahertz spectroscopy.

© 2017 Optical Society of America

Abstract-Recent advances in plasmonic photonic crystal fibers: design, fabrication and applications

Dora Juan Juan Hu,  Ho Pui Ho

https://www.osapublishing.org/aop/abstract.cfm?uri=aop-9-2-257&origin=search

Flexibility in engineering holey structures and controlling the wave guiding properties in photonic crystal fibers (PCFs) has enabled a wide variety of PCF-based plasmonic structures and devices with attractive application potential. Metal thin films, nanowires, and nanoparticles are embedded for achieving surface plasmon resonance (SPR) or localized SPR within PCF structures. This paper begins with an outline of plasmonic sensing principles. This is followed by an overview of fabrication and experimental investigation of plasmonic PCFs. Reported plasmonic PCF designs are categorized based on their target application areas, including optical/biochemical sensors, polarization splitters, and couplers. Finally, design and fabrication considerations, as well as limitations due to the structural features of PCFs, are discussed.

© 2017 Optical Society of America

Abstract-A phantom study of terahertz spectroscopy and imaging of micro- and nano-diamonds and nano-onions as contrast agents for breast cancer

Tyler Bowman, Alec Walter, Olga Shenderova, Nicholas Nunn, Gary McGuire, Magda El-Shenawee

http://iopscience.iop.org/article/10.1088/2057-1976/aa87c2/meta

Terahertz (THz) imaging is effective in distinguishing between cancerous, healthy, and fatty tissues in breast tumors, but a challenge remains in the contrast between cancerous and fibroglandular (healthy) tissues. This work investigates carbon-based nanoparticles as potential contrast agents for THz imaging of breast cancer. Microdiamonds, nanodiamonds (NDs), and nanometer-scale onion-like carbon (OLC) are characterized with THz transmission spectroscopy in low-absorption backgrounds of polydimethylsiloxane or polyethylene. The refractive index and absorption coefficients are calculated based on the measured electric fields. NDs show little effect on the THz signal, microdiamonds express resonance-like, size-dependent absorption peaks, and OLC provides a uniform increase in the optical properties even at low concentration. Due to its strong interaction with THz frequencies and ability to be activated for selective binding to cancer cells, OLC is implemented into engineered three-dimensional breast tumor models composed of phantom tissue mimicking infiltrating ductal carcinoma surrounded by a phantom mimicking healthy fibroglandular tissue. This model is imaged using the THz reflection mode to examine the effectiveness of contrast agents for differentiation between the two tissue types. In both spectroscopy and imaging, a 10% concentration of OLC shows the strongest impact on the THz signal and holds promise as a THz contrast agent.

Abstract-Nanoparticles doped film sensing based on terahertz metamaterials

Weimin Liu, . Author links open the author workspace.Fei Fan, . Author links open the author workspace.Shengjiang Chang, Jiaqing Hou, . Author links open the author workspace.Meng Chen, . Author links open the author workspace.Xianghui  Wang, Jinjun Bai, 

http://www.sciencedirect.com/science/article/pii/S0030401817306739?via%3Dihub


. Author links open the author workspace.FeiFan
A nanoparticles concentration sensor based on doped film and terahertz (THz) metamaterial has been proposed. By coating the nanoparticles doped polyvinyl alcohol (PVA) film on the surface of THz metamaterial, the effects of nanoparticle concentration on the metamaterial resonances are investigated through experiments and numerical simulations. Results show that resonant frequency of the metamaterial linearly decreases with the increment of doping concentration. Furthermore, numerical simulations illustrate that the redshift of resonance results from the changes of refractive index of the doped film. The concentration sensitivity of this sensor is 3.12 GHz/0.1%, and the refractive index sensitivity reaches 53.33 GHz/RIU. This work provides a non-contact, nondestructive and sensitive method for the detection of nanoparticles concentration and brings out a new application on THz film metamaterial sensing.

OT- LUNA BLOG-A Better, Cheaper Treatment for Poisonous Snake Bites

May 22, 2017

Brad Brooks and Zhiguo Zhou, Luna Labs

Venomous snakes are found all over the world.  In the tropical world, where they are most abundant and there is limited access to emergent medical care, they are a significant threat to public health. The World Health Organization (WHO) has designated “snakebites” as a Neglected Tropical Disease, seriously injuring 2.7 million men, women and children, and claiming some 125,000 lives every year.¹ There are more than 600 species of venomous snakes worldwide, and over 200 are considered medically important by the WHO.

Figure 1: Global distribution of venomous snakes, www.who.int

Current treatments require species-specific antivenom, so even though total envenomations (bites with injection of venom) can be high worldwide, the market for any one antivenom is relatively small.  Wyeth Pharmaceuticals (acquired by Pfizer) stopped producing CSAV that was primarily used to treat North American coral snake envenomations. And Sanofi stopped supplying Fav-Afrique, the only antivenom proven safe and effective to treat snake bites in Sub-Saharan regions.  In addition, the antivenom manufacture uses animals (e.g. goats and horses) so the serum immunoglobulin needs to be refrigerated and administered in an intensive care unit (ICU) to deal with “serum sickness”, the patient’s rejection of the animal antibodies. 

All of these factors – low competition, high manufacturing costs, and high administration costs in an ICU – lead to very expensive treatment for snake bites.  US hospitals can charge more than $150,000 to treat one snake bite. In at least one instance more than half of the charges (~$83,000) went to pharmacy costs for the antivenom medicine.^2–3

Ideally a single antivenom medicine would offer broad spectrum protection against common venomous species without the need for accurate species identification. And it would be stored and safely administered anywhere in the world.  To meet this need, Luna is developing a synthetic universal antivenom. Using biomimetic “sticky” nanoparticles, Luna’s antivenom selectively captures a broad range of venomous toxins that are primarily responsible for its lethality and local tissue damages. The sequestered toxins are neutralized and removed from the body naturally, reducing the overall concentration and enhancing the survival rate. Nanoparticles, due to their high surface area to mass ratio, dramatically increase the neutralizing capacity compared to that of immunoglobulin. Current treatments typically require continuous intravenous infusion of hundreds if not thousands of milliliters of saline that contains multiple grams of immunoglobulins over a period of several hours.  While still under preclinical investigation, the higher surface area of the nanoparticles could mean a reduction of antivenom dose and a shorter time to take effect.

The synthetic nanoparticle approach is a practically useful method for producing clinically relevant quantities of antivenom at very low costs starting with readily available compounds. These nanoparticles are stable at ambient conditions, eliminating the need of cold chain transport and storage (refrigeration), which is a huge benefit for emergent medicines in rural tropics and other resource-limited regions.

Luna’s antivenom drug candidate is currently being evaluated in preclinical animal studies for safety and efficacy. Representative snake venoms from the elapidae (e.g. mamba and cobra) and viperidae (e.g. puff adder) families are used to test its efficacy in WHO recommended animal models. If successful, the antivenom nanomedicine will provide much needed help for civilians in high risk regions and may also add a unique medical countermeasure capability to the U.S. military Special Operational Forces who are deployed in austere areas of Africa and Asia and are particularly at risk for encounters with venomous snakes. This universal antivenom technology is funded by the Department of Defense through its DARPA SBIR program.

1. http://www.snakebiteinitiative.org/
2. http://www.cnbc.com/2015/07/21/hospital-appears-to-charge-153000-to-treat-snakebite.html
3. http://www.cbsnews.com/news/rattlesnake-selfie-results-in-a-153k-medical-bill/

Abstract-Terahertz Acoustic Phonon Detection from a Compact Surface Layer of Spherical Nanoparticles Powder Mixture of Aluminum, Alumina and Multi-Walled Carbon Nanotube.

A. A. Abouelsayed, M.R. Ebrahim, W. El hotaby, S.A. Hassan, Emad Al-Ashkar

^a Spectroscopy Department, Physics Division, National Research Centre, 33 El Bohouth st. (former El Tahrir St.)-P.O. 12622 - Dokki - Giza - Egypt

^b Solid State Department, Physics Division, National Research Centre, 33 El Bohouth St. (fromer El Tahrir St.)- P.O. 12622- Dokki - Giza - Egypt

http://www.sciencedirect.com/science/article/pii/S1386142517304286

We present terahertz spectroscopy study on spherical nanoparticles powder mixture of aluminum, alumina, and MWCNTs induced by surface mechanical attrition treatment (SMAT) of aluminum substrates. Surface alloying of AL, Al₂O₃ 0.95% and MWCNTs 0.05% powder mixture was produced during SMAT process, where a compact surface layer of about 200 μm due to ball bombardment was produced from the mixture. Al₂O₃alumina powder played a significant role in MWCNTs distribution on surface, those were held in deformation surface cites of micro-cavities due to SMAT process of Al. The benefits are the effects on resulted optical properties of the surface studied at the terahertz frequency range due to electrical isolation confinement effects and electronic resonance disturbances exerted on Al electronic resonance at the same range of frequencies. THz acoustic phonon around 0.53–0.6 THz (17–20 cm ⁻¹) were observed at ambient conditions for the spherical nanoparticles powder mixture of Al, Al₂O₃ and MWCNTs. These results suggested that the presence of Al₂O₃ and MWCNTs during SMAT process leads to the optically detection of such acoustic phonon in the THz frequency range.

Abstract-Direct Writing of Flexible Barium Titanate/Polydimethylsiloxane 3D Photonic Crystals with Mechanically Tunable Terahertz Properties

http://onlinelibrary.wiley.com/doi/10.1002/adom.201600977/full

Mechanically flexible 3D terahertz photonic crystals (3D-TPCs) are created by the direct-writing technology with a composite ink system composed of polydimethylsiloxane (PDMS) and barium titanate (BaTiO3) nanoparticles. The direct-writing technology allows an easy creation of complex 3D structures with designed geometry, while the refractive indices of the composite ink can be modulated by varying the content of BaTiO3 nanoparticles. Thus, 3D-TPCs with different terahertz properties are obtained by the direct-writing technology. More interestingly, these 3D-TPCs demonstrate a unique tunable terahertz property under external force field due to their mechanical flexibility from the PDMS matrix of the composite ink. Thus, their terahertz property is responsive to external force fields reversibly, which can find novel applications in terahertz technology and other related technological applications