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Länk, N. O., Johansson, P. & Käll, M. (2018). Directional scattering and multipolar contributions to optical forces on silicon nanoparticles in focused laser beams. Optics Express, 26(22), 29074-29085
Open this publication in new window or tab >>Directional scattering and multipolar contributions to optical forces on silicon nanoparticles in focused laser beams
2018 (English)In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 26, no 22, p. 29074-29085Article in journal (Refereed) Published
Abstract [en]

Nanoparticles made of high index dielectric materials have seen a surge of interest and have been proposed for various applications, such as metalenses, light harvesting and directional scattering. With the advent of fabrication techniques enabling colloidal suspensions, the prospects of optical manipulation of such nanoparticles becomes paramount. High index nanoparticles support electric and magnetic multipolar responses in the visible regime and interference between such modes can give rise to highly directional scattering, in particular a cancellation of back-scattered radiation at the first Kerker condition. Here we present a study of the optical forces on silicon nanoparticles in the visible and near infrared calculated using the transfer matrix method. The zero-backscattering Kerker condition is investigated as an avenue to reduce radiation pressure in an optical trap. We find that while asymmetric scattering does reduce the radiation pressure, the main determining factor of trap stability is the increased particle response near the geometric resonances. The trap stability for non-spherical silicon nanoparticles is also investigated and we find that ellipsoidal deformation of spheres enables trapping of slightly larger particles.

Place, publisher, year, edition, pages
Optical Society of America, 2018
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:oru:diva-70213 (URN)10.1364/OE.26.029074 (DOI)000448556300084 ()
Funder
Swedish Foundation for Strategic Research , RMA11-0037Knut and Alice Wallenberg Foundation
Available from: 2018-11-20 Created: 2018-11-20 Last updated: 2018-11-20Bibliographically approved
Shao, L., Andrén, D., Jones, S., Johansson, P. & Käll, M. (2018). Optically controlled stochastic jumps of individual gold nanorod rotary motors. Physical Review B, 98(8), Article ID 085404.
Open this publication in new window or tab >>Optically controlled stochastic jumps of individual gold nanorod rotary motors
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2018 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 98, no 8, article id 085404Article in journal (Refereed) Published
Abstract [en]

Brownian microparticles diffusing in optical potential-energy landscapes constitute a generic test bed for nonequilibrium statistical thermodynamics and have been used to emulate a wide variety of physical systems, ranging from Josephson junctions to Carnot engines. Here we demonstrate that it is possible to scale down this approach to nanometric length scales by constructing a tilted washboard potential for the rotation of plasmonic gold nanorods. The potential depth and tilt can be precisely adjusted by modulating the light polarization. This allo`ws for a gradual transition from continuous rotation to discrete stochastic jumps, which are found to follow Kramers dynamics in excellent agreement with stochastic simulations. The results widen the possibilities for fundamental experiments in statistical physics and provide insights into how to construct light-driven nanomachines and multifunctional sensing elements.

Place, publisher, year, edition, pages
American Physical Society, 2018
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:oru:diva-68461 (URN)10.1103/PhysRevB.98.085404 (DOI)000440632900008 ()
Funder
Knut and Alice Wallenberg Foundation
Available from: 2018-08-15 Created: 2018-08-15 Last updated: 2018-08-15Bibliographically approved
Hajizadeh, F., Shao, L., Andrén, D., Johansson, P., Rubinsztein-Dunlop, H. & Käll, M. (2017). Brownian fluctuations of an optically rotated nanorod. Optica, 4(7), 746-751
Open this publication in new window or tab >>Brownian fluctuations of an optically rotated nanorod
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2017 (English)In: Optica, ISSN 2334-2536, Vol. 4, no 7, p. 746-751Article in journal (Refereed) Published
Abstract [en]

Gold nanorods can be optically trapped in aqueous solution and forced to rotate at kilohertz rates by circularly polarized laser light. This enables detailed investigations of local environmental parameters and processes, such as medium viscosity and nanoparticle-molecule reactions. Future applications may include nanoactuation and single-cell analysis. However, the influence of photothermal heating on the nanoparticle dynamics needs to be better understood in order to realize widespread and quantitative use. Here we analyze the hot Brownian motion of a rotating gold nanorod trapped in two dimensions by an optical tweezers using experiments and stochastic simulations. We show that, for typical settings, the effective rotational and translational Brownian temperatures are drastically different, being closer to the nanorod surface temperature and ambient temperature, respectively. Further, we show that translational dynamics can have a non-negligible influence on the rotational fluctuations due to the small size of a nanorod in comparison to the focal spot. These results are crucial for the development of gold nanorods into generic and quantitative optomechanical sensor and actuator elements. (C) 2017 Optical Society of America

Place, publisher, year, edition, pages
Optics Info Base, Optical Society of America, 2017
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:oru:diva-59307 (URN)10.1364/OPTICA.4.000746 (DOI)000406093300011 ()2-s2.0-85025121417 (Scopus ID)
Funder
Knut and Alice Wallenberg Foundation
Available from: 2017-08-25 Created: 2017-08-25 Last updated: 2018-08-05Bibliographically approved
Aissaoui, N., Moth-Poulsen, K., Käll, M., Johansson, P., Wilhelmsson, L. M. & Albinsson, B. (2017). FRET enhancement close to gold nanoparticles positioned in DNA origami constructs. Nanoscale, 9(2), 673-683
Open this publication in new window or tab >>FRET enhancement close to gold nanoparticles positioned in DNA origami constructs
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2017 (English)In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 9, no 2, p. 673-683Article in journal (Refereed) Published
Abstract [en]

Here we investigate the energy transfer rates of a Förster resonance energy transfer (FRET) pair positioned in close proximity to a 5 nm gold nanoparticle (AuNP) on a DNA origami construct. We study the distance dependence of the FRET rate by varying the location of the donor molecule, D, relative to the AuNP while maintaining a fixed location of the acceptor molecule, A. The presence of the AuNP induces an alteration in the spontaneous emission of the donor (including radiative and non-radiative rates) which is strongly dependent on the distance between the donor and AuNP surface. Simultaneously, the energy transfer rates are enhanced at shorter D-A (and D-AuNP) distances. Overall, in addition to the direct influence of the acceptor and AuNP on the donor decay there is also a significant increase in decay rate not explained by the sum of the two interactions. This leads to enhanced energy transfer between donor and acceptor in the presence of a 5 nm AuNP. We also demonstrate that the transfer rate in the three "particle" geometry (D + A + AuNP) depends approximately linearly on the transfer rate in the donor-AuNP system, suggesting the possibility to control FRET process with electric field induced by 5 nm AuNPs close to the donor fluorophore. It is concluded that DNA origami is a very versatile platform for studying interactions between molecules and plasmonic nanoparticles in general and FRET enhancement in particular.

Place, publisher, year, edition, pages
Cambridge, United Kingdom: Royal Society of Chemistry, 2017
National Category
Physical Sciences Chemical Sciences
Identifiers
urn:nbn:se:oru:diva-54103 (URN)10.1039/c6nr04852h (DOI)000394780200025 ()27942672 (PubMedID)2-s2.0-85008929281 (Scopus ID)
Funder
Swedish Research Council
Note

Funding Agencies:

Chalmers Area of Advance in Nanoscience and Nanotechnology

European research council, ERC

Available from: 2016-12-21 Created: 2016-12-20 Last updated: 2017-11-29Bibliographically approved
Odebo Länk, N., Verre, R., Johansson, P. & Käll, M. (2017). Large-Scale Silicon Nanophotonic Metasurfaces with Polarization Independent Near-Perfect Absorption. Nano letters (Print), 17(5), 3054-3060
Open this publication in new window or tab >>Large-Scale Silicon Nanophotonic Metasurfaces with Polarization Independent Near-Perfect Absorption
2017 (English)In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 17, no 5, p. 3054-3060Article in journal (Refereed) Published
Abstract [en]

Optically thin perfect light absorbers could find many uses in science and technology. However, most physical realizations of perfect absorption for the optical range rely on plasmonic excitations in nanostructured metallic metasurfaces, for which the absorbed light energy is quickly lost as heat due to rapid plasmon decay. Here we show that a silicon metasurface excited in a total internal reflection configuration can absorb at least 97% of incident near-infrared light due to interferences between coherent electric and magnetic dipole scattering from the silicon nanopillars that build up the metasurface and the reflected wave from the supporting glass substrate. This "near-perfect" absorption phenomenon loads more than 50 times more light energy into the semiconductor than what would be the case for a uniform silicon sheet of equal surface density, irrespective of incident polarization. We envisage that the concept could be used for the development of novel light harvesting and optical sensor devices.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2017
Keywords
Metasurfaces, colloidal lithography, high-index nanophotonics, perfect absorption
National Category
Nano Technology Chemical Sciences
Research subject
Physics
Identifiers
urn:nbn:se:oru:diva-57349 (URN)10.1021/acs.nanolett.7b00416 (DOI)000401307300046 ()28358487 (PubMedID)2-s2.0-85019171855 (Scopus ID)
Funder
Swedish Foundation for Strategic Research Knut and Alice Wallenberg Foundation
Available from: 2017-05-24 Created: 2017-05-24 Last updated: 2017-09-14Bibliographically approved
Andrén, D., Shao, L., Länk, N. O., Acimovic, S. S., Johansson, P. & Käll, M. (2017). Probing Photothermal Effects on Optically Trapped Gold Nanorods by Simultaneous Plasmon Spectroscopy and Brownian Dynamics Analysis. ACS Nano, 11(10), 10053-10061
Open this publication in new window or tab >>Probing Photothermal Effects on Optically Trapped Gold Nanorods by Simultaneous Plasmon Spectroscopy and Brownian Dynamics Analysis
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2017 (English)In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 11, no 10, p. 10053-10061Article in journal (Refereed) Published
Abstract [en]

Plasmonic gold nanorods are prime candidates for a variety of biomedical, spectroscopy, data storage, and sensing applications. It was recently shown that gold nanorods optically trapped by a focused circularly polarized laser beam can function as extremely efficient nanoscopic rotary motors. The system holds promise for-applications ranging from nanofluidic flow control and nanorobotics to biomolecular actuation and analysis. However, to fully exploit this potential, one needs to be able to control and understand heating effects associated with laser trapping. We investigated photothermal heating of individual rotating gold nanorods by simultaneously probing their localized surface plasmon resonance spectrum and rotational Brownian dynamics over extended periods of time. The data reveal an extremely slow nanoparticle reshaping process, involving migration of the order of a few hundred atoms per minute, for moderate laser powers and a trapping wavelength close to plasmon resonance. The plasmon spectroscopy and Brownian analysis allows for separate temperature estimates based on the refractive index and the viscosity of the water surrounding a trapped nanorod. We show that both measurements yield similar effective temperatures, which correspond to the actual temperature at a distance of the order 10-15 nm from the particle surface. Our results shed light on photothermal processes on the nanoscale and will be useful in evaluating the applicability and performance of nanorod motors and optically heated nanoparticles for a variety of applications.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2017
Keywords
photothermal effects, gold nanorod, optical tweezers, nanomotors, thermal reshaping, Brownian dynamics
National Category
Atom and Molecular Physics and Optics Other Chemistry Topics
Identifiers
urn:nbn:se:oru:diva-62784 (URN)10.1021/acsnano.7b04302 (DOI)000413992800048 ()28872830 (PubMedID)2-s2.0-85033232169 (Scopus ID)
Funder
Knut and Alice Wallenberg FoundationSwedish Foundation for Strategic Research
Note

Funding Agency:

Chalmers Area of Advance Nanoscience and Nanotechnology

Available from: 2017-11-23 Created: 2017-11-23 Last updated: 2017-11-23Bibliographically approved
Shao, L., Yang, Z.-J., Andren, D., Johansson, P. & Käll, M. (2015). Gold Nanorod Rotary Motors Driven by Resonant Light Scattering. ACS Nano, 9(12), 12542-12551
Open this publication in new window or tab >>Gold Nanorod Rotary Motors Driven by Resonant Light Scattering
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2015 (English)In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 9, no 12, p. 12542-12551Article in journal (Refereed) Published
Abstract [en]

Efficient and robust artificial nanomotors could provide a variety of exciting possibilities for applications in physics, biology and chemistry, including nanoelectromechanical systems, biochemical sensing, and drug delivery. However, the application of current man-made nanomotors is limited by their sophisticated fabrication techniques, low mechanical output power and severe environmental requirements, making their performance far below that of natural biomotors. Here we show that single-crystal gold nanorods can be rotated extremely fast in aqueous solutions through optical torques dominated by plasmonic resonant scattering of circularly polarized laser light with power as low as a few mW. The nanorods are trapped in 2D against a glass surface, and their rotational dynamics is highly dependent on their surface plasmon resonance properties. They can be kept continuously rotating for hours with limited photothermal side effects and they can be applied for detection of molecular binding with high sensitivity. Because of their biocompatibility, mechanical and thermal stability, and record rotation speeds reaching up to 42 kHz (2.5 million revolutions per minute), these rotary nanomotors could advance technologies to meet a wide range of future nanomechanical and biomedical needs in fields such as nanorobotics, nanosurgery, DNA manipulation and nano/microfluidic flow control.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2015
Keywords
nanomotors, gold nanorods, light scattering, surface plasmon, optical tweezers
National Category
Chemical Sciences
Research subject
Chemistry
Identifiers
urn:nbn:se:oru:diva-47764 (URN)10.1021/acsnano.5b06311 (DOI)000367280100109 ()26564095 (PubMedID)2-s2.0-84952360114 (Scopus ID)
Funder
Knut and Alice Wallenberg Foundation
Available from: 2016-01-27 Created: 2016-01-26 Last updated: 2017-11-30Bibliographically approved
Lehmuskero, A., Johansson, P., Rubinsztein-Dunlop, H., Tong, L. & Käll, M. (2015). Laser trapping of colloidal metal nanoparticles. ACS Nano, 9(4), 3453-3469
Open this publication in new window or tab >>Laser trapping of colloidal metal nanoparticles
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2015 (English)In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 9, no 4, p. 3453-3469Article, review/survey (Refereed) Published
Abstract [en]

Optical trapping using focused laser beams (laser tweezers) has been proven to be extremely useful for contactless manipulation of a variety of small objects, including biological cells, organelles within cells, and a wide range of other dielectric micro- and nano-objects. Colloidal metal nanoparticles have drawn increasing attention in the field of optical trapping because of their unique interactions with electromagnetic radiation, caused by surface plasmon resonance effects, enabling a large number of nano-optical applications of high current interest. Here we try to give a comprehensive overview of the field of laser trapping and manipulation of metal nanoparticles based on results reported in the recent literature. We also discuss and describe the fundamentals of optical forces in the context of plasmonic nanoparticles, including effects of polarization, optical angular momentum, and laser heating effects, as well as the various techniques that have been used to trap and manipulate metal nanoparticles. We conclude by suggesting possible directions for future research.

Keywords
colloidal metal nanoparticles; interparticle forces; laser heating; laser tweezers; optical force; optical manipulation; optical torque; surface plasmon resonance
National Category
Chemical Sciences
Research subject
Chemistry
Identifiers
urn:nbn:se:oru:diva-44814 (URN)10.1021/acsnano.5b00286 (DOI)000353867000009 ()25808609 (PubMedID)2-s2.0-84928974923 (Scopus ID)
Available from: 2015-06-03 Created: 2015-06-03 Last updated: 2018-06-30Bibliographically approved
Wersäll, M., Verre, R., Svedendahl, M., Johansson, P., Käll, M. & Shegai, T. (2014). Directional Nanoplasmonic Antennas for Self-Referenced Refractometric Molecular Analysis. The Journal of Physical Chemistry C, 118(36), 21075-21080
Open this publication in new window or tab >>Directional Nanoplasmonic Antennas for Self-Referenced Refractometric Molecular Analysis
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2014 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, no 36, p. 21075-21080Article in journal (Refereed) Published
Abstract [en]

Localized surface-plasmon resonance (LSPR) sensors are typically based on tracing resonance peak shifts that precisely follow changes in the local refractive index. Such measurements usually require a spectrometer, a stable light source, and an accurate LSPR position tracing technique. As a simple but efficient alternative, we investigated a self-referenced single-wavelength sensing scheme based on angle-dependent and highly directional radiation patterns originating from a monolayer of asymmetric gold nanodimers. We found that one could easily trace a model biotinneutravidin recognition reaction as well as minute bulk refractive index changes, by measuring the intensity ratio between the light scattered in two different directions with respect to the dimers. The refractometric resolution of the methodology was estimated to be on the order of Delta n approximate to 10(-5) RIU. These results may be particularly useful for label-free biosensing applications that require a combination of simple and cost-effective optical readout with a reasonable sensitivity.

National Category
Chemical Sciences
Research subject
Chemistry
Identifiers
urn:nbn:se:oru:diva-37868 (URN)10.1021/jp5064929 (DOI)000341619500040 ()
Funder
Swedish Research CouncilKnut and Alice Wallenberg Foundation
Available from: 2014-10-22 Created: 2014-10-20 Last updated: 2017-12-05Bibliographically approved
Ogier, R., Fang, Y., Svedendahl, M., Johansson, P. & Käll, M. (2014). Macroscopic Layers of Chiral Plasmonic Nanoparticle Oligomers from Colloidal Lithography. ACS Photonics, 1(10), 1074-1081
Open this publication in new window or tab >>Macroscopic Layers of Chiral Plasmonic Nanoparticle Oligomers from Colloidal Lithography
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2014 (English)In: ACS Photonics, E-ISSN 2330-4022, Vol. 1, no 10, p. 1074-1081Article in journal (Refereed) Published
Abstract [en]

Optical near-field coupling between closely spaced plasmonic metal nanoparticles is important to a range of nanophotonic applications of high contemporary interest, including surface-enhanced molecular spectroscopy, nanooptical sensing, and various novel light-harvesting concepts. Here we report on monolayers of chiral heterotrimers and heterotetramers composed of closely spaced silver and/or gold nanodisks of different heights fabricated through facile hole-mask colloidal lithography. These quasi-three-dimensional oligomers are interesting for applications because they exhibit "hot" gaps and crevices of nanometric dimensions, a pronounced circular dichroism, and optical chirality in the visible to near-infrared wavelength range, and they can be produced in large ensembles (>109) of identical orientation. We analyze the optical properties of the samples based on simulation results and find that the circular dichroism is due to strong near-field coupling and intricate phase retardation effects originating in the three-dimensional character of the individual oligomers.

Keywords
plasmonics, optical chirality, circular dichroism, hole-mask colloidal lithography, oligomers, numerical simulation
National Category
Physical Sciences
Research subject
Physics
Identifiers
urn:nbn:se:oru:diva-38652 (URN)10.1021/ph500293u (DOI)000343276800022 ()
Funder
Knut and Alice Wallenberg FoundationSwedish Foundation for Strategic Research
Note

Funding Agency:

Chalmers Nanoscience and Nanotechnology Area of Advance

Available from: 2014-11-17 Created: 2014-11-17 Last updated: 2018-09-12Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0002-2110-3071

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