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Optics Express

Optics Express

  • Editor: Andrew M. Weiner
  • Vol. 22, Iss. 9 — May. 5, 2014
  • pp: 10139–10150
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Enhancing optofluidic actuation of micro-objects by tagging with plasmonic nanoparticles

Julien Burgin, Satyabrata Si, Marie-Hélène Delville, and Jean-Pierre Delville  »View Author Affiliations


Optics Express, Vol. 22, Issue 9, pp. 10139-10150 (2014)
http://dx.doi.org/10.1364/OE.22.010139


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Abstract

We report experimentally and theoretically on the significant exaltation of optical forces on microparticles when they are partially coated by metallic nanodots and shined with laser light within the surface plasmon resonance. Optical forces on both pure silica particles and silica-gold raspberries are characterized using an optical chromatography setup to measure the variations of the Stokes drag versus laser beam power. Results are compared to the Mie theory prediction for both pure dielectric particles and core-shell ones with a shell described as a continuous dielectric-metal composite of dielectric constant determined from the Maxwell-Garnett approach. The observed quantitative agreement demonstrates that radiation pressure forces are directly related to the metal concentration on the microparticle surface and that metallic nanodots increase the magnitude of optical forces compared to pure dielectric particles of the same overall size, even at very low metal concentration. Behaving as “micro-sized nanoparticles”, the benefit of microparticles coated with metallic nanodots is thus twofold: it significantly enhances optofluidic manipulation and motion at the microscale, and brings nanometric optical, chemical or biological capabilities to the microscale.

© 2014 Optical Society of America

1. Introduction

Wet chemistry now allows the synthesis of a large diversity of particles [29

29. M. R. Jones, K. D. Osberg, R. J. Macfarlane, M. R. Langille, and C. A. Mirkin, “Templated techniques for the synthesis and assembly of plasmonic nanostructures,” Chem. Rev. 111(6), 3736–3827 (2011). [CrossRef] [PubMed]

,30

30. A. Tao, S. Habas, and P. Yang, “Shape control of colloidal metal nanocrystals,” Small 4(3), 310–325 (2008). [CrossRef]

], and particularly silica-gold raspberry-like particles [31

31. I. Pastoriza-Santos, D. Gomez, J. Pérez-Juste, L. M. Liz-Marzán, and P. Mulvaney, “Optical properties of metal nanoparticle coated silica spheres: a simple effective medium approach,” Phys. Chem. Chem. Phys. 6, 5056–5060 (2004). [CrossRef]

,32

32. T. Pham, J. B. Jackson, N. J. Halas, and T. R. Lee, “Preparation and characterization of gold nanoshells coated with self-assembled monolayers,” Langmuir 18(12), 4915–4920 (2002). [CrossRef]

]. From the material engineering point of view, these complex particles are very attractive as “micron-sized nanoparticles” because they present both micrometric size and nanoscale optical properties such as SPR [31

31. I. Pastoriza-Santos, D. Gomez, J. Pérez-Juste, L. M. Liz-Marzán, and P. Mulvaney, “Optical properties of metal nanoparticle coated silica spheres: a simple effective medium approach,” Phys. Chem. Chem. Phys. 6, 5056–5060 (2004). [CrossRef]

,32

32. T. Pham, J. B. Jackson, N. J. Halas, and T. R. Lee, “Preparation and characterization of gold nanoshells coated with self-assembled monolayers,” Langmuir 18(12), 4915–4920 (2002). [CrossRef]

]. They are also very striking systems because they are able to show how nanoscale tags can impact the mobility of microscale objects. Finally, these raspberries offer the opportunity to investigate the role of increasing complexity in optical manipulation. The goal of the present work is to present quantitative results on the metallic contribution of the optical radiation pressure on silica-gold raspberries flowing in a microfluidic channel. We evidence a significant increase of the optical force magnitude compared to pure silica particles of the same overall size even at very low metal concentration (less than 1%). We also perform numerical simulation to quantitatively address the measured forces, and quantify the role of nanometric metallic tags. These results open up the way for the optofluidic actuation of hybrid plasmonic particles within microfluidic environments.

2. Experimental design

The experimental setup is based on the optical chromatography scheme illustrated in Fig. 1(a).
Fig. 1 (a) Scheme of the experimental chromatography setup. (b) Illustration of flowing particles in the microchannel; particles are magnified by the scattering of the green laser light (c) TEM image of a silica-gold raspberry particle with core diameter D = 1.17 µm and adsorbed gold nanosdots of diameter d = 15 nm (sample α, Table 1.).
We fabricate a microfluidic device using a 50 µm internal diameter cylindrical capillary (VitroCom). It is connected to a syringe pump or to a hydrostatic pressure control and then inserted in a water-filled quartz spectroscopy cell (Hellma) mounted on an Olympus IX71 inverted microscope allowing x^ and y^ displacements; z^ is the vertical axis. A continuous wave laser beam (wavelength in vacuum λ0 = 532 nm from a Coherent Verdi Laser) with a single transverse mode and a Gaussian intensity profile is sent into the microchannel with a wave vector in the direction x^ opposed to the fluid flow.

The beam waist ω is set a few mm inside the microchannel exit at the center of the observation area of the microscope; it is controlled by a series of three fused silica lenses to be 15 µm large. Such a value ensures an overall coverage of the microchannel section by the transverse beam intensity distribution as it prevents diffraction effects by the microchannel edges. It also leads to a Rayleigh length of 1.4 mm, that allows to ignore the laser beam divergence over more than 2 mm centered around the beam waist by considering a mean beam waist ω = 17 ± 2 µm during the overall displacement of the particles. The two first lenses play the role of a telescope of magnification 6X and the third lens, of focal length 40 cm, loosely focuses the laser beam into the channel. Observation is performed with a 10X objective (Olympus UIS2 LMPLFLN) using both the white light Köhler source of the microscope and the green laser light scattered by the flowing particles; an orange band-pass filters allows to reduce the scattered intensity for naked eye observation and prevents camera saturation. Images, as that shown in Fig. 1(b), are grabbed at a frame rate of 5 fps with a USB camera mounted in place of one of the microscope eyepieces. The videos are analyzed with a homemade Matlab particle tracking program adapted from a free online code [33

33. D. Blair and E. Dufresne, “The matlab particle tracking code repository,” http://physics.georgetown.edu/matlab/index.html.

].

The particles are produced using a three-step method. First, we synthesize the silica microparticles with a constant monomer supply technique [34

34. K. Nozawa, H. Gailhanou, L. Raison, P. Panizza, H. Ushiki, E. Sellier, J. P. Delville, and M. H. Delville, “Smart control of monodisperse Stöber silica particles: effect of reactant addition rate on growth process,” Langmuir 21(4), 1516–1523 (2005). [CrossRef] [PubMed]

,35

35. K. Nozawa, M. H. Delville, H. Ushiki, P. Panizza, and J. P. Delville, “Growth of monodisperse mesoscopic metal-oxide colloids under constant monomer supply,” Phys. Rev. E Stat. Nonlin. Soft Matter Phys. 72(1 Pt 1), 011404 (2005). [CrossRef] [PubMed]

] to preserve monodispersity during particle growth; the final size of the particles is monitored by the flow rate amplitude of a diluted tetraethyl orthosilicate solution. The particles are then characterized by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). We choose two suspensions of average particle diameters, D = 1.17 µm and D = 1.46 µm with a standard deviation smaller than 3%, above the micron to guaranty optical actuation of pure silica particles with beam powers below the Watt. Gold nanodots were synthesized according to literature methods [36

36. G. Frens, “Controlled Nucleation for the regulation of the particle size in monodisperse gold suspensions,” Nature 241, 20–22 (1973).

38

38. S. Pramanik, P. Banerjee, A. Sarkar, and S. C. Bhattacharya, “Size-dependent interaction of gold nanoparticles with transport protein: a spectroscopic study,” J. Lumin. 128(12), 1969–1974 (2008). [CrossRef]

], yielding nanodots of diameter d = 15 ± 2 nm. Following the Pastoria-Santos method [31

31. I. Pastoriza-Santos, D. Gomez, J. Pérez-Juste, L. M. Liz-Marzán, and P. Mulvaney, “Optical properties of metal nanoparticle coated silica spheres: a simple effective medium approach,” Phys. Chem. Chem. Phys. 6, 5056–5060 (2004). [CrossRef]

], the silica-gold raspberries are eventually assembled by performing a coating of the silica core with (3-aminopropyl)triethoxysilane (APS) and then by adding a determined volume of citrate stabilized gold nanodots that adsorb on the APS-coated silica surface. Assuming a perfect theoretical coverage of silica beads by 100% of the nanodots added in solution, concentrations are chosen so as to adsorb ~400 gold nanodots on a 1.17 µm-diameter particle (sample α, volume fraction for 100% yield ϕ100% = 1.1%) and ~250 and ~500 gold nanodots on a 1.46 µm-diameter particle (corresponding respectively to samples β and γ with volume fractions for for 100% yield ϕ100% of 0.45% and 0.9%); see Table 1.

Table 1. Data on raspberries samples: diameter of the core silica microparticles, gold volume fraction ϕ100% estimated from quantities used in chemical synthesis, gold volume fraction ϕ deduced from cross section calculations and measured enhancement factor of optical forces compared to silica core

table-icon
View This Table
Figure 1(c) shows a TEM image of sample α, a raspberry with diameter D = 1.17 µm coated with d = 15 nm gold nanodots.

The samples are diluted to get 1.5 108 particles per mL in aqueous solution and infused in the microchannel with a 1.5 mL Terumo syringe. The flow is actuated either by a KD Scientific syringe pump or a pressure gauge. The first method, called optical chromatography mode, consists in establishing a controlled flow rate in the microchannel and using the counter-propagating electromagnetic wave to apply optical forces on the flowing particles in the opposite direction; particle are eventually immobilized when Stokes drag and optical radiation pressure are balanced. The second method, preferentially used in the present investigation is called velocimetry mode. It consists in initially immobilizing the particles within the microchannel by adjusting the hydrostatic pressure and setting them in movement by turning on the laser.

3. Theoretical aspects

The optical force Frp is then estimated from measurements of the particle velocity υ and from the second Newton law, Frp+FStokes=0, where FStokes=6πRη|υ| for a solid sphere and η is the water viscosity. However, the optical absorption of gold nanoparticles present in the shell of the raspberries will heat the surrounding water [47

47. Y. Seol, A. E. Carpenter, and T. T. Perkins, “Gold nanoparticles: enhanced optical trapping and sensitivity coupled with significant heating,” Opt. Lett. 31(16), 2429–2431 (2006). [CrossRef] [PubMed]

]. As a result, the viscosity of water will decrease as well as Stokes drag FStokes which varies linearly with η, and fitting the data without considering this issue may artificially increase the intrinsic enhancement of the optical force due to the gold layer. The temperature dependence of the viscosity of water can be estimated from the Vogel-Fulcher empiric law [48

48. P. V. Ruijgrok, N. R. Verhart, P. Zijlstra, A. L. Tchebotareva, and M. Orrit, “Brownian fluctuations and heating of an optically aligned gold nanorod,” Phys. Rev. Lett. 107(3), 037401 (2011). [CrossRef] [PubMed]

]. To calculate this overheating, we assume that neither silica nor water absorb light at the used wavelength. Using flux and temperature continuity conditions at both core/shell and shell/water interfaces, the absence of thermal gradient at the center of the particle and convergence to room temperature T at infinity, the stationary radial profile of temperature in water due to the thin composite shell is given by [47

47. Y. Seol, A. E. Carpenter, and T. T. Perkins, “Gold nanoparticles: enhanced optical trapping and sensitivity coupled with significant heating,” Opt. Lett. 31(16), 2429–2431 (2006). [CrossRef] [PubMed]

]:
T(rR+d)=T+CabsI4πΛ1r,
(3)
where Λ is the thermal conductivity of water (Λ=0.6W.K-1.m1). In our case the temperature increase T(R+d)T at the surface of the particles varies from 0 to 20 K, depending on the incident power and the volume fraction ϕ.

4. Results and discussion

To investigate the optical forces applied onto hybrid silica@gold raspberries in a microfluidic flow, we use the optical chromatography setup in the velocimetry mode illustrated in Figs. 1(a-b). The particles are initially immobilized within the microchannel by adjusting the hydrostatic pressure and then set in motion by turning on the laser. After a short time, the particles move at a constant speed, typically a few tens of µm/s depending on the laser beam power. We measure the particle velocity of both pure silica microparticles and silica@gold raspberries based on the same core particle. For pure silica microparticles, we deduce the optical force from a direct balance with the Stokes drag (ηH2O=1.103Pa.s at 20 °C). To measure the optical force enhancement induced by the metallic nanoparticles tags that partially cover the silica core (Fig. 1(c)), we proceed iteratively due to laser heating and the subsequent temperature dependence of the viscosity of water. Fixing the gold volume fraction ϕ, we first calculate the laser overheating and the water viscosity to get the Stokes drag and the enhancement factor on optical forces. Secondly, we use Mie theory to calculate the radiation pressure cross section Crp of silica@gold raspberries, deduce the optical force and calculate the enhancement factor relatively to core particles. Dichotomy in volume fraction ϕ is performed up to equality of the enhancement factors. The converging gold volume fraction ϕ is finally compared to estimates from TEM images of the raspberries.

A typical snapshot illustrating particles in the microchannel is presented in Fig. 1(b). Figure 2 shows the time varying positions of silica-gold raspberries (Table 1, sample α, silica D = 1.17 µm, gold d = 15 nm) shined by the laser at the beam power P = 0.75 W.
Fig. 2 Trajectories of 75 silica-gold raspberry particles (sample α, silica core diameter D = 1.17 µm coated by 15 nm gold nanodots) measured in the velocity mode as a function of time lapse for a laser beam of power P = 0.75 W and beam waist ω = 17 µm. The Inset shows the statistic distribution in particle velocity extracted from linear fitting of the trajectory set.
We performed linear fitting of at least 75 trajectories to measure an average velocity at a given laser power. The inset of Fig. 2 shows the velocity distribution obtained from this run with an average of 24 µm/s and a standard deviation of 6 µm/s. The trajectories being linear, this suggests that the particles remain in the Rayleigh zone where the field can be considered as almost axially uniform. Moreover, we observed that most particles move right in the center of the microchannel. This effect is ascribed to two collaborating effects: (i) the weak shear associated to the Poiseuille flow velocity profile within the microchannel before stopping particles with pressure actuation and (ii) the presence of optical gradient forces due to the transverse Gaussian profile of the laser beam, as largely demonstrated in optical chromatography experiments [7

7. T. Kaneta, Y. Ishidzu, N. Mishima, and T. Imasaka, “Theory of optical chromatography,” Anal. Chem. 69(14), 2701–2710 (1997). [CrossRef] [PubMed]

,40

40. Y. Harada and T. Asakura, “Radiation forces on a dielectric sphere in the Rayleigh scattering regime,” Opt. Commun. 124(5-6), 529–541 (1996). [CrossRef]

].

To investigate the contribution of the gold nanodots on optical forces, we performed particle velocity measurements on suspensions with different silica core diameters and gold concentrations at the surface. Figure 3 shows a significant increase of the velocity for the silica microparticles coated with gold compared to that obtained for pure silica particles of same core diameter for both D = 1.17 µm (Fig. 3(a)) and D = 1.46 µm silica core diameter (Fig. 3(b)).
Fig. 3 Velocity as function of the incident laser beam power measured for different types of particles. (a) Core dielectric particles with a diameter of 1.17µm (black empty squares) and SiO2@Au raspberries sample α (blue squares). (b) Core particles with a diameter of 1.46µm (black empty circles) and raspberries (green and red circles correspond to sample β and γ respectively). Error bars represent standard deviations. The linear fits are guides for the eye.
We observe an enhancement of the velocity by a factor 2.34 for sample α, 1.55 for sample β and 2.31 for sample γ. This behavior is interpreted as a metal-induced enhancement of the radiation pressure cross section Crp. Indeed, considering, on the one hand, the optical wavelength of the laser wave (λ0 = 532 nm) and the SPR wavelength of 15 nm gold nanoparticles (λSPR = 525 nm) on the other hand, the presence of metal increases the scattering and absorption of the incident wave, increasing de facto radiation pressure forces [23

23. M. Rodriguez-Otazo, A. Augier-Calderin, and J. P. Galaup, “Nanometer gold–silica composite particles manipulated by optical tweezers,” Opt. Commun. 282(14), 2921–2929 (2009). [CrossRef]

].

To estimate the amplitude of these enhancement factors, we performed numerical Mie calculations of the extinction, absorption, scattering cross section and the asymmetry parameter for our core-shell approach of silica@gold raspberry in order to obtain the gold volume fraction ϕ dependence of the radiation pressure cross section Crp. Results are shown in Fig. 4 for D = 1.46 µm and d = 15 nm.
Fig. 4 Wavelength dependence of the radiation pressure cross section Crp of silica-gold raspberries calculated using Mie theory for silica core diameter D = 1.46 µm, and d = 15 nm thick composite shell composed of water and gold nanodots with volume fraction ϕ = 0.20% (green), 0.45% (red), 1% (blue) and 2% (cyan). The behavior in black describes the silica core case. The vertical dashed line indicates the optical excitation wavelength of 532 nm. The Inset represents the evolution of the enhancement factor, i.e. the ratio of Crp for raspberries over Crpcore for silica core as a function of the metal volume fraction ϕ.
The four colored curves correspond to the radiation pressure cross-section of dielectric-metal particles for ϕ = 0.2, 0.45, 1 and 2%. As expected, the radiation pressure cross section Crp deeply increases when approaching the SPR, depending on ϕ, and then decreases to asymptotically collapse with the prediction for pure silica particles, in black. The comparison to pure silica particles at the used optical wavelength (indicated by the vertical dashed line) gives the theoretical variation of the expected enhancement factor versus the volume fraction ϕ of gold nanodots. The inset of Fig. 4 shows that the enhancement factor is linear in ϕ at low ϕ values.

The estimated volume fractions are almost half of ϕ100%, those suggested from the synthesis with an expected 100% adsorption yield (Table 1). Similarly, the enhancement factor for the smallest silica core (D = 1.17 µm, sample α, Table 1) leads to a metal contribution ϕ = 0.47%. Note for instance that ϕ = 0.47% correspond to an inter-particle distance of 156 nm which is compatible with a rough estimation made from geometric calculation on TEM images, Fig. 1(c), where we found a mean inter gold nanoparticles distance of 120 nm.

These volume fractions ϕ are finally used to estimate optical forces and compare them to absolute values calculated from Mie theory. In Fig. 6 we plot together the optical radiation pressure force predicted by Mie theory for the gold volume fraction ϕ obtained from the enhancement factor matching procedure and the set of optical forces measured for the various combinations of particles diameters and gold nanodot concentrations.
Fig. 6 Radiation pressure force variation versus the radius R of silica-gold raspberries predicted by Mie theory (red curve: ϕ = 0.45% as a mean between 0.43% (sample γ) and 0.47% (sample α), green curve: ϕ = 0.20%) and measured experimentally in the three raspberries samples (black-gray dots). Also shown for the comparison, are the calculation and measurements on core silica particles (black curve and empty circles respectively). The dashed curve represents the forces in the ray optics approximation for silica particles. Error bars also appear on calculations (just represented for silica particles for the sake of clearness) to take into account the weak beam size variation over the Rayleigh length during the particle displacement in the microchannel.
Results on pure silica particles are also presented, including the force estimated in the ray optics approximation as it is used in most optical chromatography investigations [5

5. S. J. Hart and A. V. Terray, “Refractive-index-driven separation of colloidal polymer particles using optical chromatography,” Appl. Phys. Lett. 83(25), 5316–5318 (2003). [CrossRef]

,7

7. T. Kaneta, Y. Ishidzu, N. Mishima, and T. Imasaka, “Theory of optical chromatography,” Anal. Chem. 69(14), 2701–2710 (1997). [CrossRef] [PubMed]

,20

20. A. Terray, J. D. Taylor, and S. J. Hart, “Cascade optical chromatography for sample fractionation,” Biomicrofluidics 3(4), 044106 (2009). [CrossRef] [PubMed]

]. The error bars associated to calculations (solely represented for pure silica) are estimated at ± 29% and originate from the beam waist δω/ω=11% and standard deviation of the radius of silica particles δR/R<3%. The error bars on experimental data points are estimated at ± 15% and originate from the standard deviation on R and the statistical error δυ/υ=12% extracted from velocity measurements (Fig. 2). The error on ω seems large but it takes into account the fact that strictly speaking, particles do not flow along a perfect cylinder of light but in a slightly converging/diverging beam so that optical forces slightly vary along the beam axis. Consequently, agreement between Mie calculations of optical radiation forces and experimental measurements is fairly good; the largest data shift between predicted and measured forces is smaller than 25%, a value which has never been reached to the best of our knowledge, except by further adaption of the laser beam parameters [7

7. T. Kaneta, Y. Ishidzu, N. Mishima, and T. Imasaka, “Theory of optical chromatography,” Anal. Chem. 69(14), 2701–2710 (1997). [CrossRef] [PubMed]

]. Note nonetheless that experimental results are systematically over evaluated by Mie calculations; this is likely due to the internal porosity of Stöber like silica that randomly scatters light and thus reduces the force efficiency [46

46. F. Garcia-Santamaria, H. Miguez, M. Ibisate, F. Meseguer, and C. Lopez, “Refractive index properties of calcined silica submicrometer spheres,” Langmuir 18(5), 1942–1944 (2002). [CrossRef]

].

Finally, to compare with classical optical chromatography schemes [5

5. S. J. Hart and A. V. Terray, “Refractive-index-driven separation of colloidal polymer particles using optical chromatography,” Appl. Phys. Lett. 83(25), 5316–5318 (2003). [CrossRef]

,7

7. T. Kaneta, Y. Ishidzu, N. Mishima, and T. Imasaka, “Theory of optical chromatography,” Anal. Chem. 69(14), 2701–2710 (1997). [CrossRef] [PubMed]

], we present in Fig. 6 calculations in the ray optics approximation for silica particles in water, using already mentioned optical indexes. They fairly approximate Mie calculations for the investigated particle radii. They also show the robustness of this approximation beyond its size range validity (here R ~λ0 while R >> λ0 would be required), and thus enlighten the traditional use of ray optics in optical chromatography. Thus, our results demonstrate that quantitative predictions can indeed be advanced for both core and much more complex core-shell micro materials when the Maxwell-Garnett formulation of the refractive index is applicable. Consequently, our experiments and calculations open the route for the study and the manipulation of hybrid particles with tunable optical properties such as multiple shell objects, micro-nano hybrids where nanometric tags present specific and tunable SPR [49

49. Y. Hu, R. C. Fleming, and R. A. Drezek, “Optical properties of gold-silica-gold multilayer nanoshells,” Opt. Express 16(24), 19579–19591 (2008). [CrossRef] [PubMed]

,50

50. S. C. Padmanabhan, J. McGrath, M. Bardosova, and M. E. Pemble, “A facile method for the synthesis of highly monodisperse silica@gold@silica core–shell–shell particles and their use in the fabrication of three-dimensional metallodielectric photonic crystals,” J. Mater. Chem. 22(24), 11978–11987 (2012). [CrossRef]

], or complex engineered biological system [51

51. M. T. Kumara, N. Srividya, S. Muralidharan, and B. C. Tripp, “Bioengineered flagella protein nanotubes with cysteine loops: self-assembly and manipulation in an optical trap,” Nano Lett. 6(9), 2121–2129 (2006). [CrossRef] [PubMed]

].They also show the way to increase the magnitude of optical forces for particle actuation in microfluidic environments.

5. Conclusion

Using an optical chromatography setup, we investigated optical forces on dielectric core microparticles and hybrid dielectric-metal micro-nano raspberries based on the same silica core. We measured the enhancement of the optical force due to the metallic shell of the raspberries and found good quantitative agreement with a numerical simulation based on Mie theory. We also showed that even at very low metallic concentrations (down to 0.2%) we can definitively differentiate the particles through optical forces, thus demonstrating that nano metallic tags can significantly increase the magnitude of optical forces at the microscale. Consequently, using these “micron-sized nanoparticles”, one can associate ease of manipulation and benefit from nano-engineered materials used as tags where the micrometric range is dedicated to transportation and where the nanometric range offers specific and tunable optical, chemical or biological properties. These results also open up new opportunities in the field of plasmonic particles manipulation and sorting, as dielectric-metal microparticles could be easily differentiated according to their metal concentration in a very fine way. One can imagine using an optical chromatography setup to discriminate mixtures of inhomogeneously decorated particles and create ultra pure sets of similar raspberries with enhanced spectral properties.

Acknowledgments

The authors acknowledge the scientific program Advanced Materials in Aquitaine (GIS Matériaux) and the Conseil Régional d’Aquitaine (Project Nano-Trans N# 20111101010) for funding. The authors would also like to acknowledge networking support by the COST Actions MP 1202 (http://www.cost-hint.cnrs.fr) and MP 1205 (http://costmp1205.eu).

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M. Rodriguez-Otazo, A. Augier-Calderin, and J. P. Galaup, “Nanometer gold–silica composite particles manipulated by optical tweezers,” Opt. Commun. 282(14), 2921–2929 (2009). [CrossRef]

24.

I. Choi, H. D. Song, S. Lee, Y. I. Yang, T. Kang, and J. Yi, “Core-satellites assembly of silver nanoparticles on a single gold nanoparticle via metal ion-mediated complex,” J. Am. Chem. Soc. 134(29), 12083–12090 (2012). [CrossRef] [PubMed]

25.

S. Balint, M. P. Kreuzer, S. Rao, G. Badenes, P. Miskovsky, and D. Petrov, “Simple route for preparing optically trappable probes for surface-enhanced Raman scattering,” J. Phys. Chem. C 113(41), 17724–17729 (2009). [CrossRef]

26.

R. Tamoto, S. Lecomte, S. Si, S. Moldovan, O. Ersen, M. H. Delville, and R. Oda, “Gold nanoparticle deposition on silica nanohelices: a new controllable 3d substrate in aqueous suspension for optical sensing,” J. Phys. Chem. C 116(43), 23143–23152 (2012). [CrossRef]

27.

S. Mühlig, C. Rockstuhl, V. Yannopapas, T. Bürgi, N. Shalkevich, and F. Lederer, “Optical properties of a fabricated self-assembled bottom-up bulk metamaterial,” Opt. Express 19(10), 9607–9616 (2011). [CrossRef] [PubMed]

28.

N. Engheta, “Circuits with light at nanoscales: optical nanocircuits inspired by metamaterials,” Science 317(5845), 1698–1702 (2007). [CrossRef] [PubMed]

29.

M. R. Jones, K. D. Osberg, R. J. Macfarlane, M. R. Langille, and C. A. Mirkin, “Templated techniques for the synthesis and assembly of plasmonic nanostructures,” Chem. Rev. 111(6), 3736–3827 (2011). [CrossRef] [PubMed]

30.

A. Tao, S. Habas, and P. Yang, “Shape control of colloidal metal nanocrystals,” Small 4(3), 310–325 (2008). [CrossRef]

31.

I. Pastoriza-Santos, D. Gomez, J. Pérez-Juste, L. M. Liz-Marzán, and P. Mulvaney, “Optical properties of metal nanoparticle coated silica spheres: a simple effective medium approach,” Phys. Chem. Chem. Phys. 6, 5056–5060 (2004). [CrossRef]

32.

T. Pham, J. B. Jackson, N. J. Halas, and T. R. Lee, “Preparation and characterization of gold nanoshells coated with self-assembled monolayers,” Langmuir 18(12), 4915–4920 (2002). [CrossRef]

33.

D. Blair and E. Dufresne, “The matlab particle tracking code repository,” http://physics.georgetown.edu/matlab/index.html.

34.

K. Nozawa, H. Gailhanou, L. Raison, P. Panizza, H. Ushiki, E. Sellier, J. P. Delville, and M. H. Delville, “Smart control of monodisperse Stöber silica particles: effect of reactant addition rate on growth process,” Langmuir 21(4), 1516–1523 (2005). [CrossRef] [PubMed]

35.

K. Nozawa, M. H. Delville, H. Ushiki, P. Panizza, and J. P. Delville, “Growth of monodisperse mesoscopic metal-oxide colloids under constant monomer supply,” Phys. Rev. E Stat. Nonlin. Soft Matter Phys. 72(1 Pt 1), 011404 (2005). [CrossRef] [PubMed]

36.

G. Frens, “Controlled Nucleation for the regulation of the particle size in monodisperse gold suspensions,” Nature 241, 20–22 (1973).

37.

S. Basu, S. K. Ghosh, S. Kundu, S. Panigrahi, S. Praharaj, S. Pande, S. Jana, and T. Pal, “Biomolecule induced nanoparticle aggregation: effect of particle size on interparticle coupling,” J. Colloid Interface Sci. 313(2), 724–734 (2007). [CrossRef] [PubMed]

38.

S. Pramanik, P. Banerjee, A. Sarkar, and S. C. Bhattacharya, “Size-dependent interaction of gold nanoparticles with transport protein: a spectroscopic study,” J. Lumin. 128(12), 1969–1974 (2008). [CrossRef]

39.

K. F. Ren, G. Gréhan, and G. Gouesbet, “Radiation pressure forces exerted on a particle arbitrarily located in a gaussian beam by using the generalized Lorenz-Mie theory, and associated resonance effects,” Opt. Commun. 108(4-6), 343–354 (1994). [CrossRef]

40.

Y. Harada and T. Asakura, “Radiation forces on a dielectric sphere in the Rayleigh scattering regime,” Opt. Commun. 124(5-6), 529–541 (1996). [CrossRef]

41.

C. F. Bohren and D. F. Hufman, Absorption and Scattering of Light by Small Particles (Wiley, 1983).

42.

A. Ashkin, “Forces of a single-beam gradient laser trap on a dielectric sphere in the ray optics regime,” Biophys. J. 61(2), 569–582 (1992). [CrossRef] [PubMed]

43.

C. Mätzler, “Matlab functions for mie scattering and absorption,” (Research Report, Institut fur Angewandte Physik, University of Bern, Switzerland, 2002). http://www.iapmw.unibe.ch/teaching/vorlesungen/radiative_transfer/HS2012/Mie_Version2.pdf.

44.

P. B. Johnson and R. W. Christy, “Optical constants of the noble metals,” Phys. Rev. B 6(12), 4370–4379 (1972). [CrossRef]

45.

A. N. Bashkatov and E. A. Genina, “Water refractive index in dependence on temperature and wavelength: a simple approximation,” Proc. SPIE 5068, 393–395 (2003). [CrossRef]

46.

F. Garcia-Santamaria, H. Miguez, M. Ibisate, F. Meseguer, and C. Lopez, “Refractive index properties of calcined silica submicrometer spheres,” Langmuir 18(5), 1942–1944 (2002). [CrossRef]

47.

Y. Seol, A. E. Carpenter, and T. T. Perkins, “Gold nanoparticles: enhanced optical trapping and sensitivity coupled with significant heating,” Opt. Lett. 31(16), 2429–2431 (2006). [CrossRef] [PubMed]

48.

P. V. Ruijgrok, N. R. Verhart, P. Zijlstra, A. L. Tchebotareva, and M. Orrit, “Brownian fluctuations and heating of an optically aligned gold nanorod,” Phys. Rev. Lett. 107(3), 037401 (2011). [CrossRef] [PubMed]

49.

Y. Hu, R. C. Fleming, and R. A. Drezek, “Optical properties of gold-silica-gold multilayer nanoshells,” Opt. Express 16(24), 19579–19591 (2008). [CrossRef] [PubMed]

50.

S. C. Padmanabhan, J. McGrath, M. Bardosova, and M. E. Pemble, “A facile method for the synthesis of highly monodisperse silica@gold@silica core–shell–shell particles and their use in the fabrication of three-dimensional metallodielectric photonic crystals,” J. Mater. Chem. 22(24), 11978–11987 (2012). [CrossRef]

51.

M. T. Kumara, N. Srividya, S. Muralidharan, and B. C. Tripp, “Bioengineered flagella protein nanotubes with cysteine loops: self-assembly and manipulation in an optical trap,” Nano Lett. 6(9), 2121–2129 (2006). [CrossRef] [PubMed]

OCIS Codes
(160.0160) Materials : Materials
(280.7250) Remote sensing and sensors : Velocimetry
(290.4020) Scattering : Mie theory
(160.4236) Materials : Nanomaterials
(350.4855) Other areas of optics : Optical tweezers or optical manipulation
(250.5403) Optoelectronics : Plasmonics

ToC Category:
Plasmonics

History
Original Manuscript: December 16, 2013
Revised Manuscript: March 3, 2014
Manuscript Accepted: March 5, 2014
Published: April 21, 2014

Citation
Julien Burgin, Satyabrata Si, Marie-Hélène Delville, and Jean-Pierre Delville, "Enhancing optofluidic actuation of micro-objects by tagging with plasmonic nanoparticles," Opt. Express 22, 10139-10150 (2014)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-22-9-10139


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  24. I. Choi, H. D. Song, S. Lee, Y. I. Yang, T. Kang, J. Yi, “Core-satellites assembly of silver nanoparticles on a single gold nanoparticle via metal ion-mediated complex,” J. Am. Chem. Soc. 134(29), 12083–12090 (2012). [CrossRef] [PubMed]
  25. S. Balint, M. P. Kreuzer, S. Rao, G. Badenes, P. Miskovsky, D. Petrov, “Simple route for preparing optically trappable probes for surface-enhanced Raman scattering,” J. Phys. Chem. C 113(41), 17724–17729 (2009). [CrossRef]
  26. R. Tamoto, S. Lecomte, S. Si, S. Moldovan, O. Ersen, M. H. Delville, R. Oda, “Gold nanoparticle deposition on silica nanohelices: a new controllable 3d substrate in aqueous suspension for optical sensing,” J. Phys. Chem. C 116(43), 23143–23152 (2012). [CrossRef]
  27. S. Mühlig, C. Rockstuhl, V. Yannopapas, T. Bürgi, N. Shalkevich, F. Lederer, “Optical properties of a fabricated self-assembled bottom-up bulk metamaterial,” Opt. Express 19(10), 9607–9616 (2011). [CrossRef] [PubMed]
  28. N. Engheta, “Circuits with light at nanoscales: optical nanocircuits inspired by metamaterials,” Science 317(5845), 1698–1702 (2007). [CrossRef] [PubMed]
  29. M. R. Jones, K. D. Osberg, R. J. Macfarlane, M. R. Langille, C. A. Mirkin, “Templated techniques for the synthesis and assembly of plasmonic nanostructures,” Chem. Rev. 111(6), 3736–3827 (2011). [CrossRef] [PubMed]
  30. A. Tao, S. Habas, P. Yang, “Shape control of colloidal metal nanocrystals,” Small 4(3), 310–325 (2008). [CrossRef]
  31. I. Pastoriza-Santos, D. Gomez, J. Pérez-Juste, L. M. Liz-Marzán, P. Mulvaney, “Optical properties of metal nanoparticle coated silica spheres: a simple effective medium approach,” Phys. Chem. Chem. Phys. 6, 5056–5060 (2004). [CrossRef]
  32. T. Pham, J. B. Jackson, N. J. Halas, T. R. Lee, “Preparation and characterization of gold nanoshells coated with self-assembled monolayers,” Langmuir 18(12), 4915–4920 (2002). [CrossRef]
  33. D. Blair, E. Dufresne, “The matlab particle tracking code repository,” http://physics.georgetown.edu/matlab/index.html .
  34. K. Nozawa, H. Gailhanou, L. Raison, P. Panizza, H. Ushiki, E. Sellier, J. P. Delville, M. H. Delville, “Smart control of monodisperse Stöber silica particles: effect of reactant addition rate on growth process,” Langmuir 21(4), 1516–1523 (2005). [CrossRef] [PubMed]
  35. K. Nozawa, M. H. Delville, H. Ushiki, P. Panizza, J. P. Delville, “Growth of monodisperse mesoscopic metal-oxide colloids under constant monomer supply,” Phys. Rev. E Stat. Nonlin. Soft Matter Phys. 72(1 Pt 1), 011404 (2005). [CrossRef] [PubMed]
  36. G. Frens, “Controlled Nucleation for the regulation of the particle size in monodisperse gold suspensions,” Nature 241, 20–22 (1973).
  37. S. Basu, S. K. Ghosh, S. Kundu, S. Panigrahi, S. Praharaj, S. Pande, S. Jana, T. Pal, “Biomolecule induced nanoparticle aggregation: effect of particle size on interparticle coupling,” J. Colloid Interface Sci. 313(2), 724–734 (2007). [CrossRef] [PubMed]
  38. S. Pramanik, P. Banerjee, A. Sarkar, S. C. Bhattacharya, “Size-dependent interaction of gold nanoparticles with transport protein: a spectroscopic study,” J. Lumin. 128(12), 1969–1974 (2008). [CrossRef]
  39. K. F. Ren, G. Gréhan, G. Gouesbet, “Radiation pressure forces exerted on a particle arbitrarily located in a gaussian beam by using the generalized Lorenz-Mie theory, and associated resonance effects,” Opt. Commun. 108(4-6), 343–354 (1994). [CrossRef]
  40. Y. Harada, T. Asakura, “Radiation forces on a dielectric sphere in the Rayleigh scattering regime,” Opt. Commun. 124(5-6), 529–541 (1996). [CrossRef]
  41. C. F. Bohren and D. F. Hufman, Absorption and Scattering of Light by Small Particles (Wiley, 1983).
  42. A. Ashkin, “Forces of a single-beam gradient laser trap on a dielectric sphere in the ray optics regime,” Biophys. J. 61(2), 569–582 (1992). [CrossRef] [PubMed]
  43. C. Mätzler, “Matlab functions for mie scattering and absorption,” (Research Report, Institut fur Angewandte Physik, University of Bern, Switzerland, 2002). http://www.iapmw.unibe.ch/teaching/vorlesungen/radiative_transfer/HS2012/Mie_Version2.pdf .
  44. P. B. Johnson, R. W. Christy, “Optical constants of the noble metals,” Phys. Rev. B 6(12), 4370–4379 (1972). [CrossRef]
  45. A. N. Bashkatov, E. A. Genina, “Water refractive index in dependence on temperature and wavelength: a simple approximation,” Proc. SPIE 5068, 393–395 (2003). [CrossRef]
  46. F. Garcia-Santamaria, H. Miguez, M. Ibisate, F. Meseguer, C. Lopez, “Refractive index properties of calcined silica submicrometer spheres,” Langmuir 18(5), 1942–1944 (2002). [CrossRef]
  47. Y. Seol, A. E. Carpenter, T. T. Perkins, “Gold nanoparticles: enhanced optical trapping and sensitivity coupled with significant heating,” Opt. Lett. 31(16), 2429–2431 (2006). [CrossRef] [PubMed]
  48. P. V. Ruijgrok, N. R. Verhart, P. Zijlstra, A. L. Tchebotareva, M. Orrit, “Brownian fluctuations and heating of an optically aligned gold nanorod,” Phys. Rev. Lett. 107(3), 037401 (2011). [CrossRef] [PubMed]
  49. Y. Hu, R. C. Fleming, R. A. Drezek, “Optical properties of gold-silica-gold multilayer nanoshells,” Opt. Express 16(24), 19579–19591 (2008). [CrossRef] [PubMed]
  50. S. C. Padmanabhan, J. McGrath, M. Bardosova, M. E. Pemble, “A facile method for the synthesis of highly monodisperse silica@gold@silica core–shell–shell particles and their use in the fabrication of three-dimensional metallodielectric photonic crystals,” J. Mater. Chem. 22(24), 11978–11987 (2012). [CrossRef]
  51. M. T. Kumara, N. Srividya, S. Muralidharan, B. C. Tripp, “Bioengineered flagella protein nanotubes with cysteine loops: self-assembly and manipulation in an optical trap,” Nano Lett. 6(9), 2121–2129 (2006). [CrossRef] [PubMed]

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