Optical trapping of gold and semiconductor nanoparticles at oil-water interfaces with a focused near-infrared laser beam

Tanaka, Shōji; Naka, Shota; Koyama, Seiya; Kameyama, Tatsuya; Torimoto, Tsukasa; Tsuboi, Yasuyuki

doi:10.1117/12.2319571

Cited by 3 publications

(5 citation statements)

References 10 publications

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“…The trapping behavior is different when the nanoscale objects are trapped at air/liquid, , liquid/liquid, and solid/liquid , interfaces. Assembling, orientation, and diffusion properties of molecules, polymers, and NPs at interfaces are different from those in bulk solution due to the surface tension, convection, and microscopic interaction between the two phases.…”

Section: Introductionmentioning

confidence: 99%

Dynamic Coupling of Optically Evolved Assembling and Swarming of Gold Nanoparticles with Photothermal Local Phase Separation of Polymer Solution

et al. 2020

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Optical trapping of gold nanoparticles (Au NPs) at a glass/solution interface initially generates a periodically aligned structure of a few NPs along the direction perpendicular to a linearly polarized laser. When the number of NPs was increased, this alignment was expanded to the outside of the irradiated focus, forming a single large assembly where the Au NPs dynamically fluctuated like a swarming of bees. The morphology was dumbbellshape, consisting of two swarms at both sides of the focus, and its size reached about 10 μm. This optically evolved assembling and swarming was studied in poly(N-isopropylacrylamide) (PNIPAM) solution, where liquid−liquid phase separation (LLPS) was induced by photothermal heating of the trapped Au NPs forming a microdroplet of highly concentrated PNIPAM. Dynamic coupling of the NPs assembling and swarming with the droplet formation of PNIPAM leads to cooperative optical evolution, through which the assembly was embedded in the single microdroplet.

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Section: Introductionmentioning

confidence: 99%

Dynamic Coupling of Optically Evolved Assembling and Swarming of Gold Nanoparticles with Photothermal Local Phase Separation of Polymer Solution

et al. 2020

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“…Optical trapping is made possible when the former gradient force is larger compared to the scattering force latter. This is typically the case in bulk solution, however, the conditions are modified at airliquid 23,24 , liquid-liquid 25 , and solid-liquid 26,27 interfaces, where the scattering force toward the interface can also immobilize the object. Thus, even small objects can be trapped at the interface with a relatively weak gradient force, which is not possible inside bulk solution and leads to new optical assembling phenomena 24,25 .…”

Section: Introductionmentioning

confidence: 99%

“…Optical trapping is made possible when the gradient force is larger compared to the scattering force. This is typically the case in bulk solution; however, the conditions are modified at air–liquid, , liquid–liquid, and solid–liquid , interfaces, where the scattering force toward the interface can also immobilize the object. Thus, even small objects can be trapped at the interface with a relatively weak gradient force, which is not possible inside bulk solution and leads to new optical assembling phenomena. , Recently, plasmonic trapping has received much attention because small objects can be easily trapped and manipulated.…”

Section: Introductionmentioning

confidence: 99%

“…This is typically the case in bulk solution; however, the conditions are modified at air–liquid, , liquid–liquid, and solid–liquid , interfaces, where the scattering force toward the interface can also immobilize the object. Thus, even small objects can be trapped at the interface with a relatively weak gradient force, which is not possible inside bulk solution and leads to new optical assembling phenomena. , Recently, plasmonic trapping has received much attention because small objects can be easily trapped and manipulated. Conventionally, metal nanostructures are prepared on glass substrates − and semiconductor needles are fabricated, , so that the interface effects may contribute to their trapping phenomena in addition to enhanced optical trapping force.…”

Section: Introductionmentioning

confidence: 99%

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Optical Force-Induced Dynamics of Assembling, Rearrangement, and Three-Dimensional Pistol-like Ejection of Microparticles at the Solution Surface

Kudo

Louis

et al. 2020

J. Phys. Chem. C

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Optical trapping and assembling dynamics of polystyrene (PS) microparticles (MPs) of 1 µm diameter is studied at its solution-air surface using a widefield microscope. Upon switching on the intense 1064 nm laser, the MPs are gathered, forming a single concentric circle (CC)-like assembly larger than the focus. It consists of a few tens of MPs and the central part of the assembly shows structural color, which indicates that the assembly is also growing in the axial direction. The MPs are dynamically fluctuating in inside the assembly, and some of them are ejected when newly coming MPs collide with the CC-like assembly from the bulk solution.The MPs speedily leaving the assembly are aligned in a linear manner, which we refer to as "pistole-like ejection". The three-dimensional (3D) dynamics was elucidated by changing laser power, MP concentration, and surface chemical property. It is directly observed that the trapping laser was scattered radially from the CC-like assembly and the ejection was induced along the scattered laser path. This pistol-like ejection is stochastically repeated upon the collision. After prolonged irradiation, the assembly rearranges to a hexagonal close packing (HCP)-like assembly, in which no pistol-like ejection was observed. We note that our observation is characteristic of the solution surface and were never observed in bulk solution.We conclude that the kinetically driven assembly formation gives rise to a CC-like structure which is meta-stable and shows the pistol-like ejection phenomenon. Later, the assembly rearranges to a thermodynamically stable HCP-like assembly. The assembling, pistol-like ejection, and its rearrangement are all driven by optical force, which is common for optical trapping-induced molecular crystallization and optically evolved assembling and swarming of gold nanoparticles (NPs).

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“…During the last years, optical trapping at interfaces (liquid/solid, liquid/liquid, liquid/gas) has gained interest among the scientific community due to the abovementioned advantage. [ 16–20 ] Pioneering in 2007, Masuhara and Sugiyama succeeded in demonstrating optical trapping‐induced crystallization of amino acids at solution surface for the first time. [ 21 ] Specifically, when the trapping laser is focused at the solution surface, amino acid molecules are gathered at and around the focus, generating a highly concentrated area that can expand to the outside.…”

Section: Introductionmentioning

confidence: 99%

Unraveling the three‐dimensional morphology and dynamics of the optically evolving polystyrene nanoparticle assembly using dual‐objective lens microscopy

Kamit

Tseng

Kudo

et al. 2021

J Chinese Chemical Soc

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Dynamically fluctuating assembly is prepared by trapping microparticles or nanoparticles at an interface. This phenomenon was previously described for 500 nm polystyrene nanoparticles optically trapped at water/glass interface, yielding a single disk‐like assembly, which size is much larger than the focal volume. In this work, we use a dual‐objective lens microscope to study the three‐dimensional shape and dynamics of such disk‐like assembly. The higher resolution of this system together with fast image acquisition (80 fps) rendered novel insights (e.g., particle fluctuation, assembly shape, interparticle distance, and so on), which could not be resolved using a conventional inverted microscope. These new insights will help to unravel the basis of this not yet fully understood “optically evolved phenomena,” which has a large potential in different research fields such as optical trapping, soft matter, and colloidal chemistry.

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Optical trapping of gold and semiconductor nanoparticles at oil-water interfaces with a focused near-infrared laser beam

Cited by 3 publications

References 10 publications

Dynamic Coupling of Optically Evolved Assembling and Swarming of Gold Nanoparticles with Photothermal Local Phase Separation of Polymer Solution

Dynamic Coupling of Optically Evolved Assembling and Swarming of Gold Nanoparticles with Photothermal Local Phase Separation of Polymer Solution

Optical Force-Induced Dynamics of Assembling, Rearrangement, and Three-Dimensional Pistol-like Ejection of Microparticles at the Solution Surface

Unraveling the three‐dimensional morphology and dynamics of the optically evolving polystyrene nanoparticle assembly using dual‐objective lens microscopy

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