Formation Mechanism and Fluorescence Characterization of a Transient Assembly of Nanoparticles Generated by Femtosecond Laser Trapping

Chiang, Wei-Yi; Chen, Jim Jui-Kai; Usman, Anwar; Kudo, Tetsuichi; Xia, Ke‐Qing; Su, Jia Quan; Sugiyama, Teruki; Hofkens, Johan; Masuhara, Hiroshi

doi:10.1021/acs.jpcc.9b04471

Cited by 5 publications

(6 citation statements)

References 49 publications

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“…These findings are explained in terms of single transient assembly formation in the optical trap [49][50][51][52] . In single NPs level, Goswami et al have reported that femtosecond laser enables manipulation and construction of 250 nm PS NPs with a specific 3D geometry.…”

Section: Discussionmentioning

confidence: 82%

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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Section: Discussionmentioning

confidence: 82%

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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“…We demonstrated that nanoparticles are gathered within the focus, forming an assembly, and ejected upon its size increase. It is worth noting that the ejection takes place in the direction perpendicular to laser polarization and alternatively switched from one side to the other [56] . This is never observed with CW laser and indicates a high potential of pulsed optical force in exploring new chemical processes.…”

Section: Optical Force Chemistrymentioning

confidence: 93%

“…It is worth noting that the ejection takes place in the direction perpendicular to laser polarization and alternatively switched from one side to the other. [56] This is never observed with CW laser and indicates a high potential of pulsed optical force in exploring new chemical processes. Indeed, femtosecond laser induces temporal force in addition to gradient and scattering forces, and efficient multiphoton absorption results in optical resonance effect in optical trapping and sometimes in laser ablation.…”

Section: Optical Force Chemistrymentioning

confidence: 99%

From Nanosecond Photochemistry to Optical Force Chemistry: My Journey

Masuhara

2021

The Chemical Record

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Laser was invented in 1960 and soon introduced to chemistry research. We started time‐resolved spectroscopy and photochemistry and initial trial was focused to nanosecond and then picosecond electronic absorption spectroscopy for studying molecular electronic excited states, charge separation in molecular complexes, and intermolecular electron transfer in solution. We considered that not only time‐resolved but also space‐resolved chemistry would be important for future laser‐based chemistry and combined pulsed lasers with optical microscopes. Spectroscopy, photochemistry, ablation, and spatial arrangement of single microparticles and microdroplets in solution were carried out. Further we shifted from micro to nano and opened a new field covering spectroscopy, ablation, phase transition, crystallization, patterning, and fabrication. The progress is summarized and discussed as time‐resolved nano spectroscopy, ablation nano dynamics, and optical force chemistry.

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“…N‐butyl‐N’‐propyl triethoxysilane perylenediimide (PDI) is a most frequently used chromophore in single molecular spectroscopy, as it is very stable and has high fluorescence quantum yield. Further its fluorescence property is well known, so that PDI is introduced to the surface of silica NPs and its density is controlled [64] …”

Section: Optical Trapping Of Silica Nanoparticles By Pulsed and Continuous‐wave Lasersmentioning

confidence: 99%

“…These results indicate that the assembly formation of NPs is a key process to understand trapping dynamics by pulsed optical force. In this Accounts we summarize our results on NP assembling dynamics of the representative dielectric NPs [61–68] and consider the characteristic mechanism.…”

Section: Introductionmentioning

confidence: 99%

Nanoparticle Assembling Dynamics Induced by Pulsed Optical Force

Chen

Chiang

Kudo

et al. 2021

The Chemical Record

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Femtosecond (fs) laser trapping dynamics is summarized for silica, hydrophobically modified silica, and polystyrene nanoparticles (NPs) in aqueous solution, highlighting their distinct optical trapping dynamics under CW laser. Mutually repulsive silica nanoparticles are tightly confined under fs laser compared to CW laser trapping and, upon increasing laser power, they are ejected from the focus as an assembly. Hydrophobically modified silica and polystyrene (PS) NPs are sequentially ejected just like a stream or ablated, giving bubbles. The ejection and bubbling take place with the direction perpendicular to laser polarization and its direction is randomly switched from one to the other. These characteristic features are interpreted from the viewpoint of single assembly formation of NPs at an asymmetric position in the optical potential. Temporal change in optical forces map is prepared for a single PS NP by calculating scattering, gradient, and temporal forces. The relative contribution of the forces changes with the volume increase of the assembly and, when the pushing force along the trapping pulse propagation overcome the gradient in the focal plane, the assembly undergoes the ejection. Further fs multiphoton absorption is induced for the larger assembly leading to bubble generation. The assembling, ejection, and bubbling dynamics of NPs are characteristic features of pulsed optical force and are considered as a new platform for developing new material fabrication method.

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Formation Mechanism and Fluorescence Characterization of a Transient Assembly of Nanoparticles Generated by Femtosecond Laser Trapping

Cited by 5 publications

References 49 publications

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

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

From Nanosecond Photochemistry to Optical Force Chemistry: My Journey

Nanoparticle Assembling Dynamics Induced by Pulsed Optical Force

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