Browsing by Author "Uda, Satoshi"

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In Situ Microscopic Observation on Surface Kinetics in Optical Trapping-Induced Crystal Growth: Step Formation, Wetting Transition, and Nonclassical Growth
(2019-07-01)
Niinomi, Hiromasa
;
Sugiyama, Teruki
;
Ujihara, Toru
;
Guo, Suxia
;
Nozawa, Jun
Optical trapping-induced crystallization (OTIC) has provided significant impacts on the control of crystallization. Although consecutive research studies have implied that the optical potential formed on the crystalline surface by light propagation contributes to the crystal growth by observing bulk crystal growth, direct observation from the viewpoint of the surface kinetics represented as Burton, Cabrera, and Frank theory is still lacking. Here, we directly show the surface state modification by microscopically observing step formation/dissolution and wetting transition of a solution thin layer over a sodium chlorate crystalline surface upon turning on/off the laser irradiation. Irradiating/stopping of the laser irradiation to the crystal led to the formation/dissociation of several tens of micron-sized islands constructed by bunched steps. It was also found that the wetting transition of the solution thin film over the entire crystal surface took place simultaneously with the laser irradiation, evidencing that the interfacial potential was modified from repulsive to attractive potential by light propagation. Moreover, the observation visualized nonclassical crystal growth like the cluster assimilation scenario. Our observation not only leads to a deeper understanding of the mechanism of OTIC but also can provide the opportunity to reach unusual crystal growth phenomena beyond the classical limit and has implications for crystal growth modified by an external field.
In Situ Observation of Chiral Symmetry Breaking in NaClO3 Chiral Crystallization Realized by Thermoplasmonic Micro-Stirring
(2018-08-01)
Niinomi, Hiromasa
;
Sugiyama, Teruki
;
Tagawa, Miho
;
Harada, Shunta
;
Ujihara, Tom
We have found that large chiral symmetry breaking in chiral crystallization can be achieved by irradiating a several milliwatts focused laser to a plasmonic nanolattice immersed in a stagnant NaClO3 saturated aqueous solution. Several hundreds of chiral crystals with the same handedness showed up in the solution after the laser irradiation in contrast to spontaneous crystallization. In situ microscopic observation for the early stage of the crystallization in the vicinity of the focal spot revealed that microbubble generation followed by large supersaturation increase, in which supersaturation reaches 360%, promotes several numbers of crystal nucleation in the vicinity of the bubble as "mother" crystal. The generation of the microbubble induced Marangoni convection, the velocity of which reaches several hundreds of micrometers per second, crushing the first appearing chiral crystal into pieces by microfluidic shear. Namely, secondary nucleation caused by microfluidic shear amplified the number of "daughter" crystals with the same handedness. This spatiotemporally controllable micromixing experiment realized by laser irradiation gives us not only a novel route bridging a light and chiral symmetry breaking but also the novel method to observe the early stage dynamics of the secondary nucleation, which was hard to observe by conventional observation technique, in real time.
Plasmonic Manipulation of Sodium Chlorate Chiral Crystallization: Directed Chirality Transfer via Contact-Induced Polymorphic Transformation and Formation of Liquid Precursor
(2020-08-05)
Niinomi, Hiromasa
;
Sugiyama, Teruki
;
Tagawa, Miho
;
Ujihara, Toru
;
Omatsu, Takashige
The control of crystallization not only impacts the production of functional crystalline materials or pharmaceuticals but also provides profit to investigate the fundamental mechanism of crystallization. Recently, we have revealed that plasmonic optical tweezers (POT) can "manipulate" the crystallization of a pharmaceutical compound from its aqueous solution by optically trapping molecular clusters, offering a novel strategy to control crystallization. Here we report a variety of unique crystallization phenomena by applying POT to sodium chlorate (NaClO3) chiral crystallization from an aqueous microdroplet loaded on a plasmonic substrate. Plasmon excitation significantly promotes crystallization intermediated by an achiral metastable crystal as a precursor. Also, the direction of the creeping of the resulting chiral crystal can be controlled. By utilizing this phenomenon, we achieved the directed chirality transfer from the chiral crystal to the achiral crystal via a forced contact-induced polymorphic transformation by intentionally making creeping chiral crystal contact with an achiral crystal. Moreover, we captured, by in situ optical microscopic observation, a liquid precursor that intermediates the NaClO3 achiral crystallization for the first time. Our results highlight the plasmonic manipulation of crystallization opening a new door not only to control crystallization but also to investigate the unprecedented fundamental process of crystallization.
Plasmonic Trapping-Induced Crystallization of Acetaminophen
(2019-02-01)
Niinomi, Hiromasa
;
Sugiyama, Teruki
;
Uda, Satoshi
;
Tagawa, Miho
;
Ujihara, Toni
We demonstrate that plasmonic trapping can control crystallization of acetaminophen from its aqueous solution. Irradiation of a focused continuous-wave near-infrared laser to a plasmonic Au nanolattice supporting a thin film of a saturated solution allowed acetaminophen molecules to crystallize in annular distribution with the center of the focal spot. The annularly distributed crystals can be spatially manipulated by changing the position of the laser focal spot. The annular pattern is rationalized by competition between electrical field gradient force as an attractive force to the focal spot and thermophoretic force as a repulsive force. It is also found that, upon stopping the laser irradiation, the crystals first transformed to highly concentrated droplets rather than directly dissolving to the solution. Relaxation of the droplets by self-diffusion to the solution followed to the crystal/droplet transformation. These two-step dissociation dynamics indicate that not only plasmonic trapping of the molecules but also the enhanced electrical field by surface plasmon contributes to drive the crystallization, and it has a possibility to show the reverse process of the two-step nucleation model. Our demonstration highlights the possibility that plasmonic trapping by designed near-field and temperature distribution can manipulate not only molecular assembly but also creation of functional crystalline materials in nanoscale.