title: Multiple pathways of crystal nucleation in an extremely supersaturated aqueous potassium dihydrogen phosphate (KDP) solution droplet.
abstract: Solution studies have proposed that crystal nucleation can take more complex pathways than previously expected in classical nucleation theory, such as formation of prenucleation clusters or densified amorphous/liquid phases. These findings show that it is possible to separate fluctuations in the different order parameters governing crystal nucleation, that is, density and structure. However, a direct observation of the multipathways from aqueous solutions remains a great challenge because heterogeneous nucleation sites, such as container walls, can prevent these paths. Here, we demonstrate the existence of multiple pathways of nucleation in highly supersaturated aqueous KH2PO4(KDP) solution using the combination of a containerless device (electrostatic levitation), and in situ micro-Raman and synchrotron X-ray scattering. Specifically, we find that, at an unprecedentedly deep level of supersaturation, a high-concentration KDP solution first transforms into a metastable crystal before reaching stability at room temperature. However, a low-concentration solution, with different local structures, directly transforms into the stable crystal phase. These apparent multiple pathways of crystallization depend on the degree of supersaturation.
authors: Frontier in Extreme Physics, Korea Research Institute of Standards and Science, Daejeon 305-340, Republic of Korea.|Department of Nano Science, University of Science and Technology, Daejeon 305-333, Republic of Korea.
authors: Sooheyong
authors: S
authors: Lee
authors: Frontier in Extreme Physics, Korea Research Institute of Standards and Science, Daejeon 305-340, Republic of Korea.
authors: Haeng Sub
authors: HS
authors: Wi
authors: Frontier in Extreme Physics, Korea Research Institute of Standards and Science, Daejeon 305-340, Republic of Korea.|Department of Physics, Soongsil University, Seoul 156-743, Republic of Korea.
authors: Wonhyuk
authors: W
authors: Jo
authors: Frontier in Extreme Physics, Korea Research Institute of Standards and Science, Daejeon 305-340, Republic of Korea.
authors: Yong Chan
authors: YC
authors: Cho
authors: Pohang Accelerator Laboratory, Pohang 790-784, Republic of Korea.
authors: Hyun Hwi
authors: HH
authors: Lee
authors: Department of Cogno-Mechatronics Engineering, Pusan National University, Miryang 627-706, Republic of Korea.
authors: Se-Young
authors: SY
authors: Jeong
authors: Frontier in Extreme Physics, Korea Research Institute of Standards and Science, Daejeon 305-340, Republic of Korea.|Department of Nano Science, University of Science and Technology, Daejeon 305-333, Republic of Korea.
authors: Yong-Il
authors: YI
authors: Kim
authors: Frontier in Extreme Physics, Korea Research Institute of Standards and Science, Daejeon 305-340, Republic of Korea; gwlee@kriss.re.kr.|Department of Nano Science, University of Science and Technology, Daejeon 305-333, Republic of Korea.
authors: Geun Woo
authors: GW
authors: Lee
keywords: in situ X-ray diffraction; in situ micro-Raman spectroscopy; liquid-droplet levitation; multipath nucleation; supersaturation