Micro-Raman observation on the H2PO4− association structures in a supersaturated droplet of potassium dihydrogen phosphate (KH2PO4)

Syed, Kamran Ajmal; Pang, Shu-Feng; Yun, Zhang; Yun-hong, Zhang

doi:10.1063/1.4773585

Cited by 31 publications

(30 citation statements)

References 36 publications

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“…As the supersaturation increases, the monomers aggregate, forming dimers, trimers, oligomer, and higher polymers. Such polymerization behaviors can be deduced from the shape of PO 2 peak at 1,077 cm −1 , which becomes progressively more asymmetric and broadens at higher supersaturation as reported previously (42)(43)(44). The P(OH) 2 Raman peak at 877 cm −1 shows a blue-shift behavior with respect to supersaturation as expected (33).…”

Section: Resultsmentioning

confidence: 65%

Multiple pathways of crystal nucleation in an extremely supersaturated aqueous potassium dihydrogen phosphate (KDP) solution droplet

Lee

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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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 KH 2 PO 4 (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 highconcentration 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.multipath nucleation | liquid-droplet levitation | supersaturation | in situ X-ray diffraction | in situ micro-Raman spectroscopy N ucleation is the first step toward crystallization, in which atoms or particles aggregate to form clusters in a metastable liquid, called crystal nuclei. The crystal nuclei in metastable liquid grow continuously if their size exceeds a critical limit, and are subsequently stabilized. Based on the classical nucleation theory (CNT) (1, 2), nucleation is mainly governed by two factors, that is, interfacial free energy and volume Gibbs free energy (or chemical potential) between liquid and crystal phases. Although the volume Gibbs free energy acts to stabilize the crystal nuclei, the interfacial free energy works as an energy barrier preventing the formation of the nuclei. If the crystal-liquid interfacial free energy creates a sufficiently high energy barrier, the liquid can be supercooled, supersaturated, or even supercompressed. In case of liquid metals (3-6), the crystal-liquid interfacial free energy arises from configurational entropy differences between crystal and liquid. That is, the greater difference in local structural orderings between crystal and liquid phases results in higher interfacial free energy, which consequently leads to a higher nucleation barrier and thus deeper supercooling. This concept has been verified in various metallic systems for elements (7) and many alloys (8-12). However, many experimental and theoretical investigations have raised questions that CNT may not be adequate to describe the initial nucleation processes in biomaterials (13-17) and minerals (18)(19)(20)(21)(22)(23)(24)(25)(26).Recently, an alternate nucleation mechanism, called multipathway nucleation (or crystallization) (13-23, 25, 26), has been proposed fo...

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Section: Resultsmentioning

confidence: 65%

Multiple pathways of crystal nucleation in an extremely supersaturated aqueous potassium dihydrogen phosphate (KDP) solution droplet

Lee

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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“…The bands ∼ (384-388 cm −1 ) are designated to the bending vibration of the O-P-O bond[35]. Samples N1 and N2 show new bands ∼ (421-423 cm −1 ) and are attributed to mixed deformation of Si-O bonds[36].…”

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confidence: 99%

Optimization of High Conducting Na3Zr2Si2PO12 Phase by new Phosphate Salt for Solid Electrolyte

Jha

Pandey

Singh

2016

Silicon

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A composition of NASICON (Na 3 Zr 2 Si 2 PO 12 ) was synthesized by the solid-state reaction method using a new compound Na 2 HPO 4 2H 2 O. The X-ray diffraction patterns of all samples exhibit monoclinic Na 3 Zr 2 Si 2 PO 12 as a major phase with a very small amount of monoclinicZrO 2 . The maximum relative density (97 %) and maximum conductivity is obtained in the samples sintered at 1200 • C (N3) which is slightly higher than β-Al 2 O 3 . The activation energy is ∼ 0.20 eV for the N3 sample which is lower than for β-Al 2 O 3 . The dilatometeric study and Arrhenius plots confirmed a phase transition of NASICON from monoclinic to rhombohedral. The micro-structural study of the samples done by scanning electron microscopy (SEM) indicated a significant influence of the processing conditions on the microstructures. Raman spectroscopy demonstrated that the sample N3 exhibits minor structural changes compared to other samples.

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“…The assignments of the 8 characteristic wavenumbers are listed in Table 4 . As seen in Table 4 , λ 2775 and λ 2176 are associated with H 2 PO 4 − , which exists in metal salt 29 . λ 1666 , λ 1541 and λ 1297 are assigned to phthalocyanine blue 24 26 30 , meanwhile, λ 988 and λ 547 are ascribed to lead chromate yellow 31 32 .…”

Section: Resultsmentioning

confidence: 99%

Nondestructive detection of lead chrome green in tea by Raman spectroscopy

Liu

Sun

Luo

et al. 2015

Sci Rep

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Raman spectroscopy was first adopted for rapid detecting a hazardous substance of lead chrome green in tea, which was illegally added to tea to disguise as high-quality. 160 samples of tea infusion with different concentrations of lead chrome green were prepared for Raman spectra acquirement in the range of 2804 cm−1–230 cm−1 and the spectral intensities were calibrated with relative intensity standards. Then wavelet transformation (WT) was adopted to extract information in different time and frequency domains from Raman spectra, and the low-frequency approximation signal (ca4) was proved as the most important information for establishment of lead chrome green measurement model, and the corresponding partial least squares (PLS) regression model obtained good performance in prediction with Rp and RMSEP of 0.936 and 0.803, respectively. To further explore the important wavenumbers closely related to lead chrome green, successive projections algorithm (SPA) was proposed. Finally, 8 characteristic wavenumbers closely related to lead chrome green were obtained and a more convenient and fast model was also developed. These results proved the feasibility of Raman spectroscopy for nondestructive detection of lead chrome green in tea quality control.

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Micro-Raman observation on the H2PO4− association structures in a supersaturated droplet of potassium dihydrogen phosphate (KH2PO4)

Cited by 31 publications

References 36 publications

Multiple pathways of crystal nucleation in an extremely supersaturated aqueous potassium dihydrogen phosphate (KDP) solution droplet

Multiple pathways of crystal nucleation in an extremely supersaturated aqueous potassium dihydrogen phosphate (KDP) solution droplet

Optimization of High Conducting Na3Zr2Si2PO12 Phase by new Phosphate Salt for Solid Electrolyte

Nondestructive detection of lead chrome green in tea by Raman spectroscopy

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