Solvents For Exfoliation Research Articles

Measurement of Hansen solubility parameters for organophilic fluoromica and evaluation of potential solvents for exfoliation

Abstract A method to measure Hansen solubility parameters for organophilic fluoromica is developed. For this purpose, fluoromica with four different intercalated molecules (surfactants) have been dispersed in various solvents. These surfactants change the fluoromica surface energies described by Hansen solubility parameters (HSP). The three Hansen solubility parameters (dispersion, polar and hydrogen bonding) of different organophilic fluoromicas have been obtained by using gravimetric analysis. The dispersion parameters for all four organophilic fluoromicas are almost identical, with a value around 17 MPa . Whereas polar and H-bonding parameters are varying with the used surfactants. Surprisingly the polar and hydrogen bonding values for hydrophobic alkyl chain tailored surfactants are higher than those for a hydrophilic surfactant with poly(ethylene glycol) chains. The determined HSP values allow calculating the dispersibility of the organophilic fluoromica in solvents via the Flory-Huggins (F-H) parameter. These F-H parameters describes the effective difference in HSP related surface energies of particles and solvent molecules and are used to identify potential solvents for an exfoliation process. With this approach, beside known solvents such as chloroform, also new potential candidates such as trichloroethylene, and benzyl ethyl ether are identified for dispersing/exfoliating modified organophilic fluoromica. This work is accompanied by X-ray diffraction (XRD) measurements to gain knowledge about the interlayer space of the different organophilic fluoromicas.

Liquid-phase exfoliation of NH4Co0.4Ni0.6PO4·H2O for energy storage device

Liquid-phase exfoliation is an effective method to fabricate thin nanosheet materials with layered structure. In this paper, we successfully synthesized NH4Co0.4Ni0.6PO4·H2O nanosheets with the thickness of about tens of nanometers through liquid-phase exfoliation under ultrasonication. Specifically, the formamide solution was chosen as the exfoliation solvent due to it is capable of entering the interlayer of bulk materials and rapidly swelling between layers. Electrochemistry tests revealed that the optimized exfoliation time was 4 days. The asymmetric battery type energy storage device AC//NH4Co0.4Ni0.6PO4·H2O nanosheets showed an energy density of 10.8 Wh kg−1 at the power density of 703.1 W kg−1. More importantly, the long-term cycle stability measurements demonstrated that NH4Co0.4Ni0.6PO4·H2O nanosheets after exfoliation had an ultra-long cycling life that still retained 102.3% of specific capacitance even 10000 continuous charge/discharge cycles.

Exfoliation Solvent Dependent Plasmon Resonances in Two-Dimensional Sub-Stoichiometric Molybdenum Oxide Nanoflakes.

Few-layer two-dimensional (2D) molybdenum oxide nanoflakes are exfoliated using a grinding assisted liquid phase sonication exfoliation method. The sonication process is carried out in five different mixtures of water with both aprotic and protic solvents. We found that surface energy and solubility of mixtures play important roles in changing the thickness, lateral dimension, and synthetic yield of the nanoflakes. We demonstrate an increase in proton intercalation in 2D nanoflakes upon simulated solar light exposure. This results in substoichiometric flakes and a subsequent enhancement in free electron concentrations, producing plasmon resonances. Two plasmon resonance peaks associated with the thickness and the lateral dimension axes are observable in the samples, in which the plasmonic peak positions could be tuned by the choice of the solvent in exfoliating 2D molybdenum oxide. The extinction coefficients of the plasmonic absorption bands of 2D molybdenum oxide nanoflakes in all samples are found to be high (ε > 10(9) L mol(-1) cm(-1)). It is expected that the tunable plasmon resonances of 2D molybdenum oxide nanoflakes presented in this work can be used in future electronic, optical, and sensing devices.

Enhanced-oxidation and electrochemical determination of honokiol and magnolol using NMP-exfoliated graphene nanosheets

Using N-methyl-2-pyrrolidone (NMP) as the exfoliation solvent, graphite powder was easily exfoliated into graphene nanosheets (GS) via ultrasonication, which was characterized using transmission electron microscopy. The measurements of scanning electron microscopy and atomic force microscopy indicated that the modification of GS obviously increased the surface roughness of glassy carbon electrode, providing high accumulation efficiency and large response surface. As a result, the oxidation signals of honokiol and magnolol were increased greatly on the surface of GS. Moreover, the oxidation mechanisms were studied for honokiol and magnolol, and one electron was transferred in the oxidation process. After optimizing the parameters such as pH value, amount of GS, accumulation potential and time, a highly-sensitive electrochemical sensor was developed for the simultaneous determination of honokiol and magnolol. The values of detection limit were evaluated to be 0.2μgL−1 and 1.0μgL−1 for honokiol and magnolol. The application of this sensor was demonstrated using Chinese traditional medicines, and the accuracy and feasibility were tested to be good using high-performance liquid chromatography.