Browsing by Author "Liu, Guodong"

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Acid dissociation of surface bound water on cellulose nanofibrils in aqueous micro nanofibrillated cellulose (MNFC) gel revealed by adsorption of calcium carbonate nanoparticles under the application of ultralow shear
(2017-08) Liu, Guodong; Maloney, Thaddeus; Dimic-Misic, Katarina; Gane, Patrick
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
At ultralow shear rate (similar to 0.01 s(-1)), acting below the yield stress of the aqueous gel, adsorption of calcium carbonate nanoparticles (<~100 nm) onto cellulose nanofibrils is induced without pigment–pigment preflocculation. Dispersant-free and polyacrylate treated dispersed carbonate particles are compared. Initially, it is seen that the polyacrylate dispersed material does not adsorb, whereas the dispersant-free carbonate adsorbs readily under the controlled ultralow shear conditions. However, repeated cycles of ultralow shear with intermittent periods in the rest state eventually induce the effect as initially seen with the dispersant-free calcium carbonate. The fibril suspension in the bulk is slightly acidic. The addition of buffer to a controlled pH in the case of the dispersant treated particles maintained a similar delay in the onset of adsorption, but adsorption occurred eventually after repeated cycles. During this cycling process, in parallel, the pH gradually drops under repeated cycles of ultralow shear, opposite to expectation, given the buffering capacity of calcium carbonate. The conductivity, in turn, progressively increases slightly at first and then significantly. The action of surface bound water on the nanofibril is considered key to the action of adsorption, and the condition of ultralow shear suggests that the residence time of the particle in contact with the nanofibril, acting under controlled strain against diffusion in the gel, is critical. It is proposed that under these specific conditions the calcium carbonate nanoparticles act as a probe of the nanofibril surface chemistry. The hydrogen bonded water, known to reside at the nanofibril surface, is thus considered the agent in the carbonate-surface interaction, effectively expressing an acid dissociation, and the calcium carbonate nanoparticles act as the probe to reveal it. An important phenomenon associated with this acid dissociation behaviour is that the adsorbed calcium carbonate particles subsequently act to flocculate the otherwise stable cellulose material, leading to release of water held in the aqueous gel matrix structure. This latter effect has major implications for the industrial ease of use of micro and nanofibrillar cellulose at increased solids content. This novel mechanism is also proposed for use to enhance the dewatering capability in general of complex cellulose-containing gel-like water-holding suspensions.
Coupling of high ion transport efficiency in hydrogel electrolytes and interfacial fusion for performance enhancement in all-solid-state paper-based self-powered electrochromic devices with low-temperature tolerance
(2025-04-14) Liu, Guodong; Chen, Shuyue; Jiang, Xiaohong; Zhang, Zhuoqing; Wang, Yaoli; Liu, Hanbin; Li, Zhijian; Gane, Patrick
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Self-powered electrochromic devices (ECDs) have gained considerable attention for applications such as smart labels, displays and rechargeable batteries, thanks to their dynamic balance between color display and energy storage capabilities. The electrochemical performance of existing ECDs, however, is often constrained by the conductivity of electrolytes, the contact interface between electrodes and electrolytes, and the severe intolerance of ECDs to low temperature environments. In this study, we couple two approaches. Firstly, we harness the Hofmeister effect to modulate the concentration of an ionic compound within the hydrogel electrolyte. This modulation enhances ion solvation and ionic conductivity, thereby facilitating internal ion transport within the self-powered ECD and accelerating the device's response time. Secondly, we illustrate how it is possible to capitalize on the designable properties of the substrate. Paper offers a unique controllable substrate structure, which can be readily modified in terms of surface micro-roughness, which, in turn, can be utilized during the forming of the gravure printed electrode. This novel optimization can improve the final surface morphology of the paper-based electrode, enhancing its surface area properties. This enhancement subsequently facilitates improved integration of the electrode interface with the hydrogel electrolyte, reducing interface impedance and increasing ion transport efficiency within the ECD. Combining this morphological effect with the increased ion solvation in the hydrogel electrolyte enables an improved electrochemical performance and cyclic stability, maintaining stability even at temperatures as low as −40 °C.