Ultrasound response of aqueous poly(ionic liquid) solution

Review on Nonconventional Fibrillation Methods of Producing Cellulose Nanofibrils and Their Applications

The production of cellulose nanofibrils (CNFs) continues to receive considerable attention because of their desirable material characteristics for a variety of consumer applications. There are, however, challenges that remain in transitioning CNFs from research to widespread adoption in the industrial sectors, including production cost and material performance. This Review covers CNFs produced from nonconventional fibrillation methods as a potential alternative solution. Pretreating biomass by biological, chemical, mechanical, or physical means can render plant feedstocks more facile for processing and thus lower energy requirements to produce CNFs. CNFs from nonconventional fibrillation methods have been investigated for various applications, including films, composites, aerogels, and Pickering emulsifiers. Continued research is needed to develop protocols to standardize the characterization (e.g., degree of fibrillation) of the lignocellulosic fibrillation processes and resulting CNF products to make them more attractive to the industry for specific product applications.

Ultrasound response of viscoelastic changes of cellulose hydrogels triggered with Sono-deviced rheometer

Sono-deviced rheometer,which enabled viscoelastic properties under ultrasound operation, was used to investigate for cellulosic hydrogels. The viscoelastic behavior was compared in cellulosic hydrogels prepared at 0.5, 1 and 2 wt% concentration in the DMAc/LiCl solution. The sono-deviced equipment could measure the effect of changes in storage modulus G' and loss modulus G" under 43 kHz ultrasound exposure. It was noted that the 43 kHz ultrasound significantly changed the values of the G', meaning that the hydrogel was soften under the exposure within few seconds. When the ultrasound exposed 50 W of the out-put power at 1% strain, the G' value of 4.2x10⁴ Pa was reduced to 4.0x10³ Pa during 5 min of the US interval. The declined lowering value of G' then returned to the original moduli value when ultrasound was stopped. The values of both G' and G" values were measured at applied strain % during viscoelastic measurements of the cellulosic hydrogels without and with ultrasound exposure. The comparison indicated that the ultrasoundhas reinforced the effect of the mechanical deformationof the hydrogel structureat the smaller mechanical strain values appliedduring the ultrasound operation. The ultrasound soften effect onthe viscoelastic change efficiently occurred in the 0.5 wt% sample and easily induced the structural deformation probably due to the breakage of hydrogen bonds in the cellulose hydrogels.

Ultrasonic degradation of diaminobenzidine in aqueous medium

By using 500 kHz high frequency ultrasound (US), 3,3'-diaminobenzidine (DAB) was treated at pH 2 under air atmosphere. The US effect of DAB absorption at 280 nm was composed at 43 and 141 kHz for the detection of fluorescence. When 100 W of US power was used, the DAB absorption band decreased with exposure time. It was noted that, a new absorption broad band at 350 nm-500 nm appeared only under 141 and 500 kHz. Also, fluorescence spectra of the treated DAB were measured when excited at 370 nm. Increasing US exposure time resulted to a broad emission band at 478 nm, indicating that 1H,1'H-5,5'-Bibenzotriazole (BBT) was produced by US exposure at 500 kHz. This product was confirmed by NMR spectroscopy to be a triazine ring formed from NH₂ proton in DAB, due to the formation of nitrite ions in the US aqueous medium at 500 kHz. Hence, DAB was degraded while BBT was formed.

Comprehensive facilitating of water oxidation reaction by ultrasonic attenuation of hydrogen-bonded structure of water

The balance between water-metal interactions and water-water hydrogen bonding (HBs) controls the process of water adsorption on metallic surfaces. In other hand, the yield of oxygen evolution reaction (OER) is dependent on the binding energy of H₂O at electrode surface. Therefore, on a specific metal substrate, attenuation of HBs may be a promising route for improving OER. In this study, the computational and experimental evidences indicate that the performance of ultrasonically irradiated deionized water (USI-DW), participated in water oxidation reaction (WOR), is different from its in the intact bulk water. To date, establishing of new electrocatalysts with lower overpotentials (η) and higher current densities (J) in OER have been mostly considered based on metals and oxide materials. Here, we ultrasonically agitated the water clusters formed by strong HBs, and as a sustainable improvement route explored its particular effects on the efficiency of OER. The molecular modeling (MM) of the (H₂O)_n clusters (n = 1-100 molecules), the corresponding IR spectra, the molecular orbitals energy levels and the adsorption of free and cluster confined H₂O molecules on the Pt surface were studied by the appropriate quantum mechanical (QM) methods. The result of deconvolution of FTIR spectra recorded for USI-DW in the -OH stretching region (∼2600-3900 cm^-1) properly confirmed the expected increase of the single water molecules. The reduction in overpotentials was 82 ± 8 mV and 158 ± 12 mV, to reach the J of 1 mA cm^-1 at the typical pHs 12.2 and 13.1, respectively.