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12. Melting Point of Ionic Liquids

Author

Shukla, Shashi Kant, Mikkola, Jyri-Pekka, Zhou, Qing, Section editor, Lu, Xingmei, Section editor, Ji, Xiaoyan, Section editor, and Zhang, Suojiang, editor

Published
2022
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20. Solution-Processable Bismuthene Nanosheets for Ultrasensitive Sensing of Heavy Metal Ions via Anodic Stripping Voltammetry.

Author

Adeniyi, Kayode Omotayo, Manavalan, Gopinathan, Zainelabdin, Ahmed, Mikkola, Jyri-Pekka, and Tesfalidet, Solomon

Abstract

Bismuthene, a two-dimensional nanostructured material derived from the environmentally friendly and nontoxic element bismuth, holds significant potential for sustainable electrocatalytic applications. However, the large-scale application of bismuthene is hindered by the absence of a high-throughput method for synthesizing solution-processable bismuthene nanosheets, which are essential for the straightforward and low-cost fabrication of bismuthene-based nanostructure devices. This study introduces a simple solvothermal method for synthesizing bismuthene nanosheets, using hexamethylenetetramine (HMTA) as a structure-directing agent and in situ-generated hydrogen (H2) from the alkaline hydrolysis of NaBH4 as the reducing agent. The structural and electron transfer properties were characterized by using microscopic, spectroscopic, and electrochemical analyses. To demonstrate the electrocatalytic application potential, a bismuthene-modified screen-printed carbon nanotube electrode was fabricated as a nanosensor for the quantitative detection of heavy metal ions in contaminated water. The nanosensor exhibited a wide linear concentration range and low detection limits of 0.1 and 0.16 ppb (μg/L) for Cd and Pb, respectively. Additionally, the sensor was integrated with a microfluidic flow cell, demonstrating its applicability for the flow-through analysis of Cd and Pb ions. The nanosensor showed high selectivity for Cd and Pb ions in the presence of other metal ions with excellent repeatability and sensor-to-sensor reproducibility, evidenced by a relative standard deviation of 2% and 10%, respectively. [ABSTRACT FROM AUTHOR]

Published
2024
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24. Ionic liquid strategy for chitosan production from chitin and molecular insights

Author

Dinh, Van Minh, Khokarale, Santosh Govind, Ojeda-May, Pedro, Sparrman, Tobias, Irgum, Knut, Mikkola, Jyri-Pekka, Dinh, Van Minh, Khokarale, Santosh Govind, Ojeda-May, Pedro, Sparrman, Tobias, Irgum, Knut, and Mikkola, Jyri-Pekka

Abstract

To produce chitosan is an interesting research. Chitosan is an important polysaccharide in terms of its various applications in industries and is produced from chitin, an abundant biopolymer in crustacean shell biomass wastes. Traditional processes for chitosan manufacture are commonly based on highly concentrated alkaline or acid solutions which are, however, severely eroding and harmful to the environment. In this study, we have described a ‘greener’ method using 1-ethyl-3-methylimidazolium acetate, [Emim][OAc] ionic liquid (IL), for decrystallization of shrimp crystalline chitin flakes followed by a microwave-mediated NaOH or tetrabutylammonium hydroxide, [TBA][OH], solution-based deacetylation for chitosan production. The decrease in crystallinity in IL pre-treated chitin was confirmed by XRD and SEM analysis which subsequently benefited chitosan production with up to 85% degree of deacetylation (%DDA) in shorter time periods (1-2 hours) and lower alkaline concentrations (20-40%). The %DDA in chitin/chitosan was estimated via FT-IR and NMR analysis. Notably, we could regenerate the ionic liquids: in case of [Emim][OAc] 97 wt.% and in case of [TBA][OH] 83 wt.% could be reused. Roles of ionic liquids in the process were discussed. Molecular dynamics (MD) simulations showed the roles of [TBA]+ cations in the molecular driving forces of [TBA][OH]-induced deacetylation mechanism. The strategy promises a sustainable and milder reaction approach to the existing highly corrosive alkaline- or acid-involved processes for chitosan production.

Published
2024
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25. An energy harvester based on UV-polymerized short-alkyl-chain-modified [DBU][TFSI] ionic liquid electrets

Author

Järvinen, Topias, Vucetic, Nemanja, Palvölgyi, Petra, Pitkänen, Olli, Siponkoski, Tuomo, Cabaud, Helene, Vajtai, Robert, Mikkola, Jyri-Pekka, Kordas, Krisztian, Järvinen, Topias, Vucetic, Nemanja, Palvölgyi, Petra, Pitkänen, Olli, Siponkoski, Tuomo, Cabaud, Helene, Vajtai, Robert, Mikkola, Jyri-Pekka, and Kordas, Krisztian

Abstract

Three short-alkyl-chain-modified [DBU][TFSI] ionic liquids (ILs) were synthesized and utilized in electrets. The electrets were prepared by mixing a UV-curable polymer with the ionic liquids followed by polymerization while applying an external electric field, thus forming spatially separated anions and cations in the proximity of opposing surfaces of the composite slabs. The immobilized surplus surface charge was measured by periodically engaging the electret with a metal counter electrode plate and detecting the displacement current using a charge amplifier. The results show that electrets based on polymerized [DBU][TFSI] ILs have a separated surface charge density of up to 64 nC × cm−2, which equals an energy harvesting density of 7.0 nJ × cm−2. Control measurements repeated after a few days to assess the stability and reproducibility of the systems showed that while charge separation reverses over time to some extent, the polymerized ionic liquid samples are resilient to exposure to atmospheric conditions and could be utilized in this type of energy harvesting scheme.

Published
2024
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42. Efficient Adsorption and Catalytic Reduction of Phenol Red Dye by Glutaraldehyde Cross-Linked Chitosan and Its Ag-Loaded Catalysts: Materials Synthesis, Characterization and Application

Author

Siciliano, Chiara C., Dinh, Van Minh, Canu, Paolo, Mikkola, Jyri-Pekka, and Khokarale, Santosh G.

Subjects
Ag/chitosan catalyst, adsorption, phenol red dye, catalyst reusability, catalytic reduction, Materials Chemistry, General Engineering, Materialkemi, cross-linked chitosan
Abstract

In this study, glutaraldehyde cross-linked chitosan support, as well as the catalysts obtained after loading Ag metal (Ag/Chitosan), were synthesised and applied for adsorption and reduction of phenol red dye in an aqueous solution. The Ag/chitosan catalysts were characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and inductively coupled plasma-optical emission spectrometry (ICP-OES) analysis techniques. The catalytic reduction and adsorption performance of phenol red dye with Ag/chitosan and cross-linked chitosan, respectively, was performed at ambient reaction conditions. The reduction of dye was carried out using sodium borohydride (NaBH4) as the reducing agent, while the progress of adsorption and reduction study was monitored with ultraviolet-visible (UV-vis) spectrophotometry technique. The reduction of the phenol red dye varied with the amount of catalyst, the concentration of NaBH4, Ag metal loading, reaction temperature, phenol red dye concentration and initial pH of the dye solution. The dye solution with a nearly-neutral pH (6.4) allowed efficient adsorption of the dye, while acidic (pH = 4) and alkaline (pH = 8, 11, 13.8) solutions showed incomplete or no adsorption of dye. The reusability of the Ag/chitosan catalyst was applied for the complete reduction of the dye, where no significant loss of catalytic activity was observed. Hence, the applicability of cross-linked chitosan and Ag/catalyst was thus proven for both adsorption and reduction of phenol red dye in an aqueous solution and can be applied for industrial wastewater treatment.

Published
2023

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