Solvent-Free and Cost-Efficient Fabrication of a High-Performance Nanocomposite Sensor for Recording of Electrophysiological Signals

Carbon nanotube (CNT)-based nanocomposites have found applications in making sensors for various types of physiological sensing. However, the sensors' fabrication process is usually complex, multistep, and requires longtime mixing and hazardous solvents that can be harmful to the environment. Here, we report a flexible dry silver (Ag)/CNT/polydimethylsiloxane (PDMS) nanocomposite-based sensor made by a solvent-free, low-temperature, time-effective, and simple approach for electrophysiological recording. By mechanical compression and thermal treatment of Ag/CNT, a connected conductive network of the fillers was formed, after which the PDMS was added as a polymer matrix. The CNTs make a continuous network for electrons transport, endowing the nanocomposite with high electrical conductivity, mechanical strength, and durability. This process is solvent-free and does not require a high temperature or complex mixing procedure. The sensor shows high flexibility and good conductivity. High-quality electroencephalography (EEG) and electrooculography (EOG) were performed using fabricated dry sensors. Our results show that the Ag/CNT/PDMS sensor has comparable skin-sensor interface impedance with commercial Ag/AgCl-coated dry electrodes, better performance for noninvasive electrophysiological signal recording, and a higher signal-to-noise ratio (SNR) even after 8 months of storage. The SNR of electrophysiological signal recording was measured to be 26.83 dB for our developed sensors versus 25.23 dB for commercial Ag/AgCl-coated dry electrodes. Our process of compress-heating the functional fillers provides a universal approach to fabricate various types of nanocomposites with different nanofillers and desired electrical and mechanical properties.

Aerobic Oxidative Desulfurization by Supported Polyoxometalate Ionic Liquid Hybrid Materials via Facile Ball Milling

With the increasingly strict limitations on emission standards of vehicles, deep desulfurization in fuel is indispensable for social development worldwide. In this study, a series of hybrid materials based on SiO2-supported polyoxometalate ionic liquid were successfully prepared via a facile ball milling method and employed as catalysts in the aerobic oxidative desulfurization process. The composition and structure of prepared samples were studied by various techniques, including FT-IR, UV-vis DRS, wide-angle XRD, BET, XPS, and SEM images. The experimental results indicated that the synthesized polyoxometalate ionic liquids were successfully loaded on SiO2 with a highly uniform dispersion. The prepared catalyst (C16PMoV/10SiO2) exhibited good desulfurization activity on different sulfur compounds. Moreover, the oxidation product and active species in the ODS process were respectively investigated via GC-MS and ESR analysis, indicating that the catalyst can activate oxygen to superoxide radicals during the reaction to convert DBT to its corresponding sulfone in the fuel.

Use of Novel Homochiral Thioureas Camphor Derived as Asymmetric Organocatalysts in the Stereoselective Formation of Glycosidic Bonds

We synthesized six new camphor-derived homochiral thioureas 1-6, from commercially available (1R)-(-)-camphorquinone. These new compounds 1-6 were evaluated as asymmetric organocatalysts in the stereoselective formation of glycosidic bonds, with 2,3,4,6-tetra-O-benzyl-D-glucopyranosyl and 2,3,4,6-tetra-O-benzyl-D-galactopyranosyl trichloroacetimidates as donors, and several alcohols as glycosyl acceptors, such as methanol, ethanol, 1-propanol, 1-butanol, 1-octanol, iso-propanol, tert-butanol, cyclohexanol, phenol, 1-naphtol, and 2-naphtol. Optimization of the asymmetric glycosylation reaction was achieved by modifying reaction conditions such as solvent, additive, loading of catalyst, temperature, and time of reaction. The best result was obtained with 2,3,4,6-tetra-O-benzyl-D-galactopyranosyl trichloroacetimidates, using 15 mol% of organocatalyst 1, in the presence of 2 equiv of MeOH in solvent-free conditions at room temperature for 1.5 h, affording the glycosidic compound in a 99% yield and 1:73 α:β stereoselectivity; under the same reaction conditions, without using a catalyst, the obtained stereoselectivity was 1:35 α:β. Computational calculations prior to the formation of the products were modeled, using density functional theory, M06-2X/6-31G(d,p) and M06-2X/6-311++G(2d,2p) methods. We observed that the preference for β glycoside formation, through a stereoselective inverted substitution, relies on steric effects and the formation of hydrogen bonds between thiourea 1 and methanol in the complex formed.

Mechanochemistry for Healthcare: Revealing the Nitroso Derivatives Genesis in the Solid State

Nitroso derivatives with unique characteristics have been extensively studied in various fields, including biology and clinical research. Although there has been substantial investigation of "nitrosable" components in many drugs and commonly consumed nutrients, there is still a need for a higher awareness about their formation and characterization. This study demonstrates how these derivatives can be produced through a mechanochemical procedure under solid-state conditions. The results include synthesizing previously unknown compounds with potential biological and pharmaceutical applications, such as a nitrosamine derived from a Diclofenac-like structure.

Solvent-free MALI-MGRE Procedure for Synthesizing 1,4-thiazolidin-4- one MALI (Mercaptoacetic Acid Looking Imine) MGRE (Mechanical Grinding Reaction Equipment)

BACKGROUND

1,3-Thiazolidin-4-ones are heterocycles whose importance in the pharmaceutical market has already been established. Many of these synthetic derivatives, which contain a thiazolidinone nucleus, are currently used in various commercial formulations or are already in clinical trials for the treatment of disease for their anticonvulsant, antihypertensive and antidiabetic activities in addition to their activity against Streptomyces. 1,3-Thiazolidin-4-ones are produced mainly by cyclo condensation between an imine (generated in situ by the reaction of an aldehyde with an amine) and α-mercaptoacetic acid, known as the MALI (Mercaptoacetic Acid Looking Imine) reaction.

OBJECTIVE

A solvent-free methodology was developed to synthesize a 1,3-thiazolidin-4-one family by the MALI reaction. An apparatus was developed to grind a solid-liquid mixture of anilines, benzaldehydes and thioglycolic acid to activate the reaction. This apparatus was named MGRE (mechanical grinding reaction equipment).

METHODS

Substituted aniline 2 (4 mmol), substituted benzaldehyde 1 (4 mmol) and thioglycolic acid 3 (12 mmol) were placed in a mortar. The reagents were macerated using the MGRE at room temperature for a specified time period. At the end of the reaction, the product was poured into ice, the precipitate formed was neutralized (with 5% NaHCO₃), and the solution was extracted in ethyl acetate and dried in MgSO₄. The solid was recrystallized from MeOH/H₂O.

RESULTS

The developed MGRE is a modification of a rod used in a mechanical stirrer. This adaptation is inexpensive and simple in construction, and it enables reactions to occur over long periods of time that would be exhaustive for manual grinding. Fifteen (1,3) thiazolidin-4-ones were produced. The products were synthesized using the solvent-free MALI-MGRE procedure.

CONCLUSIONS

The MALI-MGRE methodology developed to produce 1,3-thiazolidin-4-ones showed a good reaction scope, has an easy work-up and is solvent-free. Consequently, MALI-MGRE is classified as a green methodology. An innovation of this study is the construction of the MGRE, which involves modifying the rod in a mechanical stirrer. The equipment is easy and inexpensive to construct and may be useful for various reactions involving grinding.

Mechanochemical Applications of Reactive Extrusion from Organic Synthesis to Catalytic and Active Materials

In the past, the use of mechanochemical methods in organic synthesis was reported as somewhat of a curiosity. However, perceptions have changed over the last two decades, and this technology is now being appreciated as a greener and more efficient synthetic method. The qualified “offer” of ball mills that make use of different set-ups, materials, and dimensions has allowed this technology to mature. Nevertheless, the intrinsic batch nature of mechanochemical methods hinders industrial scale-ups. New studies have found, in reactive extrusion, a powerful technique with which to activate chemical reactions with mechanical forces in a continuous flow. This new environmentally friendly mechanochemical synthetic method may be able to miniaturize production plants with outstanding process intensifications by removing organic solvents and working in a flow mode. Compared to conventional processes, reactive extrusions display high simplicity, safety, and cleanliness, which can be exploited in a variety of applications. This paper presents perspective examples in the better-known areas of reactive extrusions, including oxidation reactions, polymer processing, and biomass conversion. This work should stimulate further developments, as it highlights the versatility of reactive extrusion and the huge potential of solid-phase flow chemistry.

Transparent and Flexible Amphiphobic Coatings with Excellent Fold Resistance via Solvent-Free Coating and Photocuring of Fluorinated Liquid Nitrile-Butadiene Rubber

Amphiphobic surfaces have been developed for various applications. However, the harsh construction conditions and multistep processes limit their practical application. Especially for those with a particular surface roughness and morphology, the amphiphobic property might provide a slight deformation. Here, a facile large-area construction of transparent and flexible amphiphobic coatings with excellent fold resistance has been established by simple casting of the fluorinated liquid nitrile-butadiene rubber (F-LNBR) followed by solvent-free photocuring. It was found that the fluorocarbon groups could concentrate onto the coating surface during the UV-induced photocuring. With a certain coating amount, a stable oleophobic coating was achieved with static contact angles of about 95° and 111° for nonpolar oil (n-hexadecane) and polar oil (diiodomethane). Most importantly, the static contact angles of water and diiodomethane of the amphiphobic coatings on the iron sheet increased after bending and remained around 131° and 120° after being completely folded in half for 100 cycles because the inner fluorocarbon groups could be squeezed out from the flexible cross-linked rubber matrix as a reservoir. Such features indicated the promising self-cleaning and surface protection of the proposed transparent and flexible amphiphobic coatings for deformable substrates.

MIL-101(Cr), an Efficient Heterogeneous Catalyst for One Pot Synthesis of 2,4,5-tri Substituted Imidazoles under Solvent Free Conditions

A chromium-containing metal-organic framework (MOF), MIL-101 (Chromium(III) benzene-1,4-dicarboxylate), was used to catalyze the one pot, three component synthesis of some 2,4,5-trisubstituted imidazoles under solvent-free conditions. The advantages of using this heterogeneous catalyst include short reaction time, high yields, easy and quick isolation of catalyst and products, low amount of catalyst needed, and that the addition of solvent, salt, and additives are not needed. This catalyst is highly efficient and can be recovered at least 5 times with a slight loss of efficiency. The structure of the metal-organic frameworks (MOF) was confirmed by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance (HNMR) were performed to confirm some of the synthesized products. Experimental data indicated that the optimum amount of catalyst was 5 mg for benzil (1 mmol), 4-chlorobenzaldehyde (1 mmol), and ammonium acetate (2.5 mmol), and the synthetic route to the various imidazoles is performed in 10 min by 95% yield, an acceptable result rivalling those of other catalysts.

Green Approaches for Sustainable Development of Liquid Separation Membrane

Water constitutes one of the basic necessities of life. Around 71% of the Earth is covered by water, however, not all of it is readily available as fresh water for daily consumption. Fresh water scarcity is a chronic issue which poses a threat to all living things on Earth. Seawater, as a natural resource abundantly available all around the world, is a potential water source to fulfil the increasing water demand. Climate-independent seawater desalination has been touted as a crucial alternative to provide fresh water. While the membrane-based desalination process continues to dominate the global desalination market, the currently employed membrane fabrication materials and processes inevitably bring adverse impacts to the environment. This review aims to elucidate and provide a comprehensive outlook of the recent efforts based on greener approaches used for desalination membrane fabrication, which paves the way towards achieving sustainable and eco-friendly processes. Membrane fabrication using green chemistry effectively minimizes the generation of hazardous compounds during membrane preparation. The future trends and recommendations which could potentially be beneficial for researchers in this field are also highlighted.

Optimization, kinetic, and scaling-up of solvent-free lipase-catalyzed synthesis of ethylene glycol oleate emollient ester

The use of enzymatic catalysts is an alternative to chemical catalysts as they can help to obtain products with less environmental impact, considered sustainable within the concept of green chemistry. The optimization, kinetic, lipase reuse, and scale-up of enzymatic production of ethylene glycol oleate in the batch mode were carried out using the NS 88011 lipase in a solvent-free system. For the optimization step, a 2³ Central Composite Design was used and the optimized condition for the ethylene glycol oleate production, with conversions above 99%, was at 70 °C, 600 rpm, substrates molar ratio of 1:2, 1 wt% of NS 88011 in 32 H of reaction. Kinetic tests were also carried out with different amounts of enzyme, and it showed that by decreasing the amount of the enzyme, the conversion also decreases. The lipase reuse showed good conversions until the second cycle of use, after which it had a progressive reduction reaching 83% in the fourth cycle of use. The scale-up (ninefold increase) showed promising results, with conversion above 99%, achieving conversions similar to small-scale reactions. Therefore, this work proposed an environmentally safe route to produce an emollient ester using a low-cost biocatalyst in a solvent-free system.

Fabrication of extended-dissolution divalproex tablets: a green solvent-free granulation technique

Objective: Divalproex sodium (DVS) is a challenging drug owing to its hygroscopicity, bitter taste, and short in vivo half-life. This study aims to produce stable taste masked DVS once daily tablets using solvent free hot melt granulation (HMG) process.Methods: A lab scale high shear mixer granulator employing six meltable lipid binders (compritol^®888 ATO, beeswax, gelucire^®50/13, precirol^® ATO5, stearyl alcohol, and geleol^®) was used for the preparation of tablets. Quality control tests were performed on granules and tablets, and Box-Behnken's design was adopted to investigate the effect of binder concentration, impeller speed, and granulation time on the drug dissolution. Shelf and accelerated stability evaluation, taste assessment, and in vivo pharmacokinetic study were conducted on the selected batches.Results: Results revealed that DVS tablets were successfully prepared, and that the in vitro dissolution of the drug was inversely proportional to the binder concentration. Beeswax and compritol^® tablets showed similar dissolution profiles to the marketed product Depakote^® 500 ER tablets (F1 < 15 and F2 > 50). The selected batches showed lower moisture content (<2%) and successfully masked the bitter taste compared to uncoated tablets based on a hydrophilic matrix. The in vivo pharmacokinetic study delineated relative bioavailability values for Beeswax and Compritol^® tablets of 95.6% and 118%, respectively, compared to the marketed product.Conclusion: The solvent free HMG process can be employed to formulate 24 h extended dissolution DVS tablets with masked bitter taste and high stability, and comparable or higher bioavailability than the marketed product.

Microwave-Assisted Catalytic Method for a Green Synthesis of Amides Directly from Amines and Carboxylic Acids

Amide bonds are among the most interesting and abundant molecules of life and products of the chemical pharmaceutical industry. In this work, we describe a method of the direct synthesis of amides from carboxylic acids and amines under solvent-free conditions using minute quantities of ceric ammonium nitrate (CAN) as a catalyst. The reactions are carried out in an open microwave reactor and allow the corresponding amides to be obtained in a fast and effective manner when compared to other procedures of the direct synthesis of amides from acids and amines reported so far in the literature. The amide product isolation procedure is simple, environmentally friendly, and is performed with no need for chromatographic purification of secondary amides due to high yields. In this report, primary amines were used in most examples. However, the developed procedure seems to be applicable for secondary amines as well. The methodology produces a limited amount of wastes, and a catalyst can be easily separated. This highly efficient, robust, rapid, solvent-free, and additional reagent-free method provides a major advancement in the development of an ideal green protocol for amide bond formation.

Phase inversion-based nanoemulsions of medium chain triglyceride as potential drug delivery system for parenteral applications

Lipid nanoemulsions are attractive drug delivery systems for lipophilic drugs. To produce nanoemulsions with droplets of very small diameter (<100 nm), we investigated thermotropic phase transitions as an alternative to the standard procedure of high-pressure homogenization. Employing shock dilution with ice-cold water during the phase inversion gives the opportunity to produce nanoemulsions without any use of potentially toxic organic solvents. The systematic investigation of the relation of the three involved components surfactant, aqueous phase and lipid phase showed that depending on the ratio of surfactant to lipid the emulsions contained particles of diameters between 16 and 175 nm with narrow polydispersity index distributions and uncharged surfaces. Nanoemulsions with particles of 50 and 100 nm in diameter showed very little toxicity to fibroblast cells in vitro. An unusual, exponential-like nonlinear increase in osmolality was observed with increasing concentration of the nonionic surfactant Kolliphor HS 15. The experimental results indicate, that nanoemulsions with particles of small and tunable size can be easily formed without homogenization by thermal cycling.

Facile and Green Synthesis of Saturated Cyclic Amines

Single-nitrogen containing saturated cyclic amines are an important part of both natural and synthetic bioactive compounds. A number of methodologies have been developed for the synthesis of aziridines, azetidines, pyrrolidines, piperidines, azepanes and azocanes. This review highlights some facile and green synthetic routes for the synthesis of unsubstituted, multisubstituted and highly functionalized saturated cyclic amines including one-pot, microwave assisted, metal-free, solvent-free and in aqueous media.

Solvent-free, visible-light photocatalytic alcohol oxidations applying an organic photocatalyst

A method for the solvent-free photocatalytic conversion of solid and liquid substrates was developed, using a novel rod mill apparatus. In this setup, thin liquid films are realized which is crucial for an effective photocatalytic conversion due to the low penetration depth of light in heterogeneous systems. Several benzylic alcohols were oxidized with riboflavin tetraacetate as photocatalyst under blue light irradiation of the reaction mixture. The corresponding carbonyl compounds were obtained in moderate to good yields.

Ordered Mesoporous Polymers for Biomass Conversions and Cross-Coupling Reactions

Amino group-functionalized, ordered mesoporous polymers (OMP-NH2 ) were prepared using a solvent-free synthesis by grinding mixtures of solid raw precursors (aminophenol, terephthaldehyde), using block copolymer templates, and curing at 140-180 °C. OMP-NH2 was functionalized with acidic sites and incorporated with palladium, giving multifunctional solid catalysts with large Brunauer-Emmett-Teller (BET) surface areas, abundant and ordered mesopores, good thermal stabilities, controllable concentrations, and good dispersion of active centers. The resultant solid catalysts showed excellent catalytic activities and good reusability in biomass conversions and cross-coupling reactions-much superior to those of various reported solid catalysts such as Amberlyst 15, SBA-15-SO3 H, and Pd/C and comparable to those of homogeneous catalysts such as heteropoly acid, HCl, and palladium acetate. A facile green approach was developed for the synthesis of ordered mesoporous polymeric solid catalysts with excellent activities for conversion of low-cost feedstocks into useful chemicals and clean biofuels.

Soft Poly(dimethylsiloxane) Elastomers from Architecture-Driven Entanglement Free Design

Soft, solvent-free poly(dimethylsiloxane) elastomers are fabricated by a one-step process via crosslinking bottlebrush polymers. The bottlebrush architecture prevents the formation of entanglements, resulting in elastomers with precisely controllable low moduli from 1 to 100 kPa, below the lower limit of traditional elastomers; moreover, the solvent-free nature enables their negligible adhesiveness compared to commercially available silicone products of similar stiffness.

Solvent- and catalyst-free huisgen cycloaddition to rufinamide in flow with a greener, less expensive dipolarophile

Give it a flow: A continuous-flow process for the synthesis of a 1,2,3-triazole precursor of Rufinamide has been developed. The protocol involves a solvent- and catalyst-free operation and utilizes reaction temperatures above the melting point of the target product to prevent microreactor clogging, resulting in a decrease of the operating time from hours to minutes.