Non-toxic Solvent System Research Articles

Stable and sustainable perovskite solar modules by optimizing blade coating nickel oxide deposition over 15 × 15 cm2 area

Perovskite solar cells have rapidly advanced, achieving over 26% power conversion efficiency on the laboratory scale. However, transitioning to large-scale production remains a challenge due to limitations in conventional fabrication methods like spin coating. Here, we introduce an optimized blade coating process for the scalable fabrication of large-area (15 cm × 15 cm) perovskite solar modules with a nickel oxide hole transport layer, performed in ambient air and utilizing a non-toxic solvent system. Self-assembled monolayers between the nickel oxide and perovskite layer improve the uniformity and morphology of the perovskite film. Perovskite solar modules with a 110 cm2 active area achieve a power conversion efficiency of 12.6%. Moreover, encapsulated modules retained 84% of their initial efficiency after 1,000 hours at 85 °C in air (ISOS-T-1). This study demonstrates progress in the large-scale production of perovskite solar cells that combine efficiency with long-term stability.

An Umpolung Approach to Acyclic 1,4-Dicarbonyl Amides via Photoredox-Generated Carbamoyl Radicals.

A method for the generation and reaction of carbamoyl radicals from oxamate salts, followed by reaction with electron-poor olefins, is described. The oxamate salt acts as a reductive quencher in the photoredox catalytic cycle, allowing mild and mass-efficient formation of 1,4-dicarbonyl products; a challenging transformation in the context of functionalized amide formation. Increased understanding has been obtained by the use of ab initio calculations, in support of experimental observations. Furthermore, steps have been taken towards an environmentally-friendly protocol, by utilizing sodium as a cheap and low mass counterion, and demonstrating successful reactions using a metal-free photocatalyst and a sustainable, non-toxic solvent system.

The phenolic profile extracted from the desiccation-tolerant medicinal shrub Myrothamnus flabellifolia using Natural Deep Eutectic Solvents varies according to the solvation conditions

Natural Deep Eutectic Solvents (NaDES) have been proposed as designer solvents for the green extraction of bioactive products from plants. Myrothamnus flabellifolia is a desiccation-tolerant medicinal shrub that has been widely studied for its phenolic properties; however, a NaDES-based approach for the extraction of phenolics has not been tested in this species. Our aim was thus to evaluate the extraction of phenolics from M. flabellifolia using four different NaDES with differing acidities using a non-targeted liquid chromatography-quantitative time-of-flight-tandem mass spectrometry (LC-QTOF-MS/MS) metabolomics approach. Anthocyanin pigments were quantified using targeted high-performance LC. Leaf material from M. flabellifolia was extracted in four different NaDES solutions (sucrose–fructose–glucose; proline–malic acid; sucrose–citric acid; and glucose–choline chloride), and the results were subjected to multivariate statistical analysis to evaluate the phenolic profiles of the different NaDES extracts. The NaDES were effective at extracting phenolic compounds from M. flabellifolia and also exhibited specificity in the suites of phenolics that they extracted, as indicated by principal component analysis. Using partial least squares-discriminant analysis, we were able to identify the phenolics that were most differentially abundant between the extracts, and a heatmap provided an indication of the types of phenolics that were extracted by the different NaDES. Furthermore, the NaDES also extracted several compounds not previously detected in M. flabellifolia using conventional organic solvents, demonstrating their use in compound discovery. The NaDES also differentially targeted anthocyanins, with the more acidic NaDES extracting higher quantities of anthocyanins and polymeric pigments. A green chemistry-based extraction technique using NaDES can thus effectively target phenolics in M. flabellifolia and offers a promising solution for future phytochemical investigations in medicinal plants using a highly efficient non-toxic solvent system that can be tailored to target particular compounds.

Preparation of graphene-embedded hydroxypropyl cellulose/chitosan/polyethylene oxide nanofiber membranes as wound dressings with enhanced antibacterial properties

Electrospun nanofiber membranes possess high specific surface area with small pores and thus can be developed as wound dressings for absorbing exudate and also preventing bacterial penetration. In this study, hydroxypropyl cellulose (H), chitosan (C) and polyethylene oxide (P) were chosen as membrane materials to increase the hydrophilicity, anti-bacterial property, and yield of nanofibers, respectively. Additionally, graphene (G) was added to enhance the anti-bacterial property of the membranes. As indicated by SEM, the HCP and HCPG solutions (containing H:4.5 wt%, C:4.5 wt%, P:0.75 wt%, without/with G:0.5 wt%) could be electrospun into HCP and HCPG nanofiber membranes with good fiber morphology using a non-toxic solvent system. Further, the membranes were crosslinked by glutaraldehyde vapor to improve the strength. The tensile strength of the membranes was 1.38–1.82 MPa with a swelling ratio up to 1330–1410%. The water vapor transmission rate (WVTR) of wet HCPG membrane was about 3100 g/m2-day, close to the recommended WVTR of wound dressings. The anti-bacterial properties of the membranes were confirmed using three tests against Escherichia coli (Gram-negative bacterium) and Staphylococcus aureus (Gram-positive bacterium). Highly hydrophilic HCP and HCPG membranes prevented the bacterial adherence. The presence of the membranes (especially graphene-embedded HCPG membrane) also greatly reduced bacterial growth. The small pore sizes of HCP and HCPG nanofiber membranes prevented the bacterial penetration to cause infection. Taken together, the HCP and HCPG nanofiber membranes possessed good mechanical properties, appropriate WVTR and high water absorption thus suitable for absorbing wound exudate. Besides, the membranes exhibited nontoxic, anti-fibroblast adhesion and anti-bacterial properties. Therefore, HCP and HCPG nanofiber membranes have the potential to become superior anti-bacterial wound dressings.

Environmentally benign one-pot multicomponent synthesis of 1,4-dihydropyridine derivatives applying montmorillonite K10 as reusable catalyst

Environmentally benign one-pot multicomponent synthesis of different 1,4-dihydropyridine derivatives using montmorillonite K10 has been achieved. The montmorillonite K10-catalyzed reaction of aromatic aldehyde, malononitrile, substituted aniline, and diethyl acetylenedicarboxylate in H2O–EtOH allows to obtain structurally diverse 1,4-dihydropyridines in high yields. Possibility to recover and reuse the acidic catalyst in up to five catalytic cycles has been demonstrated. Short reaction times, suppressed formation of side products, inexpensive and nontoxic solvent system, catalyst recovery, and simple workup procedure are the main advantages of the developed synthetic method.

Preparation and Properties of Cellulose/Poly(vinyl alcohol) Blend Films Based on Dissolution in a Non-Toxic Solvent System

Preparation and Properties of Cellulose/Poly(vinyl alcohol) Blend Films Based on Dissolution in a Non-Toxic Solvent System

Properties and applications of biodegradable transparent and photoluminescent cellulose films prepared via a green process

Cellulose was dissolved rapidly in 7 wt% NaOH/12 wt% urea aqueous solution pre-cooled to −12 °C within 2 min to obtain its solution, which is a “green” process. A series of regenerated cellulose (RC) films were prepared from the cellulose solution via a simple and low-cost method to evaluate their structure and properties as packaging and functional materials. The cellulose films were treated successfully with fluorescent dyes and photoluminescent (PL) pigments to fabricate, for the first time, novel PL materials, which exhibited strong fluorescence and long after-glow emission. The results from CP/MAS 13C NMR spectra, X-ray diffraction and tensile testing confirmed that the transparent RC films possessed an homogenous structure, excellent optical transmittance (90% at 800 nm), as well as good tensile strength. Moreover, the drawing process could significantly improve their tensile strength, which reached 138 MPa. In addition, the biodegradation tests revealed that the RC films could be biodegraded completely. This work provided a non-toxic solvent system for the preparation of the packaging films and PL materials. This process is promising on a large scale and will maintain clean air in the production environment.

Dilute solution properties of cellulose in LiOH/urea aqueous system

AbstractCellulose was dissolved rapidly in 4.6 wt % LiOH/15 wt % urea aqueous solution and precooled to –10 °C to create a colorless transparent solution. 13C‐NMR spectrum proved that it is a direct solvent for cellulose rather than a derivative aqueous solution system. The result from transmission electron microscope showed a good dispersion of the cellulose molecules in the dilute solution at molecular level. Weight‐average molecular weight (Mw), root mean square radius of gyration (〈s2〉z1/2), and intrinsic viscosity ([η]) of cellulose in LiOH/urea aqueous solution were examined with laser light scattering and viscometry. The Mark–Houwink equation for cellulose in 4.6 wt % LiOH/15 wt % urea aqueous solution was established to be [η] = 3.72 × 10−2 M in the Mw region from 2.7 × 104 to 4.12 × 105. The persistence length (q), molar mass per unit contour length (ML), and characteristic ratio (C∞) of cellulose in the dilute solution were given as 6.1 nm, 358 nm−1, and 20.8, respectively. The experimental data of the molecular parameters of cellulose agreed with the Yamakawa–Fujii theory of the worm‐like chain, indicating that the LiOH/urea aqueous solution was a desirable solvent system of cellulose. The results revealed that the cellulose exists as semistiff‐chains in the LiOH/urea aqueous solution. The cellulose solution was stable during measurement and storage stage. This work provided a new colorless, easy‐to‐prepare, and nontoxic solvent system that can be used with facilities to investigate the chain conformation and molecular weight of cellulose. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3093–3101, 2006

Bismuth Compounds in Organic Synthesis. Deprotection of Ketoximes Using Bismuth Bromide‐Bismuth Triflate.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Bismuth compounds in organic synthesis. Deprotection of ketoximes using bismuth bromide-bismuth triflate

Ketoximes undergo deprotection in CH 3CN/acetone/H 2O (3:6:1) in the presence of 20–40 mol% BiBr 3/5 mol% Bi(OTf) 3. Bismuth(III) salts are relatively non-toxic, insensitive to air and inexpensive. These features coupled with the use of a relatively non-toxic solvent system make this method an attractive alternative to existing routes for deprotection of ketoximes.

A simple and efficient chemoselective method for the catalytic deprotection of acetals and ketals using bismuth triflate.

Bismuth triflate is a highly efficient catalyst (0.1-1 mol %) for the deprotection of acetals and ketals. The procedure is very facile and selective for acetals derived from ketones and conjugated aldehydes. tert-Butyldimethylsilyl ethers are stable to the reaction conditions. The highly catalytic nature of bismuth triflate and the use of a relatively nontoxic solvent system (THF/H(2)O) make this procedure particularly attractive for large-scale synthesis.