Alkylated fullerene as lubricant additive in paraffin oil for steel/steel contacts

<p>An alkylated fullerene which bears three eicosyl chains (3,4,5-C₂₀C₆₀, <b>1</b>) was synthesized via [3 + 2] cycloaddition. At 25°C where the aliphatic chains are in the crystalline state, <b>1</b> exhibits a moderately improved solubility in paraffin oil compared to pristine C₆₀. At 80°C which is well-above the chain melting temperature (<i>T</i>_c), a significant solubility increase was observed. Upon cooling to 25°C, suspension containing plate-like aggregates composed of lamellar subunits form, which can be stable for several days. Applications of <b>1</b> as a lubricant additive in paraffin oil (PO) for steel/steel contacts both below and above <i>T</i>_c have been investigated in detail. It was found that the addition of 1.0 wt% <b>1</b> to PO can reduce the friction coefficient by ∼24% at 25°C. Moderate reduction of the friction coefficient at 90°C was also observed. Analysis on the worn surfaces revealed a pronounced antiwear property of <b>1</b> by reducing the areas of the worn surfaces and smoothing the scuffing. Our results show that alkylated fullerenes can be potentially used as a new generation of lubricant additives. Finally, the lubrication mechanisms of <b>1</b> at different temperatures were discussed.</p

Self-Assembly and Rheological Properties of a Pseudogemini Surfactant Formed in a Salt-Free Catanionic Surfactant Mixture in Water

The surface and bulk properties of bola-type dicarboxylic acid (sebacic acid, SA) and zwitterionic surfactant tetradecyldimethylamine oxide (C₁₄DMAO) mixtures in aqueous solutions were studied. Surface tension measurements indicate a pronounced synergistic effect between SA and C₁₄DMAO. In bulk aqueous solutions, rich phase behavior was observed with a varied SA-to-C₁₄DMAO ratio (ρ) and a total surfactant concentration. Typically at ρ = 0.5, a novel pseudogemini surfactant (C₁₄-S-C₁₄) forms, driven by electrostatic interaction and hydrogen bonding. The C₁₄-S-C₁₄/H₂O system exhibits rich phase behavior induced by the transition of aggregates. With increasing concentration of C₁₄-S-C₁₄, one can observe a viscous L₁ phase, an L₁/L_α two-phase region where a birefringent L_α phase is on the top of an L₁ phase, a single L_α phase, and finally a mixture of an L_α phase and a precipitate. Microstructures formed in the L_α phases were determined by freeze–fracture transmission electron microscopy (FF-TEM) and cryogenic-transmission electron microscopy (cryo-TEM) observations. Polymorphic aggregation behavior was observed with the formation of a variety of bilayer structures including unilamellar vesicles, onions, and open and hyperbranched bilayers. Rheological measurements showed that the L_α phases are viscoelastic and sensitive to temperature where a quick loss of viscoelasticity was observed at elevated temperature

Artificial Light-Harvesting System with White-Light Emission in a Bicontinuous Ionic Medium

Artificial light-harvesting systems (ALHSs), which are closely related to Förster resonance energy transfer (FRET), are among the most attractive scientific topics during the past few decades. Specifically, binary ALHSs that are composed of a fluid donor and acceptor have a simplified composition and high number density of the donor units. However, largely due to the difficulty in obtaining a fluid donor, investigation of these systems is still quite limited, especially for the ionic systems. Herein, we report a new type of binary ALHS using an ionic naphthalimide (NPI) derivative as a donor, which shows greatly improved photoluminescence for its bicontinuous liquid structure. When blending with an acceptor such as rhodamine 6G or trans-4-[4-(dimethylamino)styryl]-methylpyridinium iodide, efficient FRET was confirmed by both experimental results and molecular dynamics simulations, with an energy transfer efficiency up to ∼90%. Tunable color, including white-light emission, was achieved by tuning the acceptor/donor ratio, opening the door for a variety of applications such as light-emitting diodes and photoluminescent inks

Tunable Amphiphilicity and Multifunctional Applications of Ionic-Liquid-Modified Carbon Quantum Dots

During the past decade, increasing attention has been paid to photoluminescent nanocarbon materials, namely, carbon quantum dots (CQDs). It is gradually accepted that surface engineering plays a key role in regulating the properties and hence the applications of the CQDs. In this paper, we prepared highly charged CQDs through a one-pot pyrolysis with citric acid as carbon source and a room-temperature imidazolium-based ionic liquid as capping agent. The as-prepared CQDs exhibit high quantum yields up to 25.1% and are stable under various environments. In addition, the amphiphilicity of the CQDs can be facilely tuned by anion exchange, which leads to a spontaneous phase transfer between water and oil phase. The promising applications of the CQDs as ion sensors and fluorescent inks have been demonstrated. In both cases, these ionic-liquid-modified CQDs were found to possess novel characteristics and/or superior functions compared to existing ones

Self-Organization and Vesicle Formation of Amphiphilic Fulleromonodendrons Bearing Oligo(poly(ethylene oxide)) Chains

A new series of <i>N</i>-methylfulleropyrrolidines bearing oligo­(poly­(ethylene oxide))-appended Percec monodendrons (fulleromonodendrons, <b>4a</b>–<b>f</b>) have been synthesized. The substituted position of the oligo­(poly­(ethylene oxide)) chain(s) on the phenyl group of the Percec monodendron for <b>4a</b>–<b>f</b> was varied, which is at the 4-, 2,4-, 3,5-, 3,4,5-, 2,3,4- and 2,4,6- position, respectively. <b>4a</b>–<b>e</b> are obtained as solids at 25 °C and can self-organize into lamellar phases as revealed by X-ray diffraction (XRD) and small-angle X-ray scattering (SAXS) measurements, while <b>4f</b> appears as a viscous liquid. The substitution patterns of the oligo­(poly­(ethylene oxide)) chain(s) also significantly influence the solubility of <b>4a</b>–<b>f</b>, especially in ethanol and water. Formation of self-organized supramolecular structures of <b>4d</b> and <b>4e</b> in water as well as <b>4d</b> in ethanol is evidenced from UV–vis and dynamic light scattering (DLS) measurements. Further studies in water using various imaging techniques including transmission electron microscopy (TEM), freeze-fracture TEM (FF-TEM), cryo-TEM and atomic force microscopy (AFM) observations revealed the formation of well-defined vesicles for <b>4d</b> and plate-like aggregates for <b>4e</b>, indicating that the aggregation behavior of the fulleromonodendrons is highly dependent on their molecular structures. For <b>4d</b> in ethanol, only irregular aggregates were noticed, indicating the solvent also plays a role on regulating the aggregation behavior. After functionalization with the Percec monodendrons, <b>4a</b>–<b>f</b> can preserve the intriguing electrochemical properties of pristine C₆₀ as revealed by cyclic voltammetries. The thermotropic properties of <b>4a</b>–<b>f</b> have also been investigated. It was found that all of them show good thermal stability, but no mesophases were detected within the investigated temperature ranges

Composite Films with Ordered Carbon Nanotubes and Cellulose Nanocrystals

Composite films with oxidized carbon nanotubes (o-CNTs) incorporated in the chiral nematic liquid crystals (CNLCs) formed by cellulose nanocrystals (CNCs) were fabricated for the first time. Induced by solvent evaporation, the isotropic aqueous dispersion containing o-CNTs and CNCs gradually forms lyotropic CNLCs, and the framework of the CNLCs can be retained in the final solid films, confirmed by polarized optical microscopy observations and scanning electron microscopy observations. During this evaporation-induced self-assembly process, the predispersed o-CNTs were spontaneously integrated in the liquid crystal matrix. It is found that the incorporation of a trace amount of o-CNTs (∼1.5 wt %) can induce obvious structural changes of the films. The reflection spectrum shifts to higher wavelengths with increasing content of o-CNTs, resulting in a continuous increase of the helical pitch of the CNLC phase. Confined in the liquid crystal matrix, the randomly oriented o-CNTs in the aqueous dispersion are forced to adopt a higher degree of order. This ordered arrangement of o-CNTs combined with the intrinsic anisotropy of the CNLCs impart the composite film anisotropic conductivity as proved by the electrical resistance measurements. This new type of CNTs/CNCs composites could find applications in various fields such as sensors and photoelectronics

Metal-Free All-Carbon Nanohybrid for Ultrasensitive Photoelectrochemical Immunosensing of alpha-Fetoprotein

C₆₀ can accept up to six electrons reversibly and show exceptional light absorption over the entire UV–vis spectrum, making it a potential photoactive probe for photoelectrochemical (PEC) bioassay. However, few successful works have been reported to apply fullerenes in PEC biosensing, partially because of the low electronic conductivity and poor interfacial interactions with targeted biomolecules. Herein, we report the addressing of these two obstacles by coupling high conductive graphite flake (Gr), graphene oxide (GO) with sufficient oxygen-containing functional groups, and an alkylated C₆₀ (AC₆₀) into a metal-free all-carbon nanohybrid (AC₆₀-Gr-GO) via harnessing delicate noncovalent interactions among them through a facile mechanical grinding. It was revealed that the as-obtained AC₆₀-Gr-GO nanohybrid not only showed conspicuous enhancement of photocurrent up to 35 times but also offered rich anchors for bioconjugation. With detection of alpha-fetoprotein as an example, the AC₆₀-Gr-GO based PEC immunosensor demonstrated a broad linear detection range (1 pg·mL^–1 to 100 ng·mL^–1) and a detection limit as low as 0.54 pg·mL^–1, superior/competitive to PEC immunosensors for AFP in previous reports. By a proper reinforcement in conductivity and biointerface engineering, this work may provide a new way to use fullerenes as photoactive materials in more general PEC biosensing

Enhanced CO₂ Adsorption Capacity and Hydrothermal Stability of HKUST‑1 via Introduction of Siliceous Mesocellular Foams (MCFs)

New hierarchical composites containing micropores and mesopores were synthesized by assembling HKUST-1 (Cu₃(BTC)₂) on siliceous mesocellular foams (MCFs). The structure, morphology, and textural properties of as-prepared composites were characterized by X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, and N₂ sorption isotherms, respectively. The results suggest that the coexistence of mesoporous silicas promotes the formation of nanosized MOFs, and the mesostructures of silicas are not destroyed by MOFs. Moreover, the micropore/mesopore volume ratio can be controlled by varying the amounts of MOFs. The CO₂ adsorption capacities were calculated by breakthrough curves, which were tested in a fixed bed. The CO₂ adsorption capacity of the composites reaches 1.40 mmol/g, which is higher than that of bulk HKUST-1. The structure and CO₂ adsorption capacity of the composites after the hydrothermal treatment also have been evaluated. The results show that composite-2 has a larger CO₂ adsorption capacity of 1.68 mmol/g after steam conditioning and that the structure of HKUST-1 in the composites remain stable

Cooperative Cu/Pd-Catalyzed 1,5-Boroacylation of Cyclopropyl-Substituted Alkylidenecyclopropanes

A Cu/Pd-cocatalyzed 1,5-boroacylation of cyclopropyl-substituted ACPs with B2pin2 and acid chlorides has been developed. Using cyclopropyl-substituted ACPs as the starting material, a broad range of 1,5-boroacylated products with multiple functional groups was prepared in good yields with excellent regio- and stereoselectively. Both aromatic and aliphatic acid chlorides were tolerated in this reaction

Cooperative Cu/Pd-Catalyzed 1,5-Boroacylation of Cyclopropyl-Substituted Alkylidenecyclopropanes

A Cu/Pd-cocatalyzed 1,5-boroacylation of cyclopropyl-substituted ACPs with B2pin2 and acid chlorides has been developed. Using cyclopropyl-substituted ACPs as the starting material, a broad range of 1,5-boroacylated products with multiple functional groups was prepared in good yields with excellent regio- and stereoselectively. Both aromatic and aliphatic acid chlorides were tolerated in this reaction