Oxolinic Acid Generated Green Fluorescence Based on a Terbium-Functionalized Covalent Organic Framework.

Oxolinic acid (OXO), a classic environmental contaminant, has a terrible detrimental effect on human health. The exploration of efficient strategies to detect and detecting OXO has remarkable significance. Herein, we reported a novel terbium(III)-functionalized covalent organic framework (Bpy-DhBt-COF@Tb3+) by fixing Tb3+ on the bipyridine-connecting COF (Bpy-DhBt-COF) as a turn-on fluorescent switch toward OXO for the first time. In this platform, Tb3+ acts as the specific recognition units for OXO and the response signal, while Bpy-DhBt-COF acts as the safehaven for Tb3+. Once introducing OXO to Bpy-DhBt-COF@Tb3+, OXO can instead water molecules coordinate with Tb3+ and sensitize Tb3+ instantly, thereby producing a significant fluorescence signal. Profiting from the excellent porosity of Bpy-DhBt-COF@Tb3+, it can obtain optimal response toward OXO only within 10 s with an ultrasensitive detection limit of 12.5 nM. Furthermore, Bpy-DhBt-COF@Tb3+ displayed outstanding selectivity toward OXO than other general quinolones. Based on these, a Tb3+-based COF was explored for the first time for the turn-on fluorescence detection of an OXO with rapid response, high sensitivity, and outstanding selectivity. In this work, we not only exhibit the attractive performance of Tb3+-functionalized COF to detect OXO but also propose a prospect strategy for creating other fluorescent sensors for multiple targets.

Composite Foams of the Graphitic Carbon Nitride@Carbon Nanofibrils Conferred a Superamphiphilic Property and Reinforced Thermal Stability.

Herein, we demonstrated the preparation of novel three-dimensional (3D) superamphiphilic g-C3N4@carbon nanofibers foam (g-C3N4@CNFs) via a two-step approach: liquid nitrogen treatment-freeze-drying; the foams possessed good thermal stability. In this approach, melamine acted as a nitrogen source, and nanofibrillated cellulose (NFCs) functioned as a 3D skeleton. The thermal stability of the as-prepared g-C3N4@CNFs-3 foam was much higher than that of g-C3N4@CNFs-1, as indicated by thermogravimetric data, including an increase of the onset weight loss point (Tonset) by 238.6 °C and an improvement of the maximal weight loss rate (Tmax) by 258.8 °C. The combination of g-C3N4 with CNFs conferred a reduction in the heat release rate (ca. -86%) and the total heat release (ca. -75%). Furthermore, the composition of the hydrophilically oxygenated functional groups and hydrophobic triazine domains in g-C3N4@CNFs rendered it a unique amphiphilic property (contact angle close to 0° within 1.0 s for water and 0° within 12 ms for hexane). A high storage capacity for water and various organic solvents of the superamphiphilic g-C3N4@CNFs foam was found, up to 40-50 times its original weight. The discovery of these superamphiphilic foams is of great significance for the development of superwetting materials and may find their applications in oil emulsion purification and catalyst support fields.

Growth and Optical Properties of the Whole System of Li(Mn1-x,Nix)PO4 (0 ≤ x ≤ 0.5) Single Crystals.

A series of single crystals of Li(Mn1-x,Nix)PO4 (x = 0.00, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.08, 0.10, 0.15, 0.20, and 0.50) have been grown to large sizes up to 5 mm in diameter and 120 mm in length using the floating zone method for the first time. The comprehensive characterizations of the as-grown crystals were performed before further physical property measurements. The composition of the grown crystals was determined by energy-dispersive X-ray spectroscopy. The crystal structures were characterized by the X-ray powder diffraction method with a GSAS fitting for structural refinement, which reveals a high phase purity of the as-obtained crystals. The polarized microscopic images and Laue patterns prove the excellent quality of the single crystals. Oriented cuboids with sizes of 2.7 × 3.8 × 2.1 mm3 along the a, b, and c crystalline directions were cut and polished for further anisotropic magnetic and transparent measurements. We also first proposed a new potential application in the non-linear optical (NLO) and laser generation application for LiMPO4 (M = transition metal) materials. The optical and laser properties, such as the absorption spectra and the second harmonic generation (SHG), have been investigated and have furthermore confirmed the good quality of the as-grown single crystals.

Peanut-like MnO@C core-shell composites as anode electrodes for high-performance lithium ion batteries.

Peanut-like MnO@C core-shell composites with an internal carbon network (P-MnO@C) were prepared via an in situ synchronous graphitization and reduction process. These P-MnO@C composites exhibit high specific capacity and rate capability, good stability and excellent long-term cycling life for application in lithium ion batteries.

Comprehensive kinetic studies of acidic oil continuous esterification by cation-exchange resin in fixed bed reactors.

Biodiesel produced by esterification from molar ratio of methanol to free fatty acid (FFA) as 25:1 in presence of triglyceride was carried out with cation-exchange resin as a heterogeneous catalyst in three different scales of fixed bed reactors from minireactor (6.8 mm × 110 mm) to pilot scale reactor (70 mm × 1260 mm) at 338 K. The kinetic study of esterification was undertaken in terms of pseudo-homogeneous mechanism and performed as a first order reaction with elimination of the solid-liquid internal and external mass transfer resistances. Moreover, a kinetic model of FFA esterification was developed to illustrate the relationship between the FFA conversion and the catalyst bed height of fixed bed reactor. The model was also suitable for various resins in fixed bed reactor. The theoretical predictions were in agreement with the experimental data with root mean square (RMS) errors <10.

Continuous biodiesel production in a fixed bed reactor packed with anion-exchange resin as heterogeneous catalyst.

A continuous biodiesel production from the transesterification of soybean oil with methanol was investigated in a fixed bed reactor packed with D261 anion-exchange resin as a heterogeneous catalyst. The conversion to biodiesel achieved 95.2% within a residence time 56 min under the conditions: reaction temperature of 323.15K, n-hexane/soybean oil weight rate of 0.5, methanol/soybean oil molar ratio of 9:1 and feed flow rate of 1.2 ml/min. The resin can be regenerated in-situ and restored to the original activity to achieve continuous production after the resin deactivation. The product obtained was mainly composed of methyl esters. No glycerol in the product was detected due to the resin adsorbing glycerol in the fixed bed, which solved the issue of glycerol separation from biodiesel. It is believed that the fixed bed reactor with D261 has a potential commercial application in the transesterification of triglyceride.