Fabrication of biobased heterogeneous solid Brønsted acid catalysts and their application on the synthesis of liquid biofuel 5-ethoxymethylfurfural from fructose

A series of biobased heterogeneous solid Brønsted acid catalysts with perfect spherical microstructures are successfully fabricated directly from waste Camellia oleifera shells by a simple hydrothermal carbonization-annealing-sulfonation process. 350 °C low temperature annealing process helps to increase the activity of the catalyst due to the simultaneous maintenance of the spherical microstructure and aromatic carbon framework. As a renewable catalyst with low cost, the as-prepared materials are successfully applied on the synthesis of green renewable liquid biofuel 5-ethoxymethylfurfural (EMF) directly from fructose. In the catalytic test, the influences of reaction time and temperature, fructose concentration, and adding amount of the catalyst on the yield of EMF are investigated systematically. As a result, the optimal reaction temperature is 100 °C, the EMF yield monotonically increases with prolonging the reaction time from 3 to 24 h, the optimal fructose concentration is 0.5 mmol, and the EMF yield gradually increases with increasing the adding amount of the catalyst from 50 to 150 mg. In addition, the as-prepared catalysts exhibit considerably high stability in the current EMF synthesis system, and they can maintain a similar level of reactivity after four catalytic cycles. Keywords: Hydrothermal carbonization, Annealing, Sulfonation, 5-Ethoxymethylfurfural, Fructos

Electroabsorption Spectra of Lead Sulfide (PbS) Quantum Dots in a Polymer Film

The electric field response of lead sulfide (PbS) quantum dots with near-infrared absorption of 1000–1600 nm (corresponding to diameters of 2–5 nm) embedded in a PMMA film has been systematically studied by using electric field modulation spectroscopy. For all PbS quantum dots samples, the electroabsorption spectra across the first and second exciton bands are similar in shape to the second derivative of the absorption spectra, indicating the enhancement of the electric dipole moment following the optical transition to these exciton bands. The analysis of the electroabsorption spectra shows that the dipole moments for both first and second exciton bands increase a little bit with increasing particle size. The quadratic field dependence is observed between the modulated absorption spectrum and the electric field of PbS quantum dots doped in a PMMA film

Host-Sensitized and Tunable Luminescence of GdNbO₄:Ln³⁺ (Ln³⁺ = Eu³⁺/Tb³⁺/Tm³⁺) Nanocrystalline Phosphors with Abundant Color

Up to now, GdNbO₄ has always been regarded as an essentially inert material in the visible region with excitation of UV light and electron beams. Nevertheless, here we demonstrate a new recreating blue emission of GdNbO₄ nanocrystalline phosphors with a quantum efficiency of 41.6% and host sensitized luminescence in GdNbO₄:Ln³⁺ (Ln³⁺ = Eu³⁺/Tb³⁺/Tm³⁺) nanocrystalline phosphors with abundant color in response to UV light and electron beams. The GdNbO₄ and GdNbO₄:Ln³⁺ (Ln³⁺ = Eu³⁺/Tb³⁺/Tm³⁺) nanocrystalline phosphors were synthesized by a Pechini-type sol–gel process. With excitation of UV light and low-voltage electron beams, the obtained GdNbO₄ nanocrystalline phosphor presents a strong blue luminescence from 280 to 650 nm centered around 440 nm, and the GdNbO₄:Ln³⁺ nanocrystalline phosphors show both host emission and respective emission lines derived from the characterize f–f transitions of the doping Eu³⁺, Tb³⁺, and Tm³⁺ ions. The luminescence color of GdNbO₄:Ln³⁺ nanocrystalline phosphors can be tuned from blue to green, red, blue-green, orange, pinkish, white, etc. by varying the doping species, concentration, and relative ratio of the codoping rare earth ions in GdNbO₄ host lattice. A single-phase white-light-emission has been realized in Eu³⁺/Tb³⁺/Tm³⁺ triply doped GdNbO₄ nanocrystalline phosphors. The luminescence properties and mechanisms of GdNbO₄ and GdNbO₄:Ln³⁺ (Ln³⁺ = Eu³⁺/Tb³⁺/Tm³⁺) are updated

Fluorescence Turn-On Chemosensor for Highly Selective and Sensitive Detection and Bioimaging of Al³⁺ in Living Cells Based on Ion-Induced Aggregation

Herein, a new fluorescence turn-on chemosensor 2-(4-(1,2,2-triphenylvinyl)­phenoxy)­acetic acid (TPE-COOH) specific for Al³⁺ was presented by combining the aggregation-induced-emission (AIE) effect of tertaphenylethylene and the complexation capability of carboxyl. The introduction of carboxylic group provides the probe with good water-solubility which is important for analyzing biological samples. The recognition toward Al³⁺ induced the molecular aggregation and activated the blue fluorescence of the TPE core. The high selectivity of the probe was demonstrated by discriminating Al³⁺ over a variety of metal ions in a complex mixture. A detection limit down to 21.6 nM was determined for Al³⁺ quantitation. Furthermore, benefiting from its good water solubility and biocompatibility, imaging detection and real-time monitoring of Al³⁺ in living HeLa cells were successfully achieved. The AIE effect of the probe enables high signal-to-noise ratio for bioimaging even without multiple washing steps. These superiorities make this probe a great potential for the functional study and analysis of Al³⁺ in complex biosystems