Multicomponent Sulfonylation of Alkenes to Access ß-Substituted Arylsulfones.

A novel multicomponent sulfonylation of alkenes is described for the assembly of various ß-substituted arylsulfones using cheap and easily available K2S2O5 as a sulfur dioxide source. Of note, the procedure does not need any extra oxidants and metal catalysts and exhibits a relatively wide substrate scope and good functional group compatibility. Mechanistically, an initial arylsulfonyl radical is formed involving the insertion of sulfur dioxide with aryl diazonium salt, followed by alkoxyarylsulfonylation or hydroxysulfonylation of alkenes.

Copper(I)-Catalyzed Cross-Coupling of Arylsulfonyl Radicals with Diazo Compounds: Assembly of Arylsulfones.

A novel copper-catalyzed cross-coupling of arylsulfonyl radicals with diazo compounds is described for the synthesis of various arylsulfones under mild conditions. In this reaction, the cheap, environmentally friendly, and readily available inorganic K2S2O5 is employed as the sulfur dioxide source for providing arylsulfonyl radicals. In addition, a radical mechanism involving the insertion of sulfur dioxide with aryl radicals followed by the coupling of arylsulfonyl radicals with copper carbenes is proposed.

Radical-Mediated Cascade Spirocyclization of N-Benzylacrylamides with Polyhaloalkanes: Access to Polyhalo-Substituted Azaspirocyclohexadienones.

A novel and mild metal-free catalyzed radical-mediated cascade spirocyclization of N-benzylacrylamides with polyhaloalkanes is proposed for the preparation of polyhalo-substituted azaspirocyclohexadienones. Notably, polyhaloalkanes are employed as efficient alkyl radical sources via the cleavage of C(sp3)-H bonds. This protocol undergoes a cascade radical addition and intramolecular cyclization/dearomatization process, and enables the easy construction of multiple chemical bonds and a spiro ring in a single reaction.

A two-photon "turn-on" fluorescent probe for both exogenous and endogenous selenocysteine detection and imaging in living cells and zebrafish.

Selenocysteine (Sec) is recognized as the 21st amino acid employing as an essential building block for selenoproteins (SePs), which plays a significant role in various physiological processes. Therefore, there is an urgent need to reasonably develop some reliable and rapid methods for Sec detection in biological systems. In this work, we reported a new two-photon (TP) fluorescent probe BNT-Sec for Sec detection and imaging in living cells and zebrafish with two part: (1) a D-π-A-structured naphthalene derivative as a TP fluorophore; (2) a well-know Sec responsive site with strong intromolecular charge transfer effect (ICT) to selectively detect endogenous and exogenous. In the presence of Sec, probe BNT-Sec can initiate a Se-dependent specific aromatic nucleophilic substitution reaction, which exhibited BNT-Sec had a large fluorescence intensity enhancement with ~18.9-fold at 510 nm, a high sensitivity low LOD value' 10.6 nM, good light stability, strong specificity, pH stability and low cytotoxicity. In addition, BNT-Sec can be conveniently used to detect Sec in living cells and zebrafish for TP imaging due to the great TP measurement properties of fluorophore, exhibiting it has the potential to reveal the role of selenocysteine in physiological and pathological processes in further biological applications.

Novel synthesis of Mn: ZnSe@ZnS core-shell quantum dots based on photoinduced fluorescence enhancement.

A novel Type-I Mn: ZnSe@ZnS core-shell quantum dots (QDs) was reported through a two-step procedure by using low-cost inorganic salts and naturalbiomacromolecule as raw materials. Based on a designed structure of L-cysteine-capped Mn: ZnSe QDs in aqueous media with the controllable surface, Mn: ZnSe@ZnS core-shell QDs were formed due to photoactive ions and defect curing under continuous constant light. The influences of experimental variables, including synthesis conditions of Mn: ZnSe QDs, different types and affecting factors of photo irradiation had been systematically investigated. Under the effect of photoinduced fluorescence enhancement, the photoluminescence (PL) intensity increases significantly by about 5-10 times after 1-3 h of UV irradiation. The position of the fluorescence peak was red-shifted by about 17 nm, emitting orange-red fluorescence. The photoluminescence quantum yield (PL QY) was markedly improved (up to 35%). The structure and morphology of Mn: ZnSe@ZnS core-shell QDs were also confirmed by Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDS) in detail. The mechanism of photoinduced fluorescence enhancement was attributed to L-cysteine allowed to release S2- to form a ZnS shell, and the passivated surface non-radiative relaxation centers of Mn: ZnSe@ZnS QDs was successfully synthesized with highuniform size, excellent photoluminescence performance, and good stability, all ofwhichmakethemgood potential candidates for white LEDs, and biological labels.

Nitrogen-deficient g-C3Nx/POMs porous nanosheets with P-N heterojunctions capable of the efficient photocatalytic degradation of ciprofloxacin.

The direct shedding of piperazine rings is critical for the degradation of antibiotic persistent organic pollutants. In this work, nitrogen-deficient g-C3N4 loaded with polyoxometalates porous photocatalysts with P-N heterojunctions were carried out through the formation of chemical bonds between the nitrogen-deficient C+ in g-C3Nx and the bridging oxygen in polyoxometalates (POMs), including phosphomolybdic acid (PMA), phosphotungstic acid (PTA) and silicotungstic acid (STA). The adsorption and photocatalysis experiments confirm the ability of the g-C3Nx/POMs nanosheets to efficiently remove ciprofloxacin via the synergistic effects of adsorption and photo-catalysis. Approximately, g-C3Nx/POMs-30 exhibits the optimal degradation ability, and the degradation rates of g-C3Nx/PMA-30, g-C3Nx/PTA-30 and g-C3Nx/STA-30 could respectively reach 93.1%, 97.4% and 95.6% within only 5 min under visible light. The free radical scavenging experiment and ESR free radical capture experiments confirm that ·OH and ·O2- are free radicals that effectively degrade CIP. According to the results of the LC-MS analysis, the intermediates produced after CIP degradation and the efficient degradation pathway are proposed. The direct shedding of piperazine rings in the decarboxylation and defluorination process leads to the most efficient degradation of CIP into the small molecules.

Creation of Hollow Calcite Single Crystals with CQDs: Synthesis, Characterization, and Fast and Efficient Decontamination of Cd(II).

In this work, carbon quantum dots were first prepared through one-pot hydrothermal route of the propyl aldehyde and sodium hydroxide via an aldol condensation reaction, and a novel solid-phase extraction adsorbent of hollow calcite single crystals was prepared via the precipitation of metal nitrates by the CO2 diffusion method in the presence of CQDs and further applied for excessive Cd(II) ions removal from water. The spectra and morphologies of the etched calcite were investigated by X-ray diffraction, Fourier transform infrared spectrometry, Scanning electron microscope, and Transmission electron microscopy. The results show that the CQDs etching technique successfully furnish a strategy for manufacturing interface defects onto the calcite crystal. Bath studies were done to evaluate the effects of the major parameters onto Cd(II) adsorption by the etched calcite, such as pH, contact time, and initial Cd(II) concentration. The Cd(II) adsorption onto the new adsorbent could reach a maximum adsorption amount of 66.68 mg/g at 120 min due to the abundant exterior adsorption sites on the adsorbent. The adsorption kinetics and adsorption isotherms of Cd(II) on the etched calcite were also investigated. The experimental datum showed that the adsorption kinetics and isotherms of Cd(II) on the etched calcite were well-fitted by the pseudo-second-order kinetic model and the Freundlich isotherm model respectively. The adsorption mechanisms could be primarily explained as the formation of Cd(OH)2 and CaxCd1-xCO3 solid solution on the adsorbent surface with the help of X-ray photoelectron spectroscopy.

Water vapor sorption properties of TEMPO oxidized and sulfuric acid treated cellulose nanocrystal films.

For cellulose nanocrystal film, water adsorption is extremely important for its product performance. For gaining a deeper understanding of hygroscopic behavior, two cellulose nanocrystal films, such as TEMPO oxidized cellulose nanocrystal film (TOCNF) and sulfuric acid treated cellulose nanocrystal film (SACNF) were investigated using dynamic water vapor sorption apparatus. During the water vapor sorption process, the running time, real-time sample mass, target relative humidity (RH), actual RH and real-time temperature were all collected. Through the comparison of these collected data, significant differences in the equilibrium moisture content, sorption hysteresis and sorption kinetics were confirmed. It was important to note that TOCNF and SACNF had equilibrium moisture contents of 28.2% and 22.8, respectively, at a RH of 95%. Then, using parallel exponential kinetics (PEK) model, sorption kinetics data were accurately fitted. Furthermore, two Kelvin-Voigt elements were introduced to interpret the fitting results and calculate the modulus of TOCNF and SACNF.

Rapid Colorimetric Detection of Cartap Residues by AgNP Sensor with Magnetic Molecularly Imprinted Microspheres as Recognition Elements.

The overuse of cartap in tea tree leads to hazardous residues threatening human health. A colorimetric determination was established to detect cartap residues in tea beverages by silver nanoparticles (AgNP) sensor with magnetic molecularly imprinted polymeric microspheres (Fe3O4@mSiO2@MIPs) as recognition elements. Using Fe3O4 as supporting core, mesoporous SiO2 as intermediate shell, methylacrylic acid as functional monomer, and cartap as template, Fe3O4@mSiO2@MIPs were prepared to selectively and magnetically separate cartap from tea solution before colorimetric determination by AgNP sensors. The core-shell Fe3O4@mSiO2@MIPs were also characterized by FT-IR, TEM, VSM, and experimental adsorption. The Fe3O4@mSiO2@MIPs could be rapidly separated by an external magnet in 10 s with good reusability (maintained 95.2% through 10 cycles). The adsorption process of cartap on Fe3O4@mSiO2@MIPs conformed to Langmuir adsorption isotherm with maximum adsorption capacity at 0.257 mmol/g and short equilibrium time of 30 min at 298 K. The AgNP colorimetric method semi-quantified cartap ≥5 mg/L by naked eye and quantified cartap 0.1⁻5 mg/L with LOD 0.01 mg/L by UV-vis spectroscopy. The AgNP colorimetric detection after pretreatment with Fe3O4@mSiO2@MIPs could be successfully utilized to recognize and detect cartap residues in tea beverages.

Three-dimensional mesoporous calcium carbonate-silica frameworks thermally activated from porous fossil bryophyte: adsorption studies for heavy metal uptake.

In this paper, three-dimensional mesoporous calcium carbonate-silica frameworks have been created from the straw tufa (ST) originating from porous fossil bryophyte by a thermal activation technique. A batch of adsorption kinetic and thermodynamic experiments were used to investigate the adsorption capacity of Cd(ii) onto the samples. The ST after thermal activation has shown a significant ability for the uptake of heavy metals. It exhibited maximum adsorption capacities of 12.76 mg g-1, 14.09 mg g-1, 17.00 mg g-1, and 33.81 mg g-1 for Cd(ii) at the activation temperature of 300, 450, 600 and 750 °C, respectively. Through competitive adsorption for Cd(ii)and Pb(ii), the ST thermally activated at 750 °C exhibited maximum equilibrium adsorption capacities of 24.65 mg g-1, 25.91 mg g-1, and 30.94 mg g-1 for Cd(ii) uptake at 298.1 K, 308.1 K and 318.1 K, respectively, whereas it exhibited values of 91.59 mg g-1, 101.32 mg g-1, and 112.19 mg g-1 for Pb(ii) removal. The adsorption capacities of Cd(ii) and Pb(ii) both decrease with the addition of the other heavy metal cations, indicating that the adsorption is hindered by the competitive adsorption and the adsorption active sites on the mineral surface are readily exchangeable. The adsorption of Cd(ii) and Pb(ii) followed the pseudo-second order kinetics model well. In addition, the Langmuir model could accurately describe the adsorption isotherms. Based on the results of characterization with TEM, XRD and XPS, the adsorption mechanisms could be primarily explained as formation of Cd(OH)2 and CdCO3 as well as Cd(HCO3)2 precipitation on the surface of ST. These characteristics of ion-exchange and the adsorptive property for ST modified allow it to be widely used in artificial wetland landfill and environmental protection.

Novel molecular imprinted polymers over magnetic mesoporous silica microspheres for selective and efficient determination of protocatechuic acid in Syzygium aromaticum.

Improving sites accessibility can increase the binding efficiency of molecular imprinted polymers (MIPs). In this work, we firstly synthesized MIPs over magnetic mesoporous silica microspheres (Fe3O4@mSiO2@MIPs) for the selective recognition of protocatechuic acid (PCA). The resulting Fe3O4@mSiO2@MIPs were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectrometer (FT-IR), thermo-gravimetric analysis (TGA), Brunauer-Emmett-Teller (BET), and vibration sample magnetometer (VSM), and evaluated by adsorption isotherms/kinetics and competitive adsorption. The maximum adsorption capacity of PCA on Fe3O4@mSiO2@MIPs was 17.2mg/g (2.3 times that on Fe3O4@SiO2@MIPs). In addition, Fe3O4@mSiO2@MIPs showed a short equilibrium time (140min), rapid magnetic separation (5s) and high stability (retained 94.4% after six cycles). Subsequently, Fe3O4@mSiO2@MIPs were successfully applied for the selective and efficient determination of PCA (29.3µg/g) from Syzygium aromaticum. Conclusively, we combined three advantages into Fe3O4@mSiO2@MIPs, namely, Fe3O4 core for quick separation, mSiO2 layer for enough accessible sites, and surface imprinting MIPs for fast binding and excellent selectivity, to extract PCA from complex systems.

Comparative Performance of Three Magnesium Compounds on Thermal Degradation Behavior of Red Gum Wood.

The effect of basic magnesium carbonate (BMC), magnesium hydroxide (MH), and magnesium chloride hydrate (MCH) on thermal degradation of red gum wood was studied using cone calorimetry, Thermogravimetric-differential scanning calorimetry (TG-DSC) analysis, and X-ray diffraction (XRD) characterization. The results showed common fire retardation actions of the three compounds by releasing incombustible gas and/or water vapor to dilute combustible gas in the flaming zone, and by converting to MgO, which had a satisfactory protective wall effect on the wood. Individually, BMC absorbed heat from the wood at the pre-decomposition stage and, thus, slowed down wood pyrolysis process. It slightly increased the char yield by charring in both the charring stage and the char calcination stage. MH lost water at about 270 °C, close to the temperature at which wood thermally degraded. MH rendered wood char quickly, and the compact char layer impeded further carbonization and burning of inner wood. MCH promoted charring with Mg2+ as a Lewis acid, and increased wood char yield. MCH also released Cl· free radical and HCl at 167 °C, which easily coordinated with combustion reaction radical, and slowed down, even inhibited, the combustion chain reaction.