Ultrasonic assisted synthesis of nanocrystalline cellulose as support and reducing agent for Ag nanoparticles: green synthesis and novel effective nanocatalyst for degradation of organic dyes

In this study, nanocrystalline cellulose (NCC) prepared from microcrystalline cellulose using high‐intensity ultrasonication as mechanical method without any chemical treatment. The obtained NCC with around 30–50 nm diameters, utilized as support, reducing and stabilizing agent for in‐situ green and eco‐friendly synthesis of silver nanoparticles (Ag NPs). The catalytic activity of composite was examined for degradation of environmental pollutants. The structure of as‐synthesized composite (Ag@NCC) was characterized by ultraviolet–visible spectroscopy (UV–vis), field emission scanning electron microscopy (FE‐SEM); Transmission electron microscopy (TEM); Energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FT‐IR), X‐ray diffraction (XRD) and thermogravimetric analysis (TGA). The results of the catalytic reaction experiments showed that spherically shaped silver nanoparticles of around 20 nm distributed on the surface of nanocellulose demonstrated high catalytic efficiency towards the removal of methyl orange (MO) and 4‐nitrophenol (4‐NP).     

Molecular Design Strategy for Orange Red Thermally Activated Delayed Fluorescence Emitters in Organic Light-Emitting Diodes (OLEDs)

Pure organic molecules based thermally activated delayed fluorescence (TADF) emitters have been successfully developed in recent years for their propitious application in highly efficient organic light emitting diodes (OLEDs). In the case of orange red emitters, the non-radiative process is known to be a serious issue due to its lower lying singlet energy level. However, recent studies indicate that there are tremendous efforts put to develop efficient orange red TADF emitters. In addition, the external quantum efficiency (EQE) of heteroaromatic based orange red TADF OLEDs surpassed 30 %. Such heteroaromatic type emitters showed wide emission spectra; therefore, more attention is being paid to develop highly efficient orange red TADF emitters along with good color purity. Herein, the recent progress of orange red TADF emitters based on molecular structures, such as cyanobenzene, heteroaromatic, naphthalimide, and boron-based acceptors, are reviewed. Further, our insight on these acceptors has been provided by their photophysical studies and device performances. Future perspectives of orange red TADF emitters for real practical applications are discussed.     

g-C3N4催化石墨化碳质材料的制备及光催化性能研究

通常采用以氢氧化物作为造孔剂,过渡金属硝酸盐或氯化物作为石墨化催化剂的传统两步法策略制备多孔石墨化碳材料。然而制备过程中多涉及有毒和腐蚀性试剂,且多步骤的过程耗时较长。本文以双氰胺为原料通过热缩聚反应得到g-C₃N₄,采用高铁酸钾为催化剂一步法实现g-C₃N₄的同步碳化-石墨化,并研究其光催化性能。与传统的两步法相比,该方法耗时少、效率高、无污染。与初始的g-C₃N₄材料相比,石墨化g-C₃N₄衍生碳质材料不仅显著改善了可见光的吸收,而且大大增强了光催化活性。研究了不同石墨化温度对g-C₃N₄衍生碳质材料在可见光下降解甲基橙溶液的影响。700 ℃下制备的衍生碳质材料的降解率为12.4 mg/g。光电化学测试结果表明,多孔g-C₃N₄衍生碳质材料的光生载流子密度、电荷分离和光电流(提高了5.4倍)均得到显著提高。因此,该简便、灵活方法为提高g-C₃N₄衍生碳质材料的吸附和光催化性能提供了一种有前景的、高效的途径。     

Aggregation of Electrochemically Active Conjugated Organic Molecules and Its Impact on Aqueous Organic Redox Flow Batteries

Molecule aggregation in solution is acknowledged to be universal and can regulate the molecule's physiochemical properties, which however has been rarely investigated in electrochemistry. Herein, an electrochemical method is developed to quantitatively study the aggregation behavior of the target molecule methyl viologen dichloride. It is found that the oxidation state dicationic ions stay discrete, while the singly-reduced state monoradicals yield a concentration-dependent aggregation behavior. As a result, the molecule's energy level and its redox potential can be effectively regulated. This work does not only provide a method to investigate the molecular aggregation, but also demonstrates the feasibility to tune redox flow battery's performance by regulating the aggregation behavior.     

Efficient removal of anionic dye by protonated APTES modified hydrochar: The effect of cold-activation

The study focused on determining the effect of acidic and basic cold activation on hydrochar (HC) for the removal of methyl orange (MO). HC was prepared by hawthorn seeds (HS) under hydrothermal carbonization. HC was cold-activated with HCl and NaOH, respectively, and they were grafted with aminopropyltriethoxysilane (APTES) and protonated to obtain AHC-N⁺ (acid-activated and modified HC) and BHC-N⁺ (base-activated and modified HC) to determine the effect of acidic and basic activation. They were characterized by elemental analysis, IR, thermal analysis, zeta potential, N₂ adsorption–desorption measurements, and SEM–EDX analysis. The prepared adsorbents displayed MO adsorption due to abundant protonated amine groups. BHC-N⁺ showed higher MO adsorption than AHC-N⁺. The result showed that more protonated APTES groups grafted on the surface of HC via NaOH activation. The obtained data had a good fitting with the Langmuir isotherm and pseudo-second-order kinetic. The maximum adsorption capacity of BHC-N⁺ was 250.38 mg g⁻¹. The adsorption mechanism could be attributed to the electrostatic interactions between MO and protonated amine groups of APTES and hydrogen bonding.     

Pushing the Upper Limit of Nucleophilicity Scales by Mesoionic N-Heterocyclic Olefins

A series of mesoionic, 1,2,3-triazole-derived N-heterocyclic olefins (mNHOs), which have an extraordinarily electron-rich exocyclic CC-double bond, was synthesized and spectroscopically characterized, in selected cases by X-ray crystallography. The kinetics of their reactions with arylidene malonates, ArCH=C(CO₂Et)₂, which gave zwitterionic adducts, were investigated photometrically in THF at 20 °C. The resulting second-order rate constants k₂(20 °C) correlate linearly with the reported electrophilicity parameters E of the arylidene malonates (reference electrophiles), thus providing the nucleophile-specific N and s_N parameters of the mNHOs according to the correlation lg k₂(20 °C)=s_N(N+E). With 21<N<32, the mNHOs are much stronger nucleophiles than conventional NHOs. Some mNHOs even excel the reactivity of mono- and diacceptor-substituted carbanions. It is exemplarily shown that the reactivity parameters thus obtained allow to calculate the rate constants for mNHO reactions with further Michael acceptors and predict the scope of reactions with other electrophilic reaction partners including carbon dioxide, which gives zwitterionic mNHO-carboxylates. The nucleophilicity parameters N correlate linearly with a linear combination of the quantum-chemically calculated methyl cation affinities and buried volumes of mNHOs, which offers a valuable tool to tailor the reactivities of strong carbon nucleophiles.     

Efficient photocatalytic degradation of methyl orange dye using facilely synthesized α-Fe2O3 nanoparticles

In this paper, α-Fe₂O₃ nanoparticles were fabricated via the combustion process using glucose and sucrose as organic fuels for the first time. The fabricated products were characterized using XRD, FT-IR, HR-TEM, and UV–vis spectrophotometer. The average crystallite size of the α-Fe₂O₃ samples, which were synthesized using glucose and sucrose fuels, is 27.25 and 6.13 nm, respectively. The HR-TEM images confirmed the presence of spherical and irregular shapes with an average diameter of 31.92 and 8.83 nm for the α-Fe₂O₃ samples, which were synthesized using glucose and sucrose fuels, respectively. The optical energy gap of the α-Fe₂O₃ samples, which were synthesized using glucose and sucrose fuels, is 2.00 and 2.48 eV, respectively. Additionally, the synthesized α-Fe₂O₃ samples were employed as a photocatalyst for the degradation of methyl orange dye under UV irradiations in the absence and presence of hydrogen peroxide. The optimum pH, irradiation time, and dose of α-Fe₂O₃ that achieved the highest degradation efficiency in the presence of hydrogen peroxide (82.17 % in the case of using an α-Fe₂O₃ sample which was synthesized using glucose or 95.31 % in the case of using an α-Fe₂O₃ sample which was synthesized using sucrose) are 3, 100 min, and 0.05 g, respectively.     

Infrared spectra and UV-induced photochemistry of methyl aziridine-2-carboxylate isolated in argon and xenon matrices

Methyl aziridine-2-carboxylate (MA2C) has been isolated in low temperature argon and xenon matrices and its structure and photochemistry were studied by FTIR spectroscopy. The reactant as well as the main photoproducts were characterized by comparison of their experimental IR spectra with spectra calculated at the DFT(B3LYP)/6-311++G(d,p) level. The theoretical calculations predicted the existence of two low energy MA2C conformers, differing by the orientation of the OCCN dihedral angle. Both conformers were identified in the studied matrices. Both narrowband tunable and broadband UV irradiations of matrix-isolated MA2C yielded isomerization photoproducts resulting from cleavage of the CC and weakest CN bonds of the aziridine ring. Irradiation with UV laser-light at λ = 235 nm resulted in the formation of the E isomer of methyl 2-(methylimino)-acetate (MMIA) and the Z isomer of methyl 3-iminopropanoate (M3IP). Subsequent irradiation at 290 nm led to observation of new bands resulting from E → Z isomerization of MMIA, while bands due to M3IP remained unchanged. The photoproduced Z isomer of MMIA could be subsequently consumed upon higher-wavelength irradiation (λ = 330 nm). The initially produced MMIA conformer was found to obey the nonequilibrium of excited rotamers (NEER) principle. No photoproducts resulting from the cleavage of the strongest CN bond of the MA2C aziridine ring were observed, nor that of methyl 3-aminoacrylate (M3AA), which could in principle be obtained also by cleavage of the weakest CN bond of the MA2C aziridine ring, but would imply a different H-atom migration simultaneous with the ring opening process. These results indicate that both the differential electronic characteristics of the CN bonds of substituted aziridine rings and the type of required H-atom migration are major factors in determining the specific photochemistries of substituted aziridines. Photofragmentation reactions of MA2C were also observed, through identification of various related products, e.g., acetonitrile, methanol, methane, CO and CO₂.     

Adsorption of methyl orange on nanoparticles of a synthetic zeolite NaA/CuO

CuO supported on an NaA zeolite (CuO/NaA) was prepared with an NaA zeolite through the ion-exchange (CuO/NaA) method. The morphology and the physicochemical properties of the prepared samples were investigated by XRD, MEB, and EDS. The various parameters, such as contact time, catalyst dose, initial dye concentration, initial pH, and temperature, influencing the adsorption of methyl orange (MO) were optimized. The MO adsorption equilibrium was reached after 240 min of contact time. Removal of MO is better at neutral pH than in acidic and alkaline solutions. Among the tested models, the equilibrium adsorption data are well fitted by the Langmuir isotherm. The adsorption kinetics is best described by the pseudo-second-order model. The evaluation of the thermodynamic parameters, i.e. ΔG^o, ΔH^o, and ΔS^o, revealed that MO adsorption was spontaneous, while the activation energy (20.98 kJ/mol) indicates a physical adsorption. The photodegradation of MO decreased from 100 mg/L down to 2 mg/L when the solution is exposed to visible light.     

Removal of Anionic Dyes from Aqueous Solution with Layered Cationic Aluminum Oxyhydroxide

It is highly desired yet challenged to find an adsorbent with low cost and excellent performance in the removal of organic dyes from aqueous solution. Here we reported that a layered cationic aluminum oxyhydroxide material hydrothermally synthesized from the low-cost source materials of AlCl₃∙6H₂O, CaO and H₂O, known as JU-111, can meet such criterion in removing methyl orange(MO) and Congo red(CR). JU-111 shows fast adsorption kinetics[especially for CR(15 s)] and high adsorption capacity(MO:>1000 mg/g; CR:>2900 mg/g), surpassing most of the reported adsorbents. Comprehensive characterizations of the adsorption process of MO and CR revealed that both adsorptions were achieved via the anion exchange process. The characteristics of extremely low cost and excellent performance render JU-111 great potential in the practical applications in the removal of anionic dyes.