Binder-free all-carbon composite supercapacitors.

Carbon-based electrode materials have widely been used in supercapacitors. Unfortunately, the fabrication of the supercapacitors includes a polymeric binding material that leads to an undesirable addition of weight along with an increased charge transfer resistance. Herein, binder-free and lightweight electrodes were fabricated using powder processing of carbon nanofibers (CNFs) and graphene nanoplatelets (GNPs) resulting in a hybrid all-carbon composite material. The structural, morphological, and electrochemical properties of the composite electrodes were studied at different concentrations of GNPs. The specific capacitance (Cs) of the CNFs/GNPs composite was improved by increasing the concentration of GNPs. A maximum Cs of around 120 F g-1was achieved at 90 wt% GNPs which is around 5-fold higher in value than the pristine CNFs in 1 M potassium hydroxides (KOH), which then further increased to 189 F g-1in 6 M KOH electrolyte. The energy density of around 20 Wh kg-1with the corresponding power density of 340 W kg-1was achieved in the supercapacitor containing 90 wt% GNPs. The enhanced electrochemical performance of the composite is related to the presence of a synergistic effect and the CNFs establishing conductive/percolating networks. Such binder-free all-carbon electrodes can be a potential candidate for next-generation energy applications.

An investigation of Ca-doped MgO nanoparticles for the improved catalytic degradation of thiamethoxam pesticide subjected to visible light irradiation.

The remediation of pesticides from the environment is one of the most important technology nowadays. Herein, magnesium oxide (MgO) nanoparticles and calcium-doped magnesium oxide (Ca-doped MgO) nanoparticles were synthesized by the co-precipitation method and were used for the degradation of thiamethoxam pesticide in aqueous media. Characterization of the MgO and Ca-doped MgO nanoparticles were performed by XRD, SEM, EDX, and FT-IR analysis to verify the synthesis and variations in chemical composition. The band gap energy and crystalline size of MgO and Ca-doped MgO nanoparticles were found to be 4.8 and 4.7 eV and 33 and 34 nm respectively. The degradation of thiamethoxam was accomplished regarding the impact of catalyst dosage, contact time, temperature, pH, and initial pesticide concentration. The pH study indicates that degradation of thiamethoxam depends on pH and maximum degradation (66%) was obtained at pH 5 using MgO nanoparticles. In contrast, maximum degradation (80%) of thiamethoxam was observed at pH 8 employing Ca-doped MgO nanoparticles. The percentage degradation of thiamethoxam was initially increasing but decreased at higher doses of the catalysts. The degradation of the pesticide was observed to be increased with an increase in contact time while high at room temperature but decreased with a temperature rise. The effect of the initial concertation of pesticide indicates that degradation of pesticide increases at low concentrations but declines at higher concentrations. This research study reveals that doping of MgO nanoparticles with calcium enhanced the degradation of thiamethoxam pesticide in aqueous media.

Enhancement of photocatalytic activity of Ba-doped CoO for degradation of Emamectin benzoate in aqueous solution.

The present study was focused on the preparation of cobalt oxide (CoO) and barium-doped cobalt oxide (Ba-doped CoO) by following the co-precipitation method for the degradation of Emamectin benzoate pesticide in the aqueous medium. The prepared catalysts were characterized using SEM, EDX, and XRD to confirm the formation of catalysts and to observe the variation in the composition of catalysts during the degradation study. It can be suggested from the results of SEM, EDX, XRD, and FTIR analyses that Ba atom has successfully incorporated in the crystalline structure of CoO. The degradation of Emamectin benzoate pesticide was studied under the influence of different factors like solution pH, the dose of catalyst, contact time, temperature, and initial concentration of pesticide. It was observed that solution pH affects the degradation of the pesticide, and maximum degradation (23% and 54%) was found at pH 5.0 and 6.0 using CoO and Ba-doped CoO, respectively. The degradation of pesticides was found to be increased continuously (27-35% in case of CoO while 47-58% in case Ba-doped CoO) with the time of contact. However, the degradation was found to be decreased (23-3% in case of CoO while 47-44% in case Ba-doped CoO) with an increase in temperature. Likewise, in the beginning, degradation was observed to be increased up to some extent with the dose of catalyst and initial concentration of pesticide but started to decrease with further augmentation in the dose of catalyst and initial concentration of pesticide. It may be concluded from this study that doping of Ba considerably enhanced the photocatalytic ability of CoO for Emamectin benzoate pesticide.

Synthetic Potential of Regio- and Stereoselective Ring Expansion Reactions of Six-Membered Carbo- and Heterocyclic Ring Systems: A Review.

Ring expansion reactions fascinate synthetic chemists owing to their importance in synthesizing biologically active compounds and their efficacy in medicinal chemistry. The present review summarizes a number of synthetic methodologies, including stereoselective and regioselective pathways adopted by scientists, for framing medium- to large-size carbo- and heterocycles involving lactams, lactone, azepine and azulene derivatives via ring expansion of six-membered carbo- and heterocycles that have been reported from 2007-2022. Numerous rearrangement and cycloaddition reactions involving Tiffeneau-Demjanov rearrangement, Aza-Claisen rearrangement, Schmidt rearrangement, Beckmann rearrangement, etc., have been described in this regard.

Mixed micellar solubilization for procion blue MxR entrapment and optimization of necessary parameters for micellar enhanced ultrafiltration.

In this study, micellar enhanced ultrafiltration, MEUF, being an active methodology, has been employed to remove Procion Blue MxR (PBM) from synthetic effluent. MEUF is being applied to reduce the toxicity level of aqueous system using the micellar media of cationic surfactants i.e. Cetyl trimethylammonium bromide (CTAB) and cetylpyridinium chloride (CPC). Subsequently, the effect of addition of nonionic surfactant, Triton X-100 (TX-100), on solubilizing power of cationic surfactants is investigated. The values of partition coefficient and free energy of partition reflect the extent of interaction of the dye with the surfactants. Initially molecules of pollutants i.e. dye form ion pairs with ionic surfactants and, later on, the same is incorporated within micelle. Maximum value of free energy of partition ΔGp has been found to be -55.49 kJmol-1 and -50.43 kJmol in the presence of CPC and CTAB, respectively. The size of pollutant, thus, increases and, consequently, can be easily filtered. The effect of various factors i.e. concentration of surfactant, concentration of electrolyte (NaCl), transmembrane pressure, revolutions per minute (RPM) and pH, have been investigated to find the optimum conditions for maximum removal of PBM from aqueous system. The efficiency of MEUF has been assessed by calculating the values of rejection percentage and permeate flux. Both the surfactants were observed as strong candidates for PBM encapsulation but overall, maximum rejection percentage (R%) of 96.90% was attained by CPC.

Biosorption of metribuzin pesticide by Cucumber (Cucumis sativus) peels-zinc oxide nanoparticles composite.

Herein, a biosorbent was prepared from cucumber peels modified with ZnO nanoparticles (CPZiONp-composite) for the biosorption of metribuzin. Characterization of the composite was accomplished using FTIR, SEM, EDX, surface area pore size analyzer and pH of point of zero charge (pHpzc). Biosorption study was executed in batch concerning the impact of pH, composite dose, contact time, initial metribuzin concentration and temperature. The biosorption depends on pH and maximum biosorption was acquired at pH 3.0. Surface chemistry of the composite was studied by determining the pHpzc and was found to be 6.1. The biosorption nature was investigated using isotherms and was assessed that Freundlich isotherm is well suited for the fitting of the biosorption data owing to the highest R2. The maximum biosorption capacity of CPZiONp-composite was found to be 200 mg g-1. The biosorption data were fitted in to different kinetic models and the outcomes suggesting that pseudo second order is a satisfactory model to interpret the biosorption data owing to the highest R2. Thermodynamic parameters for instance entropy, enthalpy and Gibbs free energy were computed and revealed that biosorption of metribuzin onto CPZiONp-composite is spontaneous and exothermic process.

Revisiting the Synthesis of Betti Bases: Facile, One-pot, and Efficient Synthesis of Betti Bases Promoted by FeCl3•6H2O.

BACKGROUND: Betti bases are pharmaceutically and synthetically important scaffolds due to their diverse range of biological activities and applications in key synthetic transformations in organic synthesis. OBJECTIVE: This work has been sought to contribute to the development, design, and implementation of an improved green methodology with higher atom economy and lower E-factor values for the synthesis of Betti bases. METHODS: To realize our objectives, we screened out different catalysts and reaction conditions using one-pot multicomponent modified Mannich reaction/Betti reaction by employing 2-naphthol, benzaldehyde and pyrrolidine as model substrates. RESULTS: The developed methodology afforded functionalized Betti bases in 60-100% yields via FeCl3•6H2O catalyzed one-pot multi-component Betti reaction under neat conditions at 110 °C (5-15 min) using several aromatic aldehydes and secondary amines. CONCLUSION: A facile synthetic methodology with higher atom economy and lower E-factor values to synthesize Betti bases via FeCl3•6H2O catalyzed one-pot multicomponent Betti reaction of 2-naphthol, aromatic aldehydes, and secondary amines under neat conditions at 110 °C has been reported. The developed methodology offers various advantages, such as excellent yields (60-100%), short reaction time (5-15 min), wide substrate scope (12 examples), green reaction conditions, use of readily available catalyst, and easy purification (without column chromatography).

Photocatalysis: an effective tool for photodegradation of dyes-a review.

The disposal of dye-contaminated wastewater is a major concern around the world for which a variety of techniques are used for its treatment. The photocatalytic treatment of dye-contaminated wastewater is one of the treatment methods. Semiconductor-assisted photocatalytic treatment of dye-contaminated wastewater has gained pronounced attention recently. This review outlines the recent advancements in the photocatalytic treatment of dye-contaminated wastewater. The photocatalytic degradation of dyes follows three types of mechanisms: (1) dye sensitization through charge injection, (2) indirect dye degradation through oxidation/reduction, and (3) direct photolysis of dye. Several experimental parameters like initial concentration of dyes, pH, and catalyst dosage significantly affect the photocatalytic degradation of dyes. The photocatalytic materials can be categorized into three generations. The single-component (e.g., ZnO, TiO2) and multiple component semiconductor metal oxides (e.g., ZnO-TiO2, Bi2O3-ZnO) are categorized as first-generation and second-generation photocatalysts, respectively. The photocatalysts dispersed on an inert solid substrate (e.g., Ag-Al2O3, ZnO-C) are classified as third-generation photocatalysts. Finally, we reviewed the challenges that affect the photocatalytic degradation of dyes.

Mechanisms of halosulfuron methyl pesticide biosorption onto neem seeds powder.

The current investigation was designed to remove halosulfuron methyl from aqueous media by means of neem seed powder (NSP) in batch modes. Characterizations of NSP were carried out by using EDX, SEM, FTIR, point of zero charge and surface analysis. Optimum operation conditions were scrutinized by studying the influence of different factors like solution pH, dose of NSP, contact time, initial halosulfuron methyl concentration and temperature. Result indicates the dependency of the removal of halosulfuron methyl on solution pH and maximal removal (54%) was achieved in acidic medium (i.e. pH 3.0). To identify the chemical surface of NSP, point of zero charge of NSP was determined and was found to be 6.5 which imply that the surface of NSP is positively charged below pH 6.6 and favored the anionic sorption. Kinetics of halosulfuron methyl were demonstrated well by pseudo second order due to highest R2 (0.99) owing to the nearness between experimental and calculated sorption capacities. Isotherm results imply that Langmuir was found to the principal model to explain the removal of halosulfuron methyl and maximum monolayer sorption capacity was determined to be 200 mg g-1. Thermodynamic parameters like ΔH°, ΔG° and ΔS° were calculated from van't Hoff plot and were found negative which suggest that removal of halosulfuron methyl is exothermic and spontaneous at low temperature. These outcomes insinuate that neem seed power may be a valuable, inexpensive and ecofriendly biosorbent for the removal of pesticides.

Controlling the Energy-Level Alignment of Silicon Carbide Nanocrystals by Combining Surface Chemistry with Quantum Confinement.

The knowledge of band edges in nanocrystals (NCs) and quantum-confined systems is important for band alignment in technologically significant applications such as water purification, decomposition of organic compounds, water splitting, and solar cells. While the band energy diagram of bulk silicon carbides (SiCs) has been studied extensively for decades, very little is known about its evolution in SiC NCs. Moreover, the interplay between quantum confinement and surface chemistry gives rise to unusual electronic properties and remains barely understood. Here, we report for the first time the complete band energy diagram of SiC NCs synthesized such that they span the regime from strong to intermediate to weak quantum confinement. The absolute positions of the highest occupied (HOMO) and lowest unoccupied (LUMO) molecular orbitals show clear size dependence. While the HOMO level follows the expected behavior for quantum-confined electronic states, the LUMO energy shifts below the bulk conduction band minimum, which cannot be explained by a simple quantum confinement caused by the size effect. We show that this effect is a result of the interplay between quantum confinement and the formation of surface states due to partial and site-selective oxygen passivation.

Size-dependent stability of ultra-small α-/ß-phase tin nanocrystals synthesized by microplasma.

Nanocrystals sometimes adopt unusual crystal structure configurations in order to maintain structural stability with increasingly large surface-to-volume ratios. The understanding of these transformations is of great scientific interest and represents an opportunity to achieve beneficial materials properties resulting from different crystal arrangements. Here, the phase transformation from α to ß phases of tin (Sn) nanocrystals is investigated in nanocrystals with diameters ranging from 6.1 to 1.6 nm. Ultra-small Sn nanocrystals are achieved through our highly non-equilibrium plasma process operated at atmospheric pressures. Larger nanocrystals adopt the ß-Sn tetragonal structure, while smaller nanocrystals show stability with the α-Sn diamond cubic structure. Synthesis at other conditions produce nanocrystals with mean diameters within the range 2-3 nm, which exhibit mixed phases. This work represents an important contribution to understand structural stability at the nanoscale and the possibility of achieving phases of relevance for many applications.

Evaluation of Sorption Mechanism of Pb (II) and Ni (II) onto Pea (Pisum sativum) Peels.

The present study was carried out to know the sorption mechanism of Pb (II) and Ni (II) in aqueous solution using pea peels under the influence of sorbent dose, pH, temperature, initial metal ion concentration and contact time. SEM and FTIR were used for characterization of pea peels. The study showed that solution pH affects sorption process and the optimum pH for Pb (II) was 6.0 while for that of Ni (II) was 7.0. Pseudo-second order kinetic model was found to be the most suitable one to explain the kinetic data not only due to high value of R2 (>0.99) but also due to the closeness of the experimental sorption capacity values to that of calculated sorption capacity values of pseudo second order kinetic model. It can be seen from the results that Freundlich isotherm explains well the equilibrium data (R2>0.99). Sorption capacity of pea peels was 140.84 and 32.36 for Pb (II) and Ni (II) mg g-1 respectively. The positive value of ΔH° and negative values of ΔG° suggest that sorption of Pb (II) and Ni (II) onto pea peels is an endothermic and spontaneous process respectively.

Direct growth of polyaniline chains from N-doped sites of carbon nanotubes.

Polymer grafting from graphitic carbon materials has been pursued for several decades. Unfortunately, currently available methods mostly rely on the harsh chemical treatment of graphitic carbons which causes severe degradation of chemical structure and material properties. A straightforward growth of polyaniline chain from the nitrogen (N)-doped sites of carbon nanotubes (CNTs) is presented. N-doping sites along the CNT wall nucleate the polymerization of aniline, which generates seamless hybrids consisting of polyaniline directly grafted onto the CNT walls. The resultant materials exhibit excellent synergistic electrochemical performance, and can be employed for charge collectors of supercapacitors. This approach introduces an efficient route to hybrid systems consisting of conducting polymers directly grafted from graphitic dopant sites.