Influence of fluorine substituents on the electronic properties of selenium-N-heterocyclic carbene compounds

N-heterocyclic carbenes (NHCs) are common ancillary ligands in organometallic compounds that are used to alter the electronic and steric properties of a metal centre. To date, various NHCs have been synthesised with different electronic properties, which can be done by modifying the backbone or changing the nitrogen substituents group. This study describes a systematic modification of NHCs by the inclusion of fluorine substituents and examines the use of selenium-NHC compounds to measure the π-accepting ability of these fluorinated NHC ligands. Evaluation of the 77Se NMR chemical shifts of the selenium adducts reveals that fluorinated NHCs have higher chemical shifts than the non-fluorinated counterparts, IMes and IPh. Higher 77Se NMR chemical shifts values indicate a stronger π-accepting ability of the NHC ligands. The findings of this study suggest that the presence of fluorine atoms has increased the π-accepting ability of the corresponding NHC ligands. This work supports the advantage of the 77Se NMR chemical shifts of selenium-NHC compounds for assessing the influence of fluorine substituents on NHC ligands

Insight into biomass upgrade: a review on hydrogenation of 5-hydroxymethylfurfural (HMF) to 2,5-dimethylfuran (DMF)

Recent developments in the transformation of biobased 5-hydroxymethylfurfural (HMF) into a potential liquid fuel, 2,5-dimethylfuran (DMF), are summarised. This review focuses briefly on the history of HMF conversion to DMF in terms of the feedstock used and emphasises the ideal requirements in terms of the catalytic properties needed in HMF transformation into DMF. The recent state of the art and works on HMF transformation into DMF are discussed in comparison to noble metals and non-noble metals as well as bimetallic catalysts. The effect of the support used and the reaction conditions are also discussed. The recommendations for future work and challenges faced are specified

Optimization of glass transition temperature and pot life of epoxy blends using response surface methodology (RSM)

The aim of this work was to improve the processability of triglycidyl-p-aminophenol (TGPAP) epoxy resin. To achieve this improvement, a diluent, the diglycidyl ether of bisphenol F (DGEBF or BPF), was added to TGPAP, and the blended epoxy was then cured with 4, 4′-diaminodiphenyl sulfones (DDS). A response surface methodology (RSM) was used, with the target response being to achieve a blended resin with a high glass transition temperature (Tg) and maximum pot life (or processing window, PW). Characterization through dynamic mechanical thermal analysis (DMTA) and using a rheometer indicated that the optimum formulation was obtained at 55.6 wt.% of BPF and a stoichiometric ratio of 0.60. Both values were predicted to give Tg at 180 °C and a processing window of up to 136.1 min. The predicted values were verified, with the obtained Tg and processing window (PW) being 181.2 ± 0.8 °C and 140 min, respectively, which is close to the values predicted using the RSM

Efficient catalytic reduction of 4-Nitrophenol using Copper(II) complexes with N,O-chelating schiff base ligands

The reduction of 4-nitrophenol to 4-aminophenol by sodium borohydride was used as a model to test the catalytic activity of copper(II) complexes containing N,O-chelating Schiff base ligands. In this study, a series of copper(II) complexes containing respective Schiff base ligands, N′-salicylidene-2-aminophenol (1), N′-salicylidene-2-aminothiazole (2), and N,N′-bis(salicylidene)-o-phenylenediamine (3), were synthesized and characterized by elemental analysis, Fourier transform infrared (FT-IR), UV-Visible (UV-Vis) and electron paramagnetic resonance (EPR) spectroscopies. The results from the 4-nitrophenol reduction showed that 3 has the highest catalytic activities with 97.5% conversion, followed by 2 and 1 with 95.2% and 90.8% conversions, respectively. The optimization of the catalyst amount revealed that 1.0 mol% of the catalyst was the most optimized amount with the highest conversion compared to the other doses, 0.5 mol% and 1.5 mol%. Recyclability and reproducibility tests confirmed that all three complexes were active, efficient, and possess excellent reproducibility with consistent catalytic performances and could be used again without a major decrease in the catalytic activity

Optimization of Glass Transition Temperature and Pot Life of Epoxy Blends Using Response Surface Methodology (RSM)

From MDPI via Jisc Publications RouterHistory: accepted 2021-09-22, pub-electronic 2021-09-27Publication status: PublishedFunder: Universiti Malaysia Pahang; Grant(s): RDU190324Funder: Ministry of Higher Education, Malaysia; Grant(s): RDU190324The aim of this work was to improve the processability of triglycidyl-p-aminophenol (TGPAP) epoxy resin. To achieve this improvement, a diluent, the diglycidyl ether of bisphenol F (DGEBF or BPF), was added to TGPAP, and the blended epoxy was then cured with 4, 4′-diaminodiphenyl sulfones (DDS). A response surface methodology (RSM) was used, with the target response being to achieve a blended resin with a high glass transition temperature (Tg) and maximum pot life (or processing window, PW). Characterization through dynamic mechanical thermal analysis (DMTA) and using a rheometer indicated that the optimum formulation was obtained at 55.6 wt.% of BPF and a stoichiometric ratio of 0.60. Both values were predicted to give Tg at 180 °C and a processing window of up to 136.1 min. The predicted values were verified, with the obtained Tg and processing window (PW) being 181.2 ± 0.8 °C and 140 min, respectively, which is close to the values predicted using the RSM

Optimization of glass transition temperature and pot life of epoxy blends using response surface methodology (RSM)

The aim of this work was to improve the processability of triglycidyl‐p‐aminophenol (TGPAP) epoxy resin. To achieve this improvement, a diluent, the diglycidyl ether of bisphenol F (DGEBF or BPF), was added to TGPAP, and the blended epoxy was then cured with 4, 4′‐diamino‐diphenyl sulfones (DDS). A response surface methodology (RSM) was used, with the target re‐sponse being to achieve a blended resin with a high glass transition temperature (Tg) and maximum pot life (or processing window, PW). Characterization through dynamic mechanical thermal analysis (DMTA) and using a rheometer indicated that the optimum formulation was obtained at 55.6 wt.% of BPF and a stoichiometric ratio of 0.60. Both values were predicted to give Tg at 180 °C and a processing window of up to 136.1 min. The predicted values were verified, with the obtained Tg and processing window (PW) being 181.2 ± 0.8 °C and 140 min, respectively, which is close to the values predicted using the RSM

Waste NR latex based-precursors as carbon source for CNTs eco-fabrications

In this work, the potential of utilizing a waste latex‐based precursor (i.e., natural rubber glove (NRG)) as a carbon source for carbon nanotube (CNT) fabrication via chemical vapor deposition has been demonstrated. Gas chromatography‐mass spectroscopy (GC‐MS) analysis reveals that the separation of the lightweight hydrocarbon chain from the heavier long chain differs in hydrocarbon contents in the NRG fraction (NRG‐L). Both solid NRG (NRG‐S) and NRG‐L samples contain >63% carbon, <0.6% sulfur and <0.08% nitrogen content, respectively, as per carbon‐nitrogen‐sulfur (CNS) analysis. Growth of CNTs on the samples was confirmed by Raman spectra, SEM and TEM images, whereby it was shown that NRG‐S is better than NRG‐L in terms of synthesized CNTs yield percentage with similar quality. The optimum vaporization and reaction temperatures were 350 and 800 °C, respectively, considering the balance of good yield percentage (26.7%) and quality of CNTs (ID/IG = 0.84 ± 0.08, diameter ≈ 122 nm) produced. Thus, utilization of waste NRG as a candi-date for carbon feedstock to produce value‐added CNTs products could be a significant approach for eco‐technology

SYNTHESIS, CHARACTERISATION AND CARBON DIOXIDE ADSORPTION DESORPTION OF SOLVOTHERMOLYSED DOLOMITE

In this work, carbon dioxide adsorption-desorption characteristics were evaluated on calcined raw dolomite, unsupported solvothermolysed dolomite and supported solvothermolysed dolomite. Solvothermolysis was employed to prepare the adsorbents by using three solvents, namely; ethanol, water and polyethylene glycol (PEG). Aluminium hydroxide wasintroduced as the support andthe variable studied was ratios of Al (OH)3to dolomite. Adsorbents were calcined at 400 °C, 800°C and 1100 °C for 2 hours in air. Sample characterizationwas done using X-ray diffraction (XRD), N2 adsorption-desorption isotherms and thermogravimetric analysis (TGA). Solvothermolysis by ethanol as solvent produced the lowest average crystal size and decomposed at the lowesttemperature (650°C) with the highest weight lost at 800°C (38%) compared to other samples at the same temperature. Solvothermolysed dolomite using ethanol with 1:2 molar ratio of Al(OH)3 to dolomite (1:2 t-e Al: dolomite) resulted in lowest average crystallite size among other supported solvothermolysed ratios. Calcination at 800°C leads to decomposition of dolomite into mixed oxides. The specific surface area increases with increasing calcination temperature up to 800°C. At 1100°C, the surface area slightly decreased a sign of possible sintering. The C02 adsorption desorption studies were performed by using temperature programmed desorption (TPD) and three isothermal adsorption temperatures were used; 100 °C, 200°C and 300°C respectively. At 100 °C the adsorption capacity of C02 is the highest for all samples compared to higher adsorption temperatures. The dolomite solvothermolysed and calcined at 800°C has the highest amount of C02 adsorbed at all temperatures. At 300°C, 1:2 t-e Al: dolomite has better adsorption capacity, about twice, than raw dolomite. This study successfully discovered that solvothermolysis of dolomite using ethanol as the solvent reduced the decomposition temperature of dolomite and produced an adsorbent with better porosity and high C02 adsorption capacity

SYNTHESIS, CHARACTERISATION AND CARBON DIOXIDE ADSORPTION DESORPTION OF SOLVOTHERMOLYSED DOLOMITE

In this work, carbon dioxide adsorption-desorption characteristics were evaluated on calcined raw dolomite, unsupported solvothermolysed dolomite and supported solvothermolysed dolomite. Solvothermolysis was employed to prepare the adsorbents by using three solvents, namely; ethanol, water and polyethylene glycol (PEG). Aluminium hydroxide wasintroduced as the support andthe variable studied was ratios of Al (OH)3to dolomite. Adsorbents were calcined at 400 °C, 800°C and 1100 °C for 2 hours in air. Sample characterizationwas done using X-ray diffraction (XRD), N2 adsorption-desorption isotherms and thermogravimetric analysis (TGA). Solvothermolysis by ethanol as solvent produced the lowest average crystal size and decomposed at the lowesttemperature (650°C) with the highest weight lost at 800°C (38%) compared to other samples at the same temperature. Solvothermolysed dolomite using ethanol with 1:2 molar ratio of Al(OH)3 to dolomite (1:2 t-e Al: dolomite) resulted in lowest average crystallite size among other supported solvothermolysed ratios. Calcination at 800°C leads to decomposition of dolomite into mixed oxides. The specific surface area increases with increasing calcination temperature up to 800°C. At 1100°C, the surface area slightly decreased a sign of possible sintering. The C02 adsorption desorption studies were performed by using temperature programmed desorption (TPD) and three isothermal adsorption temperatures were used; 100 °C, 200°C and 300°C respectively. At 100 °C the adsorption capacity of C02 is the highest for all samples compared to higher adsorption temperatures. The dolomite solvothermolysed and calcined at 800°C has the highest amount of C02 adsorbed at all temperatures. At 300°C, 1:2 t-e Al: dolomite has better adsorption capacity, about twice, than raw dolomite. This study successfully discovered that solvothermolysis of dolomite using ethanol as the solvent reduced the decomposition temperature of dolomite and produced an adsorbent with better porosity and high C02 adsorption capacity

Bifunctional ternary manganese oxide/vanadium oxide/reduced graphene oxide as electrochromic asymmetric supercapacitor

A bifunctional ternary manganese oxide/vanadium oxide/reduced graphene oxide (MnO2/V2O5/rGO) was developed for asymmetric electrochromic supercapacitor (EC-SC) application. The elemental mapping revealed uniformly distributed MnO2, V2O5 and rGO, depicting homogenous synthesis of the hybrid composite. The phase composition, vibration modes and valance state of the ternary composite were analyzed via X-ray diffraction (XRD), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) analysis, respectively. Interestingly, the as-prepared MnO2/V2O5/rGO composite disclosed tremendous Csp of 1403.5 F/g, which was higher compared to MnO2/V2O5 (801.1 F/g), V2O5 (613.1 F/g), MnO2 (126.7 F/g) and rGO (60.7 F/g). MnO2/V2O5/rGO that appeared in dark green switched its visual color to orange at the charged state, confirming the electrochromic property. The bifunctional manganese oxide/vanadium oxide/reduced graphene oxide//copper-based metal-organic framework/reduced graphene oxide (MnO2/V2O5/rGO//MrGO) asymmetrical EC-SC device revealed outstanding cycling stability (90.3% charge retention over 5000 cycles), tremendous specific capacitance (652.7 F/g) and maximum specific energy (60.4 Wh/kg). MnO2/V2O5/rGO//MrGO asymmetrical EC-SC device demonstrated reversible color changes from dark green to orange at the discharged and charged states, respectively. The significantly great electrochromic and supercapacitive performance revealed that MnO2/V2O5/rGO//MrGO is an outstanding electroactive candidate for the next generation of electrochromic supercapacitors