Journal of Chemical Sciences最新文献

This study examines the intricate thermal decomposition of sweet sorghum bagasse, an agricultural residue with significant potential as a renewable energy and biofuel feedstock. Both slow and flash pyrolysis has been conducted over a temperature range of 300–450°C and flash pyrolysis experiments were performed through analytical pyrolysis via Py-GC/MS to comprehensively assess the pyrolysis behaviour and elucidate the biomass degradation pathways. In the slow pyrolysis experiments, sweet sorghum bagasse underwent controlled thermal decomposition at different temperatures (300–450°C), allowing for the investigation of the influence of temperature on product yields and compositions. The evolved volatile compounds and biochar products were analyzed to determine the impact of temperature on biomass degradation. The results revealed that 400°C is the optimum pyrolysis temperature for maximizing valuable bio-oil production with approximately 42 wt.% yields with an overall conversion of 73%. Various characterization techniques were employed to analyze the slow pyrolysis products, including GC-MS, TGA, FTIR, SEM, and XRD. Flash pyrolysis was employed to provide a detailed understanding of the rapid biomass breakdown under extreme heating conditions with a heating rate of 20°C/ms to complement the slow pyrolysis findings. This technique elucidated the primary mechanisms responsible for the degradation of sweet sorghum bagasse, shedding light on the fragmentation patterns and the formation of vital intermediate compounds during flash pyrolysis. These insights into the transient phenomena occurring during pyrolysis provide valuable information for developing efficient and sustainable biomass conversion processes.

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The pyrolysis behaviour of sweet sorghum bagasse (SSB) is comprehensively assessed using TGA, slow pyrolysis via lab scale glass tubular reactor and flash pyrolysis via analytical tool Py-GC/MS from 300–450°C. The study reveals the potential use of SSB as a renewable energy and biofuel feedstock.

A novel organic fluorescent material, namely 2,6-di([1,1'-biphenyl]-4-yl)-4-(perfluorophenyl)hepta-1,6-diene-1,1,7,7-tetracarbonitrile (DBPDT), has been synthesized and characterized in this study. Due to the special molecular packing mode in the solid state, J-aggregation, DBPDT displayed red-shifted emission compared with that in dilute solution. In this study, it was found that DBPDT showed aggregation-induced enhanced emission (AIEE) and solvatochromic properties. Assisted by quantum chemistry calculations, optical response properties to external electric field (EEF) were investigated, where it was found that external electric field (EEF) would affect the structures and optical properties of DBPDT distinctly. The optical response characteristics of DBPDT can provide an alternative structure for constructing advanced photoelectric functional materials.

Graphical abstract

A novel organic fluorescent material, namely 2,6-di([1,1'-biphenyl]-4-yl)-4-(perfluorophenyl)hepta-1,6-diene-1,1,7,7-tetracarbonitrile (DBPDT), has been synthesized and characterized in this study. Assisted by quantum chemistry calculations, optical response properties to external electric field (EEF) were investigated, where it was found that external electric field (EEF) would affect the structures and optical properties of DBPDT distinctly.

In this study, the simultaneous synthesis of poly(methyl methacrylate-b-ε-caprolactone) block copolymer was fulfilled by atom transfer radical polymerization of methyl methacrylate and ring-opening polymerization of ε-caprolactone. The synthesis of poly(methyl methacrylate-b-ε-caprolactone) block copolymer was carried out by varying the amount of ε-caprolactone monomer, the amount of methyl methacrylate monomer, the amount of 2-(2-chloroethoxy) ethanol initiator, the amount of toluene solvent, and the polymerization time. The effects of these parameters on the reaction conditions were investigated. Fourier transform infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, and static light scattering methods were used for the characterization of the synthesized block copolymer. The surface images of the block copolymer were photographed with a scanning electron microscope instrument. In addition, thermal analysis of the synthesized block copolymer was performed using a thermogravimetric analyzer. These analyses prove the formation of the block copolymer structure.

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The simultaneous synthesis of poly(methyl methacrylate-b-ε-caprolactone) block copolymer was fulfilled by the atom transfer radical polymerization of methyl methacrylate and ring-opening polymerization of ε-caprolactone. The effects of the parameters on the polymerization reaction conditions were investigated. Thermal and spectroscopic measurements prove the formation of the block copolymer structure.

Thiols are ubiquitous compounds found in almost all spheres of life, viz: from simple matter to complex human body. It has widespread applications in diverse domains such as pharmaceuticals, materials, agricultural science, fire science, laser science, catalytic systems, reagent systems, and industry. Although all sulphur compounds encompass one or the other significant properties. However, thiols containing –SH bond are vital as they act as starting substrates for many chemical reactions, are directly present in the biological systems, are abundantly found in natural products, and exhibit profound chemical and biotechnological properties. For example, the –SH group can be easily manipulated to a range of other potent functionalities such as –S–S, –SO₂Cl₂, –SOCH₃, –SOCl₂, –SONH₂, –Cl, –NH₂, –OH, etc. In this view, this review focuses on reporting detailed synthetic methodologies giving access to thiols (–SH). For interesting reading, it has been categorised as follows: (i) via isothiouronium salts; (ii) catalytic preparation of thiols using H₂S; (iii) using silanethiol/disilathiane; (iv) using thiolacetic acid/thioacetates; (v) from xanthates; (vi) reaction of sodium thiocyanate; (vii) using sodium trithiocarbonates; (viii) using Lawesson’s reagent; (ix) using phosphorus decasulfide; (x) enzymatic method; and the rest of a methods are classified under miscellaneous section.

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Synthetic methodologies to form terminal –SH bonds using various reagent systems, viz; (i) isothiouronium salts; (ii) catalytic preparation using H₂S; (iii) silanethiol/disilathiane; (iv) thiolacetic acid/thioacetates; (v) xanthates; (vi) reaction of sodium thiocyanate; (vii) sodium trithiocarbonates; (viii) Lawesson’s reagent; (ix) phosphorus decasulfide and (x) few enzymatic methods.

Among the various Schiff bases, those containing 2,4-diaminotoluene as a primary amine and 2-hydroxy-4-methoxybenzaldehyde as a carbonyl compound are new and deserve special attention because their logical spectral properties find application in analytical chemistry as a smart probe. The new Schiff base has been synthesized to its pure crystalline form. It is characterized by single-crystal XRD, FT-IR, NMR, TGA, and mass spectrometry. We have studied the spectral properties of the Schiff base and its aluminium adduct by UV-vis and fluorescence spectroscopy and rationalized them by computational analysis. The Job's plot and mass spectrometry indicate the 1:1 binding ratio between the ligand and the Al³⁺ ion. The suitable binding constant value (8.329×10³ M^–1) leads to the development of Al³⁺ sensation by the Schiff base. The sensor has an appreciably low limit of detection value of 7.638×10^–9(M), i.e., 0.00163 ppm for Al³⁺. The logical behaviour of the probe (NAND-type molecular logic gate with two inputs, Al³⁺ and EDTA) leads to the development of a renewable aluminium testing kit.

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The synthesis of poly(4-vinylbenzyl-g-β-butyrolactone) (poly(VB-g-BL)) graft copolymer was carried out by “click” chemistry of terminal azido poly(4-vinylbenzyl chloride) (PVB-N₃) and terminal propargyl poly(β-butyrolactone) (β-BL-propargyl). For this purpose, poly(4-vinylbenzyl chloride) (poly-4-VBC) was obtained using 4-vinylbenzyl chloride and 2,2′-azobis(2-methylpropionitrile) by free-radical polymerization. PVB-N₃ was synthesized using sodium azide and poly-4-VBC. β-BL-propargyl was obtained by the reaction of β-butyrolactone monomer with propargyl alcohol via ring-opening polymerization. The graft copolymer was also synthesized via “click” chemistry, employing PVB-N₃ and β-BL-propargyl. The products were thoroughly characterized by GPC, FT-IR, SEM, and ¹H-NMR. DSC and TGA were used to track the graft copolymer’s thermal characteristics. Thermal and spectroscopic measurements verified that the reactions were effectively completed.

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Poly(4-vinylbenzyl chloride) was obtained by free-radical polymerization. Terminal azido poly(4-vinylbenzyl chloride) was synthesized using sodium azide and poly(4-vinylbenzyl chloride). Terminal propargyl poly(β-butyrolactone) was obtained by β-butyrolactone and propargyl alcohol via ring-opening polymerization. Poly(4-vinylbenzyl-g-β-butyrolactone) graft copolymer was synthesized by “click” chemistry. Thermal and spectroscopic measurements verified that the reactions were completed.

Abstract

The hydrogen abstraction of ammonia by fluorine radical exhibits a peculiar mode selectivity as the ammonia inversion mode promotes the reaction more efficiently than the stretching mode. Although there were attempts to explain it in the literature, a precise understanding of the mode selectivity of this reaction is missing. In this work, using on-the-fly semi-classical trajectory calculation and quantum chemical computation, we have shown that the peculiar mode selectivity of the title reaction has a stereodynamic origin.

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Hydrophobic surface modification is an emerging concept for electrochemical gas-phase reactions like nitrogen reduction reaction to ammonia as the restricted surface wettability helps to surpass the competitive hydrogen evolution reaction. However, the extensive studies on this strategy lack a discussion on the influence of substrates on the stability of the hydrophobic coating. The present work summarizes a case study on the substrate-dependent electrochemical behaviour of the alkanethiol-coated flattened Cu foil and porous dendritic Cu foam surfaces. NRR studies reveal that the porous dendritic architecture with electrified tips and the hydrophobic coating-induced gas diffusion layer proved to be beneficial for NRR activity in Cu foam-SH. However, for a prolonged experimental hour, the flattened surface of the Cu foil could better hold the hydrophobic coating. The results corresponded with water contact angle as well as double layer capacitance measurements and a detailed X-ray photoelectron spectroscopy study. It is supposed that the prolonged exposure to applied potential alters the polarization of the Cu dendritic tips and weakens the Cu–S bond, loosening the alkanethiol layer over Cu foam.

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Hydrophobic Cu substrates facilitate electrochemical nitrogen reduction reactions owing to the better N₂ diffusion and trapping underneath the hydrophobic coating. While the NRR activity gets accelerated at the electrified dendritic tips of Cu foam, the steady hydrophobic layer over the flattened Cu foil surface ascertains long-term use of the material.

For relatively newer developments such as Li–S battery, polysulphide shuttle effect, volume expansion, and low conductivity of sulphur have been the main hurdles in the path towards its commercialisation. To get rid of the polysulphide shuttle effect, we looked at the binder material of the cathode component. An attempt at keeping up with the capacity while making components sustainable led us to explore a protein-based biopolymer, zein. The carbonyl-rich binder helped to glue the components together while the long chain of amino acids aided in preserving the performance. The UV-visible spectroscopy technique verified the adsorption of polysulphides by zein and activated carbon. The carbon host used for this study possessed a high Bruner Emmet Teller (BET) surface area of around 1900 m² g^–1, which helped to load higher amounts of sulphur, as revealed by thermogravimetric analysis. Owing to a porous host, the volume expansion effect could also be buffered to maintain the performance as observed through stability studies. The cycling study of zein binder containing cathode showed an enhanced performance of around 100 mAh g^–1 throughout the 250 cycles compared to the PVDF binder containing cathode.

In this work, we present the CO oxidation by molecular and atomic oxygen on the Cu₃ site of the Cu₁₉ cluster employing the density functional theory (DFT)-PW91PW91/[LANL2DZ, 6-31G(d)] level. The computed results demonstrate that the O atom, O₂, and CO molecule adsorptions on the copper cluster are all chemical. For the CO oxidation by O₂ molecules that leads to the formation of C–O bonds and the dissociation of O–O bonds, the Langmuir–Hinshelwood (LH) mechanism is preferred. On the other hand, the Eley–Rideal (ER) mechanism is slightly favored by the oxidation of CO by atomic oxygen. According to the intrinsic reaction coordinate (IRC) calculation, the activation energy for CO oxidation is 4.02 kcal/mol for molecular oxygen and 3.17 kcal/mol for atomic oxygen. Therefore, molecular and atomic oxygen are very reactive for CO oxidation on the Cu₁₉ cluster. To check the applicability of the global hardness response (GHR) profile satisfying the maximum hardness principle along the IRC in the metal cluster reactions, the GHR profile for the oxidation reaction of CO with molecular oxygen and atomic oxygen was computed. The results indicate that this meets the principle of maximum hardness, effectively showcasing the use of DFT methods to analyze the global hardness profile using frontier molecular orbital energy in the context of metal cluster reaction pathways.

Graphical abstract

The CO oxidation by molecular and atomic oxygen on the Cu₃ site of the Cu₁₉ cluster employing the density functional theory has been studied. The results show that the CO oxidation by atomic oxygen slightly favors the Eley–Rideal (ER) mechanism, while the CO oxidation by molecular oxygen prefers the Langmuir–Hinshelwood (LH) mechanism. Both molecular and atomic oxygen are very reactive for CO oxidation. Furthermore, the global hardness profile along the intrinsic reaction coordinate follows the maximum hardness principle.