Kinetic Studies Research Articles

Polymer Crystallization Kinetics and Thermodynamics of Some Industrial Polyamides

A comprehensive non-isothermal kinetics study on polymer crystallization processes taking place in a set of industrial polyamides comprising nylon 6, nylon 6,6, nylon 11 and nylon 12, individually, is reported. The kinetics studies elucidated that the phenomena of nucleation/diffusion underlying the nylons crystallization go to completion in a single-step. Notwithstanding, the nylons diffusion activation energies do not correspond to the universal value of segmental jump activation energy signifying polymer chains diffusion processes. The polymer chain transport phenomenon was probably the slowest one in the case of nylon 6 and nylon 6,6, and the fastest in the case of nylon 12, while intermediate for nylon 11. Furthermore, the nucleation barrier during the course of polymer crystallization was the highest for nylon 6,6, followed by nylon 6, nylon 11 and nylon 12. Our kinetics studies further predict that the crystallization of nylon 12 and nylon 11 follows, respectively, diffusion-controlled 2D growth of spherulites and a somewhat complicated nucleation/growth phenomenon. The thermodynamics of the nylons crystallization suggests that the highest structural orientation of the activated complex was attained in the case of the nylon 12 crystallization process. Interestingly, while the thermodynamics and majority of the kinetic parameters of nylon 6 and nylon 6,6 were similar/comparable, the two follow widely differing crystallization mechanisms. The most probable physical meanings of the obtained kinetics and thermodynamics parameters and their practical significance are given and discussed.

Sustainable steel production: Evaluating the reduction kinetics of iron ore self-reducing briquettes with eucalyptus charcoal

The steel industry in Brazil is responsible for around 5% of total carbon dioxide emissions, releasing around 1.85 tons of CO2 for every ton of steel produced. The use of charcoal in self-reducing iron ore briquettes can be an alternative to reduce fossil fuel consumption and reduce carbon emissions in the primary steelmaking industry, however, the particle size can affect the reduction process. This study aims to analyze the reduction kinetics of charcoal briquettes in three particle size ranges. To this end, the charcoal was characterized using thermogravimetric analysis to determine the contents of fixed carbon, ash and volatiles, analysis of sulphur in the charcoal by combustion in a tube furnace, determination of particle size by laser granulometer, elemental chemical analysis of the charcoal ash by X-ray fluorescence spectrometry. The briquettes were reduced in a thermogravimetric balance to 1100 °C with heating rates between 10 and 40 °C/min. They were characterized by X-ray diffraction. Finally, a kinetic study was carried out using the Coats-Redfern method. In all the briquettes, the controlling mechanism was diffusion. In the mixture with fines, the activation energy ranged from 31.95 to 33.72 kJ/mol and 120.29–137.17 kJ/mol. For the mixture with medium grain size, the activation energy ranged from 58.1 to 89.42 kJ/mol and 107.83–153.50 kJ/mol. X-ray diffraction revealed phases of hematite and magnetite at 800 °C, while at 900 °C phases of wustite and faialite and metallic iron were identified.

Harnessing the power of multifunctional γ-Fe2O3@CuO nanocomposites: Effective extraction of heavy metals and bacterial pathogens from contaminated water

Waterborne diseases and carcinogenic effects associated with heavy metal poisoning have drawn considerable attentionto removing heavy metals from contaminated water and killing disease-causing bacteria. In this regard, γ-Fe2O3 nanoparticles (NPs) were synthesized by ion reduction method, while CuO NPsand γ-Fe2O3–CuO nanocomposites (NCs) by hydrothermal method. XRD, FTIR, FESEM, EDX and UV–visible spectroscopy were used for system characterization. The dumbbell shape of CuO NPs and spherical shape of γ-Fe2O3 NPs and γ-Fe2O3@CuO NCs were indicated via SEM analysis. The elemental composition and successful synthesis of γ-Fe2O3@CuONCs were confirmed by EDX results. The order for elemental composition: O > Cu > Fe showed the higher content ratio of Cu and O while Fe has the lowest content. The antibacterial activities against E. Coli and B. subtili were evaluated by Minimum Inhibitory Concentration (MIC) and Zone of Inhibition. γ-Fe2O3@CuO NCs showed excellent antibacterial performance as compared to γ-Fe2O3 NPs,CuO NPs, commercial Cu NPs and Cu salt. The drastic improvement in properties of γ-Fe2O3@CuO NCs resulted in better surface contact and extensive cell membranes rupture to eliminate bacterial pathogens present in wastewater Batch adsorption experiments were performed for selective removal of toxic Pb2+ ionsexisting in polluted water. The greatest adsorption capacity was determined to be 346 mg/g, and the highest removal percentage of 95 % was achieved at pH 4 in 60 min. Isotherm models and kinetic studies indicated that Pb2+ ions followed pseudo-second-order kinetics. The results obtained from batch adsorption experiment revealed γ-Fe2O3@CuO NCs as effective nanosorbent for quick elimination of toxic metal ions from industrial wastewater.

Electrochemical determination of uric acid in presence of folic acid using synthesized cobalt oxide modified carbon paste electrode

Here, the synthesis of CoO nanoparticle by using co-precipitation method and characterized by XRD, SEM and EDAX techniques. The CoO nanoparticle used as modified carbon paste electrode for sensing the UA in presence of FA. The CoO/MCPE shows the excellence sensitivity towards the determination of both UA and FA. The kinetic electron transfer study of UA and FA shows with good linearity and both electrodes showed adsorption electrode process. The limit of detection (LOD) and limit of quantification (LOQ) was found to be 3.32 µM and 11.1 µM for FA and 6.09 µM and 20.3 µM for UA, respectively. The CoO/MCPE applied for the simultaneous electrochemical determination of UA and FA, the proposed method was used for real sample analysis.

Synthesis and structural characterization of picolinamide and thiol chelated Pt(II) complexes: Their kinetics & mechanism and theoretical approach

Picolinamide is a versatile chelating ligand and it reveals peculiar behaviour for metal chelation, particularly for its amide group. The bonding mode of N & O donor centres of an amide group depends on the metal ion, their associated charge and the other associated ligands in metal complexes. Picolinamide (pica) based Pt(II) complex C1 to C4 were synthesized and their bonding mode with Pt(II) was established by different spectroscopic analyses and theoretical approaches for their structural importance and potential anticancer activity. The complex [Pt(pica)Cl2]; C1 was synthesized and its hydrolyzed product [Pt(pica)(OH2)2](ClO4)2; C2 was obtained from hydrolysis of complex C1. The kinetic and mechanistic study for the interaction of complex C2 with l-cysteine (l-cys) and N-acetyl-l-cysteine (N-ac-l-cys) was performed in pseudo-first-order reaction condition to evaluate the rate constants, rate equation, enthalpy of activation (ΔHǂ) and entropy of activation (ΔSǂ). Sulfur chelated complex [Pt(pica)(l-cys)]+; C3 and [Pt(pica)(N-ac-l-cys)]; C4 were obtained when a 1:1 M ratio of C2 and thiol are mixed separately. Theoretical investigation on drug likeness property was evaluated by PASS prediction software. The theoretical approach on structural properties like; structural optimization, HOMO-LUMO energy, TD-DFT simulation, MEP and reactivity descriptors of the complexes were executed and analyzed with the Gaussian09 software package. Molecular docking of the complexes was executed with DNA and BSA.

Strategic decolorization of rose bengal in an aqueous environment using a zinc oxide-loaded reduced graphene oxide photocatalyst

The environmental and health hazards posed by synthetic organic dyes, such as Rose Bengal, have spurred significant concern in recent years. Herein, a novel zinc oxide/reduced graphene oxide (ZnO/rGO)-based photocatalyst is developed and used for the efficient decolorization of RB dye in aqueous solutions. The as-synthesized nanostructured material is characterized using advanced techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX) mapping to elucidate its crystalline structure, morphology, and elemental composition. The XRD pattern confirmed the wurtzite crystalline phase structure with an average size of 67.8 nm, while SEM imaging verified the successful incorporation of ZnO nanoparticles into the rGO matrix. Further, the as-prepared material was used as a photocatalyst, which demonstrated remarkable performance in RB dye decolorization, achieving ≥96.1 % degradation within just 5 min at a minimal catalyst dosage of 8.0 mg. Moreover, kinetic studies revealed that the decolorization process followed a pseudo-second-order reaction mechanism, further enhancing the understanding of the catalytic behavior. It is more interesting that the catalyst exhibited exceptional reusability for up to seven cycles with only a decrease in catalyst efficiency from 96.1 % to 77.5 %, underscoring its practical viability and sustainability. The significance of this work lies in its contribution to addressing the environmental challenges associated with synthetic dyes, particularly rose bengal, by offering an efficient and reliable photocatalytic solution. The demonstrated efficacy of the ZnO/rGO photocatalyst not only showcases its potential for large-scale rose bengal dye degradation but also suggests broader applicability for the treatment of other synthetic dye pollutants.

Selective hydrogenation of furfural to furfuryl alcohol over copper-cobalt bimetallic catalyst

Cu-based catalysts have been widely studied as selectively hydrogenated furfural. However, due to the weak hydrogenation activity of the mono-metal copper-based catalyst, the interaction with furfural is usually weak, and the accessibility of the active site is severely limited. A micro-doping strategy was proposed in this study to solve these problems. Trace amounts of cobalt metal are doped into copper using equal volume impregnation. Compared with the Cu/MgO catalyst, the bimetallic CuCo/MgO-0.04 catalyst changes metal particles' size and valence and regulates the catalyst surface's electronic environment. Electron transfer occurs between Co and Cu, and many active sites are generated for adsorption and activation of CO double bonds, and hydrogenation reactions occur with adjacent H protons to improve the selectivity of furfuryl alcohol. CuCo/MgO-0.04 catalyst has excellent catalytic performance of 100 % furfural conversion and 99.4 % furfural alcohol selectivity. Combined with experimental data, kinetic studies, and theoretical calculations, it was confirmed that the d-band center shifted up in the catalyst doped with trace metal cobalt, which optimized the adsorption energy and configuration of furfural and reduced the reaction barrier more effectively. This study provides a strategy to support the partial doping of highly dispersed Cu nanoparticles with a small amount of Co metal. It achieves excellent catalytic properties and chemical selectivity in selective hydrogenation reactions.

Kinetics study and bio-phase characteristics of drainage in paddy fields purified by a compound ecological ditch

Kinetics study and bio-phase characteristics of drainage in paddy fields purified by a compound ecological ditch

Green biodiesel production from Nannochloropsis microalgae-derived oil using ZnAl-LDH catalyst: Process optimization and kinetic study

The green production of biodiesel using Nannochloropsis microalgae, a renewable and environmentally friendly source, was successfully conducted by application of a calcined ZnAl layered double hydroxides structure (LDH) catalyst. The ZnAl-LDO catalyst was prepared through the urea synthesis method, followed by calcination at 400 °C. XRD was used to investigate the crystallite characteristics, N2-BET to analyze surface properties and pore size, and CO2-TPD to identify the active basic sites strength. Bligh and Dyer’s method was utilized for oil extraction with a yield of 38 %. Upon analyzing the fatty acid profile of derived oil, a synthetic oil containing oleic and palmitic acids was utilized in this process. The experiments were designed using the response surface methodology (RSM) method and the optimized parameters were obtained at 149.59 °C, 118.92 min, 3.91 wt% catalyst loading, and 11.68:1 methanol to oil molar ratio for the biodiesel yield of > 98 %. The pseudo-first-order esterification reaction kinetic was investigated and the activation energy was determined to be 28.53 kJ.mol−1. Furthermore, the process can be applied to microalgae solid biomass as well. In-situ transesterification of microalgae with a yield of FAME over 90 % also has been carried out.

Shock tube and comprehensive kinetic modeling study of ammonia/diethyl ether (DEE) mixtures

Ammonia (NH3) is a promising alternative clean fuel due to its carbon-free and high hydrogen content, along with the well-established infrastructure for storage and distribution. To overcome the issue of the low reactivity of NH3, a feasible strategy is co-burning ammonia with highly reactive fuels. Diethyl ether (DEE) is considered a promising alternative and biomass-oxygenated clean diesel substitute. Therefore, the NH3/DEE blend is also a promising carbon neutral alternative fuel. In this work, we measured the ignition delay times (IDTs) of NH3/DEE mixtures with DEE fractions (XDEE) of 0.05, 0.10, 0.30, and 1.00 at equivalence ratios of 0.5, 1.0, and 2.0, pressures of 1.75 and 10 bar, and temperature ranges from 1102 K to 1673 K in a shock tube. The DEE-NH3 model was proposed in this work, which included the DEE sub-model, NH3 sub-model, and some new cross-reactions between N-containing species and C-containing species. The DEE sub-model from Shrestha et al. (Fuel Communications, 2022) was modified in this work, NH3 sub-model was from our previous work (Reaction Chemistry & Engineering, 2023). The DEE-NH3 model was extensively validated by the IDTs, laminar flame speeds (LFSs), and species profiles (SPs) of NH3/DEE mixtures as well as pure DEE and NH3. The comparison of the prediction performance between the DEE-NH3 model and the Shrestha model was conducted for the ignition, flame propagation, and NH3 consumption. The effects of the cross-reactions on the NH3/DEE ignition and combustion were studied in detail.

Cobalt(II)-Catalyzed Synthesis of γ-Diketones from Aryl Alkenes and Its Utilization in the Synthesis of Various Heterocyclic Compounds.

An earth-abundant Co(II) salt-catalyzed mild and affordable synthetic route has been developed for the synthesis of industrially relevant 1,4-dicarbonyl compounds (or γ-diketones) via oxidative coupling between aryl alkenes and ketones (both cyclic and acyclic) using TBHP and DBU as the oxidant and base, respectively. 1,4-Dicarbonyl compounds are known to be synthesized using expensive metal catalysts, dual catalysts, or low-cost metal complexes combined with an additive or ligand template, which further needs to be synthesized. Herein, we report the synthesis of 1,4-dicarbonyl compounds using cobalt(II) acetate as a catalyst without any expensive co-catalyst or ligand templates. This methodology has a broad substrate scope with significant yields and good functional group tolerance. Generation of unsymmetrical 1,4-dicarbonyls at room temperature and its versatile synthetic expansion to produce synthetically and biologically valuable heterocyclic compounds are salient features of this novel methodology. In addition, various controlled experiments such as primary kinetic isotope effect study, Hammett analysis with variation of the nature of the substituents on the styrene ring, and theoretical calculations (density functional theory) unravel the mechanistic intricacies involved in this new, simple, and atom-economic methodology.

Experimental and kinetic modeling study on auto-ignition of ammonia/n-heptane mixtures at intermediate temperatures

Ignition delay times (IDTs) were measured in a shock tube facility for NH3/n-heptane mixtures with NH3 concentrations in the blending fuel ranging from 0.3 to 0.95 by molar fraction. The measurements were conducted under low pressure of 2 atm and intermediate temperatures of 1350–1500 K at equivalence ratios of 0.5, 1, and 2. With the increase of n-heptane content or equivalence ratio, there is a decrease in the IDTs of NH3/n-heptane mixtures at intermediate temperatures. A detailed mechanism was updated in this study based on the mechanism of Dong et al. Subsequently, the proposed mechanism was compared to existing blending mechanisms of ammonia and n-heptane in terms of laminar burning velocities (LBVs), IDTs, and species profiles reported in literature. The present model improved the predictions in reproducing the performed experimental measurements compared to previous mechanisms. Finally, rate of production (ROP), sensitivity analysis, and instantaneous and cumulative reaction path analysis were performed to interpret the experiment observations and deepen the understanding of auto-ignition kinetics of ammonia and n-heptane. The results indicate that intermediate species, such as C2H4 and C3H6, characterized by long lifespans and high concentrations during n-heptane decomposition, play a crucial role at elevated temperatures, while the significance of n-heptane dehydrogenation by NH2 diminishes with increasing temperature.

Photocatalytic Degradation of Tartrazine and Naphthol Blue Black Binary Mixture with the TiO2 Nanosphere under Visible Light: Box-Behnken Experimental Design Optimization and Salt Effect

In this study, TiO2 nanospheres (TiO2-NS) were synthesized by the solvothermal method. Firstly, the synthesized nanomaterial was characterized by X-ray diffraction (XRD), Fourier Transformed Infrared (FTIR), scanning electron microscopy (SEM) and UV-Vis Diffuse Reflectance Spectroscopy (DRS). To study the photocatalytic degradation of Tartrazine (TTZ) and Naphthol Blue Black (NBB) in a binary mixture, the influence of some key parameters such as pH, pollutant concentration and catalyst dose was taken into account under visible and UV light. The results show a 100% degradation efficiency for TTZ after 150 min of UV irradiation and 57% under visible irradiation at 180 min. The kinetic study showed a good pseudo-first-order fit to the Langmuir–Hinshelwood model. Furthermore, in order to get closer to the real conditions of textile wastewater, the influence of the presence of salt on TiO2-NS’s photocatalytic performance was explored by employing NaCl as an inorganic ion. The optimum conditions provided by the Response Surface Methodology (RSM) were low concentrations of TTZ (2 ppm) and NBB (2.33 ppm) and negligible salt (NaCl) interference. The percentage of photodegradation was high at low pollutant and NaCl concentrations. However, this yield became very low as NaCl concentrations increased. The photocatalytic treatment leads to 31% and 53% of mineralization yield after 1 and 3 h of visible light irradiation. The synthesis of TiO2-NS provides new insights that will help to develop an efficient photocatalysts for the remediation of contaminated water.

Photocatalytic degradation of linezolid antibiotic from aqueous solution by magnetically separable nanoheterostructure Fe3O4/ MgAl2O4/BiOBr0.5Cl0.5 synthesized Composite catalyst

The photocatalytic system has been emerging as a practical method for antibiotic removal in an aqueous medium. In this study, novel MgAl2O4/BiOBr0.5Cl0.5 heterojunction was synthesized by the decoration of different mass percentages of MgAl2O4 nanoparticles (10, 20, and 30 %) on the BiOBr0.5Cl0.5 solid solution and used for the photocatalytic degradation of linezolid antibiotic. Also, to facilitate easy separation of 10 % MgAl2O4/BiOBr0.5Cl0.5 from the solution after use, it was magnetized by Fe3O4 as 2 % Fe3O4/10 % MgAl2O4/BiOBr0.5Cl0.5. Synthesized photocatalysts were characterized by XRD, XPS, Raman, FESEM, TEM, EDX, BET-BJH, DRS, PL, Mott–Schottky, VSM, and pHpzc analyses to specify the synthesized photocatalysts and determine their chemical and physical properties. In addition, the influence of experimental parameters, including pH of the initial solution, the dosage of photocatalyst, and linezolid concentration on the performance of photocatalyst in linezolid removal, were elucidated in this study. The results showed that 10 % MgAl2O4/BiOBr0.5Cl0.5 photocatalyst was the optimal sample with a maximum removal efficiency of 95.59 % within 90 min under optimal experimental parameters (1 g/L catalyst, 10 mg/L linezolid, pH = 6.5). The kinetic studies revealed that the degradation rate of 10 % MgAl2O4/BiOBr0.5Cl0.5 photocatalyst was approximately 1.8, 2.7, 2.0, and 6.3 times faster than 20 % MgAl2O4/BiOBr0.5Cl0.5, 30 % MgAl2O4/BiOBr0.5Cl0.5, BiOBr0.5Cl0.5 photocatalyst and photolysis, respectively. Scavenger tests conducted in the same process operation revealed that h+ and •O2− play the predominant roles in linezolid photocatalytic degradation. The 2 % Fe3O4/10 % MgAl2O4/BiOBr0.5Cl0.5 photocatalyst was easily collected by magnet after each use for the next run, and its activity after five runs has reached 90 %.

Thermal treatment impact on the evolution of active phases in layered double hydroxide-based ZnCr photocatalysts: Photodegradation and antibacterial performance

Abstract This study investigated the influence of thermal treatment on the photocatalytic performance of ZnCr layered double hydroxide-based mixed metal oxides in the degradation of methylene blue and brilliant cresyl blue organic dyes under simulated solar light irradiation. The photocatalysts were synthesized using a simple coprecipitation method and subjected to thermal treatment at temperatures ranging from 100°C to 900°C. Additionally, the study explored the antibacterial activity against Escherichia coli and Staphylococcus aureus using a novel antibacterial experimental setup. It not only involved the introduction of ZnCr samples into BioPeptone/prepared cell suspension to enhance photocatalyst–bacteria cell contact but also included research on antibacterial activity induced by solar irradiation and also in the absence of light, providing crucial insights into photocatalytic antibacterial activity of ZnCr photocatalysts. Despite satisfactory efficiencies observed for all thermally treated ZnCr samples (removal efficiency ranging from 40% to 90%), ZnCr 900 (thermally treated at 900°C) exhibited exceptional performance, achieving nearly 100% removal efficiency and complete growth inhibition for both bacteria. Integrating these findings with structural and textural characterization data, as well as kinetic studies, our comprehensive analysis enhances the understanding of structure-dependent photocatalytic activities. These insights open possibilities for the application of ZnCr photocatalysts in water purification and environmental remediation.

Adsorption isotherms and kinetic studies for the defluoridation from aqueous solution using eco-friendly natural adsorbent like Terminalia Chebula

A practical technique for removing fluoride from aqueous solutions by adsorption was created using the natural adsorbent known as Terminalia Chebula with a primary emphasis on adsorption isotherms and kinetic studies. The experimental results showed the best conditions for removing fluorine ions as follows: the dosage of the natural adsorbent: 50 mg/L, contact reaction time: 40 min, shaking speed = 120 rpm, temperature = 32 °C. The amount of removal of fluorine ions was found to be >98 % fluoride within a shorter time and reached adsorption equilibrium within 40 min with a maximum defluoridation capacity of 20.92 mg/g. At lower solution pH (3 to 5), there is higher fluoride adsorption on the adsorbent surface and as the pH becomes alkaline (pH > 7) the adsorption capacity decreased. The two co-ions namely NO3− and Cl− removed the fluoride 79 % whereas, the phosphate ions did not have any marked effect on the defluoridation. The pseudo-second-order kinetic order such Langmuir, Empirical Freundlich, Temkin and Dubinin–Radushkevich isotherms can well predict the adsorption equilibrium rate to be at 0.044 mg/L with contact time (t) of 30 min. In addition to that the adsorption is characterized by SEM, X-ray diffraction and FTIR techniques. This study has ultimately found that the Terminalia Chebula is a workable, natural material for fluoride elimination.

New Instrument for Time-Resolved OH and HO2 Quantification in High-Pressure Laboratory Kinetics Studies.

We have constructed a new time-resolved high-pressure fluorescence assay by gas expansion (HP-FAGE) apparatus, optimized for the detection of OH and HO2 radicals in complex gas-phase reactions. The new instrument fills a gap in the existing experimental toolkit for chemical kinetics by enabling the quantification of two key reactive species with microsecond time resolution from high-pressure sources, which was previously not attainable. The HP-FAGE is interfaced with a flow reactor, designed for pressures up to 100 bar and temperatures up to 1000 K, in which reactions are initiated by laser photolysis of radical precursors at repetition rates of 1-10 Hz. The HP-FAGE samples gas out of the reactor into a miniature FAGE chamber, where OH is detected by resonant laser-induced fluorescence using a time-delayed probe laser pulse. HO2 is converted to OH via reaction with NO and then detected by OH fluorescence. The novel FAGE design places the probe region very close to the gas expansion, minimizing the transport time of sampled molecules and resulting in time resolution better than 20 μs for both OH and HO2. We calibrate the sensitivity of HP-FAGE, validate its performance with measurements of well-known reaction kinetics (OH + CH4, OH + OH, OH + HO2, and HO2 + HO2), and discuss prospects for its future use.

High-temperature oxidation behaviours of rare earth-based pyrochlore structured A2B2O7/yttria-stabilized zirconia thermal barrier coatings

Addressing the challenge of cost-effectively synthesizing stable thermal barrier coating materials has been a significant hurdle. This study describes the bulk synthesis of stannate-based pyrochlore compounds, specifically erbium tin oxide (Er2Sn2O7) and yttrium tin oxide (Y2Sn2O7). These synthesized pyrochlore oxides and commercially available yttria-stabilized zirconia (YSZ) were coated onto nickel super alloy. The coated specimens were subjected to thermal oxidation kinetics studies at 900 ± 5°C for 200 h, and alterations in physico-chemical characteristics, modifications in surface morphology, and variations in the composition of thermal barrier coating (TBCs) before and after exposure to oxidation conditions were evaluated. Oxidation kinetics results demonstrate that Er2Sn2O7 pyrochlore oxide has better performance than other Y2Sn2O7 and commercial YSZ TBC materials in high-temperature thermal barrier systems.

Tunable optoelectronic performances of fluorinated benzene-EDOT based hybrid electrochromic polymers

Due to its high electronegativity and small atomic radius without undesirable steric hindrance, the incorporation of fluorine atoms into the benzene unit which started from the commercially available compounds is a feasible way to tune the energy levels of polymers, and its electrochromic application is expected to achieve a new breakthrough. Herein, in this paper, benzene units with different fluorine atom numbers were selected as the core and 3,4-ethylenedioxythiophene (EDOT) as the terminal unit, three fluorinated electrochromic precursors (FPh-EDOT, 2FPh-EDOT, and 4FPh-EDOT) were designed and synthesized by Stille coupling reaction, and the corresponding fluorinated π-conjugated electrochromic polymers (P(FPh-EDOT), P(2Ph-EDOT), and P(4FPh-EDOT)) were prepared by electrochemical polymerization method. The effects of different fluorinated benzene units on the photophysics, electrochemistry, and electrochromic properties of precursors and polymers were systematically investigated, and the structure-property relationship was further revealed. All of them have low initial oxidation potentials {FPh-EDOT (0.65 V), 2FPh-EDOT (0.72 V), and 4FPh-EDOT (0.70 V)}, which makes it easy to obtain high-quality new fluorinated polymers at low polymerization potential. With the increase of the number of F atoms, the UV–vis absorption spectra and emission spectra of fluorinated monomer firstly red-shifted and then blue-shifted. The corresponding fluorinated polymers have good electrochemical activity and stability (the P(2Ph-EDOT) activity remained 82.7% after 500 cycles), making it possible to realize their electrochromic devices. All these three fluorinated polymers show obvious color change from the neutral state to the fully oxidized state (P(FPh-EDOT) changes from brown to grayish blue, P(2FPh-EDOT) changes from brown to gray, and P(4FPh-EDOT) changes from dark blue to light blue). The kinetic study further shows that all of them have distinguish electrochromic properties with good optical stability, very short response time (0.9 s for P(2FPh-EDOT) at 700 nm), and favorable coloration efficiency (130.7 cm2 C−1 for P(FPh-EDOT) at 503 nm). Overall, all these three fluorinated polymers have low optical band gap, good redox stability and electrochromic properties, are very promising electrochromic materials, which is worthy for the further research and development.

Silica@poly(chitosan-N-isopropylacrylamide-methacrylic acid) microgels: Extraction of palladium (II) ions and in situ formation of palladium nanoparticles for pollutant reduction

Most of the transition metal ions and organic dyes are toxic in nature. Therefore, their removal from water is imperative for human health. For this purpose, various types of systems have been developed to tackle either transition metal ions or organic dyes individually. A core-shell microgel system is introduced which is capable of effectively removing both types (toxic organic dyes and transition metal ions) of pollutants. A long-rod-shaped silica@poly(chitosan-N-isopropylacrylamide-methacrylic acid) S@P(CS-NIPAM-MAA) S@P(CNM) core-shell microgel system was developed by free radical precipitation polymerization method (FRPPM). S@P(CNM) was utilized as an adsorbent for extracting palladium (II) (Pd (II)) ions from water under different concentrations of S@P(CNM), several agitation times, palladium (II) ion content, and pH levels. The adsorption data of Pd (II) ions on S@P(CNM) was evaluated by various adsorption isotherms. The kinetic study was investigated by employing pseudo-2nd order (Ps2O), Elovich model (ElM), intra-particle diffusion (IPDM), and pseudo-1st order (Ps1O). Additionally, palladium nanoparticles (Pd NPs) were generated via in-situ reduction of adsorbed Pd (II) ions within the P(CNM) shell region of S@P(CNM). The resulting Pd NPs loaded S@P(CNM) exhibited the capability to reduce organic pollutants like methyl orange (MeO), 4-nitrophenol (4NiP), methylene blue (MeB), and Rhodamine B (RhB) from aqueous medium. 0.766 min−1, 0.433 min−1, 0.682 min−1, and 1.140 min−1 were the values of pseudo 1st order rate constant (kobs) for catalytic reduction of MeB, 4NiP, MeO, and RhB respectively. The S@Pd-P(CNM) system exhibits significant catalytic potential for various organic transformations.