Hasil untuk "Physical and theoretical chemistry"

Y. Adewuyi

Lu Han, S. Che

D. Schilter, James M. Camara, Mioy T. Huynh et al.

Christof Holzer, Yannick J. Franzke

The Bethe-Salpeter equation (BSE) combined with the Green's function GW method has been successfully transformed into a robust computational tool to describe light-matter interactions and excitation spectra for molecules, solids, and materials from first principles. Due to its ability to accurately describe charge transfer and Rydberg excitations, GW-BSE is already an established and cost-efficient alternative to time-dependent density functional theory. This raises the question whether the GW-BSE approach can become a more general framework for molecular properties beyond excitation energies. In this Mini-Review, we recapitulate recent endeavors along this point in terms of both theoretical and practical developments for quantum chemistry, physical chemistry, and related fields. In doing so, we provide guidelines for current applications to chemical challenges in collaboration with experimentalists as well as to future developments to extended the GW-BSE toolkit.

Liang Dong, Luofei Li, Huiyan Chen et al.

Mechanochemistry is an emerging research field at the interface of physics, mechanics, materials science, and chemistry. Complementary to traditional activation methods in chemistry, such as heat, electricity, and light, mechanochemistry focuses on the activation of chemical reactions by directly or indirectly applying mechanical forces. It has evolved as a powerful tool for controlling chemical reactions in solid state systems, sensing and responding to stresses in polymer materials, regulating interfacial adhesions, and stimulating biological processes. By combining theoretical approaches, simulations and experimental techniques, researchers have gained intricate insights into the mechanisms underlying mechanochemistry. In this review, the physical chemistry principles underpinning mechanochemistry are elucidated and a comprehensive overview of recent significant achievements in the discovery of mechanically responsive chemical processes is provided, with a particular emphasis on their applications in materials science. Additionally, The perspectives and insights into potential future directions for this exciting research field are offered.

Subhan Azeem, Muhammad Ashraf, Sadiq Hussain

Dry reforming of methane (DRM) offers a promising pathway towards carbon neutrality by converting the greenhouse gases methane (CH 4 ) and carbon dioxide (CO 2 ) into valuable syngas (CO + H 2 ). This sustainable process not only mitigates climate change but also contributes to a circular carbon economy by utilizing waste gases as valuable feedstocks. However, the successful industrial implementation of DRM hinges on the development of stable and efficient catalysts. This study investigated the influence of the ceria support source on the catalytic performance of Ni/CeO 2 catalysts. Three commercially available ceria supports from Germany, Canada, and the USA were employed, denoted as Ni-P, Ni-M, and Ni-C, respectively. These supports were impregnated with nickel and characterized using a suite of techniques, including XRD, FTIR, SEM, N 2 adsorption-desorption, and TGA. Catalytic activity and stability were evaluated within a temperature range of 550 to 750 °C. Our findings revealed that the catalytic performance is significantly influenced by the physicochemical properties of the catalyst. The Ni/CeO 2 (Ni-C) catalyst demonstrated superior activity and stability, exhibiting minimal carbon deposition as evidenced by TGA analysis and a low deactivation factor. This research provides valuable insights into the critical role of support materials in optimizing Ni/CeO 2 catalyst performance for DRM. The development of highly stable and active catalysts, such as the Ni/CeO 2 (Ni-C) catalyst, is crucial for the successful industrial implementation of DRM, contributing to a more sustainable and environmentally friendly energy future.

Laskar, Clément, Dakkoune, Amine, Julcour, Carine et al.

The overall performance of hydrometallurgical leaching operations can be limited by the presence of various types of insoluble layers coating the surface of the treated solids. The attrition-leaching process, which is carried out in a stirred reactor containing millimetric beads, can partially overcome this problem and increase the extraction yield by physically abrading the layers. Through a comparative analysis of three different systems, this work develops a constructive discussion of the attrition-leaching process. The systems of interest are (i) mineral carbonation of ferronickel slag, (ii) dissolution of a chalcopyrite concentrate in sulfuric media, and (iii) dissolution of spent Ni-MH battery black mass powder in sulfuric media. In the case of ferronickel slag and chalcopyrite, the reaction yields are improved by a factor of 10 with attrition-leaching compared to leaching only, while there is no yield improvement in the case of Ni-MH black mass batteries, highlighting that the layers observed on the grain surface do not interfere with the leaching reaction. Despite very different system chemistries and conditions, the particle size distribution is similar for the three materials, showing that particles’ behavior is controlled by the attrition environment. This work offers a simple setup for investigating the potential improvements of the kinetics and yields of leaching reaction due to concomitant attrition. It also allows a fundamental study of the physico-chemical processes involved, by testing whether a leaching reaction is hindered by an in situ passivation at the surface of a material.

Karina Chavez, Enrique Quiroga-González

Fast electrochemical phenomena occurring in supercapacitors are hard to analyze by ex situ or in situ techniques because many of them are meta-stable (the supercapacitor relaxes once it is not further polarized). In a steady state, one observes the effect of charge storage but not necessarily the mechanism. This is a problem for Raman spectroscopy, too, even though Raman spectra of the electrodes of supercapacitors are commonly recorded ex situ or in a steady state in situ. Raman operando is desired, but it represents a technological challenge since the electrochemical events in a supercapacitor are very fast (occurring within seconds), and in contrast, Raman requires from seconds to minutes to collect enough photons for reliable spectra. This work presents the development of electrodes made of thin layers of iron oxide grown solvothermally on Si wafers, with a porosified surface and resistivity of 0.005 Ωcm, to study their performance as electrodes in supercapacitors and analyze their energy storage mechanisms by cyclic voltammetry and Raman operando. Being flat and containing just iron oxide and silicon, these electrodes allow for studying interfacial phenomena with minor interferents.

Navapat KROBKRONG, Taro UEMATSU, Tsukasa TORIMOTO et al.

Silver indium sulfide (AIS)/gallium sulfide (Ga–S) core/shell QDs exhibit a narrow band-edge photoluminescence (PL) in the yellow color region, and shifting the PL wavelength is crucial for optical applications. In this study, we attempt to redshift the band-edge PL by incorporating indium sulfide (In–S) shells, which have a smaller bandgap than Ga–S and are expected to broaden the exciton wavefunction. When coated with In–S shells instead of Ga–S shells, a redshift of the band-edge PL was attained. However, an increase in defective PL and a reduction in PL quantum yield occurred due to carrier trapping associated with the extended wavefunction. To address these issues, we coated the AIS/In–S cores/shell QDs with Ga–S shells using recently developed procedures, resulting in spectrally narrow PL in the red region. Interestingly, compositional and structural analyses revealed a decrease in the In ratio, which typically leads to blue shift. The observed redshift, reaching up to 40 nm, is discussed in relation to the formation of shells with graded composition, which provide a broader wavefunction in the excited state compared to discrete shells.

Stewart F. Parker

Diiron nonacarbonyl, Fe₂(CO)₉, was discovered in 1905 and was the third metal carbonyl to be found. It was the first to be synthesized by a photochemical route. This is a challenging material to study: it is insoluble in virtually all solvents and decomposes at 373 K before melting. This means that only solid-state spectroscopic data are available. New infrared, Raman and inelastic neutron scattering (INS) spectra have been measured and used to generate a complete assignment of the vibrational spectra of Fe₂(CO)₉. Density functional theory (DFT) calculations are used to support the assignments; however, for this material, they are much less useful than expected, although the calculated intensities provide crucial information.

Cong Zhou, Jing Liu, Weiwei Zhuo

In this work, an electrochemical sensor of Gonadotropin-releasing hormone (GnRH) agonists was proposed by deposition of the conductive nanocomposite of Ag and graphene oxide on glassy carbon electrode (Ag-GO/GCE) and electropolymerization of poly(L-Serine) on nanocomposite (p-L-serine/Ag-GO/GCE). Because of excellent conductivity between Ag nanoparticles and graphene oxide nansheets, and synergic catalytic effect of Ag-GO nanocomposite and the conducting polymer, the developed GnRH sensor provides a highly porous surface and a larger effective surface area, which facilitates electron transfer and promotes the electro-catalytic performance. p-L-serine/Ag-GO/GCE exhibited good electro-catalytic and selectivity with a sensitivity of 0.74036 μA/μgml-1, a linear range of 1 to 15×107 μg/ml, and a low detection limit of 20 pg/ml (S/N = 3). Moreover, the p-L-serine/Ag-GO/GCE was successfully applied for the determination of GnRH in real blood serum of patients aged 40-50 years old who administrated GnRH for treatment of uterine fibroids and the obtained RSD≤4.20% was demonstrated to good accuracy of p-L-serine/Ag-GO/GCE for the determination of GnRH in patient blood serum and in clinical applications.

Mohd Bilal Khan, C. Sasmal

Biosurfactants are widely used in many industrial settings ranging from cosmetic to petroleum industries. Among various biosurfactants available in the market, rhamnolipid is a well-known bacterial biosurfactant produced by the Pseudomonas aeruginosa bacteria. However, despite its wide applications, no detailed and systematic study is available on the rheological characterization of this biosurfactant solution, which is an essential property to investigate for many practical applications. Therefore, this study aims to present a thorough and complete investigation of this biosurfactant's shear and extensional rheological behaviours. While steady shear and small amplitude oscillatory shear (SAOS) measurements were conducted to investigate the shear rheological behaviour, the dripping-onto-substrate (DoS) extensional rheometry technique was used to understand its extensional rheological behaviour. A chemically derived surfactant (cetyltrimethyl ammonium bromide (CTAB)) was also used in our analysis to show and discuss the qualitative and quantitative differences in their rheological behaviours. Along with the detailed rheological study, some studies on the physicochemical properties, such as surface tension, contact angle, particle size analysis, thermal stability, etc., were also conducted to make an overall comparison between the two surfactants. Both surfactants show strong shear-thinning and extensional hardening behaviors in shear and extensional rheological flows, respectively. However, the zero-shear rate viscosity and extensional viscosity are found to be larger for rhamnolipid surfactant solutions than for CTAB. The corresponding shear and extensional relaxation times also follow the same trend. Furthermore, the surface tension is found to be less, and the contact angle is found to be more for rhamnolipid biosurfactant than that for CTAB. Rhamnolipid shows more excellent thermal stability, particularly at high temperatures than CTAB. Therefore, the results and discussion presented in this study will help to choose the present rhamnolipid biosurfactant for any particular application, particularly where the knowledge of the rheological responses of a surfactant solution is essential.

Arif Ullah, Pavlo O. Dral

The future forecasting ability of machine learning (ML) makes ML a promising tool for predicting long-time quantum dissipative dynamics of open systems. In this article, we employ nonparametric ML algorithm (kernel ridge regression as a representative of the kernel methods) to study the quantum dissipative dynamics of the widely-used spin-boson (SB) model. Our ML model takes short-time dynamics as an input and is used for fast propagation of the long-time dynamics, greatly reducing the computational effort in comparison with the traditional approaches. Presented results show that the ML model performs well in both symmetric and asymmetric SB models. Our approach is not limited to SB model and can be extended to complex systems.

Boukaous, Nourelhouda, Abdelouahed, Lokmane, Chikhi, Mustapha et al.

A comparison of the thermal behaviours of different Mediterranean biomasses, based on the evaluation of their pyrolysis characteristic temperatures, their reactivity and kinetic parameters is presented. Parameters such as the activation energy and the pre-exponential factor of the pyrolysis reactions are determined by different methods (Kissinger, Kissinger–Akahira–Sunose [KAS], Coats–Redfern, nonlinear least-squares minimization [NLSM] and model distributed activation energy model [DAEM]). Furthermore, a sensitivity analysis of the kinetic parameters based on different methods is conducted. The comparison of this work with the literature, showed that thermal characteristic parameters determined using the thermogravimetric analysis (TGA) are often neglected and not used in biomass pyrolysis at laboratory scale. The kinetic parameters seem to be highly sensitive to the used kinetic methods. For a given biomass, such as the Aleppo pine husk residue, for example, the activation energy can vary from 65.80 to 197.08 kJ${\cdot }$mol$^{-1}$ depending on the used method. For this biomass, the highest average activation energy (190 kJ${\cdot }$mol$^{-1}$) was estimated by the KAS and DAEM methods. The Kissinger method yields to an activation energy close to that of cellulose calculated by the NLSM method. For all biomasses, the activation energy remains between 150 and 200 kJ${\cdot }$mol$^{-1}$ except for the Coats–Redfern method, where this value is in the range of 50–100 kJ${\cdot }$mol$^{-1}$. Therefore, it is important to have a means of recommending the most appropriate method for the determination of kinetic parameters.

Baron, Thibaut, Zarate, Ximena, Hidalgo-Rosa, Yoan et al.

Transparent and colorless solar cells are attractive new photovoltaic devices as they could bring new opportunities to harness sunlight energy and particularly for their integration in windows. In this work, a new zinc phthalocyanine was synthesized and investigated as sensitizer in dye-sensitized solar cell (DSSC) for this purpose. The zinc phthalocyanine features a benzoic acid anchoring group and six thio(4-tertbutylphenyl) substituents in ${\alpha }$ position of the phtalocyanine. The dye was characterized by absorption and emission spectroscopy and by electrochemistry. The physico-chemical properties show that the dye fulfills the criteria for such an application. A detailed computational study indicates that the electronic communication with $\mathrm{TiO}_{2}$ conduction is weak owing to the absence of overlapping of the wavefunctions of the dye with those of the $\mathrm{TiO}_{2}$ semiconductor. The photovoltaic performances of the zinc phthalocyanine were measured in $\mathrm{TiO}_{2}$-based DSSC that revealed inefficient electron injection, which certainly can be explained by the weak electronic coupling of the dye with $\mathrm{TiO}_{2}$ that limits electron injection efficiency. A strategy is proposed to make better-performing sensitizers.

Gaosheng Nie, Shizhen Dai, Hangchun Deng et al.

Composites of ultrafine tin dioxide nanoparticles grown on nitrogen-doped graphene (SnO2@NG) with high pyrrolic nitrogen content are successfully prepared via a one-step method by employing graphene oxide, tin chloride, and urea as raw materials. Morphology and microstructure of SnO2@NG are characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA), revealing evenly dispersed SnO2 nanoparticles on the surface of nitrogen-doped graphene sheets and a SnO2 content of 54.23%. The SnO2@NG electrode exhibits a specific capacitance of 289.5 F/g at a current density of 0.5 A/g in 0.5 mol/L Na2SO4 solution and retains 92.85% of its initial capacitance after 2000 charge/discharge cycles. These results prove that SnO2@NG is an excellent material for high-performance supercapacitors.

Yuta KIMURA, Yasuhiro DOMI, Hiroyuki USUI et al.

Rapid quenching is one of the methods for preparing silicide/Si composite alloy as an active material for negative electrode in lithium-ion batteries. In this study, we focused on the method’s control over the positional relation between the Si and silicide phase by changing the additive elements. Various Si-alloys and the relationship between their lithiation and delithiation properties and their arrangement was investigated.

Kuo-Lin Huang, Shi-Jie Huang

This study focuses on the electrochemical degradation of acetaminophen (AP) in the presence of individual redox mediators. The oxidation peaks of Fe(II), Ag(I), and sulfate were detected on a Windsor boron-dopped diamond (BDD) electrode in 1 M Na2SO4. The AP degradation performance using a single mediator was in the following order: Ce(IV) (from Ce(SO4)2) > Fe(III) (from Fe(NO3)3 or FeCl3) > Co(II) (from C0Cl2) ≈ Ag(I) (from AgNO3). p-BQ due to AP degradation was observed in 1 M Na2SO4 in the presence of Ce(IV) and Fe(III), while the former exhibited more and faster p-benzoquinone (p-BQ) generation than the latter. In the presence of individual mediators in 1 M Na2SO4 or NaNO3, the performance of electrochemical AP degradation, p-BQ removal, and TOC mineralization on a Diachem BDD anode occurred in the following order: Fe(III) > Ce(IV) > Fe(II) ≈ Co(II) > Ag(I), but the performance decreased when replacing Na2SO4 with NaNO3 as the electrolyte. The Cl2/Cl- redox mediator could also enhance AP degradation and TOC mineralization. The apparent pseudo first-order rate constants for AP electrochemical degradation in these solutions ranged from 2.92×10-4-4.34x10-2 1/s. An Fe(III) dosage of 100 ppm (Fe(III)/AP mole ratio = 2.7) at 0.25 A/cm2 is suggested for this electrochemical process although Fe(III) dosage in the range of 50-500 ppm could be considered. Fe(III) has good potential for use in the elctrochemical advanced oxidation process (EAOP) to significantly improve organic pollutant degradation performance.

Yan Zhang, Yu Zhou, Zonghua Wang et al.

Exploring cheap and stable electrocatalyst for the oxygen reduction reaction (ORR) is now an important issue for the large-scale application of fuel cells. Herein, we have demonstrated a facile synthesis of Nitrogen-doped porous carbons (NPC-MILs) for oxygen reduction reaction by using an amine functionalized Al-MOFs (NH2-MIL-53(Al)) as the precursor with both nitrogen source and carbon source. NPC-MILs as metal-free electrocatalysts are demonstrated promising potential for ORR. The optimized NPC-MIL-900 (carbonized at 900 °C) exhibits a likeness four-electron process and its ORR catalytic activity can be comparable to commercial Pt/C. Furthermore, chronoamperometric measurement shows that only 13% loss at the current density is occurred after 40000 s, whereas the corresponding current density loss at the Pt/C (20wt%) is as high as 31%. Chronoamperometric responses also show the NPC-MIL-900 catalyst has higher resistance to methanol in alkaline electrolyte than Pt/C. Those indicate that the NPC-MIL-900 has potential application in fuel cells.

Ya-wei Hu, Wei Wang, Huai-en Li et al.

Using a hydrothermal technique, the present study demonstrated the synthesis of a Cu metal–organic framework (Cu-MOF), [Cu(adp)(BIB)(H2O)]n (BIB = 1,4-bisimidazolebenzene; H2adp = adipic acid). Carbendazim was successfully detected by an ultra-sensitive and facile electrochemical sensor fabricated based on the [Cu(adp)(BIB)(H2O)]n-coated GCE via differential pulse voltammetry. The present study employed [Fe(CN)6]3−/4− as an electrochemical probe to investigate the electrochemical properties of our developed sensor. The charge transfer rate and electrode surface of the [Cu(adp)(BIB)(H2O)]n/GCE were both more favourable compared to those of the bare GCE. Cyclic voltammetry results suggested a desirable electrochemical performance of our developed sensor towards the detection of carbendazim. Our developed sensor was excellent towards the electrochemical oxidation of the analyte. In addition, the as-prepared electrochemical sensor showed great potential for the detection of carbendazim in water samples.