Hasil untuk "Physical and theoretical chemistry"

Anton Frisk Kockum, A. Miranowicz, S. De Liberato et al.

Light–matter coupling with strength comparable to the bare transition frequencies of the system is called ultrastrong. This Review surveys how experiments have realized ultrastrong coupling in the past decade, the new phenomena predicted in this regime and the applications it enables. Ultrastrong coupling between light and matter has, in the past decade, transitioned from a theoretical idea to an experimental reality. It is a new regime of quantum light–matter interaction, which goes beyond weak and strong coupling to make the coupling strength comparable to the transition frequencies in the system. The achievement of weak and strong coupling has led to increased control of quantum systems and to applications such as lasers, quantum sensing, and quantum information processing. Here we review the theory of quantum systems with ultrastrong coupling, discussing entangled ground states with virtual excitations, new avenues for nonlinear optics, and connections to several important physical models. We also overview the multitude of experimental setups, including superconducting circuits, organic molecules, semiconductor polaritons, and optomechanical systems, that have now achieved ultrastrong coupling. We conclude by discussing the many potential applications that these achievements enable in physics and chemistry. Ultrastrong coupling (USC) can be achieved by coupling many dipoles to light, or by using degrees of freedom whose coupling is not bounded by the smallness of the fine-structure constant. The highest light–matter coupling strengths have been measured in experiments with Landau polaritons in semiconductor systems and in setups with superconducting quantum circuits. With USC, standard approximations break down, allowing processes that do not conserve the number of excitations in the system, leading to a ground state that contains virtual excitations. Potential applications of USC include fast and protected quantum information processing, nonlinear optics, modified chemical reactions and the enhancement of various quantum phenomena. Now that USC has been reached in several systems, it is time to experimentally explore the new phenomena predicted for this regime and to find their useful applications. Ultrastrong coupling (USC) can be achieved by coupling many dipoles to light, or by using degrees of freedom whose coupling is not bounded by the smallness of the fine-structure constant. The highest light–matter coupling strengths have been measured in experiments with Landau polaritons in semiconductor systems and in setups with superconducting quantum circuits. With USC, standard approximations break down, allowing processes that do not conserve the number of excitations in the system, leading to a ground state that contains virtual excitations. Potential applications of USC include fast and protected quantum information processing, nonlinear optics, modified chemical reactions and the enhancement of various quantum phenomena. Now that USC has been reached in several systems, it is time to experimentally explore the new phenomena predicted for this regime and to find their useful applications.

T. Lu, Qinxue Chen

Energy decomposition analysis (EDA) is an important class of methods to explore the nature of interaction between fragments in a chemical system. It can decompose the interaction energy into different physical components to understand the factors that play key roles in the interaction. This work proposes an EDA strategy based on dispersion-corrected density functional theory (DFT), called sobEDA. This method is fairly easy to implement and very universal. It can be used to study weak interactions, chemical bond interactions, open-shell systems, and interactions between multiple fragments. The total time consumption of sobEDA is only about twice that of conventional DFT single-point calculation for the entire system. This work also proposes a variant of the sobEDA method named sobEDAw, which is designed specifically for decomposing weak interaction energies. Through a proper combination of DFT correlation energy and dispersion correction term, sobEDAw gives a ratio between dispersion energy and electrostatic energy that is highly consistent with the symmetry-adapted perturbation theory, which is quite popular and robust in studying weak interactions but expensive. We present a shell script sobEDA.sh to implement the methods proposed in this work based on the very popular Gaussian quantum chemistry program and Multiwfn wavefunction analysis code. Via the script, theoretical chemists can use the sobEDA and sobEDAw methods very conveniently in their study. Through a series of examples, the rationality of the new methods and their implementation are verified, and their great practical values in the study of various chemical systems are demonstrated.

Mingqi Guo, Roohollah Noori, S. Abolfathi

Freshwater ecosystems are viewed as a key medium for the transport of land-based plastics into oceans. Microplastic (MP) particles in freshwater environments demonstrate high persistence and an extensive range of size and shape distributions, which make their mobility, distribution, and fate vary distinctly depending on the prevailing environmental conditions. The inherent physical properties of different plastic polymers are constantly evolving at different specific reaction rates due to the complex weathering processes in the environment. This continuously alters the underlying mechanisms governing MP dynamics and further complicates their ultimate fate in natural aquatic systems. This paper conducts a comprehensive review of the dynamic behaviour of MPs in freshwater ecosystems, focusing on investigating the settling, aggregation, retention, and suspension processes governing their transport from the source to the sink. We provide an in-depth overview of the key theoretical foundations of MP behaviour in ambient flows and the key influential factors (i.e. size, density, shape, composition). Our findings highlight intricate interplays between MP dynamic behaviours and local hydrodynamics and water chemistry, which lead to the continuous evolution of MP physicochemical properties (e.g., size, surface charge) through interactions with suspended solids, organic natural matter, and microorganisms under light and wind exposure. This dynamic poses significant challenges in predicting MP transport processes and ultimate fate. Gap analysis highlights the discrepancy between current models based on controlled laboratory conditions and complex natural environments, signifying the need for investigating MP dynamic behaviour across a wide range of environmental conditions (e.g. simulating complex flow patterns and solution chemistries of real water bodies). Further research is needed to expand field studies to correlate environment hydrodynamics with MP abundance and to conduct mesoscale experiments that accurately reflect the effects of weathering and flow hydrodynamics on MP behaviours. Integrating detailed physical experiments with numerical modelling tools is essential for a comprehensive understanding of the interactions among various MPs and their overall impact on the environment. This facilitates robust and reliable environmental risk assessment for MP control and pollution management.

Qingfeng Zhai, Hetaishan Huang, Tom Lawson et al.

Over the last decade, carbon‐based metal‐free electrocatalysts (C‐MFECs) have become important in electrocatalysis. This field is started thanks to the initial discovery that nitrogen atom doped carbon can function as a metal‐free electrode in alkaline fuel cells. A wide variety of metal‐free carbon nanomaterials, including 0D carbon dots, 1D carbon nanotubes, 2D graphene, and 3D porous carbons, has demonstrated high electrocatalytic performance across a variety of applications. These include clean energy generation and storage, green chemistry, and environmental remediation. The wide applicability of C‐MFECs is facilitated by effective synthetic approaches, e.g., heteroatom doping, and physical/chemical modification. These methods enable the creation of catalysts with electrocatalytic properties useful for sustainable energy transformation and storage (e.g., fuel cells, Zn‐air batteries, Li‐O2 batteries, dye‐sensitized solar cells), green chemical production (e.g., H2O2, NH3, and urea), and environmental remediation (e.g., wastewater treatment, and CO2 conversion). Furthermore, significant advances in the theoretical study of C‐MFECs via advanced computational modeling and machine learning techniques have been achieved, revealing the charge transfer mechanism for rational design and development of highly efficient catalysts. This review offers a timely overview of recent progress in the development of C‐MFECs, addressing material syntheses, theoretical advances, potential applications, challenges and future directions.

Lei Zhang, Taotao Xiao, Xiayun Zeng et al.

The C2H2 separation from CO2 and C2H4 is of great importance yet highly challenging in the petrochemical industry, owing to their similar physical and chemical properties. Herein, the pore nanospace engineering of cage-like mixed-ligand MFOF-1 has been accomplished via contracting the size of the pyridine- and carboxylic acid-functionalized linkers and introducing a fluoride- and sulfate-bridging cobalt cluster, based on a reticular chemistry strategy. Compared with the prototypical MFOF-1, the constructed FJUT-1 with the same topology presents significantly improved C2H2 adsorption capacity, and selective C2H2 separation performance due to the reduced cage cavity size, functionalized pore surface, and appropriate pore volume. The introduction of fluoride- and sulfate-bridging cubane-type tetranuclear cobalt clusters bestows FJUT-1 with exceptional chemical stability under harsh conditions while providing multiple potential C2H2 binding sites, thus rendering the adequate ability for practical C2H2 separation application as confirmed by the dynamic breakthrough experiments under dry and humid conditions. Additionally, the distinct binding mechanism is suggested by theoretical calculations in which the multiple supramolecular interactions involving C-H···O, C-H···F, and other van der Waals forces play a critical role in the selective C2H2 separation.

Z. Xia, K. Poeppelmeier

Chen Yilun, Xu Zhong, Chen Ge et al.

Darko Micić, Saša D. Đurović, Saša D. Đurović et al.

IntroductionSummer savory is still not investigated thoroughly despite its potential and beneficial effects. Therefore, we aimed to investigate its chemical profile, thermal properties, extraction kinetics, and to optimize extraction process.MethodsHerein, an artificial neural network (ANN) was used as a nonlinear regression-based optimization model to optimize the microwave-assisted extraction of summer savory leaves. To achieve the goal, 17 experiments were conducted, combining different extraction times (20–40 min), ethanol concentrations (68–80%), and irradiation powers (400–800 W). Investigated responses included total phenolic content (TPC), total flavonoid content (TFC), DPPH, and ABTS assays. Kinetics was investigated by using four models, while thermal behavior was studied using DSC and TGA.ResultsThe highest outputs were: 256.36 mg GAE/g (GAE-gallic acid equivalents) (40 min, 40% ethanol, and 600 W) for TPC, 35.78 mg RU/g (rutin equivalents) (40 min, 60% ethanol, and 400 W) for TFC, 15.89 μg/mL (20 min, 60% ethanol, and 400 W) for DPPH, and 23.06 μg/mL (30 min, 60% ethanol, and 600 W) for ABTS. As a result of optimization, we obtained optimal extraction conditions (40 min, 52.8% ethanol, and 656.1 W) and predicted responses (246.50 mg GAE/g for TPC, 35.66 mg RU/g for TFC, and IC50 and EC50 values of 17.79 μg/mL and 25.79 μg mL for DPPH and ABTS assays, respectively). The experimentally obtained values for the investigated responses were 242.25 mg GAE/g, 36.30 mg RU/g, 17.10 μg/mL, and 24.48 μg/mL for TPC, TFC, IC50, and EC50, respectively. Total content of the quantified phenolic compounds was 91.47 μg/mL. The principal compound was rosmarinic acid (80.99 μg/mL), followed by chlorogenic acid (2.64 μg/mL), rutin (1.45 μg/mL), and apigenin (1.31 μg/mL).DiscussionThe validity of the developed ANN model has been confirmed experimentally after preparing the extract under optimal conditions. Kinetic modeling showed that Model II provided the best fit for TFC, while Model IV provided the best fit for TPC. Optimally prepared extract showed high antioxidant activity and thermal behavior and could be used in food and pharmaceutical industry as an additive.

M. Hong, Zhi-gang Chen

ConspectusThe ever-growing energy crisis and the deteriorated environment caused by carbon energy consumption motivate the exploitation of alternative green and sustainable energy supplies. Because of the unique advantages of zero-emission, no moving parts, accurate temperature control, a long steady-state operation period, and the ability to operate in extreme situations, thermoelectrics, enabling the direct conversion between heat and electricity, is a promising and sustainable option for power generation and refrigeration. However, with increasing application potentials, thermoelectrics is now facing a major challenge: developing high-performance, Pb-free, and low-toxic thermoelectric materials and devices.As one group of promising candidates, GeTe derivatives have the potential to replace the widely used thermoelectric materials containing highly toxic elements. In this Account, we summarize our recent progress in developing high-performance GeTe-based thermoelectric materials via exploring innovative strategies to enhance electron transports and dampen phonon propagations. First, we fundamentally illustrate the underlying chemistry and physical reason for an intrinsically high carrier concentration in GeTe, which enormously restrains the thermoelectric performance of GeTe. From our theoretical calculations, the formation energy of Ge vacancy is the lowest among the defects in GeTe, energetically favoring Ge vacancies in the lattice and leading to intrinsically high carrier concentrations. Accordingly, aliovalent doping/alloying is proposed to increase the formation energy of Ge vacancies and decrease the carrier concentration to the optimal level. We then outline the newly developed method to refine the band structures of GeTe with tuned electronic transport. On the basis of the molecular orbital theory, the energy offset between two valence band edges at the L and Σ points in GeTe should be ascribed to the slightly different Ge_4s orbital characters at these two points, which guides the screening of dopants for band convergence. Besides, the Rashba spin splitting is explored to increase the band degeneracy of GeTe. Afterward, we analyze the dampened phonon propagation in GeTe to minimize its lattice thermal conductivity. Alloying with the heavy Sb atoms can shift the optical phonon modes toward low frequency and reinforce the interaction of optical and acoustic phonon modes so that the inherent phonon scattering is enhanced. In addition, planar vacancies and superlattice precipitates can significantly strengthen phonon scattering to result in ultralow lattice thermal conductivity. After that, we overview the finite elemental analysis simulations to optimize the device geometry for maximizing the device performance and introduce the as-developed prototype GeTe-based thermoelectric device. In the end, we point out future directions in the development of GeTe for device applications. The strategies summarized in this Account can serve as references for developing wide materials with enhanced thermoelectric performance.

Wu Hanjiang, Huang Tao, Song Kexing et al.

Copper-based wire has excellent comprehensive performance and is widely used in integrated circuit packaging, electronic communication, connectors, audio and video transmission, and other fields. Based on the crystal plasticity finite element method, the crystal plasticity finite element model of multi-pass continuous drawing deformation of pure copper micro wires was established, and the reliability of the model was proved. The continuous drawing deformation behavior of micro wires under high-speed deformation and micro wire diameter scale effect was studied. The research shows that there is a fracture risk zone under the alternating action of positive and negative stress values in the deformation zone of the drawn wire. The changing drawing force and contact stress during the continuous drawing process of the wire will also reduce the stability and surface quality of the wire during the drawing process. The shear deformation and slip degree of the surface grain of the drawn wire are greater than those of the core grain, and the drawing die has a greater impact on the slip system state of the surface of the wire. With the increase in drawing passes, the mechanical characteristics inside the wire increase accordingly, and the deformation uniformity inside the grains is improved. The established model can demonstrate the deformation history characteristics and structure inheritance of the continuous wire drawing process.

Zhandong Li, Dmitry Kurouski

ConspectusHot carriers are highly energetic species that can perform a large spectrum of chemical reactions. They are generated on the surfaces of nanostructures via direct interband, phonon-assisted intraband, and geometry-assisted decay of localized surface plasmon resonances (LSPRs), which are coherent oscillations of conductive electrons. LSPRs can be induced on the surface of noble metal (Ag or Au) nanostructures by illuminating the surfaces with electromagnetic irradiation. These noble metals can be coupled with catalytic metals, such as Pt, Pd, and Ru, to develop bimetallic nanostructures with unique catalytic activities. The plasmon-driven catalysis on bimetallic nanostructures is light-driven, which essentially enables green chemistry in organic synthesis. During the past decade, surface-enhanced Raman spectroscopy (SERS) has been actively utilized to study the mechanisms of plasmon-driven reactions on mono- and bimetallic nanostructures. SERS has provided a wealth of knowledge about the mechanisms of numerous plasmon-driven redox, coupling, and scissoring reactions. However, the nanoscale catalytic properties of both mono- and bimetallic nanostructures as well as the underlying physical cause of their catalytic reactivity and selectivity remained unclear for decades.In this Account, we focus on the most recent findings reported by our and other research groups that shed light on the nanoscale properties of mono- and bimetallic nanostructures. This information was revealed by tip-enhanced Raman spectroscopy (TERS), a modern analytical technique that has single-molecule sensitivity and subnanometer spatial resolution. TERS findings have shown that plasmonic reactivity and the selectivity of bimetallic nanostructures are governed by the nature of the catalytic metal and the strength of the rectified electric field on their surfaces. TERS has also revealed that the catalytic properties of bimetallic nanostructures directly depend on the interplay between the catalytic and plasmonic metals. We anticipate that these findings will be used to tailor synthetic approaches that are used to fabricate novel nanostructures with desired catalytic properties. The experimental and theoretical results discussed in this Account will facilitate a better understanding of TERS and explain artifacts that could be encountered upon TERS imaging of a large variety of samples. Consequently, plasmon-driven chemistry should be considered as an essential part of near-field microscopy.

Ahmed M. El-Zohry

Detection of intermediates during the catalytic process by infrared techniques has been widely implemented for many important reactions. For the reduction of CO₂ into hydrocarbons on metal surfaces, CO molecule is one of the most important transient species to be followed due to its involvement in several products’ pathways, and its distinct vibrational features. Herein, basic understandings behind these utilized infrared techniques are illustrated aiming for highlighting the potential of each infrared technique and its advantages over the other ones for detecting CO molecules on metal surfaces.

Thi Ngoc Mai Pham, Thi Hieu Hoang, Thu Phuong Nguyen et al.

Adsorption characteristics of the antibiotic meropenem on a novel magnetic material synthesized by surface coating cobalt iron oxide (CFO) with gold nanoparticles (AuNPs) were systematically investigated. The AuNPs can enhance material adsorption capacity by having high affinity towards the thioether and amine groups in the meropenem structure. Au coverage on the CFO surface decreased the saturation magnetization from 55.8 emu/g to 48.8 emu/g, still allowing synthesized CFO@Au nanomaterials to be magnetically recoverable. The CFO@Au nanomaterials showed enhanced adsorption capacity of 25.5 mg/g at optimum conditions of pH 4.0 adsorption time 120 min, and adsorbent mass 0.05 g. Adsorption equilibrium was in accordance with a monolayer Langmuir isotherm, while the adsorption kinetics followed pseudo-first-order kinetics and intraparticle diffusion models. This work provides a simple method to prepare a magnetic composite material with high adsorption efficiency for meropenem and probably other thioether-containing substances.

Longhua Xu, Zhoujie Wang, Kaiqian Shu et al.

Inefficient flotation of bastnaesite remains a challenge in the production of rare earth elements. This study aimed to investigate the dissolution and adsorption behaviour of species that are commonly released into bastnaesite flotation pulp from Ca/Ba-bearing gangue minerals. The influence and corresponding mechanisms on the bastnaesite mineral surface and collectors, namely sodium oleate (NaOL), were evaluated experimentally based on micro-flotation, zeta potentials, in situ attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), and X-Ray photoelectron spectroscopy (XPS) analyses. The flotation recovery of bastnaesite significantly decreased from ∼95% to ∼25%, ∼15%, ∼80%, ∼25% when exposed to calcite, fluorite, barite, and mixed dissolved species, respectively. The zeta potential of bastnaesite was pH sensitive, indicating that H+ and OH− determine the surface potential of bastnaesite. Solution chemistry analyses revealed that the presence of the dissolved species differed at various pH values. In situ ATR-FTIR demonstrated the different effects of the dissolved species from calcite, fluorite, and barite on collector adsorption. The former two dissolved species mainly depressed the chemisorption of the NaOL monomers (RCOO‒), whereas calcite also affected the physical adsorption of the oleic acid molecular dimer (RCOOH·RCOO‒). Moreover, the barite dissolved species only affected the physical adsorption of the NaOL species. The results of XPS analysis revealed that dissolved species from these three gangues could pre-adsorbed onto bastnaesite and affected the interaction with the collector. Density functional theory calculations were employed to provide further theoretical insights into the interactions between the dissolved species from calcite, fluorite, and barite and NaOL.

D. Grasseschi, W. C. Silva, Ronald de Souza Paiva et al.

Abstract The recent advances in single-atom applications have shown that it is possible to manipulate the materials’ properties by controlling its structure at the atomic level. Immobilization of single transition metal (TM) atom with catalytic, optical, electronic, or magnetic properties onto graphene supports is an outstanding research field. A similarity between graphene surface chemistry and the classical coordination chemistry is expected, and TM anchoring on the graphene can be view as the formation of a coordination complex. The possibility of tuning the electronic and chemical properties of graphene’s coordination sites by varying its electron donor-receptor and hard-soft acid-base characteristics transforms graphene in a versatile and rich platform to pave the way for a deeper understanding of the surface coordination chemistry of other 2D materials. In this context, this review is focused on the latest advances on single atom functionalization (SAF) of graphene with transition metal ions, covering the synthesis, characterization, and its effects on graphene’s physical and chemical properties. The fundamental aspects of the coordination chemistry, and how it is related to graphene’s surface chemistry will be presented to give the basis to discuss the theoretical and experimental progress on graphene’s SAF. A parallel between graphene solid-state physics theory and classical coordination chemistry, two areas that hardly influenced each other, will be done using concepts of ligand-field theory, Pearson’s hard-soft acid-bases concept, and the molecular orbital theory of transition metal complexes.

M. Giansiracusa, E. Moreno‐Pineda, R. Hussain et al.

Magnetic exchange interactions within the asymmetric dimetallic compounds [hqH2][Ln2(hq)4(NO3)3]·MeOH, (Ln = Er(III) and Yb(III), hqH = 8-hydroxyquinoline) have been directly probed with EPR spectroscopy and accurately modeled by spin Hamiltonian techniques. Exploitation of site selectivity via doping experiments in Y(III) and Lu(III) matrices yields simple EPR spectra corresponding to isolated Kramers doublets, allowing determination of the local magnetic properties of the individual sites within the dimetallic compounds. CASSCF-SO calculations and INS and far-IR measurements are all employed to further support the identification and modeling of the local electronic structure for each site. EPR spectra of the pure dimetallic compounds are highly featured and correspond to transitions within the lowest-lying exchange-coupled manifold, permitting determination of the highly anisotropic magnetic exchange between the lanthanide ions. We find a unique orientation for the exchange interaction, corresponding to a common elongated oxygen bridge for both isostructural analogs. This suggests a microscopic physical connection to the magnetic superexchange. These results are of fundamental importance for building and validating model microscopic Hamiltonians to understand the origins of magnetic interactions between lanthanides and how they may be controlled with chemistry.

Huijun Cao, Shihui si, Xiangbin Xu et al.

The electrochemical activities of polyaniline (PANI) in different manganese (Mn) salt solutions were studied. The experimental results show better electrochemical activity for PANI in the manganese chloride (MnCl2) solution. Additionally, the electrochemical reaction performance of PANI was enhanced by the addition of lithium chloride (LiCl) in the MnCl2 electrolyte. Doping with manganese ions (Mn2+) also improved the conductivity of MnCl2. Porous carbon felt was used as the three-dimensional (3D) matrix for electrochemical sedimentation. The deposition efficiency was greatly improved by the addition of zinc ions (Zn2+) in the electrolyte. With a concentration of 0.5 M Zn2+, the deposition efficiency of Mn was 93%. With the Mn-doped PANI particle suspension as the cathode material and the 3D Zn-Mn alloy as the anode, the flow battery was tested at different charge and discharge current densities. The discharge capacity density reached 153 mAh·g-1 at 15 mA cm-2, and the average discharge voltage was more than 1.2 V, which indicates that the present cell is promising for use as high-performance rechargeable battery or energy storage.

Chelliah Koventhan, Venkatachalam Vinothkumar, Shen-Ming Chen et al.

Transition metal chalcogenide has great interest owing to unique structural properties, higher conductivity, larger electroactive surface area, and excellent catalytic response. Herein, we have synthesized flake like MoS2 via the simple hydrothermal method for electrochemical detection of Metol (MT). For spectral analysis, X-ray diffraction, Fourier transform infrared instrument, Field Emission Electron Microscopy, and elemental mapping displays successfully formation of flake-like MoS2. The electrochemical activity was tested in electrochemical impedance spectroscopy, cyclic voltammetry, differential pulse voltammetric techniques. As a result, the proposed sensor shows the excellent active surface area is 0.78 cm2, lower peak to peak separation is 0.24 V, respectively. Moreover, the flake-like electrode exhibits a wide linear range from 0.2 to 1211 μM, the low detection limit is 0.01 μM, with the higher sensitivity is 1.05 μA μM-1 cm-2 in the detection of MT. Furthermore, MoS2 modified SPCE demonstrates enrich selectivity, stability, reproducibility, repeatability during the detection of MT. Finally, the real-time application was applied in river and tap water samples with acceptable recoveries of MT detection.

Bryant A. Chambers, A. N. Afrooz, Sungwoo Bae et al.