Breaking Of Chemical Bonds Research Articles

Emergence of negative viscosities and colored noise under current-driven Ehrenfest molecular dynamics

Molecules in molecular junctions are subject to current-induced forces that can break chemical bonds, induce reactions, destabilize molecular geometry, and halt the operation of the junction. Theories behind current-driven molecular dynamics simulations rely on a perturbative time-scale separation within the system with subsequent use of nonequilibrium Green's functions (NEGF) to compute conservative, non-conservative, and stochastic forces exerted by electrons on nuclear degrees of freedom. We analyze the effectiveness of this approximation, paying particular attention to the phenomenon of negative viscosities. The perturbative approximation is directly compared to the nonequilibrium Ehrenfest approach. We introduce a novel time-stepping approach to calculate the forces present in the Ehrenfest method via exact integration of the equations of motion for the nonequilibrium Green's functions, which does not necessitate a time-scale separation within the system and provides an exact description for the corresponding classical dynamics. We observe that negative viscosities are not artifacts of a perturbative treatment but also emerge in Ehrenfest dynamics. However, the effects of negative viscosity have the possibility of being overwhelmed by the predominantly positive dissipation due to the higher-order forces unaccounted for by the perturbative approach. Additionally, we assess the validity of the white-noise approximation for the stochastic forces, finding that it is justifiable in the presence of a clear time-scale separation and is more applicable when the current-carrying molecular orbital is moved outside of the voltage window. Finally, we demonstrate the method for molecular junction models consisting of one and two classical degrees of freedom.

Nanoprodrugs encapsulated with mesoporous silica nanoparticles for combined with photothermal therapy for the treatment and care of gastric cancer

In this study, mesoporous silica nanoparticles (MSNs) were surface-modified with polymer poly(HEMA-co-PEGMA via surface-initiated atom transfer radical polymerization and a multifunctional nanoplatform MSNP@poly(HEMA-co-PEGMA-g-doxorubicin (DOX)/Rhodamine 6 G (R6G) was developed to combine photothermal (PTT) and chemotherapy therapy effectively. PTT induced by near-infrared (NIR) radiations might further destroy gastric cancer cell lines while the small-dye molecule was co-loaded into the MSNP pores. A 65 % higher cumulative drug release over 50-h occurs when the cis-aconitic anhydride link breaks under low-pH stimulation (typical physiological environment). High temperatures accelerated reversible covalent bond breakage. The accumulative release of the drug increased by 24.3 %, illustrating that higher temperatures can decrease the time needed to complete blood drug concentrations by 24.3 %. More than 90% of gastric tumour cells were destroyed after 48 h following exposure to NIR light irradiation with the prodrug delivery system, compared to DOX alone in vitro cytotoxicity tests. Because of this, rapidly reversible chemical bond breaking and photothermal activity in MSNP@poly(HEMA-co-PEGMA-g-DOX/R6G) increased the synergic impact of the chemotherapy, which offers tremendous promise in combination with the treatment and care of gastric cancer therapy.

Wettability after Artificial and Natural Weathering of Polyethylene Terephthalate

The weathering of plastics is always accompanied by a change in surface properties, especially wettability in the case of water. For plastics weathering in an aquatic environment, wettability plays an important role in transport, sedimentation, and dispersion in the water body. To quantify wettability, contact angle measurement is a fast and convenient method that requires little experimental effort. This technique was used with the aim of systematically discussing how measured values of contact angles can contribute to the assessment of the weathering state. Using polyethylene terephthalate (PET), wetting was analyzed on samples from artificial weathering and from controlled, natural weathering. Surface analytical methods were used (Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), ultraviolet and visible light spectroscopy (UV/VIS)) to analyze the parameters affecting the contact angle: (i) chemical bond breaking and formation, (ii) eco-corona formation and biofilm growth, and (iii) change in surface structure and roughness. It was found that wettability with water increased during weathering in all cases. The reasons for this varied and depended on the method of weathering. The improved wettability during artificial weathering was due to changes in the polymer surface chemistry. In natural weathering, however, the formation of eco-corona and biofilm was responsible for the changes.

Characteristics and Evolution Mechanism of Three Phase Products of Lignite by Hydrothermal Treatment Dewatering.

Baiyinhua lignite was treated by hydrothermal treatment dewatering (HTD). The production characteristics of the gas, solid, and liquid were studied. Results show that HTD is an effective means to decrease water content and water-holding capacity. When the treatment temperature was increased to 310 °C, the moisture was reduced from 26.55% to 5.27%, and the dehydration rate reached 80.20%. At the same time, the carbon content and calorific value increased during the HTD process, which increased energy density. The H/C atomic ratio increased first, then decreased with the increasing temperature. The increase in the H/C atomic ratio was due to the breakdown of aromatic ether and formation of phenolic compounds at the low temperature. The phenolic compounds started to break at the high temperature, which resulted in the decrease in the H/C atomic ratio. These results can be proven by 13C NMR analysis. Combined with the analyses of calorific value, dehydration ratio, recovery of combustible product, and heat loss, the relative balance dehydration and deoxidation efficiency were evaluated, and 250 °C is a suitable temperature for the HTD process in lignite upgrading. The HTD process promoted the breakage and decomposition of weak chemical bonds in lignite, which resulted in many organic compounds in wastewater after the HTD process. The chemical oxygen demand and biochemical oxygen demand continually increase, and the biodegradability of the wastewater is relatively good. The index of biodegradability for wastewater is greater than 0.3 even at a hydrothermal treatment temperature of 310 °C. This indicates that wastewater can be subjected to biochemical treatment at a low treatment cost. At the same time, the metal ions and nonmetallic ions in wastewater and the gas component were studied. These research results aim to provide theoretical guidance for the industrialization of lignite hydrothermal modification.

First-principles approaches and models for crystal defect energetics in metallic alloys

Many physical and mechanical properties of metallic alloys are sensitive to the formation and migration of crystal defects such as vacancies, dislocations, stacking faults, and grain boundaries. Those defect behaviors are intrinsically governed by the energetics associated with the distortion, breaking, and reforming of chemical bonds at the atomistic level. As such, first-principles calculations based on density functional theory, which accurately describe the energies and electronic structures of interatomic bonding, have been widely applied to study the formation and migration energetics of crystal defects in various alloy systems. This review article aims to provide a brief summary of the contemporary approaches and models associated with first-principles calculations for accurate modeling and prediction of energetics of various crystal defects in metallic alloys. The review also highlights the recent progress in the development of physics- or/and data-driven-based surrogate models for more efficient predictions of defect energies with first-principles accuracy in a broad range of alloy systems. Last but not least, some of the remaining challenges and issues associated with the first-principles modeling of crystal defects are discussed, along with recommendations for possible solutions.

Identifying the Molecular Properties that Drive Explosive Sensitivity in a Series of Nitrate Esters.

Energetic materials undergo hundreds of chemical reactions during exothermic runaway, generally beginning with the breaking of the weakest chemical bond, the “trigger linkage.” Herein we report the syntheses of a series of pentaerythritol tetranitrate (PETN) derivatives in which the energetic nitrate ester groups are systematically substituted by hydroxyl groups. Because all the PETN derivatives have the same nitrate ester-based trigger linkages, quantum molecular dynamics (QMD) simulations show very similar Arrhenius kinetics for the first reactions. However, handling sensitivity testing conducted using drop weight impact indicates that sensitivity decreases precipitously as nitrate esters are replaced by hydroxyl groups. These experimental results are supported by QMD simulations that show systematic decreases in the final temperatures of the products and the energy release as the nitrate ester functional groups are removed. To better interpret these results, we derive a simple model based only on the specific enthalpy of explosion and the kinetics of trigger linkage rupture that accounts qualitatively for the decrease in sensitivity as nitrate ester groups are removed.

Metabolite Fragmentation Visualization

Tandem mass spectrometry (MS/MS) is a popular technology for identifying small molecules involved in metabolism, better known as metabolites. Coupled with liquid chromatography (LC), LC-MS/MS instruments first separate, ionize, and fragment metabolites, then measure mass-to-charge ratios (m/z) and intensities of metabolite fragments. Understanding metabolite fragmentation is crucial to develop computational tools for identifying metabolites based on this spectroscopic data. Metabolite fragmentation patterns have large variations making it especially difficult for computer scientists to design and implement metabolite identification approaches. To address this interdisciplinary challenge, this article presents FragView, a web-based application providing the web service for visualizing metabolite fragmentation. Users can break chemical bonds to produce metabolite fragments and export 3D fragment structures for 3D printing. Developing FragView is an opportunity for exposing student participants to this interdisciplinary bioinformatics project. This paper summarizes the experience of training student participants in bootcamps and designing the implementation plan based on student backgrounds. Students were exposed to project meeting discussions on coding and raw data visualization and visited a lab with an LC-MS/MS instrument. FragView is an open source, freely accessible tool, released under the GPLv3 license. We will continue to improve and update FragView in the future based on feedback.

Development of QM/MM (ABEEM polarizable force field) method to simulate the excision reaction mechanism of damaged cytosine.

DNA damages are regarded as having harmful effects on cell. The base excision repair mechanism combats these effects by removing damaged bases. The deglycosylation mechanism of excising damaged bases by DNA glycosylase and the state of the leaving base have been controversial. The enzymatic reaction of DNA glycosylase to remove the damaged bases involves not only the formation and breaking of chemical bonds, but also complex polarization effect and charge transfer, which cannot be accurately simulated by the QM/MM method combined with the fixed charge force field. This work has developed the ABEEM fluctuating polarizable force field combining with the QM method, that is (QM/MM[ABEEM]), to accurately simulate the proton transfer, charge transfer and the charge distribution. The piecewise function is used as the valence-state electronegativity in the QM/MM (ABEEM) to realize the accurate fitting of the charge distribution in reaction. And the charge transfer is accurately simulated by the local charge conservation conditions. Four deglycosylation mechanisms including the monofunctional and difunctional mechanisms of four neutral and protonated cytosine derivatives are explored. It is confirmed that the monofunctional mechanism of Asp-activated nucleophile water is a better deglycosylation mechanism and the base is protonated before the reaction occurs. Protonization of the base reduced the activation energy by 10.00-17.00 kcal/mol. Asp provides the necessary charge for the reaction, and DNA glycosylase preferentially cleaves ɛC. This work provides a theoretical basis for the research of excising damaged bases by DNA glycosylase.

Surface morphology and microstructure of the hole sidewall during drilling of Polyether-Ether-Ketone(PEEK) via single-pulse laser

Polyether-ether-ketone (PEEK), as one kind of thermoplastic polymers, exhibits a great deal of remarkable properties and plays an important role in aerospace, electronics, automotive and medicine. An investigation of single-pulse laser drilling on Polyether-ether-ketone (PEEK) was reported to show the influence of irradiation energy on the hole sidewall. In-situ evolution of drilling process was observed by the high-speed camera. The surface morphology and microstructural characteristics of the hole sidewall were evaluated by different characterization techniques. The hole sidewall was divided into three parts: expanded zone at the entrance, linear zone in the middle, and U-shaped zone at the bottom. It was found that the quality of inner sidewall could be obviously improved under high single-pulse energy (>1 J), in terms of the surface morphology with small heat-affected zone (HAZ) thickness and surface roughness, as well as the least adhesion. Besides, chemical and structural characteristics of the hole sidewall changed a lot under high energy. The C content of three parts increased as the energy increased. The crystallinity of the hole sidewall decreased from 35 % to 25 % after laser-energy irradiation, but there was little change under different single-pulse energy. New diffraction peaks appeared in X-ray diffraction images and the intensity of the relative peaks in Raman spectra decreased when the energy was over 1 J. It was proven that some chemical bonds (phenyl ring (1597 cm−1) and C–O–C (1148 cm−1)) would break under high energy, contributing to mass removal of the keyhole. Moreover, the HAZ thickness of the hole sidewall was calculated based on a viscous flow model, which showed a good consistency with experimental results. These results reveal material-removal mechanism accompanying the appearance of direct decomposition of the material and breaking of chemical bonds under high energy. It can provide references for understanding mechanisms of HAZ formation and material-removal and improving surface quality for laser drilling of polymers.

Micromicelle-mechanical coupling method for high-efficiency phosphorus removal and whiteness improvement of phosphogypsum

Phosphogypsum contained harmful impurities and seriously affected its large-scale utilization. The existing stockpiling and water washing methods gradually fail to meet the requirements of environmental protection and process in the purification effect during the phosphorus chemical production process. Compared with various purification processes, although the application of phosphogypsum could be optimized, most processes had the characteristics of high energy consumption. Therefore, it was urgent to develop a new method for purifying phosphogypsum with low energy consumption, water saving, and high efficiency. In this work, the coupling of mechanical activation and chemical solubilization method successfully realized the efficient and water-saving purification of phosphogypsum. The experimental data showed that the chemical bond breakage in the phosphogypsum crystals after grinding and the promotion of the chemical microenvironment not only achieved the grain refinement of the phosphogypsum but also achieved the removal of soluble phosphorus and the improvement of the whiteness of the phosphogypsum. It provided a new idea for the large-scale utilization of phosphogypsum with improved purification efficiency, which has good industrial value and application prospects.

Molecular Dynamics Simulation of Fe-Based Metal Powder Oxidation during Laser Powder Bed Fusion.

Because the laser powder bed fusion process is generally completed in a confined space and in a very short time, it is difficult to study material oxidation during this process using traditional methods. To address this knowledge gap, in this work, we used molecular dynamics (MDs) based on a reaction force field (ReaxFF) to clarify the atomic-level interaction mechanism between metal atoms and oxygen molecules during laser powder bed fusion. The ReaxFF potential energy model has variable charges that can dynamically handle charge changes between atoms and the breaking and formation of chemical bonds that occur during oxidation reactions. We investigated the effects of laser power, scanning speed, region position, and oxygen concentration on powder oxidation. The results show that the laser power and scanning speed affected the oxidation degree by changing the energy input density, and the oxidation degree increased with the energy input density. Different forms of oxidation occurred near the melt channel due to the existence of a temperature gradient, and the degree of oxidation increased with the temperature. Atoms in the metal powder model underwent selective oxidation, which was related to the potential energy of their atomic position. A larger potential energy made it easier for iron atoms to overcome the energy barrier during the initial stage of oxidation, making them easier to oxidize.

Making and breaking of chemical bonds in single nanoconfined molecules.

Nanoconfinement of catalytically active molecules is a powerful strategy to control their chemical activity; however, the atomic-scale mechanisms are challenging to identify. In the present study, the site-specific reactivity of a model rhenium catalyst is studied on the subnanometer scale for complexes confined within quasi–one-dimensional molecular chains on the Ag(001) surface by scanning tunneling microscopy. Injection of tunneling electrons causes ligand dissociation in single molecules. Unexpectedly, while half of the complexes show only the dissociation, the confined molecules show also the reverse reaction. On the basis of density functional theory calculations, this drastic difference can be attributed to the limited space in confinement. That is, the split-off ligand adsorbs closer to the molecule and the dissociation causes less structural disruption. Both of these facilitate the reverse reaction. We demonstrate formation and disruption of single chemical bonds of nanoconfined molecules with potential application in molecular data storage.

Exploration for UV Aging Characteristics of Asphalt Binders based on Response Surface Methodology: Insights from the UV Aging Influencing Factors and Their Interactions

• Provide a new insight for exploring the UV aging mechanism of asphalt binders. • Explore the effects of some potential influencing factors and their interactions on the UV aging characteristics of asphalt binders with RSM method. • Characterize the micro properties of asphalt binders irradiated by UV light with different wavelengths through some microscopic experiments. To explore the UV aging characteristics of asphalt, effects of potential influencing factors as well as their interactions on asphalt’s properties were investigated with the aid of Response Surface Methodology (RSM). Four influencing factors, including ultraviolet irritation wavelength, irritation intensity, asphalt film thickness, and aging temperature, were selected as the response variables of RSM. And complex shear modulus aging index G*AI , DSR function aging index DAI and fatigue factor aging index FAI were selected as the responses’ values. Then, the Central Composite Design (CCD) model of RSM was adopted to establish the statistical models to analyze the effects of different variables on asphalt’s UV aging behaviors. On this basis, aging degree of asphalt under ultraviolet irradiation with different wavelengths was analyzed emphatically with Fourier Transform Infrared Spectroscopy (FTIR) and Atomic Force Microscope (AFM) tests. Meanwhile, method for speeding up the efficiency of asphalt UV aging test by reducing the asphalt film was also proposed. Test results show that UV aging rate of asphalt increases gradually with the decreasing of asphalt film and the increasing of radiation intensity and aging temperature; among them, the effect of asphalt film thickness is the greatest, while that of aging temperature is the smallest. In addition, radiations with different wavelength have different effects on UV aging behaviors of asphalt, and asphalt irradiated by UV-340 to UV-360 has the highest aging degree, which can be further proved by FTIR and AFM test results. Interactions between different factors will also affect the UV aging characteristics of asphalt, and the results are related to the types of asphalt. However, interaction between UV radiation wavelength and asphalt film thickness all have the significant effects on the UV aging behaviors of base asphalt and SBS modified asphalt. Decreasing the asphalt film thickness can effectively increase the UV aging rate of asphalt. Thus, the aging time can be appropriately reduced on the basis of thinner asphalt film, so as to improve the test efficiency. And finally, it can be found that two processes may exist during the UV aging process of asphalt, namely molecular excitation process and chemical bond breaking process. Under the two actions, unstable chemical bonds in asphalt will reach the excited state or break, and combine easily with the oxygen atom and then generate some polar oxygen-containing functional groups, thus causing the decline of asphalt’s properties.

Solvent Control of Chemical Identity Can Change Photodissociation into Photoisomerization.

In solution-phase chemistry, the solvent is often considered to be merely a medium that allows reacting solutes to encounter each other. In this work, however, we show that moderate locally specific solute-solvent interactions can affect not only the nature of the solute but also the types of reactive chemistry. We use quantum simulation methods to explore how solvent participation in solute chemical identity alters reactions involving the breaking of chemical bonds. In particular, we explore the photoexcitation dynamics of Na2+ dissolved in liquid tetrahydrofuran. In the gas phase, excitation of Na2+ directly leads to dissociation, but in solution, photoexcitation leads to an isomerization reaction involving rearrangement of the first-shell solvent molecules; this isomerization must go to completion before the solute can dissociate. Despite the complexity, the solution-phase reaction dynamics can be captured by a two-dimensional energy surface where one dimension involves only the isomerization of the first-shell solvent molecules.

(Energy Technology Division Graduate Student Award sponsored by BioLogic) Voltage as a Driving Force for Ammonia Activation

In chemical synthesis, the making and breaking of chemical bonds often requires traversing large energy differences. In fact, in 2012 the basic chemical industry accounted for close to 20% of total delivered energy consumption in the industrial sector, which itself used the most delivered energy of any end-use sector globally (54%). Traditionally, industrial chemical synthesis has relied on pressure and temperature to drive chemical reactions, and the energy to elevate the pressure and temperature generally comes from fossil fuel sources. These chemical reactors also often require centralized locations so that economies of scale make them profitable (e.g., ammonia synthesis). However, with the advent of distributed and accessible renewable electricity, it is attractive to consider driving chemical reactions that are conventionally driven with temperature and pressure with renewable electricity instead. Electrochemical reactors can be driven at mild temperatures and pressures and can take advantage of renewable electricity sources directly, enabling decentralized manufacturing. Thus, electrification of the chemical industry offers an opportunity to further integrate the chemical and energy industries, motivating and leveraging decentralized renewable energy sources and storage for chemical manufacturing. In this talk, I will first look at the broad question of how to compare electrochemical routes with traditional thermochemical routes for chemical transformations, aiming to answer the question “If I can apply mechanical energy (pressure), thermal energy (temperature), or electrical energy (voltage) to a chemical reaction, which should I use?” I will present a framework for comparing voltage, temperature, and pressure as thermodynamic driving forces to help quantitatively discriminate between energy sources. Second, I will discuss electrochemical utilization of ammonia. Ammonia has one of the largest global production rates by volume, and it is a nexus synthesis molecule: it either directly or indirectly provides nitrogen for a range of molecules including specialty chemicals, polymers, and pharmaceuticals. Ammonia is also attractive as an energy-dense, carbon-free fuel. Because of this, it represents an important target for electrification. I will discuss the kinetics of ammonia electro-oxidation, i.e., the breaking of the nitrogen-hydrogen bonds, as well as how an applied potential can help form carbon-nitrogen bonds, an electrochemical analogue to traditional reductive amination. Last, I will propose an energy storage paradigm that leverages ammonium formate, a combination of ammonia and formic acid, to store renewable electricity. I will discuss the advantages of this fuel and demonstrate how voltage can aid in the release of energy from this fuel. Overall, I will start with the broad question of why and when to use voltage in the chemical transformations, and then I will focus on how electrochemistry can aid in ammonia utilization for both synthesis reactions and energy storage purposes.

Nudged elastic band calculations of the (4H)SiX hydrogarnet type defect in Mg2SiO4 forsterite

Abstract First-principles calculations based on density functional theory (DFT) using the generalized gradient approximation (GGA) were performed to assess the energetic barriers separating different topological configurations of the (4H)SiX hydrogarnet type defect in Mg2SiO4 forsterite with the climbing image nudged elastic band (CI-NEB) method. Barrier heights are low (<0.6 eV) with respect to typical activation energies observed for H-diffusion but more comparable to those for electrical conductivity of H2O-bearing nominally anhydrous minerals. As can be expected, hydrogen bonding to O atoms both within the defect and belonging to adjacent tetrahedra plays a fundamental role in the stability of each configuration. Saddle points along the minimum energy path (MEP) typically correspond to the transition of one hydrogen bond breaking to form a new hydrogen bond such that one or more OH bonds have shifted in direction without themselves breaking. MEPs show that slightly out-of-plane torsional hopping from one configuration to another can reduce the height of the barrier. We illustrate several different reaction coordinates between symmetry equivalent pairs of configurations and non-symmetry related pairs that can result in an effective means of local charge transport by shifting the center of mass of the (4H)4+ cluster within the defect site without proton transfer to an interstitial site. Especially at low temperatures in the absence of thermally activated processes that result in the breaking of stronger chemical bonds, these types of configurational transformation mechanisms are likely to be important contributors to the dielectric behavior of nominally anhydrous silicate minerals and also affect both electrical conductivity and electrical conductivity anisotropy when investigated by AC methods such as impedance spectroscopy. The NEB method can also be used to examine more effective charge and mass transport processes that involve the dissociation of the hydrogarnet defect into more complex chemical species, which might involve similar hydrogen bond breaking and forming processes observed in this study along with more significant atomic displacements.

Study on gas production mechanism of medium- and low-rank coals excited by the external DC electric field

This study aims to further explain abnormal phenomena occurring during coal and gas outbursts and grasp the gas production effect of the micro-structure on outburst coal surface under the action of the electric field. To this end, in this study, an experimental system for gas production of coal excited by the external DC electric field was established. Then, gas production experiments were performed on medium- and low-rank coals excited by the different-strength electric fields to reveal the relationships between gas production and coal rank and excitation voltage. Subsequently, the variations of functional groups and chemical bonds on coal sample surface after the external DC electric field excitation (EFE) were measured and analyzed through Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). According to the results of the gas production experiment, gases produced by medium- and low-rank coals under EFE include CH4, CO and CO2, and the gas production volume rises with the increase in excitation voltage. The results of FTIR analysis show that the contents of hydroxyl, aliphatic hydrocarbons and oxygen-containing functional groups of medium- and low-rank coals decrease to varying extents after EFE. The results of XPS analysis disclose that the structure of C element on the surface of medium- and low-rank coals changes after EFE. Therefore, the CO, CH4 and CO2 produced by medium- and low-rank coals during EFE come from the breakage of chemical bonds and the falling-off of functional groups. The research results provide theoretical support for revealing the mechanism of coal rock dynamic disasters and exploring methods for the monitoring and pre-warning of these disasters.

Effect of Pretreatment by Freeze Vacuum Drying on Solid-State Anaerobic Digestion of Corn Straw

As a common agricultural waste, corn straw (CS) has a refractory structure, which is not conducive to anaerobic digestion (AD). Appropriate pretreatment is crucial for addressing this problem. Thus, freeze vacuum drying (FVD) was proposed. In this study, fresh CS (F-CS) pretreated (5 h, −40 °C) by FVD and naturally dried CS (D-CS) were compared. Differences in substrate surface structure and nutrient composition were first investigated. Results show that a loose and porous structure, crystallinity, and broken chemical bonds, as well as higher proportions of VS, C, N, cellulose, hemicellulose, and crude proteins in F-CS show a potential for methane production. Besides, process performance and stability were also examined in both high (4, VS basis) and low (1, VS basis) S/I ratio AD. A higher degradation ratio of hemicellulose as well as richer dissolved microbial metabolites, coenzymes, tyrosine-like proteins, and hydrolysis rate of particulate organic matter in the F-CS system enhanced the efficiency of methane conversion. The cumulative methane yield increased from 169.66 (D-CS) to 209.97 (F-CS) mL/gVS in the high S/I ratio system (p = 0.02 < 0.05), and 156.97 to 171.89 mL/gVS in the low S/I ratio system. Additionally, 16S-rRNA-gene-based analysis was performed. Interestingly, the coordination of key bacteria (Clostridium_sensu_stricto_1, Bacillus, Terrisporobacter, Clostridium_sensu_stricto_7, Thermoclostrium, UCG-012, and HN-HF0106) was more active. Poorer Methanosarcina and Methanomassiliicoccus as well as richer Methanobrevibacter and Methanoculleus stimulated the co-relationship of key archaea with diverse methanogenesis pathways. This study aims to verify the positive effect of FVD pretreatment on AD of CS, so as to provide a reference for applications in waste management.

Laboratory Research on Design of Three-Phase AC Arc Plasma Pyrolysis Device for Recycling of Waste Printed Circuit Boards

Accumulation of electronic waste (e-waste) will place a heavy burden on the environment without proper treatment; however, most ingredients contained in it are useful, and it could bring great economic benefits when recycled. A three-phase alternating current (AC) arc plasma pyrolysis device was designed for resourcing treatment of waste printed circuit boards (WPCBs). This paper focuses on the analysis of plasma pyrolysis gas products, and the results showed that the plasma could operate stably, and overcame the problems of the poor continuity and low energy of single-arc discharge. Air-plasma would generate NOx contaminants, burn the organics, and oxidize the metals; therefore, air had not been selected as a working gas. Ar-plasma can break the long chains of organic macromolecules to make a combustible gas. Moreover, the strong adhesion between the metals and fiberglass boards would be destroyed, which facilitates subsequent separation. Ar/H2-plasma promoted the decrease of carbon dioxide and the increase of combustible small molecular hydrocarbons in the pyrolysis product compared with Ar-plasma, and the increase of the H2 flow rate or plasma power intensified that promotion effect. The percentage of other components, except the hydrogen of CO2, CO, CH4, C2H4, and C3H6, accounted for 55.7%, 34.2%, 5.6%, 4.5%, and 0% in Ar-plasma, and changed to 35.0%, 29.0%, 11.2%, 24.3%, and 0.5% in Ar/H2-plasma. Ar/H2-plasma could provide a highly chemically active species and break chemical bonds in organic macromolecules to produce small molecules of combustible gas. This laboratory work presents a novel three-phase AC arc plasma device and a new way for recycling WPCBs with high value.

Light as a Tool in Organic Photocatalysis: Multi‐Photon Excitation and Chromoselective Reactions

AbstractOver the past decades, photoredox catalysis has developed to the big mature field of chemistry. Especially in the field of organic synthesis, more and more sustainable alternatives to conventional synthesis are being developed. Nonetheless, most research activities are focused on the development of new synthetic pathways, utilizing photons as a source of energy for breaking and building of new chemical bonds. We discuss here cases, where selection of the irradiation mode, light intensity (one‐, two‐ photons) or wavelength (UV, blue, green) has a crucial role on the outcome of the photocatalytic event. Thus, control over irradiation conditions influence the reaction mechanism and offers an access to highly reactive species that are otherwise hardly available. This allows for the unique chemical events to happen, such as deep reduction reactions. The principles of these concepts and their applications are reviewed for both homogeneous and heterogeneous photocatalysts.