Cleavage Of Chemical Bonds Research Articles

Direct Probing of Fe3O4 Nanoparticle Surface Temperatures during Magnetic Heating: Implications for Induction Catalysis

The presence of a temperature gradient between the magnetic nanoparticle (NP) surface and the bulk medium during induction heating has been observed across several fields. While no noticeable increase in bulk temperature is observed, biological (DNA denaturation, tumor apoptosis) and chemical (bond cleavage) evidence indicates high temperatures near/at the NP surface. Unfortunately, current methods for temperature probing rely on bulk temperature measurements (fiber-optic IR probes) or are limited by thermal stability and spatial resolution (organic molecules). To further the understanding of magnetic heating as a driving force in catalysis, as well as drug delivery/hyperthermia treatments, a more accurate description of the nanoparticle surface temperature is needed. This work uses inorganic luminescent probes in direct contact with the particle surface, entailing the deposition of YVO4:Eu3+ around a Fe3O4|SiO2 structure, to measure the local temperature. The luminescent response is calibrated in situ via a controlled temperature stage to extract the field-dependent heating. The luminescent probe results in a high spatial resolution (<5.5 nm) with temperatures up to 64 °C higher than standard fiber-optic probes. The direct contact between the photoluminescence (PL) probe and Fe3O4 allows for ballistic transport and improved temporal resolution, mimicking an adiabatic system (negligible long-range heat dissipation). Other advantages include avoiding measurements in liquid media, where the distance between the heat source and the probe cannot be controlled, adding to the uncertainty of the temperature measurement due to changes in colloidal anisotropy (which changes with the heating profile) of the magnetic cores and surface quenching of the luminescent signal.

Solar‐Driven Artificial Carbon Cycle

Comprehensive SummaryConstituting the artificial carbon cycle, for example, through recycling CO2 and converting CH4 to value‐added fuels and chemicals with solar energy, offers a sustainable future for humankind to tackle the global environmental issues and energy crisis. However, significant bottlenecks remain in such photocatalytic conversion, mainly related to the reaction activity and product selectivity. Herein, we share our efforts and systematic research progress on addressing the double bottlenecks for achieving solar‐driven artificial carbon cycle, with specifically focusing on the photocatalytic CO2 and CH4 conversion. We further elucidate the common fundamentals behind various designed photocatalytic materials systems. Toward future development, we highlight the opportunities and challenges in the research field. What is the most favorite and original chemistry developed in your research group?Selective catalytic conversion of C1 molecules by coupling solar energy.How do you get into this specific field? Could you please share some experiences with our readers?Originating from my undergraduate training, I was very interested in the controllable cleavage and formation of chemical bonds in physical world. However, the interest was just limited to the level of curiosity at that time, while this research topic seemed so sophisticated to me. Started from my graduate study, I explored the physical world with a specific focus on inorganic materials, ranging from materials synthesis to photoelectrical properties. After my postdoctoral training, I became capable of investigating the coupling of small molecules with solar energy by leveraging inorganic materials. As such, when I started my independent career, I decided to pursue my research interests in selective catalytic conversion of molecules by coupling solar energy. C1 molecules such as carbon dioxide and methane are the critical molecules to carbon cycle, which hold the key to carbon neutrality from the present viewpoint. Naturally, I focus my research on the selective conversion of C1 molecules,toward which catalytic materials are rationally designed to couple solar energy into their controllable bond breakage and formation.How do you supervise your students?When I supervise my students, I play the dual roles as mentor and coach. I mentor them to learn the key skills for research, build critical thinking, and enhance their scientific writing and communication capabilities. In the meantime, I also coach them how to design research projects, acquire a big picture for their research, and perform multidisciplinary research in collaboration with others.What is the most important personality for scientific research?Curiosity, which is the driving force to gather our enthusiasm, spirit and creativity toward scientific research with persistence.What are your hobbies?Swimming.If you have anything else to tell our readers, please feel free to do so.As a scientist, please follow your heart to identify the research interests behind curiosity as well as keep your spirit to explore the research interests.

(Invited) Next Generation Ion Exchange Membranes for Electrochemical Polymer Membrane Processes

The ion exchange membrane is a key component in many electrochemical membrane processes such as fuel cells, flow batteries and electrolysers. Typically, these ion exchange membranes are assembled in stacks and allow the transport of the charge carrying component, i.e. a cation (e.g. proton) or an anion, while retaining the other species and electrolytes preventing their crossover to the other side of the cell. Simultaneously electrons travel through an external circuit powering a device or to store energy.Conventional ion exchange membranes have two major problems: They are based on expensive materials (e.g. Nafion®e. PFSA; perfluorosulfonic acid) or on environmentally harmful chemicals and chemical reactions. Although due to its molecular structure and composition, PFSA membranes show good performances, the major limitation of PFSA membranes is the very high material costs often contributing for more than 35% to the total stack costs [1, 2].One of the major challenges of ion exchange membrane development is the tradeoff between high ion transport rates through the membrane while simultaneously preventing electrolyte crossover [3]. This talk will first present a comprehensive overview of required membrane characteristics and an extensive benchmark study of state-of-the-art performances of ion exchange membranes in different electro-membrane processes. Following on this, the challenges in ion exchange membrane development will be addressed and most importantly two new routes for the development of next generation ion exchange membranes will be presented and their characteristics will be compared to those of a series of extensively benchmarked commercially available ion exchange membranes.The first approach, electrospinning is an effective, versatile method to produce cheap ion exchange membranes [3-6]: Multiple polymers can be employed simultaneously during spinning and this is combined with high degrees of interchain entanglement. This results in an interconnected network of ionic pathways that promote high ionic conductivities confined in a matrix of an inert polymer that guarantees high rejections towards electrolytes to prevent crossover (Figure 1a). Moreover, it is a simple technique that can be easily adapted to large scale production.The second approach uses liquid crystalline (LC) polymers to make ion exchange membranes [7]. This approach has the potential to offer true molecular selectivity and a high degree of flexibility to actually tune this selectivity. LC polymer materials self-organize into structures with well defined isoporosity (Figure 1b). Subsequent template removal or chemical bond cleavage with an acid or base results in the formation of molecular pores. The pores of these materials can be functionalized and depending on the functionality, selectivity can be introduced. Depending on the bulkiness of the functional group also pore sizes can be smaller or bigger. Crosslinking of the formed structures allows control over the swelling of the material and with that reduces crossover. In this way one can rely on both charge-charge interactions as well on size sieving to separate species. The major challenge is the formation of organized structures over larger length scales and the identification of structure-property relationships and with that control over the membrane separation performance.Design principles of both newly developed membrane types are discussed, the membranes are extensively characterized and their performance in electrochemical processes is compared to that of conventional ion exchange membranes. The talk is concluded with a future outlook on the perspectives of ion exchanhe membrane development. T. Cho, et al., Energy Technol. 1 (2013) 596–608. https://doi.org/10.1002/ente.201300108.Lin, et al., J. Electrochem. Soc. 163 (2016) A5049–A5056. https://doi.org/10.1149/2.0071601jes.A. Hugo, et al., Journal of Membrane Science 566 (2018) 406. 10.1016/j.memsci.2018.09.006.Woo Park, et al., J. Membr. Sci. 541 (2017) 85–92. https://doi.org/10.1016/j.memsci.2017.06.086.Choi, et al., Macromolecules. 41 (2008) 4569–4572. https://doi.org/10.1021/ma800551w.J.B. Ballengee, P.N. Pintauro, Macromolecules. 44 (2011) 7307–7314. https://doi.org/10.1021/ma201684j.Kloos, et al., Journal of Membrane Science 620 (2021) 118849. https://doi.org/10.1016/j.memsci.2020.118849 Figure 1

Mesoporous Silica Nanoprodrug Encapsulated with Near-Infrared Absorption Dye for Photothermal Therapy Combined with Chemotherapy.

Based on the tumor microenvironment with weak acidic characteristics, a nano-drug delivery system that achieves controlled release of drugs through the pH response has been a popular strategy to improve the effectiveness of tumor therapy and reduce toxic side effects, and combining photothermal therapy (PTT) on this basis can help improve the antitumor effect. In this study, mesoporous silica nanoparticles (MSNs) were surface-modified with polymer poly(PEGMA-co-HEMA) via surface-initiated atom transfer radical polymerization, and a multifunctional nanoplatform MSN@poly(PEGMA-co-HEMA-g-doxorubicin (DOX)/indocyanine green (ICG) was designed for effective photothermal/chemotherapy combination therapy. The anticancer drug DOX was anchored to the polymer on the surface of MSN by reversible covalent bond cis-aconitic anhydride with a drug loading of 10%. Meanwhile, the small-molecule dye was loaded into the pores of MSN, and PTT mediated by near-infrared (NIR) radiation could further kill cancer cells. Under low-pH stimulation, the cis-aconitic anhydride bond breaks and DOX is released, with a 65% increase in cumulative drug release over 50 h compared to that at pH 7.4 (normal physiological environment). The high temperature induced by photothermal conversion accelerated the reversible covalent bond breakage, and the cumulative drug release at pH 5.0 for 3 h at elevated temperature up to 50 °C increased by 24.3% compared with that under normal physiological conditions (T = 37 °C), demonstrating that increasing the temperature can reduce the time required to reach blood drug concentration. In vitro cytotoxicity results revealed that the prodrug delivery system showed stronger cytotoxicity under NIR light irradiation compared with free DOX, with more than 90% of tumor cells killed after 48 h. Therefore, MSN@poly(PEGMA-co-HEMA-g-DOX)/ICG enhanced the synergistic effect of chemotherapy through photothermal action and accelerated reversible chemical bond cleavage, which has great potential in the combined therapy of cancer.

Recapture of the Nonvalence Excess Electron into the Excited Valence Orbital Leads to the Chemical Bond Cleavage in the Anion

The excess electron in the dipole-bound state (DBS) of the anion is found to be recaptured into the excited valence orbital localized at the positive end of the dipole, leading to the chemical bond cleavage of the anion. In the DBS of the 4-iodophenoxide anion, the extremely loosely bound electron (binding energy of 53 cm-1) is recaptured into the πσ* valence orbital, which is repulsive along the C-I bond extension coordinate, leading to the iodide (I-) and phenoxyl diradical (·C6H4O·) channel at the asymptotic limit. This is the first real-time observation of the state-specific relaxation (other than autodetachment) dynamics of the DBS and subsequent chemical reaction. The lifetime of the 4-iodophenoxide DBS at its zero-point energy (ZPE), which is measured for the cryogenically cooled trapped anion using the picosecond laser pump-probe scheme, has been estimated to be ∼9.5 ± 0.3 ps. Quantum mechanical calculations support the efficient transition from the DBS (below the detachment threshold) to the low-lying πσ* valence orbital of the first excited state of the anion. Similar experiments on 4-chlorophenoxide and 4-bromophenoxide anions indicate that the electron recaptures into excited valence orbitals hardly occur in the DBS of those anions, giving the long lifetimes (≫ns) at ZPE, suggesting that the internal conversion to S0 may be the major relaxation pathway for those anions.

Vitamin B12 – Bioinspiration for Catalysis

Nature constructs and decomposes complex molecules with the help of enzymes and light as the ultimate energy source. However, despite enzyme’s fundamental benefits, their industrial application can be limited by their availability, instability towards certain reaction conditions, cost, scale, lack of suitable enzyme etc. A complementary approach to sustainable methodologies relies on the formation or cleavage of chemical bonds using bioinspired methods (methods imitating the efficient and elegant designs of biology) and recruiting light, the most abundant free energy source.Vitamin B12 - a cofactor of many enzymes seems inspirational.[1,2] This type of catalysis has been successfully translated into the laboratory and used in a small collection of reactions.[2, 3] The advantage of using vitamin B12 as a catalyst lays in the complete stability of the central cobalt ion and by the definition it is nontoxic. It has also been well documented that the reaction mechanism usually follows a radical pathway, bringing a new dimension to this already interesting field.Along this line, we have developed new vitamin B12-catalyzed reactions involving reduction of Co(III) to Co(I) or Co(II) and subsequent reactions with electrophiles or radicals. Under light irradiation vitamin B12 derivative unusually catalyzes a new olefinic sp2 C-H alkylation reaction, with diazo reagents as a carbene source, instead of the expected cyclopropanation, acylation of activated olefins. Light-induced vitamin B12-catalyzed methods are also suitable for C-O bond cleavage. These key findings emphasize the unique feature of vitamin B12 as a catalyst to achieve something unachievable with other methodologies or to find a greener approach.[1] Banerjee, R. Chemistry and Biochemistry of B12, John Wiley & Sons, Inc, 1999; [2] K. ó Proinsias, M. Giedyk, D. Gryko, Chem. Soc. Rev. 2013, 42, 6605-6619. [3] Giedyk, M.; Fedosov, S.; Gryko, D. Chem. Commun. 2014, 50, 4674-4676. Figure 1

Mechanophore activation enhanced by hydrogen bonding of diarylurea motifs: An efficient supramolecular force‐transducing system

AbstractMacromolecules are efficient as mechanical transducers for mechanically induced chemical bond cleavage reactions. Although various classes of polymers have been studied as effective mechanical‐force transducers for mechanophores, alternatives to polymer chains, that is, small molecules, have rarely been studied. In this paper, the role of hydrogen bonding as small‐molecule mechanical‐force transducers for the activation of mechano‐responsive molecular units (mechanophores) in the bulk is investigated. The introduction of diarylurea linkage motifs, which are known as strong hydrogen bonding groups, enhances the mechanochemical activation of the fluorescent mechanophore tetraarylsuccinonitrile (TASN) as effectively as the attachment of a typical macromolecular transducer. Electron paramagnetic resonance measurements of mechanically activated TASN with diphenyl urea motifs demonstrate its higher carbon–carbon bond dissociation ratio compared to that of TASN without diphenyl urea motifs. This efficient supramolecular‐force‐transducing system represents a new concept in the field of mechanochemistry, namely, the enhancement of mechanochemical bond scission by simply changing the substituents of a mechanophore, even in small molecules.

Coke formation on activated carbon during catalytic upgrading of coal pyrolysis volatiles

The content of heavy pitch in tar generated from coal pyrolysis is high. To improve the quality of tar, catalysts are applied for adjusting the reaction of volatiles during coal pyrolysis. However, catalysts are easy to deactivate due to coke deposition. In this study, coke amount on activated carbon catalysts during catalytic upgrading of coal pyrolysis volatiles was investigated in the downer-bed reactor. The process of coke formation was studied at different feed time (30, 60 and 100 min) of coal. Results show that a great amount of coke is generated on the activated carbons. With the increase of feed time, the amount of coke on activated carbon increases, while the rate of coke formation decreases, thus decreasing the coke yield based on dry coal. The specific surface area and catalytic cracking activity of the activated carbon decrease with the increase of coke amount. Hence, the yields of tar and pitch increase with the increase of feed time. The relative content of oxygen-containing compounds in the tar increases with the increase of feed time, which indicates that the cleavage of weak chemical bond C–O is suppressed. That may result in a decrease in the rate of coke formation.

The Binding Strength of Reactive H*: A Neglected Key Factor in Rh-Catalyzed Environmental Hydrodefluorination Reaction

The catalyzed reduction process plays an important role in the safe handling of environmental contaminants. It is generally believed that the adsorption of pollutants and cleavage of chemical bonds with high stability is the key and rate-determining step. Herein, using the H2–D2 exchange experiment, we observed a rapid decrease in the yield of HD on the Rh nanocatalyst, a state-of-the-art choice for the reduction of fluorinated organics, which indicates that the overadsorption of H/D atoms poisoned the Rh surface. The high binding energy of H/D on Rh decreases its reactivity as a reductant and is unfavorable for the adsorption/activation of the C–F bond. This dilemma is easily overcome by depositing Rh atoms onto Pd nanowires or commercial Pd/Al2O3. In addition to reducing the size of the Rh ensemble and therefore decreasing the H binding energy, Pd also directly spills over reactive H to the nearby Rh center; Pd@Rh shows 50 times higher mass activity and can remove persistent pollutants such as hexafluorobenzene and perfluorooctane acid under environmentally relevant conditions. Interestingly, the Pd@Rh catalyst hydrogenates halogenated phenols into value-added cyclohexanone with high selectivity. This work provides new insight into the design of advantageous nanocatalysts for environmental improvement and the recovery of resources from wastewater.

Electrocatalytic Refinery for Sustainable Production of Fuels and Chemicals

AbstractCompared to modern fossil‐fuel‐based refineries, the emerging electrocatalytic refinery (e‐refinery) is a more sustainable and environmentally benign strategy to convert renewable feedstocks and energy sources into transportable fuels and value‐added chemicals. A crucial step in conducting e‐refinery processes is the development of appropriate reactions and optimal electrocatalysts for efficient cleavage and formation of chemical bonds. However, compared to well‐studied primary reactions (e.g., O2reduction, water splitting), the mechanistic aspects and materials design for emerging complex reactions are yet to be settled. To address this challenge, herein, we first present fundamentals of heterogeneous electrocatalysis and some primary reactions, and then implement these to establish the framework of e‐refinery by coupling in situ generated intermediates (integrated reactions) or products (tandem reactions). We also present a set of materials design principles and strategies to efficiently manipulate the reaction intermediates and pathways.

Characterization of oxygen-bearing geolipids in the Upper Permian Lucaogou shale, Santanghu Basin, NE China, using stepwise pyrolysis and hydrous pyrolysis

Oxygen-bearing geolipids, including fatty acids, lactones, and ketones, have been identified in abundance in the Upper Permian shale of the Lucaogou Formation in the Sangtanghu Basin in China. However, the potential for petroleum generation, possible origin, and occurrence state of these compounds remain undetermined. Pyrolysis experiments were conducted by combining flash pyrolysis with hydrous pyrolysis. Flash pyrolysis revealed that the oxygen-bearing geolipids, including fatty acids, lactones, and isoprenoid ketones, exist in both free and adsorbed states, and methyl ketones can be produced by pyrolysis at temperature above 400 °C. The evolution behaviors of pyrolyzates and gases produced at different temperatures are related to the thermal desorption and cleavage of chemical bonds in kerogen. Comparison of the oxygen-bearing compounds detected in flash pyrolysis and gases produced in hydrous pyrolysis suggested that the oxygen-bearing geolipids were possible sources of CO2 formation at low temperatures in the Lucaogou shale. The decomposition of fatty acids, lactones, and ketones causes the removal of oxygen-containing functional groups and the formation of CO2 and petroleum. Our study firstly demonstrates that the oxygen-bearing geolipids in the Lucaogou shale occur primarily in the free and/or adsorbed state, which indicates that these geolipids derived from microbial degradation. The short chain C19–C26 steranes and C26–C29 norhopanes detected in Lucaogou shale are also proved this source. Furthermore, petroleum and gases can be produced via deoxygenation of oxygen-bearing compounds, may revealing that the oxygen-bearing geolipids play a significant role in the process of petroleum generation.

DPD simulations on mixed polymeric DOX-loaded micelles assembled from PCL-SS-PPEGMA/PDEA-PPEGMA and their dual pH/reduction-responsive release.

The design of mixed polymeric micelles by a combination of two or more dissimilar polymers is a potential strategy to achieve multiple stimuli-response for anti-cancer drug delivery. However, their drug loading co-micellization behavior and multiple stimuli-responsive drug release mechanism have been poorly understood at the mesoscopic level, especially in the system that involves reduction-response due to the difficulty of simulation on the cleavage of chemical bonds. In this work, the co-micellization behavior, drug distribution regularities and dual pH/reduction-responsive drug release process of mixed micelles formed by disulfide-linked polycaprolactone-b-polyethylene glycol methyl ether methacrylate (PCL-SS-PPEGMA) and poly(ethylene glycol) methyl ether-b-poly(N,N-diethylamino ethyl methacrylate) (PDEA-PPEGMA) were studied by dissipative particle dynamics (DPD) mesoscopic simulations. A dedicated bond-breaking script was employed to accomplish the disulfide bond-breaking simulations. The results showed that PCL55-SS-PPEGMA10 and PDEA34-PPEGMA11 could be well mixed to form superior DOX-loaded micelles with good drug-loading capacity and drug-controlled release performance. To prepare the DOX-loaded micelles with optimized properties, the simulation results suggested the feed ratio of DOX:PCL55-SS-PPEGMA10:PDEA34-PPEGMA11 set to 3:4:4. Compared with the two single stimuli-response, the dual pH/reduction-response process perfectly combined both pH-response and reduction-response together, providing a higher release rate of DOX. Therefore, this study provides theoretical guidance aimed at the property optimization and micellar structure design of the dual pH/reduction-responsive mixed micelles.

Waste Organic Compounds Thermal Treatment and Valuable Cathode Materials Recovery from Spent LiFePO4 Batteries by Vacuum Pyrolysis

This study investigated the gaseous products evolution behaviors and the recovery performance of cathode materials from spent LiFePO₄ batteries by vacuum pyrolysis. The thermogravimetric-differential scanning calorimetry analysis coupled with electron ionization mass spectrometry (TG-DSC-EI-MS) results indicated that inorganic gases (H₂O, CO, CO₂), alkane gases (CH₄, C₂H₄, C₂H₆, CH₃OH, C₃H₆, C₃H₄O₃, C₄H₈O₃), and fluoride-containing gases (HF, OPF₃, C₂H₂F₂) were the resulting gaseous products in the vacuum pyrolysis of cathode materials. At the same time, the gaseous product species and relative yield were significantly affected by pyrolysis temperature. Combined with the GC-MS analysis of pyrolysis tar obtained from vacuum pyrolysis simulation experiments, it could be inferred that pyrolysis tar was formed as a result of the cleavage and recombination of chemical bonds in solvents. The simulation experiments also showed that the increase of vacuum pyrolysis temperature and decrease of residual gas pressure enhanced the recovery efficiency of cathode materials. Further, the carbon and fluorine content of the cathode materials were found to decrease slowly during vacuum pyrolysis, while the aluminum content increased. When the vacuum pyrolysis temperature was above 600 °C, Al foils ablated and even melted to strips. The phase composition of cathode materials was still LiFePO₄ after vacuum pyrolysis. The leaching performance tests of cathode materials demonstrated that the increase of vacuum pyrolysis temperature and decrease of residual gas pressure can lead to the decrease of leaching efficiency for Fe. This technology offers an efficient way to recycle organic compounds and valuable materials from spent LiFePO₄ batteries, and it has been demonstrated to be of good economic benefit and energy savings.

How Rh surface breaks CO2 molecules under ambient pressure

Utilization of carbon dioxide (CO2) molecules leads to increased interest in the sustainable synthesis of methane (CH4) or methanol (CH3OH). The representative reaction intermediate consisting of a carbonyl or formate group determines yields of the fuel source during catalytic reactions. However, their selective initial surface reaction processes have been assumed without a fundamental understanding at the molecular level. Here, we report direct observations of spontaneous CO2 dissociation over the model rhodium (Rh) catalyst at 0.1 mbar CO2. The linear geometry of CO2 gas molecules turns into a chemically active bent-structure at the interface, which allows non-uniform charge transfers between chemisorbed CO2 and surface Rh atoms. By combining scanning tunneling microscopy, X-ray photoelectron spectroscopy at near-ambient pressure, and computational calculations, we reveal strong evidence for chemical bond cleavage of O‒CO* with ordered intermediates structure formation of (2 × 2)-CO on an atomically flat Rh(111) surface at room temperature.

Ultraviolet-C and vacuum ultraviolet inducing surface degradation of microplastics

Wastewater treatment plants (WWTPs) are considerable microplastics (MPs) contributors to environmental waters. Knowledge about the MPs degradation process under ultraviolet irradiation was crucial to understanding the fate of MPs during and after water disinfection. In this study, surface alternations of polystyrene (PS), polyethylene (PE), polyvinylchloride (PVC) and polyethylene terephthalate (PET) under 254 nm (UV-C) and 185/254 nm (vacuum ultraviolet, VUV) irradiation were estimated. One-way treatment of MPs by UV or VUV with the recommended dose for WWTPs (USEPA, ~180 mJ cm−2) had little effect. In contrast, excessive exposure under twenty-times doses irradiation (3600 mJ cm−2) resulted in significant alternations on surface morphology, chemical feature and hydrophobicity. Noticeably morphology alterations, including cracks, wrinkles and protuberances, were observed for PS, PVC and PET, while PE was relatively resistant. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy revealed that UV irradiation induced cleavage of chemical bonds. Besides, simultaneous radical oxidation was predominant during VUV treatment, which contributed to the increasing generation of oxygen bonds, such as CO and CO, on all MPs surfaces. Drastic decreases of contact angle (> 20°) were observed for PS, PVC and PET even after 180 mJ cm−2 UV irradiation, indicating the UV disinfection in WWTPs can easily change their surface hydrophobicity. All these alternations weakened the adsorption capacity of non-polar benzene and polar ciprofloxacin on MPs. Generally, regular dose UV and VUV irradiation in water treatment disinfection can only induce slight effects on MPs surface characteristics and adsorption performance, while extreme dose irradiation can induce a potential reducing risk of organic contaminants migration along with MPs.

Sub-picosecond to Sub-nanosecond Vibrational Energy Transfer Dynamics in Pentaerythritol Tetranitrate.

The time scale associated with shock-induced detonation is a key property of energetic materials that remains poorly understood. Herein, we test aspects of one potential mechanism, the phonon up-pumping mechanism, where shock compression excites lattice phonon modes, transferring energy to intramolecular vibrations leading to chemical bond cleavage and reaction. Using ultrafast infrared pump-probe spectroscopy on pentaerythritol tetranitrate (PETN), we reveal sub-picosecond vibrational energy transfer (VET) from the photoexcited band at 1660 cm-1 into every other infrared-active mode in the probed frequency range 800-1800 cm-1. Energy transfer processes remain incomplete at 150 ps. Computational predictions from density functional theory are used in tandem to elucidate VET pathways in PETN.

Experimental studies on the effect of ultrasonic treatment and hydrogen donors on residual oil characteristics

Residual oil, the residue after the distillation of crude oil, imposes deleterious effects on refinery due to its high viscosity and asphaltene content. In this context, ultrasonic technology has been widely applied in refining processes given its high efficiency and minimal environmental impacts. To guide the selection of operation parameters, in this work, we probed the effect of treatment duration, power, and hydrogen donor on the characteristics of residual oil under ultrasonic treatments. Underlying mechanisms of ultrasonic treatments, in the absence and presence of hydrogen donors, were verified through systematically analyzing viscosity, component conversion, molecular weight, hydrogen distribution, and functional groups of residual oil. While viscosity reductions under low-power density treatment are caused by colloidal system disaggregation, high-power density treatment can bring in both chemical bond cleavage and colloidal system disaggregation. In addition, adding hydrogen donor can effectively prevent radical recombination, and thus increases the yield of saturate. These results provide fundamental understandings on the effects of ultrasonic treatments.

Selective Decarbonylation via Transition-Metal-Catalyzed Carbon-Carbon Bond Cleavage.

Transition-metal-catalyzed decarbonylation via carbon-carbon bond cleavage is an essential synthetic methodology. Given the ubiquity of carbonyl compounds, the selective decarbonylative process offers a distinct synthetic strategy using carbonyl groups as "traceless handles". This reaction has been significantly developed in recent years in many respects, including catalytic system development, mechanistic understanding, substrate scope, and application in the synthesis of complex functional molecules. Therefore, this review aims to summarize the recent progress on transition-metal-catalyzed decarbonylative process, from the discovery of new transformations to the understanding of reaction mechanisms, to reveal the great achievements and potentials in this field. The contents of this review are categorized by the type of chemical bond cleavage in the decarbonylative process. The main challenges and opportunities of the decarbonylative process are also examined with the goal of expanding the application range of decarbonylation reactions.

Decomposition and Energy-Enhancement Mechanism of the Energetic Binder Glycidyl Azide Polymer at Explosive Detonation Temperatures.

Replacing existing inert binders with energetic ones in composite explosives is a novel way to improve the explosive performance, on the proviso that energetic binders are capable of releasing chemical energy rapidly in the detonation environment. Known to be a promising candidate, the reaction mechanism of glycidyl azide polymer (GAP) at typical detonation temperatures higher than 3000 K has been theoretically studied in this work at the atomistic level. By analyzing and tracking the cleavage of characteristic chemical bonds, it was found that at the detonation temperature, GAP was able to release a large amount of energy and small molecule products at a speed comparable to commonly used explosives in the early reaction stage, which was mainly attributed to the decomposition of azide groups into N2 and the main chain breakage into small fragments. Moreover, N2 generation was found to be accelerated by H atom transfer at an earlier reaction step. The dissociation energy of the main chain was lowered with structure deformation so as to facilitate the fragmentation of the GAP chain. Based on this analytical study of reaction kinetics, GAP was found to have higher reactivity at the detonation temperature than at lower temperatures. The small molecules' yield rate is of the same order of magnitude as an explosive detonation reaction, indicating that GAP has the potential to improve the performance of composite explosives. Our study reveals the chemical decomposition mechanism of a typical energetic binder, which would aid in the future design and synthesis of energetic binders so as to achieve both sensitivity-reducing and energy-enhancing performance goals simultaneously.

Electrochemically Stimulated Molecule Releaseassociated with Interfacial pH Changes

External signal-stimulated release of (bio)molecules is used in many biotechnological and biomedical applications1. It has been well documented over decades, resulting in vast group of physical and chemical systems functioning differently and reacting to different signals. Among various molecule-releasing systems responding to different activating signals (e.g.; optical, magnetic, chemical, mechanical, temperature change, etc.); electrochemical systems is one of the most important and interesting research fields. Besides systems controlled by electrostatic attraction/repulsion of molecules at polarized electrode surfaces2,3, more sophisticated systems that are able to release only specific molecules are based on molecular and supramolecular systems can be tailored. In the latter case, selected molecules are included in complex structures assembled at electrode surfaces and disassembled upon electrochemical processes. Some of these systems have electrochemically cleavable covalent bonds (e.g., disulfide bonds), which results in the release of the connected molecules upon redox reaction. While the electrochemical cleavage of bonds based on the redox transformations is a very powerful and successful approach in clean model systems, it may be significantly complicated in the presence of other redox species appearing in complex biological media. Thus, more universal approaches to the electrochemically stimulated cleavage of chemical bonds should be investigated. Herein we report a new linker with a hydrolysable phenolic ester bond at basic pH (~8-10) for electrode modification. Basic pH locally produced at the electrode surface upon electrochemical reduction of oxygen resulted in the hydrolytic cleavage of the phenolic ester bond and release of the immobilized fluorescent dye used as a model compound4.ǂ These authors equally contributed to the work