Reaction Products Research Articles

Oxygen isotope fractionation during amorphous to crystalline calcium carbonate transformation at varying relative humidity and temperature

Crystalline calcium carbonate isotope compositions have been widely used to reconstruct past environments. However, if their isotopic compositions are modified because of crystallization from an amorphous precursor, their reliability as paleo-geochemical proxies can be compromised. This study explored the changes in the oxygen isotope compositions during the transformation of amorphous calcium carbonate (ACC) into crystalline carbonate under different conditions of relative humidity (RH of 33 to 95 %), temperature (T of 5 °C and 20 °C) and in the presence/absence of atmospheric CO2. The data showed that at low RH and T (e.g., RH ≤ 45 % and 5 °C) when a complete ACC-crystalline carbonate transformation did not take place then the original ACC δ18O values (δ18OCaCO3 = −15.9 ± 1.0 ‰, VPDB) were preserved throughout the experimental runtime (up to 144 days). In contrast, in fully crystallized CaCO3 (e.g., at RH ≥ 60 %) the δ18OCaCO3 values increased rapidly over the first few days, followed by a slower and gradual increase. By the end of the experiments (i.e., after 103–144 days) the crystalline δ18OCaCO3 values ranged from −10.4 ‰ to −8.1 ‰ in the presence of atmospheric CO2 and from −12.6 ‰ to −9.5 ‰ in the CO2-free experiments. These changes in oxygen isotope compositions of the CaCO3 reaction products (calcite and/or vaterite) were mainly driven by exchange with H2O from the hydrated ACC i.e. the synthesis fluid. In CO2-present experiments, oxygen isotope fractionation factors between the CaCO3 reaction products and the synthesis fluid (18αc–w) approached or exceeded oxygen isotope equilibrium values. This could be explained by a decrease in the initially high pH of the aqueous fluid released from ACC dissolution during CO2 hydration/hydroxylation, which would have increased the oxygen isotope exchange kinetics between H2O and dissolved inorganic carbon (DIC). In some experiments, the hydration/hydroxylation of 18O-enriched CO2, due to isotopic salt-effects, might have also resulted in 18O-enriched calcium carbonates and calculated fractionation factors that exceeded equilibrium values. In the CO2-free experiments, isotopic equilibrium between the crystalline phase and the synthesis fluid was not reached. This oxygen isotope disequilibrium suggests that without the pH lowering effect of the hydroxylation/hydration of CO2, the CO32− released during ACC/calcite dissolution-reprecipitation may have not isotopically equilibrated with the high pH synthesis fluid due to the long equilibration times required to reach isotope equilibrium at high pH values, leading to the self-buffering of δ18OCaCO3 values. The results suggest that the oxygen isotopic compositions of natural carbonates formed from ACC transformation in air and at low water/solid ratio (e.g., biominerals or carbonates formed in caves) are complex and cannot be used as simple proxies if the reaction kinetics (RH/CO2/T) and H2O sources are not known and quantified.

Integrated HS-SPME-GC–MS and UHPLC-O-TOF-MS-based metabolomics revealed the characteristics flavor and nonvolatile metabolites during the hydrolysis process of Boletus edulis

This research aimed to investigate the flavor characteristic, metabolites and bioactivities of Boletus edulis hydrolysates via HS-SPME-GC-MS and UHPLC-MS/MS. The Maillard reaction (MR) significantly enhanced the sensory qualities of Boletus edulis, including like-meat, caramel, continuity, and complete acceptance. The accumulation of browning precursors during MR was verified through spectral analysis. We also found that the MR enhanced the antioxidant and hypoglycemic activities of Boletus edulis hydrolysates. Furthermore, 11 VOCs were also identified as key aromatic compounds and had important impact on the flavor characteristics of Maillard reaction products (MRPs). Non-targeted metabolomics analyses revealed that the formation of MRPs was affected through amino acid metabolism, lipid metabolism and plant secondary metabolism. Briefly, the flavor and biological activity of Boletus edulis were improved through enzymolysis and MR. The results provided a theoretical foundation for deep processing and resource utilization of Boletus edulis.

A systematic survey of environmental DNA in Palau's lakes and waterfalls reveals an increase in Leptospira levels after flooding

ObjectiveLeptospirosis is an important bacterial zoonosis which is widespread in tropical and subtropical islands and influences human and animal health which has secondary economic effects. Although leptospirosis is endemic in Palau, an Oceanian Pacific Island country, few systematic surveys of potential risk factors for Leptospira infection, such as weather and host animals, have been conducted in the natural environment. We used environmental DNA metabarcoding to assess the distribution, species diversity, and abundance of pathogenic Leptospira in this endemic region to investigate the potential environmental risks. MethodsForty-two paired water samples, representing fine and rainy weather conditions, were collected from four representative waterfalls and lakes on Babeldaob Island, the largest island in Palau. High-throughput sequencing analysis was conducted for polymerase chain reaction products of leptospiral 16S rRNA and vertebrate animal mitochondrial 12S rRNA genes. ResultsWe revealed greater Leptospira diversity and abundance in samples collected after continuous rain, particularly in the presence of flooding, compared with samples collected under typhoon, monsoon, or fine weather conditions. From same samples, six mammalian species including cats (Felis catus), mice (Mus musculus), Yap flying fox (Pteropus yapensis), rats (Rattus spp.), and pigs (Sus scrofa) were repeatedly detected. These may be candidates of host animals of Leptospira in Palau; however, their detection was not clearly correlated with that of Leptospira. ConclusionWe repeatedly detected several species of pathogenic Leptospira from water samples of a wide region of Babeldaob Island. We confirmed that Leptospira contamination in freshwater environments increased under rainy conditions, particularly in the presence of flooding. This information could be used to improve public health control measures in this region.

Multimodal high-throughput approach assisted by deep learning for the analysis of ceramic saggars

The ceramic saggar is a container utilized in the production process of cathode materials for sodium-ion or lithium-ion batteries, and the characterization of saggar damage mechanisms often relies on the analysis of microstructure and composition of micro-sized areas. However, these results are often unreliable as they derive from a limited amount of data and cannot thus be utilized to perform a comprehensive and accurate analysis of the corrosion resistance mechanism of the saggar. In this study, deep learning combined with multimodal high-throughput in situ characterization methods, including array-SEM, μ-XRF, and μ-XRM, is employed to comprehensively analyze the multiscale characteristics of cordierite–mullite saggars. The 3D distribution of minerals in a 20×13×12 mm3 saggar sample is obtained. The results indicate that the direct dissolution of cordierite corrosion resistance reaction products is the primary damage mechanism of the saggar.

A preliminary evaluation of how classical separation techniques affect the solid catalyst surface features during transesterification

The aim of this study was to investigate how the classical separation methods alter the solid catalyst surface structure in heterogeneous-catalyzed transesterification, viz., centrifugal and gravitational settling-in-funnel schemes, for the first time. The FTIR spectroscopy showed that while the settling system produces vivid and smooth surface shifting as a result of long-term contact with reaction products, centrifugal separation does not entirely obliterate the identity of the post-reaction catalyst surface. In addition, the SEM analysis confirmed that smaller agglomerates, which may have resulted from the dissolution of some particles and the accumulation of organic substances that clog the catalyst pore through the formation of calcium-glycerol bonds during the decantation period, were observed in the gravitational settling system; this trait could also complicate the separation and lower the desired product recovery (biodiesel). Whereas the centrifugal separation technique revealed the presence of bigger oval-shaped agglomerates, which are anticipated to possess more unoccupied active sites for efficient catalysis. As a result, centrifugal separation produces a greater biodiesel yield (87 ± 0.9%) than the settling method (76.6 ± 2%). The fuel properties of biodiesel products were characterized in terms of acid value, kinematic viscosity, cetane number, and specific gravity, of which only the cetane number does not meet the international limit due to its aromatic content. Generally, the results of this study proved that centrifuges are a more effective method of separating heterogeneous catalysts relative to the decantation system.

Utilization of Cobalt and its Oxide/Hydroxide Mediated by Ionic Liquids/Deep Eutectic Solvents as Catalysts in Water Splitting.

With the ever-growing global demand for sustainable energy solutions, hydrogen has garnered significant attention as a clean, efficient, and renewable energy source. In the field of hydrogen production, catalyst research stands out as one of the foremost areas of focus. In recent years, the preparation of electrocatalysts using ionic liquids (ILs) and deep eutectic solvents (DESs) has attracted widespread attention. ILs and DESs possess unique physicochemical properties and are recognized as green media as well as functional materials. Cobalt-based catalysts have proven to be efficient electrocatalysts for water splitting. Incorporating ILs or DESs into the preparation of cobalt-based catalysts offers a remarkable advantage by allowing precise control over their structural design and composition. This control directly influences the adsorption properties of the catalyst's surface and the stability of reaction intermediates, thereby enabling enhanced control over reaction pathways and product selectivity. Consequently, the catalytic activity and stability of cobalt-based catalysts can be effectively improved. In the process of preparing cobalt-based catalysts, ILs and DESs can serve as solvents and templates. Owing to the good solubility of ILs and DESs, they can efficiently dissolve raw materials and provide a special nucleation and growth environment, obtaining catalysts with novel-structures. The main focus of this review is to provide a detailed introduction to metal cobalt and its oxide/hydroxide derivatives in the field of water splitting, with a particular emphasis on the research progress achieved through the utilization of IL and DES. The aim is to assist readers in designing and synthesizing novel and high-performance electrochemical catalysts.

Diseleno-albumin, a native bio-inspired drug free therapeutic protein induces apoptosis in lung cancer cells through mitochondrial oxidation

Macromolecular therapeutic is the emerging concept in the fields of drug delivery and drug discovery. The present study reports the design and development of a serum albumin based macromolecular chemotherapeutic by conjugating bovine serum albumin (BSA) with 3,3′-diselenodipropionic acid (DSePA), a pharmacologically active organo-diselenide (R-Se-Se-R). The reaction conditions were optimised to achieve the controlled conjugation of BSA with DSePA without causing any significant alteration in its physico-chemical properties or secondary structure and crosslinking. The chemical characterisation of the reaction product through various spectroscopic techniques viz., FT-IR, Raman, XPS, AAS and MALDI-TOF-MS, established the conjugation of about ∼5 DSePA molecules per BSA molecule. The DSePA conjugated BSA (Se-Se-BSA) showed considerable stability in aqueous and lyophilized forms. The cytotoxicity studies by involving cell lines of cancerous and non-cancerous origins indicated that Se-Se-BSA selectively inhibited the proliferation of cancerous cells. The cellular uptake studies by physically labelling Se-Se-BSA with curcumin and following its intracellular fluorescence confirmed that uptake efficiency of Se-Se-BSA was almost similar to that of native BSA. Finally, studies on the mechanism of action of Se-Se-BSA in the A549 (lung adenocarcinoma) cells revealed that it induced mitochondrial ROS generation followed by mitochondrial dysfunction, activation of caspases and apoptosis. Together, these results demonstrate a bio-inspired approach of exploring diselenide (-Se-Se-) grafted serum albumin as the potential drug free therapeutic for anticancer application.

Study on Selenium Assimilation and Transformation in Radish Sprouts Cultivated Using Maillard Reaction Products.

The organic selenium (Se), particularly in the form of selenoamino acids, in non-edible sections or by-products of Se-enriched plants, has the potential to generate Maillard reaction products (MRPs) during thermal treatment or fermentation. To elucidate the recycling process of organic selenium in foods and improve the utilization rate of Se, the biotransformation of organic selenium was studied by the cultivation of edible radish sprouts with Se-MPRs. Maillard reactions were simulated using selenoamino acids (SeAAs; selenomethionine and methylselenocysteine) and reducing sugars (glucose and fructose) for preparing Se-MRPs. The structures of the possible dehydrated Se-MRPs were analyzed using a HPLC-ESI-MS/MS system based on their fragmentation patterns and Se isotopic characteristics. Se absorption by the radish sprouts cultivated using Se-MRPs was estimated by the corresponding Se in the SeAAs and the total Se contents. The capabilities of SeAA transformation and total Se assimilation by the sprouts were related to the substrate composition during the Se-Maillard reaction. A particular Se-MRP (selenomethionine + fructose) increased SeAAs transformation by 33.8% compared to selenomethionine. However, glucose and fructose seemed to inhibit the transformation of the Se-MRPs to SeAAs by 10.0 to 59.1% compared to purified Se-MRPs. These results provide key references for the efficient utilization of organic Se in the cultivation of Se-enriched sprouts.

Rapid miRNA detection enhanced by exponential hybridization chain reaction in graphene field-effect transistors

Scalable electronic devices that can detect target biomarkers from clinical samples hold great promise for point-of-care nucleic acid testing, but still cannot achieve the detection of target molecules at an attomolar range within a short timeframe (<1 h). To tackle this daunting challenge, we integrate graphene field-effect transistors (GFETs) with exponential target recycling and hybridization chain reaction (TRHCR) to detect oligonucleotides (using miRNA as a model disease biomarker), achieving a detection limit of 100 aM and reducing the sensing time by 30-fold, from 15 h to 30 min. In contrast to traditional linear TRHCR, our exponential TRHCR enables the target miRNA to initiate an autocatalytic system with exponential kinetics, significantly accelerating the reaction speed. The resulting reaction products, long-necked double-stranded polymers with a negative charge, are effectively detected by the GFET through chemical gating, leading to a shift in the Dirac voltage. Therefore, by monitoring the magnitude of this voltage shift, the target miRNA is quantified with high sensitivity. Consequently, our approach successfully detects 22-mer miRNA at concentrations as low as 100 aM in human serum samples, achieving the desired short timeframe of 30 min, which is congruent with point-of-care testing, and demonstrates superior specificity against single-base mismatched interfering oligonucleotides.

Physiological, metabolome, and transcriptome analysis revealed the effect of ethyl 3-amino-3-thioxopropanoate on the browning of fresh-cut banana during storage

The quality of fresh-cut bananas is often affected by surface browning, which does not meet consumer expectations. The ethyl 3-amino-3-thioxopropanoate (EAT) is an ethyl ester organic compound screened from Maillard reaction products that may have browning inhibition effects. However, there is still a lack of research on the practical application of EAT. This study investigated the impact of exogenous EAT on the browning process and the underlying mechanisms in fresh-cut banana through a comprehensive analysis involving physiological, metabolomic, and transcriptomic approaches. Treatment with EAT effectively mitigated the discoloration of the cut surface of slices and decreased the browning index by 74 % at the end of storage. Additionally, EAT application significantly reduced polyphenol oxidase activity, increased phenylalanine ammonia-lyase activity and total phenolic content, inhibited lipoxygenase activity, decreased malondialdehyde accumulation, enhanced antioxidant enzyme activity, and improved DPPH free radical scavenging rate to 68.49 %. Moreover, 839 metabolites were identified through non-targeted metabolomics analysis. Metabolomic and transcriptomic analysis further highlighted the importance of lipid metabolism, amino acid metabolism and secondary metabolites in influencing the sensitivity to post-cutting browning. EAT treatment also influenced the expression levels of key genes related to browning. Thus, it could be speculated that the mechanism by which EAT produces its anti-browning effect may be by reducing phenolase activity, improving levels of phenols and amino acids, enhancing the antioxidant capacity of the fruit, and alleviating membrane lipid peroxidation. In summary, this study provides valuable insights into the response mechanism employed by exogenous EAT to inhibit browning in freshly cut bananas. However, the application security and mass production methods of EAT still need further clarification.

Full green assay of rosuvastatin utilizing sulphophtalein dyes: application to tablet analysis

The aim of the work was to develop a «green» and extraction-free spectrophotometric procedure for the assay of rosuvastatin in tablets. The present work describes three new spectrophotometric procedures (A, B and C) that can be utilized for routine quality control of rosuvastatin in laboratories. Materials and methods. Analytical instrumentation: Shimadzu UV-1800 double beam UV-vis spectrophotometer (Japan) with attached UV-Probe ver. 2.62 software, RAD WAG AS 200/C precise analytical balance (Poland). Rosuvastatin calcium (purity ≥98 % (HPLC)) was bought from Sigma-Aldrich Chemicals Co. (St. Louis, MO, USA). Rosuvastatin 10 mg tablets were acquired from a nearby drugstore. All solvents used in this study, including methanol, ethanol, chloroform, acetonitrile and ethyl acetate, were produced by Honeywell and had a purity of 99.9 %. BCG, BCP and BTB were acquired from Sigma-Aldrich Chemicals Co. (USA, St. Louis). All chemicals utilized in the experiment were of analytical purity. Results and discussion. New simple «green» and extraction-free spectrophotometric procedures for assay of rosuvastatin in tablets involve the formation of ion-pair complexes with sulphophtalein dyes (BCG (Method A), BCP (Method B), BTB (Method C)) have been developed. The absorbances of the coloured reaction products were registered at 405 nm (Method A) and 400 nm (Methods B, C). The concentration was linearly proportional to absorbance values in the range of 2.51-20.08 μg/mL (method A), 2.50-24.90 μg/mL (method B) and 2.51-12.56 μg/mL (method C). Estimation of LOD and LOQ parameters were obtained as 0.67 μg/mL and 2.23 μg/mL (Method A), 0.39 μg/mL and 1.32 μg/mL (Method B), 0.30 μg/mL and 1.01 μg/mL (Method C). The stoichiometric ratio of the reactive components of rosuvastatin - BCG, BCP, and BTB corresponded 1: 1. The %RSD values of intra-day and inter-day were obtained less than &lt; 1.5 %, which showed excellent repeatability and RE % data was ≤ 3 %. The effect on the environment of the proposed spectrophotometric procedures and their compliance with the GAC principles were endorsed by the output of AGREE, GAPI, and AES metrics tools. The values of these three «green» metrics show that the proposed spectrophotometric procedures had a low environmental impact compared with the reported ones. Conclusions. The developed fast, simple and cost-effective methods A, B, and C can be used for routine analysis of rosuvastatin in tablets

Microstructure, mechanical properties and strengthening mechanism of in-situ synthesized TiC/6061 nanocomposites

In-situ synthesized 1 wt%, 3 wt% and 5 wt%TiC/6061 nanocomposites were prepared by the reaction using Al-K2TiF6-C as starting materials. Microstructure, mechanical properties and strengthening mechanism of the nanocomposites were investigated. SEM observation illustrates the in-situ synthesized ceramic TiC particles show shape of a polygon and its average size is 60 nm. TEM results show that the interface between the Al matrix and TiC reinforcement is clear and no reaction products can be found. Grain refining can be observed in the composites, as the TiC content increased from 0 wt% to 3 wt%. However, grain coarsening appears in the 5 wt%TiC/6061 composites. As increasing the TiC content from 0 wt% to 5 wt%, the mechanical properties of the composites increase firstly and then decreases. The Vickers hardness, yield strength, tensile strength and elongation of the as-cast 3 wt%TiC/6061 composites achieve the maximum value of 80.7 HV, 135 MPa, 202 MPa and 15.3 %, respectively. Strengthening mechanisms of the TiC/6061 nanocomposites is the micromechanical strengthening mechanisms. As the TiC content increasing, CTE strengthening plays an important role.

Assessment of an eco-efficient process for the optimization of metal recovery in lithium cobalt oxide and lithium nickel manganese cobalt oxide batteries

The expansion of technology motivates the increase of global demands for critical minerals. In this context, the exploration of secondary sources of these components is expanding. End-of-life batteries can be seen as potential sources of lithium, cobalt, nickel and manganese for electric vehicles or diverse applications in electronic equipments. This paper provides a comprehensive evaluation of the recovery of metals from waste batteries with diverse chemistry composition. Lithium cobalt oxide (LCO) and lithium nickel cobalt manganese oxide (NMC) batteries were co-treated with polyvinyl chloride (PVC) channels under supercritical water, varying reaction temperature (400–600 °C) and PVC/Battery composition (0–3 m/m) in a tubular continuous reactor. Results show high recovery rates for all metals, with up to 90% percentage recovery of lithium and cobalt in all cases. Temperature and feed composition were identified as determining factors for the recovery of lithium from LCO batteries. In the case of cobalt, temperature was identified as the most important factor that affects its recovery. The selected optimal conditions for cobalt recovery in the solid products of reactions were identified for batteries LCO and NMC: temperature of 600 °C and PVC/Battery ratio of 3.0 and temperature of 500 °C and PVC/Battery ratio of 1.5, respectively. Environmental impacts, primarily Global Warming Potential (GWP), were minimal, with 4.71·10−5 kg CO2 eq., indicating the benefits of the process as an eco-efficient and promising route for the recycling of valuable metals.

Effect of waste glass powder on the durability and microstructural properties of fly ash-GGBS based alkali activated concrete containing 100 % recycled concrete aggregate

This research investigates the effective utilization of waste glass powder (WGP) in fly ash (FA)-ground granulated blast furnace slag (GGBS) based alkali-activated concrete (AAC) containing 100 % recycled concrete aggregate (RCA) cured at ambient temperature. FA substituted with WGP in the range of 0–25 %, and the percentage of GGBS was kept unaltered at 50 %. The influence of WGP on the strength, durability, and microstructural properties of FA-GGBS based AAC was evaluated. The experimental results showed that the strength and durability were enhanced with the increases of WGP of up to 20 %, and then started to decrease. The highest compressive strength (51.4 MPa) and ultrasonic pulse velosity (UPV) (4.35 km/s) were obtained for F30W20 (FA:GGBS:WGP - 30:50:20). In addition, sorptivity, chloride, and water permeability were reduced by 39.92 %, 56 %, and 64.13 %, respectively for optimized specimens as compared to a control sample (without WGP). Furthermore, the microstructural analysis was carried out to investigate the alteration in the mineralogical and morphology. On the basis of microstructural investigations, WGP notably enhanced the microstructure of FA-GGBS-based AAC by enhancing the formation of reaction products, including C-S-H and C-(N)-A-S-H gel. At last, this study found that CO2 emissions, energy consumption, and cost analysis were lowered by approximately 60 %, 28 %, and 41 % compared to conventional concrete of the same quality.

The wettability of pure liquid aluminum on oxide substrates

AbstractOxide particles are considered to be one of the reasons for the stability of cellular porous Al foam. Thus, the contact angle (ө) of molten pure aluminum on oxide substrates, including Al2O3, CaO·2Al2O3 (CA2), CaO·6Al2O3 (CA6), mullite (3Al2O3·2SiO2), and SiO2 was measured in a vacuum heating microscope at a temperature of 950°C to determine the value of wettability of molten aluminum on various oxides. Thereafter, the measured contact angles followed the tendency as mullite (155°) &gt; CA6 (152°) &gt; MgAl2O4 (151°) &gt; Al2O3 (149°) &gt; SiO2 (124°) &gt; CA2 (100°). Furthermore, the cross‐sectional area between molten aluminum and substrates was thoroughly analyzed, and the reaction products, such as the Al2O3 layer at the interface, have been detected. Thermo‐Calc, with the combination of available databases, was used to perform thermodynamic simulations and to discuss and predict possible reactions under the current experimental conditions.

Simulation Study for Nb‐Doped MoS2${\rm MoS}_2$ Layer in CZTS‐Based Solar Cells: Assessment of Challenges

AbstractThe unintentional formation of a layer as a reaction product between the copper zinc tin sulfide (CZTS) thin film and the Mo back contact reduces cell efficiency due to high sheet resistance and carrier recombination. To limit the formation of , an intentionally grown p‐type Nb‐doped layer can serve as an effective hole transport layer. This study presents a detailed study and calculations for CZTS/Mo‐based solar cells, providing guidelines for calibration. Optimizing cell efficiency is influenced by various interconnected factors in Nb‐doped . While a high carrier concentration in Nb‐doped is assumed to enhance efficiency, other parameters such as band state, optical absorption, and carrier mobility also play crucial roles and can limit cell performance. This simulation study evaluated the effect of Nb‐doped layers with different carrier concentrations to determine the optimal conditions for this p‐type layer. This work reveals that a very thin layer (13 nm) of Nb‐doped p‐type can achieve a maximum efficiency of 11.34% (with = 1.5 ) and that for an Nb‐doped p‐type 62 nm is 15.82 % (with = 4.03 ).

Evaluation of Kochetkov Hemiaminal hydrolysis under acidic, alkaline, and neutral conditions

The most common precursors to synthetic glycoproteins are reducing end glycosyl amines. To afford these amines, a carbohydrate is reacted with an excess of an ammonia source to yield the β-anomer, exclusively, in a reaction known as the Kochetkov amination. Although this process is the state-of-the-art method to synthesize non-functionalized, β-amino (βA) glycans, misconceptions surrounding the stability of these amines has limited their use in subsequent reactions. Here, we investigated the stability of seven amino sugars in the neutral, acidic, and basic conditions they would be subject to in common reactions using amines. In neutral and basic conditions, the amino sugars proved relatively stable with the fastest time to 50% hydrolysis being four days for only one carbohydrate. However, acidic conditions promoted rapid hydrolysis, with all amino sugars reaching over 97% hydrolysis within 2 h. Finally, we performed a bioconjugation using fluorescein isothiocyanate and βA-difucosyllactose, revealing sufficient stability of the amino product for a successful subsequent reaction.

Enhancing oil production via radical reactions during hydrothermal coliquefaction of biomass model compounds and plastics: A molecular dynamic simulation study

Recently, hydrothermal coliquefaction of biomass and plastic waste has attracted considerable research interest. However, there is a notable gap in understanding the fundamental reaction mechanisms between biomass and plastics during coliquefaction. This study focused on the coliquefaction of biomass model compounds and plastic polymers using ReaxFF molecular dynamics simulations under both subcritical and supercritical water conditions. Molecular-level tracking and probing of the reaction mechanisms between biomass model compounds and plastics were conducted to purposefully enhance oil production. The study observed related radical reactions between by-product molecules, with detailed mechanisms primarily involving (1) ▪OH radicals released by aqueous phase molecules from biomolecules, transferring as H2O molecules and facilitating plastic depolymerization, and (2) C1–C4 radicals in the gaseous phase, emitted from biomolecule and plastic, colliding and subsequently recombining to form oil molecules. Moreover, the yield of multiple products from various mixtures were evaluated by considering the key reaction parameters including reaction temperature and feedstock blended ratio. An exploration into the effect of coliquefaction on oil yield was conducted to precisely identify the optimal coliquefaction conditions. The positive effect of coliquefaction was more pronounced between biomass model compounds and aromatic polymers compared to aliphatic polymers. Analysis of reaction mechanisms and product outcomes has shown that hydrothermal coliquefaction is a viable approach to improving oil production from multi-source organic solid waste.

Plasmon-driven chemical transformation of a secondary amide probed by surface enhanced Raman scattering

Plasmon-driven chemical conversion is gaining burgeoning interest in the field of heterogeneous catalysis. Herein, we study the reactivity of N-methyl-4-sulfanylbenzamide (NMSB) at nanocavities of gold and silver nanoparticle aggregates under plasmonic excitation to gain understanding of the respective reaction mechanism. NMSB is a secondary amide, which is a frequent binding motive found in peptides and a common coupling product of organic molecules and biomolecules. Surface-enhanced Raman scattering (SERS) is used as a two-in-one in-situ spectroscopic tool to initiate the molecular transformation process and simultaneously monitor and analyze the reaction products. Supported by dissociative electron attachment (DEA) studies with the gas phase molecule, a hot electron-mediated conversion of NMSB to p-mercaptobenzamide and p-mercaptobenzonitrile is proposed at the plasmonic nanocavities. The reaction rate showed negligible dependence on the external temperature, ruling out the dominant role of heat in the chemical transformation at the plasmonic interface. This is reflected in the absence of a superlinear relationship between the reaction rate constant and the laser power density, and DEA and SERS studies indicate a hot-electron mediated pathway. We conclude that the overall reaction rate is limited by the availability of energetic hot electrons to the NMSB molecule.

Early-age structural build-up and rheological assessment of alkali-activated slag-red clay brick waste pastes: Influence of silica modulus and precursors proportions

Sustainability plays a crucial role in the current context of the cement industry, and alkali-activated materials (AAMs) are emerging as eco-efficient alternative binders. On the other hand, the massive generation of red brick waste worldwide and its lack of a defined destination emphasizes this material as an alternative precursor that has been insufficiently explored in the literature. Based on this context, the present study aims to investigate the structural build-up, reaction kinetics, and rheological properties of alkali-activated pastes based on blast furnace slag (BFS) and red clay brick waste (RBCW). Fresh properties such as structural build-up, rheology, and reaction kinetics are lacking in the literature on RCBW-based AAMs, highlighting these properties as a research gap to be filled and discussed in depth in this paper. The flow sweep test was performed, linked to yield stress and viscosity properties. The structural build-up was evaluated by strain sweep and small amplitude oscillatory shear (SAOS) tests based on viscoelastic parameters: storage modulus, loss modulus, and phase angle. Isothermal calorimetry and in-situ FTIR were also conducted to complement the analysis and provide insight into the reaction kinetics, chemical structure, and product formation. Higher silica modulus (Ms) resulted in a lower structural build-up rate and a delayed reaction. Higher content of RCBW resulted in a delayed structuration process, which was linked to a delay in the precipitation of aluminosilicate gels. Early increase in the structural build-up in 25 % and 50 % RCBW blends (Ms = 1.0) is associated with the early formation of a well-percolated network.