Surface Aggregation Research Articles

Mitigating Stripping in Asphalt Mixtures: Pretreatment of Aggregate by Thermoplastic Polyethylene Powder Coating

Thermoplastic polyethylene (PE) powder coating is proposed as a new technique to pretreat the aggregate of asphalt mixtures and improve the corresponding moisture resistance. In this paper, ethanol solution is investigated as a fluidized bed to disperse the PE powder. The surface tension of the solution, indicating the wettability of the liquid phase, decreases with increasing ethanol concentration and temperature. The PE powder could be stably dispersed into the solution when 15% ethanol solution heated to 40 to 50°C is used to reduce the surface tension of liquid to less than 40 mN/m. The suspension carrying the PE particles could be uniformly sprayed onto a hot aggregate surface (180–190°C) where the liquid phase evaporates fast while the PE powder melts and stays. The powder coating technique could prevent the aggregate from lumping and achieve a high-quality and efficient coating for aggregate. The PE monolayer model considering a hexagonal close packing of PE on aggregate surface is tentatively proposed to determine the theoretical amount of PE required to perfectly coat the aggregate. The predicted PE content was reasonably lower than that determined by the experimental results considering the ideal monolayer coating was hard to achieve. However, the modeling results could be used to determine the lower bound of the required PE content. The optimum PE content significantly increased with increasing particle size of PE and specific surface area of aggregate. The use of high-density polyethylene (HDPE) powder with a smaller particle size was more effective in the coating process. In addition, excessive PE could not further enhance the moisture resistance of asphalt mixtures efficiently. This study can contribute to both the recycling of waste plastic and the construction of durable asphalt pavements.

Molecular Dynamics Simulations on the Adsorbed Monolayers of N-Dodecyl Betaine at the Air-Water Interface.

Betaine is a kind of zwitterionic surfactant with both positive and negative charge groups on the polar head, showing good surface activity and aggregation behaviors. The interfacial adsorption, structures and properties of n-dodecyl betaine (NDB) at different surface coverages at the air-water interface are studied through molecular dynamics (MD) simulations. Interactions between the polar heads and water molecules, the distribution of water molecules around polar heads, the tilt angle of the NDB molecule, polar head and tail chain with respect to the surface normal, the conformations and lengths of the tail chain, and the interfacial thickness of the NDB monolayer are analyzed. The change of surface coverage hardly affects the locations and spatial distributions of the water molecules around the polar heads. As more NDB molecules are adsorbed at the air-water interface, the number of hydrogen bonds between polar heads and water molecules slightly decreases, while the lifetimes of hydrogen bonds become larger. With the increase in surface coverage, less gauche defects along the alkyl chain and longer NDB chain are obtained. The thickness of the NDB monolayer also increases. At large surface coverages, tilted angles of the polar head, tail chain and whole NDB molecule show little change with the increase in surface area. Surface coverages can change the tendency of polar heads and the tail chain for the surface normal.

Properties of the interfacial transition zone in rubberised concrete – an investigation using nano-indentation and EDS analysis

Concrete is the most widely used material in the world after water. Using recycled aggregate derived from waste concrete and end-of-life tyres can significantly reduce the demand for virgin materials and reduce the concrete industry's carbon footprint. Using recycled aggregates may greatly influence concrete's mechanical and other properties. The reduction in strength and stiffness is often attributed to weak bonding between aggregate and cement pastes (weak interfacial transition zone-ITZ). This paper investigates the mechanical and chemical properties of the cement paste and ITZ using statistical nano-indentation technology and X-ray energy dispersive spectroscopy. It is observed that tyre-derived aggregates form weaker bonds with cement paste, and the ITZ has a considerably lower elastic modulus than cement paste. Many nano-pores are found on the tyre-derived aggregate's surface, which may contribute to inferior performance compared to conventional concrete. The study also observes that reducing the water-binder ratio may reduce the number of nano-pores in cement paste and thus improve its mechanical behaviour.

Evaluation of the Adhesion between Aggregate and Asphalt Binder Based on Image Processing Techniques Considering Aggregate Characteristics.

Aggregate-asphalt adhesion plays an important role in the water stability of asphalt concrete. In various test standards of different countries, it is evaluated via the subjective judgment of testers using the boiling water test. The subjective judgment in the test method is detrimental to the accuracy of the adhesion evaluation. However, there is no quantitative evaluation method for the aggregate-asphalt adhesion in existing studies. Moreover, the effects of aggregate shape on adhesion are also not discussed and stipulated. Hence, an innovative method based on the Chinese boiling water test and image processing technique is put forward to quantificationally evaluate the aggregate-asphalt adhesion. Moreover, the effects of aggregate shapes on adhesion are also investigated via the proposed method from a view of aspect ratio and homogeneity. Results show that the peeling of the asphalt membrane on the aggregate surface is more serious as the complexity of the aggregate shape increases after the boiling water tests, while the effect degree gradually decreases. The effect of aspect ratio on the peeling status of asphalt membrane is lower than that of aggregate homogeneity.

Role of cobalt chloride indicator in the methane dry reforming over inexpensive allochroic silica gel supported nickel catalysts

Reducing the catalyst cost by using inexpensive support material is essential to its scale-up application in methane dry reforming (MDR) process. Herein, we report an allochroic silica gel (ASG) supported nickel catalyst for MDR reaction, considering abundant SiO2 resources and its direct granular shape. A series of catalysts were prepared by a facile impregnation method and the role of the contained cobalt chloride indicator was particularly studied. Characterization results implied that the cobalt chloride indicator was transformed into a mixture of cobalt oxides (CoOx) after calcination. The activity tests showed that ASG supported catalyst (Ni/ASG) had lower CH4 and CO2 conversion than the Co-free catalyst supported on ordinary silica gel (Ni/OSG), which is caused by the decreased Ni dispersion after Co addition. Adding Co into Ni/OSG can cause surface aggregation of CoOx species, which is less uniform than Ni/ASG. On the contrary, the 30-h stability test showed that the absence of CoOx species is detrimental to the catalyst durability due to the heavy carbon deposition of Ni/OSG. The origin of coke formation is elucidated from reaction mechanism perspective via in-situ DRIFTS analysis, where both Co-containing and Co-free catalysts are similar in CH4 stepwise dissociation and CO2 breakage forming bridged carbonyls but diverge in the carbonate intermediates. The special existence of carbonate intermediates interfere the desorption process of bridged carbonyls meanwhile enhance the interaction between C radicals and Ni actives, which further accumulate into the substantial deposited carbon.

Correlation of oxygen defects, oxide-ion conductivity and dielectric relaxation to electronic structure and room temperature ferromagnetic properties of Yb3+ doped CeO2 nanoparticles

Ce1-xYbxO2 nanoparticles synthesized using co-precipitation route were studied for properties like structural, optical, impedance and X-ray Photoelectron Spectroscopy. Existence of cubic fluorite structure found intact with heterogeneous aggregation and spherical surface morphology. Red-shifted energy gap along with formation of defects and oxygen vacancies was confirmed with UV–Vis and Photoluminescence analyses. XPS analyses were undertaken to observe the chemical states 2+ and 3+ of Yb and 3+ and 4+ of Ce cations. The magnetization results demonstrated improved ferromagnetic ordering for varying Yb doping, explained with Bound Magnetic Polarons model and F-Centre Mechanism for creation of distinct complexes, Ce4+-Vo-Ce3+ or Yb3+-Vo-Ce3+ in the CeO2 lattice. All samples' dielectric permittivity and modulus were measured in the 120 Hz–100 kHz frequency range. The ∈′ (f) and ∈″(f) plots show two distinct regions: a plateau zone at high frequency and low frequency dielectric dispersion region. These nanoparticles could be employed for photolytic, optoelectronics and energy storage applications.

Tetraalkylammonium counterion effects on lauroyl β-alanine: A chemical trapping study

The use of acyl amino acid surfactants has gained significant interest due to increasing environmental pressure from both the government and customers. Understanding the ion-specific effects (SIE) in these surfactant systems not only contributes to their practical applications in complex systems but also provides a theoretical basis for investigating SIE in protein systems. In this study, we synthesized four types of lauroyl β-alanine tetraalkylammonium salts (TAA-LA) with tetramethylammonium (TMA-LA), tetraethylammonium (TEA-LA), tetrapropylammonium (TPA-LA), and tetrabutylammonium (TBA-LA) as counterions. The SIE on their surface activities, aggregation behaviors, and interfacial molarities were examined. The critical micelle concentration of TAA-LA decrease with an increase in the size of the counterions. Chemical trapping revealed that the interfacial molarity of water and carboxylate groups followed the order TBA-LA > TPA-LA > TEA-LA > TMA-LA, whereas the interfacial amide bond molarity followed the reversed order. These results were consistent with their differences in aggregation behaviors. Specifically, LA bearing smaller TAA+ counterions formed uni-lamellar vesicles (ULVs) spontaneously, while LA with TBA+ self-assembled into double-lamellar vesicles (DLVs) of comparable sizes. Both CT and MD confirmed that TBA-LA DLVs with relatively smaller “average curvature” were more hydrated than other TAA-LA ULVs. Our results suggested that TBA+ tends to break the intermolecular hydrogen bond between amide bonds, which results in looser interfacial packing and larger “average curvature”. Our findings provide new insights into the tetraalkylammonium counterion effects on acyl amino acid surfactants and elucidate the SIE on protein systems at the molecular level.

Investigation of aggregation behavior and surface properties of cationic surface-active ionic liquids and sodium carboxymethylcellulose mixed systems

Abstract The impact of different concentrations of sodium carboxymethyl cellulose (NaCMC) on the micellization process in cationic, ester-functionalized, ethyl-substituted imidazolium-based surface-active ionic liquids (SAILs) ([C n Eeim]Br where, n = 12, 14, 16) were investigated using specific conductivity and surface tension measurements at 298 K. The study focused on determining the critical micelle concentration (CMC) of the three pure SAILs and their mixtures with NaCMC to evaluate various thermodynamic and interfacial parameters. The results showed that the CMC values decreased significantly with increasing hydrophobicity of the SAILs, while the CMC increased with a gradual increase in the NaCMC mole fraction in the SAIL–NaCMC mixed systems. It was observed that the excess free energy of micellization ( ∆ G e x m ${{\increment}G}_{ex}^{m}$ ) and the minimum free energy of surface at equilibrium ( ∆ G min s ${{\increment}G}_{\mathrm{min}}^{s}$ ) exhibited an opposite behaviour, indicating that the formed mixed micelles were stable while the formed surface was unstable. The results of this study are useful for evaluating the properties of SAIL–NaCMC mixed systems to improve and better understand their applications in the food, medical and cosmetic industries.

Interpretation of stripping at the bitumen–aggregate interface based on fluorescence tracing method

Asphalt pavement field performance largely depends on the stripping resistance at the bitumen–aggregate interface. However, the conventional stripping resistance evaluation method is unsuitable for direct and precise quantification of the retained bitumen film area on the aggregate surface that designates the stripping resistance between bitumen and aggregate phases under the action of vehicle wheels or moisture damage. This study proposed a novel fluorescence tracing method to quantify the exact area of aggregate coating loss in accordance with the bituminous-coated aggregate image processing technique. The fluorescence tracing image acquisition and analysis system for precisely calculating the bitumen stripping ratio of the bituminous-coated aggregate were established after the bitumen stripping test. The thresholding manner of the two-mode threshold algorithm was devised to segment the fluorescence-traced bituminous-coated aggregate image with high quality. The results demonstrated that the appropriate threshold value for segmenting the fluorescence-traced image mainly falls in the range of 60–70 for limestone, 90–110 for basalt, and 100–110 for both granites; the ability of aggregates based on their chemisorption capacity with bitumen is in the order of limestone, basalt, and granite; the fluorescence tracing method eliminated nearly 92.3% of the undesirable reflection on bitumen phase; the detected bitumen stripping ratio, raised by 65.87% on average and by 37.82% in the median value in contrast to the conventional visual detection manner. This research introduces a practical framework from an engineering perspective for visually quantifying the interpretation of the adhesive bond at the bitumen-aggregate interface with reasonable accuracy and confidence.

Surface and subsurface oceanographic features drive forage fish distributions and aggregations: Implications for prey availability to top predators in the US Northeast Shelf ecosystem.

Forage fishes are a critical food web link in marine ecosystems, aggregating in a hierarchical patch structure over multiple spatial and temporal scales. Surface-level forage fish aggregations (FFAs) represent a concentrated source of prey available to surface- and shallow-foraging marine predators. Existing survey and analysis methods are often imperfect for studying forage fishes at scales appropriate to foraging predators, making it difficult to quantify predator-prey interactions. In many cases, general distributions of forage fish species are known; however, these may not represent surface-level prey availability to predators. Likewise, we lack an understanding of the oceanographic drivers of spatial patterns of prey aggregation and availability or forage fish community patterns. Specifically, we applied Bayesian joint species distribution models to bottom trawl survey data to assess species- and community-level forage fish distribution patterns across the US Northeast Continental Shelf (NES) ecosystem. Aerial digital surveys gathered data on surface FFAs at two project sites within the NES, which we used in a spatially explicit hierarchical Bayesian model to estimate the abundance and size of surface FFAs. We used these models to examine the oceanographic drivers of forage fish distributions and aggregations. Our results suggest that, in the NES, regions of high community species richness are spatially consistent with regions of high surface FFA abundance. Bathymetric depth drove both patterns, while subsurface features, such as mixed layer depth, primarily influenced aggregation behavior and surface features, such as sea surface temperature, sub-mesoscale eddies, and fronts influenced forage fish diversity. In combination, these models help quantify the availability of forage fishes to marine predators and represent a novel application of spatial models to aerial digital survey data.

Wetting model of rough solid surfaces and the effect of aggregate properties on epoxy resin binder-aggregate interface wetting

In order to study the effect of aggregate characteristics on the wetting of epoxy resin binder-aggregate interface, based on the Wenzel model and Cassie model, this paper established a new wetting model of the irregular rough surface. The model regularizes the rough solid surface and can calculate the wetting depth and apparent contact angle between different irregular rough solids and liquids. The texture parameters of aggregates, the surface tension of test liquids and the contact angles of different liquids-aggregates were tested by laser confocal tester and optical contact angle measuring instrument. It was found that the surface texture parameters of different aggregates were quite different. The relative error between the apparent contact angle calculated by the prediction model and the contact angle measured by the test was less than 15 %, indicating that the prediction model had excellent prediction effect. Through the analysis of the wetting model, it is found that the surface tension of the test liquid, the lithology of the solid aggregate, the surface roughness and the texture structure are the important control parameters affecting the wetting. The surface morphology of rough solid can be designed by changing the resolution k and depth H of micropores, so as to control the wettability of solid aggregate surface and epoxy resin aggregate.

Effects of particle’s surface properties and aggregation modes on water vapor competition in heterogeneous nucleation of water vapor on the particles

Heterogeneous nucleation of water vapor on particles to promote particulate abatement is widely used in the fields of industrial dust removal pretreatment technology. Water vapor competition is a very important phenomenon in the process of particles nucleation, but due to the limitations of experimental methods, this phenomenon is difficult to observe and rarely received attention. Therefore, in order to reveal the influence of water vapor competition on particles nucleation, a direct visualization method based on the Environmental Scanning Electron Microscope (ESEM) is proposed in this work to obtain the water vapor competition process during particles nucleation at a microscopic scale. Firstly the effect of particle’s surface structure on water vapor competition in heterogeneous nucleation of water vapor on the particles is visualized by the ESEM. The results show that the embryo appears randomly at any edge of the smooth spherical particle because water vapor competition at each point on the particle’s surface is equal. While the embryo always appears on the protuberance of the convex spherical particle since water vapor competition is strongest there. Then the influence of particle’s surface energy on water vapor competition is also visualized. Water vapor preferentially nucleates on the particle with smaller contact angle, which means the higher the surface energy, the more conducive it is for water vapor competition to form embryos. Finally, the impact of particle’s aggregation modes on water vapor competition is also visualized by the ESEM. The results show that when the vapor supersaturation is constant, water vapor only nucleates on the two-close and three-circled particles while particles nucleation on the single particle is never observed. This is due to the strong water vapor competition at the particle’s junction, where the embryos will collide and coalesce to form an embryo larger than the critical size to activate particles nucleation. The results of this study will deepen the microscopic understanding of water vapor competition in the process of particles nucleation.

Continuous enzyme crosslinking modifying colloidal particle characteristics and interface properties of rice bran protein to improve the foaming properties

The improvement of rice bran protein (RBP) foaming properties by continuous Transglutaminase (TGase) enzymatic cross-linking was studied and the related mechanism was analyzed. Under the conditions of enzyme addition of 0.5 kat/kg of protein and 3 h of enzyme crosslinking time, the foam capacity value and foam volume ratio of BPR were increased to 375% and 79.45% respectively and the liquid drainage rate of RBP samples foam system was decreased. Particle size distribution, zeta potential and surface hydrophobicity indicated that TGase treatment has changed the surface properties and aggregation state of RBP affecting the adsorption of TGase treated RBP on the interface. Meanwhile circular dichroism and intrinsic fluorescence suggested that TGase treatment made the tertiary structure of RBP aggregation more compact. The behavior of the air-water interface revealed that compared to native RBP, TGase cross-linked RBP exhibited a faster and more complex adsorption process, and a higher surface dilatational modulus. Enzyme cross-linked RBP particles mainly stabilized the interfacial membrane by Pickering mechanism, and TGase could catalyze cross-linking of RBP at the interface to enhance the elastic modulus of the interface. This study provides theoretical support for application of protein particles prepared by TGase enzymatic cross-linking in foamed foods.

Microstructural evolution during H2 corrosion of Al2O3–SiO2 based refractory aggregates

Hydrogen-based direct reducing iron production (H-DRI) has caused more and more attention in metallurgical industry owing to the near-zero carbon emission. However, the strong reducibility of H2 at elevated temperature can possibly cause serious corrosion to the lining refractories of furnaces. In this study, four types of Al2O3–SiO2 based aggregates (brown corundum, bauxite, mullite and quartz) with various SiO2/Al2O3 mass ratios were utilized for the H2 corrosion test at 1673 K with a soaking time of 8 h. Based on the analysis of weight-loss ratios, phase-composition variation and reduction thermodynamics, the microstructure evolution during H2 corrosion was investigated in detail. The results indicates that the SiO2 impurity of brown corundum was partly reduced by H2 which led to the formation of rod-like or flaky intergranular grains. For bauxite, a porous structure was produced by the accumulation of rod-like or elongated grains owing to the significant reduction of intergranular silicon compounds. Nevertheless, due to the high sintering activity between the Al2O3 products from the reduction of mullite, a high densification structure was realized to effectively prevent the further H2 penetration, hence, mullite inversely obtained the better H2 corrosion resistance than bauxite in spite of its higher S/A ratio. The accumulation of SiO and H2O gases due to the high reduction rate of SiO2 led to the formation of a great deal of SiO2 fiber on the surface of quartz aggregates. The [O] provided by the phase-transformation from α-quartz to cristobalite could be partially captured by the H2 for the reduction, which caused the deterioration of corrosion. With this study, we aim to provide theoretical assistance for the refractory selection applied in hydrogen metallurgy.

Evaluation and Source Analysis of Soil Heavy Metal Pollution in a Planting Area in Wanquan District, Zhangjiakou City

Taking the soil of a vegetable planting area in Wanquan District of Zhangjiakou City as the research object, 132 surface and 80 deep soil samples were collected to test and analyze the contents of eight heavy metals such as As, Cd, Cr, Hg, Cu, Ni, Pb, and Zn and the occurrence forms of Cr and Ni. By applying geostatistical analysis and the PMF receptor model and combining three heavy metal pollution evaluation methods, the spatial distribution characteristics of soil heavy metals in the study area, the degree of heavy metal pollution, and the distribution of Cr and Ni fugitive forms in the vertical layer were clarified, and the sources and contribution rates of soil heavy metal pollution were analyzed. The results showed that the average contents of Cd and Pb in surface soils were higher than the background values of soils in Hebei Province, and the spatial distribution characteristics of Cr, Ni, Cu, Cd, Pb, and Zn in surface soils were similar. The ground accumulation index method showed that the study area was mainly free of pollution, with a small number of lightly polluted sites, and most of them were polluted with Cd. The enrichment factor method showed that the study area was mainly free-weakly polluted, with medium pollution of all elements; the significantly polluted elements in the background area were As, Pb, and Hg, and the significantly polluted element in the key area was Cd. The potential ecological risk index method showed that the study area was mainly lightly polluted, with local distribution. The potential ecological risk index method showed that the study area was mainly lightly polluted, with a local distribution of "medium" and "strong" risk points, with "very strong" risk points for Hg in the background area and "very strong" risk points for Cd in the focus area. These three evaluation results indicated that the background area was dominated by Cd and Hg pollution, whereas the focus area was dominated by Cd pollution. The study on the fugitive morphology of vertical soil showed that Cr was dominated by the residue state (F4) and supplemented by the oxidizable state (F3), and the vertical direction was dominated by the surface aggregation type and supplemented by the weak migration type. Ni was dominated by the residue state (F4) and supplemented by the reducible state (F2), and the vertical direction was dominated by the strong migration type and supplemented by the weak migration type. The sources of heavy metals in the surface soil were divided into three categories; Cr, Cu, and Ni were mainly from natural geological background sources. The contributions of Cr, Cu, and Ni were 66.9%, 66.9%, and 76.1%, respectively. As, Cd, Pb, and Zn were mainly from anthropogenic sources, with contributions of 77.38%, 59.2%, 83.5%, and 59.5%, respectively. Hg was mainly from dry and wet atmospheric deposition, with a contribution of 87.8%.

Microplastics as an adsorption and transport medium for per- and polyfluoroalkyl substances in aquatic systems: Polystyrene and undecafluorohexanoic acid interactions

The assessment of possible interactions between microplastic particles (MPP) and other emerging contaminants such as per- and polyfluoroalkyl substances (PFAS) is of great importance due to their potentially conjunctive harmful effects on the environment. Here, the colloidal behaviour of a polystyrene MPP in the presence of undecafluorohexanoic acid (UFHA), an alternative to the widely used C8 PFAS, was studied in aqueous dispersions. Adsorption of UFHA on MPP was confirmed, where it induced charge neutralization with overcharging at higher UFHA concentrations. Rates of MPP aggregation were rapid with neutral particles, while slow at low and high UFHA doses, where considerable, alternate surface charge persisted and hence, fine particle dispersion was maintained. The addition of multivalent ions influenced the surface charge and aggregation features of MPP, in both their native form and in the presence of UFHA. Concurrent adsorption of electrolytes and UFHA was observed and strongly affected the rate of MPP aggregation under some experimental conditions. This study provides new insights into the possible interactions of PFAS with MPP, which may fundamentally influence the migration of these contaminants in aqueous environments. Aggregated particles will more likely accumulate in the sediments or at the air–water interface, while individual, highly stable MPP-PFAS composites have the potential to migrate together in the water column.

Interfacial Performance of Asphalt-Aggregate System under Different Conditions Based on Molecular Dynamics Simulation

The interface between asphalt and aggregate directly determines the performance of asphalt mixtures but unavoidable weaknesses can be easily found at the interfacial bonding region. In order to evaluate the interfacial adhesion behavior between asphalt and aggregate at the atomic scale, asphalt binders and two mineral aggregates (quartz and calcite) were selected to build molecular models and molecular dynamics (MD) simulations were conducted. The interfacial energy between asphalt and aggregate was calculated and the mineral aggregate has a more significant influence on the energy compared to the binder types. Also, the simulation result indicates that saturate, aromatic, resin, and asphaltene (SARA) components have different interfacial energies with respect to the aggregates. This result can also be derived from the relative concentration of SARA components on the aggregate surface. Additionally, oxidation of the asphalt binder results in increased interfacial energy due to the enhanced intermolecular bonding generated by oxidized functional groups. The intrusion of water greatly reduces the interfacial energy, but the energy increases under the coupling effect of oxidation and moisture, especially for calcite. The grey relational grade theory was conducted to evaluate the factors affecting the adhesive energy, and the results show that the energy of the asphalt-aggregate is more sensitive to the asphaltene index than other factors.

Label-free selective and sensitive colorimetric detection of ampicillin in milk and water using silver nanoparticles

Overuse of antibiotics like ampicillin in various developing and industrializing countries leads to the evolution of drug-resistant bacteria and different adverse effects on an individual's health. Though creating a facile, sensitive, and selective method for ampicillin detection is critical, this remains a strategic task. The poly(vinyl alcohol) (PVA)-capped silver nanoparticles (AgNPs) were used to develop a colorimetric assay for the detection of ampicillin. UV-Vis spectroscopy shows a strong peak at 402 nm due to the excitation of surface plasmon resonance (SPR). The X-ray diffraction (XRD) pattern of AgNPs shows lattice planes (111) and (200) correspond to 2θ values of 38.4° and 44.67°, respectively. Transmission electron microscopy (TEM) histogram shows the large number of particles synthesized in the range of 9–13 nm. As-synthesized AgNPs were used to evaluate the selectivity of the assay against various competitive antibiotics. The colour change of the assay mixture from yellow to orange was found in the presence of ampicillin due to target-specific aggregation and localized surface plasmon resonance changed from 402 nm to 550 nm. The limit of detection (LOD) and limit of quantification (LOQ) were found to be 6.2 μM and 18.8 μM (linear range 0.5–10 μM) respectively. The colorimetric assay was used to detect the ampicillin-spiked actual samples (tap water, Yamuna River water, and milk). The developed colorimetric assay provides a real-time, rapid, and easy-to-use platform for detecting ampicillin for real sample analysis.

Tuning the aggregation structure and surface composition of reduced graphene oxide microspheres for high-rate supercapacitors

Tuning the aggregation structure and surface composition of reduced graphene oxide microspheres for high-rate supercapacitors

SHAMPOO: A stochastic model for tracking dust particles under the influence of non-local disk processes

Context. The abundances of carbon, hydrogen, nitrogen, oxygen, and sulfur (CHNOS) are crucial for understanding the initial composition of planetesimals and, by extension, planets. At the onset of planet formation, large amounts of these elements are stored in ices on dust grains in planet-forming disks. The evolution of the ice in dust, however, is affected by disk processes, including dynamical transport, collisional growth and fragmentation, and the formation and sublimation of ice. These processes can be highly coupled and non-local. Aims. In this work, we aim to constrain the disk regions where dynamical, collisional, and ice processing are fully coupled. Subsequently, we aim to develop a flexible modelling approach that is able to predict the effects of these processes acting simultaneously on the CHNOS budgets of planetesimal-forming material in these regions. Methods. We compared the timescales associated with these disk processes to constrain the disk regions where such an approach is necessary, and subsequently developed the SHAMPOO (StocHAstic Monomer PrOcessOr) code, which tracks the CHNOS abundances in the ice mantle of a single ‘monomer’ dust particle of bare mass mm, embedded in a larger ‘home aggregate’. The monomer inside its home aggregate is affected by aerodynamic drag, turbulent stirring, collision processes, and ice adsorption and desorption simultaneously. The efficiency of adsorption onto and the photodesorption of the monomer here depends on the depth zm at which the monomer is embedded in the home aggregate. We used SHAMPOO to investigate the effect of thefragmentation velocity υfrag and home aggregate filling factor ϕ on the amount of CHNOS-bearing ices for monomers residing at r = 10 AU. Results. The timescale analysis shows that the locations where disk processes are fully coupled depend on both grain size and ice species. We find that monomers released at 10 AU embedded in smaller, more fragile, aggregates with fragmentation velocities of 1 m s−1 are able to undergo adsorption and photodesorption more often than monomers in aggregates with fragmentation velocities of 5 and 10 m s−1. Furthermore, we find that at 10 AU in the midplane, aggregates with a filling factor of ϕ = 10−3 are able to accumulate ice 22 times faster on average than aggregates with ϕ = 1 under the same conditions. Conclusions. Since different grain sizes are coupled through collisional processes and the grain ice mantle typically consists of multiple ice species, it is difficult to isolate the locations where disk processes are fully coupled, necessitating the development of the SHAMPOO code. Furthermore, the processing of ice may not be spatially limited to dust aggregate surfaces for either fragile or porous aggregates.