Strong Aggregation Research Articles

Advancing High-Performance Organic Solar Cells with Carbazole-Modified 2PACz for Scalable Large-Area Fabrication.

The self-assembling molecule 2PACz tends to aggregate in thin films, which negatively impacts the performance of organic solar cells (OSCs) when used as a hole-transporting layer (HTL), particularly in large-area devices. To overcome this, a binary conjugated molecular system incorporating carbazole (Cz), which shares a similar backbone with 2PACz, is introduced. Despite the strong aggregation tendencies of 2PACz and Cz individually, their blend forms homogeneous films due to hydrogen bonding interactions between the two molecules. These interactions suppress 2PACz aggregation, resulting in smooth and well-ordered films. Devices with the modified HTL show significantly enhanced charge transfer, achieving a power conversion efficiency (PCE) of 20.10%, a fill factor of 80.3%, and a short-circuit current of 28.98mAcm- 2, outperforming those with unmodified 2PACz. Large-area devices (1.0 cm2) with the modified HTL achieve a record-high PCE of 18.56% and a retention rate of 92.7%, compared to 43% for devices with 2PACz. These findings highlight the potential of carbazole-modified 2PACz to improve both efficiency and stability in OSCs, offering a promising strategy for high-performance HTL development.

Microplastic Materials for Inhalation Studies: Preparation by Solvent Precipitation and Comprehensive Characterization.

Assessing the inhalation hazard of microplastics is important but necessitates sufficient quantity of microplastics that are representative and respirable (<4µm). Common plastics are not typically manufactured in such small sizes. Here, solvent precipitation is used to produce respirable test materials from thermoplastics polyurethane (TPU), polyamide (PA-6), polyethylene terephthalate (PET), and low-density polyethylene (LDPE). Complementary methods verified that the desired size range is achieved both in number metrics and in mass metrics. To assess if the test materials are representative of their original plastic, a range of molecular properties, particle properties, and impurities are characterized: chemical composition, molecular weight, crystallinity, molecular mobility, density, surface charge, surface reactivity, particle size in mass and number metrics, particle shape, endotoxin content, and solvent content. The test materials obtained by precipitation are compared to commercial granules as references, and to alternative test materials obtained by other synthesis routes from LDPE, TPU, PET, PA-6, polystyrene (PS), and polyvinylchloride (PVC). Charge and surface reactivity of the precipitated test materials are low. Due to storage in water, microbial contamination needed to be monitored. For PET, PA-6, and TPU, the test materials are considered as representative and fit for purpose, whereas the inherent hydrophobicity of LDPE imposed strong aggregation.

Unveiling emissive H-aggregates of benzocoronenediimide, their photophysics and ultrafast exciton dynamics.

H- and J-aggregates of many molecules can be considered ordered mesoscopic structures that behave like a single entity. This is due to coherent electronic coupling between electronic excitations of aggregated molecules, resulting in distinct electronic properties compared to the monomer. H-aggregates are generally non-emissive and, due to this property, they are considered unfit for optoelectronics applications, but they have found applications in organic light-emitting transistors. Herein, we designed t-butyl-substituted benzocoronenediimide (t-But-BCDI) forming rare emissive H-aggregates. The tertiary butyl groups are placed to inhibit the formation of strong aggregates. Photophysical studies showed that t-But-BCDI forms H-aggregates in a concentrated solution in a THF/CHCl3 mixture. A blue shift in absorption along with a decrease in the A0-0/A0-1 ratio and red-shifted weaker emission are observed for the aggregate compared to the monomer. Ultrafast transient absorption studies revealed biphasic relaxation with lifetimes of 150 (±10) fs and 13 (±2) ps, which are attributed to a higher-to-lower state transition and vibrational cooling, respectively. The transient spectral signature suggests the Frenkel-type (localized to a monomer) character of the exciton. Faster evolution at the tens of picosecond timescale suggests relaxation of the exciton state within the H-type exciton band. An extraordinarily long emission lifetime from the H-aggregated state is observed.

Surface and aggregation behavior of butynediol tetraethoxylate-based trisiloxanes

Butynediol ethoxylate-based siloxane surfactants have attracted considerable attention owing to their low foam content and strong wetting power. In this study, butynediol tetraethoxylate-based trisiloxane (TBEO-2) with a longer hydrophilic chain than that of butynediol diethoxytrisiloxane surfactant (TBEO-1) was designed and prepared by the hydrosilylation reaction, and the molecular structure of the product was analyzed by Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance spectroscopy (1H NMR and 13C NMR and 29Si NMR) and its surface and aggregation behaviors were investigated using a range of techniques. The results showed that TBEO-2 exhibits a high surface activity, strong aggregation capacity, low foam content, strong wettability, and good water solubility. Therefore, butynediol tetraethoxylate-based trisiloxane can be considered an ideal low-foam wetting agent for use in various applications.

Application of Strontium Chloride Hexahydrate to Synthesize Strontium-Substituted Carbonate Apatite as a pH-Sensitive, Biologically Safe, and Highly Efficient siRNA Nanocarrier.

Naked siRNAs are sensitive to enzymatic degradation, phagocytic entrapment, quick renal excretion, membrane impermeability, endosomal escape, and off-target effects. Designing a safe and efficient nanocarrier for siRNA delivery to the target site without toxicity remains a significant hurdle in gene therapy. CA is a unique derivative of hydroxyapatite and a highly pH-sensitive nanocarrier with strong particle aggregation and a high polydispersity index. Strontium (Sr2+), a group two divalent metal in the periodic table, has been reported for substituting calcium (Ca2+) ions from the apatite lattice and limiting particle growth/aggregation. This study used strontium chloride hexahydrate (SrCl2·6H2O) salt to develop a Sr-substituted CA (Sr-CA) nanocarrier with ∼30 nm size, spherical shape, less aggregation, homodispersity, and a fair anionic charge. Sr-CA demonstrated a large surface area-to-volume ratio, an improved cargo loading efficiency, and enhanced cellular uptake in HEK-293 cells. Moreover, Sr-CA is a pH-responsive nanocarrier responsible for its long physiological stability, efficient endosomal escape, and optimal cargo delivery within cells. These NPs have differential effects on MAPK1, MAP2K4, PIK3Ca, CAMK4, and p53 gene expression in HEK-293 cells without showing any significant cytotoxicity in cell growth properties. Gene silencing by Sr-CA-mediated siRNA delivery against MAPK1, MAP2K4, PIK3Ca, and CAMK4 genes significantly decreased the level of target gene expression and cell survival, demonstrating successful intracellular siRNA delivery in HEK-293 cells. Additionally, biocompatibility testing confirmed the biological safety of the Sr-CA nanocarrier in mice. These findings suggest that Sr-CA nanocarriers are a promising siRNA delivery system, combining high efficiency with pH-sensitive release and excellent biocompatibility, making them a viable option for future therapeutic applications.

Aggregation–Disaggregation Cycles in ERA5 Reanalysis

Abstract Understanding convective aggregation is very important for understanding tropical climate and climate sensitivity. However, we still lack a full understanding of how aggregation evolves in the real world or what phenomena and scales are analogous to the self-aggregation observed in idealized models. In this study, we apply the moist static energy (MSE) variance budget framework to ERA5 reanalysis data to study the evolution of large-scale aggregation over tropical oceans at basinwide scales. Our novel phase space diagnostics focus on the variability of observed aggregation compared to most previous self-aggregation studies, which focus more on the aggregated mean state. We visualize observed aggregation to evolve anomalously around a mean state in a cyclical fashion forming aggregation–disaggregation cycles. We find horizontal advection of MSE to play the primary role in determining when the domain aggregates or disaggregates. In contrast, all advective, radiative, and surface flux feedbacks are found important for determining the magnitude of the aggregation anomalies. Surface fluxes and horizontal advection tend to dampen aggregation anomalies, while radiative fluxes and vertical advection tend to amplify aggregation anomalies. Looking deeper into the advection terms, we find that changes in vertical advection are dominated by enhanced low-level subsidence over the dry regions during the more aggregated states. This creates an anomalous drying tendency over the dry regions, which maintains aggregation anomalies. In contrast, horizontal advection changes are found to be dominated by increased moisture advection out of the moist columns with stronger aggregation. Significance Statement The purpose of this study is to characterize and understand the evolution of large-scale convective aggregation in the real world through reanalysis data. While most previous observational studies have focused on the evolution of clouds and cloud populations with aggregation, we focus on the energetics and the impact of aggregation on redistributing moisture throughout the domain. Our framework highlights that aggregation can be visualized as a continuously occurring cyclic feature at large scales in the tropics. Further, our work provides a deeper insight into the changes in large-scale circulation that accompany aggregation and characterizes the similarities and differences between the different regions in the tropics.

Emissive Features of Perylene Diimide Derivative with β-Cyclodextrin: Probing the role of inter and intramolecular interactions.

Perylene diimide (PDI) derivatives have been extensively explored as chromophoric dyes for functional organic materials. Here, the custom synthesized tyrosine appended perylene diimide (PDI-Tyr) derivative has shown strong aggregation in aqueous medium diminishing its emissive features, which was surpassed by the supramolecular interaction with β-cyclodextrin (β-CD). Complex formation between PDI-Tyr and β-CD, proposed from the absorption and emission studies, have been substantiated by the 1H-NMR, ITC and geometry optimization data. Time-resolved emission and transient absorption studies carried out on PDI-Tyr in the absence and presence of β-CD, revealed an excited state intramolecular charge transfer (ICT) process from the tyrosine moiety to the PDI core with a time constant of ~30 ps, and the same gets retarded on encapsulation of the tyrosine groups in the βCD:PDI-Tyr (2:1) complex and the kinetics slows down to ~480ps, reviving the emissive features. The absence of a long lifetime component and the lower emission enhancement in the monomeric condition as compared to the phenyl alanine (PDI-Phe) derivative, emphasizes the major role of the ICT process in PDI-Tyr, which subdue the features of intermolecular aggregation, establishing the tunability of the emissive properties with the customization of intra and intermolecular interactions.

Endowing deep eutectic solvent with neutral and ionizable perfluoroalkyl substances extracting capability: experimental study and ab initio molecular dynamics simulation

ABSTRACT The simultaneous separation of neutral and ionizable perfluoroalkyl substances (PFASs) is challenging. The traditional solvents used for this purpose are toxic and harmful. Deep eutectic solvents (DESs) as sustainable alternatives to toxic reagents have received considerable attention in current research. In this work, an array of complementary experimental (liquid–liquid equilibrium experiments) and computational (ab initio molecular dynamics, AIMD) techniques were utilized to explore the distinct distribution behaviors, complicated interaction network, and corresponding mechanisms from multidimensional temporal and spatial perspectives. The proposed bromophenylcyanide-based eutectic solvent systems exhibited good separation and extraction performance for both neutral and ionizable PFASs. The presence of a cyano group adjacent to bromine leads to increased polarization of the C–Br bond, resulting in increased strength of the Br···F contact, which provides selectivity to some extent. For fatty acids, their disruptive effect on eutectic systems is greater because of the relatively strong aggregation that affects DES structuring. For PFASs, different categories of target monomers are confined in the DES cavities and interact with the surrounding solvent through abundant interaction sites (such as electrostatic attraction, N-H···F-C, O-H···F-C, O-H···O-H, and C≡N···O-H hydrogen bonds) without significantly disrupting the solvent structural properties by reducing the molecular mobility.

Vinylene‐Bridged Alkoxyfluorobenzothiadiazole (FOBTzE)‐Based Semiconducting Polymers for Enhanced Performance in Non‐Fullerene Organic Photovoltaic Cells

ABSTRACTTo mitigate the strong aggregation and limited solubility observed in the previously reported vinylene‐bridged alkoxyfluorobenzothiadiazole (FOBTzE)‐based polymer, PFOE4T, we designed and synthesized PBFOE‐1. This novel semiconducting polymer, based on the FOBTzE framework, incorporates an alkylthienyl‐substituted benzodithiophene (BDT) as the donor unit. PBFOE‐1 demonstrated broad and intense absorption between 300 and 700 nm with a relatively wide bandgap of 1.7 eV. Additionally, PBFOE‐1 features a low HOMO energy level (−5.43 eV) compared to PFOE4T (−5.23 eV), likely due to the incorporation of weakly electron‐donating BDT into the polymer backbone. While the PFOE4T/Y12‐based solar cell yielded a modest power conversion efficiency (PCE) of 4.37%, characterized by a short‐circuit current density (J sc) of 13.5 mA cm−2, an open‐circuit voltage (V oc) of 0.69 V, and a fill factor (FF) of 0.47, the PBFOE‐1/Y12 cell exhibited a substantially higher PCE of 10.96%. This improvement is reflected in the enhanced J sc (23.23 mA cm−2), V oc (0.84 V), and FF (0.56). The superior performance of PBFOE‐1 is primarily attributed to its improved solubility and aggregation behavior, promoting a more ordered face‐on orientation and optimal blend morphology.

Manipulating Backbone Planarity of Ester Functionalized Conjugated Polymer Constitutional Isomer Derivatives Blended with Molecular Acceptors for Controlling Photovoltaic Properties.

Exploring both electron donor and acceptor phase components in bulk heterojunction structures has contributed to the advancement of organic photovoltaics (OPV) realizing power conversion efficiencies reaching 20%. Being able to control backbone planarity of the donor polymer, while understanding its effects on the polymer conformation and photophysical properties, fosters the groundwork for further achievements in this realm. In this report, three isomeric PM7 derivatives are designed and synthesized where the benzodithiophene-4,8-dione structure is replaced by a quaterthiophene bridge carrying two ester moieties. The placement of these two ester groups varies among three configurational isomers, which ultimately influences the chain conformations and aggregation behavior of each polymer. Specifically, PM7-D3 has ester groups attached to the inner positions of the outer thiophenes showing moderate solution aggregation; PM7-D4 has ester groups attached to the inner positions of the inner thiophenes featuring a twisted backbone with no solution aggregation behavior; and PM7-D5 has ester groups attached to the outer positions of the inner thiophenes with strong solution aggregation. PM7-D5 shows the highest average power conversion efficiency of 11.4% paired with the molecular acceptor L8-BO. In addition, the differences among the polymer backbones are expressed by their state energies and carrier mobility in the corresponding fabricated OPV devices.

Completely Fused Non‐Fullerene Acceptor Enables Efficient Postprocessing‐Free Organic Photovoltaics Cells

AbstractThe photovoltaic performance of organic photovoltaic (OPV) cells can be significantly improved by regulating the aggregation structure and film formation kinetics of the constituent materials. However, many regulation strategies, including the use of additives and annealing, require complex fabrication processes and additional investments, which poses challenges for the industrialization of OPV cells. In this work, a completely fused non‐fullerene acceptor, GS‐20 is designed and synthesized, with strong aggregation properties. The incorporation of GS‐20 as a third component into the PBQx‐TF:eC9‐2Cl‐based cell accelerates aggregation of eC9‐2Cl and improves molecular stacking by promoting film deposition. The as‐cast ternary OPV cells fabricated without any post‐treatments exhibited a high VOC of 0.890 V and a maximum PCE of 19.0%. Moreover, a postprocessing‐free OPV module is fabricated using the blade coating method and obtains a satisfactory PCE of 13.5%, indicating excellent feasibility for large‐scale preparation. This work realizes an efficient postprocessing‐free OPV cell through molecular design and ternary strategy, facilitating the industrialization of OPV technology.

Regulating Intermolecular Interactions and Film Formation Kinetics for Record Efficiency in Difluorobenzothiadizole-Based Organic Solar Cells.

The difluorobenzothiadizole (ffBT) unit is one of the most classic electron-accepting building blocks used to construct D-A copolymers for applications in organic solar cells (OSCs). Historically, ffBT-based polymers have achieved record power conversion efficiencies (PCEs) in fullerene-based OSCs owing to their strong temperature-dependent aggregation (TDA) characteristics. However, their excessive miscibility and rapid aggregation kinetics during film formation have hindered their performance with state-of-the-art non-fullerene acceptors (NFAs). Herein, we synthesized two ffBT-based copolymers, PffBT-2T and PffBT-4T, incorporating different π-bridges to modulate intermolecular interactions and aggregation tendencies. Experimental and theoretical studies revealed that PffBT-4T exhibits reduced electrostatic potential differences and miscibility with L8-BO compared to PffBT-2T. This facilitates improved phase separation in the active layer, leading to enhanced molecular packing and optimized morphology. Moreover, PffBT-4T demonstrated a prolonged nucleation and crystal growth process, leading to enhanced molecular packing and optimized morphology. Consequently, PffBT-4T-based devices achieved a remarkable PCE of 17.5 %, setting a new record for ffBT-based photovoltaic polymers. Our findings underscore the importance of conjugate backbone modulation in controlling aggregation behavior and film formation kinetics, providing valuable insights for the design of high-performance polymer donors in organic photovoltaics.

Revealing pest patterns: A comparative spatial distribution analysis of insect threats in Kharif rice across the key agricultural regions in the Eastern India.

This study investigates the spatial distribution and aggregation patterns of major insect pests in Kharif rice fields during the 2023 growing season in Eastern India. The analysis focuses on key pests such as yellow stem borer (YSB), gall midge, green leaf hopper (GLH), and brown planthopper (BPH), as well as rice thrips, caseworm, whorl maggot, Gundhi bug, grasshopper, and leaf folder. Using statistical indices, this study aims to understand pest behavior across Standard Meteorological Weeks (SMWs) to better inform pest control strategies. The study reveals significant clustering and aggregation patterns among the pests. YSB exhibited variance-mean ratio (VMR) values between 1.14 (40th SMW) and 1.96 (31st SMW), with dispersion parameter (K) values ranging from 0.57 to 21.65, and a peak index of dispersion of 132.66 (43rd SMW). Similarly, gall midge showed VMR values from 6.19 to 10.48, whereas GLH and BPH recorded VMR ranges of 1.19 to 132.10 and 1.01 to 1.50, respectively. These spatial distribution trends were confirmed through values for Iwao's patchiness index and Taylor's power law, indicating strong pest aggregation in specific areas. The results underscore the need for region-specific integrated pest management strategies that take into account pest clustering and environmental factors influencing pest distribution. Although an S-curve pattern of infestation-showing gradual population increases, rapid peaks, and eventual decline-was observed, the primary focus remains spatial patterns, which are critical for optimizing pest management and improving rice crop sustainability in the region. © 2024 Society of Chemical Industry.

Intermolecular Anionic Mixed‐Valence and π‐Dimer Complexes of ortho‐Pentannulated Bisazacoronene Diimide

AbstractThis study reports the serendipitous discovery of intermolecular anionic mixed‐valence (MV) and π‐dimer species in ortho‐pentannulated BisAzaCoroneneDiimides (BACDs) during their electrochemical reduction in a non‐aqueous solvent. A library of nitrogen‐containing extended PDIs was synthesized via an aza‐benzannulation reaction followed by a Pd‐catalysed ortho‐pentannulation reaction. Ortho‐pentannulated BACDs revealed strong aggregation abilities in solution. Concentration‐dependent UV/Vis absorption spectra, variable temperature 1H NMR experiments, and atomic force microscopy coupled to molecular dynamics support their self‐assembly into columnar aggregates. Cyclic voltammetry experiments in dichloromethane reveal prominent splitting of the first reduction wave, attributed to the formation of unprecedented intermolecular anionic MV and π‐dimers in organic solvent. These species were thoroughly characterized by real‐time spectroelectrochemistry, electrochemical simulations and theoretical calculations. Remarkably, this work underscores the tuneable nature of AzaBenzannulatedPerylene Diimides (AzaBPDIs) and BACDs, emphasizing their potential as a promising scaffold for designing supramolecular materials with long‐range radical anion delocalization. The observation of this phenomenon provides insights into the fundamental behaviour of supramolecular organic semiconductors, thereby paving the way for the development of novel electronic devices and electron‐deficient materials.

Intermolecular Anionic Mixed-Valence and π-Dimer Complexes of ortho-Pentannulated Bisazacoronene Diimide.

This study reports the serendipitous discovery of intermolecular anionic mixed-valence (MV) and π-dimer species in ortho-pentannulated BisAzaCoroneneDiimides (BACDs) during their electrochemical reduction in a non-aqueous solvent. A library of nitrogen-containing extended PDIs was synthesized via an aza-benzannulation reaction followed by a Pd-catalysed ortho-pentannulation reaction. Ortho-pentannulated BACDs revealed strong aggregation abilities in solution. Concentration-dependent UV/Vis absorption spectra, variable temperature 1H NMR experiments, and atomic force microscopy coupled to molecular dynamics support their self-assembly into columnar aggregates. Cyclic voltammetry experiments in dichloromethane reveal prominent splitting of the first reduction wave, attributed to the formation of unprecedented intermolecular anionic MV and π-dimers in organic solvent. These species were thoroughly characterized by real-time spectroelectrochemistry, electrochemical simulations and theoretical calculations. Remarkably, this work underscores the tuneable nature of AzaBenzannulatedPerylene Diimides (AzaBPDIs) and BACDs, emphasizing their potential as a promising scaffold for designing supramolecular materials with long-range radical anion delocalization. The observation of this phenomenon provides insights into the fundamental behaviour of supramolecular organic semiconductors, thereby paving the way for the development of novel electronic devices and electron-deficient materials.

Chain rigidity controlled aggregation ability and solid-state microstructures for efficient stretchable conjugated polymer films

Stretchable conjugated polymer films with good electrical performance under mechanical deformation are highly desirable for soft electronics. However, the mechanical and electrical properties of these films, particularly in conjugated polymer:elastomer blends, are not fully understood at molecular level. This study explores the relationships among molecular structure, aggregation ability, film microstructure, and the electrical/mechanical properties of three diketopyrrolopyrrole -based conjugated polymers (P1, P2, P3) with decreasing backbone rigidity and their corresponding polymer:elastomer blends. The most flexible polymer P3 shows strong aggregation, which forms highly crystalline fibers to produce fragile neat film and produces large isolated crystallites restricting charge transport in blend film. As chain rigidity increases, the P1 and P2 polymers show weaker aggregation, and produce smaller crystallites in neat films with enhanced ductility. P1 and P2 based blend films display nanocrystallites polymer networks with dispersed elastomer domains. As a result, we achieved near-constant charge mobility before and after stretching under 50 % strain for P2-based blend films with well-controlled pathways for both charge transport and energy dissipation. This study demonstrates the critical role of backbone rigidity in regulating the properties of stretchable conjugated polymer films, paving the way for more reliable and deformable materials in soft electronics.

Particle crushing mechanism of recycled aggregate with different component categories: applied to pervious concrete base

This paper focuses on the particle crushing mechanism of construction solid waste recycled aggregate (CWRA), particularly recycled concrete (RC) and recycled bricks (RB), using natural gravel (NG) as a control group. Compression tests, combined with the Weibull distribution, fractal dimension theory, and relative crushing rate, were conducted to investigate the crushing behavior of these materials under different loads. Results indicate that, under the same load, the crushing degree ranks from highest to lowest as RB, RC, and NG. The Weibull distribution effectively describes the crushing state, with “fragmentation” being the primary mode for most materials, while RC also exhibits “grinding.” As the load increases, the relative crushing rate rises for all materials but slows beyond a certain load threshold, indicating greater difficulty in further crushing. The study identifies a load threshold of 400 kN, beyond which changes in void fraction and relative crushing rates become less significant, particularly in stronger aggregates. Highlights Identified that mortar attached to the RC surface is the primary cause of the increased particle crushing below 0.6 mm. Introduced Weibull distribution parameters a and b to accurately characterize the crushing state of RA particles. Revealed the errors between fractal dimension-based evaluations and the actual crushing state of RC particles. Proposed a two-stage crushing mode for RC. Determined the critical threshold value for the variation of crushing degree with load level.

Size distribution of aggregates across different aquatic systems around Japan shows that stronger aggregates are formed under turbulence

AbstractMarine aggregates, composed of various particles, play a crucial role in ocean carbon storage. The overall size distribution of the aggregates (number size spectra) is controlled by the balance between aggregation and disaggregation processes. Turbulence has been proposed to facilitate both aggregation and disaggregation by increasing the collision rate of aggregates or sometimes directly tearing them apart. Predominant processes driven by turbulence typically depend on the level of turbulence—relatively weak turbulence is associated with aggregation while stronger turbulence promotes disaggregation. Aggregate strength also plays a key role, as strongly bonded aggregates can withstand turbulence better, leading to lower disaggregation rates. While the relationship between turbulence and aggregate strength has been studied numerically and experimentally, field measurements remain limited. Here, we compare our number size spectra to turbulence intensity from the field measurements across different environmental settings around Japan to determine the effect of turbulence on aggregate strength. We combined measurements from 10 sites with different environmental settings and observed the flatter slopes (higher net aggregation rate) and shifts in the intersection lengths with an increase of turbulence, while strong turbulence is typically linked with disaggregation. Our findings suggested that stronger aggregates are formed under stronger turbulence and the overall population of strong aggregates also increases with an increase of turbulence intensity. We also compared our number size spectra with three other confounding factors (fluorescence, salinity, and aggregate compositions) to confirm the effects of turbulence are dominant in our aggregate dynamics.

Synthesis of perylene‐PEO hyperdispersants for aqueous graphene dispersion

AbstractGraphene, with excellent thermal conductivity, electrical and corrosion shielding performance has great application potential in the fields of heat dissipation coating, conductive agent and anticorrosion composite coatings. However, due to its large specific surface area, resulting strong aggregation behavior limits its application. Herein, the hyperdispersants with perylene anchoring groups are synthesized through the amidation coupling reaction between diacid anhydride and polyetheramine. The branching degree and length of hydrophilic chains on hyperdispersant are revealed to be the very important factors to affect the dispersion stability of aqueous graphene dispersion. The hyperdispersant with a single hydrophilic chain and the molecular weight 2000 of polyetheramine has the excellent dispersal activity discovered by Rheology, particle size distribution and Raman measurements. The possible mechanism is the strongest anchoring effect of perylene on graphene surface and thus achieving in best effective spatial exclusion stabilization effect of hydrophilic chains.

Dynamic simulation of street-level carbon emissions in megacities: A case study of Wuhan City, China (2015–2030)

Dynamic simulation of carbon emissions (CE) in megacities is crucial for regional carbon reduction management, however, limited simulation accuracy hinders its application in carbon reduction policies. An integrated modeling framework was developed based on high-resolution multi-source data to analyze the street-level carbon emissions in Wuhan from 2015 to 2030. First, we conducted principal components analysis on the 5 driving factors of carbon emissions (including point of interests, electricity consumption, gross domestic product, population, and nighttime light) to delineate single carbon emission character region (CECR). Then, a machine learning method was used to simulating CE and explaining the contributions of different CECRs. Multi-scenarios CE accountings also were conducted with CECR simulations and an improved cellular automata model. Results shows that: (1) CE in Wuhan showed strong aggregation during the historical period. The five CECRs formed a near-concentric circle. The changes of CECR reflected the enhancement of human activity. (2) CE gradually shifted from the central urban areas to the surrounding regions during the scenario period, showing significant spatial spillover effects. Administrative districts with lower CE density exhibited greater scenario variation in total carbon emissions, indicating a higher potential for carbon reductions. (3) The total CE of Wuhan (148.11 Mt) in 2030 is projected to increase by 42.6 % compared to 2015 in the baseline scenario, representing 105 % of the low scenario and 91 % of the high scenario. The growth rate of total CE in Wuhan significantly slows down (<1 %) under all scenarios. The high-resolution dynamic simulation of CE will provide an important scientific basis for low-carbon city management in China.