Spatial distribution, compositional pattern, and source apportionment of colloidal trace metals in the coastal water of Shandong Peninsula, northeastern China.

The Shandong Peninsula (SP) is the largest peninsula in China hosting rich economic and agricultural activities. In this study, we investigated the behavior of dissolved Mn, Fe, Cu, Zn, Cd, and Pb and their colloidal phases in the coastal and estuarine areas of SP. Pb and Zn had the highest contamination factors of 0.22-10.15 and 0.90-4.41, respectively. The <1 kDa accounted for 23-57 % of the total dissolved phase. Mn, Fe, Cu, Zn, Cd, and Pb were more likely to bind to 100 kDa-0.45 µm colloids (21-57 %). For colloidal Fe and Cu, the adsorption-release behavior had more significant effects on their dynamics. In contrast, the changes in colloidal Mn, Cd, and Pb were mainly controlled by the combined influence of temperature, dissolved oxygen, and microbial activity. However, the 1-3 kDa Zn exhibited a greater pH-dependent dispersion and was significantly positively correlated with it.

Exploring the microbial ecosystem of Berchemia polyphylla var. leioclada: a comprehensive analysis of endophytes and rhizospheric soil microorganisms.

Endophytic and rhizospheric microorganisms associated with plants play a crucial role in plant health, pest and disease defense, and fruit yield by actively participating in the plant's adaptation to its environment. In this study, high-throughput sequencing technology was employed to analyze the community structure and diversity of endophytic and rhizospheric soil microorganisms in Berchemia polyphylla var. leioclada. The results revealed significant differences in microbial diversity and community structure between the soil and plant compartments within the same geographic region. Microbial diversity and species composition varied among different geographic locations. The dominant bacteria in plants were Cyanobacteria and Proteobacteria, with dominant genera including Methylobacterium-Methylorubrum, Escherichia-Shigella and Sphingomonas. In contrast, the dominant bacteria in soil were Proteobacteria, Acidobacteriota, and Actinobacteriota, with dominant genera such as Sphingomonas, Conexibacter and Vicinamibacteraceae, with Sphingomonas was considered core groups present in all plant and soil samples. As for fungi, the dominant phyla in both plants and soil were Ascomycota, Basidiomycota, and Mortierellomycota, with different dominant genera between the two compartments, including Fusarium, Septoria, and Mortierella, totaling 59 genera. Linear discriminant analysis at the genus level identified 102 bacterial and 54 fungal indicator taxa associated with plants and soil. Co-occurrence network analysis indicated close interactions among soil bacterial microorganisms. Functional prediction of the top 10 microbial genes revealed three bacterial metabolic pathways shared between soil and plants, while the predominant fungal metabolic types were similar between the two compartments but with varying abundances. This study elucidates the diversity and interplay of endophytic and rhizospheric microorganisms in Berchemia polyphylla var. leioclada across diverse geographical regions, providing insights crucial for the plant's conservation and development.

Contaminant transformation during sediment oxygenation: Temporal variation of oxidation mechanisms mediated by hydroxyl radicals and aerobic microbes.

Sediment oxidation by oxygen is ubiquitous, whereas the mechanisms of concurrent contaminant oxidation, particularly the temporal variation of chemical and biological oxidation, remain inadequately understood. This study investigated the oxidation of two contaminants (phenol and trichloroethylene) with different responses during the oxygenation of four natural sediments with different redox properties. Results showed that contaminant oxidation was initially dominated by hydroxyl radicals (•OH) (first stage), stabilized for different time for different sediments (second stage), and was re-started by microbial mechanism (third stage). In the first short stage, the contribution of chemical oxidation by •OH was mainly determined by the variation of sediment electron-donating capacity (EDC). In the second long stage, the stabilization time was dependent on sediment redox properties, that is, the abundance and growth of aerobic microbes capable of degrading the target contaminants. A more reduced sediment resulted in a higher extent of oxidation by •OH and a longer stabilization time. When the third stage of aerobic microbial oxidation was started, the contaminants like phenol that can be utilized by microbes can be oxidized quickly and completely, and those refractory contaminants like trichloroethylene remained unchanged. The study differentiates chemical and biological mechanisms for contaminant oxidation during sediment oxygenation.

Synergistic removal performance and mechanism of Cd(II) and As(III) from irrigation water by iron sulfide-based porous biochar.

Since Cd(II) and As(III) have extremely opposite chemical characteristics, it is a huge challenging to simultaneously remove these two ions from aqueous solutions. Therefore, a novel iron sulfide-based porous biochar (FSB) was synthesized and used to evaluate its Cd(II) and As(III) removal performance and mechanisms. The characterization and batch experiments results indicated that FeS was successfully loaded on the surface of biochar and increased its adsorption sites. The iron sulfide-based porous biochar was very favorable for the removal of Cd(II) and As(III) in the weakly acidic environment. The maximum adsorption of Cd(II) and As(III) by FSB was 108.8 mg g-1 and 76.3 mg g-1, respectively, according to the Langmuir and Freundlich isothermal adsorption model, and the adsorption equilibrium time was 12 h and 4 h, respectively, according to the pseudo-second-order kinetic model. In the coexisting ion system, Cd(II) adsorption was suppressed by Ca2+, Mg2+, and humic acid, but enhanced by PO43- and As(III). As(III) adsorption was inhibited by PO43- and humic acid. Precipitation and complexation are the predominant adsorption mechanisms of Cd(II) and As(III), which contribute to the formation of Cd-O, Fe-O-Cd, As-O, Fe-O-As, ternary complex Cd-Fe-As, and stable compounds FeAsO4·2H2O and CdS. Therefore, The iron sulfide-based porous biochar can be an efficient and environmentally friendly candidate for the treatment of Cd(II) and As(III) co-polluted irrigation water.

Contaminant degradation by •OH during sediment oxygenation: Effect of abundant solid matrix in aquifer.

Aquifer oxygenation for hydroxyl radical (•OH) production has been recently proposed as a promising strategy for in-situ remediation. However, the high performance of this process was justified at low solid-to-liquid ratios (SLRs) of suspension systems. It remains unclear whether and how the performance is affected by abundant solid matrixes. Here we assessed the influence of SLR on •OH production and contaminant degradation during sediment oxygenation. Cumulative •OH increased from 21.8 to 165.2 µM when the SLR increased from 200 to 1600 g/L, while phenol degradation increased with the increase in SRL at the values lower than 1200 g/L and decreased at higher SLRs. As the main sediment component, silica exhibited a negligible effect on •OH production and phenol degradation because of the weak adsorption towards aqueous Fe(II). Whereas, the other component, alumina, significantly inhibited •OH production and phenol degradation because it strongly adsorbed Fe(II). •OH scavenging by solid reactive matrixes was mainly responsible for the inhibition at high SLRs. The scavenging effect could be mitigated by mediating the main reactive Fe(II) species from solid-adsorbed to dissolved phase with ligand addition. Our findings are important for understanding the side reactions and optimizing the remediation performance during aquifer oxygenation.

Prediction model with multi-point relationship fusion via graph convolutional network: A case study on mining-induced surface subsidence.

Accurate prediction of surface subsidence is of significance for analyzing the pattern of mining-induced surface subsidence, and for mining under buildings, railways, and water bodies. To address the problem that the existing prediction models ignore the correlation between subsidence points, resulting in large prediction errors, a Multi-point Relationship Fusion prediction model based on Graph Convolutional Networks (MRF-GCN) for mining-induced subsidence was proposed. Taking the surface subsidence in 82/83 mining area of Yuandian No. 2 Mine in Anhui Province in eastern China as an example, the surface deformation data obtained from 250 InSAR images captured by Sentinel-1A satellite from 2018 to 2022, combined with GNSS observation data, were used for modeling. The deformation pattern of each single observation point was obtained by feeding their deformation observation data into the LSTM encoder, after that, the relationship graph was created based on the correlation between points in the observation network and MRF-GCN was established. Then the prediction results came out through a nonlinear activation function of neural network. The research shows that the R2R2 value of MRF-GCN model was 0.865 0, much larger than that of Long-Short Term Memory (LSTM) and other conventional models, while mean square error (MSE) of MRF-GCN model was 1.59 899, much smaller than that of LSTM and other conventional models. Therefore, the MRF-GCN model has better prediction accuracy than other models and can be applied to predicting surface subsidence in large areas.

Mechanistic Insight into Electron Transfer from Fe(II)-Bearing Clay Minerals to Fe (Hydr)oxides.

Electron transfer (ET) is the essence of most biogeochemical processes related to element cycling and contaminant attenuation, whereas ET between different minerals and the controlling mechanism remain elusive. Here, we used surface-associated Fe(II) as a proxy to explore ET between reduced nontronite NAu-2 (rNAu-2) and Fe (hydr)oxides in their coexisting systems. Results showed that ET could occur from rNAu-2 to ferrihydrite but not to goethite, and the ET amount was determined by the number of reactive sites and the reduction potential difference between rNAu-2 and ferrihydrite. ET proceeded mainly through the mineral-mineral interface, with a negligible contribution of dissolved Fe2+/Fe3+. Control experiments by adding K+ and increasing salinity together with characterizations by X-ray diffraction, scanning electron microscopy/energy-dispersive spectrometry, and atomic force microscopy suggested that ferrihydrite nanoparticles inserted the interlayer space in rNAu-2 where structural Fe(II) in rNAu-2 transferred electrons mainly through the basal plane to ferrihydrite. This study implicates the occurrence of ET between different redox-active minerals through the mineral-mineral interface. As minerals at different reduction potentials often coexist in soils/sediments, the mineral-mineral ET may play an important role in subsurface biogeochemical processes.

Electrokinetic-Enhanced Bioremediation of Trichloroethylene-Contaminated Low-Permeability Soils: Mechanistic Insight from Spatio-Temporal Variations of Indigenous Microbial Community and Biodehalogenation Activity.

Electrokinetic-enhanced bioremediation (EK-Bio), particularly bioaugmentation with injection of biodehalogenation functional microbes such as Dehalococcoides, has been documented to be effective in treating a low-permeability subsurface matrix contaminated with chlorinated ethenes. However, the spatio-temporal variations of indigenous microbial community and biodehalogenation activity of the background matrix, a fundamental aspect for understanding EK-Bio, remain unclear. To fill this gap, we investigated the variation of trichloroethylene (TCE) biodehalogenation activity in response to indigenous microbial community succession in EK-Bio by both column and batch experiments. For a 195 day EK-Bio column (∼1 V/cm, electrolyte circulation, lactate addition), biodehalogenation activity occurred first near the cathode (<60 days) and then spread to the anode (>90 days), which was controlled by electron acceptor (i.e., Fe(III)) competition and microbe succession. Amplicon sequencing and metagenome analysis revealed that iron-reducing bacteria (Geobacter, Anaeromyxobacter, Geothrix) were enriched within initial 60 d and were gradually replaced by organohalide-respiring bacteria (versatile Geobacter and obligate Dehalobacter) afterward. Iron-reducing bacteria required an initial long time to consume the competitive electron acceptors so that an appropriate reductive condition could be developed for the enrichment of organohalide-respiring bacteria and the enhancement of TCE biodehalogenation activity.

Neural Network-Based Active Load-Sensing Scheme and Stiffness Adjustment for Pneumatic Soft Actuators for Minimally Invasive Surgery Support.

To provide a stable surgical view in Minimally Invasive Surgery (MIS), it is necessary for a flexible endoscope applied in MIS to have adjustable stiffness to resist different external loads from surrounding organs and tissues. Pneumatic soft actuators are expected to fulfill this role, since they could feed the endoscope with an internal access channel and adjust their stiffness via an antagonistic mechanism. For that purpose, it is essential to estimate the external load. In this study, we proposed a neural network (NN)-based active load-sensing scheme and stiffness adjustment for a soft actuator for MIS support with antagonistic chambers for three degrees of freedom (DoFs) of control. To deal with the influence of the nonlinearity of the soft actuating system and uncertainty of the interaction between the soft actuator and its environment, an environment exploration strategy was studied for improving the robustness of sensing. Moreover, a NN-based inverse dynamics model for controlling the stiffness of the soft actuator with different flexible endoscopes was proposed too. The results showed that the exploration strategy with different sequence lengths improved the estimation accuracy of external loads in different conditions. The proposed method for external load exploration and inverse dynamics model could be used for in-depth studies of stiffness control of soft actuators for MIS support.

Cloning and functional identification of pmKPI cDNA in Poecilobdella manillensis.

BACKGROUND: Kazal-type serine protease inhibitors play a role in physiological processes such as blood coagulation and fibrinolysis. The amino acid residues at the P1 site are different, and they inhibit different types of proteases. The inhibitory mechanism of the protease in the salivary glands of Poecilobdella manillensis is still unclear. METHODS AND RESULTS: Based on cloning, prokaryotic expression and bioinformatics analysis, we studied the role of Kazal-type serine protease inhibitors in P. manillensis and analyzed their expression by quantitative real-time PCR. The results suggested that the recombinant protein was successfully expressed in the supernatant when a prokaryotic expression vector was constructed and induced with 0.2 mmol/L IPTG at 37 °C for 4 h, and the enzymatic activity was determined. The mature protein encodes 91 amino acids and has a relative molecular weight of 9929.32 Da, and after removing the signal peptide, the theoretical isoelectric point was 8.79. It is an unstable protein without a transmembrane domain. The mature protein contains two Kazal-type domains, in which all P1 residues are Lys, consisting of an α helix and three antiparallel ß sheets. The upregulated expression of the mRNA was induced after a meal was provided, and the results showed an increasing and then decreasing trend. CONCLUSIONS: Taken together, the results indicate that mature proteins from P. manillensis inhibit thrombin activity, laying the foundation for the subsequent in-depth study of the function of genes encoding Kazal-type serine protease inhibitors.

Effects of chamber shapes on maneuverability and control property of endoscope-support soft actuators.

Introduction: Minimally Invasive Surgery (MIS) offers targeted surgical access with reduced invasiveness; however, the maneuverability challenges of traditional instruments in this domain underscore the need for innovative solutions. Soft actuators activated by fluids or gases present a promising strategy for augmenting endoscopic capabilities, thereby enhancing the surgical precision in MIS. This study aimed to explore the intricate dynamics of the interactions between soft actuators and endoscopes, with an emphasis on the pivotal role of cross-sectional chamber shapes. While previous studies have touched on the influence of chamber shapes on bending properties, we provide a comprehensive exploration. We explore how these shapes modulate friction forces, which in turn influence the interactions governing bending, response, and stiffness adjustability, all of which are essential for enhancing endoscope maneuverability in MIS contexts. Methods: A novel bilateral symmetrical air chamber design was adopted to investigate various chamber shapes. We employed finite element analysis (FEA) simulations followed by prototype testing to evaluate the interactions driven by these chamber shapes and to discern their impact on actuator properties. Recognizing the pivotal role of friction in these interactions, we conducted dedicated friction experiments. These experiments further deepened our understanding of the relationship between chamber shape and friction, and how this synergy influences the properties of the actuator. Results: Our findings showed that actuators with wider chambers generate larger friction forces, thereby enhancing the interaction and improving the bending, response, and stiffness adjustability. Additionally, the soft actuator significantly improved the maneuverability and bending radius of the endoscope, demonstrating enhanced navigation capabilities in complex environments. Discussion: The shape of a cross-sectional chamber plays a pivotal role in designing soft actuators for MIS applications. Our research emphasizes the importance of this design component, offering key insights for the development of endoscope-supporting soft actuators that can effectively handle intricate actuator-endoscope interactions, thereby enhancing surgical outcomes.

Isolation and characterization of cellulose nanocrystals from Chinese medicine residues.

Nanocellulose has become a vital material with excellent and crucial properties in the field of nanotechnology and advanced materials science. Plant-based traditional Chinese medicines are mostly plant rhizomes, which contain a large amount of cellulose, hemicellulose, and lignin. In this study, carboxylated cellulose nanocrystals (CNCs) were prepared from traditional Chinese medicine residues (CMR) by sequential periodate-chlorite oxidation without mechanical treatment. The obtained nanocelluloses were analyzed by transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and X-ray diffractometry (XRD); the carboxyl content and specific surface area were also measured, simultaneously. XRD results revealed that the crystallinity index decreased after sequential oxidation; however, the cellulose I structure was maintained. From the morphology analysis, the average length and width of CNCs were 139.3 and 10 nm, respectively. From the FTIR analysis, with the particle size decreasing, hydrogen bonds were broken and recombined. TGA results showed that the thermal property was decreased with a reduction of nanocellulose particle size and crystallinity index. This study is the first to refine utilization of traditional Chinese medicine residues as a potential source of cellulose, that is, to prepare nanocellulose efficiently with high carboxyl content which finds its application in nanomaterials.

Significant Contribution of Solid Organic Matter for Hydroxyl Radical Production during Oxygenation.

Dark formation of hydroxyl radicals (•OH) from soil/sediment oxygenation has been increasingly reported, and solid Fe(II) is considered as the main electron donor for O2 activation. However, the role of solid organic matter (SOM) in •OH production is not clear, although it represents an important electron pool in the subsurface. In this study, •OH production from oxygenation of reduced solid humic acid (HAred) was investigated at pH 7.0. •OH production is linearly correlated with the electrons released from HAred suspension. Solid HAred transferred electrons rapidly to O2 via the surface-reduced moieties (hydroquinone groups), which was fueled by the slow electron transfer from the reduced moieties inside solid HA. Cycling of dissolved HA between oxidized and reduced states could mediate the electron transfer from solid HAred to O2 for •OH production enhancement. Modeling results predicted that reduced SOM played an important or even dominant role in •OH production for the soils and sediments possessing high molar ratios of SOC/Fe(II) (e.g., >39). The significant contribution of SOM was further validated by the modeling results for oxygenation of 88 soils/sediments in the literature. Therefore, reduced SOM should be considered carefully to comprehensively understand •OH production in SOM-rich subsurface environments.

Visible and near-infrared photoluminescence of a supramolecular complex constructed from a cycloparaphenylene nanoring and an erbium metallofullerene.

Erbium metallofullerenes exhibit near-infrared photoluminescence from the Er3+ ions, which has potential applications in telecommunications, optical devices and bioscience. In this manuscript, we report the construction of a supramolecular complex of metallofullerene Er3N@C80 and cycloparaphenylene [12]CPP to adjust the near-infrared photoluminescence of Er3N@C80 through host-guest interactions. Moreover, this supramolecular complex shows a multiwavelength luminescence property. Mass spectrometry, electrochemical measurements and proton NMR spectroscopy were used to characterize the structure of Er3N@C80⊂[12]CPP. The electrochemical results of Er3N@C80⊂[12]CPP show the negatively shifted redox potentials compared to pristine Er3N@C80 and the 1H NMR signals of Er3N@C80⊂[12]CPP shift upfield compared to pristine [12]CPP. More importantly, the photoluminescence spectra show that the [12]CPP nanoring can affect the near-infrared emission of encapsulated Er3+ ions in Er3N@C80, with the characteristic emission peak of Er3+ at 1.5 µm being broadened and enhanced in the Er3N@C80⊂[12]CPP complex, while the fluorescence lifetime of Er3+ also becomes longer after assembly formation. Furthermore, the Er3N@C80 guest also can influence the photoluminescence property of [12]CPP, whose emission peaks exhibit a slight blue-shift in the Er3N@C80⊂[12]CPP complex. This study illustrates that the outer nanoring can be employed to adjust the photoluminescence of the encapsulated Er3+ ion in Er3N@C80.

A Metallofullertube of Ce2 @C100 with a Carbon Nanotube Segment: Synthesis, Single-Molecule Conductance and Supramolecular Assembly.

Tubular fullerenes can be considered as end-capped carbon nanotubes with accurate structure, which are promising nanocarbon materials for advanced single-molecule electronic devices. Herein, we report the synthesis and characterization of a metallofullertube Ce2 @D5 (450)-C100 , which has a tubular C100 cage with a carbon nanotube segment and two fullerene end-caps. As there are structure correlations between tubular Ce2 @D5 (450)-C100 and spherical Ce2 @Ih -C80 , their structure-property relationship has been compared by means of experimental and theoretical methods. Notably, single-molecule conductance measurement determined that the conductivity of Ce2 @D5 (450)-C100 was up to eight times larger than that of Ce2 @Ih -C80 . Furthermore, supramolecular assembly of Ce2 @D5 (450)-C100 and a [12]CPP nanohoop was investigated, and theoretical calculations revealed that metallofullertube Ce2 @D5 (450)-C100 adopted a "standing" configuration in the cavity of [12]CPP. These results demonstrate the special nature of this kind of metallofullertube.

Single-Molecule Magnet with Thermally Activated Delayed Fluorescence Based on a Metallofullerene Integrated by Dysprosium and Yttrium Ions.

It is vital to construct luminescent single-molecule magnets (SMMs) and explore their applications in quantum computing technique and magneto-luminescence devices. In this work, we report a luminescent single-molecule magnet with thermally activated delayed fluorescence (TADF) based on metallofullerene DyY2N@C80. DyY2N@C80 was constructed by integrating dysprosium and yttrium ions into a fullerene cage. Magnetic results suggest that DyY2N@C80 exhibits magnetic hysteresis loops below 8 K originating from the Dy3+ ion. Moreover, DyY2N@C80 exhibits TADF originating from the Y3+-coordinated carbon cage, whose luminescence peak positions and peak intensities can be obviously influenced by Dy3+. Furthermore, a supramolecular complex of DyY2N@C80 and [12]Cycloparaphenylene ([12]CPP) was then prepared to construct a single-molecule magnet with multiwavelength luminescence. The effects of host-guest interaction on photoluminescence properties of DyY2N@C80 were disclosed. Theoretical calculations were also employed to illustrate the structures of DyY2N@C80 and DyY2N@C80⊂[12]CPP.

[Optimization of Extraction Methods and Distribution Characteristics of Antibiotics and Metabolites in Sediments of a River Water-Groundwater Interaction Zone].

The river water-groundwater interaction zone is an important area for the enrichment, degradation, and transformation of pollutants and other biogeochemical processes. The distribution characteristics of antibiotics, as organic pollutants of wide concern, in the interaction zone is essential for understanding the migration and transformation process of pollutants in the environment. Due to the sensitive changes in the redox conditions and special composition of sediments in the interaction zone, this study established an effective pretreatment method for extracting 22 antibiotics and four sulfonamide metabolites in the interaction zone, and optimized the initial state of the samples, extraction temperature, pH value of the extraction solution and organic extraction solvent. The content of antibiotics in the sediments of the river water-groundwater interaction zone and lower reaches of the Hanjiang River was also analyzed. The results show that the best recovery of the target compounds is obtained by using pH 3 acetonitrile/Na2EDTA-Mcllvaine buffer(1:1, volume ratio) to digest and extract the unoxidized sediment samples at 40℃ three times using a microwave. A total of 11 antibiotics are detected in the sediments of the interaction zone in the lower reaches of the Hanjiang River, among which oxytetracycline and ofloxacin are the main compounds with the highest concentrations of 6.77 ng·g-1 and 5.81 ng·g-1, respectively. The vertical distribution of antibiotics in different sediment profiles is significantly different, which may be related to the lithology of sediments, physicochemical properties of antibiotics, and interaction between surface water and groundwater.

Mechanistic Insight into Humic Acid-Enhanced Hydroxyl Radical Production from Fe(II)-Bearing Clay Mineral Oxygenation.

Hydroxyl radical (•OH) production by electron transfer from Fe(II)-bearing clay minerals to oxygen has been increasingly reported. However, the influence of ubiquitous coexisting humic acid (HA) on this process is poorly understood. Here, we investigated the effect of different HA on •OH production during the oxygenation of reduced nontronite NAu-2 (rNAu-2), montmorillonite, and sediment. Results showed that HA could enhance •OH production, and the enhancement was related to the content of reactive Fe(II) in rNAu-2 and the electron-accepting capacity of HA. Coexisting HA leads to a new electron-transfer pathway from Fe(II) in rNAu-2 to HA (instead of the HA-Fe complex) and then to O2, changing the first step of O2 reduction from one- to two-electron transfer process with H2O2 as the main intermediate. Reduced HA decomposes H2O2 to •OH at a higher yield (13.8%) than rNAu-2 (8.8%). Modeling results reveal that the HA-mediated electron-transfer pathway contributes to 12.6-70.2% of H2O2 generation and 13.2-62.1% of •OH formation from H2O2 decomposition, with larger contributions at higher HA concentrations (5-100 mg C/L). Our findings implicate that HA-mediated electron transfer can expand the area of •OH production from the mineral surface to the aqueous phase and increase the yield of •OH production.

Spatial and environmental characteristics of colloidal trace Cu in the surface water of the Yellow River Estuary, China.

Dynamic variations in chemical composition and size distribution of dissolved copper (Cu) along the river-sea interface in the Yellow River Estuary (China) were investigated. On average, ~64% and ~8% of bulk dissolved Cu (<0.45 µm) were partitioned in the <1 kDa fraction and 1-100 kDa, respectively. The other 28% were in the 100 kDa-0.45 µm colloids, which indicates that this fraction may dominate the overall morphology of colloidal Cu. The <3 kDa Cu fraction was susceptible to environmental parameters and the >3 kDa fraction was related to the behavior of dissolved organic carbon. 1-100 kDa Cu migrated more violently than >100 kDa Cu and tended to be a stable polymer, with stability increasing towards the sea. The source of <1 kDa Cu was complex and may be supplemented by the decomposition of small molecular colloids and the addition of the sediments or particles ligands.

Construction of a double-walled carbon nanoring.

The nanoring structure of cycloparaphenylenes (CPPs) can be considered as the shortest fragment of a carbon nanotube. Herein, we successfully prepared a double-walled carbon nanoring of [6]CPP⊂[12]CPP, which can be regarded as the shortest double-walled carbon nanotube. [6]CPP⊂[12]CPP was constructed through the supramolecular assembly, and its crystallographic structure was unambiguously determined by single-crystal X-ray diffraction. The host-guest interaction and charge transfer in [6]CPP⊂[12]CPP were disclosed by UV-Vis absorption, fluorescence, and electrochemical studies. Electron paramagnetic resonance (EPR) spectroscopy disclosed the stability of the [6]CPP⊂[12]CPP cation radical, whose unpaired spin was fully delocalized on the inner [6]CPP and well protected by outer [12]CPP. Moreover, [6]CPP⊂[12]CPP shows highly enhanced photoconductivity and photocurrent under light irradiation compared to those of pristine monomers. The self-assembly behavior of [6]CPP⊂[12]CPP was also studied, and it was found that [6]CPP⊂[12]CPP molecules tend to form a square rod structure in the DMF solution. Thus, these results demonstrate that this double-walled carbon nanoring material has a great potential application in photoelectronic devices and organic semiconductors.