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The spontaneous generation of hydrogen peroxide (H 2 O 2 ) within atmospheric microdroplets, such as raindrops and aerosols, plays a crucial role in various environmental processes including pollutant degradation and oxidative stress. However, quantifying hydroxyl radicals (•OH), essential for H 2 O 2 formation, remains challenging due to their short lifespan and low concentration. This study addresses this gap by presenting a highly sensitive and selective surface-enhanced Raman scattering (SERS) nanosensor specifically designed for quantifying •OH within water microdroplets. Utilizing a phthalhydrazide (Phth) probe, the SERS technique enables rapid, interference-free detection of •OH at nanomolar concentrations. It achieves a linear detection range from 2 nM to 2 μM and a limit of detection as low as 0.34 nM. Importantly, the SERS sensor demonstrates robustness and accuracy within water microdroplets, paving the way for comprehensive mechanistic studies of H 2 O 2 generation in the atmosphere. This innovative approach not only offers a powerful tool for environmental research but also holds potential for advancing our understanding of atmospheric H 2 O 2 formation and its impact on air quality and pollutant degradation.

Although a dust-repellent surface is desirable for lunar exploration missions, its fabrication process is complicated and time-consuming. Herein, we report a simple and fast method to fabricate a lunar dust-repellent surface by texturing on an Al substrate via nanosecond laser etching. The laser-induced photothermal effect can rapidly create hierarchical papillary structures on 25 × 25 mm Al substrates (within 30 s). Both atomic force microscopy (AFM) and in situ scanning electron microscopy (SEM) reveal that such structures enable a reduced contact area between the Al substrate and lunar dust and thus reduced adhesion. The reduced dust adhesion force of Al substrates facilitates improving their antidust performance. By optimizing processing parameters, the Al substrate etched with a laser scanning spacing of 80 μm exhibits a lower dust adhesion force (9.58 nN) due to the smallest contact area with dust. Accordingly, its static antilunar dust performance (dust coverage of 1.95%) is significantly improved compared to the pristine Al substrate (dust coverage of 12.98%). Besides, the accumulated dust on the laser-etched Al substrates with low surface adhesion force is easily cleaned up by flipping and gravity (the dust residual rates are less than 17%). The Al substrate with excellent antidust ability presents good potential for lunar exploration missions.

Three-dimensional-printed silicone rubber foams, with their designable and highly ordered pore structures, have shown exceptional potential for engineering applications, particularly in areas requiring energy absorption and cushioning. However, optimizing the mechanical properties of these foams through structural design remains a significant challenge. This study addresses this challenge by formulating the research question: How do different 3D-printed topologies and printing parameters affect the mechanical properties of silicone rubber foams, and how can we design a novel topological structure? To answer this, we explored the mechanical behavior of two common structures-simple cubic (SC) and face-centered tetragonal (FCT)-by varying printing parameters such as filament spacing, filament diameter, and layer height. Furthermore, we proposed a novel two-level 3D-printed structure, combining SC and FCT configurations to enhance performance. The results demonstrated that the two-level SC-SC structure exhibited a specific energy absorption of 8.2 to 21.0 times greater than the SC structure and 2.3 to 7.2 times greater than the FCT structure. In conclusion, this study provides new insights into the design of 3D-printed silicone rubber foams, offering a promising approach to developing advanced cushioning materials with superior energy absorption capabilities.

Single-crystal lithium-rich layered oxides (LLOs) with excellent mechanical properties can enhance their crystal structure stability. However, the conventional methods for preparing single-crystal LLOs, require large amounts of molten salt additives, involve complicated washing steps, and increase the difficulty of large-scale production. In this study, a sodium tungstate (Na 2 WO 4 )-assisted sintering method is proposed to fabricate high-performance single-crystal LLOs cathode materials without large amounts of additives and additional washing steps. During the sintering process, Na 2 WO 4 promotes particle growth and forms a protective coating on the surface of LLOs particles, effectively suppressing the side reactions at the cathode/electrolyte interface. Additionally, trace amounts of Na and W atoms are doped into the LLOs lattice via gradient doping. Experimental results and theoretical calculations indicate that Na and W doping stabilizes the crystal structure and enhances the Li + ions diffusion rate. The prepared single-crystal LLOs exhibit outstanding capacity retention of 82.7% (compared to 65.0%, after 200 cycles at 1 C) and a low voltage decay rate of 0.76 mV per cycle (compared to 1.80 mV per cycle). This strategy provides a novel pathway for designing the next-generation high-performance cathode materials for Lithium-ion batteries (LIBs)., (© 2023 Wiley‐VCH GmbH.)

It's well known that the toxicity of chemicals in the environment depends not only their concentrations, but more importantly, their bio-availability. Thus, the acute toxicity test of environmental water samples is of great importance in water quality evaluation. In this work, water acute toxicity was determined via SERS approach for the first time based on the reaction between Escherichia coli (E. coli) and p-benzoquinone (BQ). The E. coli was used as the subject of toxicity assay. Under normal conditions, the BQ molecules can be transformed into Hydroquinone (HQ) by the E. coli bacteria; subsequently, the BQ will continue to react with the resulting HQ to form Quinone hydroquinone (QHQ). This process could be impaired in the presence of many toxic chemicals. Bromide modified Ag NPs was then introduced for the highly sensitive SERS detection of the product (HQ and QHQ). Several key factors that may affect water acute toxicity evaluation have been explored, which include the initial BQ and E. coli concentration, the incubation time with BQ, and the sodium chloride concentration. Later, the established system was applied for the toxicity evaluation of Cu 2+ . It was found that the IC 50 value of Cu 2+ was 0.94 mg/L, which is superior compared with literature report. This study provides a promising SERS method for assessing acute toxicity in water bodies with high sensitivity and short detection time., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Green fabrication of superhydrophobic surface by water-based processing is still challenging, because introduction of the substances with hydrophilic moieties compromises its superhydrophobicity. Herein, a plasmon-driven photochemical reduction reaction under ultraviolet light (UVA) irradiation is first discovered and is applied to deoxygenation of hydrophilic organic adsorbates on rough nano-Ag coating for the formation of stable superhydrophobic surface. A nano-Ag coating with strong localized surface plasmon resonance in the UVA region is prepared by a water-based silver mirror reaction and results in a unique chemical reduction reaction on its surface. Consequently, the low residual hydrophilic functionalities and the formed cross-linked structure of the adsorbate on Ag nanoparticles (NPs) enables the coating to exhibit stable superhydrophobicity against to both air and water. The superhydrophobic Ag NP-coated sandpaper can also be used as a surface-enhanced Raman scattering (SERS) substrate to concentrate aqueous analytes for trace detection., (© 2023 Wiley-VCH GmbH.)

Although superhydrophobic surfaces have various promising applications, their fabrication methods are often limited to 2D plane surfaces that are vulnerable to abrasion and have limited adhesion to the substrate. Herein, an ultraviolet (UV) curable ink with bulk superhydrophobicity, consisting of poly(dimethylsiloxane) (PDMS) resins, hydrophobic silica, and solvent (porogen), was successfully developed for UV-assisted direct write printing processing. After UV curing of the ink followed by solvent evaporation, the generated porous structure cooperates with silica particles to form a self-similar and hierarchical structure throughout the bulk material, which can keep its original morphology even after cyclic abrasion (over 1000 times) and thus exhibits durable superhydrophobicity. With this unique ink, UV-assisted direct write printing can not only create 2D superhydrophobic surfaces on various substrates (e.g., paper and wire mesh) but also fabricate self-supporting 3D superhydrophobic objects for various applications such as waterproofing and oil-water separation. The printed objects exhibited a stable superhydrophobicity against liquid corrosion and mechanical damage. In addition, the 3D printing approach can be used to optimize the oil-water separation performance of the superhydrophobic porous materials by tuning the pore size, thus presenting promising applications.

Li-rich layered oxide (LLOs) cathode materials are gaining increasing attention as lithium-ion batteries (LIBs) pursue greater energy density. However, LLOs still suffer from severe capacity fading and voltage decay due to their unstable crystal structure. Hence, the anion-cation dual-ion multisite doping strategy based on Mg and S atoms is used to stabilize the crystal structures of LLOs. Mg substitutes Li atoms in the Li and transition-metal (TM) layers, while S atoms occupy tetrahedral interstitial sites and lattice O sites, all of which contribute to the crystal structure stability of LLOs. Theoretical calculations show that Mg/S dual-ion multisite doping successfully reduces the energy levels of the TM 3d-O 2p and isolated O 2p orbitals, which effectively stabilizes the lattice oxygen. Therefore, multisite-doped samples exhibit promising electrochemical performance. This strategy provides a new approach to enhance the crystal structure stability of LLOs for the design of high-energy-density Li-ion batteries.

Self-powered flexible devices with skin-like multiple sensing ability have attracted great attentions due to their broad applications in the Internet of Things (IoT). Various methods have been proposed to enhance mechano-optic or electric performance of the flexible devices; however, it remains challenging to realize the display and accurate recognition of motion trajectories for intelligent control. Here, we present a fully self-powered mechanoluminescent-triboelectric bimodal sensor based on micro-nanostructured mechanoluminescent elastomer, which can patterned-display the force trajectories. The deformable liquid metals used as stretchable electrode make the stress transfer stable through overall device to achieve outstanding mechanoluminescence (with a gray value of 107 under a stimulus force as low as 0.3 N and more than 2000 cycles reproducibility). Moreover, a microstructured surface is constructed which endows the resulted composite with significantly improved triboelectric performances (voltage increases from 8 to 24 V). Based on the excellent bimodal sensing performances and durability of the obtained composite, a highly reliable intelligent control system by machine learning has been developed for controlling trolley, providing an approach for advanced visual interaction devices and smart wearable electronics in the future IoT era., (© 2023. The Author(s).)

Reducing lunar dust adhesion to various material surfaces is important for protecting equipment from damage during lunar exploration missions. In this study, we investigate the lunar dust-mitigation ability and dust adhesion force of aluminum (Al) substrates prepared using different etching methods. Among them, composite etching methods (combining chemical and electrochemical steps) can result in multiscale structures with micro- and nanoroughness, reducing the contact area between the substrate and thus decreasing lunar dust adhesion. After composite etching, the dust adhesion force of the Al substrate was significantly reduced by 80% from 45.53 to 8.89 nN. The dust adhesion force of Al substrates dominates their dust-mitigation performance in floating dust environments. The lunar dust coverage (2.19%) of the Al substrate modified by composite etching (placed with a tilt angle of 90°) was 4-fold lower than that of the pristine Al substrate (9.11%), indicating excellent lunar-dust repellence. In addition, other factors such as tilt angle of the substrate and dust loading significantly affect dust-mitigation performance of the modified Al substrates. The Al substrate with an excellent dust-mitigation ability highlights good potential for lunar exploration missions.

Surface-enhanced Raman spectroscopy (SERS) stands out in the field of microbial analysis due to its rich molecular information, fast analysis speed, and high sensitivity. However, achieving strain-level differentiation is still challenging because numerous bacterial species inevitably have very similar SERS profiles. Here, a method inspired by the black-box theory was proposed to boost the spectral differences, where the undifferentiated bacteria was considered as a type of black-box, external environmental stress was used as the input, and the SERS spectra of bacteria exposed to the same stress was output. For proof of the concept, three types of environmental stress were explored, i.e., ethanol, ultraviolet light (UV), and ultrasound. Enterococcus faecalis ( E. faecalis ) and three types of Escherichia coli ( E. coli ) were all subjected to the stimuli (stress) before SERS measurement. Then the collected spectra were processed only by simple principal component analysis (PCA) to achieve differentiation. The results showed that appropriate stress was beneficial to increase the differences in bacterial SERS spectra. When sonication at 490 W for 60 s was used as the input, the optimal differentiation of bacteria at the species ( E. faecalis and E. coli ) and strain-level (three E. coli ) can be achieved.

Passive daytime radiative cooling (PDRC) involves cooling down an object by simultaneously reflecting sunlight and thermally radiating heat to the cold outer space through the Earth's atmospheric window. However, for practical applications, current PDRC materials are facing unprecedented challenges such as complicated and expensive fabrication approaches and performance degradation arising from surface contamination. Herein, we develop scalable cellulose-fiber-based composites with excellent self-cleaning and self-cooling capabilities, through air-spraying ethanolic poly(tetrafluoroethylene) (PTFE) microparticle suspensions embedded partially within the microsized pores of the cellulose fiber to form a dual-layered structure with PTFE particles atop the paper. The formed superhydrophobic PTFE coating not only protects the cellulose-fiber-based paper from water wetting and dust contamination for real-life applications but also reinforces its solar reflectivity by sunlight backscattering. It results in a subambient cooling performance of 5 °C under a solar irradiance of 834 W/m 2 and a radiative cooling power of 104 W/m 2 under a solar intensity of 671 W/m 2 . The self-cleaning surface of composites maintains their good cooling performance for outdoor applications, and the recyclability of the composites extends their life span after one life cycle. Additionally, dyed cellulose-fiber-based paper can absorb appropriate visible wavelengths to display specific colors and effectively reflect near-infrared lights to reduce solar heating, which synchronously achieves effective radiative cooling and esthetic varieties.

Considering the harmfulness of nitrogen dioxide (NO 2 ), it is important to develop NO 2 sensors with high responses and low limits of detection. In this study, we synthesize a novel SnO-Sn 3 O 4 heterostructure through a one-step solvothermal method, which is used for the first time as an NO 2 sensor. The material exhibits three-dimensional flower-like microparticles assembled by two-dimensional nanosheets, in situ -formed SnO-Sn 3 O 4 heterostructures, and large specific surface area. Gas sensing measurements show that the responses of the SnO-Sn 3 O 4 heterostructure to 500 ppb NO 2 are as high as 657.4 and 63.4 while its limits of detection are as low as 2.5 and 10 parts per billion at 75 °C and ambient temperature, respectively. In addition, the SnO-Sn 3 O 4 heterostructure has an excellent selectivity to NO 2 , even if exposed to mixture gases containing interferential part with high concentration. The superior sensing properties can be attributed to the in situ formation of SnO-Sn 3 O 4 p-n heterojunctions and large specific surface area. Therefore, the SnO-Sn 3 O 4 heterostructure having excellent NO 2 sensing performances is very promising for applications as an NO 2 sensor or alarm operated at a low operating temperature., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Ordered topography patterns with a mechanical response are usually designed to achieve wettability switching by geometric parameter changes through mechanical stimuli. However, their fabrication often needs expensive and complicated micro/nano-fabrication processing (e.g. photolithography and ion etching). In this study, a nano-carbon black (CB)/polybutadiene (PB) coating with a Wenzel superhydrophobic state was prepared on a rubber substrate by a facile method combining solution mixing and spraying coating. By stretching the composite coating, the generated cracks divided the continuous coating into new micro-nano mastoids, resulting in the formation of new hierarchical roughness for Cassie superhydrophobicity. The Wenzel-to-Cassie transition behavior was dependent on the CB loading in the coating. During stretching, the cracks propagated more rapidly in the coating with higher CB loading and induced the desired hierarchical structure to consequently enable the Wenzel-to-Cassie transition earlier at a lower stretching strain. The stretched coating presented good anti-wetting (a sliding angle of 5°) and low water adhesion. After releasing, the coating returned to its original Wenzel state by structure recovery. Thus, the switchable wettability of the coating can be adopted for no-loss water droplet transfer by controlling the droplet adhesion through cyclic stretching-releasing, and exhibits good potential for microfluidic and biomedical applications.

Here, we report a dual-use surface-enhanced Raman scattering (SERS) substrate based on a flexible three-dimensional (3D) chitosan foam, onto which silver nanoparticles (Ag NPs) are firmly immobilized through amino groups from chitosan chains. The SERS substrate can actively collect analytes either on solid surface by swabbing or in solution by adsorption. The compressible characteristic of chitosan foam enables easy removal of solvent through gentle pressing, which can achieve fast pre-concentrating of analytes before measurements. In addition, the substrate is shape adaptable and thus is suitable for sampling contaminants on solid surfaces. The SERS substrates exhibit acceptable reproducibility (16.4% in relative standard deviation). Furthermore, it detects Raman probe Nile Blue A down to 5 pg by swabbing solid surface and Rhodamine 6G down to 10 ppb by adsorbing analyte in the solution. Three pesticide samples (triazophos, methidathion, and isocarbophos) can also be detected down to μg level with the substrate. It is believed that such a versatile SERS substrate may find great opportunity in realistic sensing applications., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Fabrication of a gel polymer electrolyte containing succinonitrile (GPE-SN) with high mechanical strength is quite challenging because the SN electrolyte always suppresses the formation of polymer networks during in situ polymerization. In this work, a mechanically robust GPE-SN was successfully prepared by using a solution immersion method. During fabrication, the paste-like SN electrolyte was transformed into a liquid SN electrolyte with low viscosity by heating at 50 °C and then infiltrated into the UV-cured highly cross-linked polyurethane acrylate (PUA) skeleton. The resulted GPE-SN film exhibits superior tensile strength (6.5 MPa) compared to the one (0.5 MPa) prepared by in situ polymerization (GPE-SN-IN). The high mechanical strength of the GPE-SN-IM film enables the LiCoO 2 /Li 4 Ti 5 O 12 film battery to withstand 100-cycle folding without electrolyte damage and capacity loss. Besides, the GPE-SN presents a high ionic conductivity (1.63 × 10 -3 S·cm -1 at 25 °C), which is comparable to GPE with a commercial liquid electrolyte (GPE-LE). Because of good thermal stability of the GPE-SN, the LiCoO 2 /Li cell with this electrolyte shows better charge-discharge cycling stability than that with GPE-LE at high temperature (55 °C). Thus, the GPE-SN prepared by our method could be a promising polymer electrolyte offering better safety and reliability for lithium-ion batteries.

Poly(chloro-p-xylylene) (PPXC) film has a water contact angle (WCA) of only about 84°. It is necessary to improve its hydrophobicity to prevent liquid water droplets from corroding or electrically shorting metallic circuits of semiconductor devices, sensors, microelectronics, and so on. Herein, we reported a facile approach to improve its surface hydrophobicity by varying surface pattern structures under different temperature and relative humidity (RH) conditions on a thermal curable polydimethylsiloxane (PDMS) and hydrophobic silica (SiO₂) nanoparticle coating. Three distinct large-scale surface patterns were obtained mainly depending on the contents of SiO₂ nanoparticles. The regularity of patterns was mainly controlled by the temperature and RH conditions. By changing the pattern structures, the surface wettability of PPXC film could be improved and its WCA was increased from 84° to 168°, displaying a superhydrophobic state. Meanwhile, it could be observed that water droplets on PPXC film with superhydrophobicity were transited from a "Wenzel" state to a "Cassie" state. The PPXC film with different surface patterns of 200 μm × 200 μm and the improved surface hydrophobicity showed wide application potentials in self-cleaning, electronic engineering, micro-contact printing, cell biology, and tissue engineering., Competing Interests: The authors declare no conflict of interest.

With the rapid development of stretchable electronics, functional textiles, and flexible sensors, water-proof protection materials are required to be built on various highly flexible substrates. However, maintaining the antiwetting of superhydrophobic surface under stretching is still a big challenge since the hierarchical structures at hybridized micro-nanoscales are easily damaged following large deformation of the substrates. This study reports a highly stretchable and mechanically stable superhydrophobic surface prepared by a facile spray coating of carbon black/polybutadiene elastomeric composite on a rubber substrate followed by thermal curing. The resulting composite coating can maintain its superhydrophobic property (water contact angle ≈170° and sliding angle <4°) at an extremely large stretching strain of up to 1000% and can withstand 1000 stretching-releasing cycles without losing its superhydrophobic property. Furthermore, the experimental observation and modeling analysis reveal that the stable superhydrophobic properties of the composite coating are attributed to the unique self-adaptive deformation ability of 3D hierarchical roughness of the composite coating, which delays the Cassie-Wenzel transition of surface wetting. In addition, it is first observed that the damaged coating can automatically recover its superhydrophobicity via a simple stretching treatment without incorporating additional hydrophobic materials., (© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Constructing a dense cross-linking layer on a polymer film surface is a good way to improve the water resistance of poly(lactic acid) (PLA). However, conventional plasma treatments have failed to achieve the aim as a result of the unavoidable surface damage arising from the charged species caused by the uncontrolled high energy coming from colliding ions and electrons. In this work, we report a modified plasma method called hyperthermal hydrogen-induced cross-linking (HHIC) technology to construct a dense cross-linking layer on PLA film surfaces. This method produces energy-controlled neutral hyperthermal hydrogen, which selectively cleaves C-H bonds by molecule collision from the PLA film without breaking other bonds (e.g., C-C bonds in the polymer backbone), and results in subsequent cross-linking of the carbon radicals generated from the organic molecules. The formation of a dense cross-linking layer can serve as a barrier layer to significantly improve both the hydrophobicity and water vapor barrier property of the PLA film. Because of the advantage of selective cleavage of C-H bonds by HHIC treatment, the original physical properties (e.g., mechanical strength and light transmittance) of the PLA films are well-preserved.

SERS optrodes were used to "fish" aqueous drops from superhydrophobic surfaces. The technique led to an improvement of 2-3 orders of magnitude in the lowest detectable amount of the Raman probe nile blue A, reaching 25 fg (34 attomoles). Further tests run on samples containing pesticide revealed that 20 pg of triazophos could be clearly detected from a single drop.

A surface enhanced Raman scattering (SERS) substrate, capable of extracting small amounts of organic species from surfaces of different types of materials with variable roughness, has been fabricated. The substrate consists of Ag NPs encapsulated in poly(vinyl alcohol) (PVA) hydrogels, commonly known as PVA "slime". Unlike traditional SERS substrates, such as colloidal suspensions, the resulting PVA slime SERS substrate presents good viscoelasticity, allowing it to conform to the surface of various materials of arbitrary roughness. Surfaces of different materials, including sandpapers, cotton, metal, and wood, previously contaminated with nile blue A (NBA) were analyzed with the PVA slime SERS substrate. Limits of detection (LOD) as low as 100 ppb (0.79 ng in a total amount on an area of ∼3 cm(2)) were achieved for all surfaces tested. Pesticides and Sudan red III on the glass surface have also been detected, with a LOD of 1.6 ng per ∼3 cm(2).

A novel and highly conductive 3-dimensional (3D) hierarchical multi-scale structure is formed by a new, simple, facile, and water-based method that enables practical production of conductive carbon nanofiller/polymer composites. More specifically, the π-π interaction between CNTs and graphene oxide (GO) is exploited to disperse conductive but non-polar CNTs with amphiphilic GO sheets to form a stable aqueous colloidal solution. Aqueous-dispersible latex-polystyrene microspheres are then added to enable the self-assembly processes of anchoring CNTs on GO and wrapping microspheres with GO-stabilized CNTs for the formation of an intriguing 3D hierarchical multi-scale structure. During this process, GO is reduced to conductive reduced-graphene oxide (RGO). The resultant RGO sheets act as "nano-walls" to prevent CNTs from randomly diffusing into the polymer bulk during thermal pressing of RGO-CNT/microspheres, which results in the formation of a 3D foam-like network of RGO-CNTs with high quality. The resultant composite with such a structure gives an ultra-low percolation threshold (0.03 vol% RGO-CNTs) and a reasonably high conductivity (153 S m(-1) at 4 vol% RGO-CNTs), which could satisfy various applications requiring both transparency and electrical conduction characteristics (e.g. transparent antistatic coatings, capacitive touch-screens, and transparent electronic devices).

There is a growing shift from liquid electrolytes toward solid polymer electrolytes, in energy storage devices, due to the many advantages of the latter such as enhanced safety, flexibility, and manufacturability. The main issue with polymer electrolytes is their lower ionic conductivity compared to that of liquid electrolytes. Nanoscale fillers such as silica and alumina nanoparticles are known to enhance the ionic conductivity of polymer electrolytes. Although carbon nanotubes have been used as fillers for polymers in various applications, they have not yet been used in polymer electrolytes as they are conductive and can pose the risk of electrical shorting. In this study, we show that nanotubes can be packaged within insulating clay layers to form effective 3D nanofillers. We show that such hybrid nanofillers increase the lithium ion conductivity of PEO electrolyte by almost 2 orders of magnitude. Furthermore, significant improvement in mechanical properties were observed where only 5 wt % addition of the filler led to 160% increase in the tensile strength of the polymer. This new approach of embedding conducting-insulating hybrid nanofillers could lead to the development of a new generation of polymer nanocomposite electrolytes with high ion conductivity and improved mechanical properties., (© 2012 American Chemical Society)

Ultrasonication is often used to disperse nano-particles in aqueous solution. However, a good dispersion of nano-particles in aqueous solution is not always achieved, due to the fact that incoming ultrasonicwaves in liquid are usually reflected and damped at the gas/liquid interface. In this work, we report a so-called wet-grinding assisted ultrasonication (GU) method, in which wet-grinding of multi-walled carbon nanotubes (MWCNTs) in chitosan solution is carried out before ultrasonication. The dispersions of MWCNTs were characterized by visual comparison, UV/vis spectroscopy, and scanning electron microscopy (SEM). The results demonstrate that the dispersion quality of chitosan/MWCNT suspension prepared by wet-grinding assisted ultrasonication is much better than that by ultrasonication or wet-grinding alone. It was found that wet-grinding could improve the water wettability of MWCNTs and eliminate the barrier of air layer around MWCNTs to ultrasonicwaves. Meanwhile, the composite from the chitosan/MWCNTs suspension prepared by GU method has an obvious improvement in mechanical property compared to pure chitosan. This simple method for integrating MWCNTs and biocompatible chitosan into a homogeneous dispersion may have great potential application in biotechnology, such as preparing composite materials for medicine, bio-fiber, biosensor, antibacterial coating, and cell cultivation., (Copyright © 2011 Elsevier B.V. All rights reserved.)

In this study, highly oriented shish-kebab structure was achieved via imposing oscillatory shear on the melts of linear low density polyethylene (LLDPE)/high density polyethylene (HDPE) blends during the packing stage of injection molding. To investigate the effect of molecular weight of HDPE on the formation of shish-kebab structure, two kinds HDPE with large melt flow index (low molecular weight) and small melt flow index (high molecular weight) were added into LLDPE matrix. The structural characteristics of LLDPE/HDPE blends were systematically elucidated through two-dimensional wide-angle x-ray scattering, scanning electron microscopy, and differential scanning calorimetry. Interestingly, an unexpected molecular weight dependence of shish-kebab structure of the prepared samples was found that the addition of HDPE with low molecular weight resulted in an higher degree of orientation, better regularity of lamellar arrangement, thicker lamellar size, and higher crystal melting temperature than that adding HDPE with high molecular weight. Correspondingly, the blend containing low molecular weight HDPE had better tensile strength. A possible mechanism was suggested to elucidate the role of HDPE molecular weight on the formation of shish-kebab structure in the oriented blends, considering the change of chain mobility and entanglement density with change of molecular weight.

In this work, a great synergistic effect of 2D clay platelets and 1D carbon nanotubes (CNTs) on reinforcing chitosan matrix has been observed for the first time. With incorporation of 3 wt % clay and 0.4 wt % CNTs, the tensile strength and Young's modulus of the nanocomposites are significantly improved by about 171 and 124%, respectively, compared with neat chitosan. This could be understood as due to the formation of much jammed fillers network with 1D CNTs and 2D clay platelets combined together, as indicated by rheological measurement. Our work demonstrates a good example for the preparation of high performance polymer nanocomposites by using nanofillers of different dimension together.

Covalent functionalization of shortened multiwalled carbon nanotubes (MWNTs) with a natural low molecular weight chitosan (LMCS) was accomplished by a nucleophilic substitution reaction. Amino and primary hydroxyl groups of the LMCS contributed mainly to the formation of MWNT-LMCS conjugates. The LMCS content in the MWNT-LMCS is approximately 58 wt %, and approximately four molecular chains of the LMCS are attached to 1000 carbon atoms of the nanotube sidewalls. Most interestingly, the amorphous packing structure of the LMCS changed dramatically when it attached to the MWNTs. The MWNTs might induce the crystalline character of the LMCS. As a novel derivative of MWNTs, the MWNT-LMCS is soluble in dimethylformamide, dimethyl acetamide, dimethylsulfoxide, and acetic acid aqueous solution. The confirmation of the chitosan-based covalent functionalization route might lead to further studies aiming for potential applications in catalysis and environmental protection.