Dressing Paraffin Wax/Boron Nitride Phase Change Composite with a Polyethylene "Underwear" for the Reliable Battery Safety Management.

Phase change material (PCM) can provide a battery system with a buffer platform to respond to thermal failure problems. However, current PCMs through compositing inorganics still suffer from insufficient thermal-transport behavior and safety reliability against external force. Herein, a best-of-both-worlds method is reported to allow the PCM out of this predicament. It is conducted by combining a traditional PCM (i.e., paraffin wax/boron nitride) with a spirally weaved polyethylene fiber fabric, just like the traditional PCM is wearing functional underwear. On the one hand, the spirally continuous thermal pathways of polyethylene fibers in the fabric collaborate with the boron nitride network in the PCM, enhancing the through-plane and in-plane thermal conductivity to 10.05 and 7.92 W m-1 K, respectively. On the other, strong polyethylene fibers allow the PCM to withstand a high puncture strength of 47.13 N and tensile strength of 18.45 MPa although above the phase transition temperature. After this typical PCM packs a triple Li-ion battery system, the battery can be promised reliable safety management against both thermal and mechanical abuse. An obvious temperature drop of >10 °C is observed in the battery electrode during the cycling charging and discharging process.

Novel controlled drug release system engineered with inclusion complexes based on carboxylic graphene.

A novel drug carrier is constructed by compositing hydrophilic hydroxypropyl-ß-cyclodextrins (HP-ß-CD) and carboxylated graphene nanomaterial (GO-COOH). Fourier transform infrared spectroscopy confirms that the two materials are successfully combined via chemical bonds. Further, a crosslinking agent of glutaraldehyde is applied to fabricate composite GO-COO-HP-ß-CD nanospheres, as demonstrated by an atomic force microscope. Dexamethasone (DEX) is selected as the model drug, and the drug loading efficiency and water solubility of the nanospheres greatly increased. Additionally, the achieved DEX/nanosphere inclusion complex exhibits better heat resistance compared with pure DEX, which is a desired property for drug processing. More importantly, different models are applied to different releasing durations to investigate in detail the release profile of DEX. The best fitting release kinetics model is given to reveal the release mechanism of the drug delivery system. The highest hemolysis rate of the DEX/nanosphere inclusion is 0.44%, far lower than the standard of 5% delivered by the American Society for Testing and Materials, ensuring its safety in practical applications. Meanwhile, recalcification tests indicate that DEX/nanosphere retains the normal blood coagulation function. In vitro cytotoxicity tests of the inclusion demonstrate that the nanospheres have no toxicity and are qualified for intravenous applications with good blood compatibility. Finally, the bioactivity of DEX after release from the carriers is investigated. Results corroborate that the drug anti-inflammation efficacy is not affected and that the biomedical function can be well retained. The engineered controlled drug release system represents a promising formulation platform for a broad range of therapeutic medicine in pharmaceutical technology.

Amorphous mesoporous nickel phosphate/reduced graphene oxide with superior performance for electrochemical capacitors.

Nickel phosphate (Ni3(PO4)2) is a promising electrode material for electrochemical capacitors, but the low intrinsic electrical conductivity and poor rate capability of Ni3(PO4)2 are the main challenges. To tackle these problems, amorphous mesoporous Ni3(PO4)2 with a pore diameter of 2-10 nm is grown on reduced graphene oxide (rGO), and a Ni3(PO4)2/rGO composite is obtained via a facile hydrothermal-calcination method in this work. The Ni3(PO4)2/rGO composite calcined at 300 °C (Ni3(PO4)2/rGO-300) possesses a uniform particle size and a high specific surface area of 198.72 m2 g-1. Benefiting from the structural characteristics, the synergistic effect of components and the high specific surface area, the Ni3(PO4)2/rGO-300 composite exhibits an extremely high specific capacitance of 1726 F g-1 at 0.5 A g-1 and an excellent rate capability of 850 F g-1 at 25 A g-1. In addition, the assembled Ni3(PO4)2/rGO-300//activated carbon asymmetric electrochemical capacitor delivers a good energy density of 57.42 W h kg-1 at a power density of 160 W kg-1. Compared with Ni3(PO4)2/rGO composites calcined at other temperatures and other nickel-phosphorus compounds reported in the literature, the Ni3(PO4)2/rGO-300 composite containing amorphous mesoporous Ni3(PO4)2 exhibits superior electrochemical performance, representing a new kind of electrode material for electrochemical capacitors.

High Interlaminar Shear Strength Enhancement of Carbon Fiber/Epoxy Composite through Fiber- and Matrix-Anchored Carbon Nanotube Networks.

To improve the interlaminar shear strength (ILSS) of carbon fiber reinforced epoxy composite, networks of multiwalled carbon nanotubes (MWNTs) were grown on micron-sized carbon fibers and single-walled carbon nanotubes (SWNTs) were dispersed into the epoxy matrix so that these two types of carbon nanotubes entangle at the carbon fiber (CF)/epoxy matrix interface. The MWNTs on the CF fiber (CF-MWNTs) were grown by chemical vapor deposition (CVD), while the single-walled carbon nanotubes (SWNTs) were finely dispersed in the epoxy matrix precursor with the aid of a dispersing agent polyimide-graft-bisphenol A diglyceryl acrylate (PI-BDA) copolymer. Using vacuum assisted resin transfer molding, the SWNT-laden epoxy matrix precursor was forced into intimate contact with the "hairy" surface of the CF-MWNT fiber. The tube density and the average tube length of the MWNT layer on CF was controlled by the CVD growth time. The ILSS of the CF-MWNT/epoxy resin composite was examined using the short beam shear test. With addition of MWNTs onto the CF surface as well as SWNTs into the epoxy matrix, the ILSS of CF/epoxy resin composite was 47.59 ± 2.26 MPa, which represented a ∼103% increase compared with the composite made with pristine CF and pristine epoxy matrix (without any SWNT filler). FESEM established that the enhanced composite did not fail at the CF/epoxy matrix interface.

Topographic guidance based on microgrooved electroactive composite films for neural interface.

Topographical features are essential to neural interface for better neuron attachment and growth. This paper presents a facile and feasible route to fabricate an electroactive and biocompatible micro-patterned Single-walled carbon nanotube/poly(3,4-ethylenedioxythiophene) composite films (SWNT/PEDOT) for interface of neural electrodes. The uniform SWNT/PEDOT composite films with nanoscale pores and microscale grooves significantly enlarged the electrode-electrolyte interface, facilitated ion transfer within the bulk film, and more importantly, provided topology cues for the proliferation and differentiation of neural cells. Electrochemical analyses indicated that the introduction of PEDOT greatly improved the stability of the SWNT/PEDOT composite film and decreased the electrode/electrolyte interfacial impedance. Further, in vitro culture of rat pheochromocytoma (PC12) cells and MTT testing showed that the grooved SWNT/PEDOT composite film was non-toxic and favorable to guide the growth and extension of neurite. Our results demonstrated that the fabricated microscale groove patterns were not only beneficial in the development of models for nervous system biology, but also in creating therapeutic approaches for nerve injuries.

Fast fabrication of NiO@graphene composites for supercapacitor electrodes: Combination of reduction and deposition.

Graphene-based inorganic composites have been attracting more and more attention since the attachment of inorganic nanoparticles instead of conducting polymeric materials to graphene sheets turns out higher capacitances and good capacity retention. Here we report a fast fabrication method to prepare NiO@graphene composite modified electrodes for supercapacitors. By this method, preparation of electrochemical active materials of NiO/graphene and modification of the electrode can be simultaneously performed, which is achieved separately by traditional method. Moreover, the problem of poor adhesion of active materials on the surface of the electrode can be well solved. The NiO particles introduced to the films exhibit pseudocapacitive behavior arising from the reversible Faradaic transitions of Ni(II)/Ni(III) and greatly improve the capacitance of the electrodes. With the increase in NiO content, highly reduced graphene can be obtained during cyclic voltammetry sweeping, leading to the increase in the electrode capacitance. The highest specific capacitance of the constructed electrodes can reach 1258 F/g at a current density of 5 A/g.

High-Performance and Omnidirectional Thin-Film Amorphous Silicon Solar Cell Modules Achieved by 3D Geometry Design.

High-performance thin-film hydrogenated amorphous silicon solar cells are achieved by combining macroscale 3D tubular substrates and nanoscaled 3D cone-like antireflective films. The tubular geometry delivers a series of advantages for large-scale deployment of photovoltaics, such as omnidirectional performance, easier encapsulation, decreased wind resistance, and easy integration with a second device inside the glass tube.

Lateral assembly of oxidized graphene flakes into large-scale transparent conductive thin films with a three-dimensional surfactant 4-sulfocalix[4]arene.

Graphene is a promising candidate material for transparent conductive films because of its excellent conductivity and one-carbon-atom thickness. Graphene oxide flakes prepared by Hummers method are typically several microns in size and must be pieced together in order to create macroscopic films. We report a macro-scale thin film fabrication method which employs a three-dimensional (3-D) surfactant, 4-sulfocalix[4]arene (SCX), as a lateral aggregating agent. After electrochemical exfoliation, the partially oxidized graphene (oGr) flakes are dispersed with SCX. The SCX forms micelles, which adsorb on the oGr flakes to enhance their dispersion, also promote aggregation into large-scale thin films under vacuum filtration. A thin oGr/SCX film can be shaved off from the aggregated oGr/SCX cake by immersing the cake in water. The oGr/SCX thin-film floating on the water can be subsequently lifted from the water surface with a substrate. The reduced oGr (red-oGr) films can be as thin as 10-20 nm with a transparency of >90% and sheet resistance of 890 ± 47 kΩ/sq. This method of electrochemical exfoliation followed by SCX-assisted suspension and hydrazine reduction, avoids using large amounts of strong acid (unlike Hummers method), is relatively simple and can easily form a large scale conductive and transparent film from oGr/SCX suspension.

A feasible way for the fabrication of single walled carbon nanotube/polypyrrole composite film with controlled pore size for neural interface.

Single walled carbon nanotube (SWNT)/polypyrrole (PPy) composite films with controlled pore size and strong adhesive force was prepared as electrode material for improving the performance of neural electrodes. SWNT film with controlled pore size was first fabricated through electrophoresis with a merit that the pore size can be well tuned by changing the concentration of metal ions in the electrolyte. An ultrathin conformal PPy layer around SWNT bundles in a uniform manner within the entire films was subsequently obtained by pulsed electropolymerization. The adhesion of the SWNT coated electrodes was tested by repeatedly inserting the coated electrode into agar gel to demonstrate the better adhesive force of the coating. Electrochemical results showed that the SWNT/PPy coated metal electrodes have much lower impedance and higher charge storage capacity than the bare metal substrates. Further in vitro culture of rat pheochromocytoma (PC12) cells revealed that the porous SWNT/PPy composite film was non-toxic and well supported the growth of neurons. We demonstrate that the prepared composite film has potential applications in chronic implantable neural electrodes for neural stimulation and recording.

Templated deposition of multiscale periodic metallic nanodot arrays with sub-10 nm gaps on rigid and flexible substrates.

Multiscale metallic nanostrucutures, which support hybrid coupling of plasmon resonances, are essential for the engineering of plasmonic devices. The fabrication of large area periodic multiscale structures still remains a challenge, considering the cost and efficiency. In this work, highly ordered multiscale Ag nanoarrays with lateral dimensions of up to 6 mm × 6 mm have been successfully fabricated on both rigid silicon and flexible polydimethylsiloxane (PDMS) substrate by thermal evaporation using ultrathin anodic aluminum oxide films as masks. Owing to the peculiarities of thermal evaporation and the variance of substrate surface energy, the unit cell of the periodic arrays consist of a core-satellite structure on silicon and randomly distributed child particles on PDMS, with gaps as small as 10 nm. The flexible Ag nanoarrays on PDMS demonstrate a broadband extraordinary optical transmission with an enhancement up to 2.7 times when normalized to the exposed area. Moreover, the transmission and diffraction properties can readily be controlled by stretching the PDMS. These tunable optical properties support the multiscale Ag nanoarrays to be applied in some optical and optoelectronic devices.

Electroactive SWNT/PEGDA hybrid hydrogel coating for bio-electrode interface.

Electric interface between neural tissue and electrode plays a significant role in the development of implanted devices for continuous monitoring and functional stimulation of central nervous system in terms of electroactivity, biocompatibility and long-term stability. To engineer an interface that possesses these merits, a polymeric hydrogel based on poly(ethylene glycol) diacrylate (PEGDA) and single-walled carbon nanotubes (SWNTs) were employed to fabricate a hybrid hydrogel via covalent anchoring strategy, i.e., self-assembly of cysteamine (Cys) followed by Michael addition between Cys and PEGDA. XPS characterization proves that the Cys molecules are linked to gold surface via the strong S-Au bond and that the PEGDA macromers are covalently bonded to Cys. FTIR spectra indicate the formation of hybrid hydrogel coating during photopolymerization. Electrochemical measurements using cyclic voltammetry (CV) and impedance spectrum clearly show the enhancement of electric properties to the hydrogel by the SWNTs. The charge transfer of the hybrid hydrogel-based electrode is quasi-reversible and charge transfer resistance decreases to the tenth of that of the pure hydrogel due to electron hopping along the SWNTs. Additionally, this hybrid hydrogel provides a favorable biomimetic microenvironment for cell attachment and growth due to its inherent biocompatibility. Combination of these merits yields hybrid hydrogels that can be good candidates for application to biosensors and biomedical devices. More importantly, the hybrid hydrogel coatings fabricated via the current strategy have good adhesion to the electrode substrate which is highly desired for chronically implantable devices.

Preparation of nano-tentacle polypyrrole with pseudo-molecular template for ATP incorporation.

Polypyrrole was electrochemically synthesized onto a gold electrode in the presence of sodium p-toluenesulfonate (TSNa) as the key dopant. Under the optimal synthesis condition, the surface morphology of PPy/TSNa was tailored and exhibited a nano-tentacle structure. The resulting rough and fuzzy morphology greatly enhanced the apparent surface area as well as the polymer film conductivity. Adenosine triphosphate (ATP) was then incorporated in the structure by subsequent ion exchanging. This procedure could be envisaged as pseudo-molecular templating to eliminate several shortcomings associated with physical templating. Fourier transform infrared (FTIR) and ultraviolet-visible (UV-vis) spectroscopy were conducted to investigate the incorporation of ATP. The pronounced rough surface of PPy/TSNa provided a higher density of active sites for ATP binding. The resulting PPy/ATP film exhibited a high charged capacity and lower impedance compared to the bare gold electrode. ATP remained stable in the PPy film; however, a negative bias to the electrode stimulated the conducting polymer to release ATP. This concept could serve as a mechanism for drug delivery and biosensing applications.

Effect of inorganic-organic composite coating on the dispersion of silicon carbide nanoparticles in non-aqueous medium.

In order to disperse silicon carbide (SiC) nanoparticles homogeneously in a non-aqueous medium, the surface of SiC nanoparticles needs to be modified via surface organic functionalization. A method of SiC nanoparticle surface modification by grafting of polyacetals via inorganic-organic composite coating was developed. The resulting graft percentage of up to 10.5% was much higher than that of direct grafting. The inorganic-organic composite coating on a SiC nanoparticle surface led to an almost complete decomposition of the secondary structure of the agglomerates and the formation of the primary structure. Dispersibility of the modified version was studied by using a transmission electron microscope (TEM) and size distribution analyser. The sedimentation experiments showed that the coated SiC nanoparticles exhibited good suspension stability in butanone. The composition of the inorganic-organic composite coating on the SiC nanoparticles was investigated by energy dispersive x-ray analyses (EDX), hydrogen nuclear magnetic resonance ((1)H NMR) and Fourier-transformed infrared spectroscopy (FT-IR). This work provides a novel concept of surface grafting modification for non-oxide nanoparticles to improve their dispersibility in non-aqueous medium.

[XPS investigation on the modified nano-Al2O3 by surface grafting].

Steric hindrance layer can be established when the surfaces of nano-Al2O3 were grafted with polyacetal, which increased the dispersibility of the nano-particles as well as the compatibility between the particles and the resin matrix. Examination of X-ray photoelectron spectroscopy (XPS) demonstrated that the peak of Al(2p) on polyacetal grafted Al2O3 surfaces almost disappeared, while that of O(1s) increased. On the contrary, peak of C(1s) increased obviously. Results of fine scanning and deconvolution into multiple sub-peaks of C(1s) indicated that 61.92% of carbon on the surfaces of nano-Al2O3 was attributed to the grafting polyacetal. This shows that an effective modification layer formed on Al2O3 surfaces, and the grafting polyacetal was chemically bound with nano-Al2O3. Based on XPS and TG analysis, it is conjectured that the grafting polyacetal is mainly distributed on nano-Al2O3 surfaces.