Pure cellulose nanofiber separator with high ionic conductivity and cycling stability for lithium-ion batteries.

Conventional polyolefin separators are constrained by poor electrolyte wettability, inferior thermal stability, and low ionic conductivity, which seriously restrict their application in high-performance lithium-ion batteries (LIBs). Herein, cellulose nanofiber (CNF) as the matrix and tert-butyl alcohol (TBA) as the dispersion medium were used to prepare the pure CNF separators for LIBs by a facile filtration method. The effects of the drying temperature on the pore structure, electrolyte wettability, mechanical properties, thermal stability, and ionic conductivity of the separators were comprehensively investigated. The results showed that the freeze-dried separator at -80 °C with TBA as the dispersion medium (TBA-FD) had the best overall performance, with the porosity and electrolyte uptake up to 70.8 % and 296 %, respectively, as well as the ionic conductivity up to 1.90 mS/cm. The CNF separators had no apparent thermal shrinkage at 160 °C, illustrating good thermal stability. Moreover, the LiFePO4/lithium metal battery assembled with the TBA-HD (tert-butyl alcohol as the dispersion medium for heat-drying at 80 °C) and TBA-FD separators displayed superior cycling stability (with a capacity retention rate up to 97.5 % and 96.4 %, respectively) and rate performance. The pure CNF separators with good performance prepared by the facile method are greatly promising for high-performance LIBs.

New insights into the aggregation and disaggregation between serpentine and pyrite in the xanthate flotation system.

HYPOTHESIS: In xanthate flotation system, the aggregation of serpentine on sulfide minerals significantly weakened their floatability. And it was generally assumed that the electrostatic attraction was of the dominant driver for coating of serpentine slimes. In this paper, the hydrophobic interaction between the "talc-like" cleavage plane of serpentine and the xanthate-hydrophobized surface of sulfide minerals was proposed as the dominated driver. EXPERIMENTS: To evaluate the aggregation of serpentine on pyrite surface, a novel experimental protocol was designed, and the aggregation behavior and mechanism in the absence and presence of sodium isobutyl xanthate (SIBX) were explored through in situ optical microscope, micro-flotation, contact angle, zeta potential and FT-IR. Afterwards, the disaggregation mechanism of 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP) to the aggregates of serpentine on pyrite surface was revealed. FINDINGS: The electrostatic attraction facilitated the slight aggregation of serpentine slimes on bare pyrite surface. The hydrophobic interaction between the "talc-like" plane of serpentine and SIBX-covered pyrite significantly promoted the aggregation between them, which remarkably weakened the floatability of pyrite. The attendance of HEDP anions reversed the surface potential of the octahedral Mg-O layers of serpentine from the positive into the negative, thus to prevent the aggregation of the HEDP-anchored serpentine with the SIBX-covered pyrite via the strong electrostatic repulsion between them. As a result, the disaggregation as well as SIBX flotation separation of pyrite from serpentine was realized. This investigation also provided new insights into the aggregation and disaggregation between serpentine and sulfide minerals during froth flotation.

Photoelectrochemical determination of cardiac troponin I based on rod-like g-C3N5@MnO2 heterostructure.

Rod-like graphite carbon nitride@MnO2 (R-g-C3N5@MnO2) heterostructure was prepared by in situ self-anchored growth of MnO2 nanosheet on the surface of R-g-C3N5. The synthesized R-g-C3N5@MnO2 heterostructure as photoactive material exhibited excellent photoelectrochemical (PEC) performance, and the prepared heterostructure-aptamer probe displayed sensitive PEC response to cTnI. Therefore, the PEC method was developed to detect cTnI based on the R-g-C3N5@MnO2 heterostructure. It was found that the linear response to cTnI was in the range 0.001-30 ng/mL under optimized conditions, and the detection limit of the proposed sensor was 0.3 pg/mL. The PEC method displays stable photocurrent response up to 8 cycles and exhibited outstanding selectivity and sensitivity. The PEC method was successfully applied to detect cTnI in serum samples. The recoveries of cTnI detection in serums reach 95.5-104%, and the relative standard deviations range from 3.20 to 4.45%.

g-C3N5-dots as fluorescence probes prepared by an alkali-assisted hydrothermal method for cell imaging.

Carbon nitride materials have become one of the highly explored carbon-based nanomaterials due to their unique properties. Herein, the novel graphitic carbon nitride quantum dots (g-C3N5-dots) were synthesized using an alkali-assisted hydrothermal method. The proposed strategy was simple, time-saving and the entire synthetic process only takes 60 min. And the prepared g-C3N5-dots showed excellent dispersion and good stability in water. What is more, the g-C3N5-dots displayed bright blue fluorescence with a high quantum yield of 12%. It was found that the g-C3N5-dots exhibited peroxidase-like activity, good biocompatibility and low cytotoxicity and can be successfully applied in cell imaging. The proposed method opens a new and efficient way for the preparation of fluorescent g-C3N5-dots and facilitates g-C3N5-dots for bioimaging and related biological sensing applications.

Effects of Sodium Alginate on the Flotation Separation of Molybdenite From Chalcopyrite Using Kerosene as Collector.

In this paper, the effect of sodium alginate (SA) on the flotation separation of molybdenite (MoS2) from chalcopyrite using kerosene as collector was systematically investigated. The results of single-mineral micro-flotation tests indicated that SA exhibited strong depression on chalcopyrite flotation while it imposed no impact on the floatability of molybdenite. However, in the chalcopyrite-molybdenite mixed-mineral flotation system, the presence of chalcopyrite significantly increased the depressing effect of SA on molybdenite flotation, leading to a considerable reduction in the flotation selectivity. The negative impact of chalcopyrite on the performance of SA in molybdenite flotation was eliminated by adding a certain dosage of kerosene prior to SA. A concentrate containing 53.43% of molybdenum (Mo) was obtained at 76.90% of recovery using 19 mg/L kerosene and 40 mg/L SA at pH 5.4. Zeta potential measurements indicated that the adsorption of SA on chalcopyrite surfaces was stronger than that on molybdenite surfaces, which agreed with the single-mineral flotation test results. The adsorption of SA on chalcopyrite was further confirmed to be chemisorption by Fourier-transform infrared spectroscopy (FTIR) spectra analyses. When Cu2+ appeared in solution, the flotation of molybdenite was strongly depressed by SA. Mechanism analyses indicated that more active sites were generated on molybdenite surfaces after the addition of Cu2+, thus promoting the adsorption of SA.

Tailoring ordered microporous structure of cellulose-based membranes through molecular hydrophobicity design.

Ordered porous polymer membranes can be facilely prepared by breath figures. Previous studies have confirmed that the solidifying of polymer is crucial for the formation of ordered porous structures, which directly depends on the hydrophobicity of polymer. However, it is still unknown how strong hydrophobicity is required. Here, cellulose acetate derivatives (CADs) were used to investigate the effect of hydrophobicity on ordered porous structures. The CADs with different hydrophobicity were firstly synthesized via simple reactions, and then the porous membranes were fabricated by the breath figure method. It was found that the pore size showed a decreasing trend with hydrophobicity, and the degree of order of porous structures firstly increased and then dropped, showing a critical hydrophobicity value for the transition of the degree of order. Therefore, it was confirmed that suitable hydrophobicity is critical for ordered porous structures of CADs while excessive hydrophobicity may impair the ordered structures.

Preparation and characterization of reinforced starch-based composites with compatibilizer by simple extrusion.

Because of the poor performance of starch-based composites, we prepared the starch-based composites with good mechanical properties by a simple two-step melt-blending extrusion. Glycerol and nano-SiO2 were firstly introduced into starch to prepare the TPS/nano-SiO2 composite by the first extrusion, and poly(butylene adipate-co-terephthalate) (PBAT) and the compatibilizers were then incorporated to obtain the improved composites by the second extrusion. The mechanical properties, thermal properties, morphology, and structure of the composites were characterized. The results showed that the strength dramatically increased after the addition of nano-SiO2 into starch, and the elongation at break was significantly improved by the incorporation of PBAT. The tensile strength was increased distinctly after the addition of the compatibilizers. All the composites exhibited good mechanical properties. The melting transition, the thermal stability, and the crystalline structure did not change with the additives, whereas the glass transition of the starch-rich phase shifted to a lower temperature. The results indicated that the combined compatibilizers had better compatibilization than each one alone.

POSS Hybrid Robust Biomass IPN Hydrogels with Temperature Responsiveness.

In order to improve the performance of traditional sodium alginate (SA) hydrogels cross-linked by Ca2+ ions to meet greater application demand, a strategy was designed to structure novel SA-based gels (named OP-PN gels) to achieve both stimulus responsiveness and improved mechanical strength. In this strategy, the SA chains are co-cross-linked by CaCl2 and cationic octa-ammonium polyhedral oligomeric silsesquioxane (Oa-POSS) particles as the first network, and an organically cross-linked poly(N-isopropyl acrylamide) (PNIPA) network is introduced into the gels as the second network. Several main results are obtained from the synthesis and characterization of the gels. For OP-PN gels, their properties depend on the content of both uniformly dispersed Oa-POSS and PNIPA network directly. The increased Oa-POSS and PNIPA network content significantly improves both the strength and resilience of gels. Relatively, the increased Oa-POSS is greatly beneficial to the modulus of gels, and the increased PNIPA network is more favorable to advancing the tensile deformation of gels. The gels with hydrophilic PNIPA network exhibit better swelling ability and remarkable temperature responsiveness, and their volume phase transition temperature can be adjusted by altering the content of Oa-POSS. The deswelling rate of gels increases gradually with the increase of POSS content due to the hydrophobic Si⁻O skeleton of POSS. Moreover, the enhanced drug loading and sustained release ability of the target drug bovine serum albumin displays great potential for this hybrid gel in the biomedical field.

Controlling the shear thickening behavior of suspensions by changing the surface properties of dispersed microspheres.

To investigate the effect of the surface properties of dispersed particles on the shear thickening behavior of their corresponding suspensions and further control this characteristic, three kinds of suspensions were prepared by mixing SiO2, SiO2-NH2, and SiO2-COOH microspheres with a poly(ethylene glycol) fluid medium, and their rheological behavior was analyzed carefully. Compared to the SiO2 microsphere suspension, the SiO2-NH2 and SiO2-COOH microsphere suspensions show a weaker thickening behavior and a greater critical shear rate due to the aggregation tendency caused primarily by the organic chains. Moreover, the rheological behavior of the three suspensions display different dependencies on the pH value, which is comprehensively determined by the interaction between the microspheres and the medium. Moreover, the critical shear stress of suspensions with different pH values could be predicted by the Wagner model, which basically proves that the interaction between the particles significantly influences the beginning of thickening. The thickening degree could be interpreted by friction theory. The critical volume fraction corresponding to the onset of discontinuous shear thickening is determined by the friction coefficient between the particles, which is greatly affected by the pH value.

Robust and stimuli-responsive POSS hybrid PDMAEMA hydrogels for controlled drug release.

A new polyhedral oligomeric silsesquioxane (POSS) hybrid hydrogels were desinged and fabricated by introducing cationic octa-ammonium (Oa)-POSS) into chemically cross-linked cationic PDMAEMA hydrogels via in situ radical freezing polymerization. The prepared gels (shorten as OP-PD gels) show considerably improved properties through the effective incorporation and dispersion of Oa-POSS particles in gels. Comparing to the Oa-POSS-free gels, the hybrid gels own better mechanical properties with higher tensile and compressive strength. Meantime, except the decreased swelling ratio in acid condition, the OP-PD gels still keep excellent swelling ability with obvious pH and temperature double responsiveness, which is affected by the content of Oa-POSS slightly. All OP-PD gels exhibit an ultrarapid deswelling rate due to the interconnected micropores structure caused by freezing and the formation of microhydrophobic region around POSS particles. Moreover, the application potential of OP-PD gels in drug release was exploited by using flutamide as target drug, the result showed that the increased Oa-POSS could improve the drug loading ability, and OP-PD gels showed well controlled-release effect in simulated human stomachic condition. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2345-2355, 2016.

A novel fast responsive thermo-sensitive poly(N-isopropylacrylamide)-clay nanocomposites hydrogels modified by nanosized octavinyl polyhedral oligomeric silsesquioxane.

The preparation of a novel fast response thremosensitive hydrogel was investigated by incorporating nanosized octavinyl polyhedral oligomeric silsesquioxane (OvPOSS) particles into inorganic clay-crosslinked poly(N-isopropylacrylamide) (PNIPA) nanocomposites hydrogels (NC gels). The resulting hydrogels named as P-NC gels involving both the strategies of NC gels and double network gels (DN gels) were successfully synthesized via a two-step technique. The second PNIPA network crosslinked by OvPOSS were polymerized in the presence of the first clay-PNIPA network. The P-NC gels were characterized by FTIR, X-ray, DSC, UV/vis,spectra, SEM, mechanical properties and swelling behaviors measurements. The key factor for preparing homogenous P-NC gels with good transparency was the low concentration of OvPOSS (c(OvPOSS)) dispersed uniformly in polymer as a cross-linker. On the contrary, the high c(OvPOSS) led to the significant aggregation of the OvPOSS particles and thus resulted in the heterogeneity of gels. The SEM images of freeze-dried P-NC gels exhibited a highly interconnected microporous network structure, which could be adjusted by varying the amount of OvPOSS. The special porous morphology brought about an attractive faster swelling/deswelling rate than that of normal NC gels. All properties of P-NC gels displayed an obvious dependence on the concentration of incorporated OvPOSS. The excellent mechanical properties, tunable LCST, especially the fast deswelling rate make these hydrogels potential candidates for applications in drug release and other biological fields.