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The selective crystallization behaviours of amorphous boscalid (BOS), BOS monohydrate and acetone/ethyl acetate/ethanol/methanol solutions are explained and predicted by mid-frequency Raman difference spectra analysis. The phase transition processes including solutions...

The cyclic performance of flexible free-standing graphene-Fe2O3 hybrid sheet is considerably improved and was fabricated by a novel one-step hydrothermal process. The X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electrochemical workstation are performed to characterize the microstructure and electrochemical performance of the graphene-Fe2O3 hybrid sheet. At a current density of 200 mA·g−1, the obtained product has a high initial discharge capacity of 1466 mAh·g−1. The nanohybrids also exhibited a considerably high reversible capacity of 765 mAh·g−1 and high Coulombic efficiency of 99.8% after 100 cycles, which benefited from the open 3D laminated nanostructure constructed by layered graphene paper and Fe2O3 nanoparticles. Therefore, the composite has excellent rate performance and stability and can be greatly extended as the anode material of lithium-ion batteries.

Supramolecular materials with room-temperature healability and recyclability are highly desired because they can extend materials lifetimes and reduce resources consumption. Most approaches toward healing and recycling rely on the dynamically reversible supramolecular interactions, such as hydrogen, ionic and coordinate bonds, which are hygroscopic and vulnerable to water. The general water-induced plasticization facilitates the healing and reprocessing process but cause a troubling problem of random self-adhesion. To address this issue, here it is reported that by modifying the hygroscopic surfaces with hydrophobic alkyl chains of dodecyltrimethoxysilane (DTMS), supramolecular plastic films based on commercial raw materials of sodium alginate (SA) and cetyltrimethylammonium bromide (CTAB) display extraordinary damage-specific healability. Owing to the hydrophobic surfaces, random self-adhesion is eliminated even under humid environment. When damage occurs, the fresh surfaces with ionic groups and hydroxyl groups expose exclusively at the damaged site. Thus, damage-specific healing can be readily facilitated by water-induced plasticization. Moreover, the films display excellent room-temperature recyclability. After multiple times of reprocessing and re-modifying with DTMS, the rejuvenated films exhibit fatigueless mechanical properties. It is anticipated that this approach to damage-specific healing and room-temperature recycling based on surface hydrophobization can be applied to design various of supramolecular plastic polysaccharides materials for building sustainable societies.

Polymerized ionic liquids (polyILs) combine the unique properties of ionic liquids (ILs) with macromolecular polymers. But anion diffusivities in polyILs can be three orders of magnitude lower than that in ILs. Endeavors to improve ion transport in polyILs urgently need in-depth insights of ion transport in polyILs. As such in the work we compared ion transport in poly (1-butyl-3-vinylimidazolium-tetrafluoroborate) (poly ([BVIM]-[BF4])) polyIL and 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]-[BF4]) IL. The diffusivities of ions in the polyIL and IL were measured and computed. According to the results of the molecular dynamics simulations performed, in the IL the coupling motion between an anion and the ions around determines the ion diffusivities, and the ion association lifetime gives the time scale of ion transport. But in the polyIL, the hopping of an anion among cages composed of cationic branch chains determines the diffusivity, and the associated anion transport time scale is the trap time, which is the time when an anion is caught inside a cage, not the ion association lifetime, as Mogurampelly et al. regarded. The calculation results of average displacements (ADs) of the polyIL chains show that, besides free volume fraction, average amplitudes of the oscillation of chains and chain translation speed lead to various diffusivities at various temperatures.

Ultra-small superparamagnetic iron oxide nanoparticles (USPIOs) have been used as vascular contrast agents in magnetic resonance imaging (MRI), mainly for their capacity to generate negative contrast. To use USPIOs as positive contrast agents, it is necessary to achieve increased colloidal stability and signal-enhancement performance. Their molecular coatings must be carefully chosen so the vascular blood-pool contrast agents must lead to long blood turnover times. However, to avoid long-term toxicological effects, they must also be cleared rapidly through the urinary or the gastrointestinal pathways. In this context, highly stable USPIOs showing “positive” contrast in MRI and optimal clearance rates, call for the development of robust biocompatible molecular coatings. In the present study, USPIOs were stabilized with multidentate block copolymer (MDBC), using a one-pot polyol synthesis method in the presence of MDBC. Two types of MDBC having pendant COOH groups in the anchoring block were developed: a po...

Two series of dual-core star-shaped polyfluorenes (DC-TPAs and DC-SBFs) based on a small quantity of green-emitting phenylmaleimide cores and a good deal of non-emissive cores were prepared by a one-pot Suzuki reaction. Triphenylamine (TPA) and 9,9-spirobifluorene (SBF) are employed as the non-emissive cores to construct DC-SBFs and DC-TPAs, respectively. Due to the π-conjugation extended by the fluorene units, the phenylmaleimide core displays a yellow emission which contributes to the white emission with the blue-emitting polyfluorene arms. DC-SBFs with four arms exhibit a better protection for emissive cores and a higher energy transfer efficiency than DC-TPAs with three arms. Consequently, the quantum yield of white emission of the polymers in the film was improved by changing TPA into SBF as the non-emissive core, reaching 0.80 for DC-SBF03. Additionally, the electrons and holes can be transported smoothly in DC-SBFs. A very high electroluminescent efficiency was obtained for DC-SBF03 with a maximum luminous efficiency of 17.4 cd A−1, power efficiency of 10.9 lm W−1 and external quantum efficiency of 6.2% when applied in the solution-processing white polymeric light-emitting devices (WPLEDs) with a LiF/Al cathode. The results denote that the non-emissive core plays a key role in the performance of the star-shaped single white polymers. It provides another way to improve the efficiencies of WPLEDs by designing simple non-emissive cores of the dual-core polymers, and avoiding the complicated synthesis of fluorophores.

Guanosine (GR) dihydrate and inosine (IR) dihydrate have similar crystal structure, water molecules are almost at the same locations in them. GR dihydrate has the reversible dehydration/hydration property and is a good candidate for materials harvesting water from atmosphere. IR dihydrate is not stable and can be easily transformed to anhydrous IR α form. In this work, doping of IR in GR dihydrate in all the range was realized for the first time by using a solution method. The successful preparation of doped dihydrate of IR and GR by the solution method was attributed to the similar molecular conformations of IR and GR in solution. The doped dihydrates could maintain the reversible dehydration/hydration property similar to pure GR dihydrate even the ratio of IR was up to 71.1 ± 1.2 mol% under a mild drying treatment with freeze-dry. A pure amorphous GR was prepared by ball milling, and it showed a similar dehydration/hydration property to GR dihydrate with a lower dehydration temperature (about 84 °C). The implementation of doping IR in GR dihydrate would shed light on the design and fabrication of functional doped organic crystals. And study on the structural insights and the dehydration/hydration processes of the doped dihydrates and the pure amorphous GR would shed light on the design and fabrication of novel hydrogen-bonded organic frameworks (HOFs) materials for water harvesting.

A microwave assisted polyol process accomplished within 10 min was developed for synthesis of superparamagnetic Fe3O4 nanoparticles (MNPs) with well controlled size between 2 and 6 nm. Effects of reaction time and temperature on the size of the MNPs were investigated through transmission electronic microscope, x-ray diffraction pattern, thermogravimetic and magnetic analysis. The results indicates that longer reaction time or higher temperature lead to formation of MNPs with larger size. As a proof-of-concept, the MNPs were utilized as peroxidase and their activity was also investigated. Oxidation of typical substrate, 3, 3’, 5, 5’ -tetramethylbenzidine, can be proceeded by using the MNPs as artificial mimic enzyme. The MNPs display the maximal catalyzed activity under the optimum condition as pH = 3.5, 40 °C and concentration of TMB and H2O2 with 120 and 110 mmol·l−1, respectively. This work provides a new way for fast synthesis of MNPs, which are of potential application in artificial mimic enzyme.

An effective mussel-inspired multidentate block copolymer strategy having pendant anchoring catechol groups (Cat-MDBC) to stabilize extremely small iron oxide nanoparticles (ESNPs) in water is reported. The resultant aqueous Cat-MDBC/ESNP colloids with diameter ≈16 nm and core diameter ≈2 nm were non-toxic to cells up to 200 μg/mL and exhibit excellent colloidal stability in physiological condition (pH=7) as well as in the presence of IgG model protein. More promisingly, they had the relaxivity ratio to be r2/r1=1.5, which is significantly lower than PEG-coated SNPs with core diameter=1.5-6 nm; further which is similar to those of Gd-DOTA T1-weighted contrast agents. These results suggest that aqueous Cat-MDBC/ESNP colloids could be a promising candidate for T1-weighted MRI contrast enhancement.

Magnetic nanomaterials have unique advantages in heavy metal ions absorption because of their large specific surface area and easy magnetic manipulation. Carbon nanotube or graphene loaded with magnetite nanoparticles (MNPs) have been utilized to fabricate absorbents with both high absorption capacity and fast magnetic capture. Herein, cheap commercial carbon black was used as a substitute for expensive carbon nanotube or graphene to fabricate nanocomposites (CB-MNP) by modified carbon black loaded with superparamagnetic MNPs. The fabrication process is accomplished by two steps. Carbon blacks (CB) were modified by nitric acid to produce a large number of carboxyl groups on the surface and make stable aqueous dispersion. Subsequently, CB-MNPs with high water stability and fast magnetic response were facilely prepared by iron precursors (the ratio of ferrous to ferric is 1:2) added into the above CB dispersion and tuned pH = 10, finally added polyacrylic acid solution under sonication. Modified CB and CB-MNPs were characterized by transmission electron microscope (TEM), dynamic laser scattering (DLS), thermogravimetric analysis and so on. Water stability and magnetic response can be controlled by changing the proportion of CB and iron precursor. As a proof-of-concept, CB-MNPs were used for absorption removal of cadmium ions. Excellent performance was demonstrated with the removal efficiency of 71.41% and removal capacity of 39.99 mg · g−1 at the initial concentration of Cd2+ as 5 × 10−5 mol · l−1. The effects of initial concentration of Cd2+, pH value and interfering anion ions were also investigated and the results indicate the potential application of CB-MNP in fast removal of heavy metal ions.

Magnetic resonance (MR) imaging, with its inherent good spatial resolution and without tissue penetration depth limitations associated with other cell tracking techniques, is considered a valuable tool to assess the effects of cellular therapy. However, in order to allow in vivo tracking of transplanted cells with MRI, the cells must be labeled with contrast agents, usually in the form of magnetic or paramagnetic nanoparticles. Typically these are iron oxides, which are associated with a number of drawbacks related e.g. to the generation of hypointensities of the MR image due to signal loss. In this study, two chemically distinct manganese oxide-based nanostructures were developed and their feasibility as labels for human mesenchymal stem cells (hMSCs) was investigated. The ability to monitor the produced particles alone or within the labeled cells in vitro using MR imaging was further evaluated. Two novel synthetic approaches, the polyol process and microwave digestion, were combined to yield a “green”, and extremely rapid means of producing water-dispersible crystalline (MnO) and amorphous (MnOx) manganese oxides. To increase their water dispersability, capping agents in the form of organic polymers, poly(vinyl pyrrolidone) (PVP) and poly(acrylic acid) (PAA), were added to the synthesis process. Crystalline MnO was not formed when PAA was used as the capping agent, since Mn ions (Mn2+) cannot be hydrolyzed to Mn(OH)2, which is an intermediate step in the formation of MnO, under the acidic conditions provided by PAA. PVP, on the other hand, served to induce a spherical shape to the formed nanocrystals. Remarkably, the relaxation times of the as-prepared amorphous MnOx were significantly shorter than those of their crystalline counterparts, and the biocompatibility was also higher for MnOx. To the best of our knowledge, this is the first report which describes the use of an amorphous MnOx as a cell label for MR imaging.

Long circulation time is critical for blood pool contrast agents used in high-resolution magnetic resonance angiography. For iron oxide particle contrast agents, size and surface properties significantly influence their in vivo performance. We developed a novel long-circulating blood pool contrast agent by introducing zwitterionic structure onto the particle surface. Zwitterionic structure was fabricated by 3-(diethylamino)propylamine (DEAPA) grafted onto the surface of ployacrylic acid coated magnetite nanoparticles via EDC/NHS [N-(3-dimethylaminopropyl)-N'-ethylcarbo-diimide hydrochloride/N-hydroxysuccinimide] coupling chemistry. Zwitterionic particles demonstrated five times lower macrophage cell uptake than the original particles and low cell toxicity. Magnetic resonance angiography indicated that zwitterionic nanoparticles had much longer in vivo circulation time than the original particles and were an ideal candidate for blood pool contrast agent. We suppose that zwitterionic modification by DEAPA and EDC/NHS can be used generally for coating nanoparticles with carboxyl surface and to prolong their circulating time.

Microwave-assisted polyol process was developed for the synthesis of magnetite nanoparticles with precisely controlled size, high crystallinity and high water solubility. The process is simple, time-saving and low energy-consuming due to the advantages of polyols and microwave irradiation combined. The crystal phases of the nanoparticles were determined by transmission electron microscopy, X-ray powder diffraction and Raman spectrum. The coating materials of the nanoparticles were analyzed by Fourier transformed infrared spectroscopy and thermal gravimetric analysis. Precise size tuning enables an easier way to adjust the relaxation properties of the magnetite nanoparticles. The colloid nanoparticles with high longitudinal relaxivity ( r 1 ) and low ratio of transverse relaxivity ( r 2 ) to r 1 have a potential application in magnetic resonance angiography.

Hybrid materials (Cu–C 60 ) formed by C 60 decorating the surface of copper clusters were prepared through pulsed laser ablation at the interface between copper solid target and a flowing fullerene solution of hexane. UV–Vis shows that the feature absorption intensity of C 60 in the copper–fullerene–hexane sol decreases, and the increased absorption band of copper-cluster sol can also be found between 190 nm and 240 nm. Element analysis indicates that copper clusters in the sample (Cu–C 60 ) are decorated mainly by C 60 . HRTEM identified that copper clusters are decorated by C 60 ; XRD reveals that the diffraction peaks of the sample have lower value and broader width than pure copper, indicating the surface of copper clusters is decorated by an amorphous material. Magnetism tested by VSM indicated that the sample has one Curie point at 203 K, suggesting that high temperature, high pressure and very rapidly cooled microarea in the method of PLA/ISFL are of importance in affecting the magnetic property of the hybrid material.

A new strategy for facile preparation of highly luminescent CdTe quantum dots (QDs) within amine-terminated hyperbranched poly(amidoamine)s (HPAMAM) was proposed in this paper. CdTe precursors were first prepared by adding NaHTe to aqueous Cd2+ chelated by 3-mercaptopropionic sodium (MPA-Na), and then HPAMAM was introduced to stabilize the CdTe precursors. After microwave irradiation, highly fluorescent and stable CdTe QDs stabilized by MPA-Na and HPAMAM were obtained. The CdTe QDs showed a high quantum yield (QY) up to 58%. By preparing CdTe QDs within HPAMAM, the biocompatibility properties of HPAMAM and the optical, electrical properties of CdTe QDs can be combined, endowing the CdTe QDs with biocompatibility. The resulting CdTe QDs can be directly used in biomedical fields, and their potential application in bio-imaging was investigated.

Long circulation time is critical for blood pool contrast agents used in high-resolution magnetic resonance angiography. For iron oxide particle contrast agents, size and surface properties significantly influence their in vivo performance. We developed a novel long-circulating blood pool contrast agent by introducing zwitterionic structure onto the particle surface. Zwitterionic structure was fabricated by 3-(diethylamino)propylamine (DEAPA) grafted onto the surface of ployacrylic acid coated magnetite nanoparticles via EDC/NHS [N-(3-dimethylaminopropyl)-N'-ethylcarbo-diimide hydrochloride/N-hydroxysuccinimide] coupling chemistry. Zwitterionic particles demonstrated five times lower macrophage cell uptake than the original particles and low cell toxicity. Magnetic resonance angiography indicated that zwitterionic nanoparticles had much longer in vivo circulation time than the original particles and were an ideal candidate for blood pool contrast agent. We suppose that zwitterionic modification by DEAPA and EDC/NHS can be used generally for coating nanoparticles with carboxyl surface and to prolong their circulating time.

Magnetic nonviral gene vectors were in situ prepared in the presence of ferrous salts and hyperbranched poly(ethylenimine)s (HPEI) with different molecular weights. HPEI, one of the most promising nonviral vectors, was not only utilized as the nanoreactor and stabilizer to prepare magnetic nanoparticles, but also skillfully used as a base supplier to avoid introducing alkali hydroxide or ammonia. Magnetic nonviral gene vectors with various magnetite contents and saturation magnetizations were obtained by changing the weight ratio of HPEI to FeSO(4).7H(2)O and the molecular weight of HPEI. MTT assays suggested that the resulting magnetite/HPEI gene vectors had lower cytotoxicity compared with pure HPEI. The magnetite/HPEI nonviral gene vectors were used for magnetofection. It was found that the luciferase expression level mediated by magnetite/HPEI in COS-7 cells under a magnetic gradient field was approximately 13-fold greater than that of standard HPEI transfection.