Core–shell structure PEO/CS nanofibers based on electric field induced phase separation via electrospinning and its application

Core–shell structured PEO‐chitosan nanofibers have been produced from electric field inducing phase separation. Chitosan, a positive charged polymer, was dissolved in 50 wt % aqueous acetic acid and the amino group on polycation would protonize, which would endow chitosan electrical properties. Chitosan molecules would move along the direction of the electric field under the electrostatic force and formed the shell layer of nanofibers. Preparation process of core – shell structure is quite simple and efficient without any post‐treatment. The core–shell structure and existence of chitosan on the shell layer were confirmed before and after post‐treatment by TEM and further supported by SEM, FTIR, XRD, DSC, and XPS studies. Blending ratio of PEO and chitosan, molecular weight of chitosan for the mobility of chitosan are thought to be the key influence factors on formation of core–shell structure. Drug release studies show that the prepared core–shell structure nanofibers has a potential application in the biomedical fields involving drug delivery. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2298–2311     

Aggregation-induced multicolor luminescent nanoparticles with adaptive and fixed cores derived from brominated tetraphenylethene-containing block copolymer

Aggregation-induced emission (AIE)-active nanoparticles (NPs) exhibiting multicolor fluorescence and high-quantum yields independent of the environment are important for the further development of next-generation smart fluorescent materials. In this work, AIE-active amphiphilic block copolymers were designed and synthesized by RAFT polymerization of a brominated tetraphenylethene (TPE)-containing acrylate (A-TPE-Br). The block copolymer exhibited typical AIE effects in selective solvents, which can be explained by hydrophobic TPE aggregated in the core during micelle formation. Luminescent core–shell NPs with a crosslinked AIE core (fixed structure) were synthesized by the Suzuki coupling reaction of the bromine groups of the assembled block copolymer and boronic acid compounds. The NPs composed of TPE/thiophene crosslinked core showed green emission in both diluted state and solid state, implying the ability to fluoresce regardless of environmental changes and molecular dispersion. Multicolor luminescent NPs capable of changing color from blue to red were synthesized by changing the coupling compounds, such as anthracene for electron-rich units and benzothiadiazole for electron-deficient units. The effects of the nature of the donor and acceptor, as well as their combination (TPE/donor/acceptor sequence), on the color and fluorescent intensity of the core crosslinked NPs in the nonpolar and polar solvents, and solid state, were investigated.     

Dual Plasmonic Au−Cu2−xS Nanocomposites: Design Strategies and Photothermal Properties

Coupling two different materials to create a hybrid nanostructured system is a powerful strategy for achieving synergistically enhanced properties and advanced functionalities. In the case of Au and Cu_2−xS, their combination on the nanoscale results in dual plasmonic Au−Cu_2−xS nanocomposites that exhibit intense photon absorption in both the visible and the near-infrared spectral ranges. Their strong light-absorbing properties translate to superior photothermal transduction efficiency, making them attractive in photothermal-based applications. There are several nanostructure configurations that are possible for the Au−Cu_2−xS system, and the successful fabrication of a particular architecture often requires a carefully planned synthetic strategy. In this Minireview, the different synthetic approaches that can be employed to produce rationally designed Au−Cu_2−xS nanocomposites are presented, with a focus on the experimental protocols that can lead to heterodimer, core–shell, reverse core–shell, and yolk–shell configurations. The photothermal behavior of these materials is also discussed, providing a glimpse of their potential use as photothermally active agents in therapeutic and theranostic applications.     

Generating New Cross‐Relaxation Pathways by Coating Prussian Blue on NaNdF4 To Fabricate Enhanced Photothermal Agents

Cross‐relaxation among sensitizers is commonly regarded as deleterious in fluorescent materials, although favorable in photothermal agents. Herein, we coated Prussian blue (PB) on NaNdF₄ nanoparticles to fabricate core–shell nanocomplexes with new cross relaxation pathways between the ladder‐like energy levels of Nd³⁺ ions and continuous energy band of PB. The photothermal conversion efficiency was improved exceptionally and the mechanism of the enhanced photothermal effect was investigated. In vivo photoacoustic imaging and photothermal therapy demonstrated the potential of the enhanced photothermal agents. Moreover, the concept of generating new cross‐relaxation pathways between different materials is proposed to contribute to the design of all kinds of enhanced photothermal agents.     

Cable-Like Core–Shell Mesoporous SnO2 Nanofibers by Single-Nozzle Electrospinning Phase Separation for Formaldehyde Sensing

In this study, we have developed a simple and efficient single-nozzle electrospinning strategy involving the phase separation of polystyrene and poly(vinylpyrrolidone) to construct cable-like core–shell mesoporous SnO₂ nanofibers. Compared with traditional multi-axial electrospinning approaches to the synthesis of core–shell nanofibers, the single-nozzle electrospinning process requires no complex multi-axial electrospinning setups or post-treatments, just drying and annealing after electrospinning. The obtained SnO₂ nanofibers show promise as a sensing material for formaldehyde at low concentrations, the detection limit being about 1 ppm. Furthermore, the nanofibers exhibited good cycling stability and selectivity, with response and recovery times toward 10 ppm formaldehyde being approximately 18 and 196 s, respectively, at an operating temperature of 195 °C.     

Magnetic Nanohybrids Loaded with Bimetal Core–Shell–Shell Nanorods for Bacteria Capture,Separation, and Near‐Infrared Photothermal Treatment

A novel antimicrobial nanohybrid based on near‐infrared (NIR) photothermal conversion is designed for bacteria capture, separation, and sterilization (killing). Positively charged magnetic reduced graphene oxide with modification by polyethylenimine (rGO–Fe₃O₄–PEI) is prepared and then loaded with core–shell–shell Au–Ag–Au nanorods to construct the nanohybrid rGO–Fe₃O₄–Au–Ag–Au. NIR laser irradiation melts the outer Au shell and exposes the inner Ag shell, which facilitates controlled release of the silver shell. The nanohybrids combine physical photothermal sterilization as a result of the outer Au shell with the antibacterial effect of the inner Ag shell. In addition, the nanohybrid exhibits high heat conductivity because of the rGO and rapid magnetic‐separation capability that is attributable to Fe₃O₄. The nanohybrid provides a significant improvement of bactericidal efficiency with respect to bare Au–Ag–Au nanorods and facilitates the isolation of bacteria from sample matrixes. A concentration of 25 μg mL^?1 of nanohybrid causes 100 % capture and separation of Escherichia coli O157:H7 (1×10⁸ cfu mL^?1) from an aqueous medium in 10 min. In addition, it causes a 22 °C temperature rise for the surrounding solution under NIR irradiation (785 nm, 50 mW cm^?2) for 10 min. With magnetic separation, 30 μg mL^?1 of nanohybrid results in a 100 % killing rate for E. coli O157:H7 cells. The facile bacteria separation and photothermal sterilization is potentially feasible for environmental and/or clinical treatment.     

药物和蛋白质与聚己内酯分层复合纳米纤维的微观结构与力学特性

应用同轴共纺技术制得芯质和表层为两种不同材料的分层复合纳米纤维.分别以乙酰螺旋酶素片剂和明胶蛋白质为芯质材料,以可生物降解的聚己内酯作为表层材料,研究了这种分层复合纳米纤维的微观结构与力学特性.结果表明,尽管药物与表层聚合物材料的溶解溶剂互不相同,但仍可以将药物包覆在壁厚小于100nm的超细纤维中.这种纤维可用作体内手术伤口缝合线或大面积创伤如烧伤伤口的敷布.在实验范围内,纤维膜的力学性能随芯质内溶质含量的提高而降低.     

Assembling of amphiphilic highly branched molecules in supramolecular nanofibers

We found that the amplification of weak multiple interactions between numerous peripheral branches of irregular, flexible, polydisperse, and highly branched molecules can facilitate their self-assembly into nanofibrillar micellar structures at solid surfaces and the formation of perfect long microfibers in the course of crystallization from solution. The core-shell architecture of the amphiphilic dendritic molecules provides exceptional stability of one-dimensional nanofibrillar structures. The critical condition for the formation of the nanofibrillar structures is the presence of both alkyl tails in the outer shell and amine groups in the core/inner shell. The multiple intermolecular hydrogen bonding and polar interactions between flexible cores stabilize these nanofibers and make them robust albeit flexible. This example demonstrates that one-dimensional supramolecular assembling at different spatial scales (both nanofibers and microfibers) can be achieved without a tedious, multistep synthesis of shape-persistent molecules.     

Soft template synthesis of donor–acceptor conjugated polymer nanoparticles: Structural effects,stability, and photothermal studies

Donor–acceptor conjugated polymer nanoparticles and nanofibers, based on Poly[4,4‐bis(2‐ethylhexyl)‐cyclopenta[2,1‐b;3,4‐b']dithiophene‐2,6‐diyl‐alt?2,1,3‐benzoselenadiazole‐4,7‐diyl] (PCPDTBSe), were synthesized using Pluronic F127 as a template. The nanomaterials were compared to previously reported PCPDTBSe nanoparticles, which were synthesized without the use of a template. Our goal was to improve on the aqueous stability and photothermal heating efficiency of the previously synthesized PCPDTBSe nanoparticles by decreasing their size and coating them with a biocompatible surfactant. The pluronic wrapped PCPDTBSe (PW‐PCPDTBSe) nanoparticles (40–60 nm) showed excellent aqueous stability compared to the PW‐PCPDTBSe nanofibers (d = 20–60 nm, l = 200–1000 nm) and previously synthesized PCPDTBSe nanoparticles (150 nm). Under stimulation from 800 nm near infrared light (3 W, 1 min), the PW‐PCPDTBSe nanoparticles showed greater heat generation (ΔT = 47 °C) compared to bare PCPDTBSe nanoparticles and PW‐PCPDTBSe nanofibers (ΔT = 35 °C for both). Cytotoxicity studies determined that both the PW‐PCPDTBSe nanoparticles and PW‐PCPDTBSe nanofibers displayed no significant toxicity toward either noncancerous small intestinal cells (FHs 74 Int) or colorectal cancer cells (CT26). Photothermal ablation studies confirmed that both the PW‐PCPDTBSe nanoparticles and the PW‐PCPDTBSe nanofibers can be used as localized photothermal agents to eradicate colorectal cancer cells due to their excellent ablation efficiency (>95% cell death at 15 µg/mL concentration). © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1622–1632     

Expanding Anti‐Stokes Shifting in Triplet–Triplet Annihilation Upconversion for In Vivo Anticancer Prodrug Activation

A strategy to expand anti‐Stokes shifting from the far‐red to deep‐blue region in metal‐free triplet–triplet annihilation upconversion (TTA‐UC) is presented. The method is demonstrated by in vivo titration of the photorelease of an anticancer prodrug. This new TTA system has robust brightness and the longest anti‐Stokes shift of any reported TTA system. TTA core–shell‐structured prodrug delivery capsules that benefit from these properties were developed; they can operate with low‐power density far‐red light‐emitting diode light. These capsules contain mesoporous silica nanoparticles preloaded with TTA molecules as the core, and amphiphilic polymers encapsulating anticancer prodrug molecules as the shell. When stimulated by far‐red light, the intense TTA upconversion blue emission in the system activates the anticancer prodrug molecules and shows effective tumor growth inhibition in vivo. This work paves the way to new organic TTA upconversion techniques that are applicable to in vivo photocontrollable drug release and other biophotonic applications.     

Photothermal Welding,Melting, and Patterned Expansion of Nonwoven Mats of Polymer Nanofibers for Biomedical and Printing Applications

We report a simple method for the photothermal welding of nonwoven mats of electrospun nanofibers by introducing a near‐infrared (NIR) dye such as indocyanine green. By leveraging the strong photothermal effect of the dye, the nanofibers can be readily welded at their cross points or even over‐welded (i.e., melted and/or fused together) to transform the porous mat into a solid film upon exposure to a NIR laser. While welding at the cross points greatly improves the mechanical strength of a nonwoven mat of nanofibers, melting and fusion of the nanofibers can be employed to fabricate a novel class of photothermal papers for laser writing or printing without chemicals or toner particles. By using a photomask, we can integrate photothermal welding with the gas foaming technique to pattern and then expand nonwoven mats into 3D scaffolds with well‐defined structures. This method can be applied to different combinations of polymers and dyes, if they can be co‐dissolved in a suitable solvent for electrospinning.     

Exploring meso-/microporous composite molecular sieves with core-shell structures

A series of core–shell‐structured composite molecular sieves comprising zeolite single crystals (i.e., ZSM‐5) as a core and ordered mesoporous silica as a shell were synthesized by means of a surfactant‐directed sol–gel process in basic medium by using cetyltrimethylammonium bromide (CTAB) as a template and tetraethylorthosilicate (TEOS) as silica precursor. Through this coating method, uniform mesoporous silica shells closely grow around the anisotropic zeolite single crystals, the shell thickness of which can easily be tuned in the range of 15–100 nm by changing the ratio of TEOS/zeolite. The obtained composite molecular sieves have compact meso‐/micropore junctions that form a hierarchical pore structure from ordered mesopore channels (2.4–3.0 nm in diameter) to zeolite micropores (≈0.51 nm). The short‐time kinetic diffusion efficiency of benzene molecules within pristine ZSM‐5 (≈7.88×10^?19 m² s^?1) is almost retainable after covering with 75 nm‐thick mesoporous silica shells (≈7.25×10^?19 m² s^?1), which reflects the greatly opened junctions between closely connected mesopores (shell) and micropores (core). The core–shell composite shows greatly enhanced adsorption capacity (≈1.35 mmol g^?1) for large molecules such as 1,3,5‐triisopropylbenzene relative to that of pristine ZSM‐5 (≈0.4 mmol g^?1) owing to the mesoporous silica shells. When Al species are introduced during the coating process, the core–shell composite molecular sieves demonstrate a graded acidity distribution from weak acidity of mesopores (predominant Lewis acid sites) to accessible strong acidity of zeolite cores (Lewis and Brønsted acid sites). The probe catalytic cracking reaction of n‐dodecane shows the superiority of the unique core–shell structure over pristine ZSM‐5. Insight into the core–shell composite structure with hierarchical pore and graded acidity distribution show great potential for petroleum catalytic processes.     

Core–Shell Crystals of Porous Organic Cages

The first examples of core–shell porous molecular crystals are described. The physical properties of the core–shell crystals, such as surface hydrophobicity, CO₂ /CH₄ selectivity, are controlled by the chemical composition of the shell. This shows that porous core–shell molecular crystals can exhibit synergistic properties that out‐perform materials built from the individual, constituent molecules.     

Photothermal Welding,Melting, and Patterned Expansion of Nonwoven Mats of Polymer Nanofibers for Biomedical and Printing Applications

We report a simple method for the photothermal welding of nonwoven mats of electrospun nanofibers by introducing a near‐infrared (NIR) dye such as indocyanine green. By leveraging the strong photothermal effect of the dye, the nanofibers can be readily welded at their cross points or even over‐welded (i.e., melted and/or fused together) to transform the porous mat into a solid film upon exposure to a NIR laser. While welding at the cross points greatly improves the mechanical strength of a nonwoven mat of nanofibers, melting and fusion of the nanofibers can be employed to fabricate a novel class of photothermal papers for laser writing or printing without chemicals or toner particles. By using a photomask, we can integrate photothermal welding with the gas foaming technique to pattern and then expand nonwoven mats into 3D scaffolds with well‐defined structures. This method can be applied to different combinations of polymers and dyes, if they can be co‐dissolved in a suitable solvent for electrospinning.     

Hyaluronic Acid (HA)‐Based Silk Fibroin/Zinc Oxide Core–Shell Electrospun Dressing for Burn Wound Management

Burn injuries represent a major life‐threatening event that impacts the quality of life of patients, and places enormous demands on the global healthcare systems. This study introduces the fabrication and characterization of a novel wound dressing made of core–shell hyaluronic acid–silk fibroin/zinc oxide (ZO) nanofibers for treatment of burn injuries. The core–shell configuration enables loading ZO—an antibacterial agent—in the core of nanofibers, which in return improves the sustained release of the drug and maintains its bioactivity. Successful formation of core–shell nanofibers and loading of zinc oxide are confirmed by transmission electron microscopy, Fourier‐transform infrared spectroscopy, and energy dispersive X‐ray. The antibacterial activity of the dressings are examined against Escherichia coli and Staphylococcus aureus and it is shown that addition of ZO improves the antibacterial property of the dressing in a dose‐dependent fashion. However, in vitro cytotoxicity studies show that high concentration of ZO (>3 wt%) is toxic to the cells. In vivo studies indicate that the wound dressings loaded with ZO (3 wt%) substantially improves the wound healing procedure and significantly reduces the inflammatory response at the wound site. Overall, the dressing introduced herein holds great promise for the management of burn injuries.     

Aggregation-induced emission of siloles

Aggregation-induced emission (AIE) is a unique and significant photophysical phenomenon that differs greatly from the commonly acknowledged aggregation-caused emission quenching observed for many π-conjugated planar chromophores. The mechanistic decipherment of the AIE phenomenon is of high importance for the advance of new AIE systems and exploitation of their potential applications. Propeller-like 2,3,4,5-tetraphenylsiloles are archetypal AIE-active luminogens, and have been adopted as a core part in the design of numerous luminescent materials with diverse functionalities. In this review article, we elucidate the impacts of substituents on the AIE activity and shed light on the structure–property relationship of siloles, with the aim of promoting the judicious design of AIE-active functional materials in the future. Recent representative advances of new silole-based functional materials and their potential applications are reviewed as well.     

Popcorn‐Shaped Magnetic Core–Plasmonic Shell Multifunctional Nanoparticles for the Targeted Magnetic Separation and Enrichment,Label‐Free SERS Imaging,and Photothermal Destruction of Multidrug‐Resistant Bacteria

Over the last few years, one of the most important and complex problems facing our society is treating infectious diseases caused by multidrug‐resistant bacteria (MDRB), by using current market‐existing antibiotics. Driven by this need, we report for the first time the development of the multifunctional popcorn‐shaped iron magnetic core–gold plasmonic shell nanotechnology‐driven approach for targeted magnetic separation and enrichment, label‐free surface‐enhanced Raman spectroscopy (SERS) detection, and the selective photothermal destruction of MDR Salmonella DT104. Due to the presence of the “lightning‐rod effect”, the core–shell popcorn‐shaped gold‐nanoparticle tips provided a huge field of SERS enhancement. The experimental data show that the M3038 antibody‐conjugated nanoparticles can be used for targeted separation and SERS imaging of MDR Salmonella DT104. A targeted photothermal‐lysis experiment, by using 670 nm light at 1.5 W cm^?2 for 10 min, results in selective and irreparable cellular‐damage to MDR Salmonella. We discuss the possible mechanism and operating principle for the targeted separation, label‐free SERS imaging, and photothermal destruction of MDRB by using the popcorn‐shaped magnetic/plasmonic nanotechnology.     

Lanthanide‐Doped Nanocrystals: Strategies for Improving the Efficiency of Upconversion Emission and Their Physical Understanding

The fundamental understanding of lanthanide‐doped upconverted nanocrystals remains a frontier area of research because of potential applications in photonics and biophotonics. Recent studies have revealed that upconversion luminescence dynamics depend on host crystal structure, size of the nanocrystals, dopant concentration, and core–shell structures, which influence site symmetry and the distribution and energy migration of the dopant ions. In this review, we bring to light the influences of doping/co‐doping concentration, crystal phase, crystal size of the host, and core–shell structure on the efficiency of upconversion emission. Furthermore, the lattice strain, due to a change in the crystal phase and by the core–shell structure, strongly influences the upconversion emission intensity. Analysis suggests that the local environment of the ion plays the most significant role in modification of radiative and nonradiative relaxation mechanisms of overall upconversion emission properties. Finally, an outlook on the prospects of this research field is given.     

Solution‐blown nylon 6–chitosan core–shell nanofiber for highly efficient affinity adsorption

A facile spinning‐based strategy was developed to fabricate chitosan (CS) surface nanofiber‐based affinity membranes for protein adsorption. The core–shell nanofiber mat of nylon 6–CS was prepared via coaxial solution blowing process. The nanofibers have a diameter range of 60–300 nm. The core–shell structure was confirmed by transmission electron microscopy, and CS was observed as a thin layer that uniformly adhered to the core. The dye ligand of cibacron blue F3GA (CB F3GA) was further covalently immobilized on the nanofibers with a content of 425 µmol/g. The pristine and CB F3GA‐attached mats were studied in protein adsorption. High bovine serum albumin adsorption capacities of 91.9 and 219.6 mg/g were obtained for pristine and CB F3GA‐attached mats, respectively. Given its properties of high flux rate and low pressure drop, CB F3GA‐attached nylon 6–CS nanofiber mat meets the requirements of highly effective affinity membrane chromatography. Copyright © 2016 John Wiley & Sons, Ltd.     

Surface‐State‐Mediated Charge‐Transfer Dynamics in CdTe/CdSe Core–Shell Quantum Dots

Herein, we report the synthesis of aqueous CdTe/CdSe type‐II core–shell quantum dots (QDs) in which 3‐mercaptopropionic acid is used as the capping agent. The CdTe QDs and CdTe/CdSe core–shell QDs are characterized by X‐ray diffraction (XRD), high‐resolution transmission electron microscopy (HR‐TEM), steady‐state absorption, and emission spectroscopy. A red shift in the steady‐state absorption and emission bands is observed with increasing CdSe shell thickness over CdTe QDs. The XRD pattern indicates that the peaks are shifted to higher angles after growth of the CdSe shell on the CdTe QDs. HR‐TEM images of both CdTe and CdTe/CdSe QDs indicate that the particles are spherical, with a good shape homogeneity, and that the particle size increases by about 2 nm after shell formation. In the time‐resolved emission studies, we observe that the average emission lifetime (τ_av) increases to 23.5 ns for CdTe/CdSe (for the thickest shell) as compared to CdTe QDs (τ_av=12 ns). The twofold increment in the average emission lifetime indicates an efficient charge separation in type‐II CdTe/CdSe core–shell QDs. Transient absorption studies suggest that both the carrier cooling and the charge‐transfer dynamics are affected by the presence of traps in the CdTe QDs and CdTe/CdSe core–shell QDs. Carrier quenching experiments indicate that hole traps strongly affect the carrier cooling dynamics in CdTe/CdSe core–shell QDs.