AbstractWhile reloadable drug delivery platforms are highly prized for the treatment of a broad spectrum of diseases, the gel–gel interface between hydrogels hinders the intergel diffusive transport of drugs and thus limits the application of hydrogels as reloadable depots. Here, this study reports the circumvention of this barrier by employing a self-healing hydrogel prepared from N-carboxyethyl chitosan and sodium alginate dialdehyde, which are cross-linked via a reversible Schiff base linkage. The injectable and bioadhesive hydrogel shows a rapid gelation time of 47 s. The dynamic self-healing process enables the efficient diffusive transport of carbon quantum dots (C-dots) into an adjacent hydrogel, and thus, the C-dots can be used to scavenge reactive oxygen species from a remote inflammation site. Specifically, the diffusive transport of the C-dots in the self-healing hydrogel after three sequential reloading steps is sevenfold greater than that in the non-self-healing counterpart. In vivo, hematoxylin and eosin staining of the murine skin at the injection site shows no apparent symptoms of inflammation in the group treated with the reloadable self-healing hydrogel. The current strategy represents a promising and straightforward route for the design of a reloadable drug delivery system for future use in clinical application.

Highly uniform core–shell polypyrrole@carbon microspheres (PPy@CM) have been successfully constructed by oxidation polymerization of pyrrole as the shell on the core of carbon microspheres. The thickness of the PPy shell can be easily controlled by modulating the weight ratio of pyrrole monomer and carbon microspheres. Hydrophilic carbon microspheres with abundant hydroxyl groups have a very strong affinity to the conjugated chains of PPy, which is responsible for the spontaneous formation of the uniform core–shell structure. Coating the PPy shell on the carbon core could increase the complex permittivity and dielectric loss due to an additional interfacial polarization. With a proper thickness of the PPy shells, the improved dielectric loss would be induced. The microwave absorbing properties of the PPy@CM powders were investigated by dispersing them in paraffin wax with 40 wt% powders in the frequency range of 2–18 GHz. The PPy@CM-0.6 (0.6 g CM) sample exhibits the maximum reflection loss of −38.1 dB at 11.6 GHz and a bandwidth of less than −10 dB covering 11.17 to 12.26 GHz with the thickness of 3 mm. In addition, the absorption peak sites and bandwidth of the PPy@CM composites can be easily modulated not only by the thickness of the absorbers but also of the PPy shell of the PPy@CM composite. Thus, the PPy@CM composites can be considered as a new type of promising lightweight microwave absorbers to satisfy the applications of microwave absorption in the 8–18 GHz range.

To solve the growing pollution issues, it is a promising alternative to develop efficient sunlight-driven photocatalysts for purifying organic wastewater. Herein, we report a new and efficient full-spectrum-responsive photocatalyst composed of Bi2S3 nanotubes incorporated with carbon quantum dots (C-dots) for rapidly degrading methylene blue (MB) and tetracycline hydrochloride (TC). Compared with naked Bi2S3 nanotubes, the as-prepared Bi2S3/C-dot nanohybrids show a remarkably higher photocatalytic efficiency for degrading MB or TC under ultraviolet (UV-), visible (vis-) and near-infrared (NIR-) light irradiation within 5 minutes. A possible mechanism is proposed for the enhanced photocatalytic activity of the Bi2S3/C-dot nanohybrids. A lower band gap as well as a wider absorbance in the UV-, vis- and NIR-regions can increase the light harvesting ability of the Bi2S3/C-dots. Meanwhile, the existence of C-dots can facilitate the charge separation of the photo-generated electron/hole pairs while electrons transfer from Bi2S3 to C-dots. Besides, an increased surface area of the Bi2S3/C-dot nanohybrids also contributes to the excellent photocatalytic activity.

We report on a novel Cu2+-complex of nitrogen-rich polymer dots for magnetic resonance imaging (MRI). The N-rich polymer dots are prepared from N-vinyl imidazole (VIm) by a one-pot hydrothermal synthesis at 220 °C (24 h) and used later on to fabricate a Cu2+-PVIm dot complex via efficient incorporation of Cu2+ into aqueous medium. The obtained Cu2+-PVIm dot complexes display relaxivity (r1 = 1.05 mM−1 s−1) two times higher than Cu2+ in aqueous solution (r1 = 0.43 mM−1 s−1) and three times higher than Cu2+ in aqueous solution coordinated with VIm monomers (r1 = 0.32 mM−1 s−1), which show a remarkable contrast enhancement for T1-weighted MRI while efficiently labeling MCF-7 cells and other biomedical applications.

•An efficient method is developed to obtain CDs with strong and stable photoluminescence.•Fluorescent carbon dots (CDs) were attached to CDs@PCL hybrids with excellent biocompatibility and biodegradability.•The CDs@PCL hybrids have a promising future in biomedicine, photocatalyst, bioimaging, and environmental analysis.In this paper, the environment-friendly, water-soluble carbon dots (CDs) with stable photoluminescence (PL) have been prepared via the one-step pyrolysis of lotus leaf. Then the as-prepared CDs containing abundant hydroxylic and carboxylic groups were employed as cocatalyst with tartaric acid (TA) in ring-opening polymerization (ROP) of ε-caprolactone (ε-CL). The low-toxic organic acid TA, as main catalyst, was used to catalyze the ROP of ε-CL efficiently. The fluorescent CDs@PCL hybrids were obviously hydrophobic and they exhibited an excellent biocompatibility, and biodegradability due to the existence of PCL. Therefore the hydrophobic, biodegradable and multi-color fluorescent CDs@PCL hybrids may have potential applications in biomedicine, photocatalyst, bioimaging, and environmental analysis. Furthermore the application of CDs in catalyzing and initiating polymerization reaction will exemplify the versatility of CDs in the most unexpected fields.

A hybrid featuring the CuInS2 quantum dots (CuInS2-QDs) on reduced graphene oxide (rGO) sheets is synthesized by a facile one-pot solvothermal approach with thiourea as S source, in which graphene oxide (GO) sheets are reduced into rGO sheets in course of the CuInS2-QDs aggregate growth. The growth mechanism of the hybrid is elucidated. It is found that adsorption of Cu2+ cations mainly takes place at epoxy/hydroxyl groups on GO sheets at room temperature and the adsorbed Cu+ cations resulting from the Cu2+ reduction at solvothermal temperature act as the nucleation for the surface growth of CuInS2-QDs into three-dimensional aggregates on GO sheets that are simultaneously reduced into rGO sheets. Our results demonstrate that the rGO/CuInS2-QDs hybrid is an effective electron acceptor with a complementary absorption property for polymer-based solar cells. The solar cells based on rGO/CuInS2-QDs hybrid and poly(1-methoxy-4-(2-ethylhexyloxy)-p-phenylene vinylene) exhibit an efficiency of 1.5%, much higher than the counterpart devices of rGO sheets. The effects of CuInS2-QDs aggregates on device performance are discussed. In the long run, this work provides a potential hybrid electron acceptor for low-cost and efficient solar cell fabrication.

•An efficient method is developed to obtain magnetic Fe3O4 NTs/PANI hybrids with PANI coating on the Fe3O4 NTs.•2. Fluorescent CDs were attached to Fe3O4 NTs/PANI hybrids and π–π interaction enhances SERS properties.•The multifunctional Fe3O4 NTs/PANI/CDs/Ag hybrids have a promising future as a recyclable photocatalyst.In this paper, the stable and environment-friendly Fe3O4 nanotubes with polyaniline (Fe3O4 NTs/PANI hybrids) have been prepared via mesoporous anodic alumina oxide (AAO) template, sol–gel method and in-situ polymerization. Then multifunctional Fe3O4 NTs/PANI/Ag hybrids have been obtained by decorating Ag nanoparticles by glucose reduction on surface of Fe3O4 NTs/PANI hybrids. The morphologies and structures of these hybrids were subsequently investigated by SEM, XRD, TEM and XPS measurements. The Fe3O4 NTs/PANI/Ag hybrids presented high catalytic activity due to the template-assisted presence, preventing Ag particulate agglomeration. Importantly, the Fe3O4 NTs/PANI/Ag hybrids achieve sensitive surface-enhanced Raman scattering (SERS) signals. Furthermore, the introduction of carbon dots (CDs) endows these hybrids good dispersion and stable photoluminescence (PL). Therefore, the obtained hybrids may have potential applications in waste water treatment, biomedicine, photocatalyst, and environmental analysis.

Horseradish peroxidase-immobilized magnetic mesoporous silica nanoparticles (MMSNs–HRP) have been synthesized by a NHS/EDC coupling between the amino groups of horseradish peroxidase (HRP) and the carboxyl groups on the MMSNs surface. It is found that the immobilized HRP on MMSNs still retain high activity and the MMSNs–HRP can eliminate the reactive oxygen species (ROS) in Chinese hamster ovary (CHO) cells induced by the addition of H2O2 aqueous solution. Further, the fluorescent MMSN–HRP–CD nanoparticles have been prepared by attaching biocompatible, fluorescent carbon dots (CDs) to MMSNs–HRP. We have also investigated the effect of an applied magnetic field on cellular uptake of MMSNs–HRP–CDs and found that the internalization of MMSNs–HRP–CDs by CHO cells could be enhanced within 2 hours under the magnetic field. This work provides us with a novel and efficient method to eliminate ROS in living cells by using HRP-immobilized nanoparticles.

In this study, a biocompatible nanoplatform has been constructed on the basis of magnetic mesoporous silica nanoparticles (Fe3O4@mSiO2) via surface modification of triphenylphospine (TPP) and then conjugation with fluorescent carbon dots (CDs). The as-prepared Fe3O4@mSiO2–TPP/CDs nanoplatform shows a very low cytotoxicity and apoptosis rate in various cell lines such as A549, CHO, HeLa, SH-SY5Y, HFF, and HMEC-1. More importantly, this nanoplatform integrates long time cell imaging, mitochondria-targeting, and magnetic field-enhanced cellular uptake functionalities into an all-in-one system. Time-dependent mitochondrial colocalization in all of the cell lines has been proved by using confocal laser scanning microscopy and flow cytometry, while the multicolored fluorescence of the Fe3O4@mSiO2–TPP/CDs could remain bright and stable after coincubation for 24 h. In addition, the cellular uptake efficiency could be enhanced in a short time as a static magnetic field of 0.30 T was applied to the coincubation system of A549 and HFF cell lines. This bionanoplatform may have potential applications in targeted drug delivery for mitochondria diseases as well as early cancer diagnosis and treatment.Keywords: bioimaging; carbon dots; cellular uptake; magnetic field; mitochondrial targeting; nanoplatform;

Highly nitrogen-doped carbon dots (N-CDs) are prepared by the pyrolysis of konjac flour under mild conditions followed with a simple extraction by ethanol and water. The N-CDs exhibit excellent pH-switched photoluminescence (PL), and their PL intensity can be facilitated by either mixing with NaOH and basic amino acids or by surface passivation with non-amine-terminated polyethylene glycols of different molecular weights. Further, the fluorescence of N-CDs can be quenched with Fe3+ and recovered with L-lysine, accompanied with a red-shift of emission wavelength. In addition, the low toxicity and strongly fluorescent N-CDs are applied for cell imaging, and the quenched fluorescence by Fe3+ can be recovered inside the living cells.

We report a facile and scalable synthesis of ultra-long (>100 μm) nanoribbons based on self-assembly of positively charged carbon dots (C-dots) and anionic oligomers of styrene and 4-styrenesulfonate (PS-PSS) in a mixture of ethanol and water (4/1, v/v). The obtained hybrid (PS-PSS)/C-dot nanoribbons show a multi-colored fluorescence and an electrical conductivity of 3.368 S m−1.

•PANI/ferrocene/C-dots nanocomposite was synthesized for the first time.•The microwave absorption of PANI/ferrocene/C-dots is enhanced because of C-dots.•The small size and quantum effect of C-dots lead to strong interfacial polarization.PANI/ferrocene/C-dots nanocomposite with a prominent microwave absorption property was synthesized by in situ polymerization of PANI/ferrocene and then incorporation of C-dots. The results of 1H NMR and fluorescence spectra indicate that ferrocene has doped into backbone of PANI while C-dots combined with PANI and ferrocene via π-π interactions. The microwave absorption of PANI/ferrocene/C-dots is remarkably enhanced compared to those of PANI and PANI/ferrocene due to the inclusion of C-dots with very small size and thus high ratio of surface atomic and interfacial polarization.

FeSiAl alloy powders in an irregular shape mixed with graphite were ball-milled for 24 h to achieve flake-shaped FeSiAl/graphite composites. The size of the milled composite particles is in the range of 5–40 μm with the average thickness less than 1 μm. The complex permittivity (ε′ − jε″) and permeability (μ′ − jμ″) are measured by using the transmission/reflection method in the frequency range of 2–18 GHz. Compared to the raw irregular-shaped FeSiAl, the complex permittivity (ε′ and ε″) of the milled composites are greatly enhanced as the weight ratio of graphite in the composite samples increases. For milled FeSiAl/graphite (weight ratio of 8:2) composites absorber with a coating layer thickness of 3 mm, the reflection loss reaches a minimum of −21.0 dB at 6.7 GHz with −10 dB bandwidth of 2.0 GHz. The microwave absorption is significantly enhanced as the weight ratio of graphite in the FeSiAl/graphite composite increases from 10% (9:1) to 20% (8:2). Moreover, the absorption bandwidth with reflection loss exceeding −10 dB can reach up to 2.4 GHz with the coating thickness only of 1.5 mm, and the absorption frequency range can be tuned easily by varying the coating thickness. The results indicate that the milled flake-shaped FeSiAl/graphite composites can be potential microwave absorbers in the higher GHz range compared with those of raw FeSiAl and milled FeSiAl absorbers.Highlights► Flake-shaped FeSiAl/graphite composites were prepared by the ball milling method. ► The simulated RL data were compared to those from the experimental one-port technique. ► Microwave absorption properties have been greatly enhanced in higher GHz frequency. ► The band width of 2.4 GHz (RL > −10 dB) was obtained with the thickness only of 1.5 mm. ► The absorption frequency range can be tuned easily by varying the thickness.

Polyaniline/graphene oxide (PANI/GO) composites in a novel structure consisting of PANI nanoparticles covered by GO nanosheets are synthesized by means of Pickering emulsion polymerization for the first time. The Fourier transform infrared (FTIR) spectra indicate the main combination mode of the PANI/GO composite includes hydrogen bonding and π–π interactions between PANI and GO. The TGA and SEM results indicate the PANI/GO composite has better morphology stability than that of pure PANI. And thus the specific capacitance and cycling stability of the PANI/GO composite have been remarkably enhanced. The improved electrochemical performance may be attributed to the GO sheets not only improve the stability of the PANI nanoparticles, but also increase electronic conductivity and reduce electrical charge transfer resistance of the PANI/GO electrode.Research highlights► The PANI/GO composite was prepared via Pickering emulsion polymerization. ► The composites consist of PANI nanoparticles covered by GO nanosheets. ► The GO sheets prevent the PANI nanoparticles from swelling and shrinking. ► The GO sheets increase electronic conductivity and reduce internal resistance. ► The composites exhibit higher specific capacitance and better cycling stability.

Highly crystalline and ferromagnetic γ-Fe2O3 nanocrystallites were prepared by controlled oxidative co-decomposition of PEG 6000 and ferrocene at a temperature of 450 ∘C under air atmosphere. The morphology, crystalline structure and preliminary magnetic properties of the as-synthesized nanocrystallites have been characterized by using transmission electron microscope (TEM), X-ray powder diffraction (XRD) and vibrating sample magnetometer (VSM). The highly crystalline γ-Fe2O3 nanocrystallites are in quasi-cubic shape with an average size of 30 nm and exhibit room-temperature ferromagnetism. The capping effect of PEG 6000 has also been investigated by thermogravimetry analysis (TGA) and Fourier transform infrared (FTIR) regarding controlling the size of the nanocrystallites and preventing the volatilization of ferrocene and thus raising the yield of the products. This simple method has a high yield of over 80% as well as low cost.

Polyanilines doped with (HCl + KCl) and (HCl + CoCl2) were prepared by co-doping method, respectively. For comparison, polyaniline emeraldine salt (ES) by doping with HCl and its emeraldine base (EB) form were also synthesized. The co-doped polyanilines, ES and EB samples were all characterized by Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy aiming to understand the transformations in the different doping status. The results show that the doping degree of K+ ions is considerably higher than that of Co2+ ions under the same co-doping conditions possibly due to different pseudoprotonation constants of EB with K+ ions and Co2+ ions. Moreover, morphology difference of polyaniline co-doped with alkaline metal ions or transition meal ions may arise from different coordination geometry of metal ions. Nevertheless, there are similar chemical transformations of quinoid units to benzenoid ones on polyaniline backbones for the ES and both co-doped samples. And the polyaniline backbones co-doped with H+ and metal cations are found to attain weaker charge delocalization than the ES which is doped solely with H+.

Nickel nanowires (Ni NWs) have great potential to be used as a living cell manipulation tool and developed into an anticancer agent. However, their candidacy as biomedical appliances need detailed human cell studies, such as study of the interaction between Ni NWs and tumor cells. The present study investigated the cytotoxicity of Ni NWs in HeLa cells. A dose-dependent inhibition of cell growth was observed by using the MTT assay. We demonstrated that Ni NWs induced oxidative stress by generation of reactive oxygen species (ROS). Apoptosis induction was evidenced by flow cytometry, annexin V binding assay and DAPI staining. DNA flow cytometric analysis indicated that Ni NWs significantly increased the percentages of cells in S phase compared with control cells. This process was accompanied by the loss of mitochondrial membrane potential. These results revealed that Ni NWs induced apoptosis in HeLa cells via ROS generation and cell cycle arrest.

We report a facile and scalable synthesis of ultra-long (>100 μm) nanoribbons based on self-assembly of positively charged carbon dots (C-dots) and anionic oligomers of styrene and 4-styrenesulfonate (PS-PSS) in a mixture of ethanol and water (4/1, v/v). The obtained hybrid (PS-PSS)/C-dot nanoribbons show a multi-colored fluorescence and an electrical conductivity of 3.368 S m−1.

Highly nitrogen-doped carbon dots (N-CDs) are prepared by the pyrolysis of konjac flour under mild conditions followed with a simple extraction by ethanol and water. The N-CDs exhibit excellent pH-switched photoluminescence (PL), and their PL intensity can be facilitated by either mixing with NaOH and basic amino acids or by surface passivation with non-amine-terminated polyethylene glycols of different molecular weights. Further, the fluorescence of N-CDs can be quenched with Fe3+ and recovered with L-lysine, accompanied with a red-shift of emission wavelength. In addition, the low toxicity and strongly fluorescent N-CDs are applied for cell imaging, and the quenched fluorescence by Fe3+ can be recovered inside the living cells.