- Excitation and phase transitions of spin density waves in graphene nanoribbons. [Journal Article]
- JPJ Phys Condens Matter 2019 Jul 17
- Anti-ferromagnetic states widely exist on graphene zigzag edges. Our previous work (Xie H, Gao J H and Han D Z, New Journal of Physics, 2018, 20(1): 013035) shows there are also various spin density …
Anti-ferromagnetic states widely exist on graphene zigzag edges. Our previous work (Xie H, Gao J H and Han D Z, New Journal of Physics, 2018, 20(1): 013035) shows there are also various spin density wave (SDW) states in the graphene nanoribbons (GNR). In this paper, we propose some excitation mechanism of these SDW by the absorbed magnetic atoms with the mean-field Hubbard model and the first-principles calculations. With the Floquet theory, we also find that by regulating the temperature or the light intensity, there are a lot of phase transitions for these SDW. The temperature or light can dramatically modify the inter-edge coupling or the spin stiffness of GNR. The artificial magnetization technique is employed to explore the establishment process of these SDW states. Some interesting intermedia phase transitions and the corresponding spin orders are discovered. This research may be helpful in the understandings and technique controls of magnetic orders in future nano magnetic devices.
- Depth-Resolved Enhanced Spectral-Domain OCT Imaging of Live Mammalian Embryos Using Gold Nanoparticles as Contrast Agent. [Journal Article]
- SSmall 2019 Jul 15; :e1902346
- High-resolution and real-time visualization of the morphological changes during embryonic development are critical for studying congenital anomalies. Optical coherence tomography (OCT) has been used …
High-resolution and real-time visualization of the morphological changes during embryonic development are critical for studying congenital anomalies. Optical coherence tomography (OCT) has been used to investigate the process of embryogenesis. However, the structural visibility of the embryo is decreased with the depth due to signal roll-off and high light scattering. To overcome these obstacles, in this study, combined is a spectral-domain OCT (SD-OCT) with gold nanorods (GNRs) for 2D/3D imaging of live mouse embryos. Inductively coupled plasma mass spectrometry is used to confirm that GNRs can be effectively delivered to the embryos during ex vivo culture. OCT signal, image contrast, and penetration depth are all enhanced on the embryos with GNRs. These results show that after GNR treatment, more accurate spatial localization and better contrasting of the borders among organs can be observed on E9.5 and E10.5 mouse embryos. Furthermore, the strong optical absorbance of GNRs results in much clearer 3D images of the embryos, which can be used for calculating the heart areas and volumes of E9.5 and E10.5 embryos. These findings provide a promising strategy for monitoring organ development and detecting congenital structural abnormalities in mice.
- Laser illumination-induced dramatic catalytic activity change on Au nanospheres. [Journal Article]
- CSChem Sci 2019 Jun 14; 10(22):5793-5800
- Understanding morphology dependent catalytic kinetics from a single nanoparticle plays a significant role in the development of robust nano-catalysts with high efficiency. Unfortunately, detailed kno…
Understanding morphology dependent catalytic kinetics from a single nanoparticle plays a significant role in the development of robust nano-catalysts with high efficiency. Unfortunately, detailed knowledge of the morphology dependent catalytic properties of single nanoparticles after shape transitions is lacking. In this work, the distinct catalytic properties of a single gold nanoparticle (GNP) after symmetry breaking were disclosed at the single-particle level for the first time. The morphology of the spherical GNP was elongated into a rod shape (i.e., gold nanorod, GNR) with a tightly focused Gaussian laser beam based on the photothermal effect. By using the fluorogenic oxidation reaction (i.e., amplex red to resorufin) as a model reaction, noticeable variation in catalytic efficiency after the shape modulation process was found at the single-particle level. The GNP displays noticeably higher catalytic efficiency which might be ascribed to the heterogeneous lattice structure on the particle surface as confirmed by transmission electron microscopy (TEM) characterization. Rearrangement of surface atoms after shape modulation normally generates a more ordered crystal structure, resulting in a lower surface energy for catalytic reaction. However, both of these nanoparticles still exhibit dynamic activity fluctuation in a temporal dependent route, indicating a distinct spontaneous dynamic surface restructuring process. These kinetic evidences might facilitate the development nanoparticle-based heterogeneous catalysts, particularly based on the morphology effect.
- Single-Cell Detection and Photostimulation on a Microfluidic Chip Aided with Gold Nanorods. [Journal Article]
- CCytometry A 2019 Jul 07
- Gold nanorods (GNRs) can be easily designed and synthesized to respond to photons in the near infrared (NIR) band. The photostimulation by laser irradiation can be mediated and enhanced by GNRs to in…
Gold nanorods (GNRs) can be easily designed and synthesized to respond to photons in the near infrared (NIR) band. The photostimulation by laser irradiation can be mediated and enhanced by GNRs to introduce localized damage to cells for photodynamic/photothermal therapy (PDT or PTT). In this study, we show that cells stained with GNRs can be detected and stimulated simultaneously by short flashes of femtosecond-laser irradiation on a microfluidic system effectively. In the relatively high-throughput cell flow, the two-photon luminescence from GNRs can be excited and detected. The GNRs also mediate and enhance the transient photostimulation of the cells. After photostimulation, cells can remain alive, go to apoptosis, or necrosis, respectively. The stimulation effect is strongly dependent on the photon density and stimulation duration. We found the cells remain alive, go to apoptosis or necrosis, dependent on the GNR staining, the laser illumination pattern and duration. Hence, our system provides a simple and effective method for high-throughput cell stimulation and analysis on chip. © 2019 International Society for Advancement of Cytometry.
- Flame Retardancy and Toughness of Poly(Lactic Acid)/GNR/SiAHP Composites. [Journal Article]
- PPolymers (Basel) 2019 Jul 03; 11(7)
- A novel flame-retardant and toughened bio-based poly(lactic acid) (PLA)/glycidyl methacrylate-grafted natural rubber (GNR) composite was fabricated by sequentially dynamical vulcanizing and reactive …
A novel flame-retardant and toughened bio-based poly(lactic acid) (PLA)/glycidyl methacrylate-grafted natural rubber (GNR) composite was fabricated by sequentially dynamical vulcanizing and reactive melt-blending. The surface modification of aluminum hypophosphite (AHP) enhanced the interfacial compatibility between the modified aluminum hypophosphite by silane (SiAHP) and PLA/GNR matrix and the charring ability of the PLA/GNR/SiAHP composites to a certain extent, and the toughness and flame retardancy of the PLA/GNR/SiAHP composites were slightly higher than those of PLA/GNR/AHP composites, respectively. The notched impact strength and elongation of the PLA composite with 20 wt. %GNR and 18 wt.% SiAHP were 13.1 kJ/m2 and 72%, approximately 385% and 17 fold higher than those of PLA, respectively, and its limiting oxygen index increased to 26.5% and a UL-94 V-0 rating was achieved. Notedly, the very serious melt-dripping characteristics of PLA during combustion was completely suppressed. The peak heat release rate and total heat release values of the PLA/GNR/SiAHP composites dramatically reduced, and the char yield obviously increased with an increasing SiAHP content in the cone calorimeter test. The good flame retardancy of the PLA/GNR/SiAHP composites was suggested to be the result of a synergistic effect involving gaseous and condensed phase flame-retardant mechanisms. The high-performance flame-retardant PLA/GNR/SiAHP composites have great potential application as replacements for petroleum-based polymers in the automotive interior and building fields.
- Tunable Superstructures of Dendronized Graphene Nanoribbons in Liquid Phase. [Journal Article]
- JAJ Am Chem Soc 2019 Jul 17; 141(28):10972-10977
- In this Communication, we report the first synthesis of structurally well-defined graphene nanoribbons (GNRs) functionalized with dendritic polymers. The resultant GNRs possess grafting ratios of 0.5…
In this Communication, we report the first synthesis of structurally well-defined graphene nanoribbons (GNRs) functionalized with dendritic polymers. The resultant GNRs possess grafting ratios of 0.59-0.68 for the dendrons of different generations. Remarkably, the precise 3D branched conformation of the grafted dendrons affords the GNRs unprecedented 1D supramolecular self-assembly behavior in tetrahydrofuran (THF), yielding nanowires, helices and nanofibers depending on the dimension of the dendrons. The GNR superstructures in THF exhibit near-infrared absorption with maxima between 650 and 700 nm, yielding an optical bandgap of 1.2-1.3 eV. Ultrafast photoconductivity analyses unveil that the helical structures exhibit the longest free carrier (3.5 ps) and exciton lifetime (several hundred ps) among the three superstructure systems. This study opens pathways for tunable construction of ordered GNR superstructures with promising optoelectronic applications.
- Templated Synthesis of End-Functionalized Graphene Nanoribbons through Living Ring-Opening Alkyne Metathesis Polymerization. [Journal Article]
- JAJ Am Chem Soc 2019 Jul 17; 141(28):11050-11058
- Atomically precise bottom-up synthesized graphene nanoribbons (GNRs) are promising candidates for next-generation electronic materials. The incorporation of these highly tunable semiconductors into c…
Atomically precise bottom-up synthesized graphene nanoribbons (GNRs) are promising candidates for next-generation electronic materials. The incorporation of these highly tunable semiconductors into complex device architectures requires the development of synthetic tools that provide control over the absolute length, the sequence, and the end groups of GNRs. Here, we report the living chain-growth synthesis of chevron-type GNRs (cGNRs) templated by a poly-(arylene ethynylene) precursor prepared through ring-opening alkyne metathesis polymerization (ROAMP). The strained triple bonds of a macrocyclic monomer serve both as the site of polymerization and the reaction center for an annulation reaction that laterally extends the conjugated backbone to give cGNRs with predetermined lengths and end groups. The structural control provided by a living polymer-templated synthesis of GNRs paves the way for their future integration into hierarchical assemblies, sequence-defined heterojunctions, and well-defined single-GNR transistors via block copolymer templates.
- Unraveling Photoexcited Charge Transfer Pathway and Process of CdS/Graphene Nanoribbon Composites toward Visible-Light Photocatalytic Hydrogen Evolution. [Journal Article]
- SSmall 2019 Jul 01; :e1902459
- Converting solar energy into chemical fuels is increasingly receiving a great deal of attention. In this work, CdS nanoparticles (NPs) are solvothermally anchored onto graphene nanoribbons (GNRs) tha…
Converting solar energy into chemical fuels is increasingly receiving a great deal of attention. In this work, CdS nanoparticles (NPs) are solvothermally anchored onto graphene nanoribbons (GNRs) that are longitudinally unzipped from multiwalled carbon nanotubes. The as-synthesized CdS/GNR nanocomposites with recyclability present GNR content-dependent activity in visible-light-driven hydrogen evolution from water splitting. In a range of 1-10 wt% GNRs, the CdS/GNR composites with 2 wt% GNRs achieves the greatest hydrogen evolution rate of 1.89 mmol h-1 g-1 . The corresponding apparent quantum efficiency is 19.3%, which is ≈3.7 times higher than that of pristine CdS NPs. To elucidate the underlying photocatalytic mechanism, a systematic characterization, including in situ irradiated X-ray photoelectron spectroscopy and Kelvin probe measurements, is performed. In particular, the interfacial charge transfer pathway and process from CdS NPs to GNRs is revealed. This work may open avenues to fabricate GNR-based nanocomposites for solar-to-chemical energy conversion and beyond.
- In vitro osteogenesis process induced by hybrid nanohydroxyapatite/graphene nanoribbons composites. [Journal Article]
- JMJ Mater Sci Mater Med 2019 Jun 28; 30(7):81
- Carbon nanotubes combine high bend and mechanical strength, which is advantageous for many structural and biomedical purposes. Recently, some biomaterials, based on carbon nanostructures and nanohydr…
Carbon nanotubes combine high bend and mechanical strength, which is advantageous for many structural and biomedical purposes. Recently, some biomaterials, based on carbon nanostructures and nanohydroxyapatite (nHAp), have been investigated as bone substitutes in order to improve regeneration. The aim of this study was to access the expression of some RNA transcripts (involved in the process of osteoblast differentiation) by mesenchymal stem cells cultured over different nanocomposite surfaces. A multi-walled carbon nanotube (MWCNT) was firstly grown using chemical vapor deposition and then exfoliated using chemical and oxygen plasma treatments to obtain graphene nanoribbons (GNR). The hybrid composites nHAp/GNR were prepared using the wet method assisted by ultrasound irradiation with different amounts of GNR (1.0, 2.0 and 3.0 wt %). Five groups were tested in cell cultures. Group 1: synthesized nHAp; Group 2: synthesized GNR; Group 3: nHAp and 1.0% of GNR; Group 4: nHAp and 2.0% of GNR and group 5: nHAp and 3.0% of GNR. Real time reverse transcription polymerase chain reactions were performed, and all data was submitted to Kruskal Wallis and Dunn tests, at a significance level of 5%. As a result, three nanocomposites with different proportions of GNR were successfully produced. After cell culture, the expression of osteogenic genes demonstrated no significant differences among the groups and periods. However, bone morphogenetic protein II (BMP II), integrin binding sialoprotein (IBSP), and Osterix highest expressions were observed in the group containing 3.0% of GNR. In conclusion, our hybrid composites may be useful in bone interventions requiring mesenchymal stem cell differentiation into osteoblasts for healing.
New Search Next
- Living annulative π-extension polymerization for graphene nanoribbon synthesis. [Journal Article]
- NatNature 2019; 571(7765):387-392
- The properties of graphene nanoribbons (GNRs)1-5-such as conductivity or semiconductivity, charge mobility and on/off ratio-depend greatly on their width, length and edge structure. Existing bottom-u…
The properties of graphene nanoribbons (GNRs)1-5-such as conductivity or semiconductivity, charge mobility and on/off ratio-depend greatly on their width, length and edge structure. Existing bottom-up methods used to synthesize GNRs cannot achieve control over all three of these parameters simultaneously, and length control is particularly challenging because of the nature of step-growth polymerization6-18. Here we describe a living annulative π-extension (APEX)19 polymerization technique that enables rapid and modular synthesis of GNRs, as well as control over their width, edge structure and length. In the presence of palladium/silver salts, o-chloranil and an initiator (phenanthrene or diphenylacetylene), the benzonaphthosilole monomer polymerizes in an annulative manner to furnish fjord-type GNRs. The length of these GNRs can be controlled by simply changing the initiator-to-monomer ratio, achieving the synthesis of GNR block copolymers. This method represents a type of direct C-H arylation polymerization20 and ladder polymerization21, activating two C-H bonds of polycyclic aromatic hydrocarbons and constructing one fused aromatic ring per chain propagation step.