Yong-Lai Zhang

Common Origin of Green Luminescence in Carbon Nanodots and Graphene Quantum Dots

Carbon nanodots (C-dots) synthesized by electrochemical ablation and small molecule carbonization, as well as graphene quantum dots (GQDs) fabricated by solvothermally cutting graphene oxide, are three kinds of typical green fluorescence carbon nanomaterials. Insight into the photoluminescence origin in these fluorescent carbon nanomaterials is one of the important matters of current debates. Here, a common origin of green luminescence in these C-dots and GQDs is unraveled by ultrafast spectroscopy. According to the change of surface functional groups during surface chemical reduction experiments, which are also accompanied by obvious emission-type transform, these common green luminescence emission centers that emerge in these C-dots and GQDs synthesized by bottom-up and top-down methods are unambiguously assigned to special edge states consisting of several carbon atoms on the edge of carbon backbone and functional groups with C═O (carbonyl and carboxyl groups). Our findings further suggest that the competition among various emission centers (bright edge states) and traps dominates the optical properties of these fluorescent carbon nanomaterials.

Curvature‐Driven Reversible In Situ Switching Between Pinned and Roll‐Down Superhydrophobic States for Water Droplet Transportation

Artifi cial superhydrophobic surfaces [ 1–10 ] with water contact angles (CAs) greater than 150 ° have been intensively investigated due to their unique “anti-water” property that could be utilized in a wide range of applications. [ 11–13 ] Recent development of intelligent devices, such as microfl uidic switches and biomedicine transporters, makes strong demands on surface wettability control, therefore, responsive surfaces have become a signifi cant issue for superhydrophobic studies. Up to now, various smart surfaces have been successfully developed as reversible switches for wettability control through a micronanostructured surface on a responsive material. [ 14–25 ] These unique tunings of surface wettability greatly contributed to refi ned control of surface wettability. With the thorough understanding of superhydrophobic phenomenon, superhydrophobic surfaces have been classifi ed into fi ve states [ 26 ] according to the details of CA hysteresis, which have been well verifi ed on different samples based on experimental results. [ 1 , 8 , 27–29 ]

Ferrofluids for Fabrication of Remotely Controllable Micro‐Nanomachines by Two‐Photon Polymerization

Miniaturized smart machines with micro-nanometer sized moving parts have now been utilized for on-site, in vivo sensing, monitoring, analysis and treatment in narrow enclosure, harsh environment, and even inside human body. [ 1–10 ] Despite the fact that a vast majority of currently available micromachines are produced with silicon by lithography, represented by Si: MEMS (silicon microelectromechanical systems) technique, a recent trend of the fi eld resorts to polymers. [ 11 ] As a designable three-dimensional micro-nanoprocessing method, two-photon photopolymerization (TPP) of photopolymers provides a novel route for fabricating micro-nanomechines with higher spatial resolution and smaller size. [ 12–14 ] However, introduction of driven force to these tiny devices for precise micro-manipulation constitutes the main problem for the advanced applications of these micro-nanomachines, for example, remote control is indispensable for intelligent micromachine that may be placed in blood vessels for health care. It is therefore of great importance to fi nd novel fabricative and driven techniques for making functional micronanomachines with precise motion control. Magnetic force drive technique which has been widely applied in macroscopical instruments would be an ideal method for remote control due to its simple, mind, safe and non-contact properties. [ 15–18 ] However, up to now, magnetic force is still not properly applied to remote control of micro-nanomachines for accomplishing desired task. Possible reason for this gap would be the lack of nanotechnology of appending magnetic components to existing micro-nanomachines, or to photopolymer precursors for laser fabrication. Generally, magnetic components such as nanoparticles which usually behave inorganic properties are really diffi cult to be introduced into polymeric carriers in a highly dispersed, largely doped fashion without signifi cant phase separation. [ 19 ] If magnetic nanomaterials can be homogeneously, largely and stably embedded in photopolymerizable resin through a simple method, magnetic force controllable micro-nanomachines would be fabricated accordingly.

Graphitic carbon quantum dots as a fluorescent sensing platform for highly efficient detection of Fe3+ ions

Reported here is a green synthesis of graphitic carbon quantum dots (GCQDs) as a fluorescent sensing platform for the highly sensitive and selective detection of Fe3+ ions. Through the electrochemical ablation of graphite electrodes in ultrapure water, uniform GCQDs with graphitic crystallinity and oxygen containing groups on their surfaces have been successfully prepared. The absence of acid, alkali, salt and organic compounds in the starting materials effectively avoids complex purification procedures and environmental contamination, leading to a green and sustainable synthesis of GCQDs. The oxygen functional groups (e.g., hydroxyl, carboxyl) contribute to the water solubility and strong interaction with metal ions, which enable the GCQDs to serve as a fluorescent probe for the highly sensitive and selective detection of Fe3+ ions with a detection limit as low as 2 nM. The high sensitivity of our GCQDs could be attributed to the formation of complexes between Fe3+ ions and the phenolic hydroxyls of GCQDs. The fluorescence lifetime of GCQDs in the presence and absence of Fe3+ was tested by time-correlated single-photon counting (TCSPC), which confirmed a dynamic fluorescence quenching mechanism.

Moisture‐Responsive Graphene Paper Prepared by Self‐Controlled Photoreduction

A facile and cost-effective preparation of moisture-responsive graphene bilayer paper by focused sunlight irradiation is reported. The smart graphene paper shows moisture-responsive properties due to selective adsorption of water molecules, leading to controllable actuation under humid conditions. In this way, graphene-based moisture-responsive actuators including a smart claw, an orientable transporter, and a crawler paper robot are successfully developed.

Flexible Nanowiring of Metal on Nonplanar Substrates by Femtosecond‐Laser‐Induced Electroless Plating

However,thelithographicrouteshowsstrongdemandsonthesurfaceflatnessofeachlayerin the multilevel chip architectures. To meet the processingnature of lithography, a global planarization of interlayermetals by chemical–mechanical polishing is therefore neededto reduce the interval between the metal layer and thephotomask, and to guarantee exposure resolution when wiresreachthesub-300nmscale.Two-photonabsorption(TPA)hasalso been tried for the fabrication of metal microstructures byusing suitable salt solutions as the metal source and photo-sensitive molecules as the photoinitiator.

Bioinspired Underwater Superoleophobic Membrane Based on a Graphene Oxide Coated Wire Mesh for Efficient Oil/Water Separation.

Inspired from fish scales that exhibit unique underwater superoleophobicity because of the presence of micronanostructures and hydrophilic slime on their surface, we reported here the facile fabrication of underwater superoleophobic membranes by coating a layer of graphene oxide (GO) on commercially available wire meshes with tunable pore sizes. Using the wire mesh as a ready-made mask, GO-embellished mesh with open apertures (GO@mesh) could be readily fabricated after subsequent O2 plasma treatments from the back side. Interestingly, the congenital microstructures of the crossed microwires in combination with the abundant hydrophilic oxygen-containing groups of the GO layer endow the resultant GO@mesh with unique underwater superoleophobic properties. The antioil tests show that the underwater contact angles of various oils including both organic reagents (undissolved in water) and vegetable oil on GO@mesh exceed 150°, indicating the superoleophobic nature. In a representative experiment, a mixture of bean oil and water that imitates culinary sewage has been well separated with the help of our GO@mesh. GO-embellished wire meshes may find broad applications in sewage purification, especially for the treatment of oil contaminations.

Biomimetic Graphene Surfaces with Superhydrophobicity and Iridescence

Triggered by the fantastic functions and bright appearance of biological systems in nature, enormous efforts have been devoted to biomimetic fabrication. For instance, butterfly wings and red rose petals have attracted increasing attention due to their excellent water repellency and splendid structural color. Consequently, colorful superhydrophobic surfaces have become a hot topic with significance in both fundamental research and practical applications. Previous studies have shown that hierarchical micro-/nanostructures on biosurfaces play a critical role in the multifunctional acquisition. On the one hand, the highly rough textures trap a wealth of air bubbles at the interface preventing a water droplet from spreading; thus, the surfaces exhibit a high water contact angle (CA>1508). Along this line, a variety of water-repellent surfaces with multiscale structures have been achieved by classical “top-down” and “bottomup” approaches. On the other hand, as inspired by many natural species that use structural color as a warning or protection, the surface microstructures are not randomly distributed but rigidly arranged in periodic micro-patterns, and therefore triggered light diffraction and scattering contribute to the brilliant appearance. However, due to technical challenges in the fabrication of uniform and well-defined nanostructures in the long-range order, most of the superhydrophobic surfaces hardly show any structural color. To date, only a few attempts to such multifunctional surfaces have been realized. For instance, Gu et al. fabricated colloidal photonic crystal films with both structural color and superhydrophobicity at the cost of long time and high temperature. Jiang et al. reported multicolor superhydrophobic coatings that depend on metal ions for the appearance of color; in their study, individual samples exhibited a single color. Wu et al. fabricated superhydrophobic surfaces with iridescence by employing multiple procedures including interference, surface modification, and chemical plating. Consequently, a facile and convenient approach for surfaces with superhydrophobicity and iridescent structural color is in urgent need. Unlike the classical slippery superhydrophobic surface represented by the famous self-cleaning lotus leaf, rose petals possess a sticky superhydrophobicity, exhibiting both a high water contact angle (CA>1508) and strong adhesion. Because of the adhesive force, flowers are able to maintain a fresh appearance, as a water droplet cannot roll off effortlessly but stays stably on the surface without any movement. To date, by tailoring the chemical composition, the geometrical structure, or interfacial capillary and van der Waals forces, superhydrophobic surfaces with high adhesion were successfully prepared. Due to their representativeness in wetting behavior and their research value in various realms, such as liquid transportation in microfluidic systems and biomedical applications, high-adhesion surperhydrophobic surfaces become increasingly important. Recently, graphene has attracted much attention due to its unique single atom-layer structure, which contributes to its wide applications in nanoelectronics, sensing devices, energy storage, and even tissue engineering. For example, graphene has proven to be a promising biocompatible scaffold that could accelerate the specific differentiation of human mesenchymal stem cells (hMSCs) into bone cells. In this case, the cell adhesion on the graphene surface plays a critical role in the long-term differentiation; therefore, a precise control of the surface wettability of graphene becomes a significant issue. Generally, superhydrophobic graphene substrates could be fabricated by using an irregular stack of graphene oxides (GO) prepared by chemical oxidation of graphite. In this procedure, to reduce the surface energy, the hydrophilic oxygen-containing groups on the GO surface have to be removed beforehand. To the best of our knowledge, modulation of the wetting property of graphene by micro-/nanostructuring and simultaneous control of chemical composition have not been realized. Moreover, despite the pioneering biomimetic fabrications of periodic micro-/nanostructures based on a wide range of materials, a bioinspired graphene surface with properties comparable to natural surfaces has not been reported yet. [a] J.-N. Wang, R.-Q. Shao, Dr. Y.-L. Zhang, L. Guo, Prof. H.-B. Sun State Key Laboratory on Integrated Optoelectronics College of Electronic Science and Engineering Jilin University 2699 Qianjin Street, Changchun 130012 (P. R. China) Fax: (+86)431-85168281 E-mail : yonglaizhang@jlu.edu.cn hbsun@jlu.edu.cn [b] H.-B. Jiang, D.-X. Lu, Prof. H.-B. Sun College of Physics Jilin University 2699 Qianjin Street, Changchun 130012 (P. R. China) Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/asia.201100882.

Structure-Function Correlations for Ru/CNT in the Catalytic Decomposition of Ammonia

formations. Our previous work on CNT-supported FeCo alloy nanoparticles for ammonia decomposition revealed that the structural confinement improves the stability rather than the intrinsic activity. [11] We herein present a preliminary study on the structural effects of CNTs when used as supports for Ru nanoparticles, and on the localization of Ru nanoparticles on ammonia. CNTs used as supports were annealed at 450, 900, and 15008C (denoted as C450, C900, and C1500, respectively) to increase the graphitization degree (electron donating ability) of the walls and to remove impurities (i.e., modify the chemistry of Ru–support interactions). Ru nanoparticles were placed inside or outside of the CNTs (denoted as Ru-in and Ruout, respectively) to sense a possible confinement effect. Table 1 summarizes the main physical properties of the CNT supports and Ru catalysts. The effects of the calcination temperature on the textural characteristics of CNT supports and on 2 wt % Ru/CNTs samples were studied by N2 adsorption–desorption measurements. All samples exhibited type V isotherms with H3 hysteresis loops, indicating that the catalysts have capillary pores. The Brunauer–Emmett–Teller (BET) surface area of C1500 was lower than those of C900 and C450, which is due

Bioinspired Photoelectric Conversion System Based on Carbon-Quantum-Dot-Doped Dye–Semiconductor Complex

Compared to natures photoelectric conversion processes, artificial devices are still far inferior in efficiency and stability. Inspired by light absorption and resonance energy transfer processes of chlorophyll, we developed a highly efficient photoelectric conversion system by introducing Carbon quantum dots (CQDs) as an electron transfer intermediary. Compared with conventional dye-sensitized semiconductor systems, the present CQD-doped system showed significantly higher photoelectric conversion efficiency, as much as 7 times that without CQDs. The CQD-doped dye/semiconductor system may provide a powerful approach to the development of highly efficient photoelectric devices.