The photoluminescent properties of graphene nanoparticle (named graphene quantum dots) have attracted significant research attention in recent years owing to their profound application potential. However, the photoluminescence (PL) origin of this class of nanocarbons is still unclear. In this paper, combining direct experimental evidence enabled by a facile size-tunable oxygenated graphene quantum dots (GQDs) synthesis method and theoretical calculations, the roles of the aromatic core, functional groups and disordered structures (i.e. defects and sp³ carbon) in the PL of oxygenated GQDs are elucidated in detail. In particular, we found that the functional groups on GQDs play dual roles in the overall emission: (1) they enable π∗ → n and σ∗ → n transitions, resulting in a molecular type of PL, spectrally invariable with change of particle size or excitation energy; (2) similar to defects and sp³ carbon, functional groups also induce structural deformation to the aromatic core, leading to mid-gap states or, in other words, energy traps, causing π∗ → mid-gap states → π transitions. Therefore, functional groups contribute to both the blue edge and the red shoulder of GQDs' PL spectra. The new insights on the role of functional groups in PL of fluorescent nanocarbons will enable better designs of this new class of materials.

Shujun Wang;Ivan S. Cole;东元 赵;Qin Li

Nanoscale

2016-4-14

A specific fullerene derivative, C₆₀(CHCOOH)₂, was introduced into the matrix network of well-ordered hexagonal mesoporous silica (SBA-15) via a chemical bond interaction. The methods included aminosilylation of the surface silanols within SBA-15 channels by 3-aminopropyl(trimethoxy) silane (APTS) and a subsequent amide reaction between amino groups of APTS/SBA-15 and carboxylic acids of C₆₀(CHCOOH)₂. The final material C₆₀(CHCOOH)₂/APTS/SBA-15 was confirmed by XRD, TEM, and BET techniques, FT-IR and UV-vis spectra. The [60]fullerene carboxylic derivative molecules were uniformly distributed in the channels of SBA-15, while pure [60]fullerene molecules remained as clusters or larger aggregate states.

Huixia Wu;Yanghui Lin;Jiawei Tang;Dong Gao;Ruifang Cai;东元 赵

Bulletin of the Chemical Society of Japan

2007

Magnesium- and zinc-based lamellar mesostructures were synthesized with nonamphiphilic mesogens as templates. The templates used were disodium chromoglycate (DSCG) and flufenamic acid (FA) which are known to exhibit lyotropic liquid-crystalline phases in aqueous solutions. Evidence for the lamellar structure was obtained from the X-ray diffraction patterns and transmission electron micrographs. The interlayer spacings in the materials prepared with DSCG and FA, 30 and 24 Å, respectively, were large compared to the molecular dimensions of the templates, suggesting the existence of a bilayer arrangement of the templates between the inorganic walls. The presence of intact template molecules within the layers was confirmed by chemical analysis, TGA, IR, and NMR measurements. Interactions between the template molecules and the inorganic layer were evident through the increase in their decomposition temperatures as compared to the pure template and by the slight weakening of the C=O bond as determined by the IR measurements. The synthesis of lamellar mesostructures with nonamphiphilic mesogens broadens the scope of the socalled "liquid-crystal template mechanism" in the sense that it is not limited to amphiphilic molecules but applies also to other molecules which can form large molecular assemblies in solutions.

东元 赵;Daniella Goldfarb

Chemistry of Materials

1996-11

Salinity difference between seawater and river water is a sustainable energy resource that catches eyes of the public and the investors in the background of energy crisis. To capture this energy, interdisciplinary efforts from chemistry, materials science, environmental science, and nanotechnology have been made to create efficient and economically viable energy conversion methods and materials. Beyond conventional membrane-based processes, technological breakthroughs in harvesting salinity gradient power from natural waters are expected to emerge from the novel fluidic transport phenomena on the nanoscale. A major challenge toward real-world applications is to extrapolate existing single-channel devices to macroscopic materials. Here, we report a membrane-scale nanofluidic device with asymmetric structure, chemical composition, and surface charge polarity, termed ionic diode membrane (IDM), for harvesting electric power from salinity gradient. The IDM comprises heterojunctions between mesoporous carbon (pore size ∼7 nm, negatively charged) and macroporous alumina (pore size ∼80 nm, positively charged). The meso-/macroporous membrane rectifies the ionic current with distinctly high ratio of ca. 450 and keeps on rectifying in high-concentration electrolytes, even in saturated solution. The selective and rectified ion transport furthermore sheds light on salinity-gradient power generation. By mixing artificial seawater and river water through the IDM, substantially high power density of up to 3.46 W/m² is discovered, which largely outperforms some commercial ion-exchange membranes. A theoretical model based on coupled Poisson and Nernst-Planck equations is established to quantitatively explain the experimental observations and get insights into the underlying mechanism. The macroscopic and asymmetric nanofluidic structure anticipates wide potentials for sustainable power generation, water purification, and desalination.

Jun Gao;Wei Guo;Dan Feng;Huanting Wang;东元 赵;Lei Jiang

Journal of the American Chemical Society

2014-9-3

While extensive commercial success has been achieved through the use of organic molecules in the synthesis of aluminosilicate zeolites, the synthesis of the germanium-based zeolite structures using organic structure-directing agents is a largely unexplored area. Here we report a novel class of germanate zeolite structures prepared with inorganic cations or organic amines as structure-directing agents. These new materials possess five 4- connected 3-dimensional topologies with large (12-ring), medium (10-ring), small (8-ring), or ultrasmall (6-ring) pores. They have a variety of chemical compositions such as various Ge to Ga (or Al) ratios and exhibit interesting structural features such as helical chains and odd-membered rings. UCSB- 15GaGe and UCSB-15AlGe are the first germanate-based structures with 5- rings. UCSB-7 refers to a collection of isostructural, large-pore zeolite- like structures constructed by the cross-linking of helical ribbons. UCSB- 3GaGe is the only known T₃⁺/T⁴⁺ (T refers to tetrahedral atoms) based zeolite structure with the net 38 topology. This structure is unusual because of its very high framework charge density unsurpassed by other amine-directed zeolite structures. GaGe-SOD2 and AlGe-SOD2 (sodalite analogues) have an unusually low framework symmetry for a sodalite structure. The cubic GaGe- SOD1 (or AlGe-SOD1) and the triclinic GaGe-SOD2 (or AlGe-SOD2) are ideal examples of the compositional and structural control of the inorganic framework by structure-directing amines. GaGe-ANA1 and GaGe-ANA2, two gallogermanate analcime analogues, are noncentrosymmetric, unlike many other analcime structures.

Xianhui Bu;Pingyun Feng;Thurman E. Gier;东元 赵;Galen D. Stucky

Journal of the American Chemical Society

1998-12-30

Efficient removal of dissolved organic matter (DOM) is a challenge in advanced water/wastewater treatment, especially for high-molecular-weight polar or charged contaminants. Herein, we report a novel type of self-supported hybrid poly(vinylidene fluoride, PVDF) membrane incorporated with mesoporous carbon. It is fabricated via a simple organic-inorganic mixture and phase inversion process, in which the mesoporous carbon is used as an inorganic additive (up to 40 wt%) for the manipulation of polymeric pore structure and distribution, porosity, thickness, surface area and fouling characteristics. The hybrid membrane combines easy scaleup of polymers and large adsorption capacity of the mesoporous carbon. It possesses high surface areas (up to 550 m² g^-1), three-dimensionally interpenetrating porous structures, improved mechanical strength and chemical property, and favorable water flux (43 to 32 L m^-2 h^-1). The membrane with 25 wt% of mesoporous carbon shows the best separation performance for large-molecular-sized microcystin-LR (M_w = 995) and Rhodamine B (M_w = 479) (3.8 and 14.8 mg g^-1, respectively). Moreover, the complementary properties allow the hybrid membrane be regenerated conveniently and reused with steady cyclic performance. This membrane-forming procedure demonstrates a trade-off relationship of thermodynamics versus kinetics. It is also affected simultaneously by particle-polymer interactions on the micron-sized interfaces during the phase inversion. Results suggest a promising route toward hybrid membranes for efficient sequestration of large-molecules of dissolved organic pollutants.

Wei Teng;Nan Bai;Jianwei Fan;Dandan Li;Rui Liu;Jianping Yang;Wei Xian Zhang;东元 赵

RSC Advances

2016

Sodium-metal sulfide battery holds great promise for sustainable and cost-effective applications. Nevertheless, achieving high capacity and cycling stability remains a great challenge. Here, uniform yolk-shell iron sulfide-carbon nanospheres have been synthesized as cathode materials for the emerging sodium sulfide battery to achieve remarkable capacity of ∼545 mA h g^-1 over 100 cycles at 0.2 C (100 mA g^-1), delivering ultrahigh energy density of ∼438 Wh kg^-1. The proven conversion reaction between sodium and iron sulfide results in high capacity but severe volume changes. Nanostructural design, including of nanosized iron sulfide yolks (∼170 nm) with porous carbon shells (∼30 nm) and extra void space (∼20 nm) in between, has been used to achieve excellent cycling performance without sacrificing capacity. This sustainable sodium-iron sulfide battery is a promising candidate for stationary energy storage. Furthermore, this spatially confined sulfuration strategy offers a general method for other yolk-shell metal sulfide-carbon composites.

Yun Xiao Wang;Jianping Yang;Shu Lei Chou;Hua Kun Liu;Wei Xian Zhang;东元 赵;Shi Xue Dou

Nature Communications

2015-10-28

Three nickel 1,4-cyclohexanedicarboxylate (1,4-CDC) coordination polymers, Ni₆(OH)₆(1,4-CDC)₃(H₂O) ₆·2H₂O (1), Ni₃(OH)₂(1,4-CDC) ₂(H₂O)₄·4H₂O (2), and Ni(1,4-CDC)(H₂O)₄ (3), have been synthesized from an identical starting mixture as temperature-dependent products. Their characteristic structures and magnetic and sorption behaviors are reported.

Jinxi Chen;Masaaki Ohba;东元 赵;Wakako Kaneko;Susumu Kitagawa

Crystal Growth and Design

2006-3

Hydrothermal reaction of nickel acetate with 3-phosphonopropionic acid and 4,4′-bipyridine resulted in two novel phosphonate compounds Ni(HO₃PC₂H₄COO)(4,4′-bpy)(H₂O) · 0.5(4,4′-bpy) (bpy = bipyridine) (I) and Ni(O₃PC₂H₄COOH)(4,4′-bpy)(H₂O)₃ · H₂O (II). Single-crystal X-ray studies reveal that self-assemblies between the ligands and metal ion result in layer (I) and chain (II) structures. Magnetic measurement of I indicate there are ferromagnetic couplings between adjacent Ni²⁺ ions (C = 1.29 cm³ mol^-1 K and θ = 2.25 K).

Zhenxia Chen;Linhong Weng;东元 赵

Inorganic Chemistry Communication

2007-4

Hierarchically porous composites with mesoporous carbon wrapping around the macroporous graphene aerogel can combine the advantages of both components and are expected to show excellent performance in electrochemical energy devices. However, the fabrication of such composites is challenging due to the lack of an effective strategy to control the porosity of the mesostructured carbon layers. Here an interface-induced co-assembly approach towards hierarchically mesoporous carbon/graphene aerogel composites, possessing interconnected macroporous graphene networks covered by highly ordered mesoporous carbon with a diameter of ≈9.6 nm, is reported. And the orientation of the mesopores (vertical or horizontal to the surface of the composites) can be tuned by the ratio of the components. As the electrodes in supercapacitors, the resulting composites demonstrate outstanding electrochemical performances. More importantly, the synthesis strategy provides an ideal platform for hierarchically porous graphene composites with potential for energy storage and conversion applications.

Ruili Liu;Li Wan;Shaoqing Liu;Lixia Pan;Dongqing Wu;东元 赵

Advanced Functional Materials

2015-1-28