-
Jigang Wang,
Yongsheng Wang, Dawei He,
Zhiyong Liu,
Hongpeng Wu,
Haiteng Wang,
Yu Zhao,
Hui Zhang,
Bingyang Yang,
Haiteng Xu,
Ming Fu
[show abstract]
[hide abstract]
ABSTRACT: Hydrophobic graphene-based material at the nanoscale was prepared by treatment of exfoliated graphene oxide with organic isocyanates. The lipophilic modified graphene oxide (LMGO) can then be exfoliated into the functionalized graphene nanoplatelets that can form a stable dispersion in polar aprotic solvents. AFM image shows the thickness of LMGO is approximately 1 nm. Characterization of LMGO by elemental analysis suggested that the chemical treatment results in the functionalization of the carboxyl and hydroxyl groups in GO via formation of amides and carbamate esters, respectively. The degree of GO functionalization can be controlled via either the reactivity of the isocyanate or the reaction time. Then we investigated the thermal properties of the SPFGraphene by using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), the TGA curve shows a greater weight loss of approximately 20% occurred indicating removal of functional groups from the LMGO sheets and an obvious exothermic peak at 176 degrees can be observed from 150 to 250 degrees. We also compared the structure of graphene oxide with the structure of chemical treated graphene oxide by FT-IR spectroscopy. The morphology and microstructure of the LMGO nanosheets were also characterized by SEM and XRD. Graphene can be used to fabricate a wide range of simple electronic devices such as field-effect transistors, resonators, quantum dots and some other extensive industrial manufacture such as super capacitor, li ion battery, solar cells and even transparent electrodes in device applications.
Journal of Nanoscience and Nanotechnology 08/2012; 12(8):6460-6. · 1.56 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Composites of polyaniline (PANI) and multi-wall carbon nanotube (MWNT) were synthesized by in situ polymerization with different MWNT content. The composites were characterized by Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The SEM photos indicated that a mass of MWNT was enchased into PANI matrix when the content of MWNT was low. With the MWNT content increases, the surface of MWNT was covered with PANI and formed the core-shell structure. From the FT-IR spectroscopy of the composites, it can be confirmed that there was interaction between PANI and multi-wall carbon nanotube. The composites had better thermal stability than pure PANI. Infrared emission property of the composites was analyzed by an IR-II infrared emissivity instrument and an infrared camera. It was found that infrared emission of the composites was lower than pure PANI in all wavelength range and infrared emissivity value was related to the content of MWNT in the composites.
Journal of Nanoscience and Nanotechnology 08/2012; 12(8):6558-61. · 1.56 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Inverse opals were prepared by replication of colloidal crystal templates made from silica spheres 298 nm in diameter. The air between the silica spheres was filled with the mixture of the monomer poly(methyl methacrylate) (PMMA) and the organic molecule Alq3 that can be subsequently polymerized. After removing the silica sphere templates, the photonic bandgap effect on the spontaneous emission of Alq3 were investigated. The dip in the fluorescence spectrum was interpreted in terms of redistribution of the photon density of states in the photonic crystal.
Journal of Nanoscience and Nanotechnology 11/2011; 11(11):9749-51. · 1.56 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Graphene oxide (GO) of approximately 1 nm was generated from exfoliated graphitic oxide using a modified Hummers method through ultrasonic treatment in water, and the GO film was reduced under protection of Ar/H2 flow at 800 degrees C. Moreover, the obtained graphene film has a high conductivity of 383 S/cm at 10-20 nm thickness.
Journal of Nanoscience and Nanotechnology 11/2011; 11(11):9456-9. · 1.56 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Nano-sized Sr2MgSiO5:Eu2+, Mn2+ phosphor was synthesized by the sol-gel method. The preparation conditions of the precursor were determined. The effect of Eu2+ and Mn2+ content on the luminescence intensity was studied. X-ray diffraction (XRD), photoluminescence spectra (PL), and photoluminescence excitation spectra (PLE) were used to characterize the samples. The results showed that the excitation bands ranged from 250 to 450 nm, and their peaks positioned around 365 nm. The emission spectrum consists of three bands: blue, green, and red, respectively. The blue and green emission bands originate from the center of the Eu2+, while the red emission band is attributed to the energy transfer from Eu2+ to Mn2+. White light can be obtained by mixing the three emission colors. The experiment results show that the Sr2MgSiO5:Eu2+, Mn2+ is a single host phosphor with superior properties for use in white light emitting diodes (white LED).
Journal of Nanoscience and Nanotechnology 11/2011; 11(11):9833-5. · 1.56 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The Sr2SiO4:Eu3+, Dy3+ phosphors for white light emitting diodes (LEDs) were synthesized by the sol-gel method. The microstructure and luminescent properties of the obtained Sr2SiO4:Eu3+, Dy3+ particles were well characterized. The results demonstrate that the Sr2SiO4:Eu3+, Dy3+ particles, which have spherical morphology, emitted an intensive white light emission under excitation at 386 nm. The phosphors show three emission peaks: the blue emission at 486 nm corresponding to the 4F(9/2)-6H(15/2) transition of Dy3+, the yellow emission at 575 nm corresponding to the 4F(9/2)-6H(13/2) transition of Dy3+, and the red emission at 615 nm corresponding to the 5D0-7F2 transition of Eu3+. At the same time, the effect of Eu3+ concentration on the emission intensities of Sr2SiO4:Eu3+, Dy3+ was investigated in detail. The phosphors used for white LEDs were obtained by combining near ultraviolet (NUV) light (386 nm) with Sr2SiO4:0.04Dy3+, 0.01Eu3+ phosphors with the characteristic of Commission Internationale de l'Eclairage (CIE) chromaticity coordinate (x, y) of (0.33, 0.34), and color temperature Tc of 5,603 K. In addition, the effect of the charge compensators (Li+, Na+, and K+ ions) on the photoluminescence (PL) emission intensities were studied.
Journal of Nanoscience and Nanotechnology 11/2011; 11(11):9439-44. · 1.56 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Ba3MgSi2O8:Eu2+, Mn2+ phosphors were synthesized by the sol-gel method and high temperature solid-state reaction method, respectively. XRD (X-ray diffraction), FT-IR (Fourier transform infrared spectroscopy), PL (photoluminescence spectra), and PLE (photoluminescence excitation spectra) were measured to characterize the samples. Emission and excitation spectra of our Ba3MgSi2O8:Eu2+, Mn2+ phosphors monitored at 441, 515, and 614 nm are depicted in the paper. The emission intensities of 441 and 515 nm emission bands increase with increasing Eu2+ concentration, while the peak intensity of the 614 nm band increases with increasing Mn2+ concentration. We conclude that the 515 nm emission band is attributed to the 4f(6)5d transition of Eu2+ ions substituted by Ba2+ sites in Ba2SiO4. The 441 nm emission band originates from Eu2+ ions, while the 614 nm emission band originates from Mn2+ ions of Ba3MgSi2O8:Eu2+, Mn2+. Nano-crystalline Ba3MgSi2O8:Eu2+, Mn2+ phosphors prepared by the sol-gel method show higher color rendering and better color temperature in comparison with the samples prepared by high temperature solid-state reaction method.
Journal of Nanoscience and Nanotechnology 11/2011; 11(11):9829-32. · 1.56 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: This paper studies the impact on the different surfactants and capacity of the oxidant for the synthesis of polypyrrole (PPy). The soluble PPy has also been studied. PPy was characterized mainly from the surface morphology, Fourier transform infrared spectroscopy, and conductivity sigma. First, using cetyltrimethylammonium bromide (CTAB) as the surfactant doped in an acid doping environment and without using ammonium persulfate (APS) as an oxidant, we determined the different capacities of the oxidant to synthesize the PPy. Scanning electron microscopy, Fourier transform infrared spectroscopy, and a four-probe conductivity meter were used to characterize the PPy. The acid doping conductivity was found to be 25 S/cm higher. Then, the solubility of polypyrrole was studied by doping with sodium dodecyl benzene sulfonate (SDBS), polyethylene glycol (PEG), and poly(styrene sulfonate) (PSS), proceeding the above-mentioned characterization.
Journal of Nanoscience and Nanotechnology 11/2011; 11(11):9836-9. · 1.56 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A composite of polyaniline (PANI) and nanoencapsulated phase-change material (PCM) with polystyrene (PS) as the shell and n-octadecane as the core was synthesized using the ultrasonic technique assisted by in situ polymerization. The composite's morphology, structure, and thermal properties were characterized by transmission electron microscopy (TEM), X-ray powder diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The results showed that the surface of the PCM nanocapsules was covered with PANI. The phase-change temperature of the nanocapsules of PCM and the composite was slightly lower than that of n-octadecane. Their latent heat was less than the calculated value based on the mass ratio of n-octadecane measured by TGA. The infrared emission properties of PANI, the phase-change nanocapsule, and the composite were studied using an IR-II infrared emissivity instrument and an infrared camera. It was found that the infrared emissivity of the composite was appreciably higher than that of PANI. However, the composite showed lower temperature than the PANI when observed by infrared camera with the increasing ambient temperature around the n-octadecane phase-change temperature. This occurred because the phase-change material in the composite absorbs so much heat that infrared emissions were obviously decreased when the ambient temperature rose.
Journal of Nanoscience and Nanotechnology 11/2011; 11(11):9665-70. · 1.56 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We prepared the exfoliation of graphite, which was necessary for the production of graphene sheets that are desirable for the fabrication of nano-composites. Then a Solution-Processable Functionalized Graphene (SPFGraphene) with functionalization groups doped with P3HT hybrid thin film-based organic photovoltaic cells (OPVCs) was systematically identified using a general device structure of, ITO/PEDOT:PSS/P3HT:SPFGraphene/LiF/Al. The effect of annealing on the photoelectric properties of the SPFGraphene was analyzed by Fourier transform infrared FT-IR spectroscopy and solar cell performance. After treatment at different annealing temperatures, with an increase in the SPFGraphene content, the short-circuit current density J(SC) and power conversion efficiency PCE of the hybrid devices increased first, reaching the peak efficiency for the 10 wt% SPFGraphene content, and then decreased. After annealing at 160 degrees C, the device containing 10 wt% SPFGraphene showed the open-circuit voltage V(OC) of 0.73 V, the J(SC) value of 3.98 mA cm(-2), fill factor (FF) value of 0.36, the PCE value of 1.046%. After thermal annealing at 210 degrees C, with the removal of the functional groups and recovery of the pi-conjugated areas, the conductivity of the graphene sheet and the charge carrier-transport mobility increased greatly, the J(SC) value of the 10 wt% SPFGraphene content device increased to 4.2 mA cm(-2), the V(OC) value decreased to 0.59 V, which may be attributed to the altered work-function value of the functionalized graphene and low quasi-Fermi levels for electrons and holes, the FF value was 0.27, and the PCE was 0.669%, which is lower than the former one. The results indicated that annealing at the appropriate temperature can improve the device performance greatly, and the functionalized graphene is expected to be a competitive candidate in organic photovoltaic applications because it is soluble, cheap, easily prepared, stable, and inert against the ambient conditions.
Journal of Nanoscience and Nanotechnology 11/2011; 11(11):9432-8. · 1.56 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Ordered ZnO nanobowl arrays over cm2 areas were prepared by magnetron sputtering using the self-assembled polystyrene spheres arrays as templates. The process started with self-assembled sedimentation of there-dimensional (3D) hexagonal polystyrene sphere arrays. By depositing ZnO within the interstitials of 3D polystyrene colloidal crystal templates using magnetron sputtering, large-area ordered ZnO nanobowl sheets were prepared after removing the spheres by annealing. The whole nanobowl sheet could be lifted off, leaving accidentally observed inverse opal structures. The sizes of the nanobowls could be controlled by the size of the polystyrene spheres, the height of nanobowl sheets could be altered by changing sputtering parameters.
Journal of Nanoscience and Nanotechnology 11/2010; 10(11):7603-6. · 1.56 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Magnetically responsive phase-change microspheres were prepared and studied in this article. In the synthetic process, oleic acid was used to modify the iron oxide nanoparticles. The ferrite nanoparticles, about 10 nm in diameter, were highly dispersed due to the oleic acid on the surface of the particles, and they were encapsulated in polymethyl methacrylate (PMMA) by microemulsion polymerization with paraffin, which could be presumed from the differential scanning calorimetry (DSC) curves. According to the morphology in the scanning electron microscopy (SEM) image, the average diameter of the microspheres was about 200 nm, a large amount of nano-sized ferrite can be observed in a transmission electron microscope (TEM) image showing the structure of the microspheres. Finally, in the magnetization curve from a vibrating sample magnetometer, the saturation magnetization of microspheres was 12.2 emu/g, which was effective in the compatibility of infrared simulation and microwave absorption.
Journal of Nanoscience and Nanotechnology 03/2010; 10(3):1733-6. · 1.56 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Ordered macroporous polymers have been prepared by replication of colloidal crystals made from silica spheres 298 nm in diameter. The colloidal crystals were prepared on a clean indium tin oxide (ITO) glass substrate by sedimentation of a solution of a silica colloidal dispersed solution. The air between the silica spheres was filled by the monomer of poly(methyl methacrylate) (PMMA) that can be subsequently polymerized. After infiltration, the silica spheres were removed by means of etching with hydrofluoric acid (HF) aqueous solution and left a polycrystalline network of interconnected pores. These macroporous ordered structures represent a promising approach for bandgap engineering and can be used as the foundation of various potential applications.
Journal of Nanoscience and Nanotechnology 03/2010; 10(3):1778-81. · 1.56 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The fabrication of the periodic ordered structures with complex shapes or heterostructures are important for many potential applications. In this paper, zinc oxide two-dimensional (2D) nanomesh and three-dimensional (3D) inverse opal complex connected structures were fabricated by the electrochemical deposition method. 2D ZnO nanosheets or sheet-like porous structures standing on the 3D ZnO inverse opals were synthesized. Two different methods: the co-deposition method and the two-step deposition method were employed for the preparation of the complex structures. The deposition process of complex structures is discussed. The photonic band gap of the complex macroporous structure was calculated using the Translight software and characterized by the micro-region reflection and transmission spectra. The exciton luminescence of ZnO can be inhibited by the inverse opal structure when the photonic band gap superposes with the luminescent band.
Journal of Nanoscience and Nanotechnology 03/2010; 10(3):1928-33. · 1.56 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: PMMA microsphere arrays are fabricated by a double replicating method with common used polystyrene colloidal crystal template. High quality ZnO inverse opals formed by electrodeposition play the key role between the PMMA microsphere arrays and polystyrene colloidal crystals. The electrodeposition method has advantage on fabricating IO structures with high solid fraction. After the subsequently in-situ polymerization of MMA in the voids of ZnO inverse opals, the ZnO is removed by hydrochloric acid solution. Microsphere arrays fabricated by PMMA or PMMA doped with Alq3 are prepared. Reflection stop bands are detected from the formed PMMA microsphere arrays. Solid fraction from 37% to 50% of the PMMA arrays can be formed by different in-situ polymerization modes of MMA. The photoluminescence of Alq3 in the PMMA spheres is partly suppressed at the wavelength of the photonic stop band induced by PMMA arrays.
Optical Materials. 32(9):1210-1215.
-
[show abstract]
[hide abstract]
ABSTRACT: Well-aligned ZnO nanorod arrays were synthesized by hydrothermal method on Si substrates that were covered with pre-deposited ZnO films as seed layers. The ZnO seed layers were deposited by RF magnetron sputtering. It is found that the seed layers prepared under different oxygen partial pressure sputtering parameters and annealing treatment have a great influence on the morphology of the ZnO nanorod arrays grown subsequently on them. Furthermore, growth positions of nanorod/microrod arrays were selectively controlled on the lithography-assist ZnO seed layer.
Journal of Alloys and Compounds 489(1):99-102. · 2.29 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Nitrogen (N) contamination in the Yellow River mainstream and its tributaries was studied using data from 1960 to 2000 from 312 monitoring sites in the Yellow River system. Data showed that N concentrations in the Yellow River have increased since 1960, especially after 1990. N concentrations in the Yellow River mainstream increased from the upper reaches (less than 1.0 mg L(-1) for TN and less than 0.10 mg L(-1) for NH4(+)-N) to lower reaches (higher than 4-5 mg L(-1) for TN and higher than 1.0 mg L(-1) for NH4(+)-N). However, the highest N contaminations (50-250 mg L(-1) for TN and 10-20 mg L(-1) for NH4(+)-N) was found in some tributaries, which was attributed as an effect of industrial wastewater and municipal sewage. Nitrogen concentrations from several monitoring sites were positively correlated with several regional socio-economic indices, such as population density, fertilization rates, livestock, industrial input and GDP. Depending on location, seasonal N concentrations contrasted among watersheds. Monitoring stations located in rural and agricultural areas showed higher N concentrations during the flood season while those located in areas with urban and industrial centers showed higher N concentration during the dry season. Mainstream flow and N concentrations showed a strong inverse relationship; with higher N concentrations as the river flow declined. Intensive water extraction for agricultural irrigation and increasing N input to the river from fertilized agricultural fields could explain the increasing N concentrations during extensive droughts.
Environmental Monitoring and Assessment 93(1-3):125-38. · 1.40 Impact Factor
