Xiaoru Li - Academia.edu (original) (raw)

Papers by Xiaoru Li

Journal of Catalysis, 2015

ABSTRACT Nickel multiply-twinned particles (Ni MTPs) imbedded onto ZSM-5 were prepared, and their... more ABSTRACT Nickel multiply-twinned particles (Ni MTPs) imbedded onto ZSM-5 were prepared, and their formation and chemical and electronic properties were characterized by HRTEM, XPS, CO-FTIR, and H2-TPD. HRTEM showed the formation of Ni MTPs with triangular, square, hexagonal, and spherical shapes. The multiply-twinned particles were composed of f.c.c. nanocrystals dominated by (1 1 1) crystal face. Ni MTPs indicate an enhanced CO adsorption capability as compared with ordinary Ni particles. Ni MTPs were electron deficient and inherently strained, which is responsible for high catalytic activity in the hydrolytic hydrogenation of cellulose.

Journal of colloid and interface science, Jan 22, 2015

A highly selective and stable catalyst based on Pt nanoparticles confined in Mesoporous TiO2-SiO2... more A highly selective and stable catalyst based on Pt nanoparticles confined in Mesoporous TiO2-SiO2 frameworks were prepared and employed for selective hydrogenation of cinnamaldehyde to cinnamyl alcohol. The as-prepared Pt/MesoTiO2-SiO2-M catalyst displayed excellent selectivity to cinnamyl alcohol (around 91%) at nearly complete conversion. Ti(2+) and stronger metal-support interaction (SMSI) played key roles on the adsorption behavior of cinnamaldehyde and activation of CO bonds. The existence of amorphous SiO2 and mixed TiO2 phases (anatase and rutile) was helpful for the formation of Ti(2+) sites and SMSI. The electron-enriched Pt surfaces and the formed Pt-TiOx system benefited the enhanced activity and selectivity.

Materials Letters, 2014

Ordered Ni/Fe shell/core structured nanocable arrays were successfully fabricated by a two-step e... more Ordered Ni/Fe shell/core structured nanocable arrays were successfully fabricated by a two-step electrodeposition process. Firstly, nickel (Ni) nanotubes were prepared by electrodeposition in nanoporous of anodic aluminum oxide (AAO) template. Then the AAO/Ni nanotube composite membrane was used as a secondary template to deposit Ferrum (Fe) nanowires into Ni nanotubes. The morphology and microstructure of the nanocables was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The chemical composition of the nanocables was confirmed by X-ray diffraction (XRD). Magnetization measurements revealed that Ni/Fe nanocable arrays have a lower remanence ratio than Ni nanotube and Fe nanowire arrays respectively.

Materials Letters, 2015

ABSTRACT Highly ordered arrays of polyamide 6 (PA6) nanotubes were successfully prepared using ph... more ABSTRACT Highly ordered arrays of polyamide 6 (PA6) nanotubes were successfully prepared using photolithography via polymer solution wetting the anodic aluminum oxide (AAO) templates. The samples were examined by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD). The crystal structure and the crystallinity of the samples were influenced by the presence of nanopores in the AAO template. Nanopore-induced crystal transformation from the α-form to the γ-form of PA6 was confirmed by XRD, and the formation of γ-form crystal was enhanced by the presence of nanopores in the AAO template. The formation of γ-form crystal was also discussed. These results indicated that nanopores provided favorable conditions for the crystallization of γ phase.

Chinese Journal of Catalysis, 2015

ABSTRACT AgxS crystals were synthesized via hydrothermal (AgxS-H) and in situ ion-exchange (AgxS-... more ABSTRACT AgxS crystals were synthesized via hydrothermal (AgxS-H) and in situ ion-exchange (AgxS-IE) methods. The samples were characterized by scanning electron microscopy, X-ray diffraction, ultraviolet-visible-near infrared absorption spectroscopy, N2 adsorption-desorption, X-ray photoelectron spectroscopy and surface photovoltage measurements. The photocatalytic performance was investigated for the decomposition of methyl blue (MB) under visible light irradiation (λ ≥ 420 nm). The AgxS-H had smaller particles, wider band gap and weaker recombination of photoinduced charges than AgxS-IE, resulting in a higher photocatalytic activity. Moreover, AgxS-H was stable, and could be reused five times without loss of photocatalytic activity. Additionally, a possible pathway for the photocatalytic degradation of MB over AgxS has been proposed, that MB was oxidized mainly by hydroxyl radicals and partly via electron holes generated in the AgxS. AgxS-H is an efficient photocatalyst and has great potential for the degradation of harmful organic dyes in wastewater.

2010 International Conference on Microwave and Millimeter Wave Technology, 2010

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Journal of Molecular Catalysis A: Chemical, 2014

ABSTRACT Bimetallic and monometallic catalysts including Cu and/or Fe species were prepared by a ... more ABSTRACT Bimetallic and monometallic catalysts including Cu and/or Fe species were prepared by a co-precipitation method and their catalytic performance was tested for the selective hydrogenation of ethyl stearate to stearyl alcohol. The bimetallic catalysts were observed to be even more active for this selective hydrogenation compared to the monometallic catalysts and their physical mixtures. With a bimetallic catalyst of Cu/Fe (4/1 in mole ratio) reduced at 200 degrees C, a selectivity to the alcohol reached to above 99% at a conversion of 97% in reaction for 4h at 230 degrees C, 3.0 MPa. Effects of composition and reduction temperature on the catalytic performance were studied and the properties of catalysts prepared under different conditions were examined by XRD, TPR, N-2 physisorption, and SEM. The relationship of the performance with the properties of the catalysts was discussed, along with the conditions under which synergistic effects of Cu and Fe species appeared and caused the enhancement of the catalytic performance.

Catalysts, 2014

Series catalysts of Ru-SnO x /Al 2 O 3 with varying SnO x loading of 0-3 wt% were prepared, and t... more Series catalysts of Ru-SnO x /Al 2 O 3 with varying SnO x loading of 0-3 wt% were prepared, and their catalytic activity and selectivity have been discussed and compared for the selective hydrogenation of m-dinitrobenzene (m-DNB) to m-nitroaniline (m-NAN). The Ru-SnO x /Al 2 O 3 catalysts were characterized by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and hydrogen temperature-programmed reduction (H 2 -TPR) and desorption (H 2 -TPD). Under the modification of SnO x , the reaction activity increased obviously, and the best selectivity to m-NAN reached above 97% at the complete conversion of m-DNB. With the increasing of the SnO x loading, the amount of active hydrogen adsorption on the surface of the catalyst increased according to the H 2 -TPD analysis, and the electron transferred from Ru to SnO x species, as determined by XPS, inducing an electron-deficient Ru, which is a benefit for the absorption of the nitro group. Therefore, the reaction rate and product selectivity were greatly enhanced. Moreover, the Ru-SnO x /Al 2 O 3 catalyst presented high stability: it could be recycled four times without any loss in activity and selectivity.

2010 IEEE 12th International Conference on Communication Technology, 2010

In this paper, we present an enhanced algorithm for frame synchronization for DVB-S2 system. The ... more In this paper, we present an enhanced algorithm for frame synchronization for DVB-S2 system. The scheme is based on multiple correlation peak value detection to achieve frame synchronization. By further analyzing the structure of the Physical Layer Header (PLHEADER) that consists of Start of Frame (SOF) and Physical Layer Signaling Code (PLSC), we find some useful properties that can enhance the frame synchronization. We also introduce some optimizations into the algorithm. Especially, the modifications made on the peak search algorithm improve the performance of the frame synchronization. The experimental results show that the frame synchronization can be achieved under large carrier frequency offset (as large as 5 MHz at 25 MSps) and low SNR threshold of -2.3 dB. Compared with previously proposed approaches, the scheme described in this paper takes less time to acquire frame synchronization and seems to be more flexibility.

Optical Design and Testing II, 2005

Eccentric photorefraction (EPR), which is used to determine the refractive error of eye, is great... more Eccentric photorefraction (EPR), which is used to determine the refractive error of eye, is greatly relied on the crescent pattern of the pupil image or on the intensity gradient in the principal meridian across the pupil. The vignetting image of the pupil, which is formed by a camera lens aperture with an eccentric light source, and contains a lot of

The Journal of Physical Chemistry C, 2010

ABSTRACT Ordered Ni/Cu shell/core structured nanocable arrays were successfully fabricated by a t... more ABSTRACT Ordered Ni/Cu shell/core structured nanocable arrays were successfully fabricated by a two-step electrodeposition process. First, nickel (Ni) nanotubes were obtained by chemical electrodeposition in nanoporous anodic aluminum oxide (AAO) template. Then the AAO/Ni nanotube composite membrane was used as a secondary template to deposit copper (Cu) nanowires into Ni nanotubes. The morphology and microstructure of the nanocables has been characterized using scanning electron microscopy and transmission electron microscopy. The chemical composition of the nanocables has been confirmed by X-ray diffraction. Magnetization measurements revealed that Ni/Cu nanocable arrays have a high remanence ratio.

The Journal of Physical Chemistry B, 2009

Patterned polystyrene (PS) nanotube arrays were successfully fabricated using photolithography vi... more Patterned polystyrene (PS) nanotube arrays were successfully fabricated using photolithography via the polymer solution-wetting method. The microstructure of these nanotubes was investigated using conventional and high-resolution transmission electron microscopy (HRTEM). Two major types of morphology were observed for these PS nanotubes, one being bamboo-like and the other being barrel-shaped. The multiwetting mechanism was proposed to explain the different morphologies. X-ray diffraction (XRD) showed that the PS nanotubes have a higher degree of crystallinity than bulk PS. In addition, crystalline lattice fringes were observed in some regions of the PS nanotubes using HRTEM. Patterned polymer nanotube arrays could be used for nanocable coating to protect from oxidation and corrosion in nanodevices.

Polymer Bulletin, 2012

Well-defined CdS nanorings with flower-like morphology were synthesized by a hydrothermal method ... more Well-defined CdS nanorings with flower-like morphology were synthesized by a hydrothermal method using poly(vinyl-pyrrolidone) as capping agent. The phase composition, morphology, structure, and optical properties of CdS nanorings were characterized by X-ray diffraction (XRD), scanning electron microscope, transmission electron microscopy, and UV-vis absorption spectroscopic techniques. The XRD pattern of the sample can be indexed to the cubic zinc blende phase CdS. According to the quantitative analysis of energy-dispersive spectrum, the Cd:S molar ratio of the sample is about 1:0.96. The possible formation mechanism of the CdS nanorings is proposed which is based on time-resolved experiments. Furthermore, the absorption peak of CdS nanorings is red-shifted to 523 nm in the UV-vis absorption spectrum.

Nanoscale Research Letters, 2008

In this work, we report that large area metal nanowire and polymer nanotube arrays were successfu... more In this work, we report that large area metal nanowire and polymer nanotube arrays were successfully patterned by photolithographic approach using anodic aluminum oxide (AAO) templates. Nanowires were produced by electrochemical deposition, and nanotubes by solution-wetting. The highly ordered patterns of nanowire and nanotube arrays were observed using scanning electron microscopy (SEM) and found to stand free on the substrate. The method is expected to play an important role in the application of microdevices in the future.

Nanoscale Research Letters, 2009

Highly ordered Ni nanotube and nanowire arrays were fabricated via electrodeposition. The Ni micr... more Highly ordered Ni nanotube and nanowire arrays were fabricated via electrodeposition. The Ni microstructures and the process of the formation were investigated using conventional and high-resolution transmission electron microscope. Herein, we demonstrated the systematic fabrication of Ni nanotube and nanowire arrays and proposed an original growth mechanism. With the different deposition time, nanotubes or nanowires can be obtained. Tubular nanostructures can be obtained at short time, while nanowires take longer time to form. This formation mechanism is applicable to design and synthesize other metal nanostructures and even compound nanostuctures via template-based electrodeposition.

Materials Characterization, 2010

Highly ordered circular patterns of copper nanowire arrays were successfully deposited into desig... more Highly ordered circular patterns of copper nanowire arrays were successfully deposited into designed anodic aluminum oxide templates. High-resolution transmission electron microscopy was used to study the microstructure of these Cu nanostructures. The results showed that the growth orientation of the copper nanowires was along [220] direction, and the broken orientation were along [2̄02̄] and [02̄2] directions, respectively. Regular cones were

Journal of Porous Materials, 2012

ABSTRACT In this work, large area polymer nanostructure arrays with different patterns were succe... more ABSTRACT In this work, large area polymer nanostructure arrays with different patterns were successfully obtained by photolithographic approach and wetting anodic aluminum oxide (AAO) templates. First of all, the AAO templates with patterns were produced by photolithographic approach. Then the AAO/pattern membrane was used as a secondary template to fabricate polymer nanostructure arrays by solution-wetting and melt-wetting methods. The morphology of the polymer nanostructures has been characterized using scanning electron microscopy and transmission electron microscopy. The different factors have been discussed in the process of experiments.

Journal of Nanoscience and Nanotechnology, 2010

Two different patterns, one being circular and the other being QDU, of copper (Cu) nanowire array... more Two different patterns, one being circular and the other being QDU, of copper (Cu) nanowire arrays were successfully produced by electrochemical deposition and photolithography. The highly-ordered patterns of Cu nanowire arrays were observed to stand freely on the substrate using scanning electron microscopy (SEM). Chemical analyses have been performed on Cu nanowires using energy dispersive X-ray spectroscopy (EDS). The results confirmed that it is mainly composed of Cu. Selected-area electron diffraction (SAED) pattern indicated the nanowires are single crystalline and the growth direction of the nanowires is along the [220] direction. With the deposition time increasing, the length of Cu nanowires increaseed.

Journal of Catalysis, 2014

A series of Ni catalysts were prepared with various supports (ZSM-5, Al 2 O 3 , SiO 2 , bentonite... more A series of Ni catalysts were prepared with various supports (ZSM-5, Al 2 O 3 , SiO 2 , bentonite, TiO 2 , and kieselguhr) and their catalytic properties were investigated for the hydrogenation of cellobiose and glucose, the reaction intermediates of cellulose hydrolysis in hot-compressed water, in order to elucidate the key factors to control the hexitols selectivity in the hydrolytic hydrogenation of cellulose. For the hydrogenation of cellobiose, hexitols were produced with a selectivity above 82% over Ni/ZSM-5, but the other checked Ni catalysts produced large amount of glycerol, ethylene glycol, and propanediol, and the product distribution strikingly depended on the catalysts used. On the basis of kinetic experiments, it was the hydrogenation/dehydrogenation ability of Ni catalyst that played a critical role in controlling hexitols selectivity. High hydrogenation and inferior dehydrogenation activity of Ni catalysts were essential for obtaining high yield of hexitols in the hydrolytic hydrogenation of cellulose. The synergistic effect of Ni active species and acid-base sites was proposed to accelerate the dehydrogenation of sorbitol and thus reducing the yield of hexitols.