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Frontiers of Materials Science


ISSN 2095-025X (Print)
ISSN 2095-0268 (Online)
CN 11-5985/TB
Postal Subscription Code 80-974
2018 Impact Factor: 1.701

, Volume 14 Issue 1

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Synthesis, characterization, antibacterial and photocatalytic performance of Ag/AgI/TiO2 hollow sphere composites
Zhihong JING, Xiue LIU, Yan DU, Yuanchun HE, Tingjiang YAN, Wenliang WANG, Wenjuan LI
Front. Mater. Sci.. 2020, 14 (1): 1-13.
Abstract   HTML   PDF (3445KB)

Dispersed TiO2 hollow spheres were successfully prepared which was obtained via Ostwald ripening under solvothermal conditions without any templates or surfactants. Then, the AgI/TiO2 was synthesized by the deposition−precipitation process. Finally, Ag/AgI/TiO2 was obtained by a photocatalytic reduction way. Their characteristics were analyzed by XRD, SEM, HRTEM, N2 adsorption−desorption measurements and UV-vis absorption spectra. To demonstrate the potential applications of such composites, their antibacterial activity against Escherichia coli (E. coli) was studied by microcalorimetry for the first time, and their photocatalytic performance for degradation of different organic dyes under simulated UV and visible light was discussed. The results indicated that Ag/AgI/TiO2 hollow spheres revealed elevated antibacterial and photocatalytic activity because of their unique morphology, hollow structure and high surface area. The mechanism of the excellent antibacterial and photocatalytic activity of Ag/AgI/TiO2 hollow spheres are discussed which are attributed to the synergetic effect of Ag, AgI and TiO2. It suggested that the new Ag/AgI/TiO2 photocatalyst has broad application prospects in solar cell, sensor, antibacterial, catalysis and nanotechnology.

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Hydrothermal growth of hydroxyapatite and ZnO bilayered nanoarrays on magnesium alloy surface with antibacterial activities
Mengke PENG, Fenyan HU, Minting DU, Bingjie MAI, Shurong ZHENG, Peng LIU, Changhao WANG, Yashao CHEN
Front. Mater. Sci.. 2020, 14 (1): 14-23.
Abstract   HTML   PDF (2475KB)

Magnesium alloy (MgA) has been extensively used as orthopedic and cardiovascular scaffolds in virtue of its good biocompatibility, unique biodegradability and excellent mechanical properties. However, poor corrosion resistance and easy infection after implantation seriously limit the potential applications of MgA in the biomedical field. Herein, we fabricated bilayered nanoarrays of hydroxyapatite nanorods (HANRs) and ZnO nanorods (ZnONRs) onto the surface of MgA (MgA–MgO–HANRs– ZnONRs) via micro-arc oxidation (MAO) treatment, microwave-assisted hydrothermal and hydrothermal methods. The morphology and chemical composition of MgA–MgO– HANRs–ZnONRs was characterized by FE-SEM, XRD and EDS, indicating that HANRs–ZnONRs bilayered nanoarrays were fabricated on the surface of MgA–MgO. The surface of MgA–MgO–HANRs–ZnONRs exhibited excellent hydrophilicity as evidenced by the low water contact angle of 3°. Compared with the original MgA, the corrosion resistance of MgA–MgO–HANRs–ZnONRs was obviously improved with decreasing the corrosive current density (icorr) of 2 orders of magnitude. The MgA–MgO– HANRs–ZnONRs performed excellent antibacterial properties with the bactericidal rate of 96.5% against S. aureus and 94.3% against E. coli.

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Facile synthesis of asymmetric patchy Janus Ag/Cu particles and study of their antifungal activity
Sudipta BISWAS, Satadru PRAMANIK, Suman MANDAL, Sudeshna SARKAR, Sujata CHAUDHURI, Swati DE
Front. Mater. Sci.. 2020, 14 (1): 24-32.
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Asymmetric patchy Ag/Cu Janus nanoparticles (NPs) were synthesized via a “seed-mediated” approach. This is the first report of synthesis of nanometer sized metal-based Janus NPs without using complicated methods. Selective adsorption of the surfactant onto the seed NPs leads to the formation of Janus type structure. Subsequently the reduction potential of Ag+/Ag0 and Cu2+/Cu0 systems directs the formation of the “patch”. The patchy Janus NPs show significant antifungal activity towards a potent rice pathogen thus offering the prospect of future application in crop protection.

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Preparation and visible photocatalytic dye degradation of Mn-TiO2/sepiolite photocatalysts
Pengfei ZHU, Zhihao REN, Ruoxu WANG, Ming DUAN, Lisi XIE, Jing XU, Yujing TIAN
Front. Mater. Sci.. 2020, 14 (1): 33-42.
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The performance of Mn-TiO2/sepiolite photocatalysts prepared by the sol-gel method and calcinated at different temperatures was studied in the photocatalytic degradation of direct fast emerald green dye under visible light irradiation, and a series of analytical techniques such as XRD, SEM, FTIR, TG-DSC, XPS, UV-vis-DRS and Raman spectroscopy were used to characterize the morphology, structure and optical properties of the photocatalysts. It is found that the anatase TiO2 was formed in all photocatalysts. Mn4+ might incorporate into the lattice structure of TiO2 and partially replace Ti4+, thus causing the defects in the crystal structure and the broadening of the spectral response range of TiO2. At the same time, TiO2 particles were dispersed on the surface of the sepiolite, which immobilized TiO2 particles with sepiolite via the bond of Ti−O−Si. Mn-TiO2/sepiolite calcined at 400 °C exhibits the highest photocatalytic activity and the degradation rate of direct fast emerald green is up to 98.13%. Meanwhile, it also shows good stability and universality.

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Microwave hydrothermal synthesis of lanthanum oxyfluoride nanorods for photocatalytic nitrogen fixation: Effect of Pr doping
Xiangyu YAN, Da DAI, Kun MA, Shixiang ZUO, Wenjie LIU, Xiazhang LI, Chao YAO
Front. Mater. Sci.. 2020, 14 (1): 43-51.
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Photocatalytic fixation of nitrogen has been recognized as a green and promising strategy for ammonia synthesis under ambient conditions. However, the efficient reduction of nitrogen remains a challenge due to high activation energy of nitrogen and low utilization of solar energy. Herein, lanthanum oxyfluoride with different doping content of Pr3+ (LaOF:xPr3+) upconversion nanorods were synthesized by microwave hydrothermal method. Results indicated that the doping of Pr3+ generated considerable defects on the surface of LaOF which acted as the adsorption and activation center for nitrogen. Meanwhile, the Pr3+ ion narrowed the band gap and broadened the light response range of LaOF because LaOF:Pr3+ can upconvert visible light into ultraviolet light, which excite LaOF nanorods and improve the utilization of solar light. The doping amount of Pr3+ had critical effect on the photocatalytic nitrogen fixation performance which reached as high as 180 μmol·L−1·h−1 when the molar ratio of Pr3+ to LaOF was optimized to be 2%.

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Mo--V--Nb--O-based catalysts for low-temperature selective oxidation of Cα--OH lignin model compounds
Lu-Lu ZHANG, Kun HAO, Rui-Kai WANG, Xiu-Qiang MA, Tong LIU, Liang SONG, Qing YU, Zhong-Wei WANG, Jian-Min ZENG, Rong-Chang ZENG
Front. Mater. Sci.. 2020, 14 (1): 52-61.
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Mo–V–Nb tri-component oxide catalysts were prepared and firstly used for the selective oxidation of Cα−OH lignin compounds. The catalytic performance of the composite oxides was obviously enhanced due to the synergistic effects of Mo and V elements. Mo5−xVxO14 phase with a variable Mo/V ratio provided suitable active sites for the oxidative dehydrogenation (ODH) of Cα−OH lignin model compound. The optimized Mo–V–Nb molar composition was confirmed as Mo0.61V0.31Nb0.08Ox/TiO2, which exhibited the prominent catalytic activity with the turnover frequency of 1.04×10−3 mmol· g(cat)−1·s−1. Even at room temperature, the catalysts showed highly-efficient ODH reaction activities. The active phase for selective oxidation reaction and the inhibiting effect of α-MoO3 phase were also discussed in the study.

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Preparation of P(St-NMA) microsphere inks and their application in photonic crystal patterns with brilliant structural colors
Guojin LIU, Pengshuai HAN, Liqin CHAI, Peng LU, Yuping HE, Lan ZHOU
Front. Mater. Sci.. 2020, 14 (1): 62-72.
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Patterned photonic crystals with structural colors on textile substrates have attracted a special attention due to the great advantages in application, which currently become a research hot-spot. This study utilized an ink-jet printing technology to prepare high-quality photonic crystal patterns with structural colors on polyester substrates. The self-assembly temperature of poly(styrene-N-methylol acrylamide) (P(St-NMA)) microspheres set to construct photonic crystals were deeply optimized. Moreover, the structural colors of prepared photonic crystal patterns were characterized and evaluated. When the mass fraction of P(St-NMA) microspheres was 1.0 wt.%, the pH value ranged from 5 to 7, and the surface tension was in the range of 63.79 to 71.20 mN/m, inks could present the best print performance. At 60 °C, prepared P(St-NMA) microsphere inks were good for printing to obtain patterned photonic crystals with regular arrangement and beautiful structural colors. Specifically, photonic crystals with different colors could be constructed by regulating the diameter of microspheres in inks, and prepared structural colors exhibited distinct iridescent phenomenon. The present results could provide a theoretical basis for the industrial realization of patterned photonic crystals by ink-jet printing technology.

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Enhancement of red emission assigned to inversion defects in ZnAl2O4:Cr3+ hollow spheres
Dong ZHANG, Jingxin CHEN, Chunyu DU, Bingjun ZHU, Qingru WANG, Qiang SHI, Shouxin CUI, Wenjun WANG
Front. Mater. Sci.. 2020, 14 (1): 73-80.
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ZnAl2O4:Cr3+ hollow spheres composed of secondary nanoparticles with single spinel phase were fabricated using carbon templets. Monitoring the emission of 687 nm, two wide excitation bands attributed to the electrons of Cr3+ transiting from 4A2g (4F) → 4T1g (4F) and 4A2g (4F) → 4T2g (4F) were observed. The broad excitation band at about 397 nm was asymmetric and consisted of two peaks, indicating that there was a trigonal distortion existing in the lattices. The intensity of all emitting peaks revealed sharp increasing trend with the sintering temperature increase, and the intensity of emission at 698 nm assigned to inversion defects was more intense than that of emission at 687 nm assigned to octahedral Cr3+ ions in the undistorted spinel lattice. The samples with higher synthesized temperature revealed longer decay time, and the relative weightage of shorter decay time component decreased with the increase of sintering temperature, indicating that the surface defects decreased.

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Investigation of post-thermal annealing-induced enhancement in photovoltaic performance for squaraine-based organic solar cells
Rui ZHU, Feiyang LIU, Zixing WANG, Bin WEI, Guo CHEN
Front. Mater. Sci.. 2020, 14 (1): 81-88.
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In this work, we have systematically investigated the post-thermal annealing-induced enhancement in photovoltaic performance of a 2,4-bis[4-(N, N-diisobutylamino)-2,6-dihydroxyphenyl] squaraine (DIBSQ)/C60 planar heterojunction (PHJ) organic solar cells (OSCs). An increased power conversion efficiency (PCE) of 3.28% has been realized from a DIBSQ/C60 device with thermal annealing at 100 °C for 4 min, which is about 33% enhancement compared with that of the as-cast device. The improvement of the device performance may be mainly ascribed to the crystallinity of the DIBSQ film with post-thermal annealing, which will change the DIBSQ donor and C60 acceptor interface from PHJ to hybrid planar-mixed heterojunction. This new donor–acceptor heterojunction structure will significantly improve the charge separation and charge collection efficiency, as well as the open circuit voltage (Voc) of the device, leading to an enhanced PCE. This work provides an effective strategy to improve the photovoltaic performance of SQ-based OSCs.

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Optimized optical design of thin-film transistor arrays for high transmittance and excellent chromaticity
Chengzhi LUO, Shiyu LONG, Guanghui LIU, COOPER, Min ZHANG, Fei AI
Front. Mater. Sci.. 2020, 14 (1): 89-95.
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Transmittance and chromaticity are essential requirements for optical performance of thin-film transistor (TFT) arrays. However, it is still a challenge to get high transmittance and excellent chromaticity at the same time. In this paper, optimized optical design by using antireflection film theory and optical phase modulation is demonstrated in low temperature poly-silicon (LTPS) TFT arrays. To realize high transmittance, the refractive index difference of adjacent films is modified by using silicon oxynitride (SiOxNy) with adjustable refractive index. To realize excellent chromaticity, the thicknesses of multilayer films are precisely regulated for antireflection of certain wavelength light. The results show that the transmittance and chromaticity have been improved by about 6% and 18‰, respectively, at the same time, which is a big step forward for high optical performance of TFT arrays. The device characteristics of the TFT arrays with the optimal design, such as threshold voltage and electron mobility, are comparable to those of conventional TFT arrays. The optimized optical design results in enhanced power-conversion efficiencies and perfects the multilayer film design on the basic theory, which has great practicability to be applied in TFT arrays.

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Corrosion resistance and hydrophobicity of myristic acid modified Mg--Al LDH/Mg(OH)2 steam coating on magnesium alloy AZ31
Zai-Meng QIU, Fen ZHANG, Jun-Tong CHU, Yu-Chao LI, Liang SONG
Front. Mater. Sci.. 2020, 14 (1): 96-107.
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A hydrophobic surface was successfully fabricated on the Mg–Al-layered double hydroxide (Mg–Al LDH)/Mg(OH)2-coated AZ31 magnesium alloy via an in-situ steam coating (SC) process and a subsequent surface modification with environment-friendly myristic acid (MA). The microstructure, composition and hydrophobicity of SC/MA composite coating were investigated by XRD, SEM, EDS, FTIR, and contact angle (CA) measurement. The corrosion behavior of the hybrid coating was evaluated by potentiodynamic polarization, EIS and hydrogen evolution test in 3.5 wt.% NaCl solution. The results showed that the LDH coating had nano-flake microstructure, which remained unchanged after modification with MA. The CA of the MA-modified coating surface reached up to 129°±3.5°, and the corrosion current density of SC/MA-2 coating decreased about three orders of the magnitude compared to that of the substrate. It is proven that the modified surface has an effective anti-corrosion effect on AZ31 alloy. The formation mechanism and the corrosion mechanism of the coating were also discussed.

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11 articles