Co-reporter:Yanzhen He, Ping Xu, Bin Zhang, Yunchen Du, Bo Song, Xijiang Han, and Huisheng Peng
ACS Applied Materials & Interfaces November 8, 2017 Volume 9(Issue 44) pp:38401-38401
Publication Date(Web):October 16, 2017
DOI:10.1021/acsami.7b09559
Sodium ion batteries (SIBs) have attracted increasing attentions as promising alternatives to lithium ion batteries (LIBs). Herein, we design and synthesize ultrasmall MnO nanoparticles (∼4 nm) supported on nitrogen-doped carbon nanotubes (NDCT@MnO) as promising anode materials of SIBs. It is revealed that the carbonization temperature can greatly influence the structural features and thus the Na-storage behavior of the NDCT@MnO nanocomposites. The synergetic interaction between MnO and NDCT in the NDCT@MnO nanocomposites provides high rate capability and long-term cycling life due to high surface area, electrical conductivity, enhanced diffusion rate of Na+ ions, and prevented agglomeration and high stability of MnO nanoparticles. The resulting SIBs provide a high reversible specific capacity of 709 mAh g–1 at a current density of 0.1 A g–1 and a high capacity of 536 mAh g–1 almost without loss after 250 cycles at 0.2 A g–1. Even at a high current density of 5 A g–1, a capacity of 273 mAh g–1 can be maintained after 3000 cycles.Keywords: anode; electrode reactions; MnO nanoparticle; nitrogen-doped carbon nanotube; Sodium ion battery;
Co-reporter:Chang Hu, Xianjie Wang, Peng Miao, Lingli Zhang, Bingqian Song, Weilong Liu, Zhe Lv, Yu Zhang, Yu Sui, Jinke Tang, Yanqiang Yang, Bo Song, and Ping Xu
ACS Applied Materials & Interfaces May 31, 2017 Volume 9(Issue 21) pp:18362-18362
Publication Date(Web):May 9, 2017
DOI:10.1021/acsami.7b04298
The lateral photovoltaic (LPV) effect has attracted much attention for a long time because of its application in position-sensitive detectors (PSD). Here, we report the ultrafast response of the LPV in amorphous MoS2/Si (a-MoS2/Si) junctions prepared by the pulsed laser deposition (PLD) technique. Different orientations of the built-in field and the breakover voltages are observed for a-MoS2 films deposited on p- and n-type Si wafers, resulting in the induction of positive and negative voltages in the a-MoS2/n-Si and a-MoS2/p-Si junctions upon laser illumination, respectively. The dependence of the LPV on the position of the illumination shows very high sensitivity (183 mV mm–1) and good linearity. The optical relaxation time of LPV with a positive voltage was about 5.8 μs in a-MoS2/n-Si junction, whereas the optical relaxation time of LPV with a negative voltage was about 2.1 μs in a-MoS2/p-Si junction. Our results clearly suggested that the inversion layer at the a-MoS2/Si interface made a good contribution to the ultrafast response of the LPV in a-MoS2/Si junctions. The large positional sensitivity and ultrafast relaxation of LPV may promise the a-MoS2/Si junction’s applications in fast position-sensitive detectors.Keywords: amorphous MoS2/Si junctions; inversion layer; lateral photovoltaic (LPV); position-sensitive detectors; pulsed laser deposition (PLD); ultrafast relaxation;
Co-reporter:Ying Yin;Peng Miao;Yumin Zhang;Jiecai Han;Xinghong Zhang;Yue Gong;Lin Gu;Chengyan Xu;Tai Yao;Yi Wang;Bo Song;Song Jin
Advanced Functional Materials 2017 Volume 27(Issue 16) pp:
Publication Date(Web):2017/04/01
DOI:10.1002/adfm.201606694
2D transition metal dichalcogenide (TMD) materials have been recognized as active platforms for surface-enhanced Raman spectroscopy (SERS). Here, the effect of crystal structure (phase) transition is shown, which leads to altered electronic structures of TMD materials, on the Raman enhancement. Using thermally evaporated copper phthalocyanine, solution soaked rhodamine 6G, and crystal violet as typical probe molecules, it is found that a phase transition from 2H- to 1T-phase can significantly increase the Raman enhancement effect on MoX2 (X = S, Se) monolayers through a predominantly chemical mechanism. First-principle density functional theory calculations indicate that the significant enhancement of the Raman signals on metallic 1T-MoX2 can be attributed to the facilitated electron transfer from the Fermi energy level of metallic 1T-MoX2 to the highest occupied molecular orbital level of the probe molecules, which is more efficient than the process from the top of valence band of semiconducting 2H-MoX2. This study not only reveals the origin of the Raman enhancement and identifies 1T-MoSe2 and 1T-MoS2 as potential Raman enhancement substrates, but also paves the way for designing new 2D SERS substrates via phase-transition engineering.
Co-reporter:Ying Yin;Yumin Zhang;Tangling Gao;Tai Yao;Xinghong Zhang;Jiecai Han;Xianjie Wang;Zhihua Zhang;Peng Zhang;Xingzhong Cao;Bo Song;Song Jin
Advanced Materials 2017 Volume 29(Issue 28) pp:
Publication Date(Web):2017/07/01
DOI:10.1002/adma.201700311
MoSe2 is a promising earth-abundant electrocatalyst for the hydrogen-evolution reaction (HER), even though it has received much less attention among the layered dichalcogenide (MX2) materials than MoS2 so far. Here, a novel hydrothermal-synthesis strategy is presented to achieve simultaneous and synergistic modulation of crystal phase and disorder in partially crystallized 1T-MoSe2 nanosheets to dramatically enhance their HER catalytic activity. Careful structural characterization and defect characterization using positron annihilation lifetime spectroscopy correlated with electrochemical measurements show that the formation of the 1T phase under a large excess of the NaBH4 reductant during synthesis can effectively improve the intrinsic activity and conductivity, and the disordered structure from a lower reaction temperature can provide abundant unsaturated defects as active sites. Such synergistic effects lead to superior HER catalytic activity with an overpotential of 152 mV versus reversible hydrogen electrode (RHE) for the electrocatalytic current density of j = −10 mA cm−2, and a Tafel slope of 52 mV dec−1. This work paves a new pathway for improving the catalytic activity of MoSe2 and generally MX2-based electrocatalysts via a synergistic modulation strategy.
Co-reporter:Jinzhen Huang, Jiecai Han, Tangling Gao, Xinghong Zhang, Jiajie Li, Zhenjiang Li, Ping Xu, Bo Song
Carbon 2017 Volume 124(Volume 124) pp:
Publication Date(Web):1 November 2017
DOI:10.1016/j.carbon.2017.08.033
Nitrogen-abundant compounds are generally regarded as perfect precursors toward in situ synthesis of nitrogen-doped carbon materials. In this study, we demonstrate a facile one-pot procedure to synthesize polyaniline-coated melamine fiber (PANI@MF) as the precursor, in which melamine fiber (MF) acts as both scaffold and nitrogen source. After high-temperature pyrolysis, wrinkled nitrogen-doped carbon nanoribbons (NCNRs) with high specific surface area (701 cm2 g−1) and cumulative pore volume (3.13 cm3 g−1) are fabricated for electrocatalytic oxygen reduction reaction (ORR). The NCNR catalyst exhibits comparative onset potential, half-wave potential, and limiting current to those of commercial Pt/C (20 wt%, E-TEK) in alkaline media, mainly due to its high specific surface area and sufficient active sites induced by synthetic effect between nitrogen atom and carbon framework. Moreover, NCNR catalyst shows enhanced stability and high tolerance to methanol crossover effect. This study is expected to broaden new horizon to the design and fabrication of new metal-free carbon-based electrocatalyst for ORR.Download high-res image (297KB)Download full-size image Herein, we demonstrate a facile one-pot pathway to synthesize nitrogen-doped carbon nanoribbons (NCNR) with high oxygen reduction reaction (ORR) performance.
Co-reporter:Kai Li;Dmitrii Rakov;Wei Zhang
Chemical Communications 2017 vol. 53(Issue 58) pp:8199-8202
Publication Date(Web):2017/07/18
DOI:10.1039/C7CC03173D
Here we demonstrate the improvement of the intrinsic electrocatalytic hydrogen evolution activity of NiPS3 by proper cobalt doping. The optimized Ni0.95Co0.05PS3 nanosheets display a geometric catalytic current density of −10 mA cm−2 at an overpotential of 71 mV vs. RHE and a Tafel slope of 77 mV dec−1 in 1.0 M KOH.
Co-reporter:Jiajie Li;Yumin Zhang;Tangling Gao;Chang Hu;Tai Yao;Quan Yuan;Xianjie Wang;Zhihua Zhang;Jikang Jian;Xinghong Zhang;Bo Song
Journal of Materials Chemistry A 2017 vol. 5(Issue 10) pp:4904-4911
Publication Date(Web):2017/03/07
DOI:10.1039/C6TA10441J
Cadmium telluride (CdTe) thin-film solar cells show great potential due to their high efficiency, thermal stability, and low manufacturing cost. However, the practical performance of CdTe solar cells is often severely restricted due to the deficiency or excess of Cu diffusion, leading to a non-ohmic contact and electrical shorts and thus performance degradation. Herein, we demonstrate an innovative strategy for the fabrication of a Cu-free back contact by depositing CdTe quantum dots (QDs) on a CdTe layer using the pulsed laser deposition (PLD) technique, and find that the average relative power conversion efficiency is significantly enhanced by ∼6.2%. More importantly, the as-prepared CdTe QDs are thermally stable and CdTe with CdTe QD/Au back contact devices show no sign of degradation during exposure to air even after nearly one year. This study provides new insight into the design and property modulation of CdTe-based photovoltaics.
Co-reporter:Jiajie Li, Yumin Zhang, Xinghong Zhang, Jinzhen Huang, Jiecai Han, Zhihua Zhang, Xijiang Han, Ping XuBo Song
ACS Applied Materials & Interfaces 2017 Volume 9(Issue 1) pp:
Publication Date(Web):December 16, 2016
DOI:10.1021/acsami.6b12547
Replacement of rare and precious metal catalysts with low-cost and earth-abundant ones is currently among the major goals of sustainable chemistry. Herein, we report the synthesis of S, N dual-doped graphene-like carbon nanosheets via a simple pyrolysis of a mixture of melamine and dibenzyl sulfide as efficient metal-free electrocatalysts for oxygen reduction reaction (ORR). The S, N dual-doped graphene-like carbon nanosheets show enhanced activity toward ORR as compared with mono-doped counterparts, and excellent durability in contrast to the conventional Pt/C electrocatalyst in both alkaline and acidic media. A high content of graphitic-N and pyridinic-N is necessary for ORR electrocatalysis in the graphene-like carbon nanosheets, but an appropriate amount of S atoms further contributes to the improvement of ORR activity. Superior ORR performance from the as-prepared S, N dual-doped graphene-like carbon nanosheets implies great promises in practical applications in energy devices.Keywords: electrocatalysis; graphene-like; metal-free; oxygen reduction reaction; S, N-doped carbon;
Co-reporter:Jianglong He, Yanzhen He, Yanan Fan, Bin Zhang, Yunchen Du, Jingyu Wang, Ping Xu
Carbon 2017 Volume 124(Volume 124) pp:
Publication Date(Web):1 November 2017
DOI:10.1016/j.carbon.2017.08.081
Nitrogen doped carbon materials, as the most promising non-metal electrocatalyst for oxygen reduction reaction (ORR), have attracted great attention because of their catalytic activities approaching to that of commercial Pt/C, good ethanol tolerance, low price and chemical stability. Here, we demonstrate the conjugated polymer-mediated synthesis of a series of nitrogen doped carbon nanoribbons (NDCNRs) through direct carbonization of polyaniline-polypyrrole (PANI-PPy) nanofibers with different monomer ratios. It is important to point out that ammonium fluoride (NH4F) applied in the carbonization process benefits for the production of more defect sites, higher surface area as well as electrochemically active surface area, and the morphology conversion from nanofibers into nanoribbons, though F element doping is not detected in the F-NDCNRs. With optimized monomer ratio (aniline:pyrrole = 1:3), the as-obtained F-NDCNRs(1:3), with higher content of graphitic-N, graphitic-N/pyridinic-N ratio and defect density, provide admirable ORR catalytic performance with an onset potential of 0.976 V vs RHE and a half-wave potential of 0.864 V vs RHE. This study provides new insights into the synthesis of efficient metal-free nitrogen doping carbon materials for ORR applications.Download high-res image (203KB)Download full-size image
Co-reporter:Ying Yin; Jiecai Han; Yumin Zhang; Xinghong Zhang; Ping Xu; Quan Yuan; Leith Samad; Xianjie Wang; Yi Wang; Zhihua Zhang; Peng Zhang; Xingzhong Cao; Bo Song;Song Jin
Journal of the American Chemical Society 2016 Volume 138(Issue 25) pp:7965-7972
Publication Date(Web):June 7, 2016
DOI:10.1021/jacs.6b03714
Molybdenum disulfide (MoS2) is a promising nonprecious catalyst for the hydrogen evolution reaction (HER) that has been extensively studied due to its excellent performance, but the lack of understanding of the factors that impact its catalytic activity hinders further design and enhancement of MoS2-based electrocatalysts. Here, by using novel porous (holey) metallic 1T phase MoS2 nanosheets synthesized by a liquid-ammonia-assisted lithiation route, we systematically investigated the contributions of crystal structure (phase), edges, and sulfur vacancies (S-vacancies) to the catalytic activity toward HER from five representative MoS2 nanosheet samples, including 2H and 1T phase, porous 2H and 1T phase, and sulfur-compensated porous 2H phase. Superior HER catalytic activity was achieved in the porous 1T phase MoS2 nanosheets that have even more edges and S-vacancies than conventional 1T phase MoS2. A comparative study revealed that the phase serves as the key role in determining the HER performance, as 1T phase MoS2 always outperforms the corresponding 2H phase MoS2 samples, and that both edges and S-vacancies also contribute significantly to the catalytic activity in porous MoS2 samples. Then, using combined defect characterization techniques of electron spin resonance spectroscopy and positron annihilation lifetime spectroscopy to quantify the S-vacancies, the contributions of each factor were individually elucidated. This study presents new insights and opens up new avenues for designing electrocatalysts based on MoS2 or other layered materials with enhanced HER performance.
Co-reporter:Yanzhen He, Xijiang Han, Yunchen Du, Bo Song, Ping Xu, and Bin Zhang
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 6) pp:3601
Publication Date(Web):October 19, 2015
DOI:10.1021/acsami.5b07865
Heteroatom-doped carbon materials have attracted significant attention because of their applications in oxygen reduction reaction (ORR) and supercapacitors. Here we demonstrate a facile poly(o-methylaniline)-derived fabrication of bifunctional microporous nitrogen-doped carbon microspheres (NCMSs) with high electrocatalytic activity and stability for ORR and energy storage in supercapacitors. At a pyrolysis temperature of 900 °C, the highly dispersed NCMSs present a high surface area (727.1 m2 g–1), proper total content of doping N, and high concentration of quaternary N, which exhibit superior electrocatalytic activities for ORR to the commercial Pt/C catalysts, high specific capacitance (414 F g–1), and excellent durability, making them very promising for advanced energy conversion and storage. The presented conducting polymer-derived strategy may provide a new way for the fabrication of heteroatom-doped carbon materials for energy device applications.Keywords: conducting polymer; microporous; nitrogen-doped carbon; oxygen reduction reaction; supercapacitor
Co-reporter:Rong Qiang, Yunchen Du, Ying Wang, Na Wang, Chunhua Tian, Jun Ma, Ping Xu, Xijiang Han
Carbon 2016 Volume 98() pp:599-606
Publication Date(Web):March 2016
DOI:10.1016/j.carbon.2015.11.054
Carbon materials, as a typical dielectric loss medium, are always the most attractive candidates for microwave absorption due to their characteristic advantages; however, much less attention has been paid to upgrading their performance by rational design on the microstructure. According to the transmission behavior and loss mechanism of electromagnetic waves, uniform yolk-shell C@C microspheres are innovatively fabricated through a “coating-coating-etching” route as a novel microwave absorber. The unique microstructure endows yolk-shell C@C microspheres with improved BET surface and pore volume as compared to solid carbon microspheres. The microwave absorption properties are evaluated in the frequency range of 2–18 GHz, and as expected, yolk-shell C@C microspheres exhibit excellent reflection loss characteristics, where strong reflection loss (−39.4 dB at 16.2 GHz) and ultra-wide response bandwidth (4.5–18.0 GHz over −20 dB) can be achieved. Such good performance is indeed superior to most carbon absorbers ever reported. Electromagnetic parameters reveal that the yolk-shell structure is favorable for the matching of characteristic impedance, and more importantly, desirable dielectric loss ability can be achieved at matched characteristic impedance. It is believed that the multiple reflections between cores and shells are responsible for the improved dielectric loss.
Co-reporter:Ying Wang;Yunchen Du;Rong Qiang;Chunhua Tian;Xijiang Han
Advanced Materials Interfaces 2016 Volume 3( Issue 7) pp:
Publication Date(Web):
DOI:10.1002/admi.201500684
Graphene-based composites offer immense potential for overcoming the challenges related to the performance, functionality, and durability in microwave absorption. In this study, a sandwich-like graphene-based composite is successfully fabricated by an interfacial engineering of amorphous carbon microspheres (ACMs) and reduced graphene oxide (rGO), with a structure of rGO/ACMs/rGO. The as-prepared rGO/ACMs/rGO composite presents comparable/superior reflection loss characteristics in the frequency range of 2.0–18.0 GHz to previous composites of graphene and high-density magnetic particles. Electromagnetic parameters and simulation results reveal that well-matched characteristic impedance and proper dielectric loss, as well as multiple reflections and interfacial polarizations derived from the unique microstructure should account for the enhanced microwave absorption of rGO/ACMs/rGO. More importantly, rGO/ACMs/rGO exhibits durable performance after being treated at high temperature for a long time. This work provides a new idea for exploring high-performance and durable microwave absorbers of graphene-based materials.
Co-reporter:Hongtao Zhao, Zhigang Li, Nan Zhang, Yunchen Du and Ping Xu
RSC Advances 2016 vol. 6(Issue 76) pp:72263-72268
Publication Date(Web):25 Jul 2016
DOI:10.1039/C6RA14085H
Gamma irradiation induced synthesis of metal or metal oxides has received increasing attention due to its mild reaction conditions. Here, we demonstrate the synthesis of aligned CoxNi1−x (x = 0.25, 0.33, 0.5, 0.67, 0.75) alloy nanobundles via a gamma irradiation induced simultaneous reduction of Co2+ and Ni2+ ions with the assistance of an external magnetic field. The formation of alloy structures was confirmed by element mapping and X-ray absorption studies. Natural ferromagnetic resonance and dielectric loss mainly contribute to the electromagnetic wave absorption of the CoxNi1−x alloy materials, and the composition also has great influence. Co1Ni2 (x = 0.33) has the strongest absorption of −10.5 dB at 13.6 GHz at a thickness of 2 mm, and the electromagnetic absorption properties can be tuned by the thickness of the CoxNi1−x alloys. We believe synthesis of metal alloys through the gamma irradiation induced reduction technique will be appealing to other areas.
Co-reporter:Zhenglong Zhang, Ping Xu, Xianzhong Yang, Wenjie Liang, Mengtao Sun
Journal of Photochemistry and Photobiology C: Photochemistry Reviews 2016 Volume 27() pp:100-112
Publication Date(Web):June 2016
DOI:10.1016/j.jphotochemrev.2016.04.001
•We reviewed plasmon-driven photocatalytic reactions in different environments.•Plasmon-driven photocatalytic reactions in ambient monitored by SERS and TERS.•Plasmon-driven photocatalytic reactions in aqueous monitored by SERS and TERS.•Plasmon-driven photocatalytic reactions in high-vacuum monitored by SERS and TERS.AbstractsThere has been an explosion of interests and activities on plasmon-driven catalytic reactions currently, which has been expanded photonic catalysis to plasmonic catalysis. Particularly, plasmonic catalysis, with activation energy provided by plasmon-induced hot electrons, can exhibit a giant catalytic action on the surface of silver or gold nanostructures, thus breaking the longstanding limitation of photonic catalysis that needs UV light generality. This new surface catalysis has been revealed in various chemical reactions by using surface-enhanced Raman scattering (SERS) and tip-enhanced Raman scattering (TERS), which are the two representative techniques supporting the hot electrons (holes) generated from plasmon-decay on plamonic nanostructures’ surface. In this review, we fully explore the principle of plamonic catalysis, and especially review the advances of plasmon-driven surface catalytic reactions monitoring by SERS and TERS in atmosphere, aqueous and high-vacuum environments. These approaches significantly broaden the applications of plasmonic catalysis such as dissociation of hydrogen, water splitting and hydrocarbon conversion.
Co-reporter:Jiayu Chu;Peng Miao; Xijiang Han; Yunchen Du; Xianjie Wang; Bo Song; Ping Xu
ChemCatChem 2016 Volume 8( Issue 10) pp:1819-1824
Publication Date(Web):
DOI:10.1002/cctc.201600172
Abstract
Surface-plasmon-induced photocatalysis has been of increasing interest as a thriving new paradigm for catalytic reactions, while the efficiency of such kind of reactions remains very limited on metal nanostructures. Herein, an ultrafast photodimerization of p-aminothiophenol (PATP) into p,p′-dimercaptobenzene (DMAB) was witnessed on the hybrid system of Ag/TiO2 by visible-light laser excitation, even under inert gas atmosphere. Hot electrons generated from plasmonic decay would transfer to the conduction band of TiO2, which enables the holes (generated in the metal nanoparticles) to trigger the immediate PATP–DMAB conversion. We believe such ultrafast reaction process, with highly enhanced efficiency, will greatly promote the research and applications of the surface-plasmon-induced or assisted catalytic reactions.
Co-reporter:Dengtai Chen;Dr. Xijiang Han;Dr. Yunchen Du;Dr. Hsing-Lin Wang;Dr. Ping Xu
ChemPhysChem 2016 Volume 17( Issue 1) pp:46-50
Publication Date(Web):
DOI:10.1002/cphc.201500874
Abstract
The cyclobutane cleavage reaction is an important process and has received continuous interest. Herein, we demonstrate the visible laser-driven cleavage reaction of cyclobutane in crystal form by using in situ Raman spectroscopy. Silver(I) coordination-induced strain and thermal effects from the laser irradiation are the two main driving forces for the cleavage of cyclobutane crystals. This work may open up a new avenue for studying cyclobutane cleavage reactions, as compared to the conventional routes using ex situ techniques.
Co-reporter:Dengtai Chen;Dr. Xijiang Han;Dr. Yunchen Du;Dr. Hsing-Lin Wang;Dr. Ping Xu
ChemPhysChem 2016 Volume 17( Issue 1) pp:
Publication Date(Web):
DOI:10.1002/cphc.201501157
Co-reporter:Leilei Kang, Jiayu Chu, Hongtao Zhao, Ping Xu and Mengtao Sun
Journal of Materials Chemistry A 2015 vol. 3(Issue 35) pp:9024-9037
Publication Date(Web):28 Jul 2015
DOI:10.1039/C5TC01759A
Graphene continues to attract tremendous interest, owing to its excellent optical and electronic properties. Based on its unique features, graphene has been employed in the ever-expanding research fields. Surface-enhanced Raman scattering (SERS) may be one of the significant applied fields where graphene can make a difference. Since its discovery, the SERS technique has been capable of ultra sensitively detecting chemical and biological molecules at very low concentration, even at the single molecule level, but some problems, such as irreproducible SERS signals, should be overcome before being practically applied for spectral analysis. Graphene can be a promising candidate to make up the deficiency of a conventional metal SERS substrate. Furthermore, graphene, serving as an enhancement material, is usually deemed as a chemically inert substance to isolate the interactions between metal and probe molecules. While, irradiated by laser, structure changes of graphene under specific conditions and the contributions of its high electron mobility in plasmon-induced catalytic reactions are often ignored. In this review, we mainly focus on the state-of-the-art applications of graphene in the fields of SERS and laser-induced catalytic reactions. The advances in informative Raman spectra of graphene are firstly reviewed. Then, the graphene related SERS substrates, including graphene-enhanced Raman scattering (GERS) and graphene-mediated SERS (G-SERS), are summarized. We finally highlight the catalytic reactions occurring on graphene itself and molecules adsorbed onto graphene upon laser irradiation.
Co-reporter:Rong Qiang, Yunchen Du, Hongtao Zhao, Ying Wang, Chunhua Tian, Zhigang Li, Xijiang Han and Ping Xu
Journal of Materials Chemistry A 2015 vol. 3(Issue 25) pp:13426-13434
Publication Date(Web):06 May 2015
DOI:10.1039/C5TA01457C
Composites of magnetic metal nanoparticles and carbon materials are highly desirable for high-performance microwave absorbers due to their compatible dielectric loss and magnetic loss abilities. In this article, novel nanocomposites, Fe/C nanocubes, have been successfully prepared through an in situ route from a metal–organic framework, Prussian blue, by controlled high-temperature pyrolysis. The resultant nanocubes are actually composed of a cubic framework of amorphous carbon and uniformly dispersed core–shell Fe@graphitic carbon nanoparticles. Within the studied pyrolysis temperature range (600–700 °C), the porous structure, iron content, magnetic properties, and graphitization degree of the Fe/C nanocubes can be well modulated. Particularly, the improved carbon graphitization degree, both in amorphous frameworks and graphitic shells, results in enhanced complex permittivity and dielectric loss properties. The homogeneous chemical composition and microstructure stimulate the formation of multiple dielectric resonances by regularizing various polarizations. The synergistic effect of dielectric loss, magnetic loss, matched impedance, and dielectric resonances accounts for the improved microwave absorption properties of the Fe/C nanocubes. The absorption bands of the optimum one obtained at 650 °C are superior to most composites ever reported. By considering the good chemical homogeneity and microwave absorption, we believe that the as-fabricated Fe/C nanocubes will be promising candidates as highly effective microwave absorbers.
Co-reporter:Wei Huang, Qiang Jing, Yunchen Du, Bin Zhang, Xiangli Meng, Mengtao Sun, Kirk S. Schanze, Hong Gao and Ping Xu
Journal of Materials Chemistry A 2015 vol. 3(Issue 20) pp:5285-5291
Publication Date(Web):21 Apr 2015
DOI:10.1039/C5TC00835B
Here we demonstrate the surface plasmon (SP) induced nitration of aromatic rings by an in situ surface enhanced Raman spectroscopy (SERS) technique. The size feature of the as-prepared Au, Ag and Ag@PDA@Au hierarchical structures allows monitoring the entire reaction process on a single hierarchical structure. With benzenethiol (BT) and HNO3 as reactants, SP induced aromatic nitration can be successfully realized without the assistance of a conventional acid catalyst, H2SO4. Experimental and theoretical studies confirm that the nitration reaction leads to para-nitrothiophenol (p-NTP). While control experiments show that SP here functions as a local heating source and the presence of metal is also necessary for this nitration reaction. This SP induced aromatic nitration reaction also displays SERS substrate-dependent reaction kinetics, which proceeds more rapidly on the Au surface. Higher laser power can generate a stronger photothermal effect, and thus an accelerated reaction rate for this reaction. We believe this finding may broaden the research areas in the SP assisted or induced catalytic reactions.
Co-reporter:Jiajie Li, Yumin Zhang, Xinghong Zhang, Jiecai Han, Yi Wang, Lin Gu, Zhihua Zhang, Xianjie Wang, Jikang Jian, Ping Xu, and Bo Song
ACS Applied Materials & Interfaces 2015 Volume 7(Issue 35) pp:19626
Publication Date(Web):August 20, 2015
DOI:10.1021/acsami.5b03845
Carbon-based nanomaterials provide an attractive perspective to replace precious Pt-based electrocatalysts for oxygen reduction reaction (ORR) to enhance the practical applications of fuel cells. Herein, we demonstrate a one-pot direct transformation from graphitic-phase C3N4 (g-C3N4) to nitrogen-doped graphene. g-C3N4, containing only C and N elements, acts as a self-sacrificing template to construct the framework of nitrogen-doped graphene. The relative contents of graphitic and pyridinic-N can be well-tuned by the controlled annealing process. The resulting nitrogen-doped graphene materials show excellent electrocatalytic activity toward ORR, and much enhanced durability and tolerance to methanol in contrast to the conventional Pt/C electrocatalyst in alkaline medium. It is determined that a higher content of N does not necessarily lead to enhanced electrocatalytic activity; rather, at a relatively low N content and a high ratio of graphitic-N/pyridinic-N, the nitrogen-doped graphene obtained by annealing at 900 °C (NGA900) provides the most promising activity for ORR. This study may provide further useful insights on the nature of ORR catalysis of carbon-based materials.Keywords: electrocatalysis; graphitic C3N4; metal-free; N-doped graphene; oxygen reduction
Co-reporter:Lu Xiong, Siwei Li, Bin Zhang, Yunchen Du, Peng Miao, Yan Ma, Yingxin Han, Hongtao Zhao and Ping Xu
RSC Advances 2015 vol. 5(Issue 93) pp:76101-76106
Publication Date(Web):01 Sep 2015
DOI:10.1039/C5RA13426A
The galvanic replacement reaction (GRR) involves a corrosion process that is driven by the difference in the electrochemical potentials of two species. Here we demonstrate the synthesis of hollow Cu2O–Au nanocomposites via a GRR process between Cu2O and HAuCl4, and subsequent conversion of the hollow Cu2O–Au nanocomposites into Au nanocages that are actually assembled of ∼10 nm Au nanoparticles. It is interesting to find that Cu2O nanocubes produced from reductive solution chemistry are actually transformed from Cu(OH)2 nanowire precursors, and the Cu2O particle size is inversely proportional to the reaction temperature. A time-dependent TEM study of the GRR process between Cu2O and HAuCl4 indicates that this reaction involves evolution of an internal hollow core and surface precipitation of Au nanoparticles, which allows the formation of hollow Cu2O–Au nanocomposites. Comparing the properties of hollow Cu2O–Au nanocomposites and Au nanocages, it is determined that the hollow Cu2O–Au nanocomposites are more catalytically active in the reduction of 4-nitrophenol into 4-aminophenol in the presence of NaBH4, and Au nanocages are two orders of magnitude more sensitive in SERS detection of the target molecule, methylene blue. We believe the findings in this work may render a better understanding of the preparation and GRR process of Cu2O nanomaterials.
Co-reporter:Leilei Kang; Xijiang Han;Jiayu Chu; Jie Xiong;Xiong He;Dr. Hsing-Lin Wang; Ping Xu
ChemCatChem 2015 Volume 7( Issue 6) pp:1004-1010
Publication Date(Web):
DOI:10.1002/cctc.201403032
Abstract
We demonstrate the plasmon-driven catalytic reactions of 4-nitrothiophenol (4NTP) on a single Ag microsphere by an in situ surface-enhanced Raman spectroscopy (SERS) technique. The highly SERS-active hierarchical Ag structures served as an ideal platform to study plasmon-driven catalytic reactions. This single-particle surface-enhanced Raman spectroscopy (SP-SERS) technique coupled with inbuilt apparatus allow us to study the impact of reaction atmospheres and laser power on the rate of dimerization and reduction of 4NTP. Contrary to that found in previous studies, 4NTP could be transformed into 4-aminothiophenol under H2O or H2 atmosphere. The broadening and splitting of the ν(CC) band during the reaction results from the frequency shift of the ν(CC) band that arises from different products. Our results suggest that the SP-SERS technique is ideally suited to study plasmon-driven catalytic reactions because of the possibility to monitor the reaction under controlled atmospheres in real time.
Co-reporter:Qing Li;Wei Gao;Shuguo Ma;Guoqi Zhang;Ruiguo Cao;Jaephil Cho;Hsing-Lin Wang;Gang Wu
Advanced Materials 2014 Volume 26( Issue 9) pp:1378-1386
Publication Date(Web):
DOI:10.1002/adma.201304218
Co-reporter:Dengtai Chen, Xijiang Han, Wen Jin, Yunchen Du and Ping Xu
Chemical Communications 2014 vol. 50(Issue 98) pp:15631-15633
Publication Date(Web):27 Oct 2014
DOI:10.1039/C4CC06808D
Visible laser induced [2+2] cycloaddition of solid-state pyridine substituted olefins into cyclobutane has been monitored by an in situ Raman technique. The laser power and wavelength can dramatically alter the reaction kinetics, as a prior melting process (heating from laser irradiation) is required for this [2+2] photoreaction.
Co-reporter:Yunchen Du, Wenwen Liu, Rong Qiang, Ying Wang, Xijiang Han, Jun Ma, and Ping Xu
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 15) pp:12997
Publication Date(Web):July 22, 2014
DOI:10.1021/am502910d
Core–shell composites, Fe3O4@C, with 500 nm Fe3O4 microspheres as cores have been successfully prepared through in situ polymerization of phenolic resin on the Fe3O4 surface and subsequent high-temperature carbonization. The thickness of carbon shell, from 20 to 70 nm, can be well controlled by modulating the weight ratio of resorcinol and Fe3O4 microspheres. Carbothermic reduction has not been triggered at present conditions, thus the crystalline phase and magnetic property of Fe3O4 micropsheres can be well preserved during the carbonization process. Although carbon shells display amorphous nature, Raman spectra reveal that the presence of Fe3O4 micropsheres can promote their graphitization degree to a certain extent. Coating Fe3O4 microspheres with carbon shells will not only increase the complex permittivity but also improve characteristic impedance, leading to multiple relaxation processes in these composites, thus the microwave absorption properties of these composites are greatly enhanced. Very interestingly, a critical thickness of carbon shells leads to an unusual dielectric behavior of the core–shell structure, which endows these composites with strong reflection loss, especially in the high frequency range. By considering good chemical homogeneity and microwave absorption, we believe the as-fabricated Fe3O4@C composites can be promising candidates as highly effective microwave absorbers.Keywords: carbon; composites; core−shell; Fe3O4; microwave absorption
Co-reporter:Weiyu Liu, Peng Miao, Lu Xiong, Yunchen Du, Xijiang Han and Ping Xu
Physical Chemistry Chemical Physics 2014 vol. 16(Issue 41) pp:22867-22873
Publication Date(Web):10 Sep 2014
DOI:10.1039/C4CP02677B
We demonstrate here a facile fabrication of n-dodecyl mercaptan-modified superhydrophobic Ag nanostructures on polyaniline membranes for molecular detection based on SERS technique, which combines the superhydrophobic condensation effect and the high enhancement factor. It is calculated that the as-fabricated superhydrophobic substrate can exhibit a 21-fold stronger molecular condensation, and thus further amplifies the SERS signal to achieve more sensitive detection. The detection limit of the target molecule, methylene blue (MB), on this superhydrophobic substrate can be 1 order of magnitude higher than that on the hydrophilic substrate. With high reproducibility, the feasibility of using this SERS-active superhydrophobic substrate for quantitative molecular detection is explored. A partial least squares (PLS) model was established for the quantification of MB by SERS, with correlation coefficient R2 = 95.1% and root-mean-squared error of prediction (RMSEP) = 0.226. We believe this superhydrophobic SERS substrate can be widely used in trace analysis due to its facile fabrication, high signal reproducibility and promising SERS performance.
Co-reporter:Hongtao Zhao, Zhigang Li, Nan Zhang, Yunchen Du, Siwei Li, Lin Shao, Deyu Gao, Xijiang Han and Ping Xu
RSC Advances 2014 vol. 4(Issue 57) pp:30467-30470
Publication Date(Web):01 Jul 2014
DOI:10.1039/C4RA05477F
We here demonstrate a facile one-step synthesis of RGO–Ni hybrid materials, where Ni2+ ions and GO are simultaneously reduced by γ-irradiation. RGO–Ni, with Ni nanoparticles well dispersed on the RGO surface, shows a more enhanced EM absorption ability than the individuals.
Co-reporter:Hongtao Zhao, Zhigang Li, Nan Zhang, Siwei Li, Lu Xiong, Shuai Liu, Wen Jin, Leilei Kang and Ping Xu
RSC Advances 2014 vol. 4(Issue 39) pp:20247-20251
Publication Date(Web):07 Mar 2014
DOI:10.1039/C4RA00065J
We have demonstrated here a facile gamma-irradiation induced direct fabrication of Ag nanoparticles on glass substrates for SERS applications. It has been found that the agents complexing with the Ag+ ions play a dominant role in enabling Ag particle growth directly on the glass substrates, whereas using bare AgNO3 solution only produced Ag particles in the solution but not on the glass substrate. Moreover, the complexing agent also decides the size and morphology of the Ag nanoparticles, where using ammonia leads to much larger Ag particles than when using ethylenediamine. The γ-ray dose can also influence the size of the Ag nanoparticles, and a higher dose usually results in larger Ag nanoparticles. The SERS performances of the as-fabricated Ag nanoparticles supported on glass substrates have been compared. The uniform Ag nanoparticles with smaller sizes prepared by using ethylenediamine as the complexing agent typically present superior SERS sensitivities. We believe that this facile and cost-effective gamma-irradiation induced fabrication of Ag nanoparticles will be of interest in SERS studies.
Co-reporter:Siwei Li, Lu Xiong, Shuai Liu and Ping Xu
RSC Advances 2014 vol. 4(Issue 31) pp:16121-16126
Publication Date(Web):24 Mar 2014
DOI:10.1039/C4RA02004A
We demonstrate a dual-acid doping technique for PANI membranes, which enables fast fabrication of homogeneous Ag nanostructures as SERS-active platforms for chemical detection. Ascorbic acid, an intrinsic reducing agent, can accelerate the Ag growth, and succinic acid plays the role of controlling the morphology of the Ag nanostructures. When ascorbic acid is used alone, bulk Ag particles are obtained, which show relatively poor SERS sensitivity (10−5 M) towards the target analyte, methylene blue (MB). Homogeneous Ag nanostructures assembled by nanosheets can be fabricated on dual-acid doped PANI membranes within 2 min. These Ag nanostructures are extremely sensitive towards both target molecules, Rhodamine B (RhB) and MB, with a detection sensitivity of 10−10 M. The as-fabricated SERS platforms can also be applied for semi-quantitative determination of the carcinogenic RhB in juice. We believe the as-fabricated highly sensitive SERS platforms can be promising in the trace detection of chemical and biological molecules.
Co-reporter:Yanzhen He, Xijiang Han, Dengtai Chen, Leilei Kang, Wen Jin, Rong Qiang, Ping Xu and Yunchen Du
RSC Advances 2014 vol. 4(Issue 14) pp:7202-7206
Publication Date(Web):09 Jan 2014
DOI:10.1039/C3RA42577K
A facile synthesis of homogeneous Ag nanostructures on modified polypyrrole (PPy) films through direct chemical deposition has been demonstrated. The as-prepared Ag nanostructures are highly sensitive and reproducible in the SERS detection of the target analyte, methylene blue (MB).
Co-reporter:Siwei Li, Ping Xu, Ziqiu Ren, Bin Zhang, Yunchen Du, Xijiang Han, Nathan H. Mack, and Hsing-Lin Wang
ACS Applied Materials & Interfaces 2013 Volume 5(Issue 1) pp:49
Publication Date(Web):December 12, 2012
DOI:10.1021/am301881q
Here we demonstrate, for the first time, the fabrication of Au nanostructures on polyaniline (PANI) membrane surfaces for surface enhanced Raman spectroscopy (SERS) applications, through a direct chemical reduction by PANI. Introduction of acids into the HAuCl4 solution leads to homogeneous Au structures on the PANI surfaces, which show only sub-ppm detection levels toward the target analyte, 4-mercaptobenzoic acid (4-MBA), because of limited surface area and lack of surface roughness. Thorny Au nanostructures can be obtained through controlled reaction conditions and the addition of a capping agent poly (vinyl pyrrolidone) (PVP) in the HAuCl4 solution and the temperature kept at 80 °C in an oven. Those thorny Au nanostructures, with higher surface areas and unique geometric feature, show a SERS detection sensitivity of 1 × 10–9 M (sub-ppb level) toward two different analyte molecules, 4-MBA and Rhodamine B, demonstrating their generality for SERS applications. These highly sensitive SERS-active substrates offer novel robust structures for trace detection of chemical and biological analytes.Keywords: gold; polyaniline; surface enhanced Raman spectroscopy; thorny nanostructures;
Co-reporter:Bin Zhang;Yunchen Du;Peng Zhang;Hongtao Zhao;Leilei Kang;Xijiang Han
Journal of Applied Polymer Science 2013 Volume 130( Issue 3) pp:1909-1916
Publication Date(Web):
DOI:10.1002/app.39332
ABSTRACT
Synthesis of Fe3O4/polyaniline (PANI) core/shell hybrid microspheres through an in situ polymerization route with the 300 nm Fe3O4 microspheres as the cores and nucleation sites for PANI is reported. PANI shell thickness, from 30 nm to 120 nm, can be controlled by modulating the weight ratio of aniline monomer and Fe3O4 microspheres. Fe3O4 microspheres that are actually comprised of many small nanoparticles display super paramagnetic feature, which has been maintained in Fe3O4/PANI core/shell hybrid materials. Fe3O4/PANI core/shell hybrid materials have enhanced microwave absorption than both the Fe3O4 microspheres and PANI, where a maximum reflection loss of −37.4 dB at 15.4 GHz has been reached from the sample with a PANI shell thickness of 100 nm. Introduction of dielectric loss, interfacial loss, and improved impedance from coating the Fe3O4 microspheres with PANI should account for the improved microwave absorption properties of the prepared Fe3O4/PANI core/shell hybrid materials. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1909–1916, 2013
Co-reporter:Leilei Kang, Ping Xu, Dengtai Chen, Bin Zhang, Yunchen Du, Xijiang Han, Qing Li, and Hsing-Lin Wang
The Journal of Physical Chemistry C 2013 Volume 117(Issue 19) pp:10007-10012
Publication Date(Web):April 22, 2013
DOI:10.1021/jp400572z
We demonstrate the use of amino acids as directing agents to synthesize hierarchical silver microspheres assembled by nanosheets with well-defined morphologies, in the absence of any other surfactants or capping agents. This fabrication method avoids the absorption of macromolecules and enables clean surface on the Ag microspheres. The chemical nature of the amino acids plays a vital role in the hierarchical structure of the Ag microspheres. As found, amino acids with simple structures and 2–3 carbon atoms like alanine and glycine lead to more loosely packed Ag microspheres, and those with more complicated structures and more carbon atoms, e.g. glycine, glutamine, and asparagine, result in close-packed Ag particles assembled by thinner nanosheets. By adjusting the concentration of AgNO3 solution, size as well as the surface roughness of the Ag microspheres can be well controlled. Individual particles of the constructed hierarchical Ag microspheres with highly roughened surface can act as sensitive SERS platforms. Detection of chemical molecules and monitoring of the plasmon-driven chemical reactions have been carried out through a single particle SERS technique.
Co-reporter:Qing Li, Ping Xu, Bin Zhang, Hsinhan Tsai, Shijian Zheng, Gang Wu, and Hsing-Lin Wang
The Journal of Physical Chemistry C 2013 Volume 117(Issue 27) pp:13872-13878
Publication Date(Web):June 18, 2013
DOI:10.1021/jp403655y
Cu2O nanocrystals with different morphologies are synthesized via a reductive solution route by controlling the reaction time and using different capping agents. Introducing poly(ethylene glycol) (PEG) leads to nearly monodispersed Cu2O nanocubes with 40 nm size and dominant {100} crystal planes. With prolonged reaction time, the nanocubes are truncated and transformed into sphere-like nanocrystals with more {111} planes exposed. In the presence of poly(vinyl pyrrolidone) (PVP), porous Cu2O nanocrystals with both {100} and {111} planes present are produced. The structure-dependent electrocatalytic activity of Cu2O nanocrystals toward oxygen reduction reaction (ORR) has been studied in alkaline electrolyte. The electrocatalytic activity measured on Cu2O {100} is higher than that on Cu2O {111}. In addition, the Cu2O nanocubes with dominant {100} crystal planes show the highest four-electron selectivity (n = 3.7) and lowest peroxide yield (15%) during the ORR. Kinetics analysis indicates that the ORR mechanism on Cu2O nanocrystals is controlled simultaneously by charge transfer and intermediate migration. The Cu2O nanocrystals also show better methanol tolerance and durability for ORR than the commercial Pt/C materials.
Co-reporter:Ping Xu, Kuan Chang, Young Il Park, Bin Zhang, Leilei Kang, Yunchen Du, Rashi S. Iyer, Hsing-Lin Wang
Polymer 2013 Volume 54(Issue 2) pp:485-489
Publication Date(Web):24 January 2013
DOI:10.1016/j.polymer.2012.12.003
Two water soluble conjugated polymers, poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and ammonium ion stabilized poly(phenylene vinylene) (P2), are found to be able to reduce noble metal ions to zero-valent metals via a direct chemical deposition technique. Au nanoparticle clusters can be obtained through reduction of Au3+ ions by PEDOT:PSS and the electronic coupling between them can be controlled by HAuCl4 concentration. Core/shell Ag/polymer nanostructures are prepared from reduction of Ag+ ions by P2, which have a ppb detection limit for 4-MBA using surface-enhanced Raman spectroscopy (SERS). This conjugated polymer mediated synthesis of metal nanoparticles may open a new avenue for fabricating nanomaterials and nanocomposites with tunable optical properties that are dominated by their structure and electronic coupling between nanoparticles.
Co-reporter:Jun Yan, Xijiang Han, Jiaojiao He, Leilei Kang, Bin Zhang, Yunchen Du, Hongtao Zhao, Cunku Dong, Hsing-Lin Wang, and Ping Xu
ACS Applied Materials & Interfaces 2012 Volume 4(Issue 5) pp:2752
Publication Date(Web):May 1, 2012
DOI:10.1021/am300381v
Here, we demonstrate a facile synthesis of homogeneous Ag nanostructures fully covering the polyaniline (PANI) membrane surface simply by introducing organic acid in the AgNO3 reaction solution, as an improved technique to fabricate well-defined Ag nanostructures on PANI substrates through a direct chemical deposition method [Langmuir2010, 26, 8882]. It is found that the chemical nature of the acid is crucial to create a homogeneous nucleation environment for Ag growth, where, in this case, homogeneous Ag nanostructures that are assembled by Ag nanosheets are produced with the assistance of succinic acid and lactic acid, but only scattered Ag particles with camphorsulfonic acid. Improved surface wettability of PANI membranes after acid doping may also account for the higher surface coverage of Ag nanostructures. The Ag nanostructures fully covering the PANI surface are extremely sensitive in the detection of a target analyte, 4-mercaptobenzoic acid (4-MBA), using surface-enhanced Raman spectroscopy (SERS), with a detection limit of 10–12 M. We believe the facilely fabricated SERS-active substrates based on conducting polymer-mediated growth of Ag nanostructures can be promising in the trace detection of chemical and biological molecules.Keywords: membrane; nanostructure; polyaniline; silver; surface-enhanced Raman spectroscopy;
Co-reporter:Jiaojiao He, Xijiang Han, Jun Yan, Leilei Kang, Bin Zhang, Yunchen Du, Cunku Dong, Hsing-Lin Wang and Ping Xu
CrystEngComm 2012 vol. 14(Issue 15) pp:4952-4954
Publication Date(Web):01 May 2012
DOI:10.1039/C2CE25257K
We here demonstrate a fast fabrication of homogeneous silver nanostructures on polyaniline films within one minute, which show highly sensitive response in SERS applications.
Co-reporter:Chenkui Cui, Yunchen Du, Tianhao Li, Xiaoying Zheng, Xiaohong Wang, Xijiang Han, and Ping Xu
The Journal of Physical Chemistry B 2012 Volume 116(Issue 31) pp:9523-9531
Publication Date(Web):July 16, 2012
DOI:10.1021/jp3024099
Composites consisting of Fe3O4 microspheres (FMS) and polyaniline (PANI), FMS/PANI, have been successfully prepared through a two-step oxidative polymerization of aniline monomers in the presence of Fe3O4 microspheres. In our two-step polymerization technique, Fe3+ and ammonium persulfate (APS) are used as the oxidants in each step. It is discovered that the two-step oxidative process plays a dominant role in the morphology of these composites: aniline oligomers oxidized by Fe3+ are mainly produced in the first stage, and “egg-like” PANI aggregates are obtained in the second stage. It can be found that embedding Fe3O4 microspheres in the polymer matrixes will not only modulate the complex permittivity but also produce magnetic resonance and loss in the composites. Therefore, the characteristic impedance and reflection loss of these composites are greatly improved. Especially, the composite with equal amount of FMS and PANI, FMS/PANI50, displays very strong reflection loss over a wide frequency range that can be manipulated by the absorber thickness. More importantly, the composites prepared from the two-step chemical oxidative polymerization using hierarchical magnetic materials have better microwave absorption and environmental stability as compared with those composites from Fe3O4 nanoparticles, one-step oxidative polymerization, and physical mixture. We believe the two-step oxidative polymerization technique can be a novel route for the design and preparation of lightweight and highly effective microwave absorbers in the future.
Co-reporter:Jia Chu, Xin Li and Ping Xu
Journal of Materials Chemistry A 2011 vol. 21(Issue 30) pp:11283-11287
Publication Date(Web):28 Jun 2011
DOI:10.1039/C1JM11058F
We demonstrate a facile synthesis and the fluorescent features of graphene oxide–CdTe hybrid materials. CdTe nanorods have been successfully grafted on to the GO surface through an amidation reaction between acyl chlorides of GO and amino groups of the L-cysteine capped CdTe nanorods. Although fluorescence of the CdTe nanorods can be completely quenched by GO, maintenance and a blue shift of the fluorescence of GO after grafting with CdTe nanorods are discovered due to an incomplete reduction of GO and the basic conditions of the amidation reaction. We believe that the intrinsic optical properties of the GO–CdTe hybrid material may make a promising candidate for graphene- and GO-based materials in optoelectronic applications.
Co-reporter:Sea-Ho Jeon, Ping Xu, Bin Zhang, Nathan H. Mack, Hsinhan Tsai, Long Y. Chiang and Hsing-Lin Wang
Journal of Materials Chemistry A 2011 vol. 21(Issue 8) pp:2550-2554
Publication Date(Web):24 Dec 2010
DOI:10.1039/C0JM02340J
We describe here a one-step synthesis of hybrid metal nanoparticles (MNPs) and polymer composites on glass substrates using poly(vinyl pyrrolidone) (PVP) as both the reducing agent and polymer matrix. With this method, it takes only one minute to produce a nanocomposite thin film that contains MNPs with controlled size and morphology. The size and morphology of gold nanoparticles can be manipulated by simply modulating the ratio between the PVP and the Au precursor, while the nearly monodispersed spherical silver nanoparticles are insensitive to the reaction conditions, which is believed to result from a better control over the crystal structure of the Ag seeds than that of the Au seeds in the presence of PVP. Moreover, the resulting MNP–polymer composites are high-quality thin films with tunable optical properties—the λmax of absorption spectra changes from 480 nm to greater than 580 nm (from blue to red color). This environmentally friendly synthetic technique may open up a new avenue for facile nanomaterial synthesis that is not accessible by conventional solution chemistry.
Co-reporter:Donghua Zhou, Yanhai Li, Jingyu Wang, Ping Xu, Xijiang Han
Materials Letters 2011 Volume 65(23–24) pp:3601-3604
Publication Date(Web):December 2011
DOI:10.1016/j.matlet.2011.08.021
Mixed surfactant solution, containing cetyltrimethyl ammonium bromide (CTAB) and sodium dodecylbenzyl sulfonate (SDBS), is used to prepare polyaniline (PANI) with soft 1D structure and high electrical conductivity. The mixed surfactants in the reaction play double roles of soft templates and dispersion reagents. The influence of CTAB–SDBS ratio on the morphology and conductive property of PANI is investigated. Through varying the proportion of surfactants, uniformly branched nanofibers with higher aspect ratio and good dispersion are obtained, which possess the highest conductivity (0.102 S·cm−1). Moreover, FT-IR spectra are measured to explain the change of structure and conductivity under assistance of mixed surfactants. As a result, the mixed surfactants have significant effect on the electron density of whole structure as well as the PANI molecular orientation.The novel method for synthesis of PANI nanofiber is proposed via a synergism of anionic surfactant (SDBS) and cationic surfactant (CTAB). The proportion of mixed surfactants has significant effect on the morphology and electrical conductivity. Uniform PANI nanofibers with the highest conductivity are obtained as 2:1 of CTAB/SDBS ratio.Highlights► Novel method for synthesis of PANI nanofibers with high conductivity is proposed. ► SDBS–CTAB mixed systems play double roles of soft template and dispersion reagent. ► Morphology and conductivity can be optimized by varying CTAB/SDBS ratio.
Co-reporter:Xueai Li ; Bin Zhang ; Chunhua Ju ; Xijiang Han ; Yuchen Du
The Journal of Physical Chemistry C 2011 Volume 115(Issue 25) pp:12350-12357
Publication Date(Web):May 23, 2011
DOI:10.1021/jp203147q
Well-defined porous Fe3O4 flower-like nanostructures have been synthesized by decomposition of the iron alkoxide precursors that are prepared by heating up the solution of FeCl3·6H2O, urea, and surfactant in ethylene glycol. Time-dependent SEM studies indicate that the structure evolution of iron alkoxide precursors contains a fast nucleation of primary nanoparticles followed by a subsequent growth. By varying the amount of surfactant in the solution, the morphology and microstructure of the iron alkoxide precursors can be controlled. After calcination, the flower-like nanostructures of the precursors are maintained in the final products Fe3O4, with each petal of the flower being transformed from a dense structure with a smooth surface into a highly porous structure consisting of interconnected nanoparticles due to the removal of organic species in the iron alkoxide by pyrolysis. Compared to traditional ferrites and ferromagnetic alloys, the complex permittivity of the flower-like porous Fe3O4 samples is modified, and the permeability presents natural magnetic resonance at about 3.0 GHz, which is higher than that of usual Fe3O4 nanoparticles and symbolizes a break-through of the Snoek’s limit. A maximum reflection loss of the flower-like porous Fe3O4 can reach −28.31 dB at 13.2 GHz with a thickness of 2 mm due to an improved impedance matching that is associated with complex permittivity, complex permeability, and the structure of the material. We believe the prepared porous Fe3O4 nanostructures can be good candidates for electromagnetic absorbing materials.
Co-reporter:Ping Xu ; Sea-Ho Jeon ; Hou-Tong Chen ; Hongmei Luo ; Guifu Zou ; Quanxi Jia ; Marian Anghel ; Christof Teuscher ; Darrick J. Williams ; Bin Zhang ; Xijiang Han ;Hsing-Lin Wang
The Journal of Physical Chemistry C 2010 Volume 114(Issue 50) pp:22147-22154
Publication Date(Web):December 1, 2010
DOI:10.1021/jp109207d
We demonstrate here for the first time a facile fabrication of silver wire (SW) structures with a wide range of sizes and morphologies through direct chemical reduction by polyaniline (PANI). The synthesis of SW is mostly determined by the nature of the PANI dopant and silver nitrate concentration. Time-resolved optical microscopy allows monitoring the growth of SWs in real time and reveals the possible growth mechanism. Temperature-dependent resistance of a SW with 150 nm diameter by a four-probe method shows typical resistance behavior of silver metal, and the electrical conductivity is 2.1 × 105 S/cm at room temperature. The morphology-dependent electrical properties of these SWs are measured using a two-probe method. The wires comprised of self-assembled silver nanoparticles usually have lower electrical conductivities than those with smooth surfaces, due to the presence of growth defects and enhanced surface scattering. Current−voltage (I−V) curve measurements in a wide potential range either break down or cause surface transformation of the SWs by a synergism of electromigration and surface diffusion. A SW network that shows surface transformation after I−V curve measurement displays a higher resistance. The study of the electrical stability of the SWs opens up a new view of the applicable feasibility of metal nanowires in nanoelectronic devices.
Co-reporter:Hongtao Zhao ; Bin Zhang ; Jusheng Zhang ; Lifang Zhang ; Xijiang Han ; Ping Xu ;Yu Zhou
The Journal of Physical Chemistry C 2010 Volume 114(Issue 49) pp:21214-21218
Publication Date(Web):November 17, 2010
DOI:10.1021/jp107903r
We here demonstrate the preparation of magnetic nanostructures (Co, Ni) with aligned morphologies through a magnetic field-assisted γ-irradiation route. It is found out that a proper magnetic field can induce the prepared magnetic nanoparticles to align into well-defined stick or chain structures, where randomly dispersed nanoparticles are obtained without the application of magnetic field. The alignment of the magnetic nanoparticles gives rise to increased magnetization and coercivity due to the enhancement in shape anisotropy. Meanwhile, compared with the scattered nanoparticles, stronger electromagnetic wave absorption properties can also be realized in the aligned nanostructures, caused by the geometrical effect. We think this alignment of magnetic nanoparticles into specific structures under the assistance of magnetic field may be appealing in improving the electromagnetic wave absorptions that are not accessible in randomly dispersed particles.
Co-reporter:Chao Wang, Xijiang Han, Xiaolin Zhang, Surong Hu, Tao Zhang, Jinyu Wang, Yunchen Du, Xiaohong Wang and Ping Xu
The Journal of Physical Chemistry C 2010 Volume 114(Issue 35) pp:14826-14830
Publication Date(Web):August 13, 2010
DOI:10.1021/jp1050386
Hierarchical cobalt assemblies such as spheres, flowers with dendritic petals, and flowers with sharp petals are successfully synthesized via a facile liquid-phase reduction method by simply adjusting the reaction conditions. The morphology evolution process and transformation mechanism from spheres to dendrites and finally to flowers have been systematically investigated. It is determined that coercivity Hc depends more on sample size than on shape anisotropy, while saturation magnetization Ms is greatly affected by pinned surface magnetic moment. Even at a thinner thickness, as-synthesized cobalt samples exhibit stronger microwave absorbing ability compared with reported cobalt in the same frequency band. Especially, the cobalt flowers with dendritic petals exhibit the strongest absorption in middle frequency because incident wave and reflected wave are totally canceled at matching thickness. The architectural design of material morphologies is critical for improving properties toward future application.
Co-reporter:Dengtai Chen, Xijiang Han, Wen Jin, Yunchen Du and Ping Xu
Chemical Communications 2014 - vol. 50(Issue 98) pp:NaN15633-15633
Publication Date(Web):2014/10/27
DOI:10.1039/C4CC06808D
Visible laser induced [2+2] cycloaddition of solid-state pyridine substituted olefins into cyclobutane has been monitored by an in situ Raman technique. The laser power and wavelength can dramatically alter the reaction kinetics, as a prior melting process (heating from laser irradiation) is required for this [2+2] photoreaction.
Co-reporter:Rong Qiang, Yunchen Du, Hongtao Zhao, Ying Wang, Chunhua Tian, Zhigang Li, Xijiang Han and Ping Xu
Journal of Materials Chemistry A 2015 - vol. 3(Issue 25) pp:NaN13434-13434
Publication Date(Web):2015/05/06
DOI:10.1039/C5TA01457C
Composites of magnetic metal nanoparticles and carbon materials are highly desirable for high-performance microwave absorbers due to their compatible dielectric loss and magnetic loss abilities. In this article, novel nanocomposites, Fe/C nanocubes, have been successfully prepared through an in situ route from a metal–organic framework, Prussian blue, by controlled high-temperature pyrolysis. The resultant nanocubes are actually composed of a cubic framework of amorphous carbon and uniformly dispersed core–shell Fe@graphitic carbon nanoparticles. Within the studied pyrolysis temperature range (600–700 °C), the porous structure, iron content, magnetic properties, and graphitization degree of the Fe/C nanocubes can be well modulated. Particularly, the improved carbon graphitization degree, both in amorphous frameworks and graphitic shells, results in enhanced complex permittivity and dielectric loss properties. The homogeneous chemical composition and microstructure stimulate the formation of multiple dielectric resonances by regularizing various polarizations. The synergistic effect of dielectric loss, magnetic loss, matched impedance, and dielectric resonances accounts for the improved microwave absorption properties of the Fe/C nanocubes. The absorption bands of the optimum one obtained at 650 °C are superior to most composites ever reported. By considering the good chemical homogeneity and microwave absorption, we believe that the as-fabricated Fe/C nanocubes will be promising candidates as highly effective microwave absorbers.
Co-reporter:Wei Huang, Qiang Jing, Yunchen Du, Bin Zhang, Xiangli Meng, Mengtao Sun, Kirk S. Schanze, Hong Gao and Ping Xu
Journal of Materials Chemistry A 2015 - vol. 3(Issue 20) pp:NaN5291-5291
Publication Date(Web):2015/04/21
DOI:10.1039/C5TC00835B
Here we demonstrate the surface plasmon (SP) induced nitration of aromatic rings by an in situ surface enhanced Raman spectroscopy (SERS) technique. The size feature of the as-prepared Au, Ag and Ag@PDA@Au hierarchical structures allows monitoring the entire reaction process on a single hierarchical structure. With benzenethiol (BT) and HNO3 as reactants, SP induced aromatic nitration can be successfully realized without the assistance of a conventional acid catalyst, H2SO4. Experimental and theoretical studies confirm that the nitration reaction leads to para-nitrothiophenol (p-NTP). While control experiments show that SP here functions as a local heating source and the presence of metal is also necessary for this nitration reaction. This SP induced aromatic nitration reaction also displays SERS substrate-dependent reaction kinetics, which proceeds more rapidly on the Au surface. Higher laser power can generate a stronger photothermal effect, and thus an accelerated reaction rate for this reaction. We believe this finding may broaden the research areas in the SP assisted or induced catalytic reactions.
Co-reporter:Weiyu Liu, Peng Miao, Lu Xiong, Yunchen Du, Xijiang Han and Ping Xu
Physical Chemistry Chemical Physics 2014 - vol. 16(Issue 41) pp:
Publication Date(Web):
DOI:10.1039/C4CP02677B
Co-reporter:Jia Chu, Xin Li and Ping Xu
Journal of Materials Chemistry A 2011 - vol. 21(Issue 30) pp:NaN11287-11287
Publication Date(Web):2011/06/28
DOI:10.1039/C1JM11058F
We demonstrate a facile synthesis and the fluorescent features of graphene oxide–CdTe hybrid materials. CdTe nanorods have been successfully grafted on to the GO surface through an amidation reaction between acyl chlorides of GO and amino groups of the L-cysteine capped CdTe nanorods. Although fluorescence of the CdTe nanorods can be completely quenched by GO, maintenance and a blue shift of the fluorescence of GO after grafting with CdTe nanorods are discovered due to an incomplete reduction of GO and the basic conditions of the amidation reaction. We believe that the intrinsic optical properties of the GO–CdTe hybrid material may make a promising candidate for graphene- and GO-based materials in optoelectronic applications.
Co-reporter:Sea-Ho Jeon, Ping Xu, Bin Zhang, Nathan H. Mack, Hsinhan Tsai, Long Y. Chiang and Hsing-Lin Wang
Journal of Materials Chemistry A 2011 - vol. 21(Issue 8) pp:NaN2554-2554
Publication Date(Web):2010/12/24
DOI:10.1039/C0JM02340J
We describe here a one-step synthesis of hybrid metal nanoparticles (MNPs) and polymer composites on glass substrates using poly(vinyl pyrrolidone) (PVP) as both the reducing agent and polymer matrix. With this method, it takes only one minute to produce a nanocomposite thin film that contains MNPs with controlled size and morphology. The size and morphology of gold nanoparticles can be manipulated by simply modulating the ratio between the PVP and the Au precursor, while the nearly monodispersed spherical silver nanoparticles are insensitive to the reaction conditions, which is believed to result from a better control over the crystal structure of the Ag seeds than that of the Au seeds in the presence of PVP. Moreover, the resulting MNP–polymer composites are high-quality thin films with tunable optical properties—the λmax of absorption spectra changes from 480 nm to greater than 580 nm (from blue to red color). This environmentally friendly synthetic technique may open up a new avenue for facile nanomaterial synthesis that is not accessible by conventional solution chemistry.
Co-reporter:Leilei Kang, Jiayu Chu, Hongtao Zhao, Ping Xu and Mengtao Sun
Journal of Materials Chemistry A 2015 - vol. 3(Issue 35) pp:NaN9037-9037
Publication Date(Web):2015/07/28
DOI:10.1039/C5TC01759A
Graphene continues to attract tremendous interest, owing to its excellent optical and electronic properties. Based on its unique features, graphene has been employed in the ever-expanding research fields. Surface-enhanced Raman scattering (SERS) may be one of the significant applied fields where graphene can make a difference. Since its discovery, the SERS technique has been capable of ultra sensitively detecting chemical and biological molecules at very low concentration, even at the single molecule level, but some problems, such as irreproducible SERS signals, should be overcome before being practically applied for spectral analysis. Graphene can be a promising candidate to make up the deficiency of a conventional metal SERS substrate. Furthermore, graphene, serving as an enhancement material, is usually deemed as a chemically inert substance to isolate the interactions between metal and probe molecules. While, irradiated by laser, structure changes of graphene under specific conditions and the contributions of its high electron mobility in plasmon-induced catalytic reactions are often ignored. In this review, we mainly focus on the state-of-the-art applications of graphene in the fields of SERS and laser-induced catalytic reactions. The advances in informative Raman spectra of graphene are firstly reviewed. Then, the graphene related SERS substrates, including graphene-enhanced Raman scattering (GERS) and graphene-mediated SERS (G-SERS), are summarized. We finally highlight the catalytic reactions occurring on graphene itself and molecules adsorbed onto graphene upon laser irradiation.
Co-reporter:Kai Li, Dmitrii Rakov, Wei Zhang and Ping Xu
Chemical Communications 2017 - vol. 53(Issue 58) pp:NaN8202-8202
Publication Date(Web):2017/07/06
DOI:10.1039/C7CC03173D
Here we demonstrate the improvement of the intrinsic electrocatalytic hydrogen evolution activity of NiPS3 by proper cobalt doping. The optimized Ni0.95Co0.05PS3 nanosheets display a geometric catalytic current density of −10 mA cm−2 at an overpotential of 71 mV vs. RHE and a Tafel slope of 77 mV dec−1 in 1.0 M KOH.
Co-reporter:Jiajie Li, Yumin Zhang, Tangling Gao, Chang Hu, Tai Yao, Quan Yuan, Xianjie Wang, Ping Xu, Zhihua Zhang, Jikang Jian, Xinghong Zhang and Bo Song
Journal of Materials Chemistry A 2017 - vol. 5(Issue 10) pp:NaN4911-4911
Publication Date(Web):2017/01/30
DOI:10.1039/C6TA10441J
Cadmium telluride (CdTe) thin-film solar cells show great potential due to their high efficiency, thermal stability, and low manufacturing cost. However, the practical performance of CdTe solar cells is often severely restricted due to the deficiency or excess of Cu diffusion, leading to a non-ohmic contact and electrical shorts and thus performance degradation. Herein, we demonstrate an innovative strategy for the fabrication of a Cu-free back contact by depositing CdTe quantum dots (QDs) on a CdTe layer using the pulsed laser deposition (PLD) technique, and find that the average relative power conversion efficiency is significantly enhanced by ∼6.2%. More importantly, the as-prepared CdTe QDs are thermally stable and CdTe with CdTe QD/Au back contact devices show no sign of degradation during exposure to air even after nearly one year. This study provides new insight into the design and property modulation of CdTe-based photovoltaics.
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