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Sun Feng,Li Na,Wang Lijia,Feng Huajun,Shen Dongsheng,Wang Meizhen 한국미생물학회 2020 The journal of microbiology Vol.58 No.11
The stabilization of quorum sensing (QS) is vital for bacterial survival in various environments. Although the mechanisms of QS stabilization in certain conditions have been well studied, the impact of environmental factors has received much less attention. In this study, we show that the supplementation of 25 μM iron in competition experiments and 50 μM in evolution experiments to casein growth cultures significantly increased the possibility of population collapse by affecting elastase production. However, the expression of lasI and lasR remained constant regardless of iron concentration and hence this effect was not through interference with the LasIR circuit, which mainly regulates the secretion of elastase in Pseudomonas aeruginosa. However, the expression of rhlR was significantly inhibited by iron treatment, which could affect the production of elastase. Further, based on both reverse transcription quantitative polymerase chain reaction and gene knock-out assays, we show that iron inhibits the transcription of ppyR and enhances the expression of mexT, both of which decrease elastase production and correspondingly interfere with QS stabilization. Our findings show that environmental factors can affect the genes of QS circuits, interfering with QS stabilization. These findings are not only beneficial in understanding the mechanistic effect of iron on QS stabilization, but also demonstrate the complexity of QS stabilization by linking non-QS-related genes with QS traits.
Quasi-Two-Dimensional Metal Oxide Semiconductors Based Ultrasensitive Potentiometric Biosensors
Chen, Huajun,Rim, You Seung,Wang, Isaac Caleb,Li, Chao,Zhu, Bowen,Sun, Mo,Goorsky, Mark S.,He, Ximin,Yang, Yang American Chemical Society 2017 ACS NANO Vol.11 No.5
<P>Ultrasensitive field-effect transistor-based biosensors using quasi two -dimensional metal oxide semiconductors were demonstrated. Quasi-two-dimensional low-dimensional metal oxide semiconductors were highly sensitive to electrical perturbations at the semiconductor bio interface and showed competitive sensitivity compared with other nanomaterial-based biosensors. Also, the solution process made our platform simple and highly reproducible, which was favorable compared with other nanobioelectronics. A quasi-two-dimensional In2O3-based pH sensor showed a small detection limit of 0.0005 pH and detected the glucose concentration at femtomolar levels. Detailed electrical characterization unveiled how the device's parameters affect the biosensor sensitivity, and lowest detectable charge was extrapolated, which was consistent with the experimental data.</P>
Renxin Xu,Huan Yang,Huajun Sun,Jing Zhou,Zhijun Yue,Xinhua Gao 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2019 NANO Vol.14 No.2
Mg0.2Mn0.8YxFe2-xO4 (x = 0.000, 0.025, 0.050 and 0.075) nanocrystalline is synthesized via hydrothermal technique. Single cubic spinel phase is confirmed by XRD and the formation of Mg0.2Mn0.8YxFe2-xO4 is verified by EDS. The average size of the nanoferrites is around 80 nm, which is examined by TEM image. Y3+ substituted Mg-Mn nanoferrites exhibit low saturation magnetization (Ms) and coercivity (Hc). Especially, the nanoferrites with x = 0.075 show the lowest Ms and Hc of 46.96 emu/g and 12.04 Oe, respectively. The ferrite composites present that the resistivity and the magnetic loss are less than 4.5 x 10 7 Ω · cm and 0.7 in the range of 2–18 GHz, respectively. The low coercivity and high resistivity indicate that the addition of Y3+ contributes to the synthesis of the excellent soft magnetic materials.
Xiong, Pan,Zhang, Xiuyun,Zhang, Fan,Yi, Ding,Zhang, Jinqiang,Sun, Bing,Tian, Huajun,Shanmukaraj, Devaraj,Rojo, Teofilo,Armand, Michel,Ma, Renzhi,Sasaki, Takayoshi,Wang, Guoxiu American Chemical Society 2018 ACS NANO Vol.12 No.12
<P>Cation-deficient two-dimensional (2D) materials, especially atomically thin nanosheets, are highly promising electrode materials for electrochemical energy storage that undergo metal ion insertion reactions, yet they have rarely been achieved thus far. Here, we report a Ti-deficient 2D unilamellar lepidocrocite-type titanium oxide (Ti<SUB>0.87</SUB>O<SUB>2</SUB>) nanosheet superlattice for sodium storage. The superlattice composed of alternately restacked defective Ti<SUB>0.87</SUB>O<SUB>2</SUB> and nitrogen-doped graphene monolayers exhibits an outstanding capacity of ∼490 mA h g<SUP>-1</SUP> at 0.1 A g<SUP>-1</SUP>, an ultralong cycle life of more than 10000 cycles with ∼0.00058% capacity decay per cycle, and especially superior low-temperature performance (100 mA h g<SUP>-1</SUP> at 12.8 A g<SUP>-1</SUP> and −5 °C), presenting the best reported performance to date. A reversible Na<SUP>+</SUP> ion intercalation mechanism without phase and structural change is verified by first-principles calculations and kinetics analysis. These results herald a promising strategy to utilize defective 2D materials for advanced energy storage applications.</P> [FIG OMISSION]</BR>
Wu, Yecun,Fuh, Huei-Ru,Zhang, Duan,Coileá,in, Cormac Ó,Xu, Hongjun,Cho, Jiung,Choi, Miri,Chun, Byong Sun,Jiang, Xuju,Abid, Mourad,Abid, Mohamed,Liu, Huajun,Wang, Jing Jing,Shvets, Igor V. Elsevier 2017 Nano energy Vol.32 No.-
<P><B>Abstract</B></P> <P>For applications in wearable human-device interfaces and optoelectronics, flexible materials capable of supporting spatial and uninterrupted bandgap tunability are of immense value. We demonstrate theoretically and experimentally the wide bandgap tunability of GaSe nanosheets, with simultaneous PL enhancement, via elastic strain engineering at room temperature. The elastic strain gives rise to a continuously variable electronic band structure profile, with a rate of 40meV/1%, and a 3-fold enhancement in PL intensity is achieved when a uniaxial strain of 1% is introduced. An additional effect is that a new exciton state arises when the strain is raised beyond 0.6%. This work suggests that strain engineering can effectively modulate/control the generation, separation, transport, and recombination of photo-induced charge carriers in GaSe, making it a valuable material for flexible optoelectronic-mechanical applications.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Wide bandgap tunability of GaSe nanosheets, with simultaneous PL enhancement, via elastic strain engineering at room temperature. </LI> <LI> A linear tuning rate of optical band gap of 40 meV/% for uniaxial strain has been achieved, comparable to monolayer MoS2. </LI> <LI> Threefold enhancement in PL intensity achieved with a uniaxial strain of 1%. </LI> <LI> Strain engineering used to control generation, separation, transport, and recombination of photo-induced charge carriers in GaSe. </LI> <LI> New exciton state demonstrated when strain is greater than 0.6%, which shifts in the direction opposite to the main exciton state. </LI> <LI> Suggests route to more efficient capture of optical spectrum, and exciton concentration and trapping by mechanical deformation. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Threshold magnetoresistance in anistropic magnetic 2D transition metal dichalcogenides
Xu, Hongjun,Hsu, Ming-Chien,Fuh, Huei-Ru,Feng, Jiafeng,Han, Xiufeng,Zhao, Yanfeng,Zhang, Duan,Wang, Xinming,Liu, Fang,Liu, Huajun,Cho, Jiung,Choi, Miri,Chun, Byong Sun,Ó,Coileá,in, Cormac The Royal Society of Chemistry 2018 Journal of Materials Chemistry C Vol.6 No.12
<P>Recently many novel magnetoresistance (MR) phenomena have been reported from studies of two dimensional (2D) materials. Here, we report on the exotic transport behavior of VS2. A large negative and quadratic MR of −10% is observed for an in-plane magnetic field B up to 14 T. Remarkably, when the applied field deviates from the in-plane orientation there is a threshold field, Bc, and the MR shows a plateau of near zero MR. When B < Bc, only a single state exists and the transition between quantum spin states is forbidden. Our work sheds new light on the MR of magnetic 2D materials with localized states and may spur further investigations.</P>
Liu, Xiao,Zhang, Duan,Wu, Ye-Cun,Yang, Mei,Wang, Qian,Coileá,in, Cormac Ó,.,Xu, Hongjun,Yang, Chen,Abid, Mohamed,Abid, Mourad,Liu, Huajun,Chun, Byong Sun,Shi, Qingfan,Wu, Han-Chun Elsevier 2017 Carbon Vol.122 No.-
<P>Graphene is moving beyond the realm of simple electronic devices toward areas such as advanced biochemical sensing. The infrared (IR) response of graphene, characterized by collective long-lived charge-carrier oscillations, could be applied in IR-absorption spectroscopy, typically used for bio-chemical analysis. However, direct light absorption by propagating plasmons in graphene is forbidden due to the large momentum mismatch. Proposed methods to overcome this bottleneck come at a cost, the use of noble metal particles on graphene reduces the spectral bandwidth and nano-structuring graphene is expensive. Here, we propose a simple and cheap method to fabricate large scale ultra-sensitive graphene based mid-IR biosensors, by introducing dielectric beads to excite mid-IR range plasmons. Interference from waves scattered by the beads excite surface plasmon polaritons, which propagate several micrometers in graphene and enhance the interaction between the molecules and mid-IR light. This method opens an interesting window for the application of graphene in bio-chemical sensing. (C) 2017 Elsevier Ltd. All rights reserved.</P>