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Vibration parameters optimum of 316L steel laser welding under high frequency micro-vibration condition
摘要： High frequency micro vibration combined with laser was applied in the laser welding process parameters were chosen by comparison of weld geometry. In detail, laser power(P) is 2.5kW, welding speed(V) is 1.2m / min, defocusing amount(DA) is -5mm. Three parameters including frequency(F), vibration acceleration(A) and angle(θ) were changed according to the orthogonal test scheme. The microstructure and the tensile properties of the welded joint were compared and analyzed. The morphology of weld tail was analyzed to describe hole stability. It was found that micro-structure and mechanical of joint was significantly influenced by A and F. In the case of vibration resonance, the higher the F, the better the ultimate tensile strength(UTS), and the higher the hardness. When F was 1360 Hz, UTS was 602 MPa. When A was increased from 10 to 60 m/s2, the UTS was improved by 10 MPa. HW and HL were even disappeared in a higher resonance state. Response surface analysis results showed that factors of F and A have significant effects on the width of weld. Width was increased by higher resonance state. It was obtained that optimum process parameters were F=1360 Hz, A= 60 m/s2 and θ = 90°. UTS was 602MPa, hardness was 214.5 Hv, and elongation was 40%. This is mainly due to the grain refinement strengthening.
关键词： Laser welding,Mechanical property,Parameter,Response surface,Vibration
更新于2025-11-28 14:24:20
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A through-bond energy transfer-based ratiometric fluorescent pH probe: For extreme acidity and extreme alkaline detection with large emission shifts
摘要： A ratiometric fluorescence pH probe 1 based on through-bond energy transfer (TBET) with a 2-(2-hydroxyphenyl)benzoxazole (HBO) as donor and a Rhodamine derivative as acceptor is developed through simple condensation reaction. The probe exhibits a ratiometric fluorescence emission (I593/I422) characteristics and linear response to extreme acidity range of 5.00-2.88, and a ratiometric fluorescence emission (I555/I422) characteristics and linear response to extreme alkaline range of 10.00-13.78, respectively. Moreover, 1 possesses highly selective response to pH over metal ions, good reversibility and excellent photostability. Probe 1 is cellpermeable and can distinguish near pH 5.55 fluctuations in Hela cells. Furthermore, 1 can be immobilized on a test paper, which shows a rapid and reversible colorimetric response to HCl/NH3 vapor by the naked-eye.
关键词： ratiometric fluorescent response,pH sensing,large emission shifts,through-bond energy transfer,fluorescent probe
更新于2025-11-21 11:24:58
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Coordination geometry-induced optical imaging of <scp>l</scp> -cysteine in cancer cells using imidazopyridine-based copper( <scp>ii</scp> ) complexes
摘要： Overexpression of cysteine cathepsins proteases has been documented in a wide variety of cancers, and enhances the L-cysteine concentration in tumor cells. We report the synthesis and characterization of copper(II) complexes [Cu(L1)2(H2O)](SO3CF3)2, 1, L1 = 3-phenyl-1-(pyridin-2-yl)imidazo[1,5-a]pyridine, [Cu(L2)2(SO3CF3)]SO3CF3, 2, L2 = 3-(4-methoxyphenyl)-1-pyridin-2-yl-imidazo[1,5-a]pyridine, [Cu(L3)2(H2O)](SO3CF3)2, 3, L3 = 3-(3,4-dimethoxy-phenyl)-1-pyridin-2-yl-imidazo[1,5-a]pyridine and [Cu(L4)2(H2O)](SO3CF3)2, 4, L4 = dimethyl-[4-(1-pyridin-2-yl-imidazo[1,5-a]pyridin-3-yl)phenyl]amine as 'turn-on' optical imaging probes for L-cysteine in cancer cells. The molecular structure of complexes adopted distorted trigonal pyramidal geometry (τ, 0.68–0.87). Cu–Npy bonds (1.964–1.989 ?) were shorter than Cu–Nimi bonds (2.024–2.074 ?) for all complexes. Geometrical distortion was strongly revealed in EPR spectra, showing gk (2.26–2.28) and Ak values (139–163 × 10?4 cm?1) at 70 K. The d–d transitions appeared around 680–741 and 882–932 nm in HEPES, which supported the existence of five-coordinate geometry in solution. The Cu(II)/Cu(I) redox potential of 1 (0.221 V vs. NHE) was almost identical to that of 2 and 3 but lower than that of 4 (0.525 V vs. NHE) in HEPES buffer. The complexes were almost non-emissive in nature, but became emissive by the interaction of L-cysteine in 100% HEPES at pH 7.34 via reduction of Cu(II) to Cu(I). Among the probes, probe 2 showed selective and efficient turn-on fluorescence behavior towards L-cysteine over natural amino acids with a limit of detection of 9.9 × 10?8 M and binding constant of 2.3 × 105 M?1. The selectivity of 2 may have originated from a nearly perfect trigonal plane adopted around a copper(II) center (～120.70°), which required minimum structural change during the reduction of Cu(II) to Cu(I) while imaging Cys. The other complexes, with their distorted trigonal planes, required more reorganizational energy, which resulted in poor selectivity. Probe 2 was employed for optical imaging of L-cysteine in HeLa cells and macrophages. It exhibited brighter fluorescent images by visualizing Cys at pH 7.34 and 37 °C. It showed relatively less toxicity for these cell lines as ascertained by the MTT assay.
关键词： optical imaging,cancer cells,turn-on fluorescence,imidazopyridine,L-cysteine,Copper(II) complexes
更新于2025-11-21 11:08:12
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Measuring the interaction of transcription factor Nrf2 with its negative regulator Keap1 in single live cells by an improved FRET/FLIM analysis
摘要： Transcription factor NF-E2 p45-related factor 2 (Nrf2) and its principal negative regulator, Kelch-like ECH-associated protein 1 (Keap1), comprise a molecular effector and sensor system that robustly responds to perturbations of the cellular redox homeostasis by orchestrating a comprehensive cytoprotective program. Under homeostatic conditions, Nrf2 is a short-lived protein, which is targeted for ubiquitination and proteasomal degradation. Upon encounter of electrophiles, oxidants or pro-inflammatory stimuli, the cysteine sensors in Keap1 are chemically modified, rendering Keap1 unable to target Nrf2 for degradation, and consequently leading to accumulation of the transcription factor and enhanced transcription of cytoprotective genes. Detailed understanding of the protein-protein interactions between Nrf2 and Keap1 has been achieved by use of various in vitro systems, but few assays are available to assess these interactions in the context of the living cell. We previously developed an imaging-based FLIM/FRET methodology to visualise and measure the interaction between Nrf2 and Keap1 in single cells. Here, our goal was to improve this methodology in order to increase throughput and precision, and decrease cell-to-cell variability. To eliminate the possibility of orientation bias, we incorporated a flexible linker between Keap1 and the FRET acceptor fluorescent protein tag. To ensure the correct image capture of Nrf2 fused to the FRET donor fluorescent protein tag, we matched the maturation time of the fluorescent tag to the half-life of the endogenous Nrf2, by using sfGFP as the FRET donor. Using a global binning approach increased the assay throughput, whereas including the measured Instrument Response Function in the analysis improved precision. The application of this methodology revealed a strong covariation of the results with the expression level of the acceptor. Taking the acceptor level into account circumvented cell-to-cell variability and enhanced sensitivity of the measurements of the Keap1-Nrf2 interaction in live cells.
关键词： FRET,live cell imaging,fluorescence lifetime,FLIM,sfGFP,protein-protein interaction,global binning,Keap1,Instrument Response Function,Nrf2
更新于2025-11-21 11:08:12
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Electrochemical synthesis of Zn: ZnO/Ni2P and efficient photocatalytic degradation of Auramine O in aqueous solution under multi-variable experimental design optimization
摘要： Present work is devoted to synthesis Zn: ZnO/Ni2P by electrochemical method and identification and properties investigation by various techniques such as SEM, EDS, XRD and DRS. The experimental results reveal have ability for degradation of Auramine O (AO) following estimation of correlation among response to (main effect and variables interactions) variable like irradiation time, nanocomposite mass, pH and initial AO concentrations by a central composite design (CCD). The optimum condition for the photo-degradation of AO by photocatalyst was 6.72, 61.66 min, 13.13 mg.L-1 and 0.014 g correspond to the pH, irradiation time, AO concentration and photocatalyst mass, respectively. At these optimum conditions, the AO photocatalytic degradation percentages with desirability of 0.94 was 95.47% using reasonable consumption of reagent. The quasi first-order kinetic model derived from Langmuir–Hinshelwood (L–H) efficiently represent real behavior of experimental data of correspond to under study system. The photocatalytic reaction, L–H rate constants and L–H adsorption constants for Zn: ZnO/Ni2P were 0.0375 min-1, 27.39 mg.min-1.L and 0.00048 L.mg-1, respectively.
关键词： photocatalytic degradation,Auremine O,electrochemical synthesis.,Zn: ZnO/Ni2P,response surface methodology
更新于2025-11-21 11:01:37
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Effect of Deposition Potential on Synthesis, Structural, Morphological and Photoconductivity Response of Cu2O Thin Films by Electrodeposition Technique
摘要： The present work describes the effect of deposition potentials on structural, morphological, optical, electrical and photoconductivity responses of cuprous oxide (Cu2O) thin films deposited on fluorine-doped tin oxide glass substrate by employing electrodeposition technique. X-ray diffraction patterns reveal that the deposited films have a cubic structure grown along the preferential (111) growth orientation and crystallinity of the film deposited at ? 0.4 V is improved compared to the films deposited at ? 0.2, ? 0.3 and ? 0.5 V. Scanning electron microscopy displays that surface morphology of Cu2O film has a well-defined three-sided pyramid-shaped grains which are uniformly distributed over the surface of the substrates and are significantly changed as a function of deposition potential. Raman and photoluminescence spectra manifest that the film deposited at ? 0.4 V has a good crystal quality with higher acceptor concentration compared to other films. UV–visible analysis illustrates that the absorption of Cu2O thin film deposited at ? 0.4 V is notably higher compared to other films and the band gap of Cu2O thin films decreases from 2.1 to 2.04 eV with an increase in deposition potential from ? 0.2 to ? 0.5 V. The frequency–temperature dependence of impedance analysis shows that the film deposited at ? 0.4 V has a high conductivity. I–V measurements elucidate that the film deposited at ? 0.4 V exhibits a good photoconductivity response compared to films deposited in other deposition potentials.
关键词： Cu2O thin films,Electrodeposition,I–V measurement,Photoconductivity response
更新于2025-11-19 16:46:39
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Phosphotellurite glass and glass-ceramics with high TeO <sub/>2</sub> content: thermal, structural and optical properties
摘要： Phosphotellurite based glasses have interesting features such as low characteristic temperatures, large glass forming ability, high thermal stability against crystallization and broad transparency window from ultraviolet (UV) to near-infrared (NIR), which makes them promising materials for photonic applications. In this work, phosphotellurite binary glasses, having composition (100 – x) TeO2–x Ba(PO3)2 with x varying from 1 to 20 mol %, were synthesized by the conventional melt-quenching method in covered gold crucibles under air. Optical, physical and structural properties of the new glass samples were investigated by differential scanning calorimetry, X-rays diffraction, Raman spectroscopy, transmission electron microscopy, linear optical absorption from UV to NIR, IR transmittance, and optical limiting experiments. Transparent glass-ceramics in the visible range were obtained for phosphotellurite samples containing 2, 4 and 6 mol % of Ba(PO3)2 and the phase crystallization was investigated through Rietveld analysis and transmission electron microscopy. The incorporation of Ba(PO3)2 into the TeO2 network drastically increases the thermal stability against devitrification and helps to shift the infrared multiphonon absorption edge to longer wavelengths. Nonlinear measurements performed with a picosecond laser at 532 nm indicate large effective nonlinear absorption coefficients for all samples. In summary, the dependence of the spectroscopic properties on the samples’ compositions revealed a promising transparent glass and glass-ceramics for photonic applications.
关键词： transparent glass-ceramics,phosphotellurite glass,optical properties,nonlinear optical response
更新于2025-11-14 17:03:37
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Cross-linking induced thermo-responsive self-healable hydrogels with temperature regulated light emission property
摘要： Self-healing hydrogels draw great attentions in past decade based on the self-healing property similar to living creatures and their potential application in bioscience. On the other hand, thermo-response of the hydrogel endow the hydrogel with smart characteristic for controlled drug loading and delivery, diagnosis, cell imaging, life simulation, etc. In this study, self-healable hydrogel with cross-linking induced thermo-response (CIT) property was prepared from TPE containing copolymer TPE-P(DMA-stat-DAA) and the LCST of the hydrogels could be regulated by copolymer composition and the structure of the cross-linkers. The light emission property, mechanical and self-healing performances of the hydrogels are also investigated intensively. The results showed the LCST of the hydrogels could be regulated to body temperature through cross-linking induced thermo-response (CIT) mechanism with PEO23 DNH cross-linking. At the same time, the hydrogels exhibit light emission property, excellent self-healing ability and good mechanical properties. Moreover, the hydrogels showed different light emission property regulated by temperature based on AIE property of the TPE.
关键词： Light emission,Self-healing hydrogel,Cross-linking induced thermo-response
更新于2025-11-14 15:26:12
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A novel “turn-on” mitochondria-targeting near-infrared fluorescent probe for determination and bioimaging cellular hydrogen sulfide
摘要： Hydrogen sulfide (H2S) has been regarded as an important gas transmitter playing vital role in cytoprotective processes and redox signaling. It is very meaningful to monitor and analyze it in biosystem for obtaining important physiological and pathological information. Despite numerous fluorescent probes for cellular H2S have been reported in past decades, only a few have capability to detect mitochondrial H2S with near-infrared (NIR) emission. Therefore, a new mitochondria-targeting NIR fluorescent probe (Mito-NSH) for detection of cellular H2S was developed by introducing 2,4-dinitrophenyl ether into a novel dye (Mito-NOH). A large "turn-on" NIR fluorescence response was obtained due to thiolysis of ether to hydroxyl group when Mito-NSH was treated with NaHS. Moreover, Mito-NSH could quantitatively detect H2S at concentration ranging from 0 to 30 μM with a detection limit of 68.2 nM, and it exerts some superior optical properties, such as large stokes shift (107 nm), highly selectively mitochondria location, fast response and high selectivity to H2S. More impressively, it was successfully applied to imaging exogenous and endogenously generated H2S in living HeLa cells via confocal fluorescence microscopy.
关键词： Fast response,NIR fluorescent probe,"Turn-on" response,Hydrogen sulfide,Mitochondria-targeting
更新于2025-09-23 15:23:52
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Highly Luminescent Nitrogen-Doped Carbon Dots as “Turn-On” Fluorescence Probe for Selective Detection of Melamine
摘要： In our work, a new and simple method for selective detection of melamine is established by developing a "turn-on" fluorescence probe based on nitrogen-doped carbon dots (N-CQDs). The N-CQDs have been facilely prepared by one-step simple hydrothermal reaction and it is highly luminescent that with 51% fluorescent quantum yield. In this sensor, the fluorescent intensity of N-CQDs was found to be efficient quenched by Fe3+, upon addition of melamine the fluorescent intensity of N-CQDs-Fe3+ could gradually recover, which may because of the competitive combination of Fe3+ and melamine leading to the departure of Fe3+ from the N-CQDs' surface. Under optimum conditions, the fluorescence intensity has a good liner relationship with melamine in the range of 2.0 to 290 μM. The probe displayed good sensitivity toward melamine with a lower detection limit of 0.67 μM. In addition, this fluorescence probe has been used for the analysis of milk samples, demonstrating the fluorescence probe has potential application in the detection of melamine.
关键词： selective detection,turn-on fluorescence probe,melamine,carbon quantum dot
更新于2025-09-23 15:23:52