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A new dual C-shaped rectangular dielectric resonator based antenna for wideband circularly polarized radiation
摘要： This article presents a new dual C-shaped rectangular dielectric resonator (DR) based antenna for generation of wideband circularly polarized (CP) radiation. The proposed antenna comprises of a pair of C-shaped rectangular dielectric DR and a metal strip with a coaxial probe. By utilization of a metal strip at the side surface of C-shaped rectangular DR, the wideband CP radiation is achieved from the proposed dielectric resonator antenna (DRA). Fundamental orthogonal modes (TEx δ11 and TEy 1δ1) are excited using the rectangular DRA with a metal strip for the generation of CP fields. The proposed antenna with dual C-shaped rectangular CP DRA provides the measured ?10 dB reflection coefficient bandwidth of 30.07% (3.22 GHz-4.36 GHz) with measured 3-dB axial ratio bandwidth of 14.81% (3.25 GHz-3.77 GHz) at the boresight. The proposed antenna covers the useful Wi-MAX band.
关键词： wideband,dielectric resonator antenna,coaxial probe,circularly polarized
更新于2025-09-23 15:23:52
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Imaging multiple Rydberg wave packets from shaper-generated two-color femtosecond pump-probe sequences
摘要： We combine a bichromatic white light polarization pulse shaping scheme with angle- and energy-resolved photoelectron spectroscopy to image the dynamics of atomic Rydberg wave packets. Background-free detection of the Rydberg dynamics is performed using shaper-generated bichromatic linearly and circularly polarized femtosecond pump-probe pulse sequences. Photoelectron momentum distributions from linearly polarized bichromatic fields feature pronounced time-, energy-, and angle-dependent dynamics, which result from the interference of s-, d-, and g-type photoelectron wave packets from the ionization of the Rydberg np and nf series. Detailed analysis of the highly differential data allows us to extract the dynamics of both Rydberg wave packets separately. The results are experimentally verified by additional pump-probe studies with bichromatic circularly polarized pulse sequences, which exclusively map the dynamics of the Rydberg nf series via g-type photoelectron wave packets.
关键词： Rydberg wave packets,pump-probe spectroscopy,photoelectron imaging,femtosecond lasers,polarization pulse shaping
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
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Mitochondria-targeted ratiometric fluorescent probes for micropolarity and microviscosity and their applications
摘要： Ambient polarity and viscosity are two important parameters that influence many chemical and biological processes of biomolecules. In biological systems especially at the cellar level, polarity affects the interaction of many proteins and enzymes as well as the cell membrane permeability. Microenvironmental viscosity has a marked impact on some physiological processes such as cellular material transportation, interactions between biological macromolecules, diffusion of reactive substances. Abnormal changes in polarity and/or viscosity have been considered as vital causes or indicators for some diseases and malfunctions such as diabetes and Alzheimer's disease. Detection of microenvironmental polarity and/or viscosity has caused much interest in many scientific areas. Mitochondria are important organelles of energy production as well as major sites of aerobic respiration in eukaryotes. They are also involved in lots of significant processes including protein translocation, the synthesis of ATP, the transportation of metabolites, etc. The mitochondrial functions are closely linked with physical chemical properties of mitochondria, namely polarity, viscosity, pH and temperature. Therefore, monitoring the changes in mitochondrial polarity and/or viscosity is fruitful for understanding some important physiological processes. However, conventional viscometers and polarity detectors are not suitable for the measurements at the cellar level. It is highly desired to develop new techniques for fast quantifying cellar polarity and viscosity. Fluorescence-based techniques have been widely applied in many scientific researches due to the merits of good accuracy, extremely high sensitivity, temporal and spatial resolution and especially bioimaging in living cells. Numerous polarity-sensitive sensors have been developed for detection of cellar polarity based on intramolecular charge transfer (ICT) mechanism. For viscosity tests, 'molecular rotors' have been proved to be promising probes for their excellent photophysical properties of ratiometric fluorescence and/or fluorescence lifetime imaging. Nevertheless, probe possesses features of both ICT and molecular rotor and could monitor polarity and viscosity simultaneously has rarely been reported. Coumarin is a well-known polarity-sensitive fluorophore, and many coumarin-based probes have been constructed for polarity. Normally, the structural characteristic of a molecular rotor is that a steric group covalently linked to a planar fluorophore with a single/double bond as the connecting rotation shaft. In view of the above points, we envisioned that if a steric group linked to a polarity-sensitive fluorophore, it may detect polarity and viscosity simultaneously. Herein, two compounds YYH1 and YYH2 with coumarin as the fluorophore and N-methyl indole as the steric group were selected to quantify microenvironmental polarity and viscosity. Compared to those with similar fluorophore reported in the references, our probes were more sensitive to polarity and/or viscosity and have longer emission wavelengths (λem = 685 nm for YYH2). Furthermore, the cationic characteristics of both compounds endows them locating in mitochondria in living cells. With compounds YYH1 and YYH2 (NMR and mass spectra are shown in Figs. S1 and S2 in Supporting information) in hand, we first investigated their photophysical properties in phosphate buffered solution (PBS). Fig. S3 (Supporting information) demonstrates that both compounds have one absorption and two emission peaks in PBS. The emission peaks of shorter wavelengths could be ascribed to the part without indole moiety. The red emission bands are resulted from the whole π-conjugation system, which are sensitive to the solvent viscosity. The emission (681 nm) and absorption (597 nm) maxima of YYH2 are at the red wavelength region and about 30 nm longer than those of YYH1, which enables the probe to be potentially applied in biological systems. Considering the strong ICT characteristic from the aminocoumarin unit to the indole part, the solvent-dependent spectral properties were studied. Both compounds display solvatochromic absorption and emission spectra (Figs. S4 and S5 in Supporting information). The absorption maximum of YYH1 shifted from 628 nm in toluene to 565 nm in PBS, while the green emission moved from 462 nm to 478 nm in the same series of solvents. However, the red emission showed little change upon polarity variation (Fig. S6 in Supporting information). Good relationship between absorption/emission wavenumber and the solvent polarity parameters (ET) verifies the ICT characteristic of the green emission (Fig. S6). The polarities of cationic compounds YYH1 and YYH2 are greater in ground state than in excited state, therefore, the absorption wavelength decreased with increasing polarity. Nevertheless, the green emission wavelength increased with increasing polarity, suggesting that the indole cation section was not involved in the green emission. In 1,4-dioxane-water binary mixture, with increasing water content, the absorption peak shifted from 613 to 565 nm and 647 to 597 nm for YYH1 and YYH2, respectively (Fig. S7 and S8 in Supporting information). The emission wavelength of YYH1 shifted from 468 nm to 478 nm without obvious intensity change when the proportion of the polar solvent water increased from 10% to 20% (Fig. 1a). Further increasing water content resulted in significant decrease in fluorescence intensity of the green emission with no appreciable wavelength change, whereas the emission at 645 nm increased steadily, with an isoemission point at 598 nm (Fig. 1a). More than 150 nm wavelength difference between the two bands provides a ratiometric response. The ratio I490/I645 decreased dramatically from 27 to 0.5 with increasing water content from 20% to 100% suggesting that YYH1 could be a potential ratiometric fluorescent probe for microenvironmental polarity. In the case of YYH2, when water content changed from 0 to 40%, both the blue (515 nm) and red (685 nm) emissions increased; while they both decreased with further increment of water content (Figs. S8b and c). The fluorescence intensity ratio I515/I685 hardly changed with water content revealing that YYH2 is insensitive to polarity (Fig. 1b). Then the spectral responses of YYH1 and YYH2 toward arbitrary changes in the viscosity were tested to understand the viscosity effect. The experimental results illustrate that YYH1 and YYH2 respond to the viscosity in different ways. In glycol-water mixed system, the absorbance at 595 nm of YYH2 increased slightly accompanied with about 12 nm red-shift with increasing glycol content, which could be probably attributed to the slight decrease of the polarity (Fig. S9 in Supporting information). As shown in Fig. 2a, the red emission of YYH2 is more sensitive to solvent viscosity than the green one: with increasing solvent viscosity from 1.0 (water) to 19.9 cp (glycol), about 10-fold and 1.7-fold fluorescence enhancements respectively for the red and green emissions were observed. The enhancement in the green emission was possibly attributed to the variation in solution's polarity. Good linear relationship between log (I685/I515) and logη of the solvent reveals that YYH2 could be applied in ratiometric detection of the media viscosity. The quantitative relationship between the ratio of I685/I515 and the solvent viscosity η is well expressed by F?rster-Hoffmann equation: log(I685/I515) = C + xlogη (C = ?0.673, x = 0.634, R2 = 0.968), where C is a concentration and temperature-dependent constant and x is a dye-dependent constant. In addition, the fluorescence life time of YYH2 also became slightly longer with increasing solution viscosity (Fig. S10 in Supporting information): It was 0.3, 0.47 and 1.46 ns in water, 1:1 water-glycol and glycol, respectively. As for YYH1, about 8 nm blue-shift of the absorption maximum was found with increasing water content from 0 to 100%. The fluorescence intensities at 490 nm and 645 nm increased to almost the same extent (Fig. S11 in Supporting information), and the ratio of I645/I490 hardly changed with viscosity (Fig. 2b). From the above results, it is clear that YYH1 and YYH2 could be employed to detect local polarity and viscosity, respectively. To evaluate the biological application of the probes, we tested both compounds in living cells (Fig. 3). The localization of the probes in two living cell lines, L929 and MCF-7 cells, were determined by co-staining cells with mitrochondria-specific dye. The bright red fluorescent region with YYH1 (a2, b2) and green signals from Mitro Tracker Green FM (a1, b1) overlapped perfectly (a4, b4). A high Pearson correlation factor Pf of 0.91 for L929 cells (0.94 for MCF-7 cells) indicates that YYH1 is a mitrochondria-targeted dye. Similar results were obtained in the case of YYH2 (Figs. 3c and d) (Pf are 0.93 and 0.92 for L929 and MCF-7 cells, respectively), revealing that both probes could localize at mitrochondria. In living cells, proteins and some other biologically related substances are the main components and involved in every process within cells. The fluctuation of protein contents could affect cellar polarity or viscosity. To verify the effectiveness and practicability of the probes in realistic samples, the effects of some biological molecules on the spectral properties of YYH1 and YYH2 were measured. Table S1 (Supporting information) showed that both the ratio I490/I645 of YYH1 and the ratio I685/I515 of YYH2 became higher upon the addition of proteins (Fig. S12-S13 in Supporting information), revealing that the presence of proteins increased the microenvironmental viscosity and decreased the microenvironmental polarity of the probes. Furthermore, it is obvious that the viscosity and polarity varied with proteins (Table S1 in Supporting information), which means that the difference in protein content and/or protein species could cause the change in cellar viscosity and polarity. It is reported that probes YYH1 and YYH2 exhibited spectral responses toward sulfite. Other relevant species except for peroxynitrite hardly influence the photophysical properties of the probes. Therefore, the presence of sulfite or peroxynitrite could interfere with bioimaging to some extent. However, it is difficult for detection of peroxynitrite in living cells by traditional analytical methods due to its short half-life under typical physiological conditions. Sulfite content in living cells is relatively low because it could easily be oxidized to sulfate by sulfite oxidase. The interference from these ions could be neglected. On the other hand, the presence of sulfite resulted in the same variation tendency of Iblue/Ired for both probes. However, the change trends of Iblue/Ired for YYH1 and YYH2 caused by polarity/viscosity were quite different. Therefore, interference from sulfite could be distinguished by using both probes for bioimaging. Next, YYH1 and YYH2 were employed to estimate the polarity and viscosity in living cells, respectively. After MCF-7 and L929 cells incubated with YYH1 (5 μmol/L) for 30 min, blue and red imaging were collected. Strong intracellular blue fluorescence and weak intracellular red fluorescence were observed in both cells. Considering that the ratio of I490/I645 (i.e. I645/I490 in Fig. 2b) hardly changed with solvent viscosity, the ratio of Iblue/Ired may indicate that the mitochondrial polarity in L929 cells is smaller than that in MCF-7 cells (Fig. 4). After incubated with YYH2 (5 μmol/L) for 30 min, brighter intracellular green fluorescence was observed in MCF-7 cells, while stronger intracellular red fluorescence was observed in L929 cells (Fig. 5). The ratio of Ired/Igreen suggests that the mitochondrial viscosity in L929 cells is larger than that in MCF-7 cells. In summary, we have synthesized two mitochondria-targeted ratiometric fluorescent probes YYH1 and YYH2 for quantification of micropolarity and microviscosity, respectively. Both probes were constructed with environment-sensitive coumarin and N-methyl indole linked through a C-C bridge. YYH1 responded to the polarity, while YYH2 responded to the viscosity sensitively. Therefore, they were used for ratiometric fluorescent detection of the mitochondrial polarity and viscosity respectively. This work may provide some ideas for design of polarity and/or viscosity fluorescent probes for bioimaging living cells.
关键词： Mitochondria,Microviscosity,Micropolarity,Fluorescent probe
更新于2025-09-23 15:23:52
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Novel rhodamine-based colorimetric and fluorescent sensor for the dual-channel detection of Cu2+ and Co2+/trivalent metal ions and its AIRE activities
摘要： A rhodamine hydrazone 1 bearing coumarin moiety was designed and prepared. Compound 1 exhibited high selectivity toward Co2+ and trivalent metal ions with fluorescence enhancement in CH3OH solution. However, 1 selectively responded to Al3+ in nearly pure H2O media and was further applied to monitor Al3+ in live cells. Moreover, 1 could also act as a colorimetric probe toward Cu2+ in either CH3OH or H2O solution. In addition, sensor 1 displayed aggregation-induced ratiometric emission (AIRE) activities in mixed H2O/CH3OH solution.
关键词： cell imaging,coumarin,fluorescent probe,Aggregation-induced ratiometric emission,metal ions,rhodamine
更新于2025-09-23 15:23:52
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Absence of free carriers in silicon nanocrystals grown from phosphorus- and boron-doped silicon-rich oxide and oxynitride
摘要： Phosphorus- and boron-doped silicon nanocrystals (Si NCs) embedded in silicon oxide matrix can be fabricated by plasma-enhanced chemical vapour deposition (PECVD). Conventionally, SiH4 and N2O are used as precursor gasses, which inevitably leads to the incorporation of ≈10 atom % nitrogen, rendering the matrix a silicon oxynitride. Alternatively, SiH4 and O2 can be used, which allows for completely N-free silicon oxide. In this work, we investigate the properties of B- and P-incorporating Si NCs embedded in pure silicon oxide compared to silicon oxynitride by atom probe tomography (APT), low-temperature photoluminescence (PL), transient transmission (TT), and current–voltage (I–V) measurements. The results clearly show that no free carriers, neither from P- nor from B-doping, exist in the Si NCs, although in some configurations charge carriers can be generated by electric field ionization. The absence of free carriers in Si NCs ≤5 nm in diameter despite the presence of P- or B-atoms has severe implications for future applications of conventional impurity doping of Si in sub-10 nm technology nodes.
关键词： photoluminescence,silicon nanocrystals,transient transmission,doping,atom probe tomography
更新于2025-09-23 15:23:52
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Amplification-free and direct fluorometric determination of telomerase activity in cell lysates using chimeric DNA-templated silver nanoclusters
摘要： A fluorogenic probe has been developed for determination of telomerase activity using chimeric DNA-templated silver nanoclusters (AgNCs). The formation of AgNCs was investigated before (route A) and after (route B) telomerase elongation reaction. Both routes caused selective quenching of the yellow emission of the AgNCs (best measured at excitation/emission wavelength of 470/557 nm) in telomerase-positive samples. The quenching mechanism was studied using synthetically elongated DNA to mimic the telomerase-catalyzed elongation. The findings show that quenching is due to the formation of parallel G-quadruplexes with a –TTA– loop in the telomerase elongated products. The assay was validated using different cancer cell extracts, with intra- and interassay coefficients of variations of <9.8%. The limits of detection for MCF7, RPMI 2650 and HT29 cell lines are 15, 22 and 39 cells/μL. This represents a distinct improvement over the existing telomeric repeat amplification protocol (TRAP) assay in terms of time, sensitivity and cost.
关键词： Biomarker,Telomers,HT29,Biosensor,G-quadruplex,MCF7,AgNCs,TRAP,RPMI 2650,Cancer probe
更新于2025-09-23 15:23:52
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Optical Imaging of Triple-Negative Breast Cancer Cells in Xenograft Athymic Mice Using an ICAM-1-Targeting Small-Molecule Probe
摘要： Purpose: The development of early, accurate diagnostic strategies for triple-negative breast cancer (TNBC) remains a significant challenge. Intercellular adhesion molecule-1 (ICAM-1) overexpressed in human TNBC cells is a potential molecular target and biomarker for diagnosis. In this study, small-molecule probe (denoted as γ3-Cy5.5) constructed with a short 17-mer linear peptide (γ3) and near-infrared fluorescence (NIRF) dye cyanine 5.5 (Cy5.5) was used to detect the expression of ICAM-1 in vitro and in vivo, and to diagnose TNBC via NIRF imaging. Procedures: Western blotting and flow cytometric analysis were used for the detection of ICAM-1 expression in MDA-MB-231 and MCF-7 cells. The cytotoxicity of the small-molecule probe γ3-Cy5.5 was detected using the CCK8 assay. The in vitro targeting of the small-molecule probe γ3-Cy5.5 was verified via flow cytometry and a laser scanning confocal microscope. Finally, the targeting of small-molecule probe in vivo and ex vivo was observed by NIRF imaging. Results: Western blotting and flow cytometry demonstrate that ICAM-1 was highly expressed in the MDA-MB-231 TNBC cell line. Laser confocal microscopy and flow cytometry results show that TNBC cells have an increased cellular uptake of γ3-Cy5.5 compared to the control probe γ3S-Cy5.5. With in vivo NIRF, a significantly higher Cy5.5 signal appeared in the tumors of mice administered γ3-Cy5.5 than those treated with γ3S-Cy5.5. The target-to-background ratio observed on the NIRF images was significantly higher in the γ3-Cy5.5 group (10.2, 13.6) compared with the γ3S-Cy5.5 group (4.4, 4.0) at 1 and 2 h, respectively. Conclusions: This is the first report of the use of ICAM-1-specific small-molecule probe for in vivo NIRF optical imaging of TNBC. This method provides a noninvasive and specific strategy for the early diagnosis of TNBC.
关键词： Triple-negative breast cancer,Near-infrared fluorescence imaging,Small-molecule probe,ICAM-1
更新于2025-09-23 15:23:52
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Surface potential tailoring of PMMA fibers by electrospinning for enhanced triboelectric performance
摘要： Triboelectric generators rely on contact-generated surface charge transfer between materials with different electron affinities to convert mechanical energy into useful electricity. The ability to modify the surface chemistry of polymeric materials can therefore lead to significant enhancement of the triboelectric performance. Poly(methyl methacrylate) (PMMA) is a biocompatible polymer commonly used in medical applications, but its central position on the triboelectric series, which empirically ranks materials according to their electron-donating or electron accepting tendencies, renders it unsuitable for application in triboelectric generators. Here, we show that the surface potential of PMMA fibers produced by electrospinning can be tailored through the polarity of the voltage used during the fabrication process, thereby improving its triboelectric performance, as compared to typically spin-coated PMMA films. The change in surface chemistry of the electrospun PMMA fibers is verified using X-ray photoelectron spectroscopy, and this is directly correlated to the changes in surface potential observed by Kelvin probe force microscopy. We demonstrate the enhancement of triboelectric energy harvesting capability of the electrospun PMMA fibers, suggesting that this surface potential modification approach can be more widely applied to other materials as well, for improved triboelectric performance.
关键词： Energy harvesting,Triboelectric generator,Surface chemistry,Kelvin probe force microscopy,Electrospinning,Poly(methyl methacrylate)
更新于2025-09-23 15:23:52
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In-Situ covalent synthesis of gold nanorods on GO surface as ultrasensitive Raman probe
摘要： In this paper, using thiolated graphene oxide (GO‐O‐SH) as substrate, gold nanorods (AuNRs) covalently linked to the GO surface by in‐situ seed growth method were first reported. The as‐prepared composites were characterized by UV–vis spectrum, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT‐IR). Experimental results indicated that the introduction of short flexible organic chain between GO and AuNRs contributed to the homogenous synthesis of gold rods, and uniform gold nanorods with aspect ratio within 3~8 were covalently linked to the surface of GO with high stability and yield. The strategy represented an outstanding improvement in comparison to the traditional route for fabricating the two GO@AuNRs composites. Furthermore, based on coupling of nanomaterials, the composites could act as high sensitive Raman probe with limit of detection (LOD) reaching 1 × 10?12 M.
关键词： covalent synthesis,Raman probe,graphene oxide (GO),gold nanorods
更新于2025-09-23 15:23:52