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Long-Range Activationless Photostimulated Charge Transport in Symmetric Molecular Junctions
摘要： Molecular electronic junctions consisting of nitroazobenzene oligomers covalently bonded to a conducting carbon surface using an established 'all-carbon' device design were illuminated with UV?vis light through a partially transparent top electrode. Monitoring junction conductance with a DC bias imposed permitted observation of photocurrents while varying the incident wavelength, intensity, molecular layer thickness, and temperature. The photocurrent spectrum tracked the in situ absorption spectrum of nitroazobenzene, increased linearly with light intensity, and depended exponentially on applied bias. The electronic characteristics of the photocurrent differed dramatically from those of the same device in the dark, with orders of magnitude higher conductance and very weak attenuation with molecular layer thickness (β = 0.14 nm?1 for thickness above 5 nm). The temperature dependence of the photocurrent was opposite that of the dark current, with a 35% decrease in conductance between 80 and 450 K, while the dark current increased by a factor of 4.5 over the same range. The photocurrent was similar to the dark current for thin molecular layers but greatly exceeded the dark current for low bias and thick molecular layers. We conclude that the light and dark mechanisms are additive, with photoexcited carriers transported without thermal activation for a thickness range of 5?10 nm. The inverse temperature dependence is likely due to scattering or recombination events, both of which increase with temperature and in turn decrease the photocurrent. Photostimulated resonant transport potentially widens the breadth of conceivable molecular electronic devices and may have immediate value for wavelength-specific photodetection.
关键词： charge transport,optoelectronics,photocurrent,molecular electronics,molecular orbital energy,tunneling barrier,HOMO?LUMO gap,photoinduced transport
更新于2025-09-23 15:22:29
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Electroburning of few-layer graphene flakes, epitaxial graphene, and turbostratic graphene discs in air and under vacuum
摘要： Graphene-based electrodes are very promising for molecular electronics and spintronics. Here we report a systematic characterization of the electroburning (EB) process, leading to the formation of nanometer-spaced gaps, on different types of few-layer graphene (namely mechanically exfoliated graphene on SiO2, graphene epitaxially grown on the C-face of SiC and turbostratic graphene discs deposited on SiO2) under air and vacuum conditions. The EB process is found to depend on both the graphene type and on the ambient conditions. For the mechanically exfoliated graphene, performing EB under vacuum leads to a higher yield of nanometer-gap formation than working in air. Conversely, for graphene on SiC the EB process is not successful under vacuum. Finally, the EB is possible with turbostratic graphene discs only after the creation of a constriction in the sample using lithographic patterning.
关键词： graphene,graphene based electrodes,molecular electronics,molecular spintronics
更新于2025-09-23 15:22:29
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Effects of different molecular chain lengths and side groups on structure and property of UV-curable waterborne cathodic electrophoretic deposition coatings
摘要： A series of UV-curable waterborne cathodic electrophoretic deposition (CED) coatings with various structures were successfully developed by introducing modified acrylic monomer with different molecular chain lengths and side groups. The length of linear chain of the modified monomer had little effect on phase separation of acrylic polymer and easily formed homogeneous structure. Owing to the longer molecular chains, the pencil hardness decreased from 2H to H and the glass transition temperature reduced to 77.7 °C. The hard side groups of the modified monomer in CED coatings exhibited opposite characteristics resulting from the steric hindrance of the rigid groups and the crosslinking network, which were more likely to exhibit partial phase separation. Therefore, the stronger rigidity of the molecular structure improved the particle size to 122.42 nm, the smoothness of the CED cured film and surface contact angle decreased. And the morphology of the films became rough and surface contact angle decreased. Besides, the adhesive force and flexibility of the films could be excellent. The surface rust of the modified CED film is not remarkable under salt spray test. The photopolymerization rate (Rp) and the double bond conversion were evaluated. It was found that the Rp and the conversion obviously decreased with increasing rigid groups in acrylate molecular chains. However, the maximum decomposition temperature of it was higher than the other samples. The residue char yield (Yc) was 5.24 wt%. The stronger rigidity of the molecular structure had better thermal stability and mechanical properties.
关键词： Cathodic electrophoretic deposition coatings,Thermal stability,Photopolymerization rate,Molecular structure
更新于2025-09-23 15:22:29
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Samarium thin films molecular plated from <i>N</i> , <i>N</i> -dimethylformamide characterized by XPS
摘要： Characterization of samarium thin films molecular plated from N,N-dimethylformamide solutions onto stainless steel substrates, with either mirrorlike or brushed finishes, was carried out using a Thermo Scientific K-Alpha x-ray photoelectron spectrometer. Survey scans of the two specimens showed the presence of samarium, carbon, and oxygen with minor amounts of sodium. High-resolution spectra were then taken of the Sm 3d, O 1s, and C 1s regions. The chemical compositions of the two samples were found to be very similar, with the key difference being the relative amounts of two carbon species. Spectra from the survey and narrow high-resolution scans of the Sm 3d, O 1s, and C 1s regions are reported herein.
关键词： thin film,electrodeposition,samarium,molecular plating
更新于2025-09-23 15:22:29
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Electrical Properties of Midwave and Longwave InAs/GaSb Superlattices Grown on GaAs Substrates by Molecular Beam Epitaxy
摘要： In the present work, we report on the in-plane electrical transport properties of midwave (MWIR) and longwave infrared (LWIR) InAs/GaSb type-II superlattices (T2SLs) grown by molecular beam epitaxy (MBE) system on GaAs (001) substrate. The huge lattice mismatch between the T2SL and GaAs substrate is reduced by the growth of GaSb buffer layer based on interfacial misfit array (IMF) technique. In order to compensate the strain in the InAs/GaSb T2SL, we utilized a special shutters sequence to get InSb-like and GaAs-like interfaces. It is found that the MWIR InAs/GaSb T2SL exhibits a p- and n-type conduction at low and high temperatures, respectively. Interestingly, the conduction change temperature is observed to be dependent on the growth temperature. On the other hand, LWIR T2SL conduction is dominated only by electrons. It is important to note that the dominant scattering mechanism in LWIR T2SL at low temperatures is the interface roughness scattering mechanism.
关键词： Hall effect,High-resolution X-ray diffraction,Type-II superlattices,Molecular beam epitaxy
更新于2025-09-23 15:22:29
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In vivo long-term investigation of tumor bearing mKate2 by an in-house fluorescence molecular imaging system
摘要： Background: Optical imaging is one of the most common, low-cost imaging tools used for investigating the tumor biological behavior in vivo. This study explores the feasibility and sensitivity of a near infrared fluorescent protein mKate2 for a long-term non-invasive tumor imaging in BALB/c nude mice, by using a low-power optical imaging system. Methods: In this study, breast cancer cell line MDA-MB-435s expressing mKate2 and MDA-MB-231 expressing a dual reporter gene firefly luciferase (fLuc)-GFP were used as cell models. Tumor cells were implanted in different animal body compartments including subcutaneous, abdominal and deep tissue area and closely monitored in real-time. A simple and low-power optical imaging system was set up to image both fluorescence and bioluminescence in live animals. Results: The presence of malignant tissue was further confirmed by histopathological assay. Considering its lower exposure time and no need of substrate injection, mKate2 is considered a superior choice for subcutaneous imaging compared with fLuc. On the contrary, fLuc has shown to be a better option when monitoring the tumor in a diffusive area such as abdominal cavity. Furthermore, both reporter genes have shown good stability and sensitivity for deep tissue imaging, i.e. tumor within the liver. In addition, fLuc has shown to be an excellent method for detecting tumor cells in the lung. Conclusions: The combination of mKate2 and fLuc offers a superior choice for long-term non-invasive real-time investigation of tumor biological behavior in vivo.
关键词： Molecular imaging,mKate2,Luciferase,Tumor cell tagging
更新于2025-09-23 15:22:29
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A UV-Responsive Multifunctional Photoelectric Device Based on Discotic Columnar Nanostructures and Molecular Motors
摘要： Orientation control of ordered materials would not only produce new physical phenomenon but also facilitate the development of fancy devices. Discotic liquid crystals (DLCs) form 1D charge transport pathway by self-organizing into columnar nanostructures via π–π stacking. However, controlling the electrical properties in such nanostructures with some direct and instant way is a formidable task for their high viscosity and insensitivity to external stimuli. Herein, the arbitrary control over electrical conductivity of such columnar nanostructures is achieved with UV light by incorporating DLCs with molecular motors. Highly ordered DLC microstripe arrays are generated on desired substrate through a capillary bridge dewetting strategy. The conductivity of the microstripes could be continuously modulated by 365 nm light due to the influence of molecular motion under UV irradiation on the electron orbital overlap of columnar nanostructures. This is so because the disorder degree of the DLC molecules is associated with the intensity of UV light and the doping concentration of molecular motors. Moreover, the device shows memory effect and reversible conductivity change. The DLC microstripe arrays are very promising for the applications in UV detectors, memory devices, optical switches, and so on.
关键词： discotic liquid crystals,tunable conductivity,molecular motors,overcrowded alkenes,optical switches
更新于2025-09-23 15:22:29
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99mTc sestamibi SPECT: a possible tool for early detection of breast cancer lesions with high bone metastatic potential
摘要： The early identification of lesions with high metastatic potential by 99mTc sestamibi high-resolution SPECT analysis could be considered a new frontier for diagnosis and/or therapy of breast lesions.
关键词： SPECT,breast cancer,molecular imaging,breast osteoblast-like cells,99mTc sestamibi
更新于2025-09-23 15:22:29
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Double-slit photoelectron interference in strong-field ionization of the neon dimer
摘要： Wave-particle duality is an inherent peculiarity of the quantum world. The double-slit experiment has been frequently used for understanding different aspects of this fundamental concept. The occurrence of interference rests on the lack of which-way information and on the absence of decoherence mechanisms, which could scramble the wave fronts. Here, we report on the observation of two-center interference in the molecular-frame photoelectron momentum distribution upon ionization of the neon dimer by a strong laser field. Post-selection of ions, which are measured in coincidence with electrons, allows choosing the symmetry of the residual ion, leading to observation of both, gerade and ungerade, types of interference.
关键词： double-slit interference,photoelectron momentum distribution,strong-field ionization,neon dimer,molecular frame
更新于2025-09-23 15:22:29
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Paired-Agent Fluorescence Molecular Imaging of Sentinel Lymph Nodes Using Indocyanine Green as a Control Agent for Antibody-Based Targeted Agents
摘要： Purpose. Paired-agent molecular imaging methods, which employ coadministration of an untargeted, “control” imaging agent with a targeted agent to correct for nonspecific uptake, have been demonstrated to detect 200 cancer cells in a mouse model of metastatic breast cancer. This study demonstrates that indocyanine green (ICG), which is approved for human use, is an ideal control agent for future paired-agent studies to facilitate eventual clinical translation. Methods. The kinetics of ICG were compared with a known ideal control imaging agent, IRDye-700DX-labeled antibody in both healthy and metastatic rat popliteal lymph nodes after coadministration, intradermally in the footpad. Results. The kinetics of ICG and antibody-based imaging agent in tumor-free rat lymph nodes demonstrated a strong correlation with each other (r = 0.98, p < 0.001) with a measured binding potential of -0.102 ± 0.03 at 20 min postagent injection, while the kinetics of ICG and targeted imaging agent shows significant separation in the metastatic lymph nodes. Conclusion. This study indicated a potential for microscopic sensitivity to cancer spread in sentinel lymph nodes using ICG as a control agent for antibody-based molecular imaging assays.
关键词： Paired-agent imaging,Antibody-based targeted agents,Control agent,Indocyanine green,Fluorescence molecular imaging,Sentinel lymph node
更新于2025-09-23 15:22:29