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Optical, charge transport and magnetic properties of palladium retrieved from photometric measurements: approaching the quantum mechanics background
摘要： A parametric Drude–Lorentz (DL) model is used to describe the spectral variation of the dielectric functions of bulk palladium samples at low and room temperature. In addition to the contribution of conduction electrons, the contribution of holes is also explicitly accounted for in the model. A simulated annealing method is applied to obtain the optimized values of the parameters involved in the model: volume plasma frequency of conduction electrons, high frequency dielectric constant, collision frequency of holes and corresponding relaxation time, and two additional parameters from which the effective mass of holes and collision frequency of conduction electrons are evaluated. Oscillatior strengths, resonance frequencies, and widths entering in the Lorentz contribution to the dielectric function are also optimized. Renormalization of the oscillator strengths requires the introduction of a new parameter in the context of the DL model: the ratio between number density of conduction electrons and number density of metal atoms, whose optimized value ?ts very well with its evaluation from band structure calculations and from independent measurements. Inclusion of this parameter in the framework allows us to evaluate additional quantities related to the charge-carrier transport: average effective masses, Fermi energies and electronic densities of states at the corresponding Fermi energies, intrinsic electrical resistivity, intrinsic mean free paths, heat capacities, mobilities, as well as paramagnetic and diamagnetic susceptibilities, for both electrons and holes. The optimized resonance frequencies are compared with energy differences between plausible interband transitions, in accordance with reported band structure diagrams and with our own band structure obtained from density functional theory calculations.
关键词： Drude–Lorentz model,palladium,density functional theory,simulated annealing,metal thin ?lms
更新于2025-11-14 15:19:41
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Millimeter-Scale Growth of Single-Oriented Graphene on a Palladium Silicide Amorphous Film
摘要： It is widely accepted in condensed matter physics and material science communities that a single-oriented overlayer cannot be grown on an amorphous substrate because the disordered substrate randomizes the orientation of the seeds, leading to polycrystalline grains. In the case of two-dimensional materials such as graphene, the large-scale growth of single-oriented materials on an amorphous substrate has remained unsolved. Here, we demonstrate experimentally that the presence of uniformly oriented graphene seeds facilitates the growth of millimeter-scale single-oriented graphene with 3×4 mm2 on palladium silicide, which is an amorphous thin film, where the uniformly oriented graphene seeds were epitaxially grown. The amorphous palladium silicide film promotes the growth of the single-oriented growth of graphene by causing carbon atoms to be diffusive and mobile within and on the substrate. In contrast to these results, without the uniformly oriented seeds, the amorphous substrate leads to the growth of polycrystalline graphene grains. This millimeter-scale single-oriented growth from uniformly oriented seeds can be applied to other amorphous substrates.
关键词： silicon carbide,amorphous substrate,single orientation,graphene,palladium silicide
更新于2025-09-23 15:23:52
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Directing energy into a sub-wavelength non-resonant metasurface across the visible spectrum.
摘要： Group 10 metals (i.e. Ni, Pd, Pt) catalyze a wide range of chemical transformations but the weak interaction of their nanoparticles with light hinders their development for photocatalytic applications. Conversely, coinage metals nanoparticles (particularly Ag and Au) exhibit intense localized surface plasmon resonances in the visible spectrum, but are relatively unreactive, limiting the scope and efficiency of their photochemical processes. Here we demonstrate the design, fabrication and characterization of a new structure containing a single layer of Pd nanoparticles that absorbs up to >98% of visible light. Furthermore, the wavelength of absorption is controlled throughout the visible range of the electromagnetic spectrum by modulating the thickness of a supporting metal oxide film. We show that the absorbed energy is concentrated in the nanoparticle layer, crucial for energy conversion applications including photocatalysis and photothermal processes.
关键词： photocatalysis,plasmonics,metasurfaces,palladium,Hot charge carriers,absorbers,critical coupling
更新于2025-09-23 15:23:52
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Doubly N-Confused Calix[6]phyrin Bis-Organopalladium Complexes: Photostable Triplet Sensitizers for Singlet Oxygen Generation
摘要： Triplet photosensitizers that generate singlet oxygen efficiently are attractive for applications such as photodynamic therapy (PDT). Extending the absorption band to a near-infrared (NIR) region (700 nm~) with reasonable photostability is one of the major demands in the rational design of such sensitizers. We herein prepared a series of mono- and bis-palladium complexes (1-Pd-H2, 2-Pd-H2, 1-Pd-Pd, and 2-Pd-Pd) based on modified calix[6]phyrins as photosensitizers for singlet oxygen generation. These palladium complexes showed intense absorption profiles in the visible-to-NIR region (500–750 nm) depending on the number of central metals. Upon photoirradiation in the presence of 1,5-dihydroxynaphthalene (DHN) as a substrate for reactive oxygen species, the bis-palladium complexes generated singlet oxygen with high efficiency and excellent photostability. Singlet oxygen generation was confirmed from the characteristic spectral feature of the spin trapped complex in the EPR spectrum and the intact 1O2 emission at 1270 nm.
关键词： Photostability,Palladium N-confused calix[6]phyrin,Triplet Photosensitizer,Singlet oxygen
更新于2025-09-23 15:23:52
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Tilted Fiber Bragg Grating Sensor Using Chemical Plating of a Palladium Membrane for the Detection of Hydrogen Leakage
摘要： A tilted ?ber Bragg grating (TFBG) hydrogen sensor coated with a palladium (Pd) membrane by the electroless plating method is proposed in this paper. A uniform layer of Pd metal is fabricated in aqueous solutions by the chemical coating method, which is used as the sensitive element to detect the change of the surrounding refractive index (SRI) caused by hydrogen absorption. The change in SRI causes an unsynchronized change of the cladding modes and the Bragg peak in the TFBG transmission spectrum, thereby eliminating the cross-sensitivity due to membrane expansion and is able to simultaneously monitor the presence of cracks in the pipe, as well as the hydrogen leakage. By subtracting the wavelength shift caused by ?ber expansion, the change of SRI, i.e., the information from the H2 level, can be separately obtained. The drifted wavelength is measured for the H2 concentration below the hydrogen explosion limit between 1% and 4%. The chemical-based coating has the advantages of a low cost, a simple operation, and being suitable for coating on long ?ber structures. The proposed sensor is able to detect the H2 signal in 5 min at a 1% H2 concentration. The proposed sensor is proved to be able to monitor the hydrogen level without the cross-sensitivity of temperature variation and expansion strains, so could be a good candidate for security applications in industry.
关键词： electroless plating,tilted ?ber Bragg grating,optical ?ber hydrogen sensor,palladium membrane
更新于2025-09-23 15:22:29
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Highly Stable and Ultrafast Hydrogen Gas Sensor Based on 15 nm Nanogaps Switching in a Palladium-Gold Nanoribbons Array
摘要： Palladium (Pd) nanogap hydrogen gas (H2) sensors based on the large volume expansion of β phase palladium hydride (β-PdH) are highly promising, owing to their fast and accurate sensing capability at room temperature in air. However, such sensors do not work well at H2 concentrations below 1%. At such low H2 concentrations, Pd exists as α-PdH, which has a slow and insufficient volume expansion and cannot completely close nanogaps. Furthermore, the lattice strains induced from the phase transition (α-PdH → β-PdH) behavior degrade the stable and repeatable long-term sensing capability. Here, these issues are resolved by fabricating an array of periodically aligned alloyed palladium–gold nanoribbons (PdAu NRB) with uniform 15 nm nanogaps. The PdAu NRB sensor enables highly stable and ultrafast H2 sensing at the full detection range of H2 concentrations from 0.005% to 10% along with the excellent limit of detection (≈0.0027%), which is sufficiently maintained even after seven months of storage in ambient atmosphere. These breakthrough results will pave the way for developing a practical high-performance H2 sensor chip in the future hydrogen era.
关键词： palladium nanogap,nanoribbon,hydrogen gas sensors,polystyrene thermal shrinkage
更新于2025-09-23 15:22:29
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Non-Evaporable Getter (NEG) Coating Using Titanium and Palladium Vacuum Sublimation
摘要： We have developed a new non-evaporable getter (NEG) coating using titanium and palladium vacuum sublimation. The inner wall of the test chamber was coated with a 1-μm Ti thin film using the Ti sublimation pumps under a vacuum of 6.5×10?? Pa (Ti-coated chamber). This chamber was then coated with a 10-nm Pd thin film using the Pd sublimation filament under a vacuum of 2.4×10?? Pa (Pd/Ti-coated chamber). The uncoated, Ti-coated, and Pd/Ti-coated chambers were baked for 6 h at a maximum temperature of 185°C. Five hours after closing the valve, the pressures in the Pd/Ti-coated chamber were about 1.4×10?? Pa even after six heating–venting cycles. The relatively low activation temperature was attributed to the low concentration of oxygen in the Pd/Ti thin films. The Pd/Ti coating can be used for vacuum systems that are frequently vented.
关键词： non-evaporable getter,titanium,thin film,palladium,vacuum
更新于2025-09-23 15:22:29
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Response Time of a Fiber Bragg Grating Based Hydrogen Sensor for Transformer Monitoring
摘要： We developed and optimized a new fiber optic sensor using palladium foils attached to optical fiber Bragg gratings (FBG) for hydrogen measurements. Fifteen in parallel processed sensors were characterized and qualified in two custom tailored experimental set ups and their response to a 5% hydrogen/nitrogen gas mixture and the same gas bubbled trough transformer oil was measured. The hydrogen response is similar for both medium and close to the theoretical maximum sensitivity, but the response time was found to be very different, much slower in oil than in gas. A theoretical comparison of hydrogen diffusion trough palladium and hydrogen absorption on the palladium surface as well as a measurement of the hydrogen uptake and diffusion trough the oil to the sensor have been done to investigate the origin of the different response time. They indicate that the response time determining step is the absorption of hydrogen on the palladium surface and that this process is slowed down in oil compared to a pure gas environment.
关键词： hydrogen sensor,fibre Bragg grating (FBG),fiber sensor,palladium based sensors,hydrogen diffusion and absorption in oil
更新于2025-09-23 15:22:29
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Rationally Designed Multifunctional Carbon-Palladium Nanohybrids for Wide Applications: From Electrochemical Catalysis/Nonenzymatic Sensor to Photothermal Tumor Therapy
摘要： Palladium nanomaterials have been widely investigated in many areas due to their high activity of catalysis and surface plasmon resonance (SPR) resulting from their special configuration of outer electron. Herein, the novel nanoparticles, reduced graphene oxide modified with palladium nanoflowers (rGO/PdNFs), were designed and synthesized by seeded growth. Their application potentials in three areas were explored, including electrochemical ethanol catalysis, nonenzymatic glucose sensor and photothermal tumor therapy. The hybrids of PdNFs and rGO increased the conductivity and active sites of PdNFs, and then enhanced the activity of catalysis. Interestingly, through control of morphologies, the absorption of PdNFs in near infrared region was enhanced compared with common palladium nanoparticles, which showed excellent potential in photothermal tumor therapy. These results indicated the stronger activity of catalysis to ethanol of rGO/PdNFs compared with the commercial Pd/C catalyst, superior sensitivity and selectivity of glucose, and effective photothermal antitumor efficacy. Overall, it is demonstrated that the multifunctional rGO/PdNFs nanohybrids could possess more application potentials.
关键词： Nonenzymatic sensor,Photothermal tumor therapy,Reduced graphene oxide,Palladium nanoflowers,Electrochemical catalysis
更新于2025-09-23 15:22:29
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High sensitivity fiber optic sensor for hydrogen detection in gas and transformer oil
摘要： This paper reports on the characterisation of a palladium (Pd) based fiber optic hydrogen (H2) sensor for health monitoring of distribution and power transformers in the electrical grid. The sensor consists of a Pd foil, which expands due to H2 absorption, and a fiber Bragg grating (FBG) that measures this expansion. Fifteen sensors were manufactured and characterised in gas and oil environments at various H2 concentrations and temperatures. In gas, the sensors were evaluated at 60°C, 75°C, 90°C, 105°C and 120°C and H2 concentrations from 0.01 to 5%. In oil, the same sensors were evaluated at 90°C and dissolved H2 concentrations from 5 to 2700 ppm. Furthermore, the influence of carbon monoxide (CO), which is often present in transformers and can impact H2 response of the sensor, was investigated. At 90°C in gas, the response to 0.01%, and 5% H2 was on average 28 pm, and 719 pm respectively. At 90°C in oil, the response to 5 ppm, and 2700 ppm dissolved H2 was on average 11 pm, and 763 pm respectively. The average, relative accuracy is better than 20% over the whole measurement range in gas and for measurements above 100 ppm in oil. These specifications make the sensor a promising candidate for online monitoring of H2 in transformers.
关键词： transformer monitoring,Hydrogen,fiber Bragg grating,palladium,gas detection
更新于2025-09-23 15:22:29