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Joint improvement of the Seebeck coefficient S and conductivity σ is a pressing issue to overcome the limit of the figure of merit ( ZT ) enhancement of thermoelectric materials. This study presents a joint improvement in the ZnO:Al films by tuning the diffusion of Au layer via substrate temperature, using a radio frequency-assisted molecular beam vapor deposition method. The phenomenon occurs in the ZnO:Al films at the room temperature (RT) substrate deposited on a 10 nm Au layer (RT-ZnO:AuAl). The films have a hexagonal wurtzite structure with an in-plane (002) preferred orientation and smooth surface. The resistivity values of the films are at the same magnitude of the transparent conducting oxide (~10 −6  Ω·m). The carrier concentration reaches 2.60 × 10 21  cm −3 for the RT-ZnO:AuAl film. The S is about 29.5 μV/K at 240 °C. Joint improvement of conductivity and Seebeck coefficient makes the PF of the RT-ZnO:AuAl film reaches 3.58 × 10 −5  Wm −1  K −2 , which is two orders of magnitude larger than that of the RT-ZnO:Au film without joint improvement. The results indicate that the higher conductivity originates from the Au layer, in-plane (002) preferred orientation, and the easily excited carriers in the ZnO:Al due to the low binding energy of the Zn 2p electrons. The large S in the film is related to the high effective masses due to the impact of the diffusion of the Au layer on electronic interactions. [ABSTRACT FROM AUTHOR]

Herein we report a novel polydopamine-silver nanoparticle-polydopamine-gold (PDA-AgNPs-PDA-Au) film based surface plasmon resonance (SPR) biosensor for horse IgG detection. The PDA-AgNPs-PDA-Au film sensing platform was built on Au-film via layer-by-layer self-assembly. Ag ion was reduced in situ to AgNPs in presence of PDA. The top PDA layer can prevent AgNPs from being oxidized and connect with antibody via Schiff alkali reaction directly. The morphology and thickness of the modified gold film were characterized using scanning electron microscope and Talystep. Experimental results show that the PDA-AgNPs-PDA-Au film sensing platform is stable, regenerative and sensitive for horse IgG detection. The detection limit of horse IgG obtained with the present biosensor is 0.625 μg mL − 1 , which is 2-fold and 4-fold lower than that obtained with biosensor based on PDA modified Au film and conventional biosensor based on MPA, respectively. Furthermore, when challenged to real serum samples, our sensor exhibited excellent specificity to horse IgG, suggesting its potential for industrial application. [ABSTRACT FROM AUTHOR]

Light transmission at the Au/air interface was measured for wedge-shaped Au film samples. Light refraction continuously changing its sign from positive to negative at the Au/air interface in the spectrum range of 470–700 nm was observed with a zero refraction occurred at about 525 nm. The results indicate that the effective refraction index n e of samples are not correlated with wedge angles, implying that n e can be considered an intrinsic characteristic of the metal material. The positive and negative refractions observed in the experiment can be attributed to the dispersive feature of the dielectric function of Au with qualitative explanation according to the mechanisms of electron transition and the boundary conditions restricted at the interface. [ABSTRACT FROM AUTHOR]

Nanoscale heat conduction with ultra-low thermal conductivity across metal-nonmetal Si/Au multilayer films has been investigated. Si/Au multilayer films with different Au thickness were prepared by magetron sputtering, of which the multilayer structures were confirmed by grazing incidence small angle X-ray scattering (GISAXS) and field emission scanning electron microscopy (FESEM). Moreover, the cross-plane thermal conductivities of the films deposition were investigated by a differential 3ω method at room temperature. It is possible that we can control thermal transport across multilayer films by constructing ultrathin Au layers. The reduced thermal conductivity (∼0.6 Wm −1 K −1 ) of multilayer films with Au thickness of 1 nm is ∼50% of that with Au thickness above 8 nm and 42% of amorphous Si film (1.44 Wm −1 K −1 ). The result is attributed to the low contribution of phonons to the overall thermal conductivity in ultrathin Au layer (below 8 nm), leading to a relatively high film thermal resistances compare to thicker Au layer due to strong electron-phonon coupling at metal-nonmetal interfaces. Meanwhile, experimental results show excellent agreement with two temperature model over 8 nm but not below 8 nm. It can be found that conventional thermal conducitvity models fail to explain the observed thermal conducitvity tendency as a function of intercalating metal layer thickness. Accordingly, a revised two temperature model (TTM) has been proposed, which shows well agreement with experimental results. The results provide us with more insight about the thermal transport mechanism of the heterogeneous multilayer system, and would give more instruction for next-generation thermoelectric material development. [ABSTRACT FROM AUTHOR]

The formation of gold microparticles on a silicon substrate through the use of energetic surface plasmons is reported. A laser-assisted plasmonics system was assembled and tested to synthesize gold particles from gold thin film by electrical field enhancement mechanism. A mask containing an array of 200 nm diameter holes with a periodicity of 400 nm was prepared and placed on a silicon substrate. The mask was composed of 60 ìm thick porous alumina membrane sputter-coated with 100 nm thin gold film. A Nd:YAG laser with 1064 nm wavelength and 230 ìs pulse width (free-running mode) was then passed through the mask at an energy fluence of 0.35 J/cm². The extraordinary transmission of laser light through alumina/gold micro-hole optical antenna created both extended and localized surface plasmons that caused the gold film at the bottom of the mask to fragment into microparticles and deposit on the silicon substrate that is in direct contact with the mask. The surface plasmon method is simpler, quicker, more energy efficient, and environmentally safer than existing physical and chemical methods, as well as being contamination-free, and can be extended to all types of materials that will in turn allow for new possibilities in the formation of structured surfaces. [ABSTRACT FROM AUTHOR]

We study semi-regular arrays of Au nanoparticles (NP) obtained via UV laser irradiation of thin Au films on glass substrate. The NP structures are prepared from films of a thickness up to 60 nm produced by discharge sputtering or pulsed laser deposition, and annealed by nanosecond laser pulses at 266 or 308 nm, respectively, at fluencies in the range of 60-410 mJ/cm. For the rare- and close-packed NP structures, consistent description of optical properties is derived from microscopic observation, measurements of the absorption, and Raman spectra, and modeling of the near-field intensity distributions. The absorption bands centered at 540-570 nm are ascribed to resonant absorption of the surface plasmons. For the band positions, half widths, and intensities, the dependence on the NP shape (partial spheres), size, size distribution, and also excitation energy is observed. The structures are characterized by markedly reduced dephasing times of ∼3 fs. It is shown, that laser annealing of thin Au films provides reliable and cost effective method for controlled preparation of semi-regular NP arrays favorable for photonic applications. [ABSTRACT FROM AUTHOR]

We demonstrate the utility of gold nanoparticles (AuNPs) as the basis of a stand-alone, inexpensive, and sensitive mercury monitor. Gold nanoparticles absorb visible light due to localized surface plasmon resonance (LSPR), and the absorbance changes when mercury combines with the gold nanoparticles. The sensitivity of the peak absorbance is proportional to the surface-area-to-volume ratio. We chose 5 nm spheres because they have the largest surface-area-to-volume ratio while still having a peak absorption in the visible range. The adsorption of 15 atoms of Hg causes a 1 nm shift in the LSPR wavelength of these particles. Assembled into a film using the Langmuir-Blodgett method, the AuNP LSPR can be tracked with a simple UV-vis spectrometer. The rate of shift in the peak absorbance is linear with mercury concentrations from 1 to 825 μgHg/mair3. Increasing the flow velocity (and mass transfer rate) increases the peak shift rate making this system a viable method for direct ambient mercury vapor measurements. Regeneration of the sensing films, done by heating to 160 °C, allows for repeatable measurements on the same film. [ABSTRACT FROM AUTHOR]

It is demonstrated that 1,4-phenylene diisocyanide (PDI)–gold oligomers can spontaneously bridge between gold nanoparticles on mica, thereby providing a strategy for electrically interconnecting nanoelectrodes. The barrier height of the bridging oligomer is 0.10 ± 0.02 eV, within the range of previous single-molecule measurements of PDI. [ABSTRACT FROM AUTHOR]

Iodide is an essential element for humans and animals and insufficient intake is still a major problem. Affordable and accurate methods are required to quantify iodide concentrations in biological and environmental fluids. A simple and low cost sensing device is presented which is based on iodide induced electrochemical etching of ultrathin gold films. The sensitivity of resistance measurements to film thickness changes is increased by using films with a thickness smaller than the electron mean free path. The underlying mechanism is demonstrated by simultaneous cyclic voltammetry experiments and resistance change measurements in a buffer solution. Iodide sensing is conducted in buffer solutions as well as in lake water with limits of detection in the range of 1 μM (127 μg L−1) and 2 μM (254 μg L−1), respectively. In addition, nanoholes embedded in the thin films are tested for suitability of optical iodide sensing based on localized surface plasmon resonance. [ABSTRACT FROM AUTHOR]