Nanoantenna-enhanced gas sensing in a single tailored nanofocus

Metallic nanostructures possess plasmonic resonances that spatially confine light on the nanometre scale. In the ultimate limit of a single nanostructure, the electromagnetic field can be strongly concentrated in a volume of only a few hundred nm(3) or less. This optical nanofocus is ideal for plasmonic sensing. Any object that is brought into this single spot will influence the optical nanostructure resonance with its dielectric properties. Here, we demonstrate antenna-enhanced hydrogen sensing at the single-particle level. We place a single palladium nanoparticle near the tip region of a gold nanoantenna and detect the changing optical properties of the system on hydrogen exposure by dark-field microscopy. Our method avoids any inhomogeneous broadening and statistical effects that would occur in sensors based on nanoparticle ensembles. Our concept paves the road towards the observation of single catalytic processes in nanoreactors and biosensing on the single-molecule level.     

支撑光学制造的几何量计量技术(英文)

几何量计量技术大量应用于光学制造业以检测零件质量和控制生产过程,是光学制造业的核心技术,涉及微纳米结构的几何量计量以及平面、球面、非球面、直纹曲面及自由曲面的面形计量.本文综述了德国联邦物理技术研究院支撑光学制造的部分计量技术.介绍了一种测量范围为25 mm×25 mm×5 mm的计量型大范围原子力显微镜(AFM),可灵活多样地测量各种微纳结构.介绍了一种新颖的AFM探针(ACP),可实现微纳结构侧壁形貌的直接、无损测量.介绍了一种应用Flared AFM探针的真三维AFM及其用于减少针尖磨损的矢量探测技术,可应用于各种纳米结构的真三维测量.介绍了可用于平面和中等曲面面形绝对测量的两种方法:差分型激光束偏转法和可溯源多路传感器法(TMS).讨论了面形测量中存在的挑战性难题.介绍了可用于面形测量的高精度三坐标测量机.     

The informative converse paradox: Windows into the unknown

Model-based interpretation of empirical data is useful. But unanticipated phenomena (interferences) can give erroneous model parameter estimates, leading to wrong interpretation. However, for multi-channel data, interference phenomena may be discovered, described and corrected for, by analysis of the lack-of-fit residual table — although with a strange limitation, which is here termed the Informative Converse paradox: When a data table (rows × columns) is approximated by a linear model, and the model-fitting is done by row-wise regression, it means that only the column-wise interference information can be correctly obtained, and vice versa. These “windows into the unknown” are here explained mathematically. They are then applied to multi-channel mixture data — artificial simulations as well as spectral NIR powder measurements — to demonstrate discovery after incomplete row-wise curve fitting and column-wise multivariate regression. The analysis shows how the Informative Converse paradox is the basis for selectivity enhancement in multivariate calibration. Data-driven model expansion for statistical multi-response analyses (ANOVA, N-way models etc.) is proposed.     

High pressure Raman scattering of silicon nanowires

We study the high pressure response, up to 8 GPa, of silicon nanowires (SiNWs) with ～ 15 nm diameter, by Raman spectroscopy. The first order Raman peak shows a superlinear trend, more pronounced compared to bulk Si. Combining transmission electron microscopy and Raman measurements we estimate the SiNWs' bulk modulus and the Grüneisen parameters. We detect an increase of Raman linewidth at ～ 4 GPa, and assign it to pressure induced activation of a decay process into LO and TA phonons. This pressure is smaller compared to the ～ 7 GPa reported for bulk Si. We do not observe evidence of phase transitions, such as discontinuities or change in the pressure slopes, in the investigated pressure range.     

Bragg Reflection Band Stop Filter for ECE on Wega

Notch filters are required to protect sensitive millimeter wave diagnostics in fusion experiments from gyrotron stray radiation in the plasma vessel. A new type of notch filter based on a waveguide Bragg reflector is presented that can provide one or more defined stop bands in one standard waveguide frequency band.     

Integrated all-diamond ultramicroelectrode arrays: optimization of faradaic and capacitive currents

Integrated all-diamond ultramicroelectrode arrays (UMEAs) were fabricated using standard photolithography processes. The array consisted of typically 45 ultramicroelectrodes with a diameter of 10 μm and with a center-to-center spacing of 60 μm. The quasi-reference and counter electrodes were made from conductive diamond and were integrated on a 5 × 5 mm(2) chip. On the UMEA, a high ratio of faradaic current to capacitive current was achieved on heavily boron-doped and hydrogen-terminated diamond surfaces at slow scan rates and in high concentration of supporting electrolyte. A sensitive and reproducible detection of dopamine was achieved on hydrogen-terminated diamond UMEA at slow scan rates. The detection limit of dopamine in the presence of ascorbic acid was 1.0 nM, which is 50-100 times lower than that obtained on the macrosized boron-doped diamond electrodes. This array is promising for sensitive and reproducible detection of analytes in solutions with low detection limits.     

ECRH for JET: A feasibility study

For JET to fulfil its mission in preparing ITER operation, the installation of an electron cyclotron resonance heating system on JET would be desirable. The study described in this paper has investigated the feasibility of installing such a system on JET. The principal goals of such a system are: current drive over a range of radii for NTM stabilization, sawtooth control and current profile tailoring and central electron heating to equilibrate electron and ion temperatures in high performance discharges. The study concluded that a 12 gyrotron, 10 MW, system at the ITER frequency (170 GHz) adapted for fields of 2.7–3.3 T would be appropriate for the operation planned in JET. An antenna allowing toroidal and poloidal steering over a wide range is being designed, using the ITER upper launcher steering mechanism. The use of ITER diamond windows and transmission line technology is suggested while power supply solutions partially reusing existing JET power supplies are proposed. Detailed planning shows that such a system can be operational in about 5 years from the time that the decision to proceed is taken. The cost and required manpower associated with implementing such a system on JET has also been estimated.     

Spectroscopic characterization of the uranium carbonate andersonite Na2Ca[UO2(CO3)3] x 6H2O

The uranium carbonate andersonite Na2Ca[UO2(CO3)3] x 6H2O was synthesized and identified with classical analytical and spectroscopic methods. The classical methods applied were powder X-ray diffraction (XRD), nitric acid digestion, and scanning electron microcopy combined with energy-dispersive spectroscopy (SEM/EDS). To characterize andersonite spectroscopically, time-resolved laser-induced fluorescence spectroscopy (TRLFS), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FT-IR) were used. Natural and synthetic andersonite samples were characterized with the nondestructive TRLFS by six fluorescence emission bands at 470.6, 486.1, 505.4, 526.7, 549.6, and 573.9 nm. In addition, andersonite was characterized by FT-IR measurements by the appearance of the asymmetric stretching vibration of the uranyl cation [v3(UO2(2+))] at 902 cm(-1) with a shoulder at 913 cm(-1). XPS measurements verified the composition of the synthetic andersonite sample. The measured intensity ratios of the XPS lines agree with the stoichiometry of Na2Ca[UO2(CO3)3] x 6H2O. The XPS features of the inner valence molecular orbitals are characteristic of the [UO2(CO3)3]4- structural moiety. These spectroscopic methods can be used to identify in a fingerprinting procedure secondary U(VI) phases in mixtures with other phases or as thin coatings on mineral and rock surfaces.     

Influence of selected factors on browning of Camembert cheese

Experimental Camembert cheeses were made to investigate the effects on browning of the following factors: inoculation with Yarrowia lipolytica, the use of Penicillium candidum strains with different proteolytic activity, the addition of tyrosine, and the addition of Mn2+ thus leading to 16 different variants of cheese. Two physical colour parameters were used to describe browning, depending on the location in the cheeses: a whiteness index for the outside browning (mould mycelium), and a brownness index for the inside browning (surface of the cheese body). Mn2+ promoted a significant increase of browning at both locations, whereas Yar. lipolytica had the opposite effect. Outside browning was significantly more intense when using the Pen. candidum strain with higher proteolytic activity. A significant interaction was found between Yar. lipolytica and Pen. candidum. The yeast had no effect in combination with a low proteolytic strain of Pen. candidum, but significantly reduced proteolysis and browning in combination with a high proteolytic strain of Pen. candidum. We further confirmed that both strains of Pen. candidum were able to produce brown pigments from tyrosine and thus both are presumably responsible for the browning activity in this type of cheese.