Gold Strip Research Articles

A simple and rapid immunochromatographic strip test for monitoring antibodies to H5 subtype Avian Influenza Virus

A colloid gold strip (CGS) test for detecting antibodies to H5 subtype Avian Influenza Virus (AIV) was developed. The test is based on membrane chromatography and uses colloidal gold conjugated with inactivated AIV-H5N1 as the tracer. On the test strip, a baculovirus expressed haemagglutinin (HA) protein was used as the capture complex at the “test line”, and anti-HA monoclonal antibody was used as the capture antibody at the “control line”. The assembled test strip was housed in a plastic case. Compared with the hemagglutination inhibition test, the sensitivity and specificity of the CGS test were 88.8% and 97.6%, respectively, in detecting H5N1 antibodies in 830 serum samples from vaccinated chickens. Because it is rapid and does not require specialized equipment or technicians, the CGS test should be useful for detecting H5N1 antibodies in the field.

The establishment of immunochromatographic tests trips with colloidal gold for early and rapid diagnostic of hemorrhagic fever with renal syndrome

Objective To establish an early,simple and rapid colloidal gold strip method for the detection of IgM against hantavirus nucleocapsid protein in patients with hemorrhagic fever with renal syndrome(HFRS).Methods Purified recombinant Hantavirus nucleoprotein(rNP)was labeled by colloidal gold particles and then sprayed and fixed on fiberglass membrane as the combination pad.Anti-Human IgM(μ-chain specific)antibody produced in goat was fixed in the detection area,and mouse antihantavirus antibody was fixed in the quality control area.Both of them were on nitrocellous membrane strip in tandem.Together with a specimen pad ahead.The conbination pad and the nitrocellous membrane were assembled into a test strip.The colloidal gold strip assay was compared with ELISA for evaluation of specificity and sensitivity.Results The colloidal gold strip tests showed positive in the serum samples from 50 cases of HFRS which was clinically diagnosed and then verified by ELISA within 10-15 minutes.Whereas 30 serum samples of healthy donors have tested negative.Conclusions Our new colloidal gold immunochromatographic test strip method was well concordant with the ELISA assay,but the former was more raoid and simole.It could be used primary medical services. Key words: Hemorrhagic fever with renal syndrome; Gold colloid; Reagent strips; Immunoglobulin M; Nucleocapsid proteins

Green’s function surface integral equation method for theoretical analysis of scatterers close to a metal interface

A method for theoretical analysis of light scattering by arbitrary shaped two-dimensional scatterers placed near a planar surface between two media is presented. We show that light scattering by an object near a planar interface can be analyzed (exactly) using Green's function surface integral equations that are form invariant with those for a scatterer in free space. All effects of the planar interface structure are built into the Green's function. An approach for calculating the Green's function is presented along with far-field approximations that enable efficient evaluation of scattering into waves propagating out of the surface plane and, in the case of a planar metal-dielectric interface, evaluation of scattering into surface plasmon-polariton (SPP) waves propagating along the interface. Finally, the method is exemplified by analysis of light scattering by a nm-thin and sub-$\ensuremath{\mu}\text{m}$-wide gold strip (resonator) placed between 5 and 200 nm above a planar gold surface. We compare the amount of scattering going into the out-of-plane propagating waves and SPPs, respectively, and, for our configuration, scattering into out-of-plane propagating waves dominates. Scattering into SPP waves has a maximum if the strip is placed approximately 20 nm from the surface. We also find that when placing the gold strip more than 50 nm from the interface, the scattering resonance wavelength is practically independent of the distance, whereas changing the distance from 50 to 5 nm results in a $\ensuremath{\sim}400\text{ }\text{nm}$ redshift of the resonance wavelength.

Solvent extraction of gold(I) from alkaline cyanide solution by dibutylcarbitol (DBC) with n‐octanol

AbstractBACKGROUND: Currently, cyanidisation is preferred for the extraction of gold because it has a number of advantages over other methods. Gold(I) can be extracted with various extractants, but there are no reports on the extraction of gold(I) from cyanide solution by dibutylcarbitol (DBC). In this work the extraction of gold(I) from alkaline cyanide solution using DBC with n‐octanol was studied. Several factors affecting the percentage extraction of gold(I), including DBC concentration, diluent concentration, equilibrium time, phase ratio, pH and gold concentration in aqueous phase, were investigated.RESULTS: The results showed that 96.2% of gold(I) could be extracted using an organic phase composed of 40% (v/v) DBC, 50% (v/v) n‐octanol and 10% (v/v) odourless kerosene. The extraction was quite fast and equilibrium could be established within 2 min. Stripping of the gold‐laden organic phase was carried out using sodium sulfite (Na2SO3) and sodium thiosulfate (Na2S2O3) solutions, with Na2S2O3 proving better than Na2SO3. The percentage stripping of gold(I) was 96.5% when the Na2S2O3 concentration was 4% (w/w), and the stripping capacity of gold(I) exceeded 311.3 mg L−1 when the phase ratio (A/O) was equal to 0.2.CONCLUSION: Gold(I) can be extracted from aqueous cyanide solution by DBC in the presence of n‐octanol and efficiently stripped by aqueous Na2S2O3 solution. This method has the potential for practical application in the extraction and separation of gold. Copyright © 2008 Society of Chemical Industry

Electrochemical Studies of Rose Bengal Using the Electrochemical Quartz Crystal Microbalance

We present the results of an Electrochemical Quartz Crystal Microbalance study of the dark electrochemical behavior of rose bengal on gold piezoelectrodes in phosphate buffer at pH=7. Five oxidation and two reduction peaks were identified. The first oxidation process (Epox1=0.52V) is attributed to the formation of a Charge Transfer Complex (CTC) of rose bengal. The second process (Epox2=0.76V) is due to the partial breakdown of that CTC. The third process (Epox3=1.12V) is the electrochemical formation of a rose bengal polymer. Peak four (Epox4=1.24V) is due to the electrochemistry of the underlying gold surface, whilst peak five (Epox5=1.45V) is attributed to a process that facilitates trans-passive polymerization. The first reduction peak (Epred1=0.42V) is due to gold oxide stripping and the second (Epred2=0.36V) is the reduction of residual charge transfer complex formed in the first oxidation process.

이중-금속 장거리 표면-플라즈몬 도파로

금속선 도파로 면과 금속 평면이 수직으로 적층된 장거리 표면-플라즈몬 도파로 구조를 제안하였으며, 표면-플라즈몬 모드의 특성을 유전체의 굴절율과 두께 변화에 대하여 이론적으로 분석하고 실험적으로 검증하였다. 위층의 금속선 도파로를 S-곡선과 Y-분기 형태로 변형시킨 이중-금속 도파로를 제작하여, 제안된 이중-금속 도파로 구조의 광 소자 응용 가능성을 살펴보았다. 제안된 이중금속 구조에서는 도파로 코어에 해당하는 두 금속 박막 사이의 유전체 굴절률을 임의로 선택하여도 장거리 표면 플라즈몬 모드가 존재할 수 있으며, 표면-플라즈몬 모드의 전파거리는 두 금속 박막 사이의 유전체 두께를 조절함으로써 증가시킬 수 있다. 또한, 이중-금속 도파로는 표면-플라즈몬을 전달할 뿐만 아니라, 삽입된 코어 유전체에 전압 및 전류를 인가하기에도 매우 적합한 구조로서, 표면-플라즈몬 능동소자 및 비선형 소자 구현에 많은 가능성을 열어줄 것으로 기대된다. We propose a novel metal-waveguide structure for sustaining long-range surface-plasmon-polaritons (LRSPP). The LRSPP waveguides are composed basically of two asymmetric metal layers: a very thin, finite-width metal strip on top of a metal slab with a dielectric gap in between them. Mode cut-off of LRSPPs excited on the double-metal waveguides is characterized by consistently investigating their dispersion relations and mode profiles. We also confirm experimentally the existence of low-loss, well-confined LRSPP modes by measuring far-field outputs emerging from an edge of the asymmetric double-metal waveguides. In the experiment, we have fabricated several types of SPP waveguide devices including straight lines, S-bend, and Y-branch consisting of gold strips (20 nm-thick, <TEX>$5{\mu}m$</TEX>-wide). Overall propagation loss of the proposed double-metal waveguides is quite comparable to that of single metal-strip waveguides, in addition the mode sizes can be tuned by increasing the core-insulator gap between the metal layers to get a higher coupling efficiency with a single-mode fiber in telecom wavelength. The proposed LRSPP waveguides may open up realization of SPP-waveguide sensors or nonlinear SPP-devices by replacing the core-insulator with a bio-fluid or a nonlinear medium.

Enhanced adsorption energy of Au1 and O2 on the stoichiometric TiO2(110) surface by coadsorption with other molecules

During heterogeneous catalysis the surface is simultaneously covered by several adsorbed molecules. The manner in which the presence of one kind of molecule affects the adsorption of a molecule of another kind has been of interest for a long time. In most cases the presence of one adsorbate does not change substantially the binding energy of another adsorbate. The calculations presented here show that the stoichiometric rutile TiO(2)(110) surface, on which one of the compounds -OH, Au(3), Au(5), Au(7), Na, K, or Cs or two different gold strips was preadsorbed, behaves differently: the binding energy of Au(1) or O(2) to such a surface is much stronger than the binding to the clean stoichiometric TiO(2)(110) surface. Moreover, the binding energy of Au(1) or O(2) and the amount of charge they take from the surface when they adsorb are the same, regardless of which of the above species is preadsorbed. The preadsorbed species donate electrons to the conduction band of the oxide, and these electrons are used by Au(1) or O(2) to make stronger bonds with the surface. This suggests that adding an electron to the conduction band of the clean stoichiometric TiO(2)(110) slab used in the calculation will affect similarly the adsorption energy of Au(1) or O(2). Our calculations show that it does. We have also studied how the preadsorption of Au(4) or Au(6) affects the binding of Au(1) or O(2) to the surface. These two gold clusters do not donate electrons to the surface when they bind to it and therefore should not influence substantially the binding energy of Au(1) or O(2) to the surface. However, adsorbing O(2) or Au(1) on the surface forces the clusters to change their structure into that of isomers that donate charge to the oxide. This charge is used by Au(1) or O(2) to bind to the surface and the energy of this bond exceeds the isomerization energy. As a result the surface with the isomerized cluster is the lowest energy state of the system. We believe that these results can be generalized as follows. The molecules that we coadsorbed with Au(1) or O(2) donate electrons to the oxide and are Lewis bases. By giving the surface high energy electrons, they turn it into a Lewis base and this increases its ability to bind strong Lewis acids such as Au(1) and O(2). We speculate that this kind of interaction is general and may be observed for other oxides and for other coadsorbed Lewis base-Lewis acid pairs.

Modulation of hard x-ray beam profiles by Borrmann pyramid

Spatial modulation of hard x-ray beam profiles is reported, using the “Borrmann pyramid” formed in dual Bragg diffraction of a single crystal, where a small angular change of the incident beam is magnified to span the entire pyramid base. As an attempt, it is demonstrated using hard x rays by (1) the linear shift of a micrometer sized mask; (2) the partial blockade of a two micron beam; and (3) the millimeter shadow of a nanoscale gold strip, which shows the potential application of Borrmann pyramids in the form of an enlarged x-ray image.

Electrokinetically driven fluidic transport in integrated three-dimensional microfluidic devices incorporating gold-coated nanocapillary array membranes

Electrokinetically driven fluid transport was evaluated within three-dimensional hybrid nanofluidic-microfluidic devices incorporating Au-coated nanocapillary array membranes (NCAMs). Gold NCAMs, prepared by electroless gold deposition on polymeric track-etched membranes, were susceptible to gas bubble formation if the interfacial potential difference exceeded approximately 2 V along the length of the gold region. Gold membranes were etched to yield 250 microm wide coated regions that overlap the intersection of two orthogonal microfluidic channels in order to minimize gas evolution. The kinetics of electrolysis of water at the opposing ends of the gold region was modeled and found to be in satisfactory agreement with experimental measurements of the onset of gas bubble formation. Conditions to achieve electrokinetic injection across Au-coated NCAMs were identified, with significant reproducible injections being possible for NCAMs modified with this relatively thin gold stripe. Continuous gold films led to suppressed injections and to a variety of ion enrichment/depletion effects in the microfluidic source channel. The suppression of injections was understood through finite element modeling which revealed the presence of a significant electrophoretic velocity component in opposition to electroosmotic flow at the edge of the Au-dielectric regions.

Characterization of long-range surface plasmon-polariton in stripe waveguides using scanning near-field optical microscopy

Propagation characteristics of long-range surface plasmon-polariton (LRSPP) guiding along thin gold stripes embedded in polymer cover layers are investigated by scanning near-field optical microscopy (SNOM). It is shown that the characterization of samples with cover layers up to 10 μm is feasible in the optical communication wavelength range. We found that the spatial dimension of the optical signal is directly related to the geometrical dimension of the guiding layer, and the light collected by the SNOM is scattered light from the surface and not the evanescent field. We also discuss the limitations of the SNOM technique for the characterization of LRSPP modes.

Quantification of Ready-Made Molecular Bilayer Junctions Having Large Structural Uncertainty

A ready-made procedure for the preparation of molecular junctions at ambient conditions is reported. Junctions were constructed from bilayers of alkyl thiols at the interfaces between gold flakes and stationary gold strips. Addition of an amine or carboxylic acid end group to the alkyl thiols drastically increased the resistance (up to TΩ over a couple of nanometers only) and the breakdown voltage of the bilayer junction. These junctions pose a severe quantification challenge because of the large uncertainty regarding their microscopic morphology. A novel quantification procedure is proposed that replaces highly nonlinear tunneling or super-exchange current voltage relations by an effective analytical relation of two characteristic parameters: equilibrium conductance and shape factor. Correlating these factors over a series of systematically varying junctions allows us to evaluate the effective contact area for transfer. This approach was also extended to the field-emission regime. Within the large sprea...

10 Gbps Optical Signal Transmission via Long-Range Surface Plasmon Polariton Waveguide

We demonstrate 10 Gbps optical signal transmission via long-range surface plasmon polaritons (LR-SPPs) in a very thin metal strip-guided geometry. The LR-SPP waveguide was fabricated as a 14 nm thick, 2.5 μm wide, and 4 cm long gold strip embedded in a polymer and pigtailed with single-mode fibers. The total insertion loss of 16 dB was achieved at a wavelength of 1.55 μm as a carrier wave. In a 10 Gbps optical signal transmission experiment, the LR-SPP waveguide exhibits an excellent eye opening and a 2.2 dB power penalty at 10−12 bit error rate. We confirm, for the first time, that LR-SPPs can efficiently transfer data signals as well as the carrier light.

Long range surface plasmon polariton waveguides at 1.31 and 1.55 μm wavelengths

We investigate characteristics of gold metal strip waveguides based on long range surface plasmon polaritons (LRSPPs) along thin metal strips embedded in a polymer for practical applications at the telecommunication wavelengths of 1.31 and 1.55μm. Guiding properties of the gold strip waveguides are theoretically and experimentally evaluated with the limited thickness and width up to ∼20nm and ∼10μm, respectively. The lowest propagation loss of ∼1.4dB/cm is obtained with a 14.5-nm-thick and 2-μm-wide gold strip at 1.55μm. With a single-mode fiber, the lowest coupling loss of ∼0.4dB/facet is achieved with a 14.5-nm-thick and 5-μm-wide gold strip at 1.55μm. The lowest insertion losses are obtained 8–9dB with 1.5cm-long gold strips of a limited thickness and width at both the wavelengths. We demonstrate a 10Gbps optical signal transmission via the LRSPP waveguide with a 14nm-thick, 2.5μm-wide, and 4cm-long gold strip. These LRSPP waveguides have potential applications for optical interconnects and communications.

Commissioning of the MAGNEX large-acceptance spectrometer

The MAGNEX large-acceptance spectrometer has been commissioned with beams from the Tandem accelerator at INFN-LNS Catania. The optics were tested with elastically-scattered 7Li, 16O and 48Ti beams with various apertures mounted after the target. The momentum dispersion was verified to be in agreement with the optics calculations. A demonstration of the particle identification capabilities of the PSD start detector and the focal plane detector was given by a measurement of the 27Al(7Li,6Li)28Al transfer reaction at a mean angle of 25°. The measured charge state distribution of 48Ti ions is in agreement with predictions for a gold stripping foil. Preliminary results of the software reconstruction of incident angle and excitation energy, obtained through matrices based on a 3D-interpolation of the measured field maps, are encouraging.

Continuous Laboratory Gold Solvent Extraction from Cyanide Solutions using LIX 79 Reagent

AbstractContinuous laboratory solvent extraction of gold from cyanide solutions has been investigated by using LIX 79 guanidine‐based extractant. Different variables that affected the extraction included aqueous pH, extractant concentration and modifier concentration. Extraction isotherms of the aurocyanide complex with respect to the other cyanoanions were compared, and the following order of selectivity was observed: Au &gt; Ag &gt; Cu &gt; Zn &gt; Fe. According to the pH isotherms, aurocyanide can be extracted in alkaline media, and a better separation with respect to other cyano anions was obtained in the pH range 10.5–11.2. From the McCabe‐Thiele diagrams, better recovery was observed when using LIX 79 and tridecanol at 10 vol.‐%. Stripping gold from the loaded organic was carried out at pH &gt; 12 by using NaOH and NaCN solutions. The pilot plant tests indicate that a two‐stage extraction followed by one strip step are more than adequate to obtain an overall process efficiency of 92 %. However, for those cases where copper is present significantly, a copper wash stage is recommended before gold stripping. In this case, stripping of copper is accomplished at a pH 10.8, whereas the gold stripping was done at a pH of 12.0.

40 Gbit ∕ s light signal transmission in long-range surface plasmon waveguides

We demonstrate a high bit-rate optical signal transmission by using long-range surface plasmon polariton (LRSPP) waves in a guided geometry. With a 40Gbit∕s optical communication signal, eye patterns and bit-error-rates were measured to access the quality of the transmission properties of the LRSPP mode. A thin gold strip line embedded in a low loss optical polymer supports a LRSPP mode, which propagates with a 2dB∕cm loss, and couples to standard single mode fibers at 1.55μm with a 2dB coupling loss. A 40Gbit∕s optical signal was transmitted via a 4cm long LRSPP waveguide without any distortion of the eye patterns. The experiment also showed error-free transmissions. These results indicate that the LRSPP waveguide is a potential transmission line for optical interconnections overcoming the inherent problems in electric interconnections.

Growth of a single layer gold stripe and investigation of the preferable growth direction on reconstructed Au(111) surface using STM

Abstract We have investigated the growth of nanometer-scale gold stripes on reconstructed Au(1 1 1) surface using scanning tunneling microscopy (STM). The experiment was carried out under the conditions of ultrahigh vacuum and room temperature. The stripes were grown by the scanning motion of the STM tip over the area containing more than one step edge with the tunnel resistance less than several tens of mega ohms (MΩs). Unlike the previous reports [J.C. Heyraud, J.J. Metoris, Surf. Sci. 100 (1989) 519; V.M. Hallmark, S. Chiang, J.F. Rabolt, J.D. Swalen, R.J. Wilson, Phys. Rev. Lett. 59 (1987) 2879], we found, by directly comparing the direction of the stripes and the orientation of the underlying lattice, that the gold stripes grow preferentially along [1,−1,0] direction and its threefold symmetric directions at (1 1 1) surface of fcc structure. We also found that the scanning direction of the STM tip does not affect the direction of the stripe growth although the growth rate is suppressed remarkably when the scanning direction is close to [1,1,−2] direction of Au(1 1 1) surface.

Micro- and nanometer-scale patterned surface in a microchannel for cell culture in microfluidic devices

A novel microdevice which had a micro- and nanometer-scale patterned surface for cell adhesion in a microchip was developed. The surface had a metal pattern fabricated by electron-beam lithography and metal sputtering and a chemical pattern consisting of a self-assembled monolayer of alkanethiol. The metal patterned surface had a gold stripe pattern which was as small as 300 nm wide and 150 nm high and both topography and chemical properties could be controlled. Mouse fibroblast NIH/3T3 cells were cultured on the patterned surface and elongated along the gold stripes. These cells recognized the size of the pattern and the chemical properties on the pattern though it was much smaller than they were. There was satisfactory cell growth under fresh medium flow in the microchip. The combination of the patterned surface and the microchip provides cells with a novel environment for their growth and will facilitate many cellular experiments.

Fabrication of long-range surface plasmon-polariton waveguides in lithium niobate on silicon

This article describes the fabrication of long-range surface plasmon-polariton waveguides comprised of a thin narrow gold stripe buried in lithium niobate claddings. The waveguides are fabricated via direct bonding and thinning of lithium niobate wafers, resulting in bulk quality claddings. The assembly is direct bonded onto a silicon support wafer. Processing details are given along with results of physical characterization conducted on structures that underwent intermediate process steps and on completed structures.

Surface plasmon polariton waveguiding: From multimode stripe to a slot geometry

Surface plasmon polariton (SPP) photonic waveguiding along laterally wide and 20nm thick gold stripes, at λ=1.55μm, exhibited multimodal behavior with some localizations of the field near the stripe’s edges. This was leveraged in a configuration comprised of two adjacent edges, creating slot waveguide geometry. The measured slot mode was predominantly a TM mode—which corresponds to the coupled fields of the two edges as was also confirmed by numerical simulation.