Gold Strip Research Articles

Designing Highly Sensitive Surface Plasmon Resonance Sensor With Dual Analyte Channels

The ease of controlling waveguide properties through unparalleled design flexibility has made the photonic crystal fiber (PCF) an attractive platform for plasmonic structures. In this work, a dual analyte channel’s highly sensitive PCF bio-sensor is proposed based on surface plasmon resonance (SPR). In the proposed design, surface plasmons (SPs) are excited in the inner flat portion of two rectangular analyte channels where gold (Au) strip is deposited. Thus, the surface roughness that might be generated during metal deposition on circular surface could be effectively reduced. Considering the refractive index (RI) change in the analyte channels, the proposed sensor is designed and fully characterized by the finite element method based COMSOL Multiphysics software. Improved sensing characteristics including wavelength sensitivity (WS) of 186,000 nm/RIU and amplitude sensitivity (AS) of 2,792.97 RIU−1 in the wide RI range of 1.30 to 1.43 is obtained. In addition, the proposed sensor exhibits excellent resolution of $5.38\times {10}^{-7}$ , signal to noise ration (SNR) of 13.44 dB, figure of merits (FOM) of 2188.23, detection limit (DL) of 101.05 nm, and detection accuracy (DA) of 0.0204 nm−1. Outcomes of the analysis indicate that the proposed sensor could be suited for accurate detection of organic chemicals, bio-molecules, and biological analytes.

Направленные поверхностные акустические волны в нецентросимметричных решетках

Spatial distribution of surface Rayleigh acoustic wave propagating along the surface of GaAs semiconductor covered by a periodic grating of gold stripes is calculated. We demonstrated that when the lattice has no center of spatial inversion the distribution of deformation for the surface wave with the Bloch wave vector kx = 0 is asymmetric and characterized by nonzero mean momentum in the interface plane and nonzero degree of transverse polarization in the plane perpendicular to the surface. The work has been supported by the Russian Science Foundation Grant No. 20-12-00194.

The Effect of Gold Nanoparticles Combined with High-Quality Nursing in Patients with Myocardial Infarction

This study was established to study the effect of gold nanoparticles combined with high-quality nursing in patients with acute myocardial infarction (AMI). Under the condition of reflux, a nano gold strip was prepared. One hundred patients with AMI who were treated from April to September 2018 at our Hospital were selected for analysis, divided equally between the observation group and the control group. The associated responses of inflammation factors related to myocardial infarction were determined by molecular analysis. The levels of factors in patients with AMI were significantly higher than those in healthy subjects (P < 0.05). These findings suggest that a nano gold strip can be used for diagnosing early myocardial infarction.

Supramolecular Gold Stripping from Activated Carbon Using α-Cyclodextrin.

We report the molecular recognition of the Au(CN)2- anion, a crucial intermediate in today's gold mining industry, by α-cyclodextrin. Three X-ray single-crystal superstructures-KAu(CN)2⊂α-cyclodextrin, KAu(CN)2⊂(α-cyclodextrin)2, and KAg(CN)2⊂(α-cyclodextrin)2-demonstrate that the binding cavity of α-cyclodextrin is a good fit for metal-coordination complexes, such as Au(CN)2- and Ag(CN)2- with linear geometries, while the K+ ions fulfill the role of linking α-cyclodextrin tori together as a result of [K+···O] ion-dipole interactions. A 1:1 binding stoichiometry between Au(CN)2- and α-cyclodextrin in aqueous solution, revealed by 1H NMR titrations, has produced binding constants in the order of 104 M-1. Isothermal calorimetry titrations indicate that this molecular recognition is driven by a favorable enthalpy change overcoming a small entropic penalty. The adduct formation of KAu(CN)2⊂α-cyclodextrin in aqueous solution is sustained by multiple [C-H···π] and [C-H···anion] interactions in addition to hydrophobic effects. The molecular recognition has also been investigated by DFT calculations, which suggest that the 2:1 binding stoichiometry between α-cyclodextrin and Au(CN)2- is favored in the presence of ethanol. We have demonstrated that this molecular recognition process between α-cyclodextrin and KAu(CN)2 can be applied to the stripping of gold from the surface of activated carbon at room temperature. Moreover, this stripping process is selective for Au(CN)2- in the presence of Ag(CN)2-, which has a lower binding affinity toward α-cyclodextrin. This molecular recognition process could, in principle, be integrated into commercial gold-mining protocols and lead to significantly reduced costs, energy consumption, and environmental impact.

Synthesis of polyurethane-imids and application in surface plasmon polaritons waveguide

The crosslinkable electro-optic (EO) polymers polyurethane-imides (PUI) were designed and synthesized with monomers azo chromophore, phenyl diisocyanate and aromatic dianhydrides. Molecular structure characteristics for the polymers were evidenced by nuclear magnetic resonance (1HNMR) and fourier transform infrared (FTIR) spectroscopy. PUI as cladding, the strip long-range surface plasmon polaritons (LRSPPs) waveguides were designed and fabricated. The LRSPPs waveguiding along 18-nm-thin and 8-µm-wide gold stripes buried in EO PUI polymers were characterized at the light wavelength of 1310 nm and 1550 nm. The results indicated that the PUI can be used as preparation surface plasmon polaritons EO polymer optical waveguide materials, due to the merits of crosslinkable property, thermal stability, good film-forming ability, high processability and low optical waveguide propagation loss in near-infrared wave band.

Design and establish a rapid diagnostic kit for Viral Nervous Necrosis (VNN) disease using immunochromatography method

Background: Our investigation has approved that Viral Nervous Necrosis was the main causative agent for the outbreak in Mullet fish in the Caspian Sea. The disease was first reported in wild golden grey mullet (Liza auratus) in 2004. Since betanodaviruses are completely resistant to environmental conditions, it is possible to move easily via commercial activities. Also, the virus can introduce horizontally through contaminated water. So, the rapid diagnosis could be very useful in control, prevention and eradication programs. Also, in Monitoring & Surveillance, fast detection of the unknown outbreak could be vital and decrease their economic impacts. Methods and materials: For the preparation of antibody-gold particle conjugates, the concentration of Abs and pH of colloidal gold should be adjusted. A different volume of 1% sodium citrate was added to obtain the desired gold nanoparticles size in 30 nm. It was conjugated with an appropriate concentration Ab and in specific pH, and then this conjugation was blocked with serum albumin bovine. Afterwards, both various volumes of antibody-gold particle conjugates were coated on the conjugate pad and different concentration of pAb are used in a test line. To assure that the test strip will work correctly, the flow must also reach the control line, which has goat anti-mouse IgG (5 mg/ml) embedded in it. Both test and control lines were spotted on the membrane by using Helena applicator. Finally, the components of the strip were assembled and then the brain specimens of suspicious grey mullets and different dilution of the virus were evaluated. Results: With using of 1 μg/μl of pAbs on the test line and 4 μl per strip of gold- antibody conjugates on the conjugate pad, the designed strip was able to detect 103 TCID50/ml concentration of VNN. Then 50 brain samples that produced positive test results by PCR. The supernatant solution from brain homogenate of VNN-infected Liza aurata was confirmed negative for VNN by subsequent PCR an IHC testing, were evaluated using immunochromatography strip. It was recognized that the sensitivity and specificity of this kit are 64 and 100%, respectively. Conclusion: The accuracy of the immunochromatography kit was identical to both real-time PCR and IHC.

Захоронения эпохи раннего железного века курганного могильника «Богомольные пески-I»

The article is dedicated to the publication of the materials of burials from the Early Iron Age, discovered during excavations of a crumbling kurgan which is a part of the cemetery “Bogomolnye Peski-I” close to the village of Nikolskoye, Enotaevsky district, Astrakhan region. In total, 14 burials were investigated during the rescue excavations, two of them relate to the Middle Ages, other seven belong to the Bronze Age. The article describes in detail 5 burials of the Early Iron Age. The dating of the burials is defined based on the materials and details of the burial rite. The earliest burial (No. 2) dates back to the Savromat era. It contained a decapitated rams carcase and a molded pot which is typical of assumed era. The rest of the burials belong to the Middle Sarmatian period (1st – 2nd centuries AD). One of the Middle Sarmatian burials was completely destroyed by robbers in ancient times. It was possible to find a lot of gold stripes of clothes among its containment, as well as a bronze cauldron with a tamga. Plaques and stripes are not typical of either the Savromat or the early Sarmatian cultures. Indeed, they are widely used in prestigious burials of the Middle Sarmatian culture. The burials No. 5 and No. 13, accompanied by a rich inventory, are of the greatest interest. A set of gold decorations for a funeral veil and a belt set of gold with turquoise inserts were found in burial No.5, which belong to the products of the Sarmatian polychrome style, typical of the Middle Sarmatian period. In addition, a gilded bronze dish related to Roman provincial dishes and an alabaster vessel were discovered there – a typical find of the Middle Sarmatian era. In burial No. 12, the most interesting findings, in addition to a large number of various beads, are intaglio gemstones made of red glass with plots of ancient mythology depicted on them, which are unique in their own way. Moreover, an interesting vessel shaped as a bird (duck) was found there as well. The close analogs to the latter are known in cemeteries of the 1st – 2nd centuries AD in the Kuban region. A feature of this kurgan is a large number of inlet burials of the Middle Sarmatian culture, whereas in general, the burials under individual mounds predominate in the Middle Sarmatian epoch. Key words: early Iron Age, barrow, Lower Volga region, Sarmatians, burial rite.

Microwave Measurements for Conductive Anisotropic Materials

Applications of anisotropic composite materials range from construction composites to electric circuit boards. Anisotropic conductivity is one of the many important measurands for anisotropic composites for identifying misalignment. However, there are only a few nondestructive, noncontact techniques available. Here, we explore waveguide ellipsometry, a new electromagnetic characterization technique, and its application to conductive anisotropic composites. We demonstrate waveguide ellipsometry and discuss the design and implementation of a novel rotation test head on a robotic arm. To validate our technique, we designed and fabricated test wafers with ideal anisotropic composites consisting of gold stripes on materials with varying sheet resistances. The measurements were compared to full-wave simulations with simulated material properties extracted with the help of composite theory and simple circuit analysis. We found a good match between the simulated and measured complex scattering (S-) parameters for all test wafers fabricated with molybdenum disilicide (MoSi2) and gold stripes. Finally, we map the measured S-parameters to simulated S-parameters with help from composite theory and circuit modeling. Broader impacts of microwave ellipsometry include in-line measurement and conductivity imaging of large-scale and 3-D parts for nondestructive evaluation.

An Improved Polymerase Cross-Linking Spiral Reaction Assay for Rapid Diagnostic of Canine Parvovirus 2 Infection.

With increasing complications of canine parvovirus infection cases, disease diagnosis and treatment have become more difficult. In this study, specificity primers for the conserved region of the VP2 gene of canine parvovirus 2 (CPV-2) were synthesized and evaluated. An improved polymerase cross-linking spiral reaction (PCLSR) method for early and rapid diagnosis of CPV-2 was established. The results showed that the amplification reaction was optimal when run at 62°C for 50 min and could be used to detect CPV-2 without any cross-reactions with other pathogens of canine infectious diseases. Reaction results were directly judged by the naked eyes, with the positive amplification tube shown as luminous yellow and the negative tube as bright purple. Compared with the previously reported polymerase spiral reaction (PSR) method for CPV-2 detection, this reaction was performed using improved primer pairs and a better dye identification method (using an indicator comprising phenol red and cresol red). The detection limit of PCLSR was 3.9 × 101 copies using gel electrophoresis or a visible dye. The positive rate of 132 clinical samples was 42.42%, which was identically the same as that of the PSR method and slightly higher than that of the colloidal gold strip method (39.39%). The newly developed CPV-PCLSR assay shows the advantage of rapid visualization of results and offers a convenient and rapid method for early CPV-2 diagnosis with higher sensitivity and specificity than the established methods.

Numerical investigation of high-speed electrically reconfigurable plasmofluidic channels for particle manipulation

Exploiting the uniquely tunable optical response and the strong optical Kerr nonlinearity of a graphene sheet conjugated by the propagating leaky surface plasmons (SPs) excited on top of gold (Au) stripes, an efficient and high-speed electrically reconfigurable plasmonic tweezer is presented. It is demonstrated that using a number of electrically and optically isolated Au stripes and topped graphene, metallic, and dielectric nanoparticles (NPs) can be trapped, sensed, guided, and sorted in a controllable manner. Also, numerical simulations show that at high enough SP fields, the fundamental SP mode is laterally self-focused by an induced laterally graded refractive index and consequently experiences weaker edge effects. It is shown that a more confined and enhanced SP mode in the nonlinear regime is beneficial to trapping and sensing applications. The proposed stacked structure of a nonpatterned graphene sheet and Au stripes offers an efficient and powerful method for developing reconfigurable plasmofluidic channels in controlling the trajectory of label-free NPs.

A Mid-Infrared Dual-Band Filter With Ultra-High Resolving Power

A mid-infrared (mid-IR) dual-band filter with ultra-high resolving power is designed and numerically investigated. It is composed of an Al2O3 layer between a gold grating and a CaF2 substrate. Each unit cell of the grating consists of two gold strips with different heights. The filter provides two high-extinction ultra-narrow stop bands. One is at a wavelength of ∼3.8392 μm with a full-width at half-maximum (FWHM) of ∼0.8 nm, and the other is at a wavelength of ∼3.8435 μm with a FWHM of ∼1.8 nm. The resolving power of the filter is >2100. The two stop bands result from the (+1) and (−1) waveguide modes, respectively. An interaction between the two resonance modes exists and affects the stop bands. We can control the interaction by adjusting the grating parameters, thus designing the FWHMs and lineshapes of the two stop bands flexibly.

Experimental Study of the Thermal Conductivity of Single-Walled Carbon Nanotube-Based Thin Films

The single-walled carbon nanotube-based thin films with a thickness from 11 ± 3 to 157 ± 18 nm have been formed using vacuum filtration. The thermal conductivity of the thin films as a function of thickness and temperature up to 450 K has been studied by the 3ω technique. It has been found that, in the region of 49 nm, the supplied heat from a gold strip started propagating with the high efficiency to the thin film plane. The thermal conductivity of the thin films with a thickness of 49 ± 8 nm was measured using the 3ω technique for bulk samples. It has been found that the thermal conductivity of the single-walled carbon nanotube-based thin films strongly depends on their thickness and temperature. The thermal conductivity sharply (by a factor of ~60) increases with an increase in thickness from 11 ± 3 to 65 ± 4 nm. In addition, it has been observed that the thermal conductivity of the thin film with a thickness of 157 ± 18 nm rapidly decreases from 211 ± 11 to 27.5 ± 1.4 W m–1 K–1 at 300 and 450 K, respectively.

Fe3O4@Au SERS tags-based lateral flow assay for simultaneous detection of serum amyloid A and C-reactive protein in unprocessed blood sample

Accurate detection of mutiple biomarkers in unprocessed blood via lateral flow immunoassay (LFA) strips remains challenging. Herein, we reported a novel surface-enhanced Raman scattering (SERS)-based LFA strip for ultrasensitive and simultaneous analysis of dual infection biomarkers by using functionalized Fe3O4@Au magnetic nanoparticles (MNPs). Antibody-modified Fe3O4@Au MNPs were designed as SERS nanotags and efficient enrichment tool. The target infection biomarkers were quickly captured and enriched from the blood sample by Fe3O4@Au nanotags. After washing to remove impurities, Fe3O4@Au nanotags acted as high-performance SERS reporters for quantitative detection of the target in the LFA strip. Through this strategy, the proposed Fe3O4@Au based LFA allowed quantified analysis of target infection biomarkers in unprocessed blood samples with the limits of detection of 0.1 ng/mL and 0.01 ng/mL for serum amyloid A (SAA) and C-reactive protein (CRP), respectively. By comparison, the proposed assay for SAA and CRP was 100-fold and 1000-fold more sensitive than standard colloidal gold strip by using the same antibodies, respectively. This magnetic SERS strip also exhibited excellent stability, specificity, and selectivity for complex samples and could be used as an effective tool for infectious disease diagnostics.

Selective transfer of gold (III) in chloride solutions through polyurethane films

Gold (III) chloride can be extracted by solvating solvents and this extends to polyurethane foams. This study has confirmed that gold (III) chloride can be rapidly transported through polyurethane films. The rate of transfer follows first-order kinetics with the rate-determining step being transport through the film. This has been confirmed by measuring the rate of stripping of gold (III) pre-loaded into the film and by using films of different thicknesses. Diffusion coefficients for the transport of gold (III) are compared with those from studies using liquid supported membranes.The loading isotherm of gold (III) in the polyurethane film has been obtained. Iron (III) and platinum (IV) are transported at negligible rates while tri-iodide ions are strongly absorbed by the film at a lower rate.

Modeling Stripe Formation on Growing Zebrafish Tailfins.

As zebrafish develop, black and gold stripes form across their skin due to the interactions of brightly colored pigment cells. These characteristic patterns emerge on the growing fish body, as well as on the anal and caudal fins. While wild-type stripes form parallel to a horizontal marker on the body, patterns on the tailfin gradually extend distally outward. Interestingly, several mutations lead to altered body patterns without affecting fin stripes. Through an exploratory modeling approach, our goal is to help better understand these differences between body and fin patterns. By adapting a prior agent-based model of cell interactions on the fish body, we present an in silico study of stripe development on tailfins. Our main result is a demonstration that two cell types can produce stripes on the caudal fin. We highlight several ways that bone rays, growth, and the body-fin interface may be involved in patterning, and we raise questions for future work related to pattern robustness.

Surface-Enhanced Raman Scattering and Fluorescence on Gold Nanogratings.

Surface-enhanced Raman scattering (SERS) spectroscopy is a sensitive sensing technique. It is desirable to have an easy method to produce SERS-active substrate with reproducible and robust signals. We propose a simple method to fabricate SERS-active substrates with high structural homogeneity and signal reproducibility using electron beam (E-beam) lithography without the problematic photoresist (PR) lift-off process. The substrate was fabricated by using E-beam to define nanograting patterns on the photoresist and subsequently coat a layer of gold thin film on top of it. Efficient and stable SERS signals were observed on the substrates. In order to investigate the enhancement mechanism, we compared the signals from this substrate with those with photoresist lifted-off, which are essentially discontinuous gold stripes. While both structures showed significant grating-period-dependent fluorescence enhancement, no SERS signal was observed on the photoresist lifted-off gratings. Only transverse magnetic (TM)-polarized excitation exhibited strong enhancement, which revealed its plasmonic attribution. The fluorescence enhancement showed distinct periodic dependence for the two structures, which is due to the different enhancement mechanism. We demonstrate using this substrate for specific protein binding detection. Similar periodicity dependence was observed. Detailed theoretical and experimental studies were performed to investigate the observed phenomena. We conclude that the excitation of surface plasmon polaritons on the continuous gold thin film is essential for the stable and efficient SERS effects.

Dyes from the Ashes: Discovering and Characterizing Natural Dyes from Mineralized Textiles.

Vesuvius eruption that destroyed Pompeii in AD 79 represents one of the most important events in history. The cataclysm left behind an abundance of archeological evidence representing a fundamental source of the knowledge we have about ancient Roman material culture and technology. A great number of textiles have been preserved, rarely maintaining traces of their original color, since they are mainly in the mineralized and carbonized state. However, one outstanding textile sample displays a brilliant purple color and traces of gold strips. Since the purple was one of the most exclusive dyes in antiquity, its presence in an important commercial site like Pompeii induces us to deepen the knowledge of such artifacts and provide further information on their history. For this reason, the characterization of the purple color was the main scope of this research, and to deepen the knowledge of such artifacts, the SERS (Surface Enhanced Raman Scattering) in solution approach was applied. Then, these data were enriched by HPLC-HRMS analyses, which confirmed SERS-based hypotheses and also allowed to hypothesize the species of the origin mollusk. In this context, a step-by-step integrated approach resulted fundamental to maximize the information content and to provide new data on textile manufacturing and trade in antiquity.

Development of ELISA and Lateral Flow Immunoassays for Ochratoxins (OTA and OTB) Detection Based on Monoclonal Antibody.

Ochratoxins were important secondary metabolites secreted by fungi, and OTA and OTB are mainly significant mycotoxin, having toxic effects on humans and animals. Therefore, it is important to establish a rapid, sensitive, and precise method for ochratoxins detection and quantification in real samples. In this study, a stable monoclonal antibody (mAb) that recognizing both OTA and OTB toxins was employed for the establishment of indirect competitive ELISA (ic-ELISA), colloidal gold nanoparticles (CGNs), and nanoflowers gold strips (AuNFs) for detection of ochratoxins in real samples. A 6E5 hybridoma cell line stable secreting mAb against both OTA and OTB toxins was obtained by fusion of splenocytes with myeloma SP2/0 cells. The 6E5 mAb had a high affinity (3.7 × 108 L/mol) to OTA, and also showed similar binding activity to OTB. The optimized ic-ELISA resulted in a linear range of 0.06–0.6 ng/mL for ochratoxins (OTA and OTB) detection. The IC50 was 0.2 ng/mL and the limit of detection (LOD) was 0.03 ng/mL. The mean recovery rate from the spiked samples was 89.315 ± 2.257%, with a coefficient variation of 2.182%. The result from lateral flow immunoassays indicated that the LOD of CGNs and AuNFs were 5 and 1 μg/mL, respectively. All these results indicated that the developed ic-ELISA, CGNs, and AuNFs in this study could be used for the analysis of the residual of ochratoxins (OTA and OTB) in food and agricultural products.

Emitting properties of a-Si:C:H films with a gold submicron grating

In this study reflection and photoluminescence spectra of a-Si:C:H thin film with gold grating on it was examined theoretically and experimentally. The hydrogenated amorphous amorphous silicon-carbon alloy films were fabricated by the PECVD technique. Arrays of gold stripes with different gold width were created by lift-off e-beam lithography. Reflection, and PL spectra has been measured by a Fourier imaging spectroscopy. The theoretical calculations are in a good agreement with experimental results. From the PL spectra it follows, that the TE polarization gives sharper and more efficient PL signal than the TM polarization, and PL efficiency almost does not depend on gold stripes widths. It was shown that only in TE modes the PL outcouples from the gratings owing to the fact that there is no plasmon’s affect in this polarization.

Gold nanostars-enhanced Raman fingerprint strip for rapid detection of trace tetracycline in water samples.

Rapid and accurate detection of antibiotics at trace levels in food represents a great challenge. Tetracycline (TC), as a sort of broad-spectrum antibiotic, has been extensively used in animal infection therapy and animal husbandry as growth promoters. Large amounts of TC residues in animal-derived foods affect food quality and safety, and cause undesirable side effects such as allergic reactions and bacterial antibiotic resistance. Here, a Raman fingerprint strip sensor was reported based on surface-enhanced Raman scattering technology and demonstrated for ultrasensitive detection of TC. In this approach, 4-aminothiophenol (4-ATP) modified gold nanostars (GNSs) were used as a strong Raman reporter, which was coated with anti-TC monoclonal antibody serving as a biorecognition to acquire both visual and Raman signals on the test line. To demonstrate the performance of this strip, TC standard solutions with concentrations ranging from 0.5 to 50ng/mL was detected, the limit of the detection (LOD) for the Raman signal was 0.04ng/mL, which was 100 times more sensitive than those of color intensity quantifications. The other analogues, oxytetracycline, and chlortetracycline were detected using this method, making them suitable for the samples with TC analogues screening.