Gold Layer Research Articles

Bilayer Magnetoplasmonic Grating for Enhancement of the Transverse Magneto-Optical Kerr Effect and Dual Sensing Performance by Surface Plasmon Resonance

Magnetoplasmonic nanostructures with magnetic and metallic compositions have received considerable attention because they can greatly enhance the transverse magneto-optical Kerr effect (T-MOKE) due to surface plasmon resonance (SPR) excitations, which can be used to realize extremely high detection performance. Here, a bilayer heterogeneous grating is proposed that comprises gold and cerium-substituted yttrium iron garnet layers on a gold film for remarkable SPR enhancement of the T-MOKE. Numerical simulations via the finite element method indicated that the proposed structure substantially improves the sensing performance of the incident angle and wavelength with high detection sensitivity and a figure of merit that is an order of magnitude better than previously reported results. Moreover, the proposed structure can be used to fabricate devices for sensing gaseous media.

A comparative analysis of a D-shaped photonic crystal sensor based on graphene plasmonic

In this paper, a D-shaped photonic crystal fiber (PCF) sensor based on surface plasmon resonance has been presented. In the proposed structure, Graphene, Gold, and Silver have been used in different configurations in order to promote the sensitivity of the sensor. According to the numerical simulations performed by the finite element method (FEM) and considering the refractive index of the analyte from 1.36 to 1.40, the maximum wavelength sensitivity of 12600 nm RIU−1 has been obtained, which is related to the structure when the Gold layer sandwiched between two Graphene layers. This is while, the maximum amplitude sensitivity of the proposed sensor is 5708 (RIU−1), which is related to the configuration that Graphene has been placed under the Silver layer. On the other hand, the proposed structure is easy to use because there is no need to fill the fiber holes with the analyte and it can be easily placed on the D-shaped surface of the sensor. The proposed sensor is appropriate to sense the biological variation because of showing strong surface plasmon resonances. The effect of the fabrication tolerance on the proposed PCF is also studied. It is expected that the proposed model will be compatible with the bio-engineering approaches.

A high magnetic field sensitivity PCF‐SPR sensor working in the near‐infrared wavelength band

AbstractA novel form of photonic crystal fiber (PCF) magnetic field sensor, utilizing surface plasmon resonance, has been developed and investigated. By depositing a layer of gold onto the interior surface of the left‐sided air hole and introducing magnetic fluid into the aperture to detect magnetic field changes, the plasma resonance effect was ingeniously combined with a dual‐core PCF to achieve magnetic field measurement. The displacement of the loss peak in the output spectrum was observed to gain insights into the magnetic field changes. By means of modulations in the thickness of the gold film, and the spacing and size of the air holes, the optimal parameters for the sensor were obtained. The optimized sensor exhibited a maximum magnetic field sensitivity of up to 6.23 nm/Oe, and the magnetic field detection resolution was approximately 10 μT, enabling precise detection of weak magnetic fields. This fiber sensor boasts a simple structure, ease of production, high sensitivity, and robust environmental adaptability, making it an attractive option for implementation.

A Novel BioNEMS Sensor Based on Tunable Plasmonic Modes of a Grating MIM Structure

In this paper, a novel optical BioNEMS (Bio Nano-Electro-Mechanical-Systems) sensor using a nanomechanical plasmonic structure is proposed to develop a high performance label-free biosensor. The present device is composed of a functionalized BioNEMS cantilever coated by a gold layer as a part of the proposed plasmonic grating waveguide. This plasmonic system is based on the light interaction with a metallic nanostructure as a metal-insulator-metal (MIM) Bragg grating where an air gap acts as the insulator. Passing patient samples through the functionalized surface of the nanocantilever, the biological interactions release a stress on the surface because of binding events. The cantilever can be thus deflected by inducing a differential surface stress. Therefore, the air gap distance (the insulator width) between two parts of the plasmonic grating structure is changed to excite surface plasmon polaritons in a different wavelength. Furthermore, the present biosensor is analyzed by numerical and analytical approaches and its functional characteristics are obtained as follows: optical sensitivity of 7872 nm/RIU, figure of merit (FOM) of 394 RIU^-1, mechanical sensitivity of 1.2 µm/Nm^-1. According to the results, the proposed label-free identification method can be used as a sensitive platform for detection of biomarkers in point of care testing (POCT) applications.

Thermal annealing effects on the electrical characteristics of alpha particles irradiated MIS device AuTa2O5GaAs

An alpha particle-irradiated MIS device made of AuTa2O5GaAs was used to study how thermal annealing affects the I-V characteristics and how the current changes with annealing temperature, radiation energy, and voltage biassing. The super-gate of the MIS structure was made by using thermal evaporation to build a 1000°A thick layer of gold under a vacuum of about 10-5 torr. At room temperature, the devices were exposed to alpha particles from the radioactive source 226Ra (0.5 Ci) with energies of 5.1, 4, 3, 1.8, and 1.2 MeV for 0–30 minutes. After 30 minutes of annealing at 150, 200, and 300 o C in a vacuum of 10-3 torr, the current-voltage (I-V) characteristics of the irradiation devices were found. During thermal annealing, different results were seen with bias voltages of 0.4, 1, and 2 V and temperatures of 150, 200, and 300 o C. Annealing the device at 150 o C doesn't change how stable it is, but annealing it at 300 o C causes ohmic conduction in the device's properties. The device's current can be fixed best when the device is heated to 200 o C and then cooled. Also, thermal annealing seems to have different effects on the I–V electrical characteristics of the devices depending on the energy of the particles and the voltage biassing.

Photonic crystal enhanced immunofluorescence biosensor integrated with a lateral flow microchip: Toward rapid tear-based diabetic retinopathy screening.

Diabetic retinopathy (DR) has accounted for major loss of vision in chronic diabetes. Although clinical statistics have shown that early screening can procrastinate or improve the deterioration of the disease, the screening rate remains low worldwide because of the great inconvenience of conventional ophthalmoscopic examination. Instead, tear fluid that contains rich proteins caused by direct contact with eyeballs is an ideal substitute to monitor vision health. Herein, an immunofluorescence biosensor enhanced by a photonic crystal (PhC) is presented to handle the trace proteins suspended in the tear fluid. The PhC was constructed by self-assembled nanoparticles with a thin layer of gold coated on top of it. Then, the PC substrate was conjugated with antibodies and placed in a microchannel. When the capillary-driven tear sample flew over the PC substrate, the immunoassay enabled the formation of a sandwich antibody-antigen-antibody configuration for PhC-enhanced immunofluorescence. The use of PhC resulted in a concentration enhancement of more than tenfold compared to non-PhC, while achieving an equivalent signal intensity. The limit of detection for the target biomarker, lipocalin-1 (LCN-1), reached nearly 3 μg/ml, and the turnaround time of each detection was 15 min. Finally, a preclinical evaluation was conducted using ten tear samples. A clear trend was observed, showing that the concentrations of LCN-1 were at least twofold higher in individuals with chronic diabetes or DR than in healthy individuals. This trend was consistent with their medical conditions. The results provided a direct proof-of-concept for the proposed PhC biosensor in rapid tear-based DR screening.

The Research on Characteristics of SAC305/Sn-37Pb/ENIG Solder Joint

The reliability of the mix alloy of lead and lead-free components with SnPb paste is an important issue for military electronics. With the increase of density in PCB assembly, the traditional HASL pad has been gradually replaced by the ENIG pad for its better flatness and solderability. But the relationship between the interfacial morphology, microstructure and reliability of the alloy of lead and lead-free components still needs to be further studied. In this paper, the microstructure on the interface of SAC305/ Sn-37Pb/ ENIG solder joint is compared with that of typical SAC305/ Sn-37Pb3/ Cu solder joint, Sn63Pb37 / ENIG solder joint. It is found that the IMC layer on the interface of SAC305/Sn-37Pb/ENIG solder joint is more closer to compound (Cu, Ni) 6Sn5, and limited reflow soldering times has little effect on the strength of SAC305/Sn-37Pb/ENIG solder joint. Based on the case study, the thickness of gold layers has a significant effect on black pad problem in ENIG pad.

Design of a nanoscale gold-coated photonic crystal fiber biosensor

A simple two-layer refractive index sensor based on surface plasmon resonance has been proposed in this work, which evinces high sensitivity for detecting unknown analytes. This sensor design includes hexagonal- and octagonal-shaped air-hole rings, which have been introduced in the first and second layers, respectively. By performing this amalgamation of different types of air holes, this gold-coated plasmonic sensing scheme provides the broad sensing limit of the analyte, which is 1.32–1.40. The sensing performance has been examined by applying the finite element method, which is being used for modeling complex and irregular-shaped geometry. The wavelength interrogation method has demonstrated a maximal wavelength sensitivity of 9,000 nm/RIU (refractive index unit). The maximal amplitude sensitivity of 1902 RIU−1 has been exhibited in the y-polarized mode using the amplitude interrogation method. Moreover, the maximal sensor resolution of 1.11 × 10−5 RIU covers the entire sensing range. Furthermore, by adjusting the air-hole diameter, pitch, and depth of the gold layer coating, many more investigations have been demonstrated in this design. This highly sensitive sensor is very convincing to be used in many applications like chemical, biological, and also in physical sensing analyses.

Wear resistance of sensors based on surface plasmon resonance phenomenon

Surface plasmon resonance is used for detecting and measuring various analytes characteristics by sensitive elements in sensor devices. At this, the problem of wear of the sensitive elements, contacting with gaseous and liquid environments whose characteristics are measured, arises during operation of sensor devices based on the surface plasmon resonance phenomenon. Wear of a surface gold nanolayer may be caused by various factors such as maintenance (cleaning before measurements), chemical reactions and abrasiveness of the environment. This problem becomes particularly significant when suspensions are measured. Solid particles in the suspensions have abrasive properties, which leads to modifications of the surface, reduction of the thickness and damage of the sensitive gold layer. As a result, more frequent replacements of sensitive elements are required significantly increasing the measurements cost. In this paper, influence of water suspensions of an optical polishing powder “Polarite” on the wear and the associated changes of the characteristics of a sensitive element is investigated. The need to find solutions of the problem of improving its wear resistance is highlighted.

Enhancement in absorption spectrum by ITO coated, down converting glass and increasing the SILAR cycles of PbS/CdS quantum dots sensitized ZnO nano with deposition of MoO3/Au/MoO3 (MAM) as a solid state solar cell

This research describes the first-of-its-kind quantum dots sensitized solar cell (DC/ITO/ZnO/PbS/CdS/MoO3/Au/MoO3) that is efficient and economical. A down-converting (DC) transparent glass was prepared. One side of DC glass was coated with indium tin oxide (ITO) by sputter-coating technique to make it conductive for electric current. Zinc oxide (ZnO) nanorods were produced by the several steps of hydrothermal process. The PbS/CdS quantum dots (QDs) were then grown on top of ZnO nanorods by using a process known as Successive Ionic Layer Adsorption and Reaction (SILAR). The final layer for the back contact was deposited as a trilayer of (MoO3/Au/MoO3).Spin coating was employed in the process of depositing MoO3 layers, while thermal evaporation was used in the process of depositing the intermediate layer of gold (Au). For the deposition of (CdS/PbS) quantum dots with different number of SILAR cycles (10, 15 and 20) were employed. Afterwards MoO3/Au/MoO3 trilayer was deposited on the quantum dots (CdS/PbS) attached with the nanorods ZnO for the complete fabrication of three devices. As compared to the other quantum dots sensitized solar cell (QDSSC), it can absorb light from both ends which produced the remarkable results. Surface morphology, elemental and structural analyses were employed by SEM, EDS and XRD methods. UV–Visible analysis was performed to identify the optical properties of the devices. Overall performances were calculated of the three different devices by their power conversion efficiencies. The highest efficiency among all three devices was 10% corresponding to the 15 SILAR cycles.

Novel approach to TNSA enhancement using multi-layered targets—a numerical study

In the context of ion acceleration driven by ultra-high contrast lasers using thin foils, there is a clear trend towards increasing ion energy when the target thickness is reduced. However when the target is too thin and the prepulse strength is not negligible, this trend is reversed due to degradation of the target mainly caused by prepulse-induced shocks, among other effects (thermal plasma expansion, early onset of transparency, etc). In this paper, we propose and motivate the use of multi-layered targets for the purpose of enhancing the target normal sheath acceleration mechanism by means of attenuating the shock waves inside the target. It is demonstrated through hydrodynamic simulations that multi-layered targets, composed of alternating layers of plastic and gold, can significantly delay the time of shock wave breakout, reducing the shock energy that breaks out of the target and shortening the plasma scale-length. This approach paves the way for enhanced laser-driven ion acceleration using thinner targets even for relatively low contrast lasers.

Four-band terahertz metamaterial absorber basedon Dirac semimetal for a refractive index sensing application.

We design a four-band narrow-band near-perfect absorber based on bulk Dirac semimetal (BDS) metamaterial in the terahertz region. The absorber has a top-to-bottom three-layer structure of a BDS layer, an insulating dielectric slab, and a gold layer. The BDS is flexible and tunable, allowing the Fermi energy level to be adjusted by changing the applied bias voltage, thus changing the absorption characteristics of the absorber. We use the time-domain finite-difference method to simulate the absorption characteristics of the absorber, which could achieve four discrete near-perfect absorption peaks at 0.98THz, 1.70THz, 2.02THz, and 2.36THz. The absorber is polarization sensitive, and the conversion between four-band absorption and three-band absorption is achieved by changing the incident polarization angle. We also change the structure of the absorber to study the absorption characteristics and break the structural symmetry to achieve a larger number of absorption peaks. Besides, the sensing performance of four-band narrow-band absorption is analyzed, and the maximum sensitivity of the absorber is 112.78GHz/RIU. The device should have vast application prospects for bio-detection and high-sensitivity biosensing detection.

Development of a surface plasmon resonance based immunosensor for diclofenac quantification in water

A Surface Plasmon Resonance (SPR) biosensor based on an inhibition immunoassay was developed for the detection of diclofenac (DCF) in aqueous solution. Due to the small size of DCF, an hapten-protein conjugate was produced by coupling DCF to bovine serum albumin (BSA). DCF-BSA conjugate formation was confirmed via MALDI-TOF mass spectrometry. The resulting conjugate was immobilized onto the surface of a sensor fabricated via e-beam deposition of a 2 nm chromium adhesion layer followed by a 50 nm gold layer onto precleaned BK7 glass slides. Immobilization onto the nano thin gold surface was accomplished by covalent amide linkage through a self-assembled monolayer. Samples were composed of a mixture of antibody at a fixed concentration and DCF at different known concentrations in deionized water, causing the inhibition of anti-DCF on the sensor. The DCF-BSA was obtained with a ratio of 3 DCF molecules per BSA. A calibration curve was performed using concentrations between 2 and 32 μg L−1. The curve was fitted using the Boltzmann equation, reaching a limit of detection (LOD) of 3.15 μg L−1 and limit of quantification (LOQ) of 10.52 μg L−1, the inter-day precision was calculated and an RSD value of 1.96% was obtained; and analysis time of 10 min. The developed biosensor is a preliminary approach to the detection of DCF in environmental water samples, and the first SPR biosensor developed for DCF detection using a hapten-protein conjugate.

Laser cleaning of paint layers on white marble surface based on cooperative use of laser-induced breakdown spectroscopy and image binarization

The key to precisely removing paint layers sprayed onto stone surfaces using laser cleaning without damaging the stone substrate is to select the optimized laser parameters based on the online monitoring methods. In this paper, a pulsed laser beam with a high-pulse repetition frequency of 100 kHz, a pulse width of 200 ns, and a wavelength of 1064 nm was used to clean 39 µm- and 31 µm- thick of gold and silver paint layers off of white marble surfaces. The optimized average laser power for removing the paint layers was determined to be 40 W using laser-induced breakdown spectroscopy (LIBS) method and an image binarization method. Under the optimized average laser power of 40 W, the optimized spot overlap ratios for cleaning the layers of gold and silver paint were determined to be 10% and 30% respectively, using the image binarization method. The corresponding optimized number of cleaning shots was 5 and 4, respectively. The laser cleaning efficiency for both the gold and silver paint layers exceeded 95%. It was thereby demonstrated that this research protocol based on the cooperative use of two online monitoring methods to determine the optimized laser parameters in sequence (average laser power → spot overlap ratio → number of cleaning shots) not only optimizes the laser cleaning efficiency for different paint layers but does so without causing any damage to the white marble substrate.

Low-Cost and Low-Profile Sub-Terahertz Luneburg Lens Beamformer on Polymer

A Luneburg lens is used to excite a leaky-wave antenna (array of slots) in the sub-terahertz (sub-THz) frequency range. The antenna is built on a 140-μm thick Cyclic Olefin Copolymer (COC) substrate. The radiating slots (58×24 slots) are etched on the polymer by a photolithographic process, for which the gold (Au) layers are first deposited by evaporation on the COC and, then, patterned by chemical etching. No metalized vias or drilling are applied to the substrate. The full system is fed by a standard WR03 waveguide, and it has been fabricated and tested. Experimental results show an input reflection coefficient better than −7 dB over a 25% fractional bandwidth, spanning from 220 GHz to 290 GHz. The radiated beam can be steered in elevation from −80° to −20° over the same band. The antenna efficiency is estimated to be 20% at the center frequency (260 GHz). This solution provides a simple alternative for low-cost and low-profile beam scanning antennas in the sub-THz range.

D-Shaped Photonic Crystal Fiber Toxic Metal Ions (Arsenic) Sensor Based on Surface Plasmon Resonance

In this work, a Photonic Crystal Fiber (PCF) sensor based on the Surface Plasmon Resonance (SPR) technology was proposed. A thin layer of gold (Au) was deposited on a D-shaped Photonic Crystal Fiber (PCF), which was coated with plasmonic chemically stable gold material with a thickness of 40nm. The performance parameters like sensitivity including wavelength sensitivity and amplitude sensitivity and resolution were evaluated by simulation using COMSOL software. The proposed sensor was created by using the finite element approach, it is numerically examined. The results show that the surface of D-shaped Photonic Crystal Fiber coated with Au behaves as a sensor to detect the refractive index (IR) of toxic metal ions. The impacts of the structural characteristics on the resonant spectra are also researched in order to improve sensing performance. The greatest amplitude sensitivity was 99.2 RIU-1 and maximum resolution was 4 x 10-5 RIU achieved within the detection range (1.351-1.363).

The Influence of Nonlocal Metal-Dielectric Environments on Physical and Chemical Processes.

ConspectusPlasmonic nanolayers and laminar metallic/dielectric multilayers were originally developed for optical cloaking applications and lensing applications that could potentially image objects whose size was below the diffraction limit. These assemblies were initially formed from gold or silver nanorods grown within an alumina mesh. However, more recently, assemblies with similar properties have also been prepared by sequential thin-layer deposition of alternating layers of gold and magnesium fluoride (MgF2). These metal/dielectric composite materials enable control of the dielectric constant in the directions perpendicular to the layers and balance the real and imaginary dielectric constants of the assembly such that the speed and the amplitude of the waves traveling through the assembly are not attenuated.In this Account, we will also focus on a few of the applications ranging from surface wetting to fluorescence quenching to enhancement of photochemical reactions. First, we will share an introduction to processes used to create these materials, which are combinations of low refractive index metals and transparent higher index materials arranged in a scalable repeating fashion. Two fabrication methods were employed: an electrochemical deposition of Ag nanorods into an anodized alumina matrix which produced materials with an anisotropic negative refractive index material within the plane of the film and lamellar metal/dielectric layers in which the negative index perpendicular to the growth direction. These alternating layers of plasmonic metals and dielectric materials were ultimately chosen to prepare films for further testing, because of their relative ease of fabrication. We will continue with a discussion of a few of the applications of both of these nonlocal dielectric composite materials including more specialized plasmonic, composite, and hyperbolic metamaterials including fluorescence quenching, photochemical reactions, and surface wetting. In each of these applications, the unique response caused by the enhancement of the electric field and the interface between hyperbolic materials and plasmonic materials as they interact photophysically with their near neighbors is presented. In each of the applications, the enhanced electric field extends from the composite substrate layer to interact with its near neighbors and beyond. The presence of this extended interaction can be observed in the form of decreased emission lifetime, enhancement of photochemical reaction rates, and changes in the surface energies measured by contact angle goniometry. In this Account, all of these situations will be addressed. Finally, we will conclude with a summary and vision for the future as well as a discussion of the unique challenges and opportunities available as research active faculty at an HBCU.

Optimization of hydrophobic nonresponsive sol-ketal acrylate gel film to hydrophilic thermo-responsive gel by graft-polymerization

This work has been done in three steps. First, the preparation of acrylate monomers; they are [dimethyl-1,3-dioxoylan-4-yl-methylacrylate (sol-ketal acrylate) (SKA)], [4-acetylphenyl acrylate (APHA)], and [4-formyl-2-methoxyphenylacrylate (VA)]. All monomers were evaluated using 1H, 13C-NMR, and FT-IR. In the next step, two kinds of polymers were prepared. Two series of copolymers and terpolymers were carried out via the free-radical polymerization; SKA with the photo-cross-linker for poly (SKA-co-DMIAm) photo-cross-linker polymer and VA and APHA with N-isopropylacrylamide for poly (NIPA-co-VA-co-APHA) functional-thermo-responsive terpolymer. All fabricated polymers were investigated by (1H-NMR, FT-IR, UV, GPC, and DSC). The phase separation temperature of polymer solutions has been measured through the turbidity and the change in transmittance to the temperatures using UV–Vis spectroscopy. Eventually, the UV was used to form the gel layer after the deposition of the gold layer. The nonresponsive gel layer was grafted with poly (NIPA-co-VA-co-APHA) to optimize the upper layer to the thermo-responsive functional layer. SPR/OW measured the swelling properties of the gel layers. The active layer will immobilize biological molecules with the primary amine group.Graphical abstractThe schematic diagram shows the steps of gel formation: The cross-linking initiated by UV; SPR/OW for film thickness; grafting for gel optimization.

Metal-Organic Framework-Decorated Nanochannel Electrode: Integration of Internal Nanoconfined Space and Outer Surface for Small-Molecule Sensing.

Ionic current measurement has been the dominant signaling strategy in nanochannel-based sensors. However, the direct probing of the capture of small molecules is still challenging, and the sensing potential of the outer surface of nanochannels is always ignored. Here, we report the fabrication of an integrated nanochannel electrode (INCE) with nanoporous gold layers modified on two sides of nanochannels, and its application for small-molecule analysis was explored. Metal-organic frameworks (MOFs) were decorated inside and outside of nanochannels, enabling the reduction of pore size to several nanometers, which is among the thickness range of the electric double layer for confined ion diffusion. Combined with excellent adsorption characteristics of MOFs, the developed nanochannel sensor successfully constructed the internal nanoconfined space that could directly capture small molecules and instantly generate a current signal. The contribution of the outer surface and the internal nanoconfined space to diffusion suppression to electrochemical probes was investigated. We found that the constructed nanoelectrochemical cell was sensitive in both the inner channel and the outer surface, signifying a novel sensing mode with integration of the internal nanoconfined space and the outer surface of nanochannels. The MOF/INCE sensor showed excellent performance toward tetracycline (TC) with a detection limit of 0.1 ng·mL-1. Subsequently, sensitive and quantitative detection of TC down to 0.5 μg·kg-1 was achieved in actual chicken samples. This work may open up a new model of nanoelectrochemistry and provide an alternative solution in the field of nanopore analysis for small molecules.

Numerical Analysis of Highly Sensitive Twin-Core, Gold-Coated, D-Shaped Photonic Crystal Fiber Based on Surface Plasmon Resonance Sensor.

This research article proposes and numerically investigates a photonic crystal fiber (PCF) based on a surface plasmon resonance (SPR) sensor for the detecting refractive index (RI) of unknown analytes. The plasmonic material (gold) layer is placed outside of the PCF by removing two air holes from the main structure, and a D-shaped PCF-SPR sensor is formed. The purpose of using a plasmonic material (gold) layer in a PCF structure is to introduce an SPR phenomenon. The structure of the PCF is likely enclosed by the analyte to be detected, and an external sensing system is used to measure changes in the SPR signal. Moreover, a perfectly matched layer (PML) is also placed outside of the PCF to absorb unwanted light signals towards the surface. The numerical investigation of all guiding properties of the PCF-SPR sensor is completed using a fully vectorial-based finite element method (FEM) to achieve the finest sensing performance. The design of the PCF-SPR sensor is completed using COMSOL Multiphysics software, version 1.4.50. According to the simulation results, the proposed PCF-SPR sensor has a maximum wavelength sensitivity of 9000 nm/RIU, an amplitude sensitivity of 3746 RIU-1, a sensor resolution of 1 × 10-5 RIU, and a figure of merit (FOM) of 900 RIU-1 in the x-polarized direction light signal. The miniaturized structure and high sensitivity of the proposed PCF-SPR sensor make it a promising candidate for detecting RI of analytes ranging from 1.28 to 1.42.