Fringe Spacing Research Articles

Acoustic field design in microfluidic geometries via Huygens-Fresnel diffraction and deep neural networks

Creating defined nonuniform acoustic fields, with particle capture locations beyond the grids and lines that are typically generated, has a range of applications in microfluidic systems. In this work, we use a unique interaction between polydimethylsiloxane (PDMS) channel geometries and a travelling substrate wave to explore the creation of nonuniform acoustic fields for microscale pattering. Surface acoustic waves (SAWs) are ideal for generating high-frequency, microscale wavelengths, though conventionally generate particle pattering via the interference between opposing SAW transducers, creating a standing SAW. Our recent work, however, has shown that patterning can alternatively be created using only a single travelling SAW and channel boundaries via diffractive effects, where fringe spacing is a function of the channel wall orientation. Unique to SAW, this creates a condition where the channel shape directly impacts the acoustic field that results, and therefore the possibility of designing acoustic fields by defining the channel geometry. To solve this inverse problem, we implement a machine-learning approach based on a Deep Neural Networks (DNN) that can define channel geometries resulting in desired acoustic fields. This submitted work will introduce the mechanisms via which this diffractive patterning occurs and the implementation of the DNN design process.

Self-Referencing Spectral Interferometric Probing of the Onset Time of Relativistic Transparency in Intense Laser-Foil Interactions

Irradiation of an ultrathin foil target by a high intensity laser pulse drives collective electron motion and the generation of strong electrostatic fields, resulting in ultrabright sources of high-order harmonics and energetic ions. The ion energies can be significantly enhanced if the foil undergoes relativistic self-induced transparency during the interaction, with the degree of enhancement depending in part on the onset time of transparency. We report on a simple and effective approach to diagnose the time during the interaction at which the foil becomes transparent to the laser light, providing a route to optically controlling and optimizing ion acceleration and radiation generation. The scheme involves a self-referencing approach to spectral interferometry, in which coherent transition radiation produced at the foil rear interferes with laser light transmitted through the foil. The relative timing of the onset of transmission with respect to the transition radiation generation is determined from spectral fringe spacing and compared to simultaneous frequency-resolved optical gating measurements. The results are in excellent agreement, and are discussed with reference to particle-in-cell simulations of the interaction physics and an analytical model for the onset time of transparency in ultrathin foils.

Physicochemical characterization of forest and sugarcane leaf combustion's particulate matters using electron microscopy, EDS, XRD and TGA

Physical characteristics and quantitative elemental composition of PM and residual ash produced from sugarcane leaves (SCL) combustion were investigated using TEM-EDS compared with forest leaves (FRL). SEM-EDS was used to analyze the microstructure and chemical composition of biomass raw leaves and PM. XRD analysis was also performed to investigate the characterization of the crystalline nanostructure, structure of PM, and residual ash compared to the TEM image processing method. The oxidation kinetics of biomass raw materials, PM, and residual ash were investigated by TGA. The morphology of fine and ultrafine agglomerate structure of SCL soot and residual ash are not significantly different from the FRL soot and residual ash. The average diameter sizes of single primary nanoparticles of SCL and FRL soot are approximately 37 nm and 35 nm, while the sizes of residual ash are about 18 nm and 22 nm, respectively. The single primary nanoparticles of soot are mainly composed of curve line crystallites of carbon fringes, while residual ash is composed of straight-line lattice fringes. The average fringe lengths of SCL and FRL soot are about 1.25 nm and 1.04 nm from the outer shell and 0.89 nm and 0.74 nm from the inner core. The interlayer spacing of curve line carbon fringes of SCL and FRL soot is approximately 0.359 nm and 0.362 nm by the TEM image analysis and it was matched with XRD analysis. The biomass PMs are mainly composed of soot, Si, Ca, and K compounds: SiO2, CaCO3, and KCl.

Large-area commercial-grating-quality subwavelength periodic ripples on silicon efficiently fabricated by gentle ablation with femtosecond laser interference via two cylindrical lenses

This paper presents a new strategy for efficiently fabricating large-area subwavelength periodic ripples with commercial grating quality on a silicon surface. Two laser beams of 800 nm, 50 fs at a repeat frequency of 1 kHz were focused on a silicon wafer via two cylindrical lenses. The spacing of the interference fringes was adjusted to excite a coherent resonance-enhanced (CRE) surface plasmon polariton (SPP). The CRE SPP efficiently induced homogeneous and extremely straight periodic ripples through gentle ablation, which avoids substantial debris and reduces the roughness of the periodic ripples. At the two edges of the ablation band after single scanning, the ripples were shallow, spaced, and exceptionally straight, which is greatly advantageous in the preparation of large-area gratings line by line. The subwavelength periodic ripples were fabricated on a silicon wafer with a diameter of 100 mm by scanning at a speed of 2 mm/s and a spacing of 1.55 mm. Compared with the alternating amorphous-crystalline ripples induced by a single laser beam, the fabrication efficiency was enhanced by 2–3 orders. Measurements with a confocal optical microscope and white light diffraction demonstrate that the periodic ripples were extremely straight, smooth, and homogeneous, similar to the gold gratings. The diffraction resolution of the nanogratings of subwavelength periodic ripples was nearly as narrow as that of commercial gratings.

Inclusion of the tunneling phase shift for interferometric particle imaging for bubble sizing

The interferometric particle imaging technique makes use of the angular oscillations of the scattered light in the forward direction for droplet or bubble sizing. The out-of-focus image consists of fringes, the spacing of which reflects the interference between the surface-reflected light and the twofold-refracted light. Total internal reflection occurs when the incident light hits the bubble at a large incident angle. The tunneling phase shift is not included in the geometric optics approximation, which leads to a deviation from Mie theory. In this work, we modified the formula for describing the fringe spacing by including the tunneling phase shift of total internal reflection. Numerical analysis and experiments showed that the modification is effective for the measurement of bubbles smaller than 60μm.

Micro Fresnel mirror array with individual mirror control

We present the design and fabrication of a miniaturized array of piezoelectrically actuated high speed Fresnel mirrors with individual mirror control. These Fresnel mirrors can be used to generate propagation invariant and self-healing interference patterns. The mirrors are actuated using piezobimorph actuators, and the consequent change of the tilting angle of the mirrors changes the fringe spacing of the interference pattern generated. The array consists of four Fresnel mirrors each having an area of 2 × 2 mm2 arranged in a 2x2 configuration. The device, optimized using FEM simulations, is able to achieve maximum mirror deflections of 15 mrad, and has a resonance frequency of 28 kHz.

Customised structural, optical and antibacterial characteristics of cinnamon nanoclusters produced inside organic solvent using 532 nm Q-switched Nd:YAG-pulse laser ablation

Biomedical values of organic natural cinnamon that are buried in their bulk counterpart can be exposed and customised via nanosizing. Based on this factor, a new type of spherical cinnamon nanoclusters (Cin-NCs) were synthesised using eco-friendly nanosecond pulse laser ablation in liquid (PLAL) approach. As-grown nontoxic Cin-NCs suspended in the citric acid of pH 4.5 (acted as organic solvent) were characterised thoroughly to evaluate their structural, optical and bactericidal properties. The effects of various laser fluences (LF) at the fixed wavelength (532 nm) on the physiochemical properties of these Cin-NCs were determined. The FTIR spectra of the Cin-NCs displayed the symmetric-asymmetric stretching of the functional groups attached to the heterocyclic/cinnamaldehyde compounds. The HR-TEM image of the optimum sample revealed the nucleation of the crystalline spherical Cin-NCs with a mean diameter of approximately 10 ± 0.3 nm and lattice fringe spacing around 0.14 nm. In addition, the inhibition zone diameter (IZD) and optical density (OD600) of the proposed Cin-NCs were measured to assess their antibacterial potency against the Staphylococcus aureus (IZD ≈ 24 mm) and Escherichia coli (IZD ≈ 25 mm) bacterial strains. The strong UV absorption (in the range of 269 and 310 nm) shown by these NCs was established to be useful for the antibacterial drug development and food treatment.

Mutual diffusion coefficient of concentrated trehalose aqueous solutions including supercooled regions measured by the Soret forced Rayleigh scattering method

We measured the binary mutual diffusion (interdiffusion) coefficient of trehalose aqueous solutions D in the concentration range from 0.1 to 0.8 mass fraction and the temperature range from 25 to 50 °C including supercooled regions under atmospheric pressure. The experimental apparatus was based on the Soret forced Rayleigh scattering (SFRS) technique, which uses the Soret effect to create a periodic spatial concentration modulation (Δw <10−5) of micrometer-order fringe spacing in a disaccharide aqueous solution due to the absorption of an optical interference grating generated by two crossing pulsed excitation laser beams (ΔT <10−2 °C). The decay of the mass diffusion process is monitored by the diffraction intensity of a probing laser beam within a few milliseconds. These characteristics of SFRS enabled us to measure highly viscous disaccharide aqueous solutions under supercooled states. The uncertainties of the experimental results were estimated to be within ±3% for low concentration and ±9% for high concentration (w > 0.55). The experimental results demonstrated that the rate of decrease in the mutual diffusion coefficient with the increasing concentration is more pronounced in supercooled regions than in dilute normal regions. We also measured the mutual diffusion coefficient of sucrose aqueous solutions at 30 °C in the supercooled regions to compare the results with those obtained from trehalose. We observed that the mutual diffusion coefficient of the trehalose aqueous solutions were smaller than those of sucrose with the increasing concentration, the ratio of Dtrehalose to Dsucrose showed an almost linear concentration-dependence towards the values that were less than half. Our findings suggest that trehalose can be more effective than sucrose in terms of the relaxation of the composition near their glass transitions.

A Low Temperature NO2 Sensor Based on SnSe2/SnO2 Heterojunction

Introduction Nitrogen dioxide (NO2) is one of the main air pollutants which is harmful to human health. A Higher concentration of NO2 may cause serious damage to respiratory system and even death. Moreover, the concentration of NO2 in the exhaled breath can be regarded as a diagnostic marker of asthma. Therefore, it is necessary to develop a low-energy consumption gas sensor which can sensitive and accurate analysis of NO2 in the atmosphere and exhaled breath.In this aspect, two dimensional (2D) layered nanostructured materials such as metal dichalcogenides (MX2, M=Mo, W, Sn etc..; X=S, Se, Te etc..) have received widespread attentions in NO2 detection due to their high specific surface area and unique electrical properties[1]. For example, SnS2 demonstrated excellent NO2 sensing properties [2]. Moreover, as reported in literature [3], the formation of SnO2/SnS2 heterostructure is beneficial to the further improvement of sensing performance. However, the gas sensing properties of SnSe are rarely reported. Therefore, the gas sensing properties of SnSe2 and SnSe2/SnO2 heterojunctions have investigated in this work. The SnSe2/SnO2 heterojunctions displays much improved sensitivity and superior selectivity toward NO2 at 120 °C. Experiment The SnSe2 powder was purchased from Chengdu Alfa Metal Material Co. Ltd. After grinding for half an hour, the SnSe2 powder was dispersed in an alcohol solution to obtain suspension by ultrasonic treatment. The paste was deposited onto the alumina substrates with Au interdigital electrodes. Then, the sensors were dried at 70 °C for 12 h. The SnSe2/SnO2 heterojunction based sensor was obtained by in-situ oxidation SnSe2 at 500 °C for 1 h in simulation air which is composed of 84.8 % dry nitrogen and 15.2 % dry oxygen. For comparison, the SnO2 sensor was also prepared by in-situ oxidation SnSe2 at 750 °C. Results and conclusions 1. Structure and MorphologyFig.1a shows the XRD patterns of SnSe2, SnO2 and SnSe2/SnO2, respectively. For the SnSe2/SnO2 sample, the diffraction peaks located at (001), (002), (003), (004), (005) lattice planes are assigned to the hexagonal SnSe2 (JCPDS Card No. 89-2939) [4], and the other diffraction peaks are consistent with tetragonal SnO2 (JCPDS No. 41-1445). No third phase was observed in the SnSe2/SnO2 sample indicating the product with high purity. This is consistent with the HRTEM analysis. As shown in Fig. 1(b), the fringe spacing of 0.296 nm and 0.192 nm are corresponded to the d-spacing of (002) and (003) crystal planes of SnSe2, whereas the fringe spacing of 0.340 nm and 0.265 nm are assigned to the d-spacing of (110) and (101) crystal planes of SnO2. Additionally, the EDX mapping images and EDX spectrum of SnSe2/SnO2 sample are shown in Fig.1c-d. It can be noticed that there only exist Sn, Se, and O elements in the composites material, and Sn (yellow), Se(red), and O (green) elements are uniformly distributed in the material, which confirming that the formation of SnO2 nanocrystals on the surface of SnSe2 and the oxidation of SnSe2 to SnSe2/SnO2 is partial.2. Gas-Sensing PropertiesFig. 2a shows the dynamic response and recovery curve of sensors to 8 ppm NO2 at 120 °C. Compared to pristine SnSe2 and SnO2 based sensor, the SnSe2/SnO2 based sensor exhibits the highest response value (5.6), which is approximately 10 times higher than that of SnSe2 based sensor (0.54). In contrast, since SnO2 didn’t work at the optimum temperature (usually at 200-400 °C), the redox reactions to induce a sensor response were almost inertia at 120 °C. The selectivity of the SnSe2/SnO2 based sensor to several VOCs, including ethanol, ammonia, formaldehyde, acetone and methanol at 8 ppm in Fig. 2b. The response towards 8 ppm NO2 is much higher compared to the other tested gases indicating a possible excellent selectivity towards NO2. The above results fully prove that the formation of SnSe2/SnO2 heterojunctions can enhance the sensing performance of materials.

Facile self assembly of uniform Cu2Cl(OH)3 nanoflowers and its photo-Fenton degradation performance for dye wastewater

The Cu2Cl(OH)3 uniform nanoflowers (f-Cu) are synthesized by the H2O2-assisted hydrothermal method, and the sample is characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), high-resolution transmission electron microscope (HR-TEM), selected area electron diffraction (SAED), UV–visible diffuse reflectance spectrum (UV-DRS) and Fourier transform infrared (FT-IR). The results show that with the increase of VH2O2/VH2O, the particles have assembled into nanoflowers. Moreover, the Cu2Cl(OH)3 nanoflowers are about 4 μm large, which consist of 5–1000 nm particles. Furthermore, Cu2Cl(OH)3 has monoclinic structure, and the lattice fringe spacing of 0.549 nm matches well with the {1 0 0} planes of Cu2Cl(OH)3, which reveal the single crystalline nature of f-Cu. Moreover, its photo-Fenton reaction degradation performance is evaluated by the decomposition of rhodamine B (RhB) as probing molecule to. It is found that f-Cu may promote the decomposition of H2O2, thus improving photo-Fenton reaction activity; and a low pH value promotes the photo-Fenton reaction. Compared with classic Fenton reaction, the photo-Fenton reaction is efficient at a wider pH range, which is promising for practical application.

EDF ring laser using cascaded-chirped long period fiber grating for temperature measurement.

A novel tunable erbium-doped fiber ring laser (EDFRL) using a cascaded-chirped long period fiber grating (C-CLPG) as a wavelength selection element is proposed. The oscillation wavelength is determined by the one of the spectral peaks of the C-CLPG used, and the oscillation output provides a high signal to noise (S/N) ratio detection and a highly sensitive measurement of the temperature due to its high power and narrow spectral output. In the experiment, it is confirmed that the wavelength of the output shifts in accordance with the temperature-induced spectral shift of the C-CLPG transmittance spectrum and the temperature sensitivity is obtained to be ∼-0.2 nm/°C within the wavelength range of 1567.30 ∼ 1575.78 nm. The oscillation wavelength range is to be limited depending on the fringe spacing of the channeled spectrum of C-CLPG, which limits the temperature measurement range, but a data processing approach to solve this problem is additionally proposed and its availability is also presented.

Green production of fluorescent carbon quantum dots based on pine wood and its application in the detection of Fe3+

Carbon quantum dots (CQDs) have novel applications as fluorescent nanomaterials in various fields. In this study, a green hydrothermal carbonisation (HTC) method is proposed to produce CQDs from pine wood (P-CQDs). The P-CQDs exhibited excellent fluorescence characteristics, with the optimal excitation wavelength being 330 nm and a corresponding emission wavelength of 447 nm. A blue light emission under ultraviolet light was observed and a typical graphene structure was seen in the HR-TEM images with a fringe spacing of 0.21 nm. Moreover, the mechanism of P-CQD formation during the HTC process was proposed. It was observed that P-CQDs demonstrated an aromatic polymer structure rich in oxygen-containing groups. This is because of the condensation, chain breaking, and chain forming reactions occurring among the hydrolytic products of the cellulose, hemicellulose, and lignin in pine wood. The fluorescence quenching results indicated that the P-CQDs selectively detected Fe3+ in an aqueous phase. This implies that these CQDs have broad application prospects for Fe3+ detection. More importantly, this signifies that the large-scale and low-cost production of CQDs and Fe3+ sensors will now be possible.

Study on the characteristics of amplitude and depth for sloshing wave by an optical method

A sloshing wave was excited by an instant impulse after a collision. The parameters of the sloshing wave were measured with laser diffraction. The diffraction patterns of the sloshing wave were obtained experimentally at different depths with the same excitation conditions. The fringe spaces and intensities of the diffraction patterns were induced in accordance with the wavelength and amplitude of the liquid sloshing wave. The amplitude of sloshing waves was linearly related to the depth of the wave. The device is simple, nondestructive, and allows real-time measurements.

Moiré fringes in nanoprecipitates in a zirconium alloy

Face-centered cubic (FCC) zirconium phase has been reported in as-cast and deformed zirconium and its alloys in recent years. The present study introduces germanium (Ge) containing FCC-Zr phase in an as-cast zirconium alloy. These precipitates were rod-like shaped and distributed in parallel, with 50–300 nm in length and 10–40 nm in width. The orientation relationship between these precipitates and the hexagonal close-packed (HCP) zirconium matrix was determined through TEM: <21¯1¯0>HCP∥〈1 1 0〉FCC, {0001}HCP∥{11¯1}FCC. Parallel moiré fringes were both observed viewed along [21¯1¯0]HCP and [1 01¯0]HCP zone axis, and how the fringe spacing was related to the crystal plane spacing was discussed.

Optically tunable terahertz-band interference fringe shift based on indium oxide

An optically tunable terahertz (THz)-band shift in interference fringes based on an indium oxide structure was investigated. An interference phenomenon formed by the combination of partial-through measurements with a shift in the periodic peaks in a THz time-domain spectroscopy system was reported. When the THz beam passes through the edge of the material sample, equally spaced interference fringes are obtained in the frequency domain and these interference fringes can be varied using a 450 nm external continuous-wave laser. The peak of the THz interference fringe shifts by almost half a period. This work offers the ability to observe THz-band interference fringes in the frequency domain and shows that these interference fringes change with variations in the intensity of the applied excitation light.

Common-path lensless digital holographic microscope employing a Fresnel biprism

Digital holographic (DH) microscopy is a nondestructive quantitative method for studying micron-sized samples with a special application in medicine, biology and materials science. Off-axis geometry of this method generates high-quality quantitative phase images employing beam-splitters, mirrors, condensers and magnifying lenses, which greatly increase the cost, size and sensitivity of the system against mechanical noise effects. The essential aim of recently proposed common-path configurations is to make viable approaches which minimize the mechanical and optical noises. Here we present a lensless DH microscopy system based on a common-path geometry using a Fresnel biprism for formation of off-axis geometry. The system comprises a lens for producing two spherical waves and by carefully choosing its parameters, we can construct a 3D imaging microscope with desired fringe spacing and overlapping region which is employed for studying many samples with different sizes, shapes and confluences. The system is compact, light-weight and robust versus mechanical vibrations. The ability to image amplitude and phase samples has been tested using standard test samples, living cells and water droplets.

Synthesis and characterization of nanocrystalline Hf6Ta2O17 ternary oxides by solvothermal method

Herein, nanocrystalline Hf6Ta2O17 ternary oxide powders have been newly synthesized from hafnium chloride and tantalum chloride as starting materials using the solvothermal method. As confirmed by powder x-ray diffraction analysis, single-phase Hf6Ta2O17 powders were prepared at a minimum temperature of 1200 °C for 1 h. The cell parameters of the Hf6Ta2O17 powders were calculated precisely by Cohen’s method, confirming the superior phase stability of the samples. Moreover, as demonstrated by a combination of characterization techniques, the nanoparticles were highly crystalline and homogenously distributed with crystallite sizes of approximately 50 nm. The measured fringe spacing of the crystal lattice is in agreement with the theoretical value, and the selected area electron diffraction pattern revealed the single-crystalline nature. Finally, the synthesized powder was densified into monolithic Hf6Ta2O17 ceramics with high relative density (97.9%) by pressureless sintering.

Quantum interference of a time-dependent wave packet of atom irradiated by an ultra-short laser pulse**Project partially supported by the National Key Research and Development Program of China (Grant Nos. 2019YFA0307700 and 2017YFA0403300), the National Natural Science Foundation of China (Grant Nos. 11627807, 11534004, C11975012, and 11774129), the Jilin Provincial Research Foundation for Basic Research, China (Grant No. 20170101153JC), and the

The wave packet evolution of an atom irradiated by an intense laser pulse is systematically investigated by using the numerical solution of the time-dependent Schrödinger equation. There are two types of spatial interference structures in the time-dependent evolution of the atomic wave packet. With the increasing of the evolution time, the interference fringe spacing for type I (type II) becomes larger (smaller). As the wavelength of the incident laser increases, the interference of the wave packet is changed from type II to type I, and the shift of interference type can be attributed to the contribution of excited states by using the energy analysis of the time-dependent wave function.

Synthesis of CdS/CdSe Core/Shell Heterostructures Using Ultrasonic Assisted Sol–Gel Method

Inverted type CdS/CdSe core/shell heterostructures were synthesized using ultrasonic assisted low cost and environmentally friendly sol–gel route. Cadmium chloride, thiourea and selenium dioxide were used as Cd, S and Se precursors, respectively. The core/shell heterostructures were analyzed by various techniques like X-ray diffraction, high resolution transmission electron microscope (HRTEM), photoluminescence and optical studies. X-ray diffractograms exhibit the cubic phase structure with its peaks shifting towards the lower angle due to compressive strain. Moire fringes are observed in HRTEM images of CdS/CdSe core/shell heterostructure due to lattice mismatch between CdS and CdSe. The interplanar spacing of moire fringes is found to be around 2.38 nm. Photoluminescence studies show the peak shifts towards the higher wavelength due to lattice mismatch between CdS and CdSe. Shift in absorption peak towards the higher wavelength makes them suitable for dye synthesized solar cells.

Gold Nanoparticles Biosynthesized Using Ginkgo biloba Leaf Aqueous Extract for the Decolorization of Azo-Dyes and Fluorescent Detection of Cr(VI)

Gold nanoparticles (AuNPs) are successfully synthesized via a facile and eco-friendly biosynthesis approach. Ginkgo biloba (G. biloba) leaf is an extract used as bio-aqueous solution for the preparation of the AuNPs. Photo-chemically, the G. biloba leaf plays dual roles wherein it serves as reducing and stabilizing agent. Through this approach, the use of toxin-induced chemical is completely avoided making the approach a green chemistry. Several synthetic parameters such as reactant concentration, media pH, reaction time and temperature are optimized which in turn enables the formation of AuNPs with uniform size. Various analytical techniques including scanning electron microscope (SEM), high resolution-transmission electron microscopic (HRTEM), X-ray diffraction (XRD), energy dispersive X-ray (EDX) spectroscopy, fringe spacing and selected area diffraction (SEAD) pattern, and dynamic light scattering (DLS) are used for AuNPs characterization. The AuNPs exhibit cubic structure and spherical shape with average size of 18.95 ± 5.95 nm. The homemade AuNPs show promises in the catalytic decolorization of azo-dyes in the presence of sodium borohydride (NaBH4). In addition, the AuNPs show appreciable sensitivity for the detection of Cr(VI) with a detection limit found to be 0.1–0.8 μM. This study is expected to spur further works on the use of metal nanoparticle for environmental pollution remediation.