654 research outputs found
Sort by
Green synthesized plasmonic nanostructure decorated TiO2 nanofibers for photoelectrochemical hydrogen production
No full textWe herein present the Au and Ag NPs synthesized via chemical reduction with green synthesized carbon nano lights (CNL) as a visible light photosensitizer for TiO2 nanofibers (TNFs) towards photoelectrochemical water splitting. The synthesized photoanodes (PA1: TNFs, PA2: Ag@CNLs/TNFs and PA3: Au@CNLs/TNFs) were probed ex-situ for morphological, structural, optical and electronic properties before being used for the PEC experiments. We first show the efficient photocatalytic activity of these photoanodes for the degradation of methylene blue under visible light irradiation. Followed by the photoelectrochemical (PEC) water splitting investigation, which reveals the substantially improved photocurrent density to 13 mA/cm2 and 18 mA/cm2, for PA2 and PA3, respectively under simulated AM 1.5 solar illumination at 1.36 V vs RHE, ~15 fold enhancement compared to that obtained for a PA1. This improvement we attributed to the synergic consequence, improved absorption and effective charge carrier separation & transport due to surface plasmonic effect, which is well evident in the decrease of measured charge transfer resistance (Rct), for PA2 (15.1 Ω) and PA3 (6.71 Ω), as compared to PA1 (139 Ω)
Fabrication of Al2O3/SiO2 multilayer reflective filters with excellent uniformity for demanding optical interference filters
No full textIn this work, we report the fabrication of a high reflective filter with excellent uniformity for demanding optical interference filters. To achieve this, films were deposited in different batches at three different angular positions using electron beam deposition technique. The coatings were carried out using indigenously designed flat jig holder without shapers. Fourteen alternating layers of high and low refractive index films were deposited on BK7 substrates of dimensions 186 × 150 mm by using aluminum dioxide (Al2O3) and silicon dioxide (SiO2) evaporation grade granuals. Individual layers in the stack were deposited at quarter wave optical thickness at a wavelength of 550 nm. To examine the optical properties of multilayer optical films, Gonio-spectrophotometer was used. Roughness and thickness of all the samples were evaluated using Stylus Profilometer and Coherence Correlation interferometer. Surface properties such as wettability, adhesion and hardness were studied. Additionally, to investigate the change in chemical bonding and structural properites of the coating materials used for evaporation before (bulk powdered material) and after deposition of thin films (material left in the crucible after deposition process), FTIR and XRD studies were carried out
Cyclodextrin-metal–organic framework (CD-MOF): From synthesis to applications
No full textPorous coordination compounds, commonly known as metal–organic frameworks (MOFs), exhibit many unique characteristics (e.g., high surface area, high porosity, and tunability). The corresponding naturally occurring counterparts, CD-MOFs have opened a new avenue of research in light of its non-toxic, edible, and renewable nature. These characteristics have led to their applications into numerous directions including drug delivery, CO2 capture, separation/purification, adsorption, sensors, food packaging, electrical conductors, memristors, photocatalysis, and polymerization. In this review, we provide a brief discussion about the available technologies for the synthesis of CD-MOFs and their applications in many prospective areas
A simple setup for measurement of the coherence length of a laser diode using holographic optics
No full textDue to improvements in the technology of laser diodes, nowadays they have become an integral part of most physics and engineering undergraduate courses. Laser diodes, which generally have low coherence, are extensively used in various educational experiments due to their compactness, ease of operation and handling, as well as their cost-effectiveness. Thus, knowledge about the coherence length of beams from these laser diodes becomes important when designing experiments using these as light sources. Generally, students find it difficult to measure coherence length with most of the existing techniques. In the present work an experimental arrangement using holographic optics is designed and demonstrated to measure the temporal coherence of a laser diode beam in a compact and easy-to-align manner. The proposed scheme is particularly suitable to measure short coherence lengths. The temporal coherence of a laser diode is measured to be 2.1 ± 0.02 mm, by varying separation between two holographic optical components. The results obtained are experimentally compared with results from a Michelson interferometer
Effect of despeckle filtering on classification of breast tumors using ultrasound images
No full textUltrasound is the most widely used imaging modality for screening of breast tumors. However, due to the presence of speckle noise in an ultrasound image, the diagnostic information gets masked and the interpretation of the breast abnormalities becomes difficult for the radiologist. The texture of the tumor region and the shape/margin characteristics are considered to be important parameters for the analysis of the breast tumors. In the present work, exhaustive experimentation has been carried out for the design of CAD systems for classification of breast tumors by considering (a) original images only, (b) despeckled images only and (c) both original and despeckled images together (hybrid approach).
Total 100 breast ultrasound images (40 benign and 60 malignant) have been used for the analysis. Initially, these images have been despeckled using six filters namely Lee sigma, BayesShrink, DPAD, FI, FB and HFB filters. Total 162 features (149 texture and 13 morphological features) have been computed from both original and despeckled breast ultrasound images and SVM classifier has been used extensively for the classification.
The results of the study indicate that the hybrid approach of CAD system design using texture features computed from original images combined with morphological features computed from images despeckled by DPAD filter yield optimal performance for classification of benign and malignant breast tumors with a classification accuracy of 96.0%. From the promising results of the study it can be concluded that the proposed hybrid CAD system design could be used as a second opinion tool in clinical setting
Electro-deposition of bactericidal and corrosion-resistant hydroxyapatite nanoslabs
No full textHerein, nanoscale hydroxyapatite (HA) with a slab-like morphology was synthesized, and its size was calculated to be in the range of 80–150 nm, as confirmed via scanning electron microscopy (SEM) and atomic force microscopy (AFM). The nanoscale HA with a slab-like structure has been referred as HA nanoslabs in the manuscript. The composition, crystallinity, wettability, bacterial resistance porosity, surface roughness and corrosion resistance of these HA nanoslabs were studied using energy dispersive spectroscopy (EDAX), X-ray diffraction (XRD), contact angle, colony count BET analyzer and profilometer and polarization techniques, respectively. The contact angle of the HA nanoslabs was found to be 22.6°, which indicated the hydrophilic nature of these nanoslabs. Their bacterial resistance was studied against the Salmonella typhi strain, and it was found that in the presence of the HA nanoslabs, the growth of the bacteria was hindered. For the corrosion resistance study, the HA nanoslabs were electro-deposited on a titanium alloy, used as a substrate. The deposition was carried out at varying currents, viz, 1 mA, 3 mA and 5 mA. The open circuit potential (OCP) and polarization were used for the estimation of the corrosion resistance of the bare and coated substrates. The corrosion potential started shifting towards noble potential, and the current density started decreasing with an increase in the electrochemical deposition current. This indicated good corrosion resistance of these nanoslabs
Self‐Powered and Broadband Photodetectors with GaN: Layered rGO Hybrid Heterojunction
No full textThe development of self‐powered and broadband (NIR–Vis–UV) photodetectors with high responsivity is essential for energy efficient futuristic optoelectronic devices. A simple approach is reported to formulate inorganic–organic (GaN/rGO: Ag NP) hybrid p–n heterojunction photodetectors clasping with transparent Au nanowire network as the top electrode. The heterojunction demonstrates excellent rectification ratio of 105 and broadband photoresponse due to GaN in ultraviolet (UV) region and silver‐loaded reduced graphene oxide (rGO: Ag NP) in visible to infrared region. Further, the reducing effect of Ag nanoparticles (Ag NPs) to GO along with its localized surface plasmon resonance is utilized to enhance the response in near infrared (NIR) and the visible region in the presented device structure. Transparent Au nanowire network works as an efficient charge collector ensuing high responsivity and fast switching characteristics. The heterojunction exhibits superior photoresponse with high on/off ratio (104), responsivity (0.266 A W‐1), and detectivity of (2.62 × 1011), under the illumination of 360 nm light. Due to the high built‐in‐potential difference at the heterojunctions, self‐powered operation is demonstrated under entire excitation wavelength (360–980 nm) range, which holds great futuristic promises for cost‐effective, stable, and efficient energy conserving electronics
Eye gaze tracking based directional control interface for interactive applications
No full textThis paper proposes an unobtrusive and calibration-free framework towards eye gaze tracking based interactive directional control interface for desktop environment using simple webcam under unconstrained settings. The proposed eye gaze tracking involved hybrid approach designed by combining two different techniques based upon both supervised and unsupervised methods wherein the unsupervised image gradients method computes the iris centers over the eye regions extracted by the supervised regression based algorithm. Experiments performed by the proposed hybrid approach to detect eye regions along with iris centers over challenging face image datasets exhibited exciting results. Similar approach for eye gaze tracking worked well in real-time by using a simple web camera. Further, PC based interactive directional control interface based upon iris position has been designed that works without needing any prior calibrations unlike other Infrared illumination based eye trackers.
The proposed work may be useful to the people with full body motor disabilities, who need interactive and unobtrusive eye gaze control based applications to live independently
Surface Modification of Ti-6Al-4V Alloy by Electrical Discharge Coating Process Using Partially Sintered Ti-Nb Electrode
No full textIn the present research, a composite layer of TiO2-TiC-NbO-NbC was coated on the Ti-64 alloy using two different methods (i.e., the electric discharge coating (EDC) and electric discharge machining processes) while the Nb powder were mixed in dielectric fluid. The effect produced on the machined surfaces by both processes was reported. The influence of Nb-concentration along with the EDC key parameters (Ip and Ton) on the coated surface integrity such as surface topography, micro-cracks, coating layer thickness, coating deposition, micro-hardness has been evaluated as well. It has been noticed that in the EDC process the high peak current and high Nb-powder concentration allow improvement in the material migration, and a crack-free thick layer (215 μm) on the workpiece surface is deposited. The presence of various oxides and carbides on the coated surface further enhanced the mechanical properties, especially, the wear resistance, corrosion resistance and bioactivity. The surface hardness of the coated layer is increased from 365 HV to 1465 HV. Furthermore, the coated layer reveals a higher adhesion strength (~118 N), which permits to enhance the wear resistance of the Ti-64 alloy. This proposed technology allows modification of the mechanical properties and surface characteristics according to an orthopedic implant’s requirement
Magnetically retrievable Ce-doped Fe3O4 nanoparticles as scaffolds for the removal of azo dyes
No full textConsidering the significant impact of magnetically retrievable nanostructures, herein, Fe3O4 and Ce-doped Fe3O4 nanoparticles were employed as scaffolds for the removal of the Reactive Black 5 (RB5) azo dye. We synthesized the Ce-doped Fe3O4 nanoparticles via hydrothermal treatment at 120 °C for 10 h with varying cerium concentrations (1.5–3.5%) and characterized them using basic techniques such as FTIR and UV-visible spectroscopy, and XRD analysis. The retention of their magnetic behaviors even after cerium amalgamation was demonstrated and confirmed by the VSM results. FESEM and EDX were used for the morphological and purity analysis of the synthesized nanoabsorbents. XPS was carried out to determine the electronic configuration of the synthesized samples. The porosity of the magnetic nanoparticles was investigated by BET analysis, and subsequently, the most porous sample was further used in the adsorption studies for the cleanup of RB5 from wastewater. The dye adsorption studies were probed via UV-visible spectroscopy, which indicated the removal efficiency of 87%. The prepared Ce-doped Fe3O4 nanoabsorbent showed the high adsorption capacity of 84.58 mg g−1 towards RB5 in 40 min. This is attributed to the electrostatic interactions between the nanoabsorbent and the dye molecules and high porosity of the prepared sample. The adsorption mechanism was also analyzed. The kinetic data well-fitted the pseudo-first-order model, and the adsorption capability at different equilibrium concentrations of the dye solution indicated monolayer formation and chemisorption phenomena. Furthermore, the magnetic absorbent could be rapidly separated from the wastewater using an external magnetic field after adsorption