ZnO:Mn nanoparticles with different Mn concentrations (0, 1 and 3 at%) have been produced by sol-gel wet chemical route. The effect of manganese doping on the structural, micro-structural, optical ...and photocatalytic properties of zinc oxide nanoparticles (ZnO NPs) has been investigated. X-ray diffraction and Raman investigations confirmed high quality monophase wurtzite hexagonal structure of pure and Mn-doped ZnO NPs; and no separate phase of dopant has been found. The chemical composition of Mn-doped ZnO NPs has been confirmed by X-ray photoelectron spectroscopic measurements. Additionally, the presence of Mn 2p3/2 peak at 640 eV in XPS spectra confirmed the addition of Mn in ZnO host matrix. TEM micrograph showed spherical shaped NPs with an average size in the range of 21–35 nm. The high resolution TEM images exhibit the highly crystalline nature and the inter-planar distances of hexagonal wurtzite ZnO:Mn nanoparticles. Raman study also confirmed the hexagonal wurtzite structure of ZnO:Mn (0, 1 and 3 at%) NPs. Optical absorption spectra showed a red shift in the absorbance band edge with increasing Mn doping in ZnO. The increasing doping level of Mn in ZnO resulted in the narrowing of bandgap and the increasing of visible light absorption. For photocatalytic behavior, the methylene blue (MB) decolorization efficiency in the very presence of synthesized pure and Mn-doped ZnO NPs has been studied under visible light irradiation. Photoluminescence measurements showed that the band edges of ultraviolet and green emissions are slightly red shifted; and PL intensity decreases with the increasing concentration of Mn in ZnO NPs. The significantly enhanced photocatalytic activity of Mn doped ZnO NPs is because of the increase in light absorption and the effective separation between photogenerated electron-hole pairs.
Rapid, selective, and highly sensitive microelectromechanical sensors are a promising technology for biosensing, medical recognition, and the detection of chemical hazards. At the same time, the ...surfaces of silicon microcantilevers cannot bond with thiols and cannot be functionalized without a bonding layer, such as gold. Therefore, in past literature, the surfaces of silicon microcantilevers have been coated with gold to facilitate their bonding with the thiol functional groups on the probe layers. However, gold coating produces thermal noise in the results owing to the metallic effect. Accordingly, this study aimed to modify the surface of silicon microcantilevers by patterning it using femtosecond laser (FSL) micromachining so that it could bond with the thiol functional groups with high sensitivity. The surface patterning of silicon microcantilevers enhances their physical, micromechanical, and chemical properties, increasing sensitivity by increasing the quality factor, specific surface area, and creating trapping areas on the microcantilever surfaces. The surfaces of the silicon microcantilever were patterned by microgrooves aligned from the free end to the bounded end, with each microgroove comprising submicrogrooves. To demonstrate their use in a biosensing applications, the modified microcantilevers were functionalized to detect severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2; COVID‐19) by immobilizing thiolated oligonucleotides on the surfaces, which worked as the probe layer. The modified biosensor was used to detect low concentrations of SSDNA sequence targets ranging from 300 nM down to 100 pM. The modified silicon‐microcantilever sensors were directly functionalized without a joining layer, such as a gold layer. The results revealed a selective response to SARS‐CoV‐2 SSDNA down to a 9‐nM concentration. To detect hazardous chemicals, the modified microcantilever was functionalized using reduced L‐cysteine to detect Pb2+ at low concentrations down to 100 pM. The results revealed enhanced sensitivity and selectivity and demonstrated that the FSL patterning activated the microcantilevers to bond with probe layers through the interaction of the silanol created on the surface with the functional groups, such as the thiols, on the probe layers. The microcantilevers patterned with 10 microgrooves exhibited higher responses than those patterned with seven microgrooves.
Structural, optical and electrochemical properties of 4-amino-3-mercapto-6-(2-(2-thienyl)vinyl)-1,2,4-triazin-5(4H)-one donor (AMT) in powder and thin film forms are studied. The thermogravimetric ...curves (TGA and DTA) of AMT solid powder are performed for recognizing its thermal stability and thermal degradation kinetics. Integral method using Coats–Redfern and Horowitz–Metzger equations are applied in the dynamic thermal data analysis. The electrochemical reduction and oxidation potential of AMT organic material are investigated
.
AMT solid powder are characterized by means of optically diffused reflectance spectroscopy (DRS) based on the Kubelka–Munk model. Field emission scanning electron microscope image is characterized by the formation of nanostructure shape with average particle size 70 nm. The optical features of the AMT organic thin films are characterized by UV–Vis–NIR spectroscopy, Photoluminescence spectroscopy (PL) and Fourier transform infrared (FT-IR) spectroscopy. The optical properties such as absorption coefficient, optical gaps, refractive index, single effective oscillator energy (
E
o
) and dispersion energy (
E
d
) of the AMT organic thin films are estimated.
In this study, rods of magnesium alloy and titanium alloy were cut to have similar height of about 5mm and size of 10 mm × 10 mm to fabricate three Mg-Ti couples. The Mg-Ti couple was heat treated at ...540 °C, 570 °C, and 600 °C. The corrosion of these couples have been investigated and compared with AZ31 alloy. Potentiodynamic polarization and electrochemical impedance spectroscopy measurements were employed to study the corrosion behavior after 1.0 h and 48 h exposure to 3.5% NaCl solutions. The morphology of surfaces was examined by scanning electron microscopy (SEM) and the profile analysis was collected using an energy dispersive X-ray (EDX) analyzer after 5 days immersion in the chloride solutions. It is found that coupling Mg with Ti reduces the corrosion of AZ31 alloy, which further decreased with the increase of the temperature of treatment. Prolonging the time of exposure from 1.0 h to 48 h remarkably decreased the corrosion of the couples as well.
Transient Liquid Phase (TLP) bonding was performed between Mg-AZ31 and Ti-6Al-4V alloys with various bonding temperatures using Cu coatings and Sn interlayers. The bonding parameters such as bonding ...pressure and bonding time were fixed at 1 MPa and 15 minutes respectively in order to study the effect of bonding temperature on the joint evolution. Bonds made at temperatures of 540, 560, 580 and 600 C showed good bond strength. The obtained bonds were investigated by Electron Probe Micro-analyzer EPMA and showed reaction layers and diffusion zones for all bonds made. The maximum joint shear strength of 78 MPa was obtained for bond made at 580 C. X-ray diffraction XRD and X-ray photoelectron spectroscopy XPS were taken for the fractured surfaces of bond made at 580 C. The analysis of the fractured surfaces found that the reaction layer contains Sn5Ti6 IMC in the titanium side and Mg2Cu IMC in the magnesium side where the fracture occurs at the diffusion zone in the mg side.
In this study, pristine and Zr-doped CeO
2
nanoparticles with chemical formula Ce
1−x
Zr
x
O
2
(x = 0, 0.05, 0.075 and 0.1) have been prepared through facile hydrothermal process. The influence of Zr ...doping on the microstructure, thermal, optical and photocatalytic properties of CeO
2
was systematically explored through various analytical techniques. Analysis of the XRD data reveals cubic fluorite structure of the samples with average crystallite size of 12, 15, 21 and 30 nm respectively for different Zr doping. The optical properties of the nanoparticles were studied through UV–visible absorption and photoluminescence (PL) spectroscopy. X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy measurements were performed to examine the chemical state and microstructure of the synthesized materials. The functional groups and mode of vibrations have been identified by the Fourier transform infrared (FTIR) spectroscopy. A reduction in the optical band gap of CeO
2
(from 3.25 to 3.10 eV) is observed on systematic Zr doping. In addition, significant enhancement in the photocatalytic performance is also noticed for the doped samples (92.2%) as compared to the pristine one (68.7%) for the degradation of methylene blue (MB) dye under visible light irradiation.
•High quality single-walled carbon nanotubes were grown on silicon substrate.•The structural, optical properties and photocatalytic activity were investigated.•The diameter of individual carbon ...nanotubes in the bundles was found ∼2 nm.•Excellent photocatalytic performance was observed under visible light irradiation.
Present work focuses on the growth of single-walled carbon nanotubes (SWCNTs) using nickel as a catalyst onto the silicon substrate through plasma enhanced chemical vapour deposition (PECVD) method. As synthesised SWCNTs have been characterized by employing various analytical techniques like XRD, SEM, HR-TEM/EDS and UV-visible absorption spectroscopy. The HRTEM micrographs revealed that the SWCNTs were mostly entangled bundles with diameters of about 2 nm. The optical absorption data were used to estimate energy bandgap of the SWCNTs and found to be 2.67 eV. The photocatalytic performance of the nanotubes was examined by the deterioration of an organic dye methylene blue (MB) under visible light irradiation. The observed results exhibit excellent photocatalytic activity of the nanotubes that may be due to the large surface defects, surface area and small energy bandgap characteristics of the nanotubes.
In this work, we report an easy, efficient method to synthesize high quality lithium-based upconversion nanoparticles (UCNPs) which combine two promising materials (UCNPs and lithium ions) known to ...enhance the photovoltaic performance of perovskite solar cells (PSCs). Incorporating the synthesized YLiF4:Yb,Er nanoparticles into the mesoporous layer of the PSCs cells, at a certain doping level, demonstrated a higher power conversion efficiency (PCE) of 19%, additional photocurrent, and a better fill factor (FF) of 82% in comparison to undoped PSCs (PCE = ~16.5%; FF = 71%). The reported results open a new avenue toward efficient PSCs for renewable energy applications.
In this paper, a unique hybrid approach to design and synthesize 2D/3D Al2O3-ZnO nanostructures by simultaneous deposition is presented. Pulsed laser deposition (PLD) and RF magnetron sputtering ...(RFMS) methods are redeveloped into a single tandem system to create a mixed-species plasma to grow ZnO nanostructures for gas sensing applications. In this set-up, the parameters of PLD have been optimized and explored with RFMS parameters to design 2D/3D Al2O3-ZnO nanostructures, including nanoneedles/nanospikes, nanowalls, and nanorods, among others. The RF power of magnetron system with Al2O3 target is explored from 10 to 50 W, while the ZnO-loaded PLD’s laser fluence and background gases are optimized to simultaneously grow ZnO and Al2O3-ZnO nanostructures. The nanostructures are either grown via 2-step template approach, or by direct growth on Si (111) and MgO substrates. In this approach, a thin ZnO template/film was initially grown on the substrate by PLD at ~300 °C under ~10 milliTorr (1.3 Pa) O2 background pressure, followed by growth of either ZnO or Al2O3-ZnO, using PLD and RFMS simultaneously under 0.1–0.5 Torr (13–67 Pa), and Ar or Ar/O2 background in the substrate temperate range of 550–700 °C. Growth mechanisms are then proposed to explain the formation of Al2O3-ZnO nanostructures. The optimized parameters from PLD-RFMS are then used to grow nanostructures on Au-patterned Al2O3-based gas sensor to test its response to CO gas from 200 to 400 °C, and a good response is observed at ~350 °C. The grown ZnO and Al2O3-ZnO nanostructures are quite exceptional and remarkable and have potential applications in optoelectronics, such in bio/gas sensors.
Cadmium sulfide (CdS) quantum dots (QDs) with cubic phase were prepared using simple precursors by chemical precipitation technique, and their thin films were grown on glass substrates by chemical ...bath deposition. The obtained quantum dots were characterized for their structural, morphological, optical, thermal and electrical properties using X-ray diffraction (XRD), field emission transmission electron microscopy, UV–visible absorption spectroscopy, Raman spectroscopy, photoluminescence, thermogravimetric analysis/differential thermal analysis and low-temperature electrical transport measurements, respectively. XRD pattern reveals that the prepared CdS QDs are highly pure and crystalline in nature with cubic phase. The average particle size, estimated to be ~2 nm, is almost in agreement with the values calculated by Brusïs formula. Selected area electron diffraction also recognizes the cubic structure of CdS quantum dots. The UV–visible spectra exhibit a blueshift with respect to that of bulk sample which is attributed to the quantum size effect of electrons and holes. The band gap of CdS QDs is calculated from absorption data using Tauc plot and found to be 2.84 eV. Energy-dispersive X-ray analysis reveals the presence of Cd and S in almost stoichiometric ratio in the prepared CdS QDs. Micro-Raman spectroscopic studies also yield convincing evidence for the transformation of structure. The emission spectra of CdS QDs show peak centered at 541 nm, which is attributed to the presence of cadmium vacancies in the lattice. The DC resistivity data at low temperatures are qualitatively consistent with the variable-range hopping model, and the density of states at the Fermi level is determined.
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