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Intrinsic zinc oxide thin films have deficiencies in terms of structural, optical and electronic characteristics, which has given rise to researches on metal doped zinc oxide films in the interest of enhancing its characteristics. Indium tin oxide, Au, Ag, Pt and Ti; which are extensively used in industrial level thin film applications but aluminum has low cost than those metals, so by doping with this on ZnO thin films, its performance and quality on the morphological, elemental, structural, optical and electrical attributes were analyzed in this research. Tuning of ZnO nanocrystalline thin films’ optical band gap, doped by different materials simplifies possible elements for photonic applications. Sol–gel spin coating method has been used for these analyses which was accustomed to gain the Al doped ZnO (AZO) parent compounds on silicon-glass substrates. Ultra violet visible spectrophotometer was used to determine band gap tuning characteristics, urbach energy, transmittance and absorption properties. The Moss-Burstein outcome imprints the blue shift with thickness increment of the absorption end and there is a clear relationship between band gap and urbach energy. Tuning of band gap value varies from 3.22 eV to 3.26 eV by varying the film thickness from 100 to 300 nm. A non-linear, non-monotonic relation has been seen for the change of optical and structural parameters of AZO thin films. Deep research of structural and optical properties represents important information to get a better perspective of band gap dependence on structural properties.

In this work, a large-area MoS2/graphene barristor device, with an electrically tunable Schottky barrier height, has been studied for detection of various gaseous analytes. The Schottky barrier height could be modulated by over 0.65 eV, allowing the drain current to be tuned by many orders of magnitude. Using diluted NO2 and NH3 gases as analytes, the performance of the barristor device was compared with individual MoS2 and graphene based planar FETs, where the barristor device outperformed its counterparts in terms of response magnitude and limit of detection. Due to the atomically thin nature of MoS2 and graphene, electric field applied to one material could not be fully screened from the other one, which allowed both materials to act as a composite structure when analyte molecules interacted with the barristor device. This apparently reversed the dopant behavior of NO2 and NH3, while increasing the device sensitivity through subthreshold operation. Both conductance and capacitance based measurements are presented to highlight the charge transfer and barrier height modulation, to support the unique sensing mechanism observed in the 2D barristor device. A lower limit of detection in low ppb is established for NO2 and low ppm for NH3, which could be further tuned by altering gate-drain bias conditions.

In this paper, a first-principles study of the newly known MAX phase borides Zr2AB2 (A = In, Tl) has been carried out. The stiffness constants, elastic moduli, mechanical anisotropy, thermal and optical properties are investigated for the first time. The structural lattice parameters are found to be consistent with previous study. The dynamical and mechanical stability of the titled compounds have been checked. Fundamental insights into the stiffness constants, elastic moduli, hardness parameters, brittleness and anisotropy indices are presented. The variation of these mechanical properties is explained based on the Mulliken population analysis and charge density mapping (CDM). The metallic nature and anisotropy in conductivity has been confirmed from the electronic band structure. The analysis of DOS revealed the dominant contribution from Zr-d orbitals to the conductivity. The higher values of ΘD and Tm, and lower value of Kmin for Zr2AB2 (A = In, Tl) compared to those of Zr2AC (A = In, Tl) suggest enhanced thermal properties of the compounds under study for practical applications. Besides, the specific heat capacities (Cv, Cp), thermal expansion coefficient, and different thermodynamic potential functions have been calculated. The technologically important optical constants have been studied with an intention to reveal their possible relevance for application purposes. The reflectivity spectra revealed the applicability of Zr2AB2 (A = In, Tl) as cover materials to diminish the solar heating. The studied physical properties of Zr2AB2 (A = In, Tl) are compared with those of other relevant 212 and 211 MAX phase nanolaminates.

In this work, we systematically investigate the effects of growth parameters on the structural and surface morphological properties of β-(AlxGa1−x)2O3 thin films grown on (010) β-Ga2O3 substrates via metalorganic chemical vapor deposition (MOCVD). By varying [TMAl]/[TEGa + TMAl] molar flow rate ratio, growth temperature and chamber pressure, (i) the structural and physical properties of β-(AlxGa1−x)2O3 films including Al incorporations, growth rates, strain properties, rocking curve full width at half maximum, and (ii) the surface morphological properties are investigated. Higher [TMAl]/[TEGa + TMAl] molar flow ratio leads to higher Al incorporation in β-(AlxGa1−x)2O3 films. Higher growth temperature promotes lower growth rates with substantial surface roughening, although the Al incorporation remains similar for a given [TMAl]/[TEGa + TMAl] molar flow ratio. In addition, increasing chamber pressure leads to lower growth rates and lower Al incorporation in the AlGaO films. This study reveals that the MOCVD growth window for (010) β-(AlxGa1−x)2O3 films becomes narrower as the Al composition increases.

The cobalt ferrite (CoFe2O4) nanoparticles were synthesized by chemical co-precipitation technique and characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), and Mössbauer spectroscopy. The CoFe2O4 nanoparticles coated with biocompatible chitosan at different concentrations to produce homogeneous suspensions were also characterized by dynamic light scattering (DLS) and hyperthermia set-up. XRD data of the sample explored the particle size near about 7 nm in as-dried condition. TEM micrograph of bare CoFe2O4 nanoparticles provided the particle size nearly too about 8 nm which is in good agreement with the XRD data. This particle size after coating with chitosan became 14 nm. EDX results of this sample confirmed its nano dimension with spinel structure. VSM results of the sample in as-dried condition showed the ferromagnetic character which has been beyond proved by Mössbauer spectroscopy. The hydrodynamic diameter (Hd) and polydispersity index (PDI) of the chitosan-coated samples also provided promising results. The samples were tested for their induction heating properties with an RF magnetic field of 20 mT and a frequency of 342 kHz. We also studied therapeutic efficiency in-vitro on 9L gliosarcoma cancer cells, which revealed > 98% of mortality through hyperthermia protocol with the same RF field and frequency using chitosan-coated CoFe2O4nanoparticles. GUB JOURNAL OF SCIENCE AND ENGINEERING, Vol 7, Dec 2020 P 69-75

Adsorption kinetic equation has been derived assuming that the process follows the behavior of a heterogeneous chemical reaction at the solid–liquid interface. This equation is converted into the Langmuir isotherm at equilibrium and describes well the unsteady-state adsorption process. Based on that, a working equation has been developed, which gives adsorption-rate-constant independent of operating parameters including concentration. Also, a kinetic model expressed as a sum of first- and second-order systems available in the literature has been applied (modified with the interface reaction concept) to determine the adsorption rate constant. Both methods gave similar results. Three dimensionless numbers have been developed to determine and distinguish pseudo-first-order and pseudo-second-order kinetics justified from the viewpoint of chemical kinetics. It is shown that curve-fitting with a high correlation coefficient could validate an empirical kinetic model, but the fitted model parameters could not automatically be related to chemical kinetic parameters if the model itself is not grounded on well-defined chemical kinetics. Finally, it is concluded that the currently applied empirical approach could not provide reliable data for comparison among similar systems, while the Langmuir kinetic equation developed based on the concept of heterogeneous reaction would be a good basis for standardization of the method for adsorption system characterization.

The physical properties including thermodynamic and optical properties, electronic charge density, Fermi surface, Mulliken bond overlap population and Vickers hardness of newly synthesized MAX phase Hf2AlC and predicted Hf2AlN phase have been explored using density functional theory for the first time. We revisit lattice and elastic constants, band structure and density of states to weigh the reliability of our calculations. The mechanical and dynamical stabilities of these compounds have been ensured. The brittle nature of Hf2AlX (X = C and N) compounds is also confirmed by the Pugh (G/B > 0.57) and Poisson ratio (

Compared to flat devices based on rigid substrates, cable-shaped dye-sensitized solar cells hold advantages of smaller size, light weight, facile fabrication, flexibility, and low cost, thus a prom...

In recent times, layered chalcogenide semiconductors have attracted great interest in energy harvesting device applications. In the present study, the structural, electronic, optical and thermoelectric properties of two isostructural chalcogenide materials, NaInS2 and NaInSe2 with hexagonal symmetry (R-3m) have been studied using the first principles method. A very good agreement has been found between our results with the available experimental and theoretical ones. The studied materials are semiconducting in nature as confirmed from the electronic band structure and optical properties. The strong hybridizations among s orbitals of Na, In and Se atoms push the bottom of the conduction band downward resulting in a narrower band gap of NaInSe2 compared to that of NaInS2 compound. Different optical (dielectric function, photoconductivity, absorption coefficient, reflectivity, refractive index and loss function) and thermoelectric (Seebeck coefficient, electrical conductivity, power factor and thermal conductivity) properties of NaInX2 (X = S, Se) have been studied in detail for the first time. It is found that all these properties are significantly anisotropic due to the strongly layered structure of NaInX2 (X = S, Se). Strong optical absorption with sharp peaks is found in the far visible to mid ultraviolet (UV) regions while the reflectivity is low in the UV region for both the compounds. Such features indicate feasibility of applications in optoelectronic sector. The calculated thermoelectric power factors at 1000 K for NaInS2 and NaInSe2 along a-axis are found to be 151.5 μW/cmK2 and 154 μW/cmK2, respectively and the corresponding ZT values are ~ 0.70. The obtained thermal conductivity along a-axis for both compounds is high (~ 22 W/mK).This suggests that the reduction of such high thermal conductivity is important to achieve higher ZT values of the NaInX2-(X = S, Se) compounds.

Sn-substituted Mg–Zn ferrites (0 ≤ x ≤ 0.10) have been synthesized using conventional ceramic technique and the mechanical, optical and high-temperature magnetic properties were studied. The formal...

In this approach, folic acid (FA) sensor was fabricated with wet-chemically prepared Fe2O3/NiO/Mn2O3 nanoparticles (NPs), which was coated on a glassy carbon electrode (GCE) in the form of thin layers to create the desired sensor. The synthesized NPs were characterized by X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (XRD), Tunneling Electron Microscopy (TEM), surface area (BET), and Field Emission Scanning Electron Microscopy (FESEM) equipped with Energy-dispersive X-ray spectroscopy (EDS). The fabricated sensor, Fe2O3/NiO/Mn2O3 NPs/Nafion/GCE is responded linearly in electrochemical method over 0.1 nM to 0.01 mM of folic acid (FA) and denoted as a dynamic range of detection (LDR). The slope of LDR is designated as the sensor sensitivity, which is appreciable (48.588 µA µM-1 cm−2). The lower limit of FA detection is evaluated at a signal-to-noise ratio of 3, and it is equal to 96.89 ± 4.85 pM. The sensor analytical parameters such as stability, reproducibility, sensitivity, response time and long-time stability in buffer phase are found as outstanding. The FA sensor was valued to analyze the biological samples and found acceptable and satisfactory results. This prospective sensor might be an efficient probe for diagnosis of bio-samples in field of health career sector.

Single β-phase (100) (AlxGa1–x)2O3 thin films were successfully grown on (100) oriented β-Ga2O3 substrates via metalorganic chemical vapor deposition (MOCVD). By systematically tuning the precursor...

Frequency-dependent dielectric constant, dielectric loss, AC conductivity values and complex impedance spectra of V2O5-added Ni–Co–Zn ferrites ([Formula: see text][Formula: see text][Formula: see text]Fe2[Formula: see text] [Formula: see text]V2O5, where [Formula: see text] 0, 0.5, 1 and 1.5 wt.%) have been investigated at room temperature. The dielectric properties of the samples follow the Maxwell–Wagner polarization model. An inverse relationship was found between dielectric constant and AC electrical resistivity for all the samples. The dielectric constants decreased with the addition of V2O5, while the electrical resistivities of V2O5-added Ni–Co–Zn ferrites are found to be larger than that of pure Ni–Co–Zn ferrite. The AC conductivity was reduced with the addition of V2[Formula: see text]to Ni–Co–Zn ferrite at lower-frequency region. However, AC conductivity shows a sharp increase at higher-frequency region, which could be attributed to the enhancement of electron hopping between the Fe[Formula: see text] and Fe[Formula: see text] ions in the ferrite matrix due to the activity of the grains. The complex impedance spectroscopy results through Cole–Cole/Nyquist plot have demonstrated a single semicircular arc. It indicates that conduction mechanism takes place predominantly through the grain/bulk property, which could be ascribed to the larger grain size of V2O5-added Ni–Co–Zn ferrites.

In situ fabrication of a sensitive electrochemical sensor using a wet-chemically prepared ternary ZnO/MgO/Cr2O3 nanofiber (NF)-decorated glassy carbon electrode (GCE) with Nafion adhesive was the approach of this study. The resultant NFs were characterized by various tools, such as powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), Brunauer–Emmett–Teller (BET) surface area analysis, and ultraviolet–visible spectroscopy (UV/Vis). The analytical parameters of the proposed toluene sensor were characterized as follows: good sensitivity (23.89 μA μM−1 cm−2), a lower limit of detection (LOD; 95.59 ± 1.5 pM), a limit of quantification (LOQ; 318.63 ± 2.0 pM), efficient response time (18 s), and the dynamic range (LDR) for toluene detection of 0.1 nM–0.01 mM. The real-time application of the sensor is to protect the environmental ecosystem, as well as the public health from the harmful effects of toluene. In an environmental application, the toluene sensor exhibited good reproducibility, robustness, LOD, LOQ, and good reliability, which are discussed in detail and compared to the literature.

Herein, a heterogeneous polymer micro valve and pump with a polypropylene (PP) membrane was developed in a low-cost manner via UV/ozone-assisted thermal fusion bonding. The proposed fabrication technique allowed for a geometrically selective bonding; consequently, the membrane was prevented from bonding with the valve seat of the diaphragm micro-valve, without patterning a protection layer or introducing an additional structure. The developed device withstands 480 kPa of static pressure and up to 350 kPa of a vibration pressure, providing sufficient bonding strength for microfluidic actuations. The fabricated micro valve and pump are fully characterized and compared with a poly(dimethylsiloxane) (PDMS) membrane glass device, showing comparable valving and pumping performance. As a result, the robust PP membrane micro valve and pump are simply implemented in a facile manner, and demonstrated excellent performance, which is highly desirable for mass production of disposable lab-on-a-chip (LOC) devices.

In this work, heterostructure SnO2/ZnO nanocomposite photocatalyst was prepared by a straightforward one step polyol method. The resulting photocatalysts were characterized by X-ray diffraction (XRD), nitrogen adsorption–desorption analyses, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and UV-vis diffuse reflectance spectroscopy (UV-vis DRS). The results showed that the synthesized SnO2/ZnO nanocomposites possessed mesoporous wurtzite ZnO and cassiterite SnO2 nanocrystallites. The photocatalytic activity of the prepared SnO2/ZnO photocatalyst was investigated by the degradation of methylene blue dye under UV light irradiation. The heterostructure SnO2/ZnO photocatalyst showed much higher photocatalytic activities for the degradation of methylene blue dye than individual SnO2, ZnO nanomaterials and reference commercial TiO2 P25. This higher photocatalytic degradation activity was due to enhanced charge separation and subsequently the suppression of charge recombination in the SnO2/ZnO photocatalyst resulting from band offsets between SnO2 and ZnO. Finally, these heterostructure SnO2/ZnO nanocatalysts were stable and could be recycled several times without any appreciable change in degradation rate constant which opens new avenues toward potential industrial applications.

A novel electrochemical (EC) chlorobenzene (CBZ) sensor was fabricated using a ternary oxide RuO2/ZnO/TiO2 nanocomposite (NC)-decorated glassy carbon electrode (GCE). The nanoparticles (NPs) were synthesized by a wet-chemical method and characterized by X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), and ultraviolet-visible (UV-vis) spectroscopy. The synthesized RuO2/ZnO/TiO2 NC was layered as thin film on a GCE with Nafion (5% suspension in ethanol) adhesive, and the as-prepared sensor was subjected to CBZ analysis using an electrochemical approach. The calibration of the proposed CBZ sensor was executed with a linear relation of current versus concentration of CBZs known as the calibration curve. The sensitivity (32.02 μA μM−1 cm−2) of the CBZ sensor was calculated from the slope of the calibration curve by considering the active surface area of the GCE (0.0316 cm2). The lower detection limit (LD; 98.70 ± 4.90 pM) was also calculated at a signal-to-noise ratio of 3. Besides these, the response current followed a linear relationship with the concentration of chlorobenzene and the linear dynamic range (LDR) was denoted in the range of 0.1 nM to 1.0 μM. Moreover, the CBZ sensor was found to exhibit good reproducibility, reliability, stability, and fast response time. Finally, the sensing mechanism was also discussed with the energy-band theory of ternary doped semiconductor materials. The sensing activity of the proposed sensor was significantly enhanced due to the combined result of depletion layer formation at the heterojunction of RuO2/ZnO/TiO2 NCs as well as the activity of RuO2 NPs as oxidation catalysts. The proposed CBZ sensor probe based on ternary oxide RuO2/ZnO/TiO2 NCs was developed with significant analytical parameters for practical application in monitoring the environmental pollutants of CBZs for the safety of environmental fields on a large scale.

A highly selective chemisensor for 2-nitrophenol detection was fabricated using ZnO/RuO2 nanoparticles (NPs) synthesized by impregnation method. The as-synthesized NPs were characterized through UV-vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), Energy dispersive X-ray spectroscopy (EDS), FTIR and X-ray diffraction (XRD). A glassy carbon electrode was modified with as-synthesized ZnO/RuO2 nanoparticles and utilized as a chemical sensor for the detection of 2-nitrophenol. The fabricated sensor exhibited excellent sensitivity (18.20 μA μM−1 cm−2), good reproducibility, short response time (8.0 s.), the lowest detection limit (52.20 ± 2.60 pM) and long-term stability in aqueous phase without interference effects. Finally, the fabricated sensor was validated as a 2-NP probe in various environmental water samples at room conditions.

Fusion-bonded epoxy-coated steel is expected to extend the service life of the reinforced concrete structure in chloride-laden environments. However, the effect of coating on the bond-strength between rebar and concrete is not well understood yet. This research, therefore, studied the effect of epoxy-coating on the bond characteristics of reinforcing bars in concrete. The bond characteristics were assessed through pullout test considering variables viz. concrete strength, embedded length and bar diameter. The load was applied to reinforcing bars embedded in concrete until bond strength between the bar and concrete exceeded. Bond strength of epoxy-coated bars was compared with that of the uncoated bars. It was found that epoxy-coating reduced the bond strength approximately 25% for Ø20mm bar and 12% for Ø16mm and Ø12mm bar. As with uncoated bar, bond strength of coated bars were also increased with concrete strength. However, the bond strength ratio between coated and uncoated bars was found almost independent of concrete strength. Based on the test results, a development length modification factor of 1.33 is proposed for Ø20mm bar and 1.15 for Ø12mm and Ø16mm bar to compensate the bond strength reduction due to the epoxy coating.

A detailed steady-state equilibrium–based simulation model was developed in Aspen Plus to demonstrate the CO2-gasification process of cow manure-derived hydrochar. Simulation was performed at gasification temperature of 700–1000 °C and equivalence ratio of 0.1–0.6 for HTC treatment temperatures between 180 and 260 °C. Various simulation outputs including gas yield, syngas composition, lower heating value, CO/CO2 conversion efficiency, H2/CO ratio, and cold gas efficiency were evaluated. Simulation results revealed that CO concentration was increased with gasification temperature while H2 concentration was initially increased until 950 °C and decreased afterwards. H2 concentration was also decreased with the increasing equivalence ratio. However, CO concentration increased initially but started to decrease after equivalence ratio of 0.3. Gasification temperature of 850 °C and equivalence ratio of 0.3 resulted in the maximum concentrations of both CO and H2 and lower heating value. Replacing CO2 with air increased the lower heating value as the concentration of H2 was increased compared to the concentration of CO.

Perovskite solar cells (PSCs) have emerged as a promising photovoltaic technology on the lab scale due to their high power conversion efficiency, simple device fabrication, all solid-state structure and the possibility to integrate traditional devices into fiber format. In this work, a three-dimensional (3D) perovskite solar cell is demonstrated using functionalized carbon nanotube (CNT) yarn as both the cathode and anode material. TiO2 and 2,2,7,-7-tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene (Spiro-OMeTAD) are used as the electron transporting and hole transporting material respectively. The TiO2 oxide layer is deposited on the top of the twisted carbon nanotube yarn and annealed with TiCl4 to generate the uniform electron transport layer. A dip coating process is employed to produce a uniform perovskite layer on top of the TiO2 oxide layer. Platinized carbon nanotube yarn is wrapped around on the top of the hole transporting layer and serves as the counter electrode. The photovoltaic characterization of the prepared cells was carried out at different cell lengths. Under AM 1.5 (100 mW cm−2) illumination it shows an enhanced power conversion efficiency (PCE) with a high open current voltage (VOC) of 0.825 V. This three-dimensional all solid-state perovskite solar cell shows a promising prospect in portable and wearable textile electronics.

A series of rare earth Y3+ ion substituted Co-Zn ferrites Co0.5Zn0.5YxFe2-xO4 (x = 0.00 to 0.08 in step of 0.02) have been synthesized by conventional double sintering technique from the oxide powders of Co, Zn, Fe, and Y. The XRD, FESEM, EDS, DC resistivity, dielectric measurements, VSM, and Curie temperature (Tc) analysis have been used to investigate structural, morphological, electrical, and magnetic properties. Single phase of cubic spinel structure has been confirmed up to x 0.06. The lattice parameter initially decreases than increases with yttrium concentrations. The FESEM image shows that the grains and grain boundaries are distinct and uniformly distributed and the purity has also been endorsed from the EDS spectra. The average grain size decreases at x = 0.02 and then increases with Y substitution. The long range mobility of charge carriers and presence of localized charge carriers with retreat from the Debye-like behavior in the compositions have been explored using electric modulus and impedance. The magnetic strength diminishes owing to existence of magnetic dilution in the A-B interactions subsequent to the Tc declines with the x contents. The value of saturation magnetization decreases with increasing Y3+ contents that indicates that the domain wall motion become tougher due to substitution of foreign ions Y3+ that possess larger ionic radius. Therefore, the Y3+ substituted Co0.5Zn0.5YxFe2-xO4 (x = 0.00 to 0.08 in step of 0.02) ferrites with high resistivity and low losses has implications to be used in high frequency and power supply devices applications.

In this article, we report the elastic, electronic, optical and thermoelectric properties of recently synthesized K2Cu2GeS4 chalcogenide. The structural parameters are found to be in good agreement with experimental results. The calculated single crystal elastic constants (Cij) show that K2Cu2GeS4 is mechanically stable. The investigated electronic band structures reveal semiconducting characteristics and are consistent with experiment. Important optical constants such as dielectric constants, refractive index, absorption coefficient, photoconductivity, reflectivity and loss function are calculated and discussed in detail. Optical conductivity is found to be in good qualitative agreement with the results of band structure calculations. The Seebeck coefficients for TB-mBJ potential within the studied temperature range vary from ∼450 to ∼200 μV/K. The anisotropic electrical conductivity and electronic thermal conductivity are observed in the layered structured K2Cu2GeS4. The power factor and electronic thermal conductivity at 800 K along xx-axis using TB-mBJ potential are found to be ∼6 μWcm−1K−2 and 0.578 Wm−1K−1, respectively and the corresponding thermoelectric figure of merit is 0.81. The obtained results predict that K2Cu2GeS4 is a promising material in thermoelectric device applications.

Citrus macroptera is a citrus fruit locally known as Shatkora and the fruit of this plant were used for various purposes especially for cooking and also as an odorant in perfume industries.In this research work, Shatkora peel was dried using a laboratory scale tray dryer. The experimental work was conducted at an inlet temperature of 40–60°C and velocities from 0.5–0.9 m/s. Besides, the thickness of the layer was varied between 2– 10 mm. The results demonstrated that the rate of drying was increased accordingly with rise in both air temperature and air velocity however a decreased in layer thickness was noticed. At high air temperature, moisture content of solid achieved equilibrium state within short period of time. On the other hand, moisture diffusivity of Shatkora was evaluated by applying Fick’s second law and the value was varied from 1.78 × 10-8 to 2.83 × 10-7. In addition, activation energy was determined by using Arrhenius type relation and 19.70 kJ/mol was obtained.

The development of piezoelectric materials has been an important topic within the ever-growing field of energy harvesting technologies. With recent advances, nanostructured piezoelectric nanogenerators have become a state-of-the-art technology for energy scavenging applications. A large variety of devices have been developed in recent decades. The performance of these electromechanical energy transformation devices has been radically increased with the use of nanostructured and novel materials. Metal oxides with perovskite structures and polyvinylidene fluoride (PVDF) are two important substrates paving the way towards enhanced piezoelectric devices in the modern era. Previously, only ferroelectric materials with strong dipole moment had the upper hand in term of electromechanical response. Further, advanced studies have shown that surface activation could lead to an increase of the organized dipole, and thus allow for avoidance of poling. This review summarizes recent advanced techniques and improvements of energy generation through this electromechanical piezoelectric system. Classification of multi-dimensional piezoelectric material based nanogenerators has also been briefly addressed.

Nanofluids have various operations and prospects in heat transfer engineering to produce novel technological equipment for cooling purposes. In response to nanofluid's possible application, the transient convective alumina-water nanofluid flow in a square vessel in the presence of magnetic field and exothermic chemical reaction has been numerically investigated. We consider a square vessel, where the lower boundary of the vessel is heated, the two vertical side walls are relatively cold, and the upper wall is insulated. The finite element method based on Galerkin scheme is used to solve the governing partial differential equations along the imposing boundary conditions. We verified the present results with the standard experimental published results. The flow and thermal forms, and local Nusselt number are investigated for the numerous appropriate parameters. The time effects on the heat transfer is examined. The result shows that as the Rayleigh number increased from 105 to 106, the heat transfer increased by 72.78%. Compared with the base fluid water, the heat transfer of the alumina-water nanofluid with a nanoparticle volume fraction of 6% increased by 10.42%. The magnetic field and the Arrhenius chemical reaction parameters regulates the nanofluid flow and the heat transfer.

Ultra-wide bandgap (~ 4.8 eV) beta phase gallium oxide (β-Ga2O3) grown by metal organic chemical vapor deposition (MOCVD) has demonstrated promising electronic transport properties with room temperature electron mobilities reaching 194 cm2/V-s and background doping as low as 9×1014 cm-3 [Zeng et al, Appl. Phys. Lett. 114, 250601 (2019)]. Commensurate with these values is a total trap concentration that is ~10x lower, with a different distribution of states throughout the bandgap than what has been observed for β-Ga2O3 grown by other methods [Zhang et al., Appl. Phys. Lett. 108, 052105 (2016), Farzana et al, Appl. Phys. Lett. 123, 161410 (2018)]. Given the promise of MOCVD-grown β-Ga2O3, a deeper understanding of the nature of defects in this material is of interest. This work provides a comprehensive picture of the current state of knowledge regarding deep levels in MOCVD-grown β-Ga2O3, including trapping properties, energy and concentration distributions in the bandgap, potential physical sources, and comparisons with other growth methods. By applying a suite of complementary defect spectroscopy methods-deep level optical spectroscopy, deep level transient spectroscopy, and admittance spectroscopy, quantitative characterization of defect states within the ~ 4.8 eV bandgap is possible. We find that, through systematically varying growth conditions, differing trends in concentrations for individual states are observed, implying that growth optimization is possible. Combined with observations made after high energy particle irradiation, we can differentiate between states of intrinsic and extrinsic origin.

This electrochemical study performed to develop a cholesterol sensor using a glassy carbon electrode (GCE) coating with ternary low-dimensional ZnO/SnO2/RuO2 nanomaterials (NMs). The ZnO/SnO2/RuO2 NMs characterized using FESEM, XPS, EDS and XRD analysis. The desired cholesterol sensor fabricated by coating a GCE with ZnO/SnO2/RuO2 NMs as a film of the thin-layer using suspension of ethanol with 5% Nafion binder, which performed to the analysis of cholesterol electrochemically in the phosphate buffer phase. The resulted electrochemical responses have exhibited the linearity from 0.1nM ~ 0.01mM of cholesterol in current versus concentration plot, which defined as a calibration curve of this sensor development. The linear concentration (0.1nM ~ 0.01mM) of cholesterol corresponding with the current response is known as the dynamic range (LDR) for detection of target analyte. The sensitivity is calculated from the slope of calibration-curve found as 11.3513 µAµM− 1cm− 2. The lower limit of detection (91.42 ± 4.57 pM) is obtained from signal/noise (S/N = 3) at 3. In the real-samples detection process, the fabricated cholesterol sensor is exhibited good reproducibility, fast response time and ability to perform in long-duration of sensor elapse time. In the end, this method is shown the reliable detection of cholesterol in the buffer phase and would be very perspective in the recent future in-term of a simple as well as reliable technique in the field of pathological diagnosis.

The 4-NPHyd (4-nitrophenylhydrazine) electrochemical sensor assembled using wet-chemically prepared ZnO/SnO2 nanoparticle (NPs) decorated a glassy carbon electrode (GCE) with conductive Nafion binder. The synthesized NPs characterized by XPS, ESEM, EDS, and XRD analysis. The calibration of the proposed sensor obtained from current versus concentration of 4-NPHyd found linear over a concentration (0.1nM~0.01mM) of 4-NPHyd, which denoted as the dynamic range (LDR) for detection of 4-NPHyd. The 4-NPHyd sensor sensitivity calculated using the LDR slope considering the active surface of GCE (0.0316 cm2), which is equal to be 7.6930 µAµM-1cm-2, an appreciable value. The detection limit (LOD) at signal/noise (S/N=3) estimated, and outstanding lower value at 94.63±4.73 pM perceived. The analytical parameters such as reproducibility, long-term performing ability and response time are found as appreciable. Finally, the projected sensor shows exceptional performances in the detection of 4-NPHyd in environmental samples.

In this work, a fully integrated active microfluidic device transforming a conventional 96-well kit into point-of-care testing (POCT) device was implemented to improve the performance of traditional enzyme-linked immunosorbent assay (ELISA). ELISA test by the conventional method often requires the collection of 96 samples for its operation as well as longer incubation time from hours to overnight, whereas our proposed device conducts ELISA immediately individualizing a 96-well for individual patients. To do that, a programmable and disposable on-chip pump and valve were integrated on the device for precise control and actuation of microfluidic reagents, which regulated a reaction time and reagent volume to support the optimized protocols of ELISA. Due to the on-chip pump and valve, ELISA could be executed with reduced consumption of reagents and shortening the assay time, which are crucial for conventional ELISA using 96-well microplate. To demonstrate highly sensitive detection and easy-to-use operation, this unconventional device was successfully applied for the quantification of cardiac troponin I (cTnI) of 4.88 pg/mL using a minimum sample volume of 30 µL with a shorter assay time of 15 min for each ELISA step. The limit of detection (LOD) thus obtained was significantly improved than the conventional 96-well platform.

In this paper, we demonstrated large-size free-standing single-crystal β-Ga2O3 NMs fabricated by the hydrogen implantation and lift-off process directly from MOCVD grown β-Ga2O3 epifilms on native substrates. The optimum implantation conditions were simulated with a Monte-Carlo simulation method to obtain a high hydrogen concentration with a narrow ion distribution at the desired depth. Two as grown β-Ga2O3 samples with different orientations ([100] and [001]) were used to successfully create 1.2 μm thick β-Ga2O3 NMs without any physical damage. These β-Ga2O3 NMs were then transfer-printed onto rigid and flexible substrates such as SiC and polyimide substrates. Various material characterization studies were performed to investigate their crystal quality, surface morphologies, optical properties, mechanical properties, and bandgaps before and after the lift-off and revealed that the good material quality was maintained. This result offers several benefits in that the thickness, doping, and size of β-Ga2O3 NMs can be fully controlled. Moreover, more advanced β-Ga2O3-based NM structures such as (AlxGa1−x)2O3/Ga2O3 heterostructure NMs can be directly created from their bulk epitaxy substrates; thus this study provides a viable route for the realization of high performance β-Ga2O3 NM-based electronics and optoelectronics that can be built on various substrates and platforms.

Yb-substituted Ni0.5Zn0.5YbxFe2−xO4 (0 ≤ x ≤ 0.20 in the step of 0.04) ferrites have been synthesized using sol–gel auto combustion method. The structural characterization of the compositions has been performed by X-ray diffraction (XRD) analysis, field emission scanning electron microscopy (FESEM), quantum design physical properties measurement system (PPMS) that ensured the formation of single phase cubic spinel structure. Crystallite and average grain size are calculated and found to decrease with increasing Yb3+ contents. Saturation magnetization (Ms) and Bohr magnetic moment (µB) decrease while the coercivity increases with the increase in Yb3+ contents and successfully explained by the Neel’s collinear two sub-lattice model and critical size effect, respectively. Critical particle size has been estimated at 6.4 nm from the DXRD vs. Ms, Hc plot, the transition point between single domain regime (below the critical size) and multi-domain regime (beyond the critical size). Curie temperature (Tc) reduces due to the weakening of A–O–B super exchange interaction and redistribution of cations, confirmed by the M–T graph. The compositions retain ferromagnetic ordered structured below Tc and above Tc, it becomes paramagnetic, making them plausible candidates for high temperature magnetic device applications. The relative quality factor (RQF) peak is obtained at a very high frequency (≥ 108 MHz), indicating the compositions could also be applicable for high frequency magnetic device applications.

We have used density functional theory to study the recently predicted MAX phase borides Hf2AB (A = Pb, Bi) in where the mechanical, electronic, thermal, and optical properties have been investigated for the first time. A good agreement of the obtained lattice constants with the reported values confirmed the well accuracy of the present calculations. The stiffness constants (Cij) attest to the mechanical stability of all title compounds. The mechanical behaviors have been scrutinized discreetly by considering the bulk modulus, shear modulus, Youngs modulus, as well as hardness parameters. The brittle nature of Hf2AB (A = Pb, Bi) borides has also been confirmed. The electronic band structure and density of states (DOS) revealed the metallic behavior of the titled materials. The anisotropy in electrical conductivity has been disclosed by considering the energy dispersion along different directions. The variation of Vickers hardness is explained in terms of the total DOS of Hf2AB (A = Pb, Bi). The anisotropic nature of the mechanical properties of the phases has also been studied. The technologically important parameters (Debye temperature, minimum thermal conductivity, and Gr\"uneisen parameter) have also been used to evaluate the thermal behaviors of the titled materials. The possibility of Hf2AB (A = Pb, Bi) for use as coating materials has been assessed by studying the reflectivity., Comment: 28 pages

Over the years, nanogenerators for health monitoring have become more and more attractive as they provide a cost-effective and continuous way to successfully measure vital signs, physiological status, and environmental changes in/around a person. Using such sensors can positively affect the way healthcare workers diagnose and prevent life-threatening conditions. Recently, the dual piezo-tribological effect of hybrid nanogenerators (HBNGs) have become a subject of investigation, as they can provide a substantial amount of data, which is significant for healthcare. However, real-life exploitation of these HBNGs in health monitoring is still marginal. This review covers piezo-tribo dual-effect HBNGs that are used as sensors to measure the different movements and changes in the human body such as blood circulation, respiration, and muscle contractions. Piezo-tribo dual-effect HBNGs are applicable within various healthcare settings as a means of powering noninvasive sensors, providing the capability of constant patient monitoring without interfering with the range of motion or comfort of the user. This review also intends to suggest future improvements in HBNGs. These include incorporating surface modification techniques, utilizing nanowires, nanoparticle technologies, and other means of chemical surface modifications. These improvements can contribute significantly in terms of the electrical output of the HBNGs and can enhance their prospects of applications in the field of health monitoring, as well as various in vitro/in vivo biomedical applications. While a promising option, improved HBNGs are still lacking. This review also discusses the technical issue which has prevented so far, the real use of these sensors.

In diffuse optical tomography (DOT) and spectroscopy (DOS) using handheld probes, tissue curvature can cause bad fiber-to-tissue contact. Understanding and minimizing image artifacts caused by these coupling errors would significantly improve DOT and DOS image quality. In this work, we utilized Monte Carlo simulations and experiments with gelatin-Intralipid phantoms to systematically study the influence of source or detector (optode) coupling errors. Optode coupling errors can increase the amplitude and decrease the phase of the measured diffuse reflectance, creating artifacts in the reconstructed absorption maps, such as hot spots on the edges. We propose an outlier removal algorithm that can correct these image artifacts, and we demonstrate its performance using simulations, phantom experiments, and breast patient data acquired with bad probe contact due to a dense or small breast. Further, we designed and implemented a new resistance-type thin-film force sensor array that provides real-time optode coupling feedback and guides the outlier removal to minimize optode coupling errors. Our approaches and study results have significant implications for reducing image artifacts arising from handheld probes, which are commonly used with mobile and wearable DOT and DOS devices.

This paper details the novel design, simulation and analysis of the digital photonic positive edge-triggered JK flip-flop using silicon micro-ring resonator as its core component. The designed silicon micro-ring resonator uses free carrier plasma dispersion electro-optic effect properties in its ring waveguide being structured as a PIN diode. There are altogether four silicon micro-ring resonators used in our proposed design, with each ring operates as specific logic mode operation. Time varying simulation have also been carried out, where two predetermined inputs for both J and K inputs, with a clock signal for CLK input, was injected into the circuit with the data rate of 1 Gbps. Its output is observed via multi-channel oscilloscope, where results are obtained with the simulation data sampling rate of 1.6 THz.

The present study was attempted to develop a suitable method for determining dissolving pulp properties such as pentosan, α-cellulose, R10, R18, viscosity, and brightness. In this study, properties are quantified first with wet chemical methods. Then, spectroscopic data of the samples were collected after running them through UV spectrophotomer and Fourier transformed-near infrared (FT-NIR) spectrophotometer. Spectroscopic data from both the instruments were pretreated with normalization, baseline correction, smoothing, Standard Normal Variate (SNV), Savitzky-Golay (S-G) smoothing with their first and second derivatives, and their combinations. Predictive models were calibrated with raw data and pretreated data from both the instruments. Results show that PLSR produce better predictive efficiency than PCR both with UV and FT-NIR data of their raw and pretreated form. In dissolving pulp, α-cellulose and R10 could be quantified with UV data treated by smoothing with moving average and S-G (first derivative) (R2 ≈ 99%) and baseline correction and smoothing with moving average (R2 ≈ 96%). Brightness could be determined with PLSR with FT-NIR raw data (R2 ≈ 92%). For R18 and viscosity, PLSR could be used FT-NIR data treated by baseline correction and smoothing with moving average (R2 ≈ 75%) and baseline correction and normalization (R2 ≈ 68%). The proposed chemometric method with pretreated spectroscopic data is a simple, rapid, and cost effective technique to determine properties of dissolving pulp.

Development of platinum group metal (PGM)-free catalysts for oxygen reduction reaction (ORR) is essential for affordable proton exchange membrane fuel cells. Herein, a new type of atomically dispersed Co doped carbon catalyst with a core–shell structure has been developed via a surfactant-assisted metal–organic framework approach. The cohesive interactions between the selected surfactant and the Co-doped zeolitic imidazolate framework (ZIF-8) nanocrystals lead to a unique confinement effect. During the thermal activation, this confinement effect suppressed the agglomeration of Co atomic sites and mitigated the collapse of internal microporous structures of ZIF-8. Among the studied surfactants, Pluronic F127 block copolymer led to the greatest performance gains with a doubling of the active site density relative to that of the surfactant-free catalyst. According to density functional theory calculations, unlike other Co catalysts, this new atomically dispersed Co–N–C@F127 catalyst is believed to contain substantial CoN2+2 sites, which are active and thermodynamically favorable for the four-electron ORR pathway. The Co–N–C@F127 catalyst exhibits an unprecedented ORR activity with a half-wave potential (E1/2) of 0.84 V (vs. RHE) as well as enhanced stability in the corrosive acidic media. It also demonstrated high initial performance with a power density of 0.87 W cm−2 along with encouraging durability in H2–O2 fuel cells. The atomically dispersed Co site catalyst approaches that of the Fe–N–C catalyst and represents the highest reported PGM-free and Fe-free catalyst performance.

Image contrast recovery coefficient (CRC) of a large ring PET scanner “macroPET” was studied with septa and without septa configuration by ac-quiring data from a laboratory made 35.7 cm square phantom filled with 18-F. Images were reconstructed with simple 2D filtered back projection using Hann, Hamming and Parsen filters with different cut-off frequencies aiming to investigate the influence of filter and cut-off frequency on image contrast with septa and without septa mode. Results indicate that the CRC, for both hot and cold lesions, is excellent for diameters ≥ 3 cm using cut-off frequencies > 0.4. For a 2 cm hot lesion CRC is around 0.8 to 0.9. CRC for 1 cm hot and cold lesions is ~0.3, as expected. There is surprisingly little difference between results with and without septa. For hot lesions, septa appear to improve CRC slightly, but for cold lesions CRC is slightly poorer using septa.

One of the challenges of quantitative Photoacoustic (PA) imaging is unmixing the optical absorption (μa) of the tissue from system response (C) and Gruneisen parameter (Γ). In this study, we have calculated the absorption coefficient and functional parameters, i.e. total hemoglobin (tHb) and oxygen saturation (sO2) of 5 blood tubes with sO2 values ranging from 24.9% to 97.6% at different depths in intralipid solution. Beer’s law is used to calculate the optical fluence in the target area. Initial values for μa and C×Γ are found by fitting a line to the log of PA beam data. These initial values are iteratively updated using a conjugate gradient method. This process is repeated for all 11 wavelengths. The absorption coefficient spectrum follows the molar extinction coefficient spectrum of deoxy hemoglobin for lower sO2 percentages, and it becomes closer to the spectrum of oxy hemoglobin when the sO2 percentage increases. The calculated absorption coefficients at 11 wavelengths are used to estimate the absolute value of the tHb and sO2 of each blood sample at different depths. The mean error of the estimated tHb values for blood tubes at all depths with respect to the real values are less than 13%. Moreover, the largest sO2 estimation error is 7.5% for the blood sample with sO2 of 24.9%. Our quantitative PA method performed well for the data collected from blood samples. We are investigating this method on our clinical data.