Showing papers in "Applied Physics A in 2020"

Investigation of barium borate glasses for radiation shielding applications

Abstract: In this paper, five barium borate glasses in the chemical composition of $$40\hbox {SiO}_2$$–$$10\hbox {B}_2\hbox {O}_3$$–xBaO–(45-x)CaO–yZnO–zMgO (where $$x = 0, 10, 20, 30$$, and 35 mol$${y}=z=6\,\hbox { mol}\%$$) have been reported for radiation protection applications. Mass attenuation coefficient ($$\mu /\rho$$) was obtained in the photon energy range of 356 keV–2.51 MeV using PHITS code for the proposed glasses. The $$\mu /\rho$$ values generated by PHITS code were verified by using both of FLUKA code and XCOM program. The $$\mu /\rho$$ values were then applied to derive effective atomic number ($${Z}_\mathrm{eff}$$), mean free path (MFP), and half value layer (HVL) for all the glasses involved. Additionally, the fast neutron removal cross sections were calculated for each glass. The results reveal that gamma-shielding properties evolve upon adding BaO content in the glasses. It is found that SBC-B35 glass has superior shielding capacity against gamma rays and fast neutrons as compared with different conventional shielding materials and commercial glasses.

Irradiation induced modification of structural and optical properties of potassium sodium niobate thin films

Abstract: In the present study, the effects of swift heavy ion induced modification on the structural, morphological and optical properties of potassium sodium niobate (KNN) thin films have been investigated. KNN thin films were deposited using RF magnetron sputtering onto Si and quartz substrates. Subsequently, as-deposited films were annealed at 700 °C in air ambience for crystallization. Eventually, these crystalline films were irradiated using 100 MeV Ag ions at various fluences ranging from 1 × 1012 to 1 × 1013 ions/cm2. The crystalline and irradiated films were characterized using various techniques such as X-ray diffraction (XRD), atomic force microscopy (AFM), Raman spectroscopy, and UV–Vis spectroscopy. XRD results reveal that the crystallinity of films decreases drastically upon irradiation and almost disappeared at 1 × 1013 ions/cm2. Raman spectra show the different vibration modes of NbO6 octahedra. Raman peaks intensity is decreased and the peaks get broadened due to irradiation which indicates the amorphous nature of films. Variation in surface morphology and roughness of films before and after irradiation is studied using AFM. The minimum value of roughness is observed at 5 × 1012 ions/cm2. Ion beam irradiation results in the variation of transmittance and optical band gap of the films. The optical band gap of crystalline KNN film is found to be 3.82 eV which decreased to 3.72 eV upon irradiation at 5 × 1012 ions/cm2. The monotonous decrease in the refractive index and packing density of films is also observed with ion fluence.

Oxyfluoro-tellurite-zinc glasses and the nuclear-shielding ability under the substitution of AlF 3 by ZnO

Abstract: This paper examines radiation-shielding abilities of oxyfluoro-tellurite-zinc glasses in the chemical form of AlF3–TeO2–ZnO under the substitution of AlF3 by ZnO. Gamma-ray- and neutron-shielding properties were tested in terms of mass attenuation coefficient (μ/ρ), half value layer, mean free path, effective atomic numbers (Zeff), effective electron density (Neff) and removal cross-section (ΣR). The μ/ρ values of the glasses were generated by Geant4 simulations over an extended energy range and then the generated data were confirmed via XCOM software. The results showed that both gamma-ray- and neutron-shielding efficiencies of the selected glasses evolved by substituting of AlF3 by ZnO. Nuclear radiation-shielding abilities of the current glass systems were compared with that of some conventional shielding materials and newly developed HMO glasses. It can be concluded that oxyfluoro-tellurite-zinc glasses could be useful to design novel shields for radiation protection applications.

Engineering the optical properties of PVA/PVP polymeric blend in situ using tin sulfide for optoelectronics

Abstract: In the present work, the optical properties of polyvinyl alcohol (PVA)/polyvinyl pyrrolidone (PVP) (1:1) polymeric blend have been tuned in situ using tin sulfide (SnS) semiconductor for optoelectronics. The solution casting technique was used to prepare plain PVA/PVP polymeric blend and different weight ratios percentages (x: 0, 0.1, 0.5, 1.0, 5.0 and 10.0 wt%) of SnS filled PVA/PVP polymeric blend nanocomposite films. The prepared films were characterized using a scanning electron microscope, X-ray diffractometer, FT-IR spectroscopic technique and UV–visible–NIR spectrophotometer. The effect of SnS concentration on the optical parameters (optical energy gap, refractive index, optical conductivity, dielectric constants, dispersion energy and average oscillator strength) has been investigated. The ability to tune the optical parameters of the prepared SnS nanocomposite polymeric blend films makes them effective candidates in many applications especially optoelectronics and optical devices.

Investigation of the physical properties of the equiatomic quaternary Heusler alloy CoYCrZ (Z = Si and Ge): a DFT study

Abstract: In this manuscript, we investigate the physical properties such as the magnetic and the electronic properties of the Co-based equiatomic quaternary Heusler alloy CoYCrZ (Z = Si and Ge). These investigations have been performed by employing the Quantum Espresso code in the framework of density functional theory (DFT). The generalized gradient approximation (GGA) of Perdew–Burke–Ernzerhof (PBE) is used for all these calculations. The band structures, and density of states calculations, show that all these materials CoYCrZ (Z = Si and Ge) exhibit a half-metallic (HM) behavior only for the structure type II. Moreover, this structure type II is found to be the most stable configuration for all these alloys. On the other hand, it has been found that the Slater–Pauling is well described for the compound CoYCrGe, only for the configuration type II. In particular, the equiatomic quaternary Heusler alloys CoYCrSi and CoYCrGe are found to be half-metallic for the structure type II. This is due to the fact that they have 100% spin polarization SP. Also, the existence of complete SP in the studied alloys is the reason for which these materials are useful for spintronic device applications.

Physical, optical and shielding features of Li 2 O–B 2 O 3 –MgO–Er 2 O 3 glasses co-doped of Sm 2 O 3

Abstract: The glassy systems acquired much concern for using in diverse implementations. For this cause, different concentrations of samarium oxide co-doped lithium magnesium borate erbium oxide were prepared by the melt-quench technique. Several physical and optical properties of all prepared glass samples were computed. XRD patterns for all prepared samples show the presence of a broad peak and the lack of sharp peaks emphasize the amorphous nature of all prepared glass samples. FTIR confirms the presence of the functional group BO3 and BO4. Ten considerable absorption bands are evident in the UV–Vis–NIR spectra of the S0 glass sample which are attributed to the presence of Er3+ ions. S1–S4 samples revealed additional six peaks that are attributed to Sm3+ ions. In addition, photon and neutron shielding features were evaluated for all prepared samples which enhanced by the increment of Sm3+ contents. In conclusion, the studied glass composition can be useful in several applications such as solid-state laser, telecommunication, and radiation shielding.

Mechanical and radiation-shielding properties of B 2 O 3 –P 2 O 5 –Li 2 O–MoO 3 glasses

Abstract: Amassed borophosphate lithium molybdate samples were synthesized by the melting classical technique. To check the conditions of these synthesized glasses, the X-ray diffractometer technique was applied. The density value of these samples was increased as well as the molar volume decreased. The mechanical characteristics were linked with Fourier-transform infrared spectrum results. The addition of MoO3 increases the polymerization degree and changes the basic boring units from BO3 to BO4, increases the polymerization degree of phosphate network and changes the negative non-bridging oxygen to positive charges. Ultrasonic velocities and elastic modulus (experimental and theoretical) are increased. This behaviour is correlated to the substitution of Li–O with Mo–O linkages. Mass attenuation coefficient of the prepared samples decreased with the energy increase and with the addition of MoO3. With the increase in photon energy and MoO3 half value layer, the tenth value layer and the mean free path values increase. Hence, the increase of MoO3 leads to a better attenuation of gamma radiation. Therefore, the glass under investigation had superior characteristics for radiation protection applications.

Multi metal oxide NiO-Fe 2 O 3 -CdO nanocomposite-synthesis, photocatalytic and antibacterial properties

Abstract: Binary NiO-Fe2O3, NiO-CdO nanocomposites, and ternary NiO-Fe2O3-CdO nanocomposite are synthesized using facile co-precipitation method, and their photocatalytic and antibacterial properties are studied. The as-obtained products are characterized using different analytical techniques. The microstructural parameters were calculated using X-ray diffraction data. UV–vis spectra technique was used to calculate the bandgap and listed 3.1, 2.7, and 2.5 eV for NiO-Fe2O3, NiO-CdO, and NiO-Fe2O3-CdO nanocomposite, respectively. The photocatalytic activity of as-obtained products was tested under visible light against methylene blue (MB) dye. The NiO-Fe2O3-CdO nanocomposite has shown higher degradation efficiency as compared to binary nanocomposites and revealed improve electron–hole separation efficiency. The photocatalytic performance of NiO-Fe2O3-CdO nanocomposite was also tested for other synthetic dyes such as rhodamine-B (RhB), methyl orange (MO), and cresol red (CR). The antibacterial performance of grown products was tested against E. coli bacteria. The ternary NiO-Fe2O3-CdO nanocomposite has shown higher antibacterial activity than binary NiO-Fe2O3 and NiO-CdO nanocomposites.

Performance analysis of graphene-based surface plasmon resonance biosensor for blood glucose and gas detection

Abstract: The present study exhibits excellent sensing characteristics of graphene-based prism-coupled surface plasmon resonance (SPR) biosensor for effectual sensing of both glucose concentrations in human blood samples in the range 25–175 mg/dl and gas with refractive index variations from 1.0000 to 1.0007 at a wavelength of 589 nm. The foremost attractiveness of the proposed SPR biosensor lies with excellent optical properties of N-FK51A-based glass prism along with the inclusion of a gold layer and a thin graphene layer. Transfer matrix method and angular interrogation technique are employed to envisage sharp SPR reflectance curves by optimizing the thickness of the gold layer and number of graphene layers. Aside this, an excellent electric field enhancement factor is accomplished near the graphene and sensing layer interface, which dramatically escalates the absorption of glucose and gas analytes. Subsequently, several performance measuring factors such as sensitivity, detection accuracy, resonance angle shift, and quality factor are thoroughly scrutinized and compared with other conventional SPR sensors. Moreover, simulation results reveal some noteworthy upshots like sensitivity of 275.15°/RIU, detection accuracy of 1.41/°, and quality factor of 76.2 that are obtained for glucose analytes, whereas sensitivity of 92.1°/RIU, detection accuracy of 2.55/° and quality factor of 230.2 are attained for gaseous analytes. Interestingly, it is found that the aforementioned parameters fitted excellently with a linear trend line, which leads to accurate investigation of glucose concentration as well as gaseous analytes. Hence the suggested structure opens up an avenue for suitable biomedical application.

Machine learning the magnetocaloric effect in manganites from lattice parameters

Abstract: Efficient solid-state refrigeration techniques have drawn increasing attention due to their potential for improving energy efficiency of refrigeration temperature control systems without using harmful gas as in conventional gas compression techniques. Research on magnetocaloric lanthanum manganites with a large maximum magnetic entropy change near room temperature shows promising results for further developments of magnetic refrigeration devices. By incorporating chemical substitutions, oxygen content modifications, and various synthesis methods, these manganites experience lattice distortions from perovskite cubic structures to pseudocubic, orthorhombic, and rhombohedral structures. Further changes in lattice parameters can also be achieved by the introduction of strain due to lattice mismatches. Empirical results and previous models through thermodynamics and first principles show that changes in lattice parameters correlate with those in MMCE, but correlations are merely general tendencies and obviously not universal. In this work, the Gaussian process regression model is developed as a machine learning tool to find statistical correlations between the MMCE and lattice parameters among lanthanum manganites. More than 100 lattices, cubic, pseudocubic, orthorhombic, and rhombohedral, with the MMCE ranging from 0.65 to $$8.00\,\hbox {J}\,\hbox {kg}^{-1}\,\hbox {K}^{-1}$$ under a field change of 5 T are explored for this purpose. The modeling approach demonstrates a high degree of accuracy and stability, contributing to efficient and low-cost estimations of the magnetocaloric effect. Furthermore, the machine learning algorithm predicts close MMCE results on epitaxial films with strained lattices against experimental results, which can provide guidance on thin film structure design and help understandings of magnetic phase transformations and magnetocaloric effects.

Bio-inspired iron oxide nanoparticles using Psidium guajava aqueous extract for antibacterial activity

Abstract: Bio-inspired synthesis of iron oxide nanoparticles (FeONPs) has been carried out by eco-friendly, low cost, and facile method using an aqueous extract of Psidium guajava (PG) leaf as a potential reducing agent. The obtained FeONPs were characterized using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–visible spectroscopy, Fourier-transform infrared spectroscopy (FTIR), vibrating sample magnetometer (VSM), and energy-dispersive spectroscopy techniques. The surface plasmon resonance peak of FeONPs was found to be 310 nm. The FTIR spectra analysis indicates the presence of various functional groups in PG extract that are responsible for the biosynthesis of FeONPs. The XRD confirmed that FeONPs were indexed into the cubic spinel lattice structure. The SEM and TEM analysis confirmed the spherical morphology of FeONPs with particle size ranging from 1 to 6 nm. The superparamagnetic nature of the formulated FeONPs was determined using VSM. The FeONPs formulated inhibit the growth of six human pathogenic strains with strong activity chiefly against Escherichia coli and Staphylococcus aureus at low concentration when compared to other standard antibacterial drugs. It is noteworthy that the formulated FeONPs are efficient as an antibacterial agent.

Utilization of carbon nanotubes in removal of heavy metals from wastewater: a review of the CNTs’ potential and current challenges

Abstract: Carbon nanotubes-based adsorbents have attracted substantial interest as potential adsorbents for heavy metals removal. However many aspects such as the interaction between the modified carbon nanotubes (CNTs) and the heavy metal ions, quantitative effect of the functional groups and regeneration of CNTs-based adsorbents are not fully understood yet. A critical review was performed to compile an extensive profile from several studies of using pristine and modified CNTs for heavy metals removal. CNTs demonstrated a great potential. However surface modification of CNTs is necessary as pristine CNTs may be ineffective in arsenite [As (III)] or arsenate [As (V)] removal. Isotherms and kinetic models for the removal of heavy metals are discussed in details. A particular focus has been placed on better understanding the mechanism of heavy metals removal using CNTs-based adsorbents, affecting factors, maximum adsorption capacity and regeneration. The effect of adsorbent dose, pH, initial concentration, and contact time were addressed by several researchers, which specifies the consistency and performance of CNTs-based materials as potential adsorbents. To elucidate the mechanism of adsorption, FT-IR, XPS, SEM, TEM and EDX results have been reviewed and discussed. It is found that Langmuir, Freundlich and second order kinetic models are the most frequently used isotherm to describe heavy metals adsorption. CNTs-based adsorbent can be efficiently regenerated.

Microstructural, morphological behavior and removal of Cr(VI) and Se(IV) from aqueous solutions by magnetite nanoparticles/PVA and cellulose acetate nanofibers

Abstract: Different contents of magnetite nanoparticles (MNPs)/graphene (G) nanosheets were incorporated into polyvinyl alcohol (PVA) and cellulose acetate (CA) electrospun nanofibers. The obtained compositions were investigated using XRD, TEM, FTIR and FESEM. The microstructural investigation displayed that nanofibers were formed with diameters around 120 nm up to 900 nm in the case of the composition at 0.1MNPs-G/PVA, while morphological features illustrated that the composition at 0.0MNPs-G/PVA fibers was formed with diameters 0.2 µm up to 0.6 µm, besides G, which was scattered through the fibers with dimensions around 17 µm. The removal efficiency of Se(IV) and Cr(VI) from aqueous solutions was evaluated and the optimum trend was obtained for the composition of 0.05MNPs-G@PVA. The high porous nanofibers may be suggested for more investigations for heavy metal removal.

Experimental studies on the gamma photons-shielding competence of TeO 2 –PbO–BaO–Na 2 O–B 2 O 3 glasses

Abstract: In this work, glass composed of (40 + x) PbO–5 TeO2–15 BaO–(20 − x) Na2O–20 B2O3 (x = 0, 5, 10, 15, and 20 mol%) was prepared via melt-quenching and the gamma-shielding competency was studied. The results showed that the density and molecular weight increased from 5.006 to 7.121 (gcm−3) and 146.579 to 178.823 (g) as Na2O was replaced by PbO. The direct and indirect bandgap energies decreased from 3.512 to 3.357 and 2.791 to 2.525 eV as the lead concentration increased from Pb40Na20–Pb60Na0. We employed the Geant4 simulation code for narrow-beam geometry with a mono-energetic photon beam imposed on a glass specimen. The mass attenuation coefficient (µ/ρ) for the fabricated glass was determined using the Geant4 simulation code. The difference between the theoretical values (XCOM) and simulated values (Geant4) was less than 7%, confirming the accuracy of the present results. The µ/ρ values increased quickly with the increasing PbO content at low photon energies, while increasing the energy reduced the increase of the µ/ρ values. The linear attenuation coefficient (LAC) was also evaluated and the results showed that increasing the density increased the attenuation behavior. The Pb60Na0 sample with the highest density (7.121 g/cm3) had the largest LAC values at all energies (in the range of 0.29–1.69 cm−1). The effective atomic number values of the fabricated samples were in the range of 33–70. Pb60Na0 glass with the lowest half-value layer is a promising candidate for radiation-shielding applications among Pb40Na20–Pb60Na0 glass.

A review on biological and biomimetic materials and their applications

Abstract: In the development of technology, a source of inspiration for mankind is the nature. Naturally, many biological surfaces having unique micro–nanostructures, such as lotus leaves, butterfly wings, rose petals and shark skin, exhibit skills and attribute beyond conventional engineering. These skills and characteristic properties are exploited by several scientists to produce bioinspired materials by mimicking biological materials. Scientists called these materials as biomimetic materials as they are developed by inspiration from nature. For the last few decades, an extensive research has been going on to introduce a wide variety of biomimetic materials which can exhibit advanced properties. This paper gives an overview of recently developed biomimetic materials such as Se-modified carbon nitride nanosheets, small intestinal submucosa, magnesium–strontium hydroxyapatite, dimethylglyoxime–urethane polyurethane, polydimethylsiloxane, Ag/Ag@AgCl/ZnO and PDTC(COOH)4/HA, along with their biological properties. In addition, the applications of the biomimetic and biological materials in various fields such as biomedical, oil–water separation, sensors, tissue engineering, genome technology and ultrasound imaging are also discussed.

B2O3–Bi2O3–TeO2–BaO and TeO2–Bi2O3–BaO glass systems: a comparative assessment of gamma-ray and fast and thermal neutron attenuation aspects

Abstract: For Pb-free 35B2O3‒35Bi2O3‒(30–x)TeO2‒(x)BaO (x = 5, 10, 15, 20, and 25 mol%) and (90–x)TeO2‒10Bi2O3‒(x)BaO (x = 10, 15, and 20 mol%) glass systems, gamma and neutron (both fast and thermal neutron) radiation shielding features were examined and compared. Within 0.015–15 MeV photon energy, mass attenuation coefficients (μ/ρ), for all samples, which have been assessed using WinXCOM program are in fair agreement with deduced MCNP5 simulation code μ/ρ results. For all selected samples, at the lowest energy, μ/ρ has bigger values whereas at higher energy regions possess lower values. Furthermore, by employing μ/ρ values, effective atomic number (Zeff), effective electron density (Neff), half-value layer (HVL), tenth-value layer (TVL), and mean free path (MFP) are figured out for both glass systems. For studied samples, with the gradual replacement of TeO2 content with BaO, the derived values of Zeff, HVL, TVL, and MFP revealed improved γ-ray shielding potentiality. Besides, within photon energy range of 0.015–15 MeV, exposure build-up factors (EBFs) and energy absorption build-up factors (EABFs) were estimated for all samples by utilizing G‒P fitting method as a function of different penetration depths (0.5, 1, 2, 3, 4, 5, 6, 7, 8, 10, 15, 20, 25, 30, 35, and 40 mfp). The 35B2O3–35Bi2O3–5TeO2–25BaO (mol%) glass relatively larger μ/ρ and Zeff values, lower HVL, TVL, and MFP values, and minimal EBF and EABF values confirm its superior γ-ray attenuation competence among all samples. Additionally, in comparison, HVL and MFP values of 35B2O3–35Bi2O3–5TeO2–25BaO (mol%) sample are lower than the respective values of some commercial γ-ray shielding glasses and different types of standard concretes, signifying its better shielding features than them. Moreover, macroscopic removal cross-section for fast neutrons (ΣR), coherent scattering cross-section (σcs), incoherent scattering cross-section (σics), absorption cross-section (σA), and total cross-section (σT) for thermal neutrons absorption were derived for both glass systems. Among all selected glasses, 35B2O3–35Bi2O3–5TeO2–25BaO (mol%) sample possesses relatively higher ΣR (0.106 cm−1) and ‘σT’ (8.809 cm−1 at 0.0253 eV neutron energy) values for fast and thermal neutrons attenuation, respectively, demonstrating its favorable absorption capability for neutrons.

Preparation of high strength graphene reinforced Cu-based nanocomposites via mechanical alloying method: microstructural, mechanical and electrical properties

Abstract: Copper (Cu)-based nanocomposites were produced by mechanical alloying process using various volume percentages of graphene up to 8 vol.%. Subsequently, nanocomposites powders were milled for 20 h, cold-pressed and subjected to different sintering temperatures up to 850 °C for 1 h in argon atmosphere. Furthermore, X-ray diffraction technique along with transmission electron microscopy (TEM) was employed to examine the milled powders. The microstructure, physical, mechanical, electrical properties and wear behavior of the sintered nanocomposites samples were determined also. The obtained TEM micrographs showed homogenous distribution of graphene in Cu matrix and noticed grains refinement. Additionally, it was responsible for measurable decreases in the densification and the electrical conductivity of the sintered bodies. Furthermore, the mechanical properties, on the contrary to work-hardening capacity, of the sintered samples were improved by the increasing in graphene contents and sintering temperatures. The weight loss and wear rate of nanocomposites reduced with both of graphene content and sintering temperature, while increased with increasing in the applied load. Taking all these results into consideration, we can conclude that Cu-graphene nanocomposites are promising candidates for industrial applications.

Influence of ZrO2 on gamma shielding properties of lead borate glasses

Abstract: In this paper, new lead borate glass system in the chemical form of 40B2O3–40PbO–20Li2O3–xZrO2; where x = 0, 0.25, 0.50, 1, and 1.5 mol% has been synthesized. Gamma-ray shielding properties of these glasses have been tested in terms of mass attenuation coefficient (μ/ρ), half value layer (HVL), effective atomic number (Zeff), mean free path (MFP), and exposure build-up factor (EBF). The μ/ρ values of the prepared glasses were generated by FLUKA Monte Carlo simulations over an extended energy range of 0.015–15 MeV, and then, the generated data were verified using the calculated values of XCOM software. The results showed that gamma-ray shielding ability of BPLZ0.00 is superior among the other prepared glasses. Moreover, the gamma-ray shielding properties of the current glass system have been compared with that of some commercial glasses and newly developed HMO glasses. It can be concluded that the prepared glass system could be useful to design and/or develop novel shields for radiation protection applications.

Comparative study on the physical properties of rare-earth-substituted nano-sized CoFe 2 O 4

Abstract: Nanotechnology manufacturing is rapidly developing and promises that the essential changes will have significant commercial and scientific impacts be applicable in an extensive range of areas. In this area, cobalt ferrite nanoparticles have been considered as one of the competitive candidates. The present study is based on the investigation of the effect of rare-earth (RE) incorporation on the physical properties of CoFe2O4. Rare-earth ions doped cobalt ferrites with composition CoRE0.025Fe1.975O4 where RE are Ce, Er and Sm have been synthesized by citrate auto combustion technique. Characterization is achieved using X-Ray diffraction (XRD) technique for structural analysis. The obtained data show that the samples exhibit a single-phase spinel structure. RE is successfully substituted into the spinel lattice without any distortion and it acts as inhibiting agent for grain growth. Room temperature M–H curves exhibit ferrimagnetism behavior with a decrease in saturation magnetization and coercivity indicating these materials can be applicable for magnetic data storage and magneto-recording devices. The electrical conductivity is studied as a function of frequency in the temperature range of 300–700 K. The conduction mechanism is attributed to the hopping mechanism. The Seebeck coefficient S is found to be positive for Ce indicating that Co/Ce ferrite behaves as a p-type semiconductor. While it is fluctuated between positive and negative for Er/Sm-doped samples throughout the studied temperature range. The cobalt doped with Er3+ and Sm3+ exhibits degenerated semiconductor trends at higher temperatures. Such data offer a new opportunity for optimizing and improving the performance of cobalt ferrite where the physical properties are decisive.

Size and shape dependence of optical properties of nanostructures

Abstract: A phenomenological model based on thermodynamical variables is used to analyze the optical properties of nanomaterials. The expression of cohesive energy given by Qi and Wang model is extended to study the variation of the energy band gap, vibrational frequency, and static dielectric constant with size for nanoparticles, nanowires, and nanofilms. The energy bandgap is observed to increase in nanostructures with a reduction in size while the reduction in the vibrational frequency of nanostructures is found with a decrease in size from model calculations. The dielectric constant is also found decreasing with the size reduction of the nanostructure to the nanoscale. As the number of surface atoms changes with change in the shape of the nanomaterial, the shape effect on optical properties is also studied. The size and shape effect are found prominent in nanostructures up to the size limit of approximately 30 nm; however, the effect of size and shape becomes less significant as the size is more than 30 nm. The model predictions are consistent with the available experimental and simulated trend which supports the validity of the model theory.

Evaluation of nuclear radiation shielding competence for ternary Ge–Sb–S chalcogenide glasses

Abstract: Chalcogenide glasses are which include germanium, antimony, and sulfur in its structure. The high physical, dielectric, optical, mechanical, and thermal features of the chalcogenide glasses lead to the occasion to evaluate its radiation shielding characteristics. Gamma ray and neutron shielding parameters were evaluated for five chalcogenide glasses doped with CdCl2 according to the formula 60(GeS2)–(40 − x)Sb2S3–xCdCl2; x = 0, 10, 20, 30, and 40 mol% glasses. The mass attenuation coefficient MAC for chalcogenide glasses was simulated using Monte Carlo simulation code (MCNP-5) in gamma photon energy between 0.015 and 15 MeV. The obtained results showed that the MAC for all studied glasses decreases with insertions of CdCl2. The highest MAC is obtained for GSC glasses without CdCl2 content and varied between 0.037 and 4.706 cm2 g−1, while the lowest MAC achieved for GSC 40 glasses with (40 mol%) CdCl2 and varied between 0.034 and 44.758 cm2 g−1. After that, the simulated MAC for all chalcogenide glasses is compared with those calculated theoretically using XCOM software. Other pivotal gamma ray shielding competences such as half value layer, mean free path and effective atomic number (Zeff), and exposure buildup factor for the chalcogenide glasses were also evaluated via the μ/ρ. Furthermore, the fast neutron removal cross section (ΣR) was also evaluated for chalcogenide glasses. GSC0 possesses the best removal cross section for fast neutron (ƩR = 0.0695 cm−1) among the present chalcogenide glasses.

Gamma shielding and compressive strength analyses of polyester composites reinforced with zinc: an experiment, theoretical, and simulation based study

Abstract: The preparation of materials with high attenuation performance is one of the major issues in the radiation shielding applications. This study is based on the investigation of gamma-shielding performances of various polyester composites reinforced with Zn. Utilizing gamma spectrometer based on HPGe detector, the mass attenuation coefficient (μ/ρ) of the present composites was measured at various photon energies between 59.5–1408 keV. The obtained experimental data were confirmed with those of MCNPX code as well as XCOM program. It is found that the attenuation coefficient values of the studied composites are in good agreement with the results of other approaches at the investigated energies. The best photon-shielding effectiveness was observed in the composite tagged with Zn (10%). The shielding characteristics of composite enhances with the addition of Zn as filler.

Actively tunable terahertz metamaterial with single-band and dual-band switching characteristic

Abstract: We present a design of tunable terahertz (THz) metamaterial (TTM) with single-band and dual-band filtering and switching characteristics. The proposed device is composed of face-to-face split-ring resonator (SRR) and a central bar. By moving the SRRs to change the gap between SRRs and central bar, the free spectrum ranges (FSR) could be bi-directionally broadened 0.14 THz and narrowed 0.19 THz at TE and TM modes, respectively. To control the coplanar moving central bar, the electromagnetic response of TTM device exhibits polarization-dependent characteristic. TTM shows the switching characteristic between single-band to dual-band resonance at TE mode and exhibits resonance-insensitive to the displacement of central bar at TM mode. These results open an avenue to be potentially used for detector, sensor, and switch in the THz-wave applications.

A structural and optical properties of Cu-doped ZnO films prepared by spray pyrolysis

Abstract: Pure and Cu doped ZnO films were grown by ultrasonic spray pyrolysis onto glass substrates at 450 °C for 30 min. This study aims to investigate the influence of Cu doping content [0.02–0.20] on structural, microstructural and optical properties. X-ray diffraction analysis reveals a structural disorder depending on Cu loading besides the appearance of CuO phase. The doping effectiveness is revealed by EDX analysis of the chemical composition of the films. The transmittance shows a decreasing tendency with increasing Cu concentration. The refractive indices increase, whereas the values of forbidden energy gap decrease with the increase in Cu dopant concentration.

Electrical and dielectric properties of Al/(PVP: Zn-TeO 2 )/p-Si heterojunction structures using current-voltage (I-V) and impedance-frequency (Z-f) measurements

Abstract: For the investigation of the influence of (PVP: Zn-TeO2) interphase layer on the electrophysical parameters, Al/p-Si structures with/without (PVP: Zn-TeO2) interlayer grown by spin-coating technique and then these factors were studied by I–V and Z–f measurements. First, the Field Emission Scanning Electron Microscopy (FE-SEM), X-ray Diffraction (XRD), Energy Dispersive X-ray Spectroscopy (EDS), and UV–Vis analyses techniques were performed to investigate the morphology, purity determination, and the optical properties of the nanostructures, respectively. Second, I–V measurements and Z–f were performed at ± 3 and 1.5 V (at 100 Hz–1 MHz), respectively. The values of ideality factor (n), barrier height (BH:ΦB), and series resistance (Rs) of them were obtained using various methods such as thermionic emission, Cheung’s and Norde functions and compared. The energy dependence of surface states (Nss) were extracted from the forward bias I–V measurements by assuming the voltage dependence of BH and n. The frequency-dependence profiles of dielectric constant (e′)/loss (e″), and ac electrical conductivity (σac) were extracted from the Z–f measurements. Experimental results show that (PVP: Zn-TeO2) interlayer leads to an increase in the e′, e″, BH, Rsh, and decrease in Nss. Therefore, Al/(PVP: Zn-TeO2)/p-Si structures can be used as an electronic part in nanoscale instead of MS structures.

Structural, optical and magnetic properties of pure and rare earth-doped NiO nanoparticles

Abstract: Pure and a series of rare earth element (RE) (Er, Sm, Gd, Pr and Y)-doped NiO nanoparticles (NPs) were fabricated by co-precipitation method in the presence of polyvinyl alcohol as a capping agent. X-ray diffraction (XRD) and transmission electron microscope (TEM) techniques were used to investigate the crystal structure and morphology of the prepared samples, respectively. The XRD patterns indicated that all the samples exhibited a single phase of face-centered cubic crystalline structure. TEM images displayed a spherical morphology of weakly agglomerated NPs. Furthermore, the chemical compositions were identified by proton-induced X-ray emission and Rutherford backscattering analysis. The metal oxide (Ni–O) functional group was confirmed by Fourier transform infrared spectroscopy with its observed band varying from 419.3 to 433.3 cm−1, depending on the RE doping element. The optical properties of the RE-doped NiO NPs were studied using UV–Vis absorption and photoluminescence (PL) spectroscopy. A small blueshift was obtained in the optical spectra of the RE-doped samples as compared to the undoped samples, implying an increase in the optical band gap. The study of the room temperature magnetic properties was done using the vibrating sample magnetometer, which revealed the coexistence of antiferromagnetic and weak ferromagnetic ordering in pure and RE3+-doped NiO NPs. The magnetization increased depending on the magnetic moments of RE dopant ions. Also, the origin of the anomalous ferromagnetism in the prepared samples may be mainly related to Ni vacancy defects, which were evinced from the results of PL.

A novel synthesis and characterization of transparent CdS thin films for CdTe/CdS solar cells

Abstract: We demonstrate the direct synthesis of CdS thin films by spin coating method with thiol-amine co-solvents system. Annealing of the films at various temperatures has been performed in the air using simple glass protector. The XRD patterns show a strong peak along (110) plane related to cubic lattice while two weak peaks at (002) and (100) planes indicate the hexagonal symmetry for the CdS thin films. The Raman peak at 305 cm−1 also confirms the formation of crystalline CdS thin films. The FTIR study also reveals the formation of CdS thin films. The SEM images reveal the surface uniformity and homogeneity of the CdS thin films. The EDX results indicate nearly stoichiometric CdS thin films. The optical band gap of CdS thin films is ~ 2.4 eV when coated at 2000 rpm and annealed at 300 °C for 5 min. These findings indicate that synthesized CdS films are potential candidates for solution-processed CdTe/CdS solar cells.

Li2O–B2O3–Bi2O3 glasses: gamma-rays and neutrons attenuation study using ParShield/WinXCOM program and Geant4 and Penelope codes

Abstract: For 25 Li2O–(75 − x) B2O3–x Bi2O3 (where x = 0, 5, 10, 15, 20, 25, 30, 35, and 40 mol%) glasses, gamma-ray and neutrons attenuation features were explored by theoretical approach using ParShield/WinXCOM program, Geant4, and Penelope codes. At 133Ba (276, 303, 356, and 384 keV), 22Na (511 and 1280 keV), 137Cs (662 keV), 54Mn (835 keV), and 60Co (1170 and 1330 keV) photon peaks, for all samples, mass attenuation coefficient (μ/ρ), effective atomic number (Zeff), effective electron density (Neff), half-value layer (HVL), and mean free path (MFP) parameters have been evaluated using ParShield/WinXCOM program. The μ/ρ values computed by WinXCOM, Geant4, and Penelope codes were compared to check the accuracy, and satisfactory agreement among the values was identified. Moreover, using G–P fitting method as a function of penetration depth (1, 5, 10, 15, 20, 25, 30, 35, and 40 mfp) within the photon energy range of 0.015–15 MeV, exposure buildup factor (EBF) and energy absorption buildup factor (EABF) were derived. For all selected glasses, the effectiveness of the neutrons attenuation has been discussed in terms of macroscopic effective removal cross-section (ΣR), coherent scattering cross-section (σcs), incoherent scattering cross-section (σics), absorption cross-section (σA), and total neutron cross-section (σT). The ‘σT’ values have been calculated within 10−4–10−8 MeV neutron energy range using the Geant4 code. The μ/ρ possessed larger values at the lowest energy and lower values at higher energy regions for all studied glasses. The μ/ρ, Zeff, HVL, and MFP values showed enhanced γ-ray shielding capability with Bi2O3 content increment in the samples. The 25 Li2O–35 B2O3–40 Bi2O3 (mol%) sample by having larger Zeq and/or Zeff value, faired lower EBF and EABF values. Largest μ/ρ and Zeff, and minimal HVL, MFP, EBF, and EABF values of 25 Li2O–35 B2O3–40 Bi2O3 (mol%) glass demonstrated its superior γ-ray attenuation ability among all examined glasses. Further, among all glasses, 25 Li2O–75 B2O3 (mol%) sample exhibits relatively higher ΣR (0.11326 cm−1) and ‘σT’ (46.109 cm−1 → 0.84607 cm−1 from 1 × 10−8 MeV → 1×10−4 MeV neutron energy) values for fast and thermal neutrons attenuation, respectively, indicating its better neutrons absorption competence.

Modern scaffolding strategies based on naturally pre-fabricated 3D biomaterials of poriferan origin

Abstract: Modern scaffolding strategies include two key ways: to produce requested 3D constructs from corresponding precursors using technological tools, or simply use naturally already pre-fabricated scaffolds if they originate from renewable sources. Marine sponges inhabit oceans since the Precambrian. These ancient multicellular organisms possess a broad variety of evolutionary approved and ready to use skeletal structures, which seem to be well applicable as 3D scaffolds in diverse fields of modern bioinspired materials science, biomimetics and regenerative medicine. In this review, most attention is paid to biosilica-, chitin-, and spongin-based scaffolds of poriferan origin with respect to their potential use.

Sol–gel synthesis and physical characterization of high impact polystyrene nanocomposites based on Fe 2 O 3 doped with ZnO

Abstract: Manufacturing of organic–inorganic composites with enhanced properties particularly, Fe2O3–ZnO/high impact polystyrene (HIPS) nanocomposites promising candidates for many requests. The presence of nanoparticles enhances the structural, thermal, and chemical stabilities, mechanical and operational performance of the nanocomposite matrices. Modified HIPS nanocomposites based on Fe2O3 doped by (0.0–0.6) ZnO were synthesized using the sol–gel method and gel casting approach. The structures, spectroscopic, dielectric and mechanical properties of the synthesized polymeric nanocomposites were investigated by XRD, TEM, FT-IR, UV–vis-DRs, terahertz (THz), dielectric and mechanical analysis. From chemical structural results, it can be confirmed the existence of ZnO in Fe2O3 and the internal structure rearrangement of iron oxide before dispersion into the HIPS matrix. The UV–Vis DRs show that the optical band gap decreases significantly with the increase of ZnO content in the nanocomposite. THz spectra in the spectral range of 0.2–2.5 THz showed an increase in the refractive indices and absorption coefficients for the prepared nanocomposites. Besides, the mechanical properties were affected by the addition of ZnO to HIPS-Fe2O3 where the elongation at break %, Young’s modulus, and maximum strength varied values relying on the applied ratio of ZnO especially for the ratio of 0.4. Finally, the produced nanocomposites can find widespread applications in optoelectronic, chemical, and biological applications besides their feasibility to apply on a large scale.