Showing papers in "Journal of Materials Science: Materials in Electronics in 2019"

Barium titanate nanostructures for photocatalytic hydrogen generation and photodegradation of chemical pollutants

Abstract: Barium titanate nanoparticles (NPs) were synthesised using a modified sol–gel technique. The structure and morphology of NPs were described using various techniques. The photocatalytic activities of the NPs were evaluated by the photocatalytic degradation of Eriochrome black T and potassium dichromate in the presence of UV light irradiation. The barium titanate NP catalyst exhibited higher photocatalytic activity for the degradation of pollutants effectively at room temperature. The different parameters effects such as pollutant initial concentration, loading of photocatalyst, initial pH values of the solution were also examined on the decolourization efficiency of the pollutants. The highest degradation efficiency was achieved for Eriochrome dark T (93%) and potassium dichromate (92%) pollutants. The prepared NPs showed 26 μmol g−1 hydrogen generation within 5 h.

Recent progress on the development of Sn–Bi based low-temperature Pb-free solders

Abstract: With the implementation of legislations on inhibiting the usage of Sn–Pb solder in consumer electronic products, Sn–Ag–Cu series solder has been gotten the most application. However, there are some stimulations from electronic manufacturers to adopt low temperature soldering such as the economic driver from the reduction in manufacturing assembly cost and the reliability driver to avoid the dynamic warpage of area array components caused from Sn–Ag–Cu solder. Sn–Bi series solder is one of the promising candidates, which met the requirements for low melting point, low cost and environment friendly. However, the disadvantage of brittleness characteristic prevented its wide practical application. In order to promote the better application of Sn–Bi based solders, many efforts have been made to improve the wettability, mechanical properties and reliability of Sn–Bi based solders. This paper will summarize the related results about Sn–Bi solder alloys from wettability, interfacial reaction, mechanical properties of Sn–Bi solder and reliabilities of Sn–Bi solder joints. Moreover, in order to improve the properties of Sn–Bi solders, researchers have done lots of works on effect of addition of element dopants. The corresponding works of effect of alloying elements on the properties of Sn–Bi solder were also focused. According to the existing research results, it provides an important basis of understanding the current development of Sn–Bi solders.

Impact of ZnO addition on structural, morphological, optical, dielectric and electrical performances of BaTiO 3 ceramics

Abstract: BaTiO3/(ZnO)x ceramics (x = 0, 2, 5 and 10 wt%) were produced via solid state reaction by using high energy ball milling. The morphological, structural, spectral, optical, electrical and dielectric properties were systematically investigated. X-ray diffraction indicated that all ceramics crystallize in the tetragonal structure. The grains size increases with ZnO additions. The optical band gap energy (Eg) was also evaluated and found to reduce with increasing ZnO concentration. The dielectric and electric properties revealed that an optimal ZnO content lead to obtain ceramic with high dielectric constant and low tangent loss, which are encouraging for radio frequencies and microwaves applications.

Nanosecond laser-irradiation assisted the improvement of structural, optical and thermal properties of polyvinyl pyrrolidone/carboxymethyl cellulose blend filled with gold nanoparticles

Abstract: Gold nanoparticles (Au NPs) supported within the polymeric matrix of polyvinyl pyrrolidone/carboxymethyl cellulose (PVP/CMC) were successfully prepared through the novel in situ method. These (PVP/CMC)/Au hybrid nanocomposites were exposed to nanosecond laser-irradiation with different powers. These nanocomposite samples were investigated before and after the irradiation process through various techniques such as X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FT-IR), ultraviolet/visible spectroscopy (UV/Vis), transmission electron microscope (TEM), differential thermal analysis (DTA) and thermogravimetric analysis (TGA) techniques. The XRD analysis depicted the amorphous nature for PVP/CMC blend and showed the characterizing peaks of Au NPs for the nanocomposite spectrum, where the intensity of these peaks was largely decreased after irradiation process. The FT-IR spectra showed that the blend components were miscible via showing the functional groups of two polymers that were interacted through the formation of a hydrogen bond and the FT-IR spectra of nanocomposite and irradiated samples were affected. Also, the mechanism of interactions between blend and Au NPs was proposed. The UV/Vis. spectra depicted the formation of Au NPs within the PVP/CMC matrix through showing the surface plasmon resonance peak (SPR) of Au NPs at 546 nm. The UV/Vis. the absorbance of this peak was increased and its position was red-shifted after the irradiation process implying the formation of smaller NPs and the narrow size distribution as confirmed by TEM micrographs. The thermal properties for prepared samples were determined through DTA and TGA techniques.

A review of metal oxide-related microwave absorbing materials from the dimension and morphology perspective

Abstract: Various wireless devices have been widely used in every aspect of life and further lead to the severe electromagnetic waves pollution. Fortunately, researchers have developed microwave absorbing materials which are able to transfer the harmful electromagnetic waves into other energy, such as thermal energy. In recent years, numerous studies on preparing microwave absorbing materials with various components, morphologies and structures have been reported. Metal oxide-related composites are widely used as microwave absorbers due to their excellent electromagnetic properties. The morphology and nanostructure would play a key role on the microwave absorbing performances, which can cause “structural effect”. The ideal microwave absorbing materials should meet following demands: widely effective absorption frequency (fE), thinner thickness (d), light-weight, and strong absorption. In this review, we summarized various common morphologies and structures of metal oxide/metal oxide-based composites, and categorized them from a dimensional perspective. The different microwave absorbing properties and mechanisms are given much attention in detail.

ZnO doped single wall carbon nanotube as an active medium for gas sensor and solar absorber

Abstract: In this paper, we reported the synthesis of high-quality ZnO-doped SWCNT (ZnO:SWCNT) nanostructures by perfume spray pyrolysis on copper substrate. The synthesized ZnO:SWCNT nanoparticle explored for the optoelectronic properties and its potential application in photonic devices. In this investigation, the ZnO:SWCNT was blended with the solar absorber of thin film organic solar cells which is found to be a successful mechanism in enhancing the photo-generated current in the devices. The best device performance was found at 6% concentration of ZnO:SWCNT by weight in the solution phase of the solar absorber. Furthermore, the pure ZnO:SWCNT as a gas sensor shows good sensitivity to ethanol at different gas loading in ppm. We observed for the first time a high gas sensing activity of ZnO:SWCNT powder which is related to surface state, oxygen adsorption, grain size and lattice defects. The article discusses about the techniques employed during gas sensing measurements using various functionalization strategies.

Dielectric properties of polyvinyl alcohol (PVA) nanocomposites filled with green synthesized zinc sulphide (ZnS) nanoparticles

Abstract: In this study, zinc sulphide nanoparticles (ZnS NPs) have been synthesized by green synthesis approach. These ZnS NPs were used as nanofiller to fabricate polyvinyl alcohol (PVA) based nanocomposite films via solution casting method. The PVA/ZnS nanocomposite films have been characterized by X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, atomic force microscopy and thermogravimetric analysis. The results from these characterization techniques evidenced the improvement in structural, morphological and thermal properties of PVA/ZnS nanocomposite films and also confirmed the incorporation of ZnS NPs in the PVA matrix. In addition to that, the dielectric properties of the PVA/ZnS nanocomposite films were investigated for different frequencies (50 Hz–1 MHz) and temperatures (40–140 °C) using an impedance analyzer. The values of dielectric constant and dielectric loss of PVA/ZnS nanocomposite films were observed to be 328.93 (50 Hz, 140 °C) and 6.02 (50 Hz, 140 °C) with 3 wt% ZnS NPs content. This enhancement in dielectric properties demonstrated the good interaction between ZnS NPs and PVA matrix. The aforementioned results evidenced that the ZnS NPs were homogeneously distributed within the PVA matrix.

Assessing the magnetic, cytotoxic and photocatalytic influence of incorporating Yb3+ or Pr3+ ions in cobalt–nickel ferrite

Abstract: Yb3+- and Pr3+-substituted cobalt–nickel ferrite nanoparticles were prepared through a sol–gel auto-combustion procedure and the effects on the cytotoxic, photocatalytic and magnetic characteristics of the resulting compounds were evaluated. As an initial step, the structure, morphology and magnetic properties of the produced particles were assessed using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), UV–visible diffuse reflectance spectroscopy (DRS), photoluminescence (PL), and vibrating sample magnetometery (VSM) techniques. The crystalline size and nanoparticles size of prepared nanostructures was in the range of 100–180 and 90–220 nm based on XRD and SEM results. Using the XRD results it was found that the product had a spinel cobalt–nickel ferrite phase structure, also containing some PrFeO3 and YbFeO3 phases as impurities. VSM results exhibited that Co0.5Ni0.5Pr0.1Fe1.9O4 has higher magnetic parameters than Co0.5Ni0.5Yb0.1Fe1.9O4, yet but the latter enjoys enhanced photocatalytic activity in degrading methyl orange (MO) under ultraviolet (UV) light irradiation.

Synthesis, structural, strength and corrosion properties of thin films of the type CuX (X = Bi, Mg, Ni)

Abstract: The paper presents the results of studying of structural and phase properties of films based on copper–bismuth, copper–magnesium, copper–nickel, obtained by the method of electrochemical deposition. The dependences of the influence of the synthesis conditions on the phase composition and the strength and corrosion properties of the synthesized films are established. Interest in two-component films based on selected metals is due to their structural properties and the prospect of using them as protective coatings. The choice of elements of bismuth, magnesium and nickel in combination with copper is due to the possibility of obtaining structures with different phases, which can have a significant impact on the corrosion properties of films when interacting with aggressive media. During tests for corrosion resistance, it was found that a decrease in the concentration of copper and copper-containing phases leads to an increase in resistance to degradation and oxidation of thin films.

Study of tungsten oxide effect on the performance of BaTiO 3 ceramics

Abstract: BaTiO3/(WO3)x ceramics (where x = 0, 0.5, 1, 2 and 5 wt%) were prepared by solid state reaction. X-ray powder diffraction, scanning electron microscope, Fourier transform-infrared spectroscopy and ultraviolet–visible diffuse reflectance spectrophotometry were used to investigate the structure, morphology and optical properties, respectively. The electrical and dielectric properties were also performed for different synthesized ceramics. A pure phase was obtained for x = 0.5 wt% ceramic, nevertheless a secondary phase was detected for x ≥ 1 wt% ceramics. The grains size increases for x = 0.5 wt% ceramic and then reduces abruptly with further increasing WO3 content. The increase of grains size and the absence of impurities were all efficient to enhance the dielectric properties. A suitable WO3 content leads to obtain ceramics having high dielectric constant and low tangent loss, which is encouraging for radio frequencies and microwaves applications.

Recent advances in nano-materials for packaging of electronic devices

Abstract: In recent years, Moore’s law had a remarkable effect on predicting the development of semiconductor technology. As the size of devices shrinks to micro scale or nano scale, Intel’s newest 10-nm logic technology is scheduled to start product shipments before the end of 2017. Moore’s law will not die out, as the research scale reaches the atomic scale, “new devices” and new interconnection methods are urgently needed. In this paper, based on emerging interconnection requirement, the contribution to the advanced electronic packaging containing novel nano-materials, such as the carbon nanotubes, nanoparticles sintering, interconnection of nano-solder, nano-silver and surface plasma nano-welding are discussed. For the next 5–10 years, two new types of interconnect solutions are gaining attentions: solder joint alternatives and Cu electrode alternatives. The former uses new materials such as graphene, carbon nanotubes and nanowires to replace traditional solder joints. The latter uses optical media to replace the traditional Cu metal. In general, advanced materials will make more and more outstanding contributions in the development of electronic packaging in the next 10–20 years.

Synergistically enhanced photocatalytic performance of Bi 4 Ti 3 O 12 nanosheets by Au and Ag nanoparticles

Abstract: In this work, we attempted to assemble Au and Ag nanoparticles (NPs) with different sizes onto Bi4Ti3O12 (BTO) nanosheets with the aim of synergistically enhancing the photocatalytic performance. The as-prepared Au–Ag@BTO composite was systematically characterized by means of TEM, XRD, XPS, FTIR, UV–vis DRS, PL spectroscopy, EIS and photocurrent spectroscopy. The TEM observation demonstrates that larger-sized Au NPs (average size: 20 nm) and smaller-sized Ag NPs (average size: 8 nm) are uniformly decorated on the surface of BTO nanosheets. Compared to bare BTO, the Au–Ag@BTO composite manifests an increased visible light absorption, increased bandgap, increased photocurrent density, decreased charge-transfer resistance and decreased PL intensity. Separately using simulated sunlight, UV light and visible light as the light source, the photocatalytic performance of the composite was evaluated by the degradation of RhB. An enhanced photocatalytic performance of the composite is observed in all the cases. Under UV irradiation, the photocatalytic enhancement is mainly ascribed to the efficient separation of photogenerated electron/hole pairs caused by the smaller-sized Ag NPs, whereas the photocatalytic enhancement under visible light irradiation is dominantly due to the LSPR effects of the larger-sized Au NPs. The synergistic photocatalytic enhancement between Ag and Au NPs is achieved under simulated sunlight irradiation. Active species trapping experiments were carried out, revealing that photogenerated holes and ·O2− radicals play a dominant and secondary role in the photocatalysis, respectively.

Tin dioxide nanoparticles with high sensitivity and selectivity for gas sensors at sub-ppm level of hydrogen gas detection

Abstract: A wet chemical method was employed to prepare Au-loaded sensor using tin dioxide (SnO2) nanoparticles (NPs) which has excellent hydrogen (H2) gas sensing properties The structural, compositional, morphological, and electrochemical properties of these materials are characterized by X-ray diffraction, field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy and electrochemical workstation, respectively The results show that the response time of Au-loaded sensor based on SnO2 NPs to 100 ppm H2 is 26 s at 350 °C, which is much shorter than that of the pristine SnO2 sensor Meanwhile, the effect of operating temperature and Au loading on ‘n’ value (factor for evaluating sensitivity response) is studied and the results demonstrated that the Au-loaded sensor based on SnO2 NPs can detect H2 gas down to 04 ppm Moreover, the Au-loaded sensor based on SnO2 NPs with an excellent selectivity to H2 gas against carbon monoxide, methane, and sulfur dioxide is illustrated in this paper, which indicates that the Au-loaded sensor using SnO2 NPs is a good candidate for practical H2 sensors and other industrial applications Statistical analysis was performed on the FESEM images of sensors based on SnO2 NPs and 05 atomic (at)% Au-loaded SnO2 NPs Roughness parameters were evaluated and a correlation was established between the morphology, topography and chemical composition of the samples

Exploration of thermoacoustics behavior of water based nickel ferrite nanofluids by ultrasonic velocity method

Abstract: Magnetic nanofluids (commonly known as ferrofluids) have captured the great attention of the researchers due to their various kinds of applications such as heat transfer, hyperthermia treatments, targeted drug delivery etc. The present experimental investigations deal with the thermoacoustic behaviour of the water based nanofluids of nickel ferrites. The magnetic nickel ferrite nanoparticles were produced by the simple and inexpensive chemical co-precipitation route. The prepared nanoparticles were exposed to different characterization tools for structural, morphological, compositional and magnetic properties analysis. X-ray diffraction analysis with Rietveld refinement confirmed the single phasic nature with nanometric crystallite size of the prepared nanoparticles. Scanning electron microscope images revealed the spherical and nanocrystalline morphology of the prepared nanoparticles. The M-H plot recorded at room temperature revealed the superparamagnetic nature of the nanoparticles. Further, the co-precipitated nickel ferrite nanoparticles with different concentrations were utilized for the preparation of the water based magnetic nanofluids. Colloidal stability of the prepared nanofluids was analyzed by UV–Vis spectroscopy technique and it revealed the stability over 11 days without separation in phase. The temperature dependent thermoacoustic properties of the prepared nanofluids were analyzed through Ultrasonic Interferometer. The interaction between particle–particle and particle–fluid are explained on the basis of thermo-acoustic parameters.

Room temperature chemiresistive gas sensors: challenges and strategies—a mini review

Abstract: One of the sources of environmental threat in recent years is the leakage of toxic gases from various industries. Sensors to detect these gases in trace level concentrations are highly required to ensure a safe living environment. In this context, many types of gas sensors such as calorimetric, conductometric, potentiometric, catalytic, and chemiresistive types have been employed to detect these gases. Among them, chemiresistive type sensors have been widely employed due to high selectivity, sensitivity, simplicity in fabrication, compactness, lower operating temperature, and low power consumption. Chemiresistive sensors are designed with inbuilt micro-heaters for improving the sensing response. However, sensors operated at elevated operating temperatures would significantly affect the stability of the sensor due to grain growth. To address this concern, many efforts have been progressing over the years towards the development of room temperature operated gas sensors. In this review, room temperature operated gas sensors developed for the detection of ammonia, acetaldehyde, ethanol, nitrogen dioxide, ozone, and aromatic VOCs have been discussed. In addition, the major challenges possessed by the sensors operated at elevated temperatures such as grain growth, change of conductivity, and variations in charge transport characteristics have been addressed. Also, the strategies to minimize the aforementioned challenges have been highlighted.

Statistical, morphological, and corrosion behavior of PECVD derived cobalt oxide thin films

Abstract: Experimental parameters have direct influences on materials properties and therefore their applications. The effect of plasma power on the properties of cobalt oxide thin films, prepared using plasma-enhanced chemical vapor deposition technique, on stainless steel substrates have been addressed in this paper. The structural, morphological, and compositional properties of these films were investigated by means of X-ray diffraction (XRD), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS) technique. The XRD patterns demonstrated the growth of polycrystalline Co3O4 thin film with a cubic spinel structure such that the intensity of (511) and (311) peaks increase as the plasma power increases to 100 W. It is observed that crystallite size increases by increasing the plasma power and the maximum crystallite size is found to be 64.8 nm for 100 W. The AFM results illustrate that the surface roughness and grain size increase by increasing the plasma power, and the film deposited at lower plasma power has more uniform and smoother surface, mainly owing to the increase in surface diffusion that in turn causes the coalescence of the grains. The results of XPS spectra indicated the formation of Co3O4 thin films on stainless steel substrates and there were no other elements other than Co, O in the XPS spectra. Additionally, stereometric analysis and fractal dimension of the 3-D surface microtexture of the AFM micrographs were analyzed and the Kolmogorov–Smirnov test was used to assess the normal distribution of quantitative variables. The results of statistical analysis corroborated the experimental results and proved that the surface roughness increased upon an increase in plasma power. Moreover, the corrosion behavior and the surface morphology of the cobalt oxide thin films were investigated using the potentiodynamic method and scanning electron microscopy. The results of these analysis proved that as the plasma power increases the corrosion resistance improves against the H2SO4. The sample which deposited at 100 W plasma power has the minimum corrosion current and the corrosion resistance of steel substrate was improved by controlling the anodic reactions resulted from a protective Co3O4 thin film. These results are useful for building and designing stainless steel devices in corrosive environments.

Tunable structures of copper substituted cobalt nanoferrites with prospective electrical and magnetic applications

Abstract: Spinel ferrites (SFs) show high potential in different aspects of modern technology. Particularly, copper ferrite represents a promising electrode material for supercapacitors and lithium based batteries. This paper is devoted to synthesizing and characterizing nanostructured copper substituted cobalt ferrites using an eco-friendly sol–gel method. Energy dispersive X-ray (EDX) and FT-IR analyses confirm the chemical composition and the successful formation of the cubic phase of CuFe2O4, respectively. XRD analyses based on Williamson–Hall (W–H) method indicate that the average crystallite size drops from 25.1 to 12.1 nm dependent on the Cu2+ content in the samples. Further, scanning electron microscopy (SEM) reveals that the CoFe2O4 (CFO) has a honeycomb structure, which gradually disappears with the soaring of Cu2+ content in the samples and converts to a porous sponge-like shape structure. The investigated copper substituted CFO holds a high specific surface area equals to 102.5139 m2 g−1 which satisfies the contaminant adsorption applications. The measured DC resistivity (ρDC = 108 Ω m) is high enough to meet the requirements of transformer cores applications. Due to the difference in the magnetic moment between Cu2+ and Co2+ cations, the coercivity of the CFO significantly depends on the Cu2+ content; it has declined by more than 50% for the system Co0.25Cu0.75Fe2O4 in comparison to the pure CFO (Hc = 1617.30 Gauss).

Calcination effect on the magneto-optical properties of vanadium substituted NiFe2O4 nanoferrites

Abstract: Vanadium substituted nickel ferrite nanoparticles (NPs), NiFe2−xVxO4 (0.0 ≤ x ≤ 0.3) were prepared by sol–gel approach. The influence of calcination on the magnetic and optical properties of NiFe2−xVxO4 (0.0 ≤ x ≤ 0.3) NPs were investigated deeply. The lattice parameters ‘a’ are almost constant with V-substitution for as-prepared and calcined samples. It was found that the calcination process both increased the crystallites size and removed the impurity phases in all products. The values of optical energy band gap, Eg, are in range of 1.38–1.69 eV and 1.39–1.56 eV for as-prepared and calcined samples, respectively. The specific magnetic parameters such as saturation magnetization Ms, remanence Mr, coercivity Hc, squareness ratio (SQR) and magnetic moment $$n_{B}$$ were determined from magnetization versus applied field measurements. The various M(H) curves exhibit ferromagnetic behavior at room temperature and 10 K. A decrease in Ms, Mr and $$n_{B}$$ values was observed with Vanadium substitution. However, an increase in Hc value was observed. The obtained magnetic results are primarily resulted from the substitution of Fe ions with V ions that will weaken the A–B super-exchange interactions. Besides, the calcination step leads to an improvement in the various Ms, Mr and $$n_{B}$$ parameters. This enhancement is due to the enlargement of crystallites size (or grains size) and the strengthening of the A–B exchange interactions caused by the calcination effect. Nevertheless, the enlargement in the crystallites size is followed by a reduction in Hc values.

Biogenic fabrication of ZnO nanoparticles using Trigonella foenum-graecum (Fenugreek) for proficient photocatalytic degradation of methylene blue under UV irradiation

Abstract: The biosynthesis is an eco-friendly, reliable, sustainable protocol for preparing nanomaterials where use of natural, biodegradable, non-toxic and safe reagents takes place. In the present work, an efficient, facile and eco-friendly approach has been used for the synthesis of zinc oxide nanoparticles (ZnO-NPs) using Trigonella foenum-graecum (Fenugreek) aqueous seed extract as bio-reducing agents and capping agent, thus eradicating the requirement of conventional reducing agents. Different characterization techniques like UV–Vis spectroscopy, UV–Visible diffuse reflectance spectroscopy, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy, photoluminescence (PL) study and energy dispersive X-ray were employed for confirmation of optical properties, shape, size, surface structure, crystalline nature and elemental proportions of the biogenic ZnO-NPs. FTIR analysis confirms the active role of bioactive phytochemical constituents present in the Trigonella foenum-graecum aqueous seed extract. XRD analyses of the as prepared ZnO-NPs are crystalline in nature and have no other impurity phase. UV–Vis spectral data suggested optical band gap energy of 2.97 eV for biosynthesized ZnO-NPs showing their small size owing to quantum confinement. UV–Vis spectra of ZnO-NPs show the characteristic absorption band at 364 nm, which can be assigned to the intrinsic band gap absorption of ZnO-NPs because of the electron transitions from the valence band to the conduction band. In addition, the efficacy of biosynthesized ZnO-NPs to act as highly efficient photocatalyst for methylene blue (MB) dye degradation under UV-light under different experimental conditions was confirmed in this study. The effect of initial dye concentration, ZnO photocatalyst dosage and the reusability tests were investigated. Improved photocatalytic behavior was discussed and influence of active species was further investigated using hydroxyl radical (●OH), superoxide anions (●O2−) and hole (h+) scavengers to explain the possible mechanism of the photocatalytic MB dye degradation under UV light irradiation.

Non-metal modified TiO2: a step towards visible light photocatalysis

Abstract: Advanced oxidation process (AOP) is a versatile photocatalytic approach to degrade various environmental pollutants. Among many photocatalysts used in AOP such as ZnO, TiO2, ZrO2, ZnS, CdS; TiO2 is the most widely adopted semiconductor material. TiO2 is a wide band gap material and absorb in UV spectrum which is a narrow region in the sun light. This benchmark makes it a less efficient photocatalyst under sunlight irradiation. To enhance the photocatalytic efficiency, the absorption band of photocatalyst should be modified in such a way that it leads to maximum absorption in the solar spectrum. The doping of nonmetals such as N, C, P and S etc. shift the band edge of the semiconductors towards the visible region and thus increases the photon absorption which successively enhances the photocatalytic efficiency. In this review, we have focused on effect of nonmetal doping on the properties and photocatalytic activity of the TiO2. Influence of various aspects such as synthesis procedure, doping source, concentration of dopant, calcination etc. are also explored towards alteration in properties and photocatalytic efficiency of nonmetals doped TiO2.

Nonlinear optical and dielectric properties of TiO2 nanoparticles incorporated PEO/PVP blend matrix based multifunctional polymer nanocomposites

Abstract: Poly(ethylene oxide) (PEO)/poly(vinyl pyrrolidone) (PVP) blend (50/50 wt%) and mixed-phase (anatase and rutile) titanium dioxide (TiO2) nanoparticles are used as organic host matrix and inorganic nanofiller, respectively, for the preparation of hybrid polymer nanocomposite (PNC) films (i.e. (PEO/PVP)–x wt% TiO2; x = 0, 1, 3, 5, 10, and 15) by solution casting method with deionized water as solvent. These PNC films are characterized by employing SEM, FTIR, XRD, UV–Vis, DSC, and DRS techniques. The effect of TiO2 nanofiller loading on the structural, morphological, thermal, optical, dielectric, and electrical properties of the PEO/PVP blend matrix, and also on the chain segmental dynamics of PEO in the PNC structures is investigated. It is revealed that the crystalline phase and spherulite morphology of PEO, and the polymer–polymer interactions in these PNC films have been primarily modified by the polymer–nanoparticle interactions. The optical energy band gap decreases, whereas UV absorbance enhances non-linearly with the increase of TiO2 concentration in the PNC films. The enthalpy of melting of the PEO irregularly reduces when the incorporated amount of TiO2 enhances in these films. The real part of complex permittivity and the dielectric loss tangent of these materials are found frequency independent in the range from 20 kHz to 1 MHz but these parameters increase non-linearly from ~ 1.6 to 2 and 0.006–0.008, respectively with the increase of TiO2 concentration up to 10 wt%, at 30 °C. The dominant contribution of interfacial polarization process increases the real part of complex permittivity of these PNC materials by about 1.3 times with the decrease of frequency from 20 kHz to 20 Hz which further enhances with the increment in the temperature of the film. The electrical behaviour of these materials has been examined by analyzing their ac electrical conductivity, complex impedance, and electric modulus spectra over the frequency range 20 Hz–1 MHz. The dc electrical conductivity of these PNC materials enhances nonlinearly with the increase of TiO2 loading in the PEO/PVP blend matrix. The optical and dielectric parameters of these flexible-type PNC materials confirm their multifunctional properties as UV absorber, optical energy band gap tuner, low permittivity tunable nanodielectric, electrical conductivity regulator, and novel host matrix for ion conducting materials. The results infer that these innovative technologically advanced engineered materials can be potential candidates for the next generation microelectronic devices.

Phase transitions, energy storage performances and electrocaloric effect of the lead-free Ba 0.85 Ca 0.15 Zr 0.10 Ti 0.90 O 3 ceramic relaxor

Abstract: Lead-free Ba0.85Ca0.15Zr0.10Ti0.90O3 (BCZT) ceramic exhibits excellent dielectric, ferroelectric and piezoelectric properties at the morphotropic phase boundary (MPB). Previously, we demonstrated that the use of the anionic surfactant sodium dodecyl sulfate (SDS, NaC12H25SO4) could enhance the dielectric properties of BCZT ceramic using surfactant-assisted solvothermal processing [1]. In the present study, structural, dielectric, ferroelectric properties, as well as electrocaloric effect and energy storage performances of this BCZT ceramic were thoroughly investigated. X-ray diffraction (XRD) measurements revealed the presence of single perovskite phase at room temperature with the coexistence of orthorhombic and tetragonal symmetries. In-situ Raman spectroscopy results confirmed the existence of all phase transitions from rhombohedral through orthorhombic and tetragonal to cubic symmetries when the temperature varies as reported in undoped-BaTiO3. Evolution of energy storage performances with temperature have been investigated. BCZT ceramic exhibits a high energy storage efficiency of ~ 80% at 120 °C. In addition, the electrocaloric responsivity was found to be 0.164 × 10−6 K·m/V at 363 K.

New method for synthesis of BaFe12O19/Sm2Ti2O7 and BaFe12O19/Sm2Ti2O7/Ag nano-hybrid and investigation of optical and photocatalytic properties

Abstract: Nanoscale BaFe12O19/Sm2Ti2O7 and BaFe12O19/Sm2Ti2O7/Ag ternary nano-hybrid were successfully synthesized by a new method for the first time. PEG, PVA, and PVP were used to investigate their effects on the morphology and particle size of final products. The photocatalytic efficiency of BaFe12O19/Sm2Ti2O7/15%Ag was improved by 59% which was higher than pure BaFe12O19/Sm2Ti2O7 for the degradation of MB. In this work, Ag was doped with BaFe12O19/Sm2Ti2O7 with the aid of improving its photocatalytic activity and stability toward degradation of dyes under visible light irradiation. Transmission electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, Fourier transform infrared, photoluminescence, diffuse reflection spectroscopy, and Field emission scanning electron microscopy were applied to characterize BaFe12O19/Sm2Ti2O7/Ag ternary nano-hybrid.

Synthesis of potent chitosan beads a suitable alternative for textile dye reduction in sunlight

Abstract: Photocatalytic degradation is an effective method for toxic dye decontamination of domestic wastewater and industrial effluents. For this purpose, copper sulphide nanoparticles-chitosan beads (CuS-CB) were synthesized. The synthesis of beads were confirmed using FTIR spectroscopy. The size of CuS nanoparticles were 60 nm analysed using XRD technique. The EDX technique confirms presence of CuS nanoparticles in chitosan beads (CB). SEM images showed smooth surface morphology with average bead size of 735 µm. The band gap energy of the catalyst was calculated in the visible region using Tauc relation and found to be 2.1 eV. The CuS-CB was applied for photodegradation of malachite green (MG) dye. The removal efficiency of the catalytic beads obtained was 95% (50 ppm) under the optimized conditions in the sunlight. The photocatalytic degradation of MG dye under solar light has shown enhanced degradation than UV region. Pseudo first kinetics fitted well to photocatalytic degradation of MG with rate constant of 3.3 × 10−2 min−1. The photocatalyst give excellent results after recycling and regeneration up to five times for the degradation of MG dye.

Facile approach to prepare ZnO@SiO2 nanomaterials for photocatalytic degradation of some organic pollutant models

Abstract: Band gap energy narrowing upon doping is consider as a general phenomenon in semiconductors. However, low surface area still the main problem that limits its wide applications. Herein, incorporation of ZnO on the surface and inside the matrix of SiO2 using CTAB as structural and capping agent have prepared via sol–gel wet chemical pathway. The crystalline size, structural and textural properties of the obtained samples were investigated through different techniques like XRD, SBET surface area, UV–Vis spectroscopy, FESEM and TEM. The results indicate that the surface area and pore volume constant decrease by insertion of ZnO nanoparticles in the pore wall and/or above the surface of silica. In the other hand, the organic materials removal enhanced due to the existence of different types of pores ranging from microspores to wide mesoporous system. Following the nanomaterials preparation and characterizations, some experiments have done to check the effect on the organic materials like dyes removal. One of these tests is COD result, which affirm the good degradation for most of MB dye that exist in the solution. Furthermore, the scavenger study results show that the ZnO@SiO2 nanomaterials displayed good photocatalytic properties compared to the bare silica one via its charge carrier and reactive hydroxyl radicals species. The scrutinization at the features of the obtained materials enable us to offering without doubt a promising photocatalyst candidate for different applications in wastewater and water treatment.

Tunable microwave absorbing property of La x FeO 3 /C by introducing A-site cation deficiency

Abstract: A novel two-dimensional electromagnetic (EM) absorbers which consist of LaFeO3 nanoparticles embedded on hierarchical amorphous carbon nanosheets were fabricated by a simple one-pot method. By inducing A-site cation deficiency in LaFeO3 perovskite, the properties of EM absorption were optimized due to the polarization of dipoles between O vacancy and Fe4+. This research is expectant to provide a new strategy for the improved EM absorption performance by inducing the A-site cation deficiency in perovskite crystal lattices. By the magnetic ferrite nanoparticles doped in the dielectric carbon sheets, we got the best La0.8FeO3−y/C possessing larger absorption bandwidth 5.4 GHz from 12.6 to 18.0 GHz and minimum reflection loss of − 20.4 dB while La0.6FeO3−y/C which hit the minimum RL value − 25.0 dB at 14.8 GHz with the thickness of 3.75 mm.

AC conductivity and dielectric characteristics of PVA/PVP nanocomposite filled with MWCNTs

Abstract: AC electrical conductivity σac of PVA/PVP blend filled with MWCNTs was studied using impedance spectroscopy over a wide frequency range of 10−1 to 107 Hz at different fixed temperatures. It was observed that the frequency-dependent nature of the ac electrical conductivity followed the Jonscher’s law and the increasing of MWCNTs content in the polymeric matrix leads to form a percolating network through the composite. On the contrary, a conductivity reduction is observed for the composition of 5 wt% of MWCNTs, which may be ascribed to the aggregation occurred in nanotubes and consequently loss of percolation. The CBH model has been suggested to agree with the conduction mechanism of σac for the present system. Also, the maximum barrier height over which the electrons hop decreases with increasing temperature. Impedance data were studied in terms of electrical modulus formalisms M* and impedance formalisms Z*. The relation between real and imaginary parts of complex impedance shows an inclined spike at low frequency and a semicircular arc at high frequency with radius decrease with increasing the temperature and could be best fitted to two equivalent circuit models. The analysis of M″ and Z″ spectra indicates that the distribution of relaxation times is independent of the temperature. The non-coincidence of peaks corresponding to M″ and Z″ indicates the deviation of non-Deby relaxation and short-range movement of charge carriers. The activation energy values, which are determined from the bulk conductivity and electric modulus, are very close.

New magnetic nanobiocomposite CoFe2O4@methycellulose: facile synthesis, characterization, and photocatalytic degradation of metronidazole

Abstract: In this work nanoCoFe2O4@methycellulose (MC) as a highly potent, magnetically separable photocatalyst by a facile, fast, and new microwave-assisted method with iron and cobalt salts on methyl cellulose in alkali medium was prepared. The nanobiomagnetic catalyst CoFe2O4@MC was characterized by field emission scanning electron microscope-energy dispersive spectroscopy (FESEM-EDS), mapping, the Brunauer–Emmett–Teller (SBET), Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), thermal gravimetric analysis, derivative thermogravimetric analysis, differential thermal analysis, vibrating sample magnetometer (VSM), and UV–Vis diffuse reflectance spectra. Powder XRD, and EDS analysis confirmed the formation of pure-phase spinel ferrites. FESEM analysis confirmed the sphere-like particle morphology of the samples with a smaller agglomeration. VSM analysis clearly showed the ferromagnetic nature of the nanoCoFe2O4@MC. The Ms value was 40.05 emu/g for simple separation by external magnetic fields. After characterization of this photocatalyst which showed its promising magnetic properties, the effective parameters of reaction time, initial antibiotic concentration, pH, photocatalyst loading, degradation kinetic, and removal efficiency of MNZ were investigated. The highest removal efficiency of 85.3% was observed in optimal conditions. The kinetic linear models showed that the nanoCoFe2O4@MC-catalyzed removal of MNZ follows either a pseudo-first order kinetic or the Langmuir–Hinshelwood equation. The new photocatalyst nanoCoFe2O4@MC was easily separated by a magnet and recycled without significant loss of photocatalytic activity after being used in four runs. This photocatalytic process is an excellent practical alternative for the removal of MNZ and similar antibiotic pollutants from various wastewaters.

Layer-by-layer preparation and characterization of recyclable nanocomposite (Co x Ni 1−x Fe 2 O 4 ; X = 0.9/SiO 2 /TiO 2 )

Abstract: Titanium dioxide (TiO2) nanocomposites have been extensively employed in many fundamental optoelectronic and photocatalytic applications due to their outstanding optical, electronic and chemical properties. In the present work, we introduce a simple layer-by-layer approach to design a magnetic TiO2 nanocomposite that could be easily recycled using an external magnetic field without affecting its quantum efficiency. The crystallinity, size, surface area, stability, morphology, purity and other optical, thermal and magnetic properties of the composite have been investigated. Surface topology, thickness and thermal conduction were also demonstrated by AC conductivity measurements at a specific temperature (55 °C). Our results revealed that the prepared composite has a semi-spherical concentric shape with an average size of about (123.4 nm), surface area of (46.13 m2/g) and zeta potential of (− 24.3 mV) as confirmed by HRTEM, surface area analyzer and zeta potential measurements. TGA and DSC analysis recorded the thermal stability of the composite up to (500 °C) while a band gap of about (3.35 eV) has been calculated. VSM analysis showed that the composite has good magnetic properties. Atomic force microscopy recorded a surface roughness of the composite of about (125 nm) while the average thickness was approximately (10.3 nm). Significant responses of the capacitance–voltage profiles in the employed Preisach model, have been also recorded.

Preparation of PVDF-TrFE based electrospun nanofibers decorated with PEDOT-CNT/rGO composites for piezo-electric pressure sensor

Abstract: We developed a high-performance electrically conductive and transparent PVDF-TrFE based electrode for piezoelectric pressures sensor using the electrospinning technique The electrode was produced by depositing the reduced graphene oxide (rGO), multiwall carbon nanotubes (rGO-MCNTs) via spray coating Various concentration of rGO and MCNTs were used and optimized for improved electrical performance of the resultant electrode The deposition of poly (3,4-ethylenedioxythiophene) (PEDOT) was successfully achieved by using vapor phase polymerization (VPP) The morphological characteristics of the as-prepared hybrid composite nanofiber mats were analyzed by using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Fourier transforms infrared spectroscopy (FT-IR), Raman spectroscopy, X-ray diffraction (X-RD), and UV–visible spectroscopy The electrical performance of the fabricated composite nanofibers was measured by using a four-point probe device The results showed significant enhancement in electrical conductivity of the hybrid nanocomposite which increased up to 3916 S cm−1 and sensitivity of the developed pressure sensor was achieved 674 kPa−1 This work suggests that the hybrid nanocomposite can be used for the transparent electrodes in a piezoelectric pressure sensor