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Recently, solar photocatalytic technology has proved to be an effective way to solve the problems of environmental pollution and energy shortage due to its green environmental protection and fast degradation rate. In this paper, a simple microwave hydrothermal method is used to prepare a novel CuO/GO heterojunction composite photocatalyst, and its chemical composition, microstructure, physicochemical properties, photothermal conversion, and photocatalytic properties are studied. The results show that the addition of GO in the CuO/GO nanocomposite photocatalyst not only effectively reduces the agglomeration of CuO nanoparticles but also makes it exhibit better photocatalytic activity than pure nano-CuO. The degradation rate of MB increased by 39.48% at 120 min of light, and as high as 94.1% at 180 min, mainly due to the construction of heterojunction at the interface and the synergistic promotion effect of light and heat. The internal mechanism of light and heat synergistic catalysis is revealed. This paper not only proposes a low-cost and efficient CuO/GO light-heat composite photocatalyst but also provides new ideas for subsequent researchers to design and prepare nanocomposite photocatalysts.

This paper is focused on optical nonlinearity in CdS nanostructured thin films, which was reviewed comprehensively and discussed in detail along with future perspective. Due to third harmonic generation in CdS materials on exposed to highly intense light that is significant feature to develop modern photonics devices. CdS chalcogenide semiconductor binary compound is one of the most particularly promising candidate for nonlinear optical applications due to their enhanced nonlinear optical properties in thin films. CdS nanostructured thin films have been shown exceptional third order nonlinear optical (TONLO) behavior near the sub band gap energy region. This review will be based on TONLO properties of CdS nanostructured thin films, which will focus on the tailoring of TONLO properties as a function of particle size, dopant and CdS polymer nanocomposite. Doping and size effect in CdS system is the important opportunity to develop it with excellent TONLO properties. This review paper will give an open area of research possibilities to search the efficient nonlinear optical CdS nanostructured thin films for advanced modern photonics applications and also will provide an idea to develop efficient materials with exceptional TONLO properties.

The two-dimensional titanium carbide MXene (Ti3C2Tx) acts as a promising pseudocapacitive material for supercapacitor electrodes. In this paper, the properties of vanadium-doped titanium carbide MXene (Ti3C2Tx) are tuned using a simple hydrothermal method to intercalate the alkali metal adsorbates (K+) into the electrode material. The synthesis of the supercapacitor device is carried on glass substrate as well as on a flexible graphite sheet. The X-ray diffraction and scanning electron microscopy are conducted to observe the change in structural properties of vanadium-doped MXene. The cyclic voltammetry and galvanostatic charge–discharge are carried out on Metrohm autolab workstation. The ratio of ammonium vanadate and MXene has been varied from 0.025:0.1 to 0.1:0.1 with a step size of 0.025 to obtain the capacitance results. The results depict that the ratio of 0.025:1 shows the highest capacitance of 258.07 mF/cm2 and 1107 mF/cm2 in 6 M KOH (20 mV/s) on glass and graphite substrate, respectively. This is mainly because the ratio of 0.025:1 provides the maximum exfoliation which allows electrolyte ions to penetrate in the active material and thus, facilitates fast electron transport resulting in high-performance supercapacitors. Further, this paper also discusses the successful fabrication of the supercapacitor devices on a flexible graphite sheet for the first time. The results show that the capacitance value on flexible substrate is at par with that of the glass substrate. To further understand the increased capacitive properties of vanadium-doped MXene, the processes involving charge transfer and mass transport are investigated by performing electrochemical impedance spectroscopy (EIS). The radius on the EIS plot of vanadium-doped MXene is smaller than that of the undoped DMSO MXene, which indicates that the vanadium doping made the charge transfer easier. Moreover, the capacitance retention of 92.7% and 82.2% is achieved on graphite as well as glass substrate after 3000 cycles.

In this paper, α-CaSiO3/Al2O3-Li2CO3 was prepared by traditional solid-state method with Li2CO3 as low-temperature sintering aid added to α-CaSiO3/Al2O3 ceramics. The effects of different Li2CO3 content on the sintering properties, microstructure, and microwave dielectric properties of α-CaSiO3/Al2O3 ceramics were studied. The phase structure, micro-morphology, and microwave dielectric properties were characterized by X-ray diffractometer, scanning electron microscope, and network analyzer. The aim of this paper is to reduce the sintering temperature and improve the microwave dielectric properties of α-CaSiO3/Al2O3 ceramics by controlling the phase structure of ceramics. The results revealed that Li2CO3 additives can not only reduce the sintering temperature from 1375 to 975 °C, but also can transfer the major phase composition from α-CaSiO3 to β-CaSiO3. The density of the microwave dielectric ceramics with 3 wt% Li2CO3 additives sintered at 975 °C can reach the optimal microwave dielectric properties with er = 6.21, Q × f = 30,471 GHz, and τf = − 34.58 ppm/°C.

The photoluminescence (PL) and thermoluminescence (TL) studies of un-doped and Eu doped zinc oxide (ZnO) nanophosphors are presented in this paper. The paper also includes characterization by XRD and SEM for structural and morphological studies of chemically synthesized ZnO nanoparticles by using zinc acetate and ammonia solution. Thiourea was used for capping. The hexagonal structure of the undoped and Eu doped ZnO nanoparticles was observed. The XRD of rare earth doped sample showed an extra peak attributed to Europium oxide. The sizes of samples were ranging from 55 to 80 nm. SEM image of undoped ZnO nanoparticle showed flower like structure, whereas, no such shape was found for Eu doped ZnO nanoparticles. The excitation wavelength dependent PL and colour chromaticity diagram for both undoped and Eu doped ZnO was studied. Five samples of Eu doped ZnO, with 0.5%, 1%, 2.5%, 3% and 3.5% molar concentration of Eu were prepared. The variations in PL and TL with different concentrations of Eu were also studied. The Maximam PL and TL intensity was recorded for the samples containing 3% of Eu. The increase in the TL intensity for both the samples was found with increasing γ dose (100–1500 Gy) without any saturation sign. The variations in TL intensity with changing heating rate (5–12 °C/s) were also studied. No change of TL glow peak position was seen for Eu doped sample. A linear increase of TL peak intensity with γ dose suggests that, this phosphor could be used for dosimetry.

Inkjet printing has proven to be a promising alternative method in the fabrication of printed electronics, besides screen printing and photolithography etching. In this work, we characterize the electrical performance of inkjet printed circuits on flexible PET and glossy photo paper. The electrical circuits were printed using a commercial Epson L310 piezoelectric printer, and the NB series silver ink and chemical-sintering PET substrate from Mitsubishi Paper Mills. This method allows rapid prototyping of electronic circuits (~ 30 min design, ~ 5 s fabrication) and quick iteration of prototypes. The system has a resolution of 250 µm electrodes and 300 µm electrical gaps, and on average, 1.5 ± 0.2 µm in thickness. The effect of printing on different substrates, geometry and overprinting on sheet resistance was also studied. It was found that double printing produced better electrodes with lower resistances. A stable conducting circuit has a sheet resistivity of

The authors of the title paper [J. Mater. Sci. Mater. Electron. 31, 13310–13320 (2020)] report to have grown a so-called l-asparagine thioacetamide (LATA) single crystal by slow evaporation of an aqueous solution containing l-asparagine monohydrate and thioacetamide in 1:1 ratio. The same research group has claimed in another paper [J. Mater. Sci. Mater. Electron. 31, 791–798 (2020)] to have grown a so-called NLO-active potassium hydrogen phthalate fumaric acid crystal (KHPF). In this comment we prove that LATA and KHPF are improperly characterized crystals and both papers are erroneous.

Electromagnetic (EM) absorbers are becoming an important tool in the recent advanced technologies as well as for environments to minimize the level of microwave radiations in specific structures or places. Indeed, they are employed in radar absorbing materials (RAMs) and in defense, communication electronics, medical equipment, human health care, laboratory environments and public safety issues. In strategic areas, where the electromagnetic interference (EMI) shielding effectiveness is essential, the components and parts made by EMI shielding materials is to be upgraded. The EM shield play a significant role in reducing the intensity of reflected and transmitted EM waves. Recently, research on EM wave absorbers is focused on polymer-based structures, and layered carbon structures. The basic qualities of polymer and carbon have been successfully applied to minimize the reflection coefficient, and maximize absorption coefficient in metrology as well as in defense equipment’s. In this context, most of the studies use composites made with polymers and carbon materials and some studies are focused on foamed structures and metamaterials. In the present work, polyaniline (PANI) and carbon fiber (CF)-based paper like sheet structures were produced by compression molding technique and their electrical and EMI shielding properties are measured in X-band (8.2–12.4 GHz) frequency range. PANI paper has been found to have an electrical conductivity of 12.48 S/cm and EMI shielding effectiveness of PANI paper is found to be − 26.82 dB at a thickness of 0.75 mm. Scanning electron microscopy (SEM) approves the coating of polymer on carbon fiber and thermogravimetric analysis (TGA) demonstrates that the presence of carbon fiber drastically improves the thermal stability of the polymer sheets .

In this paper, we have presented the synthesis of nickel oxide (NiO) nanoparticles using sol–gel method and measured its structural, electrical and humidity sensing properties using different measurement tools after annealing at three different temperatures of 200 °C, 400 °C and 700 °C for 1 h in air. Structural and morphological properties of nickel oxide nanoparticles were measured by means of X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM), respectively. XRD analysis shows the crystallographic nature of prepared NiO nanoparticles. The result shows that the average crystallite size increases with increase in annealing temperature which reveals a fine nanocrystalline grain structure. The Williamson–Hall and size-strain plots were used to study the individual contribution of crystallite size and strain on the peak broadening of NiO nanoparticles. The parameters including stress and strain were also calculated from the XRD corresponding to the cubic phase of NiO. The FESEM images confirm the mesoporous surface morphology of a nickel oxide with an increase in particle size on increasing annealing temperature. The effect of annealing on the activation energy of the pellets is also discussed in the paper. Samples in the form of pellets were exposed to humidity in the range from 10 to 90% relative humidity (RH). NiO sample annealed at 700 °C has demonstrated the highest sensing response of 47.09% at 90% RH.

The paper reports preparation and characterization of a proton conducting polymer electrolyte system comprising a blend of poly(vinylalcohol) (PVA) and poly(vinylpyrrolidone) (PVP) and liquid electrolyte of ammonium thiocyanate (NH4SCN) in the ionic liquid 1-Ethyl-3-methylimidazolium thiocyanate [C2C1Im][SCN]. The well-known solution cast technique has been used to prepare films of the blend polymer electrolyte. The films have been characterized using FTIR and Raman spectroscopy, X-ray diffraction, DSC/TGA, complex impedance spectroscopy and cyclic voltammetry. The liquid electrolyte has been found to form complex with the polymer blend system. The electrolyte system has been observed to possess very small crystallinity. The melting point of the electrolyte has been found to be 121 °C for the highest conducting composition. The ionic conductivity of the films has been observed to be ~ 10–2 S cm−1 at room temperature. The temperature dependence of ionic conductivity of the blend electrolyte shows VTF behavior. The ion conduction has been investigated with the help of dielectric behavior of the electrolyte membrane. The paper also reports confirmation of protonic conduction in the electrolyte using complex impedance spectroscopy and cyclic voltammetry.

In this paper, we present the development and performance analysis of AlNB alloy for thermal management applications. The AlNB alloy at nanoscale film thickness is grown in stack configuration of (Al-AlN-B) on modified aluminium (Al) substrates (5052) using reactive sputtering at room temperature and annealed at 400 °C under nitrogen ambient. Cubic aluminium nitride (c-AlN) structures with (200) and (220) orientations are confirmed by the X-ray diffractometer (XRD) analysis. Furthermore, the presence of AlN and boron nitride (BN) is established from Fourier-transform infrared spectroscopy (FTIR) spectra. The measured film thickness of the AlNB alloy films is in the range from ~ 157.4 to 378.8 nm, while the particle sizes are in the range between ∼80 and 300 nm. The measured roughness of the films is in the range ~ 54 and 82 nm for the three samples, by the processing of Atomic Force Microscopy (AFM) images using Nanoscope software. However, from the cumulative structure function analysis, the total thermal resistance of the light-emitting diode (LED) (Rthj-a) is reduced by about ~ 4 to ~ 23%, with samples 1 (AlN/B), 2 (AlN/B/AlN/B) and 3 (AlN/B/AlN/B/AlN) as compared to that of bare Al substrate. Previous literature on similar material indicates higher thermal resistance of about 43–53 (K/W); however, in our work, we were able to achieve low Rth of 8.5 (K/W) as reported in this paper. Furthermore, considering the structural properties, surface, and good thermal performance coupled with lower bond line thickness (BLT) in ~ 150 nm range exhibited by the grown alloy, the developed material is therefore recommended for effective thermal management application of LEDs and other solid-state devices at low and high operational current densities.

In this paper, rutile phase titanium oxide/Sb-SnO2/anatase phase titanium oxide (TiO2 (R)/C-TiO2 (A)) heterostructured nanocomposites were prepared by a sol–gel method and a hydrothermal method. By optimizing the mass ratio between TiO2 (R) and C-TiO2 (A), the rod-ball heterostructures of TiO2 (R)/C-TiO2 (A) were formed and exhibited enhanced simulated sunlight-driven photocatalytic desulfurization performance. According to the results, the desulfurization rate of TiO2 (R)/C-TiO2 (A) was 93.98% after 60 min, which is higher than C-TiO2 (A) and TiO2 (R)/TiO2 (A). In addition, the photocatalytic recyclability test indicated that after three times the reuse of TiO2 (R)/C-TiO2 (A) could still reach 85.98%. The enhanced photocatalytic performance could be attributed to the double Z-scheme heterojunction in the TiO2 (R)/C-TiO2 (A) and the uniformly structure of rod array, which resulted in the higher separation efficiency of electrons and holes. Furthermore, the results of photocatalytic active radical species trapping experiments showed that the main substances in the photocatalytic reaction are ∙O2− and h+. This paper also established the double Z-scheme heterojunction reaction mechanism.

In the present study, an integrated flexible piezoresistive pressure sensor with a silicon rubber (SR) buffer layer is proposed to optimize the workable pressure range of flexible pressure sensor. The sensitive unit of the integrated flexible pressure sensor is made of composite elastic dielectric SR filled with carbon black (CB) and carbon nanotubes (CNTs). This paper introduces the preparation process, working principle and structure design of the CB/CNTs/SR composite with an SR buffer layer. In addition, the influence of electrode structure and buffer layer is studied. A dispersible interdigital electrode structure is selected to prevent the decline of pressure sensing sensitivity in a small range. The proposed flexible pressure sensor achieves a wide pressure range of 0–120 N. Facile fabrication, high repeatability, high stability and low cost are also excellent characteristics of the sensors investigated in this paper. In this study, a design proposal for wearable equipment and wearable bionic skin study is provided.

To improve the resistive switching performance of RRAM devices, it is desirable to find electrodes with good ability of oxygen reservoir. In this paper, bipolar switching mode of TiN/SiO2/FePt devices is achieved by using FePt as oxygen reservoir, since O atoms will be absorbed by Fe atoms to form FeOx film. Therefore, the oxygen reservoir’s ability can be evaluated by the molar ratio of FeOx in FePt film and it is found that the more molar ratio of FeOx the stronger oxygen reservoir’s ability is obtained. Interestingly, the self-rectifying characteristics in the devices with FePt electrode is observed due to the different work functions between TiN (4.7 eV) and FePt (> 5 eV). Furthermore, the transition between self-rectifying mode and diode mode can be achieved by controlling the applied voltage, which is beneficial for 1D1R architecture. The study in this paper may offer a method for fabrication of oxide-RRAM based 3D crossbar array with good performances.

This paper reports for the first time the synthesis of polyhedral-like Zn(OH)2/ZnV3O8 nanostructures by a single-step sonochemical method. Particle formation and growth were controlled by using hydrazinium hydroxide and ethylenediamine under ultrasonic waves and then acidifying the medium. After synthesis and identification by XRD, EDS, and FESEM techniques, the mentioned nanostructures were used for electrochemical hydrogen storage, which showed a high potential of 3300 mAh/g storage. Metal hydroxides and multivalent ions such as vanadium are highly capable of electrochemical processes, so this paper focuses on their synthesis.

A compact wideband metamaterial absorber (MA) for Ku band applications is presented in this paper. Ku band is a part of a microwave frequency spectrum ranging from 12 to 18 GHz. The proposed MA absorbs incident wave from 11.39 to 20.15 GHz with a bandwidth of 8.76 GHz which fully covers the Ku band. The proposed structure is compact having an overall dimension of 10 mm $$\times$$ 10 mm. The structure is fabricated on the $$FR_{4}$$ substrate and the simulated result is carried using ANSYS HFSS 19.1. The absorption mechanism is illustrated by calculating effective electro magnetic (EM) parameters ( $$\epsilon _{eff}$$ & $$\mu _{eff}$$ ). Current distribution is also plotted in support of absorption mechanism. The structure is also examined at different angles ( $$0^0$$ – $$90^0$$ ) for the oblique and normal incident. The proposed MA is tested inside the Anechoic Chamber and it was found that simulated and measured result is close to each other with variation within the tolerance limit. At last comparison of the proposed MA is done with already reported MA. MA presented in this paper finds applications for satellite communication radar surveillance and other defense applications.

Dye-sensitized solar cells (DSSCs) are low cost and eco-friendly photovoltaic devices which require new ideas for further development. In this paper, we use electro-spun TiO2 nanofibers to prepare the DSSCs photoanode. In order to isolate the FTO and electrolyte species, we deposit a spin-coated TiO2 blocking layer at their interface. The performance of this cell is further improved by introducing surface plasmon resonances (SPRs) at the surface of the nanofibers. It is shown that SPRs increase the generated current in the cells by providing a higher light absorption and lower recombination. Our best cell showed an efficiency of 6.19%, which is a 28% improvement in comparison to the bare DSSC with 4.84% efficiency. The results of this paper are acquired and confirmed by XRD, FESEM, TEM, EDS, dye-loading, IPCE, J–V, and EIS measurements.

Vanadium dioxide (VO2) will undergo a reversible phase transition when under thermal, electrical or optical stimuli. The use of electric field to induce the transport properties is promising for novel switches, volatile memory and photodetectors. In this paper, VO2 nanoparticles were synthesized by the hydrothermal and post-vacuum annealing method. And then, the electro-induced MIT of the composite film filled with VO2 particles was discussed. The results show that purity VO2 (B) with different morphologies were obtained at different temperatures from 120 to 240 °C. The HRTEM images proved that the VO2 (B) nanobelts grow in the direction of the (110) plane, and the VO2 (M) nanoparticles grow along the (110) crystal plane. SEM pictures illustrate that the length of the nanoparticles becomes smaller as the preparation temperature increases. DSC reports and I-V traces proved that the VO2 (M) has an excellent performance of phase transition under heating and voltage. The results show that the hydrothermal temperature is helpful to increase the initial resistance, resistance change rate and phase change voltage of VO2 composite film. And the maximum resistance change rate before and after the MIT of samples is higher than 200. The experimental results show that the VO2 coating has an excellent voltage nonlinear response, due to the apparent switching performance, high nonlinear coefficient, and good consistency. The research data and theoretical analysis of this paper have an excellent guiding role for the application of VO2 in the electro-induced phase transition.

A multijunction or tandem technique comprising a wide bandgap top cell and a narrow bandgap bottom cell may be a major stepping stone in an attempt to obtain high-efficiency solar cells. However, easier said than done, it takes a lot to correctly optimize the structure of all the involved layers so as to possibly obtain the desired results. In this paper, a perovskite (CH3NH3PbI3)/FeSi2 (p-i-n structure) 2-terminal (2-T) monolithic tandem solar cell is proposed and investigated using AFORS-HET v2.5 1D simulator. A hydrogenated amorphous silicon (a-Si:H)/hydrogenated microcrystalline silicon oxide (µc-Si1−xOx:H) tunnel recombination junction is employed to interconnect both perovskite and FeSi2 solar cell for current matching. The influence of both top and bottom absorber layer thickness is analyzed to optimize the device performance. The study reveals an optimized 26.3% efficient perovskite/FeSi2 monolithic tandem solar cell with JSC (21.4 mA cm−2), VOC (1.63 V), and FF (74.86%). The results in this paper suggest FeSi2 material with 0.87 eV bandgap as an alternative for narrow bandgap bottom cell for the perovskite-based tandem solar cells so as to obtain much higher efficiencies.

In this paper, the synthesis of BiFe1−xMnxO3 (x = 0.05, 0.10, 015, 0.20) thin films using a sol–gel technique was proposed. The structural characteristics of the thin films were investigated by X-ray diffraction (XRD), indicating a structural transition from typical rhombohedral-R3c (BiFeO3) to orthorhombic-Pbmn (BiFe0.80Mn0.20O3). It was shown that, Mn was successfully doped into BiFeO3 films and the Fe3+ ions in the films increased after doping by the X-ray photoelectron spectroscopy (XPS) analysis. The numerical results in this paper showed that the saturation magnetization of these BiFeO3 thin films had been found to increase on doping with Mn2+ ions, reaching a maximum value of 83.5 emu/cm3 for the BiFe0.80Mn0.20O3 thin films. The numerical results also revealed that the proposed method in this paper can serve as a useful theoretical tool for gaining insight into the correlations of magnetic and structure property for BiFeO3 thin films.

It was the constant pursuit of researchers to explore catalysts with higher catalytic activity, and the use of co-catalysts to modify the performance of photocatalytic materials had a significant effect on charge separation. In this paper, the non-precious metal NiS-modified ZnCo2O4 composite catalytic material prepared by hydrothermal method had high-efficiency catalytic performance. When the weight ratio of NiS to ZnCo2O4 was 12%, the optimal catalytic activity is 3.57 mmol g−1 h−1, which was more than twice that of ZnCo2O4. The presence of NiS not only improved the specific surface area of the catalyst and its ability to respond to light, but the close interface formed by the combination of the two monomer phases accelerated the transfer and the utilization of the photocharge on ZnCo2O4 to NiS, thereby promoting the separation of electron holes and improving the photocatalytic activity of the catalyst. According to the research results, the mechanism of hydrogen production in the photocatalytic system was revealed. In this paper, NiS was used to modify the bimetallic oxide with cubic appearance, which provided a new strategy for the development of new photocatalysts.

The challenge of continuously powering the wireless sensor network located at remote areas has been resolved by the emergence of piezoelectric energy harvester. This paper evolved a new idea of using different piezoelectric materials together within segmented doubly clamped bimorph piezoelectric energy harvester (DCBPEH). The finite element modeling of the device has been presented here using COMSOL multiphysics software. This paper starts with concept of strain nodes and further better performance of segmented electrodes-based beam over the continuous electrode-based beam has been achieved. Next, a performance analysis study with continuous electrode-based beam has been carried out for different variants of two piezoelectric materials, namely, PMN-xPT and PZT. From this study, PMN-35%PT and PZT-5H piezoelectric materials are found to be best variants. Finally, the performance of segmented DCBPEH has been observed for different positioning formats of PMN-35%PT (M1) and PZT-5H (M2) piezoelectric materials on different segments of the beam. From this analysis, M1–M1–M2 and M2–M1–M1 are noted to be two favorable positioning formats which provide similar and maximum performance (7.78 mW) as compared to other formats.

This paper reports an approach for improving the photoluminescence characteristics of red-emitting Y0.95(P0.6V0.4)O4:Eu0.05 phosphors, with the incorporation of Al3+ ions, using a chemical co-precipitation process. In this paper, structural, scanning electron microscopic (SEM), photoluminescence properties, infrared spectroscopy, and CIE of the Y0.95−x(P0.6V0.4)AlxO4:Eu0.05 (x = 0.0, 0.005, 0.01, 0.015, 0.02, 0.025, 0.03, 0.035) phosphors are reported. The doping of a small amount of Al3+ ions to Y0.95−x(P0.6V0.4)AlxO4:Eu0.05 phosphors significantly enhanced the emission intensity up to x = 0.025%. The most dominant red emission intensity peak of Eu3+ for 5D0 → 7F2 transition of the Y0.975(P0.6V0.4)Al0.025O4:Eu0.05 phosphor is located at 622 nm, which is stronger than that of the free Al3+ Y0.95(P0.6V0.4)O4:Eu0.05 phosphor. The result shows that this phosphor has a certain amount of the application prospect of the white LED.

ZnS is a good candidate material for making visible light display devices. However, the blue emission of ZnS is so strong in luminescence spectra that it may harm human eyes. In this paper, we prepared the Mn and Cu co-doped ZnS quantum dots, which successfully decreased the blue photoluminescence without producing any Mn-related yellow–orange emissions, and obviously enhanced the eyes-friendly green photoluminescence at the same time. The relevant physical mechanisms have been discussed in detail. Overall, this paper realizes the suppression of blue photoluminescence and enhancement of green photoluminescence of ZnS, thereby the center of whole photoluminescence spectra of ZnS is transferred successfully from blue to green, showing a bright prospect for the application in visible display devices.

Triboluminescence is the spontaneous emission of light that results from the mechanical force applied to certain materials. This spontaneous light emission has been observed for hundreds of years. However, there are few practical applications of triboluminescence. Mechano-luminescence is a form of triboluminescence, and sometimes the terms are used interchangeably. Triboluminescence has the potential to use in many fields. This paper is a review of the history and mechanics of triboluminescence, and some applications are discussed. The types of triboluminescence covered in this paper include elastic-stress mechano-luminescence, plastic-stress mechano-luminescence, and fracture mechano-luminescence. Materials and methods in developing future applications have also been included. The research reviewed in this paper gives an insight into past and current advances in the field of triboluminescence and explains the potential for future applications.

Nickel has attracted much attention as a cheap and readily available electrocatalyst towards the electrooxidation of hydrogen peroxide (H2O2). For the electrocatalytic reaction, the larger the surface area of the electrode, the more active sites can be provided, and the better the catalytic performance of the electrode can be achieved. In this paper, a three-dimensional (3D) porous electrode was successfully prepared by a simple two-step method. Firstly, the Ni–SiO2 composite was uniformly deposited on the carbon paper (CP) by electrodeposition, and then the SiO2 component in the Ni–SiO2 composite was removed by after dealloying (AD) to form a Ni–SiO2/CP (AD) electrode with a 3D porous structure, which has high catalytic activity area and good gas–liquid mass transfer property. The prepared Ni–SiO2/CP (AD) exhibits superior catalytic activity for H2O2 electrooxidation. At normal temperature, Ni–SiO2/CP (AD) in 1.0 mol dm−3 NaOH + 0.2 mol dm−3 H2O2 electrolyte solution, the oxidation current density reached 355 mA cm−2, which is 1.85 times the Ni/CP current density under the same conditions. This study provides a new idea for preparation of high catalytic activity of Ni catalyst for the electrooxidation of H2O2.

Cu-based conductive inks are more cost effective than silver-based ones for flexible electronics. However, it is challenging to simultaneously ensure the mechanical flexibility, environmental oxidation durability, and low resistance of the sintered Cu electrodes. To achieve this goal, Cu-based conductive inks including silane coupling agents are developed and used to produce flexible Cu electrodes on cellulose paper after air–atmosphere sintering. The key factor to achieve the mechanical flexibility and environmental oxidation durability at the same time is the use of aminoethyl-aminopropyltrimethoxysilane (AEAPTMS) or 3-glycidoxypropyltrimethoxysilane (GPTMS). Negligible resistance change is observed in the sintered Cu electrode with AEAPTMS, even after 1000 repeated bending cycles with a bending radius of 5 mm and exposure at 60 °C/80% RH for 7 days. Especially, Cu electrodes produced using GPTMS show improved flexibility with negligible resistance change even after 10,000 bending cycles. To demonstrate the applicability of these Cu electrodes, a flexible paper-based movement sensor is successfully fabricated from the present Cu-based ink. This approach using silane coupling agents will contribute to the reliable operation of Cu-based flexible devices with high mechanical and environmental durability.

A study on optical and structural properties of nanoporous silicon is presented in this paper. The samples were prepared by electrochemical etching a heavily boron doped silicon wafer in a hydrofluoric acid electrolyte and flowed by in-situ sintering in ultra-high vacuum chemical vapor deposition reactor (UHVCVD) under hydrogen atmosphere at high temperature varied between 900 and 1100 °C. The structural and morphological properties were carried out using atomic force microscopy (AFM), scanning electronic microscopy (SEM) and high resolution transmission electronic microscopy (HRTEM). The optical properties were performed using the photoluminescence Spectroscopy (PL), Time Resolved Photoluminescence (TRPL), RAMAN spectroscopy and Fourier-transform infrared spectroscopy (FT-IR). It is shown that the in-situ heating at 900 °C desorbs the native oxide from the porous layer and closes the pores forming a continuous defects-free surface at the top of porous layer. The process allows obtaining stable porous layer with enhanced structural and optical properties and also tailoring the morphological properties and the visible optical emission. This paper aims at a comprehensive determination of the physical properties of sintered porous silicon, in particular, its structural and optical properties.

This paper reports synthesis of CaSrAl2SiO7:Ce3+ phosphors via traditional high temperature solid state reaction method. The phase analysis of the phosphors was carried out using powder X-ray diffraction (XRD) technique which indicates that all these compounds are of single phase of CaSrAl2SiO7 with tetragonal crystal structure. Average grain size of the phosphor was determined by using Scherrer formula. The photoluminescence (PL) study was carried out using spectrofluorophotometer. PL Excitation (PLE) spectra consist of two peaks at around 253 and 290 nm. CaSrAl2SiO7:Ce3+ emits strong violet emission located at 418 nm when excited with 290 nm. Emission is associated with 5D→4F transition of Ce3+ ions. Thermoluminescence (TL) properties of UV-irradiated phosphor were measured. Effect of different heating rates on TL glow curve was recorded and 5 °C/s is found to be optimum heating rate. There is no shift in glow peak position with increase in UV-irradiation time. TL intensity increases with increase in UV exposure time up to 35 min and then saturates. To analyse kinetic study, glow curve was deconvoluted into four different traps and their activation energies were determined by using peak shape method. Concentration dependence on PL and TL was investigated; concentration quenching in PL occurs at 1 mol% of Ce3+ and quenching in TL arises at 0.5 mol% of Ce3+. TL spectra and decay characteristic were also carried out. This paper deals with possible mechanism of PL and TL.

Excellence in the performance of MEMS-based devices such as RF switches, microfluidics, and pressure sensors are well known and by now reported. Operations of these devices are very sensitive to the environmental factors such as contamination, humidity, vibrations etc. Thus, the integration of these micro-devices with the real-life systems could be challenging without a hermetic sealing. A very common practice for these sealing is to bond a recessed cap onto a micromachined wafer using low-temperature wafer bonding mechanism known as anodic bonding or high-temperature sealing techniques such as fusion bonding for vacuum packages. Considering the limit of high-temperature bonding due to thin-film metals like nickel and gold present on the wafer and the induced bow associated with this high-temperature, this paper reveals a devising electrode designed that successfully bonded the samples at a reduced temperature well below at 250 °C. The reliability and effects of this low-temperature bonding between the silicon and Pyrex glass using destructive and non-destructive mechanisms have been investigated in this paper. The tensile strength measurements indicated a superior bonding strength of 14.12 MPa for the sample bonded at 250 °C. The induced bow height reduced from 30.3 µm (at 450 °C) to 0.3 µm (at 250 °C) meaning a significant reduction of bow up to 80.2%. Elemental composition was studied at the interface using energy dispersive X-ray spectroscopy (EDAX). To evaluate the bond quality, infra-red (IR) imaging was performed on the bonded sample pair. The interfaces were examined and analysed by scanning electron microscopy (SEM). Finally, we implemented this technique for a MEMS based pressure sensor application to prove the feasibility of low-temperature anodic bonding.

This paper reports the synthesis of undoped PbS and PbS–CdO nanocomposites by a simple soft chemical route. The thermal behavior, structural, morphological, optical, magnetic and antimicrobial properties of the synthesized samples was studied and the results are reported in this paper. The undoped PbS and PbS–CdO nanocomposite exhibit polycrystalline nature with cubic crystal structure. The crystallite size values of the PbS and PbS–CdO nanocomposites estimated using Scherrer formula were found to be equal to 24.96 and 21.89 nm respectively. TG-DTA analysis shows that the PbS–CdO nanocomposite becomes well crystallized above 400 °C. Peaks related to PbS and CdO were observed in the FTIR spectra of the composite. Magnetic studies confirm that the PbS–CdO nanocomposite exhibit ferromagnetic ordering in the form of S-shaped loop. Enhanced antibacterial and antifungal activities were observed for the PbS–CdO nanocomposite.

This paper is a comprehensive study on Newton–Raphson technique used in millimeter wave frequencies for material characterization. Various algorithms are used for extracting the complex permittivity of a material from measured S-parameters. Efficiency of the methods depends on the initial guess and the accuracy of measured S-parameters for each thickness and frequency band. In this paper, we suggest the initial-value estimation method that helps to estimate a proper value for starting the algorithm. Moreover, an alternative extraction process is modelled that does not require new measured S-parameters or extracting process for each frequency band and thickness with a composed database. The estimation process is conducted partially as V (50–75 GHz), W (75–110 GHz), and D (110–170 GHz) frequency bands.

We measured transient absorption in α-Al2O3 after pulsed electron beam irradiation to analyze the relaxation process of excited states. We used two measurement systems to obtain transient absorption in nanosecond and picosecond time scales. In the nanosecond time scale, we observed a band at 610 nm in addition to a shoulder at 420 nm. This observation is consistent with that in a previous paper, and these bands are attributed to Al interstitials according to the paper. The decay behavior of these bands was significantly different in the picosecond time scale. The difference in the decay kinetics strongly suggests that the band at 610 nm and the shoulder at 420 nm are attributed to two kinds of Al interstitials.

Photovoltaic devices are developed mainly based on p-n or p-i-n type device structures, and these devices can utilise only a fraction of the solar spectrum. In order to further improve device parameters and move towards low-cost and high-efficiency next generation solar cells, device architectures capable of harvesting all photons available should be designed and developed. One such architecture is the fully graded bandgap device structure as proposed recently based on both n-type and p-type window layers. These designs have been experimentally tested using well researched GaAs/AlGaAs system producing impressive device parameters of open circuit voltage (Voc) ~1175 mV and fill factor (FF) ~0.85. The devices have also been experimentally tested for the evidence of impurity photovoltaic (PV) effect and impact ionisation taking place within the same device. Since these structures have been experimentally proved with a well-established semiconductor, the effort has been focussed on developing these devices using low-cost and scalable electroplated semiconductors, in order to minimise manufacturing cost. This paper reviews and summarises the work carried out during the past decade on this subject. Graded bandgap devices produced using only two or three electroplated semiconductor layers have been explored and their conversion efficiencies have gradually increased from 10.0%, through 12.8% to 15.3% for different structures. While the work is progressing along this line, the paper summarises the achievements to date.

CoFe2O4 (CFO)/BaTiO3 (BTO) magnetoelectric (ME) ceramic composites were prepared by spark plasma sintering (SPS) with mechanically mixed powders. The unwanted phases, atomic interdiffusion and microcracks emerged in the conventional sintering process were prevented in the SPS process. The CFO/BTO ceramics showed great densities measured by the Archimedes method. In this paper, the ferromagnetic, ferroelectric, and ME properties of the ceramic composites were well studied. The strongly optimized ME voltage coefficient up to as high as 180 mV/cm Oe was obtained in the spark plasma sintered CFO/BTO ceramics. The theoretical ME voltage coefficients of the ceramics were also calculated by the finite-element method. The reasons for the improvement of the ME voltage coefficient and the lower experimental ME value comparing to the calculations were both discussed in this paper.

In this paper, the un-doped, Mo doped, N doped and Mo–N co-doped TiO2 nanotubes (TNTs) films were prepared by a two-step anodic oxidation method. The paper mainly investigated the origin of room temperature (RT) magnetic properties of all the samples. X-ray diffraction studies showed that the impurity of magnetic Mo atoms or N atoms were doped into anatase TiO2 lattices. It is revealed by the results of X-ray photoelectron spectroscopy and photoluminescence spectra that oxygen vacancies (Vos) exist. For all the samples the values of the saturation magnetizations (Ms) are in the order of Mo–N co-doped TiO2 > Mo-doped TiO2 > N-doped TiO2 > un-doped TiO2. Thus, the the Mo–N co-doped film achieved the highest RT Ms. The enhancement of the Ms origins from the cooperationg of the doping Vo, Mo and N. This progress provides some clues for the increase the saturation magnetization in TiO2-based dilute magnetic semiconductors at RT. The experiment results indicate that the Vos play a crucial role in RT ferromagnetic properties for TNTs films.

The photoluminescence (PL) property of CeO2/g-C3N4 mixed samples have been studied in recent years, but it is not attractive due to their lower PL emission. In this paper, a simple mixing-calcinations method was used to prepare CeO2/g-C3N4 mixed particles. In this paper, CeO2 particles were synthesized at two different temperatures (120 and 140 °C) by two-step method. The g-C3N4 powders were prepared by heating urea directly. Then, the two products were mixed together and annealed at 300 °C for 1 h by a simple mixing-calcinations method. It was found that the spindle and fascicular shapes of CeO2 were surrounded by lamellar g-C3N4 with porous surface. The strong emission and emission peaks shifting happened to CeO2/g-C3N4 particles, in which CeO2 was prepared at 120 °C, due to the mutual synergistic effect of CeO2 and g-C3N4.

In this paper BaWO4 nanoparticles were prepared via a sonochemical route based on the reaction between barium salt and Na2WO4·2H2O in water. Moreover, this method is free from any surfactant and organic solvents. The structural, morphological and optical properties of as-obtained products were characterized by techniques such as XRD, EDS, SEM, and UV–visible. The magnetic properties of as-prepared BaWO4 nanoparticles were also investigated with vibrating sample magnetometer. To evaluate the photocatalysts properties of nanocrystalline barium tungstate, the photocatalytic degradation of methyl orange under ultraviolet light irradiation was carried out. The new synthetic method presented in this paper has potential applications to fabricate other metal tungstates (BaWO4) materials.

This paper reports the Raman spectra and electrical analysis of Se-deficient Cu(In,Ga)Se2 (CIGS) films with various Cu contents. These films were deposited by low-cost two-step process consisting of sputtering of metallic precursor and subsequent selenization. Raman spectra exhibit the formation of chalcopyrite phase while signs of secondary phases like CuxSe and ordered vacancy compound are also observed. Electrical measurements show the change of main carrier source as well as the transformation of conduction type with varying Cu content. Comprehensive analysis of Raman spectra and electrical measurements qualitatively explains the relationship between electrical properties and Cu contents. Based on this relationship, the optimal range of Cu/(Ga + In) for Se-deficient CIGS solar cells is identified as 0.875–0.925, which is smaller than that for Se-sufficient CIGS solar cells due to the presence of Se vacancies. The efficiency data of CIGS solar cells fabricated with same absorber deposition process are in good agreement with this optimal range. The results of this paper could be used to estimate device performance at early process stages.

In this paper MnWO4 nanoparticles were prepared via a sonochemical method based on the reaction between manganese salt and Na2WO4·2H2O in water. Moreover, this method is free from any surfactant and organic solvents. The structural, morphological and optical properties of as-obtained products were characterized by techniques such as XRD, EDS, SEM, and UV–Visible. The magnetic properties of as-prepared MnWO4 nanoparticles were also investigated with vibrating sample magnetometer (VSM). To evaluate the photocatalysts properties of nanocrystalline manganese tungstate, the photocatalytic degradation of methyl orange under ultraviolet light irradiation was carried out. The new synthetic method presented in this paper has potential applications to fabricate other metal tungstates (MWO4) materials.

The aim of this paper is the replacing of the expensive sputtering method with the low cost sol–gel one in TCO applications. To this end two sets of indium tin oxide (ITO) thin films are compared and discussed in this paper: one obtained by r.f. sputtering and one by the sol–gel technique and dip-coating. For each of these sets of samples, a series of deposition parameters have been varied in an effort to obtain the most promising optical and electrical properties. Comparative structural, morphological and opto-electrical characterization of sol–gel and sputtered ITO-based films was performed by X-ray diffraction, Scanning electron microscopy, Atomic force microscopy, Spectroellipsometry, UV–VIS Spectroscopy and Hall Effect measurements in order to establish whether the chemical deposition method could lead to thin films with competitive properties as those obtained through the physical method. Comparable, high transmittance (85–90 %) in the VIS–NIR range (250–1050 nm) and carrier concentration values (1020–1021 cm−3) were obtained between sputtered and sol–gel ITO films. The sputtered ITO film in 75 % N2, annealed at 500 °C and the sol–gel 0.1 M ITO film with 10 layers deposited on SiO2/glass exhibit degenerate semiconductor behavior.

A simple, easy-to-use and physically meaningful predictive model is suggested for the assessment of the thermal stresses in a ball-grid-array (BGA) or a column-grid-array (CGA) system with an epoxy adhesive at the peripheral portions of the assembly. It is shown that the application of such a design can lead to a considerable relief in the interfacial stress. The paper is a continuation and an extension of the recently published paper, in which a low modulus solder was considered for the peripheral portions of the assembly. The important difference is that while the soldering temperature has been assumed to be the same for the solder material throughout the assembly, the peripheral epoxy adhesive is applied at an appreciably lower (curing) temperature than the solder at the assembly’s mid-portion. The numerical example has indicated that the application of the CGA technology enables one to achieve a 19.25 % stress relief in the case of an epoxy adhesive, while a 34.11 % stress relief could be expected in the case of a low modulus solder at the assembly ends. When a BGA technology is considered, the application of an epoxy or a low modulus solder at the peripheral portions of the assembly leads to the stress relief of about 14.42 % in the case of an epoxy and of about 12.80 % in the case of a low modulus solder. When CGA technology is used, the application of an epoxy at the peripheral portions of the assembly leads to about 8.70 % stress relief, while the application of a low modulus solder results in about 24.10 % relief. It is concluded that, with the yield stress in shear of 1.85 kgf/mm2 for the solder in the assembly’s mid-portion and 1.35 kgf/mm2—for the peripheral solder material, the application of the CGA technology in combination with an epoxy adhesive or a low modulus solder at the assembly ends might enable one to avoid inelastic strains in the solder, thereby increasing dramatically its fatigue lifetime, just because the low-cycle fatigue situation will be replaced in such a case with the elastic fatigue condition.

Band gap lowering in TiO2 is usually done by adding impurity to it. In this paper a new approach is adopted to make TiO2 thin films by unconventional sol–gel method starting with TiO2 powder reagent. The prepared gel is deposited on the microscopic glass slide by doctor blade technique. The prepared films were then subjected to X-ray diffraction for structural and microstructural analysis. Different optical parameters like, thickness, refractive index, extinction coefficient, transmittance and absorbance etc. are calculated and finally band gap of the samples are estimated and are presented in this work. Both the refractive indices and band gap are found to be lower than that reported earlier. Scanning electron microscope image shows dense and uniformly distributed TiO2 particles. The quality and novelty of this paper is that, the micro size nano thick film is prepared from powder reagent unlike other published papers and novelty lies in its very low band gap as direct transition is more favorable for TiO2 nanoparticles in anatase phase.

This paper presents the optical properties of organic material bromoindium phthalocyanine (BrInPc) thin films grown by electron beam evaporation technique. The paper describes the optical characteristics of BrInPc thin films, which have been determined using spectrophotometric measurements of the absorbance, transmittance and reflectance at normal incident of light in the spectral range 300–1,100 nm. The optical band gap energy and type of the electronic transition have been determined by analysis of spectral behavior of absorption coefficient, which reveals the probability of both direct and indirect transitions. Other optical constants, such as refractive index, extinction coefficient, complex dielectric constant and optical conductivity of thin films have been evaluated. Moreover, the width of band tails of localized states (Urbach energy), steepness parameter and width of the defect states have been determined by studying the absorption coefficient spectra just below the fundamental absorption edge.

Nitric oxide(NO), nitrogen dioxide (NO2), nitrous oxide (N2O), and their derivatives generally known as nitrogen oxides (NOx) are primary pollutants in the atmosphere originated from natural and anthropogenic sources. The paper presents investigation of electric performance of novel chemiresistor NOx gas sensors. A novel material was utilized for active sensing layer-conductive copolymer and zinc oxide blend. The main advantage of the presented solution is low-cost and environment-friendly production. A series of this type of sensors was manufactured and tested experimentally. During the tests, the gas flow was controlled and signals of sensor responses, temperature, and humidity were computer-acquired using LabVIEW program. Sensor behavior for different thicknesses of the active layer has been investigated and interpreted. The research revealed that the electrical resistance of the sensors has changed in predictable manner depending on the gas concentrations. A recurrent artificial neural network architecture is proposed as a mathematical model to classify sensor responses to gas concentrations variation in a time-dependent regime. In this research, an enhanced method for gas concentration prediction is proposed using non-linear autoregression model with exogenous input (NARX). The performed simulations show good agreement between simulated and experimental data useful for predictions of sensor gas response.