Carbon nanotube (CNT) is one of the most significant materials for the development of faster and improved performance of nanoscaled transistors. This work aims at analysing a trade-off between device performance and device size of CNT-based transistor. Acoustic and optical phonon (OP) scattering along with the elastic scattering lead to the non-ballistic performances of those transistors. The main focus of this work is mainly on finding an optimum diameter to obtain the highest degree of ballisticity (DoB) from both single-walled (SWCNT-FET) and double-walled CNT field-effect transistors (DWCNT-FET). At first, an n-type SWCNT-FET has been considered and the diameter dependence on DoB has been simulated. The effects of drain voltage, gate voltage and channel length have been investigated for such characteristics followed by a comparison with DWCNT-FET structure. First of all, it has been found that DoB along with the optimum diameter increases with the increase of (V _DS–V _GS). The increase of channel length, however, degrades the ballistic performance demanding a higher diameter to reach the optimum point. Finally, it can be concluded that optimum diameter for DWCNT-FET reaches earlier than SWCNT-FET but at lower DoB.

Vertical graphene (VG) nanosheets are directly grown on silica aerogel and silicon substrate (100) by plasma-enhanced chemical vapour deposition process in the presence of hydrogen as a reducing agent at atmospheric pressure at 800°C. The physiochemical properties of the nanohybrid were thoroughly characterised by Raman spectroscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM). The presence of full wave half maximum of D, G and D′ indicates VG nanowalls. The height (≅50 nm) of the VG nanowalls were confirmed by SEM and Raman spectroscopy but AFM reveals it as ≅ 15 nm. Surface and cross-sectional SEM show the uniform distribution of vertical growth of nanowalls and the AFM revealed surface morphology of VG nanowalls.

A partial super junction lateral double-diffused metal–oxide–semiconductor field-effect transistor with a variable-k dielectric layer (PSJ VK LDMOS) is proposed in this Letter. Low-k material and PSJ are introduced into the device. PSJ provides a low-resistance channel to reduce the specific on-resistance (R _on,sp). Furthermore, according to an enhanced dielectric layer field, low-k buried layer can sustain the high breakdown voltage (BV). To eliminate substrate-assisted depletion effect and improve the lateral BV of the proposed structure, the charge compensation layer in the device adopts a variation of lateral doping technique and is combined with the N pillar in PSJ. Ultimately, the simulation results show that BV of 795.5 V and the figure of merit (FOM) of 6.1 MW cm⁻² are achieved for PSJ VK LDMOS. BV and FOM are enhanced by 71.4 and 81.1%, respectively, compared with con. PSJ SOI LDMOS with the drift region length of 46.5 μm. Furthermore, R _on,sp of 103.4 mΩ cm² is reduced by 31.2% compared with the ‘silicon limit’ at the same BV class, which breaks the ‘silicon limit’.

A simple, rapid and a cost-effective colorimetric method for detection of Hg²⁺ in an aqueous system using silver nanoparticle (AgNP) has been developed in the present study. AgNPs were synthesised using gum kondagogu (GK), a natural biopolymer that acts as both reducing and stabilising agent. The stability of GK-AgNPs composites was determined by zeta potential and was observed to be −30.43 mV. The yellow colour spot on the nitrocellulose membrane turned colourless at Hg²⁺ concentration of 20 ppm in aqueous solution, which can be observed visually. By using inductively coupled plasma mass spectrometry, it was observed that as the concentration of Hg²⁺ increases the Ag concentration decreased. Further, scanning electron microscopy and energy-dispersive X-ray spectroscopy were used to confirm the morphological changes on membrane before and after treating with Hg^{2 +}. The interference of other metal ions was also studied to validate Hg²⁺ specificity. This method was successfully employed to screen Hg²⁺ in industrial effluents. In summary, this study entails the development of a nitrocellulose membrane based mercury sensor that has practical applicability for on-site screening of Hg²⁺ contamination in the aqueous system.

Colloidal stability of magnetic fluids with desirable magnetic properties plays an important role in cooling applications in power transformers. Colloidal stability largely depends on nanoparticles’ characteristics and quality of their dispersion in transformer oil. In this work, a detailed discussion on the development of synthesis protocols for Mn_1−x Zn _x Fe₂O₄ (MZ) fluids is described. The effect of degree of Zn-ion substitution under an optimised condition of MZ nanoparticles on the dispersion quality of MZ fluids and their magnetic properties are investigated in this work.

The present work reports a mechanical improvement in nickel-based nanocomposites reinforced by in-situ grown graphene nanosheets (GNSs). First, vertically standing GNSs (VSGNSs) were grown on Inconel 718 alloy (718) powders by plasma-enhanced chemical vapour deposition. Then these powders were used to fabricate GNSs-718 nanocomposites by using spark plasma sintering method. The microstructure and mechanical properties of the nanocomposites were investigated by Raman spectroscopy, scanning electron microscopy, transmission electron microscopy and tensile tests. Testing results showed that three-dimensional net structured VSGNSs were in-situ grown on surfaces of 718 powders. GNSs-718 nanocomposites exhibited homogeneously dispersed GNSs, which distributed mainly along grain boundaries. Transmission electron microscopy indicated that there were clean and strong interfaces between GNSs and nickel-based matrix. Compared to the unreinforced 718 alloy, GNSs-718 nanocomposites showed increased strength and elongation. The relevant strengthening mechanisms involved in GNSs-718 nanocomposites were discussed.

In this work, an enhancement mode dual gate ferroelectric gallium nitride metal oxide semiconductor-high electron mobility transistor (GaN MOS-HEMT) is proposed with enhanced linearity characteristics. The different DC characteristics of the device are analysed and compared with available experimental data of single gate un-recessed ferroelectric GaN MOS-HEMT. In order to analyse the linearity performance of the devices, a look up table-based large signal model is developed directly from technology computer-aided device simulation results built by feeding different small signal parameters. The different linearity characteristics such as input third-order intercept point (IIP3), the input gain compression point (P1dB), third-order intermodulation (IM3) and the carrier to intermodulation power ratio of both the devices are compared by harmonic balance simulation of the developed large signal models. The interlink between IIP3 and IM3 with transconductance indicates that the broader the transconductance distribution with respect to different gate voltage generates higher IIP3 and lower IM3, which results in an improved linearity performance. The dual gate device shows improved linearity performance resulting in applicability in radiofrequency front end receiver.

This work focuses on the obtention of magnetic nanoparticles functionalised with heparin (MNPH) and their interaction with Aspergillus niger lipase enzyme. The MNPH were obtained by the coprecipitation method, its characterisation was carried out by Fourier transform infrared spectroscopy, X-ray diffraction, and alternating gradient magnetometry. Functionalisation with heparin was carried out by ultrasound at various times, later the absorption of the enzyme was carried out with two temperatures 4 and 25°C at different concentrations of lipase. For the recovery of the enzyme, a Plackett–Burman design was used, which indicates that the recovered lipase maintains its enzymatic activity when the ionic strength is lower, it was characterised by sodium dodecyl sulphate-page with which it is demonstrated that it is possible to recover the lipase enzyme through the designed nanostructured system.

Electrochemical immunosensors are generally layer-by-layer or sandwich systems designed to detect an analyte in a solution. Immunosensors are mainly based on the high affinity and specificity of the antibody towards its antigen. This work aims to answer the following question: if we ‘flip’ the immunosensor and build it backwards, thus detecting the antibody with the antigen instead of detecting the antigen with the antibody, will we obtain the same immunosensors properties or not? To answer this question, they tested a system composed of glycated human serum albumin and antibody-functionalised gold nanoparticles. Impedance spectrum results showed a difference in both the sensitivity and linear range of the built impedimetric immunosensors. The sensitivity of the sensor using the antibody as a bioreceptor was approximated to 0.32 [%. [% (Glycated to total albumin])] − 1] against a sensitivity of 0.80 [%. [% (Glycated to total albumin])] − 1] for the ‘upside-down’ sensor, using the antigen as a bioreceptor. This study observed also a shift to high glycation levels in the linear range of the upside-down sensor. These differences could be explained by the effect of steric hindrance and a higher degree of freedom allowing better characteristics for the upside-down immunosensor.

The novel gas and liquid nanoelectromechanical sensor based on carbon nanotube (CNT) is presented. By exposing an electromagnetic wave to the sensor, this work evaluates the effects of nanotubes displacement, resonance frequency, and maximum output current. The permittivity effects of a medium are investigated directly on the displacement and maximum output of the CNT and sensor, respectively. The results of this research can be used in designing innovative sensors for various applications.

This work presents a simple, economical and, importantly, green process to develop a nanocomposite (NC) that covers the functions of surfactant and polymer flooding in enhancing oil recovery (EOR). Thus, xanthan coated ZnO/SiO₂ NC was prepared using the extract of the pomegranate seeds as a reducing and stabilising agent. The green synthesised NC was identified using the scanning electron microscopy, electron dispersive spectroscopy, elemental mapping, X-ray diffraction, and UV–vis analytical techniques. ZnO/SiO₂/Xanthan NC was then dispersed in low-salinity water (1:20 diluted seawater) at different concentrations, and high suspension stability of NC was observed at different periods of time. This investigation provides a novel and green pathway for preparing nano-EOR fluids.

Biomimetic synthesis of calcium carbonate (CaCO₃) with various sizes and morphologies using organic matrix has become an interesting hotspot. CaCO₃ was synthesised by the reaction of Na₂CO₃ and CaCl₂ in the presence of xanthan gum (XG). The results showed that the fresh mineralised CaCO₃/XG were microspheres with large surface area and porosity. The original CaCO₃/XG microspheres transformed to brick-like CaCO₃ after ageing 7 days at 4°C. During the morphology transformation, CaCO₃ spheres rearranged by attaching to XG molecular, and transformed from a macroscopic view of CaCO₃ microspheres to a hexahedral structure related with the XG uncoiled single chains re-associating into loose several-fold helix. The study demonstrated that environmental effect coupled XG could be one feasible approach to regulate the structure of CaCO₃.

With the increased use of nanotechnology in almost all aspects of life, there is an increasing chance of risk of plants exposure to different nanoparticles (NPs). However, the studies on its potentially harmful effects in the cultivated crops are not well studied yet. Therefore, the authors aimed to study the effects of tin (Sn) NPs on the growth and physiological aspects of Zea mays. Thus, they exposed the maize seedlings to different concentrations of SnNPs for 2 weeks, and results revealed that the SnNPs at the studied concentration were not able to affect the seedling growth at a significant level. However, it induced the oxidative stress which was confirmed by increased guaiacol peroxidase, polyphenol oxidase and catalase activity. They also discussed that exposure duration, aggregation and concentrations were contributing factors in NPs mediated metal toxicity.

The performance of low-density polyethylene (LDPE) clay nanocomposites was analysed. The inclusion of nano montmorillonite (MMT) clay in LDPE material has significantly increased the contact angle, corona ageing resistance, water droplet initiated corona inception voltage and surface discharge inception voltage of the composites. The surface charge decay rate of the samples significantly reduced on the inclusion of clay indicating modified trap distribution characteristics due to the inclusion of the filler. Dynamical mechanical analysis indicates increased storage modulus and reduced tan (δ) due to nanofillers inclusion. Laser-induced breakdown spectroscopy indicates that on inclusion of nanofillers the plasma temperature increases and crater depth decreases. In particular, increased discharge resistance, improved thermomechanical properties are observed with LDPE–MMT clay composites compared to pure LDPE.

Hexagonal-like zinc oxide (ZnO)/silver (Ag) composite was successfully synthesised by a flux/solvothermal route, and Ag nanoparticles are loaded on ZnO. Compared with pure ZnO, the attachment of Ag on ZnO can significantly increase visible-light absorption and reduce photoluminescence emission intensity. The photocatalytic performance of ZnO/Ag composite was evaluated by the degradation of Rhodamine B solution under ultraviolet (UV) light and visible light irradiation. The degradation rate of ZnO/Ag composite is obviously improved compared with pure ZnO and the commercial TiO₂ (P25) and is more than 2.5 and 2.9 times faster than that of pure ZnO under the UV and visible light irradiation, respectively. The enhanced photocatalytic activity of ZnO/Ag composite under UV irradiation was ascribed to the formation of Schottky barriers between Ag particles and ZnO. However, the superior photocatalytic activity under visible light irradiation could be attributed to the surface plasmon resonance of Ag particles.

Synchrotron X-ray absorption near-edge structure (XANES) spectra are used to complement X-ray diffractometry (XRD) in the phase identification of pressed manganese–bismuth (MnBi) pellets. The heat treatment at 1000°C for 10 min after the synthesis improves the ferromagnetic properties. The magnetisation and coercive field are further enhanced when the Mn:Bi ratio is raised to 2:1. The obtained magnetic properties are related to the MnBi peaks in XRD patterns as well as the Mn-edge XANES spectra. Although the spectra in the case of Mn:Bi ratio of 2:1 and 3:1 resemble that of MnO reference, the pre-edge is shifted by the contribution of zero valent Mn and the peak intensity is reduced. A variety of phases in MnBi alloys dictate their magnetic properties required for permanent magnets and desirable ferromagnetic properties are governed by the increase of MnBi phase at the expense of MnO.

Ultrathin porous spinel structure ZnCo₂O₄ nanosheets (ZCONSs) are successfully prepared by a facile combination of hexamethylenetetramine-assisted mild water bath reaction and a heat treatment process. The ultrathin film shape and porous of the as-prepared ZCONSs were demonstrated by a transmission electron microscope. Such a specific nanostructure of the as-prepared ZCONS provided an efficient charge transfer process, as well as an efficient mass transport process. Therefore, in the oxygen reduction reaction (ORR) test, ZCONS shows good electrocatalytic ability. Additionally, because of the ultrathin nanosheets possess enough extra free space for alleviating, so that endow long-term cycling stability, make the catalyst possesses superior durability and excellent methanol tolerance ability.

The growing increase of industrial wastewater, environmental contaminations, and the necessity of clean water has stressed the importance of removing pollutants. One of the effective means of removing pollutants from water and wastewater is by utilising zeolite. Zeolite, despite possessing unique photophysical properties (such as numerous fine cavities, the high capability to adsorb, and chemical–thermal stability), represents some limitations when being used. Depositing photocatalysts on zeolite particles to improve its removal potential is of much interest. In this work, therefore, TiO₂ nanoparticles were deposited on fine particles of zeolite. Zeolite/TiO₂ composites were evaluated by X-ray diffractometer, scanning electron microscope, Brunauer–Emmett–Teller, diffuse reflectance spectroscopy analyses. The results indicate that the presence of TiO₂ nanoparticles reduces the specific surface area. However, it causes the ability to absorb UV light. Increasing the amount of TiO₂ any further will bring about a redshift in absorption edge. Photocatalytic properties of the composites were assessed by methyl orange and cyanide ion removal examination. The 10%TiO₂ composite with the specific surface area of 34 m²/g and bandgap energy of 3.3 eV showed to be the most efficient. The superior photocatalytic performance of 10%TiO₂ sample was confirmed by the examination of producing hydrogen from water/methanol.

A self-aligned fabrication method is employed for microscale hemispherical shell resonator with integrated diamond electrodes on a silicon (Si) substrate. The millimetre-scale three-dimensional (3D) hemispherical shell resonator, with integrated electrostatic excitation and capacitive detection transducers for full control of the resonator, is fabricated on the Si substrate by employing a microelectromechanical systems process. The eight integrated diamond electrodes evenly distributed outside the hemispherical shell are fabricated using a self-aligned method, which ensures uniform capacitive gap along the whole circumference. The Boron-doped polycrystalline diamond, a material with low thermo-elastic damping and low surface losses to reach the high quality, is used as the millimetre-scale 3D hemispherical shell resonator with integrated electrodes. The fabrication process enables the production of almost perfect hemisphere mould (<2% roundness variation) with an average surface roughness of 3 nm. Vibration modes and frequencies are carried out by a scanning laser Doppler vibrometer; the elliptical mode frequency is determined to be at 81.3 kHz, with the two M = 2 degenerate modes having a relative frequency mismatch of 0.86%. This process can be further optimised to fabricate high-quality and full-symmetric microscale hemispherical resonator gyroscopes in batch.

Water contamination along with the environmental issues resulted by industrial wastewaters have caused a trend in applying semiconducting photocatalysts, among which TiO₂ composites have been particularly focused on to overcome the drawbacks of titanium(IV) oxide also known as titania. In the current investigation, waste chips of a structural steel bar with the chemical composition of Fe₂O₃ were utilised to obtain the TiO₂–Fe₂O₃ composite. X-ray diffraction (XRD), field-emission scanning electron microscopy, energy dispersive spectroscopy, diffusive reflectance spectra, and Brunauer–Emmett–Teller analyses were made to evaluate the composition and structure of the samples. Furthermore, the photocatalytic performance of the samples was studied by methyl orange (MeO) degradation. XRD spectra proved the presence of anatase and Fe₂O₃ phases in the sample of 10%wt. Fe₂O₃. The results indicate that as the Fe₂O₃ content rises, the bandgap narrows. However, the specific surface area enlarges as this amount goes up to a certain limit (10%wt.), from which any further increase leads to a reduction in the specific surface area. The obtained results of MeO decolourisation presented the Fe₂O₃ of 10%wt. and bandgap of 2.72 eV, and the specific surface area of 63 m²/g to be of the highest efficiency (96%).

The Ni foil or fluorine-doped SnO2 transparent conductive glass substrates modified by BiFeO₃ film with a different atomic ratio of Bi to Fe were prepared by the method of spin coating-calcination at a different temperature. Coupling photo-catalysis with electro-catalysis, resourceful treatment of salty organic wastewater containing methyl orange and cadmium ion was proposed and experimentally achieved. Under visible light irradiation, the highest H₂-production rate (5.46 ml/h cm²), degradation efficiency of methyl orange (51.6%), and the recovery precipitation weight of cadmium hydroxide (0.1846 g) were obtained with Ni foil modified by BiFeO₃ (Bi:Fe = 1.10:1.00) film at 550°C of calcination. X-ray diffraction, ultraviolet–visible diffuse reflectance spectroscopy, scanning electron microscopy, and the resourceful treatment test of salty organic wastewater were used to characterise the catalyst film.

Bentonite clays containing mostly montmorillonite as a nanostructure group of smectite have been used as industrial raw material in many applications. The presence of the other impurities in bentonite clays reduces the value of bentonite. Therefore, the bentonite purification is necessary. In this research, the purification and separation of montmorillonite from a low-grade natural bentonite were considered on the regular and comprehensive plan. For this purpose, a set of methods including dispersion, sodium-activation, sedimentation, sonication and centrifugation were used. In contrast to many methods, there were often complex, expensive and non-effective; this purification method was found to be effective for removing almost all quartz, carbonates and clinoptilolite as the major impurities. In this purification method, the montmorillonite content was increased from 15 to 84% with the separation yield of 80%. The influence of centrifugal force and the type of ultrasonication indicated the most critical parameters in the purification yield, the physical properties and the crystalline structure of the final products. The laser particle size distribution analysis, X-ray diffraction, semi-quantitative analysis and Fourier-transform infrared spectroscopy results showed the decrease of impure phase without any structural changes or damages in clay framework.

A novel double-layer resist method was presented in this work to decrease the negative photoresist scum. Positive photoresist was chosen as the bottom layer resist and negative photoresist as the top layer resist. This work studied the effect of viscosity and thickness of bottom layer resist on the mean number of scum. The experiment shows that the low viscosity positive photoresist AZ703, with the spin speed of 3000 r/min and the thickness of 1.10 um, had prominent effect on the removal of photoresist. To minimise the area of the top layer contact with substrate and further reduce the scum, 8 µm was selected as the optimal retracting distance d of the bottom layer resist.

By facile electrospinning and subsequent melamine-derived chemical vapour deposition strategy, a three-dimensional (3D) hierarchical binder-free carbon electrode is fabricated via in-situ growing nitrogen-rich graphitic nanotubes on carbon nanofibres. This electrode shows a 3D hierarchical nanostructure with the high specific surface. Owing to the highly conductive hierarchical structure allowing for rapid transportation of electrons and the N-doped carbon creating more Li-storage sites, the as-prepared binder-free electrode exhibits high reversible capacity, good rate capability and long cycle stability in terms of Li-ion battery.

To investigate the effect of thickness on the structural and optical properties of niobium-doped beta gallium oxide (β-Ga₂O₃:Nb) thin films, a series of β-Ga₂O₃:Nb thin films with different thicknesses were prepared by radio-frequency magnetron method. The crystalline quality is highly improved when the film thickness exceeds 145 nm. The surface exhibits different morphologies under different film thicknesses. The average transmittance of all the films are over 80% in visible range, and that the ultraviolet absorption edge shifts to longer wavelength indicates the bandgap shrinks with increasing the film thickness. Moreover, the photoluminescence spectrum measurements indicate that fewer defects were formed when the film thickness is around 145 nm.