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This article presents an efficient non-enzymatic electrochemical sensor based on catalytic oxidation by the MgFe2O4 magnetic spinel for the sensitive determination of ascorbic acid.

Three-dimensional (3D) bioprinting technology has attracted a great deal of interest because it can be easily adapted to many industries and research sectors, such as biomedical, manufacturing, education, and engineering. Specifically, 3D bioprinting has provided significant advances in the medical industry, since such technology has led to significant breakthroughs in the synthesis of biomaterials, cells, and accompanying elements to produce composite living tissues. 3D bioprinting technology could lead to the immense capability of replacing damaged or injured tissues or organs with newly dispensed cell biomaterials and functional tissues. Several types of bioprinting technology and different bio-inks can be used to replicate cells and generate supporting units as complex 3D living tissues. Bioprinting techniques have undergone great advancements in the field of regenerative medicine to provide 3D printed models for numerous artificial organs and transplantable tissues. This review paper aims to provide an overview of 3D-bioprinting technologies by elucidating the current advancements, recent progress, opportunities, and applications in this field. It highlights the most recent advancements in 3D-bioprinting technology, particularly in the area of artificial organ development and cancer research. Additionally, the paper speculates on the future progress in 3D-bioprinting as a versatile foundation for several biomedical applications.

Four iron-based triple tungstate and tellurate perovskites have been synthesized in the nanocrystalline form using a simple sol–gel citrate route: Sr3Fe2WO9 (SFWO), Ba3Fe2WO9 (BFWO), Sr3Fe2TeO9 (SFTO), and Ba3Fe2TeO9 (BFTO). Strontium-based compounds crystallize in the tetragonal space group I4/m, while barium-based compounds crystallize in the hexagonal space group P63/mmc. All compounds possess a ferromagnetic order with high values for room-temperature magnetization. The magnetic state as traced by Mössbauer spectroscopy is heterogeneously related to disorder. The compounds also possess relatively high dielectric constants (20–199.16) measured at 1 MHz and a moderate loss factor. The synthesized triple perovskite compounds were utilized in the fabrication of vertical contact mode triboelectric nanogenerators (TENGs). The working mechanism and the electrical response of the TENGs were extensively studied. The TENG device based on BFTO/Kapton triboelectric layers produces the highest output of 88 V/2.69 μA. For the first time, the surface polarity of the triple perovskite was shown using a Kelvin probe force microscopy technique (KPFM), which elucidates the positive polarity of the triboelectric layer. Furthermore, the TENG device was used to charge several capacitors and to carry out the powering of electronics that make it an excellent choice for various self-powered applications.

The rise in world pollution and energy demand has aggravated the energy crisis and depletion of non-renewable energy resources. Here, we review multifunctional materials that can be used for photoelectrochemical water splitting for clean energy production.

Triboelectric nanogenerators (TENGs) have recently attracted extensive attention from academia and industry as a promising approach for energy harvesting.

The present study investigated the possibility of complete utilization of eggshell waste (ESW) transforming it to adherent egg white protein solution, calcium chloride dihydrate, and eggshell membranes (ESM). Adherent egg white protein solution was obtained by washing ESW three times with distilled water at 25°C, followed by filtration, and analyzed for the protein content and lysozyme activity. ESM and calcium chloride were obtained simultaneously by the exposure of washed eggshells to 5% hydrochloric acid treatment at 25°C for 3 h, followed by separation by filtration. The separated ESM were washed, dried, and milled to powder and analyzed for protein and lipid content. The calcium chloride solution was exposed to the neutralization of excess hydrochloric acid by calcium hydroxide, followed by evaporation to one-tenth of volume. Calcium chloride crystals were precipitated from the concentrated solution with acetone, separated by filtration, dried at 110°C, and analyzed for chemical composition and purity. The obtained results revealed that 100 g of ESW can be transformed to 1.61 ± 0.34 g of adherent white proteins containing 485,821 U of lysozyme activity, 2.84 ± 0.16 g of ESM powder, and 108.74 ± 3.62 g of calcium chloride dihydrate of high purity.

Tin oxide is an n-type semiconducting material having superior properties that can be utilized in several applications. The warning and detection of several dangerous gases in the environment are possible by utilizing gas sensors. The comprehensive functionality of these sensors could help to reduce the risk of severe health hazards and unexpected explosion risks. Tin oxide-based gas sensors exhibit reliable gas sensing performances along with respectful sensitivity and selectivity. Tin oxides in micro-and nano-particle forms provide an extremely high surface-to-volume ratio, which is favorable for gas sensors. Processing and synthesis of tin oxide particles accompany high-temperature processes, and this paper focuses on studying the effect of sintering temperatures on the structural and grain size of the commercially available tin oxide particles. The surface morphology of the tin oxide samples sintered at three different temperatures of 1100, 1200, 1300 °C shows a clear difference in the grain size and further affecting the dielectric properties of the materials. The gas sensing performances of three tin oxide samples are investigated by fabricating a pellet-type gas sensor. The sensor with the sintering temperature of 1200 °C exhibits the best gas-sensing performance with high response and low limit of detection (LOD). Our results suggest that the sintering temperature plays a vital role in deciding the dielectric properties and grain sizes, which are important parameters that affect the gas sensing behavior of tin oxide micro-and nano-particles.

The gas-sensing equipment experienced a greater demand in different workplace environments owing to its high capability to detect the unburnt poisonous gases in the boilers or analyzing the airborne pollution levels. The recent trend toward achieving an efficient gas sensor depends on the low-power consumption and miniaturization. In addition, emerging nanomaterials have shown great potential toward gas sensing along with their outstanding electrochemical properties. This work aims toward the sensing of hydrogen gas utilizing carbon nanotubes (CNTs) directly integrated onto a Pt microheater. The pristine CNTs detect hydrogen gas through the change in the electrical resistance. The chemical reaction between the hydrogen molecule and CNTs is promoted at high temperatures by utilizing the microheater. The suggested spray-coated CNT layer survives subsequent microfabrication processes, demonstrating a robust integration method of nanomaterials into conventional microelectromechanical systems (MEMS). CNTs integrated Pt microheater is batch fabricated using a microfabrication technique, allowing a high device yield of over 90%. The fabricated gas sensors demonstrate a low power budget of a few mW and owe a fast response time. The temperature is elevated up to 420 °C by supplying 2.19 mW power for gas sensing, and the change in the rate of resistance change reached 1.82% by supplying hydrogen gas of 10% concentration. The response and recovery time from the microheater are found to be 39 and 35 seconds, respectively. Besides, the decrease in drift factor occurs when the sensor operates at too high temperatures. The gas concentration is controlled and simultaneously the rate of resistance change is evaluated which further helps to obtain a LOD value of 1200 ppm. The Raman spectra of CNTs before and after the gas-sensing experiment confirm that there is no change or degradation of the CNTs during the experimental process. The fabricated CNTs integrated Pt microheater-based gas sensor has immense potential toward sensing hydrogen gas.

The development of a new class of perovskite materials and enhancing its capability as an energy harvester that scavenges energy from various sources to power electronics systems has attracted significant attention. Herein, we report a cost-effective approach to synthesize a perovskite material, explore its properties, and further develop a high-performance flexible nanogenerator based on hybrid piezoelectric composite. The Aurivillius-based oxide, CaBi4Ti4O15 (CBTO) was fabricated via a mixed oxide reaction and crystallized in an orthorhombic symmetry at room temperature. The material properties were elucidated to act as a parallel plate capacitor that will further act as a base for the development of filter circuits. Aurivillus/PDMS composite films were used to fabricate a flexible Aurivillus-based piezoelectric nanogenerator (A-PENG) to act as a self-powered exercise counter and power the electronics. The A-PENG was systematically analyzed under different conditions such as weight percentage, before and after poling, and acceleration effects. In addition, device stability, and capacitor charging-discharging tests were performed. This study elucidated the formation of lead-free ceramic materials that were used to make a flexible composite film for the realization of a piezoelectric harvester acting as a sustainable energy source.

In the present era, global challenges are focused to meet the security of energy due to excessive energy demands. The coal and petroleum-based fossil fuels are soon fading out due to current energy-generating units; hence, the energy from renewable energy sources becomes an alternative medium and new scientific investment. Research is carried out to boost the efficiency of these devices. The multifunctional materials having superior properties are the need of the hour to provide insight towards producing low-cost energy devices. A perovskite having the chemical formula Bi1/2(Na1/4Li1/4)TiO3 (BNLTO) is synthesized using a solid-state reaction. The standard techniques were used to investigate the structural and electrical characterizations at various experimental conditions. The X-ray diffraction (XRD) spectra elucidated the presence of an orthorhombic symmetry in the synthesized sample. The high dielectric constant and low loss factor is evolved at various frequencies and temperatures. The Nyquist plot depicts the association of the combined effect of grain and grain boundary. The activation energies evaluated from the loss and modulus spectrum are noted as ~ 1.26 eV and 0.81 eV, respectively. The charge carriers contribute to the conduction mechanism at high temperature. Finally, a poled piezoelectric energy harvester is fabricated to check its capabilities for the conversion of small impact from hand palm into electrical energy.

Piezoelectric nanogenerators are dependent on a piezoelectric material for the conversion of mechanical stress into useful electrical energy. This paves the way for the development of piezoelectric material compositions starting from ceramic oxides, polymers, and organic compounds to design piezoelectric energy harvesters towards energy harvesting and self-powered sensor development. In the present work, we introduce a multiferroic composition, BiMgFeCeO6 (henceforth referred to as BMFCO), using a high-temperature reaction route. The physicochemical properties of the synthesized samples were systematically investigated, providing insight into their interesting structure–property correlation. The BMFCO particles were further blended with PDMS at different weight percentages (wt%) and converted into flexible composite films. Stability and capacitor charging tests confirm their stable and durable electrical output over a longer period. Biomechanical energy harvesting was performed by attaching the 10 wt% BMFCO–PDMS-based device (hereafter referred to as PENG10) to a computer mouse and for several body movements. Digital signal processing techniques such as wavelet transform and wavelet packet transform were employed to recognize the difference between a comfortable sound level and excessive volume based on the output recorded by a PENG attached to a speaker.

Harvesting mechanical energy from the surroundings can be a promising power source for micro/nano-devices. The triboelectric nanogenerator (TENG) works on the principle of triboelectrification and electrostatic induction. So far, metals and polymers have mostly dominated the conventional triboelectric series, but there is a need to find novel materials to extend the triboelectric series and further improve the performance of a TENG. Herein, a zeolitic imidazole framework (ZIF-67) was synthesized using a room temperature solvent-assisted route. Extensive material analysis was performed to understand its structural and chemical properties. Further, a simple vertical contact mode S-shaped TENG device (abbreviated further as S-TENG) was fabricated using an additive manufacturing approach. ZIF-67 acted as a positive triboelectric layer while Teflon/PDMS acted as a negative triboelectric layer. The multi-unit S-TENG device was further utilized for self-powered recognition of the various gaits using a digital signal processing approach. The S-TENG device based on ZIF-67 and Teflon produced a voltage of 118 V, a current of 1.7 μA, and a power density of 15 μW cm2 at a load resistance of 50 MΩ. The gait analysis of different volunteers was recorded by employing the S-TENG device and the digital signal processing route to effectively distinguish the gait patterns for the prevention of falls and injury. The S-TENG device was utilized to charge a commercial capacitor for powering a wristwatch and further it was attached to a robotic gripper for object identification.

The various sintered samples comprising of 72 wt%(Al2O3) : 28 wt%(SiO2) based ceramics were fabricated using a colloidal processing route. The phase analysis of the ceramics was performed using an X-ray diffractometer (XRD) at room temperature confirming the presence of Al2O5Si and Al5.33Si0.67O9.33. The surface morphology of the fracture surface of the different sintered samples having different sizes of grain distribution. The resistive and capacitive properties of the three different sintered samples at frequency sweep (1 kHz to 1 MHz). The contribution of grain and the non-Debye relaxation process is seen for various sintered samples in the Nyquist plot. The ferroelectric loop of the various sintered sample shows a slim shape giving rise to low remnant polarization. The excitation performance of the sample at a constant electric signal has been examined utilizing a designed electrical circuit. The above result suggests that the prepared lead-free ceramic can act as a base for designing of dielectric capacitors or resonators.

The advancement in development of lead-free materials (ceramics, single crystal, thin film) acts as a forerunner to the stepwise progression in tailoring the performance of electronic devices. The perovskite-based lead-free ceramics are gaining lot of research interest due to their utilization in several electronic applications. The lead-free ceramics having chemical formula 0.65Bi(Fe0.98Ga0.02)O3–0.35BaTiO3 (further represented as BFG-BTO ahead) was synthesized employing the high-temperature mixed oxide route. The study aims toward the correlation of structural with electrical properties, exploring the relaxation and conduction mechanism persisting in the material. The single-phase formation in the prepared system is depicted through a powder X-ray diffraction technique suggesting a rhombohedral symmetry along with the cell parameters. The SEM presents surface morphology having high densification. The influence of gallium substitution modifies the electrical parameters of BaTiO3–BiFeO3 have been studied employing impedance meter in an extensive frequency (1 kHz–1 MHz) and temperature (25–450 °C). The grains, grain boundaries, electrode effect are revealed by impedance spectroscopy at different temperatures and frequencies. The ferroelectric nature of the sample is ascribed by the P–E loop of the material.

The switchable dipole moments and high piezoelectric coefficients in ferroelectric materials are the state-of-the-art used in piezoelectric energy harvesting. Hybridizing the triboelectric (TENG) and piezoelectric (PNG) shows great potential in harvesting the biomechanical energy by utilizing the ferroelectric dipoles embedded within the polymer. Unlike most of the previous approach to increase hybrid output by the external configuration of piezoelectric and triboelectric between two contact surfaces, in this paper, the output performance is significantly enhanced by improving the output performance of TENG by introducing a ferroelectric (Ba0.85Ca0.15)(Ti0.90Zr0.10)O3−x BiHoO3 (x = 0.02, 0.04, 0.06, 0.08, 0.1) (BCZTBH termed further) particles in PDMS which acts as a negative triboelectric layer. The structural and piezoelectric properties of BCZTBH particles are correlated in this report with the necessary characterization techniques. The systematic study of integrating single unit hybrid generator (S-HG) in a stacked manner paves the way to develop cost-effective, highly efficient ferroelectric films for utilization in the next-generation energy harvesting. The performance of the device is boosted by adopting a multi-stack configuration by designing a multi-stack hybrid generator (MS-HG) that could generate an electrical output of 300 V and a power density of 157 mW m−2 upon mechanical excitations. Further, enhanced and reliable performance of the MS-HG is demonstrated as a proof of application by effectively integrating a capacitor, infrared transmitter and receiver into a self-powered wireless infrared communication module and body activity counter/monitoring.

The development of gas sensors with high sensitivity, stability, and selectivity is vital in detecting hazardous gas leaks and monitoring air pollution. The perovskite comprises a stable chemical structure and offers multifunctional properties to act as a base for several device engineering. Specifically, perovskites possess a great potential for chemical sensors with their semiconducting nature and ease to dope with other elements to further improve gas sensing properties. In this present study, a rare-earth gadolinium orthoferrite, GdFeO3 (GFO), and Co-doped GFO were systematically investigated by evaluating their structural, morphological, electrical, and gas sensing properties. A high-temperature solid-state reaction synthesized the phase-pure compounds. The magnetic properties of Co-doped GFO significantly improved than pure GFO. The pellet-type gas sensor was fabricated, which does not need any sophisticated instrumentation such as microfabrication. When exposed to 20 ppm of NO2 gas, a GdFe0.7Co0.3O3 (GFOC3) device gave 6.86% response at 200 ˚C, along with a response time of 104 s and the recovery time of 97 s. Additionally, Co-doped GFO sensors showed a detectable response even at room temperature, enabling- practical applications in an ambient environment. The gas sensor revealed stable gas response characteristics even after several months. Therefore, this study elucidates that the Co-doped GFO has better gas sensing performance compared to a bare GFO and that it is highly selective towards the NO2 gas.

Carbon quantum dots (CQDs) have recently emerged as innovative theranostic nanomaterials, enabling fast and effective diagnosis and treatment. In this study, a facile hydrothermal approach for N-doped biomass-derived CQDs preparation from Citrus clementina peel and amino acids glycine (Gly) and arginine (Arg) has been presented. The gradual increase in the N-dopant (amino acids) nitrogen content increased the quantum yield of synthesized CQDs. The prepared CQDs exhibited good biocompatibility, stability in aqueous, and high ionic strength media, similar optical properties, while differences were observed regarding the structural and chemical diversity, and biological and antioxidant activity. The antiproliferative effect of CQD@Gly against pancreatic cancer cell lines (CFPAC-1) was observed. At the same time, CQD@Arg has demonstrated the highest quantum yield and antioxidant activity by DPPH scavenging radical method of 81.39 ± 0.39% and has been further used for the ion sensing and cellular imaging of cancer cells. The obtained results have demonstrated selective response toward Fe3+ detection, with linear response ranging from 7.0 µmol dm−3 to 50.0 µmol dm−3 with R2 = 0.9931 and limit of detection (LOD) of 4.57 ± 0.27 µmol dm−3. This research could be a good example of sustainable biomass waste utilization with potential for biomedical analysis and ion sensing applications.

A lead-free bulk ceramic having a chemical formula Ba0.8Ca0.2(Ti0.8Zr0.1Ce0.1)O3 (further termed as BCTZCO) is synthesized using mixed oxide route. The structural, dielectric, impedance, and conductivity properties, as well as the modulus of the synthesized sample are discussed in the present work. Analysis of X-ray diffraction data obtained at room temperature reveals the existence of some impurity phases. The natural surface morphology shows close packing of grains with few voids. Attempts have been made to study the (a) effect of microstructures containing grains, grain boundaries, and electrodes on impedance and capacitive characteristics, (b) relationship between properties and crystal structure, and (c) nature of the relaxation mechanism of the prepared samples. The relationship between the structure and physical properties is established. The frequency and temperature dependence of the dielectric properties reveal that this complex system has a high dielectric constant and low tangent loss. An analysis of impedance and related parameters illuminates the contributions of grains. The activation energy is determined for only the high temperature region in the temperature dependent AC conductivity graph. Deviation from the Debye behavior is seen in the Nyquist plot at different temperatures. The relaxation mechanism and the electrical transport properties in the sample are investigated with the help of various spectroscopic (i.e., dielectric, modulus, and impedance) techniques. This lead free sample will serve as a base for device engineering.

In this present communication, a polycrystalline lead-free system with composition Bi0.60Li0.40Fe0.60Nb0.40O3 (BLFNO termed further) is synthesized using a cheap conventional ceramic processing route. It featured with resistive, capacitive and dielectric properties of the synthesized composition. Room temperature XRD (X-ray diffraction) technique used to determine the single phase formation, structure and lattice parameters. The SEM micrograph reveals the non-uniform distribution of grains with highly dense grain growth. The complex impedance and modulus technique help to analyze the electrical properties of the sample. The frequency and temperature dependent electrical characteristics occurring in the sample were carried out in a wide temperature (25–500 °C) and frequency (1 kHz-1MHz) range. The Nyquist plot depicts the contribution of both grain and grain boundary effect in the prepared composition. The temperature dependent AC conductivity shows the activation energy for conduction. The frequency dependent electrical modulus and impedance analysis suggest non–Debye type relaxation behavior in the sample.

The polycrystalline 0.7Bi(Fe0.98Ga0.02)O3-0.30BaTiO3 (BFG-BTO) ceramic was processed by high temperature reaction route. The room temperature X-ray spectra suggest a tetragonal symmetry. The structural refinement was also carried out. The high densification of sample formation is depicted from a scanning of the natural surface of the sample. The electrical properties were measured using a complex impedance method over a wide range of frequencies and temperatures. The overlapping large-polaron tunnelling model type of conduction mechanism is obtained from the frequency dependent ac conductivity plots. The relaxation mechanism is studied with the help of various spectroscopic tools (modulus and dielectric). The Nyquist plot indicates the non-Debye characteristics and the combined contribution of both grain and grain boundary towards the resistive property of the sample.

This paper presents the fabrication and electrical characterization of a lead-free polycrystalline complex electronic material Ba0.8Sr0.2(Zr0.1Ti0.8Ce0.1)O3 (abbreviated as BSZTCO) using standard experimental techniques. The phase identification of the material, determined using X-ray diffraction data, depicts the formation of a multi-phase system. The various electrical parameters were obtained at different frequencies (102–106 Hz) and temperatures (20–500 °C) using the phase-sensitive meter and found interesting results. Study of the micrograph of natural surfaces of the sample suggests that the ceramic sample has been formed with high density grain growth (without any cracks or voids). The transport properties and dielectric relaxation characteristics of the material have been studied using modulus and impedance spectroscopy techniques. Temperature dependence of conduction behavior (Nyquist plot) confirms the presence of bulk and grain boundary effects in the material. The charge transfer by hopping dominates the electrical transport process of the material as revealed from conductivity analysis. The dielectric relaxation of the material is studied using a complex modulus spectrum depicting non-Debye type relaxation.

In this report, Ba1Bi1Cu1Fe1Ni1Ti3O12 (BBCFNTO termed further) ceramics were synthesized using a conventional ceramic processing route. The formation of multiple phases has been confirmed from by the XRD pattern at room temperature. The surface micrograph indicates the uniform distribution of grains with distinct grain boundary. The co-relation between the impedance and dielectric parameters was realized by using a phase sensitive meter over a good temperature and frequency range. The temperature- and frequency-dependent dielectric properties are linked to the conduction mechanism. The dielectric constant (K) and loss (tanδ) are increased sharply at high-temperature region, which is expected to be the onset of dipolar relaxation phenomena. The contribution of grain boundary (GBs) and grain (Gs) effects can be identified using the complex impedance spectroscopy. This synthesized material is investigated to model multifunctional devices.

In the present paper, high temperature synthesis was used to prepare the complex electronic system 0.94 (Bi0.5Na0.5)TiO3-0.06 BaTiO3 (BNT-BT-6). The relationship between the structure and electrical properties have been presented. The crystal data (i.e. unit cell dimensions and tetragonal crystal system) was obtained by preliminary structural analysis using room temperature X-ray diffraction spectra. The unequally distributed and densely packed ceramics were observed in the SEM micrograph of the sintered sample. The vibrational modes of BNT-BT-6 system using room temperature Raman and FT-IR spectra were reported. Temperature and frequency dependent dielectric parameters of BNT-BT-6 exhibit the shift in transition temperature, enhancement of dielectric constant and decrease in dissipation factor of BNT on the addition of BT even in a small amount. Analysis of the frequency and temperature dependent electrical modulus and impedance data of the system shows that the material follows non-Debye type of dielectric relaxation process. The overview of grain effect on the capacitive and resistive characteristics of the BNT-BT-6 material was studied experimentally from the Nyquist plots. Analysis of conductivity spectra was used to calculate activation energy and determine the electrical transport mechanism of the material.