Promising Electrical Properties Research Articles

Microstructure modification in Ba-doped SnO2-based ceramics with promising thermal conductivity and electrical properties

In this paper, the thermal conductivity of Ba-doped SnO2 varistors was tested using the heat flow method, and it was found that the thermal conductivity is related to the grain boundary barrier of the samples. Introducing the reduction of impurity phases and point defects is an effective method to enhance the thermal conductivity of SnO2-based varistors. Energy dispersive spectrograms indicate that the content of spinel Co2SnO4 doped with 1mol% Ba is the least when the arrester is operated at 40°C. The positive and negative charge defects are fully compensated, thereby reducing phonon scattering and improving the thermal conductivity of the samples. Spinel Co2SnO4 occupies the position of the effective grain boundary, so the reduction of Co2SnO4 and the compensation of positive and negative defects also effectively increase the grain boundary barrier. When the doping amount of Ba is 1mol%, the optimal potential barrier height is 1.48eV, the nonlinear coefficient is 45, the leakage current is 0.8μA/cm2 and the voltage gradient is 418V/mm.

Can ZrAlN thin films be used as thermistor sensors for temperature assessment?

The electrical characteristics and conduction mechanisms of ZrAlN thin films for their potential use as thermistor sensors were assessed. Various compositions of Zr1-xAlxN were synthesized by sputtering and studied up to 200 °C to understand their sensitivity and applicability. Among the compositions studied, the ones with x = 0.34 and x = 0.46 showed the highest sensitivities, reaching values close to 3000 K. However, the thermo-resistive properties exhibited by these compositions limited their utilization above 100 °C. Zr1-xAlxN film compositions with x higher than 0.46 showed amorphous structures and were found to be insulative. Composition with x = 0.26, within the cubic phase, showed the most promising electrical properties regarding temperature sensing in the studied range. XPS analysis of this composition confirmed the presence of Zr-N and Al-N bonds, with a Zr3+ oxidation state, which suggests the availability of a free electron contributing to the electrical conduction. Impedance measurements performed at different temperatures for this composition revealed the dominant role of the grain boundaries in the conduction mechanism, based upon electron hopping between grains, overcoming the energy barrier imposed by the grain boundaries. ZrAlN thin films demonstrate negative temperature coefficient (NTC) thermistor behavior, expanding their applications beyond protective coatings to temperature monitoring.

Effect of substitution on the structural, electrical properties, and dielectric relaxor behavior in lead-free BiFeO3-based ceramics.

BiFeO3-based ceramics have recently garnered much interest among researchers owing to their valuable and outstanding characteristics. For this reason, the 0.7(Na0.5Bi0.5)TiO3-0.3(Bi0.7Sm0.3FeO3) ceramic was successfully synthesized by a solid-state route. The central purpose of this research is to investigate the substitution influence of Na, Ti, and Sm on the structural, dielectric, and electric properties of 0.7(Na0.5Bi0.5)TiO3-0.3(Bi0.7Sm0.3FeO3), as well as to explore its potential applications as it exhibits multiple novel functions. Notably, a structural transition from rhombohedral R3c to orthorhombic P4mm occurred within this material. In this respect, a suitable equivalent electrical circuit was invested to assess the contributions of grains and grain boundaries to the complex impedance results. Electrical conductivity was attributed to the correlated barrier hopping (CBH) motion of the oxygen vacancies in the sample. The temperature dependence of the dielectric constants revealed the presence of a phase transition. The local disorder provides a dependence of the real part of the permittivity on the frequency which characterizes a relaxor ferroelectric-type behavior of a lead-free material. The modified Curie-Weiss law, in addition to the Vogel Fulcher and Debye law relationships, was utilized to analyze the diffuse transition phase. Furthermore, the studied compound displayed promising electrical properties and chemical stability and proved to be a good relaxor. In this regard, a correlation between dielectric and electric behavior near the ferro-paraelectric phase transition was established.

Electromagnetic Interference shielding performance of PEDOT incorporated biodegradable jute fabrics

The rapid increase in the necessity for wireless communication and the quick development of electronic devices are growing every day. Plastics and materials which are not environment friendly are dominating the electronic industry. As a part of the technological revolution, new challenges such as environmental pollution and electromagnetic pollution are also arising. Concept of establishing sustainable future significantly require eco-friendly, biodegradable and economic materials with versatile applications. Biodegradable fabrics with excellent electronic properties are imperative for next generation due to the great demand for sustainable electronic materials. Conducting fabrics with promising electrical properties and biodegradability can replace many electronic components and thus have much potential to retard the challenges. Among various techniques to develop conducting fabrics or textiles, incorporation of conducting polymers into the fabric matrix is one of the most preferred methods. Our present work explores the possibility of designing a conducting fabric using biodegradable jute fabric. Conducting polymer PEDOT is incorporated into jute fabric by the method of in-situ polymerization with various molarities. The structural and morphological properties of the samples were analyzed. DC conductivity of the fabric found to be dependent on the molarity of PEDOT and maximum conductivity and EMI shielding efficiency was observed for jute incorporated with 1 M PEDOT. The outstanding electrical and EMI shielding properties of the novel fabric make it promising for developing sustainable materials in electronic and telecommunication industry.

Electrochemically Oxidized Carbon Nanotube Sheets for High-Performance and Flexible-Film Supercapacitors.

The development of flexible, high-performance supercapacitors has been a focal point in energy storage research. While carbon nanotube (CNT) sheets offer promising mechanical and electrical properties, their low electrical double-layer capacitance significantly limits their practicability. Herein, we introduce a novel approach to address this challenge via the electrochemical oxidation treatment of CNT sheets stacked on a polyethylene terephthalate substrate. This introduces oxygen-containing functional groups onto the CNT surface, thereby dramatically enhancing the pseudocapacitive effect and improving ion adsorption. Consequently, using the material in a two-electrode system increased the capacitance by 54 times compared to pristine CNT. The results of electrochemical performance characterization, including cyclic voltammograms, galvanostatic charge/discharge curves, and capacitance retention testing data, confirm the efficacy of the electrochemical oxidation approach. Furthermore, the mechanical flexibility of the electrochemically wetted CNT sheets was validated through resistance and discharge retention testing under repetitive bending (98% capacitance retention after 1000 bending cycles). The results demonstrate that electrochemically wetted CNT sheets retain their intrinsic mechanical and electrical properties while significantly enhancing the electrochemical performance (0.59 mF/cm2 or 97.8 F/g). This work represents a significant advancement in the development of flexible, high-performance supercapacitors with potential applicability to wearable electronics, flexible displays, and next-generation energy storage solutions.

Insight into a novel cobalt complex with promising electric energy stocker properties: A combined DFT and experimental study

A new [Co(SCN)4]·2(C5H14N2)·2(CNS), synthesized from a thiocyanic cobalt precursor and homopiperazinium organic cation in EtOH under hot and basic conditions. X-ray diffraction DATA showed that the compound is composed of one Co cation, located on a center of inversion and four thiocyanates anion, and two homopiperazinium co-ligands add to two thiocyanate ions crystallographically independent in a monoclinic unit cell with P21/c space group. N-H∙∙∙S and N-H∙∙∙N interactions form a distinctive ring–like pattern that links units in crystal packing. This work demonstrates an easy fabrication of a new compound with excellent dielectric properties. Additionally, Fourier Transform Infrared (FT-IR) spectroscopy studies the different functional groups. The dielectric study shows that the developed material has a huge dielectric constant εr≈1010. The resulting material also exhibits a reasonably low loss (tang δ < 1) at low frequencies. Hirshfeld surface (HS) was carried out to study the elemental contact of molecules in crystal packing. Theoretical investigations were performed by using DFT-B3LYP functional. The frontier molecular orbital (FMO) and natural bonding orbitals (NBO) analysis are evident for excellent reactivity and charge transfer within the complex. The global reactivity descriptors were calculated to get deep insight into the reactivity and electronic properties of the complex. For the optical and nonlinear optical (NLO) properties, the static polarizability (αo) and hyperpolarizability (βo) were calculated at the same method. The observed remarkable βo value of 58737.93 au is indicating its excellent NLO properties.

Structural, electrical and dielectric properties of ZnFe2O4/Cu2S 3D heterostructures

This work reports the fabrication of zinc ferrite-copper sulphide (ZnFe2O4/Cu2S) 3D heterostructures and subsequent investigation of the spectroscopic behaviour of various electrical parameters like conductivity, impedance and dielectric loss. The study reveals a non-monotonic behaviour of the real component of impedance (Z’), while the imaginary component of impedance (Z’) exhibits a temperature-dependent relaxation frequency, with an estimated activation energy (E a ) of 220.13 meV. The dc conductivity (σ dc ) measurements reveal the semiconducting nature of the sample and a transition from a ferrimagnetic to a paramagnetic behaviour is reported at the Curie temperature of 327 K. In case of ac conductivity (σ ac ), Jonscher’s power law σ ac = Aω n is followed and the exponent n is found to lie in the range 0.679–0.735 at different temperatures, which is best fitted into a polynomial of degree six. The temperature variation of n is suggestive of the overlapping large polaron tunnelling (OLPT) model. Further, ac activation energy (E ac ) is also calculated, which is found to be smaller than the dc activation energy (E dc ), indicating electron hopping between Fe3+ and Fe2+ ions. The numerically computed staying time (τ) of electrons in Fe3+/Fe2+ ionic sites varies with frequency as well as with temperature, ranging from 10−6s to 10−19s. A significant decrease in dielectric loss (tanδ) to the tune of 99% (from 75 at ∼100 Hz to 0.89 at ∼1 MHz) is reported at room temperature. In the present scenario, when smart materials like spinel ferrites have garnered significant attention for their promising magnetic and electric properties, our studies of the ZnFe2O4/Cu2S 3D heterostructures may provide immense possibilities for tailored applications in various electromagnetic applications.

Interface Charge Transfer in MXenes/Graphene Heterostructures for Ultrafast Photonics

AbstractTwo‐dimensional (2D) transition‐metal carbides, nitrides, and carbocyanides, known as MXenes, have attracted tremendous attention in photonics and electronics because of their promising optical, electrical, and mechanical properties. However, the potential of MXenes‐based heterostructures for ultrafast photonics has not yet been explored. In this study, a Ti3C2Tx/graphene vertical heterostructure (TG‐VHS), an excellent saturable absorber (SA), is successfully used to generate femtosecond laser pulses via passive mode‐locking. The modulation depth of the TG‐VHS is measured to be 28%, which is ≈12.7 and 1.5 times higher than that of Ti3C2Tx MXenes and graphene, respectively. Density functional theory calculations show that various heterostructure systems are formed owing to the presence of various functional groups in Ti3C2Tx, and multiple charge transfers significantly enhance the nonlinear optical characteristics of TG‐VHS. Moreover, utilizing TG‐VHS as the SA, a stable mode‐locked operation with a pulse duration as short as 356 fs at a wavelength of 1559.16 nm is achieved; harmonic mode‐locking with the highest repetition rate of 603.1 MHz is also obtained. This study provides an important strategy for developing VHS SA for ultrafast pulse fiber lasers and opens new perspectives for designing advanced MXenes‐based photonic devices.

Edge-Functionalized Graphene/Polydimethylsiloxane Composite Films for Flexible Neural Cuff Electrodes.

The design of neural electrodes has changed in the past decade, driven mainly by the development of new materials that open the possibility of manufacturing electrodes with adaptable mechanical properties and promising electrical properties. In this paper, we report on the mechanical and electrochemical properties of a polydimethylsiloxane (PDMS) composite with edge-functionalized graphene (EFG) and demonstrate its potential for use in neural implants with the fabrication of a novel neural cuff electrode. We have shown that a 200 μm thick 1:1 EFG/PDMS composite film has a stretchability of up to 20%, a Young's modulus of 2.52 MPa, and a lifetime of more than 10000 mechanical cycles, making it highly suitable for interfacing with soft tissue. Electrochemical characterization of the EFG/PDMS composite film showed that the capacitance of the composite increased up to 35 times after electrochemical reduction, widening the electrochemical water window and remaining stable after soaking for 5 weeks in phosphate buffered saline. The electrochemically activated EFG/PDMS electrode had a 3 times increase in the charge injection capacity, which is more than double that of a commercial platinum-based neural cuff. Electrochemical and spectrochemical investigations supported the conclusion that this effect originated from the stable chemisorption of hydrogen on the graphene surface. The biocompatibility of the composite was confirmed with an in vitro cell culture study using mouse spinal cord cells. Finally, the potential of the EFG/PDMS composite was demonstrated with the fabrication of a novel neural cuff electrode, whose double-layered and open structured design increased the cuff stretchability up to 140%, well beyond that required for an operational neural cuff. In addition, the cuff design offers better integration with neural tissue and simpler nerve fiber installation and locking.

Temperature-dependent thermal conductivity of MBE-grown epitaxial SrSnO3 films

As an ultrawide bandgap (∼4.1 eV) semiconductor, single crystalline SrSnO3 (SSO) has promising electrical properties for applications in power electronics and transparent conductors. The device performance can be limited by heat dissipation issues. However, a systematic study detailing its thermal transport properties remains elusive. This work studies the temperature-dependent thermal properties of a single crystalline SSO thin film prepared with hybrid molecular beam epitaxy. By combining time-domain thermoreflectance and Debye–Callaway modeling, physical insight into thermal transport mechanisms is provided. At room temperature, the 350-nm SSO film has a thermal conductivity of 4.4 W m−1 K−1, ∼60% lower than those of other perovskite oxides (SrTiO3, BaSnO3) with the same ABO3 structural formula. This difference is attributed to the low zone-boundary frequency of SSO, resulting from its distorted orthorhombic structure with tilted octahedra. At high temperatures, the thermal conductivity of SSO decreases with temperature following a ∼T−0.54 dependence, weaker than the typical T−1 trend dominated by the Umklapp scattering. This work not only reveals the fundamental mechanisms of thermal transport in single crystalline SSO but also sheds light on the thermal design and optimization of SSO-based electronic applications.

Heat reflux sonochemical synthesis of Cu3BiS3 quantum dots: Experimental and first-principles investigation of spin–orbit coupling on structural, electronic, and optical properties

Semiconductor quantum dots (QD) exhibit promising electrical and optical properties in photovoltaic cells by improving their stability and efficiency enhancement. Therefore, in this study, novel Cu3BiS3 (CBS) ultrafine QDs were synthesized to function as effective solar absorbers, using a facile heat reflux sonochemical synthesis process under inert (N2) atmosphere. Using high-resolution transmission electron microscopy (HRTEM) analysis, the size of CBS QDs was found to be in the range of 3–8 nm. Furthermore, the crystallite size (D), strain (ε), and dislocation density (δ) of the QDs were investigated in detail by confirming the orthorhombic wittichenite structure. The photocurrent density (PCD) of CBS QDs obtained at a voltage range of 0.5–1 V was found between 0.2 and 0.6 mA/cm2 under illumination; otherwise, it has a linear nature and good ohmic behavior in the range of − 0.1 V to + 0.1 V. In additionally, the spin–orbit coupling (SOC) interaction was computed using the Perdew–Burke–Ernzerhof (PBE) and Tran-Blaha-modified Becke–Johnson (TB-mBJ) functionals in the density functional theory (DFT) framework. The results showed a bandgap transition from direct to indirect with the inclusion of SOC, as confirmed by the electronic band structure. Moreover, the DFT-calculated bandgap using the TB-mBJ functional (∼1 eV) achieved near consistency with the experimentally obtained bandgap (∼1.4 eV). Therefore, based on the experimental and computational results, this study can pave the way toward developing novel copper chalcogenide QDs for application in future photovoltaic cells.

Constructing high-efficiency stretchable-breathable triboelectric fabric for biomechanical energy harvesting and intelligent sensing

Triboelectric fabrics have attracted significant attention in wearable power supplies and self-powered sensors. Simultaneously endowing triboelectric fabrics with excellent electrical properties, good stretchability and breathability remain a challenging issue. In this work, a highly-efficient stretchable-breathable triboelectric fabric is developed by using a porous composite prepared from polyethyleneimine/silica-coated titanium dioxide (PEI/SiO2@TiO2) modulated carboxymethyl cellulose/waterborne polyurethane as the tribomaterial and polyethyleneimine/carbon nanotubes conductive nanomaterial as the electrode. By systematically manipulating the mass ratio of SiO2@TiO2 NPs, PEI and well-dispersed PEI/SiO2@TiO2, the electrical performance of the optimized triboelectric fabrics can be improved by 111% compared with the unoptimized one, and it can deliver a power density of 1.62 W m−2, higher than most other reported stretchable-breathable triboelectric fabrics. The output improvement can be ascribed to the synergistic effect of the enhanced internal polarization of the well-dispersed PEI/SiO2@TiO2 and the double charge transfer mechanism originating from amino groups. More importantly, the triboelectric fabrics exhibit a good elongation of 245% and a high air permeability of 105.1 mm s−1, which is greatly favorable to the wearable comfort of users. Furthermore, the fabric exhibits good durability and stability in electrical performance during continuous dynamic deformation and long-term use, and it can be widely used for body energy harvesting, remote system control and physiological monitoring. This work provides a practical and feasible idea for constructing high-efficiency stretchable-breathable triboelectric fabric and achieves the all-in-one fabrication of triboelectric fabric with promising electrical performance, comfort performance and mechanical properties.

The role of native point defects and donor impurities in the electrical properties of ZnSb2O4: a hybrid density-functional study.

The ceramic material zinc antimony oxide ZnSb2O4 has promising electrical and magnetic properties, making it suitable for various applications such as electrochemical and energy storage. However, the effects of point defects and impurities on its electrical properties have never been revealed. Here, we employ hybrid density-functional calculations to investigate the energetics and electronic properties of native point defects and donor impurities in ZnSb2O4. The energetically favorable configurations of native point defects under selected growth conditions (O-rich and O-poor) are identified based on the calculated formation energies. The study finds no shallow donor and shallow acceptor defects with low formation energies. Still, the oxygen vacancy (VO) has the lowest formation energy among the donor-type defects under O-rich and O-poor conditions. However, it acts as a very deep acceptor, making it unlikely to provide free electron carriers to the conduction band. Moreover, electron carriers are likely to be compensated by the formation of zinc vacancies (VZn) and the zinc substituted for antimony (ZnSb), which behave as dominant acceptors. Our analysis of the charge neutrality conditions estimates that the Fermi level of undoped ZnSb2O4 would be pinned in a range that is 2.60 eV to 3.12 eV above the VBM for O-rich to O-poor growth conditions, respectively, suggesting that this material is semi-insulating. The possibility of enhancing free electron carriers by doping with Al, Ga, In, and F impurities is also investigated. Our results, however, indicate that high n-type conductivity is hindered by self-compensation in which the impurities additionally act as electron killers. Our results suggest that other impurity candidates and approaches may need to be considered to efficiently dope this material into n-type. Overall, this work paves the way for point defect engineering in this class of ternary oxides.

Single-step, catalyst-free, and green synthesis of graphene transparent electrode for organic photovoltaics

Graphene is a promising transparent conducting electrode (TCE) for organic photovoltaics (OPVs) due to its outstanding optical and electrical properties. However, the high cost and complexity of graphene synthesis on transparent substrates as well as the use of hazardous carbon sources limits the large-scale application of graphene TCEs. This work reports a single-step synthesis of graphene TCEs on glass substrates for OPVs from plant extract by Radio frequency plasma enhanced chemical vapor deposition. This approach provides fast, cheap, and catalyst-free production of graphene from a sustainable and environmentally-friendly carbon resource.The as-prepared graphene films reveal high quality structure with promising optical and electrical properties. Inverted OPV devices built on the as-synthesized graphene TCEs exhibit 80% of the power conversion efficiency of their indium tin oxide counterparts, and higher short circuit current density and open circuit voltage.

Conductivity and dielectric properties of heterostructures based on novel graphitic carbon nitride and silver nanoparticle composite film for electronic applications

Graphitic-carbon nitride (g-C3N4) (GCN) has emerged as the most promising material for the fabrication of next generation cutting–edge electronic and optoelectronic devices, due to its excellent and promising electrical and physicochemical properties. In this work we report on strategies to enhance the electrical conductivity of GCN thin films through the formation of heterostructures using silver nanoparticles (Ag). The synergistic effect of silver nanoparticles doping on structural and transport properties of GCN thin films was studied in detail. The structural and morphological changes in GCN polymer owing to the inclusion of silver nanoparticles were examined through Scanning electron microscopy, Fourier transform spectroscopy and X-ray diffractometer techniques. The conformational modifications in GCN polymer chains due to silver nanoparticles doping greatly enhanced the electrical conductivity of GCN thin films. The inclusion of silver nanoparticles in GCN polymer matrix decreases the barrier energy and enables the charge carrier hopping easily leading to improved electrical conductivity. The electrical conductivity of GCN-Ag composite thin film was enhanced by two folds due to the silver nanoparticles inclusion in comparison to conductivity of the pristine GCN thin film. The presence of Ag nanoparticles in the composite film plays a substantial role in improving the dielectric attributes of the pure GCN. Therefore, the doping by using silver nanoparticles might be a suitable strategy for effectively tailoring the electrical conductivity and dielectric properties of GCN thin films and can be used as flexible conducting electrode material towards fabrication of electronic and optoelectronic devices

Detection of VOCs and Nitrogen Containing Gaseous Molecules By Utilizing Carbon Nanotubes (CNTs) As Sensing Materials

Carbon nanomaterials are increasingly attractive as potential candidates to make new generation of sensors due to their unique nanostructures that grant their promising electrical, chemical, and physical properties. Among the group of carbon materials, carbon nanotube (CNT) is one of the most encouraging materials because of its features of high surface-to-volume ratio and unique electronic structure. These features enable CNTs the potential to become a highly sensitive sensing material. Since our project aims on detecting bio-marks from human breath, of which the concentrations are extremely low, the nature of our sensor R&D becomes extremely challenging. Consequently, using CNTs as the sensing materials ought to be our obvious choice at this stage. This choice of carbonous materials as sensing media is also on the hope to simplify the sensor’s instability problems in our R&D effort because carbon itself is very chemically inert toward many chemicals.This presentation will serve as a report of the preliminary results from a lab experiment setting to detect several human breath related bio-marks. Sensors were chemiresistive typed and constructed through drop casting on interdigitated sensor circuit. Each sensor chip contains 8 sensor pixels, and the test bed can host maximum of 16 sensor chips simultaneously. In other words, our sensor testing chamber can embed up to 128 sensors at the same time. We then performed the sensor testing against several gases. As expected, the application of nanotechnology in using CNTs enabled us to approach high sensitivity towards to several gaseous analytes, ranging from sub-ppb to sub-ppm. Noticed that, the previous study from our lab revealed that the sensitivity of sensors could be promoted by illuminations of UV light.1 It was approved that the detection limit of nitric oxides is about 27 ppm, providing reliable and stable sensitivity. To simplify the sensor fabrication and miniaturization as well as to reduce power consumption of final sensor units, in this work, we employed an external thermal power to improve the reversibility of the sensors. Two external 375W IR bulbs were used as the heating source in this setting. A dimmer and temperature control circuitry were integrated to maintain the intended operating temperatures. Moreover, we employed our test protocols and methods by functionalizing the CNTs with carboxylic group, besides utilizing the pristine CNTs. It was resulted that this sensor array was able to detect various gaseous species, including NH3, Isoprene, acetone, etc., with relatively high sensitivity.The existence of surfactants in the CNT sensing layer lowered the conductivity of sensor pixels by a great magnitude and resulted in much reduced sensors’ sensitivities. Therefore, removing surfactants in the CNT solution was made, which dramatically improved the sensors’ electric conductivities and boosted sensors’ sensitivities. However, CNT solutions with diluted surfactants destabilize the CNTs’ aqueous suspension, and lead to the non-uniform CNTs layers. The sensor pixels fabricated by using this surfactant deficient CNTs resulted in the formation of CNT bundles or clusters. The gathering of CNTs in a non-uniform fashion could dramatically reduce the sensor’s sensitivity because the bundles would short the interdigitated circuit and disable the CNTs’ sensing capability in most other area of the sensor film. We, therefore, increased the amount of surfactant in the CNT solutions. The sensors fabricated with excess amount of surfactant exhibited highly electric resistance or even non-conductance with very low or no sensitivity. A simple washing process was then developed to wash out the surfactant, which partially resolved the non-uniformity problem. The method to completely prevent the CNT bundles from formation in sensor film is in progress.In conclusion, we developed a gas sensor array that can detect various VOCs and certain nitrogen containing gas molecules with an extremely high or reasonably high sensitivities. Through applying pristine, modified CNTs or mixtures of both into sensor fabrication, the sensing properties were enhanced under an external heating source in comparison with illumination of UV light. The best sensitivity of the sensors is achieved by removing the surfactants in the sensing films. The application of external thermal energy to help on sensors’ performance gets approved. The benefit of using thermal energy vs. UV light is also discussed. G. Chen, T. M. Paronyan, E. M. Pigos, and A. R. Harutyunyan, Scientific Reports 2, 343 (2012).

An Update on Graphene Oxide: Applications and Toxicity.

Graphene oxide (GO) has attracted much attention in the past few years because of its interesting and promising electrical, thermal, mechanical, and structural properties. These properties can be altered, as GO can be readily functionalized. Brodie synthesized the GO in 1859 by reacting graphite with KClO3 in the presence of fuming HNO3; the reaction took 3–4 days to complete at 333 K. Since then, various schemes have been developed to reduce the reaction time, increase the yield, and minimize the release of toxic byproducts (NO2 and N2O4). The modified Hummers method has been widely accepted to produce GO in bulk. Due to its versatile characteristics, GO has a wide range of applications in different fields like tissue engineering, photocatalysis, catalysis, and biomedical applications. Its porous structure is considered appropriate for tissue and organ regeneration. Various branches of tissue engineering are being extensively explored, such as bone, neural, dentistry, cartilage, and skin tissue engineering. The band gap of GO can be easily tuned, and therefore it has a wide range of photocatalytic applications as well: the degradation of organic contaminants, hydrogen generation, and CO2 reduction, etc. GO could be a potential nanocarrier in drug delivery systems, gene delivery, biological sensing, and antibacterial nanocomposites due to its large surface area and high density, as it is highly functionalized with oxygen-containing functional groups. GO or its composites are found to be toxic to various biological species and as also discussed in this review. It has been observed that superoxide dismutase (SOD) and reactive oxygen species (ROS) levels gradually increase over a period after GO is introduced in the biological systems. Hence, GO at specific concentrations is toxic for various species like earthworms, Chironomus riparius, Zebrafish, etc.

Performance limitation of Cu2FeSnS4 solar cell: Understanding impact of density of defect states

Copper based quaternary chalcogenides such as Cu2ZnSnSe4 (CZTSe), Cu2ZnSnS4(CZTS), Cu2ZnSn(SxSe1−x)4, Cu2FeSnS4 (CFTS) have become area of research interest due to promising electrical and optical properties. However, CFTS is having high potential and less explored absorber material towards photovoltaic applications. This motivates the authors to carry out analysis on CFTS materials and explore opportunities to achieve high efficiency. In this work, a detailed numerical analysis of various loss mechanisms such as SRH, Auger, and Radiative recombination which degrades the CFTS solar cell performance is carried out. In general, fabricated CFTS solar cell possess traps and defects which affects their performance up to a large extent. Hence, critical analysis on solar cell in presence of traps and defects provides a clear pathway to achieve high efficiency. Many distribution techniques are applied to characterize the presence of defect states and their effect on performance. It is interesting to observe an ideal efficiency of 28% in absence of any defects and traps whereas efficiency goes down to 14% in presence of traps and defects. This analysis may help researchers to predict the presence and distribution of defects along the absorber layer.

Ex-situ n-type heavy doping of Ge1-xSnx epilayers by surface Sb deposition and pulsed laser melting

Ge1-xSnx alloys have attracted considerable attention for their promising electrical and optical properties. One of the main challenges for their successful implementation in devices concerns the fabrication of n-type heavily doped surface layers. In this work, a new methodology for ex-situ doping of Ge1-xSnx layers is investigated. It consists of the deposition of Sb atoms on the surface of Ge1-xSnx layers followed by pulsed laser melting (PLM) that ensures the diffusion of Sb into the alloy. We demonstrate that Sb is incorporated very efficiently within a relaxed Ge0.91Sn0.09 epilayer, with supersaturated 4 × 1020 cm−3 active concentrations, in line with literature records obtained in Ge1-xSnx with in-situ approaches. At the same time, we observe that the concentration of substitutional Sn close to the surface decreases from 9 to about 6 at. % after PLM, inducing a contraction of the lattice parameter perpendicular to the underlying Ge1-xSnx. These results demonstrate a possible route for ex-situ n-type heavy doping of Ge1-xSnx alloys, but indicate also that Sn redistribution and precipitation phenomena need to be carefully considered for a successful process development.

Conducting polymer-based generators for vibro-electrochemomechanical energy conversion and harvesting

Energy harvesting technologies have received much attention to alleviate providing energy crisis by batteries for different applications including sensors and actuators. Compared to other sources, mechanical energy is more available and most widely distributed. Conducting polymers as piezoionic materials have gained a large number of attention in light of their advantages of having promising electrical and mechanical properties for electrochemical energy conversion and storage. In this paper, conducting polymer-based PEDOT/IPN/PEDOT trilayer structure is proposed for electrochemomechanical energy harvesting applications. For the proposed trilayer power generator, the vibro-electrochemomechanical model is demonstrated. In this modeling approach, the mechanical behavior of the trilayer is modeled in finite element software to capture the induced strain due to vibration input. Resistive-capacitive transmission line model is implemented to model the electrochemical response of the trilayer to mechanical input which is induced strain and predict the generated voltage. Finally, the simulation results show the ability of the energy harvester to convert the 2 g and 20 mm input acceleration and displacement to electrical energy and generate 986 µW power. This model enables one to find the best parameters and also calculate the potential generating power to have an optimal design.