Defect Density Research Articles

The Influence of Defects on the Structural, Optical, and Antibacterial Properties of Cr/Cu Co-Doped ZnO Nanoparticles

In this research, Cu/Cr codoped ZnO nanoparticles (Zn₀.₉₉₋ₓCu₀.₀₁CrxO) were prepared using the sol-gel technique. The dopant ratio was systematically varied, ranging from x = 0.01 to 0.05 in increments of 0.01. This variation allowed for an exploration of the impact of defects on the structural, microstructural, optical, and antibacterial properties of Cu/Cr-codoped ZnO nanoparticles. Structural analysis of the Zn₀.₉₉₋ₓCu₀.₀₁CrxO nanoparticles was conducted using X-ray diffraction. The findings confirmed the presence of a hexagonal wurtzite structure in the ZnCuCrO nanoparticles, as determined by the c/a ratios in the range of 1.6013 and 1.6039. The surface morphology, crystallite size, and nanoparticle shapes were determined through scanning electron microscopy. The nanoparticle elemental compositions were analyzed through electron dispersive spectroscopy. The optical characteristics of the samples were assessed using a UV spectrophotometer. The energy band gaps for the nanoparticles were computed, and we discussed how dopant elements and defects affected their optical properties. We determined the refractive index using five distinct models. Notably, the highest band gap was observed for Zn₀.₉4Cu₀.₀₁Cr₀.₀5O (Eg=3.27 eV).Positron annihilation lifetime spectroscopy was employed to investigate the defect type, defect density, and crystal quality of Cu/Cr-codoped ZnO nanoparticles. The shortest lifetime τ1 obtained the highest value (0.181 ns) for Zn0.97 Cu0.01Cr0.02O nanoparticles. Zn₀.₉₉₋ₓCu₀.₀₁CrxO NPs were assessed for their antibacterial effects on E. coli (gram-negative) and S. aureus (gram-positive). Cu/Cr codoped ZnO nanoparticles show potential as materials for optoelectronic and sensor applications due to their broad band gap (Eg > 3) and high refractive index (n > 2).

Unraveling the Degradation Mechanisms of Perovskite Solar Cells under Mechanical Tensile Loads.

The short longevity of perovskite solar cells (PSCs) is the major hurdle toward their commercialization. In recent years, mechanical stability has emerged as a pivotal aspect in enhancing the overall durability of PSCs, prompting a myriad of strategies devoted to this issue. However, the mechanical degradation mechanisms of PSCs remain largely unexplored, with corresponding studies mainly limited to perovskite single crystals, neglecting the complexity and nuances present in PSC devices based on polycrystalline perovskite thin films. Herein, we reveal the underlying mechanisms of the mechanical degradation of formamidinium-based PSCs, which are the most prevalent high-performance PSC candidates. Under uniaxial tensile loads, we found that the degradation is mainly attributed to the sequential increase in the density of micropores and halide defects within the perovskite films. This phenomenon is consistent across various perovskite compositions and environmental conditions. Our findings elucidate mechanistic insights for more targeted mitigation strategies aimed at addressing the mechanical degradation of PSC devices.

Corrosion resistance and passive film stability of laser direct energy deposited TiVZrNbAl lightweight multi-principal element alloy

This work reports the corrosion behaviour of a novel laser direct energy deposited Ti45V30Zr12Nb12Al1 lightweight multi-principal element alloy (MPEA) in a 0.6 M NaCl solution. The MPEA exhibits superior corrosion resistance to typical titanium alloys, including Ti80. Its excellent corrosion resistance is attributed to a passive film with bipolar semiconducting behaviour and an amorphous structure. This unique feature inhibits anion permeation from the electrolyte and cation dissolution from the passive film. Further analyses revealed that Nb alloying effectively reduces the point defect density in the passive film, enhancing its ability to resist attacks by chloride ions.

Crystal Originated Defect Monitoring and Reduction in Production Grade SmartSiC™ Engineered Substrates

Power devices electronics based on Silicon Carbide (SiC) are emerging as a breakthrough technology for various applications. The link between the quality of SiC substrates and device performance has been widely discussed [1]. Smart Cut™ technology offers the opportunity to integrate a high quality SiC layer on a low resistivity handle wafer. Moreover the crystal quality of a single donor wafer can be replicated multiple times to provide an epitaxy-ready substrate in high volume [2]. Nevertheless, some extended grown-in defects of SiC starting material, like micro-pipes or bulk inclusions, may generate surface defects called "Crystal Originated Defects" (COD) on transferred layers. This paper explains how SmartSiC™ defect density can be reduced by limiting the number of extended defects on donor wafers. Specific inspection recipes were developed to monitor the starting material and the replicated engineered substrate: COD root-causes and effects were analyzed. We demonstrated how a well-suited quality control of donor wafers plays a major role to guarantee defect-free SmartSiC™ wafers.

Boosting the effectiveness of a cutting-edge Ca3NCl3 perovskite solar cell by fine-tuning the hole transport layer

Ca3NCl3 has unique electrical and optical properties and shows great potential as an absorber for solar cells, offering a promising solution for enhancing efficiency and reducing costs. To determine the best device layout, this study uses a device combination of Ag/FTO/ETL/Ca3NCl3/HTL/Ni, including seven HTLs and one ETL with the SCAPS-1D simulator. To improve device configuration, consider variables including thickness, temperature, doping density, defect density, and series and shunt resistance. After optimizing device parameters, the Ag/FTO/SnS2/Ca3NCl3/MoO3/Ni device outperformed the other 6-HTLs (Cu2O, CuI, CuSCN, NiO, CuSbS2, and P3HT) based devices with a power conversion efficiency (PCE) of 28.13 %, an open circuit current (VOC) of 1.36 V, a short circuit current density (JSC) of 22.892 mA/cm2, and a fill factor (FF) of 90.36 %. This proposed solar cell has exceptional performance compared to conventional thin-film solar cells, highlighting Ca3NCl3 as an appealing solution for solar energy systems while reducing toxicity issues.

Controlled Crystallization and Enhanced Performance of γ-CsPbI3 Perovskite Through Methylammonium Iodide-Assisted Coevaporation.

Cesium lead triiodide (CsPbI3) perovskites have garnered significant attention owing to their suitable bandgap for tandem silicon substrates and excellent chemical stability. However, γ-CsPbI3 prepared via low-temperature co-evaporation is limited by a narrow black phase processing window and random crystal orientation, hindering its optoelectronic performance and industrial applications. This study introduced trace amounts of methylammonium iodide (MAI) into the co-evaporation system, enhancing the crystallization process, promoting columnar grain growth, and stabilizing the γ-phase perovskite, resulting in films with improved structural integrity and reduced defect density. The optimal Pb/Cs ratio for achieving the best photoelectric performance shifted from 1:1 to 1.1:1 in the presence of MAI. Additionally, the incorporation of MAI allowed for more efficient longitudinal carrier transport, as evidenced by the enhanced photoluminescence (PL) intensity. The bandgap of CsPbI3 remained approximately at 1.7eV before the δ-phase transition, ensuring suitability for photovoltaic applications. Ultimately, a photovoltaic device with 12% efficiency is achieved in the p-i-n structure without additional post-annealing of the CsPbI3 perovskite films, demonstrating the practical benefits of MAI incorporation.

Restructuring of Cu-based Catalysts during CO Electroreduction: Evidence for the Dominant Role of Surface Defects on the C2+ Product Selectivity.

CO is the key reaction intermediate in the Cu-catalyzed electroreduction of CO2 to products containing C-C bonds. Herein, we investigate the impact of the particle size of CuO precursors on the direct electroreduction of CO (CORR) to C2+ products. Flame spray pyrolysis was used to prepare CuO particles with sizes between 4 and 30 nm. In situ synchrotron wide-angle X-ray scattering (WAXS), quasi-in situ X-ray photoelectron spectroscopy, and transmission electron microscopy demonstrated that, during CORR, the CuO precursors transformed into ∼30 nm metallic Cu particles with a crystalline domain size of ∼17 nm, independently of the initial size of the CuO precursors. Despite their similar morphology, the samples presented different Faradaic efficiencies (FEs) to C2+ products. The Cu particles derived from medium-sized (10-20 nm) CuO precursors were the most selective to C2+ products (FE 60%), while those derived from CuO precursors smaller than 10 nm displayed a high FE to H2. As the oxidation state, the particle and the crystallite sizes of these samples were similar after CORR, the differences in product distribution are attributed to the type and density of surface defects on the metallic Cu particles, as supported by studying electrochemical oxidation of the reduced Cu particles during CV cycling in combination with synchrotron WAXS. Cu particles derived from <10 nm CuO contained a higher density of more under-coordinated defects, resulting in a higher FE to H2 than Cu particles derived from 10 to 30 nm CuO. Bulk oxidation was most prominent and stable for Cu particles derived from medium-sized CuO, which indicated the more disordered nature of their surface compared to Cu particles derived from 30 nm CuO precursors and their lower reactivity compared to Cu particles derived from small CuO. Cu particles derived from <10 nm CuO initially displayed intense redox behavior, quickly fading during subsequent CVs. Our results evidence the significant restructuring during the electrochemical reduction of CuO precursors into Cu particles of similar size. The differences in CORR performance of these Cu particles of similar size can be correlated to different surface structures, qualitatively resolved by studying surface and bulk oxidation, which affect the competition between CO dimerization to yield C2+ products and undesired H2 evolution.

Device optimization of all inorganic CsPbBr3/LNMO based multi-layered perovskite light harvesters for broader capturing of solar spectrum

All inorganic Cesium lead bromide (CsPbBr3) planar perovskites have garnered enormous significance in photovoltaic applications owing to its outstanding stability against oxygen, heat and moisture. However, the power conversion efficiencies of the CsPbBr3 planar perovskites are quite low primarily due to the inferior range of light absorbance and interfacial charge recombination losses. This issue can be successfully resolved with a novel multi-absorber architecture approach which incorporates dual absorbers consisting of a lower band gap Lanthanum Nickel Manganese Oxide (La2NiMnO6 or LNMO) material along with the wider band gap CsPbBr3 material so that the light absorbance regime could be well extended for maximal utilization of the solar spectrum. Therefore, this article incorporates numerical modeling and guided optimization of all inorganic ITO/ETL/CsPbBr3/La2NiMnO6(LNMO)/HTL dual absorbers-based heterojunction structure to improvise the power conversion efficiency of CsPbBr3 based single absorber PSCs. The critical device’s parameters, such as; absorber layer and carrier transport layer thickness, defect density, temperature, doping concentration, frequency response, capacitance effects, Mott-Schottky effects as well as series and shunt resistances are thoroughly optimized and evaluated using Solar Cell Capacitance Simulator (SCAPS-1D) simulator. The proposed dual absorber layer composition produces a substantial enhancement in performance with a peak power conversion efficiency (PCE) of 26.98 %, short circuit current (Jsc) of 39.75 mA/cm2, open circuit voltage (Voc) of 0.85 V, and fill factor (FF) of 77.98 % at a device defect density of 1015 cm−3 outperforming the 11 % of PCE attained with the experimentally reported CsPbBr3 single junction counterpart along with PSCs with various dual absorbers-based composition.

Design and optimization study of all inorganic based double-absorption- layer CsPbI3/MoS2 heterojunction perovskite solar cells by SCAPS-1D

In recent years, perovskite solar cells (PSCs) continue to be a popular issue due to their high-power conversion efficiency (PCE%) and cost-effective production process. The CsPbI3 absorber layer used to produce PSCs limits the efficiency of the structure because it can absorb low-energy photons. Therefore, in this study, for the first time, CsPbI3 and CsPbI3/MoS2 single and double absorber based inorganic heterojunction PSCs were studied in detail, compared and optimized by using Solar Cell Capacitance Simulator (SCAPS-1D) software package. We discussed how the photovoltaic efficiency changed based on the open-circuit voltage (Voc), circuit current density (Jsc), quantum efficiency (QE), PCE% and fill factor (FF) relies on layer thickness, operating temperature, defect density (Nt), acceptor (NA) and donor density (ND), and heterojunction design. CuSbS2 and PCBM were chosen as the HTL and ETL layers, respectively. Depending on the results obtained from the SCAPS-1D, the optimum parameters for the Au/HTL/CsPbI3/ETL/FTO single layer device were determined as Thickness = 300 nm, Nt = 1011 cm-3, NA = 1013 cm-3, and T = 310 K. Then, the optimum parameters of MoS2 for the Au/HTL/CsPbI3/MoS2/ETL/FTO double layer-based device were determined as Thickness = 600 nm, Nt = 1010 cm-3 and ND = 1018 cm-3. It has been observed that MoS2 increases the light absorption capacity of the PSC device. As a result, the solar cell efficiency of the device with MoS2 has improved from 20.44 % to 40.66 % compared to the single-layer device. Additionally, in this study, presented a new approach for the future development at highly efficient, stable and completely inorganic PSCs integrated with transition metal dichalcogenide(TMDs; MoS2) materials.

Solving the Contradiction of Work Function and Conductivity in PEDOT:PSS to Achieve High‐Performance Perovskite Light‐Emitting Diode via Aniline Interface Modification

AbstractPoly (3,4‐ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) is one of the most widely used functional materials for hole transport layer in perovskite light‐emitting diode (LED). Tuning its work function (WF) and conductivity (κ) is a key issue for promoting perovskite LED performance. While decreasing its WF always reduces its κ and vice versa. Solving such contradiction is quite significant for promoting the development and commercialization of perovskite LED. Herein, the aniline (Ani) is employed for PEDOT:PSS interface modification. Ani inserted between PEDOT and PSS to weaken electrostatic interaction between sulfonic acid group in PSS chain and thiophene group in PEDOT chain, which results in increased delocalized electrons to enhance its κ. More importantly, the acid–base reaction decreases high acidity of PEDOT:PSS, which is an effective way to increase its WF and decrease its interface defects density. Meanwhile, such interface modification avoids PEDOT:PSS phase separation and ensures the uniformity of film. After Ani modification, the WF of PEDOT:PSS increase from 5.16 to 5.31 eV, the κ increases from 0.30 to 8.62 S cm−1, and the hole mobility enhances from 0.716 × 10−6 to 1.306 × 10−6 cm2 V−1 s−1. Modified PEDOT:PSS boost CsPbI3 LED achieving a maximum external quantum efficiency of 17.70%.

Novel insight into calcium-catalyzed steam gasification behaviors of lignite

Lignite is a low-rank coal with abundant reserves, and direct combustion causes serious environmental pollution. Calcium-catalyzed steam gasification is a cleaner technology that can convert lignite into high-value fuels and chemicals. However, the detailed structural evolution of calcium species during lignite steam gasification remains inadequately understood. The present work addresses this issue by subjecting the calcium-catalyzed steam gasification process of lignite to a detailed analysis, focusing on both the pyrolysis and gasification stages. The transitions in the chemical structures of the lignite and calcium catalysts during the pyrolysis stage were investigated in situ by Fourier Transform Infrared Spectroscopy. The morphological and chemical characterization of chars was performed using SEM-EDS, Raman spectroscopy, XPS, and N2 adsorption/desorption. The catalytic performance and gas composition were investigated by TGA and a fixed-bed reactor during the gasification stage. The results verify that the calcium catalyst reduced the initial gasification temperature of lignite by 150 °C, resulting in a 13.91% increase in the H2 concentration of the synthesis gas and an improvement of the H2/CO ratio to 20.96. The active Ca-C site and intermediate Ca-O-C formed during the co-pyrolysis stage increase the defect density of char, and the transformation of organic calcium species catalyzes the gasification of lignite. The enhanced concentration of H2 in the syngas can be attributed to the catalytic effect of CaO on the water–gas shift reaction during the gasification process. These results are expected to guide efforts in supporting catalytic conversion processes and promoting the efficient utilization of low-rank coal.

Interplay of physical and textural properties in porous, nanostructured hard‑carbons as electrode materials for non-Faradic energy storage devices

This work presents a systematic investigation on the non-Faradic energy storage ability of non-graphitizable, porosity engineered hard‑carbon nanostructures as electrode materials. The persistent challenge of inducing and tuning porosity in hard‑carbon nanostructures is overcome here, by utilizing dendritic fibrous nano silica (DFNS) as a sacrificial template for uniform and conformal deposition of carbon through thermal chemical vapor deposition, leading to the formation of porosity tuned, nanostructured hard‑carbon florets (NCF). This strategy enables precisely crafted six varieties of NCF with varying yet monodisperse dimensions (NCF 90, NCF 350, NCF 366, NCF 430, NCF 540 and NCF 600), SSA (494–719 m2/g) and textural features such as pore volume (0.67–1.24 cm3/g) and pore diameter (3.83–5.65 nm). In contrast to current understanding, NCF 366 with defect length of 16 nm, defect density of 2.65 × 1011 cm−2, micro- to mesoscale pore ratio of 0.16 and specific surface area of 535 m2/g achieves the highest energy density of 14.6 Wh/kg and power density 10.0 kW/kg, when compared to NCF 90 with higher SSA (719 m2/g) and pore volume (1.24 cm3/g). Thus, this work manifests the critical contributions of tuning the pore structures and optimizing the relative contributions from multi-scale pore structures to achieve high-performing energy storage devices.

Combined non-destructive evaluation of the damage precursors in fused silica optics

Combined non-destructive evaluation methods for fused silica’s damage precursors including UV photothermal weak absorption, ultrafast fluorescence, steady-state fluorescence, Raman spectroscopy, and stress distribution, are proposed to explain the damage mechanism from multiple perspectives. The correlation between each non-destructive characterization method and damage behaviors is simultaneously verified, in general, the damage threshold test of R on 1. The results have shown that regions with high photothermal absorption are accompanied by low damage thresholds, because the photothermal conversion process is associated with laser-induced damage. The damage threshold is also lower at locations of bright ultrafast fluorescence signals with a lifetime ranging from 1.2∼3 ns, as ultrafast fluorescence is associated with high densities of defects. A complementary relationship between the distribution of ultrafast fluorescence and the distribution of photothermal absorption signals is constructed. This indicates that the steady-state fluorescence cannot accurately evaluate the precursor’s damage performance. Furthermore, Raman spectroscopy is utilized to identify the structural changes in bond lengths and angles, as well as locations of damages coinciding with stress distribution.

Numerical analysis and device modelling of a lead-free Sr3PI3/Sr3SbI3 double absorber solar cell for enhanced efficiency.

Halide perovskites are the most promising options for extremely efficient solar absorbers in the field of photovoltaic (PV) technology because of their remarkable optical qualities, increased efficiency, lightweight design, and affordability. This work examines the analysis of a dual-absorber solar device that uses Sr3SbI3 as the bottom absorber layer and Sr3PI3 as the top absorber layer of an inorganic perovskite through the SCAPS-1D platform. The device architecture includes ZnSe as the electron transport layer (ETL), while the active layer consists of Sr3PI3 and Sr3SbI3 with precise bandgap values. The bandgap value of Sr3SbI3 is 1.307 eV and Sr3PI3 is 1.258 eV. By employing double-graded materials of Sr3PI3/Sr3SbI3, the study achieves an optimized efficiency of up to 34.13% with a V OC of 1.09 V, FF of 87.29%, and J SC of 35.61 mA cm-2. The simulation explores the influence of absorber layer thickness, doping level, and defect density on electrical properties like efficiency, short-circuit current, open-circuit voltage, and fill factor. It also examines variations in temperature and assesses series and shunt resistances in addition to electrical factors. The simulation's output offers valuable insights and suggestions for designing and developing double-absorber solar cells.

C60/CZTS Junction Combination to Improve the Efficiency of CZTS-Based Heterostructure Solar Cells: A Numerical Approach

This work presents a copper zinc tin sulfide (CZTS)-based solar cell structure (AI/ITO/C60/CZTS/SnS/Pt) with C60 as a buffer layer, developed using the SCAPS-1D simulator by optimizing each parameter to calculate the output. Optimizing the parameters, the acceptor concentration and thickness were altered from 6.0 × 1015 cm−3 to 6.0 × 1018 cm−3 and 1500 nm to 3000 nm, respectively. Although, in this simulator, we can tune the value for the acceptor concentration to 6.0 × 1022, higher doping might present an issue regarding adjustment in the physical experiment. Thus, tunable parameters need to be chosen according to the reliability of the experimental work. The defect density varied from 1.0 × 1014 cm−3 to 1.0 × 1017 cm−3 and the auger hole/electron capture coefficient was determined to be 1.0 × 10−26 cm6 s−1 for the maintenance of the minorities in theoretical to quasi-proper experimental measurements. Although the temperature was intended to be kept near room temperature, this parameter was varied from 290 K to 475 K to investigate the effects of the temperature on this cell. The optimization of the proposed structure resulted in a final acceptor concentration of 6.0 × 1018 cm−3 and a thickness of 3000 nm at a defect density of 1.0 × 1015 cm−3, which will help to satisfy the desired experimental performance. Satisfactory outcomes (VOC = 1.24 V, JSC = 27.03 mA/cm2, FF = 89.96%, η = 30.18%) were found compared to the previous analysis.

Groundwater Level Estimation With Analytical Hierarchy Method

Groundwater is an important component of the hydrological cycle and a critical resource for ecosystems and human life on Earth. Estimation of groundwater levels is important for strategic planning and management in many areas such as agriculture, industry, engineering studies, and drinking water. In particular, it is necessary to determine the groundwater accurately and clearly in order to carry out both ground and hydraulic works. In this study, the estimation of the groundwater level of Diyarbakır province was made by analytical hierarchy method. Groundwater level estimation was made using slope, geology, geomorphology, land use, precipitation, fault density, drainage density classes. Especially in areas where data supply is short, positive and accurate results can be obtained with AHP, which is a fast and practical application. It is expected that the findings obtained will benefit public and private institutions and organizations for future studies.

Blue Perovskite Lasing Derived from Bound Excitons through Defect Engineering.

All-inorganic perovskite films have emerged as promising candidates for laser gain materials owing to their outstanding optoelectronic properties and straightforward solution processing. However, the performance of blue perovskite lasing still lags far behind due to the inevitable high density of defects. Herein, we demonstrate that defects can be utilized instead of passivated/removed to form bound excitons to achieve excellent blue stimulated emission in perovskite films. Such a strategy emphasizes defect engineering by introducing a deep-level defect in mixed-Rb/Cs perovskite films through octylammonium bromide (OABr) additives. Consequently, the OA-Rb/Cs perovskite films exhibit blue amplified spontaneous emission (ASE) from defect-related bound excitons with a low threshold (13.5 μJ/cm2) and a high optical gain (744.7 cm-1), which contribute to a vertical-cavity surface-emitting laser with single-mode blue emission at 482 nm. This work not only presents a facile method for creating blue laser gain materials but also provides valuable insights for further exploration of high-performance blue lasing in perovskite films.

Synergistic adsorption and UV degradation of perfluorooctanoic acid by amine-functionalized A-center sphalerite

Perfluorinated alkylated substances (PFAS), as a category of persistent organic pollutants, have garnered extensive concern due to their resilience against environmental degradation. Herein, we developed an amine-functionalized sphalerite (ZnS) with adjustable surface amine functional groups and Zn defects (ZnS-X%[N]) by in situ coprecipitation and simple hydrothermal method in the presence of cetyltrimethylammonium bromide (CTAB). This material demonstrated efficient PFAS adsorption and subsequent photo-induced degradation under UV irradiation. The characterization results by TEM, BET, FTIR, XPS and EPR revealed that CTAB primarily influences ZnS by modulating surface amine functionalities, zinc defect density, and enhancing its photoreductive capacity. Adsorption and kinetic degradation experiments further showed that a medium CTAB concentration in ZnS-40%[N] achieves highest PFAS adsorption capacity (Cmax: 0.201 mol kg-1), and the corresponding decomposition rate was the fastest (kde: 1.53; kdf: 1.19). This efficacy is attributed to the ZnS-40%[N]'s ideal adsorptive sites and surface shallow defects. Moreover, theoretical simulation also supports the above experimental inference. Overall, ZnS-X%[N] exhibits a synergistic effect on PFAS adsorption and degradation, showcasing its potential for environmental adaptability and practical application.

Recycling of reduced graphene oxide from graphite rods in disposable zinc battery applicable to optical sensing

We report a low cost, simple method to fabricate reduced graphene oxide (rGO) optical sensors from recycled batteries. The rGO nanosheets were exfoliated by electrochemical method under the assistant of electric arc using 5 % KOH or NaOH electrolytes. The rGO nanosheets show interlayer distances ranging from 3.98 to 6.22 Å, and thicknesses from 0.62 to 6.00 nm, corresponding from 1 to 10 layers, respectively, determined from X-ray diffraction (XRD), atomic force microscopy (AFM), and transmission electron microscopy (TEM) measurements. Selected area electron diffraction (SAED) measurement indicates that rGO nanosheets content Miller-Bravais indices of (1–210) and (0–110) planes, and the hexagonal diffraction pattern of (0–110) plane of graphene sheets with d-spacing of 2.13 Å. Low defect densities in exfoliated rGO nanosheets were confirmed by ID/IG ratios ∼0.16 to 0.18 via Raman. The rGO nanosheets exfoliated in NaOH electrolyte have 19.35 % lower oxygen content compared to those exfoliated in KOH electrolyte inspected from XPS spectra. The performance of the rGO optical sensors is controlled by defects created from oxygen functional groups formed during exfoliation process. The responsivity and response (rise) time of NaOH-exfoliated rGO sensor are 0.46 A/W and 2.3 s, respectively. These values are 21 % (for responsivity) larger and 35 % (for rise time) smaller than those of KOH-exfoliated rGO sensor. The best-in-class of high gain were demonstrated in this study for the rGO optical sensors prepared from disposed graphite rods. The results demonstrate how disposed batteries can be recycled to produce photodetectors and other optoelectronic devices using cheap and relatively nontoxic methods.

Role of magnesium ions in modifying oxide growth rate on Zircaloy under breakaway corrosion regimes

General corrosion of nuclear reactor in core material like Zircaloy-2 and breakaway corrosion in particular are of great importance in ensuring its smooth long term operation. Metal ions like Mg2+ added to the coolant, to mitigate corrosion of other structural materials like Carbon steel, can get incorporated in the corrosion product oxide on Zircaloy-2 and alter its corrosion behavior. Plasma Electrolytic Oxidation (PEO) method was employed to investigate the effect of Mg2+ ions during breakaway corrosion of Zircaloy-2. The main objective was to understand the morphology, protectiveness, semiconducting properties of the Mg modified oxide films on Zircaloy-2 surface. DC potentials 300, 400 and 500 V were used to accelerate corrosion kinetics and form oxide mimicking the breakaway corrosion regime. Borate buffer (pH 9.8) was used as the electrolyte, and Mg acetate was added as Mg source for probing the effect of Mg2+ ions. Oxide morphology depended largely on the formation potentials. The presence of magnesium resulted in thinner oxides with lower defect densities. GIXRD of the oxide showed stabilization of tetragonal phase in presence of Mg at 300 and 400 V. Oxide resistance and charge transfer resistances measured by EIS were observed to be higher due to Mg incorporation at these potentials. Mg addition facilitated formation of t-ZrO2. The electrochemical measurements suggested that the presence of Mg in ZrO2 could reduce the connected porosity in the oxide thereby stifling the diffusion paths. These factors lead to improved corrosion protectiveness of the oxide formed in the presence of Mg.