Polarization-insensitive perfect absorption in van der waals hyper-structure.

Infrared perfect absorption has been widely investigated due to its potential applications in photodetectors, photovoltaics and medical diagnostics. In this report, we demonstrate that at particular infrared frequencies, a simple planar structure made up of graphene-hexagonal Boron Nitride (hBN) hyper-structure is able to nearly perfectly absorb incident light irrespective of its polarization (Transverse-Magnetic TM, or Transverse-Electric TE). By using this interferenceless technique, the hyper-structure achieves nearly zero reflectance at a wide range of angles in a narrow frequency band. We analytically predict the condition of achieving such an important feature of perfect absorption for both TM and TE polarizations. Interestingly, the infrared perfect absorption can be redshifted by increasing the thickness of the hBN layers and blueshifted by increasing the graphene's chemical potential. Such flexible control of infrared perfect absorption offers a new tool for controlling electromagnetic waves and has potential applications in photodetection and other light control applications.

2D TiO2 nanosheets decorated via sphere-like BiVO4: a promising non-toxic material for liquid phase photocatalysis and bacterial eradication.

An in-depth investigation was conducted on a promising composite material (BiVO4/TiO2), focusing on its potential toxicity, photoinduced catalytic properties, as well as its antibiofilm and antimicrobial functionalities. The preparation process involved the synthesis of 2D-TiO2 using the lyophilization method, which was subsequently functionalized with sphere-like BiVO4. Finally, we developed BiVO4/TiO2 S-scheme heterojunctions which can greatly promote the separation of electron-hole pairs to achieve high photocatalytic performance. The evaluation of concentration- and time-dependent viability inhibition was performed on human lung carcinoma epithelial A549 cells. This assessment included the estimation of glutathione levels and mitochondrial dehydrogenase activity. Significantly, the BiVO4/TiO2 composite demonstrated minimal toxicity towards A549 cells. Impressively, the BiVO4/TiO2 composite exhibited notable photocatalytic performance in the degradation of rhodamine B (k =0.135 min-1) and phenol (k = 0.016 min-1). In terms of photoinduced antimicrobial performance, the composite effectively inactivated both gram-negative E. coli and gram-positive E. faecalis bacteria upon 60-min of UV-A light exposure, resulting in a significant log6(log10CFU/mL) reduction in bacterial count. These promising results can be attributed to the unique 2D morphology of TiO2 modified by sphere-like BiVO4, leading to an increased generation of (intracellular)hydroxyl radicals, which plays a crucial role in treatments of both organic pollutants and bacteria.

Manganese and Cobalt-Free Ultrahigh-Ni-Rich Single-Crystal Cathode for High-Performance Lithium Batteries.

Current commercial nickel (Ni)-rich Mn, Co, and Al-containing cathodes are employed in high-energy-density lithium (Li) batteries all around the globe. The presence of Mn/Co in them brings out several problems, such as high toxicity, high cost, severe transition-metal dissolution, and quick surface degradation. Herein, a Mn/Co-free ultrahigh-Ni-rich single-crystal LiNi0.94Fe0.05Cu0.01O2 (SCNFCu) cathode with acceptable electrochemical performance is benchmarked against a Mn/Co-containing cathode. Despite having a slightly lower discharge capacity, the SCNFCu cathode retaining 77% of its capacity across 600 deep cycles in full-cell outperforms comparable to a high-Ni single-crystal LiNi0.9Mn0.05Co0.05O2 (SCNMC; 66%) cathode. It is shown that the stabilizing ions Fe/Cu in the SCNFCu cathode reduce structural disintegration, undesirable side reactions with the electrolyte, transition-metal dissolution, and active Li loss. This discovery provides a new extent for cathode material development for next-generation high-energy, Mn/Co-free Li batteries due to the compositional tuning flexibility and quick scalability of SCNFCu, which is comparable to the SCNMC cathode.

High Performance Inverted RbCsFAPbI3 Perovskite Solar Cells Based on Interface Engineering and Defects Passivation.

Lead halide-based perovskites solar cells (PSCs) are intriguing candidates for photovoltaic technology due to their high efficiency, low cost, and simple fabrication processes. Currently, PSCs with efficiencies of >25% are mainly based on methylammonium (MA)-free and bromide (Br) free, formamide lead iodide (FAPbI3 )-based perovskites, because MA is thermally unstable due to its volatile nature and Br incorporation will induce blue shift in the absorption spectrum. Therefore, MA-free, Br-free formamidine-based perovskites are drawing huge research attention in recent years. The hole transporting layer (HTL) is crucial in fabricating highly efficient and stable inverted p-i-n structured PSCs by enhancing charge extraction, lowering interfacial recombination, and altering band alignment, etc. Here, this work employs a NiOx /PTAA bi-layer HTL combined with GuHCl (guanidinium hydrochloride) additive engineering and PEAI (phenylethylammonium iodide) passivation strategy to optimize the charge carrier dynamics and tune defects chemistry in the MA-free, Br-free RbCsFAPbI3 -based perovskite absorber, which boosts the device efficiency up to 22.78%. Additionally, the device retains 95% of its initial performance under continuous 1 sun equivalent LED light illumination at 45 °C for up to 500 h.

Modulating the Energy Band Structure of the Mg-Doped Sr0.5Pr0.5Fe0.2Mg0.2Ti0.6O3-δ Electrolyte with Boosted Ionic Conductivity and Electrochemical Performance for Solid Oxide Fuel Cells.

Achieving fast ionic conductivity in the electrolyte at low operating temperatures while maintaining the stable and high electrochemical performance of solid oxide fuel cells (SOFCs) is challenging. Herein, we propose a new type of electrolyte based on perovskite Sr0.5Pr0.5Fe0.4Ti0.6O3-δ for low-temperature SOFCs. The ionic conducting behavior of the electrolyte is modulated using Mg doping, and three different Sr0.5Pr0.5Fe0.4-xMgxTi0.6O3-δ (x = 0, 0.1, and 0.2) samples are prepared. The synthesized Sr0.5Pr0.5Fe0.2Mg0.2Ti0.6O3-δ (SPFMg0.2T) proved to be an optimal electrolyte material, exhibiting a high ionic conductivity of 0.133 S cm-1 along with an attractive fuel cell performance of 0.83 W cm-2 at 520 °C. We proved that a proper amount of Mg doping (20%) contributes to the creation of an adequate number of oxygen vacancies, which facilitates the fast transport of the oxide ions. Considering its rapid oxide ion transport, the prepared SPFMg0.2T presented heterostructure characteristics in the form of an insulating core and superionic conduction via surface layers. In addition, the effect of Mg doping is intensively investigated to tune the band structure for the transport of charged species. Meanwhile, the concept of energy band alignment is employed to interpret the working principle of the proposed electrolyte. Moreover, the density functional theory is utilized to determine the perovskite structures of SrTiO3-δ and Sr0.5Pr0.5Fe0.4-xMgxTi0.6O3-δ (x = 0, 0.1, and 0.2) and their electronic states. Further, the SPFMg0.2T with 20% Mg doping exhibited low dissociation energy, which ensures the fast and high ionic conduction in the electrolyte. Inclusively, Sr0.5Pr0.5Fe0.4Ti0.6O3-δ is a promising electrolyte for SOFCs, and its performance can be efficiently boosted via Mg doping to modulate the energy band structure.

Designing High Interfacial Conduction beyond Bulk via Engineering the Semiconductor-Ionic Heterostructure CeO2-δ/BaZr0.8Y0.2O3 for Superior Proton Conductive Fuel Cell and Water Electrolysis Applications.

Proton ceramic fuel cells (PCFCs) are an emerging clean energy technology; however, a key challenge persists in improving the electrolyte proton conductivity, e.g., around 10-3-10-2 S cm-1 at 600 °C for the well-known BaZr0.8Y0.2O3 (BZY), that is far below the required 0.1 S cm-1. Herein, we report an approach for tuning BZY from low bulk to high interfacial conduction by introducing a semiconductor CeO2-δ forming a semiconductor-ionic heterostructure CeO2-δ/BZY. The interfacial conduction was identified by a significantly higher conductivity obtained from the BZY grain boundary than that of the bulk and a further improvement from the CeO2-δ/BZY which achieved a remarkably high proton conductivity of 0.23 S cm-1. This enabled a high peak power of 845 mW cm-2 at 520 °C from a PCFC using the CeO2-δ/BZY as the electrolyte, in strong contrast to the BZY bulk conduction electrolyte with only 229 mW cm-2. Furthermore, the CeO2-δ/BZY fuel cell was operated under water electrolysis mode, exhibiting a very high current density output of 3.2 A cm-2 corresponding to a high H2 production rate, under 2.0 V at 520 °C. The band structure and a built-in-field-assisted proton transport mechanism have been proposed and explained. This work demonstrates an efficient way of tuning the electrolyte from low bulk to high interfacial proton conduction to attain sufficient conductivity required for PCFCs, electrolyzers, and other advanced electrochemical energy technologies.

The role of band structure in Co- and Fe-co-doped Ba0.5Sr0.5Zr0.1Y0.1O3-δ perovskite semiconductor to design an electrochemical aptasensing platform: application in label-free detection of ochratoxin A using voltammetry.

Nanocomposites can offer a platform to conjugate biorecognition features of aptamer with unique size-dependent properties of a given material, which can autoprobe the binding event based on their electroactive characteristics. Herein, we design electroactive switchable aptamer probes based on co-doped single-phase semiconducting materials employing the cyclic voltammetry method to record the current signal at each step of electrochemical characterization. To do so, we utilized a facile hydrothermal method assisted by co-precipitation method such as Co-Fe-co-doped Ba0.5Sr0.5Zr0.1Y0.1O3-δ (CF-BSZY) and tuned the alignment of the energy band structure of the material to amplify the output of the electrochemical signal. At various steps, changes occurred in the electrochemical properties at the surface of CF-BSZY. The binding of the ssDNA with prepared materials enhances the current signal by the interaction with the target (ochratoxin A (OTA)) depressing the current signal and facilitating the construction of a novel design of electrochemical aptasensor. As a proof of concept, an electrochemical aptasensor for the detection of ochratoxin A (OTA) in rice samples has been developed. The electrochemical aptasensor provides a limit of detection (LOD) of 0.00012 µM (0.12 nM), with a linear range from 0.000247 to 0.74 µM and sound OTA recovery in real samples. The developed aptasensor is simply designed and is free of oligonucleotide labeling or decorative nanoparticle modifications. The proposed mechanism is generic in principle with the potential to translate any type of aptamer and target binding event into a detectable signal; hence, it can be largely applied to various bioreceptor recognition phenomena for subsequent applications.

Design of highly sensitive and selective ethanol sensor based on α-Fe2O3/Nb2O5 heterostructure.

The introduction of heterostructures is a new approach in gas sensing due to their easy and quick transport of charges. Herein, facile hydrothermal and solid-state techniques are employed to synthesize an α-Fe2O3/Nb2O5 heterostructure. The morphology, microstructure, crystallinity and surface composition of the synthesized heterostructures are investigated by scanning electron microscope, transmission electron microscope, x-ray diffraction, x-ray photoelectron spectroscopy and Brunauer-Emmett-Teller analyses. The successful fabrication of the heterostructures was achieved via the mutual incorporation of α-Fe2O3 nanorods with Nb2O5 interconnected nanoparticles (INPs). A sensor based on the α-Fe2O3(0.09)/Nb2O5 heterostructure with a high surface area exhibited enhanced gas-sensing features, maintaining high selectivity and sensitivity, and a considerable recovery percentage towards ethanol gas. The sensing response of the α-Fe2O3(0.09)/Nb2O5 heterostructure at lower operating temperature (160 °C) is around nine times higher than a pure Nb2O5 (INP) sensor at 180 °C with the flow of 100 ppm ethanol gas. The sensors also show excellent selectivity, good long-term stability and a rapid response/recovery time (8s/2s, respectively) to ethanol. The superior electronic conductivity and upgraded sensitivity performance of gas sensors based on the α-Fe2O3(0.09)/Nb2O5 heterostructure are attributed due to its unique structural features, high specific surface area and the synergic effect of the n-n heterojunction. The promising results demonstrate the potential application of the α-Fe2O3(0.09)/Nb2O5 heterostructure as a good sensing material for the fabrication of ethanol sensors.

Bismuth-Doped Nano Zerovalent Iron: A Novel Catalyst for Chloramphenicol Degradation and Hydrogen Production.

In this study, we showed that doping bismuth (Bi) at the surface of Fe0 (Bi/Fe0, bimetallic iron system)-synthesized by a simple borohydride reduction method-can considerably accelerate the reductive degradation of chloramphenicol (CHP). At a reaction time of 12 min, 62, 68, 74, 95, and 82% degradation of CHP was achieved with Fe0, Bi/Fe0-1 [1% (w/w) of Bi], Bi/Fe0-3 [3% (w/w) of Bi], Bi/Fe0-5 [5% (w/w) of Bi], and Bi/Fe0-8 [8% (w/w) of Bi], respectively. Further improvements in the degradation efficiency of CHP were observed by combining the peroxymonosulfate (HSO5 -) with Bi/Fe0-5 (i.e., 81% by Bi/Fe0-5 and 98% by the Bi/Fe0-5/HSO5 - system at 8 min of treatment). Interestingly, both Fe0 and Bi/Fe0-5 showed effective H2 production under dark conditions that reached 544 and 712 µM by Fe0 and Bi/Fe0-5, respectively, in 70 mL of aqueous solution containing 0.07 g (i.e., at 1 g L-1 concentration) of the catalyst at ambient temperature.

A Potential Checkmate to Lead: Bismuth in Organometal Halide Perovskites, Structure, Properties, and Applications.

The remarkable optoelectronic properties and considerable performance of the organo lead-halide perovskites (PVKs) in various optoelectronic applications grasp tremendous scientific attention. However, the existence of the toxic lead in these compounds is threatening human health and remains a major concern in the way of their commercialization. To address this issue, numerous nontoxic alternatives have been reported. Among these alternatives, bismuth-based PVKs have emerged as a promising substitute because of similar optoelectronic properties and extended environmental stability. This work communicates briefly about the possible lead-alternatives and explores bismuth-based perovskites comprehensively, in terms of their structures, optoelectronic properties, and applications. A brief description of lead-toxification is provided and the possible Pb-alternatives from the periodic table are scrutinized. Then, the classification and crystal structures of various Bi-based perovskites are elaborated on. Detailed optoelectronic properties of Bi-based perovskites are also described and their optoelectronic applications are abridged. The overall photovoltaic applications along with device characteristics (i.e., V OC, J SC, fill factor, FF, and power conversion efficiency, PCE), fabrication method, device architecture, and operational stability are also summarized. Finally, a conclusion is drawn where a brief outlook highlights the challenges that hamper the future progress of Bi-based optoelectronic devices and suggestions for future directions are provided.

Application of a Triple-Conducting Heterostructure Electrolyte of Ba0.5Sr0.5Co0.1Fe0.7Zr0.1Y0.1O3-δ and Ca0.04Ce0.80Sm0.16O2-δ in a High-Performance Low-Temperature Solid Oxide Fuel Cell.

Dual-ion electrolytes with oxygen ion and proton-conducting properties are among the innovative solid oxide electrolytes, which exhibit a low Ohmic resistance at temperatures below 550 °C. BaCo0.4Fe0.4Zr0.1Y0.1O3-δ with a perovskite-phase cathode has demonstrated efficient triple-charge conduction (H+/O2-/e-) in a high-performance low-temperature solid oxide fuel cell (LT-SOFC). Here, we designed another type of triple-charge conducting perovskite oxide based on Ba0.5Sr0.5Co0.1Fe0.7Zr0.1Y0.1O3-δ (BSCFZY), which formed a heterostructure with ionic conductor Ca0.04Ce0.80Sm0.16O2-δ (SCDC), showing both a high ionic conductivity of 0.22 S cm-1 and an excellent power output of 900 mW cm-2 in a hybrid-ion LT-SOFC. In addition to demonstrating that a heterostructure BSCFZY-SCDC can be a good functional electrolyte, the existence of hybrid H+/O2- conducting species in BSCFZY-SCDC was confirmed. The heterointerface formation between BSCFZY and SCDC can be explained by energy band alignment, which was verified through UV-vis spectroscopy and UV photoelectron spectroscopy (UPS). The interface may help in providing a pathway to enhance the ionic conductivities and to avoid short-circuiting. Various characterization techniques are used to probe the electrochemical and physical properties of the material containing dual-ion characteristics. The results indicate that the triple-charge conducting electrolyte is a potential candidate to further reduce the operating temperature of SOFC while simultaneously maintaining high performance.

The sintering temperature effect on electrochemical properties of Ce0.8Sm0.05Ca0.15O2-δ (SCDC)-La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) heterostructure pellet.

Recently, semiconductor-ionic materials (SIMs) have emerged as new functional materials, which possessed high ionic conductivity with successful applications as the electrolyte in advanced low-temperature solid oxide fuel cells (LT-SOFCs). In order to reveal the ion-conducting mechanism in SIM, a typical SIM pellet consisted of semiconductor La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) and ionic conductor Sm and Ca Co-doped ceria Ce0.8Sm0.05Ca0.15O2-δ (SCDC) are suffered from sintering at different temperatures. It has been found that the performance of LSCF-SCDC electrolyte fuel cell decreases with the sintering temperature, the cell assembled from LSCF-SCDC pellet sintered at 600 °C exhibits a peak power density (Pmax) of 543 mW/cm2 at 550 °C and also excellent performance of 312 mW/cm2 even at LT (500 °C). On the contrary, devices based on 1000 °C pellet presented a poor Pmax of 106 mW/cm2. The performance difference may result from the diverse ionic conductivity of SIM pellet through different temperatures sintering. The high-temperature sintering could severely destroy the interface between SCDC and LSCF, which provide fast transport pathways for oxygen ions conduction. Such phenomenon provides direct and strong evidence for the interfacial conduction in LSCF-SCDC SIMs.

Design of a novel filter paper based construct for rapid analysis of acetone.

The present work was focused to design a cheap, rapid, portable and easy to use filter paper based assay for the qualitative and quantitate analysis of acetone. Sodium alginate gel was loaded with the acetone specific optical signal probe, and subsequently coated onto filter paper surface to design portable colorimetric assays for acetone monitoring. The color of the paper sensor strip was observed to change from dark yellow to light yellowish in the presence of varying concentrations of acetone. Three different color analyzing models including RGB, HSV, and LAB were employed to probe the output optical signal, and their performance was compared in terms of better interpretation of the generated signal. The LAB model was found to provide better analytical figures of merit with a linear response for the acetone concentration ranging from 2.5 to 1500 ppm, and a limit of detection of 0.5 ppm. Furthermore, the specificity of the designed filter paper based sensor was demonstrated against different common interfering compounds. The results demonstrated the potential of our proposed filter paper based sensor as a novel tool for the analysis of acetone.

Ionic liquid coated iron nanoparticles are promising peroxidase mimics for optical determination of H2O2.

Ionic liquid coated nanoparticles (IL-NPs) consisting of zero-valent iron are shown to display intrinsic peroxidase-like activity with enhanced potential to catalyze the oxidation of the chromogenic substrate 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide. This results in the formation of a blue green colored product that can be detected with bare eyes and quantified by photometry at 652 nm. The IL-NPs were further doped with bismuth to enhance its catalytic properties. The Bi-doped IL-NPs were characterized by FTIR, X-ray diffraction and scanning electron microscopy. A colorimetric assay was worked out for hydrogen peroxide that is simple, sensitive and selective. Response is linear in the 30-300 µM H2O2 concentration range, and the detection limit is 0.15 µM. Graphical abstract Schematic of ionic liquid coated iron nanoparticles that display intrinsic peroxidase-like activity. They are capable of oxidizing the chromogenic substrate 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide. This catalytic oxidation generated blue-green color can be measured by colorimetry. Response is linear in the range of 30-300 µM H2O2 concentration, and the detection limit is 0.15 µM.

Carboxylic group riched graphene oxide based disposable electrochemical immunosensor for cancer biomarker detection.

In this work, we have developed for the first time a carboxylic group riched graphene oxide based disposable electrochemical immunosensor for cancer biomarker detection using methylene blue (MB). The developed immunosensor is highly sensitive for detection of biomarker Mucin1 (MUC1) in human serum samples. Development of this disposable electrochemical immunosensor was premeditated by applying specific monoclonal antibodies against MUC1. In this method, we explored highly conductive surface of carboxylic group (-COOH-) rich graphene oxide (GO) on screen-printed carbon electrodes (SPCE). This modified GO-COOH-SPCE was employed for the detection of MUC1 protein based on the reaction with methylene blue (MB) redox probe using differential pulse voltammetry (DPV) technique. Developed immunosensor exhibited good detection range for MUC1 with excellent linearity (0.1 U/mL- 2 U/mL), with a limit of detection of 0.04 U/mL. Upon potential application of developed biosensor, good recoveries were recorded in the range of 96-96.67% with % R.S.D 4.2. Analytical performance of the developed immunosensor assures the applicability in clinical diagnostic applications.

Biomimetic nitrogen doped titania nanoparticles as a colorimetric platform for hydrogen peroxide detection.

Nanoparticles proved a viable alternative to the already used sensing and diagnostics methods due to their low cost, good stability, easy availability and easy synthesis. In the present approach, nitrogen doped titania nanoparticles are prepared through freeze drying method, and subsequently stabilized through ionic liquid. These nanoparticles were characterized through various techniques such as X-ray diffraction (XRD), Fourier transformation infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), BET pore size and surface area analyzer, X-ray photoelectron spectroscopy (XPS) and UV-Visible diffuse reflectance spectroscopy (UV-Vis. DRS). The synthesized nitrogen doped titania nanoparticles were proved to be a novel peroxidase mimetic with great potential to catalyze oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide (H2O2) to form a blue color product. As a proof of concept, this new enzyme mimic was used as a robust nanoprobe for the detection of hydrogen peroxide with improved analytical characteristics. A linear response for hydrogen peroxide detection was obtained in the range of 10-300µmol/L, with a detection limit of 2.5µmol/L. Taking into account the valuable intrinsic peroxidase activity, the present work may find widespread applications in the field of sensors and biosensors for diverse applications.

Nano-Engineered Biomimetic Optical Sensors for Glucose Monitoring in Diabetes.

Diabetes is a rapidly growing disease that can be monitored at an individual level by controlling the blood glucose level, hence minimizing the negative impact of the disease. Significant research efforts have been focused on the design of novel and improved technologies to overcome the limitations of existing glucose analysis methods. In this context, nanotechnology has enabled the diagnosis at the single cell and molecular level with the possibility of incorporation in advanced molecular diagnostic biochips. Recent years have witnessed the exploration and synthesis of various types of nanomaterials with enzyme-like properties, with their subsequent integration into the design of biomimetic optical sensors for glucose monitoring. This review paper will provide insights on the type, nature and synthesis of different biomimetic nanomaterials. Moreover, recent developments in the integration of these nanomaterials for optical glucose biosensing will be highlighted, with a final discussion on the challenges that must be addressed for successful implementation of these nano-devices in the clinical applications is presented.

One Step Assembly of Thin Films of Carbon Nanotubes on Screen Printed Interface for Electrochemical Aptasensing of Breast Cancer Biomarker.

Thin films of organic moiety functionalized carbon nanotubes (CNTs) from a very well-dispersed aqueous solution were designed on a screen printed transducer surface through a single step directed assembly methodology. Very high density of CNTs was obtained on the screen printed electrode surface, with the formation of a thin and uniform layer on transducer substrate. Functionalized CNTs were characterized by X-ray diffraction spectroscopy (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and Brunauer-Emmett- Teller (BET) surface area analyzer methodologies, while CNT coated screen printed transducer platform was analyzed by scanning electron microscopy (SEM), atomic force microscopy (AFM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The proposed methodology makes use of a minimum amount of CNTs and toxic solvents, and is successfully demonstrated to form thin films over macroscopic areas of screen printed carbon transducer surface. The CNT coated screen printed transducer surface was integrated in the fabrication of electrochemical aptasensors for breast cancer biomarker analysis. This CNT coated platform can be applied to immobilize enzymes, antibodies and DNA in the construction of biosensor for a broad spectrum of applications.