Hole-Transport Management Enables 23%-Efficient and Stable Inverted Perovskite Solar Cells with 84% Fill Factor.

NiOx-based inverted perovskite solar cells (PSCs) have presented great potential toward low-cost, highly efficient and stable next-generation photovoltaics. However, the presence of energy-level mismatch and contact-interface defects between hole-selective contacts (HSCs) and perovskite-active layer (PAL) still limits device efficiency improvement. Here, we report a graded configuration based on both interface-cascaded structures and p-type molecule-doped composites with two-/three-dimensional formamidinium-based triple-halide perovskites. We find that the interface defects-induced non-radiative recombination presented at HSCs/PAL interfaces is remarkably suppressed because of efficient hole extraction and transport. Moreover, a strong chemical interaction, halogen bonding and coordination bonding are found in the molecule-doped perovskite composites, which significantly suppress the formation of halide vacancy and parasitic metallic lead. As a result, NiOx-based inverted PSCs present a power-conversion-efficiency over 23% with a high fill factor of 0.84 and open-circuit voltage of 1.162 V, which are comparable to the best reported around 1.56-electron volt bandgap perovskites. Furthermore, devices with encapsulation present high operational stability over 1,200 h during T90 lifetime measurement (the time as a function of PCE decreases to 90% of its initial value) under 1-sun illumination in ambient-air conditions.

Recent advances in graphene monolayers growth and their biological applications: A review.

Development of two-dimensional high-quality graphene monolayers has recently received great concern owing to their enormous applications in diverging fields including electronics, photonics, composite materials, paints and coatings, energy harvesting and storage, sensors and metrology, and biotechnology. As a result, various groups have successfully developed graphene layers on different substrates by using the chemical vapor deposition method and explored their physical properties. In this direction, we have focused on the state-of-the-art developments in the growth of graphene layers, and their functional applications in biotechnology. The review starts with the introduction, which contains outlines about the graphene and their basic characteristics. A brief history and inherent applications of graphene layers followed by recent developments in growth and properties are described. Then, the application of graphene layers in biodevices is reviewed. Finally, the review is summarized with perspectives and future challenges along with the scope for future technological applications.

Nozzle-Jet-Printed Silver/Graphene Composite-Based Field-Effect Transistor Sensor for Phosphate Ion Detection.

High concentration of dissolved phosphate ions is the main responsible factor for eutrophication of natural water bodies. Therefore, detection of phosphate ions is essential for evaluating water eutrophication. There is a need at large-scale production of real-time monitoring technology to detect phosphorus accurately. In this study, facile enzymeless phosphate ion detection is reported using a nozzle-jet-printed silver/reduced graphene oxide (Ag/rGO) composite-based field-effect transistor sensor on flexible and disposable polymer substrates. The sensor exhibits promising results in low concentration as well as real-time phosphate ion detection. The sensor shows excellent performance with a wide linear range of 0.005-6.00 mM, high sensitivity of 62.2 µA/cm2/mM, and low detection limit of 0.2 µM. This facile combined technology readily facilitates the phosphate ion detection with high performance, long-term stability, excellent reproducibility, and good selectivity in the presence of other interfering anions. The sensor fabrication method and phosphate detection technique yield low-cost, user-friendly sensing devices with less analyte consumption, which are easy to fabricate on polymer substrates on a large scale. Besides, the sensor has the capability to sense phosphate ions in real water samples, which makes it applicable in environmental monitoring.

TiO2 Nanoparticles/Nanotubes for Efficient Light Harvesting in Perovskite Solar Cells.

To enhance the light harvesting capability of perovskite solar cells (PSCs), TiO2 nanoparticles/nanotubes (TNNs) were incorporated into the active layer of PSCs. The TNN-containing cells showed a substantial increase in photocurrent density (JSC), from 23.9 mA/cm² without nanotubes to 25.5 mA/cm², suggesting that the TiO2 nanotubes enhanced the charge conduction and harvested more sunlight, which was attributed to the Mie scattering effect. Compared to the power conversion efficiency (PCE) of TiO2 nanoparticles in the active layer (14.16%), the TNN-containing cells with optimal loading of 9 wt % TiO2 nanotubes showed a high PCE of 15.34%.

Preparation of a Highly Conductive Seed Layer for Calcium Sensor Fabrication with Enhanced Sensing Performance.

The seed layer plays a crucial role in achieving high electrical conductivity and ensuring higher performance of devices. In this study, we report fabrication of a solution-gated field-effect transistor (FET) sensor based on zinc oxide nanorods (ZnO NRs) modified iron oxide nanoparticles (α-Fe2O3 NPs) grown on a highly conductive sandwich-like seed layer (ZnO seed layer/Ag nanowires/ZnO seed layer). The sandwich-like seed layer and ZnO NRs modification with α-Fe2O3 NPs provide excellent conductivity and prevent possible ZnO NRs surface damage from low pH enzyme immobilization, respectively. The highly conductive solution-gated FET sensor employed the calmodulin (CaM) immobilization on the surface of α-Fe2O3-ZnO NRs for selective detection of calcium ions (Ca2+). The solution-gated FET sensor exhibited a substantial change in conductance upon introduction of different concentrations of Ca2+ and showed high sensitivity (416.8 µA cm-2 mM-1) and wide linear range (0.01-3.0 mM). In addition, the total Ca2+ concentration in water and serum samples was also measured. Compared to the analytically obtained data, our sensor was found to measure Ca2+ in the water and serum samples accurately, suggesting a potential alternative for Ca2+ determination in water and serum samples, specifically used for drinking/irrigation and clinical analysis.

Fabrication of a solution-gated transistor based on valinomycin modified iron oxide nanoparticles decorated zinc oxide nanorods for potassium detection.

There are considerable interests to detect and monitor the abnormal level of minerals in water for avoiding/preventing any toxic effects after consumption. Herein, we report the fabrication of solution-gated field-effect-transistor (FET) based potassium sensor using iron oxide nanoparticles (Fe2O3 NPs) modified directly grown zinc oxide nanorods (ZnO NRs). The Fe2O3 NPs modification of ZnO NRs provided stability to nanorods surface and improved surface area for valinomycin immobilization. As-fabricated potassium sensor (valinomycin-Fe2O3 NPs-ZnO NRs/SiO2/Si) provided enhanced current response with increasing potassium concentration. During sensing measurements, FET sensor showed high sensitivity (4.65 µA/µM/cm2) in the linear range of 0.1 µM to 125 µM, low limit of detection (∼0.04 µM), good stability, excellent reproducibility, and favorable selectivity. Thus, good sensing performance of the FET based potassium sensor presents it as simple, low-cost, and convenient device for selective detection of potassium in solution.

Synthesis of manganese oxide nanorods and its application for potassium ion sensing in water.

Potassium is an important body mineral that control the cellular and electrical functions in the body. The potassium ion concentration change in human serum causes the risk of acute cardiac arrhythmia. Hence, it is important to monitor the potassium level in drinking water/food to control the intake and prevent its effect. This paper reports synthesis of manganese oxide (MnO2) nanorods using low-temperature sol-gel method for the fabrication of non-enzymatic potassium ion sensor. The detailed investigation of the as-synthesized MnO2 nanorods were carried out using field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The morphological and structural observations revealed that this method yield small nanorods with average length and diameters of about 210 ±â€¯10 nm and 20 ±â€¯3 nm, respectively. Further, as-synthesized α-MnO2 nanorods were used to fabricate non-enzymatic potassium ion sensor following the deposition of α-MnO2 nanorods on glassy carbon electrode (GCE) with the help of conductive binder. The electrochemical characterizations of fabricated non-enzymatic potassium sensor showed good sensing performance (i.e. sensitivity, selectivity, long term stability, and reproducibility). Moreover, applicability of the sensor to detect potassium ion in water samples were also demonstrated.

Fabrication of sensitive non-enzymatic nitrite sensor using silver-reduced graphene oxide nanocomposite.

There are increasing demands of more sensitive sensors for monitoring potential hazards in real water that may cause serious problems to human health. Herein, we report the development of a non-enzymatic nitrite sensor using nanocomposite of reduced graphene oxide decorated with silver nanoparticle (Ag-rGO). First, Ag-rGO nanocomposite was synthesized using a facile and cost-effective microwave-assisted approach. Then, as-synthesized Ag-rGO nanocomposite was used to modify glassy carbon electrode (GCE) and applied for the sensitive and selective detection of nitrite in the aqueous medium with increasing concentration of nitrite. Under optimized conditions, sensor achieved high sensitive response (18.4 µA/µM·cm2) in a wide linear range (0.1-120 µM), low limit of detection (∼0.012 µM), and good selectivity using differential pulse voltammograms (DPV). The applicability of fabricated non-enzymatic nitrite sensor was checked in real sample with satisfactory results.

Recent advances in nanowires-based field-effect transistors for biological sensor applications.

Nanowires (NWs)-based field-effect transistors (FETs) have attracted considerable interest to develop innovative biosensors using NWs of different materials (i.e. semiconductors, polymers, etc.). NWs-based FETs provide significant advantages over the other bulk or non-NWs nanomaterials-based FETs. As the building blocks for FET-based biosensors, one-dimensional NWs offer excellent surface-to-volume ratio and are more suitable and sensitive for sensing applications. During the past decade, FET-based biosensors are smartly designed and used due to their great specificity, sensitivity, and high selectivity. Additionally, they have the advantage of low weight, low cost of mass production, small size and compatible with commercial planar processes for large-scale circuitry. In this respect, we summarize the recent advances of NWs-based FET biosensors for different biomolecule detection i.e. glucose, cholesterol, uric acid, urea, hormone, proteins, nucleotide, biomarkers, etc. A comparative sensing performance, present challenges, and future prospects of NWs-based FET biosensors are discussed in detail.

Fully nozzle-jet printed non-enzymatic electrode for biosensing application.

The progress in developing the electrochemical sensors for biomolecule detection requires a facile device fabrication method. Herein, we report printing of silver (Ag) precursor and copper oxide nanoparticles (CuO NPs) inks by nozzle-jet technique to fabricate non-enzymatic glucose biosensor on flexible polyethylene terephthalate (PET) substrate. The fully printed CuO NPs/Ag/PET electrodes were characterized using electrochemical techniques for non-enzymatic biosensing of glucose. The fully printed non-enzymatic biosensor exhibited a high sensitivity (1424.2 µA mM-1 cm-2), linear range from 0.1 to 15 mM, low detection limit (0.3 µM; S/N = 3) and fast response time of ∼2 s under a working potential of +0.6 V. Additionally, printed electrodes demonstrated an excellent long term stability, high reproducibility, good selectivity and high accuracy during glucose concentration measurements in human blood and serum samples. These results indicate that the electrode fabrication using nozzle-jet printing can be regarded as a potential technique for the future development of high performance and low cost bio/chemical sensor devices.

Nonenzymatic flexible field-effect transistor based glucose sensor fabricated using NiO quantum dots modified ZnO nanorods.

Herein, we fabricated nonenzymatic flexible field-effect transistor (f-FET) based glucose sensor using nickel oxide quantum dots (NiO QDs) modified zinc oxide nanorods (ZnO NRs). The ZnO NRs surfaces were coated with NiO QDs using radio frequency (RF) magnetron sputtering to enhance the electrocatalytic feature and the surface area of ZnO NRs. Under physiological conditions (pH 7.4), the nonenzymatic f-FET glucose sensor shows two linear ranges of 0.001-10mM and 10-50mM with the high sensitivity of 13.14µAcm-2mM-1 and 7.31µAcm-2mM-1, respectively, along with good selectivity, stability and repeatability during glucose detection. The examination of human whole blood and serum samples reveal that the nonenzymatic f-FET based glucose sensor is capable of measuring glucose concentration efficiently in the presence of interfering species and thus can be offered as a promising device for further applications in clinical and non-clinical fields.

Highly Efficient Non-Enzymatic Glucose Sensor Based on CuO Modified Vertically-Grown ZnO Nanorods on Electrode.

There is a major challenge to attach nanostructures on to the electrode surface while retaining their engineered morphology, high surface area, physiochemical features for promising sensing applications. In this study, we have grown vertically-aligned ZnO nanorods (NRs) on fluorine doped tin oxide (FTO) electrodes and decorated with CuO to achieve high-performance non-enzymatic glucose sensor. This unique CuO-ZnO NRs hybrid provides large surface area and an easy substrate penetrable structure facilitating enhanced electrochemical features towards glucose oxidation. As a result, fabricated electrodes exhibit high sensitivity (2961.7 µA mM-1 cm-2), linear range up to 8.45 mM, low limit of detection (0.40 µM), and short response time (<2 s), along with excellent reproducibility, repeatability, stability, selectivity, and applicability for glucose detection in human serum samples. Circumventing, the outstanding performance originating from CuO modified ZnO NRs acts as an efficient electrocatalyst for glucose detection and as well, provides new prospects to biomolecules detecting device fabrication.

Nozzle-jet printed flexible field-effect transistor biosensor for high performance glucose detection.

Printable electronics is a subject of great interest for low-cost, facile and environmentally-friendly large scale device production. But, it still remains challenging for printable biosensor development. Herein, we present the fabrication of nozzle-jet printed flexible field-effect transistor (FET) glucose biosensor. The silver source-drain electrodes and ZnO seed layers were printed on flexible substrate by nozzle-jet printer followed by ZnO nanorods (ZnO NRs) synthesis and glucose oxidase (GOx) immobilization. Utilization of nozzle-jet printing methods resulted in highly reproducible electrodes with well-defined vertical grown ZnO NRs for high GOx loading and enhanced glucose sensing performance in a wide glucose detection range. The stability, anti-interference ability, reproducibility, reusability, and applicability in human serum samples were also assessed. Overall, biosensor fabrication using nozzle-jet printer will not only provide large scale production of highly reproducible electrodes but also reduce the fabrication cost. Additionally, printed electrodes can be modified accordingly for different analyte detection.

Solution Process Synthesis of High Aspect Ratio ZnO Nanorods on Electrode Surface for Sensitive Electrochemical Detection of Uric Acid.

This study demonstrates a highly stable, selective and sensitive uric acid (UA) biosensor based on high aspect ratio zinc oxide nanorods (ZNRs) vertical grown on electrode surface via a simple one-step low temperature solution route. Uricase enzyme was immobilized on the ZNRs followed by Nafion covering to fabricate UA sensing electrodes (Nafion/Uricase-ZNRs/Ag). The fabricated electrodes showed enhanced performance with attractive analytical response, such as a high sensitivity of 239.67 µA cm-2 mM-1 in wide-linear range (0.01-4.56 mM), rapid response time (~3 s), low detection limit (5 nM), and low value of apparent Michaelis-Menten constant (Kmapp, 0.025 mM). In addition, selectivity, reproducibility and long-term storage stability of biosensor was also demonstrated. These results can be attributed to the high aspect ratio of vertically grown ZNRs which provides high surface area leading to enhanced enzyme immobilization, high electrocatalytic activity, and direct electron transfer during electrochemical detection of UA. We expect that this biosensor platform will be advantageous to fabricate ultrasensitive, robust, low-cost sensing device for numerous analyte detection.

ZnO nanorods array based field-effect transistor biosensor for phosphate detection.

A promising field-effect transistor (FET) biosensor has been fabricated based on pyruvate oxidase (PyO) functionalized ZnO nanorods (ZnO NRs) array grown on seeded SiO2/Si substrate. The direct and vertically grown ZnO NRs on the seeded SiO2/Si substrate offers high surface area for enhanced PyO immobilization, which further helps to detect phosphate with higher specificity. Under optimum conditions, the fabricated FET biosensor provided a convenient method for phosphate detection with high sensitivity (80.57µAmM-1cm-2) in a wide-linear range (0.1µM-7.0mM). Additionally, it also showed very low effect of electroactive species, stability and good reproducibility. Encouraging results suggest that this approach presents a promising method to be used for field measurements to detect phosphate.

Highly stable hydrazine chemical sensor based on vertically-aligned ZnO nanorods grown on electrode.

Herein, we report a binder-free, stable, and high-performance hydrazine chemical sensor based on vertically aligned zinc oxide nanorods (ZnO NRs), grown on silver (Ag) electrode via low-temperature solution route. The morphological characterizations showed that the NRs were grown vertically in high density and possess good crystallinity. The as-fabricated hydrazine chemical sensors showed an excellent sensitivity of 105.5 µAµM-1cm-2, a linear range up to 98.6µM, and low detection limit of 0.005µM. It also showed better long-term stability, good reproducibility and selectivity. Furthermore, the fabricated electrodes were evaluated for hydrazine detection in water samples. We found the approach of directly growing nanostructures as a key factor for enhanced sensing performance of our electrodes, which effectively transfers electron from ZnO NRs to conductive Ag electrode. Thus it holds future prospective applications as binder-free, cost-effective, and stable sensing devices fabrication.

Development of highly-stable binder-free chemical sensor electrodes for p-nitroaniline detection.

Herein, pre-seeded fluorine doped tin oxide (FTO) glass substrates were used as an electrode for zinc oxide nanorods (ZnO NRs) growth by a low-temperature solution route in order to fabricate binder-free high-sensitive chemical sensor. The vertically-grown ZnO NRs exhibited a more favorable active morphology and improved sensing properties for p-nitroaniline (pNA) detection. On investigation with different concentrations of pNA, the ZnO NRs/FTO electrode showed an excellent sensitivity (10.18µAµM-1cm-2) and low detection limit (0.5µM) with good selectivity, outstanding long-term stability, and high reproducibility. Collectively, the present work emphasizes the potency of ZnO NRs/FTO electrodes for fabrication of an efficient and reliable chemical sensing device with improved performances.

Outstanding Antibiofilm Features of Quanta-CuO Film on Glass Surface.

Intelligently designed surface nanoarchitecture provides defined control over the behavior of cells and biomolecules at the solid-liquid interface. In this study, CuO quantum dots (quanta-CuO; ∼3-5 nm) were synthesized by a simple, low-temperature solution process and further formulated as paint to construct quanta-CuO thin film on glass. Surface morphological characterizations of the as-coated glass surface reveal a uniform film thickness (∼120 ± 10 nm) with homogeneous distribution of quanta-CuO. The antibiofilm assay showed a very high contact bacteria-killing capacity of as-coated quanta-CuO glass surfaces toward Staphylococcus aureus and Escherichia coli. This efficient antibacterial/antibiofilm activity was ascribed to the intracellular reactive oxygen species (ROS) generated by the quanta-CuO attached to the bacterial cells, which leads to an oxidative assault and finally results in bacterial cell death. Although there is a significant debate regarding the CuO nanostructure's antibacterial mode of action, we propose both contact killing and/or copper ion release killing mechanisms for the antibiofilm activity of quanta-CuO paint. Moreover, synergism of quanta-CuO with conventional antibiotics was also found to further enhance the antibacterial efficacy of commonly used antibiotics. Collectively, this state-of-the-art design of quanta-CuO coated glass can be envisioned as promising candidates for various biomedical and environmental device coatings.

Rapid methyl orange degradation using porous ZnO spheres photocatalyst.

Porous zinc oxide (ZnO) spheres were synthesized by facile low temperature solution route. The as-synthesized porous ZnO spheres were characterized in detail in terms of their morphological, structural, optical and photocatalytic properties using field-emission scanning electron microscopy (FESEM, equipped with energy dispersive spectroscopy (EDS)), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray diffractometer (XRD), UV-visible spectroscopy and Raman-scattering measurements. Nitrogen adsorption-desorption analysis was performed to determine pore size distribution from the adsorption isotherm curves using the Barrett-Joyner-Halenda (BJH) method. Morphological and structural characterizations showed porous nature of ZnO spheres with high surface area, good crystallinity, wurtzite hexagonal phase and good optical features. Next, ZnO spheres were studied as photocatalyst for photodegradation of harmful dye, methyl orange (MO). Under ultraviolet light irradiation, the decrease in MO dye concentration was monitored by UV-visible spectroscopy at different time intervals until the dye was completely degraded to colorless end product. Rapid MO dye decomposition was observed with a degradation rate of ~96.3% within the initial 120min, which is attributed to the porous nature, large specific surface area (114.6m(2)g(-1)), narrow pore size distribution (~2.5 to 25nm) evaluated from N2 adsorption-desorption isotherms analysis and excellent electron accepting features of the engineered porous ZnO spheres.

A comprehensive biosensor integrated with a ZnO nanorod FET array for selective detection of glucose, cholesterol and urea.

We report a novel straightforward approach for simultaneous and highly-selective detection of multi-analytes (i.e. glucose, cholesterol and urea) using an integrated field-effect transistor (i-FET) array biosensor without any interference in each sensor response. Compared to analytically-measured data, performance of the ZnO nanorod based i-FET array biosensor is found to be highly reliable for rapid detection of multi-analytes in mice blood, and serum and blood samples of diabetic dogs.