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We introduced a voltammetric bisphenol A (BPA) sensor based on NiCo2O4/reduced graphene oxide (rGO) nanocomposite loaded on the screen-printed electrode surface (NiCo2O4/rGO/SPE). NiCo2O4/rGO was characterised using various techniques, including X-ray diffraction (×RD), Raman spectroscopy and scanning electron microscopy (SEM). We used differential pulse voltammetry (DPV) to detect BPA concentrations. We evaluated the key analytical features of NiCo2O4/rGO/SPE for the BPA detection and the effects of important experimental parameters on the voltammetric efficiency. The voltammetric response of the proposed electrode was evaluated towards BPA. We demonstrated that the produced electrode has a wide linear dynamic range (0.03 to 475.0 μM) and a detection limit as low as 0.01 μM at S/N = 3. [ABSTRACT FROM AUTHOR]

Single-atom catalysts (SACs) are new materials with admirable stability, selectivity, and performance for multiple reactions. SACs have been reported to be significantly capable of heterogeneous catalysis because of the active sites with controllable properties and the high efficiency of atom economy utilization. The electronic and geometric features of such materials depend on their coordination and composition, thereby affecting their catalytic potentials. From an economy utilization perspective, cost-effective and environmentally friendly catalysts can be met with precise scientific design and controllable construction of SACs. The present review article is focused on recent applications of SACs in electrocatalysis such as CO2 reduction reaction (CO2RR), oxygen evolution reaction (OER), hydrogen evolution reaction (HER), oxygen reduction reaction (ORR) and electrochemical detection. We also review the related challenges and perspectives for SACs-based materials for such applications. [ABSTRACT FROM AUTHOR]

Binary transition metal oxides with encouraging electrocatalyst properties have been suggested as electrode materials for supercapacitors and methanol oxidation. Hence, in this work, a binary mixed metal oxide based on nickel and manganese (MnNi2O4) and its hybrid with reduced graphene oxide were synthesized by a one-step hydrothermal method. After physical and morphological characterization, the potential of these nanostructures was investigated for use as supercapacitor electrodes and methanol electro-oxidation. The results of the electrochemical analysis showed a substantial effect of adding rGO to the MnNi2O4. The MnNi2O4/rGO hybrid electrode supercapacitor exhibited good stability of 93% after 2000 consecutive CV cycles and a specific capacitance of 575 F g−1 at the current density of 0.5 A g−1. Furthermore, the application of this hybrid nanomaterial in the methanol electro-oxidation reaction (MOR) indicated its appropriate electrochemical efficiency and stability in methanol oxidation. Our results show that MnNi2O4/rGO can be considered as a promising electrode material for energy applications. [ABSTRACT FROM AUTHOR]

We developed and tested a 2D periodic array of cold-electron bolometers arranged into a wideband frequency selective metasurface that absorbs more than 70% of the incident power in the frequency range 100–800 GHz. The array had 10 × 10 unit cells, each containing four bolometers incorporated into a ring. The chip with bolometers was mounted on the back side of the silicon lens without a back-reflector. Preliminary experiments demonstrated voltage responsivity as high as 109 V/W for the current-biased series array. Simulation of the noise performance shows realization of background noise-limited performance with NEPtot < NEPphot for the optical power load P0 > 15 pW. Results of numerical simulation made for the unit cell of the array are presented together with the equivalent diagram based on lumped network elements. The unit cell also was developed numerically to operate in two radiation modes. [ABSTRACT FROM AUTHOR]

A systematic device-model calibration (extraction) methodology has been proposed to reduce parameter calibration time of advanced compact model for modern nano-scale semiconductor devices. The adaptive pattern search algorithm is a variant of the direct search method, which explore in the parameter space with adaptive searching step and direction. It is very straightforward, but powerful, in high dimensional optimization problem since adaptive step and direction are decided by simple computation. The proposed method iterates less but shows superior accuracy over the conventional method. It is possible to be applied to a behavioral or empirical model correspond to emerging devices, such as tunneling field-effect transistor (TFET) and negative capacitance field-effect transistor (NCFET) due to its universality in parameter calibration for the model accuracy. [ABSTRACT FROM AUTHOR]

GeAs is a layered material of the IV–V groups that is attracting growing attention for possible applications in electronic and optoelectronic devices. In this study, exfoliated multilayer GeAs nanoflakes are structurally characterized and used as the channel of back-gate field-effect transistors. It is shown that their gate-modulated p-type conduction is decreased by exposure to light or electron beam. Moreover, the observation of a field emission (FE) current demonstrates the suitability of GeAs nanoflakes as cold cathodes for electron emission and opens up new perspective applications of two-dimensional GeAs in vacuum electronics. FE occurs with a turn-on field of ∼80 and attains a current density higher than 10 , following the general Fowler–Nordheim model with high reproducibility. [ABSTRACT FROM AUTHOR]

Radiochromic films are mainly used for two-dimensional dose verification in photon, electron, and proton therapy treatments. Moreover, the radiochromic film types available today allow their use in a wide dose range, corresponding to applications from low-medical diagnostics to high-dose beam profile measurements in charged particle medical accelerators. An in-depth knowledge of the characteristics of radiochromic films, of their operating principles, and of the dose reading techniques is of paramount importance to exploit all the features of this interesting and versatile radiation detection system. This short review focuses on these main aspects by considering the most recent works on the subject. [ABSTRACT FROM AUTHOR]

This study, for the first time, reports the synthesis of CuO- and Cu2O nanoparticles (NPs) using the Salvia hispanica extract by a high-gravity technique. The original green synthesis procedure led to the formation of nanoparticles with promising catalytic and biological properties. The synthesized nanoparticles were fully characterized and their catalytic activity was evaluated through a typical Azide-Alkyne Cycloaddition (AAC) reaction. The potential antibacterial activity against gram positive (S. aureus) and gram negative (E. coli) bacteria were investigated. It was shown that the antibacterial properties were independent of the NP morphology as well as of the texture of the synthesis media. As a result, the presently synthesized nanoparticles showed very good photocatalytic and catalytic activities in comparison with the literature. From a biological perspective, they showed lower cytotoxicity in comparison with the literature, and also showed higher antioxidant and antibacterial activities. Thus, these present green CuO and Cu2O nanoparticles deserve further attention to improve numerous medical applications. [ABSTRACT FROM AUTHOR]

We present the optoelectronic characterization of graphene/silicon Schottky junctions, fabricated by transferring CVD-graphene on flat and nanotip-patterned n- and p-type Si substrates. We show that medium n-type doping results in the highest rectification. We demonstrate high photoresponsivity, exceeding 2.5 A/W under white light, which we attribute to the contribution of charges photogenerated in the surrounding region of the flat junction or to the internal gain by impact ionization caused by the enhanced field on the nanotips. [ABSTRACT FROM AUTHOR]

The present study reported a facile method for the determination of melamine in milk powder products based on the aggregation of reactant-free 5 nm gold nanoparticles (AuNPs). The strong electrostatic attraction between the positively charged exocyclic amine groups present in the melamine molecule and the negatively charged ions bound to the AuNPs induced aggregation of the AuNPs, resulting in visible color changes that could be seen with the naked eye and monitored by ultraviolet–visible (UV–Vis) absorbance spectra. The method shows high sensitivity with detection limits of 1 × 10−9 M for visual detection and 1 × 10−11 M for UV–Vis analysis, which is far below the safety limit of melamine ingestion in infant formula (1 ppm = 7.9 × 10−6 M) and the detection limit acquired by most AuNP-based melamine detection methods. Good recoveries were obtained over the range of 94.7–95.5% with a relative standard deviation of mean recovery (RSD) ranging from 1.40 to 5.81. The method provides a simple, feasible, fast and real-time detection of melamine adulterants in infant formula by the naked eye, without the aid of advanced instruments. [ABSTRACT FROM AUTHOR]

The remarkable tunability of 2D carbon structures combined with their non-toxicity renders them interesting candidates for thermoelectric applications. Despite some limitations related to their high thermal conductivity and low Seebeck coefficients, several other unique properties of the graphene-like structures could out-weight these weaknesses in some applications. In this study, hybrid structures of alumina ceramics and graphene encapsulated alumina nanofibers are processed by spark plasma sintering to exploit advantages of thermoelectric properties of graphene and high stiffness of alumina. The paper focuses on thermal and electronic transport properties of the systems with varying content of nanofillers (1–25 wt.%) and demonstrates an increase of the Seebeck coefficient and a reduction of the thermal conductivity with an increase in filler content. As a result, the highest thermoelectric figure of merit is achieved in a sample with 25 wt.% of the fillers corresponding to ~3 wt.% of graphene content. The graphene encapsulated nanofibrous fillers, thus, show promising potential for thermoelectric material designs by tuning their properties via carrier density modification and Fermi engineering through doping. [ABSTRACT FROM AUTHOR]

It is crucial to find a good material as a hole transport layer (HTL) to improve the performance of perovskite solar cells (PSCs), devices with an inverted structure. Polyethylene dioxythiophene-poly (styrene sulfonate) (PEDOT:PSS) and inorganic nickel oxide (NiOx) have become hotspots in the study of hole transport materials in PSCs on account of their excellent properties. In our research, NiOx and PEDOT: PSS, two kinds of hole transport materials, were prepared and compared to study the impact of the bottom layer on the light absorption and morphology of perovskite layer. By the way, some experimental parameters are simulated by wx Analysis of Microelectronic and Photonic Structures (wxAMPS). In addition, thin interfacial layers with deep capture levels and high capture cross sections were inserted to simulate the degradation of the interface between light absorption layer and PEDOT:PSS. This work realizes the combination of experiment and simulation. Exploring the mechanism of the influence of functional layer parameters plays a vital part in the performance of devices by establishing the system design. It can be found that the perovskite film growing on NiOx has a stronger light absorption capacity, which makes the best open-circuit voltage of 0.98 V, short-circuit current density of 24.55 mA/cm2, and power conversion efficiency of 20.01%. [ABSTRACT FROM AUTHOR]

Benefitting from the arbitrary and flexible light modulation, metasurface has attracted extensive attention and been demonstrated in different applications. However, most reported metasurface-based devices were normally composed of discrete micro or nano structures, therefore the discretization precision limited the performance of the device, including the focusing efficiency, stray light suppression, and broadband performance. In this work, an all-metallic reflective metasurface consisting of numerous quasi-continuous nanostructures is proposed to realize high-efficiency and broadband focusing. The constructed quasi-continuous metasurface (QCMS) is then verified numerically through electromagnetic simulation, and the numerical results show a higher focusing efficiency and a better stray light suppression effect, compared to a binary-phase-based metalens. Through the same design strategy, a QCMS with the ability to overcome the diffraction limit can also be constructed, and a focal spot with the size of 0.8 times the diffraction limit can be achieved. We expect that this quasi-continuous structure could be utilized to construct other high-performance devices that require continuous phase controls, such as the beam deflector, orbital angle momentum generator, and self-accelerating beam generator. [ABSTRACT FROM AUTHOR]

For highly sensitive pH sensing, an electrolyte insulator semiconductor (EIS) device, based on ZnO nanorod-sensing membrane layers doped with magnesium, was proposed. ZnO nanorod samples prepared via a hydrothermal process with different Mg molar ratios (0–5%) were characterized to explore the impact of magnesium content on the structural and optical characteristics and sensing performance by X-ray diffraction analysis (XRD), atomic force microscopy (AFM), and photoluminescence (PL). The results indicated that the ZnO nanorods doped with 3% Mg had a high hydrogen ion sensitivity (83.77 mV/pH), linearity (96.06%), hysteresis (3 mV), and drift (0.218 mV/h) due to the improved crystalline quality and the surface hydroxyl group role of ZnO. In addition, the detection characteristics varied with the doping concentration and were suitable for developing biomedical detection applications with different detection elements. [ABSTRACT FROM AUTHOR]

Lactate is an important organic molecule that is produced in excess during anaerobic metabolism when oxygen is absent in the human organism. The concentration of this substance in the body can be related to several medical conditions, such as hemorrhage, respiratory failure, and ischemia. Herein, we describe a graphene-based lactate biosensor to detect the concentrations of L-lactic acid in different fluids (buffer solution and plasma). The active surface (graphene) of the device was functionalized with lactate dehydrogenase enzyme using different substances (Nafion, chitosan, and glutaraldehyde) to guarantee stability and increase selectivity. The devices presented linear responses for the concentration ranges tested in the different fluids. An interference study was performed using ascorbic acid, uric acid, and glucose, and there was a minimum variation in the Dirac point voltage during detection of lactate in any of the samples. The stability of the devices was verified at up to 50 days while kept in a dry box at room temperature, and device operation was stable until 12 days. This study demonstrated graphene performance to monitor L-lactic acid production in human samples, indicating that this material can be implemented in more simple and low-cost devices, such as flexible sensors, for point-of-care applications. [ABSTRACT FROM AUTHOR]

Graphene has been extensively investigated in advanced photodetection devices for its broadband absorption, high carrier mobility, and mechanical flexibility. Due to graphene's low optical absorptivity (2.3%), graphene-based photodetection research so far has focused on hybrid systems to increase photoabsorption. However, such hybrid systems require a complicated integration process and lead to reduced carrier mobility due to heterogeneous interfaces. Crumpled or deformed graphene has previously been reported in electronics and optoelectronics. However, a depth study on the influence of the morphology of nanofilms (e.g., graphite or graphene) related to light absorption in photodetection devices has not been demonstrated yet. Here, we present an interesting study in terms of the effect of the deformable surface and the smooth surface of a nanofilm transferred onto Si through two transfer strategies using isopropanol injection and nitrogen blowing (to form a deformable nanofilm surface) and deionized water injection and van der Waals interaction (to form a smooth nanofilm surface). As a result, optical detection in the case of the deformable nanofilm surface was enhanced significantly (~100%) compared with that of the smooth nanofilm surface in the visible laser wavelength (532 nm). In addition, evidence from the computational simulation also firmly affirms an advancement in the optical detection of deformed nanofilm-surface-based photodetection devices compatible with the experimental results. [ABSTRACT FROM AUTHOR]

Rare earth (RE) element-doped two-dimensional (2D) transition metal dichalcogenides (TMDCs) with applications in luminescence and magnetics have received considerable attention in recent years. To date, the effect of RE element doping on the electronic properties of monolayer 2D-TMDCs remains unanswered due to challenges including the difficulty of achieving valid monolayer doping and introducing RE elements with distinct valence and atomic configurations. Herein, we report a unique strategy to grow the Sm-doped monolayer MoS2 film by using an atmospheric pressure chemical vapor deposition method with the substrate face down on top of the growth source. A stable monolayer triangular Sm-doped MoS2 was achieved. The threshold voltage of an Sm-doped MoS2-based field effect transistor (FET) moved from −12 to 0 V due to the p-type character impurity state introduced by Sm ions in monolayer MoS2. Additionally, the electrical performance of the monolayer MoS2-based FET was improved by RE element Sm doping, including a 500% increase of the on/off current ratio and a 40% increase of the FET's mobility. The electronic property enhancement resulted from Sm doping MoS2, which led internal lattice strain and changes in Fermi energy levels. These findings provide a general approach to synthesize RE element-doped monolayer 2D-TMDCs and to enrich their applications in electrical devices. [ABSTRACT FROM AUTHOR]