This study examines the photocatalytic performance of $\mathbf{A g}$-doped $\mathbf{T i O}_{\mathbf{2}}$ thin films deposited on oxidized macroporous silicon (MPS), forming $\text{TiO}_{2} / \text{SiO}_{2} / \text{MPS}$ heterostructures. Ag concentrations ranging from 0 to 1.0 % were tested, and structural and chemical analyses-including scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD)-confirmed the successful integration of $\mathbf{A g}$ into the $\mathbf{T i O}_{\mathbf{2}}$ matrix. Photocatalytic efficiency was assessed via methylene blue dye degradation, revealing an unexpected decline in contaminant removal efficiency with increasing Ag doping. Contact angle measurements indicate that this trend correlates with reduced surface hydrophilicity in porous structures coated with Agdoped $\text{TiO}_{2}$, coupled with the of $\mathbf{A g}$ in promoting rutile-phase formation.

Two-dimensional materials have a significant increase in toughness and mechanical properties and, due to the two-dimensional confinement, it presents an excellent performance in electrical and thermal aspects. Among the two-dimensional materials, molybdenum disulfide (MoS 2 ) has been attracting the attention of researchers due to its high absorbance in the infrared region and the changes in electrical and thermoelectric properties in its gap when changing from 2D to 3D. For the production of MoS 2 , the fused quartz glass substrates were subjected to previous ultraviolet treatment used to allow the deposited layers to resist wear by contact. For this, it was designed and built using a UV/Ozone treatment chamber. After substrate treatment, the MoS 2 layers were grown using a chemical vapor deposition oven with controlled temperature and inert atmosphere to avoid contamination by other elements. The samples were characterized by Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD) methods. The results show that the MoS 2 thin film was obtained, which is promising for the development of new devices for use in thermogenerators.

Polyaniline (PANI) samples were deposited through chemical and electrochemical routes onto macroporous silicon (MPS). Their chemical and electrical features were investigated. For this, Fourier transforms infrared, Raman, and energy dispersive spectroscopies were used to show the successful incorporation of PANI into the pores and the formation of silicon oxide as a consequence of the silicon instability in the aqueous solution. The electrical parameters extracted by fitting the current-potential curves using the thermionic emission model of two opposite diodes being one at the PANI/MPS interface and the other at the silicon/back contact, indicate a Schottky barrier of about 0.730 V at the first interface and between 0.795-0.840 V at the second one and becomes more significant in the measurements between two contacts at the PANI surface. The chemical analysis reveals the presence of silicon oxide in both structures. This compound was found to be the determining factor for changing the electrical behavior. A larger flat band was measured in the device made by the chemical synthesis of PANI. The impedance analysis has shown that charge transfer is determined not only by the PANI and silicon oxide conductivity but also by the depletion layer's electrical features. However, the differential activation energy analysis indicates that PANI is chemically deposited, and the charge transport occurs hopping conduction. In contrast, in the electrochemically one, the charge is through impurity band conduction.

In this research, a Concentrated Solar Power (CSP) as a Parabolic Trough Collector (PTC), using Peltier cooling modules for power generation was analyzed by the Cross-Entropy method. When comparing conventional solar electric generators with this system, we have the advantage that it is compact and lightweight and can be easily assembled and used as low-cost power generation equipment. For this system, we perform I(V) measurements and use fit models to accurately extract the model parameters. This is all in a standalone, robust, and simultaneous fit of three equations, through the global optimization method called Cross-Entropy. This is a robust method that had never been applied to extract parameters in a thermoelectric generation.

This work reports the electrical characterization of ZnSn$_\text{} x $ Ge$_\text{} 1-x $N$_\text{2}$ (ZTGN) layers $(10\% < x < 90\%)$ deposited on glass by combinatorial sputtering and further assesses the performance of silicon heterojunction (SHJ) solar cells featuring them as electron-selective contacts. Bandgap, dark conductivity, and the activation energy of the latter were found to significantly change between Sn- and Ge-rich samples. When applying ZTGN layers as electron-selective contacts for SHJ solar cells, poor solar cell performance was observed, with surprisingly similar results despite changes in material properties. From analysis and modeling of the current–voltage characteristics using several device structures, we show that the work function of the electron-selective contact lies around 4.35 eV for all investigated Sn and Ge contents, which is too high to form an excellent electron-selective contact. By comparing different solar cell architectures, we could further identify that the Ge-rich layer imposes an additional barrier to electron extraction, independently of its poor selectivity, due to its low conductivity. Doping of Ge-rich ZTGN, thus, appears as the most relevant approach to build efficient devices with a ZTGN contact layer.

Macroporous silicon films were yielded by electrochemical corrosion in HF:DMF solution, after the structure passivation with polyaniline and then this film was doped with erbium using the cyclic voltammetry method. The structural analysis by scanning electron microscopy shown us the pores formation, whereas the analysis by Fourier transform infrared spectroscopy reveals the formation of silicon oxide during the PANI deposition and the structural modification of PANI by the formation of addition functional groups by the erbium atoms. The results of the electrical measurements indicated that PANI reduces the space charge region width, as well as the amount of surface state density, but the current flow through the MPS/PANI devices is low due to the presence of SiO2 inside the structure. This effect is partially recovered by the inclusion of erbium because of its effect of further reducing the space charge region width.

Low resistive electrodes based on Co and Mo co-doped SnO2 were prepared by the conventional solid-state reaction and sintered at 1250?C for 2 h. Concentration of Co2O3 precursor was unchanged (1mol%), while MoO3 was varied (0.25, 0.50 to 0.75mol%) to promote conductivity. The structural and microstructural characterization revealed that the samples have a rutile-type structure without secondary phases and large rutile grains with low porosity. Electrical measurements on DC mode have shown a semiconductor behaviour of the SnO2 samples doped with 0.25 and 0.75 at.% of Mo at temperatures below 50K, indicating their suitability for low-temperature electronic applications. Impedance measurements indicate reduced energy barriers of less than 1meV formed between highly conductive crystallites for the SnO2 samples doped with 0.25 and 0.75 at.% of Mo. The sample with Mo content of 0.50 at.% presented a higher energy barrier at a few hundredths of eV, with space charges at the crystallite boundaries.

We report high-resolution measurements that experimentally confirm a spiral cascade structure and a scaling relationship of shrimps in the Chua's circuit. Circuits constructed using this component allow for a comprehensive characterization of the circuit behaviors through high resolution parameter spaces. To illustrate the power of our technological development for the creation and the study of chaotic circuits, we constructed a Chua circuit and study its high resolution parameter space. The reliability and stability of the designed component allowed us to obtain data for long periods of time (∼21 weeks), a data set from which an accurate estimation of Lyapunov exponents for the circuit characterization was possible. Moreover, this data, rigorously characterized by the Lyapunov exponents, allows us to reassure experimentally that the shrimps, stable islands embedded in a domain of chaos in the parameter spaces, can be observed in the laboratory. Finally, we confirm that their sizes decay exponentially with the period of the attractor, a result expected to be found in maps of the quadratic family.

In this work; resistive moisture sensors were obtained by dip coating sulfonated polycarbonate (SPC) onto silver interdigitated electrodes. Commercial polycarbonate was sulfonated with acetyl sulphate at two different sulfonation degrees corresponding to 9.0 and 18.0 mole %. Impedance spectroscopy was used to investigate the humidity sensing properties at controlled relative humidity (RH%) environments generated from standard saline solutions in the range of 11–90 RH%. For the highest sulfonated sample; in the RH% range investigated (11 to 90%); the sensor impedance changed from 4.7 MΩ to 18 kΩ. Humidity sensors made from sulfonated polycarbonate showed exponential decay behavior of the impedance at constant frequency with the environmental relative humidity. Sample 9SPC presented dielectric relaxation response for environmental humidity between 58 and 90 RH% while sample 18SPC presented dielectric relaxation response for the entire measured range between 11 and 90 RH%. Sulfonated polycarbonate could be a promising material for the fabrication of simple and cheap humidity-sensing sensors for the assessment of relative humidity of the surrounding environment, as suggested by experimental results.

The amount of information exchanged per unit of time between two nodes in a dynamical network or between two data sets is a powerful concept for analysing complex systems. This quantity, known as the mutual information rate (MIR), is calculated from the mutual information, which is rigorously defined only for random systems. Moreover, the definition of mutual information is based on probabilities of significant events. This work offers a simple alternative way to calculate the MIR in dynamical (deterministic) networks or between two time series (not fully deterministic), and to calculate its upper and lower bounds without having to calculate probabilities, but rather in terms of well known and well defined quantities in dynamical systems. As possible applications of our bounds, we study the relationship between synchronisation and the exchange of information in a system of two coupled maps and in experimental networks of coupled oscillators.

We report numerical results on the existence of periodic structures embedded in chaotic and hyperchaotic regions on the Lyapunov exponent diagrams of a 4-dimensional Chua system. The model was obtained from the 3-dimensional Chua system by the introduction of a feedback controller. Both the largest and the second largest Lyapunov exponents were considered in our colorful Lyapunov exponent diagrams, and allowed us to characterize periodic structures and regions of chaos and hyperchaos. The shrimp-shaped periodic structures appear to be malformed on some of Lyapunov exponent diagrams, and they present two different bifurcation scenarios to chaos when passing the boundaries of itself, namely via period-doubling and crisis. Hyperchaos-chaos transition can also be observed on the Lyapunov exponent diagrams for the second largest exponent.

A high-resolution codimension-two parameter space showing the abundance of complex periodic structures of an experimental chaotic circuit is reported. Such resolution was propitiated by the use of a 0.5 mV step dc voltage source as one of the control parameters. Those complex periodic structures organize themselves in a period-adding bifurcation cascade that accumulates in a chaotic region. Numerical investigations on the dynamical model were also carried out to corroborate several new features observed in the experimental high-resolution parameter space.

We report the existence of complex periodic structures, forming intricate periodic networks, embedded in chaotic regions of bi-dimensional bifurcation diagrams (parameter spaces) of a chaotic circuit model. Such circuit is composed by a negative differential conductivity (NDC) device coupled with a three variable RLC tank circuit. Particularly, we focused on a semi-insulating Gallium Arsenide (GaAs) model of nonlinear NDC device which is capable of oscillating at low frequencies. We show the presence of many types of orbits regarding their topological structures, indicating that there are topological transitions in the parameter space.

In a 2D parameter-space of an inductorless Chua's circuit model, we carried out numerical investigations and observed self-similar stability structures embedded in a sea of chaos, known until recently just in discrete-time models, namely, shrimps. We showed that those structures are self-similar and organize themselves in a period-adding bifurcation cascade in a region of the parameter-space.

We have implemented an operational amplifier inductorless realization of the Chua's circuit. We have registered time series from its dynamical variables with the resistorRas the control parameter and varying from 1300Ωto 2000Ω. Experimental time series at fixedRwere used to reconstruct attractors by the delay vector technique. The flow attractors and their Poincaré maps considering parameters such as the Lyapunov spectrum, its subproduct the Kaplan-Yorke dimension, and the information dimension are also analyzed here. The results for a typical double scroll attractor indicate a chaotic behavior characterized by a positive Lyapunov exponent and with a Kaplan-Yorke dimension of 2.14. The occurrence of chaos was also investigated through numerical simulations of the Chua's circuit set of differential equations.

MnP nanowhiskers have been grown by molecular beam epitaxy technique on the InP(100) surface. The measurements of the magnetization revealed that samples with MnP nanowhiskers exhibit ferromagnetic behavior up to room temperature. The investigation of temperature and angular dependences of ferromagnetic resonance has shown the existence of 90° anisotropy. The high values of coercive field and peak temperature obtained for the samples make it possible to consider such materials for potential applications in spintronic devices.