RESUMEN
In the context of ZnO nanorods (NRs) grown on Si and indium tin oxide (ITO) substrates, this study aimed to compare their degradation effect on methylene blue (MB) at different concentrations. The synthesis process was carried out at a temperature of 100 °C for 3 h. After the synthesis of ZnO NRs, their crystallization was analyzed using X-ray diffraction (XRD) patterns. The XRD patterns and top-view SEM observations demonstrate variations in synthesized ZnO NRs when different substrates were used. Furthermore, cross-sectional observations reveal that ZnO NRs synthesized on an ITO substrate exhibited a slower growth rate compared to those synthesized on a Si substrate. The as-grown ZnO NRs synthesized on the Si and ITO substrates exhibited average diameters of 110 ± 40 nm and 120 ± 32 nm and average lengths of 1210 ± 55 nm and 960 ± 58 nm, respectively. The reasons behind this discrepancy are investigated and discussed. Finally, synthesized ZnO NRs on both substrates were utilized to assess their degradation effect on methylene blue (MB). Photoluminescence spectra and X-ray photoelectron spectroscopy were employed to analyze the quantities of various defects of synthesized ZnO NRs. The effect of MB degradation after 325 nm UV irradiation for different durations can be evaluated using the Beer-Lambert law, specifically by analyzing the 665 nm peak in the transmittance spectrum of MB solutions with different concentrations. Our findings reveal that ZnO NRs synthesized on an ITO substrate exhibited a higher degradation effect on MB, with a rate of 59.5%, compared to NRs synthesized on a Si substrate, which had a rate of 73.7%. The reasons behind this outcome, elucidating the factors contributing to the enhanced degradation effect are discussed and proposed.
RESUMEN
Previously, there were almost no relevant studies on developing the optimal CaxMg2-xSi2O6:yEu2+ phosphor composition for its finest optical properties. This study employs two steps to determine the optimal composition for CaxMg2-xSi2O6:yEu2+ phosphors. First, CaMgSi2O6:yEu2+ (y = 0.015, 0.020, 0.025, 0.030, 0.035) was used as the primary composition of specimens synthesised in a reducing atmosphere of 95% N2 + 5% H2 to investigate the effect of Eu2+ ions on the photoluminescence properties of each variant. The emission intensities of the entire photoluminescence excitation (PLE) and photoluminescence (PL) emission spectra of the CaMgSi2O6:yEu2+ phosphors initially increased as the concentration of the Eu2+ ions increased, peaking at y = 0.025. The cause of the variations across the entire PLE and PL spectra of all five CaMgSi2O6:yEu2+ phosphors was investigated. Because the CaMgSi2O6:0.025Eu2+ phosphor had the highest PLE and PL emission intensities, in the next step, CaxMg2-xSi2O6:0.025Eu2+ (x = 0.5, 0.75, 1.0, 1.25) was used as the primary composition to investigate the effect on the photoluminescence properties when the CaO content varied. We also show that the Ca content has an apparent effect on the photoluminescence properties of CaxMg2-xSi2O6:0.025Eu2+ phosphors, and the optimal phosphor composition is Ca0.75Mg1.25Si2O6:0.025Eu2+ because it has the largest PLE and PL values. X-ray diffraction (XRD) analyses of CaxMg2-xSi2O6:0.025Eu2+ phosphors were performed to identify the factors responsible for this outcome.
RESUMEN
In this study, an absorber with the characteristics of high absorptivity and ultra-wideband (UWB), which was ranged from the visible light range and near-infrared band, was designed and numerically analyzed using COMSOL Multiphysics® simulation software (version 6.0). The designed absorber was constructed by using two-layer square cubes stacked on the four-layer continuous plane films. The two-layer square cubes were titanium dioxide (TiO2) and titanium (Ti) (from top to bottom) and the four-layer continuous plane films were Poly(N-isopropylacrylamide) (PNIPAAm), Ti, silica (SiO2), and Ti. The analysis results showed that the first reason to cause the high absorptivity in UWB is the anti-reflection effect of top TiO2 layer. The second reason is that the three different resonances, including localized surface plasmon resonance, the propagating surface plasmon resonance, and the Fabry-Perot (FP) cavity resonance, are coexisted in the absorption peaks of the designed absorber and at least two of them can be excited at the same time. The third reason is that two FP resonant cavities were formed in the PNIPAAm and SiO2 dielectric layers. Because of the combination of the anti-reflection effect and the three different resonances, the designed absorber presented the properties of UWB and high absorptivity.
RESUMEN
The human somatosensory system is capable of extracting features with millimeter-scale spatial resolution and submillisecond temporal precision. Current technologies that can render tactile stimuli with such high definition are neither portable nor easily accessible. Here, we present a wearable electrotactile rendering system that elicits tactile stimuli with both high spatial resolution (76 dots/cm2) and rapid refresh rates (4 kHz), because of a previously unexplored current-steering super-resolution stimulation technique. For user safety, we present a high-frequency modulation method to reduce the stimulation voltage to as low as 13 V. The utility of our high spatiotemporal tactile rendering system is highlighted in applications such as braille display, virtual reality shopping, and digital virtual experiences. Furthermore, we integrate our setup with tactile sensors to transmit fine tactile features through thick gloves used by firefighters, allowing tiny objects to be localized based on tactile sensing alone.
RESUMEN
Real-time detection and differentiation of diverse external stimuli with one tactile senor remains a huge challenge and largely restricts the development of electronic skins. Although different sensors have been described based on piezoresistivity, capacitance, and triboelectricity, and these devices are promising for tactile systems, there are few, if any, piezoelectric sensors to be able to distinguish diverse stimuli in real time. Here, a human skin-inspired piezoelectric tactile sensor array constructed with a multilayer structure and row+column electrodes is reported. Integrated with a signal processor and a logical algorithm, the tactile sensor array achieves to sense and distinguish the magnitude, positions, and modes of diverse external stimuli, including gentle slipping, touching, and bending, in real time. Besides, the unique design overcomes the crosstalk issues existing in other sensors. Pressure sensing and bending sensing tests show that the proposed tactile sensor array possesses the characteristics of high sensitivity (7.7 mV kPa-1), long-term durability (80 000 cycles), and rapid response time (10 ms) (less than human skin). The tactile sensor array also shows a superior scalability and ease of massive fabrication. Its ability of real-time detection and differentiation of diverse stimuli for health monitoring, detection of animal movements, and robots is demonstrated.
RESUMEN
Phosphors with composition Ca2 ZnMoO6 were synthesized at temperatures of 800-1200°C using the solid-state method. Analysis of X-ray diffraction patterns of the Ca2 ZnMoO6 powders did not reveal a double perovskite structure. When the synthesis temperature was equal to or higher than 800°C, the synthesized Ca2 ZnMoO6 powders revealed a tetragonal structure (CaMoO4 ) rather than an orthorhombic structure (Ca2 ZnMoO6 ) and the cubic structure (Sr2 ZnMoO6 ) of a double perovskite. The ZnO phase was still observed at a synthesis temperature of 1200°C. The compositions of synthesized Ca2 ZnMoO6 powders differed from the prepared powder, and the Ca2 ZnMoO6 phosphors exhibited some important novel features. First, synthesized Ca2 ZnMoO6 compositions could emit light as a phosphor no activators, called Ca2 ZnMoO6 phosphors. Effect of synthesis temperature on luminescence properties of these Ca2 ZnMoO6 phosphors was readily observed, and some important novel features and properties were noted. Second, the phosphors presented only one broad characteristic emission peak in the visible light region. Third, measurement of the chromaticity diagram of the Ca2 ZnMoO6 phosphors revealed a white-light source. Through analysis, we determined why the synthesized Ca2 ZnMoO6 phosphors had just one broad characteristic emission peak.
