Novel rare-earth (RE; e.g., europium (Eu3+), samarium (Sm3+), and praseodymium (Pr3+)) and transition metal (TM4+; e.g., manganese (Mn4+)) ion single-/co-doped double-perovskite Ca2InTaO6 (CITO) phosphors were prepared and investigated with respect to their crystal structure and photoluminescence (PL) properties. Among them, the CITO:Eu3+ phosphors were found to exhibit an ultra-high internal PL quantum yield (89.1%) and good thermal stability (78.7% at 423 K relative to the initial value at 303 K). As such, the corresponding packaged white light-emitting diode (LED) was able to display a remarkable color rendering index (CRI; = 91.51@10 mA). Besides, the potential in applications of anti-counterfeiting fields and a novel LED structure based on flexible phosphor-converted films was also studied. Moreover, due to their different thermal quenching, trivalent lanthanide (Ln3+)/Mn4+ co-doped CITO phosphors were designed for optical thermometry based on the luminescence intensity ratio (LIR) between different 4f transitions of various Ln3+ ions and 2Eg → 4A2g (Mn4+) transition. Particularly, the LIR between the 4G5/2 → 6H9/2 and 2Eg → 4A2g peaks of the CITO activated with 5 mol% Sm3+ and 0.3 mol% Mn4+ exhibited the most excellent relative sensitivity (Sr; = 3.80 %·K−1) with beneficial temperature uncertainty of 0.0648 K. Overall, these results are of significance to offer valuable databases for constructing multifunctional high-performance optical platforms using single-/co-doped double-perovskite tantalates.
- Article type
Transition metal oxide/hydroxide with multifunctional hierarchical nanostructures has attracted widespread attention in supercapacitors (SCs) because of their large accessible surface area, high electrochemical activity and superior redox chemistry. Herein, core-shell-like copper (Cu) hydroxide nanotube arrays grafted nickel aluminum layered double hydroxide nanosheets were facilely synthesized on porous Cu foam (CH NTAs@NiAl LDH NSs) for use as an efficient battery-type electrode in hybrid SCs. With the synergistic effects of NiAl LDH NSs on well-adhered CH NTAs/CF, the core-shell-like composite (prepared for 24 h) delivered a maximum areal capacity of 334.3 µAh/cm2 at a current density of 3 mA/cm2 in 2 M KOH electrolyte, which is comparatively higher than other samples synthesized at different growth times. Moreover, the core-shell-like CH NTAs@NiAl LDH NSs-24 demonstrated an outstanding cycling stability of 134.3% after 10, 000 cycles. Utilizing high capacity and stability of CH NTAs@NiAl LDH NSs-24, a pouch-type hybrid SC was further assembled with core-shell-like composite as a positive electrode and reduced graphene oxide as a negative electrode with a filter paper as a separator in aqueous alkaline electrolyte. The hybrid SC showed a high areal capacity of 250 µAh/cm2 at 2 mA/cm2 with maximum areal energy and power densities of 181.9 µWh/cm2 and 24, 991.5 µW/cm2, respectively. Successfully harvesting the solar energy via solar cell panel and subsequently delivering the stored energy to switching and proximity applications also demonstrated the real-time applicability of our hybrid SCs.
We report triboelectric nanogenerators (TENGs) composed of a flexible and cost-effective gold-coated conductive textile (CT) to convert wind energy into electricity. The Au-coated CT is employed because of its high surface roughness resulting from Au nanodots distributed on microsized fibers. Thus, the Au-coated CT with nano/microarchitecture plays an important role in enhancing the effective contact area as well as the output performance of the TENG. Moreover, the surface roughness of the Au-coated CT is controlled by adjusting the Au thermal deposition time or tailoring the diameter of the Au nanodots. At an applied wind speed of 10 m·s–1, a wind-based TENG (W-TENG) with dimensions of 75 mm × 12 mm × 25 mm produces an open-circuit voltage (VOC) of ~39 V and a short-circuit current (ISC) of ~3 μA by using the airflow-induced vibrations of an optimized Au-coated CT between two flat polydimethylsiloxane (PDMS) layers. To further specify the device performance, the electric output of the W-TENG is analyzed by varying several parameters such as the distance between the PDMS layer and Au-coated CT, applied wind speed, external load resistance, and surface roughness of the PDMS layers. Introducing an inverse micropyramid architecture on the PDMS layers further improves the output performance of the W-TENG, which exhibits the highest VOC (~49 V) and ISC (~5 μA) values at an applied wind speed of 6.8 m·s-1. Additionally, the reliability of the W-TENG is also tested by measuring its output current during long-term cyclic operation. Furthermore, the rectified output signals observed by the W-TENG device are used as a direct power source to light 45 green commercial light-emitting diodes connected in series and also to charge capacitors (100 and 4.7 μF). Finally, the output performance of the W-TENG device in an actual windy situation is also investigated.
Hierarchical core–shell-like MnO2 nanostructures (NSs) were used to anchor MnO2 hexagonal nanoplate arrays (HNPAs) on carbon cloth (CC) fibers. The NSs were prepared by a novel one-step electrochemical deposition method. Under an external cathodic voltage of -2.0 V for 30 min, hierarchical core–shell-like MnO2-NS-decorated MnO2 HNPAs (MnO2 NSs@MnO2 HNPAs) were uniformly grown on CC with reliable adhesion. The phase purity and morphological properties of the samples were characterized by various physicochemical techniques. At a constant external cathodic voltage, growth of MnO2 NSs@MnO2 HNPAs on CC was carried for different time periods. When utilized as a flexible, robust, and binder-free electrode for pseudocapacitors, the hierarchical core–shell-like MnO2 NSs@MnO2 HNPAs on CC showed clearly enhanced electrochemical properties in 1 M Na2SO4 electrolyte solution. The results indicate that the MnO2 NSs@MnO2 HNPAs on CC have a maximum specific capacitance of 244.54 F/g at a current density of 0.5 A/g with excellent cycling stability compared to that of bare MnO2 HNPAs on CC (112.1 F/g at 0.5 A/g current density). We believe that the superior charge storage performance of the pseudocapacitive electrode can be mainly attributed to the hierarchical MnO2 NSs@MnO2 HNPAs building blocks that have a large specific surface area, offering additional electroactive sites for efficient electrochemical reactions. The facile and single-step approach to growth of hierarchical pseudocapacitive materials on textile based electrodes opens up the possibility for the fabrication of high-performance flexible energy storage devices.
Amorphous nickel tungsten tetraoxide (NiWO4) nanostructures (NSs) were successfully synthesized on a flexible conductive fabric (CF) using a facile onestep electrochemical deposition (ED) method. With an applied external cathodic voltage (–1.8 V for 15 min), the amorphous NiWO4 NSs with burl-like morphologies adhered well on the seed-coated CF substrate. The burl-like amorphous NiWO4 NSs on CF (NiWO4 NSs/CF) are employed as a flexible and binder-free electrode for pseudocapacitors, which exhibit remarkable electrochemical properties with high specific capacitance (1, 190.2 F/g at 2 A/g), excellent cyclic stability (92% at 10 A/g), and good rate capability (765.7 F/g at 20 A/g) in 1 M KOH electrolyte solution. The superior electrochemical properties can be ascribed to the hierarchical structure and large specific surface area of the burl-like amorphous NiWO4 NSs/CF. This cost-effective facile method for the synthesis of metal tungsten tetraoxide nanomaterials on a flexible CF could be promising for advanced electronic and energy storage device applications.