Acidic sandy soils in tropical regions have inherently low nutrient retention due to their highly weathered nature and low organic matter content. Organic amendments, like cricket feces, offer potential for improving soil properties; however, the temporal dynamics of soil charge characteristics under different application methods and rates remain unclear, particularly in variable-charged soils. This study evaluated the effects of application methods (incorporation versus surface placement) and rates (0, 3.13, 6.25, and 12.50 Mg ha-1) of cricket feces on charge characteristics of an acidic sandy soil in Northeast Thailand. An incubation experiment monitored changes in cation exchange capacity (CEC), zero point of net charge (ZPNC), and their related properties. CEC increased with the application rates and was negatively related to ZPNC throughout the experimental period. In the early stage, during 1-5 days, the incorporation treatments produced significantly higher CEC (2.40-3.80 cmol kg-1) than the surface application treatments (2.00-3.50 cmol kg-1), associated with higher pH, organic C, dissolved organic C, and decomposition rate (k). In the later stage, by day 45, surface application treatments showed significantly higher CEC (up to 2.73 cmol kg-1) than the incorporation treatments (2.33 cmol kg-1), corresponding with greater dissolved organic C and lower k, indicating the effects of organic matter quality affected by the decomposition rate. These findings demonstrated that incorporating cricket feces led to an immediate enhancement of nutrient retention, whereas surface application brought about a more prolonged retention effect.
The increasing demand in power of modern environmental and health sensors have spurred the development of ambient energy harvesting to reduce reliance in battery. Thermoelectric generators (TEGs) are a promising technology, which convert waste or body heat into electricity. However, their power output is severely limited by the thermal impedance mismatch, particularly between the human skin and TEG interface. This work introduces a novel approach to overcome this limitation by integrating a hydrogel into the TEG system. It has been revealed that the enthalpy from the hydrogel's water evaporation effectively achieves thermal impedance matching while simultaneously maximizing the heat flux. Furthermore, by optimizing the TEG's fill-factor, we increased the power density by nearly two orders of magnitude compared to conventional TEG systems. As a proof of concept, our device combined body heat with hydrogel evaporation using an optimized fill-factor of 0.48 (using 52 % less material). This setup achieved a power density of 150 mu Wcm-2, which was sufficient to power four wireless sensors. This work demonstrates a counter-intuitive synergistic benefit, that is achieving superior thermal matching while significantly reducing thermoelectric material usage. Our findings redefine optimization approach for TEGs and offer a viable pathway toward realizing off-grid, self-powered sensors.
The synthesis of Sn-doped Sb2O3 thin films using the spin coating method aims to investigate the effect of various Sn concentrations on the optical and structural properties, which has not been previously reported. FESEM revealed some hexagonal and cubic-shaped structures on the surfaces with thicknesses ranging from 6 to 13 mu m. EDS confirmed successful Sn doping in the Sb2O3 lattice, and XRD patterns identified a cubic Sb2O3 phase for 0.1 M Sn and became to an amorphous nature for 0.2 M Sn. The structure transformed to orthorhombic from 0.3 to 0.5 M Sn. The structural properties show that the 0.3 M Sn doping exhibits minimal structural defects and disorder. In addition, the films exhibited almost 90 % transmittance in the visible region and dramatical reduction in the ultraviolet region. The 0.3 M Sn doping exhibited high absorption coefficients with the lowest Urbach energy and optimal bandgap. These findings highlight the need for high-quality optical thin films fabricated using the spin-coating method.
This article presents a tandem hydrogel‐phase change material (PCM)‐thermoelectric generator (TEG) structure for evaporation‐driven cold energy storage and electricity harvesting. The hydrogel layer facilitates water evaporation under ambient conditions, generating a cooling effect that produces “cold energy”. This energy is stored in a PCM layer as latent energy, maintaining a stable temperature gradient without volume changes or leakage. The integrated TEG converts this gradient into electricity during both charging (evaporation‐induced cooling and PCM solidification) and discharging (PCM melting and heat release) phases, enabling dual‐phase power generation. Experimental results demonstrate a maximum power output of 1.6 mW and a power density of 100 μW/cm2 at ambient condition without energy input. In addition, we demonstrate an average power output of 0.3 mW and a power density of 19 μW/cm2 for a fully charged PCM under ambient conditions, with a cooling efficiency that reduces surface temperatures of TEG by up to 5°C. This article represents the first demonstration of simultaneous storage and utilization of evaporation thermal energy for electricity generation. This innovative design combines evaporative cooling, latent energy storage, and thermoelectric conversion, advancing sustainable energy solutions for low‐grade heat environments and efficiently powering portable electronics.
Cadmium sulfide (CdS) thin films, both undoped and doped with various concentrations of potassium (K) (0.1, 0.2, 0.3, 0.4, and 0.5 M), were synthesized on borosilicate glass substrates using the sol-gel screen-printing technique. The results showed that K-doping at concentrations above 0.3 M promoted grain agglomeration, resulting in a compact morphology with no significant voids or porosity across all thin film conditions, indicating strong adherence and coverage between grains and nanoparticles (NPs). X-ray diffraction (XRD) analysis confirmed a hexagonal structure for the undoped and 0.1 M K-doped films; however, this phase disappeared at higher K concentrations. A low-intensity cubic phase was observed across all the samples. These structural observations were further validated using Raman spectroscopy. The evolution of the photoluminescence (PL) peaks with increasing K-doping concentration indicates structural distortions, suggesting that the incorporation of K+ ions may introduce new defects or degrade the crystal quality. The presence of Cd-S bonds within the films was validated by Fourier-transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS). Optical analysis showed low transmittance (0.45-1.75%) and reflectance (0.07-0.70%) values in the 550-1000 nm wavelength range, indicating distinct absorptive behavior. The energy band gap (Eg) decreased from 2.21 eV for the undoped film to 1.92 eV as the K concentration increased up to 0.4 M, then rose slightly to 2.18 eV at 0.5 M doping. Mott-Schottky analysis demonstrated a shift in the conduction band edge from-1.15 V (undoped) to between-0.68 and-0.99 V (K-doped), along with an increase in donor density from 5.329 & times; 1020 to 27.156 & times; 1020 cm-3 for the 0.2 M to 0.5 M K-doped films. According to the EIS results, the 0.4-0.5 M K-doped CdS thin films induce the generated electrons and exhibit a lower impedance with electron lifetimes due to the higher electrocatalytic activity and faster exciton recombination, causing subsequently degraded more rapidly in electrolyte region. Therefore, the optimal K-doping condition presents a highly promising active electrode material for application in electrochemical systems and other optoelectronic devices.
