Sequential Dual Coating with Thermosensitive Polymers for Advanced Fiber Optic Temperature Sensors.

We systematically designed dual polymer Fabry-Perrot interferometer (DPFPI) sensors, which were used to achieve highly sensitive temperature sensors. The designed and fabricated DPFPI has a dual polymer coating layer consisting of thermosensitive poly (methyl methacrylate) (PMMA) and polycarbonate (PC) polymers. Four different DPFPI sensors were developed, in which different coating optical path lengths and the resultant optical properties were generated by the Vernier effect, changing the sequence of the applied polymers and varying the concentration of the coating solutions. The experimental results confirmed that the PC_PMMA_S1 DPFPI sensor delivered a temperature sensitivity of 1238.7 pm °C-1, which was approximately 4.4- and 1.4-fold higher than that of the PMMA and PMMA_PC_S1-coated sensor, respectively. Thus, the results reveal that the coating sequence, the compact thickness of the dual polymer layers, and the resultant optical parameters are accountable for achieving sensors with high sensitivity. In the PC_ PMMA-coated sensor, the PMMA outer layer has comparatively better optical properties than the PC, which might produce synergistic effects that create a large wavelength shift with small temperature deviations. Therefore, it is considered that the extensive results with the PC_PMMA_S1 DPFPI sensor validate the efficacy, repeatability, reliability, quick reaction, feasibility, and precision of the temperature readings.

Simply Fabricated Inexpensive Dual-Polymer-Coated Fabry-Perot Interferometer-Based Temperature Sensors with High Sensitivity.

We designed simply fabricated, highly sensitive, and cost-effective dual-polymer-coated Fabry-Perot interferometer (DFPI)-based temperature sensors by employing thermosensitive polymers and non-thermosensitive polymers, as well as different two successive dip-coating techniques (stepwise dip coating and polymer mixture coating). Seven sensors were fabricated using different polymer combinations for performance optimization. The experiments demonstrated that the stepwise dip-coated dual thermosensitive polymer sensors exhibited the highest sensitivity (2142.5 pm °C-1 for poly(methyl methacrylate)-polycarbonate (PMMA_PC) and 785.5 pm °C-1 for poly(methyl methacrylate)- polystyrene (PMMA_PS)). Conversely, the polymer-mixture-coated sensors yielded low sensitivities (339.5 pm °C-1 for the poly(methyl methacrylate)-polycarbonate mixture (PMMA_PC mixture) and 233.5 pm °C-1 for the poly(methyl methacrylate)-polystyrene mixture (PMMA_PS mixture). Thus, the coating method, polymer selection, and thin air-bubble-free coating are crucial for high-sensitivity DFPI-based sensors. Furthermore, the DFPI-based sensors yielded stable readouts, based on three measurements. Our comprehensive results confirm the effectiveness, reproducibility, stability, fast response, feasibility, and accuracy of temperature measurements using the proposed sensors. The excellent performance and simplicity of our proposed sensors are promising for biomedical, biochemical, and physical applications.

Microwave-Assisted Expanded Graphite as a Long Cyclic Cathode for the Lithium Dual-Ion Battery.

Lithium metal (Li) has been recognized as a promising anode for most energy storage devices, owing to its high theoretical capacity. Nevertheless, Li anode present serious safety hazards and have a rapidly fading capacity, which limits its practical applications. Herein, a lithium-expanded graphite dual-ion battery (Li-EG DIB) was developed by combining a Li metal sheet as an anode with expanded graphite (EG) as a cathode. EG was produced by microwave (MW) photons energy (~1 × 10-5 eV) at different time durations (15, 30, 45, and 60 s) to allow moderate expansion between the graphite sheets and the removal of the surface functional groups that encourage the intercalation and de-intercalation of the ions; consequently, the capacity was improved. The MW-EG samples were characterized by X-ray powder diffraction (XRD), Raman spectroscopy, and Fourier transform infrared spectrophotometry (FT-IR). The EG synthesized at 45 s in MW exhibited a high capacity and a stable and long cycling life. The charge capacity of the Li-EG-45 DIB after 500 cycles at 0.05 Ag-1 was 20.3 mAh g-1 in the voltage window of 2-5 V. It is worth noting that the EG-45 electrode showed ~100% capacity retention, even after the rate test.

Scraps to superior anodes for Li-ion batteries: Sustainable and scalable upgrading of waste rust.

The abundant iron rust of no value generated from industrial scraps presents environmental problem and burden. Chemical etching and related methods deployed to convert rust into α-Fe2O3 nanoparticles, however, have serious shortcomings namely higher chemical consumption and generation of secondary pollution. In an unprecedented illustration, herein the intercalation of ammonium bicarbonate (ABC) as a gaseous bubble template into bulky iron rust is described; formation of ammonium iron carbonate hydroxide hydrate and the reduction of particle size using a simple ball milling method followed by calcination is accomplished. The salient features of ABC, optimization of ratios (rust: ABC), and the ideal calcination temperature were optimized for attaining desirable properties of meso-α-Fe2O3 NPs. The electrode obtained at 500 °C delivered a superior reversible capacity of 1,055 mAh g-1 at 1 A g-1 over 100 cycles, which is comparable to the best performance reported for meso-α-Fe2O3 NPs. The superior electrochemical performance is ascribed to the porous nature of meso-α-Fe2O3 NPs maximizing the surface area, ensuring good charge transfer kinetics and enhanced pseudocapacitive contribution. Thus, we believe that the high-energy ball milling (HEBM) process represents a novel route for the scalable recycling of iron rust scraps for promoting the sustainable production of lithium-ion batteries.

Enhancing Temperature Sensitivity of the Fabry-Perot Interferometer Sensor with Optimization of the Coating Thickness of Polystyrene.

The exploration of novel polymers for temperature sensing with high sensitivity has attracted tremendous research interest. Hence, we report a polystyrene-coated optical fiber temperature sensor with high sensitivity. To enhance the temperature sensitivity, flat, thin, smooth, and air bubble-free polystyrene was coated on the edge surface of a single-mode optical fiber, where the coating thickness was varied based on the solution concentration. Three thicknesses of the polystyrene layer were obtained as 2.0, 4.1, and 8.0 µm. The temperature sensor with 2.0 µm thick polystyrene exhibited the highest temperature sensitivity of 439.89 pm °C-1 in the temperature range of 25-100 °C. This could be attributed to the very uniform and thin coating of polystyrene, along with the reasonable coefficient of thermal expansion and thermo-optic coefficient of polystyrene. Overall, the experimental results proved the effectiveness of the proposed polystyrene-coated temperature sensor for accurate temperature measurement.