Meng-Lin Tsai

Fabricating high-performance 2D nanosheet-based semiconductor devices faces challenges due to the structural damage caused by traditional metal electrode deposition processes. This study introduces a novel polycarbonate (PC) assisted metal electrode transfer technique that effectively preserves the structural and electronic properties of MoS ₂ nanosheets. Using the proposed method, metal electrodes are successfully transferred onto MoS ₂ nanosheets via the shadow mask process (20 μm channel) and photolithography (8 μm and 3 μm channels) for photodetector and field-effect transistor (FET) fabrication, respectively. Photodetectors fabricated with transferred electrodes exhibit stable current-voltage characteristics, with the shadow mask-based photodetector achieving a maximum photoresponsivity of 0.73 µA/W under a 450 nm laser at 10 V bias. The photolithography-based photodetector demonstrates higher photoresponsivity of 3.62 mA/W due to enhanced light absorption. Additionally, the FETs fabricated using the PC transfer process show NMOS behavior with electron mobility values of up to 0.17 cm ² /V s during reverse sweeps. PC covered FETs further improve performance under ambient conditions, achieving electron mobility up to 0.517 cm ² /V s and stable switching current ratios. These findings underscore the PC assisted electrode transfer method’s advantages in maintaining material integrity, achieving stable device performance, and offering scalability for large-scale applications.

Metal-organic frameworks (MOFs) have emerged as promising candidates for supercapacitor electrode materials due to their tunable structural properties and high surface area. However, their application is often limited by inherently low electrical conductivities. To tackle this challenge, Iron (Fe) was integrated into Lanthanum benzentricarboxylate MOF (La-BTC), which was mainly synthesized through a hydrothermal method to improve the electrochemical performance of the MOFs. Using methods like X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, and field emission scanning electron microscopy (FESEM), the structural and morphological characteristics of the synthesized Fe-La-BTC were thoroughly investigated. When compared to bare La-BTC, the electrochemical performance of Fe-La-BTC in a 4 M KOH electrolyte shown a notable improvement in supercapacitor performance. More specifically, it was discovered that the capacitance of Fe-La-BTC was 158.98 F g ⁻¹ at 10 mV s ⁻¹ and 280.65 F g ⁻¹ with a current density of 2 A g ⁻¹ . These values are noticeably higher than the 180.42 F g ⁻¹ discovered for La-BTC. Additionally, Fe-La-BTC demonstrated a remarkable 78% capacitance retention across several cycles of charge and discharge. The mechanisms behind the capacitance augmentation and electron transfer of Fe-La-BTC are clarified by electrochemical tests including cyclic voltammetry (CV) and electrochemical impedance (EIS).

In this study, a one-pot hydrothermal synthesis method was used to synthesize a novel gold-yttrium trimesic acid metal-organic framework (Au-Y-TMA MOF), demonstrating significant improvements over conventional single-metal MOFs, that is, yttrium trimesic acid (Y-TMA), in both supercapacitor applications and electrochemical antibiotic detection. The X-ray diffraction patterns of Au-Y-TMA confirmed the presence and impact of Au in the Y-TMA matrix, while field emission scanning electron microscopy (FE-SEM) images revealed a heterogeneous combination of gold nanoparticles (AuNPs) and Y-TMA, suggesting a nonuniform distribution and possible interaction. The developed half-cell supercapacitor exhibited a remarkable capacitance value of 1836 F/g at a current density of 5 A/g by galvanostatic charging-discharging (GCD) measurement. The symmetric full-cell device achieved a capacitance value of 99.85 F/g at a current density of 1 A/g, with an 82% retention value for 10000 GCD curve cycles. The device also demonstrated an energy density of 8.85 Wh/kg, power density of 3.6 kW/kg, and 97% Coulombic efficiency, highlighting the superior performance of Au-Y-TMA in supercapacitor applications. Moreover, a thiolate aptamer (aptSH) was immobilized on the surface of the Au-Y-TMA electrode. Results showcased selective, sensitive (5.82%/nM), and reproducible determination of kanamycin with a detection limit of 1.14 nM. Moreover, the recovery rates of milk samples treated with kanamycin, which varied from 87% to 91%, demonstrated their practical viability. Raman-active spectroscopic analysis was performed to inculcate the kanamycin detection mechanism of the electrode. This study advances scientific understanding and underscores the potential for significant societal impact by improving energy storage technologies and ensuring food safety through sensitive antibiotic detection.

Rhenium disulfide (ReS₂) is a 2-dimensional transitional metal dichalcogenides that exhibits unique properties such as a direct band gap irrespective of thickness, weak interlayer coupling, and exceptional anisotropic properties, making it a promising material for optoelectronics applications. In this work, we synthesized ReS₂ nanoflakes on SiO₂/Si substrates using chemical vapor deposition (CVD). The effects of Re precursor-substrate distance (d) and growth temperature on flakes morphology were systematically investigated. Field-effect scanning electron microscopy images revealed that shorter Re precursor-substrate distance (d= 8 cm) favored the formation of high density and vertical flakes due to the high concentration of Re vapor. However, samples grown with the largest separation distance (d = 11 cm) and higher substrate temperature (850 °C) demonstrated a low density of planar flakes. Raman spectroscopy measurements showed the E _g, A _g, and C _p vibrational modes which belong to ReS₂. The full-width-at-half-maximum of the E _g mode at 212 cm⁻¹ is 6.7 cm⁻¹, comparable to the mechanically exfoliated ReS₂ reference. The thicknesses of the flakes range from bilayer to multilayer and the measured band gap energy is ∼1.57 eV. The XPS data verified that the atomic ratio between Re and S is 1.9, which confirms the stoichiometry of the ReS₂ flakes. Finally, the TEM images and diffraction pattern confirmed that the ReS₂ flake is a single-crystal with distorted 1 T-phase. This work emphasizes the influence of CVD parameters on the morphology of ReS₂ flakes, which is vital for developing high performance ReS₂ based optoelectronics devices.

For the first time, we report a trifluoromethyl group-incorporated aliphatic linearly-chained 2D (3F-PAH)₂PbI₄ halide perovskite (HP) with a low bandgap of 2.28 eV, minimal Pb–I–Pb bond angle distortion (∼153.5°) and a unique fluorous phase.

Ruddlesden-Popper (RP) two-dimensional (2D) halide perovskite (HP), with attractive structural and optoelectronic properties, has shown great potential in optoelectrical devices. However, the relatively wide bandgap (E_g) and stability, which cause inferior efficiency, prevent its feasibility from further applications. To tackle these issues, for the first time, a novel fluorine-containing piperidinium spacer, (3-HCF₂CF₂CH₂OCH₂-PPH⁺), abbreviated as (4FH-PPH⁺), has been designed for the stable and efficient n = 1 2D HPs. Its fluorophobicity can significantly enhance the noncovalent interactions between cations and [PbI₆]^4- octahedra. The observed E_g of the fluorinated (4FH-PPH)₂PbI₄ perovskite is found to be 2.22 eV, which is the lowest value among all fluorinated perovskites reported so far. Interestingly, this fluorinated film-based 2D perovskite photodetector (PD) exhibits the outstanding responsivity of 502 mA W^-1, photodetectivity of 5.73 × 10¹⁰ cm Hz^1/2 W^-1, and impressive response/recovery time of 42/46 ms under 450 nm at 20 V. To the best of our knowledge, it is found for the first time that the 2D HP, with the fluorinated short-chained segment included into the organic spacer, shows remarkable stability for up to 49 days. These results strongly demonstrate the potential of the 2D fluorinated short-chained (4FH-PPH)₂PbI₄ HP with a low E_g as a promising candidate for next-generation optoelectronic devices.