Synthetic Metals最新文献

In this study, we prepared an electrode material from biowaste residue for hybrid supercapacitor application. Bagasse from brewery residue was treated by oxidative calcination at 300 °C. The carbonized material was impregnated using different concentrations of potassium hydroxide (KOH), followed by thermal annealing at 850 °C to obtain activated carbon (AC). The AC obtained was used to prepare a composite with poly(3,4-ethylenedioxythiophene) (PEDOT) via in-situ polymerization process using iron (III) tosylate as oxidizing agent. Pure activated carbon attained a specific surface area (SSA) of 625 m² g⁻¹, and specific capacitance of 80.38 F g⁻¹ at 5 mV s⁻¹ while the AC-PEDOT composite presents 201 F g⁻¹ at the same scan rate, given about 250 % improvement to the specific capacitance. Likewise, the AC presented an energy density of 10.88 Wh Kg⁻¹ and a power density of 9411.59 W Kg⁻¹ at 0.5 A g⁻¹ while the AC-PEDOT composite showed energy density of 25.92 Wh Kg⁻¹ and power density of 4836.44 W Kg⁻¹ at 0.5 A g⁻¹. The results confirm the properties of AC as a supercapacitive material and a battery-like behavior for the AC-PEDOT composite, demonstrating potential for hybrid supercapacitors application.

In this work, composites of Co-Pt nanoparticles/carbon nanotubes (Co-Pt NPs/CNTs) were prepared by loading binary nanoparticles Co-Pt nanoparticles onto carbon nanotubes. These composites were utilized as highly efficient catalysts for the methanol electrocatalytic oxidation reaction (MOR). The morphology of the materials was analyzed using transmission electron microscopy (TEM), Spherical Aberration Corrected Scanning (AC-STEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The results revealed that the 5.54 nm diameter Co-Pt nanoparticles were evenly distributed on the surface of carbon nanotubes. Chronoamperometry (CA), linear scanning voltammetry (LSV), and cyclic voltammetry (CV) techniques were employed to assess the activity and stability of Co-Pt NPs/CNTs composites. Various Co-Pt NPs/CNTs composites were prepared by adjusting the ratio of Co-Pt. Through analysis of MOR performance, it was found that the Co₃Pt₁ NPs/CNTs composites exhibited superior catalytic activity with a mass activity of 4411 mA·mg⁻¹_Pt, which was 2.45 times higher than that of commercial Pt/C catalysts. This study introduced a novel approach for the preparation of high-performance Co-Pt bimetallic nanoparticles catalysts.

In this work, the role of a high boiling point green solvent additive Diphenyl ether (DPE) in device recombination processes in organic solar cell, fabricated using ultrasonic spray coating method is investigated. Without DPE and with 2.4 % DPE, the device series resistance was high of the order of 10⁴ Ω. With 0.3 %, 0.6 %, 1.2 % DPE, series resistance was less. Transient studies show that, for these contents, the rise and decay times of photocurrent was less than 5 µs. For 0.3 % DPE, nearly 3/4th photovoltage decayed with 51.4 µs lifetime and the remaining decays with 4.6 µs lifetime. With higher DPE content (1.2 %), 97 % photovoltage decay was with a longer lifetime 46.1 µs, and remaining with 1.6 µs. With further more DPE content (2.4 %), only 1 % TPV decays with shorter lifetime of 11.6 µs and 99 % decay is in longer time scale of 672 µs. In addition, a longer lifetime of over 1000 µs was also observed for this case, indicating the presence of deep traps, in addition to the shallow traps and bimolecular recombination. Morphology studies show that for 0 % and 0.3 % DPE content, stacked structure of droplets was formed in the film, but with 0.6 % and higher content, the progressively impinging droplets intermix with each other, providing more time for the film to dry. It was shown that the contribution of trap assisted recombination for varying DPE content was due to disordered PTB7 or PC₇₁BM phases, indicating a competition between PTB7 aggregation and PC₇₁BM dispersion in the coated film.

Hyperphosphorescent organic light-emitting diodes (HPOLEDs) are drawing increased attention, as the efficient Förster resonance energy transfer (FRET) from phosphorescent sensitizer to the narrowband fluorescent terminal emitter may give improved performances. In this work, we reported a class of Ir(III) phosphors based on the di-trifluoromethyl (CF₃) substituted imidazo[4,5-c]pyridin-2-ylidene chelates; i.e., (L_6F) and (L_6FB). The f-isomers exhibited efficient blue emission with peak max. 443 − 462 nm, while m-counterparts exhibited green emission between 501 – 512 nm in degassed toluene solution. The theoretical calculation indicates divergent MLCT, LLCT and ILCT contributions for distinctive isomers. OLEDs based on dopant m-Ir(L_6FB)₃ exhibited green luminescence at 505 nm, EQE_max of 20.3 % and CIE_x,y of (0.277, 0.462), while respective HPOLEDs with terminal emitter ν-DABNA showed blue hyperphosphorescence peaking at 468 nm, EQE_max of 25.2 %, CIE_x,y of (0.174, 0.204) and EQE of 22.7 % at 1000 cd·m^-2. Therefore, our finding demonstrates the effective conversion of the green electrophosphorescence to blue hyperphosphorescence via the rapid FRET process.

This study focuses on the rheological and tribological effects of the addition of graphene (GR) and functionalised multi-wall carbon nanotubes (FMWCNTs) as mono and hybrid nanoparticles in a polyester lubricant. We conduct a rheological study of viscosity in the range 30–100°C, following the ASTM D2270 standard. We also carry out a tribological study based on a four-ball test following the ASTM D4172 and ASTM D2783 standards for both wear and extreme pressure sample analysis. These studies reveal that FMWCNT has a higher degree of shear-thinning flow behaviour compared to GR nanolubricant samples. Samples with a higher GR ratio with added CTAB surfactant gave higher compared to samples with a lower GR ratio. The CTAB surfactant is found to enhance the dispersion and stability of the hybrid nanolubricant, and the hybrid nanoparticle system helps in preserving the complexity of the system, even at higher temperatures. The tribological findings show that the samples with GR tend to have a reduced coefficient of friction (COF) and increased wear scar diameter (WSD), while the samples with FMWCNTs tend to have increased COF and reduced WSD. This is due to the presence of the GR ball, which consists of nanoplatelets that have a spherical form and function as a nano ball bearing. This study explores the properties of a unique hybrid material that has promise as a lubricant additive to reduce friction and wear.

The Ni-Co nanoparticles with various Ni/Co ratios are immobilized on a Ni foam (NF) template, coated with reduced graphene oxides (rGO), and used as a novel noble-metal-free anode electrocatalyst for enhanced performance direct borohydride fuel cells. The electrochemical active surface area (EASA) of Ni₅₀Co₅₀ /rGO/NF (1515 cm²) catalyst is 45.5 times larger than NF (33.3 cm²). A comprehensive study of direct borohydride-hydrogen peroxide fuel cell (DBHPFC) by Pt/C (0.5 mg cm⁻²) as a cathode and Ni₅₀-Co₅₀/rGO/NF as an anode is accomplished, so an open-circuit potential (OCP) of 1.90 V and the maximum power density of 309 mW cm⁻² is obtained at 60 ^◦C. These results show that electrocatalyst Ni₅₀Co₅₀/rGO/NF is a suitable candidate for use as an electrocatalyst in DBHPFC due to its low cost, ease of synthesis, excellent structural stability, and high catalytic performance.

The effect of graphite nanoflakes (GNFs)/modified barium titanate (MBT) hybrid fillers on the mechanical, electrical, and thermal properties of ethylene-propylene-diene monomer (EPDM) was extensively investigated in the current study. Moreover, the effect of gamma irradiation on the different properties of the prepared nanocomposites was investigated. To accomplish this goal, EPDM/MBT composites with various GNFs contents (0, 2, 4, 6, and 8 phr) were fabricated using a conventional roll mill. Graphite was expanded by heating and subsequently modified using tween 80 surfactant, resulting in the formation of GNFs. The presence of various functional groups on the surface of the modified BaTiO₃ particles was verified by Fourier transform infrared spectroscopy (FTIR). The scanning electron microscopy (SEM) analysis revealed a uniform dispersion of GNFs in EPDM/MBT composites, with a concentration up to 6 phr. The study revealed that the mechanical properties of the nanocomposites were reinforced by the inclusion of GNFs up to 6 phr. The irradiated EPDM/MBT/6 phr GNFs nanocomposite exhibited the maximum elastic modulus value of 4.8 MPa, which was approximately 32 % higher than that of the corresponding unirradiated nanocomposite. The thermal conductivity of the irradiated EPDM/MBT/8 phr GNFs nanocomposite increased from 0.213 W/m.K to 0.260 W/m.K (22 %), while the dielectric constant increased from 4.475 to 5.551 (24 % increase) at 10³ Hz as compared to the pure EPDM/MBT composite. The enhanced electric and thermal performance of GNFs can be attributed to the mobility of their π-electrons.

Doping of 2,2′,7,7′-tetrakis(N,N-di-4-methoxyphenylamino)-9,9′-spirobifluorene(Spiro-OMeTAD), which is the most common used hole transport material in perovskite solar cells, is widely studied. Especially, bis(trifluoromethane)sulfonamide (Li-TFSI) combined with 4-tert-butylpyridine (TBP) is the most studied dopant to improve the conductivity of Spiro-OMeTAD, with conductivity around 6×10⁻⁸ S/cm. In this study, we employed a new oxidizing agent NO₂ to dop the Spiro-OMeTAD simply by vapor exposure, showing efficient doping with conductivity up to 2.53×10⁻³ S/cm and excellent film quality. The doping mechanism was further analyzed by ultraviolet-visible-near infrared spectroscopy (UV-Vis-NIR), electron paramagnetic resonance spectroscopy (EPR), Fourier infrared absorption spectroscopy (TFIR), and X-ray photoelectron spectroscopy. Our findings highlight the potential of molecular doping with NO₂ to significantly improve the conductivity of Spiro-OMeTAD, providing a deep understanding of the doping effects on Spiro-OMeTAD.

The continuous search for novel materials to meet the requirements of modern technological applications has led to the widespread use of polyaniline (PANI) composites for sensing purposes. Although research has been carried out on both chemical sensors using PANI/polymer composites and chemical sensors with impedimetric/capacitive transduction using PANI composites, there is still a gap in the use of PANI/polymer composites in impedimetric and capacitive transduction platforms for pH sensing. In this study, the influence of composite thin films consisting of PANI and poly(methyl methacrylate) (PMMA) on the sensitivity and linearity of pH sensors based on electrochemical impedance and capacitance spectroscopy (EIS/ECS) was evaluated. The sensitivity and linearity of the devices showed a dependence on the polymer content. For PANI:PMMA equal to 30:70, the EIS and ECS sensitivity reached 12.6 ± 2.7 and 18.7 ± 4.9 %/pH, respectively, after reaching its minimum value for the 50:50 sample. Similarly, the linearity values for the 30:70 sample were 92.7 % and 99.8 % for EIS and ECS, respectively. We were able to encapsulate the PANI in the PMMA matrix, which improved the control of ion diffusion and analyte access to the active redox quinoid rings on the PANI. As a result, the saturation effect of the polymer was reduced. By adjusting the relative content of PANI and PMMA, the structure and properties of the composite can be controlled, directly affecting the sensor parameters. These materials have potential applications in sensors for various fields such as food, biomedical and environmental monitoring, with the ability to tailor their properties for optimal response.

PEDOT:PSS flexible thermoelectric materials are promising for future wearable continuous power support, but it remains challenging due to low power factor. Herein, we propose a “one-stone-two-birds” strategy using L-ascorbic acid as the reductant in synthesis of tellurium nanorods and separating agent in in-situ removing PSS chains. L-ascorbic acid reduces Te⁴⁺ to Te, supplying inorganic thermoelectric materials with high Seebeck coefficient as fillers to significantly increase the Seebeck coefficient value of PEDOT:PSS. Meanwhile, L-ascorbic acid separates PSS chains from PEDOT chains, resulting in the increase of electrical conductivity at room temperature by ∼360 % due to structure transformation from benzoid structure to the quinoid structure in PEDOT. As a result, the power factor of optimal PEDOT:PSS with Te fillers and L-ascorbic acid treatment is improved significantly by ∼100 times as compared to that of pristine PEDOT:PSS. Finally, a prototype wearable thermoelectric generator was assembled by 18 legs of Te/PEDOT:PSS composites, which demonstrates a high power density of 2.3 μW·cm⁻² with good mechanical stability, flexibility and durability. The present study offers a new strategy for rational design of high-performance flexible thermoelectric materials from PEDOT:PSS.