Nanofibers of Polyaniline and Cu(II)-l-Aspartic Acid for a Room-Temperature Carbon Monoxide Gas Sensor

Mesoporous Boron Subphosphide: Intrinsic Electron Deficiency Enabling Selective Low-ppm of Chemiresistive CO Detection in Harsh Environments

Carbon monoxide (CO) is infamous for its hazardous effects, mainly because it displaces oxygen in the bloodstream. Its danger is amplified by its odorless and colorless nature, making it difficult to detect. Exposure to even low concentrations of CO (≤50 ppm) is considered harmful to human health. Common sources of CO, such as fossil fuel-powered vehicles and machinery, primarily operate under harsh high-temperature conditions. Currently, available low-ppm of CO sensors struggle in these environments typical of CO emitters, highlighting the urgent need for advanced sensors capable of reliable operation in such conditions. In this study, nanocrystalline mesoporous icosahedral boron subphosphide is synthesized via a solid-state technique and evaluated for its CO sensing capabilities. The material exhibits selective detection of low ppm of CO at temperatures exceeding 500 °C, demonstrating a significant sensing response of ∼4 toward 50 ppm of CO at 600 °C. Electronic and structural analyses attribute boron subphosphide's chemiresistive behavior to its electron-deficient nature, which is crucial for effective CO interaction. Additionally, the sensitivity of boron subphosphide to CO can be modulated under external magnetic fields, underscoring its potential for adaptable sensing applications. This work introduces boron subphosphide as a promising candidate for CO sensing in harsh conditions and provides fundamental insights into its sensing mechanism driven by intrinsic electron deficiency. The findings offer a pathway for the development of advanced sensors capable of reliably detecting low concentrations of CO in harsh environments where precise monitoring is critical to public health and safety.

Unveiling the scope and perspectives of MOF-derived materials for cutting-edge applications

Although synthesis and design of MOFs are crucial factors to the successful implementation of targeted applications, there is still lack of knowledge among researchers about the synthesis of MOFs and their derived composites for practical applications. For example, many researchers manipulate study results, and it has become quite difficult to quit this habit specifically among the young researchers Undoubtedly, MOFs have become an excellent class of compounds but there are many challenges associated with their improvement to attain diverse applications. It has been noted that MOF-derived materials have gained considerable interest owing to their unique chemical properties. These compounds have exhibited excellent potential in various sectors such as energy, catalysis, sensing and environmental applications. It is worth mentioning that most of the researchers rely on commercially available MOFs for use as precursor supports, but it is an unethical and wrong practice because it prevents the exploration of the hidden diversity of similar materials. The reported studies have significant gaps and flaws, they do not have enough details about the exact parameters used for the synthesis of MOFs and their derived materials. For example, many young researchers claim that MOF-based materials cannot be synthesized as per the reported instructions for large-scale implementation. In this regard, current article provides a comprehensive review of the most recent advancements in the design of MOF-derived materials. The methodologies and applications have been evaluated together with their advantages and drawbacks. Additionally, this review suggests important precautions and solutions to overcome the drawbacks associated with their preparation. Applications of MOF-derived materials in the fields of energy, catalysis, sensing and environment have been discussed. No doubt, these materials have become excellent class but there are still many challenges ahead to specify it for the targeted applications.

Current Advances of CO Sensing Based on Low Dimensional Materials

Carbon monoxide (CO) is a harmful gas with significant impacts on human health and the environment. Its timely detection, especially in the event of thermal runaway in automotive lithium batteries, is crucial to prevent casualties. This paper reviews the progress in the development of efficient, sensitive, and reliable CO sensors, focusing on electrochemical, optical, and resistive sensing materials. Low-dimensional materials have a large specific surface area, providing an abundant number of active sites, which has drawn extensive attention from researchers. According to the different sensor signals, we categorized these sensors into electrical and optical signal sensors. We hope that by systematically introducing the sensing mechanism and sensing performance of these two kinds of sensors, appropriate CO sensors can be developed in different application scenarios so as to realize early warning and monitoring to the maximum extent, reduce industrial losses, and ensure the life and health of personnel.

Surface modification of Co3O4 nanosheets through Cd-doping for enhanced CO sensing performance

The detection of hazardous CO gas is an important research content in the domain of the Internet of Things (IoT). Herein, we introduced a facile metal-organic frameworks (MOFs)-templated strategy to synthesize Cd-doped Co3O4 nanosheets (Cd-Co3O4 NSs) aimed at boosting the CO-sensing performance. The synthesized Cd-Co3O4 NSs feature a multihole nanomeshes structure and a large specific surface area (106.579 m2·g-1), which endows the sensing materials with favorable gas diffusion and interaction ability. Furthermore, compared with unadulterated Co3O4, the 2 mol % Cd-doped Co3O4 (2% Cd-Co3O4) sensor exhibits enhanced sensitivity (244%) to 100 ppm CO at 200 °C and a comparatively low experimental limit of detection (0.5 ppm/experimental value). The 2% Cd-Co3O4 NSs show good selectivity, reproducibility, and long-term stability. The improved CO sensitivity signal is probably owing to the stable nanomeshes construction, high surface area, and rich oxygen vacancies caused by cadmium doping. This study presents a facile avenue to promote the sensing performance of p-type metal oxide semiconductors by enhancing the surface activity of Co3O4 combined with morphology control and component regulation.

Ultrasensitive Carbon Monoxide Gas Sensor at Room Temperature Using Fluorine-Graphdiyne

Currently, most carbon monoxide (CO) gas sensors work at high temperatures of over 150 °C. Developing CO gas sensors that operate at room temperature is challenging because of the sensitivity trade-offs. Here, we report an ultrasensitive CO gas sensor at room temperature using fluorine-graphdiyne (F-GDY) in which electrons are increased by light. The GDY films used as channels of field-effect transistors were prepared by using chemical vapor deposition and were characterized by using various spectroscopic techniques. With exposure to UV light, F-GDY showed a more efficient photodoping effect than hydrogen-graphdiyne (H-GDY), resulting in a larger negative shift in the charge neutral point (CNP) to form an n-type semiconductor and an increase in the Fermi level from -5.27 to -5.01 eV. Upon CO exposure, the negatively shifted CNP moved toward a positive shift, and the electrical current decreased, indicating electron transfer from photodoped GDYs to CO. Dynamic sensing experiments demonstrated that negatively charged F-GDY is remarkably sensitive to an electron-deficient CO gas, even with a low concentration of 200 parts per billion. This work provides a promising solution for enhancing the CO sensitivity at room temperature and expanding the application of GDYs in electronic devices.

Preparation of site-specific Z-scheme g-C3N4/PAN/PANI@LaFeO3 cable nanofiber membranes by coaxial electrospinning: Enhancing filtration and photocatalysis performance

The coaxial electrospinning method for preparation of g-C₃N₄/polyacrylonitrile (PAN)/polyaniline (PANI)@LaFeO₃ cable fiber membrane (PC@PL) was designed for adsorption-filtration-photodegradation of pollutants. A series of characterization results show that LaFeO₃ and g-C₃N₄ nanoparticles (NPs) are respectively loaded in the inner and outer layers of PAN/PANI composite fibers to construct the site-specific Z-type heterojunction system with spatially separated morphologies. The PANI in cable not only possesses abundant exposed amino/imino functional groups for adsorption of contaminant molecules but also due to the excellent electrical conductivity works as a redox medium for collecting and consuming the electrons and holes from LaFeO₃ and g-C₃N₄, which can efficiently promote photo-generated charge carriers separation and improve the catalytic performance. Further investigations demonstrate that as a photo-Fenton catalyst LaFeO₃ in PC@PL catalyzes/activates the H₂O₂ generated in situ by LaFeO₃/g-C₃N₄, further enhancing the decontamination efficiency of the PC@PL. The porous, hydrophilic, antifouling, flexible and reusable properties of the PC@PL membrane significantly enhance the mass transfer efficiency of reactants by filtration effect and increase the amount of dissolved oxygen, thus producing massive •OH for degradation of pollutants, which maintains the water flux (1184 L m^-2. h^-1 (LMH)) and the rejection rate (98.5%). Profiting from its unique synergistic effect of adsorption, photo-Fenton and filtration, PC@PL exhibits wonderful self-cleaning performance and distinguished removal rate for methylene blue (97.0%), methyl violet (94.3%), ciprofloxacin (87.6%) and acetamiprid (88.9%) within 75 min, disinfection (100% Escherichia coli (E. coli) and 80% Staphylococcus aureus (S.aureus) inactivation)) and excellent cycle stability.

Optimization of a lipase/reduced graphene oxide/metal-organic framework electrode using a central composite design-response surface methodology approach

Lipase has been gaining attention as the recognition element in electrochemical biosensors. Lipase immobilization is important to maintain its stability while providing excellent conductivity. In this study, a lipase electrochemical biosensor immobilized on a copper-centred metal-organic framework integrated with reduced graphene oxide (lipase/rGO/Cu-MOF) was synthesized by a facile method at room temperature. Response surface methodology (RSM) via central composite design (CCD) was used to optimize the synthesis parameters, which are rGO weight, ultrasonication time, and lipase concentration, to maximize the current response for the detection of p-nitrophenyl acetate (p-NPA). The results of the analysis of variance (ANOVA) showed that all three parameters were significant, while the interaction between the ultrasonication time and lipase concentration was the only significant interaction with a p-value of less than 0.05. The optimized electrode with parameters of 1 mg of rGO, 30 min ultrasonication time, and 30 mg mL-1 lipase exhibited the highest current response of 116.93 μA using cyclic voltammetry (CV) and had a residual standard error (RSE) of less than 2% in validation, indicating that the model is suitable to be used. It was characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and Fourier transform infrared spectroscopy (FTIR), where the integration of the composite was observed. Immobilization using ultrasonication altered the lipase's secondary structure, but reduced its unorderly coils. The electrochemical and thermal analysis showed that the combination of Cu-MOF with rGO enhanced the electrochemical conductivity and thermostability.

Transferring and Retaining of Different Polyaniline Nanofeatures via Electrophoretic Deposition for Enhanced Sensing Performance

Nanofeatured polyaniline (PANI) electrodes have demonstrated impressive sensing performance due to the enhanced electrolyte diffusion and ion transport. However, the retaining of these nanostructures on substrates via electrophoretic deposition (EPD) faces an insurmountable challenge from the involved dedoping process. Here, camphorsulfonic acid is utilized with high steric effects to dope PANI (PANI-CSA) that can be directly used EPD without involving a dedoping process. Five different nanofeatures (sea cucumber-like, nanofiber, amorphous, nanotube, and nanorod) are synthesized, and they have been all successfully transferred onto indium tin oxide substrate in a formic acid/acetonitrile system, namely a morphology memory effect. The mechanism of retaining these nanofeatures is revealed, which is realized via the processes of dissolution of PANI-CSA, codoping and solvation, and reassembly of basic units into the original nanofeature. The enhanced protonation level by the codoping of formic acid and solvation of acetonitrile plays the key role in retaining these nanofeatures. This method is also applicable to transfer PANI/gold nanorod composites (PANI-CSA/AuNRs). The PANI-CSA/AuNRs electrode as an ascorbic acid sensor has shown an excellent sensing performance with a sensitivity up to 872.7 µA mm^-1 cm^-2 and a detection limit of as low as 0.18 × 10^-6 m.

Fabrication of a biological metal-organic framework based superhydrophobic textile fabric for efficient oil/water separation

In response to the industry's difficulty in properly separating oily wastewater discharge, researchers are investigating enhanced oil/water separation materials. In this work, a cost-effective and environmentally friendly superhydrophobic textile fabric was fabricated for effective oil-water mixture and emulsion separation. A biological metal-organic framework consisting of copper as a core metal and aspartic acid as a linker (Cu-Asp MOF) was used to improve the surface roughness of the pristine textile fabric, and stearic acid was used to lower its surface energy. The thermal gravimetric analysis investigated the prepared Cu-Asp MOF's thermal stability. X-ray spectroscopy and Fourier-transform infrared spectroscopy studied the crystal orientation and chemical composition of the Cu-Asp MOF, Cu-Asp MOF@SA, pristine textile fabric, and superhydrophobic textile fabric, respectively. The surface morphology of the pristine and modified textile fabric was studied by scanning electron microscope. The wettability results showed that the prepared superhydrophobic textile fabric has a water contact angle of 158° ± 1.3 and water sliding angle of 2° ± 0.2°. The prepared superhydrophobic textile fabric showed excellent oil-water mixture and emulsion separation performance, oil absorption capacity, chemical stability, mechanical abrasion resistance, and a high flux rate. These outstanding characteristics of the prepared superhydrophobic textile fabric greatly increase the possibility for practical applications.

Highly Selective and Low-Power Carbon Monoxide Gas Sensor Based on the Chain Reaction of Oxygen and Carbon Monoxide to WO3

Carbon monoxide (CO) poisoning can easily occur in industrial and domestic settings, causing headaches, loss of consciousness, or death from overexposure. Commercially available CO gas sensors consume high power (typically 38 mW), whereas low-power gas sensors using nanostructured materials with catalysts lack reliability and uniformity. A low-power (1.8 mW @ 392 °C), sensitive, selective, reliable, and practical CO gas sensor is presented. The sensor adopts floated WO₃ film as a sensing material to utilize the unique reaction of lattice oxide of WO₃ with CO gas. The sensor locally modulates the electron concentration in the WO₃ film, allowing O₂ and CO gases to react primarily in different sensing areas. Electrons generated by the CO gas reaction can be consumed for O₂ gas adsorption in a remote area, and this promotes the additional reaction of CO gas, boosting sensitivity and selectivity. The proposed sensor exhibits a 39.5 times higher response than the conventional resistor-type gas sensor fabricated on the same wafer. As a proof of concept, sensors with In₂O₃ film are fabricated, and the proposed sensor platform shows no advantage in detecting CO gas. Fabrication of the proposed sensor is reproducible and inexpensive due to conventional silicon-based processes, making it attractive for practical applications.

Electrospun Biodegradable Nanofibers Coated Homogenously by Cu Magnetron Sputtering Exhibit Fast Ion Release. Computational and Experimental Study

Copper-coated nanofibrous materials are desirable for catalysis, electrochemistry, sensing, and biomedical use. The preparation of copper or copper-coated nanofibers can be pretty challenging, requiring many chemical steps that we eliminated in our robust approach, where for the first time, Cu was deposited by magnetron sputtering onto temperature-sensitive polymer nanofibers. For the first time, the large-scale modeling of PCL films irradiation by molecular dynamics simulation was performed and allowed to predict the ions penetration depth and tune the deposition conditions. The Cu-coated polycaprolactone (PCL) nanofibers were thoroughly characterized and tested as antibacterial agents for various Gram-positive and Gram-negative bacteria. Fast release of Cu2+ ions (concentration up to 3.4 µg/mL) led to significant suppression of E. coli and S. aureus colonies but was insufficient against S. typhimurium and Ps. aeruginosa. The effect of Cu layer oxidation upon contact with liquid media was investigated by X-ray photoelectron spectroscopy revealing that, after two hours, 55% of Cu atoms are in form of CuO or Cu(OH)2. The Cu-coated nanofibers will be great candidates for wound dressings thanks to an interesting synergistic effect: on the one hand, the rapid release of copper ions kills bacteria, while on the other hand, it stimulates the regeneration with the activation of immune cells. Indeed, copper ions are necessary for the bacteriostatic action of cells of the immune system. The reactive CO2/C2H4 plasma polymers deposited onto PCL-Cu nanofibers can be applied to grafting of viable proteins, peptides, or drugs, and it further explores the versatility of developed nanofibers for biomedical applications use.