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Thin film chemiresistive gas sensor on single-walled carbon nanotubes-functionalized with polyethylenimine (PEI) for $${\hbox {NO}}_{2}$$NO2 gas sensing
摘要： Chemical detection of toxic gases, such as greenhouse gases is still very important as a research topic. To design gas sensor detectors based on single-walled carbon nanotubes (SWCNTs) with high sensitivity and selectivity for the toxic environment is a continuous process. The aim is to detect NO2 gas with better sensitivity. In the present work, the thin-film sensor is fabricated on SiO2 substrate and it is functionalized with polyethylenimine (PEI). It has been established that PEI functionalized SWCNTs (F-SWCNTs) show high sensitivity towards strong electron-withdrawing particles. It was found that at room temperature, SWCNTs-PEI functionalized gas sensor exhibited a higher sensitivity of 37.00% as compared with bare SWCNTs gas sensor. The gas sensor has shown the repeatable response for the entire concentration range studied. The sensing properties and the PEI functionalization duration effects on the behaviour of SWCNTs-based gas sensors were demonstrated.
关键词： NO2,Carbon nanotubes,sensor,polyethylenimine (PEI)
更新于2025-09-19 17:13:59
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Preparation and Characterization of UV-LED Curable Acrylic Films Containing Biochar and/or Multiwalled Carbon Nanotubes: Effect of the Filler Loading on the Rheological, Thermal and Optical Properties
摘要： UV-LED curable coatings represent an up-to-date attractive field due to the high curing efficiency even in the presence of high filler loadings, as well as to the absence of infrared wavelengths that may negatively impact on heat-sensitive substrates. The addition of carbonaceous materials, such as biochar (BC) and/or multiwalled carbon nanotubes (MWCNTs) could positively improve both the rheological and thermal properties. In this study we report on the synthesis and characterization of carbon-reinforced films containing nanometric (MWCNTs) and micrometric (BC) carbon-based materials. We analyze the rheological properties of the UV-LED curable dispersions, as well as the thermal and optical properties of the resulting films, establishing some correlations between filler dispersion/loading with the main observed properties.
关键词： composites,epoxy-acrylate resin,biochar,multiwalled carbon nanotubes,UV-LED curing
更新于2025-09-19 17:13:59
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Carbon Allotrope-Based Optical Fibers for Environmental and Biological Sensing: A Review
摘要： Recently, carbon allotropes have received tremendous research interest and paved a new avenue for optical fiber sensing technology. Carbon allotropes exhibit unique sensing properties such as large surface to volume ratios, biocompatibility, and they can serve as molecule enrichers. Meanwhile, optical fibers possess a high degree of surface modification versatility that enables the incorporation of carbon allotropes as the functional coating for a wide range of detection tasks. Moreover, the combination of carbon allotropes and optical fibers also yields high sensitivity and specificity to monitor target molecules in the vicinity of the nanocoating surface. In this review, the development of carbon allotropes-based optical fiber sensors is studied. The first section provides an overview of four different types of carbon allotropes, including carbon nanotubes, carbon dots, graphene, and nanodiamonds. The second section discusses the synthesis approaches used to prepare these carbon allotropes, followed by some deposition techniques to functionalize the surface of the optical fiber, and the associated sensing mechanisms. Numerous applications that have benefitted from carbon allotrope-based optical fiber sensors such as temperature, strain, volatile organic compounds and biosensing applications are reviewed and summarized. Finally, a concluding section highlighting the technological deficiencies, challenges, and suggestions to overcome them is presented.
关键词： carbon nanotubes,graphene,sensors,nanomaterials,carbon dots,optical fiber,nanodiamonds,nanocoating
更新于2025-09-19 17:13:59
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Co-doping metal oxide nanotubes: superlinear photoresponse and multianalyte sensing
摘要： Metal oxide nanotubes and standalone membranes have been extensively researched for potential applications ranging from electronics, optoelectronics, and photocatalysis, to ?ltration and gas sensing. Although the wide-bandgap of these nanotubes poses challenges for their utilization for photochemical conversion and charge transport, doped metal-oxide nanotubes provide an alternative to lower their bandgap and provide charge carriers for conduction and photochemistry. While many single-dopants have been successfully used, co-dopants can be used to manipulate the electronic density of states, photophysical and photochemical properties to obtain new and unexpected functionalities, sometimes even completely different from the individual dopants. Here the co-doped titanium dioxide (TiO2) nanotube membranes are described where the combined properties of the co-dopants differ from their monodoped counterparts. A detailed mechanistic model is provided to explain the new photophysical and photochemical properties of these co-doped metal oxide membranes, and novel functionalities resulting from such properties like superlinear photoresponse and enhanced gas sensing response. In addition, the potential applications of these functionalities are shown in photodetection and multianalyte sensing as portable devices.
关键词： electronic properties,multianalyte sensors,metal-oxide nanotubes,co-doping,photophysics
更新于2025-09-19 17:13:59
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Polarization-dependent pulse dynamics of mode-locked fiber laser with near-zero net dispersion
摘要： We demonstrate novel polarization-dependent pulse dynamics in a fiber laser cavity mode-locked by single-wall carbon nanotubes. By managing the net dispersion and polarization state, we obtain two noise-like pulsing procedures with distinctive polarization characteristics. Ultrafast polarization measurements reveal double pulses are produced by the combined effects of double-scroll chaotic polarization attractors and the polarization mode dispersion of single-mode fiber. The corresponding single-shot spectra provide evidence of coherent energy coupling between pulses during the switching process, due to the polarization hole burning of the active medium. The relative results provide new information for the polarization control of ultrafast lasers.
关键词： polarization-dependent pulse dynamics,single-wall carbon nanotubes,polarization hole burning,near-zero net dispersion,mode-locked fiber laser
更新于2025-09-19 17:13:59
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Cobalt ferrite decorated multiwalled carbon nanotubes as the electrode for efficient field electron emission
摘要： In the present study, Cobalt Ferrite (CF) nanoparticles with different weight concentrations were successfully decorated on Multi-Walled Carbon nanotubes (MWCNT) using a simple glycol assisted chemical route. The physicochemical and electronic properties of CF decorated MWCNTs (MWCNT-CF) were accomplished with the help of different techniques such as X-ray Diffraction (XRD), Raman Spectroscopy, Transmission Electron Microscopy (TEM), X-ray Photo-electron Spectroscopy (XPS) and Fourier Transform Infrared Spectroscopy (FTIR). Further, the effect of CF concentration on Field Emission (FE) characteristics of MWCNT-CF is investigated. The FE studies revealed that, CF decorated MWCNT emitter (MWCNT-CF; 1:1) exhibits lower turn on (0.52 V/μm, at 10 μA/cm2) and threshold fields (0.62 V/μm, at 100 μA/cm2) in contrast to pristine CF, MWCNT, and MWCNT-CF (1:0.5 and 1:2). Interestingly, from the MWCNT-CF (1:1) emitter, very high emission current density ~ 10408 μA/cm2 has been extracted at a relatively lower applied field of 1.18 V/μm. The enhancement in FE characteristics of MWCNT-CF emitters is attributed to lowering of work function measured from the UPS analysis and increased number of emitting sites. The results imply that very high current density field emitters can be fabricated using a simple strategy based on the decoration of MWCNT’s with CF nanoparticles.
关键词： Reflux,Cobalt Ferrite,Multiwalled Carbon Nanotubes,Field Emission,Nanoparticles
更新于2025-09-19 17:13:59
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Enhancing the performance of photovoltaic operating under harsh conditions using carbon-nanotube thermoelectric harvesters
摘要： This paper proposes a novel configuration for enhancing the efficiency of photovoltaics (PV) operating in high-temperature environment using a nano-thermoelectric carbon nanotube-based harvester attached to the backside of the solar cell (SC). The attached harvester will not only extract heat energy from the cell but will also convert this wasted heat energy into electrical energy. The proposed configuration has been fabricated and tested experimentally, where I–V measurements have been conducted. An overall enhancement in SC efficiency of 50%, with respect to reference cell, has been achieved using the proposed harvester. In addition, the harvester itself provided a power in the range of hundreds of microwatts that can be utilized in various low-power applications.
关键词： High-temperature environment,Thermoelectric harvester,Solar cell efficiency,Photovoltaics,Carbon nanotubes
更新于2025-09-19 17:13:59
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Sol-Gel Processed TiO2 Nanotube Photoelectrodes for Dye-Sensitized Solar Cells with Enhanced Photovoltaic Performance
摘要： The performance of dye-sensitized solar cells (DSCs) critically depends on the efficiency of electron transport within the TiO2-dye-electrolyte interface. To improve the efficiency of the electron transfer the conventional structure of the working electrode (WE) based on TiO2 nanoparticles (NPs) was replaced with TiO2 nanotubes (NTs). Sol-gel method was used to prepare undoped and Nb-doped TiO2 NPs and TiO2 NTs. The crystallinity and morphology of the WEs were characterized using XRD, SEM and TEM techniques. XPS and PL measurements revealed a higher concentration of oxygen-related defects at the surface of NPs-based electrodes compared to that based on NTs. Replacement of the conventional NPs-based TiO2 WE with alternative led to a 15% increase in power conversion efficiency (PCE) of the DSCs. The effect is attributed to the more efficient transfer of charge carriers in the NTs-based electrodes due to lower defect concentration. The suggestion was confirmed experimentally by electrical impedance spectroscopy measurements when we observed the higher recombination resistance at the TiO2 NTs-electrolyte interface compared to that at the TiO2 NPs-electrolyte interface. Moreover, Nb-doping of the TiO2 structures yields an additional 14% PCE increase. The application of Nb-doped TiO2 NTs as photo-electrode enables the fabrication of a DSC with an efficiency of 8.1%, which is 35% higher than that of a cell using a TiO2 NPs. Finally, NTs-based DSCs have demonstrated a 65% increase in the PCE value, when light intensity was decreased from 1000 to 10 W/m2 making such kind device be promising alternative indoor PV applications when the intensity of incident light is low.
关键词： nanotubes,X-ray photoelectron spectroscopy,dye-sensitized solar cells,semiconductor-liquid interface,charge traps
更新于2025-09-19 17:13:59
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Photoa??thermal conversion and heat storage characteristics of multia??walled carbon nanotubes dispersed magnetic phase change microcapsules slurry
摘要： The development of high-efficient working fluids with excellent photo-thermal conversion and heat storage properties is an important factor to solar thermal utilization. In this work, magnetic phase change microcapsules (MPCMs) were prepared via in situ polymerization, where melamine-formaldehyde resin (MF) and oleic acid-coated magnetic nanoparticles (OA-MNs) were used as the shell and core, respectively. The microstructure, magnetic and thermal properties of MPCMs were investigated, and the photo-thermal conversion and heat storage properties of slurries prepared by dispersing MPCMs into multi-walled carbon nanotubes (MWCNTs) nanofluids were explored. The encapsulation efficiency of MPCMs with super-paramagnetic nature achieved 63.51%, while the thermal conductivity of MPCMs was slightly increased with regard to phase change microcapsules (PCMs) and the thermal stability of octadecane was enhanced after being encapsulated. Moreover, the slurry with 0.01 wt% MWCNTs and 15 wt% MPCMs had the optimal photo-thermal conversion properties and thermal storage capacity. Beyond that, the recycled MPCMs represented excellent recyclability. Our research demonstrated that the MWCNTs-dispersed MPCMs slurry is one of ideal working fluids with excellent photo-thermal conversion and heat storage characteristics for direct absorption solar collector.
关键词： carbon nanotubes,direct absorption solar collector,photo-thermal conversion,heat storage,microcapsules
更新于2025-09-19 17:13:59
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Covalently bonded polyaniline-reduced graphene oxide/single-walled carbon nanotubes nanocomposites: influence of various dimensional carbon nanostructures on the electrochromic behavior of PANI
摘要： In this paper, water-dispersible and covalently bonded polyaniline-carbon nanostructures, including polyaniline-reduced graphene oxide (PANI-rGO), polyaniline-single-walled carbon nanotubes (PANI-SWCNTs), and polyaniline-reduced graphene oxide/single-walled carbon nanotube (PANI-rGO/SWCNTs) nanocomposites, were synthesized by grafting PANI onto p-phenylenediamine (PPD)-functionalized graphene oxide (GO) or single-walled carbon nanotubes (SWCNTs) using polystyrene sulfonate (PSS) as a macromolecular dopant agent. The structures and morphologies of the PANI, PANI-rGO, PANI-SWCNTs, and PANI-rGO/SWCNTs nanocomposites were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. The cyclic voltammetry and UV–vis spectra were performed on an electrochemical workstation and a UV–vis spectrometer, respectively. The results show that the electrochromic and electrochemical properties of nanocomposites can bene?t from the high conductivity of SWCNTs and the abundant active sites of rGO. When SWCNTs and rGO work together, their respective shortcomings are overcome, allowing the nanocomposite to exhibit the best electrochemical and electrochromic properties. The optical contrast increased from 0.38 for PANI to 0.52 for PANI-rGO/SWCNTs. The coloring and bleaching times decreased from 2.59 s and 2.39 s, respectively, for PANI to 1.33 and 0.78 s, respectively, for PANI-rGO/SWCNTs. The charge transfer resistance (Rct) decreased from 135 Ω for PANI to 30 Ω for PANI-rGO/SWCNTs. The synergistic effect of PANI, rGO, and SWCNTs can signi?cantly improve the electrochromic ability of PANI.
关键词： single-walled carbon nanotubes,reduced graphene oxide,electrochromic,polyaniline,nanocomposites
更新于2025-09-19 17:13:59