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Trace level toxic ammonia gas sensing of single-walled carbon nanotubes wrapped polyaniline nanofibers
摘要： This paper presents a two-step enhancement and a comprehensive analysis of single-walled carbon nanotubes (SWCNTs) wrapped polyaniline nanofiber (NPANI) ammonia (NH3) gas sensor at room temperature. SWCNT-PANI composites are successfully synthesized using an efficient and cost-effective rapid in situ chemical polymerization method. The structural morphology and modification of the samples are characterized using field-emission scanning electron microscopy and HRTEM. FTIR and Raman spectroscopic studies are also performed to gain a better insight into the chemical environmental interaction in the as-prepared nanocomposite. The analysis confirms the successful formation of the nanocomposite. The observed NH3 gas-sensing response at 10 ppm of SWCNT, f-SWCNT (functionalised SWCNT), and SWCNT-PANI composite sensors are 5%–6%, 18%–20%, and 24%–25%, respectively. The SWCNT-PANI composite sensors have shown higher repeatability, selectivity, long-term stability, and fast response-recovery characteristics as compared to f-SWCNTs and pristine SWCNT sensors. Concentration and temperature dependent gas-sensing studies are also analyzed. The sensor response also shows a linear relationship with NH3 gas concentration and an inverse relationship with increasing temperature.
关键词： Raman spectroscopy,rapid in situ chemical polymerization,ammonia gas sensor,polyaniline nanofiber,field-emission scanning electron microscopy,FTIR,HRTEM,room temperature,single-walled carbon nanotubes
更新于2025-09-19 17:13:59
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Non-covalent Methods of Engineering Optical Sensors Based on Single-Walled Carbon Nanotubes
摘要： Optical sensors based on single-walled carbon nanotubes (SWCNTs) demonstrate tradeoffs that limit their use in in vivo and in vitro environments. Sensor characteristics are primarily governed by the non-covalent wrapping used to suspend the hydrophobic SWCNTs in aqueous solutions, and we herein review the advantages and disadvantages of several of these different wrappings. Sensors based on surfactant wrappings can show enhanced quantum efficiency, high stability, scalability, and diminished selectivity. Conversely, sensors based on synthetic and bio-polymer wrappings tend to show lower quantum efficiency, stability, and scalability, while demonstrating improved selectivity. Major efforts have focused on optimizing sensors based on DNA wrappings, which have intermediate properties that can be improved through synthetic modifications. Although SWCNT sensors have, to date, been mainly engineered using empirical approaches, herein we highlight alternative techniques based on iterative screening that offer a more guided approach to tuning sensor properties. These more rational techniques can yield new combinations that incorporate the advantages of the diverse nanotube wrappings available to create high performance optical sensors.
关键词： optical biosensing,non-covalent solubilization,selectivity,molecular recognition,near-infrared sensors,single-walled carbon nanotubes (SWCNTs or SWNTs),fluorescence brightness
更新于2025-09-19 17:13:59
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Single-Walled boron nitride nanotubes interaction with nickel, titanium, palladium, and gold metal atoms- A first-principles study
摘要： Ab initio calculations based on density functional theory was carried out to study the electronic properties of (3,3), (4,2), (5,2) and (6,0) boron nitride nanotubes when interacting with nickel, titanium, palladium and gold metal atoms. These interactions occurred via adsorption, intercalation, nitrogen substitutional doping and boron substitutional doping. The wide band gaps intrinsic to the pristine boron nitride nanotubes were successfully tuned upon interaction with the metal atoms irrespective of the type of interactions. However, for most of the interactions that occurred via intercalation and nitrogen substitutional doping, the boron nitride nanotube was found to possess semi-metallic properties. More states were added in the density of states upon interaction in which the d orbital of the transition metal atoms was found to be the major contributor to the increase in density of states.
关键词： Transition metals,Fermi energy,Density functional theory,Band gap,Boron nitride nanotubes
更新于2025-09-19 17:13:59
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Graphenea??based polymer composites with ultraa??high ina??plane thermal conductivity: A comparison study between optothermal Raman spectroscopy and laser flash method
摘要： We developed a simple solution mixing and molding process for the incorporation of graphene nano-flakes (GNFs) in polymer films. Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and poly(ethylene-co-methacrylic acid) (PEMAA) were used for preparation of the samples. The orientation and stacking of GNFs were confirmed using a scanning electron microscope. The thermal conductivity values for these composites were obtained using (1) laser flash method (commercially available) and (2) an optothermal Raman (OTR) technique (homemade device). The former measures the thermal diffusivity (α) and one needs to measure the density (ρ) and the heat capacity (Cp) of the composites in order to measure the in-plane thermal conductivity (κ = α.ρ.Cp), while the latter measures the in-plane thermal conductivity directly from the relation between the excitation power and the position of the Raman resonance. The data obtained from Raman spectroscopy were analyzed, assuming heat propagation in three and two dimensions. The Raman results obtained based on the two-dimensional model were very close to the results obtained using the laser flash method with less than 10% difference. The OTR spectroscopy was found to be a promising technique for measuring the in-plane thermal conductivity of carbon-based polymer composites. PVDF-HFP and PEMAA composite films with very high in-plane thermal conductivity (25 W m?1 K?1) were obtained through the incorporation of GNFs (20 wt % concentration). Considering a very low thermal conductivity of these polymers (<0.2 W m?1 K?1), this corresponds to a large enhancement of roughly 12 400%. ? 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48927.
关键词： nanotubes,conducting polymers,fullerenes,graphene,thermal properties,composites
更新于2025-09-19 17:13:59
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Enhanced field electron emission of single-walled carbon nanotubes prepared by imprinting technique
摘要： In this work, single-walled carbon nanotubes (SWCNTs) field electron emitters were fabricated by imprinting SWCNTs on substrates with a silver buffer layer. It was found that the field emission properties of imprinted SWCNTs were significantly improved with turn-on field at 0.62 V/um and threshold field at 1.04 V/um, comparing to screen-printed SWCNTs emitters who had turn-on field at 1 V/um and threshold field at 2 V/um. These improvements of SWCNTs emitters were owing to the directly imprinting method which made SWCNTs have clean surface and more emitters on the substrates. The lower turn-on electric field of field emission was attributed to no impurities encapsulate on the emitters and the large aspect ratio of SWCNTs resulting in high field enhancement factor of 15800. The emission performance of the imprinted cathode was almost unchanged after many times repeated experiments. This simple and low cost technique can fabricate high performance field emission cathodes efficiently and also demonstrates potential applications in many electronic devices.
关键词： Field enhancement factor,Turn-on field,Imprinting,Field emission,Single-walled carbon nanotubes,Temporal stability
更新于2025-09-19 17:13:59
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Amino-Functionalized Single-Walled Carbon Nanotubes-Integrated Polyurethane Phase Change Composites with Superior Photothermal Conversion Efficiency and Thermal Conductivity
摘要： The development of organic phase change materials (PCMs) with good shape stability, superior photothermal conversion efficiency, and high thermal conductivity is critical for practical photothermal utilizations. Herein, novel form-stable solar-thermal conversion and storage materials (SPCMs) with superior photothermal conversion efficiency and thermal conductivity were successfully synthesized by introducing amino-functionalized single-walled carbon nanotubes (SWNTs?NH2) into poly(ethylene glycol)-based polyurethane PCM. Differential scanning calorimetry (DSC) and thermal conductivity test results showed the SPCMs possessed relatively high phase change enthalpies in the range of 124.0?126.1 J/g and that the introduction of SWNTs?NH2 effectively enhanced the thermal conductivities of SPCMs. Sunlight irradiation experiments showed that the introduction of SWNTs?NH2 into PEG-based polyurethane PCM significantly improved the solar-thermal conversion and storage efficiency of SPCMs from 44.8% to 89.3%. The light irradiation cycling tests and thermogravimetric (TG) analyses indicated that the SPCMs exhibit satisfactory reversible stability and thermal stability. Moreover, SPCMs with SWNTs?NH2 added exhibited much higher solar-thermal conversion and storage efficiency and better reversible stability than SPCM with SWNTs added. In conclusion, the synthesized SPCMs show considerable potential for solar-thermal conversion and storage applications.
关键词： Poly(ethylene glycol),Solar-thermal conversion,Thermal energy storage,Single-walled carbon nanotubes,Phase change materials
更新于2025-09-19 17:13:59
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Hydrogen‐Assisted Growth of Ultrathin Te Flakes with Giant Gate‐Dependent Photoresponse
摘要： Van der Waals (vdW)-integrated heterojunctions have been widely investigated in optoelectronics due to their superior photoelectric conversion capability. In this work, 0D bismuth quantum dots (Bi QDs)-decorated 1D tellurium nanotubes (Te NTs) vdW heterojunctions (Te@Bi vdWHs) are constructed by a facile bottom-up assembly process. Transient absorption spectroscopy suggests that Te@Bi vdWH is a promising candidate for new-generation optoelectronic devices with fast response properties. The subsequent experiments and density functional theory calculations demonstrate the vdW interaction between Te NTs and Bi QDs, as well as the enhanced optoelectronic characteristics owing to the plasma effects at the interface between Te NTs and Bi QDs. Moreover, Te@Bi vdWHs-based photodetectors show significantly improved photoresponse behavior in the ultraviolet region compared to pristine Te NTs or Bi QDs-based photodetectors. The proposed integration of vdWHs is expected to pave the way for constructing new nanoscale heterodevices.
关键词： bismuth quantum dots,plasma,heterojunctions,van der Waals,tellurium nanotubes
更新于2025-09-19 17:13:59
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Reversible Charge Transfer with Singlea??Walled Carbon Nanotubes Upon Harvesting the Low Energy Part of the Solar Spectrum
摘要： Here, the ability of a novel near-infrared dye to noncovalently self-assemble onto the surface of single-walled carbon nanotubes (SWCNTs) driven by charge-transfer interactions is demonstrated. Steady-state, Raman, and transient absorption spectroscopies corroborate the electron donating character of the near-infrared dye when combined with SWCNTs, in the form of fluorescence quenching of the excited state of the dye, n-doping of SWCNTs, and reversible charge transfer, respectively. Formation of the one-electron oxidized dye as a result of interactions with SWCNTs is supported by spectroelectrochemical measurements. The ultrafast electronic process in the near-infrared dye, once immobilized onto SWCNTs, starts with the formation of excited states, which decay to the ground state via the intermediate population of a fully charge-separated state, with characteristic time constants for the charge separation of 1.5 ps and charge recombination of 25 ps, as derived from the multiwavelength global analysis. Of great relevance is the fact that charge-transfer occurs from the hot excited state of the near-infrared dye to SWCNTs.
关键词： doping,charge transfer interactions,noncovalent functionalization,near-infrared dyes,carbon nanotubes
更新于2025-09-19 17:13:59
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Laser graving assisted fabrication of foldable supercapacitors for on-chip energy storage
摘要： Planar supercapacitors (SCs) have been regarded as promising energy devices for on-chip electronics and they should be evaluated by areal performances due to the very limited available areas. However, these SCs usually suffer from inevitable size increase for the requirement of substrates, current collectors and sealants. This work presents a kind of freestanding, foldable and quasi-solid-state SCs that single SC units were stacked in the thickness direction with a common electrode to reduce their occupied areas. The foldable SCs can be fabricated in desired patterns by laser graving and their areal performances increase linearly with the assembled units. The energy density of a 5-units foldable SC is 177.9 μWh cm-2 at the power density of 2.78 mW cm-2 and it outperforms most planar SCs. Therefore, this work provides a new reference to improve the areal properties of on-chip SCs from device design.
关键词： nanocomposites,on-chip energy storage,foldable device,supercapacitors,carbon nanotubes
更新于2025-09-19 17:13:59
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Highly sensitive ultraviolet photodetectors based on single wall carbon nanotube-graphene hybrid films
摘要： An ultraviolet (UV) photodetector was fabricated by depositing single wall carbon nanotubes (SWCNTs) on the surface of a graphene field-effect transistor (GFET) with buried gate electrode structure. A photoresponsivity with a value as high as 204.5 A/W was obtained under a 365-nm LED light illumination with an incident power of 3.9 μW. The photoresponsivity of our photodetector is about four orders higher in magnitude than that of a recently reported UV photodetector, which is based on CNTs/graphene hybrid films with a photoresponsivity of 2.3 × 10?2 A/W. With increasing the source-drain voltage of the SWCNTs modified GFET, the photoresponsivity can be further enhanced. In addition, the photoresponsivity can also be tuned by applying a small gate voltage. This work provides a simple and feasible method to create highly sensitive UV photodetectors based on all-carbon hybrid films, which are important in many applications such as military surveillance, biomedical instrumentation and environmental monitoring.
关键词： Ultraviolet,Graphene field effect transistor,Photodetector,Single wall carbon nanotubes
更新于2025-09-19 17:13:59