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Synthesis of 1D α-MoO3/0D ZnO heterostructure nanobelts with enhanced gas sensing properties
摘要： Exploring high-performance sensing materials is ultra-important for safety control. Herein, 1D α-MoO3/0D ZnO nanocomposites are prepared via a facile hydrothermal method and its microstructure is characterized through X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), energy dispersive X-ray (EDX) and X-ray photoelectron spectroscopy (XPS). It is confirmed that the as-prepared nanocomposites are constituted by 1D α-MoO3 nanobelts (200-300 nm in width), with the surface loaded with fine ZnO nanoparticles. Sensing properties of the α-MoO3 and 1D α-MoO3/0D ZnO nanocomposites to ethanol are measured and compared. Interestingly, the ZnO-decorated α-MoO3 nanobelts exhibited excellent sensitivity and selectivity to ethanol at relatively low operating temperature (250 oC) when compared with that of the raw α-MoO3 nanobelts, indicating a good candidate of 1D α-MoO3/0D ZnO nanocomposites for future ethanol detection.
关键词： One-dimensional,Heterostructure,ZnO,α-MoO3 nanobelts,Ethanol sensing
更新于2025-11-14 17:04:02
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2,4,6-Trinitrophenol detection by a new portable sensing gadget using carbon dots as a fluorescent probe
摘要： An optical sensing gadget using fluorescence of carbon dots (CDs) was developed to realize the in-field detection of 2,4,6-trinitrophenol (TNP) in tap water and lake water samples. Fluorescent CDs were prepared through a one-step hydrothermal synthetic route. The fluorescence spectra demonstrated that the CDs could specifically discriminate TNP from other nitroaromatic explosives in an aqueous medium. The fluorescence of the CDs was quenched linearly with the concentration of TNP in the range from 1 to 100 μM, with a detection limit of 0.48 μM (3σ/k). The detection mechanism was ascribed to the synergistic effect of the inner filter effect and electron transfer. In addition, a portable sensing gadget based on a high-precision RGB color sensor and a micro control unit was developed. With use of the sensing gadget and the CDs, TNP detection in tap water and lake water samples was realized. Importantly, the portable sensing gadget combined with highly stable, low-toxicity, and sensitive CDs might have great potential for application in extensive in-field sensing situations.
关键词： 2,4,6-Trinitrophenol detection,Portable sensing gadget,Carbon dots,Fluorescence analysis
更新于2025-11-14 17:03:37
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α-Fe <sub/>2</sub> O <sub/>3</sub> Polyhedral Nanoparticles Enclosed by Different Crystal Facets: Tunable Synthesis, Formation Mechanism Analysis, and Facets-dependent <i>n</i> -Butanol Sensing Properties
摘要： Three kinds of polyhedral α-Fe2O3 nanoparticles enclosed by different facets including oblique parallel hexahedrons (op-hexahedral NPs), cracked oblique parallel hexahedrons (cop-hexahedral NPs), and octadecahedral nanoparticles (octadecahedral NPs), were successfully prepared by simply changing only one reaction parameter in the hydrothermal process. The structural and morphological of the products were systematically studied using various characterizations including X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), revealing that the three kinds of α-Fe2O3 nanoparticles were enclosed by {104}, {110}/{104}, and {102}/{012}/{104} crystal planes, respectively. The exposed facets and shape of the nanocrystals were found to be affected by the adding amount of ethylene glycol in the solvent. The gas-sensing properties and mechanism of the α-Fe2O3 samples were studied and analyzed, which indicated that the sensitivity of the three samples followed the order of octadecahedral NPs (cid:2) cop-hexahedral NPs (cid:2) op-hexahedral NPs due to the combined effects of specific surface area and oxygen defects in the nanocrystals.
关键词： Polyhedron,n-Butanol,Hydrothermal synthesis,α-Fe2O3 nanoparticles,Gas-sensing
更新于2025-11-14 17:03:37
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A fluorescent probe for sequential sensing of MnO <sub/>4</sub><sup>?</sup> and Cr <sub/>2</sub> O <sub/>7</sub><sup>2?</sup> ions in aqueous medium based on a UCNS/TMB nanosystem
摘要： This paper reports the successful design of an UC fluorescence nanosystem for distinguishable and sequential detection of MnO4? and Cr2O72? based on the inner filter effect (IFE) between Gd2O3:Yb,Er upconversion nanospheres (UCNS) and 3,3’,5,5’-tetramethylbenzidine (TMB). The detection of MnO4? was realized by a stoichiometric oxidation reaction between TMB and Mn(VII), which resulted in quenching of the upconversion luminescence (UCL) by the blue product through IFE. The assay of Cr2O72?, in contrast, was based on the formation of complexes and the consumption of the oxidation product of the previous reaction. The sensing of MnO4? and Cr2O72? do not interfere with each other when Pb2+ was added as a masking agent. This provides a new strategy for sensitive and selective detection of MnO4? and Cr2O72?. The detection of MnO4? showed not only a low LOD of 0.243 μM but also high selectivity over other possible interfering ions. The sensitivity assay of MnO4? can be performed in the linear range of 1.85 to 69 μM. An excellent linear relationship was also found in the sensing of Cr2O72?, with a linear range of 18.3 to 250 μM and a LOD of 2.95 μM. The selectivity towards Cr2O72? was also proved to be good. Based on these properties, the UCNS–TMB nanoplatform is a potential chemosensor for both MnO4? and Cr2O72? ions in practical assays for waste water.
关键词： upconversion nanospheres,aqueous medium,UCNS/TMB nanosystem,Cr2O72?,MnO4?,TMB,fluorescent probe,inner filter effect,sequential sensing
更新于2025-11-14 17:03:37
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Enhanced Methane Sensing Properties of WO3 Nanosheets with Dominant Exposed (200) Facet via Loading of SnO2 Nanoparticles
摘要： Methane detection is extremely difficult, especially at low temperatures, due to its high chemical stability. Here, WO3 nanosheets loaded with SnO2 nanoparticles with a particle size of about 2 nm were prepared by simple impregnation and subsequent calcination using SnO2 and WO3·H2O as precursors. The response of SnO2-loaded WO3 nanosheet composites to methane is about 1.4 times higher than that of pure WO3 at the low optimum operating temperature (90 °C). Satisfying repeatability and long-term stability are ensured. The dominant exposed (200) crystal plane of WO3 nanosheets has a good balance between easy oxygen chemisorption and high reactivity at the dangling bonds of W atoms, beneficial for gas-sensing properties. Moreover, the formation of a n–n type heterojunction at the SnO2-WO3 interface and additionally the increase of specific surface area and defect density via SnO2 loading enhance the response further. Therefore, the SnO2-WO3 composite is promising for the development of sensor devices to methane.
关键词： methane sensing,SnO2-loaded WO3 nanosheets,exposed (200) facet,heterojunction
更新于2025-11-14 17:03:37
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Role of Yb3+ ion on the evaluation of energy transfer and cross-relaxation processes in Gd2Ce2O7: Yb3+, Er3+ phosphors
摘要： Energy transfer (ET) and cross-relaxation (CR) processes play significant roles in regulating emitting colors and intensity of upconversion (UC) materials. Calculating the coefficients in ET and CR processes can provide visual descriptions for evaluating the UC luminescence properties. Here, we find that those ET and CR processes are responsible for the color-tunable properties in Gd2Ce2O7: Yb3+, Er3+ phosphors. By solving the rate equation, mathematical expressions are established to calculate the ET and CR coefficients based on the experimental UC spectra and lifetimes. The results are benefit to evaluate the efficiencies of ET and CR processes in quantization in different Yb3+ ion concentrations doped samples. The coefficients of ET process arise from 1.05 to 7.93 × 1017 cm3s?1 while those of CR process increase from 2.69 to 72.01 × 1017 cm3s?1 with increasing the Yb3+ ion concentration, which suggest that the CR and ET processes are efficient in Gd2Ce2O7 host. Furthermore, potential temperature sensing properties are also evaluated according to the fluorescence intensity ratio of 2H11/2 and 4S3/2 levels and the maximal sensitivity (S) is achieved about 0.00337 K?1 at 503 K. This work provides an insight into the evaluation of those UC processes and reveals the capacity in color-tunable and temperature sensing aspects.
关键词： Upconversion,Mathematical expression,Cross-relaxation,Temperature sensing,Energy transfer
更新于2025-11-14 17:03:37
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Improved negative thermal quenching effect via high sensitizer doping content in NaGdF4 based active-core/active-shell architecture
摘要： The strategies of introducing interior defects and reducing mean particle size have been applied to improve negative thermal quenching effect (TQE) in Yb3+ sensitized fluoride upconversion (UC) nanocrystals (NCs) recently. Herein, an active-core/active-shell structure with high total Yb3+ doping content is used to enhance the absorption intensity of Er3+ ions. Moreover, the Er3+ activators are doped into the shell to enable the energy migration process from activators to surface defects. In this scenario, with the rise of temperature, the suppression degree of this energy migration process is enlarged followed by an improved negative TQE. Specifically, with rising the temperature from 293 K to 413 K, the integral upconversion emission intensity of 40Yb: NaGdF4@60Yb/2Er: NaGdF4 NCs increases by ~ 8.24 times, while that of NaGdF4@20Yb/2Er: NaGdF4 NCs with a similar mean particle size only enhances ~ 3.44 times.
关键词： Yb3+ concentration,upconversion,temperature sensing,negative thermal quenching
更新于2025-11-14 17:03:37
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H2 Gas Sensor Based on Pd/ZnO Nanostructures Deposited on Tapered Optical Fiber
摘要： A novel H2 sensor using tapered optical fiber coated with Pd/ZnO nanostructures have been developed. The ZnO nanostructures was synthesized and deposited onto tapered optical fiber via chemical bath deposition (CBD) method. The ZnO was characterized by FESEM, XRD and EDX to confirm the material properties. It was discovered that the sensor is sensitive towards different concentrations of H2 in synthetic air at 180oC of operating temperature. By varying the deposition time of ZnO coating, different thickness of ZnO layer can be obtained. It was observed that with 280 nm thickness, the maximum absorbance response can be achieved. Further investigation with sensor sample of as-prepared and annealed was carried out to study its sensing performance towards H2. The absorbance response of 280 nm thickness of annealed Pd/ZnO has increased 64% as compared to as-prepared Pd/ZnO upon 1% H2 exposure in the synthetic air when measured in the visible to near infra-red optical wavelength. It can be concluded that the Pd/ZnO optical fiber sensor with thickness around 280 nm provided better sensitivity in sensing H2 at 180oC as compared to other thicknesses investigated.
关键词： Optical sensors,zinc oxide,sensing material
更新于2025-11-14 15:30:11
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Highly fluorescent polyethyleneimine protected Au8 nanoclusters: one-pot synthesis and application in hemoglobin detection
摘要： Gold nanoclusters (Au NCs) with atomic precision have huge application potentials in chemo/bio sensing, catalysis, and energy conversion. However, a precise atomic control of Au NCs still remains a great challenge. Herein, we developed a facile one-pot and top-down strategy to synthesize eight-atom numbered Au NCs (Au8 NCs), aiming to understand their fundamental physical/chemical properties and explore their potential applications. The etching of gold nanoparticles by their encapsulated hyperbranched polyethyleneimine was significantly promoted by a newly proposed catalyst, hydrogen peroxide, which gave rise to brightly blue-emitting Au8 NCs (quantum yield = 28.8%). The as-prepared Au8 NCs could sense hemoglobin with a detection limit of 5.0 nM through the combination of Fenton reaction and fluorescence resonance energy transfer. And the sensing behaviour is unaffected by the presence of various interfrerents such as proteins, small molecules, anions, and metoal ions. In addition, a hemoglobin evaluation in blood samples with small relative standard deviations and satisfied recoveries was achieved using the proposed Au8 NCs nanoprobes.
关键词： Gold nanoclusters,Sensing,One-pot synthesis,Hemoglobin,Fluorescence
更新于2025-11-14 15:29:11
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Peptide-Functionalized Quantum Dots for Rapid Label-Free Sensing of 2,4,6-Trinitrotoluene
摘要： Explosive compounds, such as 2,4,6-trinitrotoluene (TNT), pose a great concern in terms of both global public security and environmental protection. There are estimated to be hundreds of TNT contaminated sites all over the world, which will affect the health of humans, wildlife, and the ecosystem. Clearly, the ability to detect TNT in soils, water supplies, and wastewater is important for environmental studies but also important for security, such as in ports and boarders. However, conventional spectroscopic detection is not practical for on-site sensing because it requires sophisticated equipment and trained personnel. We report a rapid and simple chemical sensor for TNT by using TNT binding peptides which are conjugated to fluorescent CdTe/CdS quantum dots (QDs). QDs were synthesized in the aqueous phase, and the peptide was attached directly to the surface of the QDs by using thiol groups. The fluorescent emission from the QDs was quenched in response to the addition of TNT. The response could even be observed by the naked eye. The limit of detection from fluorescence spectroscopic measurement was estimated to be approximately 375 nM. In addition to the rapid response (within a few seconds), selective detection was demonstrated. We believe this label-free chemical sensor contributes to progress for the on-site explosive sensing.
关键词： quantum dots (QDs),explosive detection,2,4,6-trinitrotoluene (TNT),label-free sensing,peptide-functionalized
更新于2025-11-14 15:23:50