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- 2018
- interdigital resonator
- microwave gas sensor
- PSE-coated
- Optoelectronic Information Science and Engineering
- King Mongkut’s University of Technology North Bangkok
- Rajamangala University of Technology Suvarnabhumi
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Selective Functionalization of High-Resolution Cu2O Nanopatterns via Galvanic Replacement for Highly Enhanced Gas Sensing Performance
摘要： Recently, high-resolution patterned metal oxide semiconductors (MOS) have gained considerable attention for enhanced gas sensing performance due to their polycrystalline nature, ultrasmall grain size (~5 nm), patternable properties, and high surface-to-volume ratio. Herein, we significantly enhanced the sensing performance of that patterned MOS by galvanic replacement, which allows for selective functionalization on ultrathin Cu2O nanopatterns. Based on the reduction potential energy difference between the base channel material (Cu2O) and the decorated metal ion (Pt2+), Pt could be selectively and precisely decorated onto the desired area of the Cu2O nanochannel array. Overall, the Pt-decorated Cu2O exhibited 11-fold higher NO2 (100 ppm) sensing sensitivity as compared to the non-decorated sensing channel, the while the channel device with excessive Pt doping showed complete loss of sensing properties.
关键词： galvanic replacement,chemical sensitization,p-type metal oxide,gas sensor,high-resolution,nanopattern
更新于2025-09-23 15:23:52
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Low-density PMMA/MAM nanocellular polymers using low MAM contents: Production and characterization
摘要： Low-density nanocellular polymers are required to take advantage of the full potential of these materials as high efficient thermal insulators. However, their production is still a challenging task. One promising approach is the use of nanostructured polymer blends of poly(methyl methacrylate) (PMMA) and a block copolymer poly(methyl methacrylate)-poly(butyl acrylate)-poly(methyl methacrylate) (MAM), which are useful for promoting nucleation but seem to present a severe drawback, as apparently avoid low relative densities. In this work, new strategies to overcome this limitation and produce low-density nanocellular materials based on these blends are investigated. First, the effect of very low amounts of the MAM copolymer is analysed. It is detected that nanostructuration can be prevented using low copolymer contents, but nucleation is still enhanced as a result of the copolymer molecules with high CO2 affinity dispersed in the matrix, so nanocellular polymers are obtained using very low percentages of the copolymer. Second, the influence of the foaming temperature is studied. Results show that for systems in which there is not a clear nanostructuration, cells can grow more freely and smaller relative densities can be achieved. For these studies, blends of PMMA with MAM with copolymer contents from 10 wt% and as low as 0.1 wt% are used. For the first time, the production strategies proposed in this work have allowed obtaining low density (relative density 0.23) nanocellular polymers based on PMMA/MAM blends.
关键词： nanostructuration,gas dissolution foaming,PMMA,MAM,block copolymer,nanocellular polymer,nanocellular foam
更新于2025-09-23 15:23:52
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Influence of precursor solution concentration on the structural, optical and humidity sensing properties of spray-deposited TiO <sub/>2</sub> thin films
摘要： In the present paper, the influence of precursor concentration on the structural, optical, and humidity sensing properties of spray-deposited titanium dioxide (TiO2) films are investigated. The TiO2 thin films were successfully deposited by spraying different precursor concentrations such as 0.075 M, 0.1 M, and 0.125 M of titanium trichloride solution onto glass substrates. X-ray diffractometry (XRD) studies confirmed the polycrystalline anatase phase of TiO2 with dominant (101) plane. The crystallite size was found to increase with the increase in precursor concentration. The micro-strain and dislocation density in the film was observed to decrease as the crystallite size increased. The UV–vis spectra confirmed the optical absorbance edge of the samples shifted toward lower wavelengths with increased precursor concentration. The humidity sensing properties of the synthesized material were measured by monitoring the change in resistance of the sample with the change in relative humidity. The material synthesized with 0.1 M precursor concentration, by using the spray pyrolysis method, shows good sensitivity and has a response time of 77.5 s and fast recovery time of 3 s.
关键词： electrical,titanium dioxide,structural,gas sensing,spray pyrolysis
更新于2025-09-23 15:23:52
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Room temperature ammonia gas sensor based on Au/ graphene nanoribbon
摘要： Graphene nanoribbon (GNR) is a strip and 1D shape of graphene which can be an appropriate candidate for gas sensing application due to its significant electrical and chemical characteristic. In this study, graphene nanoribbon is employed for the NH3 detection process. The chemical approach is applied for unzipping MWCNTs by using KMnO4, as an oxidative material in graphene oxide nanoribbon synthesis process. The gold comb-like electrodes as a sensor structure is produced by standard deposition and photolithography methods. The quality of the synthesized GNRs is investigated by different analyses such as SEM, XRD, Raman Spectroscopy, and FTIR. In addition to GNR sensor preparation, AuGNR sensor is fabricated by gold sputtering deposition on a GNR sensor surface. The experimental results for sensors indicate that AuGNR and GNR sensors could be the appropriate choices for NH3 detection. The experimental tests for AuGNR and GNR sensors are performed for different NH3 concentration at room temperature which showed 34 % and 12.1% response for 25 ppm NH3 respectively. Furthermore, in 25 ppm for the AuGNR sensor, the sensor shows 224 s for response time, and 178 s for recovery time for a graphene-based sensor. All the tests are carried out at room temperature.
关键词： GNRs,gas sensor,AuGNR,NH3 detection
更新于2025-09-23 15:23:52
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Theoretical Investigation on Electron Mobility in AlInGaN/InGaN Heterostructures
摘要： The dependences of electron mobility in AlInGaN/InGaN heterostructure on the barrier and channel alloy compositions and on temperature are investigated including six scattering processes: acoustic deformation potential (DP) scattering, piezoelectric field (PE) scattering, polar optical phonons (PO) scattering, dislocation impurity (DIS) scattering, interface roughness (IRF) scattering, and alloy disorder (ADO) scattering. The results show that ADO scattering is the most important scattering mechanism, and specifically channel alloy disorder gets severer than barrier alloy disorder except for InGaN channels with very low indium content (near 0) or extremely high indium mole fraction (near 1). The variations of the barrier strain, two-dimensional electron gas (2DEG) density, 2DEG mobility, and conductivity in AlInGaN/In0.04Ga0.96N heterostructure with full barrier alloy composition are summarized. The results indicate that relatively large aluminum content and small indium mole fraction are desired for higher conductivity. By comparing the temperature-dependent transport properties of Al0.83In0.13Ga0.04N/InGaN heterostructures with different InGaN compositions, we find that it is the ADO scattering and PO scattering that determine 2DEG mobility change and the mobility exhibits a weaker dependence on temperature with increasing indium mole fraction in InGaN channel.
关键词： scattering mechanisms,mobility,temperature,two-dimensional electron gas
更新于2025-09-23 15:23:52
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X-ray imaging demonstration of glass GEM detector with dynamic time-over-threshold-based readout
摘要： Large-scale detection is one of the important roles for gaseous detectors to play in high-energy physics. In many cases, energy resolving multi-channel readout is required. Recent micro-pattern gaseous detectors (MPGDs) have finer pitches or pixels; hence, large-sized detectors have thousands of readout channels. In those cases, it becomes important to reduce the scale and complexity of the readout circuit while keeping its energy resolving capability. The signal processing technique called dynamic time-over-threshold (dynamic ToT, dToT) achieves both the good conversion linearity from analog to digital signal and the compact circuit scale compared with conventional analog-to-digital-converter (ADC)-based readout. In this study, we developed and demonstrated a dToT-based readout circuit for glass gas electron multiplier (glass GEM, G-GEM). The readout circuit showed better linearity than that of normal ToT. We demonstrated the readout circuit by X-ray imaging with the charge-division scheme. The good linearity of the readout circuit enabled imaging over a 100 × 100 mm2 area with small distortion. We expect that the dToT-based readout would be a promising candidate for the future readout of large-scaled MPGDs.
关键词： Digital electronic circuits,Electronic detector readout concepts (gas, liquid),Analogue electronic circuits,Micropattern gaseous detectors (MSGC, GEM, THGEM, RETHGEM, MHSP, MICROPIC, MICROMEGAS, InGrid, etc)
更新于2025-09-23 15:23:52
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SO <sub/>2</sub> -sensing properties of NiO nanowalls synthesized by the reaction of Ni foil in NH <sub/>4</sub> OH solution
摘要： Nickel oxide (NiO) is a p-type metal-oxide semiconductor with wide-ranging applications. Recent studies have focused on the gas-sensing properties of this semiconductor. This study introduces an easy process for growing NiO nanowalls on a glass substrate using Ni foil and aqueous NH4OH. The morphology and structure of the NiO nanowalls are investigated and confirmed by field-emission scanning electron microscopy and x-ray diffraction (XRD) analyses. The gas-sensing properties of the prepared nanowalls are tested using a dynamic gas-testing system wherein the target gases are H2S, NO2, NH3 and SO2. Gas-sensing data show that the synthesized NiO nanowalls are highly responsive toward SO2. Additionally, a sensing device prepared based on the NiO nanowalls is found to be stable during measurements, exhibiting a linear variation with changes in SO2 concentration.
关键词： gas sensors,surface reactions,nanowalls,NiO
更新于2025-09-23 15:23:52
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Structural and electrical properties of copper doped In<sub>2</sub>O<sub>3</sub> nanostructures prepared by citrate gel processes
摘要： Copper doped indium oxide (In2?xCuxO3) nanostructures were prepared by a simple citrate gel process using indium nitrate and copper nitrate as precursors. The influence of the dopant concentration (x = 0, 0.03, 0.05 and 0.07) on the structural, morphological and the electrical properties of indium oxide was studied. The crystallite size and the surface roughness (root mean square roughness and the mean roughness) of the prepared samples increased as a function of the dopant concentration. However, the copper (Cu) concentration did not affect the basic host crystal structure. The prepared samples showed an n-type semiconducting behavior and a variation in the electrical parameters, which might be due to the confinement of the electronic states of the dopants to small volumes (less than 100 nm). Implication of the degenerate electron gas model to the experimental electrical data revealed the role of the different scattering centers in conduction electron scattering.
关键词： Indium oxide,Mean free path,Electron gas model,Citrate gel route
更新于2025-09-23 15:23:52
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Contact Lenses || Rigid Gas Permeable Corneal and Corneoscleral Lens Fitting
摘要： This chapter covers the fitting of rigid gas permeable (RGP) corneal and corneoscleral lenses, including materials, corneal shape, forces affecting lens fit, fluorescein patterns, fitting principles, special designs, computerized fitting, fitting routines, aftercare problems, lens care, identification of materials, ordering, prescription writing, and recording fits.
关键词： Rigid Gas Permeable,Corneoscleral Lens,Fluorescein Patterns,Materials,Fitting,Corneal Lens
更新于2025-09-23 15:23:52
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Ammonia sensing properties of two-dimensional tin disulphide/tin oxides (SnS2/SnO2-x) mixed phases
摘要： 2D-SnS2 flakes were synthesized via a wet chemical route and deposited as a thin film onto the Pt-interdigitated contacts of a ceramic substrate with aim to fabricate a conductometric sensor. The 2D-SnS2 sensing film was then annealed "in situ" under controlled conditions at different temperatures up to 400 °C. The morphological, microstructural and electrical properties of the sensing film, before and after the thermal treatment, were characterized by "in situ" techniques. SEM analysis has shown that the 2D flake morphology was maintained after thermal treatments, whereas Raman and EDX analysis have highlighted the partial/total modification of the SnS2 phase towards the SnO2. As a consequence of the formation of 2D-SnS2/SnO2-x mixed phases, a dramatic change of the electrical properties of the sensing film has been also observed. Conductometric gas sensors based on hybrid SnS2-SnO2-x nanoflakes were then obtained by simple self-annealing treatments of 2D-SnS2 film directly on the sensor substrate. The fabricated sensors were tested toward ammonia (NH3) as target gas. Results evidence that increasing the annealing temperature of the 2D-SnS2 sensitive film, the electrical resistance of the sensing layer decreases while the response towards ammonia increases, showing the maximum at an annealing treatment of 250 °C. This behaviour was explained on the basis of the morphological, microstructural and electrical modifications observed, highlighting the role of 2D-SnS2/SnO2-x mixed phases in determining the sensing properties towards ammonia.
关键词： Heterostructure,Gas sensor,NH3,2D-SnS2 flakes,Ammonia
更新于2025-09-23 15:23:52