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Longtime stability of silver-based SERS substrate in the environment and (bio)environment with variable temperature and humidity
摘要： The increased involving of Surface Enhanced Raman Spectroscopy (SERS) in the analytical and bioanalytical field makes this technique commercially available. However, the growing range of available SERS substrates opens the question regarding the stability of SERS substrates during their storage, transportation, and utilization. In this paper, we present systematical study of the stability of SERS enhanced response of SERS-active silver grating under various physical and chemical loads. The silver coated periodical gratings provide excellent enhancement and reproducibility of SERS signal, achieved at the macroscale. The substrate load procedures include the temperature, humidity tests, and their combination. Since the utilization of SERS substrates often involves their interaction with various (bio)environments, the effects of physiological media were studied too. In all cases, the effects of the loads were determined from the changes of SERS effectivity and reproducibility.
关键词： SERS,Substrate,Temperature,(Bio)environment,Stability,Humidity
更新于2025-09-23 15:23:52
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Reduction and compensation of humidity measurement errors at cold temperatures using dual QCM humidity sensors based on graphene oxides
摘要： One of the difficulties in measurements of relative humidity in a variety of environments is temperature-dependence especially at cold temperatures. Here, we report on the reduction and the compensation of temperature effects on humidity measurements using dual humidity sensors based on quartz crystal microbalance (QCM). Graphene oxide film is coated on quartz crystals as a humidity sensing layer for the detection of water sorption by the change of resonance frequency. Relative humidity in a test chamber, where dual QCM humidity sensors are located, is precisely controlled using a humidity generator at the temperature range from 20 °C to ?60 °C. It is found that single QCM humidity sensors measure humidity significantly higher than reference relative humidity by the generator as temperature is lowered due to the temperature-dependent resonance of quartz crystals. In an attempt to cancel out the temperature-dependent oscillation of QCM sensors, the ratio of resonance frequencies of dual QCM humidity sensors is used. Consequently, temperature-dependent errors in humidity measurement at low temperatures are evidently reduced. For the compensation of the remaining errors in the humidity measurement by dual QCM humidity sensors, a single formula is empirically obtained. After the compensation of low temperature effects, the dual QCM humidity sensors provide the measurement capability in terms of residual errors less than 1.1%rh throughout temperatures from 20 °C to ?60 °C. This study provides a useful insight to extend the applicability of QCM-based humidity sensors to environments with cold temperatures.
关键词： Compensation,Graphene oxide,Cold temperature,Quartz crystal microbalance,Humidity measurement,Humidity sensor
更新于2025-09-23 15:23:52
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The influences of temperature, humidity, and O2 on electrical properties of graphene FETs
摘要： The influences of temperature, humidity, and O2 to the gas sensing characteristics of graphene field effect transistors (FETs) have been studied as these environmental factors are often encountered in practical gas sensing applications. Both empirical results and theoretical analyses are characterized for heated graphene FET gas sensors from room temperature to 100°C under a wide range of applied gate voltages. It is found that at a constant applied gate voltage of -20 V with respect to the gate voltage at the neutrality point, the sensitivity of the device to humidity decreases; while the sensitivity to O2 decreases first, and increases afterwards as the operation temperature increases. These phenomena are explained by using the physisorption and chemisorption models between gases and the graphene surface. Furthermore, devices operate in the hole regime (the majority carrier is hole in the prototype devices) result in lower sensitivity to humidity and O2 as compared to those results of gas sensors operating in the electron regime due to the p-type doping effects of moisture and O2. As such, this work provides good foundations for graphene-based FET gas sensors in practical application environments under the influences of ambient air, temperature, and humidity.
关键词： ambient air,gas sensor,temperature,Graphene field effect transistor,humidity,oxygen
更新于2025-09-23 15:23:52
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Microstructure and tribological properties of laser cladded self-lubricating nickel-base composite coatings containing nano-Cu and h-BN solid lubricants
摘要： In the present work, nickel-base composite powder (Ni60), nickel-base composite powder with the addition of h-BN solid lubricants (h-BN/Ni60) and nickel-base composite powder with the addition of nano-Cu encapsulated h-BN solid lubricants (nano-Cu/h-BN/Ni60) were used as raw materials to synthesize three different coatings on Q235 steels by laser cladding. Microstructures of these coatings were analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman spectroscopy. Tribological properties of these coatings were investigated at the temperatures from 25 °C to 600 °C. High temperature micro-hardness measurement was performed by Vickers micro-hardness tester. The results showed that the h-BN particles survived after laser cladding and displayed a homogeneous distribution in the nickel-base composite matrix. The encapsulation of h-BN by nano-Cu resulted in an increase of h-BN content in the coating. Although the addition of nano-Cu and h-BN led to a decrease on hardness, the nano-Cu/h-BN/Ni60 coating had the lowest friction coefficient and wear rate among the three coatings in a wide range of temperature from 25 °C to 500 °C. The mechanism of wear reduction by addition of nano-Cu encapsulated h-BN solid-lubricants was also discussed in this research.
关键词： Laser cladding,Self-lubricant coating,Steel substrate,Wear,Wide temperature range,Nickel-base composite
更新于2025-09-23 15:23:52
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Tip effect of a micro-needle in a diamond-coating external field
摘要： This study investigated the mechanism of the tip effect in an external field: that is the influence of an electric field on the tip shape, and a temperature field on the film uniformity, of a micro-needle during diamond coating. A bias field during magnetron sputtering was used to investigate the electric effect on the tip and hot-filament chemical vapor deposition (HFCVD) was used to investigate the thermal effect on the tip. The results showed that, (1) in the bias field during magnetron sputtering, the tip shape was affected by the accumulation of electric charge exerting an electric force on the tip; (2) in the temperature field of HFCVD, the film uniformity on the tip degenerated as a result of the high diffusion and evaporation of activated free radicals arising from the thermal effect; this hindered the nucleation and growth of the diamond film; (3) under the action of the external field, the internal free electrons of the micro-needle moved to preferentially occupy the tip, which has a large curvature, leading to a tip effect.
关键词： Uniformity,Electric field,Deformation,Temperature,Tip effect
更新于2025-09-23 15:23:52
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Effect of post-annealing on microstructure and piezoelectric properties of ZnO thin film for triangular shaped vibration energy harvester
摘要： In this paper, a triangular shaped piezoelectric vibration energy harvester (TS-PVEH) with zinc oxide (ZnO) thin films as the piezoelectric layer is reported. The effect of post-annealing temperature on the microstructure and piezoelectric performance of ZnO thin film deposited by magnetron sputtering method is investigated firstly. The results show that the optimum post-annealing temperature of 150 °C was the most beneficial to improve the piezoelectric properties of ZnO thin films. Four prototypes of TS-PVEH with different structure parameters are fabricated and optimized. The simulation and experiment results indicate that the height and width of the triangular structure have a significant influence on the vibration mode and the output performance of TS-PVEHs. The optimization results indicate that the third prototype has the best output performance. Its open-circuit voltage and short-circuit current are 290mV and 1.25 μA, respectively, when the vibration acceleration is 5m/s2 and the frequency is 56Hz. Moreover, it has the highest load power density of 0.035μW/cm2 when the load is 0.1MΩ.
关键词： Triangular substrate,ZnO thin film,Structure optimization,Post-annealing temperature,Vibration energy harvester
更新于2025-09-23 15:23:52
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Experimental and analytical investigation of LP01-LP11 mode interference
摘要： We introduce an analytical theory of LP01-LP11 mode interference and investigate its application in curvature measurement. Under the weakly guiding condition, an analytical formulation for predicting dip wavelength in the transmission spectrum is proposed. The applicability of the proposed formulation is further explored in terms of curvature measurement based on a few-mode multi-core fiber (FM-MCF). The mechanism of curvature response is analytically presented and verified through numerical simulation and experiments. The comparison of analytical and numerical results is found to be in good agreement when curvature varies from 0 to 1.8 m?1. Meanwhile, a good agreement between the experimental and theoretical values of dip wavelength shift is also observed. Moreover, we find that the temperature effect can be eliminated by using two cores of the FM-MCF during curvature measurement. Through experimental tests, the curvature values are accurately predicted under varying temperatures with maximum error controlled within 6.6%.
关键词： LP01-LP11 mode,Few-mode multi-core fiber (FM-MCF),Mode interference,Temperature,Curvatures sensor
更新于2025-09-23 15:23:52
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Detecting the Burns temperature in Na <sub/>0.5</sub> Bi <sub/>0.5</sub> TiO <sub/>3</sub> -xBaTiO <sub/>3</sub> lead-free relaxor ferroelectrics by means of acoustic emission
摘要： Na0.5Bi0.5TiO3-xBaTiO3 ceramics samples (0 < x < 0.8) were studied by means of an acoustic emission method. The characteristic temperatures such as the Burns temperature, TB, the transition to paraelectric phase, Tp, the temperature maximum of the dielectric constant, Tm, and the intermediate temperature, T ? were detected and their dependences on x were plotted. Based on the comparison of the obtained data with the previously published ones, it is shown that the Burns temperature, TB, cannot be reliably determined by the deviation of the reverse dielectric constant, 1/ε(cid:3), from a straight line.
关键词： phase transitions,relaxor ferroelectrics,Na0.5Bi0.5TiO3-xBaTiO3,Burns temperature,acoustic emission
更新于2025-09-23 15:23:52
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Temperature-dependent characterizations on parasitic capacitance of tapered through silicon via (T-TSV)
摘要： With increasing integration density of three-dimensional ICs, temperature is one of the major concern of circuit design, which influences the performance and reliability. In this paper, the parasitic capacitance of tapered TSV (T-TSV) with respect of thermal properties is studied. The concept of the Temperature Coefficient of Capacitance (TCC) is proposed to model the sensitive of TSV capacitance to temperature. It is found that TSV capacitance is sensitive to temperature under high frequency application, and the MOS capacitance variation is the main reason for the change of TSV capacitance and the TCC increases with elevated temperature. Furthermore, the affections of TSV dimensions on TCC are discussed. It is shown that the TCC increases gradually as the TSV radius increases, while the thickness of dielectric layer is the opposite. The cylinder TSV is less thermal sensitive than tapered TSV. This paper provides basis for TSV design considering the temperature effect.
关键词： tapered through silicon via (T-TSV),parasitic capacitance,temperature effect,three-dimensional ICs (3D ICs)
更新于2025-09-23 15:23:52
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Graphene-Augmented Polymer Stabilization: Drastically Reduced and Temperature-Independent Threshold and Improved Contrast Liquid Crystal Device
摘要： Polymers reinforced with nano?llers, especially graphene in recent times, have continued to attract attention to realize novel materials that are cheap and also have better properties. At a di?erent level, encapsulating liquid crystals (LCs) in polymer networks not only adds mechanical strength, but could also result in device-based refractive index mismatch. Here, we describe a novel strategy combining the best of both these concepts to create graphene-incorporated polymer-stabilized LC (PSLC) devices. The presence of graphene associated with the virtual surface of the polymer network besides introducing distinct morphological changes to the polymer architecture as seen by electron microscopy brings out several advantages for the PSLC characteristics, which include 7-fold lowered critical voltage, its temperature invariance, and enhanced contrast ratio between ?eld-o? scattering/?eld-on transparent states. The results bring to fore the importance of working at very-dilute-concentration limits of the ?ller nanoparticles in augmenting the desired properties. These observations open up a new vista for polymer?graphene composites in the area of device engineering, including substrate-free smart windows.
关键词： temperature invariance,graphene,electro-optic properties,threshold voltage,polymer-stabilized liquid crystals
更新于2025-09-23 15:23:52