Surface enhanced Raman spectroscopy is a vibrational spectroscopy technique that enhances molecular Raman signals through noble metal nanostructures, commonly used in biological or chemical analysis in the fields of food, environment, and medicine. The controllable, repeatable preparation of nano periodic structures with high-density hotspots is currently the research highlights. This article introduces the method of using ion beam evaporation deposition and ultra-thin dual pass anodized aluminum oxide (AAO) template to prepare low-cost, large-area periodic nanodots array SERS substrates, and simulates the absorption rates of gold nanodots array with different diameters. The surface enhanced Raman spectroscopy characteristics of the SERS substrates were tested and analyzed using Rhodamine 6G as the probe molecule. The results showed that the SERS substrate of gold nanodots with a diameter of 260nm and a thickness of 35nm prepared on Si substrate can detect 10-7mol/L of Rhodamine 6G. The enhancement effect of the periodic structure of the gold nanodots at 1361.555 cm-1 is 22 times that of ordinary gold films of the same thickness.
To meet the requirements of high temperature resistance, fast response, and stable temperature measurement in neutral beam injection systems and other environments, this paper proposes a simple fiber optic temperature sensor packaged in a copper casing structure. Temperature can be accurately measured quickly and effectively shielded against external forces by this sensor. With the temperature range of -25 to 250°C, transient thermal response simulation and experimental testing of the sensor show that the packaged temperature sensor has a sensitivity of 11.2pm/°C, linearity of up to 0.996, and a response time t63 of 0.75s. Comparative tests demonstrate that the thermal response of the fiber optic grating sensor surpasses the packaged thermocouple sensor. Furthermore, the sensor can withstand impact from both lateral and longitudinal external forces, demonstrating excellent stability.
ABSTRACT The continuous emission of greenhouse gases leads to the sharp rise of environmental temperature. Its content and distribution also affect the atmosphere radiation, climate characteristics, stratosphere troposphere exchange (STE) and circulation in the near-tropopause region. Methane is the second most important greenhouse gas after carbon dioxide, and its concentration has strong gradients near the tropopause. Therefore, the sensitivity, accuracy of methane detection approach in extreme environment have been greatly restricted, and this has become a technical bottleneck for low-temperature and low-pressure gas detection. To address this, a novel 3-dimensional compensation model of temperature and pressure is reported based on the simulation of methane absorption characteristic. Through a detailed investigation, the simulation system and compensation model are evaluated, the detection accuracy is improved by an order of magnitude; the minimum detection limit is ~0.012ppm with integration time is 59s.
The belt conveyor serves as the main coal transport equipment in a coal mine and its safe operation is the lifeline of safety in coal mine production. However, traditionally, monitoring for ignition and for roller faults along the belt conveyor is problematic and so this paper puts forward an approach using radial grating vibration sensing technology for both belt conveyor roller vibration monitoring. This can then be used to predict the fault state in the roller and its position, using distributed optical fiber temperature measurement technology which can be used for ‘hot spot monitoring’. This enables better fire prevention along the belt conveyor, which plays a positive and effective role in better mine safety.
Built on a design developed from an advanced mathematical model, a practical fiber optic sensor, which is an analog of the familiar ‘hot-wire’ wind velocity monitor is developed, as an intrinsically-safe sensor device for coal mining monitoring applications. The underpinning optical fiber-based principle used is the shift in the center wavelength of a Fiber Bragg Grating which is cooled by the gas flowing over it and the device sensitivity found was determined to be ~1370pm per unit m/s wind velocity (in the range of 0-0.57 m/s), ~109pm per unit m/s in the range 0.57-2.26 m/s and ~33pm per unit m/s in the range of 2.26-5.66 m/s. In this paper, the factors that influence the device response time, such as the sensor probe surface heat transfer coefficient, wind (gas) velocity and pump power have been investigated in the laboratory. It was found that the greater the surface dissipation factor of the sensor, the shorter the response time, furthermore, the response time was observed to decrease as the wind velocity increased. A method of further shortening sensor response time using wind speed variation slope is proposed.
Surface Enhanced Raman Scattering (SERS) is typically observed with the substrate in a liquid medium and it has been proposed as a promising technique for detecting low levels of pollutants in liquids. The design and fabrication of an optical fibre SERS sensor based on Au nanoparticles (Au-NPs), which is self-assembly immobilized onto the end surface of an optical fibre is described. Two toxic materials, Rhodamine 6G (R6G) and crystal violet were analysed using this optical fibre SERS sensor combined with portable Raman spectrometer. Our proposed fabrication and analytical method offers a rapid, cheap and disposable trace detection capability for toxic materials in the field.
Optical humidity measurement is essential in current industry, especially in environment with adverse electromagnetic field and strong corrosion. This paper focus on the fabrication and test of a novel fiber bragg grating based humidity sensor. The sensor is fabricated by uniformly coating humidity sensitive material on fiber bragg grating. The sensing characteristic test of the sensor shows: the wavelength shift following humidity is linear; the minimum response time of the 2-layer coated sensor is 10 s with sensitive coefficient can be controlled by changing coating time; hygroscopic hysteresis of 3-layer coated sensor is 2.7`%RH. Therefore, the sensor is promising to be used to meet the quick response and in vivo measurement demand in industry.
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