We propose a method for evaluating thermal conductivity of a single carbon nanotube (CNT) using a fluorescent temperature sensor in liquid and air. The CNT is fixed to sensors by photofabrication. The electrode for Joule-heating of the CNT is fabricated on the sensor. Thermal conductivity of the CNT is evaluated through the temperature difference between both ends of the CNT and the heat quantity input to the CNT. In this paper, we evaluated thermal conductivity of the same CNT in air and liquid. Calculated thermal conductivity of the CNT in air (667 ± 38 [W/m·K]) is higher than that of CNT in water (484 ± 72 [W/m·K]).
In this paper, we proposed long-lifetime and high-sensitive measurement using fluorescent intensity by compensation of photo-bleaching with the difference compensation for cell measurement. Photo-bleaching of fluorescence is one of the most crucial factors to cause measurement error in physiological measurement. In our approach, difference of fluorescent intensity between imaging time is compensated using single exponential function to make the difference amount uniform in each imaging time. We evaluated the dependencies of measurable time and the sensitivity by fluorescent lifetime and the decay coefficient of fluorescent lifetime using numerical simulation. From these results, the proposed method has much higher sensitivity and longer measurable time against conventional compensation method of photo-bleaching. By using the proposed method, we demonstrate the photosynthesis activity of single Synechocystis sp. PCC 6803 in the micro chamber with gas barrier layer.
We developed a novel temperature measurement and control method using temperature dependence of quantum dots (Q-dots). We used hydrogel-tool containing Q-dots for temperature measurement and control. These tools can be manipulated in a solution by optical tweezers. We used image processing to obtain color information for measuring the temperature. We calibrated the temperature using the gel-tool in YCrCb (Y: brightness, Cr: red color difference, Cb: blue color difference) color space. Y and Cr decrease monotonously with increasing temperature, whereas and Cb do not vary monotonically with temperature change. Cr is suitable for long-time temperature measurement because the Cr is robust against brightness fluctuations. This method has a sensitivity of −1.3 %/K and an accuracy of ±0.3 K. Moreover, we also demonstrated temperature control of the local environment using focused laser with temperature monitoring using the gel-tool.
Carbon nanotube (CNT) is one of the most promising materials for various applications. There are a lot of studies on mechanical and thermal properties of a single CNT in vacuum condition. However, thermal conductivity of the single CNT in liquid are not well investigated. In this paper, we proposed evaluation of thermal conductivity of a single CNT using fluorescence temperature sensor and local laser heating in liquid. The sensor containing fluorescence dye is used for fixation of CNT, indirect heating of CNT by infra-red (IR) laser, and local temperature measurement. CNT is fixed to the sensor during fabrication process. Thermal conductivity is calculated by the temperature variation of each sensor and heat quantity passing through the CNT. We demonstrated measurement of thermal conductivities of a single CNT in liquid. The average thermal conductivity of six single CNTs was 1.2xl0 3 ± 4.6xl0 2 [W/mK].
In this paper, we propose new evaluation method for thermal conductivity measurement of single carbon nanotube (CNT) in liquid with hydrogel sensor containing quantum dot (Q-dot). Measurement of thermal property of single CNT in liquid is quite difficult because escape of the heat from measurement device. Therefore, novel evaluation method using the hydrogel sensors for both thermal input and temperature sensing was proposed. We can measure the local temperature by fluorescence intensity from the sensors. This sensor is also used for thermal input by absorption of near infrared (IR) laser to Q-dots. In our proposed model, two gelsensors are adhered to both edges of the CNT. Heat is input to CNT through the gel-sensor. Heat transferred through the CNT is detected using the other sensor by measuring the temperature at the edge of the CNT. Sensitivity of the sensor is -1.1%/K and accuracy is ±0.5 K. The error of heat input is within 5%. Thermal conductivity was calculated from the proposed method. The estimated error of the thermal conductivity in our model is about 20%. We demonstrated the preliminary evaluation of the thermal conductivity of single CNT using the gel-sensors in liquid.Index Terms -Carbon nanotube, heat conductivity, hydrogel sensor, quantum dot.
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