Nanostructured thermoelectric semiconductors represent a promising new direction that can further increase energy conversion efficiency, which requires the realization of thermoelectric nanocrystals with size comparable to their de Broglie wavelength while maintaining a high electrical conductivity. Here, we demonstrate a new facile process to grow self-assembled Sb2Te3 nanoparticles with controlled particle size and enhanced thermoelectric properties by using a catalyst-free vapor transport growth technique. The samples show much more enhanced Seebeck coefficients than that of bulk Sb2Te3 with similar charge carrier concentration. Meanwhile, the thermal conductivity measurements with pulse photothermal reflectance suggest that the these Sb2Te3 nanoparticle films show much reduced thermal conductivity as compared to that of bulk Sb2Te3. The discussed approach is promising for realizing new types of highly efficient thermoelectric semiconductors.
A two-dimensional (2D) spectral SPR sensor based on a polarization control scheme is reported in this paper. The polarization control configuration converts the phase difference between p- and s- polarization occurring at surface plasmon resonance (SPR) into corresponding color responses in spectral SPR images. A sensor resolution of 2.7 x 10(-6) RIU has been demonstrated, which corresponds to more than one order of magnitude resolution improvement (26 times) comparing to existing 2D spectral SPR sensors. Multiplex array detection has also been demonstrated with the spectral SPR imaging sensor. In a 8 x 4 sensor array, 32 samples with different refractive index values were monitored simultaneously. Detection on bovine serum albumin (BSA) antigen-antibody binding further demonstrated the multiplex detection capability of the 2D spectral SPR sensor for bio-molecular interactions. The detection limit is found to be 21 ng/ml, which is 36 times better than the detection limit previously reported by phase imaging SPR sensors. In light of the advantages of high sensitivity, 2D multiplex detection and real-time response, the spectral SPR imaging sensor can find promising applications in rapid, high throughput, non-labeling and multiplex detection of protein array for proteomics studies, biomarker screening, disease prognosis, and drug discovery.
We explore monitoring the death process of individual red blood cells (RBC) quantitatively by using thermal lens (TL) response. TL response is a noninvasive excitation/probe technique that reflects photothermal parameters (e.g., absorption, thermal diffusivity, size, etc.). Since these parameters of cells change significantly during certain biological processes, real-time TL response was performed to monitor RBC death process when incubated with ionomycin. Theoretical model developed was applied to curve-fit the TL response for extracting thermal diffusivity and size of cells. Thermal diffusivity of dying RBC is found increased by 1.7 times in comparison with healthy cell.
Red blood cells (RBCs) have been found to undergo "programmed cell death," or eryptosis, and understanding this process can provide more information about apoptosis of nucleated cells. Photothermal (PT) response, a label-free photothermal noninvasive technique, is proposed as a tool to monitor the cell death process of living human RBCs upon glucose depletion. Since the physiological status of the dying cells is highly sensitive to photothermal parameters (e.g., thermal diffusivity, absorption, etc.), we applied linear PT response to continuously monitor the death mechanism of RBC when depleted of glucose. The kinetics of the assay where the cell's PT response transforms from linear to nonlinear regime is reported. In addition, quantitative monitoring was performed by extracting the relevant photothermal parameters from the PT response. Twofold increases in thermal diffusivity and size reduction were found in the linear PT response during cell death. Our results reveal that photothermal parameters change earlier than phosphatidylserine externalization (used for fluorescent studies), allowing us to detect the initial stage of eryptosis in a quantitative manner. Hence, the proposed tool, in addition to detection of eryptosis earlier than fluorescence, could also reveal physiological status of the cells through quantitative photothermal parameter extraction.
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