Vojtěch Svatoš

In Situ Observation of Carbon Nanotube Layer Growth on Microbolometers with Substrates at Ambient Temperature

Carbon nanotubes (CNTs) have near unity infrared (IR) absorption efficiency, making them extremely attractive in IR imaging devices. Since CNT growth occurs at elevated temperatures, integration of CNTs with IR imaging devices is challenging and has not yet been achieved. Here we show a strategy for implementing CNTs as IR absorbers using differential heating of thermally-isolated microbolometer membranes in a C2H2 environment. During the process, CNTs were catalytically grown on the surface of a locally-heated membrane while the substrate was maintained at an ambient temperature. CNT growth was monitored in situ in real time using optical microscopy. During growth, we measured the intensity of light emission and the reflected light from the heated microbolometer. Our measurements of bolometer performance show that the CNT layer on the surface of the microbolometer membrane increases the IR response by a factor of (2.3 ± 0.1) (mean ± one standard deviation of the least-squares fit parameters). This work opens the door to integrating near unity IR absorption, CNT-based, IR absorbers with hybrid complementary metal-oxide-semiconductor focal plane array architectures.

Gold Nanostructured Surface for Electrochemical Sensing and Biosensing: Does Shape Matter?

ABSTRACT The construction of an electrochemical sensor based on a gold working electrode modified with gold nanostructures was achieved by galvanic deposition into an anodic alumina nanoporous template. Two approaches were investigated to fabricate the nanostructures of various sizes and shapes. First, gold deposition was performed through a thin alumina template resulting in the production of nanorods. In the second approach, alumina pores were widened to form cup-shaped nanostructures. The detailed topography of the nanostructured surfaces was characterized by scanning electron microscopy. The lengths and the diameters of the nanostructures were anticipated to have a significant influence on the surface area and thus on the capacity to promote electron-transfer reactions. This dependence was investigated by electrochemical impedance spectroscopy and cyclic voltammetry. The functionalization of electrode surface with 11-mercaptoundecanoic acid provided a basis for further bonding with analytes. A modified Randles equivalent circuit model with a constant phase element was used to interpret the impedance spectra. The interfacial properties of the modified electrodes were also evaluated by cyclic voltammetry in the presence of the Fe(CN)63−/4− redox couple as a probe. The results showed that the voltammetric behavior of the probe was influenced by surface modification. The accumulation of 11-mercaptoundecanoic acid on the nanostructured electrode surface did not result in the expected increase in charge-transfer resistance and the decreased capacitance, unlike the cup-shaped nanostructured electrode.