Imrich Gablech

Nanostructured Gold Microelectrode Array for Ultrasensitive Detection of Heavy Metal Contamination

Availability of potable water is a problem especially in developing countries as their water sources are often contaminated biologically as well as by heavy metals. Electrochemical methods are suitable for field application to monitor heavy metal contents. Noble metal electrodes with large surface areas are the subject of intensive development as they can yield an improved signal-to-noise ratio, enhanced sensitivity, and lower limits of detection (LOD). Here, we present a nanostructured Au microelectrode array subsequently modified by selective electrodeposition in lithographically defined circles within a partially cross-linked gelatin layer. This method increased its surface area by a factor of ≈1440 in comparison with an original lithography-based prepared array. The Au surface properties can be tailored by a degree of gelatin layer cross-linking. We used this array for an ultrasensitive detection of the As3+ ions content by stripping voltammetry achieving LOD of ≈0.0212 parts per billion (signal-to-noise ratio = 3.3), 470× below the content limit recommended by the World Health Organization for potable water. These nanostructured arrays were used to detect ions of other metals such as Cr, Cd, Hg, Cu, and Sb. In combination with a portable electrochemical device, we can envision an ultrasensitive heavy metal detection system for field application to monitor heavy metal contamination.

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.