Cadmium sulfide can be templated on -DNA molecules to form an aqueous dispersion of CdS/-DNA nanowires. Subsequent addition of ethylene glycol to 50% v/v is sufficient to formulate an ink suitable for printing using piezoelectric drop-on-demand technology. Printed droplet arrays show a coffee-ring morphology of individual deposits by fluorescence and Raman microscopy, but upon increasing the number of layers of printed material by repeated printing over each droplet, the dry deposit approaches closer to a disc shape. It is also possible to print parallel tracks by reducing the droplet separation in the array until neighbouring droplets overlap before they dry. The droplets coalesce to form a strip of width roughly equal to the diameter of the droplets. Evaporation-driven capillary flow sends the nanowires to the edges of the strip and when dry they form parallel tracks of CdS/-DNA nanowire bundles. Both droplets and tracks were printed onto Pt-on-glass interdigitated microelectrodes (10 m width, 10 m gap). The current-voltage characteristics of these two-terminal devices were approximately ohmic, but with some hysteresis. The conductance increased with temperature as a simple activated process with activation energies of 0.57 ± 0.02 eV (tracks) and 0.39 ± 0.02 eV (droplets). The impedance spectra of the printed films were consistent with hopping between CdS grains.

Here, the formation of carbon nanotube (CNT)-based nanohybrids in aqueous solution is reported, where DNA-wrapped CNTs (DNA-CNTs) act as templates for the growth of PbS and CdS nanocrystals, toward the formation of PbS-DNA-CNT and CdS-DNA-CNT heterostructures. Solution-processed multiplexed photoresponsive devices are fabricated from these nanohybrids, displaying a sensitivity to a broad range of illumination wavelengths (405, 532, and 650 nm). The DNA-CNT and CdS-DNA-CNT devices show a drop in the current while PbS-DNA-CNT's current increases upon light illumination, indicating a difference in the operational mechanisms between the hybrids. Furthermore, the ON/OFF photoresponse of PbS-DNA-CNT is only 1 s as compared to 200 s for the other two nanohybrid devices. The mechanisms of the different photoresponses are investigated by comparing the performance under an inert and air atmosphere, and gate dependence device analysis and transient absorption spectroscopy measurements are also conducted. The results reveal that photoinduced oxygen desorption is responsible for the slower photoresponse by DNA-CNT and CdS-DNA-CNT, while photoinduced charge transfer dominates the much faster response of PbS-DNA-CNT devices. The strategy developed is of general applicability for the bottom-up assembly of CNT-based nanohybrid optoelectronic systems and the fabrication of solution-processable multiplexed devices.