ITO electrodes allow optical observation as it has good optical transmission

[29]. Polystyrene nanospheres, 360 nm in diameter, were electrosprayed targeting these patterned electrode areas. The main parameters that were explored in the experiments were the value of applied voltage, the distance from the needle to the substrate, the solution concentration, the solution conductivity, and the deposition time. The first efforts were devoted to finding suitable experimental conditions to get a stable Taylor cone at the tip of the needle. This involved changing the distance from the needle to the substrate and changing the bias conditions. We found that a Taylor cone was created when the distance was typically between 10 to 15 cm and the applied voltage difference was between 7,500 and 14,000 V. Differences in the deposition results were also found when the substrate was grounded rather than negatively biased. Our best E7080 results were obtained

when −1,000 V was applied to the substrate and +9,000 V was applied to the needle. Once the conditions for Taylor cone creation were CP673451 found, the effects of the solution pumping rate, solution concentration, and solution conductivity were explored. No effects on the order of the deposited layers were found by just changing the solution concentration. Our best results were found for 350-μS solution conductivity and 2.2-ml/h pumping rate, provided the voltage conditions were as described above, +9,000 V at the needle and −1,000 V at

the substrate. For these conditions, the deposited film was composed of tens of ordered layers. Additionally, increasing the conductivity to the range of 4 mS by adding formic acid to the solution and decreasing the concentration of nanospheres tend to produce smaller droplets and layers of scattered nanospheres. In our experience, to get ordered layers, some liquid of the aerosol is required at the surface of the substrate and, once the conditions to get a Taylor cone are satisfied, only the pumping rate and the solution conductivity seem to play an important role and not the solution concentration. Ketotifen A summary of some of the experimental conditions we have explored is shown in Table 1. Only the conditions ON-01910 cost leading to a Taylor cone formation are shown. Table 1 List of the most relevant experimental conditions in the electrospray deposition of 360-nm polystyrene nanospheres Distance (cm) Needle’s voltage (V) Sample’s voltage (V) Deposition rate (ml/h) Conductivity (μS) Dissolution Qualitative assessment 10 10,000 −2,350 0.41 8.35 50:50 isopropanol/water nanopolystyrene Few dispersed nanospheres 10 7,500 −2,500 0.74 8.35 50:50 isopropanol/water nanopolystyrene Few dispersed nanospheres 10 14,000 0 1.3 350 Water nanopolystyrene Few dispersed nanospheres 14 14,000 0 0.3 350 Water nanopolystyrene Few dispersed nanospheres 14,5 11,570 0 2 350 Water nanopolystyrene Lots of dispersed nanospheres 14,5 9,000 −1,000 0.