Design, Fabrication, and Modification of Cost-Effective Nanostructured TiO for Solar Energy Applications - Low-cost Nanomaterials: Toward Greener and More Efficient Energy Applications - page 33

Fig. 13 a Schematic diagram of electrostatic spray and b formation of hierarchically structured
TiO 2 nanospheres by electrostatic spray. (Reprinted with permission from Ref. a, b [ 59 ].
Copyright American Chemical Society)
polymer coatings, protein films, and micro-patterns [ 234 , 235 ]. In the electrospray
process, a jet of liquid is sprayed toward a collector under a strong electric field
(Fig. 13 a). During e-spray deposition, known as induction or conduction charging,
the droplets can be charged and atomized by mechanical forces in the presence of
electric field between the solution and the depositing substrates. The electric field
provides an electric charge on the liquid surface and the charge is carried out by
the droplets detaching from the jet. The deposition efficiency of the charged
droplets is usually higher than that of the uncharged droplets, which can improve
the adhesion between the materials and substrates (Fig. 13 b) [ 59 ]. In brief, three
parameters typically determine the structures created by the electrospray method:
(1) solution conditions such as the solvents and precursors, (2) processing con-
ditions such as applied voltages, distance between the tip of the needle and col-
lector and flow rates, and (3) ambient conditions such as temperature and humidity
[ 235 , 236 ]. As a deposition technique, e-spray has many advantages, such as large
treatment areas, compatibility with various substrate geometries, and high depo-
sition rate. Moreover, electrospray devices can perform at room temperature under
atmospheric pressure, making it an energy efficient and low-cost technology [ 237 ].