known that due to their high surface to volume ratio, nanostructures (with large aspect ratios) are highly fl exible in nature which is indeed an asset for 2D fi lms as they can be rolled up in the form of tabular structures or can be used for fl exible electronics applications. However, this fl exibility could also be an issue for some applications in which these structures are supposed to remain intact under exposure to certain environmental conditions, for example gas/chemical sensing or exposure to biological species, etc. For such types of applications, slightly thicker nano-and microstructured platelet-like fi lms equipped with nanoscale features from different inorganic materials, particularly from metal oxide semiconductors, which are strongly self-supported (mechanically strong enough) in nature, are more preferable and growth of such platelet materials/fi lms with relatively large thickness (≈1 µm) and desired crystallinity (perfectly crystalline) is relatively hard to achieve. For growth of such platelet like structures, the conventional thin fi lm deposition techniques would require very long time durations under controlled vacuum conditions and therefore simpler alternatives would be highly desirable.Belonging to the metal oxide II-VI semiconductor family and with a wide band gap of ≈3.37 eV, ZnO nano-and microstructures exhibit many interesting properties suitable for electronics, optoelectronics, luminescent, biomedical, and other applications. [ 14 ] Due to non-centrosymmetric hexagonalwurtzite crystal structure, ZnO nano-and microstructures exhibit piezoelectric properties which have received immense interest regarding piezotronic, and energy harvesting applications. [ 15 ] Many types of complex shaped nano-and microstructures have already been synthesized and accordingly utilized for wide range of applications. [ 16 ] Because of these excellent advantages, ZnO has been widely used in various devices such as sensors and photo detectors, [ 17,18 ] gas sensors, [ 19 ] and piezoelectric transducers, [ 20 ] etc.1D structures of ZnO, e.g., nanowires and nanorods, etc. have shown to exhibit a sensitive response to UV light. [21][22][23][24] Naturally, self-assembled interpenetrated nanorods and individual ZnO tetrapods as well as their 3D networks have been investigated in detail. The photocurrent response of highly crystalline ZnO nanowire arrays on fl exible substrates is studied under various light illumination conditions. [ 25 ] It was also observed that UV illumination can signifi cantly infl uence the piezoelectric properties. [ 26 ] The ZnO nanowires have been used to enhance solar cell performance [ 27 ] and ultrafast photosensors. [28][29][30] A large variety of different ZnO nano-and microstructures including their 3D interconnected porous networks 2D type structures from the complex nanostructure family are of signifi cant research interest because of their high surface area suitable for a wide range of potential applications spanning from thin fi lm based advanced nanoelectronic devices to ...
