Enhanced photoresponse characteristics of ZnO polymer nanocomposite: effect of variation of surface density of nanocrystals

Abstract

Zinc oxide (40–100 nm size) nanocrystals were successfully grown on the surface of an organic polymer (cellulose) by a low-cost solution casting method. Zinc precursor (zinc nitrate hexahydrate) concentration was varied from 25–75 mM, to synthesize several sets of ZnO-cellulose nanocomposite (ZCNC). The morphology and size of the nanocrystals were studied by a field emission scanning electron microscope and due to variation in the precursor concentration, a significant change in the surface density of the nanocrystals was observed. The maximum surface density was perceived at a precursor concentration of 50 mM. The Brunauer–Emmett–Teller (BET) surface areas of the ZCNCs were estimated by the nitrogen adsorption–desorption method, and a maximum surface area of 2.861 m2/g was observed. The structure, as well as composition of the nanocomposite, were studied by X-ray diffraction and energy dispersive X-rays analysis, respectively. The electrical properties of the composite were studied by current–voltage measurement while the photoresponse was recorded by time resolve photocurrent measurement. The photocurrent of the ZCNC sensor device increased from 6.783 × 10−8 to 4.91 × 10−6 A under UV illumination. The UV response (IUV/IDark) and sensitivity of the device were 72.38 and 7138, respectively. Also, the photocurrent rise time and decay time were 8 s and 9 s, respectively. The enhanced photoresponse with short response time observed for the ZnO-cellulose nanocomposite may lead to the fabrication of inexpensive ultraviolet sensors.