Fabrication of UV sensor based on electrospun composite fibers S. Anitha a,n , B. Brabu b , K.P. Rajesh a , T.S. Natarajan a a Department of Physics, Indian Institute of Technology, Madras, Chennai 600036 India b Nanotechnology Research Center, SRM University, Chennai 603203, India article info Article history: Received 28 August 2012 Accepted 1 November 2012 Available online 9 November 2012 Keywords: Electrospinning Fibers Composite materials Nanoparticles Sensors abstract A simple, low-cost and sensitive UV sensor based on electrospun composite fibers was fabricated. Three different types of (PVA/ZnO) composites were used to fabricate the device. The solution-cast film of PVA and ZnO shows lower photocurrent than the other two fiber based devices. A comparative photo- response study has revealed the high sensitiveness of the in situ derived composite fibers of PVA and ZnO under UV illumination thus making them highly suitable for the fabrication of UV detector. We believe that the coupled effect arising from the presence of PVA and uniform distribution of ZnO are responsible for the sensitivity of UV sensor. Thus we conclude that the response of UV sensor is highly dependent on the morphology of the composites and the preparation method. & 2012 Elsevier B.V. All rights reserved. 1. Introduction Detection of UV radiation have much importance in high temperature flame detection, fire alarm and environmental mon- itoring. Encouraged by this need, several UV-detectors were developed using wide-gap semiconductors such as GaN [1,2]. In comparison to GaN and SiC, ZnO has always been considered as a promising material for optical devices, due to its wide direct band gap of 3.37 eV. In addition, owing to the large exciton binding energy (  60 meV), ZnO exhibits strong emissions even at room temperature. During the past few years, extensive research has been performed in the fabrication and performance of ZnO-based UV photodetectors [3–6]. However, the technology of ZnO-based materials and photodetectors has not seen much progress. This could inspire more research efforts to address the challenges that remain, as noted below. High-quality ZnO nanostructures are obtained with reliable control of diameter, length and construction of a device via a simple method [7]. According to the results in reference, highly efficient luminescence would be possible only when the optical devices are built from high quality ZnO. Therefore, in order to fabricate high performance UV photodetectors, it is important to prepare high quality ZnO with controlled morphology. This has to be combined with maintaining a low cost of synthesis and easy affordability. UV sensors based on electrospun fibers are com- paratively simpler to fabricate than those based on ZnO nanorods, particles and films. Controlling the morphology and particle size has led to higher efficiency of exciton generation under UV irradiation and charge separation. The performance of the device also improved with increase in the surface area. Therefore, it might be possible to enhance the UV sensitivity of the device if we replace ZnO particles and films with electrospun fibers. Our earlier research on fabrication of ZnO nanoparticles in fibrous polymer matrix has proven the high optical quality of ZnO obtained, which has further elevated the interest regarding the UV sensor applications of ZnO [8]. We present here a simple, low-cost yet effective method to fabricate UV detectors with high sensitivity. The main advantages of the scheme reported here is the direct fabrication of high quality ZnO nanoparticles in PVA matrix without introduction of intrinsic defects. Further, we have demonstrated the variation of the UV sensitivity of the composite with the method of prepara- tion by making use of three different approaches to incorporate ZnO nanoparticles in the PVA matrix. 2. Materials and methods Experimental details: Zinc acetate dihydrate, poly (vinyl alco- hol) (PVA, MW¼ 25,000) were used without further purification in this experiment. ZnO nanopowder was purchased from Sigma- Aldrich. Millipore de-ionized water was used as a solvent. Three different approaches were used to prepare composites of PVA and ZnO namely, the direct dispersion method (DDM-PVA/ZnO), the in situ sol–gel method (ISM-PVA/ZnO) and the solution-casting method. PVA fibers and in situ derived composite fibrous mem- brane were prepared according to the method described in our previous report [8]. Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/matlet Materials Letters 0167-577X/$ - see front matter & 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.matlet.2012.11.005 n Corresponding author. Tel.: þ91 44 22575855; fax: þ91 44 22574852. E-mail address: nanoanitha@gmail.com (S. Anitha). Materials Letters 92 (2013) 417–420