Surface morphology and optical properties of PVA/PbS nanoparticles Talaat M. Hammad a,n , Jamil K. Salem b , S. Kuhn c , Nadia M. Abu Shanab b , R. Hempelmann c a Physics Department, Faculty of Science, Al-Azhar University, P.O. Box 1277 ,Gaza, Palestine b Chemistry Department, Faculty of Science, Al-Azhar University, P.O. Box 1277, Gaza, Palestine c Department of Physical Chemistry, Saarland University, 66123 Saarbrucken, Germany article info Article history: Received 29 January 2014 Received in revised form 10 July 2014 Accepted 11 July 2014 Available online 9 August 2014 Keywords: Nanoparticles PbS Photoluminescence enhancement Morphology PVA abstract PVA capped lead sulfide (PbS) nanoparticles were successfully synthesized by the simple wet chemical method. The synthesized product has been characterized by powder X-ray diffraction (XRD), UV–vis spectrophotometry, FTIR spectroscopy, scanning electron microscopy (SEM), transmission electron Microscopy (TEM), energy dispersive X-ray spectroscopy (EDX) and photoluminescence studies. The size of the PVA capped PbS nanoparticles was determined From XRD and it is found that the size of the particles of the order of 42–5 nm. FTIR and EDX analyses are used to identify the presence of organic molecules and elements in the synthesized PbS nanoparticles. Significant “blue-shift” from bulk material was observed on the PbS nanoparticles using UV–vis spectra. A 10-fold increase in photoluminescence intensity is reached at 4 g PVA addition. & 2014 Elsevier B.V. All rights reserved. 1. Introduction Lead sulfide is a good IV–VI group semiconductor, which has attracted considerable attention due to its special small direct band gap (0.41 eV) and large excitonic Bohr radius of 18 nm [1,2]. PbS has been widely used in many fields such as Pb 2 þ ion selective sensor, IR detectors, solar absorber and photography [3–5]. Nano- particles of lead sulfide have been synthesized recently by differ- ent chemical methods with controlled particle size distribution [6–9]. During wet chemical synthesis of nanoparticles, organic stabilizers are normally used to prevent them from aggregation by capping their surfaces. Moreover, the introduction of stabilizers influences on the chemical properties as well as the physical properties of semiconductor materials, from stability, solubility and light emission. Capping agents with strong binding molecule form dense layer on the particle surface that stabilizes nanopar- ticles better, while weak binding molecule results to fast particle growth leading to large nanoparticles size and aggregation [10]. Therefore, the choice of a suitable capping agent, the dynamic of binding and unbinding, and its concentration becomes the pre- requisite for particle size regime, stabilization against aggregation and high quantum yield during synthesis of nanoparticles. Proper- ties of PVA (polyvinyl alcohol) like the transparency over the whole visible spectrum, good adhesion to hydrophilic surfaces, formation of oxygen resistant films and water soluble makes it a good choice for the fabrication of optical devices and colloidal stabilizer [11]. Several approaches have been made to prepare various types of PbS Nanostructures using surface passivating ligands [12,13]. Zhou et al. [14] have prepared 100 nm PbS truncated nanocubes and nanocubes by using cetyltrimethyl ammonium bromide and polyvinyl pyrrolidone (PVP) as surface passivating agents. PbS nanocubes with the size of 50 nm–80 nm have been synthesized using PVP and glycerol by Dong et al. [15]. However, the size of PbS nanocubes was too large (50–100 nm) and thus further size reduction is required to observe the quantum confinement effect. Rong et al. [16] prepared monodispersed PVP - capped ZnS and CdS particles by the microwave irradiation method which were found to be under quantum regime. The particle size was found to increase as a function of time. Yang et al. [17] observed that microwave irradiation time has no significant influence on the size of ZnS nanoparticles. Intensity of PL emission reaches its maximum and then decreases with prolonging the microwave irradiation time. Luminescent centers of the doped metal- lic ions are not formed in ZnS nanoparticles. YoungHong Ni et al. [18] prepared ZnS nanoparticles with high yields of about 95% by micro- wave irradiation in a heterogeneous system, ethylene glycol as the medium, zinc acetate dehydrate and sodium sulfide as the starting materials. Yao, et al. [19] have synthesized ZnS nanospheres under natural light at room temperature using sodium thiosulfate and zinc nitrate hexahydrate as initial materials. The PL enhancement approach for the PbS nanoparticles covered with a surface modifying agent has not been systematically discussed in the literature [20–22], especially Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/jlumin Journal of Luminescence http://dx.doi.org/10.1016/j.jlumin.2014.07.009 0022-2313/& 2014 Elsevier B.V. All rights reserved. n Corresponding author. Tel.: þ9722876672; fax: þ9722832180. E-mail address: talaathammad@gmail.com (T.M. Hammad). Journal of Luminescence 157 (2015) 88–92