Characterization and optoelectronics investigations of mixed donor ligand directed semiconductor ZnO nanoparticles Charu Narula • Inderpreet Kaur • Navneet Kaur Received: 29 August 2014 / Accepted: 28 October 2014 Ó Springer Science+Business Media New York 2014 Abstract The optical properties of mixed donor ligand directed semiconductor ZnO nanoparticles are evaluated and imine linked receptor is used as capping agents. The ZnO nanoparticles are prepared using precipitation method. The ligand is synthesized using condensation reaction between 2-aminothiophenol and 2-thiophenecarboxalde- hyde. The formation of ligand is confirmed with spectro- scopic methods including NMR and mass spectroscopy. However, UV–Vis absorption, photoluminescence, X-ray diffraction, energy dispersive X-ray and FTIR spectros- copy techniques are used for characterization of the ligand coated ZnO nanoparticles. The capping with ligand resul- ted in the successful amendment of the surface of ZnO nanoparticles, as it particularly reduced the defects related visible emission known as green luminescence and hence resulted in improvement in the UV luminescence. The UV– Vis absorption spectra also showed blue shift in the UV region for the ligand based ZnO nanoparticles due to the effect of quantum confinement. The composite (ZnO-ligands) stability is confirmed theoretically with Density Functional Theory. 1 Introduction Nanoparticles are gaining much of the attentions because of their unique physical, chemical, electrical and optical properties in comparison to their bulk counterpart due to the exciton confinement [1–4]. The impact of excitonic effects is more prominent in Quantum Dots. A strong dif- ference is observed in optical absorption, exciton energies and electron–hole pair recombination for QDs with particle size \ *30 nm [5]. Accordingly, researchers are expecting much of the use of QDs in optoelectronic applications. The blue shift in the emission wavelength and increase in the emission efficiency can be realized in case of QDs because of carrier confinement effects and hence QDs can be used for the fabrication of light emitting diodes [6–10]. The QDs can also find its application in down conversion of ultra- violet light from inorganic LEDs [11–16]. Since the absorption of QDs can be tuned from Ultraviolet to the visible region the QDs can be used for the fabrication of sensitized solar cell [17–21]. The high quantum yield (QY), high extinction coefficient, narrow emission peaks, size tunable absorbance and emission of QDs leads to its use in Bioimaging applications [22–24]. The optical absorption, quantum efficiency, luminescence intensity and spectrum of QDs are strongly dependent on surface states [25] because the energy of the surface states lie in the band gap of the QDs [26]. Surface passivation can enhance the photostability of QDs [5]. The wurtzite semiconductor Zinc Oxide has got a lot of interest in research community because of its direct wide band gap of 3.37 eV and high exciton binding energy (60 meV) [27]. It has attracted concentrated research because of its unique properties. Zinc oxide semiconductor is blessed with several favorable properties such as high electron mobility, transparency, strong room temperature C. Narula  N. Kaur (&) Centre for Nanoscience and Nanotechnology (UIEAST), Panjab University, Chandigarh 160014, India e-mail: navneetkaur@pu.ac.in I. Kaur Biomolecular Electronics and Nanotechnology Division (BEND), Central Scientific Instruments Organization (CSIO), Chandigarh 160030, India 123 J Mater Sci: Mater Electron DOI 10.1007/s10854-014-2465-2