The colloidal ZrO2 nanoparticles were hydrolytically synthesized and
characterized using x-ray diffraction and UV/Vis spectroscopy. The surface
modification of nanocrystalline particles with selected enediol ligands:
catechol (CAT), 2,3-dihydroxynaphthalene (2,3-DHN), anthrarobin (ANT)
and quercetin, was found to alter the optical properties of nanoparticles. The
formation of the inner-sphere charge-transfer (CT) complexes results in a
red shift of the semiconductor absorption onset compared to unmodified
nanocrystallites, and a decrease of effective band gap upon increase of the
electron delocalization after the inclusion of additional ring

Abazović, Nadica

Carević, Milica V.

Janković, Ivana A.

Savić, Tatjana D.

Čomor, Mirjana

Carević, Milica

Repository of the Vinča Nuclear Institute (VinaR)

     PHYSICAL CHEMISTRY 2014  12th International Conference on Fundamental and Applied Aspects of Physical Chemistry          The Conference is dedicated to the 25. Anniversary of the Society of Physical Chemists of Serbia            September 22-26, 2014  Belgrade, Serbia   II   ISBN 978-86-82475-30-9 Title: PHYSICAL CHEMISTRY 2014 (Proceedings) Editors: Ž. Čupić and S. Anić Published by: Society of Physical Chemists of Serbia, Studenski trg 12-16, 11158, Belgrade, Serbia Publisher: Society of Physical Chemists of Serbia For Publisher: S. Anić, President of Society of Physical Chemists of Serbia Printed by: “Jovan” Priting and Publishing Company; 200 Copies; Number of pages: 6+ 441; Format: B5; Printing finished in September 2014.  Text an Layout: “Jovan”  Neither this book nor any part may be reproduced or transmitted in any form or by any means, including photocopying, or by any information storage and retrieval system, without permission in writing from the publisher.  200 - Coppy priting    IV  PHYSICAL CHEMISTRY 2014  12th International Conference on  Fundamental and Applied Aspects of Physical Chemistry     Organized by The Society of Physical Chemists of Serbia  in co-operation with   Institute of Catalysis Bulgarian Academy of Sciences   Boreskov Institute of Catalysis of Siberian Branch of the Russian Academy of Sciences  Faculty of Physical Chemistry, University of Belgrade, Serbia  Institute of Chemistry Technology and Metallurgy,  University of Belgrade, Serbia  Vinča Institute, University of Belgrade, Serbia  Institute of General and Physical Chemistry, Serbia    Faculty of Pharmacy, University of Belgrade, Serbia    VInternational Organizing Committee  Chairman:  S. Anić (Serbia) Vice-chairman:  M. Gabrovska (Bulgaria)                             V. A. Sadykov  (Russia)  Members: N. Cvjetičanin (Serbia), S. N. Blagojević (Serbia), M. Daković (Serbia), T. Grozdić (Serbia), D. Jovanović (Serbia), M. Kuzmanović (Serbia), D. Marković (Serbia), J. Marković-Dimitrić (Serbia), B. Milosavljević (USA), M. Mojović (Serbia), N. Ostrovski (Serbia), I. Pašti (Serbia), M. Petković (Serbia), A. Popović-Bjelić (Serbia),  B. Simonović (Serbia), D. Stanisavljev (Serbia),  B. Šljukić (Serbia), N. Vukelić (Serbia), V. Vukojević (Sweden)  International Scientific Committee  Chairman:  Ž. Čupić (Serbia) Vice-chairmans: V. N. Parmon (Russia)                                   S. Rakovsky (Bulgaria) Members: B. Adnađević (Serbia), S. Anić (Serbia), A. Antić-Jovanović (Serbia), G. Bačić (Serbia), A. Kelarakis (Greece), R. Cervellati (Italy), V. Dondur (Serbia), Ivan Gutman (Serbia), S. D. Furrow (USA), K. Hedrih (Serbia), M. Jeremić (Serbia), A. V. Knyazev (Russia), Lj. Kolar-Anić (Serbia), V. Kuntić (Serbia), Z. Marković (Serbia),  S. Mentus (Serbia), Š. Miljanić (Serbia), M. Perić (Serbia), M. Plavšić (Serbia), D. M. F. Santos (Portugal), G. Schmitz (Belgium), I. Schreiber (Czech), P. Sevčik (Slovakia), B. C. Simionescu (Romania), N. Stepanov (Russia), D. Todorović (Serbia), M. Trtica (Serbia), V. Vasić (Serbia), D. Veselinović (Serbia)   Local Executive Committee  Chairman:              S. Blagojević Vice-chairmans:    A. Ivanović-Šašić  Members: P. Banković,  N. Bošnjaković, J. Dostanić,  A. Đerić, A. Ignjatović, A. Jović, N. Jović-Jovičić, D. Lončarević, J. Krstić, J. Maksimović, V. Marković, M. Milenković, S. Maćešić, V. Marković, B. Nedić, N. Potkonjak, D. Ranković, M. Stević, M. Žunić, M. Ristić,          PHYSICAL CHEMISTRY 2014  H-23-P   683SURFACE MODIFICATION OF ZIRCONIA NANOPARTICLES WITH SELECTED ENEDIOL LIGANDS  M. Carević, T. D. Savić, N. D. Abazović,  I. A. Janković and M. I. Čomor  University of Belgrade, Vinča Institute of Nuclear Sciences, P.O. Box 522, 11001 Belgrade, Serbia   ABSTRACT The colloidal ZrO2 nanoparticles were hydrolytically synthesized and characterized using x-ray diffraction and UV/Vis spectroscopy. The surface modification of nanocrystalline particles with selected enediol ligands: catechol (CAT), 2,3-dihydroxynaphthalene (2,3-DHN), anthrarobin (ANT) and quercetin, was found to alter the optical properties of nanoparticles. The formation of the inner-sphere charge-transfer (CT) complexes results in a red shift of the semiconductor absorption onset compared to unmodified nanocrystallites, and a decrease of effective band gap upon increase of the electron delocalization after the inclusion of additional rings.  INTRODUCTION Widespread interest in the modification of TiO2 surfaces with organic and organometallic molecules is largely motivated by the application of these materials in photocatalysis and photovoltaics [1]. Similar behavior can be expected from the other non-toxic metal oxides like ZrO2 which is the subject of this paper. In recent years, much attention has been paid to the preparation of high surface nano-zirconia, not only due to its wide application as a catalyst and catalyst support, but also for its use as an advanced material for structural engineering ceramics, oxygen sensors, fuel cells, and other interesting applications [2]. Zirconia has a large band gap, Eg = 5 eV, even larger than TiO2 (Eg = 3.2 eV) and absorbs in far UV region [3]. We hope that sensitization of ZrO2 crystals and nanoparticles with appropriately chosen molecules, enediol ligands, can lead to a significant red shift of their absorption threshold from the far UV to the visible, thus enabling and improving the absorption of the solar spectrum as well as its possible application as photocatalyst and photovoltaic material.         PHYSICAL CHEMISTRY 2014  H-23-P   684EXPERIMENTAL All chemicals used were of highest possible quality (p.a.), Milli-Q deionized water was used as a solvent. The colloidal ZrO2 dispersions were prepared by forced hydrolysis of ZrOCl2 at 75°C for 24 hours with constant steering. After hydrolysis clear dispersion was dialyzed against water until pH=5 was reached. Stoichiometric concentration of ZrO2 was ≤0.06 M dm-3. Crystal structure of the obtained zirconia was checked by using X-ray diffraction. For XRD analysis, obtained colloidal ZrO2 dispersions were dried on Si- carrier and XRD date were collected in 2 range of 10°-60°, with scanning steps of 0.05°. As can be seen (Figure 1), crystal structure of obtained material is not quite developed yet. Wide peaks and shoulders in diffractogram imply on presence of both amorphous and crystallized material. In order to confirm a formation of ZrO2 nanocrystals, obtained material was dried at 70°C, and then sintered at 600°C for 3h. XRD data of acquired powder (Inset in Fig 1.) confirmed exclusive presence of ZrO2 (mixed monoclinic and tetragonal phase). The surface modification of ZrO2 resulting in the formation of a CT complex was achieved by the addition of surface-active ligands(catechol, 2,3-dihydroxynaphthalene, anthrarobin and quercetin; structural formulas in Table 1) up to the concentrations required to cover all the surface sites. The modifications were performed in methanol and allowed to react for 24 h to ensure complete complexation. Absorption spectra of surface modified ZrO2 nanoparticles were recorded at room temperature in cells with 1 cm optical path lengths using a Thermo Scientific Evolution 600 UV/Vis spectrophotometer.  RESULTS AND DISCUSSION When ZrO2 particles are on the nanosize scale, a large fraction of the atoms that constitute the nanoparticle is located on the surface with significantly altered electrochemical properties. Among them, the existing undercoorinated defect sites are the source of novel, enhanced and selective reactivity of nanoparticles toward ligand binding. Upon binding, the new hybrid properties arise from the ligand-to-metal CT interaction due to Figure 1. X-ray diffractogram of colloidal ZrO2 dispersion. Inset: X-ray diffractogram of the same sample sintered at 600°C for 3h        PHYSICAL CHEMISTRY 2014  H-23-P   685orbital mixing between the molecular orbitals of the ligands and the conduction band orbitals of the nanoparticles.    Table 1. Ligands used for modification of ZrO2 nanoparticles, structural formulas and the effective band gaps (Eg) upon binding   ligand Structural formula Eg (eV) 1.  ZrO2 5 2. CAT OHOH3.35 3. 2,3-DHN OHOH3.44 4. ANT OHOHOH1.78 5. Quercetin 2.03   All of the ligands investigated in this work, listed in Table 1, were found to undergo binding at the surface (Fig. 2), inducing new hybrid properties of the surface modified nanoparticle colloids. These hybrid properties arise from the ligand-to-metal charge-transfer (CT) interaction. By extracting the corresponding onset energies from the absorption spectra of surface modified ZrO2 nanoparticles, the effective band gap energies (Eg= hc/λ) of CAT, 2,3-DHN, ANT and quercetin modified ZrO2 nanoparticles in methanol were calculated to be: 3.35 eV, 3.44 eV, 1.78 and 2.03 eV, respectively.  CONCLUSION All investigated ligands (CAT, 2, 3-DHN, ANT and quercetin) form inner-sphere charge-transfer complexes with ZrO2 nanoparticles (d ~4 nm). The binding of the modifier molecules to undercoordinated surface Zr atoms (defect sites) results in a significant shift in the onset of absorption to the lower energy spectral range. The lowest shift was, as expected, achieved by modification with catechol (enediol with one aromatic ring) and the highest        PHYSICAL CHEMISTRY 2014  H-23-P   686  Figure 2. Absorption spectra of bare (1) and surface modified ZrO2 nanoparticles with different ligands (0.45 mM): (2) CAT; (3) 2,3-DHN; (4) ANT, (5) quercetin. Spectra of pure modifiers are: (6)-(9), respectively.  with anthrarobin (three fused aromatic rings) and quercetin (two fused rings with one as substituent), which proves positive effect of extended electron delocalization in modification.  ACKNOWLEDGEMENT  Financial support for this study was granted by the Ministry of Education, Science and Technological Development of the Republic of Serbia (Project 172056 and 45020).  REFERENCES [1] W. Macyk, K. Szaciłowski, G. Stochel, M. Buchalska, J. Kuncewicz, P. Łabuz, Coord. Chem. Rev., 2010, 254, 2687-2701. [2] S.-F. Yin, B.-Q. Xu, Chemphyschem. 2003, 3, 277-281. [3] T. Rajh, L. X. Chen, K. Lukas, T. Liu, M. C. Thurnauer, D. M. TiedeJ. Phys. Chem. B, 2002, 106, 10543-10552. 

Surface modification of zirconia nanoparticles with selected enediol ligands

http://vinar.vin.bg.ac.rs/bitstream/id/23261/693-696(1).pdf

Surface modification of zirconia nanoparticles with selected enediol ligands

Abstract

Similar works

Full text

Available Versions

Repository of the Vinča Nuclear Institute (VinaR)