Journal of Nanoparticle Research

, Volume 13, Issue 7, pp 2829–2841 | Cite as

Controlled surface functionalization of silica-coated magnetic nanoparticles with terminal amino and carboxyl groups

Research paper


General and versatile methods for the functionalization of superparamagnetic, silica-coated, maghemite nanoparticles by surface amino and/or carboxyl groups have been established. The nanoparticles were synthesized using co-precipitation from aqueous solutions and coated with a thin layer of silica using the hydrolysis and condensation of tetraethoxysilane (TEOS). For the amino functionalization, 3-(2-aminoethylamino)propylmethyldimethoxysilane (APMS) was grafted onto the nanoparticle surfaces in their aqueous suspensions. The grafting process was followed by measurements of the ζ-potential and a determination of the concentration of the surface amino groups with conductometric titrations. The surface concentration of the amino groups could be varied by increasing the amount of APMS in the grafting process up to approximately 2.3 –NH2 groups per nm2. The carboxyl functionalization was obtained in two ways: (i) by a ring-opening linker elongation reaction of the surface amines at the functionalized nanoparticles with succinic anhydride (SA) in non-aqueous medium, and (ii) by reacting the APMS and SA first, followed by grafting of the carboxyl-terminated reagent onto the nanoparticle surfaces. Using the first method, the SA only reacted with the terminal primary amino groups (–NH2) of the surface-grafted APMS molecules. Infra-red spectroscopy (ATR FTIR) and mass spectrometry (HRMS) showed that the second method enables the bonding of up to two SA molecules per one APMS molecule, since the SA reacted with both the primary (–NH2) and secondary amino (–NH–) groups of the APMS molecule. When using both methods, the ratio between the surface amino and carboxyl groups can be controlled.


Surface functionalization Magnetic nanoparticles Silanes Amino functionalization Carboxyl functionalization Coatings 



The support of the Ministry of Higher Education, Science and Technology of the Republic of Slovenia within the National Research Program is gratefully acknowledged. The authors also thank Dr Anamarija Zega from the University of Ljubljana for the ATR-FTIR measurements and Dr Bogdan Kralj from the Centre of Excellence for Environmental Technologies for the MS analyses.


  1. Banarjee SS, Chen D-H (2009) Cyclodextrin-conjugated nanocarrier for magnetically guided delivery of hydrophobic drugs. J Nanopart Res 11:2071–2078. doi: 10.1007/s11051-008-9572-z CrossRefGoogle Scholar
  2. Bucak S, Jones DA, Laibinis PE, Hatton TA (2003) Protein separations using colloidal magnetic nanoparticles. Biotechnol Prog 19:477–484. doi: 10.1021/bp0200853 CrossRefGoogle Scholar
  3. Čampelj S, Makovec D, Drofenik M (2008) Preparation and properties of water-based magnetic fluids. J Phys Condens Matter 20:204101. doi: 10.1088/0953-8984/20/20/204101 CrossRefGoogle Scholar
  4. Čampelj S, Makovec D, Drofenik M (2009) Functionalization of magnetic nanoparticles with 3-aminopropyl silane. J Magn Magn Mater 321:1346–1350. doi: 10.1016/j.jmmm.2009.02.036 CrossRefGoogle Scholar
  5. Carroll MRJ, Woodward RC, House MJ, Teoh WY, Amal R, Hanley TL, Pierre TGS (2010) Experimental validation of proton transverse relaxivity models for superparamagnetic MRI contrast agents. Nanotechnology 21:035103. doi: 10.1088/0957-4484/21/3/035103 CrossRefGoogle Scholar
  6. Chou CM, Lien H-L (2010) Dendrimer-conjugated magnetic nanoparticles for removal of zinc(II) from aqueous solutions. J Nanopart Res. doi: 10.1007/s11051-010-9967-5
  7. Cutler P (2003) Protein arrays: the current state-of-the-art. Proteomics 3:3–18. doi: 10.1002/pmic.200390007 CrossRefGoogle Scholar
  8. Dutta RK, Sharma PK, Pandey AC (2010) Design and surface modification of potential luminomagnetic nanocarriers for biomedical applications. J Nanopart Res 12:1211–1219. doi: 10.1007/s11051-009-9801-0 CrossRefGoogle Scholar
  9. Hergt R, Dutz S, Zeisberger M (2010) Validity limits of the Néel relaxation model of magnetic nanoparticles for hyperthermia. Nanotechnology 21:015706. doi: 10.1088/0957-4484/21/1/015706 CrossRefGoogle Scholar
  10. Iler RK (1979) The chemistry of silica. Wiley, New YorkGoogle Scholar
  11. Karumanchi RSMS, Doddamane SN, Sampangi C, Todd PW (2002) Field-assisted extraction of cells, particles and macromolecules. Trends Biotehnol 20:72–78. doi: 10.1016/S0167-7799(01)01847-9 CrossRefGoogle Scholar
  12. Kralj S, Makovec D, Čampelj S, Drofenik M (2010) Producing ultra-thin silica coatings on iron-oxide nanoparticles to improve their surface reactivity. J Magn Magn Mater 322:1847–1853. doi: 10.1016/j.jmmm.2009.12.038 CrossRefGoogle Scholar
  13. Lattuada M, Hatton TA (2007) Functionalization of monodisperse magnetic nanoparticles. Langmuir 23:2158–2168. doi: 10.1021/la062092x CrossRefGoogle Scholar
  14. Lee YS, Mrksich M (2002) Protein chips: from concept to practice. Trends Biotechnol 20:14–18. doi: 10.1016/S1471-1931(02)00200-8 CrossRefGoogle Scholar
  15. Levy L, Sahoo Y, Kim K, Bergey EJ, Prasad PN (2002) Nanochemistry: synthesis and characterization of multifunctional nanoclinics for biological applications. Chem Mater 14:3715–3721. doi: 10.1021/cm0203013 CrossRefGoogle Scholar
  16. Mahalingam V, Onclin S, Peter M, Ravoo BJ, Huskens J, Rein-Houdt DB (2004) Directed self-assembly of functionalized silica nanoparticles on molecular printboards through multivalent supramolecular interactions. Langmuir 20:11756–11762. doi: 10.1021/la047982w CrossRefGoogle Scholar
  17. Makovec D, Košak A, Žnidaršič A, Drofenik M (2005) The synthesis of spinel-ferrite nanoparticles using precipitation in microemulsions for ferrofluid applications. J Magn Magn Mater 289:32–35. doi: 10.1016/j.jmmm.2004.11.010 CrossRefGoogle Scholar
  18. Masuda Y, Seo WS, Koumoto K (2001) Two-dimensional arrangement of fine silica spheres on self-assembled monolayers. Thin Solid Films 382:183–189. doi: 10.1016/S0040-6090(00)01691-6 CrossRefGoogle Scholar
  19. Moon JH, Shin JW, Kim SY, Park JW (1996) Formation of uniform aminosilane thin layers: an imine formation to measure relative surface density of the amine group. Langmuir 12:4621–4624. doi: 10.1021/la9604339 CrossRefGoogle Scholar
  20. Phelan ML, Nock S (2003) Generation of bioreagents for protein chips. Proteomics 3:2123–2134. doi: 10.1002/pmic.200300596 CrossRefGoogle Scholar
  21. Qhobosheane M, Santra S, Zhang P, Tan W (2001) Biochemically functionalized silica nanoparticles. Analyst 126:1274–1278. doi: 10.1039/b101489g CrossRefGoogle Scholar
  22. Saiyed ZM, Telang SD, Ramchand CN (2003) Application of magnetic techniques in the field of drug discovery and biomedicine. Biomagn Res Technol 1:2. doi: 10.1186/1477-044X-1-2 CrossRefGoogle Scholar
  23. Schiestel T, Brunner H, Tovar GEM (2004) Controlled surface functionalization of silica nanospheres by covalent conjugation reactions and preparation of high density streptavidin nanoparticles. J Nanosci Nanotechnol 4:504–511. doi: 10.1166/jnn.2004.079 CrossRefGoogle Scholar
  24. Socrates G (1994) Infrared characteristic group frequencies. Wiley, New YorkGoogle Scholar
  25. Tamer U, Gündogdu Y, Boyaci IH, Pekmez K (2010) Synthesis of magnetic core–shell Fe3O4–Au nanoparticle for biomolecule immobilization and detection. J Nanopart Res 12:1187–1196. doi: 10.1007/s11051-009-9749-0 CrossRefGoogle Scholar
  26. van Ewijk GA, Vroege GJ, Philipse AP (1999) Convenient preparation methods for magnetic colloids. J Magn Magn Mater 201:31–33. doi: 10.1016/S0304-8853(99)00080-3 CrossRefGoogle Scholar
  27. Weissleder R, Kelly K, Sun EY, Shtatland T, Josephson L (2005) Cell-specific targeting of nanoparticles by multivalent attachment of small molecules. Nat Biotechnol 23:1418–1423. doi: 10.1038/nbt1159 CrossRefGoogle Scholar
  28. Wu SH-Y, Tseng C-L, Lin F-H (2010) A newly developed Fe-doped calcium sulfide nanoparticles with magnetic property for cancer hyperthermia. J Nanopart Res 12:1173–1185. doi: 10.1007/s11051-009-9734-7 CrossRefGoogle Scholar
  29. Yamaura M, Camilo RL, Sampaio LC, Macedo MA, Nakamura M, Toma HE (2004) Preparation and characterization of (3-aminopropyl)triethoxysilane-coated magnetite nanoparticles. J Magn Magn Mater 279:210–217. doi: 10.1016/j.jmmm.2004.01.094 CrossRefGoogle Scholar
  30. Yang J, Lim E-K, Lee E-S, Suh J-S, Haam S, Huh Y-M (2010) Magnetoplex based on MnFe2O4 nanocrystals for magnetic labeling and MR imaging of human mesenchymal stem cells. J Nanopart Res 12:1275–1283. doi: 10.1007/s11051-009-9837-1 CrossRefGoogle Scholar
  31. Yoshinaga K, Nakashima F, Nishi T (1999) Polymer modification of colloidal particles by spontaneous polymerization of surface active monomers. Colloid Polym Sci 277:136–144. doi: 10.1007/s003960050378 CrossRefGoogle Scholar
  32. Zhang M, Cushing BL, O’Connor CJ (2008) Synthesis and characterization of monodisperse ultra-thin silica-coated magnetic nanoparticles. Nanotechnology 19:085601. doi: 10.1088/0957-4484/19/8/085601 CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media B.V. 2010

Authors and Affiliations

  1. 1.Jožef Stefan InstituteLjubljanaSlovenia
  2. 2.Faculty for Chemistry and Chemical EngineeringUniversity of MariborMariborSlovenia

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