Distance measurements in Au nanoparticles functionalized with nitroxide radicals and Gd super(3+)-DTPA chelate complexes

• Published in: Physical chemistry chemical physics : PCCP Vol. 14; no. 30; pp. 10732 - 10746
• Main Authors: Yulikov, Maxim, Lueders, Petra, Farooq Warsi, Muhammad, Chechik, Victor, Jeschke, Gunnar
• Format: Journal Article
• Language: English
• Published: 01.07.2012
• Subjects: Approximation; Deer; Gold; Mathematical analysis; Nanoparticles; Radicals; Systematic errors; Tags
• DOI: 10.1039/c2cp40282c
• ISSN: 1463-9076

Nanosized gold particles were functionalised with two types of paramagnetic surface tags, one having a nitroxide radical and the other one carrying a DTPA complex loaded with Gd super(3+). Selective measurements of nitroxide-nitroxide, Gd super(3+)-nitroxide and Gd super(3+)-Gd super(3+) distances were performed on this system and information on the distance distribution in the three types of spin pairs was obtained. A numerical analysis of the dipolar frequency distributions is presented for Gd super(3+) centres with moderate magnitudes of zero-field splitting, in the range of detection frequencies and resonance fields where the high-field approximation is only roughly valid. The dipolar frequency analysis confirms the applicability of DEER for distance measurements in such complexes and gives an estimate for the magnitudes of possible systematic errors due to the non-ideality of the measurement of the dipole-dipole interaction.