title: Nanomechanical coupling enables detection and imaging of 5 nm superparamagnetic particles in liquid.
abstract: We demonstrate that a force microscope operated in a bimodal mode enables the imaging and detection of superparamagnetic particles down to 5 nm. The bimodal method exploits the nanomechanical coupling of the excited modes to enhance the sensitivity of the higher mode to detect changes in material properties. The coupling requires the presence of nonlinear forces. Remarkably, bimodal operation enables us to identify changes of slowly varying forces (quasi-linear) in the presence of a stronger nonlinear force. Thus, unambiguous identification of single apoferritin (non-magnetic) and ferritin (magnetic) molecules in air and liquid is accomplished.
authors.affiliation: Instituto de Microelectrónica de Madrid, CSIC, Madrid, Spain.
authors.forename: Christian
authors.initials: C
authors.lastname: Dietz
authors.forename: Elena T
authors.initials: ET
authors.lastname: Herruzo
authors.forename: Jose R
authors.initials: JR
authors.lastname: Lozano
authors.forename: Ricardo
authors.initials: R
authors.lastname: Garcia
mesh_terms: D000818:Animals; D001052:Apoferritins / Q000648:ultrastructure; D005293:Ferritins / Q000648:ultrastructure; D006046:Gold / Q000737:chemistry; D006736:Horses; D008280:Magnetics; D053768:Metal Nanoparticles / Q000737:chemistry / Q000648:ultrastructure; D018625:Microscopy, Atomic Force / Q000379:methods*; D036103:Nanotechnology / Q000379:methods*; D010316:Particle Size; D012680:Sensitivity and Specificity
chemical_list: D006046:Gold; D005293:Ferritins; D001052:Apoferritins