title: A Photothermal Spectrometer for Fast and Background-Free Detection of Individual Nanoparticles in Flow.
abstract: Sensitive detection and quantification of individual plasmonic nanoparticles is critical in a range of applications in the biological, nanomaterials, and analytical sciences. Although a wide range of techniques can be applied to the analysis of immobilized particles, high-throughput analysis of nanoscale species in flow is surprisingly underdeveloped. To address this shortcoming, we present an ultrasensitive, background-free technique based on the photothermal effect and termed differential detection photothermal interferometry (DDPI). We show, both theoretically and experimentally, that DDPI can specifically extract either the phase or amplitude of a photothermal signal. We then quantitatively detect 10 and 20 nm diameter gold nanoparticles at femtomolar concentrations and at linear flow speeds of 10 mm/s. In the case of 50 nm gold particles, we operate at an even higher linear flow speed of 100 mm/s, corresponding to an analyzed volume of more than 1 nL/s. This allows quantification of particle content at attomolar to femtomolar concentrations and counting rates between 0.1 and 400 particles per second. Finally, we confirm that the signal follows the size-dependent variations predicted by Mie theory.
authors.affiliation: Institute for Chemical and Bioengineering, Department of Chemistry and Applied Biosciences, ETH Zürich , Vladimir-Prelog-Weg 1, 8093 Zürich, Switzerland.
authors.forename: Richard
authors.initials: R
authors.lastname: Maceiczyk
authors.affiliation: Department of Applied Chemistry, School of Engineering, The University of Tokyo , 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: Hisashi
authors.initials: H
authors.lastname: Shimizu
authors.affiliation: Institute for Chemical and Bioengineering, Department of Chemistry and Applied Biosciences, ETH Zürich , Vladimir-Prelog-Weg 1, 8093 Zürich, Switzerland.|Centre Suisse d'Electronique et de Microtechnique (CSEM) , Bahnhofstrasse 1, 7302 Landquart, Switzerland.
authors.forename: David
authors.identifier: 0000-0003-1914-3768
authors.initials: D
authors.lastname: Müller
authors.affiliation: Department of Applied Chemistry, School of Engineering, The University of Tokyo , 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: Takehiko
authors.initials: T
authors.lastname: Kitamori
authors.affiliation: Institute for Chemical and Bioengineering, Department of Chemistry and Applied Biosciences, ETH Zürich , Vladimir-Prelog-Weg 1, 8093 Zürich, Switzerland.
authors.forename: Andrew
authors.identifier: 0000-0003-1943-1356
authors.initials: A
authors.lastname: deMello