title: Reversed oxygen sensing using colloidal quantum wells towards highly emissive photoresponsive varnishes.
abstract: Colloidal quantum wells combine the advantages of size-tunable electronic properties with vast reactive surfaces that could allow one to realize highly emissive luminescent-sensing varnishes capable of detecting chemical agents through their reversible emission response, with great potential impact on life sciences, environmental monitoring, defence and aerospace engineering. Here we combine spectroelectrochemical measurements and spectroscopic studies in a controlled atmosphere to demonstrate the 'reversed oxygen-sensing' capability of CdSe colloidal quantum wells, that is, the exposure to oxygen reversibly increases their luminescence efficiency. Spectroelectrochemical experiments allow us to directly relate the sensing response to the occupancy of surface states. Magneto-optical measurements demonstrate that, under vacuum, heterostructured CdSe/CdS colloidal quantum wells stabilize in their negative trion state. The high starting emission efficiency provides a possible means to enhance the oxygen sensitivity by partially de-passivating the particle surfaces, thereby enhancing the density of unsaturated sites with a minimal cost in term of luminescence losses.
authors.affiliation: Dipartimento di Scienza dei Materiali, Università degli Studi di Milano-Bicocca, via Cozzi 55, I-20125 Milano, Italy.
authors.forename: Monica
authors.initials: M
authors.lastname: Lorenzon
authors.affiliation: 1] Istituto Italiano di Tecnologia, via Morego 30, IT-16163 Genova, Italy [2] Department of Physics, University of Genoa, via Dodecaneso 33, 16146 Genova, Italy.
authors.forename: Sotirios
authors.initials: S
authors.lastname: Christodoulou
authors.affiliation: Dipartimento di Scienza dei Materiali, Università degli Studi di Milano-Bicocca, via Cozzi 55, I-20125 Milano, Italy.
authors.forename: Gianfranco
authors.initials: G
authors.lastname: Vaccaro
authors.affiliation: Dipartimento di Scienza dei Materiali, Università degli Studi di Milano-Bicocca, via Cozzi 55, I-20125 Milano, Italy.
authors.forename: Jacopo
authors.initials: J
authors.lastname: Pedrini
authors.affiliation: Dipartimento di Scienza dei Materiali, Università degli Studi di Milano-Bicocca, via Cozzi 55, I-20125 Milano, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Meinardi
authors.affiliation: Istituto Italiano di Tecnologia, via Morego 30, IT-16163 Genova, Italy.
authors.forename: Iwan
authors.initials: I
authors.lastname: Moreels
authors.affiliation: Dipartimento di Scienza dei Materiali, Università degli Studi di Milano-Bicocca, via Cozzi 55, I-20125 Milano, Italy.
authors.forename: Sergio
authors.initials: S
authors.lastname: Brovelli