title: Photoswitchable NIR-Emitting Gold Nanoparticles.
abstract: Photo-switching of the NIR emission of gold nanoparticles (GNP) upon photo-isomerization of azobenzene ligands, bound to the surface, is demonstrated. Photophysical results confirm the occurrence of an excitation energy transfer process from the ligands to the GNP that produces sensitized NIR emission. Because of this process, the excitation efficiency of the gold core, upon excitation of the ligands, is much higher for the trans form than for the cis one, and t→c photo-isomerization causes a relevant decrease of the GNP NIR emission. As a consequence, photo-isomerization can be monitored by ratiometric detection of the NIR emission upon dual excitation. The photo-isomerization process was followed in real-time through the simultaneous detection of absorbance and luminescence changes using a dedicated setup. Surprisingly, the photo-isomerization rate of the ligands, bound to the GNP surface, was the same as measured for the chromophores in solution. This outcome demonstrated that excitation energy transfer to gold assists photo-isomerization, rather than competing with it. These results pave the road to the development of new, NIR-emitting, stimuli-responsive nanomaterials for theranostics.
authors: Department of Chemistry "G. Ciamician", University of Bologna, Via Selmi 2, 40126, Bologna, Italy.
authors: Sara
authors: S
authors: Bonacchi
authors: Department of Chemistry "G. Ciamician", University of Bologna, Via Selmi 2, 40126, Bologna, Italy.
authors: Andrea
authors: A
authors: Cantelli
authors: Department of Chemistry "G. Ciamician", University of Bologna, Via Selmi 2, 40126, Bologna, Italy.
authors: Giulia
authors: G
authors: Battistelli
authors: Department of Chemistry "G. Ciamician", University of Bologna, Via Selmi 2, 40126, Bologna, Italy.
authors: Gloria
authors: G
authors: Guidetti
authors: Department of Chemistry "G. Ciamician", University of Bologna, Via Selmi 2, 40126, Bologna, Italy.
authors: Matteo
authors: M
authors: Calvaresi
authors: Department of Chemistry "G. Ciamician", University of Bologna, Via Selmi 2, 40126, Bologna, Italy.
authors: Jeannette
authors: J
authors: Manzi
authors: Department of Chemical Sciences, Università degli Studi di Padova, Italy.
authors: Luca
authors: L
authors: Gabrielli
authors: Department of Chemical Sciences, Università degli Studi di Padova, Italy.
authors: Federico
authors: F
authors: Ramadori
authors: Department of Chemical Sciences, Università degli Studi di Padova, Italy.
authors: Alessandro
authors: A
authors: Gambarin
authors: Department of Chemical Sciences, Università degli Studi di Padova, Italy.
authors: Fabrizio
authors: 0000-0003-0786-0364
authors: F
authors: Mancin
authors: Department of Chemistry "G. Ciamician", University of Bologna, Via Selmi 2, 40126, Bologna, Italy. marco.montalti2@unibo.it.
authors: Marco
authors: 0000-0001-6227-0899
authors: M
authors: Montalti
keywords: gold; luminescence; nanoparticles; near infrared; stimuli-responsive compounds