Chemical sensing and imaging using fluorophore- conjugated cellulose nanocrystals Narendra Chaulagain 1 , John Garcia 1 , Navneet Kumar 1 , Harshitha Rajashekhar 1 , Xiaoyuan Liu 2 , Pawan Kumar 1 , Alkiviathes Meldrum 2 , Kazi M. Alam 1 , and Karthik Shankar 1, * 1 Department of Electrical and Computer Engineering, University of Alberta, 9211 - 116 St, Edmonton, AB T6G 1H9, Canada 2 Department of Physics, University of Alberta, 9211-116 St, Edmonton, AB T6G 1H9, Canada Received: 9 October 2022 Accepted: 21 December 2022 Ó The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2023 ABSTRACT Here, we report the use of highly fluorescent zinc phthalocyanine-conjugated cellulose nanocrystals (ZnPc@CNC) for chemical sensing and imaging appli- cations. Cellulose nanocrystals (CNCs) are crystalline nanorods synthesized through the acid hydrolysis of cellulosic resources like wood pulp, cotton fibers, carded hemp, etc. and lab-synthesized octacarboxylated zinc phthalocyanine molecules are conjugated to these CNCs forming a brightly fluorescent-conju- gated molecular aggregate (ZnPc@CNC), which was then used in both liquid suspensions and solution-processed thin films. ZnPc@CNC conjugates showed reproducible and reliable photoluminescence (PL) quenching behavior when exposed to terephthalic acid (TA) of concentration 0.2 mM to 0.8 mM. The PL sensing of TA followed modified Stern-Volmer kinetics with the Stern-Volmer constant (K app ) determined to be 147.1 M -1 . The mechanism of sensing involves the change in the electron density of the p-conjugated phthalocyanine metallo- cycle core due to the strong electronic interaction with the benzenedicarboxylic acid. This work opens the way to conjugating several other chromophores and fluorophores to CNCs for colorimetric and fluorescence-based chemical sensing using paper-like films and membranes. Likewise, highly emissive ZnPc@CNC nanocomposites were shown to behave as fluorescent staining agents on the surface of TiO 2 microrods. This technique can be used to render non-fluorescent micro- and nanomaterials emissive, enabling them to be imaged using fluores- cence microscopy. Address correspondence to E-mail: kshankar@ualberta.ca https://doi.org/10.1007/s10854-022-09724-2 J Mater Sci: Mater Electron (2023)34:538