N. Chaulagain, K.M. Alam, P. Kumar, J.C. Garcia, N. Kumar, S. Chitti, S.S. Aare, K. Shankar
University of Alberta,
Canada
Keywords: nanocrystalline cellulose, sustainable nanotechnology, construction materials, electronic materials, chemical conjugation, fluorescence
Summary:
Cellulose nanocrystals (CNCs) are rigid crystalline nanorods with typical diameters of 3-40 nm and rod lengths of 100-2000 nm [1]. CNCs are derived from natural plant fibers, are biodegradable and sustainable. They also have highly desirable properties such as a large surface area, large mechanical strength, high strength-to-weight ratio, dispersibility in hydrophilic matrices, non-toxicity, biocompatibility, etc. CNCs are being considered for a diverse array of applications that includes superadsorbents, slow-release pharmaceuticals, slow-release fertilizers, membranes, supercapacitors, reinforced concrete, drywall and electronic nanocomposites. The mass market adoption of CNCs is currently being stymied by three significant materials challenges [1]: (i) Difficulty in producing hydrophobic CNCs are that are fully dispersible in organic matrices (ii) Characterizing the internal morphology/structure of organic nanocomposites containing CNCs (due to poor contrast) and (iii) Insufficient intrinsic functionality in CNCs We demonstrate that CNCs are rendered highly photoluminescent (PL) through covalent conjugation to zinc phthalocyanine (ZnPc) molecules [2]. The resulting fluorescent CNCs are dispersible in organic solvents and were shown to perform the detection of terephthalic acid through the PL quenching mechanism [3]. ZnPc@CNC also behaved as organic memories [4]. Highly emissive ZnPc@CNC nanocomposites were shown to behave as fluorescent staining agents on the surface of TiO2 microrods [3]. CoPc conjugated CNCs exhibited long-lived charge separation and visible-light-driven photocatalytic activity [5]. Due to their 1-dimensional nanorod morphology, the incorporation of CNCs into blends with conjugated polymers resulted in highly ordered composites with tunable morphology and structure [6, 7]. In this way, functionalized CNCs behaved as structure-directing agents [6]. REFERENCES 1. A Goswami, KM Alam, P Kumar, P Kar, T Thundat, K Shankar "Mapping the surface potential, charge density and adhesion of cellulose nanocrystals using advanced scanning probe microscopy" Carbohydrate Polymers 246, 116393 (2020). 2. 5. KM Alam, P Kumar, S Gusarov, AE Kobryn, AP Kalra, S Zeng, A Goswami, T. Thundat, K. Shankar "Synthesis and characterization of zinc phthalocyanine-cellulose nanocrystal (CNC) conjugates: toward highly functional CNCs" ACS Appl. Mater. Interf. 12 (39), 43992-44006 (2020). 3. 5. N Chaulagain, J Garcia, N Kumar, H Rajashekhar, X Liu, P Kumar, A Meldrum, KM Alam, K Shankar "Chemical sensing and imaging using fluorophore-conjugated cellulose nanocrystals" J. Mater. Sci. Mater. Electron. 34 (6), 538 (2023). 4. N Chaulagain, KM Alam, P Kumar, AE Kobryn, S Gusarov, K Shankar "Zinc phthalocyanine conjugated cellulose nanocrystals for memory device applications" Nanotechnology 33 (5), 055703 (2021). 5. KM Alam et al. "Unusual electronic properties of cellulose nanocrystals conjugated to cobalt phthalocyanine: long-lived charge separation and visible-light-driven photocatalytic activity", J. Phys. Chem. C 126 (37), 15635-15650 (2022). 6. KM Alam et al. "Enhanced luminescence sensing performance and increased intrachain order in blended films of P3HT and cellulose nanocrystals", Nanotechnology 34 (20), 205703 (2023). 7. KM Alam, P Kar, UK Thakur, R Kisslinger, N Mahdi, A Mohammadpour, PA Baheti, P Kumar, K Shankar "Remarkable self-organization and unusual conductivity behavior in cellulose nanocrystal-PEDOT: PSS nanocomposites" J. Mater. Sci. Mater. Electron. 30, 1390-1399.