Functionalisation of nanochannels for the development of a sustainable and efficient low-grade waste heat harvester Kamil Rahme*, Anjali Ashokan, Ievgen Nedrygailov, Scott Monaghan, Rupa Ranjani, Paul Hurley, Subhajit Biswas and Justin D. Holmes School of Chemistry & Tyndall National Institute, University College Cork, Cork, Ireland AMBER Centre, Environmental Research Institute, University College Cork, Ireland *krahme@ucc.ie This research is supported by the European Union's Horizon 2020 research and innovation programme under grant agreement number 964251, and by Irish Government funding via the DAFM NXTGENWOOD research program (grant agreement: 2019PROG704). Abstract Organic ligands have been used to modify the surface charge in nanochannels formed in cellulose and anodised aluminium oxide (AAO) membranes, using a combination of oxidative, covalent and non-covalent chemistry approaches. Initial electrical and thermoelectric measurements performed on the membranes show that surface functionalisation enhances ionic thermoelectric effects in these nanochannels. 3. Covalent attachment of Polyelectrolyte onto AAO nanochannels Conclusions 2.2. Electrostatic LBL deposition of polyelectrolytes onto silanised AAO Motivation1 Methodologies and results 2.1. Aminosilanes containing two and three amino groups TEMPO/NaBr/NaClO oxidation in water at pH 10–11 oxidise the C6 primary hydroxyl groups in cellulose to carboxyl, generating negatively charged nanochannels under certain conditions.2,4 1. oxidation of cellulose produced from natural wood using TEMPO 1. https://translate-energy.eu/about/ 2. Tian Li et al., Nature Materials 2019, 18, 608. 3. Chih-Feng Huang et al. Polymer Degradation and Stability 2019, 161, 206. 4. Ioana A. Duceac et al. Materials 2022, 15, 5076. 5. Laura Pol et al., Nanomaterials 2019, 9(3), 478. References Acknowledgement FTIR and SEM/EDX, TGA analysis also confirm the presence of PEI 2 KD (~ 3 % weight loss). Nanochannels within AAO and cellulose membranes were functionalised. Surface functionalisation enhances ionic thermoelectric effects in the nanochannels. Further studies to explain this ionic thermoelectric effect enhancement, surface charge/pores densities and zeta potential data are in progress. 1200 1000 800 600 400 200 0 0 10000 20000 30000 40000 50000 Survey Scan CPS Binding Energy (eV) AAO-SiNH2-PAA-PEI AAO-Si-NH2 N 1sC 1s Si 2p 4000 3500 3000 2500 2000 1500 1000 1403 cm -1 C=O in COO - 2858 cm -1 Transmittance (%) Wavenumber (cm-1) AAO AAO-OH AAO-Si-NH-NH-NH2 AAO-Si-NH-NH-NH2-PAA-PEI-PAA 2930 cm -1 C-H stretching is sp 3 1710 cm -1 C=O in COOH 4000 3500 3000 2500 2000 1500 1000 500 80 85 90 95 100 1720 cm-1 C=O in COOH Transmittance (%) Wavenumber (cm-1) TEMPO treated Cellulose Cellulose T = 14K 4 M NaCl 2. Silanisation of AAO membranes with aminosilane ligands5 AAO-NH2 48.8 AAO 19.7 AAO-OH ~ 10 AAO AAO-OH AAO-NH-NH-NH2 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane (TAEPT) 3-(2-aminoethylamino)propyl]trimethoxysilane AAO-NH-NH-NH2 4000 3500 3000 2500 2000 1500 1000 500 60 70 80 90 100 110 1160 cm -1 C-N stretching Transmittance (%) Wavenumbers (cm-1) AAO untreated AAO-OH AAO-NH-NH-NH2 1650 cm-1 N-H bending 3300 cm -1 OH Stretching 2930 cm -1 C-H stretching in sp 3 FTIR analysis after TEMPO oxidation shows a new peak at 1720 cm-1 for C=O in carboxylic acid. 3500 3000 2500 2000 1500 1000 0 50 100 Transmittance (%) Wavenumber (cm -1) AAO-OH AAO-Si-EPOXY AAO-Si-EPOXY-PEI 2KD C-H stretching in Sp 3 96 97 98 99 100 101 100 200 300 400 500 600 700 800 AAO membrane untreated AAO-Si-EPOXY-PEI 2KD Weight loss (%) Temperature (oC) AAO-Si-EPOXY-PEI 2KD (2,2,6,6-tetramethylpiperidin-1-yl)oxidanyl