A Self Powered Solid-Liquid Contact Electrification Based Nanosensor for Chemically Enhanced Detection of Catechin

Abstract

The harvesting of mechanical energy based on triboelectric effect between solid-solid material and utilizing it for chemical sensing, have been proved to be simple, cost effective and robust. However, it suffers from several drawbacks such as surface instability and drift in output voltage due to several environmental factors like humidity. In this study, a self-powered triboelectric nanosensor (TENS) based on chemically enhanced solid-liquid contact electrification has been demonstrated. The TiO2 nanosheet (NS) array, grown over Ti by two-step hydrothermal process is employed as solid triboelectric material. On the other side, volatile organic solvent acetone is utilized as contact liquid to obtain higher triboelectric performance. A periodic contact separation between TiO2 NS and acetone generates a series of contact frequency independent output voltage cycles with long term stability in comparison to solid-solid contact electrification earlier. When TiO2 NS surface is forced to make a full contact with acetone, the ionization of surface groups on the TiO2 NS surface causes TiO2 NS to be fully positively charged, creating a negatively charged electrical double-layer on the contact surface of acetone to maintain the charge neutrality. As the TiO2 NS surface is moving off the acetone solution, the emerging part of its surface remains positively charged, leaving the negative electrical double-layer in the acetone solution. As a result, a potential difference is developed between TiO2 NS and acetone. Thus, it leads to transfer of electrons from ground to Ti electrode until TiO2 NS is entirely emerged from acetone, reaching an equilibrium state. The chemical modification of TiO2 NS surface with catechin promotes enhanced response voltage due to ligand to metal charge transfer complex between Ti molecules and enediol ligands of catechin, exhibiting 1 nM limit of detection(LOD) and wide linear range (1 µM to 100 µM). The output voltage has been chemically enhanced 1.59 times for 10 mM catechin concentration. Therefore, the study not only demonstrates a self-powered cost-effective nano-sensor but also explores the possibility to improve the electrical performance of solid-liquid based contact electrification through surface chemical environment engineering and through utilizing volatile organic solvents as contact liquid.