You will be shown an abstract from a biomedical research paper. Given this abstract, your task is to extract all unique entities of the following types: ["Chemical"].

Please return the output as a JSON object of the format: {"Chemical": ["Arsenic", ...]}. The keys should be entity types and values should be lists of extracted entities belonging to the corresponding type. If you cannot find entities belonging to a specific type, the value should be [].

Only output the JSON object and do not include any additional text.

Abstract:

Enhanced Triboelectric Nanogenerators and Triboelectric Nanosensor Using Chemically Modified TiO2 Nanomaterials. Mechanical energy harvesting based on triboelectric effect has been proven to be a simple, cost-effective, and robust method for electricity generation. In this study, we developed a rationally designed triboelectric nanogenerator (TENG) by utilizing the contact electrification between a polytetrafluoroethylene (PTFE) thin film and a layer of TiO2 nanomaterial (nanowire and nanosheet) array. The as-developed TENG was systematically studied and demonstrated as a self-powered nanosensor toward catechin detection. The high sensitivity (detection limit of 5 μM) and selectivity are achieved through a strong interaction between Ti atoms of TiO2 nanomaterial and enediol group of catechin. The output voltage and current density were increased by a factor of 5.0 and 2.9, respectively, when adsorbed with catechin of a saturated concentration, because of the charge transfer from catechin to TiO2. This study demonstrates the possibility of improving the electrical output of TENG through chemical modification.
{"Chemical": ["PTFE", "polytetrafluoroethylene", "TiO2", "catechin", "Ti"]}