Investigation of polypyrrole deposition time on QCM sensitivity as aspergillus niger spore sensor

• Polypyrrole deposited by vacuum thermal evaporation produces a vertical platelet structure. • The width and height dimensions of platelet structure are controlled by deposition time. • The width and height dimensions determine surface porosity and wettability are controlled by deposition time. • Surface porosity and wettability enhanced the sensitivity of aspergillus niger spore. The receptor layer on Quartz Crystal Microbalance (QCM) is vital in capturing analytes. We investigated how the morphology of the layer produced from polypyrrole (PPy) evaporated by vacuum thermal evaporator technique with varying deposition time on the porosity, wettability, and sensitivity of QCM as a sensor for Aspergillus niger ( A. niger ) spores. The morphology of the layer was observed using a Field Emission Scanning Electron Microscope (FESEM), porosity was taken from the results of the layer morphology analysis, wettability was taken from the measurement of the water contact angle with the layer surface, and sensitivity was obtained from the average gradient of the curve during changes in measurement frequency. The results show significant changes in these parameters with increasing deposition time. The morphology of the layer changes and the dimensions of the width and height of the platelets increase so that larger empty spaces between the platelets are created. Porosity increases from 56.43 to 71.11 % along with increasing deposition time from 10 to 50 s, and wettability also increases, which is marked by a decrease in the water contact angle from 51.49 to 30.83°. Sensitivity increases from 18.6 to 89.6 Hz/s due to the larger contact surface between the layer surface and the spores. The results of this study can be used as a reference in developing the addition of other materials with PPy matrix materials for appropriate analyte substances.