Nanosized particles can detect minute changes in surrounding electric fields via a phenomenon known as single-electron effect. Sensitivity can reach as much as counting single electrons. This phenomenon promises the possibilty of detection of atoms, molecules, cells or pathogens passing over or suspended around the nanosized particles whose IV characteristics is being monitored. Unfortunately, practical realization of such devices has been challenging because of their small size and low operating temperature, well below freezing temperature of regular liquids. Here we introduce PtSi/porous Si Schottky junction as a room temperature large size single-electron device capable of detecting very minute changes in the electric fields and hence identifying molecules, cells, and bacteria suspended or dissolved in liquid solutions. Encouraging results for detection of healthy and cancerous human cells as well as liquids and microorganisms are provided.