This study demonstrates the ability of graphene-based sensors to detect individual gas molecules adsorbed on their surface. The research shows that graphene, due to its exceptional electronic properties, can achieve a high sensitivity, allowing the detection of single molecules. The key findings include the observation of step-like changes in resistance when gas molecules attach or detach from the graphene surface, which correspond to changes in the local carrier concentration. The sensitivity is attributed to graphene's low noise characteristics, making it a promising material for chemical sensors and other applications requiring local probes sensitive to external charge, magnetic fields, or mechanical strain. The study also shows that graphene devices can detect changes in gas concentration as low as 1 part per billion (ppb), which is a significant improvement over previous detection methods. The devices were fabricated using micromechanical cleavage and characterized using field-effect measurements. The results indicate that the mobility of charge carriers in graphene is not significantly affected by chemical doping, even at high concentrations of impurities. This suggests that the observed constant mobility is due to the unique properties of graphene, such as its two-dimensional structure and low defect density. The study further demonstrates that the detection of individual gas molecules is possible due to the quantized changes in conductivity caused by the adsorption or desorption of single molecules. The experiments show that the changes in Hall resistivity are step-like and correspond to the addition or removal of a single electron charge. The statistical analysis of these changes confirms the detection of individual molecules, with the observed steps corresponding to the adsorption or desorption of a single molecule. The research highlights the potential of graphene-based sensors for applications requiring high sensitivity and low noise, such as environmental monitoring, industrial applications, and military use. The study also suggests that the electronic properties of graphene make it suitable for use in single-electron detectors and ultra-sensitive sensors of magnetic fields or mechanical strain. The findings contribute to the understanding of graphene's electronic behavior and its potential for future electronic applications.This study demonstrates the ability of graphene-based sensors to detect individual gas molecules adsorbed on their surface. The research shows that graphene, due to its exceptional electronic properties, can achieve a high sensitivity, allowing the detection of single molecules. The key findings include the observation of step-like changes in resistance when gas molecules attach or detach from the graphene surface, which correspond to changes in the local carrier concentration. The sensitivity is attributed to graphene's low noise characteristics, making it a promising material for chemical sensors and other applications requiring local probes sensitive to external charge, magnetic fields, or mechanical strain. The study also shows that graphene devices can detect changes in gas concentration as low as 1 part per billion (ppb), which is a significant improvement over previous detection methods. The devices were fabricated using micromechanical cleavage and characterized using field-effect measurements. The results indicate that the mobility of charge carriers in graphene is not significantly affected by chemical doping, even at high concentrations of impurities. This suggests that the observed constant mobility is due to the unique properties of graphene, such as its two-dimensional structure and low defect density. The study further demonstrates that the detection of individual gas molecules is possible due to the quantized changes in conductivity caused by the adsorption or desorption of single molecules. The experiments show that the changes in Hall resistivity are step-like and correspond to the addition or removal of a single electron charge. The statistical analysis of these changes confirms the detection of individual molecules, with the observed steps corresponding to the adsorption or desorption of a single molecule. The research highlights the potential of graphene-based sensors for applications requiring high sensitivity and low noise, such as environmental monitoring, industrial applications, and military use. The study also suggests that the electronic properties of graphene make it suitable for use in single-electron detectors and ultra-sensitive sensors of magnetic fields or mechanical strain. The findings contribute to the understanding of graphene's electronic behavior and its potential for future electronic applications.