Facile approach to the synthesis of molecularly imprinted ratiometric fluorescence nanosensor for the visual detection of folic acid

•Combination Ratiometric fluorescence with MIPs for detection of folic acid.•A facile sol–gel strategy avoids sophisticated synthesis process.•Dual-emission nanosensor realizes visualization determination for target-analytes.•Excellent performance of rapid response, high precision, sensitivity and selectivity.•Universal application to low or high levels of folic acid detection in real samples.