Mid-infrared-induced ultrafast heating for detecting alcoholic solutions.

The detection of alcoholic solutions is crucial for safety and industrial applications. This work investigates the ultrafast heating effects of methanol and ethanol aqueous solutions at varying mass fractions triggered by mid-infrared (MI) pulses, using molecular dynamics simulations. The results show that the heating effect is negatively correlated with alcohol concentration at frequencies ranging from 0.1 to 30 THz and from 45 to 50 THz. In contrast, at a frequency of approximately 40 THz, the heating effect is positively correlated with alcohol concentration. These heating effects in response to MI occur on a sub-picosecond timescale. The mechanism is attributed to the resonance effect of solutes and solvents with MI pulses observed across different frequency bands. These findings provide a foundation for enhancing the sensitivity and specificity of MI pulse-based detection of alcoholic aqueous solutions.