Ultrafast and field-based detection of methamphetamine in hair with Au nanocake-enhanced Raman spectroscopy

The disaster and devastation from abuse of Methamphetamine (MAMP) have a serious impact on people's mental and physical health. Developing a rapid and accurate method to screen drug suspects and thus control MAMP abuse is essential to social security. Hair analysis for MAMP detection is considered to be one of the most potential methods for monitoring drug abuse due to its convenient sample collection, easy for storage and long traceability period. However, the current accurate detection of MAMP in hair primarily utilizes hyphenated mass spectrometry (MS) techniques, but it is not suitable for field-based detection due to the bulky instrument. Hence, developing alternative portable detection techniques for rapid on-site detection of MAMP in hair is an urgent problem to be solved. Here, the high-performance Au nanocakes (Au NCs) were constructed as surface-enhanced Raman spectroscopy (SERS) substrates to detect MAMP in hair, realizing 5 min ultrafast and ultrasensitive detection utilizing a portable Raman spectrometer. Experiments and finite-difference time-domain (FDTD) simulations show that Au NCs have stronger enhancement than Au nanospheres (Au NPs), and 0.5 ppb (3.35 × 10^-9 M) MAMP standard is stably detected by Au NCs as an enhanced substrate. A strategy of liquid-liquid microextraction was exploited to eliminate the interference of complex matrices in hair. This method exhibited excellent reproducibility and temporal stability across different drug addicts (relative standard deviation was 5.14% within 160 s). Our approach shows great promise in public safety, providing a rapid and accurate method to detect in hair by SERS.