The abuse of fentanyl and fentanyl analogs is becoming a global problem, with over 70,000 deaths reported in the USA, and there is evidence of its abuse beginning to appear in Europe and other areas. Fentanyl is 100 times more potent than morphine, and there are fentanyl analogs that are even more dangerous. Therefore, detecting and differentiating fentanyl isomers is critical in tracking this epidemic of drug use. Surface-enhanced Raman spectroscopy (SERS) is a useful method for detecting fentanyl isomers due to its capability of yielding spectroscopic fingerprints of the analytes. In this study, theoretical and experimental methods were compared in order to distinguish para fluorofentanyl, which is one of the most common fentanyl analogues in illicit mixtures, and its isomers ortho fluorofentanyl and meta fluorofentanyl. First, density functional theory (DFT) calculations were performed to define which vibrational peaks can be utilized in the identity of these analogs. The spectra obtained from the theoretical calculations were then compared with the spectra obtained from the Normal Raman and SERS experiments. To enhance sensitivity, bimetallic gold/silver nanostars (Au/Ag NS) were synthesized to provide the SERS enhancement along with magnesium chloride or potassium bromide aggregating agents with limits of detection in the low ng/mL range. The LOD value for para-fluorofentanyl is 3 ng/mL. The obtained results show that SERS is a successful technique to detect isomers of fentanyl analogs.

中文翻译：

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通过表面增强拉曼光谱检测对、邻、间氟芬太尼

芬太尼和芬太尼类似物的滥用正在成为一个全球性问题，美国报告了超过 70,000 人死亡，并且有证据表明其滥用开始出现在欧洲和其他地区。芬太尼的效力比吗啡强 100 倍，芬太尼类似物甚至更危险。因此，检测和区分芬太尼异构体对于追踪这一毒品使用流行病至关重要。表面增强拉曼光谱 (SERS) 是一种检测芬太尼异构体的有用方法，因为它能够产生分析物的光谱指纹。在这项研究中，比较了理论和实验方法，以区分对氟芬太尼（非法混合物中最常见的芬太尼类似物之一）及其异构体邻氟芬太尼和间氟芬太尼。首先，进行密度泛函理论 (DFT) 计算，以确定哪些振动峰可用于识别这些类似物。然后将理论计算获得的光谱与普通拉曼和 SERS 实验获得的光谱进行比较。为了提高灵敏度，合成了双金属金/银纳米星 (Au/Ag NS)，与氯化镁或溴化钾聚集剂一起提供 SERS 增强，检测限在低 ng/mL 范围内。对氟芬太尼的 LOD 值为 3 ng/mL。所得结果表明SERS是检测芬太尼类似物异构体的成功技术。