A dual-mode strategy for diacetyl detection based on colorimetry and surface-enhanced Raman scattering

Diacetyl is an important food additive with rich creamy flavor whose excessive intake may cause various diseases. Herein, for the first time, we designed a dual-mode method for diacetyl detection based on colorimetry and surface-enhanced Raman scattering (SERS) technology. Diacetyl exhibited excellent oxidase-like catalytic activity under light-mediated condition, facilitating the oxidation of colorless 3,3 ',5,5 '-tetramethylbenzidine (TMB) to blue ox-TMB for colorimetric detection. Notably, diacetyl could control the oxidation process of TMB by simply adjusting light irradiation, unlike traditional enzymatic reactions that required terminators to stop the reaction. Interestingly, ox-TMB was an ideal Raman marker for SERS analysis. Then, a three-dimensional flowerlike zinc oxide/silver (ZnO/Ag) for sensitive SERS detection was prepared, which exhibited outstanding SERS effect with a high enhancement factor of 1.89 x 108 due to effective charge transfer and synergistic effect between ZnO and Ag. Based on these, SERS method was constructed to indirectly detect diacetyl, which has not been reported due to low Raman activity of diacetyl. The linear ranges of colorimetry and SERS were 0.5-60 mu M and 10-9-10-5 M respectively, with detection limits of 0.41 mu M and 0.73 nM. Obviously, the dual-mode strategy combined the simplicity and practicality of colorimetry and the high sensitivity of SERS, offering great potential applications in practical samples.