Printer-assisted array flexible surface-enhanced Raman spectroscopy chip preparation for rapid and label-free detection of bacteria

A low-cost array flexible surface-enhanced Raman spectroscopy (SERS) chip was proposed with the aim of rapid detection of bacteria. The substrate of the chip was Al foil, and the detection area arrays were printed using a laser toner. Colloidal silver nanoparticles (AgNPs) were dropped onto the detection area, with the AgNPs droplets confined within the detection area by the hydrophobic properties of the toner film. The colloidal AgNPs were dried naturally to form a SERS active chip. An A4 paper-based SERS chip was prepared using the same method for control experiments. The surface morphology of the chip was characterized by field emission scanning electron microscopy. In addition, comparison experiments were performed on the two SERS chips. The results showed that both SERS chips exhibited the best SERS enhancement when the AgNPs were added four times. The calculation of Rhodamine 6G at the 612 cm(-1) peak showed that the EF of the A4 paper-based chip and the Al foil-based chip were 6.72 x 10(7) and 1.03 x 10(8), respectively. SERS mapping results showed that the Al foil-based chip had much higher signal homogeneity than that of A4 paper-based chip. Lastly, the Al foil-based chip was used for bacterial detection. For Escherichia coli and Staphylococcus aureus, the limit of detection was 1,000 and 100 cfu/ml, and the relative standard deviation of 36 randomly selected detection points were 12.5% and 11.7%, respectively. The entire detection process was completed in a few minutes. The SERS chip has the advantages of low cost, simple manufacturing process, and short detection time; is capable of high throughput and multi-parameter detection; and is expected to provide a rapid and effective detection method for bacteria.