Graphene oxide/gold nanorod plasmonic paper – a simple and cost-effective SERS substrate for anticancer drug analysis

Abstract

Plasmonic paper has received attention as a surface-enhanced Raman scattering (SERS) substrate due to several advantages. These include low cost, high rates of sample collection, high physical flexibility and relative ease of fabrication. Here, we report the development of a plasmonic paper based on a combination of graphene oxide (GO) and gold nanorods (AuNRs) on cellulose substrates using a simple layer-by-layer immersion method. Rhodamine 6G (R6G) was selected as the probe molecule to determine the SERS efficiency. The GO–AuNR plasmonic paper composite demonstrated superior signal intensity compared to that of the paper substrate coated only with AuNRs. The signal enhancement was due to synergism between the electromagnetic enhancement (EM) originating from the AuNRs and the chemical enhancement effect (CE) originating from GO. To optimize the fabrication process, the first step was accomplished by varying the GO concentration during the paper pretreatment step. This was followed by determining the number of immersion cycles required for optimal absorption of AuNRs. The highest SERS signals derived from R6G molecules indicated that the 2 mg mL⁻¹ GO pretreatment condition followed by two immersion cycles into the AuNR solution proved to be the best condition for plasmonic paper fabrication. The enhancement factor (EF) of the plasmonic paper was calculated to be 4.56 × 10⁷ and the limit of detection (LOD) for R6G analysis was as low as 0.1 nM. Moreover, the plasmonic paper was tested in the detection of Mitoxantrone (MTX), an anti-cancer drug. We found that the LOD for detection of MTX was on the order of 5 μM. This simple and cost effective plasmonic paper offers an alternative SERS substrate which has potential in trace analysis and drug monitoring.