Hydrothermal and photoreduction synthesis of nanostructured α-Fe2O3/Ag urchins for sensitive SERS detection of environmental samples

Abstract

Semiconductor/noble-metal heterostructures as surface enhanced Raman spectroscopy (SERS) substrates have remarkable recognition due to their synergistic contribution and abundant hotspot generation. Herein, urchin-like α-Fe2O3 and α-Fe2O3/Ag heterostructures were synthesized by the hydrothermal and photoreduction methods for the SERS application. The effective photoreduction strategies avail the dense production of noble metal (Ag) on semiconductor (α-Fe2O3). The synthesized α-Fe2O3/Ag heterostructure has numerous close-neighbouring spines with nanoscale gaps, which enable the affluent formation of hotspots and the adsorption of rich analyte molecules on the α-Fe2O3/Ag heterostructure. The silver photoreduction time is optimized for utmost hotspot generation such that the Raman signal enhancement is provoked to its highest extent. The prepared α-Fe2O3/Ag heterostructure is successfully applied for the efficacious analysis of azo dyes, sunset yellow (SY) and tartrazine (TZ). The performance analysis of α-Fe2O3/Ag heterostructure presents ultra-low limit of detection of 1.23 × 10-14 M for SY and 1.10 × 10-14 M for TZ. The enhancement factors are as high as 2.79 × 1012 for SY and 3.33 × 1012 for TZ. The uniformity and reproducibility of the proposed SERS substrate show the relative standard deviation less than 10 %. Furthermore, the real-sample analysis of the α-Fe2O3/Ag based SERS substrate is performed on the SY and TZ spiked orange juice and shows satisfactory recovery values. The preceding analytical results confirm that the α-Fe2O3/Ag based SERS substrate is feasible to be applied for practical sample analysis.