Au-Ag Bimetallic Nanoparticles for Surface-Enhanced Raman Scattering (SERS) Detection of Food Contaminants: A Review

Abstract

Food contaminants, including harmful microbes, pesticide residues, heavy metals and illegal additives, pose significant public health risks. While traditional detection methods are effective, they are often slow and require complex equipment, which limits their application in real-time monitoring and rapid response. Surface-enhanced Raman scattering (SERS) technology has gained widespread use in related research due to its hypersensitivity, non-destructibility and molecular fingerprinting capabilities. In recent years, Au-Ag bimetallic nanoparticles (Au-Ag BNPs) have emerged as novel SERS substrates, accelerating advancements in SERS detection technology. Au-Ag BNPs can be classified into Au-Ag alloys, Au-Ag core-shells and Au-Ag aggregates, among which the Au-Ag core-shell structure is more widely applied. This review discusses the types, synthesis methods and practical applications of Au-Ag BNPs in food contaminants. The study aims to provide valuable insights into the development of new Au-Ag BNPs and their effective use in detecting common food contaminants. Additionally, this paper explores the challenges and future prospects of SERS technology based on Au-Ag BNPs for pollutant detection, including the development of functional integrated substrates, advancements in intelligent algorithms and the creation of portable on-site detection platforms. These innovations are designed to streamline the detection process and offer guidance in selecting optimal sensing methods for the on-site detection of specific pollutants.

Keywords: Au-Ag bimetallic nanoparticles; Surface-enhanced Raman scattering; food contaminants; sensor.

Figure 1

Schematic diagram of the types of SERS substrates based on Au-Ag bimetallic nanoparticles (Au-Ag BNPs) and their applications in food contaminants.

Figure 2

The types of Au-Ag BNPs and schematic diagrams of their model structures (orange and light blue respectively represent one of the Ag and Au elements). (A) Energy dispersive X-ray spectroscopy mapping of individual Ag/Au-NPs with atomic ratios (Ag:Au = 40:60) [38]. (B) The corresponding Au and Ag elemental mapping images of the Au@Ag NPs [39]. (C) Element mapping images of the Au-Ag JNPs [40].

Figure 3

(A) Colorimetric/SERS sensing for micrococcal nuclease (MNase)-responsive detection [62]. (B) Schematic of the preparation of three kinds of immuno-MoDAu@Ag SERS tags and MoDAu@Ag-based SERS encoding-LFIA for simultaneous detection of P. aeruginosa, E. coli O157:H7 and S. typhi [63]. (C) Schematic illustration of the synthesis process for multifunctional UAA@P/M and the procedures of UAA@P/M-integrated LFIA for multimodal bacterial detection [111]. (D) Schematic diagram of the SERS sandwich structure made of bacteria/SERS tags/AAS-NPs, used for specific bacterial identification, sensitive detection and reliable bacterial inactivation [64].

Figure 4

(A) Schematic illustration of the developed 3D SERS aptasensor based on Au-4MBA@Ag NSts-AFB₁apt- Fe₃O₄@MoS₂ NFs assemblies for AFB₁ detection [69]. (B) Schematic diagrams of the preparation of two SERS probes and the SERS-LFIA test strip sensing process for simultaneous detection of two mycotoxins [72]. (C) SERS VFA biosensor based on an ordered PNC membrane and SERS nanotags for multiplex mycotoxin detection [73]. (D) Schematic diagram of the preparation process and sensing principle of magnetic MOFs-based ratiometric SERS aptasensor [74].

Figure 5

(A) Schematic diagram of detection of pesticides on apple surfaces using CNF/GNR@Ag SERS substrate [81]. (B) Schematic overview of the synthesis of AAZ and L-AAZ and the working principle of the SERS sensor for quinalphos detection [82]. (C) Illustration of the fabrication of Ag@ZIF-8@Au and its application in SERS detection of acetamiprid [83]. (D) Schematic diagram of paper-based SERS sensor quantification of carbaryl [84].

Figure 6

(A) Schematic representation of the synthesis procedure, the SERS sensing and the self-reviving ability for the SERS substrate based on the Ag/Au/AgCl heterostructure [89]. (B) Schematic diagram of detection and analysis of three antibiotics [91]. (C) Schematic diagram of chloramphenicol detection [92]. (D) Schematic diagram of TC detection based on aptamer recognition and cascade DNA network amplification Raman aptasensor [93].

Figure 7

(A) Process of preparing Au@Ag NRs and schematic illustration of the detection of Pb²⁺ based on the aggregates of the Au@Ag NR probe [95]. (B) Principle diagram of the colorimetric and SERS dual-mode probe for determination of Hg²⁺ based on controllable etching unmodified Au@Ag NPs [96]. (C) Dual-channel biosensor based on Au@Ag15-GU nanohybrids for detection of Hg²⁺ [97]. (D) Schematic illustration of the dual-signaling SERS ratiometric platform for Hg²⁺ detection [98].

Figure 8

(A) Illustration of the preparation of Au NBPs@Ag/PDMS as SERS substrate for detecting contaminants in river bass [101]. (B) The detection process for weakly adsorbed dye molecules based on PDDA@Ag/Au-HPOC substrate [102]. (C) Schematic diagram of the enrichment procedure of colorants in beverages and SERS detection combined with GO/Au@Ag NBs membrane [103]. (D) Synthetic scheme of preparation procedure of the Ag@Au film SERS substrate [104]. (E) Schematic illustration of the SERS-active Au-Ag Janus@Au NP-engineered SERS aptasensor for the detection of SEC [105]. (F) Schematic illustration of plasmonic Au-Ag Janus NP/perovskite composite-engineered SERS immunoassay for SEC detection [106].