Functionalization techniques for improving SERS substrates and their applications in food safety evaluation: A review of recent research trends

BackgroundFood safety and quality have gained much attention in recent years and the capability to evaluate food quality and safety in a sensitive, rapid, and reliable manner is of great importance in the food industry. Therefore, surface-enhanced Raman scattering (SERS) with the advantages of excellent sensitivity, high selectivity, non-destructive nature and significant enhancement to identify the target has demonstrated a great potential for quick detection of chemical contaminants, chemical constitutes, and pathogens in food samples.Scope and approachThe enhancement of Raman signals for SERS is not only related to the interactions between substrates and samples but also the functionalization of substrates to gain SERS active substrates. In the present review, different types of substrates are briefly discussed, functionalization techniques for SERS active substrates are discussed, and applications of functionalized SERS substrate in food samples are presented.Conclusions and key findingsIt is evident that functionalization techniques for improving SERS substrates have given encouraging outcomes, which provides possibility for identifying multiple target analytes within a complex matrix, and thus could be used as a powerful analytical tool in real-world applications in food safety analysis as well as for enhancing food quality surveillance.     

Determination of chemical hazards in foods using surface-enhanced Raman spectroscopy coupled with advanced separation techniques

BackgroundSurface-enhanced Raman spectroscopy (SERS) has been validated as a highly accurate and specific technique for the discrimination, identification, and potential quantification of different types of chemical compounds. However, its application for the detection of potential hazardous chemical targets in foods has not yet been well developed due to interferences from the complicated food matrices, which could lead to challenges in spectral deconvolution and interpretation. The accurate separation and enrichment of the analyte from food samples are major challenges for analytical chemists and food technologists.Scope and approachFour promising “capturing” techniques (molecularly imprinted polymers, aptamer, antibody, and microfluidics) coupled with SERS were introduced in this review paper for the reliable and ultrafast determination of chemical hazards in food systems. These developed “one-step” or “two-step” SERS methods can achieve accurate and sensitive detection of trace level chemical hazards in agricultural products including foods.Key findings and conclusionsTandem SERS methods can be applied for rapid and reliable detection of trace level of chemical hazards in foods.     

Surface‐Enhanced Raman Spectroscopy for the Chemical Analysis of Food

Surface‐enhanced Raman spectroscopy (SERS) is an emerging and promising technique for the chemical analysis of food. The use of metallic nanosubstrates improves the sensitivity and capacity of conventional Raman spectroscopy greatly. This paper comprehensively reviews the development and applications of SERS in the chemical analysis of food, mainly focusing on food additives and chemical contaminants. The progress of SERS development and their applications in chemical analysis of food, from detection and characterization of target analytes in simple solvents to complex food matrices, is summarized. The advantages and limitations of different SERS substrates and methodologies are discussed. As most of the current SERS research on chemical analysis of food is still in an early stage, there are still several hurdles for further advancing SERS techniques into real‐world applications for complex food products. This review includes our perspectives on the future trends of the SERS technique in the field of food analysis.     

光催化自清洁表面增强拉曼光谱基底用于食品污染物可循环检测的研究进展

表面增强拉曼光谱（surface-enhanced Raman spectroscopy,SERS）是一种新兴的超灵敏分析技术,在食品安全、环境监测和临床诊断等多个领域都有应用前景。然而,传统SERS检测以金或银的贵金属纳米材料为活性基底,存在均一性和稳定较差、成本较高的问题。通过将SERS与光催化技术联用,以半导体-贵金属复合纳米材料为基底,可改善检测结果的稳定性和批次间差异性,有效降低成本。同时,利用材料的光催化降解功能可达到消除污染物和循环使用基底的目的。本文重点介绍近期光催化自清洁SERS基底用于食品污染物可循环检测的研究进展,包括无机/有机半导体-贵金属复合SERS基底的制备方法、优势和不足,及其在农药、非法添加剂和抗生素等食品中典型污染物检测和消除中的应用,最后总结了该领域现存的挑战和未来的发展趋势。     

Surface enhanced Raman spectroscopy (SERS): A novel reliable technique for rapid detection of common harmful chemical residues

BackgroundThe irrational usage of chemical substances including pesticides and drugs in agricultural and food production is a significant food safety issue due to its residues. Therefore, the detection of harmful residues in foods is an indispensable step for guaranteeing the consumer's health. Conventional methods, such as HPLC, GC-MS and LC-MS are accurate enough, but they fail to meet the requirements of the modern industry for rapid and on-line detection. Novel reliable techniques should thus be developed as alternatives.Scope and approachIn this review, fundamentals of surface-enhanced Raman spectroscopy (SERS) is introduced. Recent advances in its usage for detecting harmful chemical residues in agricultural products including pesticides, antibiotics and β₂-adrenergic agonists are discussed by two typical ways of detection improvement, and the advantages of SERS are addressed. Finally, future trends to routine use of SERS applications in harmful residues are presented.Key findings and conclusionsSERS is a promising detection technique for the detection of common harmful chemical residues with merits of simple sampling, rapid data collection and non-destructiveness. Despite rapid developments in the technology, there is much studies should be done before SERS could be used as a daily tool for the industry.     

纤维基表面增强拉曼基底的研究进展

为解决传统纤维表面拉曼增强(SERS)基底所存在的稳定性差、操作不便等问题。介绍了柔性SERS基底的优势,总结了目前各类纤维基SERS基底的研究进展及其在痕量检测领域的应用,简述了电磁增强和化学增强2种表面增强拉曼现象的基本原理。综述了纤维纸基SERS、织物基SERS、散纤维及纳米纤维膜SERS基底的制备方法及其应用,并着重介绍了织物基SERS材料的研究现状及其在在线检测应用方面的挑战与机遇。基于织物基SERS材料高度灵敏及灵活检测的特点,展望了其作为可穿戴传感器件用于即时检测和周身环境监测的前景,为拓展智能纺织品的应用领域开辟了新的思路。     

表面增强拉曼光谱技术在快速检测保健食品中非法添加药物中的应用

表面增强拉曼光谱(surface-enhanced Raman spectroscopy,SERS)技术作为一种新型的快速检测技术正在被广泛应用于保健食品非法添加化学药物的检测中。通过设计不同的SERS基底,可以搭建出集样品前处理、上机分析、匹配定性的一体化拉曼光谱检测系统。与传统的检测方式相比,SERS技术具有无损、快速、图谱指纹特性强等优点,在保健食品非法添加化学药物的快速检测中具有巨大潜力。本文主要综述了SERS的技术原理、SERS基底分类以及SERS技术在保健食品中非法添加化学药物检测中的应用,并对SERS技术在保健食品中非法添加化学药物检测方面的应用前景进行了展望,以期为保健食品中未知违禁物的识别提供理论支撑。     

表面增强拉曼光谱方法在食品安全检测中的应用研究进展

近年来国内外频发的食品安全事件使得公众对食品安全问题的关注度不断提高,快速、灵敏、可靠的评估食品质量与安全的能力在食品行业中十分重要,因此开发满足食品安全需求的高性能检测技术势在必行。表面增强拉曼光谱（surface-enhanced Raman spectroscopy, SERS）具有高特异性、高灵敏度、无损检测、可实现多重检测等优异性能,在食品安全检测领域得到广泛应用,并取得了令人瞩目的进展。本文介绍了SERS技术的理论基础,总结了增强SERS信号强度的活性基底,综述了基于SERS方法的食品安全检测应用研究进展,讨论了其未来发展趋势与前景,旨在为研究人员根据具体食品安全检测应用需求选择合适的SERS方法提供建议。     

表面增强拉曼技术在农药残留检测中的应用研究进展

食品的农药残留问题是威胁人类健康的全球性问题,表面增强拉曼光谱技术(surface-enhanced Raman spectroscopy, SERS)作为一种操作简便、快速灵敏的指纹光谱技术,在农药残留检测方面已展现出较大潜力。本文首先描述了SERS增强原理,然后简单概括了SERS基底制备的方法,以基底功能性出发,介绍了食品中农残检测中常见的两种类型的SERS基底：通用型基底、特异性基底,通过综述近年来在食品农残检测中的应用,总结了二者在检测食品中农残的特点和常用的制备工艺,旨在为更多农残检测需求提供关于SERS技术方面的启发。最后展望了SERS技术在农残检测的挑战并提出可行的建议。     

表面增强拉曼光谱快速检测食品添加剂的研究进展

近年来,食品添加剂安全问题引起了社会各界的广泛关注。而现有的常用检测方法往往具有操作复杂、分析速度慢、成本高、损伤样品等缺点,这就要求我们发展更先进的食品添加剂快速检测方法。表面增强拉曼光谱技术是一种新兴的先进检测技术,它具有样品量少、操作简便、快速、可进行无损检测等优点,克服了常规拉曼光谱灵敏度低的缺点,提高了物质检测能力,在快速分析食品添加剂中有良好的应用前景。本文按照不同食品添加剂的类别:着色剂、防腐剂、抗氧化剂、甜味剂和其他,综述了表面增强拉曼光谱快速分析限用/违禁食品添加剂的研究进展,并对目前表面增强拉曼光谱技术在该领域存在的问题进行了分析,对其未来的发展趋势与发展前景进行了展望。     

Fabrication of SERS‐Active Substrates using Silver Nanofilm‐Coated Porous Anodic Aluminum Oxide for Detection of Antibiotics

We have developed a silver nanofilm‐coated porous anodic aluminum oxide (AAO) as a surface‐enhanced Raman scattering (SERS)‐active substrate for the detection of trace level of chloramphenicol, a representative antibiotic in food systems. The ordered aluminum template generated during the synthesis of AAO serves as a patterned matrix on which a coated silver film replicates the patterned AAO matrix to form a 2‐dimensional ordered nanostructure. We used atomic force microscopy and scanning electron microscopy images to determine the morphology of this nanosubstrate, and characterized its localized surface plasmon resonance by ultraviolet‐visible reflection. We gauged the SERS effect of this nanosubstrate by confocal micro‐Raman spectroscopy (782‐nm laser), finding a satisfactory and consistent performance with enhancement factors of approximately 2 × 10⁴ and a limit of detection for chloramphenicol of 7.5 ppb. We applied principal component analysis to determine the limit of quantification for chloramphenicol of 10 ppb. Using electromagnetic field theory, we developed a detailed mathematical model to explain the mechanism of Raman signal enhancement of this nanosubstrate. With simple sample pretreatment and separation steps, this silver nanofilm‐coated AAO substrate could detect 50 ppb chloramphenicol in milk, indicating good potential as a reliable SERS‐active substrate for rapid detection of chemical contaminants in agricultural and food products.     

Trace analysis of organic compounds in foods with surface‐enhanced Raman spectroscopy: Methodology,progress, and challenges

Surface‐enhanced Raman spectroscopy (SERS) provides a potential solution for rapid analysis of trace compounds such as residual pesticides, naturally occurred toxicants, banned or restricted drugs, and food additives in complex food matrices. In this review, the basic principles of SERS and general approaches to successfully apply SERS in food analysis are covered from an applications perspective. The key steps including substrate selection and evaluation, sample preparation and simplification, spectral collection, and data analysis during the development of SERS methods for food analysis are summarized, together with the discussion of typical underlying technical barriers or major challenges of these methods and their applications. Future directions in successfully applying SERS technology as a routine analytical approach to solve real‐world food problems are analyzed. This comprehensive review summarizes the recent progress on theory, application, and scope of SERS for food analysis, providing a basic understanding of the technology; more importantly, key methodology, potential pitfalls, and possible solutions during the development of rapid SERS methods based on authors’ years of SERS experience are shared with researchers in the field.     

Potential of SERS for rapid detection of melamine and cyanuric acid extracted from milk

Melamine, a nitrogen-rich chemical, was implicated in the pet and human food recalls in 2007 and in the global food safety scares in 2008 involving milk and other milk-derived products. In this study, we investigated the feasibility of using surface-enhanced Raman spectroscopy (SERS) coupled with SERS-active gold substrates for rapid detection of trace amounts of melamine and its analogue (that is, cyanuric acid) in liquid milk. Raman signals of tested samples were significantly enhanced by SERS. The identification limit for SERS using gold substrate can reach 2 ppm of melamine in liquid milk. Partial least squares (PLS) models were established for the quantification of melamine in liquid milk by SERS: R = 0.90, RMSEP = 1.48 × 10⁻⁵. Our results demonstrate that rapid detection of melamine in milk can be achieved by SERS; while detection of cyanuric acid in milk remains a challenging task due to rapid enol-keto tautomerism of cyanuric acid. The SERS method is faster and simpler than other traditional methods, and requires minimum sample preparation. These results demonstrate that SERS could be used to detect food contaminants such as melamine in foods and food ingredients quickly and accurately.     

表面增强拉曼光谱在食品污染物快速检测中的应用

随着科技的发展,食品的种类越来越丰富,随之而来的问题是食品中引入的污染物也越来越复杂,这使得食品安全成为当今全球关注的一个重要话题,快速有效地检测食品中污染物已然成为食品检测的热点。表面增强拉曼光谱(surface-enhanced Raman spectroscopy, SERS)由于其极高的灵敏度、快速检测、指纹图谱解释能力,以及高达单分子级别的检测水平,逐渐成为检测食品中污染物的常用方法。本文针对SERS基底的发展现状,如特殊形态金属纳米颗粒和固相SERS平台,以及SERS在农兽药,掺假,天然毒素以及食源性病原体等污染物中的检测方法进行了论述,以期为表面增强拉曼光谱未来在食品污染物快速检测中的应用提供参考。     

Detection of Melamine in Gluten,Chicken Feed,and Processed Foods Using Surface Enhanced Raman Spectroscopy and HPLC

ABSTRACT: Melamine, a nitrogen‐rich chemical, was implicated in pet and human food recalls in 2007, which caused enormous economic losses to the food industry. In this study, melamine concentration in wheat gluten, chicken feed, and processed foods (that is, cake and noodle) was measured by surface enhanced Raman spectroscopy (SERS) in combination with SERS‐active substrates. SERS was able to rapidly detect 0.1% melamine in wheat gluten, 0.05% in chicken feed, 0.05% in cakes, and 0.07% in noodle, respectively. A partial least squares (PLS) model was established for the quantification of melamine in foods by SERS: R= 0.90, RMSEP = 0.33. In addition, SERS results were verified by HPLC analysis based on a simplified FDA method. Compared with HPLC, the SERS method is much faster and simpler, requires minimum sample preparation, but still yields satisfactory qualitative and quantitative results. These results demonstrate that it is an applicable approach to use SERS to screen foods, eliminate presumptive negative samples of melamine contamination from the sample population, and then verify presumptive positive samples using HPLC protocols. Combining these 2 methods could provide a more rapid and cost‐effective way for monitoring melamine contamination in increasingly large numbers of imported foods and feed products.     

基于表面增强拉曼光谱标记技术的生物传感器用于农药残留检测的研究进展

近年来,表面增强拉曼光谱（surface enhancement Raman spectroscopy,SERS）标记技术因具有高灵敏度、可多路复用、强抗光漂白性和较好的分子指纹保真度等特性而备受瞩目,并已成功应用于传感分析及生物成像领域。本综述主要总结了基于SERS标记技术的生物传感器的原理及其在农药残留快速检测领域中的最新研究进展,重点介绍了SERS标签的设计与制备及基于不同识别元件传感系统的研究现状。同时,对其面临的挑战和解决方案进行了探讨,以期促进SERS标记技术在农药残留检测及食品安全检测方面的应用。     

用于检测果蔬中农药残留的柔性表面增强拉曼散射(SERS)基底：设计策略和应用进展

随着21世纪人口的迅速增长和科技的飞速发展,果蔬中的农药残留问题已引起广泛关注。表面增强拉曼光谱(SERS)因其快速、无损和指纹识别的特性,已成为食品安全检测领域最有潜力的技术之一。柔性SERS基底的引入为非平面果蔬表面的原位检测提供了新的可能性。与刚性基底相比,柔性基底可通过“粘贴-剥离”或拭子取样的方法进行适应,实现了刚性基底无法达到的灵活性。然而,设计和制备同时具备高灵敏度、高稳定性和良好信号重现性的柔性基底仍是一项挑战。本综述首先概述了SERS的基本机理,然后深入探讨了柔性基底的构建策略,包括基底材质的选择和拉曼热点的构建方法。近年来,对于柔性基底在果蔬农残检测方面的应用实例也进行了总结。柔性SERS基底的发展前景广阔,但在实际应用中仍需克服许多困难和挑战。例如,如何确保在不同的检测环境中保持高灵敏度、高稳定性、高选择性和高重现性,如何降低成本实现大规模生产等。最后,本文针对柔性基底研发过程中的困难和挑战提出了一些可能的解决方案,并对未来的研究方向进行了展望。这些解决方案和展望旨在推动柔性SERS基底的进一步研究和应用,为果蔬农残的准确、高效检测提供支持。总体而言,柔性SERS基底为果蔬农残检测提供了新的可能性和机遇。通过深入理解其工作机理、优化设计策略并克服现有挑战,有望实现其在食品安全领域的广泛应用。     

表面增强拉曼光谱技术在食品安全检测中的最新研究进展

食品种类繁多,食品中存在的污染物问题也越来越复杂。因此,探究快速、灵敏、简单地检测食品中痕量污染物的检测技术对保障食品安全具有重要的意义,也是食品安全中非常重要的一环。近几十年来,表面增强拉曼散射(surface-enhanced Raman scattering, SERS)检测技术凭借其检测快速、无损、灵敏度高等优点,已成为食品安全检测的可靠工具。目前缺乏近几年关于SERS检测技术最新研究进展的概述。因此,本文简要综述了SERS的增强机制、增强底物及其检测技术;总结了近3年来关于表面增强拉曼光谱在食品安全检测方面的实际应用。为了更好地将SERS检测技术应用于今后食品安全的常规检测中,应研发更加低成本的技术,更简单的操作方法,开发新的SERS增强底物,将SERS检测与其他检测方法更好的结合。     

Rapid detection of multiple organophosphorus pesticides (triazophos and parathion-methyl) residues in peach by SERS based on core-shell bimetallic Au@Ag NPs

In this study, a surface-enhanced Raman scattering (SERS) approach based on silver-coated gold nanoparticles (Au@Ag NPs) was established for rapid detection of multiple organophosphorus pesticides (triazophos and methyl-parathion) in peach fruit. The Raman enhancement of Au@Ag NPs for detecting organophosphorus pesticides was stronger than those of single Ag and Au NPs. It was revealed that core size of Au NPs was a critical parameter affecting the enhancement of Raman signals by joining two plasma resonance absorptions. The Au@Ag NPs with 26 nm Au core size and 6 nm Ag shell thickness showed significant Raman enhancement, especially by the creation of hot spots through NPs aggregation induced by connection between Au@Ag NPs and target molecules. The detection limits of triazophos and methyl-parathion in peach were 0.001 mg/kg. Good recovery (93.36 to 123.6 %) and high selectivity of the SERS activity allowed excellent precision for the detection of the triazophos and methyl-parathion in peach. Compared to earlier studies, the current approach was rapid, inexpensive and simple without lengthy sample pre-treatment. This study revealed that the proposed method could be employed for the analysis of trace contaminants such as triazophos and methyl-parathion in many food matrices.