Recyclable Surface-enhanced Raman Scattering Research Articles

Low-cost Ag/ZnO nanosheets arrays as sensitive and recyclable surface-enhanced Raman scattering substrates

The development of surface-enhanced Raman scattering (SERS) substrate based on metal/semiconductor nanostructured platforms has emerged as a promising technique for achieving highly sensitive and recyclable detection across various fields, including environmental monitoring, food safety, biomedical diagnostics, and the preservation of cultural heritage. However, the design and fabrication of cost-effective metal/semiconductor nanostructures suitable for SERS substrates remain a formidable challenge. In this study, a low-cost, recyclable SERS substrate based on Ag nanoparticle decorated ZnO nanosheets (Ag/ZnO NSs) arrays was developed using hydrothermal growth and photochemical reduction approaches. The optimized Ag/ZnO NSs arrays demonstrated local electric field enhancement and multi-path charge transfer, ensuring an enhancement factor of 107 and a detection limit of 10−10 mol/L for crystal violet molecules. This research not only sheds light on the economical production of metal/semiconductor SERS substrates but also paves the way for a broader spectrum of SERS-based detection applications in diverse fields.

Elevating electron transfer of recyclable SERS sensor using AuNPs/TiO2/Ti3C2 heterostructures for detection of malachite green in sunfish

Malachite green (MG)-contaminated aquatic products pose a serious threat to animal and human health. Hence, a novel recyclable surface-enhanced Raman scattering (SERS) substrate based on AuNPs/TiO2/Ti3C2 heterostructures was developed for the detection and degradation of MG in aquatic products. Specifically, AuNPs/TiO2/Ti3C2 heterostructures were synthesized by in situ oxidation and electrostatic adsorption based on Ti3C2 nanosheets. The excellent photocatalytic and SERS performance of the AuNPs/TiO2/Ti3C2 was demonstrated by Density functional theory (DFT) calculations and experimental results, which was attributed to the enhancement of charge transfer (CT) after the formation of heterostructures. The results demonstrate that AuNPs/TiO2/Ti3C2 is highly sensitive and recyclable. The detection limit of the sensor for MG is 8.91 × 10−5 mg/L. The sensor can be recycled for five times under the condition of light, and shows satisfactory self-cleaning performance in the food matrix, providing a possible alternative solution for the recyclable detection of MG.

A recyclable SERS-DGT device for in-situ sensing of sulfamethazine by Au@g-C3N4NS in water

Although diffusion gradient in thin-film technique (DGT) has realized the in-situ sampling Sulfamethazine (SMT), the traditional DGT devices cannot be served as sensing devices but in-situ sampling devices. Here we report a recyclable surface enhanced Raman scattering (SERS) responsive DGT sensing device (recyclable SERS-DGT Sensing Device) capable of in-situ sensing of SMT in water. This is achieved by innovatively utilizing a recyclable SERS responsive liquid suspension of Au nanoparticles supported on g-C3N4 (Au@g-C3N4NS) as DGT binding phase. Au@g-C3N4NS is synthesized via in-situ growth method and embed in DGT binding phase, which exhibits good SERS activity, aqueous stability recyclable and adsorption performance. The SERS-DGT Sensing Device is valid for measuring SMT under a wide range of conditions (i.e., deployment time 24∼180 h, concentrations range of 1.031∼761.9 ng mL−1, pH 5∼9, ionic strength 0.0001∼0.05 mol L−1 NaCl, DOM concentrations 0∼100 mg L−1, four recycles). Furthermore, substrate combined with DGT binding phase, can integrate the sampling, pretreatment and SERS detection of SMT, which can be recycled, improving the reliability and efficiency of environmental monitoring. In this article, recyclable SERS-DGT Sensing Device, a platform for recyclable in-situ sensing of antibiotics, holds great potential for environmental monitoring.

Au Nanoparticles Decorated CoP Nanowire Array: A Highly Sensitive, Anticorrosive, and Recyclable Surface-Enhanced Raman Scattering Substrate.

Metal-semiconductor composites are promising candidates for surface-enhanced Raman scattering (SERS) substrates, but their inert basal plane, poor active sites, and limited stability hamper their commercial prospects. Herein, we report a three-dimensional CoP nanowire array decorated with Au nanoparticles on carbon cloth (Au@CoP/CC) as a self-supporting flexible SERS substrate. The Au nanoparticles spontaneously grew on the surface of the CoP nanowire array to form efficient SERS hot spots by a redox reaction with HAuCl4 without any additional reducing agents. Such Au@CoP/CC substrate exhibited a limit of detection of 10-11 M using rhodamine 6G as a model dye with outstanding corrosion resistance ability even under extreme acid and alkali conditions, which is better than many recently reported Au-based SERS substrates. Finite-difference time-domain simulation results demonstrated that Au@CoP/CC can provide a high density of regions with intense local electric field enhancement. Moreover, Au@CoP/CC can degrade target organic dyes for the self-cleaning and reproduction of SERS-active substrates under visible light irradiation. This work provides a novel means of using the plasmonic metal-transition metal phosphide composites for high-performance SERS sensing and photodegradation.

Recyclable Surface-Enhanced Raman Scattering Substrate-Based Sensors for Various Applications

Surface enhanced Raman scattering (SERS) has been widely used for detection and characterization benefiting from its high sensitivity and selectivity (molecular fingerprint information). However, the strong adsorption of target molecules (“memory effect”) on the nanoparticle surface inherently limits the recycle of SERS substrates. This paper focuses on the different strategies to achieve recyclable SERS substrates and their applications. First, the problems of nonrecyclable SERS substrates are discussed systematically. Then, two categories are summarized to achieve recyclable SERS substrates and their applications: (1) chemical-free cleaning methods (including photocatalytic degradation, thermal cleaning, and plasma treatment) and (2) chemical-assisted cleaning methods (including solvent washing, chemical reaction, and electrochemistry). Moreover, we put forward current challenges and potential strategies of recyclable SERS substrates.

Highly sensitive and recyclable surface-enhanced Raman scattering (SERS) substrates based on photocatalytic activity of ZnSe nanowires

The semiconductor-based SERS substrates have attracted considerable attention due to their unique optical and reusable biosensor applications. However, most substrates generally exhibit poor enhancement effects and are non-reusable, needing a complicated fabrication process. In the present study, novel recyclable SERS substrates were synthesized from ZnSe nanowires using chemical vapor deposition. SERS performance was enhanced via introducing the defects by adding Se dopant in the ZnSe and achieved the value of EF 6.92 × 107 for the Zn/Se ratio 1:1.2. The SERS efficiency of the fabricated ZnSe nanowire was probed by rhodamine 6 G (R6G) and methylene blue (MB), presenting excellent stability and reaching the sensitivity level of 10−11 M. The photocatalytic degradation of R6G molecules were experimentally investigated with Raman mapping tests using a visible light source to explore the recyclability of the SERS substrates. Our study demonstrates that the proposed ZnSe nanostructure possesses the capability to reuse up to 6 times with preserving strong SERS signal reproducibility. The bifunctional recyclable ZnSe substrate not only presents a novel method to truly enhance the SERS performance, photocatalytic behavior but is also considerable for food safety application.

Multifunctional Ag-coated CuO microbowl arrays for highly efficient, ultrasensitive, and recyclable surface-enhanced Raman scattering

Surface-enhanced Raman scattering (SERS) has been demonstrated to be an ultrasensitive and real-time analysis technique for detection of analytes with its specific fingerprint-identification feature. However, most traditional SERS-active substrates are suffering from their high expense, intricate fabrication processes and non-recyclability, which seriously hinder the applicable universality of SERS analytical technique. Thus, it is highly desired to develop highly sensitive SERS-active substrates that can be recovered in an easy way. Herein, we present a facile and inexpensive approach for fabrication of photocatalytically active Ag-coated CuO (denoted as CuO@Ag) microbowl array substrate, applicable for the highly efficient, ultrasensitive, and recyclable SERS detection. In this approach, a multifunctional CuO@Ag microbowl array is achieved based on the pre-synthesis of a quasi-2D CuO microbowl array by employing the colloidal lithography on Cu foil combined with the subsequent chemical oxidation reaction, and followed by the sputtering deposition of Ag layer on the CuO microbowl array. Importantly, this CuO@Ag microbowl array can serve as SERS-active substrate with extra advantageous feature of excellent photocatalytic activity, which enables self-degradation of analytes after the SERS-detection under visible light illumination. Remarkably, this allows for recyclable SERS detection. In the detection of model probe molecules, e.g., methylene blue (LOD: 1.3 × 10−16 M) and Aflatoxin B1 (LOD: 6.5 × 10−15 M), approximate femtomolar level can be reached. Impressively, this substrate allows multi-detection without compromising the SERS activity. The present research provides a new and cost-effective strategy for synthesizing recyclable SERS-active substrates, which suggests plausible ways in the design of multi-functional SERS-active substrates.

Electrochemistry-Regulated Recyclable SERS Sensor for Sensitive and Selective Detection of Tyrosinase Activity.

Tyrosinase (TYR) which can catalyze the oxidation of catechol is recognized as a significant biomarker of melanocytic lesions, thus developing powerful methods for the determination of TYR activity is highly desirable for the early diagnosis of melanin-related diseases, including melanoma. Herein, we develop a novel portable and recyclable surface-enhanced Raman scattering (SERS) sensor, prepared by assembling gold nanoparticles and p-thiol catechol ( p-TC) on an ITO electrode, for detecting TYR activity via the SERS spectral variation caused by the conversion of p-TC into its corresponding quinone under TYR catalysis. The developed SERS sensor has a rapid response to TYR within 1 min under the optimized conditions and shows high selectivity for TYR with the detection limit at 0.07 U/mL. Importantly, this SERS sensor can be easily regulated by applying negative voltage to achieve circular utilization, favoring the automation of SERS detection. Furthermore, the presented recyclable SERS sensor can perform well on both the determination of TYR activity in serum and the assessment of TYR inhibitor, demonstrating huge potential in the sensitive, selective, and facile detection of TYR activity for disease diagnosis and drug screening related with TYR.

Flexible and recyclable SERS substrate fabricated by decorated TiO2 film with Ag NPs on the cotton fabric

Flexible and recyclable surface-enhanced Raman scattering (SERS) substrate was fabricated based on woven cotton fabric by grafting Ag nanoparticle on the TiO2 film which was deposited on the cotton fabric. Due to the synergetic effect of heterostructure Ag/TiO2 and superior adsorption capacity of fabrics, recyclable SERS cotton fabric (RSCF) possessed excellent SERS sensitivity with a detected concentration of p-Aminothiophenol as low as 10−12 M. Furthermore, SERS performance of RSCF can be recovered after 180 min in the presence of UV light illumination, resulting from the photocatalytic property of TiO2 on the surface of RSCF. It can be further utilized to reproduce SERS performance of the RSCF through the UV-assisted cleaning. As a trial for potential application, based on the flexibility of cotton fabric, RSCF was employed to detect a pesticide (carbaryl) on the surface of a pear by simply swabbing and low concentration down to 10−4 M was reached. This work provides a potential guide towards the universal design of the flexible and recyclable SERS substrates for a promising application in the SERS rapid detection of trace-level toxic pollutants on the food.

Facile fabrication of ternary TiO2-gold nanoparticle-graphene oxide nanocomposites for recyclable surface enhanced Raman scattering

A bi-functional ternary nanocomposite was developed by decorating TiO2 and gold nanoparticles on the reduced graphene oxide nanosheets (TiO2-Au-rGO) for recyclable surface enhanced Raman scattering (SERS) detection. TiO2-Au-rGO nanocomposites have been shown to demonstrate the superior SERS performances, which can be used for highly sensitive detection of rhodamine 6 G with a limit of detection of 1.2 × 10−10 M. Subsequently, the surface can be cleaned automatically by the photocatalytic degradation of the adsorbed analytes into inorganic small molecules under visible light irradiation. This can be attributed to the excellent photocatalytic degradation ability, leading to a recyclable SERS application. After being used four times, their excellent SERS and catalytic performances can still be retained. These results suggest that the TiO2-Au-rGO nanocomposites can provide a new strategy for fabricating recyclable SERS substrates, which are highly desirable for SERS practical application.

Improved Thermal Stability of Graphene-Veiled Noble Metal Nanoarrays as Recyclable SERS Substrates.

The ability to enhance the heat resistance of noble metals is vital to many industrial and academic applications. Because of its exceptional thermal properties, graphene was used to enhance the thermal stability of noble metals. Monolayer graphene-covered noble metal triangular nanoarrays (TNAs) showed excellent heat resistance, which could maintain their original triangular nanoarrays at high temperatures, whereas bare noble metal TNAs all agglomerate into spherical nanoparticles. On the basis of this mechanism, we obtained a universal recyclable surface-enhanced Raman scattering (SERS) substrate; after 16 cycles, the SERS substrate still worked well. The improvement of the heat resistance of noble metals by graphene has a great significance to the working reliability and service life of electronic devices and the single-use problem of traditional SERS substrates.

Gold Nanoparticles and g‐C3N4‐Intercalated Graphene Oxide Membrane for Recyclable Surface Enhanced Raman Scattering

Toxic organic pollutants in the aquatic environment cause severe threats to both humans and the global environment. Thus, the development of robust strategies for detection and removal of these organic pollutants is essential. For this purpose, a multifunctional and recyclable membrane by intercalating gold nanoparticles and graphitic carbon nitride into graphene oxide (GNPs/g‐C3N4/GO) is fabricated. The membranes exhibit not only superior surface enhanced Raman scattering (SERS) activity attributed to high preconcentration ability to analytes through π–π and electrostatic interactions, but also excellent catalytic activity due to the enhanced electron–hole separation efficiency. These outstanding properties allow the membrane to be used for highly sensitive detection of rhodamine 6G with a limit of detection of 5.0 × 10−14m and self‐cleaning by photocatalytic degradation of the adsorbed analytes into inorganic small molecules, thus achieving recyclable SERS application. Furthermore, the excellent SERS activity of the membrane is demonstrated by detection of 4‐chlorophenol at less than nanomolar level and no significant SERS or catalytic activity loss was observed when reusability is tested. These results suggest that the GNPs/g‐C3N4/GO membrane provides a new strategy for eliminating traditional, single‐use SERS substrates, and expands practical SERS application to simultaneous detection and removal of environmental pollutants.

Using Ag-embedded TiO2 nanotubes array as recyclable SERS substrate

A simple strategy for synthesizing Ag-loaded TiO2 nanotube film for use as multifunctional photocatalyst and recyclable surface-enhanced Raman scattering (SERS) substrate is introduced. Highly aligned TiO2 nanotube arrays (TNTA) prepared via electrochemical anodization were used as a 3D rough host for silver nanoparticles. Ag deposits were sputtered in a vacuum, and it was found that their morphologies were mainly influenced by the diameters of nanotubes and the UV irradiation induced aging process, especially the self-migration of silver along the tubular wall. SERS and the self-cleaning effect were observed using Rhodamine 6G (R6G) as the probe molecule. The results showed that narrow nanotube and silver nanoparticles embedment contributed significantly to both the phenomenal SERS and recyclability.

Reproducible and recyclable SERS substrates: Flower-like Ag structures with concave surfaces formed by electrodeposition

Direct synthesis of three-dimensional Ag structures on solid substrates for the purposes of producing reproducible and recyclable surface-enhanced Raman scattering (SERS) applications remains challenging. In this work, flower-like Ag structures with concave surfaces (FACS) were successfully electrodeposited onto ITO glass using the double-potentiostatic method. The FACS, with an enhancement factor of the order of 108, exhibited a SERS signal intensity 3.3 times stronger than that measured from Ag nanostructures without concave surfaces. A cleaning procedure involving lengthy immersion of the sample in ethanol and KNO3 was proposed to recycle the substrate and confirmed by using rhodamine 6G, adenine, and 4-aminothiophenol as target molecules. The findings can help to advance the practical applications of Ag nanostructure-based SERS substrates.