High Surface-enhanced Raman Scattering Research Articles

Ag nanocubes monolayer-modified PDMS as flexible SERS substrates for pesticides sensing.

A new approach is presented to fabricate flexible surface-enhanced Raman scattering (SERS) substrate of Ag nanocubes monolayer-modified polydimethylsiloxane (Ag NCs/PDMS) through a powerful three-phase interface self-assemble method. The morphologies and crystal structures were characterized by scanning electron microscopy and X-ray diffraction. The self-assembled Ag NCs/PDMS substrate exhibited high SERS activity and good signal homogeneity, which was successfully used for quantitative detection of thiram; the detection limit reached 10ng/mL, and the linear range is 10-1000ng/mL. Furthermore, the flexible SERS substrates were successfully employed to detect thiram residues on factual apple samples, and trace amount (1ng/cm2) of thiram residues was detected on apple peels. The excellent SERS detection ability of self-assembled Ag NCs/PDMS substrate indicated that it will play an important role in pesticide detection in the future.

Hybridizing Silver Nanoparticles in Hydrogel for High-Performance Flexible SERS Chips.

An ideal surface-enhanced Raman scattering (SERS) substrate should have high sensitivity, long-term stability, excellent repeatability, and strong anti-interference. In the present work, single-layer carbon-based dot (CD)-capped Ag nanoparticle aggregates (a-AgNPs/CDs) with high SERS activity are synthesized and hybridized with a hydrogel to prepare novel hydrogel SERS chips. Benefiting from the unique properties of a-AgNPs/CDs and the hydrogel, the constructed hydrogel SERS chips show excellent performances. Taking crystal violet detection as an example, the hydrogel SERS chips show a detection limit of around 1 × 10-16 mol/L (high sensitivity), maintain above 96.40% of SERS activity even after 14 weeks of storage (long-term stability), and display point-to-point relative standard deviation (RSD) in one chip as low as 1.43% (outstanding repeatability) and RSD in different chips as low as 2.75% (excellent reproducibility). Furthermore, the self-extraction effect of the hydrogel enables the flexible hydrogel SERS chips to be used for analyzing various real samples including soybean milk, juices, and fruits without any complex pretreatment. For instance, the hydrogel SERS chips are able to detect trace thiram and 2-(4-thiazolyl)benzimidazole with the detection limits of 1 and 5 ppb in liquid samples, respectively, and of 1 and 2.5 ng/cm2 on the peel of fruits, respectively. The self-extraction functional flexible SERS chips offer a reliable and convenient platform for the quick detection and on-site monitoring of chemical contaminants.

Robust Encapsulation of Biocompatible Gold Nanosphere Assemblies for Bioimaging via Surface Enhanced Raman Scattering

AbstractControlled assembly of gold nanoparticles (AuNPs) into clusters is a promising avenue for the development of sensitive bioimaging and diagnostic tools based on surface‐enhanced Raman scattering (SERS). However, several challenges, such as biocompatibility or colloidal and structural stability in biological environments, remain before AuNPs can be used as a tool for in vivo bioimaging. A versatile strategy for the preparation of colloidally stable and biocompatible AuNP clusters (AuNPCs) is introduced with high SERS signals, which are used as SERS contrast bioimaging agents (SERS tags). By tuning the ligand ratio of Raman reporter molecules to stabilizing polymer on the surface of each AuNP, aggregation can be carefully controlled. The resulting AuNPCs exhibit redshifted surface plasmon resonances in the near‐infrared (NIR) region, as well as distinct electromagnetic hotspots that give rise to SERS analytical enhancement factors above 104, compared to non‐clustered spherical AuNPs. Thanks to the protective polymer shell, high levels of cellular uptake with low cytotoxicity are observed, allowing 3D SERS mapping of cells with sufficiently high spatial resolution to detect AuNPCs within intracellular organelles.

Dielectric Walls/Layers Modulated 3D Periodically Structured SERS Chips: Design, Batch Fabrication, and Applications.

As an indispensable constituent of plasmonic materials/dielectrics for surface enhanced Raman scattering (SERS) effects, dielectrics play a key role in excitation and transmission of surface plasmons which however remain more elusive relative to plasmonic materials. Herein, different roles of vertical dielectric walls, and horizontal and vertical dielectric layers in SERS via 3D periodic plasmonic materials/dielectrics structures are studied. Surface plasmon polariton (SPP) interferences can be maximized within dielectric walls besieged by plasmonic layers at the wall thicknesses of integral multiple half‐SPPplasmonic material‐dielectric‐wavelength which effectively excites localized surface plasmon resonance to improve SERS effects by one order of magnitude compared to roughness and/or nanogaps only. The introduction of extra Au nanoparticles on thin dielectric layers can further enhance SERS effects only slightly. Thus, the designed Au/SiO2 based SERS chips show an enhancement factor of 8.9 × 1010, 265 times higher relative to the chips with far thinner SiO2 walls. As many as 1200 chips are batch fabricated for a 4 in wafer using cost‐effective nanoimprint lithography which can detect trace Hg ions as low as 1 ppt. This study demonstrates a complete generalized platform from design to low‐cost batch‐fabrication to applications for novel high performance SERS chips of any plasmonic materials/dielectrics.

Highly sensitive near-infrared SERS nanoprobes for in vivo imaging using gold-assembled silica nanoparticles with controllable nanogaps

BackgroundTo take advantages, such as multiplex capacity, non-photobleaching property, and high sensitivity, of surface-enhanced Raman scattering (SERS)-based in vivo imaging, development of highly enhanced SERS nanoprobes in near-infrared (NIR) region is needed. A well-controlled morphology and biocompatibility are essential features of NIR SERS nanoprobes. Gold (Au)-assembled nanostructures with controllable nanogaps with highly enhanced SERS signals within multiple hotspots could be a breakthrough.ResultsAu-assembled silica (SiO2) nanoparticles (NPs) (SiO2@Au@Au NPs) as NIR SERS nanoprobes are synthesized using the seed-mediated growth method. SiO2@Au@Au NPs using six different sizes of Au NPs (SiO2@Au@Au50–SiO2@Au@Au500) were prepared by controlling the concentration of Au precursor in the growth step. The nanogaps between Au NPs on the SiO2 surface could be controlled from 4.16 to 0.98 nm by adjusting the concentration of Au precursor (hence increasing Au NP sizes), which resulted in the formation of effective SERS hotspots. SiO2@Au@Au500 NPs with a 0.98-nm gap showed a high SERS enhancement factor of approximately 3.8 × 106 under 785-nm photoexcitation. SiO2@Au@Au500 nanoprobes showed detectable in vivo SERS signals at a concentration of 16 μg/mL in animal tissue specimen at a depth of 7 mm. SiO2@Au@Au500 NPs with 14 different Raman label compounds exhibited distinct SERS signals upon subcutaneous injection into nude mice.ConclusionsSiO2@Au@Au NPs showed high potential for in vivo applications as multiplex nanoprobes with high SERS sensitivity in the NIR region.Graphical

Improved versatile SERS spheroid end-facet optical fiber substrate based on silver nano-dendrites directly planted with gold nanoparticles using dual-laser assisted for pesticides detection

In this work, the novel versatile surface-enhanced Raman scattering (SERS) spheroid end-facet optical fiber substrate based on directly planting Au nanoparticles (AuNPs) on the surface of Ag nano-dendrites (AgNDs) via an in-situ growth method with dual-laser assisted was successfully fabricated. The enhancement factor (EF) for Rhodamine 6G (R6G) was calculated to be 2.54 × 107 and reached the highest value compared with other AuNPs and AgNDs SERS substrates. 40-day-duration stability tests showed that the Raman intensity of R6G on AuNPs/AgNDs SERS substrate reduced only by 11.16% and improved more stable than the AgNDs SERS substrate of 44.07%. Moreover, due to high SERS performance of AgNDs nanostructures and the chemical stability of AuNPs, the AuNPs/AgNDs SERS substrates were employed for rapid detection of cypermethrin and fenthion with limit of detection (LOD) of 2.87 × 10−4 ppm and 1.7 × 10−4 ppm, respectively. The AuNPs/AgNDs SERS spheroid end-facet optical fiber platform possesses high sensitivity, good uniformity and outstanding temporal stability thus can be used for realization of integrated portable pesticide detection devices.

Fast tailoring of gold nanoflowers by an interface-modified reverse microdroplet strategy

Gold nanoflowers (Au NFs) have received great attention for surface-enhanced Raman scattering (SERS) applications, due to the high surface area, availability of conjugation sites on surface and the localized surface plasmon resonance. However, their further application is much hampered by the complicated and time-consuming synthesis process, which remains better responded. Herein, we propose a novel & straightforward interface-modified reverse microdroplet strategy to configure homogeneously dispersed Au NFs within two hours, where Au3+ was reduced by excess aniline as two-in-one medium of reductant and solvent. It is demonstrated that the reaction system is robustly directed by the dynamic built-in reaction interface, thanks to the capping effect of the in-situ formed polyaniline (PANI) and polyvinyl pyrrolidone (PVP). It is further identified that the final morphology of Au NFs is strongly determined by the nucleation & growth rates. Consequently, such a well-tailored microstructure endows the Au NFs with sound performance for SERS applications. When using methylene blue (MB) as a molecular probe, a high SERS enhancement factor above 105 is delivered. This work provides a feasible interface-assisted methodology to investigate multi-level structures, and sheds light toward simply advancing versatile nanomaterials for broad applications.

An excitation wavelength-optimized, stable SERS biosensing nanoplatform for analyzing adenoviral and AstraZeneca COVID-19 vaccination efficacy status using tear samples of vaccinated individuals

We introduce a label-free surface-enhanced Raman scattering (SERS) biosensing platform equipped with metallic nanostructures that can identify the efficacy of Oxford-AstraZeneca (AZD1222) vaccine in vaccinated individuals using non-invasive tear samples. We confirmed the hypothesis that the tears of people who receive the AZD1222 vaccine may be similar to those of adenovirus epidemic keratoconjunctivitis patients since the Oxford-AstraZeneca vaccine is derived from a replication-deficient ChAdOx1 vector of chimpanzee adenovirus. Additionally, we confirmed the potential of the three markers for estimating the vaccination status via analyzing the signals emanating from antibodies or immunoglobulin G by-product using our label-free, SERS biosensing technique with a high reproducibility (<3% relative standard deviation), femtomole-scale limit of detection (1 × 10−14 M), and high SERS response of >108. Therefore, our label-free SERS biosensing nanoplatforms with long-term storage and robust stability will enable rapid and robust monitoring of the vaccine presence in vaccinated individuals.

Fabrication of stable substoichiometric WOx films with high SERS sensitivity by thermal treatment

Generally, annealing-induced surface oxygen vacancy defects in oxides are easily healed by air. Here, stable Magnéli phase WOx films were fabricated by thermal treatment of WO3 films in vacuum at 500 °C for 4 h. Aboundant electronic levels, derived from W5+-singly charged oxygen vacancy (Vo+) defect complexes, were detected at the surface of the WOx films, which indicates the formation of stable oxygen-defect phases (Magnéli phases). The concentration of surface oxygen vacancy depends on both annealing energy and the oxygen concentration gradient between the surface and the bulk of films. The reduced WO2.88 films exhibited greatly enhanced surface-enhanced Raman scattering (SERS) performance which was even comparable to noble metals without “hot spots”. The detection limit of Rhodamine 6G was decreased from 10−1 to 10−7 M. The outstanding SERS performance was mainly attributed to defect-related levels providing additional and efficient exciton and charge-transfer resonances in the system of molecule and oxide. Combining experimental results with theoretical study, this work demonstrates that the substoichiometric WOx induced by vacuum annealing shows good stability and it is indeed a potential candidate for SERS detection.

Facile preparation of Cu2-xS supernanoparticles with an unambiguous SERS enhancement mechanism

Surface-enhanced Raman scattering (SERS) techniques benefit from the development of various substrates ranging from noble metal to semiconductor materials. Semiconductor substrates have been assumed to construct more specific structures and designable surface chemistry than noble metal substrates. Therefore, the development of semiconductor substrates may lead to the selective recognition of target molecules, more stable SERS spectra, and even low-cost fabrication of SERS substrates. In this paper, we disclose semiconductor supernanoparticles formed by a self-limiting assembly process with stable properties, easy scale-up fabrication, and high SERS enhancement. The detected concentration of analytes reaches as low as 10−8 M. The built-in hotspots and self-doping in suprananoparticles provide strong electromagnetic enhancement, and the molecular resonance and charge transfer with the target molecule contribute to chemical enhancement. Discrete dipole approximation simulation was used to further confirm the SERS enhancement mechanism. Cu2-xS supernanoparticles paved a new way to construct novel semiconductors with SERS activity.

Nanoscale engineering of ring-mounted nanostructure around AAO nanopores for highly sensitive and reliable SERS substrates

Surface-enhanced Raman scattering (SERS) is recognized as one of the most favored techniques for enhancing Raman signals. The morphology of the SERS substrate profoundly affects molecular Raman spectra. This study aimed to construct a ring-mounted nanostructured substrate via liquid–liquid two-phase self-assembly incorporated with anodic aluminum oxide (AAO) membrane transfer techniques. High-density nanoparticles (NPs) assembled on AAO membranes were ascribed to reduce the diameters of the nanopores, with Au–Ag alloy NPs to regulate the dielectric constant so as to reveal the local surface plasmon resonance tunability. SERS engineered in this way allowed for the fabrication of a ring-mounted nanostructured substrate where the distribution density of NPs and dielectric constant could be independently fine-tuned. High SERS activity of the substrate was revealed by detecting the enhanced factor of crystal violet and rhodamine 6G molecules, which was up to 1.56 × 106. Moreover, SERS of thiram target molecules confirmed the supersensitivity and repeatability of the substrate as a practical application. The results of this study manifested a low-cost but high-efficiency ring-mounted nanostructured SERS substrate that might be suitable in many fields, including biosensing, medical research, environmental monitoring, and optoelectronics.

Dendrimer stabilized nanoalloys for inkjet printing of surface-enhanced Raman scattering substrates

Research on paper substrates prepared by inkjet deposition of metal nanoparticles for sensing applications has become a hot topic in recent years; however, the design of such substrates based on the deposition of alloy nanoparticles remains less explored. Herein, we report for the first time the inkjet printing of dendrimer-stabilized colloidal metal nanoalloys for the preparation of paper substrates for surface-enhanced Raman scattering (SERS) spectroscopy. To this end, nanoassemblies containing variable molar ratios of Au:Ag were prepared in the presence of poly(amidoamine) dendrimer (PAMAM), resulting in plasmonic properties that depend on the chemical composition of the final materials. The dendrimer-stabilized Au:Ag:PAMAM colloids exhibit high colloidal stability, making them suitable for the preparation of inks for long-term use in inkjet printing of paper substrates. Moreover, the pre-treatment of paper with a polystyrene (PS) aqueous emulsion resulted in hydrophobic substrates with improved SERS sensitivity, as illustrated in the analytical detection of tetramethylthiuram disulfide (thiram pesticide) dissolved in aqueous solutions. We suggest that the interactions established between the two polymers (PAMAM and PS) in an interface region over the cellulosic fibres, resulted in more exposed metallic surfaces for the adsorption of the analyte molecules. The resulting hydrophobic substrates show long-term plasmonic stability with high SERS signal retention for at least ninety days.

Novel irregular pore peripheral plasmonic mechanism of nanocomposite metal-nanoporous AAO using new facile one-step anodization and pore widening for high SERS enhancement

Conventional surface-enhanced Raman scattering (SERS) substrates are usually performed by Ag-or-Au metal nanoparticles (Ag,Au-MNPs) in suspension-or-solid substrates. The SERS mechanism is widely explained by the hot spots and shape of Ag,Au-MNPs. Here, the facile one-step irregular-nanopore anodic aluminum oxide (AAO) with platinum-metal-film (Pt-MF) coating as the new SERS substrate is proposed. A novel SERS mechanism based on the irregular Pore Peripheral Plasmonic Mechanism (3PM) of MF-AAO is interpreted. COMSOL® simulation shows the pore peripheral of AAO may gather a strong electric field for enhancing Raman signal. The irregular pores formed in the as-prepared one-step AAO and followed by pore-widening etching can generate additional hot spots at the small interpore gap and high-curvature tips for further enhancing SERS analytical enhancement factor (AEF). Using methylene blue (MB) as a probe molecule that was generally used to practically detect industry-pollution S2- and to sanitize water for fish health, the Pt-MF-AAO SERS substrate can reach a high AEF up to 1.88 × 105, and low limit of detection (LOD) of 1 × 10−9 M. A good linearity (R2 of 0.9406) between the MB concentration and Raman intensity is achieved. The large-area (several cm2) uniformity of is good with relative standard deviation (RSD) of 7.14%.

Enhancing SERS Intensity by Coupling PSPR and LSPR in a Crater Structure with Ag Nanowires

The sensitive characteristics of surface-enhanced Raman scattering (SERS) can be applied to various fields, and this has been of interest to many researchers. Propagating surface plasmon resonance (PSPR) was initially utilized but, recently, it has been studied coupled with localized surface plasmon resonance that occurs in metal nanostructures. In this study, a new type of metal microstructure, named crater, was used for generating PSPR and Ag nanowires (AgNWs) for the generation of LSPR. A crater structure was fabricated on a GaAs (100) wafer using the wet chemical etching method. Then, a metal film was deposited inside the crater, and AgNWs were uniformly coated inside using the spray coating method. Metal films were used to enhance the electromagnetic field when coupled with AgNWs to obtain a high SERS intensity. The SERS intensity measured inside the crater structure with deposited AgNWs was up to 17.4 times higher than that of the flat structure with a deposited Ag film. These results suggest a new method for enhancing the SERS phenomenon, and it is expected that a larger SERS intensity can be obtained by fine-tuning the crater size and diameter and the length of the AgNWs.

Oil-Free Gold Nanobipyramid@Ag Microgels as a Functional SERS Substrate for Direct Detection of Small Molecules in a Complex Sample Matrix.

Surface-enhanced Raman scattering (SERS) is a super-sensitive analysis technology based on the target molecular fingerprint information. The enhancement of local electromagnetic field of the SERS substrate would increase the target molecules' Raman intensity which adsorb on the surface of nanoparticles. However, the existing adhesive macromolecules in the complex mixed sample would interfere with the adsorption of small target molecules, and it weakens the Raman intensity of target molecules. Microgels are one of the potential materials to suppress the interference of adhesive macromolecules and to avoid the complex pretreatments. However, most of the current microgel synthesis methods involve complex operations with precise instrumentation or the interference of oil and organic reagents. In this work, a simple and oil-free method was proposed to synthesize the gold nanobipyramid (Au NBP)@Ag@hyaluronic acid microgel via the condensation reaction of carboxyl and amino groups. As a proof-of-concept demonstration for small-molecule detection, the rhodamine 6G (R6G) molecules were allowed to enter inside the microgel through the meshes and adsorb on the surface of Au NBP@Ag nanoparticles within 30 min, while the macromolecule (bovine serum albumin in this case) was retained outside the microgel in the meantime. In addition, under the combined action of lightning rod effect of Au NBP and surface plasmon resonance effect of silver render the microgels with high SERS activity. The synthetic Au NBP@Ag@hyaluronic acid microgels were applied to detect 6-thioguanine in the human serum without any pretreatment process, and it showed a high signal enhancement and stable SERS signal, which can satisfy the requirement of clinical diagnosis. These results show that the proposed microgels have potential applications in the field of point-of-care testing.

Self-assembled plasmonic nanoarrays for enhanced bacterial identification and discrimination

The rapid and accurate bacterial testing is a critical step for the management of infectious diseases, but challenges remain largely due to a lack of advanced sensing tools. Here we report the development of highly plasmon-active, biofunctional nanoparticle arrays for simultaneous capture, identification, and differentiation of bacteria by surface-enhanced Raman scattering (SERS). The nanoarrays were facilely prepared through an electrostatic mechanism-controlled self-assembly of metallic nanoparticles at liquid-liquid interfaces, and exhibited high SERS sensitivity beyond femtomole, good reproducibility (relative standard deviation of 2.7%) and stability. Modification of the nanoarrays with concanavalin A allowed to effective capture of both Gram-positive and Gram-negative bacteria (bacterial-capture efficiency maintained beyond 50%) at bacterial concentrations ranging from 50 to 2000 CFU mL−1, as determined by the plate-counting method. Moreover, single-cell Raman fingerprinting and discrimination of eight different bacteria species with high signal-to-noise ratio, excellent spectral reproducibility, and a total assay time of 1.5 h was achieved under fairly mild conditions (24 μW, acquisition time: 1 s). Collectively, we believe that our biofunctionalized, SERS-based self-assembled nanoarrays have great potential to help in rapid and label-free bacterial diagnosis and phenotyping study.

Structural engineering of transition-metal nitrides for surface-enhanced Raman scattering chips

Noble-metal-free surface-enhanced Raman scattering (SERS) substrates have attracted great attention for their abundant sources, good signal uniformity, superior biocompatibility, and high chemical stability. However, the lack of controllable synthesis and fabrication of noble-metal-free substrates with high SERS activity impedes their practical applications. Herein,we propose a general strategy to fabricate a series of planar transition-metal nitride (TMN) SERS chips via an ambient temperature sputtering deposition route.These planar TMN (tungsten nitride, tantalum nitride, and molybdenum nitride) chips show remarkable Raman enhancement factors (EFs) with ~105 owing to efficient photoinduced charge transfer process between TMN chips and probe molecules. Further, structural engineering of these TMN chips is used to improve their SERS activity. Benefiting from the synergistic effect of charge transfer process and electric field enhancement by constructing nanocavity structure, the Raman EF of WN nanocavity chips could be greatly improved to 1.29 * 107, which is an order of magnitude higher than that of planar chips. Moreover, we also design the WN/monolayer MoS2 heterostructure chips. With the increase of surface electron density on the upper WN and more exciton resonance transitions in the heterostructure, a 1.94 * 107 level EF and a 5 * 10-10 m level detention limit could be achieved. Our results provide important guidance for the structural design of ultrasensitive noble-metal-free SERS chips.

Laser induced surface enhanced Raman scattering of silver thin films decorated with carbon nanoparticles

Silver (Ag) thin films decorated with carbon nanoparticles were achieved by ablating Ag/C thin film with an Nd:YAG fiber pulsed laser under the environmental conditions. The structure and optical properties of the Ag/C samples were investigated. In this study, the Surface plasmon resonance (SPR) wavelength of Ag/C samples shift from 457 nm to 527 nm was realized using a different laser scanning rate. Compared to Ag samples, Surface enhanced Raman scattering (SERS) of Ag/C samples was also observed due to decorating with nano-carbon, which demonstrates good steadiness and high SERS intensity with the concentration of Rhodamine 6G (Rh 6G) with 10−5 mol/L. In additional, the simulation results of finite-difference-time-domain (FDTD) verify SERS performance.

Au‐Nanoparticle‐Array/Aligned‐Ag‐Nanowire‐Based Flexible Dual Plasmonic Substrate for Sensitive Surface‐Enhanced Raman Scattering Detection

AbstractThe fabrication of flexible surface‐enhanced Raman scattering (SERS) substrates for sensitive detection on uneven or irregular surfaces is challenging. In this study, a flexible dual plasmonic SERS (FDPS) substrate rationally constructed using Au nanoparticle (AuNP) arrays/aligned Ag nanowires (AgNWs) and elastic polyurethane (PU) is demonstrated. It exhibits high sensitivity (detection limit of 10−8 m for melamine and 10−10 m for malachite green) and excellent reproducibility. The well‐designed structure of AuNP arrays/aligned AgNWs fabricated using block copolymer self‐assembly and oil–water–air interfacial self‐assembly successfully enhances the electromagnetic field through plasmonic coupling. In addition, the FDPS substrate retains a high SERS sensitivity after exposure to air at room temperature for 30 days because of the high stability of AuNP arrays and antioxidation characteristic of the PU covered on the aligned AgNWs. Even after undergoing stretching, bending, and twisting for 100 cycles, the FDPS substrate maintains a stable SERS activity owing to the introduction of the elastic PU. This study demonstrates a potential application of SERS detection under practical conditions for irregular surfaces and may be helpful in the development of flexible sensors.

Three-dimensional surface-enhanced Raman scattering substrates constructed by integrating template-assisted electrodeposition and post-growth of silver nanoparticles

Three-dimensional (3D) plasmonic nano-arrays can provide high surface-enhanced Raman scattering (SERS) sensitivity, good spectral uniformity and excellent reproducibility. However, it is still a challenge to develop a simple and efficient method for fabrication of 3D plasmonic nano-arrays with high SERS performance. Here we report a facile approach to construct ordered arrays of silver (Ag) nanoparticles-assembled spherical micro-cavities using polystyrene (PS) sphere template-assisted electrodeposition and post-growth. The electrodeposited small Ag nanoparticles grow into bigger stable nanoparticles during the post-growth process, which could significantly improve the SERS sensitivity. The Ag nanoparticles-assembled 3D micro-cavity array provides much more hotspots in the excitation laser beam-covered volume than the two-dimensional counterpart. The relative standard deviation (RSD) of 612 cm−1 peak of rhodamine 6G (R6G) was calculated to be 8%, and the RSD of the characteristic peak taken from substrates of different batches was less than 10%. The detectable lower concentration as low as 1 fM was achieved for an aqueous solution of R6G. Such SERS substrate also showed high sensitivity to thiram (fungicide) and paraquat (herbicide) in water with limits of detection of 0.067 nM and 2.5 nM respectively. Furthermore, it also demonstrated that SERS detection of pesticide residues on fruits can be realized, showing a potential application in rapid monitoring food safety.