Facile fabrication of Au-Ag alloy nanoparticles/Ag nanowires SERS substrates with bimetallic synergistic effect for ultra-sensitive detection of crystal violet and alkali blue 6B.

The bimetallic nanostructure of Au and Ag can integrate two distinct properties into a novel substrate compared to single metal nanostructures. This work presents a rapid and sensitive surface-enhanced Raman scattering (SERS) substrate for detecting illegal food additives and dyes of crystal violet (CV) and alkali blue 6B (AB 6B). Au-Ag alloy nanoparticles/Ag nanowires (Au-Ag ANPs/Ag NWs) were prepared by solid-state ionics method and vacuum thermal evaporation method at 5µA direct current electric field (DCEF), the molar ratio of Au to Ag was 1:18.34. Many 40 nm-140 nm nanoparticles regularly existed on the surface of Ag NWs with the diameters from 80 nm to 150 nm. The fractal dimension of Au-Ag ANPs/Ag NWs is 1.69 due to macroscopic dendritic structures. Compared with single Ag NWs, the prepared Au-Ag ANPs/Ag NWs substrates show superior SERS performance because of higher surface roughness, the SERS active of Ag NWs and bimetallic synergistic effect caused by Au-Ag ANPs, so the limit of detections (LOD) of Au-Ag ANPs/Ag NWs SERS substrates toward detection of CV and AB 6B were as low as 10-16mol/L and 10-9mol/L, respectively. These results indicate that Au-Ag ANPs/Ag NWs substrates can be used for rapid and sensitive detection of CV and AB 6B and have great development potential for detection of illegal food additives and hazardous substances in the fields of environmental monitoring and food safety.

Sensitive phenotyping of serum extracellular vesicles on a SERS-microfluidic platform for early-stage clinical diagnosis of ovarian carcinoma.

Ovarian carcinoma (OvCa) poses a severe threat to women's health due to its high mortality rate and lack of efficient early diagnosis approach. There is evidence to suggest that nanosized small extracellular vesicles (sEVs) which carrying cell-specific components from OvCa can serve as potential diagnostic biomarkers. Herein, we reported a Surface-enhanced Raman Scattering (SERS)-multichannel microchip for sEVs (S-MMEV) assay to investigate the phenotype changes of sEVs. The microchip composed of seven microchannels, which enabled the parallel detection of multiple biomarkers to improve the detection accuracy. Using SERS probes conjugated with antibodies recognizing different biomarkers including ubiquitous EV biomarkers (i.e., tetraspanins; CD9, CD81) and putative OvCa tumor biomarkers (i.e. EpCAM, CD24, CA125, EGFR), we successfully analyzed the phenotypic changes of sEVs and accurately differentiated OvCa patients from healthy controls, even at early stage (I-II), with high sensitivity, high specificity and an area under the curve value of 0.9467. Additionally, the proposed approach exhibited higher sensitivity than conventional methods, demonstrating the efficiency of precise detection from cell culture and clinical samples. Collectively, the developed EV phenotyping approach S-MMEV could serve as a potential tool to achieve the early clinical diagnosis of OvCa for further precise diagnosis and personal treatment monitoring.

Dual LSPR and CT synergy: 3D urchin-like Au@W18O49 enables highly sensitive in-situ SERS detection of dissolved furfural in insulating oils.

Assessing the levels of furfural in insulating oils is a crucial technical method for evaluating the degree of aging and mechanical deterioration of oil-paper insulation. The surface-enhanced Raman spectroscopy (SERS) technique provides an effective method for enhancing the sensitivity of in-situ detection of furfural. In this study, a homogeneous three-dimensional (3D) urchin-like Au@W18O49 heterostructure was synthesized as a SERS substrate using a straightforward hydrothermal method. The origin of the superior Raman enhancement properties of the 3D urchin-like heterostructures formed by the noble metal Au and the plasmonic semiconductor W18O49, which is rich in oxygen vacancies, is analyzed experimentally in conjunction with density-functional theory (DFT) calculations. The Raman enhancement is further amplified by the remarkable dual localized surface plasmon resonance (LSPR) effect, which generates a strong local electric field and creates numerous "hot spots," in addition to the interfacial charge transport (CT). The synergistic effect of these factors results in the 3D urchin-like Au@W18O49 heterostructure exhibiting exceptionally high SERS activity. Testing the rhodamine 6G (R6G) probe resulted in a Raman enhancement factor of 3.41 × 10-8, and the substrate demonstrated excellent homogeneity and stability. Furthermore, the substrate was effectively utilized to achieve highly sensitive in-situ surface-enhanced Raman scattering (SERS) detection of dissolved furfural in complex plant insulating oils. The development of the 3D urchin-like Au@W18O49 heterostructure and the exploration of its enhancement mechanism provide theoretical insights for the advancement of high-performance SERS substrates.

Tuning surface morphology of AuNPs film via thiourea as a stable SERS platform for methylene blue.

Gold nanoparticles (AuNPs) have been extensively utilized in various fields such as sensors, life sciences, and catalysis. In this study, AuNPs were synthesized using a reduction method and subsequently treated with thiourea in an ethanol-water environment to prepare AuNPs film using a centrifugal deposition method for first time, resulting in the aggregation of the initial small-sized AuNPs into larger microsphere-like structures. The addition of thiourea facilitated the interconnection between AuNPs, ultimately leading to the formation of large stable gold microspheres. The sheet resistance of the AuNP films transitioned from being non-conductive to exhibiting a sheet resistance of 42.6 Ω/sq following thiourea treatment. The transformation from a flat surface to tightly connected particles resembling microspheres was observed from SEM images. The thiourea treatment not only altered the morphological characteristic of the AuNPs films but also significantly increased the number of scattering sites on their surface, leading to a substantial enhancement in the Raman scattering effect for methylene blue. This structural configuration also improved the electronic conduction and stability of the treated AuNPs films. Consequently, these findings suggest that AuNPs have promising application prospects in surface-enhanced Raman scatting (SERS), as well as in flexible electronics, catalysis, adsorption, and energy fields.

Epitaxial Growth of Monolayer WS2 Single Crystals on Au(111) Toward Direct Surface-Enhanced Raman Spectroscopy Detection.

The epitaxial growth of wafer-scale two-dimensional (2D) semiconducting transition metal dichalcogenides (STMDCs) single crystals is the key premise for their applications in next-generation electronics. Despite significant advancements, some fundamental factors affecting the epitaxy growth have not been fully uncovered, e.g., interface coupling strength, adlayer-substrate lattice matching, substrate step-edge-guiding effects, etc. Herein, we develop a model system to tackle these issues concurrently, and realize the epitaxial growth of wafer-scale monolayer tungsten disulfide (WS2) single crystals on the Au(111) substrate. This epitaxial system is featured with good adlayer-substrate lattice matching, obvious step-edge-guiding effect for the unidirectionally aligned nucleation/growth, and relatively weaker interfacial interaction than that of monolayer MoS2/Au(111), as evidenced by the evolution of a uniform Moiré pattern and an intrinsic band gap, according to on-site scanning tunneling microscopy/spectroscopy (STM/STS) characterizations and density functional theory calculations. Intriguingly, the unidirectionally aligned monolayer WS2 domains along the Au(111) steps can behave as ultrasensitive templates for surface-enhanced Raman scattering detection of organic molecules, due to the obvious charge transfer occurred at substrate step edges. This work should hereby deepen our understanding of the epitaxy mechanism of 2D STMDCs on single-crystal substrates, and propel their wafer-scale production and applications in various cutting-edge fields.

Enantioselective Molecular Detection by Surface Enhanced Raman Scattering at Chiral Gold Helicoids on Grating Surfaces.

Distinct advantages of surface enhanced Raman scattering (SERS) in molecular detection can benefit the enantioselective discrimination of specific molecular configurations. However, many of the recent methods still lack versatility and require customized anchors to chemically interact with the studied analyte. In this work, we propose the utilization of helicoid-shaped chiral gold nanoparticles arranged in an ordered array on a gold grating surface for enantioselective SERS recognition. This arrangement ensured a homogeneous distribution of chiral plasmonic hot spots and facilitated the enhancement of the SERS response of targeted analytes through plasmon coupling between gold helicoid multimers (formed in the grating valleys) and adjacent regions of the gold grating. Naproxen enantiomers (R(+) and S(-)) were employed as model compounds, revealing a clear dependence of their SERS response on the chirality of the gold helicoids. Additionally, propranolol and penicillamine enantiomers were used to validate the universality of the proposed approach. Finally, numerical simulations were conducted to elucidate the roles of intensified local electric field and optical helicity density on the SERS signal intensity and on the chirality of the nanoparticles and enantiomers. Unlike previously reported methods, our approach relies on the excitation of a chiral plasmonic near-field and its interaction with the chiral environment of analyte molecules, obviating the need for the enantioselective entrapment of targeted molecules. Moreover, our method is not limited to specific analyte classes and can be applied to a broad range of chiral molecules.

Integrating, Validating, and Expanding Information Space in Single-Molecule Surface-Enhanced Raman Spectroscopy for Biomolecules.

Single-molecule surface-enhanced Raman spectroscopy (SM-SERS) is an ultrahigh-resolution spectroscopic method for directly obtaining the complex vibrational mode information on individual molecules. SM-SERS offers a wide range of submolecular information on the hidden heterogeneity in its functional groups and varying structures, dynamics of conformational changes, binding and reaction kinetics, and interactions with the neighboring molecule and environment. Despite the richness in information on individual molecules and potential of SM-SERS in various detection targets, including large and complex biomolecules, several issues and practical considerations remain to be addressed, such as the requirement of long integration time, challenges in forming reliable and controllable interfaces between nanostructures and biomolecules, difficulty in determining hotspot size and shape, and most importantly, insufficient signal reproducibility and stability. Moreover, utilizing and interpreting SERS spectra is challenging, mainly because of the complexity and dynamic nature of molecular fingerprint Raman spectra, and this leads to fragmentary analysis and incomplete understanding of the spectra. In this Perspective, we discuss the current challenges and future opportunities of SM-SERS in views of system approaches by integrating molecules of interest, Raman dyes, plasmonic nanostructures, and artificial intelligence, particularly for detecting and analyzing biomolecules to realize the validation and expansion of information space in SM-SERS.

Solid-phase extraction coupled to automated centrifugal microfluidics SERS: Improving quantification of therapeutic drugs in human serum.

Surface-enhanced Raman spectroscopy (SERS) is a powerful method in analytical chemistry, but its application in real-life medical settings has been limited due to technical challenges. In this work, we introduce an innovative approach that is meant to advance the automation of microfluidics SERS to improve reproducibility and label-free quantification of two widely used therapeutic drugs, methotrexate (MTX) and lamotrigine (LTG), in human serum. Our methodology involves a miniaturized solid-phase extraction (µ-SPE) method coupled to a centrifugal microfluidics disc with incorporated SERS substrates (CD-SERS). The CD-SERS platform enables simultaneous controlled sample wetting and accurate SERS mapping. Together with the assay we implemented a machine learning method based on Partial Least Squares Regression (PLSR) for robust data analysis and drug quantification. The results indicate that combining µ-SPE with CD-SERS (µ-SPE to CD-SERS) led to a substantial improvement in the signal-to-noise ratio compared to combining CD-SERS with ultrafiltration or protein precipitation. The PLSR model enabled us to obtain the limit of detection and quantification for MTX as 2.90 and 8.92 µM, respectively, and for LTG as 10.76 and 32.29 µM. We also validated our µ-SPE to CD-SERS method for MTX against HPLC and immunoassay (p-value <0.05), using patient samples undergoing MTX therapy. In addition, we achieved a satisfactory recovery rate (80%) for LTG when quantifying it in patient samples. Our results show the potential of this newly developed approach as a strategy for therapeutic drugs in point-of-care clinical settings and highlight the benefits of automating label-free SERS assays.

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.

Two-Orders-of-Magnitude Enhancement of SERS Activity via a Simple Surface Engineering of Quasi-Metal Single-Crystal Frameworks.

Beyond noble metals and semiconductors, quasi-metals have recently been shown to be noteworthy substrates for surface enhanced Raman spectroscopy, and their excellent quasi-metal surface-enhanced Raman spectroscopy (SERS) sensing has demonstrated a wider range of application scenarios. However, the underlying mechanism behind the enhanced Raman activity is still unclear. Here, we demonstrate that surface hydroxyls play a crucial role in the enhancement of the SERS activity of quasi-metal nanostructures. As a demonstration material, quasi-metallic MoO2 single-crystal frameworks rich in surface hydroxyls have been shown to have 100 times higher SERS activity than MoO2 single-crystal frameworks without hydroxyl functionalization, with a Raman enhancement factor of up to 7.6 × 107. Experimental and first-principles density-functional theory calculation results show that the enhanced Raman activity can be attributed to an effective interfacial charge transfer within the MoO2/OH/molecule system.

Speciation Analysis of Metals and Metalloids by Surface Enhanced Raman Spectroscopy.

The presence of metalloids and heavy metals in the environment is of critical concern due to their toxicological impacts. However, not all metallic species have the same risk level. Specifically, the physical, chemical, and isotopic speciation of the metal(loids) dictate their metabolism, toxicity, and environmental fate. As such, speciation analysis is critical for environmental monitoring and risk assessment. In the past two decades, surface-enhanced Raman spectroscopy (SERS) has seen significant developments regarding trace metal(loid) sensing due to its ultrahigh sensitivity, readiness for in situ real-time applications, and cost-effectiveness. However, the speciation of metal(loid)s has not been accounted for in the design and application of SERS sensors. In this Perspective, we examine the potential of SERS for metal(loid) speciation analysis and highlight the advantages, progress, opportunities, and challenges of this application.

Magnetic Micromotors with Spiky Gold Nanoshells as SERS Sensors for Thiram and Bacteria Detection.

Surface-enhanced Raman scattering (SERS) is widely used in all kinds of detection due to its ultrahigh sensitivity and selectivity. Micromotors, when used as SERS sensors, or the so-called "hotspots on the fly", can combine both controlled mobility and SERS sensing capacity, and are ideal for versatile in situ detection. In this work, mobile SERS sensors are successfully fabricated by growing gold nanospikes onto magnetic microsphere surfaces. These mobile micromotors can act as normal SERS sensors, characterized by the trace detection of thiram, a highly toxic fungicide. The detection limit can reach 0.1 nM, as good as most other noble metal deposited substrates. With significant magnetic gradient forces, separation of pathogenic bacteria from bulk solution is achieved once these magnetic micromotors bind with bacterial cells. Manipulated propulsion of micromotors, on the other hand, enables them to approach and contact pathogenic bacterial cells on command and further acquire Raman spectra under a controlled degree of contact, a capability never seen with passive sensors. The robotic SERS sensors have demonstrated unique sensing characteristics with controlled manipulations along with discriminative detection between bacterial species.

Highly sensitive SERS detection of melamine based on 3D Ag@porous silicon photonic crystal.

The stability, reproducibility and engineering of SERS substrate faces a great challenge in melamine SERS assay. In this work, a simple, highly sensitive, stable and cost-efficient SERS detection platform for melamine was established based on its Raman fingerprints spectrum. The Ag@ porous silicon photonic crystal (Ag@PPC) was prepared as the 3D SERS substrate by electrochemical etching and magnetron sputter technology. The main influence factors for the preparation of SERS substrate were investigated in detail. The analytical enhancement factor of the 3D SERS substrate can reach to 2.6 × 108. The 3D SERS detection platform showed a wide linear detection range of 10-4∼10 mg L-1 and a low limit of detection of 0.1 µg L-1 for melamine. Moreover, such detection platform showed good stability, high reproducibility and high recovery rates for melamine. The 3D Ag@PPC SERS substrate can be easily prepared and engineered, displaying a great potential application in food safety field.

Rapid determination of phenolic composition in chamomile (Matricaria recutita L.) using surface-enhanced Raman spectroscopy.

Flavonoids and hydroxycinnamic acids are the main responsible of the antioxidant activity of chamomile (Matricaria recutita L.). Traditional methods for the analysis of the phenolic content in vegetables often suffer from limitations such as being expensive, time-consuming, and complex. In this study, we propose, for the first time, the use of surface-enhanced Raman spectroscopy (SERS) for the rapid determination of the main components of the polyphenolic fraction in chamomile. Results demonstrate that SERS can serve as an alternative or complementary technique to main analytical strategies for qualitative and quantitative determination of polyphenol compounds in plant extracts. The method can be proposed for quasi real-time analysis of herbal teas and infusions, facilitating rapid screening of their main antioxidant components.

Branched hybridization chain reaction and tetrahedral DNA-based trivalent aptamer powered SERS sensor for ultra-highly sensitive detection of cancer-derived exosomes.

Exosomes have emerged as a promising noninvasive biomarker for early cancer diagnosis due to their ability to carry specific bioinformation related to cancer cells. However, accurate detection of trace amount of cancer-derived exosomes in complex blood remains a significant challenge. Herein, an ultra-highly sensitive SERS sensor, powered by the branched hybridization chain reaction (bHCR) and tetrahedral DNA-based trivalent aptamer (triApt-TDN), has been proposed for precise detection of cancer-derived exosomes. Taking gastric cancer SGC-7901 cells-derived exosomes as a test model, the triApt-TDNs were constructed by conjugating aptamers specific to mucin 1 (MUC1) protein with tetrahedral DNAs and subsequently immobilized on the surface of silver nanorods (AgNRs) arrays to create SERS-active sensing chips capable of specifically capturing exosomes overexpressing MUC1 proteins. The bHCR was further initiated by the trigger aptamers (tgApts) bound to exosomes, and as a result the SERS tags were assembled into AuNP network structures with abundant SERS hotspots. By optimizing the sensing conditions, the SERS sensor showed good performance in ultra-highly sensitive detection of target exosomes within 60 min detection time, with a broad response ranging of 1.44 to 1.44 × 104 particles·µL-1 and an ultralow limit of detection capable of detecting a single exosome in 2 µL sample. Furthermore, the SERS sensor exhibited good uniformity, repeatability and specificity, and capability to distinguish between gastric cancer (GC) patients and healthy controls (HC) through the detection of exosomes in clinical human serums, indicating its promising clinical potential for early diagnosis of gastric cancer.

New screen-printed electrodes for Raman spectroelectrochemistry. Determination of p-aminosalicylic acid.

BACKGROUND: The availability of new surface enhanced Raman scattering (SERS) substrates is essential to develop quantitative analytical methods. Electrochemistry is an easy, fast and reproducible methodology to prepare SERS substrates on screen-printed electrodes (SPEs). RESULTS: This work proposes new SPEs based on a three-electrode system all made of silver. Using the same ink for the whole electrode system facilitates the fabrication process, reduces production costs, and leads to excellent analytical performance. The results showed that Raman enhancement depends strongly on the type of silver ink. To demonstrate the capabilities of the new electrodes developed, 4-aminosalicylic acid was determined in complex matrices and in the presence of strong interfering compounds such as salicylic acid and acetylsalicylic acid. The proposed analytical method is based on the electrochemical surface oxidation enhanced Raman scattering (EC-SOERS) strategy. AgCl nanocrystals are generated on the working electrode surface, which amplify the Raman signal of 4-aminosalicylic acid. Good figures of merit were obtained both in the absence and in the presence of the interfering compounds, achieving a correct estimation of a 4-aminosalicylic test sample in complex matrices. SIGNIFICANCE: The new SPEs have been demonstrated to be very sensitive and reproducible which, together to the high specificity of the Raman signal, makes this methodology very attractive for chemical analysis.

Au/Ag@ZIF-8 nanocomposite as solid phase extraction adsorbent and SERS substrate for tacrolimus label-free therapeutic drug monitoring in human serum.

Surface Enhanced Raman Scattering (SERS) has been extensively utilized in therapeutic drug monitoring (TDM) due to its rapid detection speed, high sensitivity and straightforward sample pretreatment. In this study, Au/AgNPs were obtained through the reduction of AgNO3 on the surface of AuNPs. Subsequently, Au/AgNPs were embedded into the tetrahedral lattice of ZIF-8 MOFs, resulting in the formation of Au/Ag@ZIF-8 nanocomposites. The Au/Ag@ZIF-8 nanocomposites exhibit a robust electromagnetic enhancement of Au/Ag bimetallic nanoparticles and a considerable adsorption capacity of ZIF-8 MOFs. This enables the pre-enrichment of target molecules in the vicinity of the electromagnetic field of the Au/AgNPs, thereby enhancing the sensitivity of SERS detection. The SERS substrate also exhibits high stability and reproducibility, as well as molecular sieving effects, due to the fact that Au/AgNPs are embedded into the tetrahedral lattice of ZIF-8. A TDM method for tacrolimus (FK506) in human serum was developed by using Au/Ag@ZIF-8 nanocomposites as solid phase extraction (SPE) adsorbent and SERS substrates. The results showed that under the optimized conditions, tacrolimus exhibited satisfactory linearity within the concentration range of 10-5-10-11 mol L-1, with a correlation coefficient (R2) of 0.9944, and the limit of detection (LOD) was as low as 6.4 pg mL-1. The recoveries were observed to range between 92 % and 105 %, with an RSD of below 8 %. The method is highly sensitive, exhibiting a sensitivity that is 3-6 orders of magnitude higher than that of existing analytical techniques. It has the potential to be applied in a clinical setting to biological samples.

Rapid detection of African swine fever virus via SERS probe-modified sandwich hybridization assay.

Rapid and reliable detection method for African swine fever virus (ASFV) is proposed by surface-enhanced Raman spectroscopy (SERS). The ASFV target DNA can be specifically captured by sandwich hybridization between nanomagnetic beads and a SERS probe. Experimental results show that the significant Raman signal of the SERS probe with gold nanoparticles and a molecular reporter DTNB (5,5'-dimercapto-bis (2-nitrobenzoic acid)) can be adopted for detecting the hybridization chain reaction of ASFV DNA. The advantage of the SERS sandwich hybridization assay is the large response range from the single molecule level to 108 copies per mL, which not only can overcome the tedious time required for the amplification reaction but also provides a comparative method to polymerase chain reaction. Furthermore, real samples of African swine fever virus were detected from different subjects of swine fever virus including porcine reproductive respiratory syndrome virus and Japanese encephalitis virus. The proposed biosensor method can rapidly detect ASFV correctly within 15 min as a simple, convenient, low-cost detection approach. The biosensor can be used as a platform for the determination in biological, food, and environmental analytical fields.

Single-Molecule Surface-Enhanced Raman Spectroscopy: Challenges, Opportunities, and Future Directions.

Single-molecule surface-enhanced Raman spectroscopy (SM-SERS) is a powerful experimental technique for label-free sensing, imaging, and chemical analysis. Although Raman spectroscopy itself is an extremely "feeble" phenomenon, the intense interaction of optical fields with metallic nanostructures in the form of plasmonic hotspots can generate Raman signals from single molecules. While what constitutes a true single-molecule signal has taken some years for the scientific community to establish, many SERS experiments, even those not specifically attempting single-molecule sensitivity, have observed fluctuation in both the SERS intensity and spectral features. In this Perspective, we discuss the impact that fluctuating SERS signals have had on the continuing advancement of SM-SERS, along with challenges and current and potential future applications.

Fabrication of Aluminum Foil Integrated Pegylated Gold Nanoparticle Surface-Enhanced Raman Scattering Substrate for the Detection and Classification of Uropathogenic Bacteria.

Rapid detection and classification of pathogenic microbes for food hygiene, healthcare, environmental contamination, and chemical and biological exposures remain a major challenge due to nonavailability of fast and accurate detection methods. The delay in clinical diagnosis of the most frequent bacterial infections, particularly urinary tract infections (UTIs), which affect about half of the population at least once in their lifetime, can be fatal if not detected and treated appropriately. In this work, we have fabricated aluminum (Al) foil integrated pegylated gold nanoparticles (AuNPs) as a potential surface-enhanced Raman scattering (SERS) substrate, which is used for the detection and classification of uropathogens, namely, E. coli, S. aureus, and P. aeruginosa directly from the culture without any pretreatment. The substrate is first drop cast with bacterial pellets and then pegylated AuNPs, and the interaction of two on Al foil base gives identifiable characteristic Raman peaks with good reproducibility. With the use of chemometric methods such as principal component analysis (PCA), the Al foil-based SERS substrate offers a quick, effective detection and classification of three strains of UTI bacteria with the least bacterial concentration (105 cells mL-1) necessary for clinical diagnosis. In addition, this substrate was able to detect E. coli positive clinical samples by giving SERS fingerprint information directly from centrifuged urine samples within minutes. The stability of pegylated AuNPs provides for its application at the point of care with rapid and easy detection of uropathogens as well as the possibility of advancement in healthcare applications.