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Surface-enhanced Raman scattering (SERS) has been widely used in biomedical sensing with the advantages of high sensitivity and label-free. However, the fabrication of SERS substrates with good Raman activity, reproducibility, and low cost is still under development in practical applications. This paper presents a practicable method for fabricating Au NP/paper strips by using inkjet printing and seed mediated growth. Small gold seed synthesized by borohydride reduction was used as ink and printed on the filter paper. The printed gold seed grew in situ in the growth solution and formed the gold nanoparticle (Au NP)/paper strips. The fabricated paper strip was characterized by diffuse reflectance spectroscopy and scanning electron microscopy (SEM). The diffuse reflectance spectra indicated that the Au NP/paper strips had two local surface plasmon resonance (LSPR) peaks: the short one at around 540 nm and the long one located in the range of 640–840 nm. And the long LSPR peak firstly shifted to red then to blue with the increased concentrations of silver ions in growth solution. From the SEM images, the shape of grown Au NPs was diverse, including sphere, rod, ellipsoid, dimer, trimer, and big aggregates. We thought the short peak came from the LSPR of nanospheres and the transvers LSPR of rod and ellipsoid like particles, while the long peak mainly came from the plasmonic coupling of dimer along the inter-particle axis. The obtained Au NP/paper strip with the long peak located around 650 nm had the highest SERS activity, which could be attributed to the plasmon resonance induced local field enhancement and nanogap effect. Also, the SERS performance results indicated the printed SERS strips exhibited satisfied uniformity and stability, demonstrating the potential of Au NP/paper strip in real-world applications. [ABSTRACT FROM AUTHOR]

A simple and efficient pen-on-paper approach is designed to prepare hydrophilic surface enhanced Raman scattering (SERS)-active lines by directly writing on a piece of hydrophobic poly (L-lactic acid) nanofibrous paper using a pen filled with plasmonic nanoparticle ink. The pen-on-paper-line SERS substrate exhibits hydrophobic-hydrophilic focusing effects together with negligible background interference, high sensitivity, good reproducibility, and long-term stability. Furthermore, just by drawing three different plasmonic nanoparticles, the SERS activity is optimized for different molecules. Considering the complex factors involved in SERS effects of real analytes, our results provide an efficient strategy to produce optimized SERS substrates with multiple plasmonic nanoparticles. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Surface-Enhanced Raman Spectroscopy (SERS) is a powerful surface-sensitive technique for molecular analysis. Its use is limited due to high cost, non-flexible rigid substrates such as silicon, alumina or glass and less reproducibility due to non-uniform surface. Recently, paper-based SERS substrates, a low-cost and highly flexible alternative, received significant attention. We report here a rapid, inexpensive method for chitosan-reduced, in-situ synthesis of gold nanoparticles (GNPs) on paper devices towards direct utilization as SERS substrates. GNPs have been prepared by reducing chloroauric acid with chitosan as a reducing and capping reagent on the cellulose-based paper surface at 100 °C, under the saturated humidity condition (100 % humidity). GNPs thus obtained were uniformly distributed on the surface and had fairly uniform particle size with a diameter of 10 ± 2 nm. Substrate coverage of resulting GNPs directly depended on the precursor's ratio, temperature and reaction time. Techniques such as TEM, SEM, and FE-SEM were utilized to determine the shape, size, and distribution of GNPs on paper substrate. SERS substrate produced by this simple, rapid, reproducible and robust method of chitosan-reduced, in situ synthesis of GNPs, showed exceptional performance and long-term stability, with a detection limit of up to 1 pM concentration of test analyte, R6G. Present paper-based SERS substrates are cost-effective, reproducible, flexible, and suitable for field applications. [Display omitted] • In-situ synthesis of GNPs on a paper substrate for SERS applications using chitosan as a reducing agent with a detection limit of up to 1 pM. [ABSTRACT FROM AUTHOR]

This study investigates why a silver nanoparticle (SNP)-induced surface-enhanced Raman scattering (SERS) paper chip fabricated at low successive ionic layer absorption and reaction (SILAR) cycles leads to a high SERS enhancement factor (7 × 10 8 ) with an inferior nanostructure and without generating a hot spot effect. The multi-layered structure of SNPs on cellulose fibers, verified by magnified scanning electron microscopy (SEM) and analyzed by a computational simulation method, was hypothesized as the reason. The pattern of simulated local electric field distribution with respect to the number of SILAR cycles showed good agreement with the experimental Raman intensity, regardless of the wavelength of the excitation laser sources. The simulated enhancement factor at the 785-nm excitation laser source (2.8 × 10 9 ) was 2.5 times greater than the experimental enhancement factor (1.1 × 10 9 ). A 532-nm excitation laser source exhibited the highest maximum local electric field intensity (1.9 × 10 11 ), particularly at the interparticle gap called a hot spot. The short wavelength led to a strong electric field intensity caused by strong electromagnetic coupling arising from the SNP-induced local surface plasmon resonance (LSPR) effects through high excitation energy. These findings suggest that our paper-based SILAR-fabricated SNP-induced LSPR model is valid for understanding SNP-induced LSPR effects. [ABSTRACT FROM AUTHOR]

Ricin has been involved in historic and recent biothreat events. Here we developed a rapid screening method for ricin laced papers using surface enhanced Raman spectroscopy (SRES). Three sample preparation methods and two SERS substrates were evaluated and optimized for their performance on three types of letter papers. The best approach was the use of non-destructive extraction coupled with silver dendrites, which can detect ricin B chain surrogate as low as 0.044 μg in less than 10 min from paper. The extraction efficiency for the hydrophobic letters was the highest (90%) compared to the other two types of letters. We also demonstrated the great capacity of this method to discriminate ricin B from common beverage residues on letter papers, and the feasibility of using a handheld Raman device for rapid and on-site screening. [ABSTRACT FROM AUTHOR]

Rising concern about the use of non-permitted colourants, in common food items such as dals and green vegetables sold in Indian markets, have led to a demand for low-cost point-of-use chemical analysis tools. Conventional food-analysis techniques involving tedious sample preparation protocols are not suited for in-field applications. Surface Enhanced Raman Spectroscopy (SERS) is an analytical technique that is well-suited for point-of-use chemical analysis with molecular level detection capability, which can also serve as a quality assurance tool for businesses. Effective and rapid signal collection from a large-area sample within a field-setting using disposable, low-cost SERS substrates is a key challenge in implementing such a solution. Herein, we demonstrate the use of inkjet-printed thin films comprising of robust nanostructured-silver as flexible, paper-based SERS (P-SERS) swabs for the direct detection of Metanil Yellow (MY) from toor dal (yellow split pigeon peas) samples and Malachite Green (MG) from green peas and green chillies. The macroscopic uniformity of these thin-films in combination with a portable Raman spectrometer equipped with orbital raster scanning (ORS™) technology for signal collection results in an unprecedented precision (RSD ∼ 1.6%) upon characterizing samples saturated with Rhodamine-6G (R6G), a standard Raman probe. As several food-cleansing products have appeared in the marketplace, the adulterant removal efficacy of some commercially available 'washes' as well as products such as 'ozoniser', which was determined by SERS characterization of swabs before and after use, is also reported. Image 1 • Direct and Rapid detection of adulterants. • Highly repeatable SERS signals. • Assessment of the efficacy of adulterant-elimination using cleaning products available in the market-place. [ABSTRACT FROM AUTHOR]

• Hydrophobic paper realizes facile SERS detection with concentrated hotspots. • Paper-based approach allows simple, flexible and low-cost SERS measurements. • Modification by PMHS gives SERS enhancement 2.2 times higher than before. • Sensitive AgNCs@SiO 2 /PMHS modified paper ascribed to higher density of hotspots. • Label-free detection of adenine in urine is tested with a detection limit of 1 nM. Flexible paper-based surface enhanced Raman spectroscopy (SERS) substrate has attracted great attention in the sensitive detection of analytes in recent years. However, due to its inherent hydrophilic surface, the nanoparticles will not be concentrated very well on the surface of the paper. This reduces the reproducibility and sensitivity of the paper-based substrate. Herein, we demonstrate flexible hydrophobic paper-based substrate using silver nanocubes loaded on polymethylhydrosiloxane modified filter paper (AgNCs@SiO 2 /PMHS modified filter paper) to realize high sensitivity and reproducibility. The hydrophobic filter paper was obtained by dip-soaking the filter paper into PMHS solution, resulting in increased contact angle to ~112.5°. The AgNCs@SiO 2 /PMHS modified paper substrate shows high analytical enhancement factor (AEF) of 6.55 × 106, which is 2.2-fold enhancement compared to AgNCs@SiO 2 /normal paper substrate, and a low detection limit of 0.1 nM rhodamine 6G and 0.89 nM adenine. The high SERS enhancement factor and sensitivity is attributed to the high hotspots density created in the hydrophobic surface as a result of the excellent uniformity and superior sample collection efficiency compared to the normal filter paper-based substrate. Besides, the substrate shows excellent spot-to-spot and substrate-to-substrate reproducibility, with relative standard deviation (RSD) of 6.05% and 9.22%, respectively. Moreover, the AgNCs@SiO 2 /PMHS modified filter paper substrate achieved good stability; the Raman signal intensity only drops by 25.88% after 3 months of exposure to air. Therefore, this flexible hydrophobic AgNCs@SiO 2 /PMHS modified filter paper substrate with low cost fabrication and label-free SERS detection is a promising SERS platform for analytical and biological sensing applications. [ABSTRACT FROM AUTHOR]

The document is a contents list from the journal "Analyst" published by The Royal Society of Chemistry, featuring various research papers on topics such as metal surface interactions, cerumen analysis, nano-biosensing platforms, and Raman spectroscopy for leukemia diagnosis. The journal showcases innovative research in the field of chemistry, including advancements in spectroscopy techniques, biosensing platforms, and diagnostic tools. The articles cover a wide range of topics, from nanotechnology to bioanalytical assays, highlighting the diverse and cutting-edge research being conducted in the chemical sciences. [Extracted from the article]

The document from the journal "Analyst" published by The Royal Society of Chemistry in 2024 provides a comprehensive list of research papers and articles on various topics related to chemistry. The papers cover a wide range of subjects, including electrochemical approaches for biomarker detection, detection of volatile organic compounds, catalytic kinetics, and sensor development for various applications. The journal aims to connect the global chemistry community through impactful research and publications, reinvesting profits back into the field. [Extracted from the article]

A label-free detection method for noninvasive biofluids enables rapid on-site disease screening and early-stage cancer diagnosis by analyzing metabolic alterations. Herein, we develop three-dimensional plasmonic hexaplex nanostructures coated on a paper substrate (3D-PHP). This flexible and highly absorptive 3D-PHP sensor is integrated with commercial saliva collection tube to create an efficient on-site sensing platform for lung cancer screening via surface-enhanced Raman scattering (SERS) measurement of human saliva. The multispike hexaplex-shaped gold nanostructure enhances contact with saliva viscosity, enabling effective sampling and SERS enhancement. Through testing patient salivary samples, the 3D-PHP sensor demonstrates successful lung cancer detection and diagnosis. A logistic regression-based machine learning model successfully classifies benign and malignant patients, exhibiting high clinical sensitivity and specificity. Additionally, important Raman peak positions related to different lung cancer stages are investigated, suggesting insights for early-stage cancer diagnosis. Integrating 3D-PHP senor with the conventional saliva collection tube platform is expected to offer promising practicality for rapid on-site disease screening and diagnosis, and significant advancements in cancer detection and patient care. [Display omitted] [ABSTRACT FROM AUTHOR]

Excellent detection capability, a simple assay procedure, and easy device acquisition are three key factors to analyze biomarkers for disease diagnosis using a point-of-care device in resource-limited settings or in emergency situations. However, constructing a platform with the simultaneous presence of these factors to sense multiple biomarkers remains a challenge. In the spirit of "frugal science", a simple method is developed by combining a low-cost portable paper centrifuge with surface-enhanced Raman scattering (SERS) immunoassay for sample pretreatment and multiple-cytokine (IL-6, IL-1, and TNF-α) detection. The paper centrifuge can achieve rapid blood separation as a commercial centrifuge and also concentrate sandwich immune composites to generate abundant hot spots, thus enhancing the SERS signal. By analyzing three prospective cytokines (IL-6, IL-1, and TNF-α) closely related to tumors, the combined paper centrifugation–SERS immunoassay method realizes sensitive assays with detection limits down to 0.86, 0.42 and 0.22 pg/mL. Meanwhile, the proposed approach possesses capabilities of specific recognition and accurate quantitative detection for three cytokines in serum. Hence, the constructed multifunctional SERS platform is expected to be applied in the development of decentralized and battery-free diagnostic devices in facility-limited areas and field settings. [Display omitted] • A combined paper centrifugation–SERS immunoassay method is developed. • Paper centrifuge can achieve rapid blood separation as a commercial centrifuge. • Sensitive, quantitative, and specific detection for three cytokines are realized. [ABSTRACT FROM AUTHOR]

Rapid, sensitive, and quantitative detection of biomarkers is needed for early diagnosis of disease and surveillance of infectious outbreaks. Here, we exploit a plasmonic syringe filter and surface-enhanced Raman spectroscopy (SERS) in the development of a rapid detection system, using human IgG as a model diagnostic biomarker. The novel assay design facilitates multiple passages of the sample and labeling solution through the detection zone enabling us to investigate and maximize sampling efficiency to the capture substrate. The vertical flow immunoassay process in this study involves the utilization of filter paper embedded with gold nanoparticles (AuNPs) to form a plasmonic substrate. Capture antibody (anti-human IgG) is then immobilized onto the prepared plasmonic paper and inserted into a vertical flow device (syringe filter holder). Sample solution is passed through the filter paper and the target antigen (human IgG) is selectively captured by the immobilized antibody to form an antibody–antigen complex. Next, functionalized AuNPs as extrinsic Raman labels (ERLs) are passed through the filter paper to label the captured biomarker molecules forming a layered structure. This sandwiched geometry enhances plasmonic coupling and SERS signal to provide highly sensitive detection of biomolecules. Systematic studies to investigate the impact of multiple infuse/withdraw cycles of the sample and labeling solutions reveal that antigen and ERL binding are maximized with 10 and 20 cycles, respectively. The optimized assay achieves a detection limit of ∼0.2 ng mL−1 for human IgG with a total assay time of less than 5 minutes, meeting the demands for rapid point of care diagnostics. Additionally, the optimized platform was implemented in the quantitative analysis of the SARS-CoV-2 nucleocapsid protein, the typical target in commercial, FDA-approved rapid antigen tests for COVID-19. [ABSTRACT FROM AUTHOR]

A number of life-saving drugs require therapeutic drug monitoring (TDM) for safe and effective use. Currently, however, TDM is performed using sophisticated analytical techniques relegated to central labs, increasing the cost per test and time to answer. Here, using a novel vertical flow membrane system with inkjet-printed surface enhanced Raman sensors, along with a portable spectrometer, we demonstrate a low cost and easy to use device to quantify levels of flucytosine, an antifungal that requires TDM for effective patient care, from undiluted human serum. To our knowledge, this work represents the first report of a passive vertical flow sample cleanup method with surface enhanced Raman detection. We first investigated and optimized the parameters of the vertical flow system for the detection of flucytosine in spiked serum samples. Then, using an optimized vertical-flow system utilizing nitrocellulose membranes and a paper SERS sensor, we achieved detection of down to 10 μg mL −1 flucytosine in undiluted serum, with quantitative detection across the entire therapeutic range. This system reduces the assay time to about 15 min, far quicker than the current gold standards. We anticipate that this novel system will enable near-patient therapeutic drug monitoring, leading to the safe and effective administration of a number of life-saving drugs. Furthermore, it will spawn the development of SERS detection systems capable of separating target analytes from real-world biological matrices. [ABSTRACT FROM AUTHOR]

A paper-based SERS test strip combining strengths of paper chip and Raman active substrate was demonstrated to overcome challenges in spectroscopic sensing of complicated samples and realize quantitative detection of disease markers in whole blood. The precisely controlled Au NPs were not only capable of generating condensed hot spots on the fibers, but also enhanced the size exclusion effect of paper, resulting in the novel performance on both SERS detection and sample pretreatment. A biosensor for Mucin-1 is developed by equipping the Au NPs with aptamer. Combining all these merits, this small, cheap and portable test strip might find wide application in clinical diagnosis and health evaluation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Paper SERS substrate has been fabricated by drop-casting AgNPs on printing-grade paper. • Signal reproducibility and enhancement factor have been evaluated. • ELISA and PCR tests are performed to confirm the presence of rotavirus particles. • The paper-based SERS substrates can detect rotavirus in clinical stool samples. Among the different analytical techniques, surface-enhanced Raman scattering (SERS) approach is a widely used technique for the detection and analysis of various chemicals and biological samples. Present study reports a low-cost, sensitive SERS substrate that has an ability to detect rotavirus in clinical stool samples. The proposed SERS substrate has been fabricated through drop-casting of silver nanoparticles (AgNPs) on a printing-grade paper. Rotavirus particles were extracted from clinical stool samples. The presence of rotavirus antigen in stool samples was confirmed using enzyme-linked immunosorbent assay (ELISA), polymerase chain reaction (PCR), and sequencing. The characteristic Raman peaks of rotavirus (RV) particles in solution were found to be significantly enhanced when Raman signals were recorded from the paper-based SERS substrates. Using the proposed SERS substrate, rotavirus samples with concentration as low as 1% could be reliably recorded by the Raman spectrometer. The paper SERS substrate reported herein is an extremely cost-efficient platform and may find applications in other research and clinical laboratories as well. [ABSTRACT FROM AUTHOR]

Rapid and reliable identification of bacteria is an important issue in food, medical, forensic, and environmental sciences; however, conventional procedures are time-consuming and often require extensive financial and human resources. Herein, we present a label-free method for bacterial discrimination using surface-enhanced Raman spectroscopy (SERS) and partial least squares discriminant analysis (PLS-DA). Filter paper decorated with gold nanoparticles was fabricated by the dip-coating method and it was utilized as a flexible and highly efficient SERS substrate. Suspensions of bacterial samples from three genera and six species were directly deposited on the filter paper-based SERS substrates before measurements. PLS-DA was successfully employed as a multivariate supervised model to classify and identify bacteria with efficiency, sensitivity, and specificity rates of 100% for all test samples. Variable importance in projection was associated with the presence/absence of some purine metabolites, whereas confidence intervals for each sample in the PLS-DA model were calculated using a resampling bootstrap procedure. Additionally, a potential new species of bacteria was analyzed by the proposed method and the result was in agreement with that obtained via 16S rRNA gene sequence analysis, thereby indicating that the SERS/PLS-DA approach has the potential to be a valuable tool for the discovery of novel bacteria.This paper describes the discrimination of bacteria at the genus and species levels, after minimal sample preparation, using paper-based SERS substrates and PLS-DA with uncertainty estimation. [ABSTRACT FROM AUTHOR]

SERS (Surface Enhanced Raman Spectroscopy) can realize fingerprint recognition of molecular samples with high detection accuracy and sensitivity. However, rapid and convenient measurement of the Raman spectra of analytes for a point-of-care test (POCT) has put forward a high demand for portable Raman spectrometers, as well as reliable SERS substrates. Hereby, we first utilize a smartphone as a miniaturized Raman spectral analyzer, which has the revolutionary advantages of a friendly human–machine interface, fast measurement time, and good sensitivity. Meanwhile, a paper-based SERS chip was prepared based on commonly used filter paper and silver nanoparticles (AgNP), which was successfully used to detect low concentrations of typical SERS analyte model molecules including rhodamine 6G and crystal violet. The current method of smartphone-based SERS spectroscopy as a POCT device will greatly promote the application of Raman technology in a variety of scenarios, such as safety inspections, pesticide residue detection, water pollution monitoring, and so on. Coupled with paper-based SERS chips with advantages of facile preparation, low cost and good reliability, the current work proves to have a great potential for industrial production and for meeting the vast marketing demand of Raman based POCT technology. [ABSTRACT FROM AUTHOR]

This study demonstrates a novel strategy for colorimetric/surface-enhanced Raman scattering (SERS) dual-mode sensing of sulfur dioxide (SO2) by coupling headspace sampling (HS) with paper-based analytical device (PAD). The smart and multifunctional PAD is fabricated with a vacuum filtration method in which 4-mercaptopyridine (Mpy)-modified gold nanorods (GNRs)-reduced graphene oxide (rGO) hybrids (rGO/MPy-GNRs), anhydrous methanol, and starch-iodine complex are immobilized into cellulose-based filter papers. The resultant PAD exhibits a deep-blue color with a strong absorption peak at 600 nm due to the formation of an intermolecular charge-transfer complex between starch and iodine. However, the addition of SO2 induces the Karl Fischer reaction, resulting in the decrease of color and increase of SERS signals. Therefore, the PAD can be used not only as a naked-eye indicator of SO2 changed from blue to colorless but also as a highly sensitive SERS substrates because of the SO2-triggered conversion of Mpy to pyridine methyl sulfate on the GNRs. A distinguishable change in the color was observed at a SO2 concentration of 5 µM by the naked eye, and a detection limit as low as 1.45 µM was obtained by virtue of UV-vis spectroscopy. The PAD-based SERS method is effective over a wide range of concentrations (1 µM to 2000 µM) for SO2, and the detection limit for SO2 is found to be 1 µM. The HS-PAD based colorimetric/SERS method is applied for the determination of SO2 in wine, and the detection results match well with those obtained from the traditional Monier-Williams method. This study not only offers a new method for on-site monitoring of SO2 but also provides a new strategy for designing of paper-based sensing platform for a wide range of field-test applications. [ABSTRACT FROM AUTHOR]

In this study, we report the simple fabrication of an active substrate assisted by gold nanostructures (AuNS) for application in surface-enhanced Raman scattering (SERS) using copier paper, which is a biodegradable and cost-effective material. As cellulose is the main component of paper, it can behave as a reducing agent and as a capping molecule for the synthesis of AuNS on the paper substrate. AuNS can be directly generated on the surface of the copier paper by addition of halides. The AuNS thus synthesized were characterized by ultraviolet–visible spectroscopy, SEM, XRD, and XPS. In addition, the SERS effect of the AuNS–paper substrates synthesized by using various halides was investigated by using rhodamine 6G and melamine as probe molecules. [ABSTRACT FROM AUTHOR]

The fabrication of SERS substrates, which can offer the advantages of strong Raman signal enhancement with good reproducibility and low cost, is still a challenge for practical applications. In this work, a simple three-dimensional (3D) paper-based SERS substrate, which contains plasmonic silver-nanoparticles (AgNPs), has been developed by the silver mirror reaction. This paper strip was characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), etc. Pretreatment of the paper as well as the reaction time, temperature, and reagent concentrations for the silver mirror reaction were varied for further studies. With the optimized experimental parameters, the AgNPs synthesized and distributed in-situ on the paper strip could give more favorable SERS performance. The limit of detection (LOD) as low as 10 −11 M for Rhodamine 6 G (R6G) and 10 −9 M for p -aminothiophenol ( p -ATP) plus wide linear range for the log–log plot of Raman intensity versus analyte concentration were achieved. The detection of R6G in rain water was also carried out successfully. The merits of this protocol include low cost, easy operation, high sensitivity and acceptable stability, which make it ideal for the detection of environmental samples in trace amounts. [ABSTRACT FROM AUTHOR]

In this study, a novel Surface Enhanced Raman Scattering (SERS) substrate was engineered by assembling mesoporous Ti 3 C 2 T x (MesoTi 3 C 2 T x) with gold nanoparticles (AuNPs) through cross-linking with poly (diallyl dimethyl ammonium chloride) (PDDA). MesoTi 3 C 2 T x was first fabricated with a mesoporous structure and then modified with PDDA, after which the PDDA-coated MesoTi 3 C 2 T x was applied to the rough surface of glass fiber filter paper. After drying, size-controlled AuNPs were dropped on the paper base PDDA-MesoTi 3 C 2 T x substrate to form paper-based SERS substrate of PDDA-AuNPs/MesoTi 3 C 2 T x. The adsorption capacity of MesoTi 3 C 2 T x is 4.2-fold better than mono-few layer Ti 3 C 2 T x , and the distribution of AuNPs on PDDA-MesoTi 3 C 2 T x is more uniform than that on PDDA-Ti 3 C 2 T x without mesoporous. After optimization, PDDA with the molecular weight of 100–200k can make paper-based PDDA-AuNPs/MesoTi 3 C 2 T x substrate detect trace amount (10 ng/mL) of the methylene blue with significant Raman characteristic peak. The enhancement factor up to 2.09 × 106. The paper-based PDDA-AuNPs/MesoTi 3 C 2 T x was used as SERS substrate to detect the ciprofloxacin. The result of detection is accurate, stable and sensitive especially in the application for milk detection. In conclusion, the novel paper-based PDDA-AuNPs/MesoTi 3 C 2 T x constructed in this work as a SERS substrate can satisfy the needs of rapid SERS detection of veterinary drug residues in food. • A novel SERS substrate was engineered by assembling Ti 3 C 2 T x with AuNPs. • Increased surface charges make MesoTi 3 C 2 T x improve CT to perform SERS activity. • The enhancement factor of paper-based AuNPs/MesoTi 3 C 2 T x substrate up to 2.09 × 106. • The chemical enhancement mechanism revealed via experiment and DFT calculation. • The AuNPs/MesoTi 3 C 2 T x substrate can detect CIP accurate, stable, sensitive. [ABSTRACT FROM AUTHOR]

Paper-based surface-enhanced Raman scattering (SERS) substrates receive a great deal of attention due to low cost and high flexibility. Herein, we developed an efficient SERS substrate by gravure printing of sulfonated reduced graphene-oxide (S-RGO) thin film and inkjet printing of silver nanoparticles (AgNPs) on weighing paper successively. Malachite green (MG) and rhodamine 6G (R6G) were chosen as probe molecules to evaluate the enhanced performance of the fabricated SERS-active substrates. It was found that the S-RGO/AgNPs composite structure possessed higher enhancement ability than the pure AgNPs. The Raman enhancement factor of S-RGO/AgNPs was calculated to be as large as 10 9 . The minimum detection limit for MG and R6G was down to 10 −7 M with good linear responses ( R 2 = 0.9996, 0.9983) range from 10 −4 M to 10 −7 M. In addition, the S-RGO/AgNPs exhibited good uniformity with a relative standard deviation (RSD) of 7.90% measured by 572 points, excellent reproducibility with RSD smaller than 3.36%, and long-term stability with RSD less than 7.19%. [ABSTRACT FROM AUTHOR]

[Display omitted] • Facile, Flexible, and Fast sensing of spike protein with SERS paper sensor. • Low-cost / Ecofriendly green assisted production of spherical silver nanoparticles. • Paper sensor detectability is 2.4 pg/ul of spike protein of SARS-CoV-2 virus. • Spike protein sensing in saliva is achieved with SERS paper sensor. • Lab on paper ensures environment sustainability by its safe disposal. Rapid investigation on the detection of spike protein with paper sensor is projected with Surface Enhanced Raman Spectroscopy (SERS). SERS sensor with lab on paper is preceded with facile, cost-effective strategy. Silver nanoparticles with average size of 20–30 nm were produced by green chemistry approaches, followed by loading the nanoparticles on hydrophobic paper surfaces. The very low %RSD (∼1.5) with mapping scan ensembles high reproducibility. Spike protein detection analysis derived the prominent finger print regions of amide bands as well abundant amnio acids (Phenylalanine-1003 cm−1, Tryptophan- 680 cm−1, Tyrosine-1473 cm−1) respectively. The detectability of sensor is gauged to be 2.4 pg / µL. Real time analysis on human saliva spiked with spike protein exhibited diagnosis within 2 min. Developed paper sensor provide us the scope of SERS technique to bring state of art in early detection of covid infections and safe disposal after its use. [ABSTRACT FROM AUTHOR]

[Display omitted] • Proposing a novel swab-detection strategy for dye analysis in conservation science. • Fabrication of flexible paper-based SERS probes in a simple, fast and economic way. • Allowing excellent SERS performance and micro-extraction of synthetic organic dyes. • Minimally invasive SERS identification of synthetic organic dyes in real artworks. Surface-enhanced Raman scattering (SERS) has proven to be a powerful diagnostic technique for conservation science. In this work, a novel swab-based detection strategy is proposed for minimally invasive SERS analysis of synthetic organic dyes in the cultural heritage field, employing flexible paper-based SERS probes prepared with a facile, cost-efficient and reproducible recipe. It was demonstrated that Ag nanostructures/paper probes composed of interconnected Ag nanostructures immobilized on unmodified cellulose paper showed excellent SERS enhancement for the investigated synthetic organic dyes. The high flexibility and conformability of paper-based substrate allows to extract minimal amounts of dyes from the work of art by gently swabbing in a dry-state condition, thereby avoiding potential damage to colorants from close contact with solvents such as water. Dyes could be transferred via swab-based extraction method without removing any visible fragments of the paint layer, which facilitates preserving the physical integrity of the artwork. SERS detection was subsequently performed directly on flexible substrate surfaces after micro-extraction of dyes. The minimally invasive nature of this strategy has further been confirmed by the spectrophotometric color measurements and successfully applied to the identification of synthetic organic dyes on real paper artworks---Chinese woodblock New Year paintings from the late Qing Dynasty. These results highlight the great potential of flexible paper-based Ag substrates based on swab-detection method for minimally invasive analysis of organic dyes in cultural heritage. [ABSTRACT FROM AUTHOR]

Many important considerations in the design of practical Surface enhanced Raman spectroscopy (SERS) substrates are necessary, such as the low cost, simple preparation, mass production and high efficiency of sample collection, which the conventional rigid substrates are lack of. In this work, practical SERS substrates based on deposition of silver nanoparticles (Ag NPs) on commercially available low-cost filter paper were prepared by simple silver mirror reaction in a large scale, and utilized for rapid, portable and accurate identification and detection of pesticide residues at various peels. Compared with conventional substrates, this novel SERS substrate dramatically enhanced the sample collection efficiency by simply swabbing paper-based device across different surfaces without destroying the sample, meanwhile avoiding the substrate signal of real-world samples. Considering their low cost, portability, simplicity and high sample collection efficiency, Ag NP-decorated filter paper, as practical SERS substrate, are used in solving critical problems for detection of pesticide residues at various peels. SERS experiments were carried out on Ag NP-decorated filter paper combined with 'dynamic SERS' (D-SERS) due to its high detection sensitivity. The excellent detection performance of the Ag NP-based filter paper was demonstrated by detection thiram and paraoxon residues at various peels. Besides, the stability and reproducibility of the practical substrates were also involved. [ABSTRACT FROM AUTHOR]

Surface enhanced Raman is a powerful analytical tool with high sensitivity and unique specificity and promising applications in various branches of analytical chemistry. Despite the fabrication of ingenious enhancement substrate used in laboratory research, the development of simple, flexible, and cost-effective substrate is also great important for promoting the application of SERS in practical analysis. Recently, paper and filter membrane as support to fabricate flexible SERS substrates received considerable attentions. Paper-based SERS substrate has been reviewed but no summary on filter-based SERS substrate is available. Compared with paper, filter membrane has unique advantage in robust mechanics, diverse component, and tunable pore size. These characteristics endow the filter-based substrates great advantages for practical SERS analysis including simple and low-cost substrate preparation, high efficiency in preconcentration, separation and detection procedure. Therefore, filter-based substrates have shown great promise in SERS analysis in environment monitoring, food safety with high sensitivity and efficiency. As more and more work has been emerged, it is necessary to summarize the state of such a research topic. Here, the research on filter involved SERS analysis in the past eight years is summarized. A short introduction was presented to understand the background, and then the brief history of filter-based substrate is introduced. After that, the preparation of filter-based substrate and the role of filter are summarized. Then, the application of filter involved SERS substrate in analysis is presented. Finally, the challenges and perspective on this topic is discussed. [ABSTRACT FROM AUTHOR]

Sample preparation is the most common bottleneck in the analysis and processing of forensic evidence. Time-consuming steps in many forensic tests involve complex separations, such as liquid and gas chromatography or various types of extraction techniques, typically coupled with mass spectrometry (e.g., LC-MS). Ambient ionization ameliorates these slow steps by reducing or even eliminating sample preparation. While some ambient ionization techniques have been adopted by the forensic community, there is significant resistance to discarding chromatography as most forensic analyses require both an identification and a confirmation technique. Here, we describe the use of a paper substrate, the surface of which has been inkjet printed with silver nanoparticles, for surface enhanced Raman spectroscopy (SERS). The same substrate can also act as the paper substrate for paper spray mass spectrometry. The coupling of SERS and paper spray ionization creates a quick, forensically feasible combination. [ABSTRACT FROM AUTHOR]

paper-like films of reduced graphene oxide with controllable shapes and thickness were prepared via funnel filtration and thermal reduction of graphene oxide (GO), which could work as flexible surface-enhanced Raman scattering (SERS) substrates to detect Rhodamine 6G (R6G) molecules. The SERS signal intensity of R6G on annealed films was found to be related with the annealling temperature. The most intense signal was observed for the film obtained at 800 °C. While for the sample annealed at 1000 °C, no SERS signal could be detected. The underlying mechanism for the difference was discussed. The reported preparation process of flexible rGO paper is simple and cost-effective, which shows great potential in rapid biochemical analysis of agricultural products with irregular surfaces. [ABSTRACT FROM AUTHOR]

Surface-enhanced Raman spectroscopy (SERS) as a powerful analytical tool has gained extensive attention. Despite of many efforts in the design of SERS substrates, it remains a great challenge for creating a universal substrate with long-term stability and reproducible SERS signals. In this work, Ag nanocubes and graphene oxide (GO) suspension were mixed to form a stable solution and further vacuum filtrated to obtain a free-standing hybrid paper. The Ag/GO hybrid papers exhibit excellent SERS activity because of the synergistic effect of Ag nanocubes and GO sheets. GO sheets can act as both SERS enhancement substrate and framework for supporting Ag nanocubes. Moreover, GO sheets can protect Ag nanoparticles from oxidation under ambient condition for prolonged life time SERS substrate. Furthermore, we demonstrate the use of the free-standing and flexible Ag/GO hybrid paper to enable direct, real-time and reliable detection of trace amounts of analytes in aqueous systems. This novel SERS substrate is expected to be applied in real-time analysis and expands the flexibility of SERS for useful applications in the materials and life science. [ABSTRACT FROM AUTHOR]

[Display omitted] • Inkjet printing Ag nanoparticles on paper coated with chitosan or N,N, N -trimethyl chitosan to obtain SERS substrates. • Biopolymer coatings not only reduce the rugosity and porosity of the paper but also confer hydrophobicity to the paper. • SERS sensitivity and reproducibility was improved when compared with non-coated counterparts. Paper-based sensors for surface-enhanced Raman scattering (SERS) detection of water pollutants have gained much attention in the last decades. However, most of the fabricated paper-based SERS substrates still face some limitations regarding reproducibility and uniformity. In this work, we report the fabrication of hydrophobic paper-based SERS substrates with high reproducibility and uniformity by inkjet printing Ag colloidal nanoparticles (NPs) on office paper pre-treated with chitosan (CH) or N,N, N -trimethyl chitosan (TMC). We demonstrate that the previous coating of paper with such biopolymers substantially improves the SERS performance of the paper substrates. In screening experiments, crystal violet (CV) 100 μM was used as molecular probe, leading to an increase of about 9- and 7-fold in the observed SERS intensity when the papers were coated with CH and TMC, respectively. Also, the reproducibility of the substrates coated with the biopolymers increased more than 2 times compared to non-coated office paper. We suggest that the improved performance of the coated substrates is related to a more uniform deposition of the AgNPs on the paper surface due to the hydrophobic nature, low porosity and roughness of the coated paper. [ABSTRACT FROM AUTHOR]

We demonstrate the fabrication and spot-on bioassay application of a low-cost, monometallic, surface-enhanced Raman scattering (SERS) paper platform using gold nanoparticle (AuNP)-loaded screen printing inks. The AuNPs were used to enhance the Raman intensity through a surface plasmon resonance (SPR)-driven optical property and sodium carboxymethylcellulose (CMC) was used as a viscous ink to create uniform distribution of the AuNPs on the paper substrate. To minimize the coffee ring effect and uniformly disperse the nanoparticles, the size of citrate-capped AuNPs, the CMC concentration, the volume ratio of CMC solution and AuNPs, and the printing cycles were optimized. Two printing cycles of optimized ink with a 7:1 mixture of 2-wt% CMC and AuNPs produced the strongest SERS effect and an enhancement factor of 1.8 × 10 4 with a SERS paper platform based on a Rhodamine B probe molecule. The platform exhibited high reproducibility, with less than 5% spot-to-spot variation in Raman intensity. Furthermore, the SERS spectra of normal and two virus-infected tear biofluids were comparable to the SERS spectral findings of gold-deposited SERS substrates. The enhanced SERS activity and high reproducibility of a low-cost, flexible, portable, and lightweight paper platform suggest the potential of point-of-care applications of biofluids in fields ranging from clinical analysis to industry. [ABSTRACT FROM AUTHOR]

Rationally designed self-assemble, functional 3D architecture of graphene nano-meshes with unique plasmonic resonance metal nanoparticles can be excellent nanohybrid Raman scattering (SERS) substrate in spotting the low levels of environmental organic pollutants. In this study, graphene nano-mesh-Ag-ZnO metal (GNMM) nanohybrid was prepared by self-assembled hydrothermal reduction of graphene oxide (GO) followed by thermal annealing of site-localized metal-salts as a highly sensitive surface-enhanced Raman scattering (SERS) substrate. The crumpled graphene nano-meshes decorated with Ag-ZnO nanoparticles created SERS hot spots (holes) that manifested high SERS sensitivity to model organic pollutants such as methyl orange (MO), rhodamine 6G (Rh-6G) and paraquat (PQ) with detection limit as low as 10 −11 , 10 −13 and 10 −14  M, respectively. A maximum enhancement factor (EF) of 1.97 × 10 11 was obtained with PQ molecules on synthesized GNMM substrate. The enhancement in signal can be supported through charge transfer mechanism that induced strong enhancement of the local electric field on free available graphene nano-mesh edges abundant with hotspots. This novel nanohybrid SERS substrate realized self-cleaning by photocatalytic degradation of model organic Rh-6G molecules adsorbed on the nanohybrid paper and shows reusability during the detection process. Meanwhile, GNMM nanohybrid also possesses highly effective antimicrobial activities for Escherichia coli . The detection of organic pollutants by GNMM nanohybrid SERS substrate has several advantages such as low cost, easy and simple preparation method, sensitive detection and reusability that can be potentially applied for detection of variety of environmental pollutants and antimicrobial agent applications. [ABSTRACT FROM AUTHOR]

The document is a contents list from the journal "Analyst" published by The Royal Society of Chemistry. It includes various research papers on topics such as loop mediated isothermal amplification assays, detection and imaging of ATP in cells, and the effects of macular pigment carotenoids on ocular health. The journal also features papers on topics like the detection of microRNAs, serum enrichment of N-glycans, and the development of a fluorescence light-up Pb2+ sensor. The document showcases a diverse range of scientific research in the field of chemistry. [Extracted from the article]

An inexpensive and disposable paper-based lateral flow strip (PLFS) has been developed as an immunoassay, in which surface-enhanced Raman scattering (SERS) is utilized for sensing signal transduction. The Au nanostar@Raman Reporter@silica sandwich nanoparticles are developed as the SERS probes, which is the key to the high sensitivity of the device. Compared with a colorimetric PLFS, the SERS-PLFS exhibits superior performance in terms of sensitivity and limit of detection (LOD) in a blood plasma-containing sample matrix. In addition, the SERS-PLFS has been successfully used for detection of neuron-specific enolase (NSE), a traumatic brain injury (TBI) protein biomarker, in diluted blood plasma samples, achieving a LOD of 0.86 ng/mL. Moreover, the SERS-PLFS was successfully employed to measure the NSE level in clinical blood plasma samples taken from deidentified TBI patients. This work demonstrates that the SERS-PLFS has great potential in assisting screening of TBI patients in the point-of-care setting. [ABSTRACT FROM AUTHOR]

Abstract: Surface-enhanced Raman scattering (SERS) fingerprints of individual molecules offer the possibility of multiplexing as well as cancer screening. A highly sensitive, noninvasive, and rapid cancer screening platform encompassing exfoliative cytology and paper-based SERS technology is described. The SERS substrate which consists of plasmonic gold nanorods (GNRs) adsorbed on a piece of filter paper forms the flexible and three-dimensional heterogeneous scaffold for cancer screening. Different and reproducible SERS spectra are obtained from normal and cancerous cells due to specific biomolecular changes in cancerous cells. A diagnostic algorithm based on the ratio of the spectra values is adopted to distinguish between cells exfoliated from 20 normal and cancerous tissues, and a high sensitivity of 100% and specificity of 100% are achieved by I 1600/1440 (peak ratio of signals at 1600–1440cm−1) and I 1440/1340 (1440–1340cm−1), which is better than I 1600/1340 (1600–1340cm−1) with a sensitivity of 70% and specificity of 60%. The combination of exfoliative cytology and paper-based plasmonic technology enables highly sensitive, rapid, and non-invasive cancer screening and has large clinical potential. [Copyright &y& Elsevier]

Antibiotic residues are a huge threat to food safety and ecological environment and florfenicol (FF) is one of the most wide-spread antibiotics entering the food chain. Hence, rapid and sensitive methods for the detection of FF in food are highly required. In this study, we present a facile method for the fabrication of three-dimensional (3D) ZnO@Ag nanoflowers (ZnO@Ag NFs) assembling on polyester fiber membrane (PFM), which can be used as an economic surface-enhanced Raman spectroscopy (SERS) paper sensor for sensitive determination of FF traces. 3D ZnO@Ag NFs that decorated on PFM provides sufficient "hot spots" and high chemical stability for the analytical platform. Without using any expensive materials and complicated methods, this flexible SERS substrate exhibits superior sensitivity, excellent uniformity, and well-reproducibility. The SERS response of the sensor toward FF shows excellent correlation during the range of 1 × 10−9 M to 1 × 10−3 M with the limit of detection (LOD) as low as 2.23 × 10−10 M. The recovery rate ranges from 97% to 101%, indicating that the SERS detection method provides a powerful tool for detecting toxic and harmful substances in food. • 3D ZnO@Ag nanoflowers were prepared by a simple wet chemical synthesis method. • 3D nanoflower structure is easier to adsorb more noble metal nanoparticles. • ZnO@Ag nanoflowers assembling on polyester fiber membrane as SERS paper sensor. • Aggregation-induced hot spots allow the LOD of FF at 2.23 × 10−10 M. • The paper sensor is easy to make, ultrasensitive, and satisfactory in real sample tests. [ABSTRACT FROM AUTHOR]

This paper describes a rapid method for fabrication of a paper substrate coated with gold nanoparticles (GNPs) that results in the formation of a large number of hot spots on the surface and allows an adequate control of the active area. The resulting substrate is shown to be a viable material for use in quantitative surface-enhanced Raman spectroscopy (SERS) analysis. The influence of the amount of GNPs on the SERS signals (using crystal violet as a sample analyte) was correlated with field-emission scanning electron microscopy, UV-visible and theoretical studies. The use of this substrates results in larger enhancement of Raman signals and in comparably repeatability when compared to commercially available substrates. The substrate was applied to SERS-based determination of nicotine and uric acid in aqueous solution, and the respective limits of detection are 20 and 30 μg L. The results indicate that the SERS substrates may be applied to the quantification of a wide variety of molecules. [ABSTRACT FROM AUTHOR]

The strongly enhanced electromagnetic “hotspots” from the edges and tips of nanoplates are highly preferred to significantly promote the surface enhanced Raman scattering (SERS) activity. Here, Ag nanotriangles with a sharp edge of 20 nm were prepared by the reduction of AgNO 3 using N,N-Dimethylformamide (DMF) with the assistance of Polyvinyl pyrrolidone (PVP). By loading of Ag nanotriangles onto the filter paper, a flexible SERS substrate with good activity and reproducibility was obtained and the ultratrace detection of p -aminothiophenol (pATP) with a concentration as low as 10 −8 M was achieved. The sharp edges and tips boosted SERS activity was proved by the finite element method modeling of the plasmonic properties of Ag nanotriangles with different edge thicknesses (10 − 80 nm), Ag nanosheets with different tip acutances (squares and hexagons) together with Ag nanorods, nanocubes and nanospheres. The experimental and theoretical results confirmed that the interspacing created by filter paper plays an important role in enhancing the overall SERS activity. Furthermore, it is shown that the present silver nanotriangles-loaded filter paper SERS substrate can be employed to sensitive and selective detecting ultratrace military explosives picric acid (PA) of 10 −6 M. [ABSTRACT FROM AUTHOR]

In this study, a nanoporous cellulose paper-based SERS platform was developed to analyze multiplex hazardous pesticides including thiram (T1), tricyclazole (T2), and carbaryl (C) by surface enhanced Raman scattering (SERS). Gold nanorods (AuNRs) with different aspect ratios were synthesized and compared to achieve the highest SERS signals on paper-based SERS substrates. The advantage of the nanoporous cellulose nanofiber (CNF) matrix with nanoscale surface roughness is that it allows actual nanofiltration, resulting in a uniform and well-controlled AuNR distribution on the top portion of the CNF matrix. The as-prepared CNF–AuNR-based SERS platform exhibited an enhancement factor of 1.4 × 107 as well as the ability to simultaneously detect T1, T2, and C at concentrations as low as 1 nM, 100 nM, and 1 μM, respectively. In addition to analyzing triplex pesticide mixtures in solution, the SERS platform allows for a paper-based SERS swab for rapid trace detection on real-world surfaces. The detection limits for T1, T2, and C residues in apple peels were 6, 60, and 600 ng cm−2, respectively, which are much lower than the maximum residue level requirement for apple peels (2000 ng cm−2). These results demonstrate that the low-cost, flexible, lightweight, paper-based SERS platform shows powerful potential for high SERS performance and on-site SERS analysis. [ABSTRACT FROM AUTHOR]

The integration of different catalytic modalities to control precursors, intermediates, and products requires a method for understanding these complex systems. A modular analytical platform is presented here that allows for catalytic conversion reactions and the delivery of catalytically transformed analytes to subsequent surface enhanced Raman scattering (SERS) detection zones. The paper‐based platforms are compatible for studying biochemical conversion reactions and electrochemical transformations. The full oxidation of glycerol to carbon dioxide follows a cascade reaction of 9 steps, chosen to illustrate the use of a molecular, biological, and metallic catalyst. Designated catalytic reaction zones and SERS detection zones integrated into the pores of paper at specific locations allows all of the reactions to take place within the pores of the analytical platform. Multiple chemical reactions were performed in sequence and the SERS spectra of the resulting intermediates and products were measured. [ABSTRACT FROM AUTHOR]

In this report, we present a paper membrane-based surface-enhanced Raman scattering (SERS) platform for the determination of blood glucose level using a nitrocellulose membrane as substrate paper, and the microfluidic channel was simply constructed by wax-printing method. The rod-shaped gold nanorod particles were modified with 4-mercaptophenylboronic acid (4-MBA) and 1-decanethiol (1-DT) molecules and used as embedded SERS probe for paper-based microfluidics. The SERS measurement area was simply constructed by dropping gold nanoparticles on nitrocellulose membrane, and the blood sample was dropped on the membrane hydrophilic channel. While the blood cells and proteins were held on nitrocellulose membrane, glucose molecules were moved through the channel toward the SERS measurement area. Scanning electron microscopy (SEM) was used to confirm the effective separation of blood matrix, and total analysis is completed in 5 min. In SERS measurements, the intensity of the band at 1070 cm which is attributed to B-OH vibration decreased depending on the rise in glucose concentration in the blood sample. The glucose concentration was found to be 5.43 ± 0.51 mM in the reference blood sample by using a calibration equation, and the certified value for glucose was 6.17 ± 0.11 mM. The recovery of the glucose in the reference blood sample was about 88 %. According to these results, the developed paper-based microfluidic SERS platform has been found to be suitable for use for the detection of glucose in blood samples without any pretreatment procedure. We believe that paper-based microfluidic systems may provide a wide field of usage for paper-based applications. [ABSTRACT FROM AUTHOR]

Silver ink was written directly on photographic paper by robotic writing technique. The AgNPs-photographic paper substrate possessed good SERS activities, reproducibility and uniformity, as well as high stability among four months. Furthermore, AgNPs-photographic paper was used as a substrate to detect the SERS spectra of thiram residues in fruit juice and peels directly without any pretreatments. [Display omitted] • Silver ink was written on photographic paper by robotic writing technique. • The detection limit for thiram absorbed on AgNPs-photographic paper was 0.024 ppb. • The substrates exhibited good reproducibility with RSD less than 10%. • The substrate had good uniformity with RSD of 14.34% by 120 points. • AgNPs-photographic paper was used as a substrate to detect thiram in fruit juice and peels. With the widespread application of pesticide in agriculture, pesticide residues in food have posed serious health risks to human. There is an urgent requirement to detect pesticide residues in food. In this work, a sensitive and effective method was employed to measure thiram residues in fruit using surface-enhanced Raman scattering (SERS) technique. Silver ink was written on photographic paper (AgNPs-photographic paper) directly by robotic writing technique. The AgNPs-photographic paper substrates possessed good SERS activities and high stability among four months. A good linear response between the peaks intensities and the logarithmic concentrations of thiram was obtained with the limit of detection (LOD) of 0.024 ppb. The substrates also exhibited excellent reproducibility with relative standard deviation (RSD) value less than 10% from ten different substrates. SERS mapping was tested to characterize the uniformity of AgNPs-photographic paper, and the RSD value was calculated to be 14.34% at 1377 cm−1 measured by 120 points. The LOD values of apple and peach juice adulterated with thiram were 0.0024 and 0.024 ppm, respectively. The LOD values of thiram residues on apple and peach peels were both 0.25 ng/cm2. It was demonstrated that the substrates prepared by robotic writing technique had great potential for practical application in food safety inspection. [ABSTRACT FROM AUTHOR]

[Display omitted] • A wettability contrast surface was created on superhydrophilic filter-paper. • The substrate shows extreme wettability contrast of 180°. • The reduction of silver nanoparticles on the substrate helps in sensing application. A facile and cost-effective method was developed to create superhydrophobic surfaces onto a superhydrophilic commercial paper for the application of droplet splitting of microliter droplets into nano and sub-nano-liter droplets. The high wettability contrast of nearly 180° between the superhydrophobic region created via candle soot coated onto the patterned poly (dimethylsiloxane) and the paper causes the self-partitioning of a 1 µl droplet while sliding through the surface with a speed ranging from 0.001 to 7.3 mm/s. Additionally, the splitting of the droplet demonstrated for µl droplets of surface tension ranging from 72 mN/m to 38.5 mN/m. The plasmonic droplet assay for surface-enhanced Raman spectroscopy was fabricated via in-situ reduction of Ag nanoparticles onto the superhydrophilic region. The Raman scattering studies of methyl orange using the prepared substrates exhibit a limit of detection of 670 pM. Further, by using methyl orange as a probe molecule, selective detection of Hg2+ ions up to a concentration of 100 pM in nanoliter droplet volume is demonstrated. It is envisaged that these cost-effective plasmonic nanoliter droplet assays created via patterned superhydrophilic-superhydrophobic can find applications in high throughput screening, microfluidic bioassays, medical diagnosis. [ABSTRACT FROM AUTHOR]

[Display omitted] The translation of Surface Enhanced Raman Spectroscopy (SERS) from the laboratory to real-world applications such as point-of-need detection requires the fabrication of inexpensive yet quality substrates. Due to its flexibility, biodegradability, and 3D cellulosic structure, paper can be an excellent platform for the fabrication of low-cost, flexible SERS substrates that could expand the application of SERS to point-of-need sensing applications. In this mini-review, recent advances in paper-based SERS substrates along with various fabrication methods for plasmonic paper are discussed. The pros and cons of different fabrication methods are evaluated from the viewpoint of mass production. The different approaches to improving the performances of plasmonic paper substrates and additional analytical functionalities obtained from plasmonic paper substrates are discussed. Finally, opportunities and challenges in the realization of a low-cost commercial plasmonic paper substrate are also suggested. [ABSTRACT FROM AUTHOR]