Search

Treatment of cryptococcal meningitis relies primarily on flucytosine (5FC), which is also used to treat candidiasis and infections caused by Cryptococcus neoformans. High dosages of this drug, despite its therapeutic properties, may cause hazardous side effects such as bone marrow suppression, hepatotoxicity, and gastrointestinal toxicity. The detection of trace amounts of 5FC medication may aid in tracking the treatment's efficacy and mitigating unwanted effects. Surface-enhanced Raman spectroscopy (SERS) is a rapid, reliable, and precise approach for detecting extremely low amounts of biological and chemical compounds. A filter paper-based SERS biosensor coated with silver nanoparticles (AgNPs) were employed to detect the 5FC drug. The AgNPs fabricated via the chemical reduction method were characterized by FE-SEM, TEM, XRD, AFM, and UV-Vis spectroscopy. Plasmonic active sites were made by coating the filter paper substrate with AgNPs to detect the 5FC drug's molecular vibrations. As the 5FC drug was coated onto the filter paper substrate, the AgNPs interacted with it, allowing for the detection of very low concentrations of the drug. The SERS filter paper substrate could detect concentrations of 5FC as low as 10−10 M. The Raman spectra and peak signals obtained experimentally were also simulated and validated using the density functional theory (DFT) approach. Six sets of measurements were taken, and the average RSD was obtained to be 4.62%. The experimentally measured enhancement factor for recognizing molecular vibrations of the 5FC was 9.065 × 107, and it was numerically estimated as 10.044 × 107. Therefore, the fabricated SERS-based filter paper substrate is useful for drug monitoring since they can detect even trace amounts of the targeted drug. [ABSTRACT FROM AUTHOR]

Plastic pollution at the nanoscale continues to pose adverse effects on environmental sustainability and human health. However, the detection of nanoplastics (NPLs) remains challenging due to limitations in methodology and instrumentation. Herein, a "green approach" for surface-enhanced Raman spectroscopy (SERS) was exploited to detect polystyrene nanospheres (PSNSs) in water, employing untreated filter paper and a simple syringe-filtration set-up. This SERS protocol not only enabled the filtration of nano-sized PSNSs, which are smaller than the pore size of the ordinary filter paper, but also offered SERS enhancement by utilizing quasi-spherical-shaped silver nanoparticles (AgNPs) as the SERS-active substrate. The filtering of NPLs was accomplished by adding an aggregating agent to the nanoparticle mixture, which caused the aggregation of NPLs and AgNPs, resulting in a larger cluster and more hot spots for SERS detection. The optimal aggregating agent and its concentration, as well as the volume ratio between the AgNPs and NPLs, were also optimized. This SERS method successfully detected and quantified PSNSs of various sizes (i.e., 100, 300, 460, 600, and 800 nm) down to a limit of detection (LOD) of about 0.31 μg mL−1. The method was also validated against the presence of several interferents (i.e., salts, sugars, amino acids, and surfactants) and was proven practical, as evidenced by the detection of 800nm PSNSs in drinking and tap water (LODs of 1.47 and 1.55 μg mL−1, respectively). [ABSTRACT FROM AUTHOR]

Amoxicillin, an antibacterial drug commonly used in food production, requires rapid and accurate detection due to its illegal usage and potential health risks. This study focuses on the development of surface-enhanced Raman scattering (SERS) biosensors using filter paper substrates coated with silver nanoparticles (Ag NPs) for the detection of amoxicillin. The Ag NPs were prepared by employing a chemical method, and their characteristics were analyzed through various techniques. The SERS substrates exhibited an impressive limit of detection (LOD) of 10–12 M for amoxicillin, with a mean relative standard deviation (RSD) of 6.63% for repeated measurements. The experimental and simulated enhancement factors were determined as 4.044 × 104 and 2.996 × 104, respectively. These disposable, reproducible, and chemically stable substrates demonstrate great potential for SERS-based research and the development of highly sensitive biosensors. [ABSTRACT FROM AUTHOR]

BACKGROUND: Flexible surface‐enhanced Raman spectroscopy (SERS) substrates such as paper‐based substrates show great potential for rapid detection of residual chemicals on food surfaces. However, controlling the density and distribution of metallic nanoparticles adsorbed on the paper is still challenging. RESULTS: The amount of gold (Au) nanospheres (51 ± 4 nm) attached on the filter paper modified with 3‐aminopropyltriethoxysilane (APTES) was tunable, increasing as the level of APTES (2.5–15.0 g kg−1) applied for paper modification increased. Moreover, the Au nanospheres were relative evenly distributed on the filter paper modified with 2.5–10.0 g kg−1of APTES, which resulted in excellent intra‐ and inter‐reproducibility of SERS signals for pesticides including thiram, diquat dibromide, and paraquat dichloride (relative standard deviation = 2.2–10.1%). The modified paper‐based substrate could be used to detect as low as 0.05–0.2 mg L−1 of pesticides in standard solutions, and as low as 5–20 ng cm−2 of residual pesticides on apple skins with minimum sample pretreatment. CONCLUSION: This paper‐based substrate with tunable feature for the density and distribution of nanoparticles is applicable for rapid SERS detection of residual pesticides in fruits and vegetables. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

The surface plasmon resonance property of silver nanoparticles (AgNPs) makes them a top-notch material for developing sensors, especially in surface-enhanced Raman scattering (SERS). The multi-shape silver nanoparticles decorated on cellulose fiber of paper provide flexible paper-based SERS substrates with different sensitivity. The isotropic and anisotropic morphology of AgNPs on filter paper has been controlled by weak and strong reducing agents: sodium borohydride (NaBH4), ascorbic acid (L-AA), glucose, formaldehyde (HCHO). The capping agent's chitosan and the reaction conditions like the ratio of precursors and stirring speed also influence the shape, size, stability, and dispersity of AgNPs on filter paper. Multi-shape AgNPs on paper are obtained as spherical shapes (about 50–100 nm), rods (size 100–500 nm in length, 50-nm wide), or thin wings. Depending on the reduction condition, these AgNPs can be single-dispersed or stuck together to form corals on paper. The fabricated paper-based SERS substrates were investigated the optical characterization and used to detect melamine in an aqueous solution with detection limits as low as 10−8 M with the EF = 2.3 × 109. [ABSTRACT FROM AUTHOR]

Nanozymes are nanomaterials that possess intrinsic enzyme mimicking activity. In this study, the application of silver nanoparticles coated filter paper (AgNPs/FP) that exhibits a peroxidase-like catalytic activity as a potential sensor is reported. A simple chemical reduction method was used to produce AgNPs/FP. The formation of the particles on filter paper were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and surface-enhanced Raman spectroscopy (SERS). In the presence of hydrogen peroxide, AgNPs/FP oxidized the colorless o-phenylenediamine (OPD) and 3,3′,5,5′-tetramethylbenzidine (TMB) solutions to a yellow colored 2,3-diaminophenazine (DAP) and deep blue colored oxidized TMB (oxTMB), respectively. In the presence of thiocyanate, however, the peroxidase-like activity was inhibited in a concentration dependent manner. This makes the AgNPs/FP a promising catalyst and employed for colorimetric detection of thiocyanate via inhibition of the peroxidase-like activity. The application can be further extended to other environmentally and biologically important analytes. [ABSTRACT FROM AUTHOR]

Bimetallic Au@Ag nano-sea urchins (Au@Ag NSUs) functionalized with methimazole were synthesized and combined with paper tips as efficient surface-enhanced Raman scattering (SERS) substrates for ultrasensitive Cr(VI) detection. The redox reaction between methimazole and Cr(VI) ensured the reliability of quantitative Cr(VI) analysis. When droplets were continuously dropped on the tip of the paper, based on the gravity effect, the nanoparticles achieved enrichment at the front end of the tip, which further improved the sensitivity of detection. The detection limit is as low as 0.956 ng L−1, demonstrating its excellent performance in ultrarace Cr(VI) detection. Additionally, the SERS sensor was successfully applied to the detection of Cr(VI) in real water samples, such as lake water and tap water, indicating its wide application potential in environmental monitoring. This study not only provides an efficient and reliable new method for detecting Cr(VI) but also shows the great prospect of paper-based SERS sensors in practical applications. [ABSTRACT FROM AUTHOR]

Recently, filter paper (FP)-based surface-enhanced Raman scattering (SERS) substrates have stimulated significant attention owing to their promising advantages such as being low-cost, easy to handle, and practically suitable for real-field applications in comparison to the solid-based substrates. Herein, a simple and versatile approach of laser-ablation in liquid for the fabrication of silver (Ag)-gold (Au) alloy nanoparticles (NPs). Next, the optimization of flexible base substrate (sandpaper, printing paper, and FP) and the FP the soaking time (5–60 min) was studied. Further, the optimized FP with 30 min-soaked SERS sensors were exploited to detect minuscule concentrations of pesticide (thiram-50 nM), dye (Nile blue-5 nM), and an explosive (RDX-1,3,5-Trinitroperhydro-1,3,5-triazine-100 nM) molecule. Interestingly, a prominent SERS effect was observed from the Au NPs exhibiting satisfactory reproducibility in the SERS signals over ~1 cm2 area for all of the molecules inspected with enhancement factors of ~105 and relative standard deviation values of <15%. Furthermore, traces of pesticide residues on the surface of a banana and RDX on the glass slide were swabbed with the optimized FP substrate and successfully recorded the SERS spectra using a portable Raman spectrometer. This signifies the great potential application of such low-cost, flexible substrates in the future real-life fields. [ABSTRACT FROM AUTHOR]

We successfully developed an atomic layer deposition (ALD) method for making Ag noble nanoparticles on cheap, commercial filter paper consisting of three-dimensional porous glass fibers and investigated the evolution of Ag nanostructures with some key process parameters. By tuning Ag particle sizes and controlling the cycle numbers of ALD deposited Ag films, we were able to obtain high-density isolated Ag nanoparticles with average sizes in 3–9 nm without the formation of agglomerates and continuous Ag films. We proved the presence of strong localized surface plasmon resonance peaks near a target wavelength of 632 nm. We further proved the presence of surface enhanced Raman scattering (SERS) signals on the Ag coated filter paper substrates using pyridine as the test analyte. Our results demonstrate that ALD is a very promising technique for a rational design of SERS substrates and, thus, has great potential for the fabrication of large-area, low-cost SERS substrates for future commercial applications, as compared to other existing techniques. [ABSTRACT FROM AUTHOR]

An ideal surface-enhanced Raman scattering (SERS) substrate should exhibit a high electromagnetic field enhancement factor, simple preparation repeatability low cost. Here, we prepared a reproducible nanoplasmonic paper SERS substrate via a silver mirror reaction (SMR) and AgNO3-ascorbic acid (AgNO3-ASC) solution treatment method to reduce Ag nanoparticles (Ag NPs) on the surface of the flexible glass fiber filter paper (GFP). GFP with Ag NPs (AgNPs@GFP) was used for SERS to detect melamine molecules (MMs). The results showed that melamine molecules' detection limit was up to 1 ng/mL. The maximum enhancement factor of the SERS signal reached 838, and the sensitivity was 150. This strategy of fabricating SERS substrates based on GFP can provide a new way to prepare a low-cost flexible SERS substrate and increase the sensitivity of biomolecules. [ABSTRACT FROM AUTHOR]

Food safety and quality are paramount concerns for ensuring the preservation of human life and well-being. As the field of food processing continues to advance, there is a growing interest in the development of fast, instant, cost-effective, and convenient methods for detecting food safety issues. In this context, the utilization of paper-based microfluidic chips has emerged as a promising platform for enabling rapid detection, owing to their compact size, high throughput capabilities, affordability, and low resource consumption, among other advantages. To shed light on this topic, this review article focuses on the functionalization of paper-based microfluidic surfaces and provides an overview of the latest research and applications to colorimetric analysis, fluorescence analysis, surface-enhanced Raman spectroscopy, as well as their integration with paper-based microfluidic platforms for achieving swift and reliable food safety detection. Lastly, the article deliberates on the challenges these analytical methods and presents insights into their future development prospects in facilitating rapid food safety assessment. [ABSTRACT FROM AUTHOR]

Flexible surface-enhanced Raman scattering (SERS) has received considerable attention in the field of rapid analysis. However, obtaining accurate quantitative SERS results remains challenging. Here, we develop a SERS sensor based on self-assembly and mask-assisted techniques for the precise transfer of Au@PB@Ag nanoarrays onto filter paper. Prussian blue (PB) as an internal standard (IS) is used to calibrate the fluctuations in the SERS signal induced by the microstructure of the filter paper, and can generate a local plasmon resonance under a Raman laser at a wavelength of 633 nm, which enables a dual electromagnetic enhancement of the internal self-calibration and external target molecule signals. The SERS substrate has a low limit of detection of 3.96 × 10−9, a uniformity relative standard deviation (RSD) of 9.94 % (16.85 % uncalibrated), a repeatability RSD of 9.43 % (31.2 % for Au@Ag NPs), and remains stable for more than 45 days. Thiram and thiabendazole in fruit juices can be quantitatively detected using patterned transfer monolayer arrays with a common dropper. The R2 coefficients of the pesticide concentration and Raman intensity fitting curves improved from 0.9659 and 0.9499 to 0.9976 and 0.9928, respectively. Thus, paper-based Au@PB@Ag nanoarrays have facilitated the development of SERS technology for practical applications. [Display omitted] • A new approach combining mask-assisted and self-assembly techniques. • Surface-enhanced resonant Raman scattering (SERS) effects with dual electromagnetic enhancement. • IS calibration of inhomogeneities due to microstructure of filter paper. • RSD of 9.43 % for paper-based SERS sensor (compare to 31.2 % for Au@Ag NPs). • Application of the SERS method to TBZ and TRM determination in fruit juices. [ABSTRACT FROM AUTHOR]

Crystal violet (CV) is a disinfectant and antifungal agent used in aquaculture that plays a vital role in treating aquatic diseases and sterilizing water. However, its potential for strong toxicity, including carcinogenicity and mutagenicity, upon accumulation in the body raises concerns regarding its safe use. Therefore, there is a growing need for the quantitative detection of CV in its early application stages to ensure human safety. Recently, Raman spectroscopy-based surface-enhanced Raman scattering (SERS) detection research has been actively conducted; consequently, an alveolar-mimicking SERS paper (AMSP) inspired by the structure of the human lungs was developed. The AMSP was optimized through various factors, including paper type, reducing agent, reducing agent concentration, and reaction time. This optimization enhanced the surface area of interaction with the target substances and promoted hotspot formation, resulting in enhanced SERS performance. The substrate exhibited exceptional uniformity, reproducibility, and reliability. CV was successfully detected at a concentration of 1 nM in laboratory settings. Furthermore, the AMSP detected CV at 1 nM in real-world environmental samples, including fish farm water and human serum, confirming its potential as a practical detection and monitoring platform for CV in real-world samples. [ABSTRACT FROM AUTHOR]

Surface-enhanced Raman scattering (SERS) has been recognized as one of the most sensitive analytical methods by adsorbing the target of interest onto a plasmonic surface. Growing attention has been directed towards the fabrication of various substrates to broaden SERS applications. Among these, flexible SERS substrates, particularly paper-based ones, have gained popularity due to their easy-to-use features by full contact with the sample surface. Herein, we reviewed the latest advancements in flexible SERS substrates, with a focus on paper-based substrates. Firstly, it begins by introducing various methods for preparing paper-based substrates and highlights their advantages through several illustrative examples. Subsequently, we demonstrated the booming applications of these paper-based SERS substrates in abiotic and biological matrix detection, with particular emphasis on their potential application in clinical diagnosis. Finally, the prospects and challenges of paper-based SERS substrates in broader applications are discussed. [ABSTRACT FROM AUTHOR]

Sunitinib malate (SM) is a chemical compound belonging to the class of kinase inhibitors and is mainly used in cancer treatment. However, despite its effectiveness, SM can cause multiple side effects, including fatigue, nausea, vomiting, and diarrhea, which can affect the patient's quality of life. Therefore, rapid and accurate diagnosis of SM is very important in many fields, especially for human health. Surface-enhanced Raman spectroscopy (SERS), an improved method for identifying biological and chemical substances with very low concentrations, is fast, reliable, and accurate. In order to identify the SM drug, filter paper substrates covered with silver nanoparticles (AgNPs) were used as SERS biosensors. First, AgNPs were prepared using a chemical reduction method. Then, the characteristics of the produced AgNPs were examined using FE-SEM, TEM, XRD, AFM, and UV–Vis analyses. The AgNPs were then coated on the substrates to create plasmonic active sites for identifying molecular vibrations of the SM drug. By coating the SM drug onto these substrates, the AgNPs reacted with the SM drug, successfully identifying trace amounts of the drug. The detection limit of the SERS plasmonic substrates for identifying the SM drug was 10−10 M. The average RSD for six repeated measurements was calculated at 5.39%. The enhancement factor for identifying molecular vibrations of the SM drug was experimentally calculated at 2.741 × 105 and numerically as 2.504 × 105. Therefore, the results indicate that these substrates are suitable for identifying low concentrations of this drug and can be used for drug monitoring purposes. [ABSTRACT FROM AUTHOR]

An environmentally friendly and economical SERS platform was successfully developed by using a polyethylene glycol (PEG)/deionized water (DI) solvent system to activate the polyol reducing power, thereby enabling the synthesis of silver nanoclusters (AgNC). These AgNC were then loaded onto porous, flexible, and biocompatible filter papers (FP) by self-assembly technology, forming an AgNC@FP flexible substrate. This substrate has achieved highly effective detection of thiram in fruits. [Display omitted] • An environmentally friendly and economical AgNC synthesis method was proposed. • The synthetic AgNC were loaded on filter paper by a simple self-assembly strategy. • The substrate possesses the capability of efficiently detecting thiram in fruits. The polyol reduction method has performed well in Ag nanocube (AgNC) synthesis but is hindered by high-temperature requirements, impacting environmental sustainability and economy. Using polyethylene glycol (PEG)/deionized water as a solvent mitigates these issues, by leveraging PEG's high solubility, bio-compatibility, low cost, and redox properties. The synthesis conditions were optimized, resulting in relatively uniform AgNC. The synthetic AgNC were loaded on porous, cheap, flexible and biocompatible filter paper (FP) by a simple self-assembly, and the formed flexible substrate (AgNC@FP) was used for surface-enhanced Raman scattering (SERS) detection. The AgNC@FP substrate had a high enhancement factor (EF) of 9.8 × 107, with a detection limit of Rhodamine 6G (R6G) of 5.2 × 10-12 M. Meanwhile, the substrate showed good reproducibility and stability, with a relative standard deviation (RSD) of 5.9 % and a decrease in Raman signal strength of only 25 % after 30 days. Furthermore, the direct sampling of apples and pears from their surface thereby enables the rapid identification of ultra-low thiram residue concentrations, with a sensitivity of 8.3 × 10-7 M. The high SERS enhancement factor and sensitivity were attributed to the result of the high hot spot density generated by the FP surface, excellent uniformity and superior sample collection efficiency. It can therefore be concluded that this flexible AgNC@FP substrate, which is manufactured at a low cost and allows for label-free SERS detection, represents a promising SERS platform for analytical and biosensing applications. [ABSTRACT FROM AUTHOR]

Copyright of China Pulp & Paper is the property of China Pulp & Paper Magazines Publisher and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Paper is a popular platform material in all areas of sensor research due to its porosity, large surface area, and biodegradability, to name but a few. Many paper-based nanocomposites have been reported in the last decade as novel substrates for surface-enhanced Raman spectroscopy (SERS). However, there are still limiting factors, like the low density of hot spots or loss of wettability. Herein, we designed a process to fabricate a silver–chitosan nanocomposite layer on paper celluloses by a layer-by-layer method and pH-triggered chitosan assembly. Under microscopic observation, the resulting material showed a nanoporous structure, and silver nanoparticles were anchored evenly over the nanocomposite layer. In SERS measurement, the detection limit of 4-aminothiophenol was 5.13 ppb. Furthermore, its mechanical property and a strategy toward further biosensing approaches were investigated.

MicroRNAs (miRNAs) have emerged as a promising class of biomarkers for early detection of various cancers, including ovarian cancer. However, quantifying miRNAs in human blood samples is challenging owing to the issues of sensitivity and specificity. In this study, hsa-miR-200a-3p of the miR-200a sub-family, which is a biomarker of ovarian cancer, was used as the analyte to demonstrate the analytical capability of an integrated biosensing platform using an extremely sensitive surface-enhanced Raman scattering (SERS) nanotag−nanoaggregate-embedded beads (NAEBs), magnetic nanoparticles (MNPs), a pair of highly specific locked nucleic acid (LNA) probes, and a semi-automated paper-based electrowetting-on-dielectric (pEWOD) device to provide labor-less and thorough sample cleanup and recovery. A sandwich approach where NAEBs are modified by one LNA-1 probe and MNPs are modified by another LNA-2 probe was applied. Then, the target analyte miRNA-200a-3p was introduced to form a sandwich nanocomplex through hybridization with the pair of LNA probes. The pEWOD device was used to achieve short cleanup time and good recovery of the nanocomplex, bringing the total analysis time to less than 30 min. The detection limit of this approach can reach 0.26 fM through SERS detection. The versatility of this method without the need for RNA extraction from clinical samples is expected to have good potential in detecting other miRNAs. [ABSTRACT FROM AUTHOR]

Fast detection of contaminants of emerging concern (CECs) in water resources is of great environmental interest. Ideally, sustainable materials should be used in water quality monitoring technologies implemented for such purposes. In this regard, the application of bio-based materials aimed at the fabrication of analytical platforms has become of great importance. This research merges both endeavors by exploring the application of chitosan-coated paper, decorated with silver nanoparticles (AgNPs), on surface-enhanced Raman scattering (SERS) spectroscopy studies of two distinct types of CECs dissolved in aqueous samples: an antibiotic (ciprofloxacin) and a pesticide (thiram). Our results indicate the superior SERS performance of biocoated substrates compared to their non-coated paper counterparts. The detection limits achieved for thiram and ciprofloxacin using the biocoated substrates were 0.024 ppm and 7.7 ppm, respectively. The efficient detection of both analytes is interpreted in terms of the role of the biopolymer in promoting AgNPs assemblies that result in local regions of enhanced SERS activity. Taking advantage of these observations, we use confocal Raman microscopy to obtain Raman images of the substrates using ciprofloxacin and thiram as molecular probes. We also demonstrate that these biobased substrates can be promising for on-site analysis when used in conjunction with portable Raman instruments. [ABSTRACT FROM AUTHOR]

This document is a summary of a special issue of the journal Catalysts, which focuses on recent advances in the field of photocatalysis. The issue includes seven exclusive papers written by members of the editorial board and topical advisory panel. The papers cover a range of topics, including the use of gadolinium-doped bismuth ferrite for the photocatalytic oxidation of arsenite, the effect of heterovalent doping on the photoelectrochemical behavior of anatase TiO2, the synthesis of novel ternary composites for photocatalytic degradation, the preparation of metallic MoS2/WS2 dual co-catalysts for hydrogen production, the development of a photocatalyst for removing bisphenol A from water, the synthesis of Au/TiO2/WO3 heterostructures for photodegradation and dye sensing, and the design of furane-based photoinitiators for polymerization. The authors conclude that there is still much research to be done in the field of photocatalysis, particularly in terms of the type of light irradiation, substrate immobilization, and the search for new photocatalysts. [Extracted from the article]

Carbaryl is a broad-spectrum carbamate fungicide that may pose a threat to ecosystems and human health. To prevent and control the harm caused by excessive application of carbaryl, a full-dimensional divergence effect SERS sensor has been constructed. Biodegradable paper chips were used as sensor substrates. ZIF-8 with structural flexibility was grown in situ on carbon paper. A rough silver layer with surface like metal etching was clad outside the ZIF-8. Artificial antibody (AAB) with accurate grasping ability was polymerized on the surface of ZIF-8@Ag paper substrate. Au@Ag CSNPs were decorated on the AAB to provide abundant "hot spots". Every functional material layer works together to form a gap and tip region with superior plasmon resonance. The proposed SERS sensor realizes the rapid and accurate on-site screening and localization of carbaryl in food with good correlation responded in the range of 0.01–20 μg·mL−1 and a low detection limit of 5.72 × 10–‍3‌ μ g·mL−1. [Display omitted] • A full-dimensional divergence-enhanced paper-based SERS sensor has been established. • Synergistic enhancement strategy of MOF and noble metal materials. • Radiate electromagnetic fields and hot spots in three-dimensional coordinate system. [ABSTRACT FROM AUTHOR]

Rapid and precise detection of harmful substances in food products is essential for ensuring public health and safety. This study introduces a novel surface-enhanced Raman spectroscopy (SERS) substrate, composed of a molybdenum disulfide‑silver nanocomposite, applied to flexible, water-resistant filter paper for detecting melamine and bisphenol A (BPA) in milk. Optimized molybdenum disulfide (NMS) nanoflowers (NFs) were synthesized through hydrothermal methods and high-temperature annealing, then modified with silver (Ag) nanoparticles to form the NMS-Ag nanocomposite (NMSA 6). This substrate greatly enhances the Raman signal, achieving an enhancement factor of approximately 1.49 × 107 and a detection limit as low as 10−11 M for simultaneous multi-component analysis. Finite-difference time-domain (FDTD) simulations confirm the enhancement mechanism. The NMSA 6 substrate demonstrates remarkably low detection limits for BPA and melamine, facilitating the analysis of various hazardous substances. These findings highlight the substrate's potential for highly sensitive, label-free detection, presenting a viable tool for food safety monitoring. [Display omitted] • A flexible hydrophobic fiber filter paper modified with NMS NFs composite Ag NPs hybrid was prepared. • NMSA 6 has a high EF value of 1.496 × 107, and NMSA 6 was used as highly sensitive SERS substrates. • The detection limits of NMSA 6 -modified filter paper for BPA and melamine in milk are as low as 10−10 M and 10−8 M respectively. • There are three reasons for the excellent SERS activity of NMSA 6 substrate. [ABSTRACT FROM AUTHOR]

We report an innovative and facile approach to fabricating an ultrasensitive plasmonic paper substrate for surface-enhanced Raman spectroscopy (SERS). The approach exploits the self-assembling capability of poly(styrene-b-2-vinyl pyridine) block copolymers to form a thin film at the air-liquid interface within the single microdroplet scale for the first time and the subsequent in situ growth of silver nanoparticles (AgNPs). The concentration of the block copolymer was found to play an essential role in stabilizing the droplets during the mass transfer phase and formation of silver nanoparticles, thus influencing the SERS signals. SEM analysis of the morphology of the plasmonic paper substrates revealed the formation of spherical AgNPs evenly distributed across the surface of the formed copolymer film with a size distribution of 47.5 nm. The resultant enhancement factor was calculated to be 1.2 × 107, and the detection limit of rhodamine 6G was as low as 48.9 pM. The nanohybridized plasmonic paper was successfully applied to detect two emerging pollutants—sildenafil and flibanserin—with LODs as low as 1.48 nM and 3.45 nM, respectively. Thus, this study offers new prospects for designing an affordable and readily available, yet highly sensitive, paper-based SERS substrate with the potential for development as a lab-on-a-chip device. [ABSTRACT FROM AUTHOR]

Criminal practices in which an individual becomes vulnerable and prone to sexual assault after ingesting drinks spiked with doping substances have become a social concern globally. As forensic protocols require a multi‐tiered strategy for chemical evidentiary analysis, the backlog of evidence has become a significant problem in the community. Herein, a fast, sensible, and complementary dual analytical methodology was developed using a single commercial paper substrate for surface‐enhanced Raman spectroscopy (SERS) and paper spray mass spectrometry (PS‐MS) analysis to identify psychotropic substances added to alcoholic beverages irrefutably. To study and investigate this criminal practice, pharmaceutical formulations containing distinct psychotropic substances (zolpidem, clonazepam, diazepam, and ketamine) were added to drinks typically consumed at parties and festivals (Pilsen beer, açaí Catuaba®, gin tonic, and vodka mixed with Coca‐Cola Zero®). A simple liquid–liquid extraction with a low‐temperature partitioning (LLE‐LTP) procedure was applied to the drinks and effectively minimized matrix effects. As a preliminary analysis, SERS spectra combined with Hierarchical Clustering Analysis (HCA) provided sufficient information to investigate the samples further. The presence of the protonated species for the psychotropic substances in the spiked drinks was readily verified in the mass spectra and confirmed by tandem mass spectrometry. Finally, the results demonstrate the potential of this methodology to be easily implemented into the routine of forensic laboratories and to be further employed at harm reduction tends at parties and festivals to detect contaminated beverages promptly and irrefutably as an efficient tool to prevent such crimes. [ABSTRACT FROM AUTHOR]

The aim of this paper was to explore the non‐destructive application of fusion spectra model for characterization and differentiation of electrostatic copying papers that could be favourable to give forensic aid in legal cases. Two hundred fifty electrostatic copy paper samples were collected from various markets. All samples were subjected to surface‐enhanced Raman spectroscopy (SERS) analysis from 3500 to 400 cm−1 Raman shift range and attenuated total reflection‐Fourier transform infrared spectrum (ATR‐FTIR) analysis from 4000 to 400 cm−1 wavenumber range, respectively. The spectral data refracted the constituents present in the electrostatic copy papers were cellulose, inorganic filler calcium carbonate and barium sulfate. Fisher discriminant analysis (FDA), multi‐class support vector machine (MSVM) and decision tree (DT) algorithms were used to build the model. The precision rate, recall rate, F‐score and total accuracy were considered as indicators to evaluate the model's performance. The results showed that fusion models were superior to single model. The feature layer fusion model based on MSVM algorithm gave a differentiating power of 100% by grouping all the sample groups. This study demonstrated that spectral fusion model is a feasible and reliable approach for fast and non‐destructive differentiation of electrostatic copying papers. It has great potential in real application scenarios. [ABSTRACT FROM AUTHOR]

Mercury ions (Hg2+) are highly toxic heavy metals that are commonly found in natural environments. Owning to their non-biodegradability and accumulation in the food chain, the precise detection of trace amounts of Hg2+ is essential for preventing chronic accumulation and ensuring food safety. In this study, we present a dual-mode paper sensor for simultaneous colorimetric and Surface-Enhanced Raman Spectroscopy (SERS) detection of Hg2+ in tea, achieving ultrasensitive, rapid, and on-site screening. 4-Mercaptopyridine (4-MPY) was effectively chemisorbed onto the gold nanoparticles (AuNPs), acting as a signal probe for colorimetric methods. Moreover, it can produce plasmonic hot spots for SERS by interacting with the pyridine ring. To enhance the signal intensity of both colorimetry and SERS, a silver shell is in-situ grown on the surface of AuNPs captured on the paper sensor by reduction of Ag+, achieving signal amplification. The visual limit of detection (LOD) for the colorimetric biosensor is 2.5 pM, while the LOD of SERS is 0.48 pM with this dual-mode paper sensor. The sensitivity of both the colorimetric method and SERS was improved by approximately 200 and 500 times, respectively, with the designed signal amplification strategy. The system allows for multiple parallel screening of the same sample, ensuring accurate results without any false-positive or false-negative. This study provides a valuable platform for the accurate detection of various other heavy metal ions and provides effective strategies for improving the performance of colorimetric methods. • Colorimetric and SERS dual-mode paper sensor constructed for high throughput screening of mercury ions. • Recognition effect of T-rich probe and 4-MPY to Hg2+ induced the formation of sandwich structure for analysis. • Signal molecule 4-MPY adopted as the recognition probe in the designed recognition sandwich structure. • In-situ grown of Ag shell on AuNPs greatly contributed to both the colorimetric and SERS signal improvement. • Simultaneous high throughput screening of the same sample contributed to the accuracy of the detection. [ABSTRACT FROM AUTHOR]

Detecting microRNA (miRNA) biomarkers expression is of great significance for the diagnosis and treatment of lung cancer. Surface-enhanced Raman scattering (SERS) has achieved microRNA sensing for the diagnosis of primary liver cancers. In this work, we developed a SERS technology for the rapid detection of lung cancers-related miRNA (miR-196a) using bimetallic Au-Ag nanowire (AgNW@AuNPs) substrates coupled with the target hairpin DNA. The finite-difference time-domain simulation proved that a large number of "hot spots" were generated between the AgNW and AuNPs, which resulted in a huge enhancement of the signal of Raman reporters. Filter paper treated by hexadecenyl succinic anhydride hydrophobic and modified with AgNWs@AuNPs was used as capturing substrate. The detection limits of miR-196a in PBS and serum were as low as 96.58 aM and 130 aM, respectively. Studies on nonspecific sequence and single-base mismatch of miRNA demonstrated that SERS-based platform was highly selective, excellent uniform, and reproducible. Finally, the platform was used to show that the miR-196a expression in the serum of lung cancer patients was much higher than that in healthy people. The detection results indicated that the SERS platform had potential applications in cancer diagnosis and might be a viable alternative to the conventional miRNA detection method, the real-time polymerase chain reaction (RT-PCR) technology. [ABSTRACT FROM AUTHOR]

The surface-enhanced Raman scattering (SERS) properties of low-dimensional semiconducting MXene nanoflakes have been investigated over the last decade. Despite this fact, the relationship between the surface characteristics and SERSing performance of a MXene layer has yet to be comprehensively investigated and elucidated. This work shows the importance of surface morphology on the overall SERS effect by studying few-layer Ti3C2Tx MXene-based SERS substrates fabricated by vacuum-assisted filtration (VAF) and spray coating on filter paper. The VAF deposition results in a dense MXene layer suitable for SERS with high spot-to-spot and substrate-to-substrate reproducibility, with a significant limit of detection (LoD) of 20 nM for Rhodamine B analyte. The spray-coated MXenes film revealed lower uniformity, with a LoD of 50 nM for drop-casted analytes. Moreover, we concluded that the distribution of the analyte deposited onto the MXene layer is affected by the presence of MXene aggregates created during the deposition of the MXene layer. Accumulation of the analyte molecules in the vicinity of MXene aggregates was observed for drop-casted deposition of the analyte, which affects the resulting SERS enhancement. Ti3C2Tx MXene layers deposited on filter paper by VAF offer great potential as a cost-effective, easy-to-manufacture, yet robust, platform for sensing applications. [ABSTRACT FROM AUTHOR]

Thiram is a readily synthesized, cost-effective antimicrobial agent widely used to control diseases in fruits and vegetables. Given the potential health hazards associated with thiram residues and advancements in detection methods, it is crucial to develop a rapid and sensitive technique for detecting these residues on fruit surfaces. Here, we prepared the Ag@filter paper (Ag@FP) surface-enhanced Raman scattering (SERS) substrate in a controlled manner and innovatively developed a capillarity-assisted SERS (CA-SERS) detection method. Sampling can be completed in less than 1 min by either wiping or using the CA-SERS method. Utilizing a portable Raman device, the detection limit for thiram residues on apple surfaces can reach as low as 0.005 ng/cm2 with the CA-SERS detection method. Furthermore, the substrate is cost-effective, can be prepared in just 7 min, and remains stable at room temperature for up to 40 days. Additionally, we developed a cost-effective, centimeter-scale auxiliary detection device to facilitate efficient on-site detection. [Display omitted] • A controllable silver nanoparticle surface-enhanced Raman scattering substrate (Ag@FP) has been developed. • A highly sensitive capillary-assisted SERS (CA-SERS) detection method was innovated. • CA-SERS is able to complete sample collection in only 1 min. • An affordable, miniaturized auxiliary detection device was developed for rapid on-site testing. [ABSTRACT FROM AUTHOR]

Surface-enhanced Raman spectroscopy (SERS) is an emerging analytical technique for chemical analysis, which is favourable due to its combination of short measurement time, high sensitivity and molecular specificity. However, the application of SERS is still limited, largely because in real samples the analyte is often present in a complex matrix that contains micro/macro particles that block the probe laser, as well as molecular contaminants that compete for the enhancing surface. Here, we show a simple and scalable spray-deposition technique to fabricate SERS-active paper substrates which combine sample filtration and enhancement in a single material. Unlike previous spray-deposition methods, in which simple colloidal nanoparticles were sprayed onto solid surfaces, here the colloidal nanoparticles are mixed with hydroxyethyl cellulose (HEC) polymer before application. This leads to significantly improved uniformity in the distribution of enhancing particles as the film dries on the substrate surface. Importantly, the polymer matrix also protects the enhancing particles from air-oxidation during storage but releases them to provide SERS enhancement when the film is rehydrated. These SERS-paper substrates are highly active and a model analyte, crystal violet, was detected down to 4 ng in 10 μL of sample with less than 20% point-by-point signal deviation. The filter paper and HEC effectively filter out both interfering micro/macro particles and molecular (protein) contaminants, allowing the SERS-paper substrates to be used for SERS detection of thiram in mud and melamine in the presence of protein down to nanogram levels without sample pre-treatment or purification. [ABSTRACT FROM AUTHOR]

[Display omitted] • Sustainable and low-cost SERS substrates developed for water contaminants detection. • AgNPs deposited on paper coated with PLA NPs form the sensing substrates. • PLA NPs create a nano-rough film that reduces the porosity and hydrophilicity of paper. • Substrate performance depends on the PLA drying temperature. • Efficient detection of paraquat and ciprofloxacin in mineral water. Developing cost-effective and sensitive Surface-Enhanced Raman Spectroscopy (SERS) paper platforms represents a significant step forward for detecting specific water contaminants at ultra-low concentrations in remote regions of the globe. However, the hydrophilic, irregular, and porous nature of common paper often results in poor reproducibility and lack of uniformity of paper sensors. In this study, we developed efficient SERS substrates by combining office paper, polylactic acid nanoparticles (PLA NPs), and silver nanoparticles (AgNPs) using a two-step drop-casting method. In these substrates, the PLA NPs create a nano-rough film that reduces porosity and hydrophilicity of paper, while the AgNPs provide SERS activity. The film's packaging ability was optimized by adjusting the drying temperature of the PLA colloid, which significantly influenced the paper's wettability. Additionally, the drying temperature was found to substantially affect the loading of AgNPs on the substrate surface. Initial tests with rhodamine 6G as a model analyte showed that the optimal SERS response was achieved at a drying temperature of 100 °C, with a sixfold concentration of the Ag colloid. The effectiveness of these paper-based sensors was further demonstrated by detecting pesticides and antibiotics in mineral water, specifically paraquat and ciprofloxacin, with detection limits of 1 µM and 200 µM, respectively. [ABSTRACT FROM AUTHOR]

[Display omitted] • Trace analytes, along with SiO 2 @Au CSSs can be enriched on a paper-based super-hydrophobic substrate. • Excellent sensitivity and reproducibility are achieved on the SERS platform. • The SERS platform enables effective detection of various contaminants and multicomponent residues in real samples. • This SERS platform exhibits satisfactory chemical durability. Achieving highly sensitive surface-enhanced Raman scattering (SERS) detection requires precise collection of trace target analyte molecules into small hot spot regions. In this study, we propose a convenient and cost-effective method to construct a high-performance SERS platform based on the super-hydrophobic delivery (SHD) effect to overcome the diffusion limit during sample evaporation. A paper based super-hydrophobic substrate (PBSH substrate) was employed as a concentrator to enrich the analytes, along with SiO 2 @Au core-satellite structures (SiO 2 @Au CSSs) to form "molecule in hot spot" matrices. Benefiting from the SHD effect and the high SERS activity of SiO 2 @Au CSSs in three-dimensional space, we achieved excellent SERS sensitivity and reproducibility. This platform exhibits a good linear response for detecting Rhodamine 6G (R6G) across concentration ranges from nanomolar (10−7 M) to femtomolar (10−13 M) levels, with a low relative standard deviation (RSD) of 6.42 % observed across 30 randomly selected spots. Moreover, the platform enables sensitive detection of various contaminants and multicomponent residues of pesticides and organic dyes in real samples, exhibiting great practical potential in the field of food safety. [ABSTRACT FROM AUTHOR]

A paper-based surface enhancement of a Raman scattering substrate consisting of silver-nanowires stacked on glass-fiber filter paper was prepared. At the same time, the DNA-embedding molecule Eva Green was introduced as a signaling molecule for surface-enhanced Raman scattering (SERS) detection. Polymerase chain reaction (PCR) was used to amplify target genes and the method was developed into a rapid molecular diagnostic system. The total detection time of the developed detection method was 40 min, including 30 min of PCR amplification and 10 min of SERS measurement. After 30 PCR cycles, bacterial DNA with an initial concentration of 20 fg/μL and a bacterial suspension with an initial concentration of 7.2 × 101 CFUs/mL could be detected. When the enrichment culture time was 4 h, target bacteria with an initial contamination inoculation volume of 1.5 CFUs/mL could be detected in artificially contaminated samples. The method is fast and highly sensitive, and has not been applied to the detection of V. parahaemolyticus. [ABSTRACT FROM AUTHOR]

• A versatile SERS chip based on CMOF-enforced carbon paper was firstly constructed. • CMOF provided a pre-concentration effect for increasing sensitivity and stability. • Uniform electrodeposition of Au NPs can be contributed to superior reproducibility. • The SERS chip showed low LOD, wide linear range and good reusability for diazepam. • Diazepam in aquatic products was recognized with excellent practical applicability. Herein, a versatile surface enhanced Raman scattering (SERS) platform was firstly constructed by integrating conductive metal organic framework (CMOF) with controlled electrodeposition of Au nanoparticles (Au NPs) on flexible carbon paper (CP-CMOF@Au) for sensitively recognizing diazepam (DZP) in aquatic products. The CMOF not only provided a pre-concentration effect for boosting sensitivity, but also dramatically improved the intrinsic electrical conductivity contributing to homogeneous distribution of Au NPs and forming SERS-active "hot spot" with superior stability and reproducibility. Based on CP-CMOF@Au chip, DZP can be sensitively detected with low limit of detection of 0.64 ng mL−1 and wide linear detection range from 0.001 to 10 μg mL−1. Also, DZP in aquatic products can be collected and recognized using multiple approaches (drip coating, soaking and wiping) with excellent reusability and satisfactory recovery of 85.8–103.3%. This method would provide an ingenious SERS strategy for rapidly monitoring DZP in aquatic products with good practical applicability. [ABSTRACT FROM AUTHOR]

Surface-enhanced Raman Scattering (SERS) has become a powerful spectroscopic technology for highly sensitive detection. However, SERS is still limited in the lab because it either requires complicated preparation or is limited to specific compounds, causing poor applicability for practical applications. Herein, a micro-macro SERS strategy, synergizing polymer-assisted printed process with paper-tip enrichment process, is proposed to fabricate highly sensitive paper cartridges for sensitive practical applications. The polymer-assisted printed process finely aggregates nanoparticles with a discrete degree of 1.77, and SERS results are matched with theoretical enhancement, indicating small cluster-dominated hotspots at the micro-scale and thus 41-fold SERS increase compared to other aggregation methods. The paper-tip enrichment process moves molecules in a fluid into small tips filled with plasmonic clusters, and molecular localization at hotspots is achieved by the simulation and optimization of fluidic velocity at the macro-scale, generating a 39.5-fold SERS sensibility increase in comparison with other flow methods. A highly sensitive paper cartridge contains a paper-tip and a 3D-printed cartridge, which is simple, easy-to-operate, and costs around 2 US dollars. With a detection limit of 10 −12 M for probe molecules, the application of real samples and multiple analytes achieves single-molecule level sensitivity and reliable repeatability with a 30-min standardized procedure. The micro-macro SERS strategy demonstrates its potential in practical applications that require point-of-care detection. [Display omitted] [ABSTRACT FROM AUTHOR]

This study aims to develop a flexible, paper-based gold nanoparticle (AuNP) surface-enhanced Raman scattering (SERS) sensor coupled with deep learning algorithms for the rapid detection of dibenz (a,h)anthracene (DbA) and benzo(b)fluoranthene (BbF) in mussels. The SERS sensor was fabricated on a hydrophobic paper substrate and incubated with varying concentrations of DbA and BbF in spiked mussel samples before SERS spectra collection. Deep learning algorithms, including Convolutional Neural Networks (CNNs) and Long Short-Term Memory (LSTM) networks, were employed to analyze the complex SERS spectral data. The SERS sensor demonstrated excellent sensitivity with limits of detection of 0.09 ng/mL for DbA and 0.10 ng/mL for BbF. LSTM outperformed traditional machine learning techniques, achieving R2p > 0.99 with minimal prediction errors. Real sample analysis showed excellent agreement with HPLC-FLD methods. These findings present a promising approach for rapid, sensitive, and reliable detection of PAHs in mussels, enhancing food safety monitoring and regulatory compliance. • Developed a flexible paper-based AuNP SERS sensor for DbA and BbF detection in seafood. • LSTM network outperformed other models in analyzing SERS spectra. • Achieved low limits of detection: 0.09 ng/mL for DbA and 0.10 ng/mL for BbF. • Real sample analysis showed excellent agreement with HPLC-FLD method. [ABSTRACT FROM AUTHOR]

Background: Chlorpyrifos is a commonly used organophosphorus pesticide in agriculture. However, its neurotoxicity poses a huge threat to human health. In the present study, a chitosan‐modified filter paper‐based surface enhanced Raman scattering active substrate (Ch/AgNPs/paper) was fabricated and used to detect trace amounts of chlorpyrifos in 120 treated wheat samples. Results: Results showed that the Ch/AgNPs/paper substrate could be used to enhance the chlorpyrifos spectral fingerprint only up to a concentration of 0.000558 mg L−1. Following Raman spectra acquisition, three pre‐processing methods, including Savitzky–Golay (Savitsky–Golay filter with a second order polynomial) smoothing with first derivative and second derivative and normalization, were used to reduce baseline variation and increase resolutions of spectral peak features of the original spectra dataset. Then, prediction models based on partial least squares were established for detecting chlorpyrifos pesticide residue in wheat. The partial least squares model with normalization yielded optimal result, with a correlation coefficient of 0.9764, root mean square error of prediction of 1.22 mg L−1 in the prediction, and relative analysis deviation of 4.12. Five unknown samples were prepared to verify the accuracy of the prediction model. The predicted recoveries were calculated to be between 97.25% and 119.38% with an absolute t value of 0.598. The value of a t‐test shows that the prediction model is accurate and reliable. Conclusion: The present study demonstrates that the proposed method can achieve rapid detection of chlorpyrifos in wheat. © 2022 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

In this study, we developed a simple, inexpensive and easily fabricable paper-based SERS substrate with high sensitivity and reproducibility. The filter paper has natural pleats and small pores that allow the metal nanoparticles to be deposited and arranged on the paper to form large area SERS 'active sites'. Silver nanoparticles can be embedded and grown on cellulose nanocrystals framework through the in situ reduction to form cellulose nanocrystal–silver (CNC–Ag) composites, which are coated on the filter paper to form composite paper-based substrates. The CNC–Ag composites further filled the pores on the surface of the filter paper and improved the adhesive rate of metal nanoparticles, thus the reproducibility of the SERS sensor has been improved. At the same time, because it has the agglomerating effect on samples, the hydrophobic dodecyl mercaptan covered on paper-based substrates can improve detection limit of analyte. Furthermore, we demonstrate that paper-based SERS substrates can efficiently detect two substances, including phenylethanolamine A and metronidazole. The limits of detection for phenylethanolamine A and metronidazole were found to as low as 5 × 10−9 M and 2 × 10−7 M, respectively. The paper-based SERS substrates offer great potential for label-free and on-site detection of trace substances. [ABSTRACT FROM AUTHOR]

Chlorpyrifos is one of the most widely used organophosphate insecticides in agricultural production. Nevertheless, the residues of chlorpyrifos in agricultural by-product seriously threaten human health. Thus, the ultrasensitive detection of chlorpyrifos residues in agri-food products is of great demand. Herein, an AuNP/HNT-assembled disposable paper SERS substrate was prepared by an electrostatic self-assembly method to detect chlorpyrifos residues. The AuNP/HNT paper substrate exhibited high SERS activity, good reproducibility, and long-term stability, which was successfully used for quantitative detection of chlorpyrifos; the detection limit reached 7.9 × 10−9 M. For spiked apple samples the calculated recovery was 87.9% with a RSD value of 6.1%. The excellent detection ability of AuNP/HNT paper-based SERS substrate indicated that it will play an important role in pesticide detection in the future. AuNP/HNT assembled disposable paper SERS substrate was prepared by an electrostatic self-assembly method to detect chlorpyrifos residues in fruits. [ABSTRACT FROM AUTHOR]

Paper‐based surface‐enhanced Raman spectroscopy (SERS) sensors can be fabricated easily by dropcasting or inkjet printing colloidal Au nanoparticles onto cellulose‐based filter papers. They are flexible, economical, and sensitive and provide the crucial advantage of point‐of‐need sampling for application in the field. In this study, paper‐based SERS sensors are fabricated through inkjet printing of a colloidal Au sol onto a filter paper substrate. We have characterized their SERS performances with benzenethiol and pyridine molecules using a handheld Raman analyzer. Due to the heterogeneous loading of the Au nanoclusters on the paper substrate, we introduce the concept of receiver operating characteristic as an alternate measurand to quantify the performance of these sensors. With their inherent filtration sampling capability, we demonstrate the use of paper SERS sensors for the detection of chemical aerosols. Lastly, we present the use of a precision materials printer to deposit quantifiable amounts of analyte (fentanyl) uniformly across the active sensing area of a paper SERS sensor. This will allow for analyte‐loaded certified references to be prepared and used in the field as standards for comparison. [ABSTRACT FROM AUTHOR]

• PDADMAC/PSS/Au@Ag NRs filter paper is a kind of disposable environment-friendly flexible SERS substrate. • The PDADMAC/PSS modified filter paper showed the potential of SERS substrate for nanoparticle self-assembly. • The prepared paper-based SERS substrate had high SERS activity and good reproducibility. • PDADMAC/PSS/Au@Ag NRs filter paper realized the "paste-reading" detection of MP, TMTD and CPF on the pericarp. The goal of food safety supervision is to directly identify the pesticide residues on the surface of fruits and vegetables. This study proposed to develop a facile, non-destructive, and sensitive method based on surface-enhanced Raman scattering (SERS) to detect non-systemic pesticides on the surface of fruits and vegetables. The composite material was prepared by loading CTAB guided Au@Ag NRs with positive charge onto filter paper which was modified with PDADMAC(+) and PSS(−) using electrostatic adsorption. Au@Ag NRs with bimetallic synergies were effectively adsorbed in the fiber grid to generate 3D SERS hotspots within a few microns of depth. The results showed that the 3D composite flexible substrate had a high SERS activity, great repeatability, and sensitivity when the method was utilized to detect 4-MBA, methyl-parathion, thiram and chlorpyrifos. Three kinds of non-systemic pesticides on the peel could be detected directly and quickly owing to the arbitrary bending of the substrate, demonstrating the efficiency of the SERS "paste-reading" method. The acquired findings demonstrated that PDADMAC/PSS/Au@Ag NRs composite filter paper had the potential to provide rapid feedback for in- situ analysis of pesticide residues on the surface of fruit and vegetable. [ABSTRACT FROM AUTHOR]

[Display omitted] • A highly sensitive SERS platform was developed using gold nanoparticles for Al3+ ion detection. • Nanoparticle aggregation enhanced the SERS signal through the co-assembly of His and 4-MBA on Au NPs. • Histidine modified on Au NPs facilitated the anchor point creation for enhanced Al3+ ion capture. • Introduction of paper-based plasmonic strips loaded with His-4-MBA-Au NPs for practical Al3+ ion detection. The adverse effects of Al3+ ions on human health necessitate the development of ultra-sensitive detection methods for Al3+ ions. In this regard, the compact and portable design of the detection substrate is of utmost importance for achieving in-situ and sensitive detection of Al3+ ions. In our study, we have successfully developed a surface-enhanced Raman scattering (SERS) platform with gold nanoparticles (Au NPs) that was modified with histidine (His) and 4-mercaptobenzoic acid (4-MBA) for the SERS detection of Al3+ ions. His and 4-MBA molecules are attached to the Au NPs through a co-assembly strategy. His with amino and carboxyl groups imparts the Au NPs with an aggregation effect against Al3+ ions, while 4-MBA provides the SERS responsiveness. The coordination effect of Al3+ ions leads to the aggregation of Au NPs, creating hot spots around the 4-MBA molecules and thereby enhancing the SERS signals. Based on this principle, we have constructed a SERS analysis method for detecting Al3+ ions in solution. Furthermore, the paper-based plasmonic strips loaded with His-4-MBA-Au NPs have been successfully employed for the SERS detection of Al3+ ions. These strips exhibit a significantly higher enhancement factor of 9.77 × 106 compared to the solution system, thanks to the physical aggregation of the strips. The Au NPs tend to generate localized electromagnetic hot spots on the surface of strips, playing a critical role in achieving superior SERS performance. The limit of detection (LOD) of His-4-MBA-Au NPs for Al3+ detection is as low as 7.38 nM. The fabricated strips have also undergone repeatability testing and analysis of real samples. The established platform for the detection of Al3+ ions holds great promise for portable and on-the-spot analysis. [ABSTRACT FROM AUTHOR]

Surface-enhanced Raman spectroscopy (SERS) has been transformed into a useful analytical technique with significant advantages in relation to sensitive and low-concentration chemical analyses. However, SERS substrates are expensive and the analyte sample preparation is complicated; hence, it is only used in limited areas. We have fabricated a tattoo paper-based SERS substrate by using non-complicated inkjet printing. The sensitivity of the SERS substrate was increased by removing the carbon residues via exposure to ultraviolet light without damaging the substrate. Thus, low concentrations of pesticides (up to 1 μM thiram) were measured. The SERS substrate was attached to the curved surface of an apple to demonstrate its advantages, such as the flexibility and easy attachability of tattoo paper, and its feasibility was verified by measuring 1 μM thiram on the apple's surface. Due to its economic cost, simple usage, and rapid measurement, it will be helpful for the identification of both agricultural adulterants and food adulterants and for water-based pollutant detection. It will also possibly be helpful for medical purposes related to human body surfaces in the future. [ABSTRACT FROM AUTHOR]

[Display omitted] • The combination of SERS and colorimetry improves the reliability of the result. • The electrostatic interaction in the method allows for the desirable performance. • The hydrophobic treatment of paper substrate avoids the complex processing. • The enrichment of the hydrophobic substrate increases the detection sensitivity. For on-site analysis, the combination of surface enhanced Raman scattering (SERS) and colorimetry, as a dual-mode detection, can effectively improve the accuracy of detection, and reduce the influence of instrument fluctuation, which greatly improves the accuracy and reliability of the results. However, the preparation of SERS/colorimetry substrates are usually time-consuming and costly, which limits their practical applications. In this paper, a hydrophobic paper-based SERS/colorimetry substrate can be prepared by a simple spraying method. The hydrophobicity is introduced by the structures formed with polydimethylsiloxane and polymethylmethacrylate, which leads to high detection sensitivity due to its enrichment effect. Moreover, the electrostatic interaction between Ag nanoparticles and the analytes further enhances the performance of SERS and colorimetry in detection of thiram and aspartame. It also provides a new method for the detection of aspartame with colorimetry. Finally, the detection limits of SERS and colorimetry for thiram and aspartame are 0.1 mg/L and 0.1 g/L, 1 mg/L and 0.1 g/L, respectively. The paper-based SERS/colorimetry substrate makes the results more reliable through dual-mode detection, which shows great potential in the detection of real samples. [ABSTRACT FROM AUTHOR]

[Display omitted] • Surface-enhanced Raman scattering (SERS) method was used to detect the antiviral drug Acyclovir. • SERS-active plasmonic substrates were prepared using filter paper substrates decorated with silver nanoparticles. • Developed SERS-active substrates indicated favorable reproducibility and chemical stability, with a limit of detection (LOD) of 10-12 M. • FDTD simulations were carried out, and the electric field distributions as well as the enhancement factor of the developed SERS-active substrates were obtained. Acyclovir (ACV) drug, a common antiviral agent, is frequently used as the primary clinical treatment method for treating hepatitis B, herpes simplex, and varicella zoster viruses due to its potent therapeutic effect. In patients with compromised immune systems, this medication can stop cytomegalovirus infections, and high doses of this drug are required; however, such prescription leads to kidney toxicity. Therefore, timely and accurate detection of ACV is crucial in many areas. Surface-Enhanced Raman Scattering (SERS) is a reliable, rapid, and precise approach for the identification of trace biomaterials and chemicals. Filter paper substrates decorated with silver nanoparticles (AgNPs) were applied as SERS biosensors to detect ACV and control its adverse effects. Initially, a chemical reduction procedure was utilized to produce AgNPs. Afterward, UV–Vis, FE-SEM, XRD, TEM, DLS, and AFM were employed to examine the properties of prepared AgNPs. In order to prepare SERS-active filter paper substrates (SERS-FPS) to detect Molecular vibrations of ACV, AgNPs prepared by immersion method were coated on filter paper substrates. Moreover, the UV–Vis DRS analysis was carried out to assess the stability of filter paper substrates and SERS-FPS. The AgNPs reacted with ACV after being coated on SERS-active plasmonic substrates and could sensitively detect ACV in small concentrations. It was discovered that the limit of detection of SERS plasmonic substrates was 10-12 M. Moreover, the mean RSD for ten repeated tests was calculated as 4.19%. The enhancement factor for detecting ACV using the developed biosensors was calculated to be 3.024 × 105 and 3.058 × 105 experimentally and via simulation, respectively. According to the Raman results, SERS-FPS for the detection of ACV, fabricated by the present methods, showed promising results for SERS-based investigations. Furthermore, these substrates showed significant disposablity, reproducibility, and chemical stability. Therefore, the fabricated substrates are capable to be employed as potential SERS biosensors to detect trace substances. [ABSTRACT FROM AUTHOR]

Sodium thiocyanate (NaSCN) is a naturally antibacterial component in milk, but excessive consumption of thiocyanate may cause potential risks to human health. Currently available methods for the detection of thiocyanate have some disadvantages such as poor sensitivity and high price. Here, we report a robust and cost-effective method to detect NaSCN based on paper substrates deposited with in situ reduced Ag nanoparticles by surface-enhanced Raman spectroscopy (SERS). Densely packed multilayer AgNPs provide uniform narrow nanogaps, which exponentially enhance the Raman signals. Moreover, these homogeneous narrow hotspots ensure that this method has high sensitivity (the limit of detection is 10−12 mol L−1), a wide linear range (from 10−9 mol L−1 to 10−4 mol L−1), and remarkable reproducibility (the coefficient of variation within a SERS sensor is 6.5%). Spiked milk samples were detected and the recovery rates of NaSCN were in the range of 95.1%–108.0%. This paper-based SERS sensor offers great potential for sensitive NaSCN detection and milk analysis. [ABSTRACT FROM AUTHOR]

Paper is a popular platform material in all areas of sensor research due to its porosity, large surface area, and biodegradability, to name but a few. Many paper-based nanocomposites have been reported in the last decade as novel substrates for surface-enhanced Raman spectroscopy (SERS). However, there are still limiting factors, like the low density of hot spots or loss of wettability. Herein, we designed a process to fabricate a silver–chitosan nanocomposite layer on paper celluloses by a layer-by-layer method and pH-triggered chitosan assembly. Under microscopic observation, the resulting material showed a nanoporous structure, and silver nanoparticles were anchored evenly over the nanocomposite layer. In SERS measurement, the detection limit of 4-aminothiophenol was 5.13 ppb. Furthermore, its mechanical property and a strategy toward further biosensing approaches were investigated. [ABSTRACT FROM AUTHOR]

Glutathione (GSH) acts a crucial role in the normal operation of manifold life activities and is closely bound up with many human diseases. Here, a SERS-colorimetric bimodal paper-based biosensor based on Mn-doped CDs/silver nanoparticles (Mn-CDs/AgNPs) has been fabricated for high-efficiency quantification of intracellular GSH. The Mn-CDs/AgNPs with fine oxidase-like characteristic and SERS enhancement ability has been assembled onto the Whatman filter paper (WFP) to cleverly fabricate paper chip (Mn-CDs/AgNPs@WFP) which can trigger the oxidation of colorless 3,3′,5,5′-tetramethylbenzidine (TMB) into blue TMBox and simultaneously enhance the SERS signal of TMBox. However, the introduction of GSH inhibits the oxidation of TMB, leading to color fading of paper chip and diminishment of SERS signal. Considering this, the bimodal paper-based sensing platform can be exploited for SERS-colorimetric detection of GSH, manifesting excellent selectivity, reliable stability, and satisfactory precision. The detection limits of SERS and colorimetric detection modes are as low as 0.41 μM and 0.53 μM, respectively. Furthermore, this proposed bimodal biosensor has been successfully utilized for the determination of intracellular GSH and validated by commercial GSH assay kit, which provides a mighty and convenient tool for intracellular GSH detection and can boost future effort about exploitation of other multimode paper-based biosensors as well as promote their appliances in disease diagnosis. [ABSTRACT FROM AUTHOR]

Paper-based analytical devices (PADs) have encountered a wealth of applications in recent years thanks to the numerous advantages of paper as a support. A silver nanoflower (AgNF) modified paper-based dual substrate for both surface-enhanced Raman spectroscopy (SERS) and ambient pressure paper spray mass spectrometry (PS-MS) was developed. AgNFs were immobilized on nylon-coated paper modified with silver and ethylenediamine. The developed substrate was characterized via scanning electron microscopy and infrared spectroscopy. The densely packed nanoscale petals of the AgNFs lead to a large number of so-called hot spots at their overlapping points, which result in an enhancement of the Raman signal. In addition, the presence of the AgNFs produces an increase in the sensitivity of the mass spectrometric analysis as compared with bare paper and nylon/Ag-coated paper. The dual substrate was evaluated for the identification and quantification of ketoprofen in aqueous standards as well as human saliva from healthy volunteers. The method enables the determination of ketoprofen with a limit of detection and limit of quantification via PS-MS of 0.023 and 0.076 mg L−1, respectively, with a relative standard deviation (RSD) of 3.4% at a concentration of 0.1 mg L−1. This dual substrate enables the simple and fast detection of ketoprofen with minimal sample preparation, providing complementary Raman and mass spectrometric information. [ABSTRACT FROM AUTHOR]