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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]

Glucose plays a key role in the regulation of the levels of blood sugar, and the body closely monitors it to maintain proper metabolic function. Although glucose is essential for human health, its excessive consumption can lead to negative effects such as obesity and diabetes. As a result, high-sensitive and accurate glucose detection is considered an essential measure in clinical analysis. Surface-enhanced Raman scattering (SERS) is an accurate method for identifying trace substances. In the present study, SERS-active substrates were used for detecting different concentrations of glucose. First, gold nanoparticles (AuNPs) were prepared by employing a chemical reduction method. Afterward, the fluorine-doped tin oxide (FTO) glass substrates were decorated with AuNPs using the electrodeposition method. Then, glucose was deposited as an analyte on SERS substrates. Interestingly, the limit of detection (LOD) of SERS-active FTO-covered glass substrates (SERS-FGS) for the detection of glucose was 10−9 M. Density functional theory (DFT) method was used to simulate and validate the Raman spectra and peak signals obtained experimentally. Moreover, the average relative standard deviation (RSD) was calculated as 3.06% for ten repeated measurements. Furthermore, the enhancement factor for these SERS-based biosensors, for the identification of molecular vibrations of 10−5 M glucose, was obtained to be 1.4310 × 104 experimentally and 1.5397 × 104 numerically. Therefore, the SERS-FGS developed in this study showed promising results for detecting glucose and controlling diseases, such as diabetes and other problems resulting from an abnormality in glucose levels. [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]

The residue of methyl parathion (MP) pesticide on agricultural products causes some health-related problems; therefore, it is necessary to identify the amount of this pesticide on these products. Surface Enhanced Raman Spectroscopy (SERS) is a fast, reliable, as well as accurate technique for detecting trace pesticides, biological substances, and chemicals. For this purpose, filter paper substrates (FPS) coated with gold nanoparticles (AuNPs) were used as SERS-active sensors to detect MP. First, AuNPs were fabricated by a simple chemical reduction method. Then, UV–Vis, XRD, TEM, FE-SEM, and DLS were employed to characterize the prepared AuNPs. Afterward, the AuNPs were coated dropwise on FPS to prepare flexible SERS-active substrates (Flex-SERS-Subs) to detect molecular vibrations of MP. The limit of detection (LOD) of detecting MP was obtained to be 10−12 M. The Raman spectra and peak signals acquired via experiments were validated using the density functional theory (DFT) method. Moreover, the RSD was calculated to be 3.39% for ten repeated measurements. In addition, the enhancement factor was calculated by experimental and numerical methods to be 9.820 × 104 and 10.324 × 104, respectively. Therefore, the developed method showed promising outcomes for the related investigations and has the potential to lead the development of similarly fabricated sensors for the detection of trace pesticides. [Display omitted] • Filter paper substrates coated with AuNPs were used as flexible SERS sensors to identify methyl parathion. • Limit of detection (LOD) of detecting MP using these substrates was found to be 10−12 M, making it highly sensitive. • Raman spectra and peak signals were simulated and validated using the DFT method, ensuring accurate results. • RSD was calculated to be 3.39% for ten repeated measurements, indicating good reproducibility of the developed sensors. • Enhancement factor (EF) for detecting MP was found to be approximately 105 experimentally and via FDTD simulation. [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]

• SERS-active substrates were prepared using the electrodeposition method, which is simple and repeatable. • By depositing silver nanoparticles on FTO glass substrates by electrodeposition method, the fabricated biosensor showed high sensitivity, stability, and reproducibility. • Rapid, accurate, ultrasensitive, and low-cost detection of the amino acid histidine up to a concentration of 10−9 resulted using the developed SERS biosensor prepared by coating silver nanoparticles on FTO glass substrates and electrodeposition method. • FDTD simulations were carried out, and the electric field distributions as well as the enhancement factor of the developed SERS-active substrates were obtained. The amino acid histidine is an important bioactive molecule for growth and tissue repair and has an influential role as a neurotransmitter in the human musculoskeletal and central nervous systems. Therefore, excessive deficiency of this amino acid and the proteins induced by it causes many diseases. For this reason, the specific and sensitive detection of the amino acid histidine is very important. Surface-enhanced Raman scattering (SERS) is a sensitive method for detecting low concentrations of various substances, especially biomaterials. The silver nanoparticles (AgNPs)-coated substrates were employed in the present investigation to detect the amino acid histidine to control the diseases caused by it. First, a chemical method named Tollens was applied to fabricate AgNPs, and then, the Fluorine-doped tin oxide (FTO) substrates were coated with AgNPs by applying voltage and through the electrodeposition technique. Therefore, AgNPs were fabricated using the Tollens method, as well as the size distribution of nanoparticles was specified as being equal to 130–150 nm by employing dynamic light scattering. Moreover, UV–Vis spectroscopy was employed for the characterization of prepared substrates and AgNPs. The results show that the plasmonic peak tends toward longer wavelengths following the self-array of AgNPs. In addition, it was proved by the field-emission scanning electron microscope (FE-SEM) images that AgNPs on the surface of FTO substrates were distributed non-uniformly. The limit of detection (LOD) was equal to 10−9 for SERS-active substrates for the purpose of detecting this amino acid. Moreover, for ten repeated calculations, the mean relative standard deviation (RSD) was achieved to be 3.86%. Furthermore, the values for the enhancement factor were obtained to be 1.344 × 105 and 1.389 × 105 via experimental and simulation methods, respectively. Thus, the results obtained from Raman indicate that by applying the developed methods, SERS-active substrates coated with AgNPs for the detection of amino acid histidine show advantageous results for SERS-based investigations and can cause the development of nanosensors. [ABSTRACT FROM AUTHOR]

By measuring the inelastic scattering of monochromatic light, Raman spectroscopy is a method used to examine vibrational, rotational, and other low-frequency modes in a system. However, compared to other spectroscopic methods like infrared spectroscopy, Raman signals are often weak, which limits their use in the bulk of applications where high sensitivity is needed. Surface-enhanced Raman spectroscopy (SERS) amplifies Raman signals for highly sensitive examination via nanostructured surfaces, such as metal nanoparticles. Nanopore and nanocavity-based structures, such as porous membranes and plasmonic nanoholes, show localized increases in electromagnetic fields, allowing for very sensitive optical detection. These structures are promising for a range of analytical and diagnostic applications in nanotechnology and biotechnology because of their excellent sensitivity and specificity. The present study aimed to conduct a review of the state-of-the-art SERS substrates based on nanopore/nanocavity structures. This study presents some interesting and significant results regarding the use of these structures in various fields. Moreover, future research directions are discussed in the final sections. The authors hope that this review provides researchers and academics insights into the application of nanopore/nanocavity SERS substrates and structures in different areas, such as biosensing, environmental monitoring, food safety, forensic applications, art, and archaeology. [ABSTRACT FROM AUTHOR]

Agriculture products with lindane residues pose serious health threats, including infertility in men and women and some types of cancer. Reproductive issues, such as decreased fertility and abnormal development, have been linked to long-term lindane exposure. In the present study, silver nanoparticles (AgNPs) coated on glass slides were developed through simple and cost-effective methods to be used as surface-enhanced Raman scattering (SERS) sensors. Then, different concentrations of lindane solutions (10−1 to 10−10 M) were prepared via serial dilution, deposited on the substrates and evaluated via Raman spectroscopy. Moreover, density functional theory (DFT) calculations were performed to validate the empirical results. For investigating the enhancement factor (EF), along with experimental calculations, the finite difference time domain (FDTD) method was used for the simulation of electric field distribution surrounding the modeled substrate. The limit of detection (LOD) for the identification of lindane using the developed sensors was obtained to be 10−10 M. In addition, EFs were computed to be 105 and 1.2967 × 105 for the concentration of 10−6 M using experimental and numerical methods, respectively. These simple, cost-effective, and straightforwardly developed substrates can be considered sensitive sensors for many applications. Future research should focus on the detection of trace lindane in real samples, including agricultural and food products. [ABSTRACT FROM AUTHOR]

Surface-Enhanced Raman Spectroscopy (SERS) is a sensitive vibration spectroscopy method applied to analyze a variety of analytes, including toxins and pesticides. The SERS method is an accurate method for detecting significantly low concentrations of biomaterials and chemicals. In the present study, in order to detect atrazine pesticide, the glass fiber substrates coated with silver nanoparticles have been used as SERS plasmonic nanosensors. First, silver nanoparticles were prepared by applying a chemical approach named the Tollens' method, and the SERS plasmonic substrates (SPS) were fabricated by depositing the colloidal silver solution on a glass fiber substrate. The SERS plasmonic nanosensors were fabricated by self-assembling the silver nanoparticles and after functionalization of glass fiber substrate using 3-aminopropyl triethoxysilane (APTES). For this purpose, silver nanoparticles were chemically prepared, and their size distribution was determined to be 140–150 nm using dynamic light scattering (DLS). Ultraviolet–visible spectroscopy was applied for the optical characterization of colloids of silver nanoparticles and the prepared substrates. The results indicate the displacement of the plasmonic peak toward longer wavelengths after self-assembly of the nanoparticles. Field emission scanning electron microscopy images indicated the non-uniform distribution of silver nanoparticles on the surface of glass fiber substrates. Atrazine pesticide was employed as an analyte to investigate the performance of SERS plasmonic substrates (SPS). The detection limit of SPS for detecting atrazine pesticide was equal to 10−12 M, and the average relative standard deviation for ten repeated measurements was obtained to be 4.02%. With reducing the solution concentration to 10−12 M, the intensity of Raman modes decreased significantly so that only some peaks were clear. Moreover, the quantum mechanics calculation and molecular dynamics simulation were performed to clarify the molecular interactions between atrazine and silver nanoparticles. By increasing the concentration of atrazine, the Lennard-Jones potential was increased following the experimental results of Raman spectroscopy. • Silver nanoparticles (AgNPs) deposited on glass fibers as SERS-active substrates significantly amplify electric fields under laser light emitted to their surface. • The quantum mechanics calculation and molecular dynamics simulation were performed to clarify the molecular interactions between atrazine and silver nanoparticles. • Fast and sensitive detection of Atrazine up to the concentration of 10−12 M due to the porous structure of silver nanoparticles (AgNPs) on glass fibers as SERS-active substrates. [ABSTRACT FROM AUTHOR]