Size Of Silver Nanoparticles Research Articles

SpICP-MS characterisation of released silver nanoparticles from (nano)textile products

The low limits of detection and information regarding the concentration and size distribution of nanoparticles provided by single particle inductively coupled plasma mass spectrometry (spICP-MS) has been taken in advance for assessing released silver nanoparticles from (nano)textiles (nanosilver textiles). The releasing procedure consisted of using orbital-horizontal shaking (100 rpm, 20 °C, 30 min) and ultrapure water (10 mL) as an extractant, and it was found to guarantee silver nanoparticles stability (silver nanoparticle concentration and size distribution). Stability of released silver nanoparticles was further investigated at several filtration (0.22, 0.45 and 5.0 μm) and centrifugation conditions, stages required for fluff removal after extraction and just before spICP-MS determinations. Filtration using 5.0 μm filters was found to not affect silver nanoparticles concentrations and size distributions. The extractive procedure plus spICP-MS has shown a limit of detection and a limit of quantification for silver nanoparticle number concentration of 4.59 × 104 and 1.53 × 105 silver nanoparticles per gram of textile, respectively, whereas a limit of detection in size of 12 nm was obtained. Repeatability of the overall procedure was 14% (silver nanoparticle concentration) and 6% (mean silver nanoparticle size). Similarly, analytical recovery assays using standard silver nanoparticles of 20, 40, and 60 nm led to recoveries within the 102–113% range. The high degree of fixation of the AgNPs to the fabric and the softness of the extraction process to guarantee the integrity of the nanoparticles has led to a non-quantitative extraction (extraction percentages between 0.3 and 9.0% depending on the textile sample). However, the methodology developed has proven to be highly efficient for the characterization of the extracted AgNPs, and robust since the stability of the released AgNPs during the extraction procedure.

Characterization of Silver Nanoparticle Electrolysis Method with UV-Vis Spectrometer, Atomic Absorption Spectrophotometer, and Particle Size Analyzer

This work reports the production and characteristics of silver nanoparticles by electrolysis method at different voltages and electrolysis time with respect to their soluble concentration. This research is an experimental research. The research sample was the result of a solution of silver nanoparticles by the electrolysis method. The purpose of this research was to determine the effect of electrolysis voltage on the concentration of silver nanoparticles, the effect of electrolysis time on the concentration of silver nanoparticles, and characterization using UV-Vis, AAS and PSA. In this research there are two stages, namely the production stage and the characterization stage. The production of silver nanoparticles was carried out using 99% AgBr rods and aquades by electrolysis method. Characterization was carried out by testing on UV-Vis, AAS and PSA spectrometers to determine light absorption, ionic silver concentration and silver nanoparticle size. The results of this research indicate that the greater the electrolysis voltage and time, the higher the concentration of the solution obtained. The concentrations obtained at each voltage were 38 ppm, 42 ppm and 54 ppm. Characterization using UV-VIS spectrometer showed that the silver nanoparticle solution at each concentration was able to absorb light at wavelengths of 419.50 nm, 442 nm and 431 nm with absorbance peaks of 1,158, 2,989, and 0.904. Characterization using AAS showed that the content of silver nanoparticles in solution at each concentration were 8.7 ppm, 15 ppm and 17 ppm. Characterization using PSA showed that the solution at each concentration had silver nanoparticle sizes were 110.7 nm, 209.2 nm, 175.2 nm.

Probing the structure sensitivity of dimethyl oxalate partial hydrogenation over Ag nanoparticles: A combined experimental and microkinetic study

Silver nanoparticles of different sizes have been synthesized to study their catalytic performance in dimethyl oxalate (DMO) partial hydrogenation to methyl glycolate (MG). Then, a detailed microkinetic analysis based on the results of DFT calculations has been performed to elucidate the origin of the observed size-dependent kinetics, where tabulated thermodynamic properties of gas-phase species are used to ensure the thermodynamic consistency of the reaction. Calculated results show that the turnover frequency for DMO consumption is much higher on Ag(211) than on Ag(111), suggesting the stepped surface dominates the kinetics. The hydrogenation of DMO on the two surfaces occurs along the same dominant reaction pathway, and the rate-determining step for the partial and deep hydrogenation of DMO is DMO and MG dissociation, respectively. The finding that the MG selectivity increases while the DMO hydrogenation activity decreases with the Ag nanoparticle size reveals the structure sensitivity of DMO partial hydrogenation.

Genotoxic evaluation of silver nanoparticles in catfish Clarias gariepinus erythrocytes; DNA strand breakage using comet assay

In the present study, the neutral comet assay was applied for determination DNA double strand breakage in the African catfish Clarias gariepinus exposed variable concentrations and size of silver nanoparticles and ions. The parameters, tail % DNA; tail length, tail area; tail intensity; tail moment, olive tail moment, head mean intensity exhibited variability in the treatment and recovery periods. The silver small sized nanoparticles affect significantly (P < 0.0001) all the comet parameters in comparison to other treatments. In the case of recovery, the high sized nanoparticles with high concentration exhibited the significant effects in all parameters in comparison to other treatments. Moreover, correlation between exposure and recovery periods for each parameter was found to be significantly lower (P < 0.05). A positive insignificant correlation (R = 0.79) was recorded between % TDNA of the exposure period and erythrocyte alterations of the same period. On the other hand, such %TDNA was positively correlated (0.81–0.96) with more biochemical and histopathological parameters and negatively correlated (-0.85—0.88) with some other parameters. No micronuclei were recorded in association with AgNPs or Ag-induced DNA damages and other erythrocytes alterations. DNA damage was identified as follows: undamaged (%TDNA 0–10%), low damaged (%TDNA >10–20%), moderate damaged (%TDNA ≥20–40%) and sever damaged (%TDNA ≥ 40%). The undamaged DNA exhibited more or less decline with Ag and AgNPs whereas the damaged DNA increased with fluctuation especially with Ag and all concentration of AgNPs except for 40 nm/100 µg/L. After 15-day recovery, fluctuation in undamaged and damaged DNA was evident due to insufficient period of DNA repair with individual variations. No hedgehogs (%TDNA <85%) were recorded in both periods of exposure and recovery since low percent of severe damage was recorded. These findings emphasize on the adverse impacts of AgNPs especially those of small size and/or of high concentration on fishes.

Size controlled synthesis of silver nanoparticles: a comparison of modified Turkevich and BRUST methods

Abstract In the present investigation, silver nanoparticles were synthesized and a comparative analysis was performed of modified Turkevich and BRUST methods. Silver nitrate precursor was reduced by trisodium citrate dihydrate and ascorbic acid was used as a surfactant. Based on Turkevich and BRUST methods, the process variables, i.e., temperature, reducing agent concentration, stirring speed, mode of injecting reducing agent/precursor to large excess volume of either precursor/reducing agent were studied. The size of the particles was preliminarily ascertained by DLS studies and it was found that modified BRUST method yielded silver nanoparticles with average particle size of 25 nm, while modified Turkevich method furnished nanoparticles with average particle size of 15 nm. The silver nanoparticles were characterized by employing the UV/visible, Zeta sizer, scanning electron microscopy (SEM) and energy dispersive microscopy (EDX) techniques. Results revealed that the silver nanoparticles size can be controlled by optimizing the conditions of modified Turkevich and BRUST methods.

Structure-Morphology-Antimicrobial and Antiviral Activity Relationship in Silver-Containing Nanocomposites Based on Polylactide.

Green synthesis of silver-containing nanocomposites based on polylactide (PLA) was carried out in two ways. With the use of green tea extract, Ag+ ions were reduced to silver nanoparticles with their subsequent introduction into the PLA (mechanical method) and Ag+ ions were reduced in the polymer matrix of PLA-AgPalmitate (PLA-AgPalm) (in situ method). Structure, morphology and thermophysical properties of nanocomposites PLA-Ag were studied by FTIR spectroscopy, wide-angle X-ray scattering (WAXS), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) methods. The antimicrobial, antiviral, and cytotoxic properties were studied as well. It was found that the mechanical method provides the average size of silver nanoparticles in the PLA of about 16 nm, while in the formation of samples by the in situ method their average size was 3.7 nm. The strong influence of smaller silver nanoparticles (3.7 nm) on the properties of nanocomposites was revealed, as with increasing nanosilver concentration the heat resistance and glass transition temperature of the samples decreases, while the influence of larger particles (16 nm) on these parameters was not detected. It was shown that silver-containing nanocomposites formed in situ demonstrate antimicrobial activity against gram-positive bacterium S. aureus, gram-negative bacteria E. coli, P. aeruginosa, and the fungal pathogen of C. albicans, and the activity of the samples increases with increasing nanoparticle concentration. Silver-containing nanocomposites formed by the mechanical method have not shown antimicrobial activity. The relative antiviral activity of nanocomposites obtained by two methods against influenza A virus, and adenovirus serotype 2 was also revealed. The obtained nanocomposites were not-cytotoxic, and they did not inhibit the viability of MDCK or Hep-2 cell cultures.

Ag/CoFe2O4 as a Fenton‐Like Catalyst for the Degradation of Methylene Blue

AbstractSurface plasmon resonance (SPR) effect of noble metal nanoparticles has been widely exploited in surface‐enhanced Raman spectroscopy, optical biosensing, and photocatalysis. In this work, silver nanoparticles were deposited on the surface of cobalt ferrite (CoFe2O4) to prepare a composite Fenton‐like catalyst. Such catalyst was utilized to degrade methylene blue under visible light through activating peroxymonosulfate (PMS). The effects of the loading and particle size of silver nanoparticles, the dosage of the catalyst, PMS concentration, and other variables on the catalytic efficiency were explored. The catalytic efficiency of the composite catalyst is 3.8 times higher than that of CoFe2O4 under optimal conditions. The enhanced catalytic activity can be ascribed to the SPR effect of silver nanoparticles, which can expand the absorption range in the visible region, promote the separation of photogenerated electron‐hole pairs, and accelerate the conversion rate of M(III)/M(II) in CoFe2O4 (M=Co, Fe).

Cytotoxic Potential of Bio-Silica Conjugate with Different Sizes of Silver Nanoparticles for Cancer Cell Death

Well-defined silver nanoparticles were doped into bio-based amorphous silica (Ag-b-SiO2) with different silver contents (from 2 to 20 wt%) by a solvent-free procedure. The four as-synthetized samples were hydrogenated at 300 °C to ensure the formation of zero-valent Ag nanoparticles. The prepared samples were characterized by X-ray powder diffraction (XRD), elemental analysis, N2 sorption measurements, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy (HR-TEM). The characterization data confirmed the formation of well-defined zero-valent silver nanoparticles in the range of 3–10 nm in the low-loading samples, while in high-loading samples, bulky particles of silver in the range of 200–500 nm were formed. The in vitro cytotoxic activities of the Ag-b-SiO2 samples were tested against the tumor cell lines of breast (MCF-7), liver (HepG2), and colon (HCT 116) over a concentration range of 0.01 to 1000 g. The prepared samples exhibited a wide range of cytotoxic activities against cancer cells. An inverse relationship was observed between the silver nanoparticles’ size and the cytotoxic activity, while a direct relationship between the silver nanoparticles’ size and the apoptotic cell death was noticed.

Effects of silver nanoparticle size, concentration and coating on soil quality as indicated by arylsulfatase and sulfite oxidase activities

Recently, the nanotechnology industry has seen a growing interest in integrating silver nanoparticles (AgNPs) into agricultural products, which increases soil exposure to these particles. This demands an investigation into the effect of AgNPs on soil health. Changes in soil enzyme activities upon exposure to AgNPs can serve as early indicators of any adverse effects that these particles may have on soil quality. This study aimed to determine the effects of AgNP size, concentration, coating, and exposure time on the activities of two sulfur cycle enzymes, arylsulfatase and sulfite oxidase. To investigate the sensitivity of soil enzyme activity to AgNP contamination, silt loam soil samples were treated with 30, 80, and 200 nm-sized AgNPs coated with citrate, lipoic acid, and polyvinylpyrrolidone at 1, 10, and 100 mg Ag kg -1 soil, with the changes in enzyme activities monitored at 3 h, 3 d, and 30 d after treatment. For comparison, the effects of silver (Ag) ions on the enzyme activities were studied under similar treatment conditions. For most of the concentrations tested, the inhibitory effects of AgNPs on different enzymes differed, with a much stronger effect on sulfite oxidase activity than on arylsulfatase activity. The AgNP concentration and exposure time played much important roles than coating type and particle size in the effects of AgNPs on soil enzyme activities.

Silver-containing osteoplastic nanocomposites based on polyvinylpyrrolidone copolymers

The influence of technological factors on the preparation of silver nanoparticles has been studied when using polyvinylpyrrolidone as a reducing agent and stabilizer of the dispersion of nanosized particles. The effect of temperature, polyvinylpyrrolidone content and concentration of silver ions on the kinetics of silver reduction as well as the shape and size of nanoparticles has been determined. Based on the UV study of reagent solutions, the conclusion was confirmed that polyvinylpyrrolidone of a higher molecular weight is a more effective reducing agent of silver. The way of interaction between silver salts and polyvinylpyrrolidone with formation of vinylsuccinimide units in the structure of macromolecules has been proposed. The influence of the nature of silver salt on the shape and size of silver nanoparticles has been established. In the case of the use of silver nitrate, the silver nanoparticles are more homogeneous and they are mainly formed as triangular prisms and polyhedra of different sizes. In the case of the reduction of silver using silver acetate, the formed nanoparticles have a predominantly spherical shape. Nanosized particles with a wide size distribution are formed at the ratio of polyvinylpyrrolidone:AgNO3&gt;20:1 (wt.). As this ratio decreases, the stabilization of the formed nanoparticles weakens, which leads to an increase in the size of silver particles up to the formation of nanocrystals with a size of several hundred nanometers. Silver-containing composites based of the polyvinylpyrrolidone copolymers filled with hydroxyapatite in the form of porous blocks and films were synthesized, and their bactericidal and fungicidal properties were investigated. The developed porous composites can be used in medicine as osteoplastic to replace damaged bone tissue.

Controlling size and stabilization of silver nanoparticles for use in optimized chitosan-dialdehyde xylan wound dressings

Controlling size and stabilization of silver nanoparticles for use in optimized chitosan-dialdehyde xylan wound dressings

Influence of Polyvinylpyrrolidone Concentration on Properties and Anti-Bacterial Activity of Green Synthesized Silver Nanoparticles.

Environmentally green synthesis of stable polyvinyl pyrrolidone (PVP)-capped silver nanoparticles (PVP-AgNPs) was successfully carried out. The present study focused on investigating the influence of adding PVP during the synthesis process on the size, optical properties and antibacterial effect of silver nanoparticles produced. An aqueous extract of Eucalyptus camaldulensis leaves was used as a reducing agent. The effects of different PVP concentrations and reducing time on the synthesis of nanoparticles (NPs) were characterized by UV–Vis spectrophotometry, scanning electron microscopy (SEM), energy dispersive spectrum (EDX), Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS) and nano tracker analysis (NTA). The addition of PVP was studied. The prepared PVP-AgNPs were spherical with an average size of 13 nm. FTIR analysis confirmed that PVP protects AgNPs by a coordination bond between silver nanoparticles and both N and O of PVP. DLS results indicated the good dispersion of silver nanoparticles. PVP-AgNPs were found to be stable for nearly 5 months. Antibacterial studies through the agar well diffusion method confirmed that silver nanoparticles synthesized using PVP had no inhibitor activity toward Gram-positive and Gram-negative bacteria as opposed to silver nanoparticles prepared without adding PVP, which showed a significant antibacterial activity towards some of the tested pathogens.

Investigation of Synergistic Effect of Silver Nanoparticles Using Yogurt Lactobacillus Flora on Escherichia Coli with Multiple Drug Resistance

Background and Objective: Currently, many valuable drugs have lost their impact on Escherichia coli, and Escherichia coli drug resistance is the major reason for the treatment failure of nosocomial infections caused by this bacterium. This study aims to investigate the effect of silver nanoparticles using yogurt Lactobacillus flora on Escherichia coli with multiple drug resistance. Materials and Methods: This cross-sectional-experimental study was conducted in 2019 on Escherichia coli strain from some clinical centers in Ardabil, Iran. The isolates were performed based on approved biochemical tests to identify Escherichia coli bacteria. Antibiotic susceptibility testing was carried out by diffusion method. Then, its physical and chemical properties were determined by spectrophotometry (UV), SEM microscopy, and FESEM. Then, the synergistic effect of silver nitrate growth inhibitor was investigated using yogurt Lactobacillus flora by disk diffusion method according to standard (CLSI). Findings: In the present study, out of 100 samples, 37 strains of Escherichia coli were positive. The highest resistance of Escherichia coli isolates was to ciprofloxacin with 87% and the highest susceptibility was to nitrofurantoin with 76%. The size of silver nanoparticles according to the image of TEM and FESEM was both shown to be 16 nm in diameter. Silver nitrate using yogurt lactobacilli flora was able to reduce the combination of Escherichia coli strains with antibiotics, especially ciprofloxacin. Conclusion: The results of the present study showed that silver nanoparticles synthesized using yogurt lactobacilli flora with a diameter of 16 nm have antimicrobial activity against Escherichia coli. Considering the effectiveness of silver nanoparticles using yogurt Lactobacillus flora on ciprofloxacin-positive Escherichia coli, it can be used as a candidate drug against Escherichia coli in the future.

Lagenaria siceraria peel waste aqueous extract mediated silver nanoparticles for degradation of Congo red dye

Green chemistry involves design, manufacture, use and disposal of chemical products with minimal or no use or generation of hazardous products. With a growing outlook towards environmental sustainability, people are currently looking at conservation and protection of natural resources for the wellbeing and health of present and future generations. The use of biodegradable kitchen waste for the synthesis of silver nanoparticles is a method which adheres to the principles of green chemistry and environmental sustainability. In the present study, aqueous extract of biodegradable peel waste of Lagenaria siceraria has been used for the synthesis of environment friendly silver nanoparticles. The method reduces the cost involved, makes use of aqueous medium and non-toxic biodegradable ingredients for the synthesis of silver nanoparticles. Characterization of silver nanoparticles was carried out. Reaction parameters like concentrations of reacting species, ratio of reactants, temperature and reaction time were optimized using UV-Visible Spectrophotometry. The SPR band was found at 420 nm indicating the formation of spherical isotropic small sized silver nanoparticles in the size range of 10 to 50 nm. The characterization of the silver nanoparticles with XRD and TEM revealed the crystalline nature of the particles and their morphology. The silver nanoparticles have been employed in the degradation of water soluble benzidine based anionic diazo dye, Congo red dye, which is employed in textile dyeing. The silver nanoparticles acted as nano catalyst in the dye degradation process. The method can be further scaled up and employed for the treatment of industrial waste waters coming from textile industry.

Synthesis of silver nanoparticles (AgNPs) of leaves extract of Rhynchoglossum notonianum wall. for enhancing its bioavailability and antibacterial activity

Objective: Silver nanoparticles (AgNPs) derived from Rhynchoglossum notonianum Wall. leaf were the subject of this investigation to examine their synthesis, characterisation, and biological activity. Materials and Methods: Aqueous extracts of Rhynchoglossum notonianum Wall leaves and 0.1 M silver nitrate were used to make AgNPs. Particle size, Zeta potential, UV-Vis spectroscopy, and SEM were used to determine the AgNPs properties. Results: Rapid and homogeneous size and shape silver nanoparticles were synthesised utilising Rhynchoglossum notonianum Wall. extract. When methanolic leaf extracts of Rhynchoglossum notonianum Wall. were combined with an aqueous silver ion complex solution, the surface Plasmon vibrations were excited, resulting in the production of MERNAgNPs. UV-Visible spectroscopy was used to characterise the nanoparticles. The widening of the peak in the UV-visible spectrum suggested polydispersion. The silver nanoparticles in solution have a surface Plasmon band of 420nm. Aqueous silver nitrate solution is diffused throughout the reaction time, with no signs of agglomeration. The average particle size (z-average) was “132.6nm”, the polydispersity index was “0.248”, and the zeta values were -25.1mV with a 100% peak area. This implies a stable silver nanoparticle.

Precise laser-induced local modification of AZO:Ag films and their optical properties

The paper presents precise modifications of ZnO:Al thin films with silver nanoparticles by CW laser leading to the improvement of the composite structure and optical properties. The violet laser wavelength (405 nm) was chosen to be far from the plasmon resonance wavelength. The morphology of the obtained ZnO:Al thin films with silver nanoparticles was investigated. It was detected that under an exposure by laser power densities I0 = 0.89 MW/cm2 and I0 = 1.07 MW/cm2 and scanning velocities Vsc = 100 μm/s and Vsc = 50 μm/s, the film structure became denser, the size of ZnO:Al crystallites increased, and the size of silver nanoparticles decreased. The effects of laser radiation on the optical characteristics of the samples were then investigated. Particularly, a blue shift of the plasmon resonance peak and an increase in the bandgap from 3.27 eV to 3.36 eV were obtained. Additionally, numerical modeling was performed based on a photothermal film processing mechanism and clearly explained the observed effects.

Tailoring the size of silver nanoparticles by controlling mixing in microreactors

Microreactors are commonly regarded by their high mass transfer rates associated to their small diameters. Although this is true, especially when compared to batch systems, mixing is frequently exclusively dominated by diffusion in single phase flow microreactors, being the fast mixing of reactants an aspect often overlooked during their design. This paper presents the first quantitative analysis of the effect of mixing of precursors on the size and distribution of metal nanoparticles synthesized in flow microreactors. Silver nanoparticles with a range of sizes are continuously synthesized by controlling mixing efficiency in rationally-designed microreactors. The particle size decreases as the mixing index increases due to an increase in nucleation rate and thus the resulting nuclei concentration. Herein, the mixing efficiencies of different 3D curved microreactors are quantitatively evaluated using accurate simulations of their concentration profiles, avoiding the so-called numerical diffusion errors using a novel method based on backward particle tracking. A method based on forward particle tracking is improved to simulate the residence time distributions (RTD) in microreactors at a reduced computational cost. Curving the reactors channels is known to lead to the formation of Dean vortices however, these well-defined rotations lead to stagnant zones. The mixing efficiency can be enhanced and the RTD narrowed by periodically changing the direction of the Dean vortices along the length of the channel. In addition, we demonstrate the effect of the configuration of the inlet streams relative to the curvature of the reactor and thus, the Dean vortices, on the resulting mixing. These results provide rational design guidelines for the design of microreactors to manipulate advection as a way of manipulating the reaction rates as demonstrated here to control nanoparticle sizes.

Ag nanoparticles enhance immune checkpoint blockade efficacy by promoting of immune surveillance in melanoma

Immune checkpoint blockade (ICB) therapy, represented by programmed cell death protein 1 (PD-1) and its ligand (PD-L1) monoclonal antibodies (mAbs), has shown an obvious benefit for melanoma immunotherapy, but the overall response rate is still low. To find an effective combination therapy strategy, we successfully produced small size silver nanoparticles coated with sucrose (S-AgNPs) as potent adjuvants. The antitumor effects of S-AgNPs were tested in vitro and comparatively investigated in immunodeficient and immunocompetent mice with melanoma. Fluorescence-activated cell sorting and immunofluorescent staining analysis were conducted to identify the tumor microenvironments. The expression of PD-L1 in tumors was tested by multiple methods. The combination therapy and potential toxicity of S-AgNPs and PD-1 mAbs were assessed in melanoma-bearing mice. In our findings, S-AgNPs presented potent antitumor effects, good druggability and low systemic toxicity. Functionally, we found that S-AgNPs exhibited better antitumor effects in immunocompetent mice. Mechanistically, we showed that S-AgNPs suppress tumor cell proliferation by inducing cellular apoptosis and promote cytotoxic CD8+ T cell infiltration and activity. Preclinically, S-AgNPs showed excellent local antitumor activity and mild systemic immunotoxicity with PD-1 mAbs in the inhibition of melanoma proliferation, providing a novel clinical combination treatment strategy.

A Drug Stability Study Using Surface-Enhanced Raman Scattering on Silver Nanoparticles

Pharmaceutical product quality is of vital importance for patient safety. Impurities and potential degradation products can cause changes in chemistry, pharmacological and toxicological properties by having a significant impact on product quality and safety. Stress-testing (forced degradation) studies of pharmaceutical preparations became necessary to assure degradation mechanisms and potential degradation products. Consequently, it is crucial to understand the nature of possible degradation products. Surface-enhanced Raman spectroscopy (SERS) is a powerful vibrational spectroscopic technique that can provide valuable information about changes in a molecular structure with its intrinsic finger-print property. In this study, a forced degradation study was conducted on pemetrexed (PMT), an antifolate chemotherapy drug, in order to identify its likely chemical degradation products. The degradation mechanism of PMT was investigated under various experimental conditions; basic (0.1 M NaOH), acidic (0.1 M HCl), and oxidative (3% H2O2v/v). We used silver nanoparticles (AgNPs) of average size 60 nm as SERS substrates. The study shows that SERS can be a fast and reliable technique to study the stability and possible degradation mechanisms of drugs under several different conditions.

Impact of silver nanoparticles size on SERS for detection and identification of filamentous fungi

Using the proper size of nanoparticles as an active substrate, Surface-enhanced Raman scattering (SERS) can provide a reliable technique for detecting and identifying fungi, including Alternaria alternata, Aspergillus flavus, Fusarium verticilliodes, and Aspergillus parasiticus that have been associated to biodeterioration and biodegradation of cultural heritage materials. In this research spherical silver nanoparticles (AgNPs) of average size of 10, 30 and 60 nm were synthesized using the wet chemical method with good yield and their size and shape distributions were examined using small-angle X-ray scattering (SAXS). The protocol for fungi sample preparation proved to be critical for producing high-quality and reproducible SERS spectra. We found that the effect of AgNPs on SERS signal enhancement is size dependent under the same experimental conditions; the SERS intensity of fungal strains using 60 nm achieved up to 2.3x105 enhancement, about twice as intense as those produced with 30 nm, and 10 nm produced a minor broad weak peak barely discernible around 1400 cm−1, similar to the NR spectra profile in the 550–1700 cm−1 spectral region, and the SERS signals using 60 nm showed high reproducibility, with less than 20% variance. Furthermore, we used principal component analysis (PCA) to statistically classify the SERS spectrum into four separate clusters with 99 percent variability so that the four fungal strains could be clearly detected and identified. The SERS technique, in combination with the PCA developed in this study, provides a simple, rapid, accurate, and cost-effective analytical tool for detecting and identifying filamentous fungal strains.