Search Results (17)

This research focused on the synthesis of triangular silver nanoplates (TSNPs) with sharp corners using a photomediated seed growth method. The TSNPs produced had an average edge length of 27.2 ± 9.2 nm and a (110) crystalline plane structure. In terms of optical properties, the TSNPs displayed three key absorbance peaks at approximately 400 nm, 500 nm, and 660 nm, which correspond to out-of-plane dipolar resonance, in-plane quadrupolar resonance, and in-plane dipolar resonance, respectively. The prepared TSNP colloidal solutions served as surface-enhanced Raman spectroscopy (SERS)-active materials for detecting paraquat residue in aqueous samples. We optimized the mixing time of the liquid SERS with the sample, maintaining a 1:1 volume ratio. The findings showed a remarkable enhancement of the Raman signal with 10 min mixing time using laser excitation at a wavelength of 785 nm. This study achieved the development of novel SERS-active substrates capable of detecting pesticides with excellent accuracy, sensitivity, and reproducibility for both qualitative and quantitative analysis in tap water, river water, drinking water, and cannabis water. Additionally, it paved the way for using the SERS technique as a promising approach in the areas of food safety and environmental monitoring, especially in the organic farming field. Full article

Iodine is an essential element for the synthesis of thyroid hormones. Iodine deficiency leads to a range of health consequences known as iodine deficiency disorders. To assess the iodine nutritional status of a population, urinary iodine (UI) is typically measured. This work introduces a novel and simple analytical method for determining UI using silver triangular nanoplates (AgTNPs) after interfering substances are removed via solid-phase extraction (SPE). The AgTNPs were synthesized and characterized using Transmission Electron Microscopy, UV–vis spectroscopy, and zeta potential measurements. The limit of detection of iodide of the AgTNPs assessed spectrophotometrically was 35.78 µg I⁻/L. However, urine samples interfered with the colorimetric reaction. Thus, an SPE methodology was developed and optimized to eliminate urine interferents that hinder AgTNP performance. A logistic regression analysis was conducted to validate the combined application of SPE and AgTNPs for the qualitative determination of UI. This work demonstrated that the developed SPE methodology eliminates these interferents and extracts iodide from the sample, allowing the accurate determination of UI using AgTNPs. This reliable sample preparation method was then used on actual human urine samples to accurately identify UI deficiency levels. The proposed methodology offers an effective and environmentally friendly approach for monitoring iodine status, without requiring highly complex equipment. Full article

Surface-enhanced Raman scattering (SERS) is a powerful technique for detecting trace amounts of chemicals due to its capacity to significantly amplify the Raman signal of the molecules of these substances. This is particularly relevant in food systems where monitoring antibiotic residues is critical for food safety. Traditional SERS substrates typically utilize colloidal silver nanospheres (AgNSs), but anisotropic silver nanoparticles with numerous sharp tips can further enhance SERS sensitivity, enabling lower detection limits suitable for food safety regulations. In this study, we describe a straightforward synthesis of colloidal silver triangular nanoplates (AgTNPls), featuring multiple sharp tips, using only four common reagents: silver nitrate, trisodium citrate, sodium borohydride (NaBH₄) and hydrogen peroxide (H₂O₂), all at room temperature. By carefully controlling the sequence of reagent addition, specifically introducing H₂O₂ after NaBH₄, we achieved a two-step synthesis. In the first step, AgNSs seeds form, and in the second, these seeds convert into AgTNPls, resulting in a colloid of relatively uniform AgTNPls with an edge length of approximately 52 nm. The resulting AgTNPls colloid, combined with an aluminum foil, produced an SERS substrate with high enhancement factor of 3.2 × 10⁹ (using rhodamine 6G as a test molecule). Applied to enrofloxacin (an antibiotic widely used in livestock and aquaculture) detection, this substrate achieved a detection limit as low as 0.39 µg/L (0.39 ppb), with enrofloxacin detectable at concentrations down to 5 µg/L. This highly sensitive SERS substrate holds great promise for rapid, accurate detection of antibiotic residues in food products, aiding regulatory compliance and food safety assurance. Full article

Adsorption of silver nanoparticles on polymers may affect the processes in which they participate, adjusting the analytical characteristics of methods for the quantitation of various substances. In the present study, a composite material based on silver triangular nanoplates (AgTNPs) and polyurethane foam was proposed for chemical analysis. The prospects of its application for the solid-phase/colorimetric determination of organic thiols were substantiated. It was found that aggregation of AgTNPs upon the action of thiols is manifested by a decrease in the AgTNPs’ localized surface plasmon resonance band and its significant broadening. Spectral changes accompanying the process can be registered using household color-recording devices and even visually. Four thiols differing in their functional groups were tested. It was found that their limits of detection increase in the series cysteamine < 2-mercaptoethanol < cysteine = 3-mercaptopropionic acid and come to 50, 160, 500, and 500 nM, respectively. The applicability of the developed approach was demonstrated during the analysis of pharmaceuticals and food products. Full article

In this study, differently shaped silver nanoparticles used for the synthesis of gold nanoclusters with small capping ligands were demonstrated. Silver nanoparticles provide a reaction platform that plays dual roles in the formation of Au NCs. One is to reduce gold ions and the other is to attract capping ligands to the surface of nanoparticles. The binding of capping ligands to the AgNP surface creates a restricted space on the surface while gold ions are being reduced by the particles. Four different shapes of AgNPs were prepared and used to examine whether or not this approach is dependent on the morphology of AgNPs. Quasi-spherical AgNPs and silver nanoplates showed excellent results when they were used to synthesize Au NCs. Spherical AgNPs and triangular nanoplates exhibited limited synthesis of Au NCs. TEM images demonstrated that Au NCs were transiently assembled on the surface of silver nanoparticles in the method. The formation of Au NCs was observed on the whole surface of the QS-AgNPs if the synthesis of Au NCs was mediated by QS-AgNPs. In contrast, formation of Au NCs was only observed on the edges and corners of AgNPts if the synthesis of Au NCs was mediated by AgNPts. All of the synthesized Au NCs emitted bright red fluorescence under UV-box irradiation. The synthesized Au NCs displayed similar fluorescent properties, including quantum yields and excitation and emission wavelengths. Full article

Nanotechnology offers new possibilities in molecular diagnostics, with nanoparticles gaining attention as biosensor upgrades. This study evaluates gold-coated silver nanoplates coated with PEG for enhanced protection, aiming to detect Spike protein with higher sensitivity, and emphasizes the importance of considering complex environments and appropriate controls for specific binding and accurate analysis. The sensitivity of antibody-coated PEGAuTSNPs as tools for immunoassays is demonstrated through fibronectin (Fn)– anti-fibronectin binding within an isolated extracellular matrix as a complex and native environment of Fn. Moreover, the optimal functionalization volume of Spike protein was determined (4 µg/mL of PEGAuTSNP). Anti-Spike was added to confirm binding, while the TJP1 protein was used as a negative control. The same experiment was used in the presence of horse serum to simulate a complex environment. According to Localized Surface Plasmon Resonance analysis and Dynamic Light Scattering size measurements, anti-Spike exhibited a stronger affinity for the nanoplates, causing TJP1 to be replaced by the antibody on the nanoplates’ surface. Future research will involve exploring alternative complex environments, filtering larger molecules, and the optimization of immunoassay performance. Full article

In this study, we conducted a one-step photochemical synthesis to produce silver nanoparticles (AgNPs) with irregular morphology. The synthesis process involved the photoconversion of Ag nanoseeds into self-assembled Ag nanostructures of various morphologies using a high-pressure sodium lamp with a wavelength of 589 nm, corresponding to an energy of 2.1 eV. During the synthesis, the color of the colloidal Ag nanoseeds gradually changed as the irradiation time increased, transitioning from yellow to brown, juniper green, basil green, ocean green, aegean blue, and finally to true blue. We characterized the morphological evolution of the resulting AgNPs, as well as their optical properties and aggregation behavior, using transmission electron microscopy, UV-vis spectroscopy, and dynamic light scattering. Furthermore, we evaluated the impact of the self-assembled morphology of the AgNPs on their surface-enhanced Raman scattering efficiency, using R6G as the target analyte. The results revealed that the colloidal AgNPs synthesized under a visible light irradiation time of 1 h consisted of circular nanoplates, hexagonal nanoplates, trapezoid nanoplates, and triangular nanoplates. These colloidal AgNPs exhibited excellent SERS activity when used as an SERS-active substrate in the form of an aqueous solution, enabling the detection of low concentrations of R6G down to 10⁻¹² M. Full article

Triangular silver nanoplates (TSNPs) exhibit unique optical and antimicrobial properties due to their shape, sharp edges, and vertices. In this study, TSNPs were incorporated into biopolymer blends (bacterial cellulose (BC) with polylactic acid (PLA), polycaprolactone (PCL), and polyhydroxybutyrate (PHB)). Antimicrobial activity of materials was tested against Escherichia coli ATCC 95922 and Staphylococcus aureus ATCC 25923 (10⁶ CFU/mL). After incubation (24 h at 37 °C, 100 rpm), optical density was measured at 630 nm. In order to assess biosensing applications, specifically fibronectin (Fn) behavior, TSNPs were protected with gold (AuTSNP) and analyzed via sucrose sensitivity test and monitored by localized surface plasmon resonance (LSPR). Additionally, AuTSNPs were coated with polyethylene glycol (PEGAuTSNP). Fibronectin functionalization of PEGAuTSNPs and pH-conformation was monitored (FnPEGAuTSNP). Eventually, adequate Fn and anti-Fn antibody concentrations were determined. BC/PHB/TSNPs showed antimicrobial activity against E. coli and S. aureus with 80 and 95% of growth inhibition, respectively. The sucrose sensitivity test indicated that the LSPR_λmax of the spectra is directly proportional to the sucrose concentration. LSPR_λmax of Fn-PEGAuTSNPs at pH 7 and pH 4 were measured at 633 and 643 nm, respectively. A total of 5 µg of Fn was determined to be adequate concentration, while 0.212 mg/mL of anti-Fn antibody indicatied system saturation. Full article

Curcumin and triangular silver nanoplates (TSNP)-incorporated bacterial cellulose (BC) films present an ideal antimicrobial material for biomedical applications as they afford a complete set of requirements, including a broad range of long-lasting potency and superior efficacy antimicrobial activity, combined with low toxicity. Here, BC was produced by Komagataeibacter medellinensis ID13488 strain in the presence of curcumin in the production medium (2 and 10%). TSNP were incorporated in the produced BC/curcumin films using ex situ method (21.34 ppm) and the antimicrobial activity was evaluated against Escherichia coli ATCC95922 and Staphylococcus aureus ATCC25923 bacterial strains. Biological activity of these natural products was assessed in cytotoxicity assay against lung fibroblasts and in vivo using Caenorhabditis elegans and Danio rerio as model organisms. Derived films have shown excellent antimicrobial performance with growth inhibition up to 67% for E. coli and 95% for S. aureus. In a highly positive synergistic interaction, BC films with 10% curcumin and incorporated TSNP have shown reduced toxicity with 80% MRC5 cells survival rate. It was shown that only 100% concentrations of film extracts induce low toxicity effect on model organisms’ development. The combined and synergistic advanced anti-infective functionalities of the curcumin and TSNP incorporated in BC have a high potential for development for application within the clinical setting. Full article

Plasmonic photocatalysis, combing noble metal nanoparticles (NMNPs) with semiconductors, has been widely studied and proven to perform better than pure semiconductors. The plasmonic effects are mainly based on the localized surface plasmon resonance (LSPR) of NMNPs. The LSPR wavelength depends on several parameters, such as size, shape, the surrounding media, and the interdistance of the NMNPs. In this study, graphene-modified plate-like BiVO₄ composites, combined with silver nanoplates (AgNPts), were successfully prepared and used as a photocatalyst for CO₂ photoconversion. Triangular silver nanoplates (TAgNPts), icosahedral silver nanoparticles (I-AgNPs), and decahedra silver nanoparticles (D-AgNPs) were synthesized using photochemical methods and introduced to the nanocomposites to compare the shape-dependent plasmonic effect. Among them, T-AgNPts/graphene/BiVO₄ exhibited the highest photoreduction efficiency of CO₂ to CH₄, at 18.1 μmolg⁻¹h⁻¹, which is 5.03 times higher than that of pure BiVO₄ under the irradiation of a Hg lamp. A possible CO₂ photoreduction mechanism was proposed to explain the synergetic effect of each component in TAgNPts/graphene/BiVO₄. This high efficiency reveals the importance of considering the compositions of photocatalysts for converting CO₂ to solar fuels. Full article

Optical sensors based on silver triangular nanoplates (AgTNPs) are insufficiently studied as probes for the spectrophotometric determination of biologically active compounds. In the present article, an interaction between label-free AgTNPs and bioflavonoids in the presence of silver(I) ions was assessed to outline the possibilities of AgTNPs as a colorimetric probe for the fast and sensitive determination of bioflavonoids. It is shown that the interaction was accompanied by a bathochromic shift of the local surface plasmon resonance band of nanoparticles and an increase in its intensity. Seven bioflavonoids differing in their structure were tested. The influence of the structure of analytes and the main external factors on the analytical signal is discussed in detail. It was found that the detection limits of bioflavonoids in the selected optimal conditions increased in the series morin < rutin = quercetin < taxifolin and came to 0.9, 1.2, 1.2, and 2.0 μmol L⁻¹, respectively. Chrysin, naringenin, and naringin were found not to affect the spectral characteristics of AgTNPs. The suggested approach was applied for the spectrophotometric determination of flavonoids in pharmaceuticals and onion peel. Full article

An innovative antimicrobial technology for plastic surfaces is presented. We report the synthesis and scale-up of triangular silver nanoplates (TSNPs) and their integration into polycaprolactone (PCL) and polylactic acid (PLA) polymers through a solvent-casting technique. The TSNPs have a high geometric aspect ratio and strong local surface plasmon resonance (LSPR) response, which provides an effective tool for monitoring their integrity during processing and integration with the biodegradable plastics. An aqueous-based seed-mediated chemical method was used to synthesize the TSNPs, and characterisation was carried out using TEM and UV (Ultraviolet)-VIS (Visible) spectroscopy to measure LSPR profiles. The UV-VIS spectra of silver seeds and TSNPs exhibited characteristic peaks at 395 and 600 nm respectively. Synthesized TSNPs were coated with thiol-terminated polyethylene glycol (SH-PEG) and transferred into chloroform in order to effect compatibility with PCL and PLA. TSNP/PCL and TSNP/PLA composite films were prepared by solvent casting. The morphological structure, thermal, mechanical, and antimicrobial properties of the TSNP-incorporated composite films were evaluated. Results showed the TSNP-treated films had a rougher surface than the bare films. Insignificant changes in the thermal properties of TSNP-treated films compared to bare ones were also observed, which indicated the thermal stability of the composite films. The tensile strength and antimicrobial properties of the composite films were increased after TSNP incorporation. TSNP/PCL and TSNP/PLA films exhibited improved antimicrobial activity against Escherichia coli and Staphylococcus aureus with antimicrobial effect (AE) values ranging between 0.10 and 0.35. The obtained results and demonstrated TSNP production scalability validate the TSNP treated PCL and PLA films as a composite material with desirable antimicrobial effect for wide-ranging surface applications. Full article

Nowadays, analytical systems based on silver triangular nanoplates (AgTNPs) have been shown as good prospects for chemical sensing. However, they still remain relatively poorly studied as colorimetric probes for sensing various classes of compounds. This study shows that these nanoparticles are capable of being oxidized by peroxides, including both hydrogen peroxide and its organic derivatives. The oxidation was found to result in a decrease in the AgTNPs’ local surface plasmon resonance band intensity at 620 nm. This was proposed for peroxide-sensitive spectrophotometric determination. Five peroxides differing in their structure and number of functional groups were tested. Three of them easily oxidized AgTNPs. The effects of a structure of analytes and main exterior factors on the oxidation are discussed. The detection limits of peroxides in the selected conditions increased in the series peracetic acid < hydrogen peroxide < tert-butyl hydroperoxide, coming to 0.08, 1.6 and 24 μmol L⁻¹, respectively. tert-Butyl peroxybenzoate and di-tert-butyl peroxide were found to have no effect on the spectral characteristics of AgTNPs. By the example of hydrogen peroxide, it was found that the determination does not interfere with 100–4000-fold quantities of common inorganic ions. The proposed approach was successfully applied to the analysis of drugs, cosmetics and model mixtures. Full article

In this work, we prepared different morphologies of silver nanoparticles: nanosphere, triangular nanoplates, hexagonal nanoplates, and quasi-spherical shapes, through one-step synthesis. Hydrogen peroxide was used as the oxidizing agent during the reduction of silver nitrate by sodium borohydride, in the presence of tri-sodium citrate and poly-vinyl-pyrrolidone. The obtained silver nanoparticles were fully characterized by UV-Vis spectroscopy, Dynamic Light Scattering and Scanning Electron Microscopy, and successfully used as Surface Enhanced Raman Scattering (SERS) substrates. The effect of shape and morphology on the Raman scattering enhancement was evaluated by using methylene blue as target molecules. The Raman measurements demonstrated that the prepared substrates are reliable and sensitive with analytical enhancement factors, estimated to be around 10⁵ with a concentration of methylene blue 1 μM. When triangular and hexagonal nanoplates were tested with different concentrations of analyte, they demonstrated a good linearity in Raman intensity with a good detection of methylene blue 0.1 μM. Full article

Triangular silver nanoplates were prepared by using the seeding growth approach with the presence of citrate-stabilized silver seeds and a mixture of gelatin–chitosan as the protecting agent. By understanding the critical role of reaction components, the synthesis process was improved to prepare the triangular nanoplates with high yield and efficiency. Different morphologies of silver nanostructures, such as triangular nanoplates, hexagonal nanoprisms, or nanodisks, can be obtained by changing experimental parameters, including precursor AgNO₃ volume, gelatin–chitosan concentration ratios, and the pH conditions. The edge lengths of triangular silver nanoplates were successfully controlled, primarily through the addition of silver nitrate under appropriate condition. As-prepared triangular silver nanoplates were characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS), UV-Vis, Fourier transform infrared spectroscopy (FT-IR), and X-Ray diffraction (XRD). Silver nanoplates had an average edge length of 65–80 nm depending on experimental conditions and exhibited a surface plasma resonance absorbance peak at 340, 450, and 700 nm. The specific interactions of gelatin and chitosan with triangular AgNPs were demonstrated by FT-IR. Based on the characterization, the growth mechanism of triangular silver nanoplates was theoretically proposed regarding the twinned crystal of the initial nanoparticle seeds and the crystal face-blocking role of the gelatin–chitosan mixture. Moreover, the antibacterial activity of triangular silver nanoplates was considerably improved in comparison with that of spherical shape when tested against Gram-positive and Gram-negative bacteria species, with 6.0 ug/mL of triangular silver nanoplates as the MBC (Minimum bactericidal concentration) for Escherichia coli and Vibrio cholera, and 8.0 ug/mL as the MBC for Staphylococcus aureus and Pseudomonas aeruginosa. The MIC (Minimum inhibitory concentration) of triangular Ag nanoplates was 4.0 ug/mL for E. coli, V. cholera, S. aureus, and P. aeruginosa. Full article