Search Results (66)

In this work, ZnO nanoparticles were synthesized via a plant-mediated green route using Prosopis tamaulipana extract as a reducing and stabilizing agent and subsequently modified with silver to obtain Ag-modified ZnO powders. Structural and morphological characterization techniques confirmed the formation of nanocrystalline ZnO with a hexagonal wurtzite structure, submicrometric agglomerates composed of nanosized primary particles and a high degree of phase purity, indicating the effectiveness of the synthesis approach. The photocatalytic performance of the Ag-modified ZnO materials was evaluated under natural solar irradiation using methylene blue as a model organic contaminant in aqueous solution. Visual observations, together with absorbance, temperature and electrical conductivity measurements, demonstrated an effective and progressive degradation of the dye over a 5 h irradiation period. The observed increase in electrical conductivity under illumination was associated with enhanced charge carrier generation and improved separation efficiency, as well as the formation of reactive oxygen species, promoted by the presence of Ag as an electron sink. These results confirm that green-synthesized Ag-modified ZnO nanoparticles exhibit enhanced photocatalytic activity and are promising multifunctional materials for sustainable water sanitation applications. Full article

Silver nanoparticles are metallic particles with very small dimensions and excellent optical, electrical and biological properties. Lately, they have shown promising results in biosensing applications. In the material’s fabrication, the synthesis parameters remain the main aspect to be considered once a certain application is targeted. Therefore, this work presents the synthesis of silver nanoparticles using a chemical reduction based on various volumes of reducing and stabilizing agents. The multiple synthesis methods proposed were tested and optimized in order to achieve the best results for further biosensing applications. In this regard, sodium borohydride (NaBH₄) was used as reducing agent in volumes of 400 μL and 1 mL, while trisodium citrate (TSC) was proposed in much smaller volumes of 10, 20, and 50 μL. The optical and morphological analysis obtained from UV-VIS and TEM microscopy confirmed the formation of nanoparticles in case of all synthesis. The average diameters of silver nanoparticles were in the range between 21 and 27 nm, with high homogeneity for the samples with 20 and 50 μL of TSC. FT-IR analysis confirmed the TSC functionalization on the AgNPs’ surface. SERS analysis and the bulk sensitivity method also showed good surface results, leading to the assumption that both reducing and stabilizing agents can influence the final properties of the material. LSPR biosensing of para-aminothiophenol was tested, and was proven to have detection capabilities at concentrations as low as 10⁻⁷ M. Overall, the results proved that the synthesis method with a smaller amount of reducing agent and a moderate quantity of stabilizing agent has superior properties for biosensing applications. Full article

The electronic setup based on Arduino has been designed to determine the range of light frequency where photocatalytic activity occurs most effectively in the presence of nanosized silver during the electromagnetic radiation exhibition. As a compound used to find such activity, the methylene blue dye has been chosen, which is commonly used as a redox indicator. The range of light frequency occurred near the local plasmon frequency of silver nanoparticles. Full article

Antimicrobial polymeric coatings rely not only on their surface functionalities but also on nanoparticles (NPs). Antimicrobial coatings gain their properties from the addition of NPs into a polymeric matrix. NPs that have been used include metal-based NPs, metal oxide NPs, carbon-based nanomaterials, and organic NPs. Copper NPs and silver NPs exhibit antibacterial and antifungal properties. So, when present in coatings, they will release metal ions with the combined effect of having bacteriostatic/bactericidal properties, preventing the growth of pathogens on surfaces covered by these nano-enhanced films. In addition, metal oxide NPs such as titanium dioxide NPs (TiO₂ NPs) and zinc oxide NPs (ZnONPs) are used as NPs in antimicrobial polymeric coatings. Under UV irradiation, these NPs show photocatalytic properties that lead to the production of reactive oxygen species (ROS) when exposed to UV radiation. After various forms of nano-carbon materials were successfully developed over the past decade, they and their derivatives from graphite/nanotubes, and composite sheets have been receiving more attention because they share an extremely large surface area, excellent mechanical strength, etc. These NPs not only show the ability to cause oxidative stress but also have the ability to release antimicrobial chemicals under control, resulting in long-lasting antibacterial action. The effectiveness and life spans of the antifouling performance of a variety of polymeric materials have been improved by adding nano-sized particles to those coatings. Full article

Efficient terahertz sources with controllable characteristics such as frequency range and polarization state are being rapidly researched and developed to suit various practical applications. To address this need, we realized the idea of combining micro- and nano-sized materials by fabricating micrometer-scale split-ring resonators made of a metal nanostructured film. We found that the peak frequencies of the emitted terahertz waves are in good correspondence with the terahertz resonance frequencies of the split-ring resonators. A possible mechanism is that a surge current was induced inside the split-ring resonators as a result of photoexcitation with the help of plasmon resonance around nanostructures, and the induced current emitted terahertz waves reflecting the resonance properties of the split-ring resonators. Although the silver nanostructures constituting the rings are random and homogeneous, the induction of the current parallel to the sample surface is enabled by the oblique incidence excitation, which breaks the symmetry along the sample surface. The present study shows the possibility of making compact terahertz emitters with flexibly tunable spectral shape, potentially leading to the development of terahertz sources optimized for specific spectroscopic uses. Full article

The utilization of nano-sized drug delivery systems in herbal drug delivery systems has a promising future for improving drug effectiveness and overcoming issues connected with herbal medicine. As a consequence, the use of nanocarriers as novel drug delivery systems for the improvement of traditional medicine is critical to combating infectious diseases globally. In line with this, we herein report the biosynthesis of silver nanoparticles (AgNPs), gold nanoparticles (AuNPs), and bimetallic nanoparticles (BMNPs) as antibacterial agents against pathogenic bacterial strains using Annona squamosa L. leaf extract as a bio-reductant and bio-stabilizing agent. The as-synthesized metal nanoparticles were characterized by transmission electron microscopy (TEM), ultraviolet–visible (UV–Vis) absorption spectroscopy, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and the dynamic light scattering (DLS) method. The as-synthesized MNPs had an average particle size of 6.98 nm ± 2.86 nm (AgNPs), 21.84 ± 8.72 nm (AuNPs), and 2.05 nm ± 0.76 nm (BMNPs). The as-synthesized AgNPs and BMNPs showed good antibacterial activity against pathogenic bacterial strains of Gram-positive Staphylococcus aureus (ATCC 25923) and Gram-negative Escherichia coli (ATCC 25922). The obtained results offer insight into the development of benign nanoparticles as safe antibacterial agents for antibiotic therapy using Annona squamosa L. leaf extract. Full article

The ubiquitous use of products containing AgNPs results in the entry of nanoparticles into the environment. Both nanoparticles and Ag⁺ released upon their oxidative dissolution have a toxic effect on living microorganisms. The antibacterial activity of spherical silver nanoparticles of 10.8 ± 0.8 nm and 22.7 ± 2.2 nm in size stabilized by carbonate ions was studied against Escherichia coli and other bacteria. The biocidal action of silver increases as the particle size decreases. Analysis of these results and other known data made it possible to substantiate a linear proportional relationship between the minimum inhibitory concentration (MIC) or the half-maximal inhibitory concentration (IC50) and silver nanoparticle size and determine empirical parameters for this relationship. The antibacterial activity (toxicity) is directly proportional to the specific surface area of nanosized silver. Full article

Silver nanowires (AgNWs) have excellent electrical conductivity and nano-sized effects and have been widely used as a high-performance electromagnetic shielding material. However, silver nanowires have poor mechanical properties and are prone to fracture during the preparation of composite materials. In this study, PVDF/rGO/AgNW composites with a segregated structure were prepared using low-pressure compression molding and the AgNW-backfilling process. The low-pressure compression of the composite significantly improves its electromagnetic shielding performance because the low-pressure process can maintain the AgNWs’ integrity. The backfilled AgNWs played a vital role in increasing the path of electromagnetic wave propagation and the absorption of electromagnetic waves. The backfilled amount of AgNWs was only 1 wt%, which increased the composite material’s conductivity by one order of magnitude. The total electromagnetic interference shielding (SE_T) of the composite materials increased by 23.3% from 24.88 dB to 30.67 dB. The absorption contribution (SE_A/SE_T) increased from 84.2% to 92.8%, significantly improving the electromagnetic interference shielding and the absorption contribution of the AgNWs in the composites. This was attributed to the backfilling of the porous structure by the AgNWs, which promoted multiple reflections and enhanced the absorption contribution. Full article

In this study, pure TiO₂ gels were synthesized by applying the sol–gel method, using Ti(IV) butoxide with the addition of two different solvents, namely ethylene glycol (EG) and isopropanol (isop), with only air moisture present. It was established using XRD that the gel prepared with the addition of EG was amorphous even at 400 °C, while the other gel was amorphous up to 300 °C. It was found that TiO₂ (anatase) had a dominant crystalline phase during heating to 600 °C, while at 700 °C, TiO₂ (rutile) appeared. The as-obtained powdered materials were annealed at 500 °C and subsequently underwent photocatalytic tests with paracetamol. Additionally, the TiO₂ samples were modified with Ag⁺ co-catalysts (10⁻² M), using photofixation by UV illumination. The photocatalytic activity of the Ag-modified powders was also tested in the photodegradation of a commonly used paracetamol in aqueous solution under UV light illumination. The obtained data exhibited that the annealed samples had better photocatalytic efficiency and decomposed paracetamol faster in comparison to the non-annealed sol–gel powders. The highest degradation efficiency was observed for the TBT/isop/Ag material, with degradation efficiencies average values of 65.59% and 75.61% paracetamol achieved after the third cycle of photocatalytic treatment. The co-catalytically modified powders had higher photocatalytic efficiency in comparison to the pure nanosized powders. Moreover, the sol–gel powders of TBT/EG, TBT/EG/Ag (10⁻² M), TBT/isop, and TBT/isop/Ag (10⁻² M) demonstrated the ability to retain their photocatalytic activity even after three cycles of use, suggesting that they could find practical use in the treatment of pharmaceutical wastewater. The observed photocatalytic efficiency and positive impact of silver make the prepared powders a desirable choice for pharmaceutical drug degradation, helping to promote environmentally friendly and effective wastewater treatment technology. Full article

The objective of this research was to develop a surface modification for the NiTi shape memory alloy, thereby enabling its long-term application in implant medicine. This was achieved through the creation of innovative multifunctional hybrid layers comprising a nanometric molecular system of silver-rutile (Ag-TiO₂), known for its antibacterial properties, in conjunction with bioactive submicro- and nanosized hydroxyapatite (HAp). The multifunctional, continuous, crack-free coatings were produced using the electrophoretic deposition method (EPD) at 20 V/1 min. Structural and morphological analyses through Raman spectrometry and scanning electron microscopy (SEM) provided comprehensive insights into the obtained coating. The silver within the layer existed in the form of nanometric silver carbonates (Ag₂CO₃) and metallic nanosilver. Based on DTA/TG results, dilatometric measurements, and high-temperature microscopy, the heat treatment temperature for the deposited layers was set at 800 °C for 2 h. The procedures applied resulted in the creation of a new generation of materials with a distinct structure compared with the initial nanopowders. The resulting composite layer, measuring 2 μm in thickness, comprised hydroxyapatite (HAp), apatite carbonate (CHAp), metallic silver, silver oxides, Ag@C, and rutile exhibiting a defective structure. This structural characteristic contributes significantly to its heightened activity, influencing both bioactivity and biocompatibility properties. Full article

Nanosized Ag and CeO₂ particles obtained through the hydrothermal method were physically mixed to obtain composite antibacterial agents. The comparative experiments of antibacterial properties showed that the antibacterial activity of the nanocomposites was improved compared to the nanoparticles alone, which indicated that the synergistic antibacterial effect existed between Ag and CeO₂. On the one hand, ICP-MS results showed that the existence of CeO₂ suppressed the silver ion release rate and provided the composite with the ability of antibrowning; on the other, EPR data indicated that more hydroxyl radicals (·OH) were generated by the interfacial interaction between nanosized Ag and nanosized CeO₂. Hence, for the Ag-CeO₂ composite antibacterial agent, hydroxyl radicals played an important role in causing bacterial death. Full article

Using biodegradable wastes represents a viable alternative to creating a sustainable economy that benefits all humans. The present study aimed to use daily used waste products, tea (TE) and eggshell (ES) wastes, to synthesize silver (AgNPs) and titanium oxide (TiO₂NPs) nanoparticles, respectively. Firstly, the green-synthesized nanoparticles were characterized using an ultraviolet-visible spectrophotometer (UV-VIS), Scanning (SEM), transmission electron microscope (TEM), Dynamic light scattering (DLS), zeta potential analysis, X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy. Then, followed by their cytotoxic assessment against normal human skin fibroblast (HSF) cells using sulforhodamine B (SRB) assay, AgNPs_TE (300 and 470 nm) and TiO₂NPs_ESE (320 nm) formation was confirmed using UV-vis spectra. SEM and XRD showed their crystalline shape. TEM images determined the nano-size of AgNPs_TE (25 nm) and TiO₂NPs_ESE (120 nm), which appeared smaller in comparison with DLS analysis (299.8 and 742.9 nm), with zeta potentials of −20.5 mV and −12.6 mV, respectively. There was a great difference in both NPs’ sizes using TEM and DLS measurements because DLS is known to be more sensitive to larger particles due to their light scattering. FTIR detected the functional groups found in TE and ESE that were responsible for the synthesis, capping, and stabilization of the synthesized AgNPs and TiO₂NPs. The SRB assay reveals the safety of TiO₂NPs on normal HSF cells with an IC50 > 100, while AgNPs have a high cytotoxic effect with an IC50 = 54.99 μg/mL. Full article

A carbonate-hydroxyapatite-based antibacterial implant material with low cytotoxicity was synthesized. The silver ion (Ag⁺) was incorporated into CHA material, resulting in silver-doped carbonate hydroxyapatite (CHA-Ag). The microwave-assisted precipitation method was used to synthesize the CHA-Ag material. The amount of Ag⁺ was varied at 0.005, 0.010, and 0.015 mol fractions (${\chi }_{Ag}$). The XRD results showed that the diffractograms corresponded with hydroxyapatite (ICSD 98-05-1414), without any additional phase. The presence of carbonate ions was indicated by vibrations at wavenumber of 871, 1411, and 1466 cm⁻¹ in the infrared spectra. The CHA-Ag materials were agglomerates of nanosized particles with low crystallinity. The particle size and crystallinity of the materials decreased due to the incorporation of CO₃²⁻ and Ag⁺. The incorporated Ag⁺ successfully inhibited peri-implant-associated bacterial growth. The antibacterial ability increased alongside the increase in the Ag⁺ amount. The pre-osteoblast MC3T3E1 cell could grow up to >70% in the MTT assay, despite the use of Ag⁺ as a dopant. The cell viability was higher in the CHA-Ag-containing media than in the CHA-containing media. The MTT assay also revealed that the CHA-Ag cytotoxicity decreased even though the Ag⁺ amount increased. The CHA-Ag-15 had the lowest cytotoxicity and highest antibacterial activity. Therefore, the optimal amount of Ag⁺ in the CHA-Ag formulation was ${\chi }_{Ag}$ = 0.015. Full article

The transformation of high-molecular DNA from a random swollen coil in a solution to a discrete nanosized particle with the ordered packaging of a rigid and highly charged double-stranded molecule is one of the amazing phenomena of polymer physics. DNA condensation is a well-known phenomenon in biological systems, yet its molecular mechanism is not clear. Understanding the processes occurring in vivo is necessary for the usage of DNA in the fabrication of new biologically significant nanostructures. Entropy plays a very important role in DNA condensation. DNA conjugates with metal nanoparticles are useful in various fields of nanotechnology. In particular, they can serve as a basis for creating multicomponent nanoplatforms for theranostics. DNA must be in a compact state in such constructions. In this paper, we tested the methods of DNA integration with silver, gold and palladium nanoparticles and analyzed the properties of DNA conjugates with metal nanoparticles using the methods of atomic force microscopy, spectroscopy, viscometry and dynamic light scattering. DNA size, stability and rigidity (persistence length), as well as plasmon resonance peaks in the absorption spectra of systems were studied. The methods for DNA condensation with metal nanoparticles were analyzed. Full article

Glutathione (GT) is a complexing agent that plays a key role in the functioning of a living cell. Gold nanoparticles are often used as transducers of nanosized biosensors, since they have the optical and chemical properties necessary for sensory applications, and make it possible to form a sensitive layer with the desired recognition element. Silver nanoparticles (AgNPs) also have attracted increasing interest to sensor applications due to the narrower plasmon resonance band compared to gold nanoparticles, but different surface chemistry. The purpose of this study is to provide an information about GT-coated AgNPs evolution as a system consisting of AgNPs transducer and GT recognition element. AgNPs are transformed through Ag⁺ to amorphous Ag, while GT promotes AgNPs to be dissolved, and gets decomposed by reactive oxygen species (ROS) during the transformation. Full article