Search Results (111)

Background/Objectives: Airborne viral diseases pose a health risk, due to which there is a growing interest in developing filter materials capable of capturing fine particles containing virions from the air and that also have a virucidal effect. Nanofiber membranes made of poly(vinylidene fluoride) dissolved in N,N-dimethylacetamide and functionalized with copper, silver, and zinc nanoclusters were fabricated via electrospinning. This study aims to evaluate and compare the virucidal effects of nanofibers functionalized with metal nanoclusters against the human influenza A virus A/WSN/1933 (H1N1) and SARS-CoV-2. Methods: A comprehensive characterization of materials, including X-ray diffraction, scanning electron microscopy, microwave plasma atomic emission spectroscopy, thermogravimetric analysis, contact angle measurements, nitrogen sorption analysis, mercury intrusion porosimetry, filtration efficiency, and virucidal tests, was used to understand the interdependence of the materials’ physical characteristics and biological effects, as well as to determine their suitability for application as antiviral materials in air filtration systems. Results: All the filter materials tested demonstrated very high particle filtration efficiency (≥98.0%). The material embedded with copper nanoclusters showed strong virucidal efficacy against the SARS-CoV-2 alpha variant, achieving an approximately 1000-fold reduction in infectious virions within 12 h. The fibrous nanowire polymer functionalized with zinc nanoclusters was the most effective material against the human influenza A virus strain A/WSN/1933 (H1N1). Conclusions: The materials with Cu nanoclusters can be used with high efficiency to passivate and kill the SARS-CoV-2 alpha variant virions, and Zn nanoclusters modified activated porous membranes for killing human influenza A virus A7WSN/1933 (H1N1) virions. Full article

In this work, we investigate the fundamental usability of fluorescent DNA-templated silver nanoclusters (DNA-AgNCs) as sensors for Point-of Care-Testing (PoCT) applications. We developed a microfluidic platform for the generation of droplets containing DNA-AgNCs in defined, different chemical environments. The droplets are read out fluorescently at two different emission wavelengths. For the pre-evaluation for the usage of biologically relevant matrices with DNA-AgNCs, the response of two different DNA-AgNCs to a variation in pH and sodium chloride concentration was acquired. Our compact and simple setup can detect DNA-AgNCs well below 100 nM and allows the characterization of the fluorescence response of DNA-based biohybrid nanosensors to changes in the chemical environment within short measurement times. The model DNA-AgNCs remain fluorescent throughout the physiologically relevant chloride concentrations and up to 150 mM. Upon shifts in pH, the DNA-AgNCs showed a complex fluorescence intensity response. The model DNA-AgNCs differ strongly in their response characteristics to the applied changes in their environments. With our work, we show the feasibility of the use of DNA-AgNCs as sensors in a simple microfluidic setup that can be used as a building block for PoCT applications while highlighting challenges in their adaption for use with biologically relevant matrices. Full article

Water contamination due to microbial proliferation remains a critical global challenge, especially with increasing urbanization, industrial activities, and the use of agrochemicals, and it requires the development of innovative methods for their purification that are not harmful to the environment and humans. In this study, innovative antibacterial nanocomposite coatings, composed of zirconia and silver nanocluster, were developed and deposited via eco-friendly co-sputtering physical vapor deposition (PVD) method onto electrospun polymeric membranes (PCL and PAN-PCL) for water filtration applications. Structural and morphological analyses, including XRD and UV-Vis spectroscopy, confirmed the deposition of a composite coating, consisting of an amorphous zirconia matrix embedding silver nanoclusters, homogeneously distributed on one side of the polymeric fibers. Wettability evaluations showed an increase in hydrophobicity after coating, particularly affecting the filtration performance of the PCL membranes. Antibacterial tests revealed strong inhibition against Staphylococcus epidermidis (Gram-positive) and partial efficacy against Escherichia coli (Gram-negative). Filtration tests of contaminated solutions revealed a 99% reduction in Bacillus subtilis, significant inhibition of Listeria monocytogenes, and limited effect on E. coli, with no bacterial proliferation observed on the coated membranes. These results underscore the effectiveness of ZrO₂/Ag nanocomposites in enhancing microbial control and suggest a promising, scalable strategy for sustainable and safe water purification systems. Full article

Silver nanoclusters that are confined inside zeolites can give off intensive tunable emission across the visible region under UV excitation. In this research, a series of silver nanoclusters loaded with R-FAU/Ag (R = Li, Na, K) zeolites were synthesized and then applied as phosphors for LEDs. The XRD and SEM measurements showed the R-FAU/Ag (R = Li, Na, K) zeolites have high crystallinity and a size distribution of 0.7–1.25 μm. Under excitations of 310–330 nm ultraviolet radiation, Li-FAU/Ag, Na-FAU/Ag, and K-FAU/Ag exhibit monotonically declining emission intensities and red-shifted emissions with peak wavelengths of 520, 527, and 535 nm, respectively. By using silicone-based epoxy resin as the packaging material, a series of LEDs were fabricated by mixing R-FAU/Ag (R = Li, Na, K) phosphors. It is indicated that the Li-FAU/Ag-LED shows the strongest intensity of 94.9 mcd, much higher than that of the LEDs made from Na-FAU/Ag (63.7 mcd) and K-FAU/Ag (74.2 mcd) phosphors. Additionally, the chromaticity coordinate of the Li-FAU/Ag-LED is located at (0.2651, 0.4073) and has a high color temperature of 7873 K. Thermal test data showed that upon heating to 440 K, the intensities of R-FAU/Ag (R = Li, Na, K) LEDs decreased to 81%, 79%, and 75% of their initial intensities measured at 280 K, respectively. This research proposes a method for regulating the luminescent properties of silver nanoclusters in FAU zeolite by modifying the extra-framework cations and demonstrates excellent performance in LED products. Full article

The measurement of humidity is of great significance for precision instruments, semiconductor integrated circuits, and element manufacturing factories. The oxygen-containing groups and noble metals in graphene-based sensing materials can significantly influence their humidity-sensing performance. Herein, 1,3,5-benzenetricarboxylic acid-functionalized reduced graphene oxide (H3BTC-rGO) loaded with Ag nanocluster nanocomposites (H3BTC-rGO/Ag) was synthesized via a facile one-step reduction method. The H3BTC-rGO/Ag-based sensor exhibited excellent humidity-sensing performance, including a higher sensitivity of 88.9% and a faster response/recovery time of 9 s/16 s towards 50% RH than those of other GO-, rGO-, and H3BTC-rGO-based sensors. The proposed humidity sensor was tested in the range of 0% to 100% RH and showed excellent sensitivity even at a low relative humidity of 0–10% or a high relative humidity of 90–100%. In addition, the H3BTC-rGO/Ag-based sensor had excellent selectivity, reliable repeatability, and good stability over 30 days under different relative humidities. Compared with H3BTC-rGO-200, the H3BTC-rGO/Ag-0.25-based sensor exhibited a low hysteresis of less than ±5% RH. The high performance was ascribed to the high density of the carboxyl groups and good conductivity of H3BTC-rGO, as well as the catalytic role of the Ag nanoclusters, resulting in high water adsorption rates. The potential applications of the H3BTC-rGO/Ag-based humidity sensor in human exhalation monitoring are also discussed. This work provides a reference for the application of graphene-based flexible sensors in monitoring very wet and dry environments. Full article

The use of DNA as a scaffold for nanoclusters is particularly interesting due to its structural versatility and easy integration with aptamers. In their structure, aptamers often contain non-canonical forms of DNA, i.e., G-quadruplexes (GQs). Four-stranded GQs are used to construct nanomachines and biosensors for monitoring changes in the concentration of potassium ions. In the present study, we continue our work related to the synthesis of silver nanoclusters formed on a bifunctional DNA template. By attaching a cytosine-rich domain (C12) to a G-quadruplex-forming sequence—human telomeric (Tel22) or thrombin-binding aptamer (TBA)—we constructed bifunctional templates for fluorescent silver nanoclusters (C12) with the ability to detect potassium ions (GQs). The changing localization of the C12 domain from the 3′ to 5′ end of the oligonucleotide was a successful way to improve the fluorescence properties of the obtained fluorescent probes. The best performance as a probe for potassium ions was exhibited by C12Tel22-AgNCs, with an LOD of 0.68 mM in PBS. The introduction of the fluorescent cytosine analog tC leads to an LOD of 0.68 mM in PBS and 0.46 mM in Tris-acetate. Additionally, we performed AFM, TEM, DLS analysis, and cellular studies to further investigate the structural properties and behavior of the Tel22C12-AgNCs in biological contexts. Full article

This research introduces a novel synthetic method for introducing highly luminescent silver nanoclusters (AgNCs). The technique relies on coffee Arabica seed extraction (CSE), which is the focus of this study. Our developed and manufactured ecologically friendly approach has enhanced the selectivity of AgNCs for Hg(II) ions. The coffee extract was employed in the synthesis process to stabilize and enhance the quantity of AgNCs generated. Various advanced techniques were used to characterize the AgNCs precisely in their prepared condition concerning size, surface modification, and composition. The fluorescence quenching of the AgNCs was the mechanism via which the CSE-AgNCs reacted to the principal metal ions in the experiment. Using this sensing methodology, a very accurate and selective sensing method is provided for Hg(II) in the dynamic range of 0.117 µM to 1.4 µM, with a limit of detection (LOD) equal to 35.21 nM. Comparative research was conducted to determine how selective CSE-AgNCs are for Hg(II) ions compared to other ions. Consequently, a notable degree of selectivity of AgNCs towards these Hg(II) metal ions was achieved, allowing the sensitive detection of Hg(II) metal ions, even their interfering metal ions, in the environment. AgNCs can detect Hg(II) at acceptable values within the nanomolar range. Based on their characteristics, Hg(II) ions were detected in real samples using CSE-AgNCs. Full article

Biofilms are resistant microbial cell aggregates that pose risks to the health and food industries and produce environmental contamination. The accurate and efficient detection and prevention of biofilms are challenging and demand interdisciplinary approaches. This multidisciplinary research reports the application of a deep learning-based artificial intelligence (AI) model for detecting biofilms produced by Pseudomonas aeruginosa with high accuracy. Aptamer DNA-templated silver nanocluster (Ag-NC) was used to prevent biofilm formation, which produced images of the planktonic states of the bacteria. Large-volume bright-field images of bacterial biofilms were used to design the AI model. In particular, we used U-Net with ResNet encoder enhancement to segment biofilm images for AI analysis. Different degrees of biofilm structures can be efficiently detected using ResNet18 and ResNet34 backbones. The potential applications of this technique are also discussed. Full article

Background/Objectives: In the race to develop new antibiotics to combat multidrug-resistant bacteria, particularly the ESKAPE pathogens which pose a significant threat to public health, silver nanoclusters (AgNCs) have emerged as a promising alternative. This article focuses on the potential of novel silver nanoclusters as an antimicrobial agent against Staphylococcus aureus, a high-priority pathogen known for its ability to cause persistent nosocomial infections and develop protective biofilms. Methods: In this study, we successfully synthesized AgNCs at pH 7 using an eco-friendly photoreduction method with poly acrylic acid (PAA) and poly methacrylic acid (PMAA) as stabilizers. This methodology produced fluorescent AgNCs, demonstrating their stability in aqueous solutions for at least three months and highlighting the effectiveness of PAA and PMAA as stabilizing agents. The AgNCs were incubated with S. aureus suspension, and the antimicrobial capability at different concentrations and times of incubation were determined. Also, the AgNCs hemocompatibility was studied by exposing the clusters to rat blood cells. Results: The in vitro assays revealed that AgNCs capping with PAA or PMAA has antimicrobial activity in low doses (the determination of minimum inhibitory concentration (MIC): 0.2 µg/mL, and the determination of minimum bactericidal concentration (MBC): 2 µg/mL) and without cytotoxicity (hemolysis less than 10%) to rat blood cells until 1 µg/mL. In the presence of both AgNCs (5 µg/mL), bacterial growth was completely inhibited within just 3 h. Conclusions: The findings of this study highlight the potential of silver nanoclusters as effective antimicrobial agents against S. aureus. Their stability, low toxicity, and rapid bactericidal activity make them promising candidates for further development in antimicrobial applications. Full article

Here, we demonstrate through AFM imaging and CD spectroscopy that the binding of silver ions (Ag⁺) to poly(dGdC), a double-stranded (ds) DNA composed of two identical repeating strands, at a stoichiometry of one Ag⁺ per GC base pair induces a one-base shift of one strand relative to the other. This results in a ds nucleic acid-Ag⁺ conjugate consisting of alternating CC and GG base pairs coordinated by silver ions. The proposed organization of the conjugate is supported by the results of our Quantum Mechanical (QM) and Molecular Mechanics (MMs) calculations. The reduction of Ag⁺ ions followed by the partial oxidation of silver atoms yields a highly fluorescent conjugate emitting at 720 nm. This fluorescent behavior in conjugates of long, repetitive ds DNA (thousands of base pairs) with silver has never been demonstrated before. We propose that the poly(dGdC)–Ag conjugate functions as a dynamic system, comprising various small clusters embedded within the DNA and interacting with one another through energy transfer. This hypothesis is supported by the results of our QM and MMs calculations. Additionally, these DNA–silver conjugates, comprising silver nanoclusters, may possess conductive properties, making them potential candidates for use as nanowires in nanodevices and nanosensors. Full article

Palladium-doped silver nanoclusters (NCs) have been highlighted for their unique physicochemical properties and potential applications in catalysis, optics, and electronics. Anion-directed synthesis offers a powerful route to control the morphology and properties of these NCs. Herein, we report a novel Pd-doped Ag NC, [Pd(H)Ag₁₃(S){S₂P(OⁱPr)₂}₁₀] (PdHAg₁₃S), synthesized through the inclusion of sulfide and hydride anions. This NC features a unique linear S-Pd-H axis enclosed in a 4-5-4 stacked arrangement of silver atoms. The distinctive hydride environment was characterized by NMR spectroscopy, and the total structure was determined by single-crystal X-ray diffraction (SCXRD) and supported by computational studies. Mass spectrometry and X-ray photoelectron spectroscopy (XPS) further confirmed the assigned composition. This unique construct exhibits promising hydrogen evolution reaction (HER) activity. Our findings highlight the potential of anion-directed synthesis for creating novel bimetallic NCs with tailored structures and catalytic properties. Full article

Polydispersed Ag species-modified TiO₂ samples with abundant oxygen vacancies were successfully prepared through the calcination of atomically precise Ag₃₃ nanocluster-loaded TiO₂ at an optimal temperature under a nitrogen atmosphere. The ligands of the Ag₃₃ nanoclusters are removed by extracting lattice oxygen from TiO₂ during the calcination, leading to the formation of CO₂, SO₂, and H₂O vapor. This process simultaneously induces Ag species sintering on the surface of TiO₂. The resulting nanocomposites exhibited excellent catalytic activity for the reduction of nitroarenes with NaBH₄ as the reductant. This is attributed to the produced Ag species on the oxygen-deficient TiO₂, which act as active centers for the catalytic process. Full article

Direct preparation of silver nanoclusters is of great significance for their applications. In this work, by selecting sodium cyanoborohydride as a weak reducing agent to control the kinetics of the reduction reaction, we successfully prepared silver nanoclusters protected by thiol-containing ligands, including mercaptosuccinic acid, cysteine, and glutathione. Based on the silver nanoclusters protected by mercaptosuccinic acid, silver–gold alloy nanoclusters were obtained through a gold doping reaction. Spectroscopic and particle size analyses showed that the silver–gold alloy nanoclusters exhibited aggregation-induced emission enhancement (AIEE) properties. A fluorescent probe for aluminum ions was developed based on the silver–gold alloy nanoclusters. In the presence of methionine and mercaptoacetic acid, the probe demonstrated good selectivity for aluminum ion detection. The linear range of this detection method was 0 to 192 μM, with a detection limit of 1.6 μM. The working mechanism of this detection method was further investigated through spectroscopic analysis. Full article

A helium ion microscope (HIM) with a focused He⁺-ion beam of variable flux and energy can be used as a tool for local nanoscale surface modification. In this work, we demonstrate a simple but versatile use of the HIM focused He ion beam to fabricate conducting metallic nano- and microstructures on arbitrary substrates of varied types and shapes by directly patterning pre-deposited initially discontinuous and highly insulating (>10 TΩ/sq.) ultrathin metal films. Gold or silver films, measuring 3 nm in thickness, thermally evaporated on solid substrates have a discontinuous nanocluster morphology. Such highly resistive films can be made locally conductive using moderate doses (2 × 10¹⁶–10¹⁷ cm⁻²) of low-energy (30 KeV) ion bombardment. We show that an HIM can be used to directly “draw” Au and Ag conductive lines and other patterns with a variable sheet resistance as low as 10 kΩ/sq. without the use of additional precursors. This relatively straightforward, high-definition technique of direct writing with an ion beam, free from complex in vacuo catalytic or precursor chemistries, opens up new opportunities for directly fabricating elements of conformal metallic nanocircuits (interconnects, resistors, and contacts) on arbitrary organic or inorganic substrates, including those with highly curved surfaces. Full article

The formation of conductive copper patterns on mica holds promise for developing cost-effective flexible electronics and sensing devices, though it is challenging due to the low adhesion of mica’s atomically flat surface. Herein, we present a wet-chemical method for copper patterning on flexible mica substrates via electroless copper deposition (Cu-ELD). The process involves pre-functionalizing 50 µm thick muscovite mica with a titanium dioxide (TiO₂) layer, via a sol–gel dip-coating method with a titanium acetylacetonate-based sol. Photolithography is employed to selectively activate the TiO₂-coated mica substrates for Cu-ELD, utilizing in situ photodeposited silver (Ag) nanoclusters as a catalyst. Copper is subsequently plated using a formaldehyde-based Cu-ELD bath, with the duration of deposition primarily determining the thickness and electrical properties of the copper layer. Conductive Cu layers with thicknesses in the 70–130 nm range were formed within 1–2 min of deposition, exhibiting an inverse relationship between plating time and sheet resistance, which ranged from 600 to 300 mΩ/sq. The electrochemical thickening of these layers to 1 μm further reduced the sheet resistance to 27 mΩ/sq. Finally, the potential of Cu-ELD patterning on TiO₂-functionalized mica for creating functional sensing devices was demonstrated by fabricating a functional resistance temperature detector (RTD) on the titania surface. Full article