Size Of Ag Nanoparticles Research Articles

Lavender-mediated solvent-free biomechanochemical synthesis of antibacterially active Ag/AgCl nanoparticles using a Taguchi design**This article was presented at IWAMSN 2024, Danang, Vietnam, 22–26 Sept 024. (ANSN-2024-0256).

Abstract A bionanocomposite containing Ag/AgCl nanoparticles and plant biomass was prepared via solvent-free biomechanochemical synthesis utilizing planetary ball milling of lavender plant and silver nitrate powders in this work. The impact of four input parameters, namely milling speed, milling time sample mass and plant-to-AgNO3 mass ratio was assessed via a ‘Design of Experiments methodology’, namely Taguchi orthogonal array. In this way, optimum conditions were identified and analysis of variance and regression analysis was performed. The obtained Ag and AgCl were nanocrystalline, their content varying depending on the milling conditions. Agar well diffusion assay has shown the antibacterial action in all the analyzed samples, being slightly higher for Staphylococcus aureus than Escherichia coli. The regression analysis has shown that the crystallite size of Ag nanoparticles is the most important parameter influencing the antibacterial action. In the end, the sample under optimum conditions was prepared and the values predicted with Taguchi methodology were compared with those obtained experimentally, showing a decent match in parameters calculated from XD-ray diffraction and antibacterial action.

Novel thermally conductive coating for cotton fabrics based on reduced graphene oxide decorated with in situ synthesized silver nanoparticles

The application of thermally conductive materials as coating on fiber surfaces represents an innovative technology solution for conveying heat dissipation capability to IR-opaque textiles. In this work, a sustainable and scalable approach to manufacture a hybrid nanocomposite coating for cotton, formed by Reduced Graphene Oxide (RGO) sheets functionalized by histidine (His) and decorated by Ag nanoparticles (NPs), is reported for increasing thermal conductivity of cotton fabrics. Tens nm in size Ag NPs were synthesized, in situ, at the coordinating sites of the His-RGO modified cotton impregnated by H2O/CH3OH solutions of the AgNO3 precursor, under UV-light exposure, without using chemical reductants. The physical chemical properties of the nanocomposite modified fabrics were comprehensively investigated, integrating chemical, structural and morphological analysis, with characterizations of their thermal, electrical, oxygen permeability, surface wettability and mechanical properties. Thermal conductivity of cotton was measured by Differential Scanning calorimetry (DSC) technique, which was here validated by Transient Plane Source (TPS) method, assessing the effectiveness of DSC in measuring thermal conductivity of textiles. The resulting coating exhibits a thermal conductivity, which was twice as high as untreated cotton, maintaining its breathability, increasing its flexibility, while simultaneously reducing its wettability. This notable enhancement can be attributed to the synergistic effect of the conductive Ag nanostructures formed among the His-RGO sheets within the nanocomposite, and it matches the thermal conductivity achieved by current state-of-the-art methods, while offering additional advantages of being more eco-friendly, scalable, and sustainable. The reported characterization of the structural properties of the achieved coating opens the venue to interesting perspectives towards its application in passive conducting cooling textiles for personal thermal comfort management.

Metallo‐Surfactant Complex‐Assisted Biomimetic Synthesis of Silver Nanoparticles: Exploring Relativistic Effects in Catalytic and Sensing Applications

AbstractA biological reduction method for silver nanoparticles was employed using Cassia alata extract from plant leaves, which functions as a reducing agent and the metallo‐surfactant [Co(dqn)2(C12H27N)2]3+ (dqn = dipyrido[3,2‐f:2′,3′‐h]‐quinoxaline; C12H27N)2 = dodecylamine) acting as both stabilizing and capping agent. The ratio of Ag nanoparticles (AgNPs) formation was adjusted to be equal to the amount of AgNO3, along with variations in the amount of plant leaf extract, the metallo‐surfactant, pH, surrounding temperature, and the length of interaction periods. High‐resolution transmission electron microscopy (HRTEM), field emission scanning electron microscopy (FE‐SEM), energy‐dispersive spectroscopy (EDS), and energy‐dispersive X‐ray analysis (EDAX) were used to confirm the formation of AgNPs. The infrared results indicate the presence of hydroxyl, amine, and carboxylate groups in the extract plays a crucial role in the reduction process. Additionally, the metallo‐surfactant acts as a capping agent for the silver nanoparticles, preventing agglomeration. By adjusting the acidity of the solution and the quantity of the additive metallo‐surface active agent utilized, the size of AgNPs can be precisely regulated. The relativistic effects observed in this metallo‐surfactant‐assisted silver nanoparticle demonstrate excellent reduction capabilities for nitro compounds, effective dye degradation, and mercury sensing applications.

Plasmonic hemispherical Ag nanoparticles on silicon substrate: A comprehensive study of optical properties

In this work, we demonstrate a comprehensive study of the optical properties of hemispherical Ag nanoparticles (AgNPs) on a single-crystal (c-Si) wafer. The fabricated method involves a galvanic displacement reaction of Ag on c-Si and annealing in oxygen atmosphere at 500 °C. Substrates with different morphological parameters of AgNPs were obtained by varying the volume ratio of Ag in the deposition solution. Using the quasinormal modes (QNMs) theory formalism, the localized surface plasmon resonance (LSPR) multipole positions were determined as a function of the AgNP size and incidence angle. Also, the effective field approximation and QNMs methods were used to calculate the specular reflectance of the disordered hemispherical array on c-Si. Thus, the experimentally obtained LSPR positions in the reflectance spectra were described. Finally, surface-enhanced Raman scattering (SERS) demonstrated reliable detection of brilliant green triphenylmethane dye (1 nM), methyl red dye (10 nM) and hemoglobin from bovine blood (1 mM). The dependence of the SERS enhancement factor on the LSPR position and the absorption band of the analyte was established, the maximum value of which was 1.1 × 107. In summary, this study suggests that the numerical and experimental investigation of the optical properties of hemispherical AgNPs on c-Si contributes to the field of optical sensing.

Modulating Silver Performance in Electrocatalytic Oxidation of HCHO via SMSI between Ag-Co3O4 Interfaces.

The replacement of oxygen evolution reactions with organic molecule oxidation reactions to enable energy-efficient hydrogen production has been a subject of interest. However, further reducing reaction energy consumption and releasing hydrogen from organic molecules continue to pose significant challenges. Herein, a strategy is proposed to produce hydrogen and formic acid from formaldehyde using Ag/Co3O4 interface catalysts at the anode. The key to improving the performance of Ag-based catalysts for formaldehyde oxidation lies in the strong SMSI achieved through the well-designed "spontaneous redox reaction" between Ag and Co3O4 precursors. Nano-sized Ag particles are uniformly dispersed on Co3O4 nanosheets, and electron-deficient Agδ+ are formed by the SMSI between Ag and Co3O4. Ag/Co3O4 demonstrates exceptional formaldehyde oxidation activity at low potentials of 0.32V versus RHE and 0.65V versus RHE, achieving current densities of 10 and 100mA cm-2, respectively. The electrolyzer "Ag/Co3O4||20% Pt/C" achieves over 195% hydrogen efficiency and over 98% formic acid selectivity, maintaining stable operation for 60 hours. This work not only presents a novel approach to precisely modulate Ag particle size and interface electronic structure via SMSI, but also provides a promising approach to efficient and energy-saving hydrogen production and the transformation of harmful formaldehyde.

Synergistic enhancement of plasmon induced photocatalytic and photoelectrochemical performance on ZnWO4/Ag2O@Ag hybrid-heterostructures

A novel hybrid photocatalyst, ZnWO4/Ag2O@Ag heterostructure was synthesized using a simple one-pot microwave treatment with varying concentrations of silver. Physico-chemical characterization was performed to elucidate the synthesized nanohybrids' properties. The photocatalytic activity of both pristine and heterostructure samples was evaluated through the degradation of cationic MB dye. Among the varied Ag concentrations, the 9 % Ag-doped ZnWO4/Ag2O heterostructure exhibited superior degradation performance, with a degradation rate of 93 % achieved within 45 min, surpassing both other Ag concentrations (89 % (90 min) for 1 % Ag, 87 % (80 min) for 3 % Ag, 90 % (80 min) for 5 % Ag and 91 % (45 min) for 7 % Ag) and pristine ZnWO4 (91 % (90 min)) samples. This catalytic enhancement can be attributed to the formation of heterostructures, plasmon-induced absorption enhancement within specific wavelength ranges, and reduced charge recombination rates. UV–visible studies revealed Ag nanoparticles of various sizes in the heterostructures, supported by surface plasmon resonance (SPR) peaks at 480 and 550 nm, respectively. Trapping experiments indicated that •OH and •O2− were the active species in MB reduction for pure and heterostructure samples. Furthermore, the hybrid heterostructure samples exhibited high stability and reusability in photocatalytic degradation. These findings suggest that the ZnWO4/Ag2O heterostructure photocatalysts are promising candidates for environmental remediation applications.

Simple and reversible method to control the surface energy of ITO branched nanowires for tuning wettability of micro/nanoscale droplets

Reversible control of hydrophobic and hydrophilic surfaces has gained attention due to their potential applications in microfluidic devices, membranes for electrochemical cells, and sensors. While external stimuli such as temperature and electric field can regulate surface properties, they cannot be selectively applied to specific regions, which limits the patterning of areas with different surface energies. Here, we present a simple and reversible method for converting hydrophobic and hydrophilic properties through surface treatments involving nonpolar (−CFx) or polar groups (–OH) on indium tin oxide branched nanowires (ITO BRs). The formation of nonpolar groups results in superhydrophobic surface. Subsequent ultraviolet ozone treatment, using a shadow mask, induces the exposed area to transition into a superhydrophilic state, while the unexposed area retains superhydrophobicity. This demonstrates the potential for selective-area surface energy patterning. Furthermore, we investigate the wetting behavior of nanoscale Ag nanoparticles (NPs) on surface-modified ITO BRs. It is observed that size and shape of Ag NPs depend on the surface energy of ITO BRs. Consequently, controlling the surface energy leads to the formation of unique geometric structure of Ag NPs, enhancing plasmonic light absorption and scattering at specific resonant wavelengths.

Square versus hexagonal lattices effects on the optical and dielectric properties of plasmonic Ag–LiNbO[formula omitted] composite

We investigate the effect on the optical and transport properties of square and hexagonal lattice arrangements of silver nanoparticles (NPs) in uniaxial LiNbO3 as optically active layer within a multilayer configuration. This multilayer is constituted by Indium Tin Oxide (ITO), the polymer PMMA and a substrate of SiO2. The effective dielectric function of the ensemble of Ag NPs and uniaxial LiNbO3 crystal are treated through the Bruggeman approximation. The multilayer absorbance for s- and p-polarization at normal and oblique incidences are determined by means of the Transfer Matrix Method. Changes in the ratio between the diameter of the nanoparticles, D, and the distance between particles or pitch, P, are analyzed. A change in the D/P ratio implies a different filling factor. For small D/P ratio, the calculated absorbance for square- and hexagonal-lattices are equivalent; however, for greater D/P factor, the hexagonal lattice clearly shows higher absorbance values. Moreover, the Brewster angle seems to be sensitive to the Ag NPs size as well as the type of arrangement (square or hexagonal). The ac-electrical conductivity of the effective medium layer of the two arrangements in the perpendicular and parallel directions of the Ag NPs plane were analyzed. Our results demonstrate that the ac-conductivity is higher for hexagonal lattice than for square case, which means a higher density of Ag NPs. In addition, for the perpendicular direction, in the hexagonal-lattice (D/P = 0.5), we have found the negative epsilon (NE) condition, characteristic of metamaterials.

Rational design of stable Cu and AuCu nanoparticles for investigations of size-enhanced SERS applications

BackgroundWhile significant progress has been made to clarify the effects of Au and Ag nanoparticle size on SERS enhancement, research on the size effects of copper nanoparticles and copper-related nanoalloys on SERS enhancement remain scarce. Nanoscale copper (Cu) is important because of its unique sensing and catalytic properties; however, research on its size and compositional effects remains a significant challenge because of the intricate fabrication process and difficulty in preventing oxidation. ResultsOur study elucidated the size-dependent, surface-enhanced Raman scattering (SERS) of Cu NPs, particularly the sensing capabilities of both electromagnetic (EM) SERS at 1.5 × 103 and chemical enhancement (CE) SERS at 3.6 × 104 of approximately 58 nm Cu NPs. Additionally, a solution aging examination revealed preservation of the metal-related core structure, surface plasmon resonance, and SERS features of the PSMA/ONPG-coated Cu NPs for up to 7 days. With the introduction of galvanic replacement reactions and laser ablation syntheses, the incorporation of Au atoms enabled the fabrication of 7–75 nm AuxCuy nanoparticles by using the remaining Cu core after aging in water, which offered precise control over the Cu/Au ratio from 5/95 to 29/71. SERS measurements of the large AuxCuy nanoparticles amplified up to 1.4 × 104 of the EM-mediated vibrational signals from the adsorbed molecules. The strong Au–S chemical bonds of the Au-rich AuxCuy nanocrystals increased the CE SERS to 5.5 × 104, whereas the Au3Cu1 crystals at the AuxCuy interface decreased the CE SERS but improved the electron transfer for catalysis via SERS detection. SignificanceOur research provides further insight into the structural and size effects of Cu and AuCu alloys used as SERS enhancers and offers avenues for designing cutting-edge SERS catalytic sensors tailored to Cu-related catalytic reactive structures.For the first time, we also manipulated the Cu atomic structure and surface composition to understand the significance of surface effects on SERS substrates of the Cu series from a nanoscale analytical perspective.

The disruptive effect on the bacterial cell wall explored of the ultrasmall particle-sized Ag nanoparticles supported with Zn Cu-based hybrid nanoagents

The smaller the particle size of Ag nanoparticles, the higher their antibacterial activity against drug-resistant strains, and the greater their potential for application in living organisms. Therefore, preparing Ag nanoparticles with ultra-small particle sizes has become one of the greatest challenges at present. In this study, 1.75 nm Ag was uniformly anchored on the surface of a highly biocompatible carrier to synthesize Fe3O4/ZnO@Cu2S@Ag (FCA) nanocomposites. The antibacterial activity and mechanism of FCA were investigated, and the material was used to treat wound infections caused by bacteria. At a concentration of 175 μg/mL, the antibacterial rate of Escherichia coli, Staphylococcus aureus, and drug-resistant Salmonella was over 99.99 % within 45 min. The antibacterial activity is mainly composed of •OH and multiple cations. The antibacterial mechanism involves •OH and multiple cations synergistically targeting and damaging the bacterial cell wall, altering the secondary structure of the bacterial cell wall, leading to leakage of bacterial contents and bacterial death. Additionally, FCA exhibited high biocompatibility, curing bacterial infections within 7 days and completely eliminating bacterial burden. These findings elucidate the role of antibacterial activity in composite antibacterial materials and suggest that FCA has clinical application potential in treating bacterial infections.

Synthesis of silver nanoparticles embedded on silica by gamma irradiation for utilization as antimicrobial agents

Silver nanoparticles deposited on silica (Ag nano/SiO2) have been prepared by Co-60 gamma irradiation of the mixture Ag+/SiO2/H2O/ethanol. The reduction of Ag+ in the suspension of SiO2 is brought by e-aq and H· generated during the radiolysis of water/ethanol solution. The presence of SiO2 prevents agglomeration of Ag clusters. The conversion dose (Ag+® Ag0) was determined by UV-Vis spectroscopy. Transmission electron microscopy (TEM) characterized the size of Ag nanoparticles. As a result, the particle sizes were determined to be in the range of 5-20 nm for an Ag+ concentration of 5 mM. The crystal structure of silver nanoparticles was also investigated by X-ray diffraction (XRD). In addition, the antifungal activity of Ag nano/SiO2 was tested against Aspergillus niger var Tieghn by plate count method. The results indicated that the antifungal efficiency of Ag nano/SiO2 was about 64, 71, 81, 82, and 96% at the concentrations of Ag nanoparticles of 30, 50, 70, 100, and 150 ppm, respectively.

Green synthesis and characterization of silver anchored ZnO nanoparticle as the antimicrobial reinforcement for polylactide films

AbstractThe aqueous extract of endophytic fungi (Periconia sp.) was effectively used as a reducing agent to anchor Ag nanoparticles on the ZnO surface. The XRD, UV‐Vis, SEM‐EDX and TEM analyses were performed to ensure the formation of AgNP@ZnO architecture. TEM analysis confirmed that the 4–20 nm sized Ag nanoparticles were anchored evenly on the surface of ZnO with 16–78 nm in size. The antimicrobial study showed the superior performance of AgNP@ZnO functional nanoparticles than the pristine ZnO against pathogenic bacteria Staphylococcus aureus (gram‐positive) and Escherichia coli (gram‐negative). Hence, AgNP@ZnO functional particles were effectively explored as antimicrobial reinforcement for fabricating composite films using polylactic acid (PLA) as a matrix. The obtained nanocomposite films showed excellent antibacterial activity, which increases with increasing AgNP@ZnO loading.

A Study on Prediction of Size and Morphology of Ag Nanoparticles Using Machine Learning Models for Biomedical Applications

The synthesis of silver nanoparticles (AgNPs) holds significant promise for various applications in fields ranging from medicine to electronics. Accurately predicting the particle size during synthesis is crucial for optimizing the properties and performance of these nanoparticles. In this study, we compare the efficacy of tree-based models compared with the existing models, for predicting the particle size in silver nanoparticle synthesis. The study investigates the influence of input features, such as reaction parameters, precursor concentrations, etc., on the predictive performance of each model type. Overall, this study contributes to the understanding of modeling techniques for nanoparticle synthesis and underscores the importance of selecting appropriate methodologies for accurate particle size prediction, thereby facilitating the optimization of synthesis processes and enhancing the effectiveness of silver nanoparticle-based applications.

Quartz fiber supported Ag nano-islands as flexible SERS substrate with stable distributed “hot-spot” in rapid detection of pesticide residue

Island-shaped Ag nanoparticles are prepared under the support platform of quartz fabric by a simple chemical deposition method. The prepared flexible SERS substrate in this study demonstrates highly sensitive, excellent signal reproducibility and stability. The enhancement ability can be adjusted by varying concentration of Ag+ during synthesizing process, which would lead to the variation of size and gaps of Ag nanoparticles, thus affecting the LSPR effect. Moreover, the prepared SERS substrate shows great practical potential in rapid detection of contaminated fruit with different sampling method.

Insights into support effects of Ag/SiO2 catalysts for dimethyl glycolate semi-hydrogenation to methyl glycolate

Support materials play vital roles in heterogenous catalysis via the so-called support effects, and understanding on the support effects is beneficial for the design of high-performance catalysts. Herein, we represent detailed investigations on the support effects of Ag catalysts for dimethyl glycolate (DMO) semi-hydrogenation to methyl glycolate (MG), where G6 silica with amorphous mesopores, SBA-15 with parallel mesopores and silica nanospheres (MSNS) with center-radial ones were employed as the supports. The hydrogenation activity decreases in the order of Ag/MSNS > Ag/SBA-15 > Ag/G6 while the MG selectivity in the order of Ag/G6 > Ag/MSNS > Ag/SBA-15 at the same reaction conditions, indicating remarkable support effects on both activity and selectivity. Structural characterizations, temperature programmed experiments and in-situ FTIR of DMO adsorption experiments demonstrate that the weak confinement effect of G6 leads to the larger sized Ag nanoparticles and weakened activation of DMO and H2, which contributes to low hydrogenation activity. In contrast, the ordered mesoporous SBA-15 and MSNS deliver well confinement effects for Ag nanoparticles and the activation of DMO and H2, but the distinct pore structures result in different activation and diffusion behaviors. Finally, DMO conversion and MG yield are well correlated with the competitive adsorption of H2 versus DMO on Ag catalysts, indicating such competitivity as a descriptor for DMO semi-hydrogenation over Ag catalysts.

Portable and highly enhanced surface enhanced Raman scattering and photocatalytic activity of cost-effective hierarchical hollow metal organic frameworks heterostructures induced by etched titanium sheet

In order to effectively detect and remove organic toxics in wastewater, the facile construction of plug and play bifunctional materials is very vital. Herein, a kind of metal-organic frameworks (MIL-53 (Fe) with hollow tubular structure was induced by an etched Ti sheet (ET), and then small sized Ag nanoparticles (Ag NPs) were in-situ anchored evenly on the internal and external surfaces of MIL-53 (Fe). Subsequently, a new type of bifunctional material (ETMA) was assembled. Surface enhanced Raman scattering (SERS) and photocatalytic activity of the material were investigated with crystal violet (CV, a carcinogenic and teratogenic toxic) as an analyte. The results found that trace amount of CV (1 × 10−12 M) can still be sensitively detected by the fabricated ETMA, and analysis enhancement factors as high as 6.9 × 105 even though only 1.39 wt % Ag was contained in the ETMA. Moreover, nearly 100 % of CV can be rapidly degraded by the ETMA after irradiated for 15 min, which was 44.47 times and 7.27 times faster than those of ET-Ag (ETA) and ET-MIL-53 (Fe) (ETM), respectively. Additionally, the removal efficiency of total organic carbon (TOC) was as high as 75.44 %. The remarkable enrichment effect, the strong interaction among components, and the synergistic effect in the target ETMA material were responsible to the dramatically enhanced SERS and photocatalytic performances. In addition, the cost-effective ETMA exhibited excellent uniformity, repeatability, stability, and recyclability towards the detection and removal of CV in actual water samples, showing great potentials in monitoring and removing organic pollutants in practical ecological environment.

Colour-Passive radiative cooling in optoelectronics with Silver/Quantum dot decorated silica multifunctional hybrid structures

The integration of solar cells into the architectural design is hindered by challenges such as passive cooling and colouration appeal. The present study proposes an approach to overcome these obstacles by developing colourful solar cells that maintain optimal performance while addressing limitations related to heat accumulation from plasmon metal nanoparticles and quantum dots (QDs). To attain this, silver/silica microsphere composites combined with CdSe/ZnS core/shell QDs are fabricated with two distinct sizes of Ag nanoparticles embedded around SiO2 microspheres. Upon coating CIGS cells with this hybrid structure, a visually striking vivid green colouration is observed, while ensuring performance efficiency. Furthermore, the radiative cooling capability of these cells is evaluated through indoor and outdoor experiments. Significantly, a substantial temperature reduction of up to 3.2 °C in CIGS cells is achieved when the hybrid structures were applied to the cell's surface under high solar irradiance. The study represents a significant contribution to innovative strategies targeted at achieving passive cooling effect and enhancing aesthetic integration in building-integrated photovoltaics applications.

Edge-site selective decoration of silver nanoparticles on TiO2 nanosheets for the rapid catalytic reduction of nitroarenes

In this study, we aim to construct an edge-site selective deposition of silver nanoparticles on TiO2 nanosheets (Ag-TiO2NSs) for the catalytic reduction of toxic nitroarenes (NAs) using NaBH4 medium. The as-prepared Ag-TiO2NSs were characterized by various analytical techniques such as XRD, HR-TEM, SEM-EDAX, elemental mapping and XPS analyses. The HR-TEM images confirmed that the Ag nanoparticles (AgNPs) size of around 3.05 ± 0.5 nm in diameter exhibited the selective growth specifically on the edges of the TiO2NSs. Additionally, it was observed that the TiO2NSs exhibited a high exposure of (101) facets. The prepared Ag-TiO2NSs catalyst exhibited remarkably high catalytic activity in the reduction of 4-nitrophenol (4-NP) (∼6 min, Kapp: 9.2 × 10−3 s−1 and TOF: 1.13 × 10−6 mol mg−1 min−1), which was comparable to or surpassing the catalytic performance of most of the previously reported Ag-based catalysts. Moreover, the catalyst showed an excellent catalytic reduction ability of other NAs such as 4-nitroaniline (4-NA) (∼10 min, 2.8 × 10−3 s−1), 4-(4-nitrophenyl)morpholine (4-NM) (∼8 min, 6.0 × 10−3 s−1), and 4-(2-fluoro-4-nitrophenyl)morpholine (4-FNM) (∼11 min, 4.2 × 10−3 s−1). In addition, the Ag-TiO2NSs exhibited commendable recyclability, with a minimal decrease in the activity over four consecutive recycling operations. The exceptional catalytic performance could be attributed to the smaller size of the AgNPs along with the synergistic effect between AgNPs and their interfacial contact with the (101) facet exposure of TiO2NSs. The Ag-TiO2NSs catalyst demonstrated the potential application for the catalytic reduction of 4-NP in a fixed bed reactor, operating under mild reaction conditions.

Ultrasound-Driven Deposition of Au and Ag Nanoparticles on Citrus Pectin: Preparation and Characterisation of Antimicrobial Composites.

Pectin is a renewable, non-toxic and biodegradable polymer made of galacturonic acid units. Its polar groups make it suitable for complexing and supporting metallic nanoparticles (NPs). This work aimed to produce antibacterial nanocomposites using pectin and acoustic cavitation. The metal NPs (Au or Ag) were deposited using ultrasound (US, 21 kHz, 50 W) and compared with those achieved with mechanical stirring. The impact of the reducing agents (NaBH4, ascorbic acid) on the dispersion and morphology of the resulting NPs was also assessed. Characterization by diffuse reflectance (DR) UV-Vis-NIR spectroscopy and field emission scanning electron microscopy (FESEM) showed that the use of US improves the dispersion and decreases the size of both Au and Ag NPs. Moreover, with Au NPs, avoiding external reductants led to smaller NPs and more uniform in size. The prepared NPs were functionalized with oxytetracycline in water and tested against Escherichia coli (gram negative) and Staphylococcus epidermidis (gram positive) via the Kirby-Bauer test. The results show a better antibacterial activity of the functionalized nanoparticles compared to antibiotic-free NPs and pure oxytetracycline, advising the potential of the nanoparticles as drug carriers. These findings underscore the significance of US-assisted synthesis, paving the way to new environmentally friendly antimicrobial materials.

Enhanced control over size, areal density, and shape of substrate-supported Au and Ag nanoparticles by solid-state dewetting and alloying

The ability to manipulate the dimensions, areal density, and form of substrate-supported Au and Ag nanoparticles (NPs) is highly desirable for utilizing their plasmonic properties in biosensing, photovoltaics, and nanophotonic applications. The transformation of thin films into the substrate-supported nanostructures by solid-state dewetting (SSD), provides an avenue to manipulate the dimensional aspects of nanostructures simply and cost-effectively on a large scale. However, spontaneous agglomeration of the film produces randomly distributed and non-uniform nanostructures that must be controlled. Here, we have systematically studied the effect of annealing temperature, between 200 °C and 750 °C, on the dewetting morphology evolution of Au, Ag, and Au–Ag bilayer ultrathin films sputter deposited on the c-plane (0001) sapphire substrates. Regardless of the film thickness, Ag films dewet faster than Au films and produce spherical NPs, compared to faceted Au NPs, with broader size distribution. Whereas, by the SSD of Au–Ag bilayer ultrathin films, highly spherical and monodisperse AuAg bimetallic NPs can be fabricated. Furthermore, we have shown the possibility of fabricating the AuAg bimetallic NPs of varying compositions by adjusting the thickness of individual layers, thus enabling us to smoothly tune the spectral location of plasmonic resonance within the visible range.