Fabrication of Au-Ag Bimetallic Nanoparticles Using Pulsed Laser Ablation for Medical Applications: A Review.

In recent years, the synthesis of Au-Ag bimetallic nanoparticles has garnered immense attention due to their potential applications in diverse fields, particularly in the realm of medicine and healthcare. The development of efficient synthesis methods is crucial in harnessing their unique properties for medical applications. Among the synthesis methods, pulsed laser ablation in a liquid environment has emerged as a robust and versatile method for precisely tailoring the synthesis of bimetallic nanoparticles. This manuscript provides an overview of the fundamentals of the pulsed laser ablation in a liquid method, elucidating the critical factors involved. It comprehensively explores the pivotal factors influencing Au-Ag bimetallic nanoparticle synthesis, delving into the material composition, laser parameters, and environmental conditions. Furthermore, this review highlights the promising strides made in antibacterial, photothermal, and diagnostic applications. Despite the remarkable progress, the manuscript also outlines the existing limitations and challenges in this advanced synthesis technique. By providing a thorough examination of the current state of research, this review aims to pave the way for future innovations in the field, driving the development of novel, safe, and effective medical technologies based on Au-Ag bimetallic nanoparticles.

A comparative study on the influence of single and combined ultrasounds assisted flake graphite flotation.

Ultrasound has emerged as a promising technique for improving the mineral flotation performance. However, limited research exists regarding the influence of different ultrasound types on the flotation process. Specifically, the impact of combined ultrasound and the comparison of horn- and bath-type ultrasounds on flotation have not been fully investigated. To address this knowledge gap, a comprehensive study to explore the effects of different ultrasonic pretreatments on the flotation of flake graphite was conducted. A Box-Behnken design is employed to analyze the effects of combined ultrasound on graphite flotation. By characterizing the properties of graphite samples before and after the ultrasonic treatment, the aim is to elucidate the mechanism underlying the impact of ultrasound on graphite flotation. The experimental results indicated that the ultrasonic cavitation intensity exerted a significant influence on the graphite flotation recovery. Both horn- and bath- type ultrasounds contributed to flotation, but horn-type ultrasound demonstrated a more pronounced effect, leading to a 7% increase in flotation recovery, whereas bath-type ultrasound resulted in only a 2% increase. Furthermore, the cavitation intensity of combined ultrasound was found to be higher than that of single-frequency ultrasound in the same duration. However, the performance of graphite flotation was better with short duration combined ultrasound pretreatment, while the opposite trend was observed for a long duration ultrasound pretreatment. These findings may inform the development of more efficient and effective ultrasonic pretreatments for flotation separation processes.

Carbon dots-based fluorescence enhanced probe for the determination of glucose.

In this work, a novel "turn-on" fluorescence sensor for the detection of H2O2 and glucose was developed based on green fluorescent carbon dots (CDs). The CDs was newly prepared by a facile one-pot hydrothermal method with Eosin Y and branched polyethylenimine as precursors. Interestingly, in the presence of H2O2 and HRP, the fluorescence of the CDs enhanced significantly with a red-shift emission due to their "aggregation". Meanwhile, the oxidation of glucose catalyzed by glucose oxidase could generate H2O2. Thus, a simple sensing system based on the CDs as fluorescent probes was constructed for H2O2 and glucose determination, avoiding the fluorescence quenching and subsequent recovery process in conventional turn-on strategy. The method showed good selectivity and sensitivity for glucose sensing with the detection limit of 0.12 µM. The method was further applied to glucose detection in real samples. The obtained results demonstrated the simplicity, selectivity and practicality of the method. This work expands the carbon nanomaterials with fluorescence emission enhancement properties. It provides a new and direct "turn-on" strategy for H2O2 and glucose detection, which could be a simple and effective tool for screening biological substances involved in H2O2-generation reaction.

Fabrication and Characterization of Au-Decorated MCM-41 Mesoporous Spheres Using Laser-Ablation Technique.

This study reports the synthesis of Au-decorated MCM-41 mesoporous nanoparticles using a laser-ablation technique. It was observed that the number of Au attached to MCM-41 nanostructures was dependent on the amount of encapsulated Cationic surfactant (cetyl ammonium bromide (CTAB) volume. The chemical group of the prepared nanoparticles was analyzed by FT-IR spectroscopy, where different absorption peaks corresponding to Au and MCM-41 were observed. The observed band region was ∼1090, 966, 801, 2918, and 1847 cm-1 for different samples, clearly confirming the successful preparation of MCM-41 with CTAB and Au-decorated MCM-41 nanoparticles using environmentally friendly laser-ablation approach. The surface morphology of the prepared nanoparticles were performed using TEM techniques. The TEM analysis of the MCM-41 specimen showed silica spheres with an average size of around 200 nm. Furthermore, Raman spectroscopy was done to evaluate the chemical structure of the prepared nanoparticles. It was seen that the prepared Au NPs decorated the MCM-41 system facilitated strong Raman peaks of CTAB. In addition, eight distinct Raman peaks were observed in the presence of Au NPs. This new functionalized method using the laser-ablation approach for mesoporous nanoparticles will participate effectively in multiple applications, especially the encapsulated molecule sensing and detection.

Wettability of Nanostructured Transition-Metal Oxide (Al2O3, CeO2, and AlCeO3) Powder Surfaces.

Wettability has been the focal point of many studies in metal oxide materials due to their applications in water-gas shift reactions, organic reactions, thermochemical water splitting, and photocatalysis. This paper presents the results of systematic experimental studies on the wettability of surfaces of nanostructured transition-metal oxides (TMOs) (Al2O3, CeO2, and AlCeO3). The wettability of nanoparticles was investigated by measuring contact angles of different concentrations of water-based nanofluids (0.05-0.1 wt%) on the glass slide. The morphology, the heterostructure, and the nature of incorporated nanoparticles were confirmed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Characteristic diffraction patterns of the nanomaterials were evaluated using energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) techniques. The contact angles of water-Al2O3, water-CeO2, and water-AlCeO3 were measured as 77.5 ± 5°, 89.8 ± 4°, and 69.2 ± 1°, respectively. This study suggests that AlCeO3 is strongly water-wet (hydrophilic), while CeO2 is weakly water-wet (hydrophobic). It further demonstrated that the sizes and compositions of the nanoparticles are key parameters that influence their wetting behaviors.

Exploring the Relationships between Gas Dispersion Parameters and Differential Pressure Fluctuations in a Column Flotation.

Flotation separation, which is the most important mineral beneficiation technique, is dependent on gas dispersion (hydrodynamic conditions). Thus, many investigations have focused on the precise determination of hydrodynamic conditions such as Reynolds number of the bubbles, bubble velocity, and bubble diameter. However, few studies have examined their relationships with pressure fluctuations in a column flotation. This study introduced the differential pressure fluctuations as an actual variable that could be considered to determine the collection zone's hydrodynamic conditions in a cyclonic microbubble flotation column. In general, the outcomes indicated that superficial gas velocity had the most substantial relationship with the differential pressure fluctuations among other flotation factors (such as pump speed, superficial gas velocity, superficial water velocity, and frother dosage). Furthermore, a high coefficient of determination (R 2 > 0.77) for the equation generated to assess the relationships demonstrated that differential pressure fluctuations could be used as a promising tool to determine the hydrodynamic parameters' characteristics in the flotation columns.

The effect of ultrasound on bulk and surface nanobubbles: A review of the current status.

The generation, and stability of nanobubbles are of particular interest for fundamental research and have potential application in numerous fields. Several attempts were made in the literature to produce nanobubbles through acoustic cavitation. However, the generation and stability mechanisms of nanobubbles in the acoustic field are unclear. Here, we review the effect of ultrasound parameters on bulk nanobubbles and surface nanobubbles. On this basis, we discuss the proposed generation and stability mechanisms of nanobubbles from the perspective of transient and stable acoustic cavitation. Moreover, we propose some future research directions for a deeper understanding of the role of ultrasound in the generation and stability of nanobubbles.

Synthesis of Electrospun TiO2 Nanofibers and Characterization of Their Antibacterial and Antibiofilm Potential against Gram-Positive and Gram-Negative Bacteria.

Recently, titanium dioxide (TiO2) nanomaterials have gained increased attention because of their cost-effective, safe, stable, non-toxic, non-carcinogenic, photocatalytic, bactericidal, biomedical, industrial and waste-water treatment applications. The aim of the present work is the synthesis of electrospun TiO2 nanofibers (NFs) in the presence of different amounts of air-argon mixtures using sol-gel and electrospinning approaches. The physicochemical properties of the synthesized NFs were examined by scanning and transmission electron microscopies (SEM and TEM) coupled with energy-dispersive X-ray spectroscopy (EDX), ultraviolet-visible spectroscopy and thermogravimetric analyzer (TGA). The antibacterial and antibiofilm activity of synthesized NFs against Gram-negative Pseudomonas aeruginosa and Gram-positive methicillin-resistant Staphylococcusaureus (MRSA) was investigated by determining their minimum bacteriostatic and bactericidal values. The topological and morphological alteration caused by TiO2 NFs in bacterial cells was further analyzed by SEM. TiO2 NFs that were calcined in a 25% air-75% argon mixture showed maximum antibacterial and antibiofilm activities. The minimum inhibitory concentration (MIC)/minimum bactericidal concentration (MBC) value of TiO2 NFs against P. aeruginosa was 3 and 6 mg/mL and that for MRSA was 6 and 12 mg/mL, respectively. The MIC/MBC and SEM results show that TiO2 NFs were more active against Gram-negative P. aeruginosa cells than Gram-positive S. aureus. The inhibition of biofilm formation by TiO2 NFs was investigated quantitatively by tissue culture plate method using crystal violet assay and it was found that TiO2 NFs inhibited biofilm formation by MRSA and P. aeruginosa in a dose-dependent manner. TiO2 NFs calcined in a 25% air-75% argon mixture exhibited maximum biofilm formation inhibition of 75.2% for MRSA and 72.3% for P. aeruginosa at 2 mg/mL, respectively. The antibacterial and antibiofilm results suggest that TiO2 NFs can be used to coat various inanimate objects, in food packaging and in waste-water treatment and purification to prevent bacterial growth and biofilm formation.

Does gas supersaturation by a chemical reaction produce bulk nanobubbles?

HYPOTHESIS: Supersaturation of dissolved gas is the most commonly reported method for generating long-lived bulk nanobubbles. However, these reports are treated with skepticism because of the lack of techniques that directly show that these particles are gas filled bubbles. Therefore, this work has tested the hypothesis that supersaturation obtained by a chemical reaction produces long-lived nanosized bubbles in bulk using an established protocol that relies on evaluating the density of nanoparticles and measuring their response to external pressure. EXPERIMENTS: Nanoparticles were generated using a chemical reaction between aqueous solutions of ammonium chloride and sodium nitrite. Standard nanoparticle sizing techniques, such as nanoparticle tracking analysis and dynamic light scattering, were utilized to determine the size and stability of the nanoparticles. Resonant mass measurement was used to measure the buoyant mass of the nanoparticles, and their compressibility was investigated by measuring their size under the application of external pressure. FINDINGS: The formation of nanoparticles was consistent with the kinetics of nitrogen gas evolution produced in the reaction, where the nanoparticle size was shown to be dependent on the pH and concentration of the reactants. However, the chemical reaction was found to generate incompressible nanoparticles with a density larger than that of the solvent, confirming that these particles were not gas-filled bubbles.

Generation of nanoparticles upon mixing ethanol and water; Nanobubbles or Not?

HYPOTHESIS: The debate as to whether nanoparticles that are formed upon mixing ethanol and water are nanobubbles or other nanoparticles has continued over the past decade. In this work, we test the hypothesis that long lived bulk nanobubbles are produced upon mixing ethanol and water, using techniques that probe the density and the pressure response of the nanoparticles. EXPERIMENTS: Nanoparticles were generated spontaneously upon mixing high-purity ethanol and high-purity water. The size distribution of these nanoparticles was obtained using nanoparticle tracking analysis. The mean density of the nanoparticles was determined using resonant mass measurement, and the response of the nanoparticles to the application of external pressure was measured using dynamic light scattering. FINDINGS: The ethanol-water mixture was found to produce only positively buoyant particles, with a mean density of 0.91 ±â€¯0.01 g/cm3, and the external pressure had only a minimal effect on the size of these nanoparticles. Degassing the solvents before mixing led to a significant reduction in the number of nanoparticles produced. Allowing the solutions to re-gas restored their ability to produce nanoparticles. These experiments reveal that ethanol-water mixing produces nanoparticles that result from the accumulation of material at the interface of dissolving bubbles.

Armoured nanobubbles; ultrasound contrast agents under pressure.

HYPOTHESIS: Robust methods for differentiating long-lived nanobubbles from other nanoparticles are required. Evaluation of the density and compressibility of nanoparticles should enable nanobubbles to be differentiated from other nanoparticles, although the response of nanobubbles to pressure can be strongly influenced by a coating of insoluble surfactant. Here we evaluate the response of nanobubbles armoured with a coating of insoluble surfactants in order to determine if they can be differentiated from other nanoparticles. EXPERIMENTS: Dynamic light scattering was used to size candidate nanoparticles under the influence of external pressure and resonant mass measurements were employed to assess the density of candidate nanoparticles. FINDINGS: The resonant mass measurement revealed a significant population of lipid-coated gas nanobubbles. These nanobubbles are proven to be gas entities, by their response to application of pressure. The pressure at which the gas within the nanobubbles condenses is shifted to higher pressure due to the mechanical resistance of the lipid shell, which shields the bubble contents from up to ∼0.8 atm. of the external pressure The presence of lipids of low solubility at the nanobubble-solution interface effectively results in a negative Laplace pressure, which stabilizes these nanobubbles against dissolution.

A History of Nanobubbles.

We follow the history of nanobubbles from the earliest experiments pointing to their existence to recent years. We cover the effect of Laplace pressure on the thermodynamic stability of nanobubbles and why this implies that nanobubbles are thermodynamically never stable. Therefore, understanding bubble stability becomes a consideration of the rate of bubble dissolution, so the dominant approach to understanding this is discussed. Bulk nanobubbles (or fine bubbles) are treated separately from surface nanobubbles as this reflects their separate histories. For each class of nanobubbles, we look at the early evidence for their existence, methods for the production and characterization of nanobubbles, evidence that they are indeed gaseous, or otherwise, and theories for their stability. We also look at applications of both surface and bulk nanobubbles.

Cleaning with Bulk Nanobubbles.

The electrolysis of aqueous solutions produces solutions that are supersaturated in oxygen and hydrogen gas. This results in the formation of gas bubbles, including nanobubbles ∼100 nm in size that are stable for ∼24 h. These aqueous solutions containing bubbles have been evaluated for cleaning efficacy in the removal of model contaminants bovine serum albumin and lysozyme from surfaces and in the prevention of the fouling of surfaces by these same proteins. Hydrophilic and hydrophobic surfaces were investigated. It is shown that nanobubbles can prevent the fouling of surfaces and that they can also clean already fouled surfaces. It is also argued that in practical applications where cleaning is carried out rapidly using a high degree of mechanical agitation the role of cleaning agents is not primarily in assisting the removal of soil but in suspending the soil that is removed by mechanical action and preventing it from redepositing onto surfaces. This may also be the primary mode of action of nanobubbles during cleaning.