A green process for preparing silver nanoparticles using spinning disk reactor

Nano guardians of the heart: A comprehensive investigation into the impact of silver nanoparticles on cardiovascular physiology

Globally, cardiovascular diseases (CVDs) constitute the leading cause of death at the moment. More effective treatments to combat CVDs are urgently required. Recent advances in nanotechnology have opened the door to new avenues for cardiovascular health treatment. Silver nanotechnology's inherent therapeutic powers and wide-ranging applications have made it the center of focus in recent years. This review aims to analyze the chemical, physical, and biological processes ofproducing AgNPs and determine their potential utility as theranostics. Despite significant advances, the precise mechanism by which AgNPs function in numerous biological systems remains a mystery. We hope that at the end of this review, you will better understand how AgNPs affect the cardiovascular system from the research done thus far. This endeavor thoroughly investigates the possible toxicological effects and risks associated with exposure to AgNPs. The findings shed light on novel applications of these versatile nanomaterials and point the way toward future research directions. Due to a shortage of relevant research, we will limit our attention to AgNPs as they pertain to CVDs. Future research can use this opportunity to investigate the many medical uses of AgNPs. Given their global prevalence, we fully endorse academics' efforts to prioritize nanotechnological techniques in pursuing risk factor targeting for cardiovascular diseases. The critical need for innovative solutions to this widespread health problem is underscored by the fact that this technique may help with the early diagnosis and treatment of CVDs.

Recent advances of Au@Ag core-shell SERS-based biosensors

The methodological advancements in surface-enhanced Raman scattering (SERS) technique with nanoscale materials based on noble metals, Au, Ag, and their bimetallic alloy Au-Ag, has enabled the highly efficient sensing of chemical and biological molecules at very low concentration values. By employing the innovative various type of Au, Ag nanoparticles and especially, high efficiency Au@Ag alloy nanomaterials as substrate in SERS based biosensors have revolutionized the detection of biological components including; proteins, antigens antibodies complex, circulating tumor cells, DNA, and RNA (miRNA), etc. This review is about SERS-based Au/Ag bimetallic biosensors and their Raman enhanced activity by focusing on different factors related to them. The emphasis of this research is to describe the recent developments in this field and conceptual advancements behind them. Furthermore, in this article we apex the understanding of impact by variation in basic features like effects of size, shape varying lengths, thickness of core-shell and their influence of large-scale magnitude and morphology. Moreover, the detailed information about recent biological applications based on these core-shell noble metals, importantly detection of receptor binding domain (RBD) protein of COVID-19 is provided.

Green synthesis of silver nanoparticles and their antibacterial effects

Antibacterial resistance is by far one of the greatest challenges to global health. Many pharmaceutical or material strategies have been explored to overcome this dilemma. Of these, silver nanoparticles (AgNPs) are known to have a non-specific antibacterial mechanism that renders it difficult to engender silver-resistant bacteria, enabling them to be more powerful antibacterial agents than conventional antibiotics. AgNPs have shown promising antibacterial effects in both Gram-positive and Gram-negative bacteria. The aim of this review is to summarize the green synthesis of AgNPs as antibacterial agents, while other AgNPs-related insights (e.g., antibacterial mechanisms, potential toxicity, and medical applications) are also reviewed.

Recent Advances in the Preparation of Barium Sulfate Nanoparticles: A Mini-Review

The potential for barium sulphate nanoparticles to be used in a variety of important fields has sparked a lot of attention. Methods for obtaining this material by milling (top-down approach) are not very popular due to the difficulty of controlling the size and shape of particles, as well as changes in their physicochemical properties during milling. More promising is the bottom-up approach, which is the interaction of Ba2+ and SO42− ions in a liquid environment. Direct precipitation is the simplest method; however, it does not allow control of the particle size. Microemulsions, microreactors membrane dispersion, as well as spinning disc reactors are used to overcome drawbacks of direct precipitation and allow control of particle size and shape. This is ensured mainly by intensive controlled micromixing of the precursors with concentrations close to saturated ones. The present review focuses on recent advances in the production of barium sulfate nanoparticles using various approaches, as well as their advantages and limitations. The issues of scaling up the techniques are also considered, and promising methods for obtaining BaSO4 nanoparticles are also discussed.

Empirical Modelling of Hydrodynamic Effects on Starch Nanoparticles Precipitation in a Spinning Disc Reactor

Empirical correlations have been developed to relate experimentally determined starch nanoparticle size obtained in a solvent–antisolvent precipitation process with key hydrodynamic parameters of a spinning disc reactor (SDR). Three different combinations of dimensionless groups including a conventional Reynolds number (Re), rotational Reynolds number (Re_ω) and Rossby number (Ro) have been applied in individual models for two disc surfaces (smooth and grooved) to represent operating variables affecting film flow such as liquid flowrate and disc rotational speed, whilst initial supersaturation (S) has been included to represent varying antisolvent concentrations. Model 1 featuring a combination of Re, Re_ω and S shows good agreement with the experimental data for both the grooved and smooth discs. For the grooved disc, Re has a greater impact on particle size, whereas Re_ω is more influential on the smooth disc surface, the difference likely being due to the passive mixing induced by the grooves irrespective of the magnitude of the disc speed. Supersaturation has little impact on particle size within the limited initial supersaturation range studied. Model 2 which characterises both flow rate and disc rotational speed through Ro alone and combined with Re was less accurate in predicting particle size due to several inherent limitations.

Colorimetric Detection Based on Localized Surface Plasmon Resonance Optical Characteristics for Sensing of Mercury Using Green-Synthesized Silver Nanoparticles

Development of selective colorimetric detectors that can use green-fabricated silver nanoparticles' (AgNPs) with localized surface plasmon resonances (LSPRs) to rapidly, simply, and selectively detect Hg(II) ions was undertaken in this study. Onion extract was used for synthesising photo-induced green crystalline silver nanoparticles (NPs). The formation of nanoparticles is enhanced when ultrasound irradiation is present; bioligands could serve as stabilizing and reducing agents. Different methods of measurement, including UV-Vis, TEM, SEM/EDAX, FT - IR, and XRD, are effective for characterization of nanoparticles. The spherical nature of green-fabricated AgNPs is confirmed by TEM. High-density, spherical, and uniformly formed silver nanoparticle shapes were found in silver nanoparticle SEM images. The arrangement of AgNPs in the form of face-centered cubic structures was confirmed by XRD patterns. The formation of impurity-free AgNPs was confirmed using the EDAX analysis results. Hg2+ with excellent sensitivity was sensitively and selectively detected by employing green-synthesized silver nanoparticles. The reduction of Ag (1) to Ag (0) was confirmed by a slight increase in Hg (II) concentration and progressive reduction of green-synthesized AgNPs, whose absorbance changed abruptly. The reduction of LSPRs by the phosphate buffer medium enables AgNPs to sensitively and selectively detect Hg2+ ions by providing good environment. Besides, a selective, sensitive, simple, and rapid method that is proposed for detecting Hg (II) ions in samples of water is presented in the study. Harmful mercury ions in real samples of water (tap and ground water) can colorimetrically and selectively be detected using the AgNPs. The results showed an RSD of below 6% and over 92% of good recovery.

Synthesis of silver nanoparticles using oxidized amylose and combination with curcumin for enhanced antibacterial activity

Many kinds of multi-drug-resistant microorganisms have appeared. Moreover, monotherapy is increasingly no longer adequate for many complicated bacterial infections. Therefore, development of efficient combination antibacterial agent is becoming crucial. Herein, we present a hybrid antibacterial agent with enhanced antibacterial activity and high aqueous dissolubility based on silver nanoparticles and curcumin. The silver nanoparticles were firstly synthesized using oxidized amylose as an environmentally friendly reducing agent and stabilizer. Then, curcumin was added into the above mixture to get the hybrid antibacterial agent. The hybrid antibacterial agent presented high dissolubility in aqueous solution and enhanced antibacterial activity. In addition, the hybrid antibacterial agent presented good antioxidant activity and cell compatibility. Overall, the developed hybrid antibacterial agent has a potential to combat multiple bacteria-induced infections of wound surfaces.

Tailoring Cu Nanoparticle Catalyst for Methanol Synthesis Using the Spinning Disk Reactor

Cu nanoparticles are known to be very active for methanol (MeOH) synthesis at relatively low temperatures, such that smaller particle sizes yield better MeOH productivity. We aimed to control Cu nanoparticle (NP) size and size distribution for catalysing MeOH synthesis, by using the spinning disk reactor. The spinning disk reactor (SDR), which operates based on shear effect and plug flow in thin films, can be used to rapidly micro-mix reactants in order to control nucleation and particle growth for uniform particle size distribution. This could be achieved by varying both physical and chemical operation conditions in a precipitation reaction on the SDR. We have used the SDR for a Cu borohydride reduction to vary Cu NP size from 3 nm to about 55 nm. XRD and TEM characterization confirmed the presence of Cu₂O and Cu crystallites when the samples were dried. This technique is readily scalable for Cu NP production by processing continuously over a longer duration than the small-scale tests. However, separation of the nanoparticles from solution posed a challenge as the suspension hardly settled. The Cu NPs produced were tested to be active catalyst for MeOH synthesis at low temperature and MeOH productivity increased with decreasing particle size.

Vortex Fluidic Chemical Transformations

Driving chemical transformations in dynamic thin films represents a rapidly thriving and diversifying research area. Dynamic thin films provide a number of benefits including large surface areas, high shearing rates, rapid heat and mass transfer, micromixing and fluidic pressure waves. Combinations of these effects provide an avant-garde style of conducting chemical reactions with surprising and unusual outcomes. The vortex fluidic device (VFD) has proved its capabilities in accelerating and increasing the efficiencies of numerous organic, materials and biochemical reactions. This Minireview surveys transformations that have benefited from VFD-mediated processing, and identifies concepts driving the effectiveness of vortex-based dynamic thin films.

Colorimetric Detection Based on Localised Surface Plasmon Resonance Optical Characteristics for the Detection of Hydrogen Peroxide Using Acacia Gum-Stabilised Silver Nanoparticles

The use of nanoparticles in sensing is attracting the interest of many researchers. The aim of this work was to fabricate Acacia gum–stabilised silver nanoparticles (SNPs) using green chemistry to use them as a highly sensitive and cost-effective localised surface plasmon resonance (LSPR) colorimeter sensor for the determination of reactive oxygen species, such as hydrogen peroxide (H₂O₂). Silver nanoparticles were fabricated by the reduction of an inorganic precursor silver nitrate solution (AgNO₃) using white sugar as the reducing reagent and Acacia gum as the stabilising reagent and a sonication bath to form uniform silver nanoparticles. The fabricated nanoparticles were characterised by visual observation, ultraviolet-visible (UV-Vis) spectrophotometry, transmission electron microscopy (TEM) analysis, energy-dispersive X-ray spectroscopy (EDAX), thermogravimetric analysis (TGA), and Fourier transform infrared spectroscopy (FT-IR). The TEM micrographs of the synthesised nanoparticles showed the presence of spherical nanoparticles with sizes of approximately 10 nm. The EDAX spectrum result confirmed the presence of silver (58%), carbon (30%), and oxygen (12%). Plasmon colorimetric sensing of H₂O₂ solution was investigated by introducing H₂O₂ solution into Acacia gum–capped SNP dispersion, and the change in the LSPR band in the UV-Vis region of spectra was monitored. In this study, it was found that the yellow colour of Acacia gum–stabilised SNPs gradually changed to transparent, and moreover, a remarkable change in the LSPR absorbance strength was observed. The calibration curve was linear over 0.1–0.00001 M H₂O₂, with a correlation estimation (R²) of .953. This was due to the aggregation of SNPs following introduction of the H₂O₂ solution. Furthermore, the fabricated SNPs were successfully used to detect H₂O₂ solution in a liquid milk sample, thereby demonstrating the ability of the fabricated SNPs to detect H₂O₂ solution in liquid milk samples. This work showed that Acacia gum–stabilised SNPs may have the potential as a colour indicator in medical and environmental applications.

Mesquite Gum as a Novel Reducing and Stabilizing Agent for Modified Tollens Synthesis of Highly Concentrated Ag Nanoparticles

The synthesis that is described in this study is for the preparation of silver nanoparticles of sizes ranging from 10 nm to 30 nm with a defined shape (globular), confirmed by UV-vis, SEM, STEM and DLS analysis. This simple and favorable one-step modified Tollens reaction does not require any special equipment or other stabilizing or reducing agent except for a solution of purified mesquite gum, and it produces aqueous colloidal dispersions of silver nanoparticles with a stability thatexceeds three months, a relatively narrow size distribution, a low tendency to aggregate and a yield of at least 95% for all cases. Reaction times are between 15 min and 60 min to obtain silver nanoparticles in concentrations ranging from 0.1 g to 3 g of Ag per 100 g of reaction mixture. The proposed synthetic method presents a high potential for scale-up, since its production capacity is rather high and the methodology is simple.The synthesis that is described in this study is for the preparation of silver nanoparticles of sizes ranging from 10 nm to 30 nm with a defined shape (globular), confirmed by UV-vis, SEM, STEM and DLS analysis. This simple and favorable one-step modified Tollens reaction does not require any special equipment or other stabilizing or reducing agent except for a solution of purified mesquite gum, and it produces aqueous colloidal dispersions of silver nanoparticles with a stability thatexceeds three months, a relatively narrow size distribution, a low tendency to aggregate and a yield of at least 95% for all cases. Reaction times are between 15 min and 60 min to obtain silver nanoparticles in concentrations ranging from 0.1 g to 3 g of Ag per 100 g of reaction mixture. The proposed synthetic method presents a high potential for scale-up, since its production capacity is rather high and the methodology is simple.

Higee Technologies and Their Applications to Green Intensified Processing

Higee technologies which involve the application of high gravity fields, typically of the order of 100–1000 g, in order to intensify the fluid dynamics, mixing and heat/mass transfer in processing fluids, have long been considered promising candidates for achieving process intensification. This chapter explores the recent advancements in applying well known Higee technologies such as the spinning disc reactor (SDR) and rotating packed beds (RPB) as well as more recent versions of the latter such as the rotor–stator SDR (RSSDR) and the rotating zig-zag bed (RZB) for achieving green processing benefits. Examples of several industrially-relevant applications such as polymerisation, reactive-precipitation, catalytic and enzymatic transformations and CO2 sequestration amongst others are presented and discussed.

Green and energy-efficient methods for the production of metallic nanoparticles

In the last decade, researchers paid great attention to the concept of "Green Chemistry", which aims at development of efficient methods for the synthesis of nanoparticles (NPs) in terms of the least possible impact on human life and environment. Generally, several reagents including precursors, reducing agents, stabilizing agents and solvents are used for the production of NPs and in some cases, energy is needed to reach the optimum temperature for reduction. Therefore, to develop a green approach, researchers had the opportunity to investigate eco-friendly reagents and new energy transfer techniques. In order to substitute the harmful reagents with green ones, researchers worked on different types of saccharides, polyols, carboxylic acids, polyoxometalates and extracts of various plants that can play the role of reducers, stabilizers or solvents. Also, there are some reports on using ultraviolet (UV), gamma and microwave irradiation that are capable of reducing and provide uniform heating. According to the literature, it is possible to use green reagents and novel energy transfer techniques for production of NPs. However, these new synthesis routes should be optimized in terms of performance, cost, product quality (shape and size distribution) and scale-up capability. This paper presents a review on most of the employed green reagents and new energy transfer techniques for the production of metallic NPs.

Green synthesis of biogenic metal nanoparticles by terrestrial and aquatic phototrophic and heterotrophic eukaryotes and biocompatible agents

The size, shape and controlled dispersity of nanoparticles play a vital role in determining the physical, chemical, optical and electronic properties attributing its applications in environmental, biotechnological and biomedical fields. Various physical and chemical processes have been exploited in the synthesis of several inorganic metal nanoparticles by wet and dry approaches viz., ultraviolet irradiation, aerosol technologies, lithography, laser ablation, ultrasonic fields, and photochemical reduction techniques. However, these methodologies remain expensive and involve the use of hazardous chemicals. Therefore, there is a growing concern for the development of alternative environment friendly and sustainable methods. Increasing awareness towards green chemistry and biological processes has led to a necessity to develop simple, cost-effective and eco-friendly procedures. Phototrophic eukaryotes such as plants, algae, and diatoms and heterotrophic human cell lines and some biocompatible agents have been reported to synthesize greener nanoparticles like cobalt, copper, silver, gold, bimetallic alloys, silica, palladium, platinum, iridium, magnetite and quantum dots. Owing to the diversity and sustainability, the use of phototrophic and heterotrophic eukaryotes and biocompatible agents for the synthesis of nanomaterials is yet to be fully explored. This review describes the recent advancements in the green synthesis and applications of metal nanoparticles by plants, aquatic autotrophs, human cell lines, biocompatible agents and biomolecules.

Hybrid, silica-coated, Janus-like plasmonic-magnetic nanoparticles

Hybrid plasmonic-magnetic nanoparticles possess properties that are attractive in bioimaging, targeted drug delivery, in vivo diagnosis and therapy. The stability and toxicity, however, of such nanoparticles challenge their safe use today. Here, biocompatible, SiO₂-coated, Janus-like Ag/Fe₂O₃ nanoparticles are prepared by one-step, scalable flame aerosol technology. A nanothin SiO₂ shell around these multifunctional nanoparticles leaves intact their morphology, magnetic and plasmonic properties but minimizes the release of toxic Ag⁺ ions from the nanosilver surface and its direct contact with live cells. Furthermore, this silica shell hinders flocculation and allows for easy dispersion of such nanoparticles in aqueous and biological buffer (PBS) solutions without any extra functionalization step. As a result, these hybrid particles exhibited no cytotoxicity during bioimaging and remained stable in suspension with no signs of agglomeration and sedimentation or settling. Their performance as biomarkers was explored by selectively binding them with live tagged Raji and HeLa cells enabling their detection under dark-filed illumination. Therefore, these SiO₂-coated Ag/Fe₂O₃ nanoparticles do not exhibit the limiting physical properties of each individual component but retain their desired functionalities facilitating thus, the safe use of such hybrid nanoparticles in bio-applications.

Silver nanoparticles: green synthesis and their antimicrobial activities

This review presents an overview of silver nanoparticles (Ag NPs) preparation by green synthesis approaches that have advantages over conventional methods involving chemical agents associated with environmental toxicity. Green synthetic methods include mixed-valence polyoxometallates, polysaccharide, Tollens, irradiation, and biological. The mixed-valence polyoxometallates method was carried out in water, an environmentally-friendly solvent. Solutions of AgNO(3) containing glucose and starch in water gave starch-protected Ag NPs, which could be integrated into medical applications. Tollens process involves the reduction of Ag(NH(3))(2)(+) by saccharides forming Ag NP films with particle sizes from 50-200 nm, Ag hydrosols with particles in the order of 20-50 nm, and Ag colloid particles of different shapes. The reduction of Ag(NH(3))(2)(+) by HTAB (n-hexadecyltrimethylammonium bromide) gave Ag NPs of different morphologies: cubes, triangles, wires, and aligned wires. Ag NPs synthesis by irradiation of Ag(+) ions does not involve a reducing agent and is an appealing procedure. Eco-friendly bio-organisms in plant extracts contain proteins, which act as both reducing and capping agents forming stable and shape-controlled Ag NPs. The synthetic procedures of polymer-Ag and TiO(2)-Ag NPs are also given. Both Ag NPs and Ag NPs modified by surfactants or polymers showed high antimicrobial activity against gram-positive and gram-negative bacteria. The mechanism of the Ag NP bactericidal activity is discussed in terms of Ag NP interaction with the cell membranes of bacteria. Silver-containing filters are shown to have antibacterial properties in water and air purification. Finally, human and environmental implications of Ag NPs to the ecology of aquatic environment are briefly discussed.

Green Nanotechnology from Tea: Phytochemicals in Tea as Building Blocks for Production of Biocompatible Gold Nanoparticles

Phytochemicals occluded in tea have been extensively used as dietary supplements and as natural pharmaceuticals in the treatment of various diseases including human cancer. Results on the reduction capabilities of phytochemicals present in tea to reduce gold salts to the corresponding gold nanoparticles are presented in this paper. The phytochemicals present in tea serve the dual roles as effective reducing agents to reduce gold and also as stabilizers to provide robust coating on the gold nanoparticles in a single step. The Tea-generated gold nanoparticles (T-AuNPs), have demonstrated remarkable in vitro stability in various buffers including saline, histidine, HSA, and cysteine solutions. T-AuNPs with phytochemical coatings have shown significant affinity toward prostate (PC-3) and breast (MCF-7) cancer cells. Results on the cellular internalization of T-AuNPs through endocytosis into the PC-3 and MCF-7 cells are presented. The generation of T-AuNPs follows all principles of green chemistry and have been found to be non toxic as assessed through MTT assays. No 'man made' chemicals, other than gold salts, are used in this true biogenic green nanotechnological process thus paving excellent opportunities for their applications in molecular imaging and therapy.