Influence of the size and charge of nonstoichiometric silver sulfide nanoparticles on their interaction with blood cells

Silver sulfide (Ag₂S) nanoparticles synthesized using different precursors have been characterized by dynamic light scattering measurements and high-resolution transmission electron microscopy. In addition to Ag₂S nanoparticles, we have detected Ag₂S/Ag heterostructures. Using optical microscopy, we have examined interaction of the nanoparticles with red cells of peripheral blood. The results of the interaction have been shown to depend on the particle size and charge. A red cell solution containing large, negatively charged particles coagulated, whereas small, positively charged Ag₂S nanoparticles were concentrated around red cells.     

The preparation of silver sulfide nanoparticles in lamellar liquid crystal and application to lubrication

The silver sulfide (Ag₂S) nanoparticles were prepared by the reaction of AgNO₃ and Na₂S in the lamellar liquid crystal (LLC) formed by Triton X-100, n-C₁₀H₂₁OH and H₂O. The size of the particles is about 2-3 nm. The existence of Ag₂S nanoparticles can improve the lubrication of the lamellar liquid crystal.     

Room temperature synthesis and electrochemical application of imidazoline surfactant-modified Ag2S nanocrystals

Well-dispersed Ag₂S nanocrystals with size of about 20~30 nm were prepared in distilled water at room temperature with the assistance of imidazoline surfactant quaternary ammonium salt of 2-undecyl-1-dithioureido-ethyl-imidazoline (SUDEI) prepared in-house. The products were characterized by TEM, XRD, and FT-IR, respectively. The influence of SUDEI concentration on the dispersion of Ag₂S products was briefly discussed. Furthermore, the obtained Ag₂S nanocrystals product was applied into DNA hybridization analysis, and the results indicated that the detection limit of target ssDNA was up to pmol/L, showing that the DNA probe labeled with Ag₂S nanoparticles is of promising application value in electrochemical DNA detection analysis and biosensors.     

Synthesis of Ag2S and Ag2Se nanoparticles in self assembled block copolymer micelles and nano-arrays fabrication

This paper describes a simple approach based on self assembled polystyrene-block-poly(4-vinylpyridine) (PS-P4VP) copolymer micelles for the fabrication of ordered 2-dimesional nano-arrays of Ag₂S and Ag₂Se. The nanoparticles were synthesized directly inside the P4VP micelles core at room temperature and nano-arrays were obtained by spin coating on silicon wafer. High resolution-transmission electron microscopy and powder X-ray diffraction characterization suggests the nanoparticles are crystalline. Higher band gap energy (1.76 eV for Ag₂S and 1.35 eV for Ag₂Se) compared to their bulk materials obtained from the absorption studies reveals that the nanoparticles are within the quantum confinement regime.     

Silver sulfide nanoparticles with a carbon-containing shell

Silver sulfide nanoparticles have been synthesized through chemical deposition from aqueous solutions of silver nitrate and sodium sulfide in the presence of sodium citrate as a complexing agent and stabilizer. The nanoparticles have a Ag₂S core with a monoclinic crystal structure, covered with a carbon-containing citrate shell. Varying initial reactant concentrations, we can obtain core/shell nanoparticles with a tailored Ag₂S core size and carbon-containing shell thickness.     

Evaluation of the toxicities of silver and silver sulfide nanoparticles against Gram‐positive and Gram‐negative bacteria

In this study, the endogenous lipid signalling molecules, N ‐myristoylethanolamine, were explored as a capping agent to synthesise stable silver nanoparticles (AgNPs) and Ag sulphide NPs (Ag₂ S NPs). Sulphidation of the AgNPs abolishes the surface plasmon resonance (SPR) maximum of AgNPs at 415 nm with concomitant changes in the SPR, indicating the formation of Ag₂ S NPs. Transmission electron microscopy revealed that the AgNPs and Ag₂ S NPs are spherical in shape with a size of 5–30 and 8–30 nm, respectively. AgNPs and Ag₂ S NPs exhibit antimicrobial activity against Gram‐positive and Gram‐negative bacteria. The minimum inhibitory concentrations (MIC) of 25 and 50 μM for AgNPs and Ag₂ S NPs, respectively, were determined from resazurin microtitre plate assay. At or above MIC, both AgNPs and Ag₂ S NPs decrease the cell viability through the mechanism of membrane damage and generation of excess reactive oxygen species.Inspec keywords: cellular biophysics, biomembranes, transmission electron microscopy, nanomedicine, microorganisms, molecular biophysics, antibacterial activity, nanofabrication, silver, biomedical materials, surface plasmon resonance, nanoparticles, materials preparation, silver compounds, lipid bilayersOther keywords: Gram‐negative bacteria, Gram‐positive bacteria, endogenous lipid signalling molecules, N‐myristoylethanolamine, capping agent, silver nanoparticles, Ag sulphide NPs, sulphidation, surface plasmon resonance, concomitant changes, transmission electron microscopy, minimum inhibitory concentrations, resazurin microtitre plate assay, cell viability, membrane damage, reactive oxygen species, Ag toxicities, Ag, Ag₂ S     

Preparation of Z-scheme Au-Ag2S/Bi2O3 composite by selective deposition method and its improved photocatalytic degradation and reduction activity

In this work, Z-scheme Ag₂S/Bi₂O₃ composites were fabricated through the precipitation of Ag₂S nanoplates on the surface of Bi₂O₃ microrods. Consequently, Au nanoparticles were selectively deposited on the Ag₂S nanoplates surface to obtain.Au-Ag₂S/Bi₂O₃ composites using near-infrared light photodeposition method. The characterization results indicate that the Ag₂S nanoplates were uniformly anchored on Bi₂O₃ surface, and Au nanoparticles were highly dispersed on the surface of Ag₂S nanoplate instead of Bi₂O₃. Acid orange 7 (AO7), Rhodamine B (RhB) and Cr(VI) were chosen as model reactant for the evaluation of photocatalytic degradation and reduction activity of the products under simulated sunlight irradiation. After the decoration of Ag₂S nanoplates, the photocatalytic activity of Ag₂S/Bi₂O₃ is much higher than that of bare Bi₂O₃, and the optimal catalytic efficiency is achieved by 12 %Ag₂S/Bi₂O₃ sample. More importantly, the photocatalytic activity of 12 %Ag₂S/Bi₂O₃ sample can be further enhanced by the selective decoration Au nanoparticles on the Ag₂S nanoplates. Among the ternary composites, 2Au-12 %Ag₂S/Bi₂O₃ sample with the Au content of 2% exhibits highest catalytic efficiency for 60 min (AO7: 96%; RhB: 56%; Cr(VI): 65%). The possible mechanism for the improvement of the photocatalytic activity of Bi₂O₃ by Ag₂S and Au decoration was proposed.     

Facile Aqueous‐Phase Synthesis of Biocompatible and Fluorescent Ag2S Nanoclusters for Bioimaging: Tunable Photoluminescence from Red to Near Infrared

Low toxicity and fluorescent nanomaterials have many advantages in biological imaging. Herein, a novel and facile aqueous‐phase approach to prepare biocompatible and fluorescent Ag₂S nanoclusters (NCs) is designed and investigated. The resultant Ag₂S NCs show tunable luminescence from the visible red (624 nm) to the near infrared (NIR; 724 nm) corresponding to the increasing size of the NCs. The key for preparing tunable fluorescent Ag₂S NCs is the proper choice of capping reagent, glutathione (GSH), and the novel sulfur‐hydrazine hydrate complex as the S^2? source. As a naturally occurring and readily available tripeptide, GSH functions as an important scaffold to prevent NCs from growing large nanoparticles. Additionally, GSH is a small biomolecule with several functional groups, including carboxyl and amino groups, which suggests the resultant Ag₂S NCs are well‐dispersed in aqueous solution. These advantages make the as‐prepared Ag₂S NCs potentially applicable to biological labeling as well. For example, the resultant Ag₂S NCs are used as a probe for MC3T3‐EI cellular imaging.     

Self-assembly of nanoparticles to prepare of dendritic AgCl–Ag<Subscript>2</Subscript>S nanocomposites through a simple one-pot hydrothermal approach and its photocatalytic activity

Herein, AgCl–Ag₂S nanocomposites with dendritic morphology were synthesized via a simple one-pot hydrothermal route for the first time. AgNO₃, HCl, and thioacetamide were utilized as starting reagents. The as-prepared AgCl–Ag₂S nanocomposites were extensively characterized by techniques such as X-ray diffraction patterns, scanning electron microscopy, energy dispersive X-ray spectroscopy and diffused reflectance UV–visible spectrum. The results showed that the nanoparticles were self-assembled to prepare AgCl–Ag₂S nanocomposites with dendritic morphology. The efficiency of AgCl–Ag₂S nanocomposites as a photocatalyst for the decolorization of methyl orange (MO) using visible light irradiation has been evaluated. As a result, an enhanced photocatalytic efficiency of AgCl–Ag₂S nanocomposites compared to AgCl nanostructures was obtained due to absorption of wider range of light wavelength by AgCl–Ag₂S nanocomposites.     

Controllable preparation of Ag2S quantum dots with size-dependent fluorescence and cancer photothermal therapy

Although Ag₂S quantum dots (QDs) have attracted extensive attention in the fields of diagnosis and therapy, it is still a challenge to prepare Ag₂S QDs with well-controlled size distribution. Herein, size-tunable Ag₂S QDs with glutathione (GSH) as ligands were prepared via a facile aqueous precipitation method. The QDs are precisely prepared through carefully controlled growth of Ag2S QDs by varying the heating time. Morphology and structure characterization verify that Ag₂S QDs with 2.0–5.8 nm in diameter are coordinated with GSH through thiol group. The as-prepared Ag₂S QDs exhibit broad absorption spectra and narrow fluorescence emission spectra in the near-infrared region. Meanwhile, the QDs perform excellent and stable photothermal effect with a photothermal conversion efficiency up to 58.6%. More importantly, it is found that the size of Ag₂S QDs has a significant influence on the fluorescence intensity and photothermal effect. The cell viability evaluation in vitro demonstrates that Ag₂S QDs have low cytotoxicity to 293 T cells and Hela cells by methyl thiazolyl tetrazolium test. This paper proposes a convenient route to prepare unique Ag₂S QDs, which are capable to act as ideal theranostics probes for photothermal therapy and simultaneously monitoring the therapeutic effect for effective cancer treatment.     

Synthesis of worm-like Ag2S nanocrystals in W/O reverse microemulsion

High-aspect-ratio of worm-like Ag₂S nanocrystal with length up to several micrometers and a diameter of 25-50 nm has been successfully prepared by a Triton X-100/cyclohexane/hexanol/water W/O reverse microemulsion in the presence of TAA (Thioacetamide) as a sulfur source and EDTA (ethylene diamine tetraacetic acid) as a chelating ligand. The products were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and UV-vis diffuse reflectance absorption spectra. The results indicate that the morphology and size of Ag₂S nanocrystal can be readily controlled by modulating the mole ratio of Ag⁺ to EDTA, the molar ratio of water to surfactant (ω₀), and the aging time.     

Synthesis of SERS active Ag2S nanocrystals using oleylamine as solvent,reducing agent and stabilizer

Semiconductor Ag₂S nanocrystals have been prepared via a facile solution growth method, in which AgNO₃ and sulfur (S) powder are used as precursors, oleylamine is used and can function as both reducing agent and stabilizer during the synthetic process. The experimental results demonstrate that the as-synthesized Ag₂S nanocrystals, which have uniform size are monoclinic Ag₂S. Furthermore, surface-enhanced Raman scattering (SERS) spectrum of rhodamine 6G can be obtained on the Ag₂S nanocrystals modified substrate, indicating novel optical response of Ag₂S nanocrystals. The SERS effect of Ag₂S nanocrystals should attract much interest in fundamental physics as well as device application points of view.     

Nitrobacter sp. extract mediated biosynthesis of Ag2 O NPs with excellent antioxidant and antibacterial potential for biomedical application

In this study, extracellular extract of plant growth promoting bacterium, Nitrobacter sp. is used for the bioconversion of AgNO₃ (silver nitrate) into Ag₂ O (silver oxide nanoparticles). It is an easy, ecofriendly and single step method for Ag₂ O NPs synthesis. The bio‐synthesized nanoparticles were characterized using different techniques. UV‐Vis results showed the maximum absorbance around 450 nm. XRD result shows the particles to have faced centered cubic (fcc) crystalline nature. FTIR analysis reveals the functional groups that are involved in bioconversion such as C–N, N–H and C=O. Energy‐dispersive X‐ray spectroscopy (EDAX) spectrum confirms that the prepared nanoparticle is Ag₂ O NPs. Particle size distribution result reveals that the average particle size is around 40 nm. The synthesized Ag₂ O NPs found to be almost spherical in shape. Biosynthesized Ag₂ O NPs possess good antibacterial activity against selected Gram positive and Gram negative bacterial strains namely Salmonella typhimurium, Staphylococcus aureus, Escherichia coli and Klebsiella pneumoniae when compared to standard antibiotic. In addition, Ag₂ O NPs exhibits excellent free radical scavenging activity with respect to dosage. Thus, this study is a new approach to use soil bacterial extract for the production of Ag₂ O NPs for biomedical application.Inspec keywords: nanomedicine, nanoparticles, silver compounds, antibacterial activity, ultraviolet spectra, visible spectra, X‐ray diffraction, Fourier transform infrared spectra, X‐ray chemical analysis, particle size, free radicalsOther keywords: free radical scavenging activity, Ag₂ O, AgNO₃ , Klebsiella pneumoniae, Escherichia coli, Staphylococcus aureus, Salmonella typhimurium, Gram negative bacterial strains, Gram positive bacterial strains, particle size distribution, energy‐dispersive X‐ray spectroscopy spectrum, functional groups, Fourier transform infrared analysis, faced centred cubic crystalline nature, XRD, UV‐Vis results, bio‐synthesised nanoparticles, silver oxide nanoparticles, silver nitrate bioconversion, plant growth promoting bacterium, extracellular extract, biomedical application, antibacterial potential, antioxidant potential, Ag₂ O NPs, extract mediated biosynthesis, Nitrobacter sp     

Intensified photocatalytic degradation of 2, 4–dicholorophenoxyacetic acid using size-controlled silver nanoparticles: Effect of pre-synthesis extraction

In this study, ultrafine silver (Ag) nanoparticles were synthesised in Orthosiphon stamineus (OS) extract via facile electrochemical method. Different pre–synthesis extraction methods, namely ultrasonic assisted extraction hydro–distillation (UAE–HD) and classical aqueous extraction (AE) were used and compared. UAE–HD attained the highest total phenolic compounds at 8563.90 mg/kg. The Ag nanoparticles prepared via pre–synthesis extraction of UAE–HD (Ag_UAE-HD) and classical AE (Ag_AE) gave ultrafine sizes of 2 nm and 15 nm, respectively. It was suggested from the characterisation results that the phenolic compounds present in the OS extract had a significant role in the capping and stabilisation of Ag nanoparticles. Moreover, it was also demonstrated that the size of the Ag nanoparticles could simply be altered by varying the amount of total phenolic content (TPC) using different pre–synthesis extraction methods prior to the synthesis of Ag. Next, the photocatalytic activity of the Ag nanoparticles was tested towards the degradation of 2, 4–dicholorophenoxyacetic acid (2,4–D) herbicide. The synthesised Ag nanoparticles also showed outstanding photocatalytic activity with maximum degradation efficiency of up to 99.78% at pH 3, 0.01 g L⁻¹ of catalyst dosage and 10 mg L⁻¹ of 2, 4-D concentration. High amount of TPC contributed to the low energy band–gap (E_g) of Ag_UAE-HD catalyst and significantly inhibited the electron-hole recombination as well as enhanced the photocatalytic activity. The figures of merit based on electric energy consumption (E_EO) indicate that less energy was consumed during the degradation of 2,4–D in the presence of Ag_UAE-HD compared with other catalysts. Therefore, it could be concluded that Ag_UAE-HD is a promising material for high photocatalytic degradation efficiency of 2,4–D under optimal condition.     

Synthesis and physical properties of un- and Zn-doped Ag2S nanoparticles

This study is devoted to the sonochemical synthesis of un- and Zn-doped silver sulfide (Ag₂S) nanostructures and evaluation of the parameters that affect its structural, morphological and optical properties. To unravel any changes in the characteristics of the particles, the XRD and FESEM techniques, in addition to photoluminescence (PL), Raman and UV–Vis–NIR spectroscopies, were applied. According to the analyses, 15?min sonication using 200?W power can provide the highest quality of the Ag₂S crystals. Moreover, it was found out that Zn doping shifts the XRD peaks of Ag₂S to higher angles and declines crystallinity of the samples while it does not change the spherical shape of the Ag₂S particles. The other impact of Zn presence in the crystal lattice of Ag₂S was declared to be increasing the size of the Ag₂S nanostructures. Importantly, based on the PL results, the un- and Zn-doped Ag₂S particles present several emission bands lying in the visible spectrum of light due to their specific optical near band emission (NBE) and crystal defects. As the Tauc plots spectra demonstrated, increasing the Zn concentration decreases the optical band gap energy of the Ag₂S nanostructures. Also, the Raman results unraveled the impact of synthesis conditions on the optical and crystalline properties of the grown structures.     

Converting ultrafine silver nanoclusters to monodisperse silver sulfide nanoparticles via a reversible phase transfer protocol

To achieve better control of the formation of silver sulfide (Ag₂S) nanoparticles, ultrasmall Ag nanoclusters protected by thiolate ligands (Ag₄₄(SR)₃₀ and Ag₁₆(GSH)₉) are used as precursors, which, via delicate chemistry, can be readily converted to monodisperse Ag₂S nanoparticles with controllable sizes (4–16 nm) and switchable solvent affinity (between aqueous and organic solvents). This new synthetic protocol makes use of the atomic monodispersity and rich surface chemistry of Ag nanoclusters and a novel two-phase protocol design, which results in a well-controlled reaction environment for the formation of Ag₂S nanoparticles.

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Ultrasmall Pb:Ag2S Quantum Dots with Uniform Particle Size and Bright Tunable Fluorescence in the NIR‐II Window

Ag₂S quantum dots (QDs) are well‐known near‐infrared fluorophores and have attracted great interest in biomedical labeling and imaging in the past years. However, their photoluminescence efficiency is hard to compete with Cd‐, Pb‐based QDs. The high Ag⁺ mobility in Ag₂S crystal, which causes plenty of cation deficiency and crystal defects, may be responsible mainly for the low photoluminescence quantum yield (PLQY) of Ag₂S QDs. Herein, a cation‐doping strategy is presented via introducing a certain dosage of transition metal Pb²⁺ ions into Ag₂S nanocrystals to mitigate this intrinsic shortcoming. The Pb‐doped Ag₂S QDs (designated as Pb:Ag₂S QDs) present a renovated crystal structure and significantly enhanced optical performance. Moreover, by simply adjusting the levels of Pb doping in the doped nanocrystals, Pb:Ag₂S QDs with bright emission (PLQY up to 30.2%) from 975 to 1242 nm can be prepared without altering the ultrasmall particle size (≈2.7–2.8 nm). Evidently, this cation‐doping strategy facilitates both the renovation of crystal structure of Ag₂S QDs and modulation of their optical properties.     

Ag2S morphology controllable via simple template-free solution route

Different morphologies of Ag₂S nano- and micro-materials, including spokewise micrometer bars, microfibers, nanowires, worm-like nanoparticles and nanopolyhedrons have been obtained controllably by a facile one-step method at room temperature. Powder X-ray diffraction (XRD), X-ray photo-electron spectroscopy (XPS) and scanning electron microscope (SEM) were employed to characterize the structure and compositions of those nanomaterials. Furthermore, ultraviolet visible (UV–vis) spectra of Ag₂S with different morphologies show different spectral features. In this route, no any organic template materials were added into the reaction container. The concentrations of ammonia, Ag⁺, S^2? and their ratios in the solution may play an important role on the morphologies and sizes of the products.     

Electrical properties of R-phycoerythrin containing Ag<Superscript>0</Superscript> nanoparticles in its channels

The electrical properties of R-phycoerythrin modified with Ag⁰ nanoparticles (Ag⁰ ? R-PE) as a candidate material for biosensors were studied were studied. Modification was ensured by a known procedure: synthesis of Ag⁰ nanoparticles in R-phycoerythrin channels through the addition of AgNO₃ to an aqueous R-phycoerythrin solution. According to electron microscopy results, the Ag⁰ ? R-PE contains predominantly elongated Ag⁰ nanoparticles 6.2 ± 0.5 nm in length, which form structures similar to rows 20–60 nm in length. The electrical conductivity, dielectric permittivity, and dielectric loss of the Ag⁰ ? R-PE have been measured in the frequency range from 0.01 Hz to 1 MHz. Filling the channels in R-phycoerythrin molecules with Ag⁰ nanoparticles has been shown to increase the alternating current electrical conductivity and dielectric loss of the material at low frequencies by more than 200 times and its dielectric permittivity by 40 times. Ag⁰ nanoparticles increase the direct current conductivity of R-phycoerythrin from 5 × 10^–14 to 2.5 × 10^–11 S/cm. The electrical properties of Ag ? R-PE are comparable to those of conductive polymer composites that contain metallic nanowires and are used in designing multifunctional films and smart materials.     

Preparation and photocatalytic activity of graphene-modified Ag2S composite

This paper presents a novel visible-light photocatalyst, graphene-modified Ag₂S (GR/Ag₂S), prepared by a facile and effective hydrothermal method with AgNO₃, thioacetamide and graphene oxide (GO) as the precursor. The catalytic activities of the GR/Ag₂S hybrids with different GR content (2%, 4%, 6%) were evaluated by photocatalytic decolourisation of rhodamine B (RhB) solution under visible-light irradiation. The improved photocatalytic activity of GR/Ag₂S composites compared with pure Ag₂S is observed and attributed to the enhanced absorption of organic dyes and increased separation efficiency of photogenerated electron?hole pairs. The 4% GR/Ag₂S sample exhibits the best photocatalytic activity than the others.