Structural and spectroscopic characterization of prepared Ag2S nanoparticles with a novel sulfuring agent

Antimicrobial activity of silver sulfide quantum dots functionalized with highly conjugated Schiff bases in a one-step synthesis

In the present paper, low-dimensional Ag2S QDs were fabricated for the first time, with four different dithiocarbazate derivative Schiff bases (SB) as capping agents in a one-pot synthesis. These SB-capped Ag2S QDs were almost spherical with an average size range of 4.0 to 5.6 nm, which is slightly smaller than conventional thioglycolic acid (TGA)-capped Ag2S QDs. We demonstrate that the growth of Gram-positive bacteria (Bacillus subtillus and Staphylococcus aureus), Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa), and a prevalent fungal pathogen (Candida albicans) are inhibited more when the bacterial and fungal cells were nurtured with the synthesized SB-Ag2S QDs, compared with TGA-Ag2S QDs or free unbound Schiff bases. The minimum inhibitory concentration (MIC) results confirmed that even low concentrations of SB-Ag2S QDs were able to inhibit bacterial (MIC 5-75 μg mL-1) and fungal growth (MIC 80-310 μg mL-1), and in some cases they performed better than streptomycin (8-25 μg mL-1). Lethality bioassay results confirmed that SB-Ag2S QDs were not toxic to brine shrimp (Artemia salina). The results show that capping agents are essential in the design of functional Ag2S QDs, and highlight that Schiff bases provide an excellent opportunity to optimize the biological activities of silver based QDs.

Silver chalcogenide nanoparticles: a review of their biomedical applications

Silver chalcogenide (Ag2X, where X = S, Se, or Te) nanoparticles have been extensively investigated for their applications in electronics but have only recently been explored for biomedical applications. In the past 10 years, Ag2X, primarily silver sulfides at first, have become of great importance as quantum dots, since they not only possess excellent deep tissue imaging properties in the near-infrared regions I and II, but also have low toxicities. Their appealing properties have led to numerous recent developments of Ag2X for biomedical applications. Furthermore, Ag2X have been discovered in the past 2-3 years to be potent X-ray contrast agents, adding to the numerous biomedical uses of these nanoparticles. In this review, we discuss the most recent advances in silver chalcogenide nanoparticle use in areas such as bio-imaging, theranostics, and biosensors. Moreover, we examine the advances in synthetic approaches for these nanoparticles, which include aqueous and organic syntheses routes. Finally, we discuss the advantages and current limitations in the use of silver chalcogenides for different biomedical applications and their potential for advancement and expansions in use.

High-responsivity hybrid α-Ag2S/Si photodetector prepared by pulsed laser ablation in liquid

We report the synthesis of α-Ag2S nanoparticles (NPs) by one-step laser ablation of a silver target in aqueous solution of thiourea (Tu, CH4N2S) mixed with cationic cetyltrimethylammonium bromide (CTAB) as surfactant. The effect of the CTAB surfactant on the structural, morphological, optical, and elemental composition of Ag2S NPs was evaluated using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and UV-vis spectroscopy. The optical absorption decreased and the optical energy gap of α-Ag2S increased from 1.5 to 2 eV after the CTAB surfactant was added to the Tu solution. XRD studies revealed that the synthesized Ag2S NPs were polycrystalline with a monoclinic structure and that crystallinity of the nanoparticles was improved after adding CTAB. Raman studies revealed the presence of peaks related to Ag-S bonds (Ag modes) and the longitudinal optical phonon 2LO mode. Scanning electron microscopy investigations confirmed the production of monodisperse Ag2S NPs when using the CTAB surfactant. The optoelectronic properties of α-Ag2S/p-Si photodetector, such as current-voltage characteristics and responsivity in the dark and under illumination, were also improved after using the CTAB surfactant. The responsivity of the photodetector increases from 0.64 to 1.85 A/W at 510 nm after adding CTAB. The energy band diagram of the α-Ag2S/p-Si photodetector under illumination was constructed. The fabricated photodetectors exhibited reasonable stability after three weeks of storage under ambient conditions with a responsivity of 70% of the initial value.

Nanostructured silver sulfide: synthesis of various forms and their application

The results of experimental studies on nanostructured silver sulfide are analyzed and generalized. The influence of small particle size on nonstoichiometry of silver sulfide is discussed. Methods for the synthesis of various forms of nanostructured Ag2S including nanopowders, stable colloidal solutions, quantum dots, core – shell nanoparticles and heteronanostructures are described. The advantages and drawbacks of different synthetic procedures are analyzed. Main fields of application of nanostructured silver sulfide are considered.

The bibliography includes 184 references.

Synthesis of silver nanoparticles using bacterial exopolysaccharide and its application for degradation of azo-dyes

In this study, the synthesis and characterization of exopolysaccharide-stabilized sliver nanoparticles (AgNPs) was carried out for the degradation of industrial textile dyes. Characterization of AgNPs was done using surface plasmon spectra using UV-Vis spectroscopy, X-ray diffraction (XRD) and Raman spectroscopy. The morphological nature of AgNPs was determined through transmission electron microscopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM), which indicated that the AgNPs were spherical in shape, with an average size of 35 nm. The thermal behaviour of AgNPs revealed that it is stable up to 437.1 °C and the required energy is 808.2J/g in TGA-DTA analysis. Ability of EPS stabilized AgNPs for degradation of azo dyes such as Methyl orange (MO) and Congo red (CR) showed that EPS stabilized AgNPs were found to be efficient in facilitating the degradation process of industrial textile dyes. The electron transfer takes place from reducing agent to dye molecule via nanoparticles, resulting in the destruction of the dye chromophore structure. This makes EPS-AgNPs a suitable, cheap and environment friendly candidate for biodegradation of harmful textile dyes.

Structural, spectroscopic (FT-IR, FT-Raman, NMR) and computational analysis (DOS, NBO, Fukui) of 3,5-dimethylisoxazole and 4-(chloromethyl)-3,5-dimethylisoxazole: A DFT study

The theoretical and computational analysis of two isoxazole derivatives 3,5-dimethylisoxazole and 4-chloromethyl-3,5-dimethylisoxazole were carried out along with some of the experimental evidences. The density functional theory calculations of these compounds were done with DFT/B3LYP/6-31+G(d,p) basis set using Gaussian 09 software. From the DFT calculations, the optimization geometry, vibrational analysis, electronic properties, local reactivity descriptors, natural bond orbitals, and other structural properties of the title compounds were elucidated. The chemical shifts of every C and H atom of the title compounds were calculated using Gauge Independent Atomic orbitals (GIAO) method for both proton and carbon NMR spectra. The molecular electrostatic potential of DMI has been found out and the difference in MEP on addition of chloromethyl group is also discussed. The hyperpolarizability calculations of the investigated molecules shows that the nonlinear optical activity of CDMI is greater when compared to DMI.

Facile synthesis of S-Ag nanocomposites and Ag2S short nanorods by the interaction of sulfur with AgNO3 in PEG400

A facile, eco-friendly and inexpensive method to prepare Ag2S short nanorods and S-Ag nanocomposites using sublimed sulfur, AgNO3, PVP and PEG400 was studied. According to x-ray diffraction and scanning electron microscopy of the Ag2S, the products are highly crystalline and pure Ag2S nanorods with diameters of 70-160 nm and lengths of 200-360 nm. X-ray diffraction of the S-Ag nanocomposites shows that we obtained cubic Ag and S nanoparticles. Transmission electron microscopy shows that the molar ratio of PVP to Ag(+) plays an important role in controlling the size and morphology of the S-Ag nanocomposites. When the molar ratio of PVP to Ag(+) was 10:1, smaller sizes, better dispersibility and narrower distribution of S-Ag nanocomposites with diameters of 10-40 nm were obtained. The formation mechanism of the S-Ag nanocomposites was studied by designing a series of experiments using ultraviolet-visible measurement, and it was found that S nanoparticles are produced first and act as seed crystals; then Ag(+) becomes Ag nanocrystals on the surfaces of the S nanoparticles by the reduction of PVP. PEG400 acts as a catalyzer, accelerating the reaction rate, and protects the S-Ag nanocomposites from reacting to produce Ag2S. The antimicrobial experiments show that the S-Ag nanocomposites have greater antimicrobial activity on Staphylococcus aureus, Aspergillus niger and blue mold than Ag nanoparticles.

Synthesis and Functions of Ag2S Nanostructures

The paper presents a review about synthesis and applications of Ag2S nanostructures. As the modern photoelectric and biological materials, Ag2S nanomaterials are potentially useful for both structure and function purposes. Ag2S is a direction narrow band gap semiconductor with special properties. Ag2S nanostructures have been widely researched in chemistry and biochemistry fields because of their unusual optical, electrical, and mechanical properties. It can also be used in many fields, such as photovoltaic cells and infrared detector. In the past few years, Ag2S nanostructures have been synthesized by various methods. The article mainly discusses the four types of preparation methods. Moreover, this article shows a detailed review on the new properties, fabrication, and applications of Ag2S nanocrystals.