Synthesis of Silver Nanoparticles by Hydrothermal Processing

Hydrothermal water treatments of silver acetate (CH3COOAg) were investigated to reveal the factors controlling the formation of silver nanoparticles (AgNPs) with uniform size distribution. The effects of reaction time and concentration of silver acetate solution on the synthesis of Ag nanoparticles were studied, and the fabricated products were characterized. The hydrothermal water treatments of CH3COOAg were carried out between the temperatures of 250 - 450 °C in a batch reactor. In supercritical water regions, at 400 °C and a pressure of 31.5 MPa, silver particles are rapidly synthesized due to reaction rate increases at a low dielectric constant of supercritical water. The preparation of the silver particles with 30-80 nm in size showed a highly crystalline structure identified by XRD and TEM observations.

“NOT IMPORTANT” : an analysis of the Tibet photo service medium format negatives at the Tibet Museum

This thesis approaches a body of 1,428 6x6 cm gelatin silver acetate negatives in the Tibet Museum’s photographic archives in Dharamsala, India. This material, labelled “not important” by an archivist at their collecting institution, contains images of the Tibetan community in exile, made by the Tibet Photo Service (TPS) studio between 1962 and 1987. The practical component of this project involves arranging and rehousing the negatives for accessibility and preservation purposes. The theoretical component of this project provides a contextual framework for the TPS medium format negatives, unpacking the reasons behind their exclusion from care and display. Additionally, it engages the negatives as sites of “articulation and aspiration” of the Tibetan exile community. The objects and their images are recontextualized from material that is “not important” to social and political documents that serve as a subjective historical record of the foundational years of the Tibetan community in India.

“NOT IMPORTANT” : an analysis of the Tibet photo service medium format negatives at the Tibet Museum

This thesis approaches a body of 1,428 6x6 cm gelatin silver acetate negatives in the Tibet Museum’s photographic archives in Dharamsala, India. This material, labelled “not important” by an archivist at their collecting institution, contains images of the Tibetan community in exile, made by the Tibet Photo Service (TPS) studio between 1962 and 1987. The practical component of this project involves arranging and rehousing the negatives for accessibility and preservation purposes. The theoretical component of this project provides a contextual framework for the TPS medium format negatives, unpacking the reasons behind their exclusion from care and display. Additionally, it engages the negatives as sites of “articulation and aspiration” of the Tibetan exile community. The objects and their images are recontextualized from material that is “not important” to social and political documents that serve as a subjective historical record of the foundational years of the Tibetan community in India.

The antimicrobial activity of silver acetate against Acinetobacter baumannii in a Galleria mellonella infection model

Background The increasing prevalence of bacterial infections that are resistant to antibiotic treatment has caused the scientific and medical communities to look for alternate remedies aimed at prevention and treatment. In addition to researching novel antimicrobials, there has also been much interest in revisiting some of the earliest therapies used by man. One such antimicrobial is silver; its use stretches back to the ancient Greeks but interest in its medicinal properties has increased in recent years due to the rise in antibiotic resistance. Currently antimicrobial silver is found in everything from lunch boxes to medical device implants. Though much is claimed about the antimicrobial efficacy of silver salts the research in this area is mixed. Methods Herein we investigated the efficacy of silver acetate against a carbapenem resistant strain of Acinetobacter baumannii to determine the in vitro activity of this silver salt against a World Health Organisation designated category I critical pathogen. Furthermore, we use the Galleria mellonella larvae model to assess toxicity of the compound and its efficacy in treating infections in a live host. Results We found that silver acetate can be delivered safely to Galleria at medically relevant and antimicrobial levels without detriment to the larvae and that administration of silver acetate to an infection model significantly improved survival. This demonstrates the selective toxicity of silver acetate for bacterial pathogens but also highlights the need for administration of well-defined doses of the antimicrobial to provide an efficacious treatment.

INFLUENCE OF POLIGUANIDINE ON THE SELF-ORGANIZATION PROCESS IN CYSTEINE-SILVER SOLUTION

Выполнены реологические, структурные и антибактериальные исследования гидрогелей, получаемых на основе L-цистеина, ацетата серебра и полигексаметиленгуанидин гидрохлорида (ПГМГ-ГХ). Установлено, что водные растворы на основе L-цистеина и ацетата серебра хорошо смешиваются с водным раствором ПГМГ-ГХ, образуя прозрачные гидрогели. Предложена модель строения пространственной сетки геля. Показана высокая антимикробная активность гидрогеля по отношению к тест-культурам патогенных и условно-патогенных микроорганизмов. Rheological, structural, and antibacterial studies of hydrogels based on L-cysteine, silver acetate, and polyhexamethylene guanidine hydrochloride (PHMG-GC) have been carried out. It was found that aqueous solutions based on L-cysteine and silver acetate mix well with an aqueous solution of PHMG-GC, forming transparent hydrogels. A model of the structure of the spatial grid of the gel is proposed. High antimicrobial activity of the hydrogel was shown in relation to test cultures of pathogenic and opportunistic microorganisms.

INFLUENCE OF LIGHTING ON THE SELF-ORGANIZATION PROCESS IN CYSTEINE-SILVER SOLUTION

Комплексно исследовано влияние дневного освещения на процесс самоорганизации в цистеин-серебряном растворе (ЦСР) и гидрогелях на его основе. Установлено, что ЦСР на основе L-цистеина и ацетата серебра под действием освещения окрашивается сначала в желтый, а затем в коричневый цвет, что является следствием плазмонного резонанса на образующихся наночастицах серебра (НЧС) в ЦСР и гидрогелях. Предложена модель формирования НЧ в гидрогеле. The effect of daylight on the self-assembly process in cysteine-silver solution (CSS) and hydrogels based on it has been comprehensively studied. It was found that CSS based on L-cysteine and silver acetate under the action of illumination first turns yellow and then brown, which is a consequence of plasmon resonance on the resulting silver nanoparticles in CSS and hydrogels. A model for the formation of silver nanoparticles in a hydrogel is proposed.

Production of 1-Butyl-3-Methylimidazolium Acetate [Bmim][Ac] Using 1-Butyl-3-Methylimidazolium Chloride [Bmim]Cl and Silver Acetate: A Kinetic Study

Since most of the literature alternatives used to produce the ionic liquid 1-butyl-3-methylimidazolium acetate [Bmim][Ac] are very slow and require different solvents, we have used in this work a new process to produce the [Bmim][Ac] by the reaction of the ionic liquid 1-butyl-3-methylimidazolium chloride [Bmim]Cl with silver acetate (AgAc) where silver chloride (AgCl) precipitates as a by-product. The genuine experimental work and kinetic analyses presented here indicate that the reaction rate constant k = 7.67x1012 e(−79.285/RT). That is, the Arrhenius constant k o = 7.67x1012 L/mol.s and the activation energy E a = 79.285 kJ/mol. The very high value of the Arrhenius constant indicates that the reaction of [Bmim]Cl with silver acetate to produce [Bmim][Ac] and silver chloride is extremely fast.