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Constitution of a Chemical Reaction and Reaction Balancing
Published in John Andraos, Reaction Green Metrics, 2018
An alternative process that avoids the use of cyanide involves treating the raw gold ore with aqua regia (3 parts conc. HCl: 1 part conc. HNO3). The strong acid solution dissolves the gold and results in an aqueous solution of chloroauric acid (HAuCl4). Another way to obtain chloroauric acid is to treat the raw gold ore with hydrochloric acid and chlorine gas. The chloroauric acid is then treated with either hydrazine hydrochloride, sulfur dioxide, oxalic acid, ferrous sulfate, sodium metabisulfite, or formic acid to precipitate the purified gold. Write out balanced chemical equations for all transformations described.
Nanostructured Sensors
Published in Banshi Dhar Gupta, Anand Mohan Shrivastav, Sruthi Prasood Usha, Optical Sensors for Biomedical Diagnostics and Environmental Monitoring, 2017
Banshi Dhar Gupta, Anand Mohan Shrivastav, Sruthi Prasood Usha
The chemical method involves three most important elements: precursor (salt), reducing agent, and the stabilizer. In the case of gold nanostructure synthesis, usually chloroauric acid (HAuCl4) is used as the precursor, which is reduced to gold atoms and further growth of them leads to the synthesis of different nanostructures. Various types of reducing agents such as citrates and bromides can be used for these. Below, we shall discuss few of the chemical methods used for the synthesis of gold nanostructures.
Synthesis and characterization of Black Au nanoparticles deposited over g-C3N4 nanosheets: enhanced photocatalytic degradation of methylene blue
Published in Environmental Technology, 2022
Mojdeh Atashkadi, Alireza Mohadesi, Mohammad Ali Karimi, Seyed Zia Mohammadi, Vida Haji Aghaei
Although gold is a type of noble metal, it is a highly reactive photocatalyst at nano dimensions. Rather than simplicity in preparation, AuNPs present high chemical stability, water-solubility, nontoxicity, and biocompatibility. They effectively absorb visible light, improve direct electron transfer, and produce long-lived charge carriers due to the Fermi level and strong interactions with resonant photons [19]. Coloured AuNPs possess attractive optical properties arising from the localized surface plasmon resonance (LSPR), a collective coherent oscillation of the conduction band electrons which are excited by the incident light [20]. Gold nanoparticles are generally prepared through the reduction of chloroauric acid precursor (HAuCl4) by two common reducing agents: tri-sodium citrate (SC) and sodium borohydride (SB). Several approaches have been reported and reviewed for the synthesis of AuNPs. The seed-mediated growth method which was used in the 1990s is the most reliable, flexible, and accessible experimental procedure to synthesize and supervise the shape of AuNPs. This most popular approach involves two steps: nucleation and growth. Due to the low activation energy, the autocatalytic growth of the preformed seeds occurs in the growth solution containing gold precursor, reducing reagent, and shape-directing reagent [21]. To address the inherent weakness of the bare g-C3N4, the incorporation of AuNPs is a favourable solution. This composition called plasmonic photocatalyst is expected to be quite powerful in the degradation of organic dyes under UV-Visible light irradiation [22], which is well documented in numerous reports.
Biosynthesis of gold nanoparticles using sansevieria plant extract and its biomedical application
Published in Inorganic and Nano-Metal Chemistry, 2023
Sara Peivandi, Hamid Dehghanzadeh, Amin Baghizadeh
The chloroauric acid powder was purchased from Merck (Germany) and a certain amount of it was dissolved in deionized water, and 1 mM gold hydrogen tetrachloride solution (HAuCl4.3H2O) was obtained. The resulting solution was kept away from light and refrigerated for use in all stages of the experiment.