The effect of salt addition on the stability of colloidal suspensions of silver and gold nanoparticles

Koloidi so disperzni sistemi, kjer je ena snov, sestavljena iz mikroskopsko razpršenih netopnih delcev, suspendirana v drugi. Zaradi majhnosti koloidnih delcev, ki imajo večjo površino na maso v primerjavi z večjimi delci istih snovi, to povzroči drugačne fizikalne in kemijske lastnosti. Pomembna značilnost koloidnih sistemov je stabilizacija delcev, ki preprečuje njihovo združevanje ali usedanje. V koloidnih sistemih delujejo različne sile med delci, vključno z elektrostatskimi, van der Waalsovimi in steričnimi silami. Pomembna za razumevanje obnašanja koloidnih sistemov je povezava med Brownovim gibanjem in teorijo Derjaguin-Landau-Verwey-Overbeek (DLVO), kjer teorija DLVO opisuje ravnotežje med odbojnimi in privlačnimi silami, Brownovo gibanje pa stabilizacijo z naključnim gibanjem delcev. V nalogi sem z eksperimentalnima tehnikama merjenja zeta potenciala in dinamičnega sipanja laserske svetlobe (DLS) opravila nekaj meritev agregacije koloidne suspenzije nanodelcev srebra in zlata v odvisnosti od koncentracije NaCl. Zlati in srebrni nanodelci kažejo katalitično aktivnost, pri čemer imajo nanodelci zlata odlično katalitično aktivnost pri oksidacijskih reakcijah, nanodelci srebra pa so pogosto učinkovitejši pri redukcijskih reakcijah. Zlati nanodelci so znani po nizki toksičnosti in biokompatibilnosti, kar omogoča medicinsko uporabo. Srebrni nanodelci imajo antibakterijskih lastnosti in jih najdemo v izdelkih za osebno nego, medicinskih pripomočkih in tekstilnih materialih.Colloids are dispersed systems where one substance consisted of microscopic dispersed insoluble particles is suspended in another. Due to the small size of the colloidal particles, which have a greater surface area per mass compared to larger particles of the same substances, this causes different physical and chemical properties. An important characteristic of colloidal systems is particle stabilization, which prevents them from agglomerating or settling. In colloidal systems, various forces act between particles, including electrostatic, van der Waals and steric forces. Important for understanding behavior of colloidal systems is the connection between Brownian motion and the theory of Derjaguin-Landau-Verwey-Overbeek (DLVO). The DLVO theory describes the balance between repulsive and attractive forces, where Brownian motion describes stabilization by random movement of particles. With experimental techniques measurement of zeta potential and dynamic laser light scattering (DLS) I performed some measurements of aggregation of colloidal suspension of silver and gold nanoparticles depending on NaCl concentrations. Gold and silver nanoparticles show catalytic activity, where gold nanoparticles have excellent catalytic activity in oxidation reactions, whereby silver nanoparticles are often more efficient in reduction reactions. Gold nanoparticles are known for their low toxicity and biocompatibility, which allows their medical use. Silver nanoparticles have antibacterial properties and are found in personal care products, medical devices and textile materials