Microspheres and Nanorods Produced in the Dissolution of Mildly Carboxylated Cellulose Fibers in Alkaline Solutions

A mild etherification of spruce kraft pulp was performed to introduce 1.3 and 2.5 mmol/g carboxyl groups on cellulose chains. 1.3 mmol/g carboxymethyl fibers (CMF) were dissolved partially in alkaline water to form balloons and collars on the tracheid and their ultra-structure was investigated. Primary wall, expanded S1, swollen S2, wrinkled S3, spiral bands of S1, parallel microfibrils of S2 and their transverse splitting were observed on swollen fibers. It is indicated that balloons, collars and wrinkled S3 were formed due to different cellulose microfibril features in different layers of tracheid cell wall. Microspheres with a size up to about 0.6 µm were observed by field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). It is shown that they originated from transverse splitting of S2 microfibrils and contain bundles of well-known cellulose nanocrystals (CNC). After homogenization and sonication of an aqueous dispersion of 2.5 mmol/g CMF, electroacoustic spectroscopy showed the presence of nanorods with a size distribution of 18-208 nm. Similar sizes were observed by TEM.

INFLUENCE OF SYNTHESIS CONDITIONS ON AGGREGATIVE STABILITY OF Ag ALCOSOLS

Впервые в работе представлены результаты исследования влияния типа спиртовой среды на свойства высококонцентрированных золей наночастиц серебра. С помощью спектрофотометрии установлено наличие селективной полосы поглощения, обусловленной поверхностным плазмонным резонансом наночастиц серебра. Измерение дзета-потенциала показало, что вне зависимости от типа среды поверхность наночастиц серебра заряжена отрицательно. Обнаружено, что наиболее агрегативно устойчивые частицы, сохраняющие стабильность в концентрированных растворах хлорида натрия, получены в среде изопропилового спирта и характеризуются дзета-потенциалом, равным -99,8 мВ. For the first time, the paper presents the results of investigation the effect of the type of alcoholic medium on the properties of highly concentrated sols of silver nanoparticles. Spectrophotometry revealed the presence of a selective absorption band corresponding to the surface plasmon resonance of silver nanoparticles. Measurement of the zetta potential showed that, regardless of the type of medium, the surface of silver nanoparticles is negatively charged. It was found that the most aggregatively stable particles that retain stability even in concentrated sodium chloride solutions were obtained in isopropyl alcohol and are characterized by the zetta potential equal to -99,8 mV. Keywords: silver nanoparticles, optical properties, electroacoustic spectroscopy, zeta potential, nanoparticle stability.