NaBH4 as reducing agent The copolymers in anionic form were used as matrices for AgNP synthesis.
Plasmon resonance absorption for all silver sols was observed at UV-vis spectra (Figure 2). The shoulder at first higher energy AZ 628 ic50 maximum in the range 275 to 282 nm may correspond to both small particles of 2 to 4 nm and Ag+ ions. The second maximum is situated at 390 to 410 nm; it corresponds to the plasmon absorption of Ag particles of 10 to 15 nm in size. Maximum intensity depends on polymer matrix type. The most efficient matrix for nanoparticle preparation is D70-g-PAA20 with the most compact internal structure (Table 1). The matrices of PAA and D70-g-PAA which are close in compactness reveal similar efficiency for nanoparticle SBI-0206965 nmr synthesis. The shoulders in the plasmon peaks (Figure 2) imply that the synthesized sols contain either polydisperse nanoparticles with a significant fraction of aggregates for sols synthesized in linear PAA matrices or a high rate of small particles for nanosystems prepared in branched polymer matrices. Such conclusion was proved by TEM image analysis of silver sols. The TEM image and a size histogram are presented in Figure 3. Two types of particles are observed for sols synthesized in polyelectrolyte matrices (Figure 3). The first fraction corresponds to small spherical particles of 3 to 4 nm in size; the
second one displays aggregated granules and spherical particles of 10 to 15 nm in size. Ag NPs synthesized in polyelectrolyte matrices differ from those prepared in non-ionic branched or linear matrices described previously [28, Belnacasan mw 29]. It was shown that in non-ionic matrices, only spherical particles of 10
to 15 nm in size were formed. The bimodal size distribution of nanoparticles synthesized in polyelectrolyte matrices can be explained by the existence of two types of functional groups in the hydrolyzed macromolecules: amide and carboxylate ones. That can lead to two types of bonding with silver ions and provides two mechanisms of Ag NP formation. Figure 2 UV-vis absorption spectra of silver sols synthesized in the polymer matrices. D70-g-PAA20 (1), D70-g-PAA5 (2), and PAA (3). T = 20 C. The reductant is borohydride. Figure 3 TEM image (a) and nanoparticle size distribution (b) in silver sols synthesized in D70-PAA5 matrix. The reductant is sodium borohydride. The effect oxyclozanide of temperature on the process of silver sol formation is demonstrated in Figure 4. Highly concentrated stable sols were obtained using all branched polyelectrolytes as host polymers. An increase of temperature caused further Ag NP aggregation. This is revealed in the appearance of a shoulder of the resonance peak at 420 to 440 nm (Figure 4). Stable Ag sols could not be synthesized in linear PAA matrix. We observed the appearance of some precipitate at 40°C and 60°C. The phase separation occurred immediately at 80°C, while colloids synthesized in branched matrices remained stable.