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Rapid continuous microwave-assisted synthesis of silver nanoparticles to achieve very high productivity and full yield: from mechanistic study to optimal fabrication strategy.

Dzido G, Markowski P, Małachowska-Jutsz A, Prusik K, Jarzębski AB - J Nanopart Res (2015)

Bottom Line: Systematic studies of silver nanoparticle synthesis in a continuous-flow single-mode microwave reactor using polyol process were performed, revealing that the synthesis is exceptionally effective to give very small metal particles at full reaction yield and very high productivity.Owing to its much higher reactivity, silver acetate was shown to be far superior substrate for the synthesis of small (10-20 nm) spherical silver nanoparticles within a few seconds.The performed studies indicate an optimal strategy for the high-yield fabrication of metal particles using polyol method.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemical Engineering and Process Design, Faculty of Chemistry, Silesian University of Technology, Ks. M. Strzody 7, 44-100 Gliwice, Poland.

ABSTRACT

Systematic studies of silver nanoparticle synthesis in a continuous-flow single-mode microwave reactor using polyol process were performed, revealing that the synthesis is exceptionally effective to give very small metal particles at full reaction yield and very high productivity. Inlet concentration of silver nitrate or silver acetate, applied as metal precursors, varied between 10 and 50 mM, and flow rates ranged from 0.635 to 2.5 dm(3)/h, to give 3-24 s reaction time. Owing to its much higher reactivity, silver acetate was shown to be far superior substrate for the synthesis of small (10-20 nm) spherical silver nanoparticles within a few seconds. Its restricted solubility in ethylene glycol, applied as the solvent and reducing agent, appeared to be vital for effective separation of the stage of particle growth from its nucleation to enable rapid synthesis of small particles in a highly loaded system. This was not possible to obtain using silver nitrate. All the observations could perfectly be explained by a classical LaMer-Dinegar model of NPs' formation, but taking into account also nonisothermal character of the continuous-flow process and acetate dissolution in the reaction system. The performed studies indicate an optimal strategy for the high-yield fabrication of metal particles using polyol method.

No MeSH data available.


Related in: MedlinePlus

Particles size distributions histograms (by DLS) and UV–Vis spectra of samples produced using Ag-acetate (20 mM) and different reaction times
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Fig6: Particles size distributions histograms (by DLS) and UV–Vis spectra of samples produced using Ag-acetate (20 mM) and different reaction times

Mentions: In order to increase productivity, experiments were also carried out for larger inlet concentrations (20 and 50 mM) of Ag-acetate, i.e., well above its solubility limit in EG, which to the best of our knowledge was not explored before toward the synthesis of silver particles. On the whole, all these experiments ended up in the synthesis of very small particles, typically of less than 10 nm in size and at full reaction yield, which took us by surprise, but can be of major practical significance. Moreover, while the size distribution patterns (by DLS) of particles obtained from most rapid process (3 s, 150 °C exit temp.) appeared to be somewhat spread out (T19, Fig. 6) those of particles formed more slowly (6 or 24 s) tended to be more narrowly distributed and NPs were quite small, less or about 10 nm in size (T11, T20, and T25, Fig. 6), which again is quite attractive. However, more importantly, the same observations were also made for the systems with Ag-acetate content of 50 mM. Again, silver particles achieved from a rapid process (6 s, T13) appeared to be very small, yet their PSD was not so narrow (Fig. 5), in contrast to those obtained from less intensive heating (12–24 s), which were more narrowly distributed and quite small, prevalently in the range of 8–20 nm (cf. T14, Fig. 5). The results obtained again seem to comply with the LMD mechanism of particle formation, provided that the limited solubility of Ag-acetate in EG, and hence a need for its dissolution in the reaction system, is taken into account in addition to high reactivity. The rate of the former is not significantly affected by the change in temperature, but by vigorous particle oscillations. In effect, in a medium and high temperature region, where the rate of metal substrate reduction could potentially be very high, the rate of dissolution controls the rate of substrate reduction and hydrolysis and thus concentration of the final species, which cannot easily reach a critical supersaturation level. Yet owing to a continuous dissolution, and hence supply of Ag-acetate into the reaction zone, the concentration of these species can be maintained higher than a saturation level in a large section of the reactor. On the whole, this results in the attachment of more slowly generated species to very small particles formed in large amount in initial stages, resulting in their slow growth further downstream. In effect, the steps of nucleation and growth are effectively separated, in agreement with the postulates of LMD model for the synthesis of uniform particles (LaMer and Dinegar 1950; Fivet and Brayner 2013). However, not less importantly perhaps, the identified mechanism of silver nanoparticles’ formation from Ag-acetate also paves the way to a robust, cost-effective fabrication method of very high yield and productivity.Fig. 6


Rapid continuous microwave-assisted synthesis of silver nanoparticles to achieve very high productivity and full yield: from mechanistic study to optimal fabrication strategy.

Dzido G, Markowski P, Małachowska-Jutsz A, Prusik K, Jarzębski AB - J Nanopart Res (2015)

Particles size distributions histograms (by DLS) and UV–Vis spectra of samples produced using Ag-acetate (20 mM) and different reaction times
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4300398&req=5

Fig6: Particles size distributions histograms (by DLS) and UV–Vis spectra of samples produced using Ag-acetate (20 mM) and different reaction times
Mentions: In order to increase productivity, experiments were also carried out for larger inlet concentrations (20 and 50 mM) of Ag-acetate, i.e., well above its solubility limit in EG, which to the best of our knowledge was not explored before toward the synthesis of silver particles. On the whole, all these experiments ended up in the synthesis of very small particles, typically of less than 10 nm in size and at full reaction yield, which took us by surprise, but can be of major practical significance. Moreover, while the size distribution patterns (by DLS) of particles obtained from most rapid process (3 s, 150 °C exit temp.) appeared to be somewhat spread out (T19, Fig. 6) those of particles formed more slowly (6 or 24 s) tended to be more narrowly distributed and NPs were quite small, less or about 10 nm in size (T11, T20, and T25, Fig. 6), which again is quite attractive. However, more importantly, the same observations were also made for the systems with Ag-acetate content of 50 mM. Again, silver particles achieved from a rapid process (6 s, T13) appeared to be very small, yet their PSD was not so narrow (Fig. 5), in contrast to those obtained from less intensive heating (12–24 s), which were more narrowly distributed and quite small, prevalently in the range of 8–20 nm (cf. T14, Fig. 5). The results obtained again seem to comply with the LMD mechanism of particle formation, provided that the limited solubility of Ag-acetate in EG, and hence a need for its dissolution in the reaction system, is taken into account in addition to high reactivity. The rate of the former is not significantly affected by the change in temperature, but by vigorous particle oscillations. In effect, in a medium and high temperature region, where the rate of metal substrate reduction could potentially be very high, the rate of dissolution controls the rate of substrate reduction and hydrolysis and thus concentration of the final species, which cannot easily reach a critical supersaturation level. Yet owing to a continuous dissolution, and hence supply of Ag-acetate into the reaction zone, the concentration of these species can be maintained higher than a saturation level in a large section of the reactor. On the whole, this results in the attachment of more slowly generated species to very small particles formed in large amount in initial stages, resulting in their slow growth further downstream. In effect, the steps of nucleation and growth are effectively separated, in agreement with the postulates of LMD model for the synthesis of uniform particles (LaMer and Dinegar 1950; Fivet and Brayner 2013). However, not less importantly perhaps, the identified mechanism of silver nanoparticles’ formation from Ag-acetate also paves the way to a robust, cost-effective fabrication method of very high yield and productivity.Fig. 6

Bottom Line: Systematic studies of silver nanoparticle synthesis in a continuous-flow single-mode microwave reactor using polyol process were performed, revealing that the synthesis is exceptionally effective to give very small metal particles at full reaction yield and very high productivity.Owing to its much higher reactivity, silver acetate was shown to be far superior substrate for the synthesis of small (10-20 nm) spherical silver nanoparticles within a few seconds.The performed studies indicate an optimal strategy for the high-yield fabrication of metal particles using polyol method.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemical Engineering and Process Design, Faculty of Chemistry, Silesian University of Technology, Ks. M. Strzody 7, 44-100 Gliwice, Poland.

ABSTRACT

Systematic studies of silver nanoparticle synthesis in a continuous-flow single-mode microwave reactor using polyol process were performed, revealing that the synthesis is exceptionally effective to give very small metal particles at full reaction yield and very high productivity. Inlet concentration of silver nitrate or silver acetate, applied as metal precursors, varied between 10 and 50 mM, and flow rates ranged from 0.635 to 2.5 dm(3)/h, to give 3-24 s reaction time. Owing to its much higher reactivity, silver acetate was shown to be far superior substrate for the synthesis of small (10-20 nm) spherical silver nanoparticles within a few seconds. Its restricted solubility in ethylene glycol, applied as the solvent and reducing agent, appeared to be vital for effective separation of the stage of particle growth from its nucleation to enable rapid synthesis of small particles in a highly loaded system. This was not possible to obtain using silver nitrate. All the observations could perfectly be explained by a classical LaMer-Dinegar model of NPs' formation, but taking into account also nonisothermal character of the continuous-flow process and acetate dissolution in the reaction system. The performed studies indicate an optimal strategy for the high-yield fabrication of metal particles using polyol method.

No MeSH data available.


Related in: MedlinePlus