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Silver nanoparticles coated with natural polysaccharides as models to study AgNP aggregation kinetics using UV-Visible spectrophotometry upon discharge in complex environments

Silver nanoparticles coated with natural polysaccharides as models to study AgNP aggregation kinetics using UV-Visible spectrophotometry upon discharge in complex environments
Silver nanoparticles coated with natural polysaccharides as models to study AgNP aggregation kinetics using UV-Visible spectrophotometry upon discharge in complex environments

This study provides quantitative information on the aggregation and dissolution behaviour of silver nanoparticles (AgNPs) upon discharge in fresh and sea waters, represented here as NaCl solutions of increasing ionic strength (up to 1 M) and natural fjord waters. Natural polysaccharides, sodium alginate (ALG) and gum Arabic (GA), were used as coatings to stabilize the AgNPs and the compounds acted as models to study AgNP aggregation kinetics. The DLVO theory was used to quantitatively describe the interactions between the AgNPs. The stability of AgNPs was established using UV-Visible spectrophotometry, including unique information collected during the first seconds of the aggregaton process. Alginate coating resulted in a moderate stabilization of AgNPs in terms of critical coagulation concentration (~ 82 mM NaCl) and a low dissolution of < 10% total Ag in NaCl solutions up to 1 M. Gum Arabic coated AgNPs were more strongly stabilized, with ~ 7–30% size increase up to 77 mM NaCl, but only when the silver ion content initially present in solution was low (< 10% total Ag). The ALG and GA coated AgNPs showed a strongly enhanced stability in natural fjord waters (ca. 5 h required to reduce the area of the surface plasmon resonance band (SPRB) by two fold) compared with NaCl at an equivalent ionic strength (1–2 min period for a two fold SPRB reduction). This is ascribed to a stabilizing effect from dissolved organic matter present in natural fjord waters. Interestingly, for AgNP-GA solutions with 40% of total silver present as unreacted silver ions in the NP stock solution, fast aggregation kinetics were observed in NaCl solutions (SPRB area was reduced by ca. 50% within 40–150 min), with even more rapid removal in fjord waters, attributed to the high amount of silver-chloride charged species, that interact with the NP coating and/or organic matter and reduce the NPs stabilization.
Silver nanoparticles, Aggregation, Oxidation, Alginate, Gum Arabic, Fjord waters
0048-9697
7-16
Lodeiro, Pablo
f6c1011a-06d0-4095-bc45-2e15e9e492d0
Achterberg, Eric P.
685ce961-8c45-4503-9f03-50f6561202b9
Pampín, Joaquín
00243774-6202-4544-aa0c-9432edf8007d
Affatati, Alice
27b66928-da5d-46e9-b56e-69568909c44a
El-Shahawi, Mohammed S.
d8455239-8d6a-4565-bcf5-2ee7ff9723ff
Lodeiro, Pablo
f6c1011a-06d0-4095-bc45-2e15e9e492d0
Achterberg, Eric P.
685ce961-8c45-4503-9f03-50f6561202b9
Pampín, Joaquín
00243774-6202-4544-aa0c-9432edf8007d
Affatati, Alice
27b66928-da5d-46e9-b56e-69568909c44a
El-Shahawi, Mohammed S.
d8455239-8d6a-4565-bcf5-2ee7ff9723ff

Lodeiro, Pablo, Achterberg, Eric P., Pampín, Joaquín, Affatati, Alice and El-Shahawi, Mohammed S. (2016) Silver nanoparticles coated with natural polysaccharides as models to study AgNP aggregation kinetics using UV-Visible spectrophotometry upon discharge in complex environments. Science of the Total Environment, 539, 7-16. (doi:10.1016/j.scitotenv.2015.08.115).

Record type: Article

Abstract


This study provides quantitative information on the aggregation and dissolution behaviour of silver nanoparticles (AgNPs) upon discharge in fresh and sea waters, represented here as NaCl solutions of increasing ionic strength (up to 1 M) and natural fjord waters. Natural polysaccharides, sodium alginate (ALG) and gum Arabic (GA), were used as coatings to stabilize the AgNPs and the compounds acted as models to study AgNP aggregation kinetics. The DLVO theory was used to quantitatively describe the interactions between the AgNPs. The stability of AgNPs was established using UV-Visible spectrophotometry, including unique information collected during the first seconds of the aggregaton process. Alginate coating resulted in a moderate stabilization of AgNPs in terms of critical coagulation concentration (~ 82 mM NaCl) and a low dissolution of < 10% total Ag in NaCl solutions up to 1 M. Gum Arabic coated AgNPs were more strongly stabilized, with ~ 7–30% size increase up to 77 mM NaCl, but only when the silver ion content initially present in solution was low (< 10% total Ag). The ALG and GA coated AgNPs showed a strongly enhanced stability in natural fjord waters (ca. 5 h required to reduce the area of the surface plasmon resonance band (SPRB) by two fold) compared with NaCl at an equivalent ionic strength (1–2 min period for a two fold SPRB reduction). This is ascribed to a stabilizing effect from dissolved organic matter present in natural fjord waters. Interestingly, for AgNP-GA solutions with 40% of total silver present as unreacted silver ions in the NP stock solution, fast aggregation kinetics were observed in NaCl solutions (SPRB area was reduced by ca. 50% within 40–150 min), with even more rapid removal in fjord waters, attributed to the high amount of silver-chloride charged species, that interact with the NP coating and/or organic matter and reduce the NPs stabilization.

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More information

Published date: 1 January 2016
Keywords: Silver nanoparticles, Aggregation, Oxidation, Alginate, Gum Arabic, Fjord waters
Organisations: Ocean and Earth Science

Identifiers

Local EPrints ID: 383874
URI: http://eprints.soton.ac.uk/id/eprint/383874
ISSN: 0048-9697
PURE UUID: ca7cdfab-e1ca-4ebc-95d1-964b2a250325

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Date deposited: 10 Nov 2015 14:59
Last modified: 08 Jan 2022 12:26

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Contributors

Author: Pablo Lodeiro
Author: Joaquín Pampín
Author: Alice Affatati
Author: Mohammed S. El-Shahawi

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