Anais do Workshop INEO 2023

THE FORMATION OF COLLOIDAL AGGREGATES INDUCED FOR DIFFERENT ADDITION METHODS: STANDARD ADDITION (SA) AND EXTERNAL STANDARD (ES).

Published in 12/12/2023 - ISBN: 978-65-272-0088-8

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Paper Title
THE FORMATION OF COLLOIDAL AGGREGATES INDUCED FOR DIFFERENT ADDITION METHODS: STANDARD ADDITION (SA) AND EXTERNAL STANDARD (ES).
Authors
  • Marcelo José dos Santos Oliveira
  • Rafael Jesus Gonçalves Rubira
  • Cibely da Silva Martin Sonvesso
  • Santiago Sánchez-Cortés (Or); CSIC
  • Carlos José leopoldo Constantino
Modality
Pôster
Subject area
Síntese e caracterização de materiais
Publishing Date
12/12/2023
Country of Publishing
Brasil
Language of Publishing
Inglês
Paper Page
https://www.even3.com.br/anais/workshop-do-ineo-2023/614297-the-formation-of-colloidal-aggregates-induced-for-different-addition-methods--standard-addition-(sa)-and-external
ISBN
978-65-272-0088-8
Keywords
Aggregation mechanism, SERS, TEM, addition methods, detection
Summary
The objective of this work is to detect and optimize the detection of pesticides in aqueous medium using surface-enhanced Raman scattering (SERS), with emphasis on the effect of the different Ag nanoparticle (AgNPs) aggregation mechanisms. The difference in aggregation can lead to the formation of hot spots in the suspension. In general, colloidal suspensions of Ag nanoparticles can aggregate by two mechanisms: RLCA1 (reaction-limited colloid aggregation) and/or DLCA1 (difusion-limited colloid aggregation) aggregates. The mechanism depends on the adsorption of the analyte on the metal surface charge, and in this case of thiabendazol-TBZ. The effect can vary depending on the process used to add the analyte solution to the Ag colloid. In this study, we present the results from two methods: standard addition (SA), in which TBZ solution aliquots are added to the same Ag colloid aliquot, and external standard (ES), in which each aliquot of the TBZ solution is added to an aliquot of pure Ag colloid. These methods were analyzed by UV-Vis, transmission electron microscopy (TEM), and SERS techniques. At low concentrations of TBZ (SA = 6.3x10-7 M and ES = 6.0x10-6 M) there is no significant effect between both methods regarding the plasmon resonance (extinction spectra) and even no difference in comparison to the original suspension in the absence of TBZ. This is because at low the change in the surface electric charge is negligible in AgNPs, and strong electrostatic repulsions between AgNPs avoid an intensive aggregation1,2. However, via TEM, closed globular aggregates are observed. On the other hand, at high concentrations of TBZ (SA = 5.5x10-5 M and ES = 3.0x10-5 M), electrostatic repulsion is decreased among AgNPs. Thus, was observed a drastic decrease in the extinction band of Ag colloid at 405 nm related to isolated AgNPs, the emergence of a band at longer wavelengths (? > 693 nm), and a displacement of this band for longer wavelengths with increased concentration of TBZ1,2. This band is related to the aggregates of the AgNPs, whose TEM images reveal a globular morphology, but are more open (branched). SERS measurements showed detection limits of 9.0x10-9 (SA) and 6.9x10-8 M (ES). In addition, it was possible to observe that, above the concentration of 9.7x10-7 M, the SERS signal has its intensity decreased. Such a concentration coincides with the extinction spectrum that occurs the most drastic spectral change. 1. Weitz, D. et al.. Universality laws in coagulation. Chemom. Intell. Lab. Syst. 10, 133–140 (1991). 2. Sánchez-Cortés, S., et al.. Morphological Study of Metal Colloids Employed as Substrate in the SERS Spectroscopy. J. Colloid Interface Sci. 167, 428–436 (1994). Acknowledgements: FAPESP 2021/05460-6, 2022/09619-2, 2018/22214-6, INCT/INEO, CNPq, CAPES.
Title of the Event
Workshop do INEO 2023
City of the Event
Nazaré Paulista
Title of the Proceedings of the event
Anais do Workshop INEO 2023
Name of the Publisher
Even3
Means of Dissemination
Meio Digital

How to cite

OLIVEIRA, Marcelo José dos Santos et al.. THE FORMATION OF COLLOIDAL AGGREGATES INDUCED FOR DIFFERENT ADDITION METHODS: STANDARD ADDITION (SA) AND EXTERNAL STANDARD (ES)... In: Anais do workshop INEO 2023. Anais...Nazaré Paulista(SP) Hotel Estância Atibainha, 2023. Available in: https//www.even3.com.br/anais/workshop-do-ineo-2023/614297-THE-FORMATION-OF-COLLOIDAL-AGGREGATES-INDUCED-FOR-DIFFERENT-ADDITION-METHODS--STANDARD-ADDITION-(SA)-AND-EXTERNAL. Access in: 05/12/2024

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