Detection of Silver Nanoparticles Based on Porphyrine- Induced Aggregation

Content Provider	Semantic Scholar
Author	Rysiavets, Anastasiya Panarin, A. Yu. Terekhov, Sergei
Copyright Year	2018
Abstract	Silver nanoparticles (AgNPs) with their unique optical properties due to excitation of localized plasmons have recently been objects of intensive research. Such NPs have the broad spectrum of analytical usage in biosensorics and genomics, cellular structures visualization, precision drug delivery, treatment of tumor diseases, etc. An expansion of AgNPs application will lead to the growth of their production volume, increase in the probability of entering the environment and, as a result, accumulation in the human body. There is concern about the potential human and ecosystem hazards associated with their exposure to silver nanoparticles [1]. In this situation, it is important to develop a simple, reliable and sensitive method of detection small quantities of AgNPs in solutions. In order to analyse plasmonic particles, particularly silver NPs, we propose to use the resonance light scattering spectroscopy. To enhance sensitivity of the method, preliminary analyte-induced aggregation was applied. Such approach is driven by the fact that the cross-section of scattering process significantly increases with the increase of particle size. As an agglomerate forming molecules we used water-soluble cationic and anionic porphyrins, which act as electrostatic bridges between the metallic NPs. To develop a scattering-based technique for determining of silver NPs spectral manifestation of the surface plasmon resonance of nanoparticles upon their interaction with porphyrins has to be characterized. Thus this study focuses on interaction of cationic Cu(II)-tetrakis(4-N-methylpyridyl) porphyrin (CuTMPyP4) and Cu(II)-tetrakis(2-Nmethylpyridyl) porphyrin (CuTMPyP2), as well as anionic Cu(II)-5,10,15,20-tetrakis(4-sulphonatophenyl) porphyrin (CuTPPS4) with colloidal solution of Ag NPs. Silver NPs were synthesized by reduction of AgNO3 with glucose (50 mM) in water solution of 10 mМ NaHCO3 (as a pH-regulator) and 1 mM sodium citrate (as a stabilizer). The resulting silver particles were purified from the synthesis medium components by centrifugation (20000 rpm, 30 min). The size of Ag NPs assessed by transmission electron microscopy and extinction spectra was about 30 nm. It was observed, that in the presence of cationic porphyrins (CuTMpyP4 and CuTMpyP2) the surface plasmon resonance maximum in the absorption and light scattering spectra of Ag NPs has been significantly increased and shifted to the longer wavelengths. It has been suggested that such behaviour is due to aggregation of nanoparticles. This was supported by transmission electron microscopy images which showed formation of agglomerates of Ag NPs. On the other hand, addition of anionic porphyrin (CuTPPS4) to Ag NPs solution did not lead to any meaningful spectral changes. The described observations can be explained by Coulomb attraction between cationic porphyrin molecules and negatively charged AgNPs, and repulsion between the nanoparticles and anionic CuTPPS4 molecules. These results give a foundation for the development of optical method of detection noble metal NPs in aqueous solutions. In order to progress with practical application of the method, it is important to evaluate the limit of detection of NPs. For this reason extinction and scattering spectra for different amount of NPs in mixture with cationic porphyrin CuTMPyP4 were registered. To calculate the concentration of NPs in solutions we also measured extinction spectra of NPs in absence of porphyrin. Accordingly to the position and intensity of the bands in these spectra and taking into the account the data which are presented in work [2], concentrations of NPs were determined. Based on the calculated results we can conclude that 0,5 ∙ 10 M is the limit of detection of Ag NPs by scattering spectra. To use the measured data for determination of NPs in solutions we have built the calibrated dependency of scattering intensity on concentration of NPs. Thereby, the resonance light scattering spectroscopy allows a quantitative analysis of containment of silver NPs in solution.
File Format	PDF HTM / HTML
Alternate Webpage(s)	http://www.openreadings.eu/thesismanager/thesis18/197Rysiavets.pdf
Language	English
Access Restriction	Open
Content Type	Text
Resource Type	Article