Longitudinal surface plasmon resonance of gold nanoparticles as an indicator for interparticle fusions controlled by tetronics
Graphical abstract
Introduction
S – G method [[1], [2], [3], [4]] is widely applicable method for the synthesis of shape controlled morphologies of a variety of nanomaterials. This method produces exciting morphologies especially for Au and Ag NPs in the presence of surface active agents like surfactants [5,6]. In this method, first a seed solution is prepared by reducing metal ions into their zerovalent states in the presence of a strong reducing agent like NaBH4 and then, the tiny seed NPs are subjected to the growth process in the second step to produce shape controlled bigger morphologies in the presence of shape directing agents [2]. Generally, ionic surfactants are used in the S – G method because ionic surfactants demonstrate their strong interfacial adsorption on the free metallic surfaces. They possess the ability to completely passivate crystal planes such as {100} and {110} from further participating in the crystal growth to produce shape controlled morphologies [[1], [2], [3], [4], [5], [6]]. Apart from the ionic surfactants, water soluble polymers such as dextran [7,8] and PVP [[9], [10], [11], [12]] also demonstrate their excellent potential in producing shape controlled morphologies. This ability originates from the presence of partially polar functionalities in the polymer which allow the polymer macromolecule to interact electrostatically with free metal surfaces of growing nucleating centers that in turn directs the crystal growth in a specific direction.
“Tetronics” [[13], [14], [15], [16], [17], [18]] is another important category of micelle forming water soluble star polymers which exhibit completely different behavior from that of the conventional water soluble polymers due to the presence of three dimensional molecular configuration (Fig. 1). They allow their micelles (Supporting information, Figs. S1 and S2) to act as nanoreactors and facilitate the synthesis of NPs by using their surface cavities which are produced by the self-aggregation of polyethylene (PEO)–polypropylene (PPO)–PEO blocks on the surface of their micelles [13,14]. The participation of the micellar cavities only provides the colloidal stabilization to the growing nucleating centers while they are not good shape directing agents and hence, shape controlled monodisperse morphologies are usually not produced in these reactions [13,14]. However, when tetronics are used in an S – G method for the synthesis of Au NPs, they show a completely unique behavior of NPs synthesis with the appearance of prominent longitudinal surface plasmon resonance (LSP) of Au NPs in every reaction without the formation of “one dimensional morphologies” like rods, wires, or ribbons [[19], [20], [21]]. Usually, the LSP is the consequence of later morphologies due to the surface plasmon resonance (SPR) from the one dimensional NPs. Thus, the appearance of LSP in the case of S – G reaction is a unique characteristic feature of tetronics and a best indicator of NP–NP interactions rather than the absorbance due to SPR from one dimensional morphologies. In this study, we show that how tetronics drive the interparticles fusions of Au NPs during the S – G method that generates interesting photophysical properties of nanomaterials based on LSP. The main objective is to focus on the mechanistic aspects of interparticles fusions during the growth reactions and the participation of tetronic micelles to promote such interactions responsible for LSP.
Section snippets
Materials
Tetrachloroauric acid (HAuCl4), sodium borohydride (NaBH4), ascorbic acid, and trisodium citrate (Na3Cit) were obtained from Aldrich. Tetronics, T904 (EO = 15, PO = 17) average molar mass = 6700, T908 (EO = 114, PO = 21) average molar mass = 25,000, and T1307 (EO = 72, PO = 32) average molar mass = 18,000 are the trade names of the star polymers from BASF. They were the gifts from BASF, BASF Corp. Parsippany, NJ, USA. Ultra pure water (18 MΩ cm) was used for all aqueous preparations.
S – G method
Synthesis
S – G reactions
Fig. 2a shows a typical UV–visible scans of S – G reaction sequences of three steps i.e. A1 ➔ A2 ➔ A3 at low pH (2.5) and B1 ➔ B2 ➔ B3 at high pH (12.5), of Au NPs synthesized in the presence of T904. In the case of A1, A2, and A3 samples, two prominent peaks are observed. The first one at 520 nm appears in each case whereas the second one around 700 nm red shifts with total ~50 nm in A2 and A3 during the reaction sequence. Interestingly, the second absorption peak around 700 nm is absent when
Discussion
All above results indicate that it is the acidic reaction conditions of S – G process those promote the interparticle fusions during the growth process and various mechanistic steps are resented in Fig. 6. It causes the appearance of LSP which appears in the near IR wavelength region and is related to the aspect ratio of the one dimensional nanometallic shape [25,27]. A higher aspect ratio shifts the LSP at a much longer wavelength and higher intensity is related to the greater number of such
Concluding remarks and applicability
S – G method is the most common method for the synthesis of nanomaterials to achieve shape controlled morphologies where small seeds are subjected to a stepwise reduction reaction to generate desired morphologies. The shape directing agents usually surfactant molecules play a significant role in this method. However, if an appropriate templating agent like tetronic is used, it is possible to put the growing NPs in an ordered fashion with unique photophysical behavior (Fig. 6) which can be used
CRediT authorship contribution statement
Lavanya Tandon: Methodology. Pankaj Thakur: Project administration. Poonam Khullar: Resources, Funding acquisition. Mandeep Singh Bakshi: Conceptualization, Writing - review & editing.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgment
These studies were supported by starts up funds from UWGB. These studies were partially supported by the financial assistance from DST under nanomission research project [ref no. SR/NM/NS-1057/2015(G)], New Delhi. P.K. acknowledges the TEM studies done by SAIF Lab, Nehu, Shillong. Tetronics were received as a gift from BASF Corp., Parsippany, NJ, USA.
References (38)
- et al.
Micellization and solubilization of a model hydrophobic drug nimesulide in aqueous salt solutions of tetronic (R) T904
Colloids Surf. B: Biointerfaces
(2011) - et al.
Formation of gold nanoparticles in a free-standing ionic liquid triggered by heat and electron irradiation
Micron
(2019) - et al.
Thermal stability of gold nanorods in an aqueous solution
Colloids Surf. A Physicochem. Eng. Asp.
(2010) Engineered nanomaterials growth control by monomers and micelles: from surfactants to surface active polymers
Adv. Colloid Interf. Sci.
(2018)Colloidal micelles of block copolymers as nanoreactors, templates for gold nanoparticles, and vehicles for biomedical applications
Adv. Colloid Interf. Sci.
(2014)- et al.
Controlling the topography and surface plasmon resonance of gold nanoshells by a templated surfactant-assisted seed growth method
J. Phys. Chem. C
(2013) A simple method of superlattice formation: step-by-step evaluation of crystal growth of gold nanoparticles through seed-growth method
Langmuir
(2009)- et al.
Preparation and growth mechanism of gold nanorods (NRs) using seed-mediated growth method
Chem. Mater.
(2003) - et al.
Seed-mediated synthesis of gold nanorods: role of the size and nature of the seed
Chem. Mater.
(2004) - et al.
Anisotropic noble metal nanocrystal growth: the role of halides
Chem. Mater.
(2014)
Anisotropic nanoparticles and anisotropic surface chemistry
J. Phys. Chem. Lett.
Synthesis of size-tunable polymer-protected gold nanoparticles by femtosecond laser-based ablation and seed growth
J. Phys. Chem. C
Ecofriendly route to synthesize nanomaterials for biomedical applications: bioactive polymers on shape-controlled effects of nanomaterials under different reaction conditions
ACS Sustain. Chem. Eng.
Formation of PVP-protected metal nanoparticles in DMF
Langmuir
Effect of catalysis on the stability of metallic nanoparticles: Suzuki reaction catalyzed by PVP-palladium nanoparticles
J. Am. Chem. Soc.
Rapid transformation from spherical nanoparticles, nanorods, cubes, or bipyramids to triangular prisms of silver with PVP, citrate, and H2O2
Langmuir
Recent developments in shape-controlled synthesis of silver nanocrystals
J. Phys. Chem. C
Multifunctional photo-physiochemical properties of tetronic 304 in aqueous phase: mechanistic aspects of Au(III) reduction into Au(0)
J. Photochem. Photobiol. A Chem.
PH and thermo-responsive tetronic micelles for the synthesis of gold nanoparticles: effect of physiochemical aspects of tetronicsle
Phys. Chem. Chem. Phys.
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