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. 2011;12(3):1464-73.
doi: 10.3390/ijms12031464. Epub 2011 Feb 24.

pH dependent molecular self-assembly of octaphosphonate porphyrin of nanoscale dimensions: nanosphere and nanorod aggregates

Sheshanath V Bhosale  1 , Mohan B Kalyankar, Santosh V Nalage, Cecilia H Lalander, Sidhanath V Bhosale, Steven J Langford, Ruth F Oliver
Affiliations

pH dependent molecular self-assembly of octaphosphonate porphyrin of nanoscale dimensions: nanosphere and nanorod aggregates

Sheshanath V Bhosale et al. Int J Mol Sci. 2011.

Retraction in

Abstract

Self-assembled nanostructures of zwitterionic octaphosphanatoporphyrin 1, of either nanoparticles or nanorods, depending on small changes in the pH, is demonstrated based on the J-aggregates. Porphyrin 1 self-assembled into nanosphere aggregates with a diameter of about 70-80 nm in the pH range 5-7, and nanorod aggregates were observed at pH 8.5. Hydrogen bonding, π-π stacking and hydrophilic interactions play important roles in the formation of this nanostructure morphology. Nanostructures were characterized by UV/Vis absorbance, fluorescence, atomic force microscopy (AFM) and transmission electron microscopy (TEM). This interesting pH dependent self-assembly phenomenon could provide a basis for development of novel biomaterials.

Keywords: AFM; TEM; aggregation; molecular self-assembly; porphyrin.

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Figures

Figure 1.
Figure 1.
(a) Schematic representation of the self-assembly of the OctaPhosPor 1 into: nanosphere aggregates at pH 5–7, and further aggregation of 1 into nanorods at pH 7–9 in water; (b) protonation and aggregation mode of OctaPhosPor 1.
Figure 2.
Figure 2.
Absorption spectrum of OctaPhosPor 1 (1 × 10−4 M) at pH 9.0 (broken curve) and 5.0 (solid curve), inset figure shows as an expansion of Q-bands (490–690 nm).
Figure 3.
Figure 3.
OctaPhosPor 1 shows a pH dependent (10.4–3.0) change in fluorescence spectrum at a concentration of 1 × 10−4 M, λex at 418 nm.
Figure 4.
Figure 4.
Atomic force microscopy (AFM) height images of OctaPhosPor 1 (10−4 M) upon spin-cast on silicon wafer plate after the solvent has evaporated, gives nanospheres in water at pH 7.0: (a) height image (scale bar = 1 μm); (b) magnified view of height image a (scale bar = 400 nm); (c) height image (scale bar = 1 μm); (d) Transmission electron microscopy (TEM) micrograph of 1 on holey, carbon-coated copper grids (scale bar = 100 nm); (e) high magnification of d; and (f) cross-section analysis magnified region from image c, provides a mean diameter of ca. 75 nm and a height of 30 nm.
Figure 5.
Figure 5.
(a) Atomic force microscopy (AFM) height images of 1 (10−4 M) upon spin-cast on silicon wafer plate after the solvent has evaporated; Inset = high magnification of AFM image (b) Transmission electron microscopy (TEM) micrograph of 1 on holey, carbon-coated copper grids (scale bar = 500 nm), shows nanorods in water at pH 8.5. Inset = high magnification of TEM image.
See this image and copyright information in PMC

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